5451 5455.output

* GB785859 (A)
Description: GB785859 (A) ? 1957-11-06
Improvements in or relating to ribbon type burners
Description of GB785859 (A)
PATENT SPECIFICATION
785,859 Date of A pplication and filing Complete Specification Jan 17,
1956.
),; IV No 1562/56.
A pplication made in United States of America on April 19, 1955.
Complete Specification Published Nov 6, 1957.
Inidex at Acceptance:-Classes 75 ( 1)9 TM)I 2; and 75 ( 3), F 7 (B: E:
5).
International Classification:-F 2 ltg lF 23 f.
COMPLETE SPECIFICATION
Imlpralvtenaeltnts in or D Fdaltin Rg to 9 nfibbcli Type BU Iews 14 i
I, JOHN HAROLD FLYNN, a citizen of the United States of America, of
234, Elk Avenue, New Rochelle, New York, United States of America, do
hereby declare the invention, for which I pray that a patent may be
granted to me, and the method by which it is to be performed, to be
particularly described in and by the following statement:0 This
invention relates to gas burners of the so-called ribbon type, and
particularly to burners of this type adapted to provide two or more
spaced ribbons or bands of flame from a single burner body.
As is well known in the art, ribbon burners comprise in general a
hollow casting forming a casing or housing adapted to be supplied with
a combustible gaseous fuel mixture which is permitted to issue through
ports extending longitudinally of the burner body and is ignited upon
emergence from these ports to provide the aforesaid ribbons of flame
Burners of this type, but providing only a single ribbon of flame, are
known.
For increased heating capacity, dual or multiple flame ribbon burners
are often desirable and are commonly used, for example, as the heating
units in ovens of the traveler or continuous type for baking biscuits
crackers, bread and the like from dough material transported through

the oven on conveyor bands Each individual burner is disposed across
the width of the oven, that is, transversely of the direction of
travel of the conveyor band, to provide an even distribution of heat
thereacross, and a series of these burners is arranged in side-by-side
relation along the length of the oven to maintain the desired heating
effect throughout its extent Since ovens of this type may attain
considerable length, as much for example as two hundred and fifty feet
or more, a large number of burners may be required.
Each of these burners must have means for igniting the gas issuing
from its ports, and lPrice 3 s 6 d l where there are two or more
spaced ports, as in the case of the burners here under consideration,
ignition means for both such ports must be provided High tension
sparking electrodes are generally used for this purpose 50 and, in
order to reduce the number of such electrodes required in an
installation, it has heretofore been proposed to provide but one
electrode per burner to ignite the gas at one main burner port and to
incorporate in the 55 burner, crossover means for causing propagation
of the flame from such first main port across the intervening body of
the burner to the other port spaced from the first.
While, as just stated, such a crossover 60 arrangement has been
proposed heretofore.
it is subject to certain serious disadvantages.
particularly with respect to lack of sufficient structural rigidity
under sustained operation at the high temperature to which such
burners 65 are necessarily subjected Since the burners are suspended
between longitudinal frame members in the oven, and owing to the
construction and arrangement of the crossover pilot arrangement
heretofore employed, such 70 prior burners have had a tendency to warp
or sag in the middle after relatively short periods of use This
results in uneven heat distribution across the oven and leads to the
need for frequent replacement of the burners, all at 75 substantial
expense Such prior burners have a further disadvantage in that they
produce a continuous zone or area of overheating owing to the
unvarying position throughout the oven of the crossover pilot flame,
resulting 80 in further unevenness in operation of the oven.
Accordingly it is a general object of this invention to provide an
improved multiple port ribbon burner and integral crossover 85 pilot
construction, whereby, upon ignition at a first main port of the
ribbon burner, propagation of the flame across the intervening body of
the burner to a second main port will be ensured under all conditions
Because 90 of the obvious hazard involved should gas issuing from one
main burner port fail to be ignited promptly on issuing from the
burner port, absolute dependability of cross-piloting is essential
This must be true for all possible starting conditions of the burner,

ranging from low turndown or standby to maximum heat output condition
Burners according to the present invention are effective in meeting
these requirements.
In line with the foregoing, it is a further object to provide a burner
of this type having improved mechanical strength and design whereby
any tendency of the burner body to warp or sag is completely
eliminated, even when exposed for long periods to high operating
temperatures, thus ensuring both uniformity of heating operation and
lower replacement cost The design is such also that local 'hot-spots"
or zones of overheating along an oven, due to the crossover pilot
flame, can be easily avoided while employing but a single, standard
form of burner body construction This of course results in a further
economy, as it becomes unnecessary to stock different types of
burners, one type being adaptable for use at any point in an oven.
Briefly, the foregoing objects and advantages are obtained in
accordance with the invention disclosed herein by providing, at one or
more points along the body of a multiple-port ribbon burner an
improved integral crossover pilot for cross-ikiting the main burner
ports Unlike prior constructions, the crossover arrangement herein
disclosed permits the burner body to be made substantially without
transverse interruption in its wall or web, with the result that the
new burner is not subject to the tendency to sag which has
characterised burners of this general type heretofore As a further
measure, longitudinal or dorsal reinforcing ribs running
longitudinally of the burner body are provided to increase its
transverse strength.
A feature of the invention is the provision of a shield at the
crossover point on the burner which permits the employment of a
minimum cross-piloting flame but which nevertheless ensures positive
travel or propagation of flame from one main port to the other under
any operating condition and by providing the crossover at a point
asymmetric to the midpoint on the burner length, localized
overheating, due to alignment of successive crossover flames in a
series of burners along an oven, can be avoided This is made possible,
while employing but a single standard design of burner, by installing
burners in alternate end-for-end arrangement along the oven so as to
effect a staggering of the position of the crossover flame across the
width of the oven The staggering effect can of course be further
increased by providing more than one available crossover point on the
burner body, although only one such point on any particular burner is
used.
Specific constructions of burner according to the present invention
will now be 70 described, by way of example only, with reference to
the accompanying drawings in which Figure 1 is a side elevation,

partially broken away and partially in section, of a ribbon 75 burner
embodying a preferred form of the crossover pilot; Figure 2 is an end
view, looking from the right, of the burner shown in Figure l:
Ficure 3 is a fragmentary part-se 2 tional 80 plan view of the burner
shown in Figure 1; Fisure 4 is a section taken mainly along the line
4-4 of Figure 1 but also showinou details of the crossover pilot:
Figure 5 is a fragmentarv end section on 85 the line 5-5 of Ficure 4:
Figures 6 and 7 are, respectivelv side and part-sectional end
elevations of the metal shield employed in the crossover pilot:
Ficure 8 is a fragamentary underplan view 90 of the shield shown in
Figure 6:
Figure 9 is a developed view of the shield of FI>-yures 6 and 7; Fi
ure 10 is an enlareed sectional view of a jet: 95 Figure 11 is a
section similar to Figure 4 of au alternative construction:
Fi-ure 12 is a fragmentary section on the line 1 I-12 of Figure 11:
Fioures 13 and 14 illustrate the alternative 100 shield of Fi-ures 11
and 12; and Figure 15 is a aerspective view of burners of the present
invention installed in a typical band oven.
The preferred form of dual flame gas 105 burner 20 illustrated in
Figures 1 to 10 includes an elongated tubular body or casing formed
from an integral iron casting 21 At its opposite ends the casino 21
has end walls 22 and 24, each of which has a like, centrally 110
located, tapped aperture 26 28 respectively.
Either one of these apertures is adapted to receive the externally
threaded end of a pipe for supplying under pressure a suitable
combustible gaseous mixture into the hollow 115 interior 25 of the
casing 21, while a matching threaded plug is adapted to be placed in
the opposite end of the casing to close that end against the escape of
gaseous fuel The burner 20 is adapted to be supported at its 120 ends
in a horizontal position in a conventional band oven 23, as shown in
Figure 15.
As there illustrated, a series of burners 20 are disposed transversely
of the oven, and each burner is supplied with a combustible 125 gas
mixture from manifolds 30, 32 extending the length of the oven An
endless metal band 33 travels through the oven and carries, in the
present instance, goods to be baked on the lower run of the band 130
Referring again more particularly to Figures 1 to 5, the burner body
or casing 21 has on diametrically opposite sides external ribs 34, 36,
each extending longitudinally of 785,859 location of the crossover
pilots in an oven installation to be staggered along the oven.
This will be discussed more fully hereinafter 70 Each of the bosses
58, 60 comprises an arcuate rib 62 cast intergrally with the casing
and extending laterally across one half thereof This rib serves to
increase substantially the wall or web thickness of the 75 burner

casing at this point The rib 62 includes two similar semicircular
spaced ridges 64 extending along opposite edges of the rib and merging
at their opposite ends into the exposed lateral faces of the ribs 34,
36 of the 80 casing, as shown more particularly in Figures 2 and 3 of
the drawings Along the adjacent inner edges of each of the ridges 64
there is a shoulder 66, and between these shoulders, an arcuate web 68
whose external surface is 85 depressed slightly below the horizontal
surfaces of the shoulders 66 The outer surface of this arcuate web
likewise merges at its ends with the ribs 34, 36 at the upper edges of
the slots 38, 40, respectively 90 As shown more particularly in Figure
4, the web 68 is drilled to provide an aligned series of radial pilot
gas ports or holes 70 running transversely of the burner Each hole 70
extends through the wall of the cas 95 ing 21 into the interior 25
thereof, and each is counterbored and tapped and has a hollow threaded
tip or jet 72 inserted therein As shown more particularly in Figure
10, such tips provide constricted pilot orifices 74 for 100 the
controlled escape of gas for cross-piloting purposes This arrangement
does not substantiallv interrupt the continuity of the burner casing
wall, so that the strength of the burner, particularly with respect to
trans 105 verse bending or sagging, is virtually unaffected.
In order to get propagation of the pilot flame from the main port 38
along the line of pilot jets 72 to the other main port 40, each 110
crossover formation has a cover means consisting of an arcuate
perforated shield 76 of sheet metal, such as stainless steel, which
extends across the boss 58 or 60 and is supported on the ridges 64
clear of the pilot jets 115 72 in the web 68 The shield 76 is
initially formed from relatively thin flat blank stock.
Figure 9 illustrates a strip of such stock which has been perforated
to provide two centrally located parallel rows of equally 120 spaced
small holes 78, and mounting screw holes 80, 82 This strip is then
formed into the arcuate channel shape shown in Figure 6, in which the
central panel 84 is dropped slightly with respect to the flanking
shoulders 125 86 (Figures 5 and 7) The panel 84 extends in a smooth
arc throughout the extent of the strip, whilst the shoulders 86 are
flattened, as at 88, at the ends of the strip In this manner, small
protruding lips 90, 91 (Figures 130 4 and 8) are formed by the central
panel 84 at its opposite ends, the purpose of which will appear more
fully presently.
The shield 76 is adapted, to be secured to the casing from a point
near one of its ends to a point the same distance from the opposite
end Each of the side ribs 34, 36, is formed with a longitudinal slot
38, 40, respectively, passing through the casing from the interior to
the exterior thereof, and extending substantially throughout the
length of the ribs, as seen in Figure 1 These slots 38, 40, constitute

the main ports of the burner and each has disposed within it, in
face-toface relationship, a group of transversely corrugated or
crimped metal ribbons or bands 42 made of stainless steel or other
nonoxidising material These divide the main ports into series of
closely spaced high, medium and low velocity gas jets extending
longitudinally throughout the extent of the respective slot 38 or 40
Gas escaping through these jets from the interior of the casing 21
produces a continuous ribbon or band of flame when the fuel is ignited
at the main burner ports A conventional high tension sparking
electrode 43, (Figure 3), mounted by suitable clamp means at one side
of the burner, is employed to effect ignition of the fuel at one end
of the main port 38.
Once ignited the flame then travels the length of this main burner
port and across to the other main port 40 as will presently be
described.
The burner body or casing 21 also includes tipper and lower external
or dorsal ribs 44, 46 extending longitudinally from a point adjacent
one end of the casing to a point similarly spaced from its other end,
and upper and lower internal ribs or fins 48, 50, substantially
coextensive with the respective external ribs 44 46 The lower internal
fin is continuous throughout its length,, while upper fin 48 has an
upward relief or depression 49 at two points along its extent, as best
seen in Figures 1 and 5, for fuel distribution purposes, but is
otherwise continuous Additional reinforcing of the casing 21 is
supplied by vertical posts or tie ribs 52 which extend across the
interior of the casing between the fins 48 and 50 on either side of
the depressions 49, as shown in Figures 1 to 3 The casing is also
provided with internal baffles 54, 56, adjacent the ends and
intermediate the extent of the hollow interior 25 of the casing, which
assist in getting proper distribution of gas to the several ports.
At points approximately one-third and one-half the distance along the
body or casing 21 from one end thereof, there is provided a respective
external integral, arcuate crossover boss 58, 60, each of which
extends between the main port slots 38, 40 Only one of these bosses-in
Figures 1-5, the boss 58is used on any given burner to provide
crossignition from the main port 38 to the port 40 when fuel issuing
at the former is ignited.
While only one of these crossover points is used in any given burner,
two such points are made available in order to have but a single
design of burner, yet permit the transverse 785,859 either boss 58 or
60, whichever is selected, and the boss is drilled and tapped, as at
92 (Figures 3 and 5) in the ridges 64 and on the faces of the ribs 34,
36, to receive screws 94.
These latter pass through the holes 80, 82, of the shield and hold it

flush against the boss.
The shoulders 86 of the shield engage the ridges 64 and the central
panel 84 overlies the pilot jets with clearance, thus providing a
semi-annular flame chamber or tunnel 96 beneath the shield into which
the jets discharge As will be noted more especially from Figure 5, the
holes 78 in the panel 84 are disposed on either side of the centre
line of the orifices 74 of the jets 72 These permit combustion air to
enter the chamber or tunnel without destroving the baffling effect of
the shield in promoting deflection of the gas issuing from the jets 72
Owing to the projection of the lips 90, 91, at the ends of the shield,
the chamber 96 is open at opposite ends but it is otherwise closed,
except for the holes 78, across the ridges 64 of the crossover boss.
When a combustible gas is admitted to the burner and current supplied
to the electrode 43, the gas is ignited at the left hand end of the
port 38, as viewed in Figures 1 and 3, and the flame travels to the
right along this port At the same time gas flows from the several
pilot jets 72 under the shield at the crossover point As the flame at
the port 38 reaches the crossover gas from the jets is ignited at the
end of the shield 76 where the lip 90 projects out over the main port
The flame is picked up at the end of the shield and, supported by
combustion air picked up at the lips and flowing in through the holes
78 travels from jet to jet beneath the shield until all the jets 72
are lighted At this point, gas issuing from the main port 40 is
ignited by flash-back from the lip 91 and thereafter the flame travels
along the port 40 until it is also completely lit The flame
propagation is sufficiently rapid to insure against any dangerous
accumulation of unignited gas, even when the crossover point is remote
from the ignition electrode.
A cover means, such as the shield 76, is essential to get directed
propagation of the pilot flame just described throughout the extent of
the crossover Without the shield, a substantially continuous open
crossover port from one main port to the other is necessary to get the
flame to travel across the intervening body of the burner But such a
port greatly weakens the burner and results in its sagging Moreover,
such a port causes a lot more gas to escape at the crossover pilot
than is desirable and produces a poini in the burner of substantially
greater heat output than that at other points along the burner.
The mere provision of a series of individual jets, even though quite
closely spaced, in order to overcome the foregoing objections, will
not produce a dependable crossover pilot With the shield in place,
however, cross-i-nition is ensured I under all conditions.
This is true not only for all gas locities ironi minimum turn-down to
maximum heat out 7 s) put conditions, but for any position of the
burner, this is, whether the crossover pilot is on the upper or lowver

side of the burner.
During burner operation the pilot flame burns both within the chamber
96 and out 75 side the central panel 84 of the shield, but in any
event is of very low height compared to the usual crossover pilot
flames obtained heretofore While the flame is continuous in the sense
that it ensures cross-ignition from 8 '3 one end of the crossover to
the other, it appears to be a flashing rather than a stead flame.
In a specific design of burner having an overall length of
approximately 41 ' and a 85 maximum width of 3-5/8 " from face to face
of the ribs 34, 36 the web 68 of the crossover is provided with
nineteen 3116 " diameter piloting tips or jets 72 spaced 9 apart over
the extent of the semicircular web The 90 orifices in these tips are
of the order of 1/16 " diameter The width of the chamber 96 formed by
the ridges 64 is about 3/8 ".
while the distance between the web 68 and the panel 84 is 3 /16 " The
shield 76 is pre 95 ferably of 0 020 " stainless sheet steel and the
holes 78 are preferably 0 059 " diameter on one-eighth inch centres,
this providing a total of about 94 such holes in the shield The
overhang of the lips 90 91 at the ends is 118 '10 ') to 3,'16 " beyond
the respective lateral faces of the main burner ports.
Figures 11 to 14 illustrate an alternative crossover pilot
construction according to the invention which differs from the
preferred 105 arrangement shown in Figures 1 to 10 primarily in
respect of the form of shield employed Here, the burner 100 has a boss
102 similar to the boss 58 previously described except that there is
an internal 11 ( semiannular recess 104 running centrally of the boss
betwen the main port slots 106, 108.
Internal longitudinal reinforcing fins 110.
112, are provided as before, and fin 110 is chamfered, as at 114
(Figure 12) adjacent 115 each side of the recess 104 to allow proper
fuel distribution to the crossover jets 116.
The latter are equally spaced around the central web 118 of the boss,
each providing metered discharge of gas 12 t In place of the unitary
perforated metal shield of the preferred construction, a strip of
corrugated metal ribbon 120 (Figures 13 and 14) is employed This has a
width just sufficient to pass between the ridges 122 on the 125 boss
102 and to lie against and be supported by shoulders 124 on the
adjacent inner edges of the ridges 122 (Figure 12) The shoulders 124
hold the ribbon spaced radially outward from the jets 116 to define a
semiannular 13 f) flame space 126 The depth of the shoulders below the
outer surfaces of the ridges 1 '2 is substantially that of the
thickness of the corrugated ribbon 120, and preferably a 785,859
burner port, and the cover means partly overhangs each main burner
port orifice.

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* GB785860 (A)
Description: GB785860 (A) ? 1957-11-06
Improvements in or relating to rotary piston blowers
785,860 o Date of Application and filing Complete Specification Jan
17, 1956.
' No 1576/56.
Application made in Germany on Jan 17, 1955.
Index at Acceptance:-Class 110 ( 2), A( 1 85 A: 21): X: 3 B).
International Classification:-Fo 4 d.
COMPLETE SPECIFICATION "Improvements in or relating to Rotary Piston
Blowers" I, MANFRED DUNKEL, a German citizen, personally responsible
partner of E Leybold's Nachfolger, of 504, Bonner Strasse, K 6
In-Bayental, Germany, a German Kommanditgesellschaft, do hereby
declare the invention, for which I pray that a patent may be granted
to me, and the method by which it is to be performed, to be
particularly described in and by the following statement:The present
invention relates to rotary piston blowers of the Roots type with
auxiliary pumps for operation in vacuum where shafts and rotary
pistons are cooled, and has for object improvements in such
arrangements.
Roots blowers are known to be used for one or more high vacuum stages
in a multistage pump arrangement for very low suction pressures Much
higher compression ratios can be obtained in a chamber under vacuum

than one at higher or positive pressures because flow resistance in
the gaps or slots of the blower is much higher and the resulting
return flow is reduced This is in itself an advantage, but there is
also the concommitant disadvantage of reduced heat conductivity of the
gas at low pressure This will lead to unduly high temperature of the
rotors as well as of the vacuum seals of the shaft The rotors will
expand considerably at high temperature, and this may cause mutual
fouling of the rotors or of rotor and casing, leading to seizure of
the pump.
It is known to prevent the temperature rise of rotors or rotary piston
blowers by interior cooling Air, water or oil for instance, may be
used as a cooling agent The cooling agent enters through a
longitudinal bore of the rotor shaft into the hollow rotor, and flows
through it to run out again through the shaft.
On applying such methods of cooling to rotary piston blowers which
operate at negative pressures in excess of 40 Torr, particular
difficulties will, however, be enlPdeie 3 s 6 d l countered These
difficulties, the nature of which will be briefly described, can be
obviated according to the invention When using air or water cooling,
both shafts of the rotors must extend outside the apparatus in 50
order to provide inlet and outlet for the cooling air or water, as the
bearing chambers will, when working under vacuum, normally be
evacuated by connecting them to the auxiliary pump This, however,
demands 55 additional work in design and construction.
Difficulty of control is a further disadvantage of air or
water-cooling, making it frequently impossible to prevent overcooling.
In accordance with the invention these 60 difficulties can be obviated
by cooling the shafts by a fluid, preferably oil, which circulates in
a vacuum In this way it is not necessary to extend the rotor shafts to
the exterior of the apparatus for the purpose of 65 providing inlet
and outlet for the cooling fluid The circulating cooling fluid will in
turn pass through a heat exchanger, where it is cooled down to the
required temperature The simplest method is air cooling, but 70
cooling with a liquid, as a rule with water, also has its particular
advantages as in this case the amount of liquid admitted to the heat
exchanger can be controlled by a thermostat immersed in the liquid
circulating 75 in the pump In this way, the temperature in the rotor
can also be set to the required value In this connection one or two
fluid pumps can be driven by the shafts of the rotary piston, or may
be directly coupled with 80 them.
In order that the invention may be more readily understood, reference
will now be made to the accompanying drawings, in which Figs 1 and 2
show two embodiments 85 thereof by way of examples.
In Fig 1, the ends of the shafts 1 and 2 are provided with

longitudinal bores 3, 4, 5 and 6 which are connected to the rotors 11,
12 by bores 7, 8, 9 and 10 Cooling oil is 90 injected by the pipes 13
and 14 which pass through stuffing boxes 15, 16 to the left of the
Figure and carried by centrifugal force into the rotors It enters
through the bores 3 and 4 through the bores 7 and 8 at right angles
thereto into the chamber of rotors 11, 12.
An exchange of heat takes place between the heated inner wall of each
rotor and the cooling oil The oil leaves the inner chamber through the
bores 9 and 10, emerges through the holes and bores 5, 6 at the right
side of the bearings and collects in the emptied bearing housing 17
acting as an oil sump The pipes 13 and 14 can be sealed by packing
towards the inner chamber of the shaft This packing preferably
comprises lip packings (of the cup ring type) There it is cooled down
to a constant temperature level by the cooling coil 18 and the
thermostat 19 and is delivered again by the circulation pump 20,
arranged below-the oil level, to the injection pipes 13 and 14 A cover
21 for the evacuated bearing is arranged at the left of the Figure,
and is connected to the housing 17 by an oil pipe 22 The circulation
pump has to be arranged below the oil level because as a result of the
low pressure above the oil the pump cannot be used for sucking but
only for delivery The oil under pressure, which is provided by the
circulation pump, can also be used for cooling and lubrication of the
bearings, gear wheels and shaft packings.
Where the centrifugal force is not sufficient for the delivery of the
cooling agent to the rotor, the injection tubes 13 and 14 can be
tightened by lip packings replacing the stuffing boxes 15 and 16, and
the cooling agent be forced under pressure through the rotors.
Fig 2 shows a further embodiment The shafts 1 and 2 are provided with
continuous longitudinal bores and -are not in connection with the
inner chambers of the rotors The transmission of heat is effected
through the metal connection between shafts and rotors.
As in Fig 1, pipes 13, 14 extend into the borings of the rotor shafts
The fall in pressure necessary for the fluid flowing through the
shafts is obtained by the diaphragms 23 and 24 (originally designated
15 and 16 in Fig 2) This operation requires that the cross-section of
the shaft borings be greater than the annular cross-section formed
from diaphragm 23 and pipe 13 or diaphragm 24 and pipe 14 The cooling
means only flows through the shafts in which the circumiference is
similar to Fig 1 The cooling oil is injected through the shafts, the
oil, as described in connection with the first embodi 60 ment,
entering the rotor shafts through bores on the left side of the Figure
but leaving the rotor shafts on the right side With sufficiently high
centrifugal force the pressure for the passage through the rotor
shafts is pro 65 vided by the diaphragms 23 and 24, otherwise the

diaphragms have to be replaced by lip packings Apart from this, the
recirculation of the cooling agent is similar to that in the
embodiment of Fig 1 70
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* GB785861 (A)
Description: GB785861 (A) ? 1957-11-06
Louvre
785,861 o, Date of Application and filing Complete Specification Jan
19, 1956.
No 1842 /56.
Application made in South Africa on Jan 19,1955.
Index at Acceptance:-Class 137, A 2 C 1.
International Classification:-F 24 f.
COMPLETE SPECIFICATION " Louvre " We, Ai R Li TE Louv R Es, SOUTH
AFRICA, LIMITED, of 49, Coventry Street, Ophirton, Johannesburg, Union
of South Africa, a company registered in the Union of South Africa, do
hereby declare the invention, for which we pray that a patent may be
granted to us, and the method by which it is to be performed, to be
particularly described in and by the following statement:-
This invention relates to louvres comprising several louvre boards
each edge-mounted in a pair of slotted holders which are carried on
side frames The louvre boards are usually glass blades and adjustable
by pivotal movement of the holders about the pivot pins.
In current practice penetration of the blades into their slots is

limited by stop surfaces with which they make contact, and when thus
located they are commonly constrained against removal by closing the
open end of the slots, for instance by bending over one of the walls
defining the slot This procedure presupposes a bendable material and
virtually excludes cast or extruded metals.
In any case nefarious prising open of the bent-over zones of the
holders is not unduly difficult, and once this has been achieved the
blades may be removed to allow ingress to the room.
The object of the present invention is to provide a simple locking
device for the blades which adds little if anything to the cost of the
louvre.
According to the invention the louvre includes, in at least one holder
of each pair and preferably both, an insert which is located between
the board and the slot, is shaped to prevent withdrawal of the board
from the slot, and is itself constrained against withdrawal from the
slot.
Stated more specifically, each insert comprises a first formation that
engages the holder and constrains the insert against withdrawal, and a
second formation that engages the board to prevent it from being drawn
out of the slot The first formation may be a tongue that engages a
recess in the holder, while the second formation may be an end flange
that overlies the edge of the board.
The invention is illustrated in the accom 50 panying drawings in which
Fig 1 is a face view of the louvre, Fig 2 is an "exploded" view of one
holder, a board and an insert; Fig 3 is a section on the line 3-3 of
Fig 55 1 drawn to a larger scale and Fig 4 is a section on the line
4-4 of Fig 3.
In the drawings the frame in which the glass blades are mounted is
numbered 10 60 The blades, numbered 11 are each edgemounted in slots
12 provided in a pair of holders 13 The holders are pivotally mounted
about pivot pins 14 located about midway of each holder and journalled
in the 65 side members of the frame 10.
The holders are ganged together at one or both sides of the frame by a
bar 15 that is moved, to open and close the blades in concert, by
mechanism, which, not being pertin 70 ent to this invention, is not
illustrated The mechanism is actuated by a handle 16.
Examination of Fig 2 will show that each holder 13 has a shoulder 17
near to its outer end, that is to say the end that is at the out 75
side of the frame 10 The shoulder extends across the slot 12 to limit
the penetration of the blade into the slot Towards its inner end one
wall 12 a of the slot has a shallow rebate 18 with a sloping floor 19
that results 80 in a definite step 20 in the wall 12 a.
The wall 12 a in the zone 30 between the step 20 and the outer
extremity of the holder is set back somewhat so that the width of the

slot 12 is slightly greater in that zone than it 85 is in the zone 30
a beyond the step 20.
The slot is dimensioned in the zone 30 a to receive the blade 11
snugly and with no significant play When the blade has been inserted
into its pair of holders, a sheet metal 90 insert 21, preferably of
spring steel, occupies the space in the zone 30 between the blade and
the wall 12 a.
The insert is shaped to provide a flat body 22, a side flange 23 and
an end flange 24.
The two flanges are connected at their meeting edges the insert being
drawn rather than bent, so that the body and the flanges form a single
rigid entity.
When the insert is in its place in the assembly the side flange 23 is
sandwiched between the blade edge 1 a and the floor 12 b of the slot,
so that it is constrained against movement in the plane of the blade,
while the end flange 24 overlies the edge lib of the blade Thus, if
the insert is itself constrained against withdrawal from the slot 12,
the blade 11 will be likewise constrained.
To achieve constraint of the insert against withdrawal it and the
holder are formed with interengaging formations that are designed to
allow free entry of the insert into the assembly before
interengagement occurs A convenient device for this purpose is a
tongue 25 that is pressed out of the body 22 and deformed to be
oblique to its plane, the free end 25 a of the tongue being directed
towards the flanged end 24 of the insert When the insert is propelled
into the slot 12 between the blade 11 and the wall 12 a, the natural
resiliency of the metal of the insert allows the tongue to bend into
the plane of the body 22, until the free end 25 a of the tongue passes
the step 20, which occurs as the end flange 24 encounters the edge 1
lb of the blade The tongue then springs back for its free end 25 a to
interengage with the step 20 and effectively constrain the insert
against withdrawal.
The inserts may be located either after insertion of the blade into
its holders, or simultaneously with such insertion.
When assembly has been completed the blade is securely held in the
holders, being constrained against movement in two dimensions by the
holders and in the third by the inserts The inserts are themselves
constrained against movement, in two dimensions by the blade and
holder and in the third by the steps 20.
While the tongues 25 have been shown 50 pressed out of the bodies 22
of the inserts, they could equally well occur in the side flanges 23,
in which case the steps 20 would be cut within the floors 12 b of the
slots 12.

* Sitemap
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* Legal notice
* Terms of use
* 5.8.23.4; 93p
* GB785862 (A)
Description: GB785862 (A) ? 1957-11-06
Improvements in and relating to heat exchange systems
A high quality text as facsimile in your desired language may be available
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The EPO does not accept any responsibility for the accuracy of data
and information originating from other authorities than the EPO; in
particular, the EPO does not guarantee that they are complete,
up-to-date or fit for specific purposes.
COMPLETE SPECIFICATION.
Improvements in and relating to Heat Exchange Systems.
We, FOSTER WHEELER LIMITED, a British
Company, of Foster Wheeler House, 3
Ixworth Place, London, S.W.3, do hereby declare this invention, for
which we pray that a patent may be granted to us, and the method by
which it is to be performed, to be particularly described in and by
the following statement:
This invention relates to heat exchangers of the type in which heat is

exchanged between a liquid such as molten sodium or radio-active water
and a second fluid such as steam or non-active water where it is
extremely important that the two fluids should not come into contact.
In a "shell and tube" heat exchanger, in which the tubes are fed with
one fluid inlet and outlet headers separated from the shell space
through which the other fluid is circulated, by plates in which the
tubes are mounted, the most likely point for leaks to occur is at the
joints between the tubes and the tube plates. It is therefore
desirable to use double tube plates so that, in the event of a leakage
of either fluid at a tube joint the fluid will only penetrate in to
the space between the tube plates and the two fluids will not come
into contact.
It is an object of this invention to improve the security of such a
heat exchanger. In accordance with the invention a gas or vapour inert
to either of the fluids, is supplied to this space between the tube
plates under a pressure substantially equal to that of the liquid or
one of the liquids.
The liquid or one ob the liquids in such systems is usually maintained
under pressure by an inert gas such as nitrogen supplied to an
expansion tank and the gas is conveniently supplied to the space
between the tube plates from the same source at its point of
application to the liquid system either directly or by means of a
diaphragm transmitter.
This arrangement relieves the liquid tube joint of any substantial
pressure difference in operation and thus minimises the risk of liquid
leakage. This may make permissible the use of an otherwise unsuitable
nonwelded or non-brazed joint.
Preferably the expansion tank in such a system is arranged in
accordance with our
Application No. 37800/54 (Serial No.
772,765) and the gas supply for the tube plate space drawn from the
gas space of the tank.
The space between the tube plates may conveniently communicate with
units for detecting the leakage of either fluid.
A typical heat exchanger in accordance with the invention is shown in
the accompanying drawing by way of example.
The drawing shows a shell and tube heat exchanger having double tube
plates 10 12 and 101, 121 so as to minimise the risk of the gaseous
fluid such as steam on the tube side coming into contact with a liquid
such as molten sodium on the shell side in the event of a leak
developing at any of the joints between the tubes 14 and the plates 10
and 101. The tube joints may be made by expanding welding or brazing
or any combination of those methods.
The spaces 16 and 16l between the double tube plates are each provided

with two pipe connections 18, 20 and 181 and 201. The connections 18,
181 are provided for the supply of a gas under a pressure
substantially equal to that of the liquid and inert to either of the
heat exchanging fluids.
In the type of system referred to above in which steam is superheated
by heat exchange with molten sodium maintained under pressure by
nitrogen gas supplied to a header tank, the connections 18, 181 would
be connected to the gas space of the tank.
The connection 20 and 201 communicate with units for detecting the
leakage of either fluid.
What we claim is : -
1. A "shell and tube" heat exchanger for exchanging heat between a
liquid and a second fluid having double tube plates in which a gas or
vapour inert to either of the heat exchanging fluids is supplied to
the space between the tube plates under a pressure substantially equal
to that of the liquid or one of the liauids.
2. A heat exchanger according to Claim 1 in which the space between
the tube plates is provided with a connection to a unit for detecting
leakage of either fluid.
3. A shell and tube heat exchanger substantially as described with
reference to the accompanying drawing.
4. A heat exchange system including a heat exchanger according to any
preceding claim in which a liquid such as molten sodium is maintained
under pressure by an inert gas such as nitrogen supplied to an
expansion tank and in which the gas is supplied to the space between
the tube plates of the heat exchanger from the expansion tank.
PROVISIONAL SPECIFICATION.
Improvements in and relating to Heat Exchange Systems.
We, FOSTER WHEELER LIMITED, a British
Company, of Foster Wheeler House, 3
Ixworth Place, London, S.W.3, do hereby
declare this invention to be described in the following statement:
This invention relates to heat exchangers
of the type in which heat is exchanged between a gaseous fluid such as
steam and a liquid such as molten sodium where it is extremely
important that the two fluids should not come into contact.
In a "shell and tube" heat exchanger, in
which the tubes are fed with one fluid from inlet and outlet headers
separated from the
shell space through which the other fluid is circulated by plates in
which the tubes are
mounted, the most likely point for leaks to
occur is at the joints between the tubes and the tube plates. It is
therefore desirable to use double tube plates so that, in the event of

a leakage of either fluid at a tube joint the fluid will only
penetrate in to the space between the tube plates and the two
fluids will not come into contact.
It is an object of this invention to improve the security of such a
heat exchanger. In accordance with the invention a gas inert
to either of the fluids, is supplied to the space between the tube
plates under a
pressure sulbstantially equal to that of the liquid.
The liquid in such systems is usually maintained under pressure by an
inert gas such as nitrogen supplied to a header tanK and the gas is
conveniently supplied to the space between the tube plates from the
same source at its point of application to the liquid system.
This arrangement relieves the liquid tube joint of any substantial
pressure difference in operation and thus minimises the risk of liquid
leakage.
Preferably the header tank in such a system is arranged in accordance
with our
Application No. 37800/54 (Serial No.
772,765) and the gas supply for the tube plate space drawn from the
gas of the tank.
The space between the tube plates may conveniently communicate with
units for detecting the leakage of either fluid.
The tube joints may be made by expanding, welding or brazing or any
combination of these methods.
* GB785863 (A)
Description: GB785863 (A) ? 1957-11-06
Improvements in or relating to carbonization of carbonaceous materials
Date of Application and filing Complete Specification: Feb 7, 1956.
I S i l D No 3780/56.
Application made in United States of America on Feb 14, 1955.
Application made in United States of America on June 23, 1955.

Complete Specification Published: Nov6, 1957.
Index at acceptance:-Class 55 ( 1), AK( 1: 4: 5 B: 6 A).
International Classification:-Cl Ob.
COMPLETE SPECIFICATION
Improvements; in or relating to Carbonization of Carbonaceous
Materials We, THE M W KELLOGG COMPANY, a corporation organised under
the laws of the State of Delaware, United States of America, of Foot
of Danforth Avenue, Jersey City 3, State of New Jersey, United States
of America, do hereby declare the invention, for which we pray that a
patent may be granted to us, and the method by which it is to be
performed, to be particularly described in and by the following
statement:-
This invention relates to method and means for treating solid
materials and more particularly to method and apparatus for the
fluidized treatment of carbonaceous materials such as coal, shale,
lignite, oil sands, etc, at low temperatures Still more particularly,
it relates to unitary method and means for drying, preheating,
pretreating and carbonizing fluidized carbonaceous materials at low
temperatures.
The treatment of carbonaceous solids to form valuable liquid, gaseous
and solid products is well known in the art An example of one process
frequently employed entails the treatment of solids, such as coal at
elevated temperatures whereby volatile materials are released from the
solids and a valuable solid residue is formed It has been the practice
in the past to carry out carbonization in both non-fluid and fluid
systems; however, the present invention is concerned with a
carbonization process of the fluid type wherein the various steps are
performed with a finely divided feed material which is maintained in a
highly turbulent state of agitation by the passage therethrough of a
fluidizing medium.
In carrying out fluidized carbonization of carbonaceous materials, it
has been found that several process steps are necessary in order to
provide a workable operation and assure a maximum yield of desirable
vapor, liquid and solid products More usually, the first step in the
carbonization process concerns the proper preparation of the raw feed
material This involves not only proper selection and sizing of the
carbonaceous solids to provide a readily fluidizible feed, but also
includes drying the k Price 3 solids to a minimum moisture content
prior to further processing It has been found that certain finely
divided carbonaceous materials, though easily fluidized at low
temperatures, when subjected to more elevated temperatures suffer a
change in physical characteristics and become soft and gummy and the
particles tend to agglomerate For example, many coals pass through a
so-called " plastic " state, usually at a temperature between about

7000 F and about 8000 F wherein the coal particles tend to stick
together and form large particles which resist fluidization Several
methods of combating this agglomerating tendency of coals and other
carbonaceous materials have been suggested, one of the more successful
of which comprises subjecting the finely divided solid particles to a
mild oxidation treatment prior to further high temperature processing
It has been found that this method of treatment alters the physical
characteristics of the carbonaceous material so as to minimize
agglomeration of the solid particles The changes which take place in
the solids in a treatment of this type are not clearly understood;
however, according to one theory the mild oxidation " case hardens "
the particles thereby substantially nullifying their sticking
tendencies when they pass through the plastic state.
When processing carbonaceous materials, therefore, the step after the
drying operation preferably involves pretreating the dry solid
particles at an elevated temperature in the presence of a limited
amount of oxygen During this process a portion of the vaporizable
compounds present in the carbonaceous solids are released The third
and last step in the conventional solids carbonization process
concerns the treatment of carbonaceous material at a still higher
temperature whereby the remaining vaporizable compounds are released
therefrom and a carbonaceous product residue is produced The
vaporizable portion of the coal which is commonly known as " tar "
comprises numerous organic compounds having a wide range of boiling
points As used herein, the term " tar " includes any volatile organic
785863 compounds released from the coal, either liquid or vapor and
either cracked or uncracked The composition of the carbonaceous
residue remaining after vaporization of the tar depends on the type of
carbonaceous feed material used For example, when carbonizing coal the
residue material is commonly called "char " Although the description
and discussion of the invention will be directed primarily to coal
carbonization, the term " char " will be used hereinafter in a broader
sense to designate any residue solids remaining after carbonization.
In addition to the three processing steps just described, a fourth
operation is usually necessary In carrying out the drying step it is
usually preferred to heat the carbonaceous feed only to the minimum
temperature necessary to remove the surface water, which is, of
course, the boiling point of water at the pressure conditions
maintained during this operation The pretreating operation, however,
is carried out at an elevated temperature, substantially above the
temperature at which the solids leave the drying zone Only a portion
of the heat required in this operation is supplied by the oxygen
consumed therein The remaining heat required is furnished by what may
be called a preheating step It is possible to provide the required

preheat in conjunction with the drying operation or the pretreating
operation, or it may be made an entirely separate and independent part
of the carbonization process.
Each of the aforementioned processing steps, i.e, drying, preheating,
pretreating and carbonization is customarily carried out in a separate
vessel, which necessitates the use of numerous transfer lines and
standpipes, and extensive supporting steel work Such installations
besides being mechanically complex have poor thermal efficiency and
result in a process with high utility costs.
It is an object of this invention to provide an improved method and
means for carrying out a solids carbonization process.
Another object of this invention is to provide unitary method and
apparatus for carrying out the successive steps of drying, preheating,
pretreating and carbonizing of carbonaceous materials.
It is still another object of this invention to provide improved
method and means for increasing product yield in the carbonization of
carbonaceous materials.
These and other objects of the invention will become more apparent
from the following detailed description and discussion.
In the method of this invention, the aforementioned objects are
achieved by providing a unitary carbonization system comprising drying
and preheating zones superimposed upon a carbonizing zone and a
pretreating zone disposed within the carbonizing zone, said
pretreating zone being in open communication with the carbonizing zone
and below the level of the solids present therein.
In carrying out the process of this invention, a finely subdivided
solid carbonaceous feed is introduced into a drying zone where 70 the
solids are elevated in temperature and retained in a fluidized state
for a period of time sufficient for the removal of surface water.
The solids are thereafter passed downwardly as a confined stream into
a fluidized solids bed 75 in a pretreating zone of higher temperature
wherein they are subjected to a mild oxidation and then passed
upwardly and directly into an adjacent and superposed fluidized solids
bed in a carbonizing zone of still higher term 80 perature where
volatile constituents of the carbonaceous solids are removed, without
the use of external transfer lines or standpipes.
It is within the scope of this invention to treat various carbonaceous
materials in the 85 manner described, including coals, shales,
lignites, asphalts, oil sands, etc The invention is particularly
exemplified, however, by its application to the treatment of coal, and
further discussion of the invention is directed to 90 the use of this
material It is not intended, however, that this particular application
should limit the scope of the invention in any way.
The first step to be considered in a process 95 for the carbonization

of coal as previously mentioned is concerned with surface water
present in the coal feed which may, unless removed, prevent
fluidization of the coal One of the problems encountered when handling
100 carbonaceous materials such as coal in a fluidized system results
from the tendency of the finely divided solids to agglomerate because
of water condensed thereon Most coals coming from a treating plant,
for example, have a 105 relatively high surface or "free" water
content, usually between about 2 and about 15 per cent by weight, or
higher Unless removed, this moisture causes the finely divided coal
particles to stick together and resist 110 fluidization Even after
fluidization is achieved, moisture may cause packing or bridging in
process equipment of restricted cross section, such as, for example in
feed hoppers, standpipes, etc It is not always economically fea 115
sible to remove all the moisture from the coal; however, it has been
found that agglomeration and packing of coal particles due to the
presence of water is minimized if between about per cent and about 90
per cent of the 120 water initially present is removed.
It has been suggested in the past to dry carbonaceous solids with air
and other gases at high temperatures This method, although workable,
suffers from several deficiencies Be 125 cause of the low heat
capacity of most gases, sufficient heat for drying is not provided by
this method unless the drying gas is present in large quantities and
at elevated temperature The use of a large amount of gas is 130
785,863 of coal from the low temperature zone through the heater to
the high temperature zone and back to the low temperature zone to
provide both the sensible heat acquired by the dry solids and the heat
of vaporization of the 70 water released therefrom When operating in
accordance with the zonal temperature ranges given, the amount of coal
circulated relative to the raw coal feed rate is between about 2 and
about 5 pounds per pound 75 The heat transfer surface required for
drying and preheating the coal is preferably provided by a
conventional shell and tube heat exchanger with the solids being
passed through the tubes in indirect heat exchange 80 with a hot fluid
passed through the exchanger shell The heat required to dry the coal
is provided by a fluid heating medium which may be a petroleum oil or
vapor, or mixtures thereof, or other liquid or vapor material 85 which
is easily transported and can withstand relatively high temperatures
In general, liquid heating fluids are more satisfactory than gases
because of their high specific heats and low volume relative to gases
90 Examples of suitable heating fluids are residual petroleum oils,
synthetic heat transfer liquids, inorganic salt mixtures, lead,
mercury, etc The temperature at which the heating medium is employed
varies with the tem 95 perature maintained in the drying zone and with
the heat transfer characteristics of the heating medium Usually, it is

preferred to introduce the heating medium at a temperature between
about 3500 F and about 10000 100 F Temperatures greater than this are
not desirable because of the danger of over heating coal particles in
contact with the heat transfer surface.
The amount of heat exchange surface re 105 quired to carry out the
drying and preheating operations varies depending on several factors
including the quantity of coal to be heated, the amount of moisture in
the coal, heat transfer coefficients, etc More usually a surface 110
area between about 0 02 and about 0 30 square feet per pound of fresh
coal feed per hour is sufficient to provide the desired drying and
preheat.
Operation of the drying portion of the car 115 bonization process in
the manner previously described provides a dry, easily fluidizable
solid material which may be subjected to further processing without
danger of agglomeration or equipment plugging due to water This 120
method of operation is carried out without the disadvantages of
previous drying methods and results in only slightly more than the
minimum dust recovery problem Operation in the manner described also
has positive advantages 125 in that the drying step is carried out
with a high degree of thermal efficiency and a minimum amount of heat
exchange equipment It has been found in the operation of conventional
indirect heat exchangers wherein heat 130 expensive because of
compression requirements, and it complicates the recovery of solids
from the drying medium The use of elevated temperatures is also
undesirable since high temperature may cause a substantial part of the
volatile material in the coal to vaporize and mix with the drying
medium and thus further complicate the recovery problem Furthermore,
high gas temperatures may elevate the temperature of the coal to the
plastic state and cause agglomeration of the coal particles thereby
resulting in an inoperable condition.
Other methods of drying coal have also been suggested; however, all of
the processes presently in use suffer from serious deficiencies of one
type or another In the drying process disclosed herein, drying
problems are reduced to a minimum by using a two zone drying and
preheating system and supplying the heat required for this operation
through indirect heat exchange In carrying out the drying operation,
raw coal suitably subdivided for fluidization, that is, of a size
between about and about 400 mesh is introduced into a first zone
wherein it is commingled with dry heated coal in sufficient quantity
to elevate the entire mass of coal to a temperature suitable to effect
the removal of water The dry coal is then passed through a heater
where it is further elevated in temperature by indirect heat exchange
with a hot fluid and then into a second zone The higher temperature
coal in the second zone serves as the source of the coal commingled

with the wet coal feed, and in addition, provides preheated coal for
the next phase of the carbonization process The entire drying and
preheating step is conveniently conducted in a fluid system with both
the low and high temperature zones containing a dense phase bed of
fluidized coal Adequate turbulence to maintain each dense phase bed is
provided by maintaining a linear gas velocity therein between about 0
5 and about 5 feet per second, or more usually between about 0 75 and
about 3 _ feet per second Under normal operating conditions the
density of the beds thus provided varies between about 10 and about 40
pounds per cubic foot The temperatures in the two zones may vary,
depending on the residence time of the coal in each zone and the
moisture content of the raw coal feed However, usually the first zone
is operated at a temperature between about 2200 F and about 3250 F,
and the second zone is preferably maintained at a temperature of
between about 3500 F and about 6000 F.
Fluidization of the solids in the low temperature zone is partially
provided by moisture released from the coal and may be augmented by
the introduction into this zone of air or an inert gas such as, for
example flue gas, steam, etc The coal in the high temperature or
preheating zone is maintained in a fluid state by the introduction of
a similar gasifying medium.
It is necessary to circulate a sufficient amount 785,863 is
transferred to a mixture of entrained solids and gases that the rate
of heat transfer is sensitive to the concentration of solids in the
fluid stream, with streams of high solids concentrations giving
substantially higher heat transfer coefficients than gaseous mixtures
containing only a few solids It is important, therefore, when
transferring heat in this manner to prevent dilution of the gas solids
stream with additional gases, for example water vapor By operating the
drying step in the aforedescribed manner, substantially all of the
moisture removed from the coal is separated therefrom in the first low
temperature zone This assures a minimum amount of vaporization of
water from the coal in its passage through the exchanger and therefore
a minimum dilution of this stream The net result is a process having a
constant high heat transfer rate.
Another reason and advantage in carrying out the drying process as
described relates to the velocity of the solid-gas stream flowing
through the heat exchanger When using a tubular solids heater it is
necessary to pass the fluidized solids therethrough at a rather high
velocity, usually between about 10 and about feet per second in order
to overcome the pressure drop in the exchanger tubes and maintain the
solids in a fluidized state This i particularly true in an up-flow
type of heater wherein the solids tend to settle in a direction
opposite to the flow of the fluidizing medium If solids containing

water are passed through the exchanger, being heated in the course
thereof, the water is converted to steam which increases the velocity
of the gassolids stream and may create a serious erosion problem.
The proposed method of operation provides still a further advantage by
virtue of the removal of water from the coal prior to the heating step
Passage of coal through the heater requires the use of standpipes and
transfer lines which of necessity employ sharp bends and turns In
addition, conventional exchangers, more usually of the tube and shell
type, also present flow paths of restricted cross section An attempt
to pass a wet coal through such a system might very well lead to
agglomeration of the coal particles and plugging, the very results
which are sought to be prevented by the drying step This operating
hazard, as well as those previously mentioned, of course, is avoided
by the drying method described herein.
After leaving the drying zone, the coal passes downwardly as a
confined stream through a carbonization zone and into a pretreating
zone enclosed within the carbonization zone In the pretreating zone
the coal is contacted with air or other oxygen containing gas and
partially burned to provide the pretreating and case hardening effect
previously discussed The temperature at which this important process
step is carried out may vary over a range between about 600 ' F and
about 8250 F; however, more usually it is preferred to pretreat the
coal in a more narrow range of temperature, that is between about 70
6500 F and about 800 F As in the previous operations, the coal
pretreatment is carried out in a conventional dense phase fluidized
bed, wherein the coal is maintained in a turbulent fluid state
by-passage therethrough of a gasi 75 form medium Adequate turbulence
to maintain the dense phase bed is provided by maintaining a linear
gas velocity therein between about O 5 and about 5 feet per second
Under normal operating conditions, the density of the 80 dense phase
bed thus provided varies between about 10 and about 40 pounds per
cubic foot.
Generally, a portion or all of the fluidizing medium is supplied in
conjunction with the oxygen required for pretreating This may be 85
accomplished by diluting the oxygen with air, by using air alone or by
diluting air or oxygen with steam or other inert gas Thus, it is
within the scope of the invention to supply the pretreatment oxygen to
the pretreating 90 zone in a gaseous stream of varying oxygen content
The amount of oxygen required for pretreating is usually between about
0 02 and about 0 08 pounds per pound of dry coal feed.
To provide sufficient time for the pretreating 95 combustion reactions
to take place, the rate of introduction of coal to the pretreating
zone is adjusted to allow an average particle residence time therein
of between about 10 and about minutes Upon entering the pretreating

100 zone, dry preheated coal at a relatively low temperature becomes
intimately mixed with higher temperature pretreated coal and is
swiftly elevated to the temperature level prevailing in this zone As
the temperature of the 105 dry coal is increased, a portion of the
lower boiling tar components present in the coal are vaporized and
passed into the fluidization and combustion gases Since oxygen is
relatively non-selective in its action, this phase of the 110
carbonization process may involve the consumption of a portion of the
tar For this reason, it is desirable to limit the introduction of
oxygen to the pretreating zone to the minimum amount necessary to
prevent agglomera 115 tion of the solids and maintain an operable
system Equally important to the operability of the pretreating system
is the temperature of the solids bed maintained therein Consideration
of this important point is taken up 120 in detail at a later point in
the discussion.
As previously mentioned, the pretreating zone is disposed within the
carbonizing zone.
For reasons to be more fully considered later, the coal pretreatment
step is carried out in a 125 dense phase fluidized bed of solids
adjacent to and in upwardly open communication with a second dense
solids bed which is contained within the carbonization zone The
preheated solids introduced into the pretreating zone 130 785,863 the
other hand, the grid need not be limited to this location and other
physical arrangements may be used when desired.
In addition to the desirable process features which result therefrom,
the pretreating and 70 carbonization vessel arrangement presents a
number of advantages of a mechanical nature.
For example, the arrangement of the two zones in effect eliminates one
vessel, simplifies the transfer of solids from the preheater 75 to the
pretreater and from there to the carbonizer, decreases solids recovery
costs by eliminating one set of cyclones, eliminates the transfer line
which would be required if the pretreating and carbonization steps
were car 80 ried out in separate vessels, etc, thereby providing a
highly efficient process both thermally and mechanically.
Pretreated coal, fluidizing and combustion gases, and volatile tar
compounds released 85 from the coal in the pretreating zone pass into
the carbonization zone wherein the major portion of the volatile
components in the coal are removed and a valuable residue char is
formed.
This, the major step of the process, as far as 90 product formation is
concerned, is also conveniently carried out in a dense phase fluidized
bed similar to the drying, preheating and pretreating beds previously
described In order to effect removal of the volatile coal components,
95 a large amount of heat must be introduced to the combustion zone

Conventionally, this heat may be supplied from one or more of several
sources, for example it may be provided in an inert gas such as a fuel
gas heated to a high 100 temperature, or it may be supplied from a
combustible gas such as fuel gas mixed with oxygen or it may be
furnished from the combustion of oxygen or an oxygen containing gas
with a portion of the carbonaceous feed This 105 invention is
concerned primarily with the method of supplying heat wherein a
portion of the carbonaceous feed, viz pretreated coal, is burned with
oxygen or an oxygen containing gas However, it is within the scope of
the 110 invention to supply a portion of the heat by either of the
other two methods mentioned.
When using the aforementioned method of providing heat, the gasiform
fluidizing medium required to maintain the dense phase in the 115
carbonization zone is generally furnished by the combustion gases If
necessary, however, deficiencies in the quantity of fluidizing medium
may be made up by the introduction into the carbonization zone of a
flue gas, steam 120 or other extraneous inert gas.
The carbonization of coal to remove distillable tars therefrom and
produce a char residue product is conducted over a wide range of
temperatures usually between about 7000 125 F and about 24000 F The
preferred thermal range of operation is determined to a great extent
by the type of liquid product desired; for example, when it is
preferred to distill the coal tars with a minimum of cracking of vola
130 completely fill this zone and pass upwardly therefrom into the
carbonization solids bed.
The carbonized solids or char on the other hand occupy only a portion
of the carbonization zone, the remainder comprising a conventional
dilute phase of relatively very low solids concentration superposed
above the dense phase char bed By this arrangement of one zone within
another, a common vapor space is provided which serves to accommodate
the fluidizing and combustion gases from both zones.
It is necessary to the efficient operation of the carbonization
process that the pretreating and carbonization steps be kept separate
and carried out at substantially different temperatures Thus, it is
essential that solids from the higher temperature char bed be
prevented from passing into the pretreating zone In the method of this
invention, pretreating and carbonization are maintained as separate
operations by placing a grid or perforated plate between the two zones
The number and size of the openings in the grid or plate are fixed to
provide sufficient pressure drop to prevent back mixing, that is
passage of solids from the carbonization zone to the pretreating Zone,
but insufficient to prevent the flow of solids from the pretreating
zone The grid preferably encloses the entire top of the pretreating
zone in order that the solids entering the carbonization zone may be

uniformly distributed over a maximum area Under normal operating
conditions the cross-sectional area of flow through the grid is
between about 1 per cent and about 10 per cent of the cross-sectional
area of the pretreating zones The openings of the grid are usually
circular in nature and are of a sufficient size to allow passage of
the largest coal particles More usually holes between about -4 and
about 1 inch in diameter are adequate The major factor in preventing
back mixing through the grid is the high velocity of vapors and solids
therethrough It is contemplated sizing the area of flow through the
grid to provide a pressure drop between about -t and about 3 psi With
this drop in pressure, velocities through the grid are in the order of
between about 50 and about 200 feet per second By the aforedescribed
means of dividing the two zones, it is possible to maintain them in
open communication, yet at substantially different temperatures, and
at the same time introduce pretreated solids and vapors into the
carbonization zone in an evenly distributed manner.
As will become apparent from the subsequent discussion, the physical
location of the separating grid is important in determining
carbonization product yields More usually the pretreating zone openly
communicates with the dense char bed in an upward direction.
This is necessary if the gases and pretreated solids are to be
introduced into the carbonization zone in an evenly distributed manner
On 785,863 tile constituents, namely low temperature carbonization,
the temperature is held to a minimum of about 7000 F and not more than
about 10000 F The type of coal is also of importance in establishing
the operating temperature since some coals are more difficult to
distill than others Contra to the pretreatment step, which is carried
out entirely in the dense phase, the carbonization zone contains a
dense phase bed superposed by a disperse or dilute phase which may
have a solids concentration as low as 0 001 pounds per cubic foot
Gases from both zones pass into this phase which provides a
preliminary rough separation of vapors and solids Further solids
separation is provided by conventional means, such as, for example
cyclones, filters, etc.
Substantially all of the desirable constituents of coal are removed at
the aforementioned carbonization temperatures within avery short
period of time, that is between about 0 25 and about 10 minutes As a
further precaution to prevent agglomeration of the coal particles in
the carbonizing zone, it is preferred to maintain a substantial ratio
of char to fresh feed therein This serves to dilute the fresh
pretreated coal, which provides the desired beneficial effect;
however, it also makes it necessary to substantially increase the coal
residence time At the usual char to fresh feed ratios maintained in
the carbonization zone, that is between about 5 pounds per pound and

about 50 pounds per pound, the particle residence time therein is
between about 2 minutes and about 200 minutes, more usually between
about 20 minutes and about minutes.
Carbonization may be carried out over a wide range of pressures;
however, the pressure is usually maintained between atmospheric and
500 psig, preferably between about atmospheric and about 100 psig
Since a driving force is necessary for the passage of coal from the
pretreating zone into the carbonization zone the pretreating zone must
operate at a pressure above the pressure in the carbonization zone;
more usually the differential pressure between the two zones is
between about and about 2 psi By virtue of its physical location above
the pretreating zone, the drying zone may operate at a pressure either
higher or lower than the pressure in the former zone More usually, it
is convenient to maintain the pressure in the drying zone lower than
the pressure in the pretreating zone and as a result the drying zone
is ordinarily operated at zetween about 1 and about 20 psi less than
the pretreating zone.
As previously mentioned, this invention is not limited in its scope to
the treatment of coal, but encompasses the use of other carbonaceous
feed materials, for example shales, asphalt, oil sands, etc Similar
processing considerations are important and similar operations are
required when carbonizing these feed materials other than coal The
conditions appropriate for each specific feed material are well known
to those skilled in the art and for this reason do not need repeating
here.
The use of a unitary system for carrying 70 out the carbonization of
coal provides unexpected advantages and allows the use of several
novel processing schemes For example, in the conventional coal
carbonization unit wherein the coal pretreating step is car 75 ried
out in a separate vessel it is necessary to withdraw pretreated coal
from this vessel and pass it through a transfer line to a
carbonization zone Since oxygen is used in the carbonization zone as
well as in the pretreating 80 zone, it has also been the practice to
introduce pretreated solids and oxygen together into the carbonization
zone More usually the oxygen in the form of air has been used for
fluidizing and transporting the 85 pretreated solids between the two
zones.
This method of moving the pretreated solids is effective; however, it
has been found that it results in an excessive consumption of tar
compounds by burning, thereby reducing 90 the amount of tar produced
in the process.
The reason or reasons for this are not clearly understood but are
believed to be related to the time during which tar vapors and oxygen
are in contact In order to obtain an effective 95 coal pretreatment,

it is necessary to provide an average coal particle residence time in
the pretreating zone of several minutes Since oxygen is introduced
into the pretreating zone continuously, the solids in this zone, are,
of neces 100 sity, in contact with oxygen for substantially this
period of time On the other hand, gases entering and released in the
pretreating zone reside therein for only a few seconds, more usually
between about 5 and about 20 seconds 105 and subsequently pass from
this zone Thus, tar vapors released from the coal in the pretreating
zone are in contact with oxygen for a very short period of time
compared to the time of oxygen-solids contact When the pre 110 treated
coal and effluent gases from the pretreating zone, containing oxygen
are passed to a carbonization zone through a transfer line, the total
time of contact between the tar vapors and oxygen is substantially
increased, 115 by as much as 100 per cent or more depending on the
length of the transfer line and the velocity of the gases therein The
additional few seconds of contact time between the coal particles and
oxygen provided by use of the 120 transfer line is, however,
insignificant If it is assumed that oxygen shows equal preference for
tar and coal it is obvious that the combustion of tar is increased by
use of a processing method which includes the use of a 125 transfer
line with oxygen in the transferring medium.
When utilizing the conventional method of transferring solids from a
pretreating vessel to a separate carbonization vessel, it has fur 130
785,863 In the method of this invention, this is accomplished by
introducing combustion oxygen into a dense phase bed of char in the
carbonization zone in the lower portion thereof whereby the oxygen is
substantially con 70 sumed before the fluidizing and combustion gases
pass into the upper portion of the bed.
The pretreated coal is introduced into the top portion of the same
dense phase bed below the surface thereof and is heated by contact
with 75 the hot char in a relatively oxygen-free atmosphere Both
during and after the solids heating process, the char is in contact
with ascending fluidization and combustion gases These vapors exert a
stripping effect on the char and 80 assist in the removal of volatile
tar components Thus the favorable results of this operation may be
attributed to a combination of heating and stripping although it is
probable that the primary separating effect is provided 85 by the heat
transferred to the pretreated coal.
The total gases from both zones after leaving the solids bed enter the
dilute phase thereabove and are passed from the system.
In addition to the advantages already men 90 tioned, the proposed
method of operation eliminates another defect of previous
carbonization processes Because of the relatively low temperatures
used in the pretreating operation, it is difficult to provide for com

95 plete consumption of the oxygen introduced into the pretreating
zone As a result, the effluent gases from this zone usually contain
some free oxygen In normal operations, for example the amount of
oxygen "break 100 through" may be as high as 10 to 15 per cent of the
total introduced When pretreating is carried out in a conventional
manner in a separate vessel in a conventional dense phase bed,
unconsumed oxygen passes into the dilute 105 phase of the pretreating
zone and reacts therein with tar vapors released from the coal In the
method of this invention, there is no dilute solids phase in the
pretreating zone and oxygen which is not consumed in this zone passes
110 into a dense phase bed of char in the carbonization zone along
with the combustion gases and pretreated coal Here the oxygen has at
least an equal change to react with solids rather than tar, thus
effectively increasing the 115 tar yield.
The depth of solids bed required in the carbonization zone to
successfully carry out the invention depends on several factors,
including the velocity of the lluidizing medium 120 therein, the
degree of turbulence in the fluidized bed, the temperature at which
carbonization is carried out and the diameter of the bed In general,
it has been found that a bed of depth normally maintained in
commercial 125 catalyst regeneration processes is adequate although
deeper beds may be used to assure the complete absence of tar-oxygen
contact The depth of coal maintained in the pretreating zone is less
critical; however, here too the de 130 ther been found that
substantial amounts of coke are deposited on the transfer line The
result is a restriction in the flow between the two vessels which may
eventually cause a shutdown This phenomenon also apparently is related
to the residence time of the tar vapors in the transfer line At the
temperatures maintained in the pretreating zone it is not difficult to
visualize some thermal cracking of the tar compounds Any appreciable
deposition of coke due to cracking would of course immediately become
apparent in such a zone of relatively small cross-section.
It is also possible that the coking is due either partially or
entirely to the combustion of tar in the transfer line rather than by
cracking.
Whichever the cause, however, the occurrence of coke as described
presents a problem which can seriously affect the operability of the
carbonization process.
In the method of this invention these problems are avoided by passing
pretreated solids directly from the pretreating zone into the
carbonizing zone without the use of a transfer line, thus minimizing
contact between the tar vapors and oxygen and reducing the time during
which these vapors are maintained at the pretreating temperature
Oxygen required in the carbonization zone is introduced into this zone

separately from the pretreated solids.
The direct passage of solids between the two zones is provided by
using contiguous openly communicating zones disposed within a single
vessel in the manner previously described.
Solid particles leaving the pretreating zone pass through the grid or
perforated plate into the carbonization zone where they are
immediately commingled with high temperature char solids The heat
transfer characteristics of the dense highly turbulent char bed are
such that the pretreated coal is rapidly heated to carbonization
temperature During this process, the remaining and major portion of
the volatile constituents of the coal are vaporized and pass upwardly
through the char bed.
Thus the solids region adjacent to the grid separating the two zones
is particularly rich in volatile materials The separate introduction
of pretreated coal and oxygen into the carbonization zone is effective
in reducing the consumption of tar already vaporized; however, unless
the pretreated coal is maintained free from contact with oxygen in
this zone for a period of time sufficient for the remaining tars to be
distilled, a substantial portion of these volatile components may also
be consumed Thus, in addition to passing the pretreated solids
directly from the pretreating zone to the carbonization zone, it is
further desirable to introduce these solids into a region of the
latter zone which is free or relatively free of oxygen, whereby
remaining tar materials are distilled therefrom and removed from the
carbonization zone before the pretreated coal enters the region of
combustion.
785,863 gree of oxygen consumption is an important factor in
determining bed depth Usually in either zone a bed of between about 10
feet and about 40 feet in depth is maintained, although, if desired,
more shallow beds and beds up to feet in depth may be used It is not
necessary that the beds be of equal depth and either may be greater or
lesser in depth than the other.
Both the pretreating and carbonization steps are carried out in
conventional fluid beds which are maintained by passing a fluidizing
medium through finely subdivided particles of solids The amount of
vapor and solids introduced into these beds per unit of time is
important in determining both the volume of the beds and the degree of
solids turbulence therein It is desirable in carrying out these
processing steps, to maintain solids beds of relatively constant size
having a sufficient flow of fluidizing medium therethrough to provide
adequate turbulence of the fluidized solids.
Therefore, control of vapor and solid flow rates to the fluid beds is
of utmost importance.
In carrying out the pretreating of finely subdivided coal particles,

it has been found that the rate of combination of oxygen with coal at
a given temperature is dependent on the size distribution of the coal
particles, that is on the amount of coal surface presented to the
oxygen If the coal particles increase in size the coal surface is
decreased and the amount of oxygen consumed in unit time is also
decreased On the other hand, when the coal particles decrease in size
the reverse occurs.
Conventionally, coal particle size distribution on a commercial scale
is provided by mechanical crushing and grinding Any variation in the
operation of the equipment employed for this purpose, which is not
uncommon, usually means a change in the size distribution of the coal
produced As previously mentioned, if the coal particle size suddenly
increases the amount of oxygen consumed in the pretreater decreases
and the temperature therein also dedecreases If this occurs, the
obvious solution which springs to mind is to introduce more oxygen
into the pretreating zone This has the effect of increasing the
concentration of oxygen in the pretreating zone whereby the combustion
reaction rate is accelerated and the temperature may be brought back
to its former level Unfortunately, however, introduction of more
oxygen into this zone requires decreasing the quantity of air
introduced into the carbonization zone unless the temperature in the
latter zone is also increased Obviously, an increase in carbonization
temperature is undesirable from the viewpoint of uniformity of
operation and product yields Furthermore, withdrawal of oxygen from
the carbonization zone decreases the vapor velocity in this zone and
affects the degree of turbulence and size of the dense phase bed
maintained therein, both of which are equally undesirable Still
another disadvantage of increasing the amount of oxygen entering the
pretreating zone lies in the fact that only a portion of the
additional oxygen is consumed in the pretreatment and the remainder
along with the unreacted por 70 tion of the original oxygen passes
from the pretreating zone into the carbonization zone.
Here it is consumed at least in part by reactions which involve tar
rather than the nonvolatile portion of the coal 75 In the method of
this invention it has been found that the problem of temperature
decrease due to changes in the size distribution of the fresh coal
feed is substantially eliminated and effective temperature control ob
80 tained in the pretreating zone by recycling a small, variable
quantity of hot char from the carbonization zone to the pretreating
zone.
Not only is this method of temperature control simple in operation,
but it is without the 85 defects attendant with attempts to control
the temperature by varying the oxygen to carbon ratio The amount of
char required for effective temperature control may vary at any

instant from as low as zero to about 5 pounds 90 per hour per pound of
coal present in the pretreating zone; however, more usually the
quantity of char required to compensate for temperature upsets is
relatively low, that is between 0 01 and about 2 pounds per hour 95
per pound of coal present in the pretreating zone The recycle char
flow rate may be controlled manually or more usually by the
installation of a temperature controller in the recycle line It is
contemplated that a small 100 amount of char will be recycled
continuously when using this method of temperature control in order to
prevent plugging of the recycle line The amount of heat introduced
into the pretreating zone in this continuous char 105 stream, however,
is very small compared to the total heat required in the pretreating
zone, usually not more than about 5 per cent thereof.
During normal operation a major portion, 110 more usually at least 90
per cent of the oxygen introduced into the pretreating zone is
consumed therein Because of this, the problem of increasing
pretreating temperature due to a decrease in the average particle size
of the 115 coal is not nearly as critical as temperature movement in
the opposite direction The unconsumed oxygen even if totally reacted
can raise the pretreating temperature only a few degrees The major
reason for temperature 120 control is to prevent excessive drops in
temperature which may affect the operability of the process On the
other hand, increases in pretreating temperature will rarely, if ever,
have any deterimental effect on operability, al 125 though increased
temperature may lower the yield of tar products Other operating
changes besides particle size may affect the temperature in the
pretreating zone; for example, there may be a temporary variation in
the 130 785,863 the heat transfer coefficients of the flowing streams
and other operating variables; however, more usually a surface area
between about 0 01 and about 0 10 square feet per pound of char
product per hour is adequate to 70 provide the desired cooling.
Normally, only a portion of the heat contained in the product char can
be removed economically by indirect cooling, particularly when using a
common circulating heat ex 75 change fluid To further cool the char
and provide a more easily handled product, water is injected into the
partially cooled fluidized char which is then passed into a receiver
or char hopper The quantity of water used for 80 this purpose may
vary; however, usually it is preferred to limit it to not more than
the amount necessary to cool the char to the dew point of water at the
pressure existing in the receiver, thus converting the entire quantity
of 85 cooling water to steam By operating in this manner, advantage is
taken of the high vaporization heat of water to provide maximum
cooling with a minimum of water consumption and at the same time
provide additional 90 vapors to maintain the char in the hopper in a

fluidized state The cooled product is then conveniently removed from
the hopper, defluidized by contact with additional water which
condenses the fluidizing steam and is 95 passed from the system by
means of a conveyor or other suitable means.
The water used to cool the hot char may be introduced thereto prior to
entry of this material into the char hopper, or after the 100 char
enters the hopper, or a portion may be admitted at both localities It
is preferred that the char be cooled to as low a temperature as
possible; however, if a suitable use for higher temperature steam
exists, the amount of cool 105 ing water may be controlled to provide
a char temperature in the receiver substantially above the dew point
of water Also, although it is preferred to maintain the char in the
hopper in a fluidized states the defluidization of this 110 material
may be accomplished therein by inereasing the amount of cooling water
introduced into the char to the point where liquid water is present in
the hopper The char is then removed from this vessel as a slurry 115
rather than as a fluidized mass.
The amount of water required to accomplish the second stage of the
char cooling process varies with the initial temperatures of both the
char product and the water and the 120 final temperature of the char
More usually the water is introduced at a low temperature, i e.
between about 600 F and about 100 F The pressure in the char hopper or
receiver is also desirably maintained at a low level, usually 125 less
than the pressure in the carbonizer, viz.
between about 0 and about 5 psig Setting the pressure establishes the
dew point temperature and accordingly the amount of water required as
quench, which is usually between about 130 rate of introduction of
fresh coal into this zone It is within the scope of this invention to
provide a degree of temperature control by the aforedescribed method
immaterial of the causes of temperature variation, however, the
proposed mode of operation is directed primarily to eliminating the
problem resulting from recurrent variations in feed coal particle
size.
Hot char product from which the major portion of the volatile
constituents of the coal have been removed is withdrawn from the lower
portion of the carbonizer and is passed through a cooler wherein the
temperature of the char is lowered by indirect heat exchange with a
fluid cooling medium When operating in accordance with the ranges of
process variables previously enumerated the amount of this material
varies between about 0 6 and about 09 pounds per pound of wet feed
coal.
The remainder of the raw material delivered to the process is now in a
vapor state, comprising a mixture of steam, combustion gases and tar
vapors The apparatus used in conjunction with the char cooling

preferably comprises one or more conventional tubular heat exchangers
similar to those previously described in conjunction with drying and
preheating the coal feed The type and quantity of cooling fluid passed
through the exchanger may be varied to meet the particular needs of
the process In general, fluids similar to those previously disclosed
for use in drying and preheating the coal are used This operation is
simplified and the cost is substantially reduced, if a common fluid
medium is used for both coal drying and preheating, and for cooling
the product char When operating with this type of system, a continuous
circulating fluid stream is provided, which extracts heat from the hot
char product and transfers it to the fresh coal feed Inasmuch as the
heat removed from the char in the cooling operation may not be
sufficient to provide the heat required for drying and preheating the
coal feed, or vice versa, it is desirable when using a common heat
exchange fluid to provide an additional heat source, such as for
example a conventional tubular heater, or an additional source of
cooling, such as for example a water cooler, which ever is required.
In this preliminary cooling step, the char temperature is usually
reduced to between about 7000 F and about 4000 F, although it may be
brought to a still lower temperature if desired The cooling fluid may
be introduced to the cooler at any low temperature; however, when a
common circulating stream is used the inlet temperature, of necessity,
conforms to the temperature of the fluid leaving the heaters which
serve the drying and preheating stages of the carbonization process,
i.e between about 6500 F and about 3500 F.
The size of the cooler required varies with the amount and temperature
of the char product, 785,863 0.05 and about 0 15 pounds per pound of
char product.
The cool char which accumulates in the char hopper forms a dense
fluidized solids bed above which there exists a conventional dilute
phase zone of low solids concentration The solids density in the dense
phase bed is usually between about 15 and about 25 pounds per cubic
feet; whereas, the concentration of solids in the dilute phase is very
small, often less than 0 1 pounds per cubic feet Vapors and solids
leaving the hopper dilute phase pass through conventional separation
means, for example cyclones, for the removal of a major portion of the
solids and thence to a secondary solids recovery system In order to
minimize the facilities required for separating entrained solids, the
overhead gases from the feed coal drier and preheater, which contain
entrained coal particles, are also introduced into the secondary
solids recovery system.
In one embodiment, this system comprises a vertical elongated
scrubbing tower, with baffles suitably dispersed therein to provide
good liquid-vapor contact Within this tower, the combined vapors from

the drier and preheater and char hopper are scrubbed with water to
remove entrained coal and char particles As in the preceding cooling
step, the quantity and temperature of the scrubbing water is
controlled to maintain a suitable temperature within the scrubber so
that a minimum amount of the steam introduced in the two vapor streams
is condensed Preferably the scrubbing liquid is supplied by recycling
a warm solids-water slurry from the bottom of the scrubber and
combining with this stream necessary makeup water from an outside
source Since the solids-water slurry is at the dew-point temperature
of the steam in the scrubber, usually between about 212 F and about
2400 F, this method of operation provides a relatively high
temperature scrubbing stream and a minimum of steam is condensed in
the process In addition, by recycling, it is possible to closely
control the scrubbing operation for maximum solids removal.
The recovered solids are removed from the scrubbing system as a slurry
in the scrubbing water This slurry is conveniently mixed with char
removed from the char hopper in order to lower its temperature and to
reduce the dust problem associated with the finely divided solids
product As a result of this, the product char solids contain a mixture
of coal and char; however, the amount of coal recovered in this
operation is insignificant when compared to the char, being only
between about 0 1 and about 0 8 per cent thereof by weight, and when
combined with the char is insufficient in quantity to alter its
properties or characteristics.
It is apparent that the aforedescribed method of solids recovery
offers several important advantages The combination treatment of gases
from the char hopper and the drying and preheating zones substantially
reduces the number of cyclones or other solids recovery equipment
required In addition, controlling the scrubbing operation to prevent 7
C condensation of the fluidizing steam provides an important heat
economy and reduces the amount of scrubbing water required for the
operation Furthermore, introducing recovered coal into the char
product not only provides a 75 convenient method of disposing of this
material, but also increases the char yield without affecting the
properties of the char.
As previously mentioned, the effluent vapors from the carbonizer
comprise gaseous products 80 of combustion and various tar compounds
plus a small amount of entrained char The major portion of the tar
materials in the gases condense to liquids at ordinary temperatures
and form a valuable product of the carbonization 85 process To effect
the separation of the normally liquid tar, the carbonizer gas stream
is passed to a quench tower where the vapors are contacted with a low
temperature liquid tar.
This material not only provides the cooling 90 effect necessary to

condense liquid tars but also effects the removal of entrained solids
from the gases The scrubbing and condensing liquid is preferably
obtained by circulating tar condensed in the quench tower through a 95
cooler and recycling it to the upper portion of the tower Within the
tower are provided suitable baffles or plates whereby intimate contact
between ascending gases and downflowing liquid is effected The
pressure at which this 100 operation is carried out is controlled by
the pressure in the carbonization zone, being somewhat lower, usually
between about 10 and about 2 psig It has been found that the major
portion of the desirable liquid tar compounds 105 are condensed by
cooling the carbonizer gases to between about 150 F and about 800 F.
The remaining vaporous tar compounds and combustion products form a
gas, which although low in heat content, may be used as a 110 fuel If
desired, of course, a further separation between the uncondensed tar
compounds and combustion and fluidization gases may be effected.
In the past, difficulty has been encountered 115 in physically
separating all of the condensed tar constituents from the uncondensed
tar vapors and combustion gases Experience has shown that when tar
vapors are quenched in the manner described, a portion of the tar 120
condenses as very small droplets which form a dispersion or "fog" in
the uncondensed gases The dispersed tar is unaffected by subsequent
after-cooling of the gases and is separated therefrom only with
difficulty, 125 usually by passing the gases through a special
separating means, such as, for example, a Cottrell precipitator It has
been found that a major portion of this entrained liquid tar may be
successfully removed in the quench tower 130 785,863 tion of the drier
vessel 10; however, in the lower portion thereof, the dry coal is
confined within an annular space lying between the walls of the drier
and a cylindrical elongated conduit extending upwardly through the 70
bottom of the drier Within this conduit lies a preheating zone 14 in
which there is maintained a higher temperature dense bed of coal
particles which overflow continuously into the lower temperature dry
solids bed 12 Above 75 the dense beds of dry and preheated coal is a
dilute phase 16 of low solids concentration.
Water vapors released from the coal pass up-wardly through this space
into a cyclone 18 from which separated solids are returned to 80 the
dense phase of dry coal, and from which the vapors leave the drier
through conduit 20.
To provide the sensible heat required to heat the wet coal and the
latent heat of vaporization of the water present therein, a 85 stream
of dry coal is removed from the annular drying zone 12 through conduit
22, entrained in fluidizing steam and passed upwardly through conduit
26 and coal heater 28 wherein the temperature of the coal is in 90
creased to about 4800 F From the heater the hot coal is passed into

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