High level introduction
Mainstream syngas = steam reforming processes
Ammonia; methanol; hydrogen/HyCO
Town gas
Steam reforming; low pressure cyclic
Direct reduction iron (DRI)
HYL type processes; Midrex type processes
2. Syngas Flowsheets – Presentation
Coverage
High level introduction
• Mainstream syngas = steam reforming
processes
Ammonia; methanol; hydrogen/HyCO
• Town gas
Steam reforming; low pressure cyclic
• Direct reduction iron (DRI)
HYL type processes; Midrex type processes
3. Introduction
In each case, various plant flowsheets
exist
• either: original design
• or: resulting from uprate/revamp
Preferred flowsheets have evolved over
time
• influenced by plant size
4. Simplified Steam Reforming NH3 Plant
H2O
H/C
feed
H/C
purification
Removes
impurities (S,
Cl, metals)
Steam
reforming
Converts to
H2, CO, CO2 +
H2O + CH4
H2O
Shift
WGS reaction:
H2O + CO <=>
CO2 + H2
H2
Hydrogen
purification
Removal of
CO, CO2 +
maybe CH4
6. Simplified Steam Reforming H2 Plant
H2O
H/C
feed
H/C
purification
Removes
impurities (S,
Cl, metals)
Steam
reforming
Converts to
H2, CO, CO2 +
H2O + CH4
H2O
Shift
WGS reaction:
H2O + CO <=>
CO2 + H2
H2
Hydrogen
purification
Removal of
CO, CO2 +
maybe CH4
7. Simplified Steam Reforming HyCO Plant
H2O
H/C
feed
H/C
purification
Removes
impurities (S,
Cl, metals)
Steam
reforming
Converts to
H2, CO, CO2 +
H2O + CH4
H2O
CO2 recycle to
reformer feed
H2/CO
Liquid
CO2
Removal
8. Simplified Steam Reforming MeOH Plant
H2O
H/C
feed
H/C
purification
Removes
impurities (S,
Cl, metals)
Steam
reforming
Converts to
H2, CO, CO2 +
H2O + CH4
H2O
Syngas
compression
Purge gas to
feed or fuel
Methanol
synthesis MeOH
Converts
CO/CO2 + H2
=> MeOH
9. Hydrocarbon Purification Section
Historically – up to three parts
• Hydrogenation or hydrodesulphurisation
catalytic breakdown of organic sulphur
compounds to H2S (also RCl to HCl)
• Chloride removal (only if Cl present) -
absorb HCl
• Sulfur removal - absorb H2S
Additionally – a fourth optional part
• Ultrapurification
Various designs depending on
• feed composition; plant design
10. Hydrocarbon Purification Section
H/C
feed
HDS
Breaks down
organo-S and
RCl
H2
HCl
absorption
Removes HCl
by chemical
reaction
H2S
absorption
Removes H2S
by chemical
reaction
Ultra-
purification
Polishes out
trace S
impurities
13. Hydrocarbon Purification Section -
Flowsheet
Different variants found across syngas
plants
HDS usually installed
• Occasionally left out when total S is low
and organo-S is very low (< 2 ppm as
mercaptan, RSH)
HCl removal less usual
• More common in refinery H2 plants using
off gas feed
H2S removal always present
14. Hydrocarbon Purification Section -
Flowsheet
H2S removal – single bed or lead/lag ?
• Single bed found where H2S (or total S to HDS) is
low and predictable
• E.g. gas purified to a pipeline spec’n of << 10 ppm
• Bed must be a realistic size to last T/A interval
• Otherwise lead/lag: design bed life 6 – 12 months
Ultrapurification
• Special situations – NOT for all
• AND not installed in all the “special situations”
15. Hydrocarbon Purification Section –
Flowsheet (cont.)
Ultra-purification applications
• Pre-reformers
• Natural gas fed steam reformers
stressed high heat flux; low
steam:carbon ratio
• Naphtha fed steam reformers
low steam:carbon ratio
• Precious metal steam reforming catalysts
• GHRs
16. Steam Reforming Section - Options
Generally
• feature tubular reformer (“primary”;
“steam reformer”)
• may include 2nd or 3rd stage to the
reforming section
pre-reformer
• part of initial design or later retrofit
post reformers
• two types usually considered
• secondary
• gas heated reformer
17. Steam Reforming Section -
Options
H/C
feed
Pre-
reformer
Converts to
H2, CO, CO2 +
H2O + CH4
Secondary
reformer
Drives CH4
slip down +
other fact0rs
H2O
Steam
reformer
Converts to
H2, CO, CO2 +
H2O + CH4
H2O Air or O2
Ammonia: Optional Normal Usual
Hydrogen: Optional Normal Rare
HyCO: Optional Normal Rare
Methanol: Optional Normal Rare
18. Steam Reforming Section - Options
What proportion of plants feature all
three parts ?
Many ammonia plants
• Topsoe units with pre-reformer (e.g.
India)
• Uprate options which add a pre-
reformer for capacity and efficiency
gains (e.g. ABF; Kemira)
19. Steam Reforming Section - Pre-
reformer
Single adiabatic reactor
• upstream of the steam reformer
• uses high activity Ni based catalyst
Converts hydrocarbons to methane,
CO, CO2 and H2
• Eliminates C2 and higher hydrocarbons
from feed
• Makes life easy for the steam reformer
!!
20. Steam Reforming Section - Pre-
reformer: Why ?
High efficiency/low energy plants
Low steam export – benefit if steam not
required
Smaller and high heat flux reformers
• Lower reformer capex (offset by pre-
reformer capex)
Simplified and robust steam reformer
operation
Means to deliver feedstock flexibility (not
only means) between lighter and heavier
feeds
21. Steam Reforming Section - Pre-
reformer: Why Not ?
Additional equipment
• Capex (offset by smaller reformer ?)
• Opex (catalyst; maintenance; ….)
Complicated and delicate pre-reformer
operation
• Easily damaged expensive catalyst
Low steam export – problem if steam export
valued/required
Economics suggest that pre-reformer is not
the only solution if feedstock flexibility is
required
26. Steam Reforming Section - Tubular
Steam Reformers
Design based upon
• overall strongly endothermic reaction
requires large heat input
• process gas through catalyst filled tubes
• tubes located in fired furnace
Various designs dependent on process
designer and plant
27. Tubular Steam Reformers - Ammonia
Designs
• 200 - 500 tubes arranged in rows
• downflow usually
upflow rare
• capacity range (approximate)
500 – 3300 mtpd
• differing designs favoured by certain
contractors
top fired
side fired
terrace wall
28. Tubular Steam Reformers - Hydrogen
Small plant design - usual
• 6 - 40 tubes arranged in a circle
• upflow and upfired
• single central burner
offered by Axsia-Howmar, Howe-Baker,
Hydrochem, Glitsch
• other geometries are found
• capacity range (approximate)
500 - 16000 Nm3/h
0.5 - 15 MMSCFD
29. Tubular Steam Reformers - Hydrogen
Larger designs
• 50 - 500 tubes arranged in rows
• downflow usually
upflow rare
• capacity range (approximate)
10 - 150 kNm3/h
10 - 125 MMSCFD
• differing designs favoured by certain
contractors
top fired
side fired
terrace wall
30. Tubular Steam Reformers - Methanol
Designs
• 400 - 900 tubes arranged in rows
• downflow usually
upflow rare
• capacity range (approximate)
2000 – 5000 mtpd
• differing designs favoured by certain
contractors
top fired
side fired
terrace wall
35. Steam Reforming Section - Secondary
Reformer
To Waste
Heat Boiler
Process
Steam
Hydrocarbon
Feed
HDS
Fuel
Steam
Generation
and
Superheating
Combustion
Air
Pre-heat
Air/Oxygen
36. Steam Reforming Section – Secondary
Reformer Introduction
Three key components
• Burner Design
• Mixing Volume
• Catalyst
All must be designed
correctly to maximize
performance
Air/Oxygen
Steam Reformer
Effluent
To Waste
Heat Boiler
37. Steam Reforming Section – Secondary
Reformer: Ammonia
Ammonia plants fire the burner with AIR
• Adds O2 AND N2
N2 is inert in secondary (more or less) &
through shifts/CO2 removal/methanation
N2/H2 + residual CH4 go to
• Compression & NH3 synthesis loop
Burner air provides the N2 required for NH3
synthesis
Thus – secondaries are common in NH3
plants
40. Steam Reforming Section – Secondary
Reformer: H2/HyCO/MeOH
H2/HyCO/MeOH plants must fire with O2
• N2 is not required in the process
• N2 cannot be tolerated in the process
Source of O2 required
• Local air separation unit (ASU) may not be
available
• Over-the-fence from industrial gas company may
be expensive
• Construction/operation of ASU adds cost &
complexity
THUS - O2 fired secondary's are less common
41. Steam Reforming Section – Secondary
Reformer: MeOH
NOTE: Lurgi MeOH process design features
O2 fired secondary
• Includes “mega-methanol” process
Lurgi relatively successful in recent years
THUS - O2 fired secondaries are relatively
common in MeOH industry area
42. Steam Reforming Section – ‘GHR’ Post
Reformer Retrofit
Steam
Hydrocarbon
Feed HDS
Fuel
Steam
Generation
and
Superheating
Combustion
Air
Pre-heat
Reformed
Gas
Process
Additional gas + steam feed
Gas
Heated
Post-
Reformer
Waste
Heat
Boiler
HDS
Preheat
Mixed
Feed
Preheat
43. Steam Reforming Section – ‘GHR’
GHRs are used in other ways
• E.g. full replacement of the primary
reformer
Various designs exist from Air
Products, Technip, Topsoe, Kellogg as
well as Johnson Matthey
44. Shift & Hydrogen Purification Sections
Consider shift + purification together
• design options are intimately linked
Historically preferred designs linked to
available catalyst/absorbent technology
Not required on HyCO and MeOH plants
45. Shift & Hydrogen Purification Sections
Water gas shift reaction
Purification
• Either: CO2 removal and methanation
(NH3 & old H2)
COx + H2 => CH4 + H2O
yields ~96 % H2
• Or: PSA unit (newer H2)
yields 99.9+ % H2
CO + H2O CO2 + H2 (+ heat)
46. Shift & Hydrogen Purification Sections –
Ammonia Plants
Designs feature HTS and LTS beds in series
with inter-cooling
HTS
From Steam
Reforming
Liquid
CO2
Removal
LTS
H2O
CO2 feed to urea
plant
Methanation H2
COx + H2 =>
CH4 + H2O
47. Shift & Hydrogen Purification Sections –
Ammonia Plants
Design options – Linde LAC process
• use tubular ITS followed by PSA unit
From Steam
Reformer
PSA H2ITS
H2O
Purge gas to
fuel
48. Shift & Hydrogen Purification Sections –
Hydrogen Plants
Designs 1970s to mid-1980s
• LTS catalyst developed
• HTS and LTS beds in series with inter-cooling
HTS
From Steam
Reforming
Liquid
CO2
Removal
LTS
H2O
CO2 to vent
Methanation H2
COx + H2 =>
CH4 + H2O
49. Shift & Hydrogen Purification Sections –
Hydrogen Plants
Older plants built up to ~1970
• pre-date LTS catalyst development
• two HTS beds in series with inter-cooling
HTS
From Steam
Reforming
Liquid
CO2
Removal
HTS
H2O
CO2 to vent
Methanation H2
COx + H2 =>
CH4 + H2O
50. Shift & Hydrogen Purification Sections –
Hydrogen Plants
Designs since mid-1980s
• PSA units improved significantly
• HTS followed by PSA unit
From Steam
Reforming
PSA H2
HTS
H2O
Purge gas to
fuel vent
51. Shift & Hydrogen Purification Sections –
Hydrogen Plants
Design options
• include additional LTS before PSA unit
favoured in some large new plants
(>105 kNm3/h or 90 MMSCFD)
HTS
From Steam
Reforming PSA H2LTS
H2O
Purge gas to
fuel vent
52. Shift & Hydrogen Purification Sections
– Hydrogen Plants
Design options
• use MTS followed by PSA unit
From Steam
Reformer
PSA H2MTS
H2O
Purge gas to
fuel vent
54. Steam Reforming Based Town Gas
Processes
Various flowsheets exist
• HKCG; CityGas; Dakota Gas
• Rely on standard syngas reactor units
55. Cyclic Town Gas - Process Outline
Reactor design features
• hydrocarbon, O2(air), steam feeds
• packed bed of catalyst
• burner in top of reactor
Burner provides heat
• increases temperature of catalyst bulk
• partial combustion of the hydrocarbon
Catalyst provides reforming and shift
activity
56. Cyclic Town Gas - Process Outline
Hydrocarbon feed varies
• natural gas to naphtha
• may contain sulphur (ie not
desulphurised)
Catalyst becomes deactivated
• C & S
• Fe scale
• regeneration may be required
• regen can be part of process (eg cyclic TG
plants) or physical cleaning
57. DRI Processes – Types using Steam
Reforming
HYL type flowsheets
Midrex type flowsheets
Lookalikes exist in each category
59. DRI Processs - Features of HYL III Steam
Reformer
Natural gas feedstock
Downflow + down-fired
Typical conditions
• S/C ratio 1.9 - 2.5
• pressure 6 - 7 barg
• exit temperature 840°C (1545°F)
• methane slip 2.0 - 2.5 mol % (dry)
Steam reformer catalysts
• same types as HyCO (+H2/NH3/MeOH)
plants
• feed purity to < 0.1 ppm S required
60. DRI Processes - Typical Midrex Process
Iron Oxide
Direct
Reduced
Iron
Exhaust
Stack
Flue
Gas
Natural
Gas
Feed Gas
Main Air Blower
Combustion Air
Process Gas
Compressor
Reformer
Top Gas
Scrubber
Cooling Gas
Compressor
Reducing Gas
Scrubber
Top
Gas
Reduction
Zone
Shaft/
Reduction
Furnace
Cooling
Zone
61. DRI Processes - Features of Midrex Type
Reformer
Natural gas feedstock
Upflow + up-fired
Typical conditions
• From recycle gas
CO2 ~15 mol %; CO ~15 mol %; H2O gives S/C
~0.6
S required against metal dusting (up to 10
ppm)
• pressure 1 - 2 bara
• exit temperature 930°C (1706°F)
• methane slip 1.0 mol % (dry)
Specialized S tolerant reformer catalysts
62. Summary
High level review of syngas
flowsheets
Key differences and options
highlighted
Increased awareness but many
further layers of detail exist