1. Re-Using Vent gas of calciner as
heat source for Fluidised bed
dryer of Plant-04
MENTOR :
Yati varshneya
SUBMITTED BY:
Priyanka Agrawal

2. Contents
1. Introduction
2. Heat flowing out of calciner vent.
3. Heat required in FBD
4. Modification required
5. Suggestions

3. Introduction
 Plant-04 is an absorbent making plant which manufactures
chlorine and sulphur guard.
 These absorbents are used in the petroleum refineries for
absorbing the impurities like sulphur and chlorine from crude
oil.
 The basic unit operation involved in manufacturing of these
absorbent are mixing, Granulation, Drying, Calcination,
Screening.

4. Mixing
Pan
Granulation
Fluidised
Bed Drying
Calcination Screening
Flow sheet of Material Flow
Introduction

5. Introduction
 In plant-04, 5 different types of absorbent are produced which differ in
their composition and method of manufacturing.
 In manufacturing of two of these products both drying and calcination
are required.
 So, for this the hot gas coming out of calciner vent can be used as
heat source for the fluidised bed dryer.
 The production of this product is approximately 200 MT/month and is
produced for four months/based on S&OP in a year.

6. Heat flowing out of calciner vent
39%
recycle
Vent gas
~2500m3/hr
T = 260°C
6 lakh KJ
T = 700°C
Hot gas
out
4500m3/hr
Schematic Diagram of Calcination Process

7. Heat flowing out of calciner vent
Approximately 6 lakh kilo joule of heat is coming out from calciner vent.
Blower air quantity (m3/hr) 4500
Recycle value 0.39
Vent gas (m3/hr) 2745
Approx. Vent flow rate (m3/hr) 2500
Temperature of vent gas °C 260
Reference temperature °C 61
Heat coming out (KJ/hr) 6,12,484.7
 Presently calciner is operated at 39% recycle of vent gas back to calciner
and rest is released into the atmosphere.
 The vent gas is at a very high temperature of 260°C so this heat can be utilised.
 In calculation the value of the flow rate of vent gas is approximated
to 2500m3/hr.
Heat coming out =
flow rate*density*specific heat*(Temp. Of vent gas-Reference temp)

8. Heat required by FBD
The main objective of FBD is to remove moisture of material and
for which hot air is passed through FBD.
So the heat load on FBD can be calculated in two ways:
1. Heat required by material.
2. Heat supplied to air by burner

9. 552 kg/hr
T = 25°C
T = 60 °C
Heat required by FBD
1. Calculating Heat required by Material
Control Volume
Mixing
Chamber

10. Assumption
 Heat capacity of material in and out are same.
 In the FBD only moisture gets removed, no CO2 removal.
 The amount of material being carried to the cyclone separator by air is
negligible.
NOTE: The analysis is based on the data taken from 7-june-2015 to 14-
june-2015.
Formulae used
Heat load on FBD = heat needed to vaporise water +
heat needed to raise material temp.
Heat needed to vaporise water
= water to be vaporised *latent heat of vaporisation of water
Heat needed to raise material temp. =
mass flow rate of material*specific heat of material*(outlet temp. - inlet temp.)
Heat required by FBD

11. Material flow rate(kg/hr) 552. 00
Temperature at inlet(°C) 25.00
Temperature at outlet(°C) 60.00
Moisture content at inlet (%) 18.00
Moisture content at outlet(%) 2.00
water to be vaporised(kg/hr) 88.32
Latent heat of vaporisation(KJ/kg) 2,258.00
Heat needed to vaporise water(KJ/hr) 1,99,426.56
Cp of material(KJ/kgK) 0.85
Mass of dry Solid (kg/hr) 452.64
Heat needed by material(kg/hr) 13,488.22
Heat load on FBD (kg/hr) 2,12,914.78
Approximately 2.2 lakh kilo Joule of heat needed to be supplied to
the materiall
Heat required by FBD

12. 2. Calculating Heat supplied to air by burner
7300m3/hr
T = 61°C
T = 35°C
T = 35°C
Heat required by FBD
Mixing
Chamber

13. To calculate the flow rate of air Anemometer was used.
At different positions velocity were taken under following situation
1. The damper at fresh air inlet of fbd was fully opened.
2. The velocity measurements were done after removing the mesh.
Assumption:
1. Considered the pipe to be perfectly cylindrical at the cross section
where velocity was calculated at different points.
2. Flow is Turbulent means flatter velocity profile.
3. The average velocity across the cross section was taken in calculation.
4. The burner is 98% efficient.
Formulae Used:
Flow rate = flow area* average velocity
Heat supplied to air by burner =
air flow rate*density*specific heat of air*(temp. at fbd inlet – fresh air temp.)
Heat required by FBD

14. Flow rate of air (m3/hr) 7,314.06
Temp of air at inlet(°C) 35.00
Temp of air at fbd in (°C) 61.00
heat supplied to air by burner (KJ/hr) 2,34,117.42
Approximately 2.34 lakh kilo Joule of heat needed to be supplied to be
supplied by the burner.
So, from the two methods of calculation heat required by FBD can be
approximated to 2.34 lakh KJ.
Heat required by FBD
LPG requirement for fulfilling this heat requirement
heat supplied to air by burner (KJ/hr) 2,34,117.42
Calorific value (KJ/kg) 48,070.00
burner efficiency 0.98
LPG required(kg/hr) 4.97
The LPG required by theoretical calculation comes out to be 5kg/hr
Plant LPG totalizer reading for duration under consideration is 2.05kg/hr
but is 4 kg/hr also in other days.
The possible reason for this congruity can be improper calibration of LPG totalizer.

15. Modification required
Pipe of Length =6m including the two 90°bend.
Diameter of pipe = 300mm excluding insulation, same as diameter of vent line.
The line would be installed diagonally from the point near the place where
the 39% recycle valve is to the point on the roof above which dilution chamber is.
Butterfly valve is required to control flow of gas depending on the temperature
required at FBD inlet.
Fabric filter will be required to remove 70 mg/m3 of particulate matter present
in vent gas.

16. Line to be added
to present system
Modification Required
Mixing
Chamber

17. 39%
recycle
4500m3/hr
33 – 71%
recycle
Length = 6m
Dia = 300mm
Pressure Drop = PD by fabric filter + 30Pa
2500 m3/hr
Velocity = 10m/s
T=260°C
Modification Required
Flow rate of vent air
= 850- 1800m3/hr
Flow rate of fresh air
= 5550- 6500m3/hr
Flow rate at FBD in
= 7300m3/hr
Mixing
Chamber

18. Mixing
Chamber
Hot Air
Generator
Burner
Supply Fan
Hot air
Generator
Burne
r
Blower
Ground floor
1st floor
2nd floor
Vent Gas
39% Recycle
L=350m
L=275m

19. Temp. of air at FBD inlet(°C) 61 90
Temp of vent air(°C) 260 260
Temp. of fresh air(°C) 35 35
Flow rate of vent air (m3/hr) 2500 2500
Flow rate of FBD inlet (°C) 7300 7300
Fraction of vent air 0.33 0.71
Flow rate of vent air(m3/hr) 843.56 1784.4
Flow rate of fresh air (m3/hr) 6,456.4 5515.56
Heat required by FBD(KJ/hr) 2,33,667.5 494296.6
Calorific value KJ/kg 48,070.00 48,070.00
burner efficiency 0.98 0.98
LPG consumption (kg/hr) 4.960188267 10.49270595
LPG consumption per month(kg/month) 3571.335552 7554.748284
cost of LPG(Rs./kg) 40 40
Cost saved (Rs.) per month 1,42,853.42 3,02,189.93
Modification Required

20. Suggestions
 Screening should be done just after granulation process and
oversized particle should be recycled.
 Can control the burner firing from FBD inlet temp. reading instead
of cyclone inlet temp.
 One RTD should be placed near the outlet of the FBD for getting
correct value of product temp.

21. Thank You