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priyanka_re-using vent gas

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priyanka_re-using vent gas

  1. 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. 2. Contents 1. Introduction 2. Heat flowing out of calciner vent. 3. Heat required in FBD 4. Modification required 5. Suggestions
  3. 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. 4. Mixing Pan Granulation Fluidised Bed Drying Calcination Screening Flow sheet of Material Flow Introduction
  5. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 16. Line to be added to present system Modification Required Mixing Chamber
  17. 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. 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. 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. 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. 21. Thank You

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