Products - Various Process-Steps and Reaction Zones in the Gasifier

Various Process-Steps and Reaction Zones in the Gasifier

  • Coal is lifted and delivered to the bunker by a skip-hoist, Bucket-Elevator or Conveyor System.
  • From the Bunker, coal is fed to the Extended Shaft through double-bell feeder system automatically as per the set exit temperature of gas.
  • Fed coal travels downwards and gets dried and preheated. Due to prolonged stay of coal in the Extended Shaft and the gas getting better physical contact with coal interface, substantial heat transfer from gas to coal takes place and at the same time high volatile-matters of coal get stripped off and enter the gas-phase in turn auto-carbureting the latter.
  • When the coal enters the generator proper, reaction between coal and air along with steam occurs and following reactions take place zone wise from bottom to top.

 

  • Oxidation Zone:
    The reaction are : C + O2 = CO2
  • Primary Reduction Zone:
    The reaction are : C + H2O = CO + H2
    C + 2H2O = CO2 + 2H2
    C + CO2 = 2CO
  • Secondary Reduction Zone:
    The Reaction are : C + CO2 = 2CO
    CO + H2O = CO2 + H2
  • Ash Zone:
    The Ash zone under the Oxidation zone through which calculated quality of Air saturated with steam enters and receives heat from the ash which, on the other hand, gets cooled down.
  • Distillation Zone:
    The distillation zone starts from the top of the bottom shell and extends upwards to about 2500 mm or so in which considerable quality of volatile matters (about 85%) is picked up by gas.
  • Pre-heating and Drying Zone:
    At the top there is Pre-heating and Drying zone which starts from the distillation zone and extends to the top of extended shaft where the incoming

Features of Plant

  • Coal is used as main feed-stock
  • Use of all types and grades of coal (A Grade to F Grade of Indian Coal)
  • Low Operating Cost / Semi to Full Automatic
  • Lesser Man power
  • Environment friendly
  • Requires low cleaning & provides consistent production of gas
  • Process involves gasification of coal providing smooth & faster gasification, consistent flow of coal
  • Plant design provides higher coal-throughput and higher gas make per MT of coal
  • Higher Thermal Efficiency of Plant (88% to 92% against 65% to 70% in single/ conventional double stage Gasifier.
  • Continuous process and having advantage of superior control
  • Plant is Operational friendly and conforms to all Pollution Control Board norms which was not available on single / conventional type of Gasifiers.
  • It has superior instrumentation to control all process parameters
  • Safety Features — There is no gas leakage as plant has sealing arrangement of coal feeding system, poke holes and ash bowl. Water seals are provided at desired locations to take care of over pressure. High and low level alarms are provided on the jacket boiler steam drum.
  • Gaseous Effluents —There is no gaseous effluent
  • Liquid Effluents - The liquid effluent of about 0.5 MT to 1.5 MT / per day of light tar is generated in Mixing-cum-Washing Chamber, which can be used as CTF in duel feel burner in place of Furnace Oil. The Phenol collected in the Mixing Chamber is circulated for washing and cooling of gas.
  • Solid Effluent — The Ash Granules discharged from the plant is non-toxic and can be used as filling material, Cement plant, Road Repairs or brick making.
  • Noise Level — The noise level is below 60 db as the plant design controls and results into low noises.
  • Purity of Gas — With mixing cum washing Chamber and separator, the dust and tar particles of above 40 microns are removed from the final gas. The Tar vapour is completely burnt out in the furnaceഊIndia Industrial Enterprises Pvt. Ltd.

Economy in Coal Gasification

  • Consideration
    Cost of Indian ‘F’ Grade Coal → Rs. 2000/- MT
    Cost of Furnace Oil → Rs. 30000/-KL
    Heat to be generated → 10 x 10 6 KCal
  • Average cost of generation of Producer Gas with ‘F’ grade coal Æ Rs. 1.20/-Nm 3
  • Producer Gas required for generation of 10 million KCal of heat with ‘F’ Grade coal → 8000 Nm 3
    ¾ which cost to → Rs. 10000/-
  • Furnace Oil required for generation of 10 million KCal of heat → 1042 ltrs.
    ¾ which cost to → Rs. 32000/-

Thus cost in Producer Gas firing is even less than One — Third the cost of Furnace Oil firing.