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About Producer Gas Plant

Many industries were using Producer Gas as a cheap Gaseous Fuel since Mid- Nineteenth Century. Producer Gas was generated from the reaction of Air and Steam with Coal in single-stage generators either made of bricks in the initial

stages or steel with water jacket or refractory lining in the later versions. Before extensive production of Natural Gas and other Petro-fuels at a moderately lower cost, Producer Gas had been a versatile fuel owing to several advantages over the solid fuels , viz, ease of production, better thermal efficiency in the application, ease of control, smoother flame etc. As a result many industries all over the world have been using Producer Gas as a cheaper energy in various field of applications viz, glass and ceramics, Refractory, Lime-kilns, Dryers, Heating furnaces, etc but with limited flame temperature up to 1000° to 1100°C.

But the Producer Gas in earlier 19 th Century from conventional Single Stage design had several disadvantages. In these gasifiers Producer Gas used to come from one side at the top of the gasifier at a temperature of 470°C to 500°C resulting in the following disadvantages:

  1. As the gas was coming out from one side of the Producer, there will be always a preferential flow which will not permit the old coal bed to come under gasification reaction resulting in poor quality of gas.
  2. Because the coal bed is not coming under reaction, there will be not adequate reduction reaction which will cause a high temperature at the outlet gas of the producer and causing thermal cracking of the coal tar which will form soot and gumming materials and will get deposited in the pipe line. Due to this cracking of coal tar and deposit of soot, the pipe line gets frequently chocked and is a laborious job to get the pipe line cleaned.
  3. The Calorific value of Producer Gas was low.
  4. No consistency in Gas quality and quantity.
  5. Frequent interruptions in the process due to chocking and cleaning of pipe line.
  6. Because of shallow bed it can perform only with high grade of coal.
  7. Single off-take from one side, will cause preferential flow of air-steam mixture resulting in non-uniform gasification reaction.
  8. Operational hazards due to heavy clinkering and jamming of the fire-bed.
  9. Low Thermal Efficiency.
  10. Limited use in industries due to low flame-temperature.
  11. Gasifiers were not pollution-free.


Due to above disadvantages, the source of energy in industries gradually changed from Producer Gas to Petro-gas, Fuel Oils which was available at low cost, had abundance of supply with low investment cost and Electricity so long as these were comfortably cheaper. But due to Global Energy crisis and price-hike of all kinds of Petro fuels, industries have tried to switch over to cheaper fuel. As coal is abundantly found in our country, industries should resort to Gaseous fuel based on coal.ഊIndia Industrial Enterprises Pvt. Ltd.

Schematics & Graphical Representations

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Auto Safety Features - animated schematic

New Generation Producer Gas Plant as developed and Patented (Patent No. 202603) by IIEPL.

  • Gives uniform quality of Gas having Higher CV.
  • High ash coal could be gasified.
  • Operational hazard such as choking of pipe line due to cracking of coal tar could be avoided.
  • Higher thermal efficiency due to gasification reaction throughout the bed and also due to auto carbonization of coal in the extended shaft resulting in higher reactivity.

Installations

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Objective of the New Generation Producer Gas Plant

The objective of the new technology was to produce a clean and consistent quality Producer Gas of higher Calorific Value from any grade of Indian Coal of A to F grade. With this objective in view, a deep coal — bed has been introduced above the insignificant product gas space and minimal distillation zone of the single stage gas-producer. The product gas has been diverted fully through this extended coal bed to come out from the top of the extended shaft at a temperature much below cracking temperature of Tar and the tar remains always at vapour phase.

The Basic Design Features of New Generation Producer Gas Plant with their advantages

  • The extended shaft is so precisely calculated that the feed coal while moving downwards gets stripped off its volatile matter to a great extent and itself is transformed to ‘Near coke’ state for a higher reactivity and smoother and faster gasification almost similar to coke gasification. The product gas on the other hand, while moving upwards counter current to the incoming coal stream gets auto carbureted with the stripped and distilled volatile matters of coal to a higher calorific value
  • Perfection of the Coal charging system for better distribution of coal.
  • Provision of Double off-takes for producer gas from the top of the Extended Shaft for uniform gasification and full utilization of fire-bed.

The above novel features of auto-enrichment of Gas with inbuilt distillation of coal in an Extended Shaft Gasifier have improved the kinetics of gasification, specific mass-flow of gas per unit empty cross-section of Gasifier, Gas make per MT of coal, Calorific Value and consistency of Gas quality to a great extent.

The Constructional Features of New Generation Producer Gas Plant

The prime parts of a 100% Top Off-Take Producer Gas Plant are:

  • Overhead Coal Bunker
  • Coal Feeding System
  • Skip—Hoist, Bucket Elevator or Conveyor System for lifting of Coal
  • Refractory lined Extended Shaft
  • Water Jacketed Bottom Shell or Generator Proper
  • Grate Stool with Grate Rings
  • Grate Rotation System with Guide and Support Rollers
  • Ash-Bowl with bottom seal and skirt
  • Double Gas off-takes from the top of Extended Shaft
  • Washing cum Mixing chamber
  • Steam Drum
  • Air-Blowers with associated steam—air mixer/saturator, BST Controller
  • Piping and Fittings for Gas, Water, Steam and Air
  • Gas vents from outlet off-takes
  • Ash Removing System
  • Tar Settling and Removing System
  • Instrumentation with PLC/DCS
  • Electricals including M.C.C, Cabling, Lighting, Earthing etc
  • Building and Structurals including insulation

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.