| ‘…………….the rising oil fuels have triggered the use solid fuel combustion systems’. Coal usage is becoming more widespread worldwide because coal reserves are much greater than oil and gas reserves combined. As oil and gas reserves become depleted, coal will become increasingly competitive. Coal-firing will remain the primary choice where security of supply is important or where coal supplies are relatively less expensive.
New technologies are being developed that enable coal to compete against other fuels more effectively. Many technologies are gasification based. Gasification technologies are more environmentally friendly and efficient for a number of applications.
Gasification process
CASE Coal Gasifier carbonaceous material undergoes Four processes
Drying & Charge Pre Heat : The producer gas flowing upstream through the reactor dries up the newly injected coal, thus making the next stage (pyrolysis) easier and efficient.
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Pyrolysis : Also called de-volitization occurs when the heated coal releases char and volatile resulting in weight loss for coal. The volatiles being light in weight move upwards and the char moves downstream for the next process (Reduction). |
| Reduction: In this process the char is acted upon by the Carbon dioxide and steam generated from the final process of gasification (Oxidation). Here the Carbon Dioxide and steam combines with char to give Carbon Monoxide and Hydrogen. |
| Oxidation : During this process the reduced Carbon (Char) is burnt by blowing controlled air into the reactor. Steam is injected simultaneously (Carbon is oxidized in the presence of steam to generate Carbon Dioxide and Hydrogen. |
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Producer Gas composition
Producer gas has the following composition:
CO: 15-20%; H 2:15-20%; CH 4: 2-6%; CO 2: 7-10%; N 2: 40-50%
Types of gasifiers
- Single Stage Crude Gas Gasifier.
- Double Stage Crude Gas Gasifier.
- Double Stage Clean Gas Gasifier.
Application
- Steel re-heating Furnaces.
- Power Generation.
- Ceramic Plants.
- Glass Manufacturing Plants.
- Paper Mills.
- Aluminium Plants.
- Zinc Manufacturing Plants.
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