100 Million Tonnes Coal Gasification by 2030

100 Million Tonnes Coal Gasification by 2030

Q. Why is it news/context?

·      Ministry of Coalhas prepared a National Mission document to achieve 100 MT Coal Gasification by 2030.

Q. What is Coal gasification?

·     Coal gasification is the process of producing syngas—a mixture consisting primarily of carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), methane (CH4), and water vapour (H2O)—from coal and water, air and/or oxygen.

·   Coal gasification is future. It is considered as cleaner option compared to burning of coal. Gasification facilitates utilization of the chemical properties of coal

·  In current practice, large-scale coal gasification installations are primarily for electricity generation (both in conventional thermal power stations and molten carbonate fuel cell power stations), or for production of chemical feedstocks.

·     The hydrogen obtained from coal gasification can be used for various purposes such as making ammonia, powering a hydrogen economy, or upgrading fossil fuels.

·     Alternatively, coal-derived syngas can be converted into transportation fuels such as gasoline and diesel through additional treatment, or into methanol which itself can be used as transportation fuel or fuel additive, or which can be converted into gasoline.

·    Natural gas from coal gasification can be cooled until it liquifies for use as a fuel in the transport sector.

Q. What is the Environmental impact of modern coal gasification?

·    The Coal gasification processes require controls and pollution prevention measures to mitigate pollutant emissions. Pollutants or emissions of concern in the context of coal gasification include primarily:

1.Ash & slag

·  Non-slagging gasifiers produce dry ash similar to that produced by conventional coal combustion, which can be an environmental liability if the ash (typically containing heavy metals) is leachable or caustic, and if the ash must be stored in ash ponds.

·  Slagging gasifiers, which are utilized at many of the major coal gasification applications worldwide, have considerable advantage in that ash components are fused into a glassy slag, capturing trace heavy metals in the non-leachable glassy matrix, rendering the material non-toxic.

·    This non-hazardous slag has multiple beneficial uses such as aggregate in concrete, aggregate in asphalt for road construction, grit in abrasive blasting, roofing granules,etc 

 2. Carbon dioxide (CO2)

·        CO2 is of paramount importance in global climate change.

1.   Mercury

2.   Arsenic

 3. Particulate matter (PM)

·        Ash is formed in gasification from inorganic impurities in the coal. Some of these impurities react to form microscopic solids which can be suspended in the syngas produced by gasification.

4.   Sulfur dioxide (SO2)

·        Typically coal contains anywhere from 0.2 to 5 percent sulfur by dry weight, which converts to H2S and COS in the gasifiers due to the high temperatures and low oxygen levels. These "acid gases" are removed from the syngas produced by the gasifiers by acid gas removal equipment prior to the syngas being burned in the gas turbine to produce electricity, or prior to its use in fuels synthesis.

5.   Nitrogen oxides (NOx)

·        (NOx) refers to nitric oxide (NO) and nitrogen dioxide (NO2). Coal usually contains between 0.5 and 3 percent nitrogen on a dry weight basis, most of which converts to harmless nitrogen gas. Small levels of ammonia and hydrogen cyanide are produced, and must be removed during the syngas cooling process. In the case of power generation, NOx also can be formed downstream by the combustion of syngas in turbines.

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