Coal and Coal as Chemical Feedstock | Chemical Technology - Chemical Engineering PDF Download

Table M-II 1.4: Distribution of Coal Resources (million tones) 

Table M-II 1.7: Status of CBM Blocks  

Sources: India Exploration and Production Activities 2007-08 

Coal Production and Consumption

The global coal production in 2011 was 7 billion tones of which China accounted for approximately half of the production and consumption. Total coal production in India during 2009-10 was 532.29 million tones. Lignite production in 2009-10 was 23.95 million tones

Types of Coal

Coal are classified into various grades based on the composition and calorific value and degree of coalification that has occurred during its formation. Coal may be also classified as hard or soft coal, low sulphur or high sulphur coal. Coal may be also classified in rock types based on petro logical components known as maceral. Based on maceral content coal may be classified as clarain, durain, fusain and vitrain . Classification of different type of coal is mention in Table M-II 1.8.
Ultimate analysis of non-coking (Thermal) coal from three power stations (Kahalgaon, Simhadri, and Sipat) is shown in Table M-II 1.9 along with analysis of Ohio coal in the United States and Long Kou coal from China. 

Table M-II 1.8: Classification of Different Type of Coal 

Assesment of Coal Quality 

Coal quality plays an important role in its efficient utilization as fuel and for gasification. It should have high calorific value, high carbon content with low ash content, low sulphur, low moisture, low cost. The quality of coal depends upon it rank. The coal rank is arranged in ascending order 

Lignite→  Sub-bituminous coal → bituminous coal→  anthracite 

Coal quality can be assessed by proximate, ultimate analysis and calorific value of the coal. Proximate analysis involves determination of moisture, volatile matter, ash and fixed carbon. Ultimate analysis involves determination of carbon and hydrogen,, nitrogen, sulphur, oxygen  Calorific value is represented as higher calorific value (HCV) or Gross calorific value (GCV) and Lower calorific value (LCV) or Net calorific value (NCV). Another term used to express energy content is Useful heating value (UHV).UHV is defined as UHV kcal/kg=[8900-138x( percentage of ash content+ percentage of moisture content)] 

Coal as Fuel 

Coal accounts for 53 percent of the commercial energy sources in India which is high compared to the world average of 30percent. The 11^th plan projected India’s coal demand to grow at 975 per annum against 5.7 percent during 10^thplan almost two-fold increase. The commercial coal consumed by India 72 percent for power, 14 percent for steel, 9percent for cement and 9 percent for others. Allocation of coal blocks to private companies are given in Table M-II 1.10.

Table M-II 1.10: Allocation of Coal Blocks to Private Companies  

Coal originally was utilized as fuel. Many of the petrochemicals now derived from petroleum and natural gas was referred as coal chemicals. With starting of coke oven plants it became source of organic and some inorganic chemicals. Coal tar from coke-oven plants continues to be a source of aromatics, naphthalene and other valuable aromatics like pyridine, picoline, quinolene. Before the coming of petrochemical production a large number of organic chemicals was produced from acetylene produced from calcium carbide route in which coal was a important feed. Various coal chemicals derived from coal is given in Figure M-II 1.1

China has come in a big way for production of chemicals from coal because of the huge coal reserves. With the rising cost of crude oil and dwindling crude oil reserves, coal has again received attention all over the world to utilize coal as an alternative source of chemical feedstock. Various routes for production of organic and inorganic chemicals from coal are

• Coal carbonization and coal tar distillation
• Coal gasification and use of synthesis gas as feed stock for ammonia production
• Coal liquefaction by hydrogenation
•  Coal to methanol technology
• Coal to olefin technology  
• Coal to plastic technology
• Acetylene from calcium carbide made from lime and coal 

Coal Carbonization and Coal Tar Distillation 

 Coal carbonization and coal tar distillation is integral part of coke oven nits in steel plant for production of coke where large number of chemicals like ammonia, naphtha, aromatics etc are produced benzene, toluene, xylenes were earlier produced from coal tar distillation obtained from coke oven plant.

Coal Based Power Generation 

Coal Gasification and Use of Synthesis Gas as Feed Stock for Ammonia Production: Partial oxidation of coal is used for production of synthesis and ammonia. CO from partial oxidation is converted to CO2which is used for Urea manufacture. Synthesis gas CO+H2 is used as chemical feedstock for production of large number chemicals.

Coal Liquefaction by Hydrogenation 

Coal can be converted to naphtha by direct or indirect liquefaction. Coal can be also converted into naphtha via FT process. 

 Figure M-II 1.1: Coal as Chemical Feed Stock

Coal to Methanol Technology The process involves the production of synthesis gas from coal via partial oxidation followed by conversion of synthesis gas to methanol 

Coal to Olefin Technology Methanol can be converted to dimethyl ether, which can be used as a gasoline blend or converted to olefin through olefin synthesis reactions. 

Coal to Plastic Technology

Olefin produced from the coal route can be use for the manufacture of plastic. Coal gasification and production of fuel from FT process getting significant attention. Coal gasification and production of synthesis gas is now considered to be a major potential on purpose source of commodity petrochemicals. The cost of coal and higher cost of chemicals derived from coal has been major constraint in its utilization as a substitute for petroleum and natural gas.