Coal to Liquid Technology: An Alternative Source for Transportation

 About 96% of all energy used in the transport comes from petroleum. Increasing energy demand and rise in vehicle ownership lead to have an energy supply balance. In the world coal reserves are ten times more abundant and more evenly distributed. Can liquefying the coal be an alternative fuel source for transportation?

Coal Liquefaction is a process that has been around a long time. This technology was extensively used by Germans during the period of World War II. In 1960’s South Africa faced the world oil embargo during which they switched towards the coal liquefaction and they are producing 70% of the liquid fuel needs. Recently China had shifted its focus towards coal liquefaction and is been successful in implementing the direct liquefaction plants. India having some of the largest coal reserves in the world can liquefaction change the scenario of the Indian liquid fuel needs?

Coal liquefaction is a process that converts coal from a solid state to liquid fuels, to produce the substitutes of petroleum products. The conversion of coal to liquid fuel can be processed by various liquefaction processes but they are broadly classified into two types i.e. Direct Coal Liquefaction (DCL) and Indirect Coal Liquefaction (ICL).

Direct Coal Liquefaction was developed by Friedrich Bergius during the period of World War II and it is also known as Bergius Process. In this process, the dry coal is mixed with recycled solvent to form coal slurry which is subjected to high temperature and high pressure in the presence of hydrogen gas and catalyst. The liquid products that are produced are of low quality and they require further refining to achieve high grade fuel products. Various catalysts are used to improve the rates of conversion of the coal to liquid fuel. The direct processes that are processed in the companies at present is the modification and extension of the Bergius process.

Indirect Coal Liquefaction is the multi step process in which the first requires the gasification of coal to produce syngas (a mixture of CO and H₂ gas). The second constitutes of conversion of syngas into liquid fuels using one of these methods i.e. Fischer-Tropsch process or Methonal process. F-T process is the oldest ICL process where syngas is subjected to chemical refinement to produce liquid fuels in the presence of catalyst. In Methonal or Mobil process, the syngas is converted to methonal which is subsequently converted into liquid fuel over a catalyst. Initial syngas can be obtained from coal alone or from coal-biomass mixture.

These processes produce whole lot of products which include clean petroleum and diesel, synthetic waxes, lubricants, methonal and dimethyl ether.  These fuels are sulfur free, low in particulates and nitrogen oxides. One tonne of coal can yield almost one-half tonne of liquids. Process has been developed to use coal from low ranked lignite to high volatile bituminous coal. They can be used for power generation, transportation and cooking. The coal rich country which has high oil prices and concerned with increasing oil import price is best suitable for coal liquefaction process.

Coal liquefaction process is significant energy consumption process which at industrial scales requires multibillion dollar capital investment which presents a high investment risk. The life cycle of liquefaction process emits large amounts of greenhouse gas. The coal-biomass mixture has an advantage over pure coal which emits much lower greenhouse gas. There has been a pocket size effect of lowering the greenhouse gas through sequestration. The increase in coal mining will again result in environmental consequences.

India has a significant potential to invest in coal to liquid technology as there is an increasing demand of oil imports and the oil price reaching its pinnacle. India being one of the largest emitter of greenhouse gas, this process will further increase those emissions which will be the area of improvisation. In India, Oil India Limited has successfully tested the direct coal liquefaction technology in the Northern Coalfields Limited. Ministry of Coal has allotted two coal blocks in Talcher coalfields to M/s Strategic Energy Technology Systems Ltd. and Ramchandi Block to M/s Jindal Steel & Power Ltd. with production capacity of about 80,000 barrels of oil per day per project which are expected to commence by 2018.