Abstract
Gasification of carbon containing feedstocks followed by hydrocarbon synfuels production has received much attention particularly in China and the United States in recent times due to rapidly rising prices of natural gas and oil. Coal’s exploitable resources have a potential to quench mankind's thirst for energy at the current rate for five times longer than gas resources. Proven recoverable coal reserves of about 990 billion metric tons offer a tremendous resource for the production of energy and chemicals in North America, Russia, China, Australia, India, Germany, and South Africa, each with more than 50 billion metric tons of coal reserves.
A number of synfuels technologies have been proposed using coal including methanol, dimethyl ether (DME) naphtha/gasoline, and diesel. All of these processes emit a large volume of CO2 which in principle could be captured and stored. The challenge is how to harness this enormous amount of coal resource, which constitutes about 26% of world primary energy demand, most economically and without further unduly impairing the environment.
The United States, Russia and China have the largest coal reserves in the world, but China and India together account for almost three-quarters of the recent increase in coal demand in developing countries and two-thirds of the increase in world coal demand. Import of GTL fuels from arbitraged Middle Eastern natural gas currently makes more sense for India. Hence, promotion of CTL in India may not be appropriate at the moment, and we have focused our strategic review on the United States and China.
Basic Coal to Liquids (CTL) technology begins with direct or indirect liquefaction of coal, both of which are described in this report. The economic focus of this report, however, is on indirect coal liquefaction. Economic analyses are provided for production of middle distillates from coal in order to maximize diesel fuel production using commercial iron or cobalt catalysts. In addition, we profile different types of coal gasification technologies (including entrained bed, fluidized bed, and fixed bed technologies), syngas cleaning and processing options, and coal/biomass cogeneration technology in detail.
Other alternative CTL fuels technologies include coal to methanol and coal to DME.
Methanol is an alternative fuel to gasoline in spark ignition engines, and dimethyl ether is an alternative fuel for diesel engines. Technologies to produce these alternative liquid fuels are reviewed.
Finally, in the last two sections of this report, we investigate the latest developments in synthesis and catalysis for F-T diesel, and direct DME synthesis, including parameters and features of CTL catalysts and an overview of recent R&D catalysis for F-T, methanol, and DME.
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