Production of gasoline from coal based on the STF process

Abstract

The growing demand for motor fuels, particularly in a number of countries which own coal but not crude oil, is promoting a rising interest in converting coal into synthetic liquid fuels. The formation of valuable liquid products from coal may be an option for using coal deposits located in remote areas, since the longdistance transport of liquids with high energy content is more economical. The coal liquefaction process includes the production of synthesis gas from coal and the subsequent conversion of synthesis gas into liquid fuels (gasoline, diesel, jet fuel). Several well-established technologies are known both for coal gasification and fuel synthesis. At the beginning of this decade, a novel process was developed for the production of high-octane gasoline from synthesis gas (“Syngas To Fuel” - STF®). A STF demonstration plant is operated by Chemieanlagenbau Chemnitz GmbH and Technische Universität Bergakademie Freiberg. It includes the conversion of syngas into methanol and the subsequent conversion of methanol into gasoline in isothermal reactors, which are advantageous in terms of selectivity compared to adiabatic systems. After the STF plant was started up in Freiberg in June 2010, the whole process was systematically optimized and successfully operated in a series of long-term test campaigns, using synthesis gas generated by the autothermal reforming of natural gas. The STF process allows gasoline to be produced from different feedstock including coal. Based on the test results, technical and economical parameters were calculated for the overall coal-toliquid conversion. For flow sheet simulations, the commercial software Aspen Plus was used. Gasoline output and energy efficiency were the main optimization parameters. Investment costs and operation expenses were assessed for different scale-up scenarios. Using the economic characteristics and the calculated gasoline output, the production costs were estimated and compared with current world market prices. The influence of the variable boundary conditions on the final product price was considered in order to evaluate the potential for cost optimization. The determined technical and economic parameters for the CtL process under consideration, based on STF technology, were benchmarked against commercialized CtL processes. The study also included other technologies for the generation of valuable products based on different feedstocks.