Traditional liquefaction methods for coal, and other heavy fossil hydrocarbons (HFH), can be divided into two general categories. The first is indirect liquefaction, where the coal is first gasified to synthesis gas that is then used for chemical and fuel production. The second method is direct liquefaction, where the coal chemicals and fuels are either extracted/refined from the coal or the coal undergoes a series of thermochemical reactions. Most of these traditional methods of coal liquefaction have significant energy requirements and environmental impact. Conventional techniques for direct coal liquefaction will generally result in lower CO2 emissions compared to indirect techniques, but will typically require relatively higher temperatures and higher pressure hydrogen to obtain significant product yield and quality. Operation at high temperature and high pressure results in high energy requirements, water consumption, and capital costs. Therefore, alternative methods for conversion of HFH to value-added chemicals and fuels are required to reduce the capital costs, the operating costs, and the environmental impact of HFH liquefaction and in order to make facilities such as coal-to-liquids (CTL) plants feasible.
USPTO Backgrounds
USPTO Backgrounds