Coal Liquefaction Process Development

Abstract

The traditional method of liquefying coal operates at extreme conditions consisting of hydrogen pressures of over 2000 pounds per square inch and temperatures of over 450°C. The elevated hydrogen pressure is necessary to hydrogenate the reaction mixture and liquefy the coal molecules. As a result, the processing equipment is very expensive and safety is a major concern. The coal liquefaction process invented at West Virginia University does not use hydrogen overpressure and operates below 500 pounds per square inch. The WVU process has produced 4500 pounds of cleaned de-ashed coal extract referred to as centrate. The centrate was processed into coal tar binder pitch by Koppers Inc. and finally into electrodes for the steel industry by GrafTech International Ltd. The electrodes were tested and passed all of the commercialization tests. Quantex, a Canadian company, licensed the technology from the university in 2007 with the intention of commercializing the process. However, the process had several deficiencies to overcome before it could be economically viable and move towards commercialization. The centrifuge system removes ash and other solid materials from the mixture after the coal has been liquefied. In the process existing in 2007, the centrifuge residue, or tails, contains only 20% by weight of the ash material with the remaining 80% consisting of valuable products or unreacted coal. Without first increasing the efficiency of ash removal from the coal either before or after the liquefaction reaction, the process cannot be economically viable and is unable to be commercialized. Another drawback of the original process is the reaction and centrifuge systems were not designed or operated to produce reliable mass balance results. The reaction system was redesigned and constructed incorporating the previously redesigned centrifugation system to produce clean, de-ashed centrate and other products from the raw materials. A vacuum distillation system was designed and constructed that produces quality pitches and condensed liquid volatiles from the clean, de-ashed centrate produced from coal in the previous reaction step. The coking system was designed and constructed to process the coal derived pitches into commercial grade coke and additional condensed volatiles. Each of the three operating systems produces reliable and repeatable mass closure results for individual experiments. All of the products can be collected and samples taken for further analytical analysis. A complete mass balance analysis for the overall process was performed from the raw material through the products produced. The end products were subjected to and passed testing for commercial standards. The potential for commercialization has been enhanced by this research and the technology now can be properly analyzed.