Drying of Low-Rank Coal (LRC)—A Review of Recent Patents and Innovations

Abstract

Despite being geographically dispersed, abundant, and accounting for almost half of the world's coal reserves, low-rank coals (LRCs) find limited use due to their high moisture content and high propensity for spontaneous combustion. Reducing the moisture content of low-rank coal enhances its heating value and reduces transportation costs, thus increasing its economic value. In addition, dried low-rank coals have been proven to improve plant efficiency, enhance safety, and reduce greenhouse gas emissions. Although numerous technologies for coal drying already exist, it is often challenging, if not impossible, to find one that is cost-effective in all aspects. When selecting a dryer for coal upgrading applications, factors such as particle size/size distribution, throughput, energy consumption, material handling capabilities, safety, carbon footprint, capital and operating costs, return on investment, etc., are important considerations. This article provides an overview of the patent literature along with the archival literature that deals with drying of coal as well as biomass, which is relevant to coal drying.