Coal preparation is an indispensable stage in coal production, during which run-of-mine coal is transformed into products (clean coal) suitable for the market. By-products (coal gangue, coal slime, and middlings) are also produced during this process, which are complex mixtures containing small amounts of coal and many impurities (minerals). However, in recent years, against a background of rising energy demand and growing yield of by-products, the Chinese Government has successively promulgated a series of policies to encourage and support comprehensive utilization of coal by-products. As a result, the comprehensive utilization of coal by-products has attracted considerable research interest and resulted in the publication of many academic articles (mostly written in Chinese). However, few previous studies have addressed the problems and negative effects of comprehensive utilization of by-products. Consequently, the purpose of this paper is to provide a comprehensive literature review and analysis of the comprehensive utilization of coal-preparation by-products in China. The key focus of the review is on revealing problems during processing and giving indications of potential solutions. In addition, the paper also gives recommendations for future work in the field. To this aim, this study reviews the body of knowledge on the topic, through a systematic review of the literature. After searching for publications in four databases (Elsevier, Springer Link, CNKI, and ACS) and a standard Internet search engine, 203 studies (published from 1982 to 2017) have been included in the review due to their relevance for the stated aims. This study makes a significant contribution to the literature because it interprets the comprehensive utilization of coal-preparation by-products from a new viewpoint. Despite its advantages, the comprehensive utilization of by-products is associated with negative impacts that cannot be ignored, so it is very important to consider environmentally benign methods of utilizing these by-products. The findings of the present study can provide valuable information for researchers interested in the field, and hopefully motivate and promote relevant research and policy-making in the near and long-term. (C) 2018 Elsevier Ltd. All rights reserved.
