Development of China′s coal preparation industryand technologies

The paper presents a brief review of the gradual progress of the coal preparation plants, since the founding of the People′s Republic of China, in the aspects of plant design and construction, advances of coal cleaning technologies, raw coal treatment rate, and the entrusted missions, as well as the historical course of the country′s coal preparation industry starting from start-up and growth to transition from a phase of rapid growth to a stage of high-quality development. Following that, some significant achievements obtained during the course of development of coal cleaning technologies, processes and equipment are briefly summarized. In the 50s of the 20th century, the coal preparation industry started to be established, for undertaking then the mission to supply cleaned coal for the iron and steel industry. In 1956, Tangshan Coal Research Institute and Tangshan Coal Preparation Design Institute (TCPDI) were established in succession. During the first and the second Five-Year Plan periods, six coal jigging plants were set up with technical assistance provided by the former USSR and Poland. In 1958, the first independently designed heavy-medium separation shop came into being. In 1959, an independently designed and built coal preparation plant made its debut, laying a foundation for the coal preparation industry of the country. In the 60s of the 20th century, ten plants with a total designed capacity of 16.4 Mt/a were introduced from Poland, making it possible for China to drastically increase its raw coal treatment capacity and to start using jigging + heavy medium separation + flotation combined processes in design of plants. In 1970 an independently designed and built plant which used all home-made equipment, the first of its kind in China, was set up, through which the experience for the development of the coal cleaning industry and related technologies was accumulated. In the period of 1980—2000, the coal preparation industry was in its growing stage with its mission focusing on energy conservation. Following the implementation of the reform and opening up policy, a large batch of large-sized plants operating with high-performance equipment and a high automation level were set up through independent innovation, assimilation of introduced foreign technologies and running plants in form of joint ventures with foreign partners, and also in this period, in the plants built according to the general design specifications complied by TCPDI for the design of the 1.8 Mt/a plant, the coal washing operation with closed washwater circuit was made preliminary possible. And complete sets of advanced washing equipment for the 3.0～4.0 Mt/a plants were also introduced from Germany, the U.S. and Poland, making it possible for such plants to operate with jigging + heavy-medium separation + flotation combined processes as a general practice. In 1987, the first extra-large 15.00 Mt/a power coal washing plant featuring the use of heavy-medium vessel plus heavy medium cyclone for respectively washing coarse coal and small coal was introduced from the U.S. Before 1990, the 1.8 Mt/a Jinyang plant operating with the use of ϕ710/500 3-product H.M. cyclone was introduced from the USSR. The introduction of complete sets of equipment from overseas countries helped promote to a large extent the growth of the coal preparation industry and the development of the related technologies. During the 9th Five-Year Plan period, a series of major research-derived achievements was obtained, for instance, in the development of new washing processes and equipment, allowing large-sized plants to operate with a simplified washing system featuring the use of large-size and highly efficient all-heavy medium washing equipment. This is more than sufficient to cater to the needs for the building of new plants and technical transformation of old plants each with an annual capacity of less than 4 million tons, all with the use of self-developed equipment, no matter what kind of coal was treated and what washing processes were employed therein. In 2000, the amount of raw coal treated totaled 337 million tons with a treatment rate of 33.7%. Among the different washing methods used, the jigging, heavy medium separation, flotation, and dry cleaning and other methods accounted for 52%, 28%, 14% and 6% respectively. Starting from the onset of the 21th century, as the source of clean coal technology and a crucial basis for realizing clean and high-efficiency utilization of coal, the coal preparation sector was seen to enter a rapid growth phase which was characterized by the predominant use of heavy medium separation method, emergence of large-size and intensive plants, sharp rise of power coal treatment rate, and transition of production of only fuel coal to production of both fuel coal and chemical materials. In the 13th Five-Year Plan period, the successful application of the all-wet, all-heavy-medium separation system with an annual capacity of over 10 million tons, the high-capacity dry cleaning technology, low-rank coal slime flotation technology and underground raw coal destoning technology pushed China′s coal preparation technology to stand globally at either forefront or a leading position. By 2020 the raw coal treatment rate and comprehensive utilization rate of refuse had reached 74.1% and 72.2%, respectively. Up to the year 2021, 2400-plus plants above the designated scale were in operation with an combined treating capacity of 3.4 billion tons a year, and the average treating capacity of an individual plant increased to 1.4 Mt/a from 300,000 t/a in 2000. The number of superlarge plants each having a capacity of over ten million tons a year amounted to 84, reaching an aggregate capacity of over 1.3 billion tons a year, which accounted for 38.2 percentage of the total raw coal treated in that year. Among the cleaning methods employed, the jigging heavy-medium separation, flotation, and dry cleaning and other methods accounted for 8%, 80%, 6%, and 6%, respectively. Several dozen of plants reached the medium level in terms of intelligentization. In order to meet the needs for reaching the strategic goals of achieving carbon peaking and carbon neutrality, promote supply-side structural optimization, upgrade consumption-side energy efficiency, it is proposed to strengthen the research work on separation of macerals, dry cleaning of fine coal, upgrading of bulk low-rank coal slime, comprehensive utilization of refuse and making breakthrough in basic theory of coal preparation. Plus, endeavors should be made to clean all the coal that needs to be separated, so as to promote the transition and upgrading of the coal preparation industry to make it safer, greener, smarter and more efficient.