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“The “eaves effect” enables comprehensive coal pyrolysis Author/Source: Collaborative Group on Advanced Processing and Hydrogenation of Coal Tar Date: 2022-05-15 Views: 24 Recently, Shaanxi Dongxinyuan Chemical Co., Ltd. achieved a daily production volume of 5,827.4 tons of semi-coke, breaking its own historical record and becoming the first company in China to exceed the designed production capacity for semi-coke. This is another notable achievement for the company: by applying its independently developed core technology, the “eaves effect”, it has carried out technical upgrades on its carbonization furnace equipment, thereby improving the quality and output of clean coal. This accomplishment fills a gap in China regarding the comprehensive pyrolysis of coal across all particle sizes—fine coal, granular coal, and lump coal. The upgrading of coal, also known as coal pyrolysis, refers to a complex process in which coal is heated in an air-free environment, resulting in a series of physical and chemical changes. It serves as the key to the efficient and clean utilization of coal based on its different quality levels. Coal pyrolysis can be classified into various types of carbonization furnaces based on the heating method, such as external heating, internal heating, and combined external and internal heating. Among these, the most representative and widely used method is the endothermic rectangular furnace process, which has resulted in an annual production capacity of nearly 60 million tons in Yulin, Shaanxi. However, this process also has some shortcomings, including a limit of 38 pieces of raw coal per batch (with a particle size of 30–80 millimeters), as well as high production costs. The furnace has poor air permeability, and the flame nozzles inside the furnace tend to clog due to slag formation, which results in uneven furnace temperatures and affects the control of the pyrolysis temperature as well as the stable operation over long periods of time. At the same time, coal cinder dust mixes into the gas, forming colloids with tar, which affects its quality. In recent years, Dongxinyuan Company has focused on the clean and efficient utilization of coal in a differentiated manner, conducting research and development along the lines of coal pyrolysis, comprehensive utilization of waste gas from coal processing, and advanced processing of coal tar. Over a period of more than 5 years, it has carried out over 3,000 technical upgrades, resulting in a series of key innovative technologies. The 1.8 million tons/year semi-coke production facility of Dongxinyuan Company also utilizes an internally heated vertical carbonization furnace. The company has ambitiously set its goal on the comprehensive pyrolysis of coal across all particle sizes—fine coal, seed coal, and lump coal—in order to reduce production costs. Since the air inlets on the furnace channel walls of vertical furnaces are usually horizontal holes that come into direct contact with the falling powder, this leads to excessively high local temperatures at these inlets, causing coking and blockages. As a result, the temperature control in the carbonization furnace becomes uneven and its operation becomes unstable. The company worked hard on improving these air inlets, developing innovative optimization designs, and created a patented core technology known as the \"eaves effect,\" which helped to remove obstacles to comprehensive pyrolysis processes. “The so-called ‘eaves effect’ refers to the fact that we designed a specially shaped flue brick for vertical furnaces, creating a cavity between the air inlet and the coal material, just like the eaves of a rural house. ”Song Ruchang told the reporters that with this cavity, the technical problem of coking and blockage at the air inlet has been solved. In September 2021, Dongxinyuan Company began to carry out technical upgrades on two carbonization furnaces, including modifying their internal structure, increasing the area of the nozzles, and preventing blockages in those nozzles. The upgrades were carried out sequentially using a method that allowed operations to continue without interruption. As of April this year, the company has completed a total of 5 carbonization furnaces, accounting for one-third of the total 15 furnaces. At the site of Dongxinyuan Company’s semi-coke production facility, it was observed that after simple processing, all types of coal—pulverized coal, fine coal, and lump coal—were fed into a single process for comprehensive pyrolysis. Ji Yanfei, the director of the Lanthanum Carbon Gas Production Plant, explained that after the modification of the carbonization furnaces, thanks to more complete combustion within the furnaces and more precise temperature control, the technical problem of coking at the burner openings was resolved. Compared to traditional vertical rectangular furnaces, the modified furnace not only broadens the range of usable raw materials; the daily outputs of semi-coke, coal tar, and coal gas have increased by 29%, 50%, and 20% respectively. Moreover, it has enabled the plant to operate in a stable, reliable, continuous, fully utilized, and efficient manner, with a notable improvement in the quality of the semi-coke produced. In 2021, Dongxinyuan Company produced 1.77 million tons of semi-coke, achieving the highest production capacity among similar facilities in the industry. The company produced 539,000 tons of semi-coke in the first quarter of this year, an increase of 87,000 tons compared to the previous year. Currently, at Dongxinyuan Company, the amount of coal fed into the furnace per ton of semi-coke has been reduced from over 1.55 tons to less than 1.4 tons. The overall energy consumption for producing semi-coke is merely 67.53 standard coal equivalents per ton, which is far below the industry’s advanced benchmark of 190 standard coal equivalents per ton. As a result, production costs have been significantly cut, and energy consumption levels have dropped considerably. It is reported that the remaining 10 carbonization furnaces will be upgraded one after another within this year. On November 20, 2021, at an evaluation meeting organized by the Shaanxi Provincial Petroleum and Chemical Industry Federation, expert participants spoke highly of Dongxinyuan Company’s comprehensive pyrolysis technology. They noted that the company utilizes full-particle-size low-rank coal pyrolysis technology as its core, and employs a technology for producing clean fuel oil from hydrogen and coal tar. This process boasts high energy efficiency and low carbon dioxide emissions, thereby forming an innovative industrial chain for the clean and efficient conversion of coal based on its quality characteristics. The experts recommended accelerating the industrial application and promotion of this technology.