Zhonghe gasification appeared at the 2021 China nitrogenous fertilizer and Methanol Technology Conference: create an environmental protection closed loop for the synthetic ammonia gasification section. Ammonia is the main raw material for the chemical fertilizer industry and basic organic chemical industry. The production process of synthetic ammonia is also one of the sources of environmental pollution. According to statistics, at present, China's nitrogen fertilizer industry still has a production unit capacity of atmospheric pressure intermittent fixed bed gasification process of nearly 20 million tons / year, accounting for about 40% of the total production capacity. Its production process produces a large number of "three wastes" pollutants. In 2021, "carbon peak and carbon neutralization" were written into the government work report, and it was emphasized that "strive to achieve carbon peak by 2030 and carbon neutralization by 2060". The road of carbon neutralization transformation is being opened, and the environmental protection transformation of synthetic ammonia industry has also become the focus of relevant enterprises. Yu Kuangshi, general manager of Zhonghe gasification, made a keynote report at the 2021 China nitrogenous fertilizer and methanol technology conference
At the 2021 China nitrogenous fertilizer and Methanol Technology Conference opened on July 21, Zhongke Hefei Coal Gasification Technology Co., Ltd. (hereinafter referred to as "Zhonghe gasification") put forward a series of comprehensive disposal schemes for the environmental protection transformation of coal gasification technology in the synthetic ammonia industry, including circulating fluidized bed gasification (CGAs) to syngas, resource utilization of gasification fine slag, fixed bed intercooling transformation and other technologies, From the source process of coal to gas to the disposal of gasification fine slag that puzzles entrained flow bed users, and then to the environmental protection transformation of traditional fixed bed gasification, a closed loop of harmless treatment has been formed.
How is this comprehensive solution implemented? Yu Kuangshi, general manager of Zhonghe gasification, made a detailed interpretation at the meeting.
Circulating fluidized bed coal gasification (CGAs) technology solves problems from the source
Clean and efficient utilization of coal is the source of solving carbon emission. At present, in the synthetic ammonia industry, coal gasification technology is divided into three categories: fixed bed, fluidized bed and entrained flow bed. Fixed bed gasification is a "veteran" technology in the field of synthetic ammonia, but this technology can only use high-cost lump coal and has serious pollution; The entrained flow bed is not suitable for small and medium-sized synthetic ammonia enterprises because of large initial investment, long construction cycle and high operation cost. Compared with the above two technologies, CGAs technology has the advantages of strong coal adaptability, low operation cost, short construction cycle, good environmental protection indicators, high matching with the scale of small and medium-sized synthetic ammonia enterprises and no need to stop production during transformation. Therefore, CGAs technology has also become the best choice for such enterprises. Yu Kuangshi, general manager of Zhonghe gasification
With the support of the national "863" program, the Institute of Engineering Thermophysics, Chinese Academy of Sciences has successfully developed circulating fluidized bed gasification (CGAs) technology. In order to better promote the industrialization of this technology, in 2016, the Institute of Engineering Thermophysics cooperated with Anhui Chaohu Economic Development Zone to establish Zhonghe gasification.
Yu Kuangshi said: "the conversion efficiency and performance index of the circulating fluidized bed gasification system after coupling fine slag treatment are not lower than that of the entrained flow bed, but the project investment is only 50% of the entrained flow bed, which provides an innovative path for the gas making section for small and medium-sized synthetic ammonia enterprises." Xinjiang Yihua coal gasification unit project site
CGAs technology has the core advantages of strong coal adaptability, low energy consumption and cost, high overall energy efficiency, high technical reliability, flexible load regulation and low emission of three wastes. In 2020, Zhonghe gasification completed the Xinjiang Yihua coal gasification unit project, which is the first circulating fluidized bed gasification system in China to produce syngas from high alkali coal. Before the transformation, the synthetic ammonia gasification unit in Yihua, Xinjiang had problems in wastewater and tar discharge, and the coal consumption, oxygen consumption and steam consumption were large. CGAs technology solves the problems of strong contamination of high alkali coal, easy coking, large fluctuation of ash melting point, poor slurry forming, and the inability to use gasification processes such as fixed bed slag, entrained flow bed coal water slurry and entrained flow bed pulverized coal, which reduces the cost per ton of ammonia by more than 200 yuan. At the same time, it provides technical and equipment support for the efficient and clean utilization of high alkali coal with huge reserves in Xinjiang. In the same year, Guizhou Hongsheng chemical gas head reconstruction project constructed by CGAs technology was also successfully applied to synthetic ammonia production. Ten fixed bed gasifiers were replaced by one gasifier, and local anthracite with low activity and difficult gasification by traditional technology was used. The gas production is more efficient, clean and cheap. The unit is the first circulating fluidized bed gasifier with anthracite as raw material in China, Its successful operation was selected as the "highlight of the transfer and transformation of scientific and technological achievements in 2020" of the Chinese Academy of Sciences.
At present, CGAs technology has realized the rapid industrial application in the field of coal to clean industrial gas and coal to synthetic ammonia feed gas, and has completed more than 70 industrial product level applications in more than 30 users in alumina, metal magnesium, casting and other industries.
CGAs technology realizes the efficient and clean utilization of different coals. As a pulverized coal gasification technology, circulating fluidized bed will produce some fine slag in the process of coal gasification, just like entrained flow bed. For the treatment of fine slag, Zhonghe gasification also has a set of "special tricks".
The resource treatment of gasification fine slag has increased the income of enterprises by hundreds of millions
In recent years, with the popularization of entrained flow bed and circulating fluidized bed technology, the disposal of gasification fine slag has become a major problem perplexing enterprises. At present, the treatment of fine slag is mainly based on low-value utilization such as landfill or brick making. Yu Kuangshi takes an example: "a medium-sized enterprise using entrained flow gasification produces about 700 tons of fine slag a day, accumulating more than 200000 tons a year, but the storage capacity of the landfill is limited, which will restrict the production of the enterprise in serious cases."
Therefore, seeking the reduction and harmless treatment of fine slag has become a common concern of the industry. To solve this problem, the Institute of Engineering Thermophysics of Chinese Academy of Sciences has developed preheating melting gasification technology and residual carbon combustion technology. Gasification fine slag basically does not contain volatile matter, has poor reaction activity, is not easy to burn or gasify, and is difficult to be treated with conventional technology. For users who need syngas, the preheating melting gasification technology can be used to gasify the fine slag into syngas. This gasification technology breaks through the technical problems such as fine slag particle size, low volatile content, high ignition temperature and difficult comprehensive utilization. At the same time, this technology can cooperate with the treatment of hazardous wastes containing heavy metals and fix the heavy metals in harmless glass. For users with steam demand, circulating fluidized bed combustion technology is used to produce ultra-high temperature and ultra-high pressure steam with the heat generated after combustion, and clean and efficient cascade utilization of coal is realized through system integration. The two technologies can not only reduce and harmless treatment of fine slag, but also realize resource utilization.
In 2020, Zhonghe gasification signed a 290t / D fine slag fusion gasification project with Shandong Rongxin Group Co., Ltd. to treat fine slag by preheating fusion gasification technology. After the project is put into operation, the hazardous wastes in the plant can be treated together, which not only saves the disposal cost, but also the produced syngas will be used to synthesize ethanol, which is expected to increase the income of hundreds of millions of yuan for the enterprise every year.
The resource utilization technology of fine slag can be expanded to more fields. The collaborative disposal of other carbon based industrial solid wastes, such as coal slime and pulverized coal ash, not only widens the utilization ways of carbon based solid wastes, but also reduces the production cost of end products.
Intercooling transformation technology extends the service life of fixed bed
With the tightening of national environmental protection policies year by year, fixed bed technology will gradually withdraw from the historical stage. However, for some small and medium-sized synthetic ammonia enterprises with limited bearing capacity, the cost of complete withdrawal of fixed bed is too high and still takes time.
So, in the face of urgent environmental protection problems, what should these small and medium-sized enterprises do? The transformation of seriously polluted section has become a feasible path, and the relevant policies have also made clear requirements for it. In the comprehensive treatment plan for air pollution of industrial furnaces and kilns and the comprehensive treatment plan for volatile organic compounds in key industries (Exposure Draft), it is pointed out that "if fixed bed intermittent gasifiers are used in nitrogen fertilizer and other industries, accelerate the change of gas cooling from direct water washing to indirect cooling."
What is the difference between "direct water washing" and "indirect cooling"? Yu Kuangshi explained that during the purification and cooling process of gasification, the direct water washing method leads to the direct contact of tar, phenol cyanide and other harmful substances with water, resulting in chemical wastewater, which is difficult to treat. Indirect cooling avoids the contact between pollutants and water through indirect heat exchanger, dry and wet separation and separate treatment, so as to reduce the difficulty of subsequent treatment and improve the environmental protection benefits. Site visit of Shanxi Jinfeng fixed bed gasification indirect cooling upgrading project
It is noteworthy that this set of indirect cooling and dry dust removal process is the purification and cooling system that has been applied in the circulating fluidized bed coal gasification unit for many years. Based on this, Zhonghe gasification has innovatively developed a set of indirect cooling technology suitable for the transformation of intermittent fixed bed, which closely combines the widely verified water-cooled cyclone pre dust removal, dry dust removal and indirect cooling technology, It forms an integrated process of gas dust removal, purification and indirect cooling, which solves the problem of high pollution of direct cooling circulating water while recovering gas dust. The separated dust is transported to the ash bin in the plant by pneumatic ash transportation, and the ammonia nitrogen component in the condensate is reused by ammonia evaporation system. Site visit of Shanxi Jinfeng fixed bed gasification indirect cooling upgrading project
The technology has been implemented in the fixed bed indirect cooling upgrading project of Tianyuan, Jinxiang and Jinfeng enterprises under Jinneng holding group. At the site of Jinfeng project, the dry dust is transported to the ash bin through the closed bin pump and then loaded through the automobile bulk machine. Although the conveying is dry dust, there is no dust in the whole process, which is fully automated, and the treated condensate is also transparent. Water quality difference before and after intercooling transformation
Chen Zhiyun, assistant general manager of Jinneng holding equipment manufacturing group regional company, said that the intercooling system of Tianyuan company has been put into operation since January 2021, and the detection index of dust content at the outlet of intercooling bag is less than 10mg / Nm3, which has solved a common problem of environmental protection for coal chemical enterprises. Therefore, Jinmei Tianyuan was rated as the only "B-class environmental protection enterprise in Jincheng city" and qualified to not stop production in polluted weather. Chen Zhiyun, assistant general manager of Jinneng holding equipment manufacturing group regional company, made a report on inter cooling transformation at the meeting
From circulating fluidized bed coal gasification (CGAs) technology to intercooling transformation technology of fixed bed, Zhonghe gasification provides two environmental protection transformation schemes with low cost and high efficiency for small and medium-sized synthetic ammonia enterprises. At the same time, for the fine slag generated by entrained flow bed and fluidized bed, Zhonghe gasification also puts forward reduction, harmless and resource-based solutions to form an environmental protection closed loop in the gas making process of synthetic ammonia. The above scheme can also be applied to coal to methanol, coal to hydrogen and other industries.
In the future, Zhonghe gasification and Engineering Thermophysics Research Institute will adhere to the "two wheel drive" strategy, closely follow the industry demand, continue technological innovation, improve the utilization rate of coal energy, promote source emission reduction, save energy and improve efficiency under the "double carbon" strategy, and help the downstream products of coal chemical industry develop towards refinement and high added value with high-quality syngas.
