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Steam coal with supercritical water: put an end to coal burning pollution from the source
Added:2019-10-09     Views:     Typeface:【LargeMiddleSmall

At present, coal is the main energy in our country, but a large number of coal-fired has serious pollution. Traditional coal-fired, coal-fired boilers and their power generation technologies all adopt the form of "burning coal by fire". The total energy efficiency and coal electricity conversion rate are low, pollution is serious, water consumption is large, and the cost of desulfurization, denitrification, dust and carbon dioxide elimination is high.

The scientific research team, led by Guo Lijin, academician of Chinese Academy of Sciences and professor of State Key Laboratory of multiphase flow of power engineering of Xi'an Jiaotong University, has developed a series of completely independent intellectual property technologies, commonly known as "supercritical water gasification of coal for hydrogen generation" after 20 years of scientific and technological research, and successfully transformed coal chemical energy into hydrogen energy directly and efficiently from the source. The formation and emission of sulfide, nitride and PM2.5 were eliminated.

Major achievements industrialization project with a price of 150 million

On December 25, 2016, the first major scientific research achievement industrialization project of Xi'an Jiaotong University - "coal supercritical water gasification hydrogen generation multi generation technology" was officially launched. Major leaders of the Ministry of education, NSFC, NEA, CNNC, Shaanxi Province and Xi'an Municipal Government participated in the kick-off and report meeting of industrialization of the project.

On the same day, Xi'an Jiaotong University transferred the intellectual property rights and related technologies of the technological achievements to the mixed ownership technology industrialization investment company, super clean energy of Shaanxi Zhonghe Jiaotong University, which was jointly founded by CNNC quanlian investment fund management (Beijing) Co., Ltd., Hong Kong Rifu Investment Co., Ltd. and Xi'an Beiqi Energy Technology Development Co., Ltd. at a price of 150 million yuan. Source Technology Co., Ltd. The company raised 1 billion yuan to demonstrate the industrialization of the technology. Taking 50MW power generation and cogeneration units, alternative products of coal-fired industrial heating steam boiler as the starting point of the project demonstration, it is determined to complete the construction and operation of the project within three years, and accelerate the promotion and demonstration of the technology in coal efficient and clean utilization, environmental protection, etc.

"This technology is also being studied abroad, but it's all behind us. They did not form a large-scale continuous production device. Our large-scale pilot plant has been running for thousands of hours without any problems. " "At present, various coal chemical enterprises also produce hydrogen and steam, so as long as some units are replaced, they can be used," Guo said. This technology can be used by all industrial enterprises that use coal as raw material. "

New technology ends "burning coal by fire"

As soon as the "supercritical water coal steaming" technology of Xi'an Jiaotong University came into being, it caused a shock in the industry and aroused widespread concern in the society.

"As a revolutionary technology," supercritical water steam coal "is fundamentally different from traditional coal-fired power generation and coal gasification power generation. Traditional coal-fired power generation, including coal gasification power generation, is to put coal in the air, use fire to burn, and generate oxidation reaction with oxygen, which is an exothermic process. This kind of heat energy can be used. The hot gas flows in the coal-fired boiler, is absorbed by the water in the boiler, and then becomes water vapor, which drives the steam turbine to do work. This is often called steam turbine power generation. Compared with steam turbine power generation, there is also a higher efficiency, called gas turbine power generation. Because the material of the device needs more high temperature resistance and higher performance requirements, the processing technology is particularly difficult. " Guo liejin told Science and technology daily, "the oxidation reaction will naturally produce sulfur dioxide and nitrogen oxides, plus the particulate matter raised during coal combustion, which is what PM2.5 comes from!" If the enterprise wants to desulfurate, denitrate and dedust in the future, it needs to install dedusting device. This cost is very high for enterprises. Running these devices at the same time consumes energy. In this way, the overall efficiency is not high. On average, it is more than 40 percent. "

Supercritical water refers to water when the pressure and temperature reach a certain value (nearly 22Mpa, 374 ℃), the density of water expanded due to high temperature is exactly the same as that of water vapor compressed due to high pressure. At this time, there is no difference between the liquid and gas of water, and they are completely blended together, becoming a new kind of liquid with high pressure and high temperature. Guo Liejin used the popular language to describe the progressiveness of "supercritical water steam coal" technology: "we do not need air to enter the technology, just mix coal and water and let them react." The whole process is not oxidation reaction, there is no traditional combustion process, but reduction reaction. Hydrogen is burned, water is obtained, the product is clean, and supercritical water vapor with high temperature and pressure is obtained, which can also make the steam turbine work. The efficiency is higher than the traditional one, and there is no pollution. "

Guo Lijin's team has successfully developed a series of experimental facilities, including supercritical fluidized bed, which can complete the complete vaporization of coal. Above 700 ℃, the carbon gasification rate of all kinds of coal types in China has reached 100%. The integration and optimization of thermodynamics, chemical reaction kinetics model and reaction system for hydrogen production by supercritical water gasification have been completed. The pilot scale demonstration system with coal treatment capacity of 1t / h has been successfully completed. Through technical and economic analysis, when the coal treatment capacity of the system reaches 83.3t/h, the price of hydrogen can be reduced to 0.7 yuan. Based on supercritical water coal gasification and multi-stage hydrogen fueled steam turbine, a new type of thermal cycle power generation system has been proposed. The main characteristics of the system are high efficiency of coal power generation, carbon dioxide enrichment and environmental friendly and pollution-free. In order to solve the problem thoroughly, this technology has completely completed the theoretical innovation, laboratory regular experimental research and pilot test.

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