The general trend of the energy production and consumption revolution is the clean and efficient use of energy. Facing increasingly prominent energy and environmental problems, promoting energy transformation and achieving clean and efficient use of energy have become important tasks for China's energy development. It is predicted that China's energy consumption demand will continue to grow steadily until 2030. The increase in energy consumption will mainly be provided by clean energy, but the annual coal consumption will remain at about 3.5 billion tons.
Therefore, the clean and efficient conversion of coal is an important support for winning the battle against pollution and defending the blue sky, and is an important content of the coal energy revolution. After years of research and technological development, the coal clean and efficient conversion technology has made a series of breakthroughs and has become an important support for the sustainable and healthy development of China's coal industry.
Coal is an important basic energy and chemical raw material in China, which provides important support for national economic development and social stability. At present, the main uses of coal are direct combustion power generation and industrial heating, which are generally inefficient and polluting. This not only causes a huge waste of resources, but also causes severe environmental pollution and a large amount of greenhouse gas CO2 emissions. China's proven recoverable reserves of oil and gas are only 10% and 3% of the world's per capita value.
n 2018, China ’s net oil imports were 440 million tons, an increase of 11% year-on-year, and its dependence on foreign countries was as high as 69.8%; natural gas imports were 125.4 billion cubic meters, a year-on-year increase of 31.7%, and its foreign dependence was 45.3%. Clean and efficient conversion of coal can not only alleviate the tight situation of China's energy supply and ensure national energy security, but also an inevitable choice to build a clean, low-carbon, safe and efficient energy system in China.
Survey of Clean and Efficient Conversion of Coal at Home and Abroad
The development of coal conversion is mainly affected by factors such as resource conditions, changes in oil prices, technical equipment levels, and government policies. In terms of clean coal conversion, foreign countries started earlier. Western developed countries and major coal consumer countries have been supporting the research and development of clean coal conversion and related technologies, and have mastered a series of core technologies.
Although foreign countries have certain advantages in basic research and key technology research and development of coal transformation and utilization, they are still in the high-end technology research and development and reserve stage. Due to the different energy structures of different countries, investment in R & D and industrialization in the field of clean coal conversion is different. Currently, only a few countries such as South Africa and the United States have carried out some project demonstrations and commercial operations.
In recent years, China's technology in clean coal conversion has developed rapidly and achieved a series of major results. Successfully developed 2000-3000 tons / day coal water slurry and dry coal powder gasification technology and put it into commercial operation. 1 million tons / year direct coal liquefaction demonstration project and 4 million tons / year indirect coal liquefaction demonstration project were completed and put into operation. 10 A number of 600,000 tons / year methanol-to-olefin industrial units were put into commercial operation.
Major technologies for clean and efficient coal conversion
Coal conversion and utilization technology is the chemical conversion of coal into gas, liquid and solid products or semi-products, and then further processed into energy and chemical products. At present, clean and efficient conversion and utilization of coal are mainly divided into pyrolysis, gasification, and liquefaction (direct liquefaction and indirect liquefaction). The coal chemical industry currently under development is mainly a modern coal chemical industry based on traditional coal chemical industry and aimed at the clean utilization and efficient conversion of coal.
1. Coal pyrolysis technology
Coal pyrolysis technology is to extract the hydrogen-rich components in coal by pyrolysis to extract chemical raw materials or high-quality liquid fuels to improve coal utilization efficiency. After the energy crisis in the 1970s, coal pyrolysis technology has been widely valued by scholars from various countries, and a variety of new pyrolysis technologies and processes have been developed, such as the American Food Machinery Corporation (FMC) and the Office of Coal Research (OCR, Office of Coal Research) COED pyrolysis process, and rapid coal pyrolysis technology developed by Japan Coal Energy Center and Japan Iron and Steel Group.
China is the country with the most active R & D and investment in coal pyrolysis technology in the world. Table 1 shows the typical coal pyrolysis technology in China. At the current stage, coal-pyrolysis-based cogeneration technology has shown obvious advantages in energy conservation and consumption reduction, and should be based on the principle of demonstration and promotion in suitable regions, and develop a large-scale, integrated pilot coal chemical industry. . The technical bottlenecks of coal pyrolysis technology such as difficult product gas-solid separation, low oil and gas yield or poor quality, low energy utilization efficiency, serious environmental pollution, and low industrialization level still require a lot of research by relevant companies and research institutes.
2. Coal gasification technology
Coal gasification is one of the core technologies for efficient and clean utilization of coal. It is a leader in modern coal chemical industry, whether it is coal liquefaction based on oil products, or coal chemical based on chemical products such as ammonia, methanol, and olefins. Choosing the right coal gasification technology is the key to the entire production process. Since the 1980s, China has successively introduced a variety of coal gasification technologies, including German Lurgi technology, American Texaco technology, Dutch Shell technology, and German GSP technology.
However, these technologies have the disadvantages of unstable operation, high investment, and poor adaptability to domestic coal types in the process of localization. In recent years, in accordance with China's actual situation, a variety of independent and innovative coal gasification technologies have been developed (Table 2). By the end of 2017, there were a total of 318 gasification furnaces with independent intellectual property rights, gasification capacity of 377,000 tons / day, and a total market share of 51.6%. China's independent innovation coal gasifier is more suitable for China's national conditions and coal types, and has made great contributions to the development of China's coal chemical industry. The goals of large-scale coal gasification technology, truly achieving zero sewage discharge, comprehensive utilization of slag waste and solids, and drastic reduction in water consumption are the focus of coal gasification technology research.
3. Direct coal liquefaction technology
Direct coal hydro liquefaction technology is the direct conversion of coal and hydrogen into liquid oil by hydrocracking under the action of a catalyst. Direct coal liquefaction products can be used as oil products for military and civil aviation aircraft, rockets and armored vehicles to meet China's increasing demand for special oil products. After 1973, coal liquefaction processes were successively developed in western countries due to the oil crisis, but only in the laboratory research and pilot development stages.
Shenhua Group has started research and development of direct coal liquefaction fuel preparation technology since the "10th Five-Year Plan" period. In 2010, it completed the construction of the world's first million-ton liquefaction plant and became the leader in direct coal liquefaction industrialization. Direct Liquefaction Core Process Enlargement "" Manufacturing and Installation of Very Large Equipment "" Safe and Stable Long-Term Operation of the First Industrialized Demonstration Unit "Three Global Technical Problems, and Has Obtained US, Japan, Russia, Australia, Canada, Ukraine, India Patents in 9 countries including Indonesia and Indonesia. At present, the liquefaction technology still has problems such as large hydrogen consumption, light weight of products, imbalance of solvent oil, and low oil yield, which need to be further optimized and improved through long-term stable operation.
4.Indirect coal liquefaction technology
Indirect coal liquefaction is a technology that first converts coal gas to syngas, and then uses a certain catalyst to convert the obtained syngas into various liquid fuels and chemicals under appropriate temperature and pressure. South Africa's Sasol's coal indirect liquefaction technology is the world's earliest commercialization technology; in addition, other petrochemical companies in the world have also carried out a lot of research and development work for a long time, typically the Dutch Shell Company ’s SMDS technology , Mobil's MTG synthesis technology, etc.
At present, China's coal indirect liquefaction technology has entered the stage of commercial development. Shanghai Yankuang Mining Co., Ltd. has carried out research and development of coal indirect liquefaction technology since 2002, and successfully developed three-phase slurry bed low-temperature Fischer-Tropsch synthesis and high-temperature fixed fluidized bed fees. Support synthesis technology. Zhongke Synthetic Oil Technology Co., Ltd. has developed a complete set of high-temperature slurry-bed Fischer-Tropsch synthesis and oil processing technology, forming an integration of "basic research-engineering technology development-engineering design and contracting-catalyst production-special special equipment processing and manufacturing" Technology research and development and industrialization support system.
The world's largest single-scale Shenhuaning coal 4 million tons / year coal indirect liquefaction and oil industry demonstration unit was successfully built and put into production using independent research and development technology of Zhongke Synthetic Oil Technology Co., Ltd., which was successfully put into operation on December 21, 2016 and December 2017 On the 17th, the entire line achieved stable and full load operation, marking a substantial step in China's energy strategic technology reserves. As of the end of 2018, seven coal indirect liquefaction projects have been completed in China, with a total capacity of 7.7 million tons per year (Table 3). Currently, the demonstration projects have achieved long-term stable operation. With the successful operation of these demonstration projects, China's coal-to-liquid technology has been further verified.
Progress of Clean Coal Conversion Technology in Chinese Academy of Sciences
The research and development of clean and efficient coal utilization technology has always been the dominant strategic direction of the Chinese Academy of Sciences. More than 30 years ago, the Chinese Academy of Sciences strategically deployed clean conversion and utilization technologies such as coal-to-liquid, coal-to-olefin, and coal-to-glycol for the energy structure of China's coal-rich and lean oil. Today, self-developed clean utilization technologies such as coal combustion, coal-to-olefins, coal-to-glycol, and coal-to-oil have emerged from the cocoon and are among the internationally advanced.
Circulating fluidized bed combustion technology has been widely used; the world ’s first 600,000-ton coal-to-olefins plant operates steadily, with an annual coal-to-olefins capacity of 10 million tons; the 200,000-ton coal-to-ethylene glycol industry demonstration technology is becoming more complete; The 160,000-180,000-ton demonstration unit of oil technology has been operating stably, and various technical indicators are leading internationally. The 4 million-ton / year synthetic oil production project has reached full system full-load operation.
During the "Twelfth Five-Year Plan" period, the Chinese Academy of Sciences focused on the strengths of 10 research institutes while maintaining its traditional advantages, and organized the implementation of the strategic pilot science and technology project "Key Technologies and Demonstrations for Clean and Efficient Cascade Utilization of Low-rank Coal". A special study puts forward a solution for comprehensive utilization of low-order coal with high energy efficiency, low pollution, low emissions, and high value that is suitable for the characteristics of China's resources. -Fischer-Tropsch synthesis-oil co-processing "and" pyrolysis-gasification-synthetic liquid fuels and chemicals "three clean and efficient step utilization methods.
Through the special implementation, it has broken through many major strategic and key technologies such as pyrolysis, combustion, gasification, synthesis, and CO2 utilization, and has completed several major demonstration transformation projects to accelerate the development of the new generation of coal chemical industry and clean and efficient combustion power generation industry. Promote the structural adjustment and upgrading of China's coal utilization industry and regional economy, and have a profound impact on the healthy development of our economy.
Key Directions for Clean and Efficient Conversion of Coal
After decades of efforts, China has mastered modern coal chemical technologies such as coal-to-liquid, coal-to-olefin / aromatics, and coal-to-ethylene glycol. The industrialization of technology is also at the forefront of the world, and the enthusiasm for development in various places is also high. However, some problems exist in coal chemical projects due to lagging planning, inconsistent understanding, local government requirements for local transformation, and blind investment by enterprises.
In terms of medium and long-term planning, the clean and efficient conversion and utilization of coal in China mainly focuses on the national economic and social development strategic needs. Aiming at the key scientific and technological bottlenecks in the development and utilization of coal in our country, through theoretical innovation, technological innovation and management innovation, we can build a clean and efficient coal mine in China Continue to develop and utilize technology and management systems, focus on breakthroughs in key technologies, carry out engineering demonstration verification, realize technological integration and innovation, and greatly improve the level of independent innovation and comprehensive technical capabilities of China's coal development and utilization.
By 2030, realize the transformation of coal into a scientific development mode, and the scientific coal production capacity will increase from about 55% to more than 90%. It will break through a batch of key technologies and major equipment, and form a technology system for harmless development and resource utilization of coal mines. International standard setter and technology leader in coal development.
In the future, China ’s research on the clean and efficient conversion and utilization of coal will focus on the research on basic scientific issues in the reaction and catalysis of direct conversion of coal / syngas to fuels and chemicals; research on key technologies for coal-based clean gas, key technologies for coal-based liquid fuels and bulk chemicals Wait.
Clean Fuel from Coal Conversion
1. Coal gasification and natural gas production technology
Research on large-scale and efficient coal gasification technology suitable for China's typical coal types, develop high-reliability coal sensible heat recovery technology and medium-temperature coal dust removal and purification; develop new gas targets such as supercritical coal gasification, hydrogenated coal gasification, and catalytic gasification 化 技术。 Technology. Develop high-efficiency, low-cost coal-to-natural gas catalysts; develop short-flow, low-cost coal-to-natural gas processes; integrate and optimize technologies for coal-to-natural gas process energy and quality, improve coal-to-natural gas energy conversion efficiency; and reduce production energy and water consumption.
Expected results: Breakthrough in key technologies for large-scale coal gasification adapted to typical coal types in China, achieve long-term safe and stable operation, reduce gasification investment costs by about 30%; break through large-scale key technologies for industrialization of coal-based natural gas, and form independent intellectual property rights The short-process clean coal-to-natural gas technology has significantly improved energy efficiency; 4 billion cubic meters of coal-to-natural gas projects can all use domestic technologies and catalysts, which significantly reduces the cost of catalysts.
2. Coal liquefaction to produce oil
Develop new technologies and catalyst technologies for coupling coal mild hydrogenation and indirect liquefaction, develop technologies for liquefied oil production of fuels, high-value oil products, oxygen-containing clean fuels, and chemicals, and study comprehensive utilization technologies of high-end carbon materials and asphalt from liquefaction residue , Research on direct liquefaction-Fischer-Tropsch synthesis integrated coupling technology and carry out engineering demonstration.
Expected Result: Complete direct-indirect liquefaction coupling and co-production of special oil and aromatics industrial technology verification for million-ton coal, system energy efficiency is more than 55%, and system water consumption is reduced by 30%; mild hydrogenation liquefaction for million-ton coal Industrial technology verification.
Coal-based bulk chemicals
1. Technology for preparing oxygenates from coal conversion
Carry out research on the synthesis of oxygenates from coal via synthesis gas or methanol, develop high-activity and high-selectivity catalysts and complete reaction processes; develop complete sets of oxygen-containing clean fuel / chemical technologies such as coal-to-ethylene glycol, ethanol, and low-carbon mixed alcohols.
Expected Result: Technical verification of 500,000 tons / year coal-to-ethylene glycol industrial unit completed; complete technology development of coal-to-polymethoxy dimethyl ether, synthesis gas to low-carbon alcohol, and coal to ethanol development; Demonstration device verification. A complete set of technologies such as direct synthesis of ethanol from syngas.
2. Coal conversion to olefin / aromatics technology
Investigate methanol-to-olefin catalysts and processes with high efficiency, high olefin yield, and flexible control of ethylene and propylene; study high-performance catalysts, reactors, and complete process technologies for methanol to aromatics. Developed a composite high-efficiency catalyst for direct synthesis of olefins / aromatics.
Expected results: Industrial technology verification for million-ton methanol-to-olefins and methanol-to-aromatics completed; formation of a complete olefin / aromatics synthesis gas synthesis technology, in which the selectivity of target products for direct conversion of synthesis gas reaches more than 80%, and the comprehensive energy efficiency of syngas improve.
