The representative direct coal liquefaction processes in the world include the new liquefaction (IGOR) process in Germany, the HTI process in the United States and the NEDOL process in Japan. The common characteristics of these new liquefaction processes are that the reaction conditions of coal liquefaction are much milder than those of the old liquefaction process, and the production cost is reduced, and the pilot scale-up test has been completed. At present, there is no industrial production plant, mainly because the production cost is not competitive compared with cheap oil. The future development trend is to reduce the ash and inert components of coal by developing more active catalysts and top treatment of coal, and further reduce the production cost.
I the Igor process in Germany
198 1 year, Ruhr Coal Mine Company of Germany and Feiba Petroleum Company improved Burgess method for producing liquid fuel from coal hydrocracking, and built a semi-industrial experimental device with a daily processing capacity of 200 tons of coal, with the operating pressure reduced from 70 MPa to 30 MPa and the reaction temperature at 450 ~ 480℃. The solid-liquid separation was changed to filtration and centrifugation in vacuum flash evaporation method, and asphaltene was difficult to be hydrogenated, so it was left in the residue for gasification to produce hydrogen. The yield of light oil and medium oil can reach 50%.
Process characteristics: Circulating solvent hydrogenation, liquefied oil upgrading and direct coal liquefaction are connected in series in a high-pressure system, which avoids the energy loss caused by lowering the temperature and pressure of materials and increasing the temperature and pressure in a separate process, and methanates carbon dioxide and carbon monoxide on a fixed-bed catalyst to minimize carbon loss. Investment can save about 20% and improve energy efficiency.
Second, the HTI process in the United States.
The process is developed on the basis of two-stage catalytic liquefaction and H-Coal process, and adopts a suspended bed reactor developed in recent ten years and an iron-based catalyst patented by HTI.
Process characteristics: mild reaction conditions, reaction temperature 420 ~ 450℃, reaction pressure17 MPa; Adopt a special liquid circulating fluidized bed reactor to realize the full backmixing reactor mode; The catalyst is an iron-based colloidal high-activity catalyst prepared by HTI patented technology, and the dosage is small; The high temperature separator is connected in series with an online hydrogenation fixed bed reactor to hydrotreat liquefied oil; In the solid-liquid separation, the method of critical solvent extraction is used to recover the heavy oil in the liquefied residue to the maximum extent, thus greatly improving the recovery rate of liquefied oil.
Three. NEDOL technology in Japan
From 1978 to 1983, at the initiative of the Japanese government, Japan Steel Pipe Company, Sumitomo Metal Industry Company and Mitsubishi Heavy Industries Company developed three direct liquefaction processes respectively. All projects are implemented by NEDO. During the period of 1983, all liquefaction processes were tested in different scales, and the daily output was 0.1~ 2.4t. The technical institutions of new energy industry no longer supported each process independently, but merged these three processes into NEDOL liquefaction process, mainly liquefying sub-bituminous coal and low-rank bituminous coal. Twenty companies merged to form Japan Kerosene Co., Ltd., which is responsible for designing, building and operating a small-scale pilot plant with a production capacity of 250 tons/day. However, due to funding problems, the project was shelved in 1987. 1t/d process supporting unit (PSU) was installed and put into production on 1988 as planned, with a total investment of 30 million USD. For various reasons, the project has been pushed forward intermittently. 1988 re-planned the project, and the production capacity of the pilot liquefaction plant was redesigned to150 t/d. The new plant was started in Kashima in June of 199 1 year and completed in early June of 1996.
From March 1997 to February 1998, five more liquefaction plants were built in Japan. These five liquefaction plants liquefied three different kinds of coal (Tanito Harum coal and Adaro coal in Indonesia and Ikeshima coal in Japan), and there was not much problem. Many data and results were obtained in the liquefaction process. For example, after 80 days of continuous coal feeding and successful operation, the yield of liquefied oil reached 58wt% (dry ashless coal), the concentration of coal slurry reached 50%, and the cumulative production time was 6200 hours.
Four. Russian FFI process
The characteristics of Russian coal hydro-liquefaction process are as follows: firstly, the instantaneous vortex silo pulverized coal drying technology independently developed is adopted, which leads to thermal crushing and pore cracking of coal, the moisture content is reduced to 1.5 ~ 2% in a short time, and the specific surface area of coal is increased several times, which is beneficial to improving the reaction activity. This technology is mainly suitable for drying lignite with high internal moisture. Secondly, advanced and efficient molybdenum catalysts, namely ammonium molybdate and molybdenum trioxide, are adopted. The addition of catalyst is 0.02 ~ 0.05%, and the recovery rate of molybdenum in the catalyst can reach 85 ~ 95%. Thirdly, for high-activity lignite, the liquefaction pressure is lower, which can reduce the investment and operation cost of the factory and make the equipment less difficult. Due to the use of molybdenum catalyst, the liquefaction reaction pressure of Russian high activity lignite can be reduced to 6 ~ 10 MPa, which reduces investment and power consumption, reduces cost and improves reliability and safety. But for bituminous coal liquefaction, the pressure must be increased.
Both coal and crude oil are fossil fuels, but the difference is that coal has high carbon content, low hydrogen content and compact structure. The carbon content of coal is generally 60% to 90%, and some anthracite coals even contain more than 95% carbon, while the hydrogen content is generally around 5%. Compared with liquid fuel, coal is not easy to handle and transport. Most importantly, coal cannot be directly supplied to internal combustion engines and other internal combustion engine equipment for direct use. At present, these equipments are widely used in various transport vehicles, and the consumption of crude oil used to transport fuel exceeds 50% of the total world oil consumption.
The extensive use of liquid fuel has attracted the research of coal-to-oil in various countries. In history, the United States, Japan, Britain, Germany and other major countries have carried out large-scale coal liquefaction research and development projects, and a variety of coal liquefaction technologies have emerged, but South Africa is still the only country that commercialized coal liquefaction. The rapid rise of international oil prices since 2004 has attracted the interest of many countries, including China, in the industrialization of coalified oil.