Coal pyrolysis needs to eliminate the bottleneck of semi-coke utilization

The long-settling coal pyrolysis of Sinochem Xinwang.com has now become hot again. Coal pyrolysis projects have been launched successively throughout the country, and most of them are concentrated in Inner Mongolia and Shaanxi, where coal resources are abundant, and coal used is low-grade coal with low quality. However, if semi-coke is to be effectively utilized, it is necessary to expand the application of semi-coke produced by coal pyrolysis in industrial boilers, power generation, and other industries, or to take the path of cogeneration of heat, electricity, gas, oil, and chemicals so as to solve the problem of restricting coal. With the use of semi-coke for pyrolysis development, Li Peiyu, a technical consultant of Shaanxi Yanchang Petroleum Group's Xiwan Coal Chemical Project Preparation Department, told reporters.

Coal pyrolysis, also known as dry distillation or thermal decomposition of coal, refers to the process of heating coal to remove tar and coal gas from the coal to obtain tar, gas, and semi-coke. According to the data from the test results and related data released by Huamei Engineering Technology Co., Ltd., a senior consultant of Hualu Engineering Technology Co., Ltd., currently domestic pyrolysis can produce approximately 0.4 to 0.5 tons of semi-coke per tonne of brown coal, due to domestic pyrolysis process and coal. Different kinds of tar and gas production will be different, low-temperature tar has 40 to 74 kilograms, gas production in the 127 to 1000 cubic meters.

Tang Hongqing, senior engineer of China National Synthetic Oil Engineering Co., Ltd., said that the semi-coke has a high ash content and is not economically reasonable for long-distance transportation. It is only suitable for on-site conversion and combustion. A person in charge of the Hangzhou Gathering Group told the reporter that the half-coke price of 4000-5000 kcal/kg had a price of 800 yuan, and the ordinary bituminous coal with a calorific value of 6,000 kcal/kg in Gansu and Northern Shaanxi had a price of 600 tons. If yuan and semi-coke are shipped to the East China market, they are not economical.

Insiders pointed out that after the low-grade coal is upgraded, the calorific value is improved, but it is still relatively low compared to ordinary bituminous coal. Ma Zhanyu, chief engineer of Sichuan Aba Sushun Power Generation Co., Ltd., revealed that the semi-coke market price has been higher than lump coal. Currently, the lump coal market price in Yulin area is between 600 and 700 yuan/ton, and semi-coke is between 800 and 900 yuan/ton. After the semi-focal less volatile, burning alone is not easy to ignite. In addition, the demand for semi-coke in blast furnace injection, ferroalloy, calcium carbide, and synthetic ammonia is limited. Existing pulverized coal boilers or circulating fluidized bed boilers are mostly designed according to bituminous coal. If semi-coke is used, existing equipment and controls are also required. The process of retrofitting and adjusting will undoubtedly increase the cost, plus the current semi-coke market price is higher than bituminous coal, so the power plant does not use semi-coke.

Tang Hongqing believes that there is still a problem with the use of semi-coke. Although some companies have announced that semi-coke can be used as a civilian fuel, calcium carbide, ferroalloy, iron blast furnace blasting materials, high-quality raw materials for gasification and adsorption materials, but in fact, the use of steel is high temperature coke, not semi-coke Most of the semi-coke is not a raw material for coal gasification. The semi-coke has high ash content and high hardness, and some semi-coke ash content is as high as 35%. Therefore, whether made of coal-water slurry or dry powder gasification, it is easy to plug the gasifier, and the gasification cost of effective synthesis gas is also high. All show that semi-coke utilization still has problems in engineering. At present, there is no set of industrialized demonstration devices that use semi-coke as a raw material for gasification. Wang Yang, a researcher at Shanxi Coal Chemistry Institute, believes that if semicoke is used as a raw material for gasification, it still faces the problem of raw material preparation. Since semicoke already removes volatiles, low volatiles will lead to a decrease in reactivity and carbon conversion rate.

At present, the technology that adapts to the gasification of the semi-coke has not yet come out, but the research and development of the coal gasification technology of our country has already presented the diversity. Some experts suggest that domestic research institutions should pay attention to the development of gasification technology for semi-coke and provide technical support for gas, oil, chemicals, and other polygeneration systems.

China's coal pyrolysis only stays at the stage of blue carbon-tar-gas, and blue carbon and tar are simply sold as primary products and gas is vented or burned directly. This extensive production method will reduce energy conversion efficiency. Xu Gang, a senior researcher at the National Development and Reform Commission's Institute for Restructuring and Reform, said that the scale of coal pyrolysis and the amount of tar and gas that can be produced are replaced by semi-coke as raw coal, coal for heating, and coal for industrial boilers. Scale is determined. If semi-coke cannot be effectively used, the production of tar and gas cannot be carried out naturally. In this sense, companies can only use the coal-pyrolysis heat, electricity, gas, oil, chemicals, and other polygeneration systems to increase the deep processing and utilization of blue coal, gas, and tar, so that coal can be truly clean. Efficient, environmentally friendly use, and new ways to use pyrolysis.