Questions about space furnaces

If the space furnace is successfully put into commercial operation in Henan and Anhui, then as reported in the newspapers, it has three advantages over similar international systems such as those owned by Shell and Texaco: first, it requires less investment, saving one-third compared to projects of similar scale； Second, the construction period is short, being one-third shorter than that of Shell boilers ； Third, the operation procedure is simple, suitable for the actual conditions of China’s coal chemical industry, and easy to implement on a large scale. At present, its disadvantage is something that the aerospace research institutes, as well as Henan and Anhui provinces, are working to address: they are constantly improving the aerospace furnaces and related facilities to achieve full operational capacity and enable long-duration operation (Henan can maintain stable operation for 5 days, while Anhui can do so for 15 days). They will be driving at the end of the month).

Coal quality requirements for HT-L powder gasification: The HT-L powder gasification process has a wide range of compatibility with different types of coal; brown coal, sub-bituminous coal, bituminous coal, as well as petroleum coke can all be used as feedstocks for gasification. Even coal types with high ash content, high moisture, and high sulfur levels can be used. However, from the perspective of economic operation, not all types of coal can achieve good economic benefits. Therefore, users should carefully select the appropriate type of coal to ensure the stable operation of the equipment while meeting the design requirements. General requirements for coal types in HT-L powder gasification units Coal type analysis parameters Range of values Total water (AR ； %) 4.5~30.7 Ash content (%) ； MF) 5.7~35.0 Oxygen content (% ； MF) 5.3~16.3 Total sulfur (% ； MF) 0.3~5.2 Total chlorine (% ； MF） 0.01~0.41 Na2O (% ； on Ash) 0.1~3.1 K2O(%; on Ash) 0.1~3.3 CaO(%; on Ash) 1.2~23.7 Fe2O3 (on Ash) 5.9~27.8 SiO2(%; on Ash) 24.9~58.9 Al2O3(%; on Ash) 9.5~32.6 High calorific value (MJ/kg; MF) 22.8~33.1 1. Moisture: The moisture in coal includes surface moisture and internal moisture. Surface water is the moisture on the surface of coal particles; it comes from **mechanical coal mining**, rainwater during storage or transportation, and water used to prevent the dispersion of natural ash. Although the surface moisture of coal has no impact on gasification, high surface moisture increases transportation costs. Unstable surface moisture can also lead to fluctuations in the thermal energy consumption of the coal drying system. The water content on the surface suddenly increases; in order to maintain a stable level of water storage in the furnace, the coal drying system has to increase fuel consumption, which leads to waste of raw materials and environmental pollution. The level of surface water is related to coal mining, storage, and transportation methods, and it can be changed through human effort. Therefore, the content of external water meters should be reduced as much as possible to save costs and facilitate operation. Internal moisture in coal is the coal’s inherent moisture, that is, its bound water, which exists in the coal in a chemical form. High internal moisture in coal also increases transportation costs. More importantly, removing internal water requires more heating fuel than removing external water. Therefore, the higher the internal water level, the greater the moisture content in the pulverized coal fed into the gasifier. This increases the energy required for vaporizing the water, reduces the proportion of useful gases in the crude syngas, thereby lowering the gasification efficiency and increasing coal consumption. 2. Ash: Ash is the inert material in coal that does not participate directly in the gasification reaction; however, the melting of this ash consumes a large amount of heat generated during the coal’s gasification process. The higher the ash content in coal, the fewer the effective gas components after gasification. For the same mass of coal fed into the gasifier, coal with a high ash content produces less gas, generates more slag, and results in higher energy consumption. According to the information provided. Under the same reaction conditions, an increase of 1% in ash content leads to a rise of 0.7%~0.8% in oxygen consumption, as well as an increase of 1.3%~1.5% in coal consumption. The higher the ash content, the greater the coal and oxygen consumption required for gasification, and the faster the slag wears down the components inside the furnace ； Furthermore, the greater the amount of ash and slag, the greater the impact on coal transportation and the ash and slag water treatment system in the gasifier; as a result, the slag removal load on the systems used for handling the gasifier and its ash and slag also increases, which accelerates the wear and damage to pipes and equipment. In severe cases, it can affect the normal operation of the gasification furnace. However, since the HT-L powder coal gasification unit uses a cold-wall structure to resist slag with slag itself, if the ash content is too low, the heat loss in the gasifier increases, and it is also unfavorable for protecting the furnace walls from slag, thereby affecting the service life of the gasifier. 3. Ash melting point and ash composition: The HT-L powder gasification unit uses liquid slag discharge to ensure smooth slag removal from the gasifier. The normal operating temperature should be about 200°C higher than the ash fusion temperature FT (flow temperature). If the melting point of coal ash is too high, it is necessary to increase the gasification operation temperature. Increasing the operating temperature is beneficial for carbon conversion and slag discharge from the gasifier, but if the temperature is too high, the heat dissipation from the water walls in the radiation chamber increases, and the steam output of the boiler also rises significantly, which reduces the efficiency of cold gas utilization and thus affects the economic viability of the gasifier’s operation. Therefore, choosing coal types with a low ash fusion point can reduce the operating temperature and improve the efficiency of coal utilization. Furthermore, if the ash melting point of coal is low, the operating temperature can be reduced; compared to coal with a high ash melting point, it is not necessary to consume large amounts of oxygen to react with carbon to produce CO2 in order to maintain a higher operating temperature. The yield of effective gas is high. For coals with high ash fusion points, it is generally possible to modify the melting properties of the coal ash by adding fluxes, in order to ensure the proper operation of the gasification furnace. Coal ash is mainly composed of SiO2, Al2O3, CaO, MgO, TiO2, as well as Na2O and K2O. Generally speaking, the higher the ratio of acidic components in coal ash such as SiO2, Al2O3, and TiO2 to basic components such as Fe2O3, CaO, MgO, and Na2O, the higher the ash melting point. The composition of coal ash usually has little impact on the gasification reaction; however, excessive amounts of certain components can affect the melting properties of the ash, leading to poor slag discharge from the gasification furnace or blockages at the slag outlet.