Requirements of space furnaces for coal quality
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What are the requirements of space furnaces regarding coal types and quality? Which types of coal and which properties of coal are more suitable for space furnaces?
What I found online regarding the general requirements for coal types in rocket furnaces, the analysis parameters for coal types, and the range of values for 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
Space furnaces have high requirements regarding the viscosity of ash, as this affects the slag scraping process; the viscosity should generally be between 5–25 Pa·S. Additionally, the operating temperature must be at least 50°C when the ash viscosity meets the required standards, with a typical requirement of over 100°C. Therefore, the requirements for coal used in such furnaces are quite stringent. However, space furnaces can use coal with a high ash melting point, and coal with an ash melting point above 1300°C can also be considered for use.
Space furnaces are said to be capable of gasifying lignite, but no plants have been seen using them. Lignite has an excessively high moisture content, resulting in a high coal grinding load; its high volatile matter content has little impact on the reaction temperature in a fluidized bed. The quality of the bituminous coal used in Yulin is approximately as follows: moisture content of 15%, ash content of 12–20%, sulfur content of 1%, volatile matter of 30%, fixed carbon content of 47–55%, and calorific value of 5400–5800 kcal. When using Shanxi anthracite, coal blending is required due to its high ash content, high sulfur content, and high ash melting point.