Physical Properties of Low Rank Coal in Superheated Steam Drying Process

摘要

Superheated steam drying (SSD) of low rank coal (LRC) is applied to improve physical properties of coal and reduce greenhouse gas emissions. Now there are still many huge challenges of superheated steam drying coal technology, drying equipment and automatic control technology in large-scale application. Advantage heat and mass transfer of SSD comparing with hot air (flue gas) drying showed important significance to saving energy and reducing greenhouse gas emissions. The results show that superheated steam as drying medium has little effect on temperature of dried coal. As increasing of temperature and flow of superheated steam, temperature of dry coal increases rapidly after a slowly increase. By comparing physical properties of coal when inner water phase change before and after in the superheated steam drying process, that physical properties no-obvious change range of coal is in the moisture content of 7-12%. The rationality of 8-10% of engineering experience is explained. It can be choose as well as drying system energy consumption characteristics of reference index. The limit energy consumption of superheat steam drying may lower than 450 kJ /kg h_2o, explore and discuss the rationality or technology that the minimum energy consumption is 120 kJ /kg h_2o.