Study On Selenium Release And Absorption Methods During Coal Combustion

China's fossil energy structure,which relies mainly on thermal power generation,has caused a large amount of pollutants to be released to the environment and the atmosphere of human beings during coal combustion.Heavy metal selenium is the most volatile heavy metal in coal.The poisoning incident has caused widespread concern and research on selenium emissions.However,there are few studies on the release rules of various forms of selenium in the process of coal combustion.At the same time,the method of collecting selenium in flue gas needs to be improved.This article focuses on these two points.Lignite,bituminous coal,and anthracite coal are selected for combustion and ashing at different temperatures,and ash obtained at different temperatures is extracted step by step to obtain the selenium content in each form at each temperature.It is found through analysis that selenium in anthracite has a concentrated release phase,while bituminous coal and lignite have two release phases.The main reason is that the composition of selenium in anthracite is simpler than that of bituminous coal and lignite,and it mainly exists in the form of sulfide and residue,and there are also a certain amount of organic matter in the other two kinds of coal.Analysis of the change in the occurrence morphology at different temperatures found that the selenium ash in the sulfide-bound state of coal was released first,the release temperature of the selenium in the organic-bound state was similar to the ignition point of coal,and the residual selenium in the mineral lattice was finally released.These three combined selenium may be converted into water-soluble and ion-exchanged selenium during the decomposition and release process.At 1000?,the selenium in coal basically releases more than 95%.At the same time,bituminous coal with a higher selenium content is selected as the selenium source for combustion in a tube furnace.After the tube furnace is connected to a gas impingement bottle to absorb selenium in the flue gas,a laboratory-level absorption method is studied.Through the improvement of laboratory equipment,including methods such as heating pipelines,reducing flue gas flow,and changing absorption solutions,the absorption efficiency of selenium has been improved,from the original 20%to 60%.It can be used as a reference for the on-site of coal-fired power plant gas sampling test.