Migration Of Harmful Elements And Its Controlling Mechanism During The By-products Of Coal Washing Combustion

As an energy, Coal caused the air pollution when coal combustion.which is themost important reason that denounced by people.The transferring disciplinarian ofharmful elements during the coal combustion is the hotspot in the academiccommunity. The harmful elements distribute to the fly ash and bottom ash and fluegas after coal combustion.So far, System research about harmful elements on themigration behavior and environmental effect when coal-byproduct used as the fue isvery little.Therefore, Intensive study of harmful elements about the migrationbehavior and the environmental effect during coal-byproduct combustion that appearsextremely urgent.This paper choose some coal preparation plants and power plants to samplingwhich located in Shanxi, Shandong, Jiangxi, Anhui and Jiangsu. Combination withsampling and laboratory simulation study, what used to do the research on migrationof harmful elements and its controlling mechanism during the by-products of coalwashing combustion.The elements such as As, B and Cr that are very difficult to be abstracted.Themodes of occurrence about As, B and Cr are essentially the same,they all occur inresidual form.The elements in the samples which come from different place also havethe same modes of occurrence, The modes of occurrence about the elements of As, Band Cr don’t have differences between samples from different origin. The modes ofoccurrence about Mn are basically the same, The most mode of occurrence of Mn isFe-Mn. As well, The mode of occurrence about Mn is not due to where the samplesgained. Mn is mainly occur in inorganic form. The mode of occurrence of Cd due tothe coal quality. Cd in coal gangue, coal slurry and middling coal is not only simlelyin the inorganic form, there is a part of Cd occurring in the organic form. Theelements in coal by-products and their combustion productions have different modesof occurrence. The elements in coal gangue and its combustion productions almostlyhave the same modes of occurrence, But after combustion,the modes of occurance ofelements in coal slurry and middings (coal) will change. The main modes of occurrence and extraction ratio about elements are different between the samplesfrom different places.The emissions trendency of the same elements in different coal gangue and coalslurry during laboratory simulation study is basically the same.It illustrates thatdifferent places of coal gangue and coal slurry will not affect the emissions ofdifferent harmful elements. The emissions of elements during combusting is mainlycontrolled by their chemical properties. As the change of temperature, the emissionsof each element in coal gangue and coal slurry during combustion is mainly due tothe thermal decomposition and vitrification of clay minerals. The differentcompositions between coal gangue and coal slurry mainly lead to their differentcombustion mechanism. Combustion temperature to900℃and30minutes’combusti-on time is the optimum combustion condition about coal gangue and coal slurry in thetube furnace and muffle furnace.The optimum oxygen flow of tube furnace is50mL/min.The enrichment ability of elements in fly ash is greater than slag. Betweendifferent coal by-products combustion, the enrichment ability of elements is different,Their discrepant compositions may be the reason for this phenomenon. Theproduction rate of slag are basically the same in the laboratory simulation researchand power plant. The contents of each element in the slag with the tube furnace andmuffle furnace are much smaller than in the slag sampled in the power plant. Thedifferences are due to the REDOX atmosphere and the particle size, etc. Mostharmful elements are hard to release when coal gangue roasting to the finishedbrick.It is very different from the situation that the content of harmful elements in flyash and slag when coal gangue combusting.This may be caused by the differenttechnology between combustion and roasting.