Existence Form Of Sodium In High Sodium Coals From Xinjiang And Its Effect On Pyrolysis

ZhunDong coalfield is the largest coal field in Xinjiang at now,and it's sodium content is high,that will affect the rational utilization of coal,the economic benefits and the environmental benefits.Due to some questions haven't be solved chearly,such as the Sodium's distribution characteristics in the spatial of coal,the sodium's chemical forms in coal and the sodium's impact of pyrolysis and so on,so it will restrict the degree of the large-scale use and the ways.If those questions can be solved,they can provide theotical guidance for the comprehensive of ZhunDong coal.Taking the Montenegro head open-pit coal mine of ZhunDong coalfield in Qitai county as the research area,this paper explored the spatial distribution features of sodium,and the main source of sodium in coal.This article gathered the coal samples from no.7 and no.8 coal seams,took off ash from the coal samples,analysised the raw coal and the demineralized coal by using of FTIR?XPS?²³Na NMR and TG/MS,etc.The conclusions are as follows:1.The content of Na₂O showed a trend of first decrease and then increase from the north to the south of the study area,also showed a thend of decrease from the east to the west of the study area;these distribution characteristics of sodium Is derived from the hydrochemistry type of groundwater,the runoff characteristics of groundwater and the buried depth of coal seam.2.The characteristics of coal structure are as follows:the length of carbon chain of aliphatic hydrocarbons was more longer,the main form of oxygen were ether,hydroxyl that followed by carboxylic acid and carbonyl;the main form of nitrogen functional groups was pyrrole nitrogen,the main sorts of organic sulfur were sulfoxide sulfur and sulfone sulfur.Among of those,a large number of oxygen atoms in the structure of coal provided conditions for the geometrical forms of sodium.3.There were two kinds of geometrical forms of sodium:organic and inorganic forms.The organic shapes of sodium were mainly R-ONa and R-COONa,The inorganic forms of sodium was that exciting in the mineral or as ionic compounds solubling in water,such as NaHCO₃,Na₂SO₄,Na₂CO₃,NaCl,etc.The sodium content from NaCl of coal was higher,and this sodium was brought into coal seam by ground water,and controled the macro distribution characteristics of sodium content of coal seam.4.The pyrolysis performance of demineralized coal is following:reduced the temperature of the maximum weight loss rate in coal pyrolysising,made a direction of cryogenic that the starting temperature of H₂,CH₄ and CO₂ and the temperature of the biggest gas evolution rate,changed the curve peak type of gas evolution rate.The reason of the phenomenon properly was that organic sodium combining with coal structure from the start,then organic sodium played a catalytic effect in the process of pyrolysis always.But,the rolysising pyprocess of raw coal wes effect by organic and inorganic sodium,especially NaCl in inorganic sodium,the product that combined sodium with chloride ions was not easy to volatile in high temperature conditions,so these sodium ions couldn't combine with coal showed the catalytic effect after the process of connecting to oxygen containing functional groups.In addition,the product changed the space structure of the coal,blocked the coal to heat up,thus influenced the heat and mass transfer in the process of pyrolysis,and influenced the pyrolysis of coal.