高碱煤中钠基化合物对灰熔融特性的影响

摘要

选取新疆准东煤田高钠煤(五彩湾煤和天池煤)为研究对象,研究了准东煤中碱金属钠的赋存形态和钠基化合物对煤灰熔融特性影响机制.向低温灰中添加不同比例的Na2O然后制取其高温混灰,利用X射线衍射仪分析矿物质组分在不同成灰温度下演化规律,探究碱金属钠对准东煤灰熔融特性的影响机制.结果表明:准东煤中钠以水溶钠形式为主;天池煤随着钠含量的增加,灰熔融温度先降低后趋于稳定;五彩湾煤随着钠含量的增加,灰熔融温度先降低后升高.天池煤掺混10%,Na2O导致灰熔融温度降低,是由于煤灰中白云石、氢氧化钙分解产生大量CaO,碱金属钠促进CaO与煤灰中Si、Al等反应生成含钙钠的低温共熔体,且有低熔点矿物无水芒硝生成;五彩湾煤掺混10%,Na2O导致灰熔融温度降低,是由于煤灰中新生成低熔点的钙铁辉石和无水芒硝,且碱金属钠促进钙铝黄长石和镁黄长石等含钙矿物质的低温共熔反应,掺混过量Na2O导致灰熔融温度升高,这是由于煤灰中生成了大量高熔点矿物质.%Zhundong Wucaiwan coal and Tianchi coal were selected as research objects to study the occurrence form of alkali metal sodium and the influence mechanism of sodium-based compound on coal ash melting charac-teristics.By adding different proportion of Na2O to low temperature ash and making high temperature ashes,the evolution of mineral components at different ashing temperature was analyzed by X-ray diffractometer to analyze the influence mechanism of alkali metal sodium on ash melting characteristic.The results show that water soluble sodium is the main sodium,the ash melting temperature of Tianchi coal increases first and then tends to be stable with increasing Na2O ratio,and the ash melting temperature of Wucaiwan coal decreases first and then increases with increasing Na2O ratio.The reason for the decreasing ash melting temperature with the addition of 10% Na2O to Tianchi coal is that the decomposition of minerals in coal ash generates CaO under high temperature,high con-tent of alkali metal sodium then promotes the low temperature eutectic reaction between CaO and Na、Si、Al, forming low temperature co-melt,and meanwhile thenardite of low melting point is generated in coal ash.The reason for the decreasing ash melting temperature with the addition of 10% Na2O to Wucaiwan coal is that heden- bergite and thenardite of low melting point are formed in coal ash,and alkali metal sodium promotes the low tem-perature eutectic reaction between gehlenite and akermanite.The reason for the increasing ash melting temperature with the addition of excessive Na2O to Wucaiwan coal is that there exist minerals of high ash melting point in coal ash.