氯化钠蒸气对高钠煤煤灰钠捕获性能及其烧结温度的影响

Effect of NaCl vapor concentration on sodium-capturing performance and sintering temperature of coal ash

新疆的高钠煤是一种开采成本低、灰分低、含硫量低的优质燃料,但较高的钠含量导致其在燃烧利用的过程中易出现沾污结渣等现象,严重阻碍了高钠煤的开发利用。以2种高钠煤(五彩湾煤(WCW)、哈密煤(HM))和1种低钠煤(平朔煤(PS))作为实验对象,在900℃下燃烧制灰,并将所制煤灰置于38%、51%和76%的NaCl蒸气下进行钠捕获实验,使用ICP-OES测得钠捕获前后煤灰的钠含量,采用XRD分析钠捕获前后煤灰中矿物质的变化,采用压降法测量钠捕获前后煤灰的烧结温度,深入探究不同NaCl蒸气体积分数下煤灰烧结特性的衍变规律。结果表明:在3种NaCl蒸气体积分数下,3种煤灰样品中PS煤灰的钠捕获量最大,HM煤灰次之,WCW煤灰最低。Si、Al能增强煤灰的钠捕获性能,而Ca则会与Si、Al发生反应,从而抑制Si、Al对NaCl蒸气的化学固定,不利于煤灰的钠捕获。随NaCl蒸气体积分数升高,钠捕获量增大,煤灰的烧结温度降低幅度与其钠捕获量呈正相关。HM、WCW煤灰烧结温度降低幅度均大于PS煤灰,一方面是由于HM和WCW煤灰固钠后生成的含钠化合物的熔点低于PS煤灰,另一方面NaCl蒸气体积分数升高促进了低熔点含钠化合物的生成。PS煤灰在900℃下尚未发生烧结,其结构疏松、内部孔隙多,与NaCl蒸气反应完全程度相对较高,其烧结温度受NaCl蒸气体积分数影响最小。

Zhundong coal in Xinjiang is a kind of high-quality fuel with low mining cost,low ash yield and sulfur content,but high sodium content leads to the fouling and slagging during its combustion process,which seriously hinders the further utilization of the sodium-rich coal.In this study,two kinds of sodium-rich coals,the Wucaiwan coal(WCW)and the Hami coal(HM),and one low sodium-content coal,the Pingshuo coal(PS),were burned into ash at 900℃,and the sodium capture experiments of the coal ashes were conducted in the atmosphere of the NaCl vapor with 38%,51%and 76%concentration.The sodium content in the coal ash before and after the sodium capture experiment was measured by the ICP-OES analyzer,and the mineral changes in the coal ash samples were analyzed by XRD.Finally,the pressure drop method was used to determine the sintering temperature of the coal ash sample,and then the effect of the sodium vapor concentration on the sintering characteristics of the coal ash was explored.The results show that in the range of the employed NaCl vapor concentrations,in terms of the sodium-capturing amount,the PS coal ash is the highest,the HM coal ash is the second,and the WCW coal ash is the lowest.Silicon and aluminum in the coal ash samples can enhance its sodium-capturing performance,while calcium in the coal ash will react with the silicon and aluminum contained in the minerals,and thus result in the decrease in the chemical fixation capability of the silicon and aluminum for the sodium contained vapor,which is not conducive to the sodium capture process of the coal ash samples.With the increase of NaCl vapor concentration,the sodium-capture amount increases,and the decrease in the sintering temperature of the coal ash is positively correlated with the sodium-capturing amount.The decrease in the sintering temperature of the HM and the WCW coal ashes is greater than that of the PS coal ash because the melting point of the sodium-containing compounds produced by the chemical fixed sodium of the HM and the WCW coal ashes is lower than that of the PS coal ash and the forming reaction of low melting point sodium-containing compounds is promoted by the increasing the NaCl vapor concentration.In addition,the sintering behavior of the PS coal ash with loose structure and rich internal pores was not observed at 900℃,thus the reaction degree of the ash with the NaCl vapor was relatively high,and its sintering temperature of the resulted ash was less affected by the NaCl vapor concentration.