Influence of sewage sludge on ash-melting characteristics during combustion of high sodium coal of Wucai Wan

doi:10.16085/j.issn.1000-6613.2018-0152

Abstract

Abstract: The X-ray diffraction (XRD) analysis combined with ash melting temperature measurements were used to study the morphological changes of minerals in the combustion process of high sodium coal of Wucai Wan and the effects of sewage sludge on the formation characteristics of ash. The results showed that when the sludge addition mass ratio of sludge/coal (S/C)=4, (F_s)_sludge=1150℃, the sludge could not significantly increase the ash melting temperature. Modifying the molar ratio of (SiO₂/Al₂O₃) of sludge to 2, it was found that F_s was higher than 1235℃ so that the ash melting temperature was highly increased when the ratio of S/C was greater than 1. Indicators such as R_b/a、R_b/a(+P)、R_b/a×Na and so on were good in predicting of fouling and slagging of the co-combustion of high sodium coal and sludge. Combusting at 800-1100℃, the main minerals in ash such as albite, hedenbergite, hauyne were with low melting point and high meltability under air atmosphere. Nepheline and other high melting point minerals were fusibility and disappear at low temperature. When adding sludge to coal, the new formed minerals with high melting temperature such as Ca₃(PO₄)₂, Ca₂P₂O₇ and CaAl₂Si₂O₈, which help to raise the ash melting temperature, were formed in the ash. But high (SiO₂/Al₂O₃) ratio and Fe content in sludge were readily to react with aluminum silicates to produce amorphous substance with a low melting point. And it will inhibit the role of P in the sludge to increase the ash melting temperature.

Key words: high sodium coal of Wucai Wan, ammonium dihydrogen phosphate (NH₄H₂PO₄), sludge, ash-melting characteristics, waste treatment, coal combustion, morphology

摘要： 通过X射线衍射（XRD）谱图分析结合灰熔融温度测定，研究了五彩湾高钠煤灰中矿物转化机理及城市污泥对高钠煤灰分特性的影响。试验结果表明：当污泥添加质量比为S/C（sludge/coal）=4时，结渣指数（F_s）_sludge=1150℃，污泥提高灰熔融温度程度较小。对污泥改性使其（SiO₂/Al₂O₃）物质的量比为2，添加至煤中，当S/C > 1时，F_s > 1235℃，灰熔融温度明显提高。R_b/a、R_b/a（+P）、R_b/a×Na等指标可良好预测高钠煤与污泥混合物燃烧的沾污、结渣倾向。煤在空气气氛下，燃烧温度800～1100℃，灰中主要矿物钠长石、钙铁辉石、蓝方石等熔点低，高熔点矿物霞石等助融性强、消失温度低。而添加污泥后，混合物灰中新生成Ca₃（PO₄）₂、Ca₂P₂O₇、CaAl₂Si₂O₈等高熔点物质，有利于提高煤灰熔融温度。而污泥中（SiO₂/Al₂O₃）比、Fe含量高，会对硅铝酸盐等产生助熔作用，抑制污泥中P提高灰熔融温度的作用。

关键词: 五彩湾高钠煤, 磷酸二氢铵, 污泥, 灰熔融特性, 废物处理, 煤燃烧, 形态学

CLC Number:

TQ534

SUN Baomin, GAO Manda, SU Yifeng, DING Shixing. Influence of sewage sludge on ash-melting characteristics during combustion of high sodium coal of Wucai Wan[J]. Chemical Industry and Engineering Progress, 2018, 37(08): 2991-3000.

孙保民, 高满达, 苏逸峰, 丁世兴. 城市污泥对五彩湾高钠煤灰熔融特性的影响[J]. 化工进展, 2018, 37(08): 2991-3000.

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