工业固废对高灰熔点煤灰熔融特性的影响及机理

Effect and mechanism of industrial solid waste on ash fusibility of high ash melting temperature coal

煤灰的熔融特性是气化用煤的重要指标,工业生产中钙基和铁基助熔剂被广泛用于降低高灰熔点煤灰的熔融特征温度。本文选取了4种含钙和含铁的工业固废,即脱硫石膏、电石渣、赤泥和钢渣,作为助熔剂,考察了高温弱还原性条件下工业固废添加对高灰熔点潞安煤灰熔融特性的影响,并分析了工业固废的添加与高温下煤灰矿物质组成的关系。结果表明:工业固废添加量为2%~8%时,高熔点潞安煤灰的熔融特征温度均降低,但影响程度不同。随着赤泥和电石渣添加比例的增大,潞安煤灰的熔融特征温度显著降低,添加4%的赤泥和电石渣时,煤灰的流动温度分别降低至1376℃和1392℃;添加钢渣和脱硫石膏,且添加量为2%时,煤灰的流动温度降低至1380℃和1410℃,但随着添加比例的增大,降低的幅度变小。添加赤泥时,潞安煤灰中莫来石和硅线石含量减少,生成了低熔点的钙铁辉石和铁尖晶石;添加电石渣时,高温下主要生成的矿物质为低熔点的钙长石;添加钢渣时,煤灰中莫来石与氧化物反应转变为低熔点的钙长石和单斜辉石;添加脱硫石膏时,高温下主要的矿物质为低熔点的钙长石。综合考虑四种含钙和含铁工业固废添加对煤灰熔融性和气化设备的影响,含铁工业固废钢渣和含钙工业固废电石渣可作为降低高灰熔点煤灰熔点的助熔剂,且添加比例为4%时,煤灰的流动温度能够满足气流床气化炉对煤灰流动温度的要求。

The fusibity of coal ash is an important index of coal in gasification,and calcium-and iron-based fluxes are widely used in industry to reduce the fusion temperature of coal ash with high ash melting temperature.In this paper,industrial solid wastes containing calcium and iron including desul-furization gypsum,calcium carbide slag,red mud and steel slag were selected as fluxes,and the effects of the addition of industrial solid wastes on the fusibity of Lu'an coal ash with high melting temperature under high-temperature and weak reducing conditions were investigated,and the relationship between the addition of industrial solid wastes and the mineral composition of the ash was also analyzed.The results showed that all the ash fusion temperatures of Lu'an coal ash decreased with the addition of industrial solid waste,while it showed different effects.It was significantly decrased with the increase of the addition proportion of red mud and calcium carbide slag.The flow temperature(FT)of Lu’an coal ash was lowered to 1376℃and 1392℃when 8%red mud and calcium carbide slag were added.When the addition of steel slag and desulfurization gypsum was 2%,the FT of Lu’an coal ash was decreased to 1380℃and 1410℃,while it slightly decreased with the increase of the addition ratio.When adding red mud,the content of mullite and silica in Lu'an coal ash decreased,and low melting point calcium iron pyroxene and iron spinel were generated.For the addition of calcium carbide slag,the main minerals at high temperatures were low melting point anorthite.When the steel slag was added,the mullite in the coal ash reacted with oxides and transformed into low melting point clinopyroxene and anorthite.For the addition of desulfurization gypsum,low melting point anorthiter was the main minerals at high temperatures.Considering the effect of industrial solid waste addition on ash fusibility and other components on gasification,steel slag and calcium carbide slag can be used as fluexs to reduce the ash fusion temperature of coal with high melting temperature in gasification,and the FT of Lu'an coal with high ash fusion temperature can meet the requirements of the fusibility of coal ash for the entranied flow gasifiers when the addition of steel slag,and carbide slag was 4%.