高温配煤对新疆高碱煤灰熔融特性的影响

Influence of coal blending on fusion characteristics of high alkali coal ash in Xinjiang

为了研究配煤对新疆高碱煤灰熔融行为的影响机制,采用碱金属含量差异较大的2种典型新疆准东煤按不同比例混合,探究混煤灰熔融过程中各个特征温度的影响规律及调控机制。利用XRD、SEM-EDX、XRF等对样品进行分析表征,考察单一煤灰和混煤灰在高温下的化学组成、矿物组成和微观形貌演变规律。利用Factsage对煤灰在高温下的相态转变及矿物组成变化进行热力学计算,揭示配煤对新疆高碱煤灰高温熔融行为的影响机制。结果表明,高碱煤灰中较高含量Na 2 O,在高温下形成长石类矿物,是导致灰熔融特性温度较低的主要原因。配煤改变了煤灰化学组成,使得煤灰中矿物质在高温下的演化行为发生变化,从而决定了混煤灰具有不同的熔融特性。但混煤灰的熔融温度变化与配煤比例呈现非线性关系。当MC煤与BS煤配比为1∶4时,混煤灰具有最低的灰熔融温度,当MC煤与BS煤配比为4∶1时,混煤灰熔融温度最高。高温煤灰中低熔点矿物拉长石、透辉石和培长石能够与石英和莫来石发生低温共熔,导致灰熔融温度降低。热力学计算结果表明,长石、堇青石、辉石和石英矿物质之间相互作用,在高温下形成低熔融温度共熔体,使得形成液相温度降低。热力学计算结果与X射线衍射结果具有相似性。

In order to study the influence mechanism of coal blending on the ash melting behavior of high-alkali coal in Xinjiang,two typical Xinjiang Zhundong coals with large differences in alkali metal content were used to explore the influence and control mechanism on the melting characteristics of blended coal ash.The ash samples were analyzed by XRD,SEM-EDX,and XRF,and the chemical composition,mineral composition,and microscopic morphology evolution of single coal ash and mixed coal ash were investigated at high temperatures.The phase transformation and mineral composition of were simulated by Factsage to reveal the mechanism of influence of coal blending on the high-temperature melting behavior of high-alkali coal ash in Xinjiang.Studies have shown that high alkali coal ash has high Na_(2)O content,and feldspar minerals formed at high temperatures are the main reasons for the low melting temperature of ash.Coal blending changes the chemical composition of coal ash and changes the evolution behavior of minerals in coal ash at high temperature,which determines that mixed coal ash have different melting characteristics.However,the ash fusion temperature of blended coal has a nonlinear relationship with the proportion of coal blending.When the ratio of MC coal to BS coal is 1∶4,the blended ash has the lowest ash fusion temperature,and when the ratio is 4∶1,the blended ash fusion temperature is the highest.The low-melting-point minerals labradorite,diopside and bytownite in high-temperature coal ash can undergo low-temperature eutectic with quartz and mullite,resulting in a decrease in ash melting temperature.Thermodynamic calculation results show that feldspar,cordierite,pyroxene and quartz minerals interact to form a low melting temperature eutectic at high temperature,which reduces the formation temperature of liquid phase.The thermodynamic calculation results are similar to the X-ray diffraction results.