高碱煤的清洁高效转化及资源化利用对实现双碳目标具有重要战略意义,液态排渣锅炉在燃用高碱煤方面存在较大优势,但目前尚缺乏全烧高碱煤的灰沉积和元素迁移特性相关研究。研究了准东煤在20MW卧式液态排渣炉上燃烧时的积灰结渣特性和元素迁移规律。通过在捕渣屏前后设置灰沉积探针1和2,研究了换热器表面灰沉积对传热效率的影响。结果表明,初始层形成阶段通过探针表面的热流密度迅速下降,随沉积物的生长热流密度缓慢下降,沉积物生长趋于稳定时,热流密度也会在一定范围内波动。按照探针表面的热流密度变化速率,可将灰沉积的形成过程分为3个阶段,分别为快速下降阶段、缓慢下降阶段和稳定阶段。探针1和2最终稳定的相对热流密度分别为0.75和0.83。此外,通过分析炉膛不同位置灰渣和沉积物的外观形貌、矿物组成和化学成分,探究了元素迁移对积灰结渣的影响。灰沉积的微观表征表明,Al2O3、Fe2O3、SiO2等氧化物在高温区渣样中富集,而CaO、MgO、Na2O、SO3则主要出现在低温区域的沉积物中。换热器表面沉积初始层的形成与碱金属及其硫酸盐的冷凝密切相关,高温和低温区域样品中的平均Na2O质量分数分别为1.38%和4.70%。铁元素会在渣中富集并充当助溶剂的作用,与硅-钙-镁-铝体系形成低温共熔体,从而导致灰熔融温度降低。

The clean and efficient conversion and resource utilization of high-alkali coal have significant strategic importance for achievingthe " dual carbon" targets. Liquid slag boilers have considerable advantages in burning high-alkali coal, but there is still a lack of research on the ash deposition and elemental migration characteristics of coal that is entirely burned with high alkali. This study investigatedthe ash deposition and slagging characteristics and the elemental migration patterns of Zhundong coal during combustion in a 20 MW horizontal liquid slag boiler. Ash deposition probes 1 and 2 were set up before and after the slag trap to study the effect of ash deposition on theheat transfer surface on thermal efficiency. The results indicate that during the initial layer formation stage, the heat flux density across theprobe surface rapidly decreases, and as the deposit grew, the heat flux density gradually decreases, and when the deposit growth becomesstable, the heat flux density will fluctuate within a certain range. The formation process of ash deposition can be divided into three stagesaccording to the rate of change of heat flux density on the probe surface: a rapid decline phase, a slow decline phase, and a stable phase.The final stable relative heat flux densities of probes 1 and 2 are 0. 75 and 0. 83, respectively. In addition, by analyzing theappearance, mineral composition, and chemical composition of the ash and deposits at different positions in the furnace, the impact of elemental migration on ash deposition and slagging was explored. The micro-characterization of ash deposition shows that oxides such asAl2O3, Fe2O3, and SiO2 are enriched in the high-temperature slag samples, while CaO, MgO, Na2O, and SO3 are mainly found in thedeposits of the low-temperature area. The formation of the initial layer on the heat transfer surface is closely related to the condensation ofalkali metals and their sulfates, with the average mass fractions of Na2O in the high- and low-temperature area samples being 1.38% and4.70%, respectively. The iron element is enriched in the slag and acts as a flux, forming a low-temperature eutectic with the silicon-calcium-magnesium-aluminum system, which leads to a reduction in the ash melting temperature.

0 引言

1 试验

   1.1 燃烧装置和煤样分析

   1.2 取样系统和分析方法

2 结果与讨论

   2.1 形态样貌

   2.2 热流密度

   2.3 XRF分析

   2.4 XRD分析

3 结论