生物质热转化过程中积灰沾污结渣特性及趋势预测研究进展

Research progress on the fouling and slagging characteristics of biomass ash and its trend prediction

为阐明生物质灰的沾污结渣特性及其趋势预测研究现状,使生物质能热转化利用过程更加安全,在综合分析生物质灰沾污结渣的危害及机制的基础上,从沾污结渣特性与沾污结渣预测两方面归纳国内外研究进展,梳理出影响结渣的主要因素——灰分组成、反应温度、气氛和添加剂等;并对沾污结渣趋势的预测方法和研究趋势进行分析。针对实际工程中锅炉受热面结渣和腐蚀问题,可以采用混烧、混入添加剂、水洗、酸洗、改变受热面材料、优化锅炉和烟道结构设计、优化反应条件等措施解决。在生物质灰沾污结渣趋势预测方面,目前并没有完整的统一标准,简单沿用煤灰的结渣指标存在严重的不适应性,且现有的预测方法通常只考虑固态或熔融成分对结渣的影响,而忽略了碱金属、氯、硫等元素挥发与温度变化的关系。因此,以热转化过程中碱金属的气-固分配趋势为基础,结合不同温度下生物质灰的特点及成灰特性,建立适用于不同温度下生物质灰的沾污结渣预测模型,是下一步研究应重点关注的问题。

During the thermal conversion and utilization of biomass,the safety problems caused by ash fouling,slagging,and corrosion on the heating surface of boiler or equipment seriously restrict the efficient utilization of biomass energy.To clarify the fouling and slagging characteristics of biomass ash and its trend prediction,and to make the thermal conversion and utilization of biomass energy safer,this paper first summarized the harm and mechanism of fouling and slagging of biomass ash.Then,the research progress at home and abroad was summarized from two aspects,namely,biomass ash fouling and slagging characteristics and prediction.The main factors affecting ash fouling and slagging behaviors were summarized,including biomass ash components,temperature,atmosphere,additives,and other external factors.Finally,the evaluation methods for predicting ash slagging tendency were summarized,and future research trends were prospected.In view of the problems of slagging and corrosion on boiler heating surface in practical engineering,some measures can be adopted to solve or alleviate them,such as mixed firing,mixing additives,water washing,pickling,changing heating surface materials,optimizing boiler and flue structure design,optimizing reaction conditions and so on.In terms of biomass ash fouling and slagging prediction,nowadays,there is no unified standard for predicting biomass ash slagging.It is seriously inadaptable to simply use the slagging index of coal ash,and the existing prediction methods usually only consider the influence of solid or melting salts on slagging after thermal transformation but ignore the relationship between temperature variation and the volatilization of alkali metals,chlorine,sulfur,etc.Therefore,based on the gas-solid distribution law of alkali metals during the thermal conversion process as well as in combination with the characteristics of biomass ash and ash formation at different temperatures,the establishment of a dynamic fouling and slagging prediction model for biomass ash at different temperatures should be the focus of the next research.