生物质合成灰的烧结熔融特性和矿物转变规律实验研究

Experimental Study on Sintering and Melting Characteristics and Mineral Transformation Law of Synthetic Biomass Ash

【目的】研究生物质在流化床燃烧过程的结焦问题,分析钾盐形式和含量对生物质灰烧结熔融特性的影响。【方法】借助扫描电子显微镜耦合能谱仪、X射线衍射仪、X射线荧光分析仪和FactSage热力学计算软件,通过实验分析了生物质合成灰的烧结熔融特性和矿物转变规律。【结果】在流化床的典型运行温度750~950℃范围内,合成灰的烧结熔融程度随温度以及钾盐质量分数的增加而加剧。此外,钾盐形式不同,其对生物质合成灰的烧结熔融特性的影响也有显著差异:钾盐为K_(2)CO_(3)时,合成灰中液相比例最高可达34.36%,合成灰由此发生严重烧结;钾盐为KCl时,大部分K和Cl元素在750~850℃逃逸,合成灰的烧结程度较K_(2)CO_(3)有所减弱;钾盐为K2SO4时,合成灰中液相含量最少,烧结熔融程度也最弱。【结论】改变钾盐的存在形式并控制床温,有望缓解生物质在流化床燃烧过程的结焦问题。

[Objective]The coking problem of biomass in fluidized bed combustion process was studied,and the influence of potassium salt form and content on the sintering and melting characteristics of biomass ash was analyzed.[Methods]The sintering and melting characteristics and the mineral transformation law of synthetic biomass ash were analyzed by experiments with scanning electron microscope coupled energy dispersive spectrometer,X-ray diffractometer,X-ray fluorescence,and FactSage thermodynamic calculation software.[Results]In the typical operating temperature range of 750-950℃,the sintering and melting degree of synthetic biomass ash aggravates with the increase of temperature and potassium salt mass fraction.In addition,the effects of different forms of potassium salt on the sintering and melting characteristics of biomass synthetic ash are also significantly different.When the potassium salt is in the form of K_(2)CO_(3),the liquid phase in the synthetic ash could reach up to 34.36%,leading consequently to severe sintering of the ash.When the potassium salt is in the form of KCl,most of K and Cl elements escape at 750-850℃,and the sintering degree of synthetic ash is weakened in comparison with the K_(2)CO_(3) situation.When the potassium salt is in the form of K2SO4,the liquid phase in the synthetic ash is the least,and the sintering and melting degree is also the weakest.[Conclusion]Changing the form of potassium salt and controlling the temperature of fluidized bed are expected to alleviate the coking problem of biomass in fluidized bed combustion.