Wang Hui, Cheng Lihua, Pu Jianglong, Zhao Jigang
College of Biological, Chemical Sciences and Engineering, Jiaxing University, 118 Jiahang Road, Jiaxing, Zhejiang Province 314001, China.
Guangdong Provincial Engineering Technology Research Center of Petrochemical Corrosion and Safety, Guangdong University of Petrochemical Technology, Maoming, Guangdong Province 525000, China.
ACS Omega. 2021 Jun 9;6(24):16066-16075. doi: 10.1021/acsomega.1c01949. eCollection 2021 Jun 22.
The flow temperature (FT) of the coal ash from the Liuqiao no. 2 mine in North Anhui Province (C00) is too high (∼1520 °C) to fit the Shell gasifier due to its relatively high content of SiO and AlO. To solve this problem, a series of coals were blended with C00 with different ratios, and the relations between FT and the ash composition were investigated. The coal ash was analyzed by X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy-EDX to elucidate the mechanism of the improved ash fusion performance and the slag formation in the waste heat boiler of the gasifier. It is shown that FT is relevant to the coal ash compositions as well as the structures formed at high temperatures. The existence of alkaline oxides (CaO, MgO, and FeO) decreases the coal ash FT to a low level. The FT can decrease to <1350 °C to cater to the Shell gasifier by blending C00 and C03 with a mass ratio of 4:6 owing to the plentiful alkaline oxides in C03. The FTIR results indicate that the high flow temperature of C00 is attributed to the formation of mullite at high temperatures. The coal blending with various ratios changes the compositions of CaO, MgO, and FeO, which can form some low-melting-point eutectic compounds with SiO and AlO under high temperatures, inhibit the formation of mullite, and thus decrease the ash FT. The coal ash FT was found to have a good linear relation with the ash compositions, which can sever as a reference to the coal blending. According to the model parameters, it is shown that Mg has the most significant promoting effect on the decrease in FT of the coal ash. The caking tendency of fly ash increases with the rising Ca content and an excessive Ca-based fluxing agent used in the coal blending will lead to the aggregation of the Ca-rich clasts around the fly ash particle, resulting in the plugging of the waste heat boiler in the gasifier. Therefore, the Mg-based fluxing agent is more promising to improve the ash fusion performance and reduce the caking tendency of the coal fly ash.
皖北刘桥二矿（C00）的煤灰流动温度（FT）过高（约1520℃），由于其相对较高的SiO和AlO含量，无法适配壳牌气化炉。为解决这一问题，将一系列煤与C00按不同比例混合，并研究了FT与灰分组成之间的关系。通过X射线衍射、傅里叶变换红外（FTIR）光谱以及扫描电子显微镜-能谱仪（SEM-EDX）对煤灰进行分析，以阐明气化炉余热锅炉中灰熔融性能改善及炉渣形成的机理。结果表明，FT与煤灰成分以及高温下形成的结构有关。碱性氧化物（CaO、MgO和FeO）的存在会将煤灰FT降低到较低水平。由于C03中含有丰富的碱性氧化物，将C00与C03按质量比4:6混合，FT可降至<1350℃，以适配壳牌气化炉。FTIR结果表明，C00的高流动温度归因于高温下莫来石的形成。不同比例的配煤改变了CaO、MgO和FeO的组成，它们在高温下可与SiO和AlO形成一些低熔点共晶化合物，抑制莫来石的形成，从而降低灰FT。发现煤灰FT与灰分组成具有良好的线性关系，可为配煤提供参考。根据模型参数，表明Mg对煤灰FT降低的促进作用最为显著。随着Ca含量的增加，飞灰的结焦倾向增大，配煤中使用过量的钙基助熔剂会导致富含Ca的碎屑聚集在飞灰颗粒周围，从而导致气化炉余热锅炉堵塞。因此，镁基助熔剂在改善灰熔融性能和降低煤飞灰结焦倾向方面更具前景。
