Niu Maofei, Fu Yungang, Liu Shuqin
School of Chemical & Environmental Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
ACS Omega. 2022 Mar 1;7(10):8526-8535. doi: 10.1021/acsomega.1c06336. eCollection 2022 Mar 15.
The Lurgi gasifier in China is one of the most suitable technologies to produce synthetic natural gas (SNG) from coal; however, a large amount of byproduct ash is discharged during the Lurgi gasification process, causing many environmental problems. Based on ash samples collected from a commercial Lurgi gasifier in a Chinese coal-to-SNG plant, this paper studied the mineral composition and microscopic appearance of gasification ash with different particle sizes. The typical minerals were identified and investigated by comparing them with the ash from a laboratory fixed-bed reactor. The results showed that the main high-temperature minerals in the Lurgi gasification ash with different particle sizes under the gasification condition of 4 MPa and 1100 °C were anorthite (CaAlSiO), augite (CaFeSiO), hematite (FeO), and gehlenite (CaAlSiO). As the particle size of the Lurgi gasification ash increased, the quartz content increased but the residual carbon content decreased. Additionally, the high-temperature minerals were more likely to agglomerate with fine particles of the ash. The FactSage modeling showed that calcium-bearing minerals were formed earlier than iron-bearing minerals. The high FeO content in ash hindered the transformation of calcium-bearing minerals into the high-melting-point mullite, resulting in a low ash flow temperature. Additionally, the fine ash had a relatively high content of calcium-bearing minerals which was not conducive to its utilization as an additive in cement and concrete.
鲁奇气化炉是中国最适合用于由煤生产合成天然气（SNG）的技术之一；然而，鲁奇气化过程中会排放大量副产品灰渣，引发诸多环境问题。基于从中国一家煤制SNG工厂的商业鲁奇气化炉收集的灰渣样本，本文研究了不同粒径气化灰渣的矿物组成和微观形貌。通过与实验室固定床反应器的灰渣进行对比，识别并研究了典型矿物。结果表明，在4MPa和1100℃的气化条件下，不同粒径的鲁奇气化灰渣中的主要高温矿物为钙长石（CaAlSiO）、辉石（CaFeSiO）、赤铁矿（FeO）和钙铝黄长石（CaAlSiO）。随着鲁奇气化灰渣粒径增大，石英含量增加而残余碳含量降低。此外，高温矿物更容易与灰渣细颗粒团聚。FactSage模型显示含钙矿物比含铁矿物更早形成。灰渣中高含量的FeO阻碍了含钙矿物向高熔点莫来石的转变，导致灰渣流动温度较低。此外，细灰渣中含钙矿物含量相对较高，不利于其作为水泥和混凝土添加剂的利用。
