Asia-Pacific Journal of Chemical Engineering最新文献

{"title":"Preparation of calcium aluminate and spinel by hydrolysis and calcination from secondary aluminum dross","authors":"Yuqin Zhao, Zhengping Zuo, Zhanbing Li, Jianbo Zhang, Wen Fen Wu, Wei Ping Ma, Ganyu Zhu, Shaopeng Li, Fei Wang","doi":"10.1002/apj.3117","DOIUrl":"https://doi.org/10.1002/apj.3117","url":null,"abstract":"The direct extraction of alumina from secondary aluminum dross (SAD), which is a dangerous solid waste, is difficult. Moreover, this process easily produces a large amount of solid waste residue, which is not easily utilized. In this paper, a new green process was developed to prepare calcium aluminate and Mg‐Al spinel from SAD by hydrolysis–calcification roasting. The effects of calcium oxide (CaO) content, sintering temperature, and holding time on the properties of calcium aluminate were investigated by single‐factor experiments. The phase transformation mechanism of calcium aluminate was studied by thermodynamic analysis, X‐ray diffraction analysis, X‐ray fluorescence spectroscopy, and scanning electron microscopy. Under the optimal conditions (Ca/Al molar ratio of 0.8, sintering temperature of 1300°C, and holding time of 2 h), the main calcium aluminate phases are CaAl<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> and Ca<jats:sub>2</jats:sub>Al<jats:sub>2</jats:sub>SiO<jats:sub>7</jats:sub>, the soluble alumina content of the calcium aluminate sample is 49.71 wt.%, and the main phases of the acid‐insoluble residue are Mg‐Al spinel and a very small amount of CaTiO<jats:sub>3</jats:sub>. The Ca/Al ratio is the key factor affecting the calcium aluminate phase—with increasing Ca/Al ratio, the calcium aluminate phase is transformed from CaAl<jats:sub>4</jats:sub>O<jats:sub>7</jats:sub> to CaAl<jats:sub>2</jats:sub>O<jats:sub>4</jats:sub> and eventually to Ca<jats:sub>12</jats:sub>Al<jats:sub>14</jats:sub>O<jats:sub>33</jats:sub>, and the Si‐containing phase changes from Ca<jats:sub>2</jats:sub>Al<jats:sub>2</jats:sub>SiO<jats:sub>7</jats:sub> to CaSiO<jats:sub>4</jats:sub>.","PeriodicalId":8852,"journal":{"name":"Asia-Pacific Journal of Chemical Engineering","volume":"27 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141866152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Study on the influence of unloading disturbance of initial load stress on the microstructure and thermodynamic behavior of granular coal","authors":"Hui‐yong Niu, Si‐wei Sun, Qing‐qing Sun, Hai‐yan Wang, Hong‐Yu Pan, Xi Yang, Xiao‐dong Yu","doi":"10.1002/apj.3130","DOIUrl":"https://doi.org/10.1002/apj.3130","url":null,"abstract":"With the advancement of coal mining, the pre‐mining stress on the coal seam increases. After mining, the coal seam fractures and unloads, leaving granular coal in the goaf with a high risk of spontaneous combustion. To investigate the oxidation behavior and underlying mechanisms of granular coal in goafs at various depths, fresh coal was subjected to static stresses ranging from 4 to 16 MPa and then underwent unloading treatment to generate granular coal with varying initial stresses. Subsequently, simulations of granular coal in goafs at various depths were conducted. Structural characteristics (pores and functional groups) and oxidation heat production performance of the granular coal after unloading were analyzed using a low‐temperature nitrogen adsorption instrument, a Fourier infrared spectrometer, and a simultaneous thermal analysis system. The findings suggest that as the initial loading stress increases, the number of micropores and mesopores within the unloaded bulk coal decreases, while the number of macropores increases. Furthermore, important oxidation‐active structures, including ‐OH, ‐CH<jats:sub>3</jats:sub>, ‐CH<jats:sub>2</jats:sub>‐, C=O, and ‐COOH, gradually increase, with a slight decrease observed after exceeding 8 MPa. The pressure‐unloading process leads to a gradual decrease in the characteristic temperature of the bulk coal, with the characteristic temperature increasing after exceeding 8 MPa, although it still remains lower than that of the raw coal. As the burial depth of the goaf increases, the oxidation behavior of the unloaded granular coal becomes more pronounced, leading to an increased tendency and risk of spontaneous combustion. If the initial loading stress on deep coal seams is excessive, the oxidation heat production capacity of the resulting unloaded granular coal may be slightly diminished, yet it still poses a significant disaster risk. The research results can provide valuable insights for mitigating and managing spontaneous combustion risks in coal seam mining operations conducted at different depths.","PeriodicalId":8852,"journal":{"name":"Asia-Pacific Journal of Chemical Engineering","volume":"24 1","pages":""},"PeriodicalIF":1.8,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141777541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}