Zhao Lijun
Advanced Materials Research Center, National Institute of Clean-and-Low-Carbon Energy, Future Science City, Changping District, Beijing 102211, China.
Materials (Basel). 2025 Aug 4;18(15):3661. doi: 10.3390/ma18153661.
An advanced alkali-acid (NaOH-HCl) chemical method was used to deash aluminum-rich coals (ARCs) with a high ash content of 27.47 wt% to achieve a low ash content of 0.46 wt%. In the deashing process, aluminum in the coal ashes was dissolved in both alkali solutions and acid solutions. The deashing alkali solutions with dissolved coal ashes were regenerated by adding CaO, and the resulting precipitates were added with sodium bicarbonate for aluminum extraction. High temperatures increased aluminum extraction, and excessive sodium bicarbonate addition decreased aluminum extraction. The deashing acid solutions were concentrated by evaporation, and silica gels formed during the process. The obtained mixtures were calcinated at 350 °C for the decomposition of aluminum chlorides, and soaked with water at 60 °C to remove the soluble chlorides. For the insoluble oxides after soaking, diluted alkali solutions were used to extract the aluminum at 90 °C, and aluminum extraction failed due to the formation of albite in the presence of sodium, aluminum and silicon elements as proved by XRD and SEM/EDS. When silica gels were separated by pressure filtering, aluminum extraction greatly increased. Aluminum extractions were accordingly made in the form of sodium aluminate from the deashing solutions of coals, which could be advantageous for sandy alumina production.
采用先进的碱-酸（NaOH-HCl）化学方法对灰分含量高达27.47 wt%的富铝煤（ARC）进行脱灰处理，使其灰分含量降至0.46 wt%。在脱灰过程中，煤灰中的铝溶解于碱溶液和酸溶液中。通过添加CaO对含有溶解煤灰的脱灰碱溶液进行再生，并向所得沉淀物中添加碳酸氢钠以提取铝。高温提高了铝的提取率，而过量添加碳酸氢钠则降低了铝的提取率。脱灰酸溶液通过蒸发进行浓缩，在此过程中形成硅胶。将所得混合物在350 °C下煅烧以分解氯化铝，并在60 °C下用水浸泡以去除可溶性氯化物。对于浸泡后的不溶性氧化物，使用稀碱溶液在90 °C下提取铝，但由于在钠、铝和硅元素存在的情况下形成了钠长石，XRD和SEM/EDS证明铝提取失败。当通过压滤分离硅胶时，铝的提取率大大提高。相应地，从煤的脱灰溶液中以铝酸钠的形式进行铝提取，这可能有利于砂状氧化铝的生产。
