In this work, the influence of KCl concentration on the gasification characteristics of lignite coal char between 800–1100 °C is studied through the experiments of temperature programmed gasification and isothermal gasification using a thermogravimetric analyzer. The gasification kinetics, characteristic parameters, and the reaction mechanism of catalytic gasification is explored using the random pore model (RPM). In view of temperature programmed gasification, the gasification rate of coal char is relatively slow when the temperature is below 700 °C, and only when the temperature is higher than 700 °C, the gasification starts to accelerate. Results show that with the existence of a catalyst, the temperature required for gasification reaction is reduced and the gasification reaction rate is increased. Furthermore, the higher concentration of KCl leads to the shorter half reaction time, the higher gasification rate, and the stronger catalysis. In addition, the activation energy of AW-char (the char from acid-washed coal) is the highest, while the activation energy and the energy level required for the gasification reaction are reduced by adding KCl. Based on the analysis of the catalytic mechanism, it is found that the unified mechanism of catalytic gasification of alkali and alkaline earth metals is applicable for the KCl catalysis on coal char gasification.

UV chemical degradation is a low-cost and sustainable wastewater treatment technology that protects the environment. In this study, computational fluid dynamics (CFD), mass transfer, and photochemical kinetic models combined with the continuous flow mode of UV/H₂O₂ were applied for the photochemical reaction of internal airlift circulation photocatalytic reactor to improve the efficiency of the reaction. Results show that with the increase in gas flow rate, the turbulence intensity and internal circulation effect of liquid in the reactor can be enhanced under the condition of constant baffle spacing. The CFD simulation prediction results of the chemical components in the liquid flow show that H₂O₂ has a high correlation with the OH radical formation, which depends on the intensity of UV. Thus, the degradation rate of methylene blue (MB) has a high correlation with UV intensity. The degradation efficiency of MB is improved with the increase in gas velocity by comparing the experimental data with the numerical simulation data. The experimental data are generally lower than the numerical prediction data, and although a certain difference range is observed, the overall prediction results are better.

A 5-month anaerobic co-digestion was conducted using landfill site closure leachate as the inoculum stock solution and kitchen waste as the digestion material. This study investigated biogas production at varying kitchen waste loading rates, as well as changes in humic substances and microbial diversity in the digestate. The results demonstrated that when the waste loading rate was ≤ 2% (%w/w, dry mass ratio of kitchen waste) , the anaerobic co-digestion system efficiently degraded the kitchen waste, with over 90% of total gas production occurring within one day after the experiment commenced, indicating the rapid completion of the gasification process. The analysis of the digestate from the anaerobic co-digestion showed that the humic substance content was more than 20 times greater than that of landfill site closure leachate within 1 month, but the value approached the landfill site closure leachate within 5 months. This indicated the biological transformation of kitchen waste into humic substances was completed within 1 month, and these humic substances formed was essentially degraded within 5 months. The anaerobic co-digestion accelerated the process of kitchen waste spoilage. Additionally, the bacterial and archaeal communities in landfill site closure leachate and the digestate from the anaerobic co-digestion were analyzed, revealing that dominant bacterial groups were Proteobacteria(29.73% ~ 58.34%), Firmicutes(12.76% ~ 27.18%), and Bacteroidetes(9.07% ~ 28.17%), while the archaeal community included Methanobacterium(2.73% ~ 38.19%), Methaneta(1.05% ~ 40.09%), Methanosarcina(8.94% ~ 58.07%), and Methanoculleus(0.57% ~ 33.19%). These findings indicate that landfill site closure leachate serves as the primary source of methanogenic bacteria, and external sewage inoculum is unnecessary for the anaerobic co-digestion of landfill site closure leachate and kitchen waste. These research results will offer data support and technical support for the sustainable utilization of organic solid waste.