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Pipeline transportation of liquid CO2 can not only prevent coal mine fires, but also effectively store greenhouse gase CO2 in underground, which is in line with the current global economic development model. Due to the temperature difference of the mine environment and the inclination of the roadway, heat exchange and large pressure drop will inevitably occur in the pipeline. In order to avoid the phase change of liquid CO2 during transportation, it is necessary to consider factors such as ambient temperature, wind speed, insulation cotton, pipeline inclination, and terrain elevation to ensure safe, cost-effective transportation. Based on the commercial simulation software ASPEN HYSYS V8.4, this paper simulates the process of liquid CO2 transportation. The results show that the inclination of the pipeline has a great influence on the CO2 transportation process among environmental factors and is conducive to liquid CO2 transportation.

To solve the environmental problems caused by greenhouse gas emissions, porous materials based on alkaline solid wastes (fly ash and slag) were prepared in this study. Besides, the preparation scheme of the porous materials was optimized through an orthogonal test by taking the compressive strength and static CO2 adsorption capacity as the target parameters. The two target parameters of the porous materials prepared under the optimal ratio are 15.395 N and 0.83 mmol/g. On the basis of the optimal ratio, zeolite composite porous materials were prepared by adding different types of zeolite, which further improves the CO2 adsorption capacity of the porous materials. Furthermore, the micro-morphologies, CO2 adsorption performances, and mechanical properties of the porous materials were analyzed by a scanning electron microscope (SEM), the Brunauer–Emmett–Teller (BET) method, and a universal testing machine. It is discovered that the addition of different types of zeolite decreases the compressive strength but significantly improves the CO2 adsorption performance as it can promote the specific surface area and the pore volume. Moreover, the best performance is achieved with the addition of 13X zeolite. In this case, the adsorption capacity reaches 2.68 mmol/g, about 3.2 times greater than that of the porous materials without zeolite. The CO2 adsorbent proposed in this study, which boasts excellent mechanical property and CO2 adsorption performance, is applicable to goafs and has a bright prospect in the comprehensive utilization of solid wastes and the control of global warming. [ABSTRACT FROM AUTHOR]

Alkaline waste such as calcium carbide slag is an ideal material for mineralizing CO2 and promoting atmospheric carbon reduction. In this study, the structural parameters of a mixing device and a thermal extraction method for the high-efficiency mineralization of CO2 using alkaline waste were optimized. First, the influence of structural parameters was studied by means of numerical simulation, and it was found that when the length–diameter ratio, blade angle, spacing, and diameter of the mixing device were 3, 15, 6 cm, and 14 cm respectively, 2.14 t CO2 can be mineralized within 1 h. The amount of heat extracted from mineralization of 1 t CO2 reached 189.60 MJ. In addition, the winding configuration of the heat pipe, which is beneficial for extracting more reaction heat, was optimal, and a model of the relationship between the heat pipe outlet water temperature and flow velocity at the outlet of the heat pipe was established. This study provides theoretical guidance for the field application of alkaline waste for high-efficiency mineralization of CO2, which can accelerate the realization of peak CO2 emissions and carbon neutrality. [ABSTRACT FROM AUTHOR]

Smoldering of coal is a considerable source of danger in coal mines because it can lead to a gas explosion, which can cause heavy casualties. This work investigated the apparent smoldering reaction model of coal and its kinetic parameters, which are needed to study smoldering fire in a closed fire area of a coal mine. A series of thermogravimetric tests at different oxygen concentrations were performed, and the change in the pyrolysis and oxidation reaction with the oxygen concentration was analyzed. It is concluded that the apparent reaction model of smoldering coal should include a three-step pyrolysis reaction (i.e., drying, depolymerization, and polycondensation) and a five-step oxidation reaction (i.e., oxidation of coal, semi-coke, and three types of char). A genetic algorithm is used to identify the optimal kinetic parameters of the smoldering reaction. It is determined that in atmospheres with different oxygen concentrations, coal has different kinetic parameters. When studying smoldering fire in a closed fire area of a coal mine, it is suggested to adopt the kinetic parameters of the smoldering reaction in a 1% oxygen concentration atmosphere. [ABSTRACT FROM AUTHOR]