Preparation and properties of zeolite-fly ash-slag composite porous materials: CO2 adsorption performance and mechanical property.

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.

Influence of Mine Environmental Factors on the Liquid CO2 Pipeline Transport System with Great Altitude Difference.

To prevent coal spontaneous combustion and store CO2 in the coal mine, it is necessary to establish a fire-prevention pipeline transport system which continuously injects a large amount of liquid CO2 from the ground to the underground area directly. At present, few studies are focused on the law of liquid CO2 transport with great altitude difference. Moreover, the complex transport environment in the coal mine affects the design and application of the pipeline transport system for ground direct injection of liquid CO2. This study explores the influence of environmental factors at different depths in the coal mine on the liquid CO2 transport. Excessive altitude difference, ambient temperature and airflow velocity may lead to the boiling of liquid CO2 during pipeline transport and a sudden drop in CO2 temperature and pressure, which may cause danger in the pipeline transport system. The critical insulation thickness is determined based on the occurrence of the boiling of CO2. In addition, the influence law of adding an insulating layer of different thicknesses to the CO2 pipeline system is obtained. This study is of great significance to the establishment of a pipeline system that safely transports liquid CO2 from the ground to the underground mine.

Preparation and CO2 Adsorption Properties of Porous Particles Based on Alkaline Solid Wastes.

Goaf filling is an effective method of preventing goaf disasters in mines. If the filling material can mineralize and absorb a large amount of CO2, then the goaf will provide a huge amount of space for carbon storage, which will help to achieve carbon peaking and carbon neutrality. The purpose of this article is to prepare a kind of porous particle with high porosity and a large specific surface area that can be used to fill the mined-out area and adsorb a large amount of CO2 by using the mineralized solid waste as the aggregate. Taking the compressive strength and CO2 adsorption capacity as the objective function, a chemical foaming method and an orthogonal experiment were used to determine the optimal ratio of porous particles. The results showed that when the masses of carbide slag, oleic acid, cetyltrimethylammonium bromide, sodium hypochlorite, and water were 19.5, 0.3, 0.07, 1.35, and 15 g, respectively, the pore sizes of the prepared porous particles had a gradient distribution, i.e., micropores, mesopores, and macropores accounted for 18.75, 80.93, and 0.32%, respectively. In addition, the compressive strength reached 79.4 N, and the static CO2 adsorption capacity was 117.43 cm3/g. The superimposed calculation of the adsorption capacity and mineralization capacity showed that 1 ton of solid waste can theoretically store approximately 0.66 ton of CO2. The pseudo-first-order kinetic model can well fit the adsorption process of an adsorbent for CO2, which proves that the adsorption process of adsorbent for CO2 is a physical adsorption mechanism. The porous particles prepared based on solid waste are harmless and simple in the preparation process. They can fill the underground space of mines after adsorbing CO2 and realize the integration of solid waste utilization, carbon storage, and underground space disaster management, with significant social, economic, and ecological benefits.

Optimized structural parameters and heat extraction capacity of a mixing device for constant pressure CO2 mineralization using alkaline waste.

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.

Characteristics and main factors of foam flow in broken rock mass in coal mine goaf.

To protect the environment and reduce the occurrence of coal mine fire, foam injection in goafs is an effective measure for preventing and extinguishing mine fires. The flow characteristics of foams injected into goafs have a significant impact on the prevention and extinguishment of such fires. To study the flow characteristics of foam injected into a goaf, we first independently constructed a set of experimental platforms for the visualization of goafs. Next, we performed physical experiments on foam injection using similarity theory. Flow characteristics were simulated under different foam concentrations, flow rates, and goaf porosities. The exponential function was found to provide a good fit to the trajectory of the foam's stacking edge in the goaf. According to the foam injection volume, the trend of the fitting equation parameter a could be divided into two stages. The first stage was the rapidly decreasing stage, and the second stage was the stable stage. It was inferred that the stacking height and diffusion radius of the foam under different conditions were related to the speed of liquid film drainage. The results of this study can provide a valuable reference for the use of fire prevention and extinguishment technology in the goaf.

Preparation and properties of cellulosenanofiber (CNF) /polyvinyl alcohol (PVA) /graphene oxide (GO): Application of CO2 absorption capacity and molecular dynamics simulation.

In order to solve the environmental problems caused by greenhouse gas emissions, cellulosenanofiber (CNF)/polyvinyl alcohol (PVA)/graphene oxide (GO) aerogel was obtained by step-by-step heating, tert-butanol replacement, freeze-drying, and high-temperature activation in this paper. The micromorphology, specific surface area, pore size distribution, and thermal stability of the prepared aerogels were analyzed by scanning electron microscopy, automatic surface area and porosity analysis, and thermo-gravimetric analysis. The interaction state and adsorption mechanism of CO2 and aerogel physical adsorption were described by Materials Studio simulation. The results showed that the adsorption process conformed to the Langmuir adsorption isotherm. After carbonization, the thermal stability of the aerogel was good (mass loss rate <1%). With the increase of GO content, its specific surface area increased (392.41 m2/g) and CO2 adsorption capacity increased (432.76 cm3/g at 273 K). The simulation results show that hydrogen bond energy and van der Waals adsorption are the main factors that help in adsorption of CO2 on the surface aerogel, and electrostatic adsorption is the secondary adsorption factor. The application of green material carbon-based aerogels is also in line with the concept of sustainable development.

Effect of Silane Treatment on Mechanical Properties of Polyurethane/Mesoscopic Fly Ash Composites.

In view of the accidents such as rock mass breakage, roof fall and coal slide in coal mines, polyurethane/mesoscopic fly ash (PU/MFA) reinforcement materials were produced from polymethylene polyphenylene isocyanate (PAPI), the polyether polyol, flame retardant, and MFA using stannous octanate as a catalyst. 3-Glycidoxypropyltrimethoxysilane (GPTMS) was grafted on MFA surface, aiming to improve the mechanical properties of PU/MFA composites. The analyses of infrared spectroscopy and compression resistance reveal that the GPTMS can be successfully attached to the surface of MFA, and the optimum modification dosage of GPTMS to MFA is 2.5 wt % (weight percent). On this basis, the effect of GPTMS on the mechanical properties of PU/MFA reinforcement materials during the curing process was systematically investigated through a compression test, a fracture toughness test, a three-point bending test, a bond property test, and a dynamic mechanics analysis. The results show that the compression property, fracture toughness, maximum flexural strength, and bond strength of PU/MFA composites increase by 21.6%, 10.1%, 8.8%, and 19.3%, respectively, compared with the values before the modification. Furthermore, the analyses of scanning electron microscope and dynamic mechanics suggest that the coupling agent GPTMS can successfully improve the mechanical properties of PU/MFA composites because it eliminates the stress concentration and exerts a positive effect on the crosslink density and hardness of PU/MFA composites.