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To prevent coal spontaneous combustion and store CO 2 in the coal mine, it is necessary to establish a fire-prevention pipeline transport system which continuously injects a large amount of liquid CO 2 from the ground to the underground area directly. At present, few studies are focused on the law of liquid CO 2 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 CO 2 . This study explores the influence of environmental factors at different depths in the coal mine on the liquid CO 2 transport. Excessive altitude difference, ambient temperature and airflow velocity may lead to the boiling of liquid CO 2 during pipeline transport and a sudden drop in CO 2 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 CO 2 . In addition, the influence law of adding an insulating layer of different thicknesses to the CO 2 pipeline system is obtained. This study is of great significance to the establishment of a pipeline system that safely transports liquid CO 2 from the ground to the underground mine.

Using porous materials as a carrier to adsorb and store CO 2 in the vast underground mine goaf is a feasible and effective route to achieve "emission peak" and "carbon neutrality", because this method boasts the advantages of a large storage capacity and remarkable safety. In this research, first, alkaline waste carbide slag was adopted to mineralize and store CO 2. Afterward, a new type of environmentally friendly porous particles for efficiently adsorbing and storing CO 2 in the mine goaf was prepared through the one-step synthesis method using mineralized carbide slag (CS) as the aggregate, oleic acid (OA) as the anionic surfactant, cetyl trimithyl ammonium bromide (CTAB) as the cationic surfactant and sodium hypochlorite (NaClO) as the foaming agent. According to the single-factor experiment results, the optimal ratio of porous particles with a high porosity and a large specific surface area was concluded, i.e., CS = 65–67.5 wt%, OA = 2.75–3.25 wt%, CTAB = 0.2–0.28 wt%, NaClO = 4.25–4.5 wt% and H 2 O = 40 wt%. Under this ratio, the particles enjoy excellent compressive strength and CO 2 static adsorption capacity, i.e., 102.4–110.7 N and 213.7–321.4 cm3/g, respectively. By adding the amount of CO 2 mineralized by alkaline waste (0.41 g/g) and the CO 2 adsorption capacity of waste-based porous particles (321.4 cm³/g), it is calculated that one ton of solid waste can absorb about 1 tons of CO 2. This research discloses the effects of various factors on the compressive strength and CO 2 adsorption capacity of porous particles and provides important guidance for the development of high-performance porous CO 2 adsorbents in the goaf. • Millimeter-grade CO 2 adsorbent with graded pores was prepared from alkaline solid waste. • The optimum ratio of adsorbent with high strength and adsorption capacity was determined. • The CO 2 adsorbent prepared by 1 ton of solid waste stores about 1 tons of CO 2. [ABSTRACT FROM AUTHOR]

In this paper, tetraethylenepentamine (TEPA)-functionalized solid waste-based porous particles were prepared by the wet impregnation method, and their functionalization characteristics and CO 2 adsorption performances at different TEPA loadings were investigated. Through a scanning electron microscope test and a N 2 adsorption/desorption test, it is found that, as the TEPA loading increases from 4 wt% to 20 wt%, the specific surface area and pore volume of the samples decrease slowly and micropores gradually disappear. Besides, the CO 2 adsorption capacity of the samples was tested by a fixed-bed adsorption experimental device at 298 K and 0–1 bar. The results show that the CO 2 adsorption capacity reaches the maximum (71.29 mg/g) at a 12 wt% TEPA loading, which is attributed to the high content of affinity sites in CO 2. Furthermore, the effect of temperature (298–398 K) was investigated at 1 bar. It is concluded that an appropriate increase in adsorption temperature can enhance the flexibility of TEPA and greatly reduce its diffusion resistance. The highest adsorption capacity (83.05 mg/g) is achieved at 348 K. Then, the effect of pressure (0–40 bar) was analyzed at the optimal temperature (348 K) and optimal TEPA loading (12 wt%), and the results suggest that the adsorption capacity gradually strengthens with the increase in pressure, ultimately reaching a peak of 204.06 mg/g. The adsorption selectivities of CO 2 /N 2 and CO 2 /H 2 are 14.88 and 9.66, respectively, indicating that the porous particles have a stronger affinity for CO 2 than for N 2 and H 2. The infrared spectra prove the formation of carbamates, which confirms that CO 2 is sequestered in porous particles by chemical adsorption. The adsorption kinetics and adsorption thermodynamics results reveal the presence of both physical and chemical adsorptions of 12 wt% TEPA-porous particles in the adsorption process, and the chemical one is dominant. [Display omitted] [ABSTRACT FROM AUTHOR]

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 CO 2 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 CO 2 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 CO 2 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. • New graphene oxide-based composite aerogels were synthesized. • CO 2 uptake capacity was evaluated. • The aerogel has good thermal stability. • The interaction energy between aerogel and CO 2 was simulated. [ABSTRACT FROM AUTHOR]

The CO 2 storage technology of abandoned coal mines has problems such as high gas separation costs and incomplete CO 2 separation in the gas capture stage, which hinders the development of abandoned coal mines for CO 2 storage. Regarding the issue above, a new type of carbon dioxide adsorption material has been prepared. Cellulose whiskers/silica composite aerogels were synthesized from skim cotton using tetraethyl orthosilicate (TEOs) and alkaline silica solution as silica precursors through a sol-gel process. The obtained aerogel has a rich porous structure with a specific surface area in the range of 34.7–170.1 m2/g, pore volume in the range of 0.06–1.52 cm3/g, and average pore size in the range of 4.5–11.9 nm. The sample CSA-TEPA-70% showed excellent adsorption performance, with a maximum adsorption capacity of 2.25 mmol/g. The Avrami fractional-order kinetic model can fit the CO 2 adsorption process of the adsorbent well. This adsorbent has broad prospects in the CO 2 capture process. [Display omitted] [ABSTRACT FROM AUTHOR]