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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]

In this paper, a new kind of environmental friendly double‐network gel material was prepared. The first network structure was formed by the graft copolymerization of sodium lignosulfonate (LS) and acrylic acid (AA), and the second network structure was formed by the chelation reaction of sodium alginate (SA) and carbide slag clarified solution (Ca2+). Through an orthogonal experiment, the effects of raw material addition on the compressive strength and apparent viscosity of the gel were analyzed. According to the analysis results, the optimal experimental ratio was obtained, i.e., 2 wt% of LS, 0.25 wt% of SA, 15 wt% of AA, 0.1 wt% of MBA and 0.3 wt% of APS. Furthermore, the structure of the gel are characterized by FTIR, XRD, SEM, XPS, and TG‐DTG, and the results prove that the gel successfully polymerized and a stable three‐dimensional network structure is formed. The results of water absorption experiment disclose that the gel is sensitive to ions and pH, and the water absorption rate reaches 121.25 times. In addition, the results of the air leakage experiment and fire extinguishing experiment show that the gel can effectively cover the surface of crushed coal and densely fill the gaps, demonstrating a good plugging capability and fire extinguishing capability. [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]

Microcapsules containing isophorone diisocyanate were fabricated in oil-in-water emulsion. The emulsification effect of different emulsifiers during the capsule synthesis was systematically investigated by optical microscope. Three kinds of shell materials were discussed to obtain the high core content, smooth-surfaced, and robust capsule by scanning electronic microscope and Fourier transform infrared spectroscopy. Self-healing performance of corresponding self-healing epoxy composites was fully evaluated by accelerated corrosion test and mechanical test. The results demonstrated that high core content and smooth-surfaced capsules with dense composite shell could be synthesized in polyvinyl alcohol emulsion, and the core content of the optimized capsules was determined as 71.3–84.6 wt% at the capsule size from 35 µm to 154 µm. In addition, the optimized capsules had good processing properties and the corresponding self-healing epoxy composites exhibited excellent core release and self-healing performance. [ABSTRACT FROM AUTHOR]

Ultrasonic receiving wave can reflect physical properties and damage degree of coal samples. Therefore, it is of great significance to deeply study the parameters of ultrasonic. In this paper, time-domain characteristics of receiving wave are analyzed systematically, which present good correlation with stress. The frequency spectrum of receiving wave is obtained using Fast Fourier Transform (FFT), and peak frequency and centroid frequency are calculated. During the entire loading process, peak frequency fluctuates around 110 kHz, but corresponding centroid frequency decreases obviously at the end stage of loading. According to multifractal theory, the multifractal spectrum of wavelet packet energy characteristics is calculated. The results show that wavelet packet energy distribution has obvious multifractal characteristics, and multifractal parameter Δ α presents downward trend before coal samples buckling failure. Based on damage process of the coal samples, the reason of change in Δ α value is related to damage degree of coal samples. This research is of great significance for understanding the deformation and failure process of coal samples using ultrasonic technology. [ABSTRACT FROM AUTHOR]

This study details an in situ Fourier transform infrared spectroscopy analytical system that was employed to follow chemical variations in the functional groups on coal surface during the oxidation process at low temperatures. In the reported in situ Fourier transform infrared spectroscopy system, a special chamber was used to contain the coal powders, and a gas inlet tube and a programmable heater were used to simulate different reaction atmospheres and temperatures. The comparisons between in situ and ex situ Fourier transform infrared spectroscopy spectra indicate that the in situ Fourier transform infrared spectroscopy data offer a more accurate reflection of changes in the functional groups. The real-time changes of aliphatic hydrocarbon groups and oxygen-containing groups in a lignite coal sample were analyzed from 30°C to 220°C using in situ Fourier transform infrared spectroscopy. The experimental results indicate that the chemical variations in the functional groups are affected by their relative chemical activities. The results show that the presence of aliphatic groups on the coal surface varies with temperature. Over the range of 30–70°C the presence of these groups decreases, but then their abundance increases over the range of 70–180°C and finally decreases again when the temperature is increased to between 180°C and 220°C. With respect to oxygen-containing functional groups, three various trends were observed as the test temperature was varied. Our conclusion was that these variations are a function of the reaction activities of the various oxygen-containing functional groups. [ABSTRACT FROM AUTHOR]

A binary emulsion system via combination of sodium dodecylbenzenesulfonate (SDBS) and polyvinyl pyrrolidone (PVP) was employed to prepare microcapsules containing isophorone diisocyanate. The effect of different concentrations of SDBS and PVP on the size and distribution of capsules was investigated. The results showed that uniform and size‐controllable capsules were synthesized by synergistic function of SDBS and PVP. Characteristics of capsule were studied by optical microscopy, Fourier transform infrared spectrometry, scanning electron microscopy, thermal gravimetric analysis, and 1H NMR. The results revealed that the core content and yield of the spherical capsules were approximately 65.7 and 79 wt %, respectively, at the capsule diameter of ~115 μm. The residue core content of microcapsules was approximately 44.7 wt % after immersion in water for 10 days. And its self‐healing epoxy coatings showed excellent corrosion resistance performance after accelerated corrosion tests. These results exhibited the feasibility and great application prospect of the multiemulsifiers system in the microcapsule synthesis process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48045. [ABSTRACT FROM AUTHOR]

Fire prevention and extinguishing and CO2 sequestration in coal mine gob require continuous transportation of liquid CO2 in pipelines with large height difference (from ground to underground). However, the temperature and pressure variation of liquid CO2 in pipelines with large height difference is still unclear, which hinders the design of a liquid CO2 pipeline transportation system. The influence of pipe diameter and inlet parameters (temperature and pressure) on the variation of temperature and pressure of liquid CO2 along the 1000 m vertical pipeline was studied in this paper. The study found that for each pipeline diameter considered there existed a range of flowrates where safe flow conditions could be ensured, at which no phase transition occurs throughout the length of the pipeline. When the transporting flow is larger than the maximum limit flow, phase transition occurs dramatically, which will lead to a sudden drop in temperature and pressure. When the transporting flow rate is lower than the minimum limit flow rate, phase transition of CO2 occurs slowly along the pipeline. According to the requirement of underground fire prevention and extinguishing for transporting flow rate and the economic cost of the pipeline system, the optimum diameter is 32 mm, and the corresponding safe transporting flow range is 507–13,826 kg/h. In addition, when the inlet pressure is constant, if the inlet temperature is too high, phase transition of CO2 occurs dramatically at the entrance. For a 1000 m vertical pipe with diameter of 32 mm, when the inlet pressure is 14 bar, 16 bar, 18 bar, 20 bar, 22 bar, 24 bar, the corresponding maximum allowable inlet temperatures are −30 °C, −26 °C, −23 °C, −19 °C, −16 °C and −13 °C, respectively. This research has significant guidance for safety transportation scheme of liquid CO2 from coal mine surface to underground. [ABSTRACT FROM AUTHOR]

In order to gain a knowledge of the heat emitted from a variety of sources at the blind heading of an underground gold mine, the present study conducts an in situ measurement study in a blind heading within the load haul dumps (LHDs) that are operating. The measurements can provide a reliable data basis for the setting of numerical simulations. The results demonstrate that the distances between the forcing outlet and the mining face (denoted as Zm), as well as the heat generation from LHDs (denoted as QL), has brought significant impacts on the airflow velocity, relative humidity, and temperature distributions in the blind heading. Setting Zm to 5 m could achieve a relative optimal cooling performance, also indicating that when the LHD is fully operating in the mining face, employing the pure forcing system has a limited effect on the temperature decrease of the blind heading. According to the numerical simulations, a better cooling performance can be achieved based on the near-forcing-far-exhausting (NFFE) ventilation system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The use of coal combustion inhibitors, which are mostly sprayed on the surface of the coal that remains in the mining region (post-mining inhibition), has a significant effect on preventing spontaneous burning of coal, although their duration of action is limited. Pre-inhibition (pre-mining inhibition) prolong the inhibition duration and offers the chance to change the temperature of the inhibition fluid. This results in the suggestion of a hydrothermal inhibition strategy that emphasises the influence of inhibition fluid temperature on the inhibitory effect in order to achieve accelerated inhibition. Infrared tests and temperature-programmed oxidation are used to explore the inhibition law and mechanism of inhibition temperature on the spontaneous combustion of different coal orders. The findings demonstrated that when the inhibition temperature increased to 30 °C, 40 °C, 50 °C, 60 °C and 70 °C, the average inhibition rate and cross point temperature increased dramatically while the rates of oxygen consumption, exothermic rate, and CO production continuously dropped. Simultaneously, the coal's content of more reactive groups, such methyl and methylene, dropped, and the coal's risk to self-heat reduced. At the 70 °C inhibition temperature, the lignite coal showed the maximum inhibition rate (65.28%). This research is crucial to advancing the inhibitor's application technology and efficiency of inhibition. • A method for hydrothermal fluid inhibition to actively prevent coal spontaneous combustion was proposed. • Increasing inhibition temperature significantly reduces oxygen consumption rate and CO production. • Increasing inhibition temperature significantly increases the cross point temperature and the inhibition rate. • Increasing inhibition temperature can further reduce the key active groups on coal surface. [ABSTRACT FROM AUTHOR]

A pressurized inhibition method is proposed based on the pre-inhibition process to study the inhibition law and mechanism of the pre-inhibition pressure on the coal spontaneous combustion, with a purpose of enhancing the inhibiting effect of chloride salt inhibitors. In this work, inhibited coal samples were prepared by immersing raw coal in high-temperature and high-pressure reactor at 1 MPa, 2 MPa, 3 MPa, 4 MPa, and 5 MPa, respectively, using MgCl 2 solution with a mass concentration of 20 %. The variation rules of the characteristic parameters, such as the indicator gas concentration, inhibition rate, surface microscopic morphology, and reactive groups, of various coal samples with the elevation of the pre-inhibition pressure were investigated using the programmed temperature-raising oxidation system, infrared spectroscopy, and SEM. It was found that the pre-inhibition pressure was in the range of 1–4 MPa, and with the increase of pre-inhibition pressure, the gas-producing concentration and the content of active groups of coal decreased, and the inhibition rate increased significantly. Increasing the pre-inhibition pressure can significantly improve the inhibition effect, and the optimum pre-inhibition pressure is 4 MPa. Continuing to increase the pre-inhibition pressure will destroy the pore structure of the coal and reduce the inhibition effect. [ABSTRACT FROM AUTHOR]

Highlights: [•] It is a linear relationship between and the adiabatic R 70 self-heating rate. [•] A rapid method was developed to determine R 70, which need a time shorter than 1.5h. [•] The was used as an index to classify the spontaneous combustion tendency of coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dopamine hydrochloride functionalized double-walled self-healing microcapsules. • Polydopamine bridges organic and inorganic wall materials. • Microcapsules have good compactness, temperature resistance and repair properties. • Molecular dynamics simulation reveals the microscopic mechanism of microcapsules. With the widespread application of cement-based materials, the self-healing problem of microcracks has become increasingly prominent. Self-healing microcapsule technology has received widespread attention due to its excellent healing properties. However, traditional single-walled microcapsules have a series of defects in the actual application process. To better solve this problem, this study used the method of secondary wall construction to prepare dopamine hydrochloride functionalized E-51@MPF/SiO 2 double-walled self-healing microcapsules. By combining in situ polymerization and the sol–gel method, based on single-walled MPF, polydopamine-loaded nano-SiO 2 particles are introduced to form a double-layer coating structure. Subsequently, a series of microcharacterization experiments were carried out to analyze in detail the morphology, functional groups, particle size, and thermal stability of the functionalized double-walled microcapsules. A uniaxial compression experiment was performed to verify the healing properties of the microcapsules. The results show that dopamine hydrochloride-functionalized double-walled self-healing microcapsules have good compactness, temperature resistance, and healing properties and have excellent particle size. To further analyze the microscopic synthesis mechanism, molecular dynamics simulation was used to elaborate on the two angles of mean square displacement and density distribution. This research innovated self-healing microcapsule technology and improved the safety of cement-based materials in the application process. [ABSTRACT FROM AUTHOR]

Goaf filling is an effective method of preventing goaf disasters in mines. If the filling material can mineralize and absorb a large amount of CO 2 , 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 CO 2 by using the mineralized solid waste as the aggregate. Taking the compressive strength and CO 2 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 CO 2 adsorption capacity was 117.43 cm 3 /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 CO 2 . The pseudo-first-order kinetic model can well fit the adsorption process of an adsorbent for CO 2 , which proves that the adsorption process of adsorbent for CO 2 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 CO 2 and realize the integration of solid waste utilization, carbon storage, and underground space disaster management, with significant social, economic, and ecological benefits.