Influence of coal properties on dust suppression effect of biological dust suppressant

A hydrogel microparticle based on alginate encapsulation for microbial dust suppression: Enhancing control of dust-suppressing bacteria and coal dust consolidation

This study addresses the issue of unsuitable storage and application of liquid microbial dust suppressants in open-pit coal mines by employing microbial encapsulation technology. Sodium alginate-encapsulated dust suppression hydrogel microparticles with a diameter of ~2.57 mm were prepared, which solidify the dust suppressant, enhancing storage, transport, and application. These hydrogel microparticles demonstrate resistance to fracture force (up to 0.724 N) and springiness (0.516 mm). X-ray Diffraction analysis shows that the microparticles promote calcite-type CaCO3 nucleation and growth, exhibiting greater thermal stability and higher residual mass compared to liquid cultures. Dust suppression experiments reveal that hydrogel microparticles significantly improve coal dust consolidation, reducing dust dispersion. X-ray Photoelectron Spectroscopy and quantum chemical analysis show weak van der Waals interactions between the hydrogel and oxygen atoms on coal dust, with hydroxyl groups forming hydrogen bonds with urea molecules to promote urea aggregation. The carboxylate groups in sodium alginate facilitate calcium ion adsorption, serving as nucleation sites for calcium carbonate. This continuous calcium carbonate growth consolidates the hydrogel microparticles with coal dust, forming a mineralized layer that effectively suppresses dust.

Preparation of Consolidated Dust Suppression Materials Based on Pectin: Graft Modification Experiment and Reaction Mechanism

The natural material pectin was used as the matrix to prepare a dust suppressant. The regression model in response to the grafting ratio was established, and the optimum modification scheme was determined. The amount of monomer, initiator, cross-linking agent, and reaction temperature was 3.20 g, 0.20 g, and 0.15 g and 92 °C, respectively. Through Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy tests, not only the formation of the product in graft copolymerization reaction was validated but also the wettability of pectin was significantly improved. The surface morphology of pectin before and after modification was observed by a scanning electron microscope. After graft copolymerization treatment, the surface of pectin presented a dense grid structure, which proved that the pectin-modified dust suppressant can play a crucial role in wetting and condensing coal dust. Contact angle tests were used to characterize the effect of pectin modification on the wettability of bituminous coal before and after modification. The results of contact angle tests showed that when the droplets just contacted the bituminous coal flakes, the contact angle of modified pectin droplets on the flakes was the smallest, and the value was 55.21°. Compared with pure water droplets and unmodified pectin droplets, it decreased by 21.66° and 18.50°. The modification reaction process and dust suppression mechanism were explained at the molecular level.

Preparation of an environment-friendly microbial limestone dust suppressant and its dust suppression mechanism

The development of an efficient and environmentally friendly dust suppressant is crucial to address the issue of dust pollution in limestone mines. Leveraging the synergistic microbial-induced calcium carbonate precipitation (MICP) technology involving NaHCO3 and dodecyl glucoside (APG), the optimal ratio of the dust suppressant was determined through single-factor and response surface tests. The dust suppression efficacy and mechanisms were analyzed through performance testing and microscopic imaging techniques, indicating that the optimal ratio of the new microbial dust suppressant was 20% mineralized bacteria cultured for 72 h, 0.647 mol L-1 cementing solution, 3.142% NaHCO3, and 0.149% APG. Under these conditions, the yield of calcium carbonate increased by 24.89% as compared to when no NaHCO3 was added. The dust suppressant demonstrated excellent wind, moisture, and rain resistance, as well as curing ability. More calcite was formed in the dust samples after treatment, and the stable form of the dust suppressant contributed to consolidating the limestone dust into a cohesive mass. These findings indicate that the synergistic effect of NaHCO3 and APG significantly enhanced the dust suppression capabilities of the designed microbial dust suppressant.

A Novel Microbial Compound Inhibitor and Its Efficacy in Preventing and Controlling Mine Fire Risks: A Case Study on Low-Rank Coal Spontaneous Combustion

To guarantee the safety and sustainability of coal mining by effectively mitigating the substantial risk associated with coal spontaneous combustion, this study proposes a multifaceted prevention strategy aligned with green environmental principles. A compound flame retardant with a physicochemical control mechanism was prepared using indigenous microorganisms to mineralize residual coal after mining, utilizing Bacillus pasteurelli as a substitute material for inorganic salts. Under laboratory conditions simulating coal self-combustion, biobased flame retardants were employed to investigate the physical and chemical transformations of heat and mass evolution from ambient temperature to combustion in two representative low-rank coals. By quantitatively comparing alterations in microbiome-based groups among raw lignite, bioretarded lignite, and two control samples, the inhibitory mechanism of biobased materials on the oxygen reaction pathway was elucidated. The findings substantiated that biobased modification can consolidate the methyl and methylene groups present in aliphatic hydrocarbon side chains, which are prone to instigating low-temperature oxidation reactions. Additionally, the preventive performance of biobased flame retardants was assessed through temperature-programmed experiments, which involved estimating the critical self-heating temperature, oxygen consumption, and gas production rates of compared coal samples. The results demonstrated significant enhancements in the resistance to spontaneous combustion following bioretarded modification. Notably, the identification grade of long flame coal shifted from easy to moderate susceptibility to spontaneous combustion. Furthermore, biobased flame retardants exhibited remarkable flame retardancy rates of approximately 80% for lignite, thereby validating their efficacy as more environmentally friendly and technologically advanced substitute materials for inhibiting spontaneous combustion in low-rank coals.

Study on the influence pattern and efficiency enhanced mechanism of acoustic-chemical spray dust reduction

To study the influence pattern and efficiency enhanced mechanism of acoustic-chemical spray method on dust reduction, a self-developed acoustic excitation test platform, viscosity test, surface tension experiment and sinking experiments were used to investigate the chemical spray properties and the wetting behavior of coal dust excited by acoustic waves. The self-developed acoustic-chemical spray dust reduction simulation platform was used to study the influence of acoustic waves on coal dust reduction effect and its efficiency enhanced mechanism. The results showed that the surface tension and viscosity of the chemical spray solution fluctuated between 0.4 mN/m and 0.4 mPa·s along with the variations in acoustic wave frequency and sound pressure level (SPL), thereby confirming that acoustic waves had on effected on chemical spray solution properties. However, the wetting time of the chemical spray solution on coal dust increased by 33.64 % at an acoustic frequency (f) of 1300 Hz and SPL of 120 dB because of the liquid interface vibrations caused by acoustic waves. With an increasing of acoustic frequency, the dust reduction efficiency demonstrated a parabolic trend and reached its maximum value at f = 1300 Hz. The dust reduction efficiency also increased exponentially along with increasing SPL. Acoustic waves not only increased the collision frequency between particles and droplets by changing the trajectory of dust but also accelerated the wetting and agglomeration effect of chemical spray reagents on coal dust by causing vibrations at the gas-liquid interface, thereby enhancing the dust reduction efficiency. Compared to the dust reduction efficiency of chemical spray technology, the total dust reduction efficiency was increased by 8.53 %, and the respirable dust reduction efficiency was increased by 21.93 %. The effect of acoustic waves on the respirable dust reduction efficiency was more significant than that on total dust.

Effect of surfactant on urease-producing flora from waste activated sludge using microbially induced calcite precipitation technology to suppress coal dust

The wettability of microbially induced calcite precipitation (MICP) is a challenge in dust suppression. Herein, the tolerance of urease-producing flora to surfactants was investigated. The optimal tolerance concentrations of the urease-producing flora to sodium dodecylbenzene sulfonate (SDBS, anionic surfactant), alkyl polyglycoside (APG, non-ionic surfactant), and cocamidopropyl betaine (CAB, zwitterionic surfactant), and were 0.2%, 0.1%, and 0.05%. The cetyltrimethylammonium bromide (CTAB, cationic surfactant) inhibited urease production by urease-producing flora. The mineralization products of SDBS, APG, and CAB treatments were all transformed into calcite. The wind resistance test showed that the mass loss of all samples is less than 0.1%. The rain resistance and hardness tests showed that 0.2% SBDS had the best effect, followed by 0.1% APG and 0.05% CAB, and finally, No surfactants. Microbiome analysis showed that the abundance of Sporosarcina and Unclassified_bacillaceae reduced, and the intense competition between Paenalcaligenes and Sporosarcina are essential reasons for reducing urease activity. SDBS and APG could reduce the pathogenic risk of microbial dust suppressants. This study will facilitate the practical application of microbial dust suppressants.

Research on the air supply adjustment technology of breath-following powered air-purifying respirators

In the hope of reducing the air supply flow of the powered air-purifying respirator (PAPR) and extending the service life of the filter, a breath-following powered air-purifying respirator (BF-PAPR) that can dynamically adjust the air supply flow according to the breathing flow is proposed. The BF-PAPR changes the air supply flow by adjusting the speed of the variable-frequency centrifugal fan according to the air velocity at the half mask outlet (v_hm) monitored by the modular wind speed transmitter. In the study, the air supply flow adjustment model of the BF-PAPR is developed. It is found that the filtration resistance barely influences v_hm. In addition, under the same mean inhalation flow, the minimum outlet air velocity increases first and then decreases with the increase of the duty cycle variation coefficient (λ), while the maximum outlet air velocity decreases first and then increases. Moreover, the minimum air supply flow of the BF-PAPR is achieved when the standard value of the air velocity is 13.4 m/s and the value of λ is 1. The BF-PAPR can reduce the air supply flow by 6.5%-8.6% and the energy consumption by approximately 20% compared with the PAPR, which is beneficial for reducing the usage cost and extending the continuous working time.

Synergistic interactions of microbial fuel cell and microbially induced carbonate precipitation technology with molasses as the substrate

The application of microbially induced carbonate precipitation (MICP) technology is critical, but many challenges remain. In this paper, a microbial fuel cell (MFC) is used to treat molasses wastewater, and the effluent is used as the substrate to promote the growth of urease-producing bacteria. The results showed that the maximum voltage of MFC was 500 mV, and the maximum power density was 169.86 mW/m². The mineralization rate reached 100% on the 15^th day, and the mineralized product was calcite CaCO₃. According to the microbial community analysis, the unclassified_Comamondaceae, Arcobacter, and Aeromonas, which could improve the OH^-, signal molecular transmission and small molecular nutrients to promote the urease activity of urease-producing bacteria. The above conclusions provide a new way to reuse molasses wastewater efficiently and to apply MICP technology in dust suppression.

Study on MICP dust suppression technology in open pit coal mine: Preparation and mechanism of microbial dust suppression material

With the recent increases in energy demands, the dust hazards of coal mining caused by transportation, loading and unloading and other processes are becoming increasingly serious. To control dust in open pit coal mines more environmentally friendly and efficiently, and to promote the use and development of non-in situ high-yield urease microorganisms for dust suppression in coal mines, Bacillus pasteurii was selected for dust suppression experiments in this article. Additionally, the growth of microorganisms in the coal dust microenvironment was simulated, and the effect of microbial mineralization products on the calorific value of upper coal dust was further studied. Our findings indicated that Bacillus pasteurii induced dust suppression by forming a calcite precipitate with non-uniform particle size to coal dust cementation. Moreover, after a single spray, the wind erosion resistance efficiency was 84% when the wind speed was set at 10 m/s. The growth of microorganisms and urease activity in the coal dust leachate were largely equal to those in the control group, reaching a peak at approximately 24 h, that the maximum growth quantity of OD₆₀₀ was about 1.5, and the maximum urease activity was 11 mmol·L^-1·min^-1. The difference between the peak heat release rate of mixed coal dust and pure coal was only 4.82 kW/m², which would not affect the value of coal products. Non in-situ Bacillus pasteurii can be growth metabolized normally in the microenvironment of coal dust. Finally, the mechanism of coal dust suppression by mineralization of microbial bacterial solution to form calcium carbonate was described by a reaction equation, which is important for further application and development of microbial dust suppressants.

Experimental study on ratio optimization and application of improved bonded dust suppressant based on wetting effect

Traditional bonded dust suppressants have high viscosity, insufficient fluidity and poor permeability problems, which is adverse to the formation of a continuous and stable solidified layer of dust suppressant solution on the surface of a dust pile. Gemini surfactant has efficient wetting performance and environmental protection performance, it is introduced as a wetting component to improve the flow and penetration performance of bonded dust suppressant solution, polymer absorbent resin (SAP) and sodium carboxymethyl starch (CMS) were selected as the main components of dust suppressant. A proportioning optimization model was constructed based on response surface methodology (RSM), and the concentration of each dust suppression component was selected as the independent variable, water loss rate, moisture retention rate, wind erosion rate and solution viscosity were chosen as the dependent variables in this model. The optimal formulation of the improved bonded dust suppressant was obtained by analyzing the laboratory experiments and field tests data. The results show that the effective time (≥15d) of the newly developed dust suppressant is 45 times longer than that of pure water (≈1/3d), and 1.875 times longer than that of the comparative dust suppressant (8d), the comprehensive cost is 27.36% lower than that of the similar dust suppressant product for mining enterprises.Implications: This paper presents the research idea of optimizing the bonded dust suppressant based on the improvement of wetting performance. And the paper used response surface method to obtain a wetting and bonding composite dust suppressant formulation. The field test shows that the dust suppressant has good dust suppression performance and economic benefits. This study laid the foundation for the development of new and efficient dust suppressants, and had important theoretical and application values for reducing dust environmental hazards and preventing occupational diseases.

Synthesis and performance determination of a glycosylated modified covalent polymer dust suppressant

Traditional polymer dust suppressants are limited due to environmental pollution, while polymer gels have attracted attention due to the advantages of environmental protection and good biocompatibility. The purpose of this research is to prepare a new type of dust suppressant with a gel network structure, which was synthesized from soybean protein isolate and glycosylated with xanthan gum. The experimental results showed that the product obtained by reacting 0.2 % xanthan gum and 0.1 % soybean protein isolate at 90 °C for 4 h has the best binding effect on coal dust, and the coal husk hardness can reach 83 HA. The microscopic reaction and structure of the product were analyzed by infrared spectroscopy, X-ray diffractometer, and scanning electron microscope, and the results revealed the structural change and specific reaction process of the product. In addition, through molecular dynamics simulation, the dust suppression effect was confirmed and the mechanism of action between dust suppressant and coal was revealed. The performance test of the dust suppressant showed that its viscosity is 23.4 mPa·s, the contact angle at 1 s is 10.01°, the PM10 dust suppression efficiency can reach 98.10 %, the water retention is 44.44 % higher than that of water, and thermal stability is improved.

Carboxymethyl cellulose sodium gel: A modified material used to suppress coal dust pollution

To reduce the environmental pollution caused by coal dust, a new type of dust inhibitor with a wide application range, high efficiency, and production simplicity was synthesized by modifying sodium carboxymethylcellulose (CMC-Na) with acrylamide (AM). Through molecular dynamics simulations and experiments, the surfactant composition and concentration were optimized. The experimental results showed that the graft copolymer of CMC-Na and AM (CMC-Na-co-AM) had more pores on the microscopic surface and a unique fiber network structure, which greatly increased its contact area with coal dust. After 14 h of drying at 60 °C, coal samples that were sprayed with the dust suppression agent retained >50% of the water in the spray, which was 9 times greater than the water retention of coal samples sprayed with just water. Additionally, the ability of the dust suppression agent to resist wind erosion was 6 times that of water. The CMC-Na-co-AM dust suppression agent showed that it could effectively inhibit the spread of coal dust under strong winds, offering a solution to the problem of coal dust pollution in coal production and storage.