Coal Slurry Research Articles

Improving the Storage Stability of Coal Water Slurries Use of a pH-Responsive Thickener

Improving the Storage Stability of Coal Water Slurries Use of a pH-Responsive Thickener

Modification of grouting materials and mechanical properties of coal slurry couplings

Overrunning grouting is used to reinforce the weak zone of the large mining face to prevent accidents, such as flake gangs and roofing, caused by surrounding broken rock and soft coal body. In this study, hydroxypropyl methyl cellulose (HPMC) was used to improve the bonding performance of cement. The influence mechanism of HPMC on cement hydration was analyzed from the perspective of the chemical composition at the microscopic level by testing the properties of the modified material to comprehensively investigate the performance of the material. The results revealed that (1) a novel type of grouting material obtained by adding a certain proportion of HPMC to ultrafine cement effectively improved slurry performance and enhanced the grouting effect; (2) the modification effect was the best when 0.5 wt% HPMC was added. Furthermore, the stability of cement slurry increased by 16.5 %, and the initial setting time was delayed to 2945 min, which provided sufficient time for the slurry to penetrate fractured coal rock; (3) HPMC changed the polymerization morphology of cement particles in the slurry and induced the reaction of large particles with ultrafine cement particles to form an elastic network structure in the solution, which was adsorbed on the surface of the coal body to enhance bonding performance; (4) HPMC changed the pore structure of the specimen, provided space for the formation of alumina, and polymerized with cement particles to form super flaky and bundled aluminite. It improved the mechanical properties of the added solids; and (5) HPMC-modified cement slurry and the added solids form the mutual bite, calcium alum interspersion, and network elastic suction cups, which improved the bonding performance of the coal slurry coupling by 172.8 times and boosted the tensile strength of coal slurry coupling.

Novel desulfurization technology by employing coal gangue slurry as an absorbent: Performance and mechanism study

The elimination of SO2 pollutants from coal fired flue gas through using industrial solid waste as absorbent has received widespread attention. Herein, a novel process on SO2 purification by employing coal gangue slurry is proposed for the first time. The effects of different operating variables on SO2 absorption efficiency were studied, indicating that coal gangue slurry has superior desulfurization performance. The desulfurization capacity can reach up to 33.12 g SO2/L coal gangue slurry. In addition, the desulfurization active substances and products are determined based on the analysis of the composition of gas, liquid and solid phase substances during the desulfurization process. It is found that the Fe3+ dissolved from coal gangue have a significant effect on the efficient absorption of SO2. The HSO3− formed by the dissolution of SO2 in water can be rapidly converted into SO3•− radicals under the catalytic action of trace Fe3+, thereby inducing active oxidizing substances, such as SO5•−, SO4•−, HO2• and HO•, to promote the transformation of SO2 towards SO42−. Subsequently, SO2 removal pathways are revealed. This result has important implications for the industrial application of coal gangue slurry desulfurization technology.

Preparation of refined coal oil-water slurry by blending coal tar with ultra-clean coal filter cake

Preparation of refined coal oil-water slurry by blending coal tar with ultra-clean coal filter cake

A feed-regulated water-only cyclone for improving the separation performance of clean coal from coal slime

Due to the challenges of separation and high costs, coal slime is often directly burned without further separation processing, leading to environmental pollution. Therefore, a feed-regulated water-only cyclone has been proposed to improve the coal slime separation efficiency by controlling the suspended bed. This method optimizes particle characteristics by incorporating a pre-desliming hydrocyclone, the characteristics of particles were optimized to regulate the hindered settling in suspension layer. Response surface experiments were conducted to investigate the impact of structural parameters on separation efficiency, Additionally, under optimal parameter conditions, particle size and density were characterized, and a simulation analysis was conducted using CFD–EDEM. The results showed that the maximum separation efficiency achieved in the experiment was 35.31%. Particle characterization analysis also revealed that, after feed regulation, the proportion of particles with a size of 0.045 mm within high density exceeded 75%. Industrial application experiments demonstrated the feasibility of obtaining a high-quality coal product with over screen yield of 9.29% and an ash content of 9.47%. This transformation of coal slurry into a valuable resource has generated significant economic benefits for enterprises and will address the environmental pollution issue caused by direct combustion and improper disposal.

Study on motion behaviour of coal water slurry particles under vibration conditions

This study uses computational fluid dynamics (CFD) to simulate the motion behavior of coal-water slurry (CWS) particles under vibration conditions. Results show that without vibration, the coal particles settle to the bottom of the container due to gravity, forming distinct regions of low, transition, and high concentration. Under low vibration intensity, the slight energy activates particle motion and promotes settlement. Under high vibration intensity, violent reciprocating motion causes severe shaking and uncertainty, resulting in non-uniform particle distribution and back mixing. Particle velocity distribution is significantly influenced by vibration, with higher frequencies and amplitudes resulting in greater velocities. Additionally, particle pseudo-temperature is higher in the near-wall area due to collisions with particles and wall surfaces. Low frequency and amplitude promote particle settlement, increasing compactness in the bottom area and reducing concentration in the top area. The findings provide valuable insights into CWS behavior under vibration conditions, which can be used to optimize the design and operation of CWS handling and transportation systems.

Study of a Novel Fluidized Bed Flotation Column with Enhanced Bubble Dispersion

Flotation machines and flotation columns are widely used as separation equipment for coal sludge. In order to obtain better flotation results for different particle sizes, the bubble distribution and size in the flow field need to be studied. In this paper, a novel three-phase fluidized bed flotation column (TFC) was designed, and the shear effect of liquid velocity (0.198 m/s, 0.226 m/s, and 0.254 m/s) and static bed height (0.1 m, 0.2 m, and 0.3 m) on the bubbles in the mineralized flow field region was investigated and evaluated for the formation of bubbles by shear in laboratory and semi-industrial experiments. The results show that the increase in filling bed height has a very obvious strengthening effect on the reduction of bubble diameter, and after the filling bed height reaches a certain value, the filling bed height will weaken the effect of apparent gas velocity on bubble diameter. The apparent gas velocity has different influencing effects on bubble diameter, and under conditions of low water velocity, the increase in the apparent gas velocity contributes to the reduction of bubble diameter. The conclusions of this study are expected to optimize the operating parameters of the flotation mineralization process and enrich the study of TFC, which can provide a reference for the design of future TFC studies.

SBSNet: selective branch segmentation network of coal flotation froth images

ABSTRACT Flotation is a physical and chemical process that uses the difference between mineral surface properties to separate valuable minerals from worthless minerals through the attachment of bubbles. The visual information of the flotation foam surface can reflect the flotation effect and will be closely related to the flotation conditions, directly indicating the degree of mineralization of the foam layer. Considering the problem that coal slurry foam images are difficult to segment due to the mutual adhesion of bubbles and fuzzy boundaries, in this work, we proposed a new and effective segmentation algorithm for extracting coal slurry flotation foam edge information. Based on the encoder and decoder structure, a selective multi-branch input segmentation deep neural network model was designed. We evaluated the proposed method and model using a self-built coal slurry foam image segmentation dataset. The intersection over union, mean intersection over union, and PA evaluation indicators of this method increased by 12.8376%, 7.2716%, and 1.457%, respectively, compared with those of the U-Net model. The experimental results showed that the selective branch segmentation network model had high accuracy and robustness in extracting coal slurry bubble edge information, and it could effectively solve the problem of difficult segmentation of coal slurry foam images. This study provided a foundation for optimizing flotation process parameters and realizing intelligent flotation site parameters.

Failure analysis of the end surface of the burner nozzle made of UMCo50 material in long-term high temperature oxygen-enriched sulfur-chlorine environment

As the core device of coal water slurry gasification technology, the failure of the burner nozzle will bring serious technical and safety problems. The purpose of this paper is to determine the mechanism of burner failure based on the characteristics of corrosion products and cracks. The results showed that the Cr2O3 oxide film on the surface of UMCo50 was damaged under the effect of mechanical erosion, high temperature and stress, and the corrosive elements S and Cl in the combustion chamber made it further cracked and peeled off. Therefore, the matrix was corroded and cracks occurred. During the crack propagation process, more M23C6 carbides were precipitated at the grain boundary, it caused Cr-depleted at the grain boundary, which reduced the corrosion resistance of the matrix near the grain boundary. The exfoliation of carbides distributed along the grain boundary also accelerated crack propagation. Through XPS and XRD analysis, it was found that the main corrosion products on the crack surface of the failed parts were: Cr2O3, CoCr2O4, CoO, Fe2O3, FeS. According to the causes of failure analysis, the corresponding improvement measures are put forward.

Impact of anthracite blending and SDS addition on slurryability and stability of Indian high ash coal water slurry

ABSTRACT The conventional modes of transporting coal frequently result in substantial fiscal challenges and environmental deterioration. Slurry-based hydraulic transportation of coal through pipelines has proven to be a feasible and efficient method, offering economic benefits, reliability and minimal ecological damage. Due to the limited and rapidly depleting reserves of high-rank coal, the scientific community is compelled to utilize high ash coal (HAC) to meet the growing demands of the population. The HAC slurry is characterized by poor slurryability, stability and low calorific value. This research presents a straightforward solution to enhance the slurryability and stability of Indian HAC while improving its calorific value. Anthracite and anionic additive sodium dodecyl sulfate (SDS) were added in Indian HAC to prepare a high solid loading blended slurry with improved stability. The rheological characteristics, stability and zeta potential of prepared slurry samples were assessed and analyzed to determine the optimum anthracite proportion and SDS concentration. The optimum anthracite proportion and SDS concentration for low apparent viscosity and maximum stability were 30% and 0.6%, respectively. The inclusion of anthracite and SDS at optimal proportion yielded a slurry with 66% solid concentration, indicating a surge of 14% in the maximum possible solid loading.

Waste to Energy-Effects of Complex Components of Organic Wastewater on Coal Water Slurry Stabilizers

Coal water slurry is an advanced and efficient coal utilization technology, prepare coal water slurry by gasification wastewater can realize the recycling of wastewater and improve the combustion or gasification efficiency of the slurry. Stabilizer is an important component to ensure fluidity and stability in industrial applications of coal water slurry, and the complex substances in wastewater for coal water slurry preparation have a great influence on the stabilizer. Therefore, in this paper, the influence of the major substances in gasification wastewater on the stabilizer is studied. Results show that (a) Ammonia nitrogen substances have adverse effects on stabilizers, because the ionized NH4+ in the solution will bond with the polar groups on the stabilizer, which will affect the stabilizer to lose its effectiveness and reduce the stability of the slurry. (b) Small organic molecules have little effect on stabilizers, this is because the binding strength and quantity of stabilizer to water molecules is much larger than that of organic matters such as phenolic substances. (c) Highvalent metal ions have a greater impact on stabilizers, the metal ions easily form gels or precipitates with the stabilizer, causing it to lose its effectiveness, and also have an electrostatic effect with the carboxyl group on the side chain of the stabilizer, which makes the stabilizer easy to aggregate together and lose the steric hindrance effect, finally cause the stability of the slurry reduced. The conclusion of the influence of substances in wastewater on stabilizer can provide a technical reference for the selection of suitable wastewater and stabilizer to prepare coal water slurry, then promoting the efficient use of energy.

Experimental investigation of buried flexible HDPE pipe

Buried pipes are used mainly for water supply and drainage, among many other applications such as oil, liquefied natural gas, coal slurries, and mine tailings. The pipes used may be rigid (reinforced concrete, vitrified clay, and ductile iron) or flexible (steel, UPVC, aluminum, fiberglass, and high-density polyethylene), although the distinction between them is blurring. Deflection or buckling determines the design of flexible pipes. HDPE pipes are preferred due to their light weight, long term chemical stability and cost efficiency. This project aims to design and fabricate an experimental setup of the model trench as a steel tank filled with the desired type of soil and flexible pipe with the required depth and loading provisions to simulate uniform loading and record the behavior, i.e., deflection of the flexible plastic pipe, compare the observation with the theoretical results, and infer the findings. The deflection characteristics were to be measured with the help of a dial gauge fixed inside the pipe. Additionally, the objective is to study the load deformation behavior of the buried pipe and stress variation across the cross section of the pipe under static loading, along with the influence of depth of embedment and density of backfill on the deformation and stresses in the pipe and the deformation behavior of the buried pipe when soil is reinforced with geogrid reinforcement, and evaluate the structural performance of the pipe. Based on the conclusions, various recommendations can be made in terms of the application of buried flexible HDPE pipes in place of conventional pipes and thereby reducing the risk of leakage and damage and also compensating the cost of pipe systems economically.

Flocculants and Modifiers for More Efficient Flotation and Processing of Coal Sludge

Flocculants and Modifiers for More Efficient Flotation and Processing of Coal Sludge

Removal of selected contaminants of the soil and water environment on a model isolation barrier

Landfill leachate poses a threat to the soil and water environment. Protection against their migration is provided by sealing the bottom and sides of the landfill called containment barriers. Natural clay are used for their construction. Fine-grained industrial waste of a mineral nature has been proposed as an alternative to them. Two-component mixtures of ash from solid fuel combustion and waste coal sludge have been developed. The basic expected property of an isolation barrier is its impermeability. Also important is the sorption capacity of the material from which the barrier is made. Hence, the purpose of the study was to evaluate the potential of the obtained mixtures to remove selected heavy metals and PAHs from aqueous solutions. The examinations of static batch sorption and sorption under flow conditions were conducted in columns. Solutions containing Zn(II), Cd(II), and Pb(II) ions with initial concentrations of 100, 200, and 500 mg L−1 were used in the experiment. For all mixtures, regardless of the initial concentration, batch sorption of metals exceeded 99%. In polymetallic solutions, the competitive phenomena between zinc and cadmium ions were confirmed, resulting in a decrease in the efficiency of their removal from the solution. The column tests carried out using raw leachate from a municipal landfill showed the effectiveness of the mixture in removing PAHs, particularly noticeable for di- and hexacyclic hydrocarbons. The removal rate of the 5 analyzed PAH groups ranged from 47.49 to 70.0%. The obtained results confirmed the high sorption capacity of the tested material, which allows considering its use as a sorbent in environmental engineering.

Arsenic removal from coal by ferric chloride enhanced leaching under ultraviolet irradiation during flue gas desulphurization with coal slurry

ABSTRACT During coal combustion, the harmful element arsenic can be released into environment and cause potential significant harm to human beings. Therefore, it is very important to study the removal of arsenic from coal before combustion. In this work, simulated SO2-containing flue gas was used to leach arsenic from coal in a 1 L UV photoreactor. The effects of FeCl3, ultraviolet (UV), pH and the Cl−/Fe3+ molar ratio on arsenic leaching and SO2 removal were experimentally investigated and the enhancing mechanism was analysed. Experimental results demonstrated that FeCl3 and UV could efficiently increase iron and arsenic leaching percentages and SO2 removal efficiency. UV irradiation could induce the oxidation of most trivalent arsenic. The arsenic leaching percentage was significantly larger than that of iron. Low pH was favourable for iron and arsenic leaching. The optimal Cl−/Fe3+ molar ratio was determined to be 3:1. The introduced ferric chloride could not only increase the concentrations of free radicals and ferric iron oxidants, the chloride ion might also impede the formation of passive coatings, thus increasing the arsenic leaching percentage, intensifying the oxidation of trivalent arsenic and enhancing the removal of SO2.

Study on the mechanism of anionic composite surfactant pretreatment to promote flotation of clay-rich coal slurry: Interfacial interaction

Clay-rich coal slurries suffer from low yield and high ash content during flotation. In this study, the effective recovery of clay-rich coal slurries was facilitated by pretreatment with sodium hexametaphosphate (SHMP) and sodium polycarboxylate complex surfactants. Contact angle and adhesion force tests show that complex surfactants reduce the wettability of the coal. Fourier transform infrared (FTIR) spectroscopy shows that the ring structure of SHMP leads to P-Π stacking with the benzene ring structure on the coal and hydrogen bonding with the oxygen-containing functional groups. Sodium polycarboxylate can combine with the hydroxyl groups on the coal and the oxygen-containing functional groups exposed after multipoint diffusion coverage of SHMP by the multihydroxyl structure on the chain. Atomic force microscopy (AFM) tests show that the complex surfactant is adsorbed on the coal surface by hydrophobic and electrostatic attraction. Adsorption occurs in the form of single- and double-layer adsorption. Zeta potential measurements and scanning electron microscopy (SEM) results show that the addition of a complex surfactant attenuates slime entrainment. Flotation tests show that after pretreatment with the surfactant complex, the cleaning coal yield is increased by 45.14% and the ash content is decreased by 7.92% compared with froth flotation. The flotation effect shows an obvious improvement. The above results help to elucidate the mechanism for composite surfactants to improve the flotation separation effect based on mesoscopic and microscopic aspects and strive to provide theoretical support for efficient flotation.

Synergistic enhancement of coal slurry water sedimentation and dehydration process using PDMDAAC/PAM

Currently, most coal processing plants use a single pharmaceutical system with large dosage and poor sedimentation effect, resulting in poor subsequent dehydration effect. In this study, poly dimethyl diallyl ammonium chloride (PDMDAAC) as coagulant, and polyacrylamide (PAM) as flocculant, were used for synergistic enhancement of the coal slurry water sedimentation and dehydration process. The best pharmaceutical system was determined by integrating the evaluation indexes in the sedimentation and dehydration process. The mechanism of synergistic enhancement of coal slurry water sedimentation and dehydration process using PDMDAAC/PAM was revealed by analyzing zeta potential, SEM, XPS and FTIR spectroscopy results. Moreover, the Box–Behnken response surface methodology was used to determine the order of significance of coagulant dosage (Cc), flocculant dosage (Cm), and coal slurry water concentration (Cs) on the combined sedimentation and dehydration indexes, and Cm > Cs > Cc. Further, the correlation models between the combined sedimentation and dehydration indexes and each factor were established, the pharmaceutical system was further optimized, and model accuracy was verified. The optimal dosage of PDMDAAC10040 was 2.96 mg/L, and that of PAM2610 was 2.31 mg/L. Then, the industrial trials were conducted at the Tara Trench coal processing plant. Interestingly, after replacing the chemical regime, the efficiency of the thickener and filter press has been significantly improved, resulting in a 33.33% reduction in cost. This research can provide significant theoretical guidance and technical support for industrial applications.

Study on quantitative structure–activity relationship of amine surfactants in coal reverse flotation

AbstractWith the deterioration of underground coal quality, hundreds of millions of tons of coal slime in China need to be treated using flotation methods every year. However, the design and selection of coal slurry flotation collectors lack theoretical guidance. In this paper, the quantitative structure–activity relationship (QSAR) model between the molecular structure descriptors of collectors and the flotation recovery and selectivity index is established by using pure kaolinite/clean coal flotation experiments and molecular simulation techniques. Flotation results showed that the flotation recovery rate of kaolinite by collectors with larger head group size, such as DDMAC, DDP, and DTAC, is higher than that of the other collectors with smaller head group size. DDA, DDP, and DD have similar flotation capabilities for clean coal, and their selectivity was slightly better than others. The QSAR model between the molecular structure descriptor and the selectivity index was successfully constructed by combining flotation experiments and molecular simulation results. The reliability of this model has been proven through theoretical analysis and flotation experiments. The molecular simulation results indicate that all eight collectors can advertise on 001 (−) surface of kaolinite, but the final advertisement configuration is different. DDA has less coverage on the surface of kaolinite. When the collector is DDA, the concentration of water molecules near the 001 (−) surface of kaolinite is the highest, indicating that the collector DDA has the weakest effect on improving the hydrophobicity of the 001 (−) surface of kaolinite. DDMAC and DDBAC have the best facilitation to the surface hydrophobicity of kaolinite 001 (−). The research results have theoretical guidance significance for the selection and design of mineral flotation collectors.

Analyzing the flotation kinetics of long-flame coal slurry using water-soluble emulsified collector mixtures

This article investigates the variations in flotation responses of long-flame coal using emulsified collector mixtures, utilizing various flotation kinetic (FK) models for analysis. The fitting process was carried out using the Origin software. The Fourier transform infrared spectroscopy (FTIR) results indicated that as the number of adjacent H atoms increased, the absorption peak on the surface of long-flame coal, processed by various emulsified collector mixtures, gradually shifted towards short-wave numbers. Moreover, the X-ray photoelectron spectroscopy (XPS) results suggested that COC/COH groups on the coal surface could form hydrogen bonds with oxygen-containing functional groups (OCFGs) in the surfactant molecular structure. Furthermore, the hydrophobic groups of the benzene ring in 4-dodecyl phenol (4-DDP) could adsorb onto the coal surfaces through π-π bonds, enhancing the surface hydrophobicity of long-flame coal. Moreover, the flotation performance of long-flame coal was significantly improved using the emulsified mixture of kerosene and 4-DDP, achieving a peak recovery of 39.86 %. The second-order model with a rectangular distribution of floatability led to an excellent fitting to the flotation process of long-flame coal when employing the emulsified mixtures.

Combined effect of particle size distribution and cationic –anionic mixture surfactant on high ash coal water slurry

With the shortage of petroleum products and the depletion of the oil layer, the most significant scientific challenge is to use fuel most economically. Due to easy availability and low cost, more than decades of coal has been used in India for power generation in power plants. As CWS (coal-water slurry) has been accepted in many industries due to its low cost, easy handling, and low emission, still more research is needed to be done to work with multimodal high ash coal and simultaneously to save energy (like pumping power and to enhance the combustion temperature). In this experiment, the effect of high ash content coal in multimodal coal water slurry with additives and without additives and particle size distribution, shear rate, and shear stress on the rheological behavior of CWS has been investigated. By suitable combination, adding fine coal particles with the coarser, different samples were prepared and found that coal concentration of 67 % by weight having a viscosity within permissible value and after mixing with additives concentration of 50 % of CTAB (Cetyltrimethyl ammonium bromide) and SDC (Sodium di-dodecyl sulphate) the apparent viscosity reduces to the minimum value. Adding more CTAB in the slurry will increase the viscosity, and in the presence of these additives, the stability of MSA-1 is 18 days at a weight concentration of 67 %, meaning the slurry will work for 18 days. Significantly less work has been done in high-ash coal with multimodal samples. Here, an attempt has been made with this high ash multimodal sample along with the combination of mixture surfactant to achieve high concentration with less viscosity.