Coal Slurry Research Articles

Study on the degree of influence of coal chemical structure on its wetting characteristics

The wettability of coal plays a crucial role in determining the effectiveness of mine dust reduction, coal flotation, and coal water slurry preparation. This property is influenced by various factors, including coal structure and liquid properties. To investigate the impact of coal’s chemical properties on its wetting behavior, we employed different experimental to characterize the chemical structures of six types of coal. Utilizing contact angle experiments and gray slope correlation analysis, we determined the correlation between each chemical structure parameter and the wetting characteristics of the coal samples. Our findings revealed that 6#Yangquan anthracite has the lowest wettability and its contact angle is 85.3°. Within the coal’s functional group structure, the CH2 symmetric stretching vibration exhibited the highest correlation (0.944) with coal wetting properties. Regarding the elemental composition of coal, oxygen exhibited a higher correlation with coal-wetting properties (carbonyl oxygen structure, 0.788; phenol hydroxyl and ether oxygen bond, 0.798; carboxyl oxygen structure, 0.734). In the carbon skeleton structure of coal, the protonated aryl carbon exhibited the highest correlation degree of 0.944. These results offer insights into the selection of evaluation indices for assessing the influence of coal wetting characteristics and optimizing the hydrophilic and hydrophobic features of the coal surface.

Enhancement, application, and challenges of chromium–corundum high‐temperature refractories

AbstractChromium–corundum, as a common refractory material, is broadly applied in high‐temperature kilns due to its superior thermal stability and high melting point. Unfortunately, this refractory is susceptible to corrosion and destruction under extreme furnace conditions by chemical erosion, mechanical wear, and thermal shock, which significantly shortens its useful life. Accordingly, in recent years, the issue of how to improve the slag corrosion resistance, mechanical, and sintering properties of chromium–corundum refractories has aroused widespread attention. In this work, the corrosion behavior and application status of chromium–corundum refractories in Ausmelt furnace, waste incinerator, coal water slurry gasifier, and HImelt melting reduction furnace are analyzed and discussed. To improve the service life of chromium–corundum refractories, the enhancement method and mechanism of sintering performance, mechanical properties, slag corrosion resistance, and thermal shock resistance are also summarized. Finally, some suggestions and prospects are made for the enhancement and longevity of chromium–corundum refractories.

The effect of modified oily sludge on the slurry ability and combustion performance of coal water slurry

Abstract The aim of this study is to find a solution to the challenging problem of disposing oily sludge (OS). Three different types of modifiers, namely, sodium hydroxide (NaOH), sodium dodecylbenzene sulfonate (SDBS), and polyoxyethylene polyoxypropylene polyether (AE) were employed for the simple modification of OS. The influence of modified OS on slurry ability and combustion performance were investigated. The results showed that OS modified by NaOH and SDBS can increase the concentration of coal OS slurry. However, the influence of AE modification on slurry concentration is intricate. In terms of combustion performance, the change in activation energy results in NaOH and SDBS modifications decrease T i and T h of coal OS slurry, while AE modification increases T i and T h of coal OS slurry.

Dynamic risk assessment of a coal slurry preparation system based on the structure-variable Dynamic Bayesian Network.

In order to strengthen the safety management of coal slurry preparation systems, a dynamic risk assessment method was established by using the bow-tie (BT) model and the Structure-variable Dynamic Bayesian Network (SVDBN). First, the BT model was transformed into a static Bayesian network (BN) model of the failure of a coal slurry preparation system by using the bow-tie model and the structural similarity of the Bayesian cognitive science, based on the SVDBN recursive reasoning algorithm. The risk factors of the coal slurry preparation system were deduced using the Python language in two ways, and at the same time, preventive measures were put forward according to the weak links. In order to verify the accuracy and feasibility of this method, the simulation results were compared with those obtained using GeNIe software. The reasoning results of the two methods were very similar. Without considering maintenance factors, the failure rate of the coal slurry preparation system gradually increases with increasing time. When considering maintenance factors, the reliability of the coal slurry preparation system will gradually be maintained at a certain threshold, and the maintenance factors will increase the reliability of the system. The proposed method can provide a theoretical basis for the risk assessment and safety management of coal slurry preparation systems.

Coal slurry foam image enhancement based on multiscale convolutional network

Coal slurry foam image enhancement based on multiscale convolutional network

Study on Ultra-Long-Distance Transportable Concentration Gradient of Coal Gangue Slurry with Different Gradations

Coal gangue, the primary solid waste generated during the coal mining process, is typically disposed of on the surface, where it gradually accumulates to form gangue piles that significantly contaminate the surrounding environment. Filling technology has been widely employed for the safe and efficient disposal of coal gangue due to its sustainability, safety, and efficiency. However, there is still a lack of theoretical research on the concentration of gangue slurry in long-distance filling pipeline transportation. Therefore, a calculation model of the ultra-long-distance transportable concentration of coal gangue slurry with different grades was constructed based on the static anti-segregation performance and Bingham model. In addition, the relevant parameters of the calculation model of the ultra-long-distance transportable concentration of coal gangue slurry in this mine were determined using the 8 km pipeline transport of coal gangue slurry in one mine as the technical background. It was subsequently demonstrated that the yield stress, plastic viscosity, and mass concentration of the various grades of gangue slurry in this mine exhibit an increasing exponential function, while the slurry density and mass concentration exhibit an increasing linear function, and the mass concentration and actual flow rate correspond to a quadratic polynomial increment. Finally, the minimum and maximum concentrations for different grades of gangue slurry that can be transported over long distances in this mine were determined. This work provides theoretical and practical guidance on how to select the concentration of gangue slurry for long-distance pipeline transport.

Combustion characteristics and thermokinetics of coconut shell, coal water slurry, and biomass

Combustion characteristics and thermokinetics of coconut shell, coal water slurry, and biomass

Exergy-based method for evaluating the dynamic optimization of a supercritical water fluidized bed

Dynamic optimization of hydrogen production from coal gasification within an industrial-scale supercritical water fluidized bed is studied. Coal slurry and supercritical water mass flow rates are selected as the manipulated variables to investigate the optimal operation for scenarios involving variations in hydrogen demand. For the temperature-constrained scenario, supercritical water mass flow rate and temperature are manipulated. The results demonstrate that the optimal time-dependent profiles of the manipulated variables enable the supercritical water fluidized bed to meet variable demands of hydrogen and improve availability. Dynamic exergy methods are implemented to assess the thermodynamic behavior of different optimization schemes for efficient operation. The results show that more attention should be paid to the process of adjusting the mass flow rates of coal slurry and supercritical water simultaneously to vary the hydrogen yield because it requires the largest energy consumption. Manipulating the supercritical water mass flow rate causes less exergy destruction at a temperature constraint of 600 °C, but more exergy destruction at a temperature constraint of 700 °C.

Study on the impact of APAM residue on the settlement characteristics of coal slurry agglomerates

ABSTRACT Residual dosage has a significant impact on the settling characteristics of coal slurry flocs and the sedimentation efficiency of coal slurry. This study conducted sedimentation stirring experiments to measure the supernatant grayscale, floc size, settling velocity, and residual anionic polyacrylamide (APAM) under varying energy inputs. The investigation focused on the correlation between different levels of APAM residual and the settling characteristics of coal slurry flocs. The results show that having APAM residuals in the first three stages helps with sedimentation. This leads to lower residual levels, higher grayscale in the supernatant, bigger floc sizes, and better settling velocities. However, in the fourth stage, as APAM residual levels increased once more, the supernatant grayscale decreased linearly, floc breakup became severe, and settling velocities neared stagnation. In the second stage, a correlation was noticed between higher APAM residual levels and better settling properties of coal slurry flocs. By studying residual dosage and energy input, guidance on how to optimize the sedimentation efficiency of the thickener and reduce dosage can be provided.

Experimental study on ash reduction by classification flotation

ABSTRACT Poor endowment conditions, with abundant reserves of high-impurity and low- quality coal resources, characterize the coal resources in our country. As the primary source of carbon emissions, the coal industry faces a critical challenge in actively contributing to environmental protection and carbon reduction within the context of striving for carbon peak and carbon neutrality. With the widespread application of mechanized coal mining and the deteriorating geological conditions of coal resources, coal slurry particles have become increasingly fine. Additionally, a large amount of gangue minerals mixes with the coal slurry, resulting in an increase in ash content and a decrease in floatability. This places higher demands on the separation of high-ash, difficult-to-float coal slurry. This issue has become a core concern that needs to be addressed within the coal industry. This study employs a classification flotation technology to reduce ash content and improve the quality of low-quality coal slurry. The research primarily focuses on the flotation ash reduction effects of the grain size of −0.5 mm and classified grain-size coal slurry under various pulp concentrations, collector concentrations, and frother concentrations. It also analyzes the impact of a rougher and two cleaner flotation processes on the flotation efficiency. Experimental results indicate that the optimal reagent concentrations and process parameters differ for each particle size of the coal slurry. Under the best flotation conditions, the experimental results for the rougher and two cleaner flotation processes are as follows: For the grain size of −0.5 mm coal slurry, the clean coal yield is 48.40%, with an ash content of 11.02%. For the grain size of − 0.5 + 0.125 mm coal slurry, the clean coal yield is 50.53%, with an ash content of 10.72%. For the grain size of − 0.125 + 0.045 mm coal slurry, the clean coal yield is 49.56%, with an ash content of 9.24%. For the grain size of −0.045 mm coal slurry, the clean coal yield is 48.73%, with an ash content of 10.97%. Notably, the classified grain-size coal slurry exhibits higher clean coal yields and lower ash content than the grain size of −0.5 mm coal slurry, highlighting the significant importance of classification flotation for coal slurry.

Tribo-Erosion Analysis of HVOF Colmonoy-88-Coated Pump Impeller Steel in Coal Ash Particle Slurries

Abstract Coal ash slurries hold paramount importance in the service life of the coal and mining industries, significantly impacting their operational efficiency and durability. The literature reveals that the prominent dominating parameters such as rotational speed, concentration, time duration, and particle shape and size have a major impact on erosion wear. This research aims to explore the effects of coal ash slurries on Colmonoy-88-coated pump impeller steel, employing a combination of design of experiments (DOE) and digital image analysis (DIA). Through slurry experiments, it is observed that erosion wear increases non-linearly with an increase in influencing parameters. The particle size emerges as the most significant factor, followed by concentration, speed, and time. Additionally, DIA is leveraged to validate the influence of various erodent particle sizes on the erosion wear of the pump impeller steel. Results indicate that coal particles possess irregular shapes and sizes compared to fly ash and bottom ash, consequently resulting in larger erosion wear due to their lowest circularity factor (0.72). Furthermore, smaller particles exhibit lower erosion wear-rates compared to larger ones. This study sheds light on the intricate dynamics of erosion wear in the context of coal ash slurries, offering insights crucial for optimizing pump impeller steel durability in similar operational environments.

Flow Field Characteristics and Flotation Efficacy in a Pulse Jet Flotation Machine: A Comprehensive Investigation

The design and optimization of flotation machines hold significant importance in enhancing the industrial-grade coal beneficiation process. In this research, the flow field characteristics and flotation performance of a novel pulse jet flotation machine (PJFM) were investigated. The results showed that a PJFM equipped with an innovative pulse cavity can improve the mineralization efficiency of coal due to the coupling of multiple jet shapes. The aeration performance of this PJFM also exceeds the usual desired targets of coal flotation machines, which are characterized by an aeration uniformity coefficient higher than 70% and dominant bubbles of 100~200 μm and 200~300 μm, including a small amount of −100 μm bubbles. The cavitation of the pulse jet achieved the modification of the coal particle surface, and subsequently, the electric potential of the coal largely decreased in absolute value, and the floatability of the coal significantly improved. The concentrate yield of step release flotation increased by 12.42%, while the ash content was only 0.45% higher. Furthermore, in the early stage of flotation, the flotation rate of 0~0.074 mm coal slurry is the fastest and is preferentially floated; in the later stage, the flotation of 0.25–0.5 mm particles dominates. The PJFM demonstrates enhanced particle size selectivity and superior performance in selective flotation.

Trace Elements in Pernik Sub-Bituminous Coals and Their Combustion Products Derived from the Republika Thermal Power Station, Bulgaria

The contents of 49 trace elements in sub-bituminous Pernik coals and their waste products from preparation and combustion processes were investigated. The studied coals have trace element contents higher than the respective Clarke values for brown coals and some of them may pose environmental concerns. The elements Li, Rb, Cs, Ba, Sc, Y, La, Ce, Nd, Sm, Eu, Er, Ga, Zr, Sn, V, Nb, Ta, W, F, Cu, Zn, In, Pb, Cr, Co, Ni, and Th in the feed coals have concentrations that exceed twice the Clarke values. Most element contents in bottom ash are enriched compared with those in feed coal. Some of the volatile elements are equal or significantly depleted including Sn, Mo, Sb, F, Bi, Cd, Ge, and Pb. Fly ash has higher contents of Ga, Zr, Hf, Sn, V, Nb, Mo, and F in comparison with bottom ash. Most elements have a significant positive correlation with ash yield, indicating their inorganic association. The mixed wastes (coal slurry, bottom ash, and fly ash) in the disposal pond are slightly depleted of most of the elements studied with the exclusion of Cl, Ba, and Br. The Pernik coals and their waste products are unpromising for the extraction of REY due to their low element contents.

Experimental and theoretical insight into the effect of a novel composite dispersant on the properties of coal pitch water slurry

To optimize the utilization efficiency of coal pitch (CP), an innovative composite dispersant was designed and employed in the preparation of coal pitch water slurry (CPWS) by effectively combining modified sodium lignosulfonate (MLS) and amphoteric polycarboxylate (AAD) based on the principle of complementary advantages. The effects of the proportion of MLS to AAD on the characteristics of CPWS were systematically analyzed and assessed by various technical methods, including apparent viscosity, rheological behavior, static stability, adsorption behavior, etc. Results indicated that the CPWSs utilizing distinct composite dispersants belonged to the category of yield pseudoplastic fluids and had a good correlation with the Herschel-Bulkley model. Among them, the CD-2, composite dispersant with a mass ratio of MLS:AAD = 1:1, exhibited superior performance in terms of viscosity reduction and stabilization properties. It demonstrated the maximum adsorption capacity (5.23 mg/g) and adsorption layer thickness (7.22 nm) compared to other dispersants. Meanwhile, it could significantly increase the wettability (with a contact angle of 74.5°) and the absolute Zeta potential value (32.5 mV) of CP. The density functional theory (DFT), molecular dynamics (MD) simulation, and extended Derjaguin-Landua-Verwey-Overbeek (eDLVO) theory were carried out to investigate the interaction mechanism of composite dispersant with CP and the interaction energy among CP particles. The differences in energy levels between the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HUMO) of MLS and AAD were significantly smaller than that of H2O. The hydrophobic groups of composite dispersants were efficiently adsorbed onto CP, while the hydrophilic groups adsorbed water molecules, with an adsorption energy reaching −169.36 kcal/mol. The steric hindrance of composite dispersant exerted a crucial influence on the dispersion of CPWS, enabling CP particles to be stabilized in water. The present study offers a novel approach to enhance the characteristics of CPWS and establishes a theoretical foundation for the design of efficient composite dispersants.

Adsorption mechanism and interactions of coal particles modified with a novel hyperbranched dispersant

This account, a hyperbranched dispersant (Es-SAF-DBM-PSS) was assembled with the skeleton of Es-SAF-DBM (the functional modification of hydroquinone-based sulfonated acetone formaldehyde (SAF)) and numbers of linear polystyrene sodium sulfonate (PSS) chains by single electron transfer living radical polymerization (SET-LRP) in the system of PhBr2m4/Cu wire/PMDETA. The structure of the synthesized Es-SAF-DBM-PSS was detected by FTIR, 1H NMR, XPS, UV and GPC. Series of tests about the polymerization kinetics of Es-SAF-DBM-PSS were executed. Effects of temperatures and initiator concentration on the apparent polymerization rate were investigated, the results showed the low activation energy and higher initiation rate fitted the characteristic of SET-LRP. The rheological behaviors of Es-SAF-DBM-PSS as dispersant applied to coal water slurry (CWS) were tested. The following results were found as expected: the best usage of Es-SAF-DBM-PSS was only 0.3%, maximum coal content reached 63.7%, the viscosity dropped as low as 1000mPa·s. And the penetration ratio of slurry mixed with Es-SAF-DBM-PSS was still 100% even after 35days. Adsorption mechanism and interparticle interactions of coal particles modified with Es-SAF-DBM-PSS were investigated by Langmuir equation, dynamic equations and extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) theory, the results showed the excellent dispersion and stability performance of Es-SAF-DBM-PSS were mainly related to the specific hyperbranched structure.

Enhancement in kerosene droplet–coal particle collision and adsorption by bubble trailing vortex in coal slurry conditioning: Energy evolution of collision process

AbstractUnderstanding the collision between kerosene droplets and coal particles in the bubble trailing vortex region is crucial for enhancing slurry conditioning. We found the area of the bubble trailing vortex region increased as the bubble size increased via the Fluent 6.3.26 software. A kerosene droplet velocity range of 0.074–0.106 m/s and a coal particle velocity range of 0.062–0.104 m/s were obtained if a bubble had a diameter of 0.3 mm. We employed a high‐speed motion acquisition system and observed the collision process, which was divided into two stages: Compression and Rebound. The critical motion distance increased as the kerosene droplet size increased, and sufficient kerosene droplet motion distance and enough kinetic energy normally resulted in a rebound phenomenon. The attenuation energy was almost positively linear to the initial energy, and the energy attenuation coefficient of the collision process was fitted to 0.626. Our results can provide valuable insight into mineral separation.

Demineralization of fine and ultrafine coal particles of Talcher area by oil agglomeration technique

ABSTRACT The costs of fine coal cleaning cannot surpass the fetched recuperation within the included clean coal to be financially practical. In this present study, percentage of ash and yield of the agglomerated coal, Percentage of OMR (Organic matter recovery) and AR (Ash rejection) have been calculated for the coal slurry of size ranges from 0.07 mm to 0.3 mm. The result of the three parameters (ash, yield, and fixed carbon) were calculated by varying particle size, type of oil (sunflower oil, castor oil, and kerosene oil), amount of oil doses and the speed of the impeller. The results show an increase in value of fixed carbon percentage, decrease in the value of ash percentage of the agglomerated recovered clean coal. But the value of yield and quality of the recovered clean coals are almost around 10% and more than 95% and also are independent of the agitation speed of the impeller. The estimated values of ash rejection by the proposed techniques were between 97% and 99% with an increase in the calorific value of 88%. which is a promising technique and can be applied for the pilot scale unit.

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.