Water Slurry Research Articles

Preparation of pitch semi-coke water slurry and its properties of slurryability and gasification

ABSTRACT A new strategy for the preparation of pitch semi-coke water slurry (p-SCWS) with pitch as raw material and semi-coke powder was proposed. The slurryability and gasification performance of p-SCWS were evaluated by apparent viscosity, stability, FTIR, XRD, and TG/DTG characterization methods. Compared with SCWS, the hydrophilic functional groups of SCWS prepared by coal pitch (CP), modified pitch (MP), and petroleum pitch (PP) increased significantly. p-SCWS and SCWS have similar pseudoplastic rheological properties-shear thinning. p-SCWS exhibits better stability than SCWS, with the lowest WSR at 0% and the highest at 8.49%. The addition of pitch lowered the initial (Ts) and final reaction temperatures (Te) of gasification, increased the activation energy and pre-exponential factor, and enhanced the gasification activity. The Ts and Te of CP-SCWS showed the most significant decrease, reaching 869.95°C and 1010.96°C, respectively, compared to 902.39°C and 1075.60°C for SCWS. The activation energy and pre-exponential factor were highest for PP-SCWS.

Enhancement of interaction between Shenhua coal and GON-based dispersant with “surface-to-surface” adsorption by regulating the oxidation degree of GON: Experiments and simulations

The present study focuses on the synthesis of several graphene oxide nanosheet (GON)-based dispersants with an adsorption mode of “surface-to-surface” for the preparation of Shenhua coal (SC) water slurry (SCWS), achieved by grafting allyl polyoxyethylene ether (APEG) onto GON edges with varying degrees of oxidation using emulsion polymerization and esterification techniques. The impacts of the oxidation degree of GON on its structural characteristics and the performance of GON-based dispersants in SCWS were comprehensively assessed through a range of experimental techniques, alongside molecular dynamics (MD) simulations. Results demonstrated that with the increase in oxidation degree, there was an elevation of oxygen-containing groups, in which the content of COH decreased while the content of COC increased. Among all dispersants, GA-2, which was synthesized using GON-2 as the raw material with a graphite-to-KMnO4 mass ratio of 1:2.5, exhibited superior viscosity-reducing and stabilizing abilities compared to other dispersants. All SCWSs demonstrated pseudoplastic fluid behavior and showed good agreement with the Herschel-Bulkley model. After the adsorption of dispersants in SC, both the Zeta potential and surface wettability of SC significantly improved, especially with GA-2. The interaction mechanism between the dispersant and SC was analyzed by establishing and employing three adsorption models (M-1, M-2, and M-3). The interfacial adsorption structure confirmed that the dispersant exhibited “surface-to-surface” mode on coal through hydrophobic interaction, hydrogen bonding, and π–π interaction. Energy studies revealed that M-2 with the highest Eads (−105.31 kcal/mol) demonstrated superior adsorption strength compared to M-1 and M-3. Investigations into water molecule mobility revealed that the interaction between the GON-based dispersant and SC resulted in a reduction of water molecule mobility, thereby promoting water molecule aggregation to facilitate the formation of hydration films and enhance SCWS stability. In summary, an optimal oxidation degree of GON was found to be crucial for enhancing the performance of GON-based dispersants; higher oxidation levels may hinder dispersant adsorption on coal surfaces by converting hydroxyl and carboxyl groups into epoxide groups, thus impairing the conjugated structure.

Impact of atomizer design on slurry fuel atomization behavior

The paper presents experimental findings on the atomization characteristics of coal–water slurries with and without petrochemicals. The fuels were based on flame coal filter cake (slime), which is a typical coal processing waste, flame coal of different particle sizes, wood biomass (sawdust), used transformer oil, and water. The atomized flow characteristics—droplet size and velocity as well as jet angle—were found to depend on the atomizer dimensions and slurry rheology. The experimental data were used to calculate the slurry atomization efficiency factor. The findings were generalized to provide a mathematical description of how the slurry composition and atomizer geometry affect the slurry atomization behavior. Approximations were obtained for atomization characteristics that can be used to predict the jet angle as well as droplet radii and velocities. The developed mathematical tool can be employed to calculate the spraying characteristics when using devices like external-mix twin-fluid atomizers. The approach proposed for data generalization can be applied to adapt the set of approximation equations to other types of nozzles.

Effect of plasma-activated water on the settling characteristics of ultrafine kaolinite

Coal slurry water is a complex multiphase system, and its settling characteristics are influenced not only by the solid phase coal slime but also by the liquid phase water. This paper firstly explores the effect of plasma-activated water (PAW) on the settling of ultrafine kaolinite through settling experiments, turbidity tests & dynamic observations. The findings show that PAW significantly improves the settling behavior of ultrafine kaolinite, manifested by an increased settling velocity, higher final settling height, shorter settling end time, and reduced turbidity of the supernatant. Furthermore, the potential mechanisms by which PAW enhances the settling of ultrafine kaolinite are analyzed through laser particle size detections, fractal dimension calculations, zeta potential measurements & contact angle determinations. The mechanism analysis indicates that PAW not only reduces the electrostatic repulsion of ultrafine kaolinite particles but also enhances the hydrophobicity, thereby increasing both the size and density of ultrafine kaolinite flocs, which improves the settling performance of ultrafine kaolinite. This study not only provides new insights for enhancing ultrafine kaolinite settling with PAW but also offers new approaches for the efficient settling of coal slurry water.

Exploring the impact of poly(sodium styrene sulfonate) dispersants’ architecture on their performance in coal water slurry preparation

In this work, the architecture of poly(sodium styrene sulfonate) (PSSNa) dispersants were flexibly tailored by various strategies. Three categories of PSSNa dispersants with different topologies were obtained, namely, linear structured PSSNa (1-A-PSSNa), three-arm star PSSNa (3-AS-PSSNa) and six-arm star PSSNa (6-AS-PSSNa). The molecular weights (Mn) of these dispersants were adjusted in the range of 3200–26,200 g/mol by varying the feeding ratio of monomer to initiator. In addition, the polydispersity index (PDI) of resultant dispersants were also varied by using different polymerization technologies, such as atom transfer radical polymerization (ATRP) and conventional free radical polymerization technique (RP). Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) verified these architecture parameters of resultant PSSNa dispersants. Afterwards, the impact of these architectural factors on the performance of PSSNa dispersants in coal water slurry (CWS) preparation were evaluated. The results revealed that with the Mn of dispersants increased from 9800 to 26,200 g/mol, the apparent viscosity of CWS increased by around 11 %. The comparison between dispersants with approximate Mn (26,200 and 26,900 g/mol) and very different PDI (1.27 and 2.25) indicated that wide PDI are favourable for the performance. This work also confirmed that the topology of dispersants has a significant impact on their performance. The maximum coal loaded can increase from 63.9 % to 64.3 % when 1-A-PSSNa dispersant was replaced by 6-AS-PSSNa. Meanwhile, these architectural factors have a limited impact on the fluid type of CWSs, as all CWSs obtained in this work were pseudoplastic fluids regardless of the used dispersants. The potential mechanism was investigated using various technologies, such as the measurements of zeta potentials, contact angles, and low-field nuclear magnetic resonance spectra. The results revealed that topologizing did not alter the interaction between dispersant and coal surface. However, due to the special features of topological polymers, they can grant adsorbed coal particles with enhanced electrostatic repulsion and steric hindrance, which facilitated the dispersion of coal particles.

Effect of the main components in gasification wastewater on the surface properties of coal water slurry

AbstractCoal water slurry is an advanced and efficient clean coal technology; using gasification wastewater to prepare coal water slurry can recycle wastewater and improve energy utilization efficiency. As the complex substances in wastewater have a great influence on the slurry properties, the effects of organic matter, metal ions, and ammonia nitrogen in gasification wastewater on the surface properties of coal water slurry are studied in this paper in order to provide new ideas for slurry mechanism of coal water slurry prepared from wastewater. Results show the following: (a) Compared with ordinary coal water slurry, the concentration of coal water slurry prepared from wastewater with high organic content increased by 2.9%, while the concentration of coal water slurry prepared from wastewater with high ammonia nitrogen content decreased by 2.1%. (b) The contact angles of coal water slurry prepared with phenols, alcohols, and urethane are reduced by 2.8°, 6.3°, and 1.5°, respectively, so organic matter can change the hydrophilicity of coal particles and affect slurryability. (c) Mg2+ and Ca2+ have basically no effect on slurry. Fe3+ reduces the absolute value of Zeta potential by 33.1, and Cu3+ increases that by 22.8, as they affect the slurryability by changing the surface potential of coal particles and the absorption of additives. (d) Ammonia nitrogen influences the slurryability by changing the pH value of the slurry. The conclusion of the influence mechanism of organic matter, metal ions, and ammonia nitrogen in wastewater on slurryability can provide a technical reference for the selection of suitable wastewater to prepare coal water slurry.

Carboxyalkylated Lignin as a Sustainable Dispersant for Coal Water Slurry.

Coal water slurry (CWS) has been considered a cleaner and sustainable alternative to coal. However, the challenging suspension of coal particles in CWS has created a major obstacle to its use in industry. This study presents a novel approach to enhance the stability and rheological properties of coal water slurry (CWS) through the utilization of carboxyalkylated lignin (CL) as a dispersant. The generated CL samples had high water solubility of around 9 g/L and a charge density of around 2 mmol/g. All CLs were able to stabilize the coal suspension, and their performance decreased due to the increase in the alkyl chain length of carboxyalkylated lignin. Carboxymethylated lignin (CL-1) improved the stability of the coal suspensions with the lowest instability index of less than 0.6. The addition of CLs reduced the contact angle of the coal surface from 45.3° to 34.6°, and the increase in the alkyl chain length hampered its effect on contact angle changes. The zeta potential measurements confirmed that the adsorption of CL enhanced the electrostatic repulsion between coal particles in suspensions, and the zeta potential decreased with the increased alkyl chain length of CLs due to increased steric hindrance. The rheology results indicated that CLs demonstrated shear thinning behavior. This innovative method showcases the affinity of carboxyalkylated lignin to improve the performance of CWS, offering an environmentally friendly alternative for producing a cleaner product, i.e., sustainable coal water slurry, with improved suspension stability.

Investigation of the impact of environmental conditions on the mechanical properties of thin-film copper wafers

Thin-film copper offers excellent film texture for multilevel interconnections in integrated circuit fabrication due to its superior resistance to electromigration and high electrical conductivity. To perform a chemical mechanical planarization process during semiconductor fabrication of copper, it is necessary to have a thorough understanding of the nanomechanical properties of thin-film copper. In this study, thin-film copper and reacted passivation layers on silicon substrate wafers are investigated for their nanomechanical properties under various environmental conditions. The results of this study indicate that thin-film copper passivation layers have different properties in deionized (DI) water and polishing slurry environments compared to thin-film copper exposed to ambient air. Interestingly, variations in temperature within wet environments do not significantly affect the properties of thin-film copper wafers; but changes in properties are largely driven by chemical processes. The insights gained from this study emphasize the significance of considering both the passivation layers and wet environments in semiconductor fabrication processes, which contributes to the advancement of copper-based interconnect materials and optimization of the chemical mechanical planarization process in semiconductor manufacturing.

Waste to energy-study on the optimal types and dosage of additives for coal wastewater slurry

Abstract As a clean and efficient fuel derived from coal, coal water slurry can be produced by using industrial wastewater, promoting resource recirculation and environmental preservation. To maintain fluidity and stability during industrial applications of coal wastewater slurry, stabilizers play a crucial role. To promote the energy utilization of industrial wastewater, this article conducted a comparative study on different stabilizers for coal wastewater slurry. The results are as follows: (a) Compared with other stabilizers, xanthan gum makes the water separation rate of the coal wastewater slurry the lowest, and the slurry still maintained good stability after standing for 1 week and 1 month; (b) If the coal wastewater slurry requires a short storage time, the slurry properties with a blending ratio of 0.05% of xanthan gum will be the best; if the coal wastewater slurry requires a longer storage time, it can be made with a blending ratio of 0.10% of xanthan gum. The conclusion presented in this paper offers valuable insights for selecting stabilizers during the preparation of coal wastewater slurry.

دراسة إنتاج الغاز الحيوي من مخلفات الطعام باستخدام الهضم الالهوائي

The primary goal of this research is to look at the feasibility of food waste biomass (fruits and vegetables) to produce biogas by anaerobic digestion. This study demonstrated the possibility of utilizing sludge and cow manure in energy production rather than being a source of pollution and treating it in natural ways. This study compares inoculums (tap water, 1:1 cows’ manure, tap water slurry, and sewage sludge) for the best methane yield with weight ratios 1:1, 1:2, and 2:1 food waste: inoculum. Temperature varied from room temperature to 55⸰C to determine the best operating conditions for methane production. The volatility of fatty acids (VFAs) and pH were measured during the experimental work. The results concluded that the cows’ manure slurry and the sludge were more effective in increasing the pH than tap water, which ranged from 6.15 to 6.47 and from 5.53 to 6.47 for cow manure and sludge respectively. At the same time, Tap water neither increase the pH more than 5.7 nor produce any gas. The highest amount of methane (4.44%) was obtained by mixing food waste and cow manure slurry at a ratio of 1:1 and maintaining a temperature of 42⸰C. To further increase the methane concentration, improving the operating conditions such as using a semi-batch reactor and controlling the pH and other parameters is necessary.

Study on slurry forming performance and slurry combustion characteristics of diesel modified coal

In this study, modified low rank coal water slurry (M-LRCWS) was prepared by using diesel modified low rank coal (LRC) and compared with low LRC water slurry (LRCWS) to investigate the slurry formation mechanism and combustion characteristics of coal water slurry. Meanwhile, the combustion kinetics of coal-water slurry was investigated using kinetic methods to probe the combustion reaction mechanism. The results showed that the slurry formation concentration of LRC was 70 %, while the slurry formation concentration of M-LRCWS was 72 %, which was an increase of 2 %. The diesel modification positively affected the stability of CWS. The comprehensive combustion characteristics index of the same slurry deteriorated with increasing heating rate. At the same heating rate, M-LRCWS has better combined combustion performance, higher flammability and more stable ignition performance. Combustion kinetics calculations showed that the reaction activation energies were 105.50 kJ/mol for M-LRCWS and 99.59 kJ/mol for LRCWS using the FWO method, and 93.48 kJ/mol for M-LRCWS and 92.68 kJ/mol for LRCWS using the Starink method. The activation energy of M-LRCWS is slightly higher than that of LRCWS, which indicates that the diesel fuel is encapsulated in the coal particles and it is difficult to activate the substance. As a result, the dispersion system is more stable and favorable for storage and transportation. The physical functions of LRCWS and M-LRCWS were calculated using the Achar differential equation and the Coats-Redfern integral equation, and the results showed that both LRCWS and M-LRCWS followed the tertiary reaction (F3) mechanism.

Comparative experimental study of ash formation behaviors during the fixed-bed gasification of coal water slurry and dry pulverized coal prepared from Shenmu coal

The mechanism of ash formation during coal gasification is very important for the safety and stability of gasifier operation. This study comparatively investigated the ash formation behaviors during the gasification of coal water slurry and dry pulverized coal. Shenmu coal was gasified in a CO2 atmosphere at 900 °C using a fixed-bed reactor to prepare chars and ashes. Computer-controlled scanning electron microscopy was employed to characterize the compositions and particle sizes of minerals in the raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash. Morphological characteristics reveal that, during gasification, coal water slurry gasification char exhibits obvious agglomeration compared to the dry pulverized coal gasification char. The changes of mineral compositions indicate that, during both coal water slurry and dry pulverized coal gasification, minerals follow nearly identical transformation pathways, but the degrees of transformation are different. The influence of char agglomeration on heat transfer may be the reason for the less transformation of K Al-silicate and kaolinite during the coal water slurry gasification. Furthermore, in comparison to dry pulverized coal gasification, more Ca in calcite and S in pyrite transfer into gypsum during the coal water slurry gasification. The results from thermodynamic equilibrium calculations indirectly suggest that this may be attributed to the limited internal diffusion of CO2 within coal water slurry gasification char resulting from char agglomeration during gasification. Overall particle size distributions of minerals in raw coal, coal water slurry gasification ash, and dry pulverized coal gasification ash demonstrate that the degrees of mineral fragmentation are almost consistent during both coal water slurry and dry pulverized coal gasification. However, differences in the degrees of mineral transformation led to different particle size distributions of various minerals between coal water slurry gasification ash and dry pulverized coal gasification ash. This study mainly focuses on the influence of water in coal water slurry on ash formation, and it has not considered the influence of other factors, such as ash content, hydrophilicity, caking property, and gasification reactivity of coal, which need further research to explore.

Molecular simulation of the slurrying mechanism in microplastic semi-coke water slurry.

This study explores the interaction between particles in microplastic semi-coke water slurry at the molecular level using molecular simulation methods, specifically DFT calculations and MD simulations. In addition, the experiment of slurry preparation was carried out to study the viscosity and stability of the slurry. The electrostatic potential analysis shows that the interaction between microplastics and dispersant molecules occurs on atoms with large electronegativity or oxygen-containing functional groups, and the energy gap of frontier molecular orbitals indicated that PVC interacts most easily with the dispersant (0.39eV), followed by PS (1.08eV) and PET (3.65eV). In addition, it is also noted that due to the steric hindrance effect, the adsorption energy was opposite to the DFT calculation results: PET was - 213.338kcal/mol (NNO) which was highest, followed by PS (- 107.603kcal/mol, NNO), and PVC (NNO) was lowest which was - 94.808kcal/mol. And RDF shows similar results, which the probability of water molecules in the PET system was the highest, followed by PS, and finally, PVC. The MD results are consistent with the viscosity and stability characterization results of the slurry which PET has the lowest viscosity of 87.3mPa·s. Finally, this study provides new ideas for the treatment of microplastics and the improvement of the performance of semi-coke water slurry and reveals the interaction mechanism between microplastics and semi-coke water slurry. All calculations were performed using Materials Studio (MS) version 2020 software, BIOVIA Corporation. The DFT calculation was carried out through the DMol3 module. The DFT calculations include electron density, electrostatics, orbitals, and population analysis. In DMol3 module, the GGA-PBE function was selected to consider gradient changes in density in the simulated calculation. The DFT-D correction was selected, and all electrons were calculated by DNP for accurate core potentials and the DNP file was 4.4. MD simulation was performed through the Forcite module. MD simulation mainly focuses on relative concentration distribution analysis, radial distribution function, and adsorption energy calculation. All molecular geometry optimizations are performed in the Forcite module. In the molecular dynamic part, all simulations used PCFF forcefield. The NVT ensemble was adopted and using the Nosé thermostat.

Preparation of good fluidity coal water paste based on the modified compartment stacking theory

ABSTRACT Coal water paste (CWP) is a mixture of pulverized coal and water with a mass concentration of more than 70 wt%. CWP has a higher coal concentration than traditional coal water slurry (~60 wt%), so it can significantly improve the efficiency of gasification and combustion. However, the preparation and rheology of paste is extremely complicated due to its high concentration and material complexity. In this paper, to obtain the preparation method of CWP which could meet the engineering demands, the effects of coal particle size distribution, grading ratio, and type and amount of dispersant on rheology of CWP are investigated. Based on the modified compartment stacking theory, the improved preparation method of CWP has been proposed, which introduces the influence of coarse particle shape. The particle size ratio of coarse and fine particles is about 12, the particle size ratio of fine and ultra-fine particles is about 5, the optimal three-peak grading ratio is 6:1:3. The preferred dispersant is pure naphthalene dry powder (PNDP), and its addition amount is 1.4 wt%. The flow grade of CWP (71 wt%) could reach A without any other modifications or treatments.

Au-TiO2 nanoparticles enabled catalytic treatment of oil and gas produced water in slurry and vacuum membrane distillation systems

Produced water (PW) treatment and reuse provide a promising alternative to address freshwater scarcity and reduce the environmental impacts associated with PW disposal. Efficient treatment of PW is challenging due to its complex matrix and hypersalinity. This study developed innovative gold-doped titania (Au-TiO2) nanoparticles to enable effective treatment of PW collected from the Permian Basin with salinity of ∼118 g/L. The mechanisms of removing organics and ammonia in PW in slurry and vacuum membrane distillation (VMD) systems were investigated via thermocatalysis, photocatalysis, and photo-thermocatalysis. Photocatalysis and photo-thermocatalysis were found more effective for organic removal than thermocatalysis. A baseline study using glucose as a representative of easily degradable organic carbon showed that thermocatalysis and photocatalysis mineralized 23.2 % and 93.1 % glucose, respectively. However, photo-thermocatalysis and thermocatalysis degraded only 17.4 % and 7.5 % dissolved organic carbon (DOC), and 56.2 % and 49.2 % NH3-N in PW, respectively. Au-TiO2 coating on ceramic membranes improved the distillate flux of photo-thermocatalytic membrane distillation (PMD) compared to no catalysts coating in VMD (7.14 versus 6.75 kg per hour per m2). Both PMD and VMD rejected >99.9 % of salts and >96 % DOC, and PMD had slightly higher DOC and salt removal rates. In contrast, normalized permeate flux using pristine membranes (hydrophobically modified without catalysts coating) decreased to zero after 29 h of operation while normalized flux with TiO2-coated membranes under UV on and UV off were 57.5 % and 53.7 % on average, which is much lower than that with Au-TiO2 coated membranes in both UV on (91.3 %) and UV off (88.1 %) cases, indicating Au-TiO2 coating significantly improved membrane anti-fouling propensity and durability during treatment of complex PW. Targeted analysis of three groups of petroleum hydrocarbons and 70 volatile organic compounds showed that only 2-butanone and acetone were detected in the distillates with removal efficiencies of 80 % for 2-butanone in both PMD and VMD, and acetone was removed by 75.4 % in PMD and 69.2 % in VMD. Au-TiO2 nanoparticles demonstrated excellent catalytic performance for PW treatment in slurry and immobilized PMD systems.

From hydratable alumina bonded high chrome castables to shaped product for coal water slurry gasifier

The gasifier is a key equipment of coal gasification technology, enabling efficient and clean utilization of coal resources. However, the aluminum phosphate bonded high chrome brick lining in the gasifier experienced premature failure due to the migration of phosphate in reducing gases such as H2 and CO, as well as increased slag penetration and thermal spalling. In this study, a high chrome castable was prepared using hydratable alumina as a binder and fired at 1600 ℃ to replace the traditional phosphate bonded high chrome brick. The impact of curing temperatures (25℃, 40 ℃, and 60 ℃) on the properties of the high chrome castable was investigated, with corresponding hydrates examined through XRD, FTIR, TG-DSC, and SEM analyses. Results revealed that higher curing temperatures accelerated the hydration process of hydratable alumina. At higher curing temperatures, more well-developed micro-nano sized boehmite and bayerite phases were formed within the castables, filling their pores effectively and enhancing their properties after drying at 110 ℃. Moreover, during heat treatment these micro-nano sized hydrates decomposed into submicron/nano sized alumina which readily reacted with Cr2O3 to form (Cr-Al)2O3 solid solution. This phenomenon facilitated the sintering of castables fired at 1600 ℃ and optimized internal structure, ultimately leading to the enhanced mechanical properties and improved slag resistance.

Simulations on coal water slurry gasification by molecular dynamics method with ReaxFF.

Coal water slurry (CWS) is a new type of liquid coal product with low pollution, which is mainly used in the chemical industry to produce syngas (CO + H2). It is of great significance to study the microscopic mechanism of CWS gasification reaction for improving the efficiency of coal gasification. In this paper, the method of molecular dynamics based on reaction force fields (ReaxFF-MD) is used to study the gasification process of CWS/O2 system at different temperatures. The results show that, in the range of 1600-2400 K, the macromolecular network structure of lignite is decomposed into a large number of small molecular structures and a small number of light tar free radical fragments, and the types and quantities of reaction products increased rapidly. At 2400-4000 K, the free radical fragments of light tar are further decomposed and reacted with gasification agents, but the types and quantities of reaction products have little change. At 3600 K, a full gasification reaction occurred in the system, and the content of syngas is the highest. The model was established and optimized by Materials Studio (MS) software. Based on ReaxFF-MD method, Lammps software was used to simulate the gasification process of CWS/O2 system, and the reaction force field files containing C, H, O, N, and S element were used. By calculating the activation energy of gasification reaction, the rationality of the model and calculation method was illustrated. The post-processing of the results was implemented using OVITO, ChemDraw software, and self-programmed Python scripts.

Heat transfer coefficient evaluated for a designed jacketed vessel for parameter optimization in coal water slurry preparation using dual impellers

ABSTRACT This study examines the heat transfer coefficient during coal water slurry preparation in a jacketed vessel, focusing on key parameters influencing heat transfer. A dual impeller system is utilized to enhance mixing and heat transmission capacity. Using the Ant Colony Optimization (ACO) method, the equipment is designed, comprising a cylindrical flat-bottom tank with an impeller diameter of 0.079 m, a height of 0.3 m, and four uniformly positioned detachable flat baffles around the vessel’s perimeter. Experiments are conducted using the L27 orthogonal array at three different levels, varying impeller speed, clearance height to tank diameter ratio, slurry height to tank diameter ratio, and distance between the two impellers. Two categories of dual impeller experiments, propeller and Rushton, are examined. Statistical analysis indicates that impeller speed and Z/T ratio significantly influence heat transfer coefficient, while C/T ratio and distance between impellers have a lesser impact. In both propeller and Rushton experiments, impeller speed and Z/T ratio have the most substantial effect on heat transfer coefficient, contributing 62.907% and 59.47%, respectively, in propeller and Rushton experiments. These findings underscore the importance of impeller speed and Z/T ratio in enhancing heat transfer coefficient during coal water slurry preparation in a jacketed vessel.

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.