Coal Slurry Research Articles

Experimental study of adhesion tension of wet coal dust and coal slurry

ABSTRACT The coal dusting process produces corrosive and adhesive coal slurry, which corrodes the surface of equipment and reduces its service life. To investigate the effect of velocity and water contents on the adhesion tension of wet coal dust and coal slurry, this paper experimentally measures the adhesion tension of wet coal dust and coal slurry in contact with metal surfaces. The results show that the trends of the adhesion pull and displacement relationship between wet coal dust and coal slurry are basically the same; the adhesion pull obtained by fast lifting is larger than that of slow lifting under the same water content, and the adhesion pull of coal slurry is larger than that of coal dust; the exponential decay function and the peak normal distribution function of adhesion pull are used to fit the change process of the adhesion pull and validate it. Through the validation experiments, we verify the two functions accuracy and reliability, which can provide expressions with high credibility for the prediction of the results of adhesion pull under the conditions of this experiment. Meanwhile, it also provides assistance for the selection and preparation of coal dust and coal slurry, which can help to improve the energy utilization and economic efficiency in the process of coal processing, conveying, and storage.

Effect of settling vortex of coal slime flocs with different sizes on the settlement of microfine particles

This article explores the flow field changes and micro vortex formation mechanisms caused by coagulation and sedimentation of coal slurry flocs of different sizes. The collision adhesion rate, motion trajectory and force analysis of fine particles under micro vortex disturbance. Particle image velocimetry (PIV) and high-speed camera were used to capture deposition process of coal slime flocs, the changes of flow field and fine particles were analyzed by numerical simulation. The smaller flocs form a single vortex ane larger flocs show periodic vortex shedding, resulting in increase fluid velocity and larger interference area. The collision adhesion rate of fine particles in the 3.4 mm floc settling disturbance area is the largest, 9.45 %;Particles<0.3 mm are easily sucked into vortices, while particles>0.3 mm are disturbed by vortices and change their motion trajectory towards the vortex center. It is mainly affected by gravity, pressure gradient force, flow field resistance, and centrifugal force.

Research on visual features and identification of coal and gangue in simulated underground mine environments

ABSTRACT In underground mine environments, factors such as low light intensity, diffusion of dust particles, and coal slurry coverage interfere with coal gangue identification. To further realize coal-gangue sorting underground, we analyzed the coal-gangue visual characteristics coupled with the above factors. The analysis reveals that both smoke environments and coal slurry coverage tend to make the coal-gangue visual features more consistent. There are still differences in coal-gangue visual features under smoke environments, while coal slurry coverage leads to gangue exhibiting coal-related feature information. To improve the detection capability of coal gangue in underground environments, this study adopts a coal gangue recognition method based on the DG module and YOLOX-PSB network: Utilize the DG module to achieve dehazing and then use the YOLOX-PSB model for object detection. The proposed method was validated through ablation experiments, and the results showed that the detection accuracy reached 99.6%, with an FPS of 98. The proposed method enables real-time detection and exhibits the best robustness in complex environments, realizing reliable and efficient performance.

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.

Systematic Exploration of the Interactions between Pyrite and Coal from the View of Density Functional Theory

Coal is often adhered to by pyrite during slime flotation, causing an increase in the sulfur content of clean coal. In order to study the mechanism of pyrite adhesion to coal surfaces, different coal structural units were built and optimized, and the most stable adsorption model of them on pyrite surfaces was determined. The mechanism of pyrite particles adhering to the surface of coal slurries was explored with the method of DFT. The results showed that the interaction mechanism between pyrite surface and Ph-OH and Ph-O-CH3 was the result of a weak interaction between the H atom of Ph-OH and Ph-O-CH3 and the S atom of the pyrite surface. The interaction mechanism between the pyrite surface and Ph-COOH and Ph-CO-CH3 was both as a result of H-S interactions and weak Fe-O interactions. On the whole, there were weak interactions between pyrite particles and the coal slurry, and the pyrite particles can spontaneously adsorb on the surface of the coal slurry.

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.

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.

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.

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.

Reducing the Energy Consumption during Microwave Drying of Coal Slime Dough by Optimizing Parameters: Experiment and Modeling.

Reducing the energy consumption in microwave drying processes is essential for the sustainable management of coal slime. Utilizing a self-constructed microwave thermogravimetric apparatus, the research investigates critical parameters, including microwave power, spherical diameter, and granule size, affecting drying kinetics and energy efficiency. The results show that it was observed that the drying process progresses through three distinct stages, marked by variations in temperature and moisture content: the initial warming phase, a steady drying stage, and a final phase where the drying rate decreases; optimal pellet sizes for efficient moisture evaporation and diffusion were identified, with smaller particles enhancing heat transfer and drying efficiency; and the Nadhari model was determined to best represent the drying kinetics of coal slime under microwave radiation. The findings indicate a positive correlation between drying efficiency and particle size while being inversely related to increased microwave power for smaller granules. A direct positive relationship between moisture migration and increased power levels was established, while an inverse relationship with the enlargement of particle sizes was observed, negatively affecting the efficiency. For granule sizes of 30, 40, and 50 mm, a decrease in activation power was recorded, with values of 8.215 ± 2.301, 7.936 ± 1.547, and 3.393 ± 0.248 W·g-1, respectively; and through the comparative analysis of energy consumption, it was demonstrated that for coal slurry particles sized 0.15-0.18 mm subjected to a drying duration of 600 s, an increase in power leads to a reduction in drying efficiency, whereas larger diameter contributes to improved efficiency.

Combined preparation and application of geopolymer pavement materials from coal slurry-slag powder-fly ash mining solid waste: A case study

The solid waste treatment problem generated in the process of coal mining has always been an important factor restricting safe and environmentally friendly production, and the coal slurry from the coal mine road surface is a new type of mine solid waste, so it is of great significance to treat and efficiently utilize the coal slurry. Currently, a common method of solid waste utilization is to add modifying reagents to prepare functional materials. Select coal slurry, slag powder and fly ash as raw materials, and sodium sulfate and sodium hydroxide were used as alkali exciters to prepare coal slurry based geopolymer pavement material (CSGPM). Response surface methodology was used to establish regression equations between the design optimization objectives (coagulation time, compressive strength) and the variables (mass fraction, mass ratio of slag powder to fly ash, mass ratio of sodium sulfate to sodium hydroxide). The effects of two-by-two interactions of the factors on the optimization objective were explored, and the use of different raw materials was obtained. Under the optimal proportioning parameters, the coagulation time of CSGPM was 33 min and the compressive strength of 24 h of curing was 11.20 MPa. In addition, the generation mechanism of AFt and C-S-H gel substances inside the specimen was explained with the help of microscopic scanning. CSGPM showed good mechanical properties in both load-bearing numerical simulations and acoustic emission tests. Numerical simulation was used to establish the relationship between the design objective of the roadbed (maximum subsidence of the roadbed after bearing) and the design variable (thickness of CSGPM paving). Comparative analyses yielded an optimal subgrade surface layer design thickness of 5 cm, with a maximum subsidence of 0.0033 m after bearing vehicles. Synchronization of roadbed material and concrete damage in combined specimen acoustic emission tests with uniform load transfer. The final coal mine pavement was successfully paved and the total cost of CSGPMD is 63.2 per cent of C30 concrete. Those results are important for the preparation of new pavement functional materials.

Performance and Environmental Assessment of Biochar-Based Membranes Synthesized from Traditional and Eco-Friendly Solvents.

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into water bodies (lakes, rivers, and aquifers) can lead to adverse health effects not only for freshwater bodies and plant life but also for humans. This study focused on two major experiments. The first experiment involved the use of biochar to create a biochar-polysulfone (BC-PSf) flat-sheet multifunctional membrane to remove organic contaminants, and the other major experiment compared eco-friendly (gamma-valerolactone-GVL; Rhodiasolv® PolarClean-PC) and petroleum-derived solvents (i.e., N-methyl-pyrrolidone-NMP) in the fabrication of the biochar-polysulfone membranes. The resulting membranes were tested for their efficiency in removing both positively and negatively charged organic contaminants from the collected water at varying pH values. A comparative life cycle assessment (LCA) with accompanying uncertainty and sensitivity analyses was carried out to understand the global environmental impacts of incorporating biochar, NMP, GVL, and PC in the synthesis of PSf/NMP, BC-PSf/NMP, PSf/GVL, BC-PSf/GVL, PSf/PC, and BC-PSf/PC membranes at a set surface area of 1000 m2. The results showed that the addition of biochar to the membrane matrix increased the surface area of the membranes and improved both their adsorptive and mechanical properties. The membranes with biochar incorporated in their matrix showed a higher potential for contaminant removal than those without biochar. The environmental impacts normalized to the BC-PSf/GVL membrane showed that the addition of biochar increased global warming impacts, eutrophication, and respiratory impacts by over 100% in all the membrane configurations with biochar. The environmental impacts were highly sensitive to biochar addition (Spearman's coefficient > 0.8). The BC/PSf membrane with Rhodiasolv® PolarClean had the lowest associated global environmental impacts among all the membranes with biochar. Ultimately, this study highlighted potential tradeoffs between functional performance and global environmental impacts regarding choices for membrane fabrication.

Study on the distribution of high ash slime in liquid-solid fluidized bed with different heights

ABSTRACT Liquid-solid fluidized bed (LSFB) sorting has been widely used in coarse coal slurry sorting in coal preparation plants in China. In this paper, the vertical distribution of high-ash fine sludge in the LSFB column was studied in depth, and the results showed that in the vertical direction of the column, the gradient of ash change of the + 0.25 mm particles was obviously larger than that of the −0.25 mm particles. For + 0.25 mm particles, the low-density fine coal particles accumulate in the middle and upper parts, while the high-density particles accumulate in the middle and lower parts, and the overflow −0.25 mm particles are basically uniformly distributed in each density class. In the overflow port and the upper part of the column, the ash content of −0.25 mm particle size is obviously higher than that of + 0.25 mm particle size, and the −0.125 mm high ash and fine sludge basically accumulate in the upper part of the LSFB, and eventually enter the overflow to seriously pollute the fine coal. This study is of great significance for the development and application of LSFB sorting machine and the optimization of coarse coal slurry sorting and recovery process.

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.

Особенности сжигания композиционных водоугольных топлив

Russia has large coal reserves, on the average up to 173 billion tons. Although, the share of coal generation in Russia is relatively small (about 20–22 %), it reaches 65 % in the Siberian Federal District. Russia cannot deny coal, but it is necessary to update and improve energy efficiency of Thermal Power Plants (TPP) and boiler houses that burn coal. Currently, technologies have been developed to produce and use composite coal-water fuel (CWF) with various additives, primarily of organic origin to improve its target characteristics. A study of the characteristics of such coal-water suspensions has proved the promising outlook of their use as fuel in large and small Thermal Power Plants, both from an economic and environmental safety points of view. However, the lack of experimental data on the issues of combustion of composite coal-water fuel in bench-scale and semi-industrial conditions hinders the further development of CWF technology. Thus, it is relevant to study the features of combustion of composite coal-water fuels from coals of varying degrees of metamorphism. To prepare experimental batches of composite CWF, raw coals and coal slurries of various stages of metamorphism (grades D, SS, T) have been used. They were burned in a bench-scale semi-industrial plant. The research results have been processed using the methods of mathematical statistics and regression analysis. The influence of mechanical activation of CWF on the viscosity and temperature of its ignition and combustion has been established. The features of combustion of composite coal-water fuel using pneumomechanical injectors of two types are determined. The composition of harmful emissions during the combustion of CWF has been determined. The possibility to use composite coal-water fuel to ignite high-power boilers has been established. It has been proved that the combustion of CWF is environmentally safer compared to the combustion of coal and other types of fuel.

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.