Preparation Of Coal Water Slurry Research Articles

Preparation of high-concentration coal-water slurry based on the bearing model method of spherical particles

ABSTRACT Coal-water slurry (CWS), a mixture of pulverized coal, water, and additives, is a clean liquid coal-based fuel for gasification. Superhydrophobic surface modification using a secondary particle-second liquid system is an effective CWS preparation method. In this study, the effect of the sphericity of the secondary particles on the rheological properties of CWS samples was investigated. Spherical secondary particles were found to roll in the film layer of the second liquid, resulting in a lower apparent viscosity of the CWS. The bearing model refers to the spherical secondary particle on the surface of the coal particle, similar to the balls in a bearing, which can transform sliding friction into rolling friction. The bearing model can effectively reduce frictional resistance. By modifying the coal particles with the suspension of secondary particles in the second liquid, a 73% CWS sample with good fluidity was prepared. The apparent viscosity of the 73% CWS prepared without any modification of the coal particles was 13,329.2 mPa·s, and the flow grade was C. The apparent viscosity of the 73% CWS prepared using coal particles modified with the spherical glass bead suspension was 2102.8 mPa·s, and its flow grade was A.

Effect of cavitation treatment of coal-water slurries on a droplet average size in a jet

Relevance. Transition to environmentally friendly energy technologies, due to modern requirements for environmental protection, involves the search and creation of new energy sources, including fuels. One of the ways to meet these requirements and maintain the same level of energy production by thermal power plants is the transition to multicomponent fuels. The most promising and affordable boiler fuels from the point of view of energy, ecology and economy are coal-water slurries. In this regard, the study of the properties and characteristics of such fuels is relevant in many countries. Aim. Experimental studies of the effect of the coal-water fuel cavitation treatment duration on a droplet average size in a jet after spraying with a pneumatic nozzle and substantiation of the efficiency of such approach for practical application. Object. Experimental studies were carried out with coal-water slurries based on long-flame coal (D grade) with addition of 10 and 20 wt % by weight of pyrogenetic liquid. A slurry, consisting of just coal and water, without the addition of pyrogenetic liquid, was used as a reference sample. Method. The coal-water slurries were prepared in a rotary hydrodynamic cavitation generator. A pneumatic nozzle with external mixing was used to spray the coal-water slurries. The average size of fuel droplets after spraying was determined using the Interferometric Particle Imaging method. Results. Experiments on the preparation of coal-water slurries with pyrogenetic liquid showed an increase in the dynamic viscosity of the fuel. An increase in the duration of treatment of the slurries in a rotary hydrodynamic cavitation generator reduced the viscosity by 54%. The average size of droplets in the jet was reduced by 22%.

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

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

Reliability based design of propeller and Rushton impellers for maximizing the overall heat transfer coefficient in coal gasification

The present study aims to identify the optimal process parameters to maximize the Overall Heat Transfer Coefficient for preparation of coal-water slurry used for gasifier in power plants. For this purpose, a jacketed vessel is designed with radial flow (rushton) and axial flow (propeller) impellers to prepare the coal-water slurry. Experiments have been conducted using L9 orthogonal array for Impeller speed (N), ratio of clearance height with diameter of tank (C/T) and ratio of slurry height with tank diameter (Z/T) parameters at three different levels for designed jacketed vessel. The best ranking is arranged in ascending order for propeller Z/T ratio, impeller speed and C/T ratio, for rushton impeller speed, Z/T ratio and C/T ratio. Statistical analysis reveals the percentage contribution of parameters for maximize of heat transfer coefficient in descending order in propeller Z/T ratio (64%), impeller speed (34.92%) and C/T ratio (1.07%), for rushton impeller speed (60.08%), Z/T ratio (36.86%) and C/T ratio (2.48%).

Thermogravimetric, kinetic study and gas emissions analysis of the thermal decomposition of waste-derived fuels

A wide range of wastes can potentially be used to generate thermal and electrical energy. The co-combustion of several types of waste as part of water-containing waste-derived fuels is a promising method for their recovery. In this research, we use thermogravimetric analysis and differential scanning calorimetry to study the thermal behavior and kinetics of coal slime, biomass, waste oils, and blends on their basis. We also analyze the concentrations of gaseous emissions. The results show that biomass, oils, and coal slime significantly affect each other in the course of their co-combustion when added to slurry fuels. The preparation of coal-water slurry based on slime and water reduced the ignition and burnout temperature by up to 16%. Adding biomass and waste oils additionally stimulated the slurry ignition and burnout, which occurred at lower temperatures. Relative to dry coal slime, threshold ignition temperatures and burnout temperatures decreased by 6%–9% and 17%–25%, respectively. Also, the use of biomass and waste oils as part of slurries inhibited NOх and SO2 emission by 2.75 times. According to the kinetic analysis, added biomass and waste turbine oil provide a 28%–51% reduction in the activation energy as compared to a coal-water slurry without additives.

Investigation on pH influence for the effective transportation of coal water slurry using experimental design

ABSTRACT The present study aims to identify the pH values in preparation of coal water slurry (CWS) that were evaluated. Rheological characteristics and stability of coal water slurry (CWS) were observed with two types of impellers at pH varying from 6.99 to 7.24. The results showed that the concentration of coal water slurry, rheological characteristics and stability of CWS for propeller and rushton impellers. The parameters that are most effected on the objectives are impeller speed (N) and ratio of clearance height with diameter of tank (C/T). The third parameter, ratio of slurry height with tank diameter (Z/T), is not effecting on output. The pH values of concentrated coal water slurry are favorable to transport to coal gasifier. For propeller impeller, the pH values vary from 6.99 to 7.15; for Rushton impeller pH values vary from 7.12 to 7.24 comparatively Rushton impeller having more base which is most favorable and obtain good CWS concentration. The influence of coal particle size is also investigated on pH values for optimal parameters of equipment.

Experimental and computational studies of polycarboxylate dispersant effect on the properties of low‐rank coal water slurries

AbstractThe disadvantages of low‐rank coal in the preparation of coal water slurry (CWS) are well known, but the synthesis of suitable dispersants is a promising solution. Polycarboxylate dispersant (PC) is expected to be an efficient CWS dispersant due to its flexible and controllable structure. In this study, a series of binary PC dispersants were synthesized by controlling the ratio of acrylic acid (AA) to sodium styrene sulfonate (SSS), initiator fraction, and temperature, and the optimal PC was selected based on the apparent viscosity of 72# CWS at 100 s−1. The properties of 72# CWS were studied: This CWS exhibited shear‐thinning behavior, >14 static stability, and >55 wt% maximum solid loading, indicating the satisfactory performance of the optimal PC. The experimental results (including adsorption tests and zeta potential measurement) and molecular dynamics simulation showed that PC was effectively adsorbed on the surface of the coal particles by a horizontal multipoint adsorption mode, mainly through the interaction between the hydrophobic groups of the PC molecule and the hydrophobic areas of the coal particles. The hydrophilicity of the coal particles was therefore improved and the stability of their hydration layer was also enhanced, which accounted for the good static stability of 72# CWS. The amount of PC adsorption and the improved absolute zeta potential were associated with the decent properties of 72# CWS. This study is significant for promoting the molecular design of CWS dispersants based on their adsorption behavior.

Quasi-hot spraying of coal-water slurries with pyrogenetic water additives

Experimental results of the influence of thermal preparation of coal-water slurries on their rheological properties and spraying characteristics are presented. The slurry density was found to increase by 14% at a temperature of 293 K with the substitution of water in coal-water fuel with a similar by weight amount of pyrogenetic water (no more than 25%). Preliminary thermal preparation of coal-water slurries up to 333 K reduces its density by 7%. The experimental results showed that the greatest influence of thermal preparation of the studied slurries on their dynamic viscosity is characteristic of the temperature range from 293 to 323 K. At such temperature values, a decrease in the slurry viscosity is by 17–20% in comparison with two-component coal-water fuel. Preheating of slurries before spraying, in the temperature range from 293 to 333 K, makes it possible to increase the jet spraying angle by 21–29% compared to conventional two-component coal-water fuel at a temperature of 293 K. The velocity of droplets of the investigated coal-water fuels in the range of changes in their initial temperature from 293 to 333 K varies slightly. The difference is no more than 5%. Increase in the pyrogenetic water concentration in coal-water fuel of more than 25% by weight is impractical for lignite due to the dramatic increase in its viscosity. In the studied range of the third component concentration of the slurry, increase in the average size of fuel droplets is about 8%. Preheating of CWF before spraying can significantly reduce the average size of the droplets. The changes are 5–9% in comparison with coal-water slurry at a temperature of 293 K. Thermal preparation of slurries, according to the results of thermal imaging studies of coal-water fuel jet, affects the thermal contour of the jet and the geometry of its temperature zones.

Quasi-hot spraying of coal-water slurries with pyrogenetic water additives

The relevance of the work is explained by the absence of the results of the heating effect of multicomponent coal-water slurries on rheological properties and characteristics of spraying in the literature.PURPOSE. Efficiency substantiation of thermal preparation of coal-water slurries based on pyrogenetic liquid by the results of experimental studies.METHODS. When solving this problem, the Brookfield RVDV-II+Pro rotary viscometer, general-purpose hydrometers, and the Interferometric Particle Imaging method were used.RESULTS. It was found that when water in coal-water fuel is replaced by a similar amount of pyrogenetic liquid (no more than 25%), the density of the slurry increases by 14% at a temperature of 293 K. Preheating of coal-water slurries to 363 K reduces the increase in the density value to 7%. The experimental results showed that the greatest influence of the thermal preparation of the studied slurries on their dynamic viscosity is characteristic of the temperature range from 293 to 333 K. At such temperatures, a decrease in the viscosity of the fuel is possible by 17-20%. Preheating of slurries before spraying in the temperature range from 293 to 333 K makes it possible to increase jet spraying angle by 21-29% in comparison with two-component coal-water fuel at a temperature of 293 K. Substitution of more than 25% by weight of water with pyrogenetic liquid in coal-water fuel is impractical for the studied grade of coal from the point of view of a significant increase in viscosity. Preheating coal-water fuel before spraying reduces the average droplet size by 5-9%.CONCLUSION. The efficiency of thermal preparation of coal-water slurries based on pyrogenetic liquid by the results of experimental studies of rheological properties and spraying characteristics was substantiated.

Model to predict packing efficiency in coal water slurry: Part2 prediction and application

Increasing the solid loading of coal water slurry (CWS) by 1 wt% in the gasification process can reduce the emission of CO2 by 15 million t/a indirectly in China alone. The compartment packing model can guide the preparation of CWS with lower viscosity, and thus increase solid loading. In this paper, the verification, discussion and application of the compartment packing model on the prediction of the viscosity are conducted, which also shows some interesting findings. The packing efficiency obtained by the compartment packing model can clearly point out the sample with the lowest viscosity, though the viscosity and solid loading of the samples are quite different. Moreover, the trend of viscosity from different gradation groups can also be illustrated on the order that the higher the packing efficiency, the lower the viscosity. For CWS made by Hailar coal at 45 wt%, the packing efficiency increases from 72.9% to 82.3%, the viscosity decreases to accordingly from 1862 mPa·s to 411 mPa·s. It is found that the traditional experience (double peak or three peak particlegradation) is not valid to design a particle size distribution (PSD) for lowest viscosity. The effective index for PSD with lowest viscosity is the packing condition that the fine particles efficiently fill all the void of the large particles, namely the highest packing efficiency. Therefore, the concept of systematic gradation is proposed that at same concentration and additive, the slurry with lowest viscosity can be predicted by the highest packing efficiency, which can be screened out by the compartment packing model from all the possible combination of grinded samples.

Preparation of high concentration coal water slurry with good fluidity based on only modified fine particles under bimodal distribution using the second fluid and the second particle

Coal water slurry (CWS) is the clean and efficient liquid coal-based fuel. CWS with the high solid content, low viscosity and good fluidity is conducive to efficient gasification and pipeline transport. Surface modification of particle has been demonstrated to contribute to improving the rheology of slurry. In this study, the slurry preparation method of selective particle modification was proposed, which focuses on the effect of modified particle size. Three different methods of surface modification with the kerosene suspension containing ultrafine particles were studied and compared. In method Ⅰ, the suspension was direct added to the mixture of coarse and fine particles. In method Ⅱ and method III, the suspension only modified the coarse and fine particles respectively, then mixing the composite particles with another particle. The apparent viscosity, fluidity and the hydrophobicity of the particle surface were researched. Method III was found to be optimum for reducing apparent viscosity and improving fluidity. The thin hydrophobic oil membrane that coats the surface of the fine particles like an “air cushion”, which can effectively reduce the friction between the particles. The concentration of CWS prepared by method III can increase from 62.7 wt% to 67.0 wt%, and the slurry still has a good fluidity.

A mathematic model based on eDLVO and Lifshitz theory calculating interparticle interactions in coal water slurry

The emission of CO2 can be greatly reduced by increasing the solid loading of coal water slurry (CWS) in the gasification industry. In this paper, a mathematic model based on eDLVO and Lifshitz theory is proposed to calculate the interaction between two coal particles and guide the preparation of CWS to increase the solid loading. Lifshitz theory is adopted to calculate the retardation Hamaker constant and van der Waals interaction, which has relatively wide applicability and less assumption. Equations of hydrophobic interaction and electrical double layer are properly simplified with assumptions. It is found that the low rank coal particles in dilute solution are difficult to cross the energy barrier to form aggregations, due to large electrical double layer repulsive interaction. While for bituminous coal, even in dilute solution, the particles will attract with each other. All the coal particles in high concentration CWS will naturally attract with each other to form aggregations, due to higher ion concentration that compressed the electrical double layer with lower absolute value of zeta potential. More energy is dissipated to break the aggregating structure, thus increasing the shear viscosity. Our model can be applied to explain and quantify the influence of ions and pH successfully. For SHH CWS with pH above 9.35, the viscosity of CWS is sharply reduced to 1/3 of original value, which is caused by the greatly increase of the absolute value of zeta potential, as quantified by eDLVO model.

Research on the preparation of coal water slurry with high chloride and concentrated brine

Research on the preparation of coal water slurry with high chloride and concentrated brine

Research on the preparation of coal water slurry with high chloride and concentrated brine

Research on the preparation of coal water slurry with high chloride and concentrated brine

Optimization of process parameters for preparation of coal water slurry using ant colony optimization and hydrodynamic simulation

ABSTRACT The Ant Colony Optimization algorithm is one of the leading optimization algorithms for nondeterministic polynomial hard problems. The aim of the present work is to find the maximum power of the agitator and selection of the motor power load for agitation equipment by assuming 80% of the maximum power of the agitator for preparation of coal water slurry. The parameters considered for optimization are the particle diameter of solids, jacketed vessel diameter and height, and density of the slurry. They affect the mass ratio and viscosity of the slurry. Sensitivity analysis was conducted with various combinations of ants’ parameters to enhance the result. From the optimization result, the power of the propeller, paddle, and rushton impellers is 13.58 Watts, 54.34 Watts, and 108.67 Watts. The power of the rushton impeller compared with the that of propeller and paddle is around 87.5% and 49%. VisiMix software is used to predict the turbulent shear near the impeller with optimized parameters obtained from ACO. The turbulent shear stress of the rushton impeller of 18.9 N/mm2 is high when compared with the other impellers. The developed algorithm has been justified with standard formulation and found to be satisfactory for implementing maximum power in agitation for uniform suspension to improve heat transfer.

Upgrade of low rank coal by using emulsified asphalt and its application for preparation of coal water slurry with high concentration

The hydrophilic surface and developed pore structure restricted the application of abundant low rank coals (LRC) for the preparation of coal water slurry (CWS) with high concentration. In this work, emulsified asphalt was applied as an effective and low cost modifier to modify coal surface and improve the slurry making performance of LRC. The successful modification was verified by various technologies, such as chemical titration, X-ray photoelectron spectroscopy (XPS) and Zeta potential measurements. The results revealed that the oxygen containing groups located at LRC surface were covered by emulsified asphalt, which further caused the decrease of Zeta potential. The influence of modification on wettability of coal was also evaluated by contact angle and moisture re-adsorption. It showed that the hydrophobicity of LRC significantly increased, which is accompanied with the reduction of inherent moisture. Besides, the results of nitrogen adsorption and scanning electron microscope (SEM) verified that the hydrophobic layer formed by emulsified asphalt blocked the pores of LRC. The modified LRC also exhibited better adsorption ability to the widely used anionic dispersant naphthalene sulfonate formaldehyde condensate (NSF) than that of raw coal (RC) and microwave dehydration coal (MDC). Anyhow, modified LRC possessed the characteristics as high rank coal. Afterwards, modified coal was applied to prepare CWS. The results showed that CWS prepared by modified LRC exhibited superior slurry making performance as compared to RC and MDC. The surface modification reduced the inherent moisture and promoted the adsorption of dispersant, which increased the free water amount and enhanced electrostatic repulsion and steric hindrance among coal particles. Accordingly, the maximum concentration for CWS increased, and the static stability enhanced.

The effect of isoamyl alcohol and sec-octyl alcohol on the viscosity of coal water slurry

In this work, the addition of isoamyl alcohol and sec-octyl alcohol on the viscosity of coal water slurry (CWS) was investigated and comprehensively analyzed. The surface tension, contact angle, dispersant absorbed amount, the microstructure of the particles as well as surface functional groups of coal powder was impacted by the addition of alcohols in the CWS. The isoamyl alcohol and sec-octyl alcohol lowers the surface tension and also partially absorbs to the coal particle surface, which would reduce the dispersant absorbed amount of the coal surface. The results show that both the isoamyl alcohol and sec-octyl alcohol can effectively reduce the viscosity of CWS under the amount of organic alcohol below to its solubility, and sec-octyl alcohol exhibits preferable performance than isoamyl alcohol. Our results anticipate to provide a convenient way to reduce CWS viscosity and could also be a reference for CWS preparation with such wastewater containing alcohol compounds.

Synthesis of a novel amphoteric copolymer and its application as a dispersant for coal water slurry preparation.

In this work, a novel amphoteric copolymer named Poly(sodium p-styrenesulfonate–co-acrylic acid-co-diallyldimethylammonium chloride) (P(SS-co-AA-co-DMDAAC)) was synthesized via free radical polymerization. Afterwards, P(SS-co-AA-co-DMDAAC) was explored for use as a dispersant in coal water slurry (CWS) preparation. The structure of P(SS-co-AA-co-DMDAAC) was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance. The synthetic conditions were optimized as the feed ratio of AA to SS was 1 : 1 (for Yulin coal) or 1.5 : 1 (for Yili coal), and DMDAAC dosage was 4.0 wt% (for Yulin coal) and 6.0 wt% (for Yili coal) toward total monomers. The performances of P(SS-co-AA-co-DMDAAC) as a dispersant for CWS were evaluated by various technologies, such as apparent viscosity, zeta potential, static stability and contact angle measurements. The results revealed that the optimized dosage of P(SS-co-AA-co-DMDAAC) in CWS preparation was 0.3 and 0.4 wt% for Yulin coal and Yili coal respectively. In this optimum condition, CWS prepared using P(SS-co-AA-co-DMDAAC) as dispersant showed a typical shear thinning behaviour and excellent stability, which are desired in industries. The rheological models also confirmed the pseudo-plastic characteristics of CWS. Finally, compared with the widely used anionic dispersant naphthalene sulphonate formaldehyde condensate (NSF) and poly(sodium p-styrenesulfonate) (PSS), P(SS-co-AA-co-DMDAAC) developed in this work exhibited better slurry making performance. The introduction of cationic functional groups promoted the adsorption of the dispersant, which further enhanced the electrostatic repulsion and steric hindrance among coal particles. Accordingly, the viscosity of CWS decreased and static stability enhanced.

Dispersion mechanism of coal water slurry prepared by mixing various high-concentration organic waste liquids

High-concentration organic waste liquids have complex components and their treatment is difficult. These liquids also contain hydrophobic organic pollutants. The preparation of waste liquid coal water slurry (WCWS) can aid with environmental protection and resource utilization. In this study, xanthan gum was selected from 11 types of additives because it overcomes the problem of solution incompatibility during the mixing of various high-concentration organic waste liquids. The experimental results showed that with 0.08 wt% addition of xanthan gum, no stratification occurred in the mixed waste liquid and the apparent viscosity of the WCWS was 921.1 mPa∙s. In this study, the role of xanthan gum was studied, and the effect of its addition on the coal particle surface was characterized by zeta potential and contact angle measurement. In addition, various interaction energies in the WCWS system were calculated using the extended DLVO theory. The results showed that xanthan gum introduced steric hindrance interaction energy into the WCWS system, enabling the system to be stably dispersed.

Additives the panacea of coal water slurry

Indian high ash coal was used for the preparation of coal water slurry consisting of coarse and fine particles in the proper proportion. Four bimodal samples were prepared with the combination of four coarse fractions such as (212 µm–300 µm, 90 µm–300 µm, 150 µm–212 µm, 75 µm–150 µm) with fine fraction of (<38 µm) in different proportion and labeled as S1, S2, S3 and S4 respectively. Additives are the guiding factor for the flow of the slurry in pipeline. These samples were tried in the presence of different additives like bio, chemical and the combination of chemical and bio additives. In this study bio additives like Sapindous Mukorossi, Saponin from Shikakai, chemical additive like different alcohol groups, and combination of bio and chemical additive like saponin from Shikakai mixed with DDAB (Di dodecyl ammonium bromide), SDBS (Sodium do decyl benzene sulphate) were used. A comparative study revealed saponin from Shikaki when mixed with chemical additive DDAB in the proportion of 0.95:0.05 by weight gives a better result of 70% of coal loading.