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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 NO х and SO 2 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. [Display omitted] [ABSTRACT FROM AUTHOR]

Low-rank coal is an ideal future development coal for coal-water slurry (CWS) due to its abundant resource, but low-rank coal is tougher to produce slurry than high-rank coal. Herein, a new-type macromolecular additive, tannic acid grafted carboxymethyl cellulose sodium (TAC), was designed and prepared to enhance the rheological properties of CWS using Hongshaquan coal in Xinjiang (Coal-HSQ). This work shows that trace amounts of TAC can effectively improve the fluidity of CWS in comparison with calcium lignosulfonate (CLS). Through contact angle and a novel surface characterization method in this field called microscopic infrared imaging, the analyses reveal the hydrophobicity of the Coal-HSQ surface modified by TAC is improved, which is beneficial for enhancing the fluidity of CWS. The apparent viscosity of CWS can be reduced to the lowest point (674.8 mpa·s), as CWS slurry concentration is 55 wt% and TAC addition is only 0.2 wt%. Finally, the highest slurry concentration of CWS prepared with 0.2 wt% TAC can be increased to 56.3 wt%. [ABSTRACT FROM AUTHOR]

Based on the response surface methodology, the pH change characteristics of coal-water slurry containing potassium permanganate (KMnO4) under the action of hydrogen sulfide (H2S) were studied, and the relationship between the factors of coal seam H2S content determination was explored. The effect coal rank, temperature and H2S inflow on the pH change of coal-water slurry was analysed. Through response surface methodology analysis, discovering H2S inflow had a significant effect on pH change of the solution, and the interaction between temperature and H2S inflow had a relatively significant effect on pH change of the solution. The optimal conditions were as follows: 36 mL H2S inflow, 36.5 °C temperature and medium rank coal. The conditions which had a significant effect on pH change of the solution, and compared with the experimental verification group, the error was small. Analyzing on influence factors of pH change of coal-water slurry, which provides a reference for the subsequent determination of H2S content. [ABSTRACT FROM AUTHOR]

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%.

In this paper, based on Fluent software, a five-nozzle gasifier reactor was established to simulate the gasification process of oil-based drill cuttings coal-water slurry. The influence of concentration and oxygen/carbon atomic ratio on the gasification process of oil-based drill cuttings coal-water slurry was investigated. The results show that when the oxygen flow is constant, the outlet temperature of gasifier decreases, the content of effective gas increases, and the carbon conversion rate decreases with the increase of concentration;When the ratio of oxygen to carbon atoms is constant, the effective gas content rises and the temperature rises with the increase of the concentration, and the carbon conversion rate reaches the maximum value when the concentration of oil-based drill cuttings coal-water slurry is 65%; When the concentration is constant, the effective gas content decreases and the outlet temperature rises with the increase of the oxygen/carbon atom ratio, and the carbon conversion rate reaches 99.80% when the oxygen/carbon atom ratio is 1.03. It shows that this method can effectively decompose the organic matter in oilbased drill cuttings and realize the efficient and cooperative treatment of oil-based drill cuttings. [ABSTRACT FROM AUTHOR]

The results of studies of calorific value and dynamic viscosity of coal-water slurries with addition of a pyrogenetic liquid are presented. It was found that addition of small quantities (not more than 10 wt.%) of a pyrogenetic liquid raises the calorific value of the slurries by 6%. [ABSTRACT FROM AUTHOR]

An experimental study of the ignition and combustion processes of coal-water slurry (CWS) droplets based on coal enrichment waste in a high-temperature oxidizer at 650–850 °C with a syngas addition was carried out. The fuel slurry was a mixture of finely dispersed solid combustible particles (coal sludge, 10–100 µm in size) and water. The syngas was a product of biomass pyrolysis and two waste-derived fuels in a laboratory gasifier. Composition of the syngas was controlled by a precision analytical gas analyzer. The feasibility of co-firing CWS with syngas was experimentally established. Under such conditions, the CWS droplets ignition process was intensified by 15–40%, compared to fuel combustion without the addition of syngas to the combustion chamber. The greatest positive effect was achieved by adding the gas obtained during the biomass pyrolysis. The ignition delay times of CWS droplets are 5.2–12.5 s versus 6.1–20.4 s (lower by 15–39%) when ignited in a high-temperature medium without adding syngas to the combustion chamber. Based on the results obtained, a concept for the practical implementation of the CWS combustion technology in a syngas-modified oxidizer medium is proposed. [ABSTRACT FROM AUTHOR]

Coal has long remained a promising and widely used energy resource all over the world. Special emphasis is usually put on the research and development of environmentally friendly technologies for the use of coal and coal processing waste. The development of slurry fuels based on coal waste is one of the promising ways to use raw materials with energy potential, recover wastes, and reduce the environmental load. However, no combustion technology has yet been created for heterogeneous wastes as water-based slurries. The physical principles and parameters of the corresponding processes have not been studied adequately. In this research, the environmental combustion indicators (CO2, CO, H2, NOx, and SO2 concentrations) of slurries based on water and petrochemical, coal, and plant wastes were analyzed for the first time in a wide range of temperatures covering all the typical stages of thermochemical fuel conversion: pyrolysis (400–700 °C), gasification (700–900 °C), and combustion (700–1000 °C). We established the key patterns and aspects of changes in gas concentrations at all the main stages during the thermal decomposition of fuels. The use of water-based fuels at the pyrolysis stage was notable for up to 96% higher concentrations of the key combustible gases (CO, H2). The temperature extrema were 50–100 °C lower than those of bituminous coal. In terms of the key anthropogenic emissions (CO2, NOx, and SO2), the combustion of slurries also appeared to be 20–77% more environmentally friendly than that of coal depending on the temperature conditions and fuel composition. The maximum positive effect from adding biomass to coal-water slurries was achieved in the temperature range of 850 to 1000 °C. The research findings can be used for developing the technologies for thermal recovery of waste as water slurries, in particular, by intensifying the pyrolysis, gasification, and combustion. [ABSTRACT FROM AUTHOR]

In this paper, the co-combustion process of coal-water slurry (CWS) and pulverized coal fuel (PCF) in E500 pilot boiler when using staged afterburning scheme, was investigated based on numerical simulation. A complex three-dimensional mathematical model and numerical methodology was used to describe the CWS and PCF co-combustion, as well as subprocesses in the combustion chamber. The proposed mathematical model was tested based on data obtained from a full-scale experiment. A good compliance was shown between the computational results and the experimental data. A detailed comparative analysis of the effect of changes in the design of a pilot boiler when using a three-stage combustion scheme and the flare-drip combustion technology for CWS on the physical-chemical processes in the combustion chamber and environmental indicators was carried out for the first time. The change of circulation zones depending on the method of coal fuel supply during three-stage combustion was investigated. Calculations have shown that the implementation of the proposed changes reduced the underburning of solid carbon from 1.9% to 0.51%. It was revealed that using CWS as a reducing agent diminishes the amount of harmful NO x emissions by more than 40% compared to the basic version. [ABSTRACT FROM AUTHOR]

The article presents the results of studies of spraying multicomponent coal-water slurries with hot air. Coal, water, ethanol, and pyrogenetic liquid were used as fuel components. It has been established that, in comparison with a two-component coal-water fuel, the jet opening angle increases by 14–25%, which significantly increases the jet volume and the ignition zone. The droplets velocity in the jet increases by 9–13% when the air is heated by 50 K; with further heating, the increase in droplets velocity is insignificant (not more than 4%). It has been proved that spraying the studied coal-water slurries with hot air allows reducing the average droplet size in the jet by 7–12% compared to cold spraying (at 293 K). [ABSTRACT FROM AUTHOR]

One of the ways to minimize anthropogenic emissions from coal combustion is to replace conventional schemes used for the introduction of coal dust into the furnaces of power plants through the injection of water-containing fuels. In this research, the three most promising schemes for fuel combustion were implemented: (i) the simultaneous introduction of coal particles and water droplets into the combustion chamber; (ii) steam injection into the fuel particle combustion zone; and (iii) the introduction of coal–water slurries into the furnace. Three methods of supplying water to the combustion zone were evaluated using the multi-criteria decision-making technique. Experimental research was conducted to record a range of process characteristics: the time of the gas-phase and heterogeneous ignition, the time of complete combustion, minimum ignition temperatures, maximum combustion temperatures, the completeness of the fuel burnout and the concentrations of the main gaseous emissions. It has been found that the most favorable scheme for coal particle combustion in water-steam environments is to produce fuel slurries. The cumulative indicator integrating the energy and environmental characteristics is 7–47% higher for slurries than for the other examined schemes for burning coal particles and slime. [ABSTRACT FROM AUTHOR]

Enhancing energy efficiency by coal–water slurry preheaters in the gasification process, the geometry of ladder-type fold helical baffles and shell–inlet velocity have an important effect on thermo-hydraulic performance of preheaters. A variance-based global sensitivity analysis procedure was built by metamodel of prognosis, and optimization results were compared between genetic algorithm and particle swarm optimization. The simulation results illustrate that heat transfer coefficient per unit pressure drop (K/ΔP) increases when folding angle and folding ratio increase, and K/ΔP decreases with increasing relative height and shell–inlet velocity. As for K/ΔP, the coefficient of prognosis of full model is 99.03%, and total effects of shell–inlet velocity, folding angle, folding ratio and relative height is 70.34%, 25.01%, 8.74%, and 7.87%, respectively. Based on reduced spaces with most influential parameters, optimization cases show genetic algorithm is more efficient and provides better results, folding angle, folding ratio, relative height and shell–inlet velocity are 50°, 0.6, 0.5 and 1.4 m s–1 when maximizing K/ΔP. The research results provide theoretical guidance for selection, design and optimization of coal–water slurry preheaters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Methane hydrate reduces ignition delay of composite slurry fuels. • Methane hydrate reduces gas emissions from the combustion of composite slurry fuels. • Methane hydrate increases the degree of combustion of composite slurry fuels. • A new scheme is proposed for composite liquid fuel and gas hydrate co-combustion. • Mathematical equations are obtained for predicting ignition characteristics. Combustion of composite slurry fuels based on industrial and municipal waste is an effective way to both recover the said waste and address the problem of fossil fuel depletion. The flexible composition of such fuels can be adjusted to include raw materials available in any specific region of the world. Another benefit they provide is the opportunity to recover waste in different proportions to conventional fuels. There is, however, a problem of long ignition delay times of composite slurry fuels, especially if they contain a significant proportion of water or high-moisture wastes. Here we suggest intensifying their ignition by involving methane released from gas hydrates. Gas hydrates contain a large amount of water that reduces the concentrations of sulfur, nitrogen, and carbon oxides in flue gases. The experimental findings have shown that the involvement of gas hydrate reduces the ignition delay time of a coal-water slurry droplet by more than four times. Adding gas hydrate also contributes to higher combustion temperature and degree of fuel combustion. On the basis of the results obtained, we propose a coal-water slurry/gas hydrate co-combustion system for energy production facilities. [ABSTRACT FROM AUTHOR]

Coal-water slurries have been actively studied during the last decade due to the fact that much less oxides of sulfur, nitrogen and carbon are formed during their combustion in furnaces of power boilers compared to coal. The main problem that hinders the widespread implementation of such fuels in the energy sector is their long (up to 30-40 s) ignition delay times. Significant (up to 56%) reduction of the ignition delay time is possible when a small (up to 8% by weight) amount of available and relatively inexpensive liquid combustible organic compounds is added to the suspension. The purpose of this work is to substantiate the possibility of significant reduction of the ignition delay times of coal-water fuels by introducing a third component into the coal - water suspension - isoamyl, isopropyl or ethyl alcohol in relatively small (from 3 to 8% by weight) concentrations. Mechanism, characteristics and conditions of ignition of the studied rather promising fuel compositions have been established by the results of experimental studies of ignition process of multicomponent coal-water fuel droplets based on lean coal with alcohol additives in a medium of oxidizer (still air) heated to high temperatures (from 873 K to 1273 K) with recording of heating, ignition and combustion processes by a high-speed video camera (shooting speed up to 105 frames per second). Experiments have shown that stable ignition delay time of the studied suspensions based on lean coal decreases by 11-56% with an increase (from 3 to 8%) in the mass concentration of one of the alcohols in the composition of coal-water fuel at the initial characteristic size of droplets from 1.0 to 2.5 mm. Each studied composition was compared with conventional coal-water fuel burned under similar conditions. Increase in the mass concentration of alcohol in the composition of coal-water fuel reduces the value of the flash point by 27-30%. The viscosity of alcohol-coal-water fuels increases by 7.0 to 40% when the researched alcohols are added to the coal-water slurry. Influence of mass concentration of isoamyl, isopropyl and ethyl alcohols in the composition of coal-water fuel on the characteristics of initiation of ignition and combustion processes established in experiments justifies the possibility of sufficiently effective application of such three-component suspensions in the power industry. Necessary and sufficient conditions for the ignition of alcohol-coal-water fuel droplets have been established based on a mathematical model and experimental data. Increase in the cost of such fuels has been analyzed in comparison with conventional coal-water slurry. It has been shown that the most attractive from the energy and economic points of view is coal-water fuel with isoamyl and isopropyl alcohols in the composition. The obtained results are of significant practical value, as they illustrate the possibility of achieving optimal ignition and combustion conditions for promising multicomponent coal-water suspensions with alcohol additives in the furnaces of boiler plants. [ABSTRACT FROM AUTHOR]

An experimental study of the ignition and combustion processes of coal-water slurry (CWS) droplets based on coal enrichment waste in a high-temperature oxidizer at 650–850 °C with a syngas addition was carried out. The fuel slurry was a mixture of finely dispersed solid combustible particles (coal sludge, 10–100 µm in size) and water. The syngas was a product of biomass pyrolysis and two waste-derived fuels in a laboratory gasifier. Composition of the syngas was controlled by a precision analytical gas analyzer. The feasibility of co-firing CWS with syngas was experimentally established. Under such conditions, the CWS droplets ignition process was intensified by 15–40%, compared to fuel combustion without the addition of syngas to the combustion chamber. The greatest positive effect was achieved by adding the gas obtained during the biomass pyrolysis. The ignition delay times of CWS droplets are 5.2–12.5 s versus 6.1–20.4 s (lower by 15–39%) when ignited in a high-temperature medium without adding syngas to the combustion chamber. Based on the results obtained, a concept for the practical implementation of the CWS combustion technology in a syngas-modified oxidizer medium is proposed.

By adding water to fuels, several objectives are pursued, with the main ones being to stabilize combustion, minimize the anthropogenic gaseous emissions, homogenize and stabilize the fuel, as well as improve its fire and explosion safety. Water can be injected into the furnace as droplets or vapor and introduced as part of fuel samples. Water often serves as a coupling or carrier medium for the delivery of the main fuel components. In this paper, we compare the combustion behaviors of high-potential slurry fuels and gas hydrates. We also analyze the contribution of in slurries and gas hydrates to the combustion process. The values of relative combustion efficiency indicators are determined for gas hydrates and slurry fuels. The conditions are identified in which these fuels can be burned effectively in power plants. The research findings can be used to rationalize the alternative ways of using water resources, i.e., gas hydrate powder and promising composite fuel droplets. The results can also help predict the conditions for the shortest possible ignition delay, as well as effective combustion of gas hydrates as the most environmentally friendly new-generation alternative fuel. [ABSTRACT FROM AUTHOR]

• The interaction of PC R /PC B with bituminous coal was explained at molecular level. • Adsorption conformation of PC R /PC B on coal were figured out by MD simulations. • PC B /PC R adsorb on the surface of coal according to the Langmuir isotherm. • PC B is greater than PC R in promoting adsorption and mobility of water molecules. • The interaction energy suggests PC B is more favorable for molecular expansion. The adsorption conformations of random-structure polycarboxylic acid (PC R) and block-structure polycarboxylic acid (PC B) on coal surfaces were analyzed from a microscopic perspective. This analysis involved a combination of molecular dynamics (MD) simulations and experiments. The saturation adsorption amount of PC B was found to be significantly much larger than that of PC R. Additionally, observations from the contact angle and X-ray photoelectron spectroscopy confirmed that PC B exhibited superior wetting performance on coal compared to PC R and had a greater adsorption layer thickness. The relative concentration changes and the mean square displacement (MSD) of water indicate that the better adsorption of PC B on the coal surface makes the water molecules more evenly distributed, which improves hydration, increases the thickness of the "adsorption layer", and enhances the mobility of water molecules. The interaction energy suggests the block structure of PC B is more favorable for molecular extension due to its well-defined structure. This provides a theoretical and experimental basis for expanding the molecular sequence structure design of polycarboxylic acid dispersants. [ABSTRACT FROM AUTHOR]

A novel sulfonic-cellulose succinate half ester (S-CSHE) dispersant for coal–water slurry (CWS) was successfully synthesized using cotton linters, sulfamic acid and succinic anhydride in DMF by a one-pot synthesis. The effects of the synthetic condition of S-CSHE as a dispersant for CWS were studied. An S-CSHE with a maximum degree of substitution of 0.98 was obtained under these optimized conditions. The synthesized samples were characterized by GPC, FT-IR spectroscopy, 13C-NMR, and SEM. The molecular weight was from 2.2 × 103 to 1.2 × 104, revealed by GPC; FT-IR spectra analysis revealed characteristic absorptions of the sulfonic-cellulose succinate half ester; SEM images showed smooth cellulose structures, while the S-CSHE had a compact surface. Effects of S-CSHE on the fluidity of application as the dispersants for the CWS prepared from Chinese Zhundong coal were studied further. The CWS application performance investigations showed that S-CSHE can most effectively reduce CWS viscosity, and perform excellent dispersity and stability. When the dosage of S-CSHE was up to 0.5 wt.%, the maximum coal content of CWS may reach 70 wt.%, and the apparent viscosity of CWS was 487 mPa·s. The CWS prepared using S-CSHE (0.38 wt.%) for Zhundong coal showed the rheological characteristics of shear-thinning, and is consistent with the Herschel–Bulkley model. This work found a new route for utilizing cotton linters cellulose and enlarged the selecting range of the dispersant for CWS. It has a positive significance for efficient and clean utilization of Xinjiang Zhundong coal. [ABSTRACT FROM AUTHOR]

An experimental study is performed to examine the pressure drop characteristics during the flow of coal-water slurry suspension using a pilot-plant test loop. The effect of slurry concentration, particle size, and flow velocity on the pressure drop characteristics during the transportation through a horizontal pipeline has been investigated. The present study considers both the unimodal and bimodal particle size distributions for the preparation of coal-water slurry. The pressure drop characteristics for both unimodal and bimodal coal-water slurry are analyzed for a wide variety of slurry concentrations ranging from 30% to 60%, which covers from low to high concentrations. The pressure drop characteristics are also analyzed for different flow velocities ranging from 2 to 5 m/s. It is found that the amount of pressure drop during the flow of coal-water slurry suspension in horizontal pipeline is the function of solid concentration, particle size, and flow velocity. It is also found that the bimodal coal-water slurry significantly reduces the pressure drop during the flow as compared to unimodal coal-water slurry. The maximum reduction in pressure drop during the flow is observed by bimodal coal-water slurry prepared by adding 30% of coarser particles in finer coal particles. [ABSTRACT FROM AUTHOR]

In this work, different concentrations of coal-water slurry and coal-oil-water slurry were prepared and pyrolyzed at various temperatures of 800–1000 °C. The chemical characteristics and combustion reactivities of chars and the formation mechanism of main gas components of CO, CO 2 , CH 4 , and H 2 were investigated. With the water content of the coal-water slurry increasing, the formation of CO and CH 4 were hindered, while CO 2 and H 2 were promoted. For the coal-oil-water slurry, oil promoted CH 4 and H 2 production but inhibited CO and CO 2. Moreover, the variation of the nitrogen-containing pyrolytic gas during pyrolysis was studied for various concentrations of coal-water and coal-oil-water slurries at different temperatures. The relative content of HCN and NH 3 gradually increased with the increase of pyrolysis temperature and water content. For coal-oil-water slurry, the waste lubricating oil promoted the formation of HCN and NH 3 , with the relative content of HCN being much higher than that of NH 3. To study the mechanism of nitrogen migration during pyrolysis, Lammps was used to simulate pyrolytic behavior of pyrrole and pyridine under N 2 and steam atmospheres. The increase in temperature promoted the decomposition of pyrrole and pyridine, thereby promoting the production of HCN and NH 3. Finally, the properties and the combustion reactivities of the chars were analyzed. The water and oil content in the coal-water slurry increased the structural ordering degree of chars but decreased the combustion reactivities. • Water and waste lubricating oil affected pyrolysis gas composition. • Waste lubricating oil promoted the formation of HCN and NH 3. • Water and oil increased the structural ordering degree of chars. • Water and oil decreased the combustion reactivity of chars. [ABSTRACT FROM AUTHOR]

Coal-water slurry can be prepared by blending coal chemical wastewater. The wastewater is composed of shift condensate, low-temperature methanol washing wastewater, MTO wastewater and torch condensate in a proportion of 3∶2∶1∶1.The proportion of fresh water and wastewater is 3∶7,the prepared CWS has a solid content of 61.0%,a rotational viscosity of 784.7 mPa·s, a 24-hour penetration rate of 98.0%,a 72-hour water separation rate of 6.1%,and a pH value of 8.1.The particle size distribution of the CWS is reasonable. Mixing different types of coal chemical wastewater to prepare coal-water slurry reduces the amount of wastewater treatment, reduces the cost of wastewater treatment, and realizes the resource utilization of wastewater. [ABSTRACT FROM AUTHOR]

One of the ways to minimize anthropogenic emissions from coal combustion is to replace conventional schemes used for the introduction of coal dust into the furnaces of power plants through the injection of water-containing fuels. In this research, the three most promising schemes for fuel combustion were implemented: (i) the simultaneous introduction of coal particles and water droplets into the combustion chamber; (ii) steam injection into the fuel particle combustion zone; and (iii) the introduction of coal–water slurries into the furnace. Three methods of supplying water to the combustion zone were evaluated using the multi-criteria decision-making technique. Experimental research was conducted to record a range of process characteristics: the time of the gas-phase and heterogeneous ignition, the time of complete combustion, minimum ignition temperatures, maximum combustion temperatures, the completeness of the fuel burnout and the concentrations of the main gaseous emissions. It has been found that the most favorable scheme for coal particle combustion in water-steam environments is to produce fuel slurries. The cumulative indicator integrating the energy and environmental characteristics is 7–47% higher for slurries than for the other examined schemes for burning coal particles and slime.

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Coal processing waste is generated annually in large volumes by the coal exporting countries. More than 70% of run-of-mine coal is enriched. At the same time, typical coal processing waste (slime, flotation waste, mid-coal and tailings) make up at least 10–15% of the raw coal mass. Approximately 220–300 million tons of coal processing waste is generated annually at coal-preparation plants in Russia and China. The results of experimental researches in recent years illustrate the growing interest in such wastes as promising energy components. In this paper, we performed a comparative analysis of the main physical properties, ignition and combustion characteristics of several types of coal processing waste. The comparison is made for typical flotation waste (filter cakes or coal slime) generated in Russia and China. It is shown that for wastes from different countries the ignition delay times differ by no more than 50% and the heat of combustion by 9–15%. Concentrations of main anthropogenic emissions were determined. Generalization is made using criterion expressions to illustrate the advantages and disadvantages of coal processing waste incineration in comparison with pulverized coal combustion. [ABSTRACT FROM AUTHOR]

Coal-water slurries are promising fuels for thermal power engineering. One of the main problems with their combustion is formation of fairly large (with characteristic sizes of more than 1 mm) droplets during spraying with nozzles. It results in their late ignition in the furnaces of steam and hot water boilers. The aim of this work is to establish by experimental results distribution of coal-water fuel droplets by size with the addition of isopropyl alcohol after coaxial spraying and justify the effectiveness of using this alcohol as the third component that affects the number and diameter of fuel droplets after spraying. It was found that the number of small droplets (no more than 100 micrometers) in the jet increases by 19% in comparison with typical coal-water fuel after spraying coal-water fuel prepared on the basis of lignite due to the introduction of IPA (no more than 3% by weight). Concentration of small droplets (no more than 100 µm) increases by 16% after spraying coal-water slurry prepared on the basis of long-flame coal and addition of no more than 3% by weight of isopropyl alcohol in comparison with typical coal-water fuel. Increase in the proportion of isopropyl alcohol in the slurry composition to no more than 5% by weight is the reason for increase of sufficiently large (more than 400 micrometers) droplets of such fuel after spraying by 14%. The number of fuel droplets of small sizes decreases similarly to large fragments after spraying coal-water slurry prepared on the basis of lean coal with small weight (no more than 3%) additives of isopropyl alcohol. Increase in the viscosity of fuels in several times is conditioned by increase in the concentration of the third component. This significantly degrades jet characteristics after spraying. The expansion angle of the jet increases by 20%. Medium-sized droplets (200–600 micrometers) and fairly large fragments (more than 600 micrometers) prevail in the jet. Concentration of droplets up to 200 micrometers in the diameter decreases. The results obtained are of sufficient practical significance, because they illustrate the possibility of increasing the number of small fuel droplets after spraying. The efficiency of insertion a small amount (no more than 3% by weight) of isopropyl alcohol additive into the composition of coal-water fuel was experimentally proven, and the application feasibility results in the analysis of optimal ignition conditions for droplets of alcohol-coal-water slurries in conditions corresponding to the combustion chambers of steam and hot water boilers. [ABSTRACT FROM AUTHOR]

The present study was carried out in an attempt to reduce head loss in 90° pipe bends for conveying coal-water slurry suspensions using computational fluid dynamics (CFD). Bend geometries were modified by altering the r/D ratios within the range of 1.5–3.0. Numerical simulations were performed using several turbulence models for a solid concentration range of 30–60% (by weight) and the results were validated with experimental data. An Eulerian multiphase model along with an SST k-ω turbulence scheme was found most appropriate and shows decent agreement with experimentation results. The mean sizes of coal particles were taken as 16 μm. Results show that head loss was increased with flow velocity and solid concentration. It was also observed that r/D ratio has a significant impact on head loss characteristics. The minimum drop in head loss was observed in a pipe bend having an r/D ratio of 2.0. The effect of flow separation and secondary flows on turbulence, flow velocity and distribution of the solid suspension inside the bend geometry was also studied with the help of contours. [ABSTRACT FROM AUTHOR]

Parameters of the process of coal-water fuels spraying (characteristics of the fuel jet) with addition of liquid waste from processing of industrial rubber goods have been studied. It has been established that application of this additive in the composition of coal-water fuel leads to an increase in the viscosity of the fuel, as well as increase in the spraying angle. Nonlinear dependences of the velocity of sprayed fuel particles and their size distribution on the concentration of the additive in the fuel composition have been experimentally established. Application of liquid waste from the processing of industrial rubber goods as an additive to coal-water fuel is advisable when the additive content does not exceed 8 wt%. [ABSTRACT FROM AUTHOR]

The development and application of high-efficiency coal-water slurry (CWS) dispersants can foster the clean utilization of natural coal. CWS with excellent flowability and stability requires good adsorption capacity of dispersant on pulverized coal surface, which is influenced substantially by the architecture and hydrophilicity of dispersants molecule. In this study, a series of neutralized sulfonated poly(styrene- alt -maleic anhydride) (NSPSM) with different molecular weight (M n) and sulfonation degree (SD) were synthesized by self-stabilized precipitation polymerization (2SP), gas-solid heterogeneous sulfonation reaction (GSR) and neutralization reaction with NaOH. The performance of NSPSM for CWS, and their dispersion and stabilization mechanisms were investigated in detail. Under optimized conditions, maximum slurry concentration (MSC) and water separation ratio (WSR) of slurry with NSPSM could reach 66.5% and 2.0%, respectively, which are superior to commercial naphthalene sulfonate formaldehyde condensate (NSF) dispersant. The outstanding dispersibility of NSPSM was ascribed to its improved adsorption capacity due to increased charge density along polymer chain, which can prevent agglomeration among coal particles through electrostatic repulsion. [Display omitted] • Gas-solid heterogeneous sulfonation reaction were adopted to synthesize CWS dispersants. • The relationship between sulfonation degree and M n of PSM, and slurryability was investigated systematically. • Adsorption isotherms tests unveiled that the adsorption capacity was significantly enhanced due to increasing charge density. • Water separation ratio of CWS with NPSM6200-117%S can be reduced to 2.0%, which was superior to commercial NSF. [ABSTRACT FROM AUTHOR]

[Display omitted] • A stabilizer in a small proportion (1%) has little effect on ignition and combustion. • Ignition and burnout can be improved by increasing the reactive additive share. • Sodium lignosulfonate is the most promising non-oil stabilizer. • Soy lecithin is less promising according to a set of indicators. • Re-equipment of a thermal power plant for burning waste-derived slurry can pay off in 1 year. The paper presents the results on the influence of stabilizing additives on the viscosity, sedimentation, ignition, combustion and emission profile of fuel slurries derived from coal slime. Soy lecithin, sodium lignosulfonate, rapeseed oil, and diesel fuel of 1 wt% were stabilizers. A slurry without stabilizers and with waste turbine oil were tested for a comparison. All the mixtures met the standard viscosity required for pumping and spraying (less than 1,000 mPa·s at a shear rate of 100 s−1). The use of additives reduced the proportion of the separated liquid during fuel storage (up to 6 times). Diesel fuel with a share of 1% reduced the ignition temperature of a fuel slurry by 30 °C and accelerated gas-phase ignition by 10–12%. The slurries with additives of waste turbine oil and sodium lignosulfonate were the most effective. Their integral efficiency indicator was 0.906 and 0.865, respectively. In feasibility study, the transition from bituminous coal to stabilized fuel slurries were analyzed, considering the new technological chain and equipment, the generated power and fuel cost. The cost for the full cycle of preparation of the slurry coal slime–water–soy lecithin will be 7.5% higher than when using bituminous coal. For the rest of the studied fuels, the estimated payback period for capital investments is about 1 year. [ABSTRACT FROM AUTHOR]

By adding water to fuels, several objectives are pursued, with the main ones being to stabilize combustion, minimize the anthropogenic gaseous emissions, homogenize and stabilize the fuel, as well as improve its fire and explosion safety. Water can be injected into the furnace as droplets or vapor and introduced as part of fuel samples. Water often serves as a coupling or carrier medium for the delivery of the main fuel components. In this paper, we compare the combustion behaviors of high-potential slurry fuels and gas hydrates. We also analyze the contribution of in slurries and gas hydrates to the combustion process. The values of relative combustion efficiency indicators are determined for gas hydrates and slurry fuels. The conditions are identified in which these fuels can be burned effectively in power plants. The research findings can be used to rationalize the alternative ways of using water resources, i.e., gas hydrate powder and promising composite fuel droplets. The results can also help predict the conditions for the shortest possible ignition delay, as well as effective combustion of gas hydrates as the most environmentally friendly new-generation alternative fuel.

A novel sulfonic-cellulose succinate half ester (S-CSHE) dispersant for coal–water slurry (CWS) was successfully synthesized using cotton linters, sulfamic acid and succinic anhydride in DMF by a one-pot synthesis. The effects of the synthetic condition of S-CSHE as a dispersant for CWS were studied. An S-CSHE with a maximum degree of substitution of 0.98 was obtained under these optimized conditions. The synthesized samples were characterized by GPC, FT-IR spectroscopy, 13C-NMR, and SEM. The molecular weight was from 2.2 × 103 to 1.2 × 104, revealed by GPC; FT-IR spectra analysis revealed characteristic absorptions of the sulfonic-cellulose succinate half ester; SEM images showed smooth cellulose structures, while the S-CSHE had a compact surface. Effects of S-CSHE on the fluidity of application as the dispersants for the CWS prepared from Chinese Zhundong coal were studied further. The CWS application performance investigations showed that S-CSHE can most effectively reduce CWS viscosity, and perform excellent dispersity and stability. When the dosage of S-CSHE was up to 0.5 wt.%, the maximum coal content of CWS may reach 70 wt.%, and the apparent viscosity of CWS was 487 mPa·s. The CWS prepared using S-CSHE (0.38 wt.%) for Zhundong coal showed the rheological characteristics of shear-thinning, and is consistent with the Herschel–Bulkley model. This work found a new route for utilizing cotton linters cellulose and enlarged the selecting range of the dispersant for CWS. It has a positive significance for efficient and clean utilization of Xinjiang Zhundong coal.

The composite quasi-liquid fuels made of different industrial waste become more and more attractive for scientists during last years. Coal-water slurry is one of the popular types of such compositions. Addition of the waste petrochemicals into the slurry allows decrease of the ignition delays of such composite for up to 27%. However, it has a non-trivial effect onto the atomization dynamics of the slurry making the size and velocity distributions of the aerosol more stable during propagation of the aerosol cloud. This, in turn, leads to more predictable ignition and combustion of the aerosol. [ABSTRACT FROM AUTHOR]

The present study investigates head loss for flow of coal–water slurry inside 90° pipe bend. The experiments were conducted with slurries of different solid concentrations, varying from 31.4 to 60.8% (by weight). Pulverized coal samples with particle sizes of less than 53 µm were used to prepare the slurry. During experimentation, average flow velocity was kept in the range of 2–5 m/s. Extensive rheological experimentation was performed to analyze the flow characteristics of coal–water slurry with and without the addition of additive namely sulfonic acid. Sulfonic acid was mixed with coal–water slurry in proportions of 1–4% (by weight) at higher concentrations (i.e., 60.8%). Coal–water slurry showed Newtonian behavior at low concentrations of 30%; above, it shows pseudoplastic behavior. The head loss across the pipe bend increases as the solid concentration of slurry increases and decreases as the proportion of an additive increases. Losses occurring in bend curves were given in terms of bend loss coefficient. The bend loss coefficient decreased as flow velocity increased and increased as solid concentration increased. The present study also highlights the role that solid concentration plays with regard to settling velocity of coal–water slurry. A trend of decreasing settling velocity was observed while the solid concentration (by weight) of the slurry was increased. [ABSTRACT FROM AUTHOR]

The main purpose in this study was to understand the interactions of coal particles with three amphiphilic humic acid-based polymers, which were designed and synthesized through the copolymerization of humic acid (HA) with maleic anhydride-polyethylene glycol 400 monoester, methacrylatoethyl trimethyl ammonium chloride or both of them, respectively, abbreviated as HAM, HAD and HMD. The adsorption quantities of HMD and HAD increased monotonically with the equilibrium concentration of dispersant, which were well described by Freundlich adsorption equation, but the Langmuir adsorption equation was more suitable for HAD dispersant. Besides, the wettability of HMD solutions on the coal surface was better than others. Moreover, the HMD dispersant exhibited better viscosity-reducing and stabilizing capability for coal-water slurry (CWS) than that of HAD and HAM, which were due to the strong adsorption force that was good for improving the hydrophily and enhancing the steric hindrance and electrostatic repulsion among coal particles. Unlabelled Image • Three humic acid-based dispersants were synthesized and used as dispersants for CWS. • The adsorption isotherms of HMD and HAD were well described by Freundlich equation. • The wettability of HMD solutions on the coal surface was better than others. • The HMD showed the better viscosity-reducing and stabilizing ability in CWS than others. • The excellent performances of HMD were due to strong adsorption and steric hindrance. [ABSTRACT FROM AUTHOR]

Coal–water slurry or coal–water mixture (CWS or CWM) is a complex solid–liquid dispersion. Several research works have been done concerning the production and use of CWSs being developed worldwide in several different governmental, industrial and academic facilities. In the present paper, studies on the developments achieved in the past three decades with regard to the field mentioned above are systematically reviewed, with particular regard to several different aspects during the combustion process. The structure and properties of the coal are highlighted, as are the different additives used and their adaptability with different types of coal, where the particle size distributions are of great importance in determining both the slurryability of coal and the rheological behavior of a produced CWS for its intended characteristics. At a time when there is much debate about the end of the age of coal as a primary source of thermal and electrical energy, alternative forms of use that can contribute to the reduction of pollutant emissions, as well as particles, in the atmosphere offer alternatives that may allow us to continue using coal, at least during this transition period until a viable alternative is found. In-depth knowledge of these coal slurries may allow, in the future, the development of similar products produced from fuels derived from biomass, such as charcoal or torrefied biomass. [ABSTRACT FROM AUTHOR]

The present study is conducted to investigate the flow characteristics of coal–water slurry having high solid concentrations in slurry pipeline using commercial computational fluid dynamics. An Euler–Lagrange multiphase approach is used to simulate the flow of coal–water slurry in 50, 100, and 150 mm diameter straight pipelines. The simulations are carried out using various turbulence models and the results obtained are compared with the experimental results presented in the literature. It is found that the shear stress transport (SST) k–ω turbulence model shows good agreement in comparison to other turbulence models. The SST k–ω turbulent scheme is used to solve the governing equations of two-phase model. Simulations are carried out for coal slurry velocity range 2–5 m/s. Numerical simulation results show that the pressure drop in pipeline increases non-linearly with increase in velocity, solid concentration, and particle size. Extensive simulation is also carried out to estimate the effect of pipe diameter on the pressure drop characteristics through pipeline. It is observed that the pressure drop decreases with the increase in pipe diameter. It is found that the particle sizes have significant influence on pressure drop, solid concentrations, and velocity distributions during the flow of coal–water slurry in a pipeline. [ABSTRACT FROM AUTHOR]

Coal-fired power stations produce of tens millions tons of ash and slag waste, and hundreds of millions cubic meters of gas emissions annual. As part of this work analysis of current methods to reduce anthropogenic emissions in the ash produced by the processing (combustion) of traditional coal fuels was made, advantages and disadvantages of each methods were highlighted. It is shown that both low levels of emissions in the ash and combustion products is difficult to ensure. As a result, it was proposed to use promising coal-water slurry containing petrochemicals instead of pulverized coal. The experimental research into maximum concentrations of anthropogenic emissions from the combustions of coal-water slurry containing petrochemicals. The experimental research into maximum concentrations of anthropogenic emissions by the combustions of coal-water slurry containing petrochemicals basedfilter-cakes were conducted

Bending of pipes is a major problem facing the engineers during the construction of a long pipeline for transporting coal–water slurry. However, the use of 90° bends in slurry transportation is restricted because it causes high head loss, and so very high pumping power is required to overcome this resistance. In this context, the present study is carried out to reduce the head loss for the flow of coal–water suspension across 90° pipe bends by varying bend geometry. Rheological experiments were performed to study flow characteristics of coal–water suspension with/without the additive. Coal–water slurry exhibits Newtonian behavior at a solid concentration of 30 wt% and pseudoplastic flow nature at concentration above 30%. Head loss experiments were carried out on a pilot plant test loop for a solid concentration of 30.27–61.56% with flow velocity ranging from 2 to 5 m/s. The r / D ratio for the pipe bend varied within the range of 1.5–2.5. The present study reveals that the head loss across pipe bends increased as solid concentration and flow velocity was increased. The optimum r / D ratio value for a minimum head loss was found to be 2.0. Also, significant decreases in apparent viscosity and head loss were perceived with the addition of a small amount of sulfonic acid. Power required to pump coal–water slurry was decreased by 15.93% with the use of an additive. A correlation for the head loss in terms of solid concentration, flow velocity, and r / D ratio was also developed. [ABSTRACT FROM AUTHOR]

Findings of more efficient energy recovery methods are focused on composite fuels consisting of coal, water, and waste materials. The use of such slurry fuels has enormous environmental benefits due to the potential for waste utilization and low emissions of harmful oxides to the atmosphere during the combustion process. In this study, we report the effect of waste glycerol on the rheological properties of coal-water fuel (CWS). The addition of glycerol to CWS increases the viscosity (from 45.5 to 184.2 mPa·s at a shear rate of 100 rpm) and density (from 1.08 to 1.11 g/cm3) of these suspensions. The utility of choice of the most favorable parameters is equal to 0.85 for both CWS and CWS with added glycerol. Due to the fact that CWS is dosed to heated chamber, its modification with glycerol results in easier nebulization into the combustion chamber, lowering of the solidification temperature and increasing the calorific value of the resulting fuel. During combustion of CWS with glycerol, the amount of SO2 and NOx emitted is reduced by half as compared to the emission of these gases during hard coal combustion. [ABSTRACT FROM AUTHOR]

The paper analyzes the processes occurring on the interaction of high-power nanosecond laser pulses with a coal–water mixture prepared from gas-coal waste. It was found that the rate of production of a mixture of CO and H2 sharply increased at a laser radiation intensity higher than 8 J/cm2. This was expressed in a sharp increase in the concentration of the combustible components of synthesis gas (CO, up to 0.57 vol %) and in a noticeable acceleration of the growth of the mass of a gas–aerosol fuel mixture upon the absorption of laser pulses (by 40%). At low pulse energy densities, the generation of a finely dispersed (particle size, 30–70 μm) fuel aerosol was a predominant process. Gasification came into play above the effective ablation threshold when the weight ratio between synthesis gas and the sprayed aerosol reached 1 : 3. Thus, the action of laser pulses makes it possible to convert coal preparation wastes into a highly flammable gas–aerosol fuel mixture. [ABSTRACT FROM AUTHOR]

By comparison with linear polyacrylic acid/styrene sulfonate(PAA-SSS)and nonylphenol polyoxyethylene ether(NP-8), the relationship between the comb type polycarboxylate(PC-350)and the adsorption performance of Bin-chang coal on its surface was studied. The effect of different dispersants on the surface Zeta potential was analyzed. The study found that the linear PAA-SSS adsorbed horizontally on the coal particles with the lowest adsorption amount and adsorption rate. The electrostatic repulsive force makes the slurry have good fluidity, but its stability is poor;NP-8 has a single point tail adsorption method, which has a larger adsorption capacity and a faster adsorption rate, but its viscosity reduction performance is not good;The comb type PC-350 is adsorbed by the comb type, its adsorption capacity and adsorption rate are medium, and its slurry performance(dispersion viscosity reduction and stability)is the best. It has the electrostatic effect of the ionic side groups to ensure dispersion and viscosity reduction. The introduction of the steric hindrance of the hydrophilic side chain of the polyether increases the stability of the slurry. [ABSTRACT FROM AUTHOR]

The composite quasi-liquid fuels made of different industrial waste become more and more attractive for scientists during last years. Coal-water slurry is one of the popular types of such compositions. Addition of the waste petrochemicals into the slurry allows decrease of the ignition delays of such composite for up to 27%. However, it has a non-trivial effect onto the atomization dynamics of the slurry making the size and velocity distributions of the aerosol more stable during propagation of the aerosol cloud. This, in turn, leads to more predictable ignition and combustion of the aerosol.

Since an average annual temperature for the storage and transportation of composite liquid fuels (CLF) in different countries can vary significantly, covering subambient temperatures and even negative, the challenge of providing their high stability, appropriate to industrial use fluidity classes, and rheology due to the use of functional additives becomes urgent. The study develops the new formulation of CLF tested for phase separation, sedimentation stability, fluidity, and rheology after 72-h holding at temperatures from −5 °C to 25 °C. CLF are based on coking coal and coal sludge particles with the addition of dispersants, diluting agents, viscosity and water loss reducers. Analyzing stability and fluidity, CLF based on 50 wt% of the coal sludge and 48 wt% of water (or 20 wt% glycerol solution when holding at 0 °C and −5 °C) with the addition of 1 wt% acid sodium polyphosphate as a deflocculant and diluent and 1 wt% isononylphenol as a dispersant is determined as the most stable composition. Three factors are established that determine the combined effect of dispersants and regulators of physical-chemical properties on rheology. An analysis of rheology and stability identified additional three promising coal-based compositions containing a coal phosphate reagent, acidic sodium pyrophosphate, isononylphenol, and mono- and dialkylphenols. [Display omitted] • Coking coal sludge-based fuel stability and rheology are studied at subambient temperatures. • Three samples stay useable for industrial use at low (even −5 °C) temperatures for 72 h. • Effect of dispersants and physical-chemical property regulators on rheology is due to 3 factors. • Fuel has passed long-term temperature-dependent sedimentation, fluidity, phase separation tests. [ABSTRACT FROM AUTHOR]

Coal–water slurry or coal–water mixture (CWS or CWM) is a complex solid–liquid dispersion. Several research works have been done concerning the production and use of CWSs being developed worldwide in several different governmental, industrial and academic facilities. In the present paper, studies on the developments achieved in the past three decades with regard to the field mentioned above are systematically reviewed, with particular regard to several different aspects during the combustion process. The structure and properties of the coal are highlighted, as are the different additives used and their adaptability with different types of coal, where the particle size distributions are of great importance in determining both the slurryability of coal and the rheological behavior of a produced CWS for its intended characteristics. At a time when there is much debate about the end of the age of coal as a primary source of thermal and electrical energy, alternative forms of use that can contribute to the reduction of pollutant emissions, as well as particles, in the atmosphere offer alternatives that may allow us to continue using coal, at least during this transition period until a viable alternative is found. In-depth knowledge of these coal slurries may allow, in the future, the development of similar products produced from fuels derived from biomass, such as charcoal or torrefied biomass.