Coal-water Slurry Fuels Research Articles

Influence of cavitation treatment on the properties of coal-water slurries with pyrogenetic liquid and characteristics of their atomization by a pneumatic nozzle

Experimental studies were conducted to investigate the rheological properties and atomization characteristics of coal-water slurries sprayed by a pneumatic nozzle with addition of pyrogenetic liquid. The research object was coal-water slurries prepared on the basis of long-flame coal using a rotary hydrodynamic cavitation generator. The dynamic viscosity of samples was investigated using a Reotest-2 rotary viscometer. The droplet size of atomized slurries was determined by the interferometric particle imaging method. A pneumatic nozzle designed for spraying of coal-water slurry fuels was used. The calorific value of coal-water slurry compositions was estimated by a theoretical method using Mendeleev's equation for calculating the lower heating value of combustion of organic substances with a certain elemental composition. It was found that cavitation treatment of a two-component coal-water fuel for 90 s leads to a 48% decrease in its viscosity. It was shown that substitution of water with a similar amount of pyrogenic liquid (5 to 20%) leads to an increase in the viscosity of coal-water fuels. The cavitation treatment of such slurries reduces the viscosity of the respective three-component coal-water fuels by 27–45%. According to the results of static sedimentation studies, coal particles start to precipitate 24 h after the onset of cavitation treatment. The treatment of the slurries under consideration for 27 and 90 s in a rotary hydrodynamic cavitation generator was established to reduce the average droplet size in the jet after spraying with a pneumatic nozzle by 5.5% and 6.5%, respectively. The introduction of pyrogenetic liquid into the composition of coal-water fuels increases their calorific value by 6.9%. It can be concluded that the use of pyrogenetic liquid in the composition of coal-water slurry fuels followed by their treatment in a rotary hydrodynamic cavitation generator can solve the problem of low reactivity of coal-water slurries.

A Highly Efficient Waste-Free Technology of Water and Fuel Preparation for Thermal Power Stations

A highly efficient, economical, and waste-free technology for the purification of natural waters for thermal power plants has been developed. The preliminary purification of water involved microfiltration on tubular ceramic membranes made of clay minerals according to a technology developed at the Dumansky Institute of Colloid Chemistry and Water Chemistry, NAS of Ukraine; the degree of retention of suspended solids and iron and manganese compounds on the membranes was 99.9, 99.8, and 60%, respectively. The high separation capacity of such membranes is due to the modification of their surface by water contaminants with the formation of a self-organizing dynamic membrane that serves as an additional barrier. The dynamic membrane formation contributed to the retention of up to 24.0% of the co-occurring ions, Ca2+ in particular; this is typical for ultrafiltration membranes. Further desalination was performed with low-pressure reverse osmosis membranes; two stages of reverse osmosis turned out necessary to achieve a total ion content of 0.5 mg/dm3 in the make-up water of a steam turbine unit of a thermal power plant (TPP). The retentate of the second stage of reverse osmosis, for which the total ion content is 50–60 mg/dm3, can be used for technical purposes at TPPs. The salt content of the retentate formed after the first stage of reverse osmosis was ~3 g/dm3, and thus insufficient for further transformation into secondary material resources; however, the introduction of waste recycling systems is considered to be the modern direction in protecting the environment from technological influence. The retentate of the first stage of reverse osmosis was concentrated using an original concentrating electrodialyzer developed at the Dumansky Institute of Colloid Chemistry and Water Chemistry, NAS of Ukraine; some design modifications that distinguish this electrodialyzer from the conventional ones were proposed and patented. Electrodialysis treatment of the retentate for 2.5 hours at a current density of 2.5 A/dm3 enabled the production of a solution with the ion content of ~105 g/dm3. This brine can be converted into sodium hypochlorite or caustic soda and hydrochloric acid by electrolysis. The diluate with a mineralization of ~200.5 g/dm3 and a total organic carbon content of ~148.3 g/dm3 can be used for the preparation of coal-water slurry fuels for power generation and metallurgy. The basic technological schemes of make-up water purification for the needs of thermal power plants and the preparation of slurry fuel systems based on coal and reverse osmosis waste that contains organic substances are proposed.

Environmental study of use of coal-water slurry fuel as an alternative to traditional fuels

In this work we consider coal-water slurry fuels as an alternative to the traditional types of fuels, in particular, coal. Assessment is performed using a software tool for calculating the combustion process of coal-water slurry fuels. The obtained results will allow one to perform computer-aided environmental calculations during CWS combustion in experimental and industrial plants.

Industrial Waste as Part of Coal–Water Slurry Fuels

Industrialized regions of the world are actively polluting the environment. In this research, we consider one of the developed industrial regions, Siberia (Russia), as an example. The paper presents typical volumes of annually stored waste, in particular, waste of oil production and a refinery (76 800 tons), liquid and watered waste of the municipal sector (167 875 tons), and food waste (5906 tons). The parameters of ignition and combustion of such wastes are studied in the compositions of coal–water slurry fuels with petrochemicals. The experimental results demonstrate that most of the wastes in the industrial region under study have high potential (according to environmental, economic, and energy criteria) as additives to fuels. In particular, a comprehensive comparative analysis shows that the ignition delay time for fuel slurries with waste can be reduced by 10–60%; the minimum ignition temperature, by 10–45 °C; and concentrations of NOx and SO2 emissions, by 5–50%. The combustion heat of composite fu...

The Potential Incorporation of Biochar into a Char-Water Fuel — Study of Chemical and Physical Properties

Biochar has the potential to be used for a wide range of applications. One of these includes utilisation as a char-water fuel, with the aim of substituting less sustainable fuels in the future. This paper reports the chemical and physical properties of biochar produced from sugarcane bagasse for use as a char-water fuel. Sugarcane bagasse was pre-treated with diammonium phosphate (DAP) and pyrolysed to increase the yield of biochar. An untreated sample of bagasse was also converted to biochar for comparison. The treated samples were formulated into char-water fuel and analysed for rheological behaviour. Viscosities were comparable to that reported for coal-water slurry fuels and, in some cases, other biological by-products (i.e. biooils), but were higher than diesel or gasoline. Thermal gravimetric analysis (TGA) and particle size distribution were conducted on the char samples and the energy content was measured using bomb calorimetry. The energy content of the char-water fuel would be similar to that of coal-water fuels if beneficiation of the biochar to remove ash components can be performed.

Environmentally and economically efficient utilization of coal processing waste

High concentrations of hazardous anthropogenic emissions (sulfur, nitrogen and carbon oxides) from solid fuel combustion in coal burning plants cause environmental problems that have been especially pressing over the last 20–30 years. A promising solution to these problems is a switch from conventional pulverized coal combustion to coal-water slurry fuel. In this paper, we pay special attention to the environmental indicators characterizing the combustion of different coal ranks (gas, flame, coking, low-caking, and nonbaking coals) and coal-water slurry fuels based on the coal processing waste – filter cakes. There have been no consistent data so far on the acceptable intervals for the anthropogenic emissions of sulfur (SOx), nitrogen (NOx) and carbon (CO, CO2) oxides. Using a specialized combustion chamber and gas analyzing system, we have measured the concentrations of typical coal and filter-cake-based CWS combustion products. We have also calculated the typical combustion heat of the fuels under study and measured the ratio between environmental and energy attributes. The research findings show that the use of filter cakes in the form of CWS is even better than coals in terms of environment and economy. Wide utilization of filter cakes solves many environmental problems: the areas of contaminated sites shrink, anthropogenic emissions decrease, and there is no need to develop new coal mines anymore.

Organic coal-water fuel: Problems and advances (Review)

The study results of ignition of organic coal-water fuel (OCWF) compositions were considered. The main problems associated with investigation of these processes were identified. Historical perspectives of the development of coal-water composite fuel technologies in Russia and worldwide are presented. The advantages of the OCWF use as a power-plant fuel in comparison with the common coal-water fuels (CWF) were emphasized. The factors (component ratio, grinding degree of solid (coal) component, limiting temperature of oxidizer, properties of liquid and solid components, procedure and time of suspension preparation, etc.) affecting inertia and stability of the ignition processes of suspensions based on the products of coaland oil processing (coals of various types and metamorphism degree, filter cakes, waste motor, transformer, and turbine oils, water-oil emulsions, fuel-oil, etc.) were analyzed. The promising directions for the development of modern notions on the OCWF ignition processes were determined. The main reasons limiting active application of the OCWF in power generation were identified. Characteristics of ignition and combustion of coal-water and organic coal-water slurry fuels were compared. The effect of water in the composite coal fuels on the energy characteristics of their ignition and combustion, as well as ecological features of these processes, were elucidated. The current problems associated with pulverization of composite coal fuels in power plants, as well as the effect of characteristics of the pulverization process on the combustion parameters of fuel, were considered. The problems hindering the development of models of ignition and combustion of OCWF were analyzed. It was established that the main one was the lack of reliable experimental data on the processes of heating, evaporation, ignition, and combustion of OCWF droplets. It was concluded that the use of high-speed video recording systems and low-inertia sensors of temperature and gas concentration could help in providing the lacking experimental information.

Evaluation of the effects of coal grinding in terms of coal water slurry preparation

Coal Water Slurry (CWS) is a specific form of solid fuel. It occurs in the form of finely ground coal particles and water. Depending on the use, the content of combustible matter is from 40 to 70% by weight. The attractiveness of the fuel is primarily its properties, i.e. liquid form, high energy efficiency (for water evaporation 4% energy is used – for CSW with 70% concentration of coal), decreased environmental impurities (lower NOx emission) and reduced risk of explosion. The advantages of CWS fuels, the possibility of independence from petrochemical fuels, wide availability of coal and emphasis on the use of cleaner technologies are the driving force for development of slurry fuel technologies. The major parameters characterizing the fuel suspension are: solid phase concentration (share of coal in the slurry expressed as either weight or volume fraction of dry coal), time stability (resistance to delamination and separation of the dispersed phase from the continuous phase) and viscosity, determining the flow of suspension. The mentioned parameters are dependent on the susceptibility of coal for production of aqueous suspensions (slurrability), conditioned by natural properties of coal, such as: coalification degree, petrographic composition and surface properties. They are also dependent on the slurry fuel preparation process: particle size, solid phase concentration, used additives (stabilizing and dispersion agents) and modification of primary coal properties (ash removal, change of surface properties). Preparation of sustainable, high concentrated CWS fuel coal is promoted by the hydrophobic nature of the coal surface, characteristic for coals of higher coalification. A great technological problem is to obtain a highly concentrated coal slurry fuel from less coalified hydrophilic steam coals. The paper presents the results of lab scale research on the CWS prepared from Polish steam coal by wet grinding in mill drum and vibrating. The milling process was carried out in a batch system by varying the composition of the grinding media and varying degrees of working space filling. The feed was pre-ground steam coal mixed with water at the ratio of 1: 1. The changes of particle size, viscosity and stability of suspensions in time were assessed. The milling effectiveness was higher for the vibrating mill. After the same milling time the quality of the obtained product was higher. The obtained milling degree was depended on the share and composition of grinding aids. In the investigated range (10-30% share mill working space), the use of higher share of grinding aids caused higher milling degree of coal. A trend was observed that stronger fragmentation of coal was achieved with the use of polydisperse composition of aids distinguished by smaller diameters. The changes of granulation influenced the viscosity and stability of the obtained product. The lower the mean particle size, the higher the viscosity and stability of the obtained product was particularly noted for the vibrating mill.

Technological limitations and features of burning coal-water slurry fuels in ship power plants

technological limitations and features of burning coal-water slurry fuels in ship power plants

03/02522 Thermodynamic analysis of the gasification of coal water slurry fuels for a circulating fluidized bed gasifier: Tsui, H. et al. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2002, 216, (A5), 343–353

03/02522 Thermodynamic analysis of the gasification of coal water slurry fuels for a circulating fluidized bed gasifier: Tsui, H. et al. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 2002, 216, (A5), 343–353

Thermodynamic analysis of the gasification of coal water slurry fuels for a circulating fluidized bed gasifier

To validate the concept of coal gasification in the integrated coal gasification combined cycle (IGCC), a novel laboratory gasifier consisting of a circulating fluidized bed and a cyclone combustor has been constructed. This paper reports a thermodynamic analysis conducted to predict the maximum capacity and the condition for best operation of this circulating fluidized bed gasifier, which has an inside diameter of 0.3048m and a height of 2.5 m. The equilibrium feed rates of materials and the quality of the product gas are described as a function of the reactor temperature, the thermal capacity of the gasifier, and the water concentration in coal water slurry fuel. The results of parametric analysis show that the thermal efficiency decreases, but the efficiency of desulfurization increases as the reactor temperature increases. The thermal capacity of the gasifier has no influence on the quality of the product gas. The thermal efficiency and the efficiency of desulfurization decrease as the water concentration in the coal water slurry increases. The desulfurization in the gasifier at equilibrium conditions is very efficient and meets the EPA regulations of the USA.

99/00209 Coal-water slurry fuel production: its evolution and current status in the United States

Interest in the US in utilizing bituminous coal in a slurry form has evolved substantially over the last two decades. In the mid-1970`s, technologies to utilize coal-oil mixtures (COMs) as potential fuel oil replacements for utility and industrial boilers were developed as a consequence of escalating world oil prices. To further reduce dependency on imported oil, interest shifted away from COMs to coal-water slurry fuels (CWSFs) because higher solids loadings were obtainable while eliminating the use of oil. Research which focused on the use of CWSF as a potential fuel oil replacement peaked in the mid to late-1980`s as a result of a decline in world oil prices. During the late 1980`s and early 1990`s, coal suppliers and coal-fired utilities began to evaluate the production of CWSF using bituminous coal fines from fine coal cleaning circuits in an effort to reduce dewatering/drying costs. This marked a philosophical change in the driving force behind the utilization of CWSF in the US. In an effort to broaden the supply of coal fines, The Pennsylvania State University (Penn State) and the Pennsylvania Electric Company (Penelec) surveyed a series of fine coal impoundments in western Pennsylvania to determine the quality, cleanability, and slurryability ofmore » the coal fines contained therein. The development and commercialization of recovery technologies, cleaning techniques, and CWSF reentrainment circuits, coupled with an interest by utilities to utilize low-cost fuels, has fostered the recovery of impounded coal fines. In addition to the fine coal impoundments, fine coal cleaning circuits which actively dispose of process water having suspended coal fines (e.g. centrifuge effluent) are being examined to determine if the fines can be recovered and thickened into a low solids CWSF. The paper describes required physical and chemical properties of a CWSF for boiler applications. There is a growing awareness that CWSF is a fuel form that can be cofired with coal. The current political, environmental, and economic climates mandate greater efficiency in the production and use of coal. Coal suppliers and coal-fired utilities must establish the actual cost of the CWSF production for the technology to move forward. Coal-fired utilities that own fine coal impoundments and/or operate fine coal cleaning circuits need to determine how these coal fines can be used to reduce operating cost.« less

98/01152 Preparation of coal-water slurry fuels from impounded bituminous coal fines: Morrison, J. L. et al. Suppl. Coal Fines: Unclaimed Fuel, Pap. Int. Tech. Conf. Coal Util. Fuel Syst., 21st, 1996, 13–24. Edited by Serkin, S. D., Coal & Slurry Technology Association, Washington, DC

98/01152 Preparation of coal-water slurry fuels from impounded bituminous coal fines: Morrison, J. L. et al. Suppl. Coal Fines: Unclaimed Fuel, Pap. Int. Tech. Conf. Coal Util. Fuel Syst., 21st, 1996, 13–24. Edited by Serkin, S. D., Coal & Slurry Technology Association, Washington, DC

98/00372 Assessment of coal-water slurry fuels for electric power generation in Southern Indiana. Part 1. Detailed resource characterization

Impounded coal fines, a by-product of wet coal preparation techniques, are a potential fuel resource for electric power generation due to their abundance and characteristics when burned as a coal-water slurry fuel (CWSF). Recent work by the Pennsylvania Electric Company and others has shown that co-firing CWSF composed of cleaned material from slurry impoundments can reduce emissions of nitrogen oxides by as much as twenty percent. The commercial reality of using impounded coal fines as a CWSF depends more on coal cost, processing requirements, and the value of emission reduction credits than on the quality or abundance of the material. Many Southern Indiana slurry impoundments, including those selected for characterization in this study, contain over one-million tons of fine coal. The older impoundments have a higher percentage of coarse coal. One impoundment filled prior to 1975 averages fifty percent coal particles greater than 30 mesh (600 {mu}). Improvements in preparation plant fine coal recovery circuits are reflected by an increasing percentage of less than 200 mesh (75 {mu}) coal in more recently filled impoundments. Another impoundment filled in 1995 averages forty-nine percent coal and mineral particles finer than 200 mesh. Bench scale sink/float testing showed that separating particles with amore » specific gravity greater than 1.7 produced a fine coal with ten percent ash and three percent sulfur. This is similar in quality, but finer in particle size, to the coal currently used in a typical coal fired power station burning typical Illinois Basin coals. Detailed characterization of two inactive impoundments highlighted the differences between coal fines in an older impoundment and one filled in the last ten years.« less

98/00246 Utilization of coal pond fines as feedstock for coal-water slurry fuels

98/00246 Utilization of coal pond fines as feedstock for coal-water slurry fuels

98/00178 Preparing and handling coal-water slurry fuels: potential problems and solutions

Environmentally driven regulations are requiring continuous and significant changes in diesel fuel quality in many parts of the world. Further tightening of specifications are being considered for the future, with trends to lower density, sulphur, and distillation end point, as well as higher cetane number, to meet with more stringent levels of new motor power and environmental regulations.Hydroprocessing is extensively practised in petroleum industry to upgrade fuels refinery streams. In this paper, pilot plant data is presented of a moderate pressure technology developed to produce diesel fuel comply with actual and near future environmental regulations using feedstocks since medium to high contaminants content. This technology is based on Co-Mo and Ni-Mo γ-alumina supported proprietary catalysts, with high activity to sulphur and aromatics compounds commonly encountered in these petroleum fractions. Discussion will be driven to show the effect of process conditions on product quality and mains difference in catalysts performance. A series of Isthmus/Maya crude oils mixtures was prepared to test catalyst efficiency, but for the sake of explicitness, only three of these are reported in this work. Hydrodesulphurisation and hydrodenitrogenation activities are quite similar in both catalysts, but aromatic saturation is much more effective in Ni-Mo version. This fact is important when domestic refineries make more intensive use of light cycle oil as a mix component in the feedstock to fulfil demand.

97/04537 Dependence of the rheological behavior and static stability of coal water slurry fuels on the structural characteristics of dispersant: Sun, C. G. et al. DGMK Tagungsber., 1997, 9702, (Proceedings ICCS '97, Volume 1), 495–498

97/04537 Dependence of the rheological behavior and static stability of coal water slurry fuels on the structural characteristics of dispersant: Sun, C. G. et al. DGMK Tagungsber., 1997, 9702, (Proceedings ICCS '97, Volume 1), 495–498

97/03535 Upgrading of low-rank coals and their preparation of highly loaded coal water slurry fuels

Several low-rank coals were selected and heat-treated at a special designed apparatus to improve their slurryability, the characteristics of the changes of CWS rheological behavior were studied in detail. Significant results were obtained that the upgradings of types of low-rank coal can cause a great improvement on their slurryabilities which depends on the rank of the parent coal, and the preferable upgrading temperature were found to be 300{degrees}C for most of the low-rank coals studied in this paper. The static stability of CWS also show a obvious regular changes with upgrading temperature.

97/03529 Preparing and handling coal-water slurry fuels: potential problems and solutions

97/03529 Preparing and handling coal-water slurry fuels: potential problems and solutions

97/03830 Assessment of coal-water slurry fuels for electric power generation in Southern Indiana. Part 1. Detailed resource characterization

97/03830 Assessment of coal-water slurry fuels for electric power generation in Southern Indiana. Part 1. Detailed resource characterization