Coal-water Slurry Fuel Research Articles

Atomization and Combustion of Coal-Water Slurry Fuel Sprayed by a Pneumatic Nozzle

Atomization and Combustion of Coal-Water Slurry Fuel Sprayed by a Pneumatic Nozzle

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.

The impact of cavitation-activated water on combustion dynamics and environmental characteristics of coal-water slurry fuel

Among the new coal technologies the burning of low-grade coal in the form of coal-water slurry fuel (CWSF) is of a great interest. The basis of CWSF is a highly concentrated coal-water slurry consisting of finely ground coal, water or other liquid and plasticizing agents. The development of CWSF technology is highly relevant for solving global problems of resource conservation and ecology. The study is dedicated to CWSF properties with respect to Kansk-Achinsk coal and water. This paper presents the results of the influence of CWSF’s preliminary cavitation water treatment on the combustion dynamics of fuel, (including the features of the combustion temperature trends, delayed ignition time and time of complete combustion) and on its environmental characteristics. A rotary-type hydrodynamic oscillator at high angular velocity (10000 rpm) was used in supercavitation mode. It is shown that the technology of cavitation water treatment leads to a change in the dynamics of CWSF’s combustion and to an additional decrease in NOx emissions by 1.6 times, CO2 by 1.3 times.

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.

Results of Study of Sulfur Oxide Reduction During Combustion of Coal-Water Slurry Fuel Through use of Sulfur Capturing Agents

It is shown that an effective way of burning high sulfur coal is to burn coal-water slurry fuel (CWF) prepared on its basis containing a sulfur capture agent (SCA) entered in the slurry at the stage of preparation. The technique of thermodynamic analysis of chemical reactions during CWF burning has been developed including burning in the presence of SCA. Using the developed calculation program, the optimal temperature conditions have been determined as required for the effective reduction of sulfur oxides in flue gases when using different types of SCA. According to the results of calculating the composition of CWF combustion products when entering various substances in the burner space as SCA it has been determined that magnesite, calcite, and dolomite are the most effective natural minerals. The analysis of calculated and experimental data proves the efficiency of SCA addition as well as validity of the obtained results.

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.

The Research of Coal-Water Slurry Fuel Ignition and Artificial Composite Liquid Fuel Droplets in Academic Context

There are new types of composite fuels, such as coal-water slurry fuel and artificial composite liquid fuel that can be used to exploit the limited energy sources more effectively. Such composite fuels consist of coal fine particles and water (or liquid industrial waste). This paper presents the experimental study of the ignition of coal-water slurry fuel and artificial composite liquid fuel droplets during convective heating carried out at the National Research Tomsk Polytechnic University. The ignition delay time of the fuels has been determined when the heat source temperature varied from 350 to 600°C. The analysis reported here has revealed droplet ignition mechanisms for four different fuel compositions.

The Case of Coal Water Slurry Fuel for Industrial Use in Pakistan

This research presents the case for design and development of Coal Water Slurry (CWS) Plant for industrial use in Pakistan. After exclusive comparison between coal quality quantification for CWS it was found that Darra mines at Pakistan provide best coal for CWS. Highly volatile, A and B Bituminous coal and Sub-Bituminous coal is selected for making CWS because of its low Sulfur contents, Ash contents and high heating value through experimentation. The purpose of this research was to present a complete blue print for the production of coal water slurry fuel in Pakistan. The measured viscosity and heat contents of the tested CWS are of the order 490 mPa-sec and 23.8 KJ/kg, respectively.

Водовугільне паливо: стан проблеми і перспективи використання

Водовугільне паливо: стан проблеми і перспективи використання

Mixing narrow coarse and fine coal fractions – The maximum volume fraction of suspensions

A main objective of coal-water slurry fuel (CWSF) preparation is to achieve maximum loading of coal. In the absence of a strong colloidal attractive force, the maximum loading is determined by the packing density of the particles which in turn is a function of the particle size distribution. In this study, coal fractions of different mean sizes with a narrow distribution were separated by sieving. Mixtures of different mean coarse to fine size ratios were then prepared. For each size ratio, different amounts of coarse particle contents were prepared. With these different mixtures, water was added to produce the CWSF. The maximum volume packing density, φmax, for each mixture was determined using a rheological vane yield stress technique. The determination of φmax involving the direct yield stress measurements of extremely high concentration suspensions is an entirely new and accurate approach. It was found that the highest φmax was obtained when the coarse to fine ratio was ∼10 located at a coarse coal content of 70wt%. This result is consistent with that obtained by theoretical modelling of bimodal mixing of monodisperse size spheres with a size ratio of 10. At lower size ratio, φmax obtained at the optimum coarse coal content was lower.

Vibration mills in the manufacturing technology of slurry fuel from unbeneficiated coal sludge

Coal-water slurry fuel (CWSF) is economically viable provided that its ash content does not exceed 30% and the amount water in the fuel is at most 45%. Two impoundments were revealed that have considerable reserves of waste coal useful for commercial manufacture of CWSF without the beneficiation step. One of the CWSF manufacture steps is the comminution of coal sludge to have a particle size required by the combustion conditions. Vibration mills, which are more compact and energy-intensive that drum mills, can be used in the CWSG manufacture process. The rheological characteristics of CWSF obtained from unbeneficiated waste coal were determined.

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.

Partitioning behavior of trace elements during pilot-scale combustion of pulverized coal and coal–water slurry fuel

Release pathways for inorganic hazardous air pollutants (IHAPs) from a pilot-scale, down-fired combustor (DFC) when firing pulverized coal (PC) and coal–water slurry fuel (CWSF) were identified and quantified to demonstrate the effect of fuel form on IHAP partitioning, enrichment and emissions. The baghouse capturing efficiency for each element was calculated to determine the effectiveness of IHAP emission control. Most of the IHAPs were enriched in the fly ash and depleted in the bottom ash. Mercury was found to be enriched in the flue gas, and preferentially emitted in the vapor phase. When firing CWSF, more IHAPs were partitioned in the bottom ash than when firing PC. Significant reduction of Hg emissions during CWSF combustion was also observed.

An investigation on polycyclic aromatic hydrocarbon emissions from pulverized coal combustion systems

Results from a series of tests conducted to study the emission of polynuclear or polycyclic aromatic hydrocarbons (PAHs) from bench-scale and small industrial, water-tube boiler are discussed. A Middle Kittanning, and Upper Freeport seam coals were used in the study. Samples were extracted from the reactor outlet and from the inlet and outlet sides of the research boiler's (RB) baghouse using EPA promulgated methods. Only acenaphthene and fluoranthene were detected in down-fired combustor (DFC) samples. In addition to these two, naphthalene was detected in the RB samples. Emission factors ranged from 80 to 320 μg/kg of fuel fired. Although there were minor trends in the emissions' data, given the reproducibility limits for PAH compounds, no significant differences were found in the emissions with respect to the fuel type or form (pulverized coal (PC) vs. coal–water slurry fuel (CWSF), and raw vs. cleaned coal) and firing conditions (high and low excess air). The PAH emissions showed a decrease with increase in the firing rate. A bench-scale drop-tube reactor (DTR) was used to study the effects of temperature and residence time on PAH formation. The results revealed near constant PAH concentrations in the solid-phase samples, while the PAH concentrations in the vapor-phase samples increased as a function of temperature. At a temperature of around 1300°C, the rate of PAH formation was exceeded by the rate of PAH oxidation, and PAH concentrations in the vapor phase began to decrease.

00/00515 The effect of fuel form on trace element emissions in an industrial-scale coal-fired boiler

Eleven of the fourteen inorganic hazardous air pollutants identified in Title 3 of the Clean Air Act Amendments of 1990 are present in the flue gas of pulverized coal-fired boilers. The designated elements include: antimony (Sb), beryllium (Be), chlorine (Cl), cobalt (Co), manganese (Mn), nickel (Ni), selenium (Se), fluorine (F), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and phosphorus (P). Determining the risk of these elements in the environment is difficult at best. However, regulating their emission into the environment has some scientific basis and merit. Approximately 137.5 tons of mercury were emitted in the US by combustion sources in 1994--1995, with coal-fired utility boilers accounting for 37.4% (or 51.6 tons) of the total. Control of trace element emissions from coal-fired utility boilers requires an understanding of the manner in which they occur in coal, their behavior during and after combustion and their form in the stack gas. The multimedia behavior of trace elements during combustion can be traced to their volatility within the combustion and post-combustion environment. The temperature distribution within the combustion system, the mechanism of char and ash formation (e.g. duration of char burnout and char and cenosphere morphology) and the combustion efficiency determinemore » the partitioning of trace elements during combustion. These factors can be affected by the form in which a fuel is fired, e.g., pulverized coal (PC) versus coal-water slurry fuel (CWSF). This paper presents preliminary results of emissions testing aimed at determining the effect of fuel form on the penetration and partitioning of trace elements in an industrial-scale boiler. The tests were conducted on a 2 MMBtu/hr research boiler, in which Middle Kittanning Seam coal (hvA bituminous) from Jefferson County, Pennsylvania was burned in pulverized form and as a CWSF. The tests were conducted in accordance with the procedure outlined in EPA Methods 5 and 29 to measure trace elements in the gas and particulate phases of the flue gases generated during coal combustion. Further studies will include analysis of droplet and particle size, char morphology, and the size, distribution and composition of the mineral matter in the two fuels.« less

00/00395 A comparison between ceramic membrane filters and conventional fabric filters for fine particulate removal from a coal-fired industrial boiler

Penn State is developing technologies for ultralow emissions when firing coal-based fuels, i.e., micronized coal and coal-water slurry fuel (CWSF) in industrial boilers. Emissions being addressed are SO{sub 2}, NOx, fine particulate matter (PM{sub 10} and PM{sub 2.5}), and air toxics (trace elements and volatile organic compounds). Results from trace element and polynuclear aromatic hydrocarbon emissions testing, when firing coal-based fuels, are reported elsewhere in these proceedings. This paper discusses the evaluation of ceramic membrane filters for fine particulate removal in a package boiler when firing micronized coal and CWSF.

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

98/00372 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

97/03508 Engineering development of two advanced physical coal cleaning processes for premium fuel applications

Under a DOE/PETC cost-shared contract, an Amax-led team of coal companies and engineering and research organizations has been working on engineering development of two advanced physical coal cleaning processes for premium fuel applications. Both column flotation and selective agglomeration processes appear capable of producing ultra-clean coal, which when converted to a highly loaded coal-water slurry fuel (CWF) can replace premium fuels (oil and gas) in many utility and industrial boilers and advanced power systems. The paper presents an overview of the project and highlights the accomplishments made to date.

Effect of the Occurrence and Modes of Incorporation of Alkalis, Alkaline Earth Elements, and Sulfur on Ash Formation in Pilot-Scale Combustion of Beulah Pulverized Coal and Coal-Water Slurry Fuel

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of the Occurrence and Modes of Incorporation of Alkalis, Alkaline Earth Elements, and Sulfur on Ash Formation in Pilot-Scale Combustion of Beulah Pulverized Coal and Coal-Water Slurry FuelSharon Falcone Miller and Harold H. SchobertCite this: Energy Fuels 1994, 8, 6, 1208–1216Publication Date (Print):November 1, 1994Publication History Published online1 May 2002Published inissue 1 November 1994https://doi.org/10.1021/ef00048a007RIGHTS & PERMISSIONSArticle Views141Altmetric-Citations17LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts