Coal-water Suspensions Research Articles

The influence of the initial moisture content of cedar needles on the time characteristics of the ignition of coal-water suspensions

The results of experimental studies of the influence of the initial moisture content of cedar needles on the time characteristics of ignition of coal-water suspensions based on D-grade thermal coal are presented. Biomass (fallen and freshly cut cedar needles) was used as an additive accelerating the ignition process. An analysis was carried out of the influence of the initial moisture content of the plant additive in the composition of water-soluble suspensions on the ignition delay times. It has been established that the initial moisture content of cedar needles does not have a significant effect on the time characteristics of the fuel ignition process (the difference does not exceed 4%), but the addition of needles leads to a significant reduction in the ignition delay times (the VUS ignites faster on average by 15%).

Оценка эффективности завихрения воздуха при распылении водоугольных суспензий пневматической форсункой

Due to modern requirements for environmental protection, introduction of environmentally friendly power engineering technologies involves search and development of new energy sources. One of the ways to meet these requirements and maintain the same level of energy production by thermal power plants is to use multicomponent fuels. The most promising and affordable heavy fuel oil from the point of view of energy, ecology and economy are coal-water slurries (CWS). In this regard, the study of the properties and characteristics of such fuels is relevant. The coal-water slurries have been prepared in a rotary hydrodynamic cavitation generator. A pneumatic atomizer with external mixing is used to spray the coal-water slurries. Interferometric Particle Imaging method is used to determine the average size of fuel droplets after atomization. The authors have conducted experimental studies of the characteristics of atomization of coal-water slurries based on lignite and pyrogenetic liquid with a pneumatic atomizer with a tangential supply of a spraying agent. A three-stage method to prepare lignite-based slurries with pyrogenetic liquid has been tested. It has been established that when using this technique, the fluidity of coal-water fuel is maintained even with the introduction of 20 % by weight of pyrogenetic liquid into the composition of coal-water slurries when replacing both water and coal in equal proportions. The kinematic viscosity of coal-water suspensions increases when pyrogenetic liquid is added, despite a decrease in the concentration of the solid component. The change of suspension density is insignificant. The results of the study of atomization process have shown that the tangential air supply to the atomizer leads to an increase of the jet spraying angle by 6° compared with direct supply. At the same time, the average droplet size in the jet of a two-component CWS with direct air supply is 8 % smaller. The results of the study have made it possible to obtain completely new knowledge that can significantly advance domestic and world science and technology in the field of power engineering, namely the technology of coal-water fuels atomization. Experimental studies have determined the main patterns of influence of the CWS properties and the method of spraying agent supply on the formation of a gas-drop jet. Such patterns will provide conditions for the effective atomization of quite viscous CWS in the combustion chambers of energy boilers. The results obtained will enable designers and constructors to develop highly efficient designs of steam and hot water boilers and gasifiers fueled by CWS.

Physicochemical characteristics of highly concentrated suspensions with some types of Ukrainian coal

ABSTRACT The investigation results of granulometric composition, zeta potential, sedimentation stability, and viscosity of some water-coal suspensions made of Ukrainian coal from the “Stepova” mine, Lviv-Volyn region, are reported. The most effective granulometric composition of the water-coal suspension consisting of the rough and fine fractions is found from the analysis of the abovementioned physicochemical characteristics of the suspensions. Based on the complex investigation of the zeta potential of the dispersed phase particles, viscosity, and sedimentation stability of the suspensions, it was established that the best technological effectiveness can be expected for the suspensions containing 60% of the rough fraction (sized between 100 and 250 µm) and fine particles sized between 20 and 40 µm. In such systems, the particles form a quasi-stable structure, where the lower-charged small particles are located in the interparticle space between the highly charged bigger particles. All particles bear the same charge, increasing the system’s sedimentation stability and avoiding decomposition for at least 5 days. This time seems reasonable for the preparation, storage, and pumping of the suspensions while their viscosity and stability meet the relevant technological requirements.

Impact of woody biomass in the composition of coal-water suspensions on their transportation and combustion

Relevance. A promising fuel from an environmental point of view is coal-water suspensions. Multiple studies have shown that when they are burned, emissions of anthropogenic gases into the Earth's atmosphere are significantly reduced compared to emissions from coal burning. But the large-scale introduction of coal-water suspensions into the overall balance of energy production is difficult due to a significant delay in their ignition, which can reach several tens of seconds at relatively low oxidizer temperatures (Tg≤1073 K). One of the possible ways to solve this problem is the use of new technologies for preparation for combustion, for example, the use of additional microwave heating of fuel and the introduction of special additives into the composition of coal-water suspensions, which accelerate their ignition. The introduction of such additives into the fuel composition can lead to a significant change in the rheological characteristics. Aim. To determine the degree of impact of the concentration and type of wood additive in the composition of the coal-water suspension on the rheological characteristics of droplets of coal-water fuel, as well as the possibility of reducing the duration of thermal preparation of the latter when exposed to microwave heating. Object. Water-coal suspension based on long-flame thermal coal and on long-flame thermal coal with the addition of sawdust and pine needles (Bio-water-coal suspension). Methods. Experimental studies to determine the time characteristics of water-coal suspension ignition were carried out using a high-speed video camera FASTCAM. Fuel combustion was carried out in a flow-through combustion chamber equipped with magnetrons for additional microwave heating of the fuel. Dynamic viscosity was determined using a Brookfield RVDV-II + Pro viscometer. Results. It has been established that the addition of microwave heating can significantly (up to 15%) reduce the ignition delay of water-coal suspension and Bio-water-coal suspension at relatively low oxidizer temperatures (673 K). Experimental studies shown that the type of biomass affects the time characteristics of fuel ignition at ambient temperatures up to 753 K; with a further increase in the temperature of the oxidizer, the type of additive does not have a significant effect. It is shown that when studying the rheological characteristics of the water-coal suspension, the dynamic viscosity of Bio-water-coal suspension does not go beyond the characteristic value of 1200 Pa s at a shear rate of 100 rpm when no more than 2% of pine sawdust and no more than 6% of pine needles are introduced into the water-coal suspension.

Effect of coal suspension concentration and gas-air medium temperature on liquid droplets collisions

Relevance. Understanding the mechanisms of liquid droplets interaction with each other is important for many industrial and technical applications related to solving a range of problems like slag removal in a high-temperature environment, obtaining components of the desired fraction in the food industry, etc. Aim. Establishment of the main patterns of suspension droplets interaction in a gas-air environment with temperature variation. Methods. Using shadow high-speed video recording, the main patterns of the binary collision of suspensions droplets were determined. The paper introduces the results of experimental studies of the characteristics of collisions of droplets of coal-water suspensions in a gas-air environment with a temperature of 90–120°C. Parameters of the generated droplets: radius 1.0–2.2 mm, velocity 0.5–2.0 m/s. Results and conclusions. The authors have determined the modes of collision of droplets of suspensions (coagulation and separation) and the main characteristics of secondary fragments and constructed the maps of the modes of interaction of drops of suspensions with each other when varying the concentration of solid particles in the suspension, the temperature of the gas-air environment and the time the target drop spent in a gas-air environment with an elevated temperature. The conditions were established for the coagulation of droplets, as well as their intensive secondary grinding to intensify their drying, ignition and combustion in boiler furnaces. It was established that an increase in the temperature of the gas-air environment leads to a significant change in the size and properties of droplets, as well as to the occurrence of oscillatory phenomena in the system. It is substantiated that collision of droplets of suspensions in a gas-air environment with elevated temperature is complex and multi-parametric. Its characteristics depend on a combination of factors (surface tension and liquid viscosity, size and shape of droplets, speed of their movement, density and viscosity of gas-air environment). The authors obtained mathematical expressions to describe the boundaries of the modes of the studied processes and schemes for using the results obtained in order to increase the efficiency of the corresponding technological processes.

Особенности сжигания композиционных водоугольных топлив

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

Effect of the Initial Moisture Content of Cedar Needles on the Time Characteristics of the Ignition of Coal–Water Suspensions

Effect of the Initial Moisture Content of Cedar Needles on the Time Characteristics of the Ignition of Coal–Water Suspensions

TECHNOLOGY AND EQUIPMENT FOR OBTAINING OF UNIVERSAL HYDROCARBON FUEL

An analysis of methods and equipment for obtaining hydrocarbon fuel was carried out. The purpose of the work is the development of technology and heat-mass exchange equipment for the production of universal hydrocarbon fuel, suitable for use in all types of thermal power plants. Heat and mass exchange equipment has been developed, with the help of which it is possible to obtain universal hydrocarbon fuel with a maximum size of coal particles no larger than 3 microns. The use of water-coal suspensions as an energy fuel allows to increase the technical, economic and environmental indicators of power plants. Thus, during the transition to coal-hydrogen fuel, it was possible to increase its thermal capacity from 13.2 to 21.1 MW when 70 % of coal was replaced by coal-hydrogen fuel. Currently, there are various methods and equipment for the preparation of hydrocarbon fuel. However, they all have certain drawbacks. The main disadvantages of the methods of obtaining hydro-coal fuels are multi-stage, metal-intensive, high energy costs, carrying out physico-mechanical and expensive chemical demineralization of coal, etc. Also, the disadvantages are the limited frequency of hydraulic shock pulses during processing in one cycle, which is insufficient when preparing highly concentrated suspensions that meet the requirements for liquid composite fuel intended for direct combustion. In order to improve the quality of the resulting suspension due to more effective grinding and increasing the amount of its solid component, heat and mass exchange equipment was developed, which can be used to obtain universal hydrocarbon fuel for burning in boilers, furnaces, various thermal power equipment, internal combustion engines, etc. As heat and mass exchange equipment, rotary pulsation devices operating according to the method of discrete-pulse energy input were used. Bibl. 18, Fig. 4, Tab. 3.

Ecological and technological efficiency of the innovative coal-watercoal cluster of housing and communal serviсes

The possibilities of increasing the ecological and technological efficiency of the innovative coal-watercoal cluster of housing and communal services, including the mechanics of coal destruction in a hydraulic shock installation, are considered. The creation of an experimental coal-watercoal cluster of housing and communal services involves the use of innovative coal-watercoal technology in boilers under construction or in operation, including the processing of solid coal fuels into innovative coal-water fuel suspension with subsequent combustion in specially equipped furnaces. The set tasks of managing environmental and technological qualities in the process of preparing an innovative coal-water fuel suspension based on statistical analysis of the granulometric composition correlate with the tasks of obtaining micro- and ultrafine coal-water suspensions in order to achieve high environmental and technological qualities. The control of an innovative coal-watercoal fuel technology based on automatic control of the granulometric composition using the natural fracturing of coal for the control action during the destruction of coal by the method of water hammer is proposed. Technological patterns of reducing the negative technogenic impact on the geospheres are revealed, including a method for managing the environmental and technological qualities of an innovative water-coal suspension based on automatic control of the granulometric composition during coal grinding by the hydraulic shock method.

Coal-water suspensions: preparation, properties, characteristics (a brief overview)

RELEVANCE. A review of the current state of research on coal-water slurries in Russia and abroad is presented. Coal-water slurries are promising alternative types of energy fuels. Their use in the energy sector will allow generating thermal and electrical energy. It is possible to use a fairly wide range of substances as components of such fuels. One of the preferred types are various waste. The analysis of modern literature has shown a fairly wide range of directions for the study of multicomponent coal-water slurries.THE PURPOSE. To provide information on the current state of research in the field of technologies for the preparation, spraying and combustion of coal-water fuels, as well as on existing and promising additives to such slurries.METHODS. The study was carried out by the method of collecting and structuring information.RESULTS. The review of the current state of research in the field of technologies for the preparation, spraying and combustion of coal-water fuels, as well as existing and promising additives to such slurries, was carried out. It was found that additives of liquid combustible waste and biomass contribute to reducing the ignition delay time. At the same time, such additives do not reduce the quality characteristics of spraying multicomponent coal-water slurries. A number of components reduces the amount of emissions of combustion products of such fuels into the atmosphere. The influence of additives and components of coal-water slurries on their characteristics and properties was analyzed. It was shown that liquid components contribute to the intensification of ignition and combustion processes. In addition, their introduction into the fuel composition has a positive effect on the rheological properties of slurries, the characteristics of their spraying, combustion and the concentration of harmful emissions.CONCLUSION. Coal-water slurries are promising alternative types of energy fuels. The introduction of combustible components into the composition of coal-water slurries can significantly improve the rheological properties, which can improve the storage and transportation characteristics of such fuels. The established positive characteristics and properties of coal-water slurries provide prerequisites for the full-scale introduction of such fuels into industrial power engineering.

Influence of the Component Composition of Coal–Water Suspensions on the Volumes of Anthropogenic Gases Produced on Their Combustion

Influence of the Component Composition of Coal–Water Suspensions on the Volumes of Anthropogenic Gases Produced on Their Combustion

Influence of the Component Composition of Coal–Water Suspensions on the Volumes of Anthropogenic Gases Produced on Their Combustion

Experimental studies were carried with coal–water suspensions (CWSs) based on brown coal (grade 2B) with the addition of woody biomass of different types (pine sawdust and pine needles) in various concentrations (2, 4, and 6 wt %) on a fuel basis with a water content of 50%. It was shown that the addition of woody biomass to the coal–water suspensions is promising. An increase in the weight concentration of biomass in the CWSs significantly decreased the volume of anthropogenic emissions generated upon fuel combustion.

METHOD OF OBTAINING WATER-COAL SUSPENSION AND HEAT AND MASS EXCHANGE EQUIPMENT FOR ITS APPLICATION

The analysis of methods and equipment for obtaining water-coal suspensions was carried out. The purpose of the research is to improve the quality of the resulting suspension due to more effective grinding and increasing the amount of its solid component. Heat and mass exchange equipment has been developed, with the help of which it is possible to achieve an increase in the efficiency of hydraulic impact due to an increase in the frequency of pulsations when obtaining water-coal suspensions. The use of water-coal suspensions as an energy fuel makes it possible to improve the technical, economic and environmental performance of power plants. Thus, during the conversion of the boiler to water-coal fuel, it was possible to increase the thermal power of the boiler from 13,2 to 21,1 MW when replacing 70 % of coal with water-coal fuel. Currently, there are different methods and equipment for the preparation of water-coal suspension. However, they all have certain drawbacks. The main disadvantages of the method of obtaining water-coal suspensions are multi-stage, metal consumption, difficulty of installation and start-up, high energy costs, and the resulting suspension is of insufficiently high quality. Also, the disadvantages are the limited frequency of hydraulic shock pulses during processing in one cycle, which is insufficient for the preparation of highly concentrated suspensions that meet the requirements for liquid composite fuel intended for direct combustion. In order to improve the quality of the resulting suspension due to more effective grinding and increasing the amount of its solid component, heat and mass exchange equipment was developed, with the help of which it is possible to achieve an increase in the efficiency of the hydraulic impact action due to an increase in the frequency of pulsations during the production of water-coal suspensions. As heat and mass exchange equipment, rotary pulsation devices (RPD) operating according to the method of discrete-pulse energy input (DPEI) were used. The DPEI method involves the creation of a large number of working bodies or working elements evenly distributed in the water, which transform stationary thermal, mechanical or other types of energy into energetically powerful pulses, discrete in time and space.

Analysis of the accumulation the sedimentary mass in coal-water slurries

The problem of assessing the sedimentation stability of water-coal suspensions, which are a promising type of fuel, possessing the advantages of both liquid fuels and coal, which can be effectively used as a substitute for liquid petroleum fuel (fuel oil), is considered. However, coal-water suspensions have not found wide application at present, which is promoted, in particular, by unresolved issues related to their sedimentation stability: in the production, storage, and transport of suspension, an important qualitative characteristic is its stability over time: the higher it is, the more qualitative is the suspension. The paper proposes a method of solving the problem of predicting the value of particle sedimentation during the sedimentation process, which allows us to calculate the dynamics of sediment accumulation over a certain period of time from the beginning of sedimentation at a given depth of dispersion. The implementation of the calculation method as a systematic approach to determining the dynamics of sediment accumulation is shown on the example of sedimentation analysis data of 50 % water-coal suspension from coal from the Neryungri deposit. It is shown that the proposed method of solving the problem of predicting the size of sedimentation of particles during the sedimentation process allows to calculate the dynamics of sediment accumulation for a certain period of time at a given depth, as well as to determine the minimum sedimentation time, at which the particles of maximum size sediment completely.

Ignition and combustion characteristics of coal - water fuels based on coal & semi-coke

AnnotationThe article presents the results of experimental and theoretical studies of the ignition processes of coal- water fuel (CWF) drops made from coals of various degrees of metamorphism and coal semi-coke of these coals. It is shown that the preliminary torrefaction of coal leads to a significant improvement in environmental performance (50–60% reduction in flue gas concentrations of the main anthropogenic coal combustion products: nitrogen oxides NOx and sulfur SOx) of coal- water fuel combustion processes. This effect is most pronounced during the combustion of CWF based on lignite. Also, according to the results of the experiments, the ignition delay times of typical droplets (in the initial state), and then particles (after drying the near-surface fuel layer) of coal- water fuel s based on coals and coal semi-coke were established. It has been established that the ignition delay times of coal- water fuel particles based on pre-torrefied coals at relatively low ambient temperatures (Tg≤873 K) are on average 20% higher than when igniting CWF droplets based on natural coal. Under conditions of high-temperature heating, the ignition delay times of CWF particles made from natural coal and semi-coke differ insignificantly (no more than 2%).Based on the results of the experimental studies, a mathematical model of the ignition process of a coal- water fuel drop based on semi-coke was developed, which differs from the known ones in a relatively simple description of the most significant processes of thermal preparation and ignition, but at the same time retains a fairly high predictive potential. Using the previously developed method of quasi-stationary "thermal approximation" with the selection of an asymptotic estimate, an analytical solution is derived for the essentially nonlinear problem of coal- water fuel droplet ignition. ColloquiumAn analysis of modern political discourse shows that the information entropy associated with the problem of the anthropogenic impact of mankind on the planet's atmosphere as a result of the operation of energy facilities is constantly growing. At the same time, the constant growth of energy consumption in the world makes it necessary to introduce more and more new heat and power generating capacities. For a long time (the last 30 years) it was believed that the solution to all energy problems is the large-scale introduction of non-traditional renewable energy sources (solar batteries and wind power generators - RES) into the overall balance of energy generation. However, recent events in North America and Western Europe show that the potential for using renewable energy sources is significantly limited, and electricity generation from these renewable energy sources is still significantly unstable. In this regard, a new impetus for development is acquiring coal energy. However, the main problem of coal power engineering, the anthropogenic impact of thermal power plants on the planet's atmosphere, remains unresolved. This situation creates prerequisites for the development of new "clean" coal technologies with complete sequestration of anthropogenic emissions generated during coal combustion. This article presents the results of experimental and theoretical studies of the combustion processes of coal-water suspensions prepared from pre-torrefied coals. As a result of preliminary thermal (pyrolysis under conditions of high-temperature heating in an inert environment) preparation of coal, gaseous pyrolysis products are formed and removed into the external environment, a large proportion of which are hydrogen sulfide (the main source of sulfur oxides) and hydrocyanic acid (the main source of nitrogen oxides). After the preliminary pyrolysis of coal, a mixture of coke carbon and the mineral part of coal remains. When burning a coal-water suspension based on torrefied coal, only carbon dioxide and water vapor are formed. The latter can be relatively easily condensed and returned back to the power generation cycle (or disposed of). Accordingly, the combustion of CWF based on torrefied coal creates the prerequisites for the fundamental justification of the technology for environmentally friendly combustion of coal in the combustion chambers of gas turbine plants operating on the Allam cycle.

A Review of Methods, and Analytical and Experimental Studies on the Use of Coal–Water Suspensions

Research in the field of building mathematical models for combustion processes has been ongoing ever since the chemical reactions of combustion were first discovered. The authors of this review have systematized mathematical models of coal–water suspension (CWS) combustion processes, the sequence of analytical and experimental studies, and have also shown the global genesis of the CWS use. In addition, this review touches upon a topic that is inextricably linked with the combustion of CWS, namely their transportation from the place of coal mining to their place of thermal utilization. For developing countries, their own energy independence is in the foreground, as it is the basis for their economic independence and also a means for other sectors of their economy to be protected from the impact of market changes in fuel prices in the future spot world market. The authors of this review explored the possibility of using Kyrgyz brown coal and transporting it through a coal pipeline from a mountainous area to an industrial site for thermal utilization in specialized steam boiler units. As the economic analysis showed, for the conditions of the Republic of Kyrgyzstan, the use of CWS and coal pipelines with rising prices for natural gas is economically justified. The recommendations of the authors are used in scientific reports and methodological recommendations for the energy and mining sectors of the Republic of Kyrgyzstan, how the recommendations can also be applied to similar conditions in the highlands of Russia, China, and India.

Ignition of water-coal fuel droplets during radiative-convective- conductive heating in relation to boilers operating on the technology of circulating fluidized bed

• Inert material significantly accelerates the ignition of a drop of coal-water fuel. • The effect of an inert material is most pronounced at moderate temperatures (Tg = 873 K). • At high oxidizer temperatures, the inert material does not affect the ignition process. • Inert material leads to dispersion of the near-surface layer of the fuel. One of the most promising options for reducing anthropogenic heating of coal-fired power plants on the environment is the use of not homogeneous coal as the main fuel, but coal-water suspensions. But the combustion of coal-water fuels is associated with the solution of the problem of large values of the ignition delay times for such fuels. Therefore, an important task of great practical importance is the selection (or development) of technologies for combustion of coal-water suspensions in the furnaces of steam and coal-water boilers. The article presents the results of experimental studies of the coal-water fuel drops ignition processes. They were carried out in order to establish the temporal characteristics and conditions of ignition under conditions of a flare mode and combustion in a circulating fluidized bed of an inert material. According to the results of experiments, it was found that at moderate temperatures of the environment (T g ≤ 873 K), particles of inert material (sand) accelerate the ignition of coal-water fuel drops. With high-temperature heating, the ignition delay times for these two fuel combustion technologies are identical in relation to the combustion of coal-water fuels prepared from typical (for energy purposes) semi-anthracite and high-volatile A bituminous coal. Colloquium. The energy crisis in autumn 2021 showed the problem of the rapid transition of the world community from traditional thermal energy to the energy of non-traditional renewable energy generators (wind, sun, biomass). It became obvious that in the next few decades, developed countries will be forced to use coal as their main energy source. Therefore, at present, an urgent task is to reduce the concentration of anthropogenic oxides in the flue gases of coal-fired power plants. One of the most promising technological solutions to this problem is the combustion of coal in the composition of coal-water fuel (CWF). But the technologies of combustion of coal-water fuels in the furnaces of steam and hot water boilers have not yet been developed, mainly due to the problem of large values of the ignition delay times for droplets of such fuels. Therefore, furnace devices of the traditional design of the chamber type with flare combustion of CWF have not yet been developed. One of the promising technologies for the combustion of coal-water fuel can be the technology of a circulating fluidized bed of inert material. But the results of studies of the coal-water fuels drops ignition processes under conditions corresponding to combustion devices operating on the technology of a circulating fluidized bed have not yet been published.

Investigation of ash removal from fine grain coal-water suspension by hydrophobic flocculation using Taguchi (L16) experimental design

ABSTRACT In this study, it was aimed to remove ash from fine-grained coal-water suspensions and a series of hydrophobic flocculation experiments were performed using the Taguchi (L16) experimental design to determine the experimental optimum conditions. Five different controllable process variables such as amount of sodium silicate, suspension pH, amount of waste vegetable oil, flock growth time, and precipitation time, which are effective in hydrophobic flocculation of coal, and four different levels of each variable were investigated. Optimum conditions were determined as amount of sodium silicate 1 mL, pH = 3, amount of waste vegetable oil 4 mL, flock growth time 7 min and precipitation time 1 min. According to the optimization results obtained, the high calorific value (5450 kcal/kg) clean coal with 15.46% ash content and 100% combustible recovery was obtained with 57.52% ash removal. In addition, the contributions of each factor to hydrophobic flocculation of coal were determined with one way variance analysis (ANOVA). The most influential factor was determined as the pH value with a contribution of 61.34%.

Complex processing of high-carbon ash and slag waste

The paper considers a current issue of ash and slag processing for the Polyus Aldan JSC, that has accumulated over 1 million tons of this waste. Following the results of the review of Russian and foreign literature, four promising areas of their use were selected: road construction, building materials, reclamation of disturbed lands, and inert aggregates. To assess the possibility of implementing the selected disposal directions, the samples of ash and slag waste of the enterprise were sampled and analyzed. Fuel characteristics, chemical and mineral composition, as well as physico-chemical and mechanical properties of waste were determined. Taking into account the results of complex laboratory studies and the requirements of regulatory documents, each of the selected areas of using ash and slag waste was evaluated. It was found that their disposal by traditional methods has limitations, mainly related to the high content of unburned fuel residues. The high content of combustible substances and the high specific heat of combustion with a relatively low ash content suggested the possibility of thermal disposal of the studied waste. Based on the literature data, the characteristics of the preparation of organic coal-water suspensions based on the studied ash and slag waste were selected. As a result of a series of experiments on their flaring, the expediency of using the obtained fuel at the enterprise under consideration has been proved. The authors note the possibility of using ash obtained after thermal waste disposal in the road construction industry. The prospects for further research of technologies for the preparation and combustion modes of suspension fuel based on ash and slag waste are determined.

Сорбційні властивості природних вуглецевих матеріалів при видаленні пар із водних розчинів

SORPTION PROPERTIES OF NATURAL CARBON MATERIALS IN THE SEPARATION OF SURFACTANTS FROM WATER SOLUTIONS © I.V. Yakupova, I.M. Kosygina, Phd, A.S. Makarov, Doctor Of Technical Sciences, I.M. Kryuchko (INSTITUTE OF COLOID AND WATER CHEMISTRY NAS OF UKRAINE, Akademika Vernadskogo Blvd., 42, Kyiv, 03142, Ukraine) More than 40 % of the world's electricity production comes from thermal power plants. The main (97.5 %) type of fuel for Ukrainian thermal power plants is coal, which is explained by the cheapness and availability of this raw material. Low efficiency and environmental problems in the use of coal determine the relevance of the search for alternative fuels in Ukraine, and one of the main ones is coal-water fuel – a highly concentrated dispersed system in which a dispersed fraction of coal of any calorific value and a liquid phase consisting of water with plasticizer additives are used as a combustible base and stabilizers. To give stability and the necessary fluidity, a small amount of a surfactant plasticizer is introduced into the suspension. The formation of surfactant adsorption layers on the surface of particles of the dispersed phase is a necessary condition for the formation of the structure of suspensions and its stabilization. The amount of surfactant adsorption, in addition to the physicochemical composition of coal, is largely affected by the nature of the surface and the cellular structure of materials. To study the sorption efficiency of carbon materials, rigid surfactants widely used in the construction industry were used: sodium salt of sulfonated naphthalene formaldehyde (NF), dophene (technical NF), sulfomelamin formaldehyde (SMF), sodium lignosulfonate (LSTNa). The processes of surfactant adsorption on coal of Ukraine with different degrees of metamorphism have been studied. Conclusions are drawn that allow a better understanding of the processes of interaction of surfactants with solid particles of sorbents. It has been established that the sorption properties of surfactants with the use of carbon sorbents decrease in the series LST → dophene → NF → SMF, which is explained by the structure of surfactants. Comparative characterization of the data obtained also allows us to state that the sorption properties with respect to surfactant compounds increase in a number of studied carbon sorbents: lean coal (P) → long-flame gas coal (DG) → anthracite. The similarity of adsorption processes on the surface of coal grade DG and anthracite gives grounds for the assumption that the mechanisms of stabilization of water-coal suspensions by surfactant compounds during the creation of water-coal fuel are similar. Keywords: natural coal, surfactant, adsorption, outer layer, micelles, aggregation. Corresponding author I.M. Kosygina, e-mail: kosygina@ukr.net