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In the article, using numerical methods, studies have been conducted to determine the effect of the moisture content of the burnt coal on the characteristics of the heat and mass transfer process. The combustion chamber of the PK-39 boiler of the real energy object of the Republic of Kazakhstan (Aksu TPP) was chosen as the object of the study. Temperature (T) and concentration (O2, CO, CO2) fields were calculated for Ekibastuz coal with working moisture equal to 5, 7, 9 and 11%.It is shown that an increase in the moisture content of coal leads to a decrease in temperature both in the area of the burners and at the outlet from the combustion chamber. The concentrations of oxygen, water and carbon dioxide also decrease with decreasing working moisture along the entire height of the combustion chamber. In the area where the burners are located, with an increase in moisture, the amount of carbon monoxide CO formed decreases; however, above the active combustion zone, an increase in moisture leads to a less intense process of afterburning of carbon monoxide CO to carbon dioxide CO2. The results of computational experiments on the combustion of pulverized coal in the combustion chamber of operating power object (boiler PK-39 at Aksu TPP) are compared with experimental data obtained in the course of field experiments carried out directly at the Aksu TPP.

This paper presents new results of computational experiments on the implementation of Overfire Air (OFA) technologies using an example of a combustion chamber of the BKZ-75 boiler of the Shakhtinskaya power plant (Shakhtinsk, Kazakhstan) burning high-ash Karaganda coal. The effect of mass air flow through special nozzles located above the burner level on the flow aerodynamics, temperature fields, concentration fields of carbon monoxide CO and nitrogen NO over the entire volume of the combustion chamber was studied. The studied characteristics were compared for various percentages of supplying additional air through OFA injectors: OFA is 0% (basic version), 10% and 18 %. It was shown that the installation of OFA injectors leads to a change in the field of the total velocity vector, temperature, and concentrations of carbon oxides and nitrogen. An increase in the percentage of air supplied through OFA injectors to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36% and nitrogen oxide NO by 25% compared with the base case. The obtained results will optimize the process of burning pulverized fuel in the combustion chamber of the BKZ-75 boiler, increase the efficiency of fuel burnout, reduce harmful emissions and introduce OFAtechnology at other coal-burning thermal power plants.

Emission of thermal power stations and boilers is regulated in accordance with the unified national regulatory requirements, taking into account the specifics of energy production, its life-sustaining function and is aimed at ensuring that air pollution is prevented as much as possible. The purpose of the regulation of emissions of thermal power plants is to limit its adverse impact on the air basin by developing, for the entire thermal power plant and each source of emissions on it, the maximum allowable emissions – control (in grams per second) and per annum (in tons per year), ensuring sanitary hygienic standards. Sanitary standards include the maximum permissible concentration, which reflects the level of components in the air that is safe for humans. In practice, several substances are simultaneously present in the air, the presence of which causes multicomponent air pollution. The atmospheric pollution index, which is calculated for a group of substances, is often used as a complex indicator of the degree of air pollution. Currently, mostly applied methods of component-wise assessment of atmospheric air quality are used in practice. When calculating atmospheric pollution by boiler houses, the total volumes of fuel combustion products are determined experimentally or by calculation. This article provides empirical formulas for calculating the above standards – the volume of flue gases, the maximum one-time emissions of ash, sulfur oxides, carbon and nitrogen for various boilers with known technical characteristics. Also, using the above formulas, a comparative analysis of the level of air pollution depending on the quality of various types of fuel burned in various types ofboilers.

Using numerical methods, the basic characteristics of heat and mass transfer processes in the furnace chamber of the BKZ-75 boiler of the Shakhtinskaya TPP (Kazakhstan) were studied during a forced partial stop of the supply of coal dust through the burners. Two modes of fuel supply were studied; a direct-flow method of supplying air mixtures, when two direct-flow burners are working and two are in emergency mode and vortex method of supplying air mixtures - two vortex burners with a swirl angle of the air mixture flow and their inclination the center of symmetry of the boiler by 30? and two are in emergency mode. The computational experiments allowed to obtain the distributions of the total velocity vector, temperature fields, concentration fields of CO, NO2 throughout the entire volume of the combustion chamber and conduct a comparative analysis for the two investigated emergency mode (direct-flow and vortex). Based on the results, it can be concluded that in the case of a forced partial stop of the supply of coal dust, the use of the vortex method of supplying air mixtures improves heat and mass transfer processes and allows minimizing emissions of harmful substances.

In this work, a comprehensive study of thermal processes and aerodynamic and concentration characteristics of the combustion chamber of the boiler BKZ-75 of the Shakhtinskaya thermal power plant (Kazakhstan) are presented. A comparison of the characteristics of the combustion processes for two cases is given for the direct-flow method of supplying the mixture - the burners are located on opposite-side walls and the swirl-air mixture supplying method - burners with a swirl angle of the air mixture flow and their inclination to the centre of symmetry of the boiler by 30 degrees. The research results allow us to determine the optimal technological parameters of the studied object, to improve the methodology for the numerical study of heat and mass transfer processes in high-temperature and chemically reacting flows in the presence of turbulence, and also develop appropriate technological solutions for installing burner devices (direct-flow or swirl) in the studied combustion chamber.

The methods of numerical simulation are used to study the processes of heat and mass transfer in thecombustion chamber of an operating coal-burning Kazakhstan thermal power plant. Computational experiments wereperformed on the combustion of high-ash Karaganda coal in the combustion chamber of the BKZ-75 boiler(Shakhtinsk, Karaganda region). As a result of numerical simulation of the combustion processes, the distributions ofthe total velocity vector, temperature fields, concentration fields of nitrogen oxides NO over the entire volume of thecombustion chamber and at its exit were obtained. A comparative analysis of the characteristics of heat and masstransfer processes for the two studied modes of supplying fuel to the combustion chamber through burner devices isgiven for the direct-flow method of supplying the mixture when the burners are located on opposite side walls andthe vortex method of supplying the mixture when the burners are installed at a 30-degree angle from the center ofsymmetry of the boiler. It is shown that the vortex method of supplying air mixtures allows optimizing thecombustion of high-ash coal, since in this case there is an increase in temperature in the core of the torch and adecrease in it at the exit from the combustion chamber, which has a significant effect on the chemical processes ofthe formation of combustion products. The average value of the concentration of nitrogen oxide NO at the outlet ofthe combustion chamber decreases when using burner devices with a swirl of the mixture flow and conforms tonorms the maximum permissible concentration.

The aim of the work is to create new computer technologies for 3D modelling of heat and mass transfer processes in high-temperature physicochemically reacting environments that will allow to determine the aerodynamics of the flow and heat and mass transfer characteristics of technological processes occurring in the combustion chambers in existing coal-fired thermal power plants of the Republic of Kazakhstan. The novelty of the research lies in the use of the latest information technologies of 3D modelling, which will enable project participants to obtain new data on complex heat and mass transfer processes when burning pulverized coal in real combustion chambers operating in Kazakhstan’s Thermal Power Plants (TPP). A numerical simulation, including thermodynamic, kinetic and threedimensional computer simulation of heat and mass transfer processes when burning low-grade fuel, will allow finding optimal conditions for setting adequate physical, mathematical and chemical models of the technological process of combustion of burning high ash coals. The computer modelling methods proposed for the development are new and technically feasible, since coal-fired power plants all over the world use all types of coal. The developed technologies will allow replacing or eliminating the conduct of expensive and labour-consuming natural experiments on coal-fired power plants.

Using numerical methods, studies have been carried out to determine the effect of the introduction of the technology of two-stage combustion of high-ash Karaganda coal on the main characteristics of heat and mass transfer processes in the furnace of the BKZ-75 boiler at Shakhtinskaya TPP (Kazakhstan). Various regimes of supplying additional air into the combustion space, the volume of which varied from 0% (traditional basic version) to 30% of the total volume of air required for fuel combustion, have been investigated using 3D computer modeling methods. The performed computational experiments made it possible to obtain the distributions of the total velocity vector, temperature fields, concentration fields of carbon monoxide CO and nitrogen dioxide NO2 over the entire volume of the furnace and at the outlet from it. The introduction of the two-stage combustion technology made it possible to optimize the combustion of high-ash coal, since in this case there is an increase in the temperature in the torch core and a decrease in it at the outlet from the furnace, which has a significant effect on the chemical processes of the formation of combustion products. Based on the results obtained, it can be concluded that an increase in the percentage of air supplied through additional injectors to 18% leads to a decrease in the concentrations of carbon monoxide CO by about 36%, and nitrogen dioxide NO2 by 25% compared to the base case. A further increase in the volume of additional air leads to a deterioration in these indicators. The results obtained will make it possible to optimize the combustion of low-grade fuel in the furnace of the BKZ-75 boiler, increase the efficiency of fuel burnout, reduce harmful emissions into the atmosphere, and introduce a two-stage combustion technology at other coal-fired TPPs.

Over the past decades, the consumption rates of fossil energy resources has not declined, despite fundamental changes in the political, economic and social structures of society. According to experts, the share of coal in the global fuel and energy balance is more than 27%, thanks to which almost 45% of the world's electricity is generated. For each country in the world, the structure of the national energy balance is determined by the availability of its own sources of fuel and energy resources. In the Republic of Kazakhstan, coal reserves are estimated at 30 billion tons, which is 3.4% of the world's coal reserves. However, Kazakhstan's coal is characterized by low calorific value and high ash content, its combustion leads to the formation and delivery of large quantities of pollutants in air, soil and water. Pollution of the atmosphere is one of the global problems of mankind, whose solution is to optimize the combustion process and realization stringent environmental requirements for specific emissions of harmful substances with waste gases. To solve this difficult task, there is a need to improve equipment, introduce new technologies and use alternative methods for organizing a combustion process, the basis of which is to study the processes of heat and mass transfer in the presence of combustion. Irreplaceable powerful method of theoretical research of currents at availability of burning is numerical modelling. The results of a three-dimensional numerical simulation of aerodynamics, temperature flow and carbon oxides are presented. Studies have been carried out for a pulverized-angle flame of various dispersity. A comparative analysis of the obtained results with the results of the field experiment is carried out. The obtained results will allow choosing the optimal variant of the combustion process organization in order to increase its efficiency and reduce the negative impact on the environment.

In this article, a study of the processes of heat and mass transfer in high-temperature and thermochemically activated reacting flows in a real physicochemical system (turbulent flows with physicochemical transformations in combustion chambers) in three-dimensional geometry using numerical methods was carried out. As a result of computational experiments vector distribution full velocity, temperature fields, fields of concentrations of nitrogen oxides NO over the entire volume of the combustion chamber were obtained and a comparative analysis was carried out for the two boilers. The results obtained allow us to conclude that the use of plasma preparation of a pulverized coal torch for combustion has a positive effect on the process of heat and mass transfer and allows minimizing emissions of harmful substances.

In this paper the results obtained by the method of numerical modelling of Ekibastuz coal burning in furnace of Kazakhstan Power Plant. Numerical experiment was carried out on the basis of three-dimensional equations of convective heat and mass transfer, taking into account the heat propagation, heat radiation, chemical reactions and multiphase structure of the medium to predict the influence of different water content in coal on overall furnace operation and formation of combustion products.