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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.

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.

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.

The article is devoted to the complex research processes of heat and mass transfer occurring in the real conditions of solid fuel (coal) combustion. Development of technological processes with economic and ecological advantages are the main purpose for many researches in thermal physics and technical physics. The complex processes of heat and mass transfer in the presence of combustion are non-stationary, strongly non-isothermal with a constant change in the physical and chemical state of the environment. It greatly complicates their experimental study. In this case, studying of heat and mass transfer in high-reacting media with simulation of physical and chemical processes occur during combustion of pulverized coal is important for the solution of modern power engineering industry and ecology problems. In this regard, a comprehensive study of heat and mass transfer processes at high-temperature media observed. Investigations based on the achievements of modern physics by using numerical methods for 3D modeling. Numerical experiments are conducted to describe and study aerodynamic characteristics, heat and mass transfer processes during the burning of pulverized Kazakhstan low-grade coal. The results obtained are of great practical importance, since they allow us to develop recommendations for the improvement and design of new combustion chambers and burners, and also can be useful in optimizing the whole process of burning fossil fuels. G M T Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский Английский Испанский Итальянский Казахский Китайский Трад Китайский Упр Корейский Русский Турецкий Французский Звуковая функция ограничена 200 символами Настройки : История : Обратная связь : Donate Закрыть

The emissions of harmful substances such as sulphur and nitrogen oxides from thermal power plants are major source of adverse impact on the environment. In this regard, it remains be urgent the deeper studying of the solid fuel combustion processes. In this paper, two global schemes of formation and destruction of harmful nitrogen compounds NOx studied during combustion of low-grade Kazakh coal in a real industrial boiler BKZ-75.

In the present paper, a study of furnace processes in the combustion chamber of the real energy boiler BKZ-160 of Almaty TPP-3 (Kazakhstan) using three-dimensional modeling methods has been carried out. Calculations of the combustion chamber for flame combustion of pulverized coal have been performed. The main purpose of this paper was to study the effect of fractional fuel composition on the concentration characteristics of the combustion process. Numerical simulation was carried out with two models of coal particle size distribution: monodisperse fuel flame (coal particle size identical and equal to 60 μm) and a polydisperse fuel flame (coal particle diameter varies from 10 to 120 μm). The polydisperse distribution corresponds to the fractional distribution (percentage of total coal particles) calculated for this boiler: the first fraction - 10% with d p =10 μm; 20% with d p =30 μm; 40% with d p =60 μm; 20% with d p =100 μm; 10% with d p =120 μm.The numerical simulation results of the influence of the pulverized coal particle size composition on concentration characteristics of combustion process are presented. The distributions of oxidizer (oxygen) and combustion products (NO, CO, CO 2 ) are shown. Areas with the greatest concentration of gas products of burning are determined, regularities of formation of products and their concentration at the exit of fire chamber are also determined. The effect of fractional fuel composition on the obtained characteristics is sufficiently large, the empirical data obtained directly at TPP-3 show better convergence with the result of the computational experiment that confirms simultaneously the adequacy of the used physical and mathematical statement of the problem, as well as the validity of using the model of polyfractional distribution.

Numerical experiments on the torch combustion of the coal dust prepared by a plasma-thermochemical treatment for combustion have been done using the method of three-dimensional simulation. It is shown that the plasma preparation of coal for combustion enables one to optimize the process, improve the conditions for inflammation and combustion and minimize the emissions of harmful substances.

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.

Computational fluid dynamics (CFD) becomes more and more reliable tool to analyze the furnace opera-tion under different conditions. This paper provides and overview of the current possibilities of 3D–Finite Volume tool FLOREAN developed at the Institute for Heat and Fuel technology TU Braunschweig. This program is used for simulations of combustion processes in industrial furnaces. FLOREAN has been applied for the calculation of a fur-nace chamber of Aksu power station fired with low grade coal of Ekibastuz (Kazakhstan). Distributions of different parameters such as temperature, fluid flow properties (velocities, pollutant substances such as CO, NOx) etc. are si-mulated. These simulations can be used to design furnaces, optimize furnace operation and minimize pollutant emis-sions.

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.

In this paper the results obtained by the method of numerical modeling 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

Combustion of a pulverized coal torch has been numerically simulated on the basis of the equations of multicomponent turbulent two-phase flows. The results of three-dimensional simulation of conventional and plasma activated coal combustion in a furnace are presented. Computer code Cinar ICE was verified at coal combustion in the experimental furnace with thermal power of 3 MW that was equipped with plasma-fuel system. Operation of the furnace has been studied at the conventional combustion mode and with plasma activation of coal combustion. Influence of plasma activation of combustion on thermotechnical characteristics of the torch and decrease of carbon loss and nitrogen oxides concentration at the furnace outlet has been revealed.

Plasma activation promotes more effective and environmentally friendly low-rank coal combustion. This paper presents Plasma Fuel Systems that increase the burning efficiency of coal. The systems were tested for fuel oil-free start-up of coal-fired boilers and stabilization of a pulverized-coal flame in power-generating boilers equipped with different types of burners, and burning all types of power-generating coal. Also, numerical modeling results of a plasma thermochemical preparation of pulverized coal for ignition and combustion in the furnace of a utility boiler are discussed in this paper. Two kinetic mathematical models were used in the investigation of the processes of air/fuel mixture plasma activation: ignition and combustion. A 1-D kinetic code PLASMA-COAL calculates the concentrations of species, temperatures, and velocities of the treated coal/air mixture in a burner incorporating a plasma source. The 1-D simulation results are initial data for the 3-D-modeling of power boiler furnaces by the code FLOREAN. A comprehensive image of plasma-activated coal combustion processes in a furnace of a pulverized-coal-fired boiler was obtained. The advantages of the plasma technology are clearly demonstrated.

Plasma fuel systems that increase the coal burning efficiency are discussed. The systems were tested for fuel oil-free startup of boilers and stabilization a pulverized-coal flame in power-generating boilers equipped with different types of burner and burning all types of power-generating coal. Plasma ignition, thermochemical treatment of an air-fuel mixture prior to combustion, and its burning in a power-generating boiler were numerically simulated. Environmental friendliness of the plasma technology was demonstrated.