The optimization of the boiler furnace’s aerodynamics is considered in order to increase the efficiency of burning power-generating fuel by the example of burning lean Kuznetsk coal in a solid slag removal scheme. Combustion options have been proposed and investigated in schemes with direct injection of coal dust and with an intermediate coal dust hopper. The schemes use direct-flow burners with an counter-displaced arrangement and nozzles with a downward inclination, and staged combustion of fuel is used. A study of the furnace’s aerodynamics on an isothermal bench was carried out. The results of physical modeling were compared with the data of numerical modeling of an isothermal bench. It is noted that combustion schemes differ in the intensity of vortex formation in the active combustion zone. A numerical simulation of fuel combustion in the boiler furnace was performed using the two indicated combustion schemes. The purpose of the simulation was to obtain the distribution of temperatures, gas velocities, concentrations of combustion products, nitrogen oxide emissions, degree of burnout in the furnace volume and other characteristics that affect the efficiency, reliability, and environmental safety of the boiler. The results of model studies showed that the developed schemes provide high efficiency of burning lean Kuznetsk coal with solid slag removal and, at the same time, low emissions of nitrogen oxides. An additional verification of the numerical model was carried out by comparing the gas temperatures by the height of the furnace obtained by its numerical simulation and thermal zone calculations. A comparison of the temperatures of the gases at the outlet of each zone showed their good agreement (the difference was no more than 30°C).

Two schemes of lean Kuznetsky coal combustion with solid slag removal are proposed and investigated in the work: for the scheme with direct pulverized coal injection and for the scheme with pulverized coal bunker. Both schemes are based on the use of direct-flow burners and nozzles with a counter-displaced arrangement, the orientation of burners with a downward angle, and the use of staged fuel combustion. The possibility of a stable and efficient operation of the proposed schemes was tested in the ANSYS Fluent software package. The simulation results showed steady fuel combustion, carbon-in-ash losses of not more than 2% and a concentration of nitrogen oxides in flue gases of not more than 350 mg/m3.

Heat and mass transfer processes and decomposition of organic compounds in a pyrolysis reactor are simulated using the ANSYS Fluent software package. Simulation of the pyrolysis of organic compounds, in contrast to simulation of their combustion, is dealt with only in a few studies. However, there are many engineering applications of this process, including thermal decomposition of various wastes where the use of pyrolysis, due to its specifics, seems to be very promising. Because of the wide variety of organic compounds, implementation of their processing in practice using the pyrolysis process depends heavily on the properties of a given feed and requires theoretical justification. A pyrolysis reactor equipped with a mixer is described, and the problem in the computer simulation of wetted polypropylene’s thermal decomposition is formulated. Polypropylene is a component of many medical products, such as catheters, transfusion systems, disposable syringes, etc. It has the highest decomposition heat among all components of medical waste and controls the maximum time of their decomposition. A description is given of a two-phase mathematical model consisting of the well-known mass, momentum, and energy conservation equations, mass transfer equation, and equation of state. The results from calculation of the propylene pyrolysis and the dynamics of thermal decomposition of a solid phase in a reactor are presented. The time of moisture evaporation and pyrolysis of a specimen at 600°С was determined. The hydrodynamic and heat transfer characteristics of the process enabling the performance of a thermal processing package and the requirements for the design of a test facility are considered. The results on the rate and time of polypropylene decomposition offer prospects for predicting the throughput capacity and loading frequency for the investigated reactor.

The important problem of developing the low-cost technologies that will be able to provide a deep decrease in the concentration of nitrogen oxides while maintaining fuel burn-up efficiency is considered. This paper presents the results of the aerodynamics study of the furnace of boiler TPP-210A on the base of the physical and mathematical models in the case when boiler retrofitting from liquid to solid slag removal with two to three times reduction of nitrogen oxide emissions and replacing the vortex burners with direct-flow burners. The need for these studies is due to the fact that the direct-flow burners are "collective action" burners, and efficient fuel combustion can be provided only by the interaction of fuel jets, secondary and tertiary air jets in the furnace volume. The new scheme of air staged combustion in a system of vertical vortexes of opposite rotation with direct-flow burners and nozzles and direct injection of Kuznetsky lean coal dust was developed. In order to test the functional ability and efficiency of the proposed combustion scheme, studies on the physical model of the boiler furnace and the mathematical model of the experimental furnace bench for the case of an isothermal fluid flow were carried out. Comparison showed an acceptable degree of coincidence of these results. In all studied regimes, pronounced vortices remain in both the vertical and horizontal planes, that indicates a high degree of mass exchange between jets and combustion products and the furnace aerodynamics stability to changes in regime factors.

This paper describes different ways of efficiency improvement in pellet fuel bed combustion and proposes methods of pellet fuel combustion, ensuring high environmental and energy performance. The constriction in the form of a convergent-divergent passage in the furnace chamber with simultaneous delivery of the secondary air at the point of maximum dispersal of the exhaust gases has reduced unburned combustible losses by 39%. At the same time, the constriction has reduced heat transfer surface area and residence time of hot gases in the furnace chamber, which increased the exhaust gases temperature at the combustion chamber outlet by 98°C. Ansys CFX software package was actively used for numerical simulation during the development of innovative furnace chamber design. To verify simulation results, the firing test bench was designed.

Nowadays the problem of improvement of pulverized coal combustion schemes is an actual one for national power engineering, especially for combustion of coals with low milling fineness with significant portion of moisture or mineral impurities. In this case a big portion of inert material in the fuel may cause impairment of its ignition and combustion. In addition there are a lot of boiler installations on which nitrogen oxides emission exceeds standard values significantly. Decreasing of milling fineness is not without interest as a way of lowering an electric energy consumption for pulverization, which can reach 30% of power plant's auxiliary consumption of electricity. Development of a combustion scheme meeting the requirements both for effective coal burning and environmental measures (related to NOx emission) is a complex task and demands compromising between these two factors, because implementation of NOx control by combustion very often leads to rising of carbon-in-ash loss. However widespread occurrence of such modern research technique as computer modeling allows to conduct big amount of variants calculations of combustion schemes with low cost and find an optimum. This paper presents results of numerical research of combined schemes of coal combustion with high portion of inert material based on straight-flow burners and nozzles. Several distinctive features of furnace aerodynamics, heat transfer and combustion has been found. The combined scheme of high-ash bituminouos coals combustion with low milling fineness, which allows effective combustion of pointed type of fuels with nitrogen oxides emission reduction has been proposed.

MPEI conducts researches on physical and mathematical models of furnace chambers for improvement of power-generation equipment fuel combustion efficiency and ecological safety. Results of these researches are general principles of furnace aerodynamics arrangement for straight-flow burners and various fuels. It has been shown, that staged combustion arrangement with early heating and igniting with torch distribution in all furnace volume allows to obtain low carbon in fly ash and nitrogen oxide emission and also to improve boiler operation reliability with expand load adjustment range. For solid fuel combustion efficiency improvement it is practical to use high-placed and strongly down-tilted straight-flow burners, which increases high-temperature zone residence time for fuel particles. In some cases, for this combustion scheme it is possible to avoid slag-tap removal (STR) combustion and to use Dry-bottom ash removal (DBAR) combustion with tolerable carbon in fly ash level. It is worth noting that boilers with STR have very high nitrogen oxide emission levels (1200-1800 mg/m3) and narrow load adjustment range, which is determined by liquid slag output stability, so most industrially-developed countries don’t use this technology. Final decision about overhaul of boiler unit is made with regard to physical and mathematical modeling results for furnace and zonal thermal calculations for furnace and boiler as a whole. Overhaul of boilers to provide staged combustion and straight-flow burners and nozzles allows ensuring regulatory nitrogen oxide emission levels and corresponding best available technology criteria, which is especially relevant due to changes in Russian environmental regulation.

Results obtained by the numerical study of a solid fuel combustion scheme with bottom blowing using Ekibastuz and Kuznetsk bituminous coals of different fractional makeup are presented. Furnace chambers with bottom blowing provide high-efficiency combustion of coarse-grain coals with low emissions of nitrogen oxides. Studying such a combustion scheme, identification of its technological capabilities, and its further improvement are topical issues. As the initial object of study, we selected P-57-R boiler plant designed for burning of Ekibastuz bituminous coal in a prismatic furnace with dry-ash (solid slag) removal. The proposed modernization of the furnace involves a staged air inflow under the staggered arrangement of directflow burners (angled down) and bottom blowing. The calculation results revealed the specific aerodynamics of the flue gases, the trajectories of solid particles in the furnace chamber, and the peculiarities of the fuel combustion depending on the grinding fineness. It is shown that, for coal grinding on the mill, the overall residue on the screen plate of 90 µm (R 90 ≤ 27% for Ekibastuz coal and R 90 ≤ 15% for Kuznetsk coal) represents admissible values for fuel grind coarsening in terms of economic efficiency and functional reliability of a boiler. The increase in these values leads to the excess of regulatory heat losses and unburned combustible losses. It has been established that the change in the grade of the burned coal does not significantly affect the flow pattern of the flue gases, and the particles trajectory is essentially determined by the elemental composition of the fuel.

Power generating unit no. 4 of Troitskaya State District Power Plant (SDPP) is incapable of operating with a nominal load of 278 MW because of high aerodynamic drag of the gas path. At present, the maximum load of the two-boiler single-turbine unit is 210 MW practically without a possibility of adjustment. The results of numerical simulation of the gas flow for the existing gas path from the electrostatic precipitator (EP) to the smoke exhausts (SEs) and two flue designs proposed for renovation of this section are presented. The results of simulation show that the existing flue section has high aerodynamic drag, which is explained by poor, as regards aerodynamics, design. The local loss coefficient, in terms of the dynamic pressure in the sucker pocket of the smoke exhaust is equal to 4.57. The local aerodynamic loss coefficient after renovation at the considered section according to the first version would make 1.48, and according to the second version 1.325, which would reduce losses at this section by more than a factor of three, and ensure the power unit operation with the rated load.