Vortex Furnace Research Articles

Numerical modelling of heat transfer processes in coal-fired vortex furnace with bottom-port secondary blowing: ecological performance comparison for two types of coal fuel

The work is devoted to numerical 3D modelling of aerodynamics and pulverized-coal combustion processes in a novel vortex furnace of a boiler unit for thermal power stations. A prospective retrofitting design of this furnace, featuring additional tangential blowing at the bottom part of the vortex combustion chamber, has been studied. The firing regimes using two types of siberian coal (black coal, brown coal) are considered. Numerical results for the studied combustion regimes in the modified vortex furnace are presented, including the fields of velocity, temperature, species and dispersed phase concentrations, and the comparative analysis of NOx emissions for two types of coal.

INVESTIGATION OF THE FUEL-AIR FLOW INSIDE A VORTEX FURNACE WITH A FLUIDIZED BED USING A SPECIAL AIR-DISTRIBUTING NOZZLE

The article presents the results of an experimental study of the fuel-air flow inside a vortex furnace with a fluidized bed using a special air distribution nozzle. Nowadays, the issue of dependence on fossil energy resources is the most important problem for the countries of Europe. One of the promising solutions to this problem is the use of vortex solid fuel furnaces for burning low-calorie types of fuel, such as waste from the woodworking and agricultural industries. Our country has developed agricultural and woodworking sectors of the economy, so the amount of waste from these industries is significant, which allows them to be used to cover the energy needs of the state. At the same time, there is a significant number of solid fuel boilers on the territory of Ukraine that can be used for this task. The main difficulties in burning low-grade fuels in solid-fuel boilers are the low level of efficiency of these vortex furnaces and insufficient theoretical information about this. To conduct the experiment, a special installation in the form of a cylinder with a nozzle inside is used. The nozzle has a plate inclination of 15 °, which does not exceed 10% of the total live cross-sectional area of the chamber of the experimental setup. In the course of the experiment, the boundary conditions for the formation of a vortex flow at different amounts of fuel and different air flows were determined, and the values of pressure loss and flow velocity were shown. The results are presented in graphical and tabular form. For example, for 2.9 kg of sawdust, the maximum speed of vortex flow formation is 0.72 m/s, for 5.8 kg this value is 0.57 m/s. The obtained results make it possible to formulate recommendations for the improvement of existing solid fuel furnaces due to the use of special nozzles for the intensification of combustion processes. This creates prospects for the development of the country's energy sector. Keywords: fuel combustion, vortex furnaces, furnace aerodynamics, special nozzle.

The Coal Dust Combustion Scheme for an Invert Furnace of an A-USC M-Shaped Boiler

The M-shaped boiler construction for the advanced ultrasupercritical steam parameters (A-USC) is proposed in this work. The boiler was designed to operate in a 500 MW unit on low volatile hard coal. This design allows reducing the pipelines length of the high cost steam pipelines made of nickel alloys. A downstream (invert) furnace is offered for this boiler type. The coal dust burning scheme design using the direct-flow burners and nozzles in a system of vertical and horizontal tangential torches and the solid ash removal are proposed. This approach was extensively used earlier on standard shaped boilers, and it was upgraded now for an invert furnace. The goals are achieved by conducting research on the physical furnace model and thermal furnace processes numerical simulation by computational fluid dynamics software. The most significant research results were as follows: the oxidizer stage supply was performed along the torch length and furnace height; the dynamic jet pressure on the furnace walls was excluded; a high degree of coal burnout was ensured due to the vortex furnace aerodynamics implementation; the uniform furnace section filling with air jets was performed; turbulent jets ejection was significantly higher than that for a flat submerged jet; chemical underburning loss did not exceed 0.1%; and unburned carbon loss was 0.8%. The carbon monoxide concentration at the furnace outlet in terms of air excess ratio equal to α=1.4 was 226 mg/nm3 . The nitrogen oxides concentration in the flue gases (normalized) was 424 mg/nm3 . The results significance obtained during the research is efficient solid fuel use with high technical and economic boiler performance.

Investigation of the fuel-air flow inside a vortex furnace with a fluidized bed using a special air-distributing nozzle.

The search for resources alternative to fossil sources of thermal energy is a constant component of the development of the energy sector of any country. This issue is now most urgent due to various political processes and the constant decrease of the total amount of non-renewable natural resources. One of the ways to implement the issue of replacing natural gas, coal and other types of fossil fuels is the burning of waste from agriculture and the woodworking industry. But this is associated with a significant number of technical difficulties and an insufficient theoretical basis for implementation. The article presents the results of an experimental study of the fuel-air flow inside a fluidized-bed vortex furnace using a special air-distributing nozzle. A nozzle with a 15ͦ slope of the plates is used, which does not exceed 10% of the total area of ​​the free section of the chamber of the experimental setup. In the course of the experiment, the limiting conditions for the formation of a vortex flow at different amounts of fuel and different air flow rates are indicated, and the values ​​of pressure losses and flow rates are shown. So for 2.9 kg of sawdust, the maximum speed of formation of a vortex flow is 0.72 m/s, for 5.8 kg this value is 0.57 m/s. The results obtained make it possible to formulate recommendations for the improvement of existing solid fuel furnaces through the use of special nozzles to intensify combustion processes. In the future, it is planned to consider other types of solid fuel and the influence of different angles of inclination of the blades on the air distribution nozzle on the aerodynamic characteristics inside the vortex furnace. All this will make it possible to formulate recommendations for the improvement of existing solid fuel vortex furnaces.

COMBUSTION OF COMPOSITE PEAT-COAL MIXTURES IN A VORTEX FIREPLACE

The results of the numerical study of peat and brown coal combustion processes in avortex furnace with a power of 2.5 MW are presented. The processes in a vortex furnace with counterswirling flows with an upper supply of fuel and primary air and a supply of secondary air at thebottom of the furnace are studied. The removal of slag occurs in the bottom of the furnace. Theparticle size of fuel is from 25 microns to 250 microns. The calorific value of peat is 12.3 MJ/kg, thevolatile content is Vdaf=38 %, humidity is Wp=40 %, the stoichiometric coefficient is 7 kg air/kg fuel.The calorific value of brown coal is 13.9 MJ/kg, volatile content Vdaf=25-35 %, humidity Wp=30 %,stoichiometric coefficient is 4.3 kg air/kg fuel. The ash content of the fuel varies from Ap=20 % toAp=35 %. Ash content and humidity are Аp+Wp=65 %. It has been found that at ash content ofАp=30-35 % and humidity Wp=30-35 % the combustion process is unstable due to the problem ofremoving moisture and ash from the furnace volume. The temperature of the flue gases at the outletof the furnace when burning peat is found to be 1711 ºC, and the temperature of the ash is 1380 ºC,which ensures solid ash removal. The temperature of flue gases during the combustion of brown coalis 1888 ºC. A higher air excess coefficient is noted: a=2.36 in the process of burning peat and a=2.0when burning brown coal. The calculation results indicate that this ensures a high degree of cokecombustion in the particles that are captured: 99.8 % (peat particles) and 93.9 % (lignite). Theunderburning of fuel particles that are carried away is 0 % (peat) and 3.04 % (lignite). Theunderburning of fuel particles that are captured is 0.06 % (peat) and 0 % (lignite). The ratio ofoncoming flows is 0.2, which ensures the minimum hydraulic resistance of the furnace. Peat andbrown coal are similar to each other in chemical composition after the stages of coalification.Therefore, similar characteristics of combustion processes can be obtained by burning a composite mixture of peat/lignite (50 %/50 %), both in pulverized combustion and in the combustion of briquettegranules and water-fuel suspension – water-peat-lignite.

Numerical simulation of the processes of burning lignite in a vortex furnace with swirling countercurrent flows

Abstract This work presents the results of a numerical study of the working processes of burning lignite in a vortex furnace with swirling countercurrent flows. The results of computer simulation of the processes of burning lignite with a moisture content of 30%, an ash content of 20% and 35% and a higher calorific value of Qрв = 13.9 MJ/kg and 9.7 MJ/kg, respectively are given. The fields of temperature distribution, gas velocity and particle trajectory in the volume and at the outlet of the furnace are determined. The values of the swirling flow velocity near the exit from the furnace reach 150-170 m/s. Mechanical underburning is 3.7% and 9.4% depending on the ash content. The results of a numerical study have showed that the diameter of lignite particles affects their combustion process: coke particles with an initial diameter from 25 microns to 250 microns burn out by 96%. The furnace provides a complete combustion of pulverized coal particles - 99.8% and of volatiles - 100% at volumetric heat stress in the 2500 kW/m3 furnace. The afterburning of fuel particles containing carbon is ensured by their circulation

Scheme of incineration of wood waste in a furnace with a circulating boiling bed

Cyclonic-vortex technology of solid fuel combustion allows to reduce the furnace volume of the boiler unit, dimensions and weight. Mixing of fuel particles and air in a swirling stream provides intensive heat exchange and fuel combustion in a limited furnace volume. The results of improving the thermal scheme of combustion of pulverized fuel (wood waste) in a circulating fluidized bed are presented. The results of numerical calculations showed the possibility of burning sawdust with a particle diameter of 25 μm to 750 μm. When the air-fuel mixture is supplied from the bottom of the furnace, and the secondary air from the top of the furnace, ash is removed in liquid form through a slot in the lower part of the furnace. It was found that with a sawdust moisture content of 10%, ash content Ac = 0.6%, a higher combustion heat of 17.7 MJ / kg, particle entrainment is 19.2 %, the degree of particle burnout is 92.5%, which requires afterburning of entrainment in a circulating boiling layer. One of the ways to improve Ukraine's fuel and energy balance is to use alternative sources of heat to natural gas, namely solid fuels or wood industry waste. It is necessary to involve specialized technologies for burning solid fuels. Currently, there is an incomplete theoretical and practical knowledge about the processes of burning wood waste.The use of natural gas as a source of thermal energy occupies a significant part of Ukraine's fuel and energy balance. To increase the share of solid fuels, it is necessary to study in more detail the processes of their combustion and the use of methods of intensification of heat transfer processes in the furnaces of solid fuel boilers. The results of numerical calculations showed that the use of vortex furnace instead of direct flow in the scheme CKS increases the residence time of particles in the furnace, which reduces the multiplicity of fuel circulation, reduce the size and weight of the furnace

Aerodynamic Characteristics of the Combustion Process of Sawdust in a Vortex Furnace with Counter-Swirling Flows

The aim of this work is to study the working processes of burning the low-quality fuels, namely, the saw dust in the swirling-type furnaces with an opposite twisted motion of the air. The goal was achieved using the physical and mathematical modeling of the flows interaction. The article presented the results of numerical study of aerodynamic characteristics of burning the saw dust in the swirling-type furnace with the opposite twisted air flows. For the research, the facility was used for the saw dust burning with the air supply into the lower and upper zones of burning. The most essential result of the work was modeling of the working process at the ratio of the flows of the primary air and secondary air without the fuel admixture, equal to 0.2. The tangential rate of the flow changed according to the horizontal sections from 3-5 m/s to 40-42 m/s and with respect to the furnace height from 51 m/s to 30 m/s. The average angular rate of the mixture changed relatively the furnace height in the ranges of 171-500 l/s to 100—300 l/s. The significance of the results obtained consists in determination of the possibility of increasing the efficiency of the work of the furnace facilities at the expense of the introduction of the primary and secondary air flows. In this situation, the optimal ratio of consumptions of primary and secondary air was 0.2. Thus, in this work the consumption of primary air was 1.285 kg/s, the consumption of the secondary air was 0.255 kg/s.

Investigation of the direct-flow jets vortex motion in the M-shaped boiler invert furnace

For advanced ultra-supercritical parameters (A-USC) of steam, the design of an M-shaped boiler is proposed, designed to operate in a 500 MW unit on a lean coal (grade TR). The boiler profile is selected from the condition of minimizing the length of the main steamlines made of expensive nickel-alloy steel. With regard to this boiler, a scheme has been developed for pulverized coal combustion in an invert furnace using direct-flow burners and nozzles. Research has been carried out on the physical model of the furnace in the implementation of this combustion scheme: a qualitative study of the trajectories of the burner jets, jets of secondary and tertiary air obtained by their hot spark visualization; quantitative determination of the main characteristics of burner jets and their weight gain. The studies have shown the high efficiency of the recommended scheme of the furnace-burner device: a staged supply of the oxidizer along the flame length and along the furnace height is organized; the dynamic pressure of jets on the furnace wall tubes is excluded; vortex furnace aerodynamics should provide a high degree of burnout of coal dust particles; air jets evenly fill the horizontal section of the furnace; the ejection capacity of turbulent jets is much higher than for a flat submerged jet.

Aerodynamic characteristics of the sawdust combustion process in a vortex furnace

The article presents the results of a numerical study of the behavioral characteristics of the process of burning sawdust with a diameter from dmin = 25 μm to dmax = 750 μm in a vortex furnace with counter swirling air flows. The fields of static pressure and absolute velocity in the furnace volume are given. The change in flow density, volume concentration of particles along the height of the furnace is shown. Consumption concentration of particles is 0.094 kg / kg of air. Currently, one of the main directions of Ukraine's strategic development is to achieve energy independence. To achieve this, it is necessary to implement systems for the use of energy resources available in our country. Since a significant part of the country's economic activity is occupied by agricultural activities, the use of low-grade fuels, most of which are waste in this area, is relevant and profitable for economic and environmental reasons. Reconstruction of boilers, improvement of methods and ways of combustion in vortex furnaces of low-grade fuels will significantly reduce the consumption of imported natural gas and bring the country closer to the status of energy-independent state. coke burnout is 100%. The value of the volume concentration of particles β <3 · 10-2 characterizes the aerodynamic mode of motion of particles in the furnace as the mode of gas suspension. In the course of research, the main characteristics of the process of burning sawdust in a vortex furnace with counter-swirling air flows, namely: higher gas velocity is observed in the near-wall area in the lower part of the furnace; when the diameter of the fuel particles increases, the zone with the maximum coke content in them moves from the lower zone of the furnace to the upper; the gas pressure varies slightly both in height and in the cross section of the furnace.

Numerical modeling of peat burning processes in a vortex furnace with countercurrent swirl flows

The paper presents the process of peat burning in a swirl furnace with counter-current swirl flows and the results of a numerical study. The cyclone-vortex technology of solid fuel combustion allows the furnace volume of a boiler unit, its dimensions and weight to be reduced. The aim of the work is a numerical study of the combustion of pulverized peat in a cylindrical vortex furnace with counter-current swirl flows. The results of computer simulation of the combustion of pulverized peat with a moisture content of 40%, an ash content of 6%, and a higher heat of combustion QpH = 12.3 MJ/kg are presented. The results of the influence of the design parameters of the furnace and heat load (from 100-15%) are given as well. When the heat load is reduced to 15%, the entrainment of unburnt particles increases. The cooled and adiabatic furnace is studied. A significant entrainment of unburned particles is observed in a cooled furnace. The fields of temperature distribution, gas velocity, and particle trajectory in the volume and at the outlet of the furnace are determined. The 3-D temperature distribution in the furnace volume indicates the combustion of peat particles at temperatures (1300-1450?C). Values of the tangential velocity of a swirl flow near the furnace outlet reach 150-370 m/s, which ensures the efficiency of separation of fuel particles and a reduction in heat loss due to mechanical underburning (up to 0.06%). The results of a numerical study show that the diameter of peat particles affects the combustion process, namely coke of particles with an initial diameter from 25-250 ?m burns out by 96%, and particles with a diameter of about 1000 ?m are carried away from the furnace and do not burn. The furnace provides a complete combustion of dust particles of peat by 99.8% and volatiles by 100%.

Areas of using environmentally friendly fuel combustion technologies at TPPs of the Irkutsk Region

The use of coal as the main fuel at thermal power plants in the Irkutsk Region, the significant moral and physical depreciation at many of them of the main generating equipment, mainly boiler plants, due to the long service life, determine the relevance of environmental considerations in organizing rational energy supply to regional consumers in the future. The study of the age composition, technical and environmental characteristics of the boiler equipment of thermal power plants in the region. A review of advanced technologies for burning fuel in large installations with the aim of producing thermal and electric energy. Based on an analysis of the state and environmental characteristics of thermal power plants in the Irkutsk Region, a review of advanced technologies for burning fuel in large thermal power plants, the main directions of the future use of these technologies at thermal power plants in the region are considered, taking into account their features and environmental characteristics in order to reduce harmful emissions. The list of thermal power plants recommended for conversion to natural gas burning is determined, as well as the list of thermal power plants where it is advisable to use boilers with a ring furnace or boilers with a low-temperature vortex furnace. The potential volume of reduction of harmful emissions from the introduction of advanced technologies for fuel combustion at thermal power plants of the region is estimated.

Aerodynamic structure of a swirling turbulent flow in a vortex furnace

Insufficient study of the swirling flow structure, stability of high-temperature circulating zones, intensity of fuel and oxidizer mixture formation and other determining phenomena in the vortex furnaces indicates insufficiency of scientific substantiation of the methods for their calculation. Therefore, further detailed studies of aerodynamics of a turbulent swirling flow in a vortex chamber with intersection of the main flow by the inlet tangential jets aimed at the development of promising combustion devices seem to be relevant. The results of numerical simulation of the turbulent swirling flow aerodynamics with preference given to the modern models of turbulence and numerical schemes of high-order approximation are presented.

Inner aerodynamics of the improved four-vortex furnace model

The internal aerodynamics of a perspective vortex furnace chamber of a pulverized coal boiler with a diagonal arrangement of burners is studied using the non-contact optical method of flow diagnostics: Particle Image Velocimetry - PIV. The results of PIV measurements, characterizing the complex spatial structure of a swirled flow in an isothermal laboratory model of the furnace device, are presented. The velocity distribution in the vortex chamber volume is obtained, and the flow structure in the form of four conjugate closed vortices with curved axes is visualized.

Studying the Flow Structure in a Promising Vortex Furnace

The internal aerodynamics of an isothermal laboratory model of a modified four-vortex furnace for a pulverized coal boiler have been experimentally studied. The digital tracer imaging (particle image velocimetry) technique was used to determine average flow velocity distributions and streamline projections in several sections of the model in various regimes of furnace operation determined by the velocity ratio of flows supplied via primary (main) and secondary nozzles. Conditions for the formation of a stable flow structure with four symmetric conjugated vortices in the entire volume of the furnace, as well as the domain of parameters leading to a nonregular spatial vortex structure, were determined.

DEVELOPMENT OF THE DESIGN SCHEME OF THE COMBUSTION CHAMBER FOR BURNING OF WOOD CHIPS THE OLD SLEEPERS

А calculation scheme for the utilization of chips of old wooden sleepers in a vortex furnace is proposed. The vortex furnace provides two zones of reaction of a combustible substance with air: the primary zone is the gasification of old sleepers and the afterburning of the solid residue with a lack of air oxygen, the secondary zone is the burning of the gas phase. The initial data for the thermodynamic calculation is given. The results of the equilibrium calculation of the thermal decomposition of wood on the grate and the combustion of gasification products are presented for different values of the excess air factor, as well as some experimental data. A comparison of the calculation results with the experimental data is carried out.

Investigation of inner aerodynamics of the four-vortex furnace model

The internal aerodynamics of a perspective vortex furnace chamber of a pulverized coal boiler with a diagonal arrangement of burners is studied using the non-contact optical method of flow diagnostics. The results of laser Doppler anemometry, characterizing the complex spatial structure of a swirling flow in an isothermal laboratory model of the furnace device, are presented. The velocity distribution in the vortex chamber volume is obtained, and the flow structure in the form of four conjugate closed vortices with curved axes is visualized.

Combustion of Solid Fuel in a Vortex Furnace with Counter-swirling Flows

Combustion of Solid Fuel in a Vortex Furnace with Counter-swirling Flows

Numerical study of aerodynamics and brown coal combustion in the vortex furnace with air excess variation

The results of numerical modelling of 3D turbulent two-phase reacting flow with account for all the principal heat and mass transfer processes during the pulverized brown coal combustion in the vortex furnace of a power plant boiler unit have been presented. For two computational cases where air excess coefficient α was varied (set to 1.15 and 1.25), the detailed aerothermochemical 3D structure of reacting flow in the furnace volume has been revealed. The comparison of integral heat engineering parameters and NOx emissions obtained in the two cases has shown a slightly improved vortex furnace performance in the case α=1.25.

Identification of possible non-stationary effects in a new type of vortex furnace

The article presents the results of an experimental study of pressure and velocity pulsations in the model of improved vortex furnace with distributed air supply and vertically oriented nozzles of the secondary blast. Investigation of aerodynamic characteristics of a swirling flow with different regime parameters was conducted in an isothermal laboratory model (in 1:25 scale) of vortex furnace using laser Doppler measuring system and pressure pulsations analyzer. The obtained results have revealed a number of features of the flow structure, and the spectral analysis of pressure and velocity pulsations allows to speak about the absence of large-scale unsteady vortical structures in the studied design.