RU2731081C1 - Method for flare combustion of a fuel-air mixture and device for realizing a method using an electro-ionization igniter - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: invention relates to power engineering and can be used at thermal power plants, in boiler houses, etc. to provide self-ignition of boiler from cold state. Device for ignition and maintenance of combustion of fuel-air mixture includes housing divided into mixing area of fuel-air mixture and area of ignition chamber, unit of rod electrodes for generation of electric discharge, fuel pipeline and air pipeline, ignition zone of fuel-and-air mixture, zone of fuel-air mixture combustion. Ignition chamber area is divided into two parts: an accelerating section with low heat capacity and heat transfer of structural elements, made without muffling elements, and an accumulating section with high heat capacity of structural elements, made with a muffle, fuel line complete with electrode unit, tangentially connected to zone between sections with low and high heat capacity, two secondary air pipelines tangentially connected to sections with low and high heat capacity and providing movement of ignition area from section with low heat capacity to section with high heat capacity due to change of ratio of forward pressure in pipelines of secondary air. Fuel pipelines complete with electrode unit are two, each of which is tangentially connected separately to sections with low and high heat capacity, providing the possibility of movement of the area of ignition and burning of the flame from the section with low heat capacity to the section with high heat capacity due to ignition and disconnection of electric discharge on separate electrode units on the corresponding sections.

EFFECT: invention allows igniting fuel mixture with high content of moisture and low level of volatile components, as well as water-coal fuel mixture with minimum specific energy costs and to minimize mechanical carryover at the moment of kindling to safe level and to ensure stabilization of combustion of coal-dust and water-coal fuel mixtures with low reactivity.

5 cl, 2 dwg

Description

The invention relates to power engineering and can be used at thermal power plants, boiler rooms, etc. to ensure self-ignition of the boiler from a cold state and to ensure the stabilization of the combustion of pulverized coal and water-coal fuel mixtures with low reactivity.

There is a known method of burning low-grade coals and a plasma torch for its implementation (patent RU No. 2059926, C1, MKI F23D 1/00, F23Q 13/00, 1992), which consists in generating an electric plasma arc in a plasma torch-igniter with rod electrodes, heating the air mixture in arc plasma, ignition and stabilization of the combustion of air mixture. Generation of an electric plasma arc is carried out in the air mixture supply channel made in the burner. For this, an electric plasma arc is initially generated in the specified channel and its plasma flows excite the main arc, while the plasmatron-igniter is moved along the rod elements as they eroded destruction.

The disadvantage of this method is the high energy consumption of the igniter plasmatron, as well as the small volumetric contact of the arc discharge of the plasmatron and the pulverized coal mixture. In this case, the chemical activation of pulverized coal particles occurs only due to the thermal effect of the arc plasma, with a temperature of up to 6000 degrees, on the flows of the fuel mixture adjacent to the plasma jet. Local high-temperature impact on the fuel mixture leads to explosive evaporation of mineral components of the fuel in this local area with their further condensation on the surfaces of the burner, which leads to slagging of these surfaces and a decrease in the efficiency of the burner. In this case, a significant proportion of coal particles, not in contact with the hot plasma, enters the furnace in a cold state, does not participate in combustion reactions and contributes to the formation of mechanical entrainment from the furnace.

A device for oil-free kindling of a boiler with an inductor is known (Energy-saving systems for kindling and lighting the torch of boiler furnace chambers: monograph by VA Dubrovsky, MV Zubov. - Krasnoyarsk: Siberian Federal University, 2012, p. 94). The presented device contains a dust source, an air supply channel, a pilot burner, an ignition-signaling device, an electric heater made in the form of a magnetic inductor coil with a muffle. The ignition burner is connected to the combustion chamber and is made in the form of an annular channel surrounded by a magnetic inductor coil. Boiler firing works as follows. The inductor and the ignition-signaling device are turned on. The annular channel and the muffle are warmed up due to the combustion of flammable fuel in it. Then dust is fed, which, due to centrifugal force, is thrown to the outer hot wall of the ring at the inductor, mixed with air, crushed on impact and ignited by an ignition-signaling device. After stabilization of the combustion of the flame in the pilot burner and its entry into the operating mode, the ignition-signaling device is turned off, and then the inductor is also turned off. Due to the fact that all the dust heats up before being fed to the pilot burner of the boiler furnace, ignition occurs more efficiently and trouble-free kindling of the boiler is ensured.

However, in the described technical solution, the heating of the dust by the magnetic coil of the inductor does not provide the required level of activation for igniting the dust at lower temperatures, and is also accompanied by high energy costs for heating.

There is a known method of fuel combustion, adopted as a prototype (patent RU No. 2410603, Device for flaring fuel, C1, IPC F23C 99/00, F23Q 5/00, 2019), which consists in the fact that the fuel is ignited by an electric discharge, stabilizes and intensifies combustion of the torch, acting on the zone of flame formation with an alternating electric current of high frequency, forming a diffuse electric discharge in the zone of flame formation, and maintain the electrostatic potential of the pre-flame zone at a level that provides the required parameters of the torch combustion.

Known device for plasma ignition of pulverized coal, adopted as a prototype, contains a housing, rod electrodes for generating an electric arc, a fuel line and a secondary air line (patent RU No. 2410603, C1, MKI F23Q 5/00, F23Q 13/00, 2009). The body is divided by a transverse baffle into resonance and cooling chambers. In the center of the partition, a secondary air passage is made and rod electrodes are installed in it with the possibility of longitudinal movement, and their working part is directed into the resonance chamber, and an electric arc is created by an alternating current of high frequency in the resonance chamber with the formation of an acoustic field.

The disadvantages of this method and device, adopted as prototypes, is the low heating rate of the burner structure at the initial stage of starting from a cold state, as a result of which there is a large mechanical entrainment of unburned coal dust into the boiler furnace, which increases the risk of increasing the concentration of unburned dust in the furnace, above the critical to blast the level. In addition, at a low heating rate, the possibility of using low-reactive fuels when operating boilers is limited.

The problem solved by the proposed invention is to create a method and device for its implementation using electro-ionization ignitors, which allow, with minimal specific energy consumption, to provide the maximum heating rate of the torch and burner design elements that ensure stable and complete combustion of the fuel mixture with low reactivity at the heating stage from a cold state, thereby minimizing mechanical entrainment into the furnace, eliminating the risk of cotton or explosion in the boiler.

The achievement of the technical result provided by the invention becomes possible due to the fact that the electroionization ignition at the initial stage of heating the burner from the cold state occurs in the area with low heat capacity and heat transfer, as a result of which heat losses due to its accumulation in the surrounding structures and heat transfer to the environment are minimized. The minimization of these heat losses leads to the maximum rate of growth of the temperature of the burner walls and, as a consequence, the temperature of the flame in the burner in the ignition zone to a level sufficient for stable ignition of low-reaction fuels and minimization of mechanical entrainment of unburned fuel into the boiler furnace. When the specified temperatures are reached in the section with low heat capacity, a gradual rise in temperature occurs in the muffle section, due to the redistribution of heat fluxes. After reaching the temperature of the muffle section of the values required for the process, the zone of electroionization ignition is transferred to the muffle section and further work on which ensures stable ignition when supplying increased volumes of fuel with an increase in the thermal power of the burner. At the same time, a minimum level of mechanical entrainment into the boiler furnace is ensured by stabilizing the temperature in the ignition zone. Simultaneously with this, the active part of the torch exits into the furnace chamber of the boiler and is warmed up. At the same time, in the section of the burner with a low heat capacity, the secondary air supply circuit can switch to cooling the section with a low heat capacity, where the rate of temperature rise is no longer required. Such switching ensures the cooling of the part of the burner with a low heat capacity to the permissible values for reliability and safety, while heating the secondary air, in turn, increases the efficiency of the entire combustion process.

The movement of the area of electroionization ignition from the area of low heat capacity and heat transfer to the area of high heat capacity, according to the present invention, can be performed using several methods implemented in the devices:

- by redistributing the pressure of the secondary air in areas with low and high heat capacity, based on the aerodynamic conditions providing the position of the ignition zone;

- by turning off the discharge in the electrode block in the area with low heat capacity and turning on the discharge in the electrode block in the area with high heat capacity.

For the second case, the enhancement of the effect of increasing the heating rate in the section with low heat capacity can be achieved by supplying fuel with a higher reactivity to this section.

Strengthening the effect of increasing the thermal power after the initial heating is ensured by adding the connection of additional sections with the electrode blocks of the burner to the area with high heat capacity.

To implement the described method according to the invention, the following devices are proposed.

The design of the device body has a cylindrical shape and consists of two parts. The first part with low heat capacity and heat transfer to the environment consists of an inner cylindrical metal generatrix surrounded by an outer closed cavity with air. It is possible to pump secondary air through this cavity. The inner cylindrical generatrix, made of metal, has a low heat capacity, which minimizes heat losses from the torch for heat accumulation by the surrounding structures and ensures a rapid increase in the temperature of its surface during torch burning. The outer closed cavity is thermally insulated from the inner one, and in the gap between them, at the initial stage, there is stationary air with low thermal conductivity. In this case, a low coefficient of heat transfer from the inner metal generatrix to the environment is provided, and, consequently, minimization of heat losses from the flame and an increase in the heating rate of the burner walls.

The second part of the housing having a high heat capacity is made in the form of a muffle. When heating the muffle, stabilization of the flame combustion and the possibility of increasing the amount of the combustible fuel mixture are provided, thus increasing the thermal power of the burner.

The burner fuel line is tangentially integrated into the forming cylindrical part of the burner. In the area where the fuel line is connected to the burner, an electric discharge electrode unit is located, which ensures effective activation of the fuel mixture, which is twisting in a spiral, inside the burner.

The secondary air ducts are separately connected to the sections with low and high heat capacity tangentially along the direction of rotation of the fuel mixture.

Fuel lines complete with electrode blocks in different versions are joined to the burner, either on the line of demarcation of these sections (when using one fuel line, see Fig. 1.), or separately in areas with low and high and heat capacity (when using two fuel lines, see Fig. . 2.).

In the section of the burner with a low heat capacity, the secondary air circuit can be connected both directly to the inner region of the burner, and by connecting this section of the burner to the air duct of the inner air cavity, providing cooling of the inner generatrix.

To increase the thermal power of the burner, it is possible to section the muffle section of the burner by adding sections with separate fuel lines complete with electrode blocks made according to the standard design.

From the prior art, no solutions have been identified that have features that coincide with the distinctive features of the invention. Therefore, it can be argued that the proposed technical solutions meet the requirement of an inventive step.

The essence of the invention is illustrated by the attached drawings

FIG. 1 shows a longitudinal and cross-section of a burner device for electroionization ignition of a coal fuel mixture with one fuel inlet.

The proposed burner device using electroionization ignition of the fuel-air mixture contains a housing (1), divided into two parts, an accelerating section (2) with low heat capacity and heat transfer of structural elements, made without muffle elements and an accumulating section (3) with a high heat capacity of structural elements, made with a muffle (4), a fuel line (5) complete with an electrode block (6) tangentially connected to the area between areas with low and high heat capacity, two secondary air ducts (7) tangentially connected separately to areas with low and high heat capacity , a power source (9) for generating an electric discharge (8), which forms an ignition zone (10) for the torch (11) during the heating up of the burner device, an ignition zone (12) for the torch (11) during the stationary operation of the burner device.

FIG. 2 shows a longitudinal section of a burner device for electroionization ignition of a coal fuel mixture with two fuel inputs.

The proposed burner device using electro-ionization ignition of the fuel-air mixture comprises a housing (1) divided into two parts, an accelerating section (2) with low heat capacity and heat transfer of structural elements, made without muffle elements, and an accumulating section (3) with a high heat capacity of structural elements, made with a muffle (4), two fuel lines (5, 15) complete with electrode blocks (6, 14) tangentially connected, respectively, to sections with low and high heat capacity, two secondary air ducts (7) tangentially connected separately to sections with low and high heat capacity, electric discharge (8, 16), initiated on the block of electrodes connected to the power source (9, 13), ignition zone (10) for the flame (11) during the heating up of the burner device, ignition zone (12) for the flame (11) during the stationary operation of the burner.

The proposed method and device for flaring the fuel mixture is implemented as follows.

Fuel and primary air are supplied to the inner section of the housing (1) with a low heat capacity through the fuel line (5). An alternating current of high frequency is supplied from the power source (9) to the block of rod electrodes (6), as a result of which an electrical discharge (8) is initiated. The ratio of the flow rates of the secondary air supplied through the air ducts (7) along the sections of the chamber is selected so that the fuel mixture is squeezed out to the section with low heat capacity (2). The fuel mixture is activated and ignited, passing through the electro-ionized plasma, forming an ignition zone (10) in the inner region of the area with low heat capacity (2). After complete warming up of this section of the burner and reaching stable combustion of the torch, the minimum mechanical entrainment of fuel into the boiler furnace is ensured. Further, there is a gradual heating of the section (3) with the muffle (4). After heating the muffle (4) to temperatures of stable flame combustion, the ratio of the secondary air flow rates through the air ducts (7) is selected in such a way as to bring the fuel mixture directly to the section with the muffle (4), bypassing section (2) and shifting the ignition to the zone (12 ). After that, the heat load on the section with low heat capacity (2) decreases and this section switches to the cooling mode with secondary air through its internal air cavity.

The main flame (11) is forced into the boiler furnace zone, part of the heat load on the burner is removed, after which it becomes possible to increase fuel consumption without the risk of increasing mechanical entrainment.

After increasing the fuel consumption to the required values, a steady combustion mode is ensured with minimal energy consumption to ensure the process.

In the case of using a device with two fuel inlets (5) and (15), the transition of the ignition zone (10) to the ignition zone (12) occurs when the power source (9) is turned off, the initiation of the electric discharge (8) is stopped, the power source is turned on (13 ), initiation of an electric discharge (16), fuel supply through the fuel line (15), and formation of an ignition zone (12).

In the version of the burner with two fuel inlets, it is possible to supply different types of coal in terms of reactivity. At the same time, an increase in the effect of increasing the heating rate in the area with low heat capacity (2) is provided due to the supply of fuel with a highly reactive ability through the fuel line (6), as a result of which the heat release in the ignition zone (10) increases. For the transition of ignition from zone (10) to zone (12), fuel with low reactivity is supplied through the fuel line (15), thus providing an optimal economical mode of fuel use.

The proposed invention makes it possible to ignite a fuel mixture with a high moisture content and a low level of volatile components, as well as a water-coal fuel mixture with minimal specific energy consumption and to minimize mechanical carryover at the time of ignition to a safe level.

Claims (5)

1. The method of flare combustion of a fuel-air coal mixture, which consists in the fact that inside the burner create an electric discharge in the ignition zone of the torch, supply the fuel-air mixture to the ignition zone of the torch, act with a diffuse electric discharge on the zone of formation of the flame of the torch and carry out flare combustion of fuel, characterized in that, that the process of flame ignition is carried out with regulation of the rate of the flame temperature rise and the temperature of the burner walls in the area of flame combustion, by moving the position of the flame ignition zone inside the burner to the area with low heat capacity and heat transfer of the burner structure, where the rate of flame temperature rise increases, and after the temperature regime and ensuring the minimization of mechanical entrainment, the position of the flame ignition zone is moved to the area with a high heat capacity of the burner structure, where the rate of the flame temperature rise decreases, heat accumulation increases, the temperature the flame is stabilized, providing an increase in heat output and optimization of fuel use. 2. A device for ignition and maintenance of combustion of a fuel-air mixture, containing a housing divided into a mixing area of the fuel-air mixture and an ignition chamber area, a block of rod electrodes for generating an electric discharge, a fuel line and an air pipeline, an ignition zone of a fuel-air mixture, a zone of a combustion flame of an air-fuel mixture, characterized by that the area of the ignition chamber is divided into two parts: an accelerating section with low heat capacity and heat transfer of structural elements, made without muffle elements, and an accumulating section with a high heat capacity of structural elements, made with a muffle, a fuel line complete with a block of electrodes tangentially connected to the zone between areas with low and high heat capacity, two secondary air pipelines tangentially connected separately to areas with low and high heat capacity and ensuring the movement of the ignition area from the area and with a low heat capacity to a section with a high heat capacity due to a change in the ratio of the pressure head in the secondary air pipelines. 3. Device according to claim 2, characterized in that there are two fuel lines complete with the block of electrodes, each of which is tangentially connected separately to sections with low and high heat capacity, making it possible to move the area of ignition and combustion of the torch from a section with low heat capacity to a section with high heat capacity due to the ignition and shutdown of the electrical discharge on individual electrode blocks in the corresponding areas. 4. The device according to claim 3, characterized in that the muffle part consists of several sections with separate built-in fuel lines, complete with blocks of rod electrodes, providing an increase in the thermal power of the torch when the ignition passes to the area with high heat capacity. 5. The device according to claim 3, characterized in that a separate fuel line complete with an electrode block of a section with low heat capacity and heat transfer is connected to a fuel system with fuel with increased reactivity, and a separate fuel line complete with an electrode block of a section with a high heat capacity is connected to a fuel system with fuel of reduced reactivity, ensuring the optimization of fuel use.

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