WO2019221640A1

WO2019221640A1 - Device and method for flame combustion of fuel

Info

Publication number: WO2019221640A1
Application number: PCT/RU2019/050061
Authority: WO
Inventors: Павел Борисович СТЕРЛИГОВ; Юрий Иванович НАУМОВ
Original assignee: Общество с ограниченной ответственностью "КОТЭС Инжиниринг"
Priority date: 2018-05-15
Filing date: 2019-05-15
Publication date: 2019-11-21
Also published as: EP3627047A4; EP3627047A1; EP3627047B1; RS64712B1

Abstract

The invention "Device and method for flame combustion of fuel" relates to the field of power generation and can be used in thermal power stations, in boiler houses, etc., for optimizing and controlling the combustion process and for allowing firing of boilers and for stabilizing the burning of fuel, for example pulverized coal, during the flame combustion thereof, without the use of an additional highly reactive fuel. The claimed invention allows stable ignition, burning and effective combustion of fuel, including even low-reactive fuel, by the connection of a constant voltage source to at least one of the rod electrodes, relative to the shell of the ignition chamber, and the mounting of a flame-generating chamber, to which a secondary air duct leads, at the outlet of the ignition chamber.

Description

Device and method for flaring fuel

[0001] Technical Field

[0002] The invention relates to energy and can be used in thermal power plants, boiler houses, etc. to optimize and control the combustion process and ensure the ignition of boilers and stabilize the combustion of fuel, for example, coal dust, during its flaring without the use of additional highly reactive fuel.

[0003] Background

[0004] A technical solution is known, disclosed in patent N ° RU2514534 (F23Q 5/00; published on 04/27/2014), which contains the following set of essential features: feeds the air-fuel mixture into the ignition zone, creates an electric arc discharge in the ignition zone, ignites the air-fuel mixture, flares fuel in the combustion chamber.

[0005] All of the above features are common with the proposed technical solution.

[0006] The application of the known method of ignition and flaring of fuel is difficult when burning low-reactive fuels, such as coal dust, due to the difficulty of providing the process of ignition and maintaining the burning of the torch. This is due, first of all, to the relatively high cost of electric energy, which is 2-3% of the thermal power of the ignited torch. The resource of continuous operation of devices that implement these methods, at the same time, is tens of hours, which makes it difficult to use them for continuous use to control the combustion mode of fuel during its flaring.

[0007] There is a known method of burning pulverized coal, taken for the prototype described in patent N ° RU2498159 (F23Q 5/00; published 10.1 01.2013), which consists in creating an electric arc discharge in the ignition zone, the air-fuel mixture is fed into the zone ignitions, ignite the air-fuel mixture in the ignition zone, create a diffuse electric discharge and act by diffuse electric discharge on the border zone of the formation of the flame of the burning fuel and carry out the flaring of the fuel.

[0008] A technical solution is known, disclosed in patent for invention N ° RU2377467C2 (IPC F23D 1/00; published December 27, 2009), which is a device for flaring fuel. This device contains an ignition chamber, the inner surface of which has a cylindrical shape, a feed channel for the fuel mixture in this chamber, a plasma torch equipped with rod electrodes. The plasma torch is mounted on the side surface of the ignition chamber, at its entrance. The device also contains a nozzle of the ignition chamber, in which the plasmatron is installed, and a secondary air channel. [0009] In the design of this device, there is no separation into the ignition chamber and the cooling chamber, secondary air is supplied directly to the ignition chamber. In this regard, the risk of rapid separation of the torch and its extinction during operation of this device increases, which is a significant disadvantage of the known device.

[0010] The technical solution disclosed in the patent for invention N ° RU2059926Cl (IPC F23D 1/00, F23Q 13/00; published on 05/10/1996), which is a fuel flaring device, is known. This device contains a channel for supplying fuel mixture, a secondary air channel with a swirl installed in it, a plasma torch igniter with rod electrodes. This device is characterized in that the plasmatron-igniter with rod electrodes is installed in the feed mixture, the electrodes are made of graphite and placed along the entire length of the feed mixture, and the plasmatron-igniter is equipped with double-flow nozzles and installed with the possibility of longitudinal movement between the rod electrodes, the plasma torch nozzles are oriented at the ends of the electrodes.

[OOP] From the point of view of operation, this device is characterized by low reliability of ignition of pulverized coal fuel, as well as a large specific electric power of the burner and its large size. This, in turn, leads to high specific energy costs during operation of the known device, which is a significant drawback. In addition, due to the rapid wear of the rod electrodes, it becomes necessary to replace them, which complicates the process of servicing the known device for flaring fuel. As a prototype, the well-known technical solution is disclosed in the invention patent N ° RU24l0603Cl (IPC F23Q 5/00, F23Q 13/00; published on January 27, 2011), which is a device for flaring fuel. This device comprises a housing, rod electrodes connected to a source of high-frequency alternating current, for generating an electric arc, a channel for supplying fuel mixture and a secondary air channel, according to the invention, the housing is divided into an ignition chamber and a cooling chamber, wherein the secondary air passage is installed in the cooling chamber with installed in it with rod electrodes. The indicated features are common with the proposed technical solution.

[0012] The disadvantage of this device is the limited thermal power of the initiated flare and the impossibility of organizing the optimal process of burning the entire volume of fuel, since the design of the known device is focused only on the creation of the initiating flare. The supply of secondary air to the ignition chamber also limits the volume of flammable pulverized coal due to the need to increase air volumes and, as a consequence, the values of the flow rate of the mixture are unacceptable, in terms of flame separation. The disadvantages of this device include the low reliability of ignition of low-reactive fuels (lean, ballasted and watered fuels, such as coal water). This is primarily due to the subsequent ignition of the main torch from the received torch. When burning fuel with a high degree of slag formation, slagging of the surfaces of the ignition chamber can occur, which requires constant maintenance. This leads to a decrease in the reliability of the ignition system.

[0013] Summary of the invention

[0014] The objective of the claimed invention is to provide a device and method that would be able to provide stable ignition and efficient combustion of the entire amount of pulverized coal supplied to the burners of the boiler, with reduced requirements for combustible fuel (ballasted, lean, waterlogged coal), and temperature fuel and air supplied to the burner, which ensures that the boiler starts up from a cold state with cold components and with minimal electrical energy consumption without the use of a high reaction nnogo fuel. That ensures the reliability of the boilers and the safety of the processes of kindling and fuel combustion.

[0015] The technical result of the claimed invention is the possibility of flaring fuel, including low reaction, and increasing the efficiency of its combustion.

[0016] The efficiency of fuel combustion is understood to mean the generation of thermal energy with its minimum losses (minimum excess air, that is, close to the stoichiometric value, as well as minimal chemical and mechanical underburning of the fuel).

[0017] The reason for the impossibility of achieving the above technical result is that in known technical solutions when flaring low-reaction fuel, for example, coal dust, when changing its technical composition (humidity, ash, etc.), the intensity of chemoionization processes can decrease and, as a consequence, a decrease in the electrostatic potential of the flame zone of the flame, which leads to unstable combustion of the fuel and the extinction of the flame.

[0018] Given the characterization and analysis of known technical solutions, we can conclude that the task of ensuring sustainable ignition and stabilizing the combustion mode of fuel during its flaring is relevant today.

[0019] The technical result provided by the invention is achieved in that the fuel flaring device comprises an ignition chamber, an alternating current source, at least two rod electrodes connected to an alternating current source, a fuel mixture supply channel, a secondary air channel and a cooling chamber, between the chamber Ignition and cooling made passages for the installation of rod electrodes. The inventive device for flaring fuel is characterized in that at least one of the rod electrodes is connected, relative to the shell of the ignition chamber, a constant voltage source, and at the output of the ignition chamber a torch forming chamber is installed, to which a secondary air channel is connected. This device design allows the excitation of a diffuse electric discharge between the electrodes, which produces ionization and ignition of the fuel mixture. In this case, due to chemoionization processes, a highly ionized pre-flame zone of the torch is formed, which is the main condition for ensuring heterogeneous chemical reactions of oxidation of the fuel mixture, which makes it possible to efficiently burn low-reaction fuel, i.e., the oxidation reaction, which has a high chemical reaction rate. The presence of at least one rod electrode, connected to it, relative to the shell of the ignition chamber, with a constant voltage source, allows you to maintain a highly ionized state of the pre-flame zone of the torch and to ensure that the necessary conditions for the complete combustion of the fuel mixture during its flaring are fulfilled. In addition, the presence of a secondary air channel connected to the torch forming chamber ensures the formation and burning of the torch in the furnace by supplying secondary air to the torch forming chamber through the secondary air channel. Thus, the creation of the possibility of flaring fuel is achieved, as well as increasing the efficiency of burning low reactive fuel.

[0020] The rod electrodes are mounted on heat and conductive racks, the other end of which is mounted on support plates placed in the cooling chamber in isolation relative to the conductive surfaces of the device. This allows, on the one hand, to reliably fix the rod electrodes, and on the other hand, to remove excess heat from the rod electrodes and base plates. This leads to an increase in the life of the rod electrodes, increasing the reliability of the device for efficient combustion of low-reaction fuel.

[0021] In addition, the cooling chamber is provided with a channel for supplying sealing air, and the secondary air is supplied to the flare chamber. This allows you to remove heat from the rod electrodes by supplying sealing air to the cooling chamber, which leads to efficient heat removal from the electrodes of the device, which increases the reliability of the device for efficient burning of low reaction fuel. Also, the supply of secondary air to the chamber of the formation of the torch ensures optimal formation of the torch and, as a result, the efficiency of burning low-reactive fuel using the inventive device for flaring fuel.

[0022] The technical result is achieved using the method of burning pulverized coal, which consists in creating an electric arc discharge in the ignition zone, supplying the air-fuel mixture to the ignition zone, igniting the air-fuel mixture in the ignition zone, creating a diffuse electric discharge, acting on the diffuse electric discharge on the border zone of flame formation and carry out flaring of fuel, while setting the value of the electrostatic potential border zone of flame formation at a given level, providing the required parameters of fuel combustion during its flaring.

[0023] Description of the Drawings

[0024] The implementation of the invention is described hereinafter in accordance with the accompanying drawings, which are presented to illustrate the essence of the invention and in no way limit the scope of the invention.

[0025] The following drawings are attached to the application:

[0026] FIG. 1 is a schematic diagram of a device for flaring fuel;

[0027] FIG. 2 is a schematic diagram of an ionization block;

[0028] These figures have the following positions:

[0029] 1: the feed channel of the fuel mixture;

[0030] 2: an ionization unit;

[0031] 3: a torch forming chamber,

[0032] 4: an alternating current source;

[0033] 5: a constant voltage source;

[0034] 6: ignition chambers;

[0035] 7: cooling chambers;

[0036] 8: rod electrodes;

[0037] 9: current and heat conductive racks;

[0038] 10: insulators;

[0039] 1 1: support plates;

[0040] 12: fasteners;

[0041] 13: passages for electric cable;

[0042] 14: passage for introducing cooling air;

[0043] 15: aisle for racks.

[0044] Detailed Description of the Invention

[0045] Numerous implementation details are set forth in the following detailed description of an embodiment of the invention to provide a clear understanding of the present invention. However, it is obvious to a person skilled in the art how to use the present invention, both with and without implementation details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the understanding of the features of the present invention.

[0046] Furthermore, it is clear from the foregoing that the invention is not limited to the foregoing implementation. Numerous possible modifications, changes, variations and substitutions, preserving the essence and form of the present invention, are obvious to those skilled in the field of specialists. [0047] The present invention is directed to a device and method that would be able to provide stable ignition and efficient burning of the entire amount of pulverized coal supplied to the burners of the boiler, with reduced requirements for combustible fuel (ballasted, lean, watered coals), and temperature the supplied fuel and air to the burner, which ensures the start-up of the boiler from a cold state with cold components and with minimal energy consumption without the use of highly reactive fuel.

[0048] As a fuel mixture, any known fuel air mixture can be used. A fuel mixture is a mixture of air or an oxidizing gas, for example, oxygen, and fuel. The fuel used can be in any aggregate state (solid, liquid or gaseous), however, the necessary condition is the size of the particles or drops of fuel, if solid or liquid fuel is used as a component of the fuel mixture, respectively. The particle size for solid fuels should not exceed 60 microns. At the same time, for liquid fuel, the droplet size should not exceed 10 microns. Examples of solid fuels that can be used as a component of air mixtures are coal, peat, wood waste, etc. Examples of liquid fuels that can be used as a component of air mixtures are petroleum products, coal-water fuels, etc.

[0049] As an alternating current source 4, an alternating current source of any known design can be used, for example, a commercially available converter of the power source of a plasma generator IRBI943-5.4 UHL3.1V. As a constant voltage source 5, a constant voltage source of any known design can be used, for example, a commercially available high voltage source, built according to the voltage multiplication scheme, IVNR-5/50. The ionization unit 2 contains an ignition chamber 6, a cooling chamber 7, rod electrodes 8 mounted on current and heat-conducting racks 9, supporting insulators 10 mounted outside the ignition chamber 6, which serve as a support for the plate 11 connected by fasteners 12 to insulators 10 and stand 9. In the cooling chamber 7, which is hermetically sealed, passages are made for the electric cable 13, passage 14 for introducing cooling air and passage 15 for racks 9.

[0050] The feed channel of the fuel mixture 1 may be made of any known structural material, for example, steel. The ionization unit 2 can be made of any known conductive structural material, for example, steel. The rod electrodes 8, the racks 9 and the support plate 11, in turn, can be made of any known current-conducting and heat-conducting material, for example, copper or bronze. The chamber forming the torch 3 can be made of any known heat-resistant material. As an example, the torch forming chamber 3 can be made of heat-resistant alloy steel, for example, steel grade X20H35. In addition, the torch forming chamber 3 may have an internal high temperature thermal insulation coating made using any known refractory material, for example, material made on the basis of chamotte powder, refractory clay, etc., resistant to temperature in the temperature range, the upper limit of which reaches 1500 ° C - 1700 ° C.

[0051] The operation of the device and the implementation of the method of flaring plasma fuel is as follows:

[0052] create an electric arc discharge in the ignition zone, supply the air-fuel mixture to the ignition zone, ignite the air-fuel mixture in the ignition zone, create a diffuse electric discharge, apply a diffuse electric discharge to the boundary zone of flame formation and carry out flaring of the fuel, while maintaining the electrostatic the potential of the border zone of flame formation at a given level.

[0053] It is known, [Lauton D., Weinberg F. Electrical aspects of combustion. / Per. with English, ed. V.A. Popova. M .: Energia, 1976. - 296 s], that the process of flame formation, the stability and intensity of the combustion of the entire torch depend on the state of the pre-flame zone, which is especially important when burning low-reaction fuel (coal dust, carbon-coal fuel) which cannot be burned in conventional conditions that require the use of additional measures, for example, pre-heating of the fuel and oxidizer.

[0054] In the ignition chamber 6 through the channel 1 for supplying the fuel mixture serves prepared aerosol mixture of fuel. From the AC source 4, AC voltage is applied to the rod electrodes 8 in the frequency range 1-30 kHz, the breakdown of the interelectrode space occurs, as a result of which the electrical circuit is closed. As a result of this, a diffuse electric discharge is excited, which produces ionization and ignition of the fuel mixture. In this case, due to chemoionization processes, a highly ionized pre-flame zone of the torch is formed, which is the main condition for ensuring heterogeneous chemical reactions of oxidation of the entire volume of the fuel mixture. Due to the relatively high electrical conductivity, the diffusion discharge acquires an equal electrostatic potential, which provides the required electrostatic potential of the pre-flame zone. With a change in this potential, a change in the intensity of the ionic wind takes the flame products of combustion into the ignition zone and supports the processes of fuel ignition along with chemical processes in the highly ionized regions of the diffuse discharge and the flame zone of the flame. With a decrease in the voltage of a constant-voltage source, the potential of the pre-flame zone of ignition decreases, while the concentration of charges in the pre-flame zone of the torch, the amount of ionic wind and, as a result, the intensity of the torch burning up to its extinction decrease. Ensuring the occurrence of heterogeneous chemical processes is the main condition for burning low-reactive fuels, including coal-water fuels. To ensure high the ionized state of the flame zone of the flame, at least one rod electrode 8 is supplied with an electrostatic potential from a constant voltage source 5 relative to the conductive surface of the ignition chamber 6. The ignition chamber 6 can be made as part of the channel 1 for supplying the fuel mixture. The ignited aerosol mixture enters the torch formation chamber 3, where the main chemical processes take place. Further, the formed torch containing highly activated components of the fuel and the oxidizing agent enters the furnace of the boiler, in which the complete combustion of the fuel is carried out. When changing the characteristics of the fuel, its volume, etc. regulate the value of the potential of the pre-flame zone, providing the required parameters of the flame burning. The range of variation of the electric potential is in the range from 0, 1 to 5 kV.

[0055] To ensure the formation and combustion of the torch in the furnace, secondary air is supplied through the secondary air channel to the torch forming chamber 3. Excess air in the chamber forming the torch 3 is set taking into account the organization of fuel combustion in the furnace.

[0056] The heat generated on the rod electrodes 8 is removed through the conductive racks 9 to the support plate 1 1, which is cooled by the seal air entering under the shell of the ionization unit 2. After that, the heat is discharged into the ignition chamber of the torch 3 through passages 15 for the conductive racks 9, made in the ignition chamber of the torch 3. Part of the thermal energy from the rod electrodes 8 and racks 9 is removed by the flow of fuel mixture, which ensures the durability of the rod electrodes 8.

[0057] At the exit from the flame forming chamber 3, a fuel mixture is obtained with a temperature in excess of 700 ° C. and a combustible content in the gas phase of up to 50%. Such a mixture burns steadily, which makes it possible to increase the reliability of the torch burning even in a cold furnace, which makes it possible to use this device for firing up boilers without the use of highly reactive fuel, providing a high degree of fuel burnout.

[0058] The frequency of operation of the AC source 4 is selected from the conditions for ensuring a stable diffuse discharge and technical limitations associated with the technical implementation, is in the range of 3-50 kHz. To limit the erosion of the rod electrodes 8, the amplitude value of the current should be in the range of 0, 1 - 2 A, which ensures the durability of the rod electrodes 8 without replacing them.

[0059] The options for implementing the sequence of actions in the method and device described in the text of this application are confirmed by tests, but are not the only ones possible and are presented with the aim of most clearly disclosing the essence of the invention.

[0060] The claimed invention is technologically advanced and easy to use and manufacture.

Claims

Formula

1. A device for flaring fuel containing an ignition chamber, an alternating current source, at least two rod electrodes connected to an alternating current source, a fuel mixture mixture supply channel, a secondary air channel, a cooling chamber, and passageways for installing rod ends are made between the ignition and cooling chamber electrodes, characterized in that, at least to one of the rod electrodes, relative to the shell of the ignition chamber, a constant voltage source is connected, and at the output to ignition chamber forming measures set torch to which secondary air passage is brought.

2. The device for flaring fuel according to claim 1, characterized in that the rod electrodes are mounted on heat and conductive racks, the other end of which is mounted on support plates placed in the cooling chamber in isolation relative to the conductive surfaces of the device.

3. The fuel flaring device according to claim 1, characterized in that the cooling chamber is provided with a channel for supplying sealing air, and the secondary air is supplied to the flare chamber.

4. The method of flaring fuel, which consists in creating an electric arc discharge in the ignition zone, feeding the air-fuel mixture into the ignition zone, igniting the air-fuel mixture in the ignition zone, creating a diffuse electric discharge, applying a diffuse electric discharge to the border zone of flame formation, and flaring fuel, characterized in that while maintaining the electrostatic potential of the border zone of flame formation on given level.