RS64712B1 - Device and method for flame combustion of fuel - Google Patents

Description

Description

Technical field

[0001] The invention relates to the field of energy and can be used in thermal power plants, boiler houses, etc. in order to optimize and control the combustion process and ensure the ignition of boilers and stabilization of fuel combustion, for example coal dust, in the process of its combustion without using additional highly reactive fuel.

State of the art

[0002] A known technical solution is described in patent no. RU2514534 (F23Q 5/00; published on 04/27/2014) which contains the following set of essential features: the air-fuel mixture is fed into the ignition zone, an electric arc discharge is created in the ignition zone, the air-fuel mixture is ignited and the fuel is burned in the combustion chamber.

[0003] All the aforementioned characteristics are common with the proposed technical solution.

[0004] The known procedure of fuel ignition and combustion is difficult to apply when burning low-reactive fuels, for example coal dust, due to the complexity of ensuring the ignition process and maintaining the burning of the torch. First of all, it is due to the relatively high consumption of electricity, which accounts for 2-3% of the thermal power of the burning torch. At the same time, the continuous operation resource of such devices in which these procedures are applied amounts to tens of hours, which makes it difficult to use them during continuous operation in order to control the mode of fuel combustion in the process of its combustion.

[0005] There is a well-known procedure for burning powdered coal, which is considered to be the closest prior art, and the said procedure is described in patent no.

RU2498159 (F23Q 5/00; published 10/11/2013), which consists of creating an electric arc discharge in the ignition zone, bringing the air-fuel mixture to the ignition zone, igniting the air-fuel mixture in the ignition zone, creating a diffuse electric discharge and applying the diffuse electric discharge to the boundary zone of fuel flare formation and fuel ignition.

[0006] The technical solution described in patent no. RU2377467C2 (IPC F23D 1/00; published 27.12.2009) and it is a device for burning fuel. The mentioned device contains an ignition chamber, the inner surface of which is cylindrical in shape and which has a supply connection for bringing the air-fuel mixture into the mentioned chamber and a plasmatron with rod electrodes. The plasmatron is placed on the side surface of the ignition chamber in its entrance part. The device also contains an ignition chamber nozzle in which the plasmatron is placed and a secondary air connection.

[0007] The design of this device does not provide separation between the ignition chamber and the cooling chamber, so secondary air is supplied directly to the ignition chamber. This increases the risk of sudden separation of the torch and its extinguishing during the operation process of the mentioned device, which is a significant disadvantage of this known device.

[0008] The technical solution described in patent no. RU2059926C1 (IPC F23D 1/00, F23Q 13/00; published 10.05.1996), which is a device for burning fuel. This device consists of an air-fuel mixture supply port, a secondary air port in which a vortex device is placed, and a plasmatron for ignition with rod electrodes. The mentioned device is characterized by the fact that the plasmatron igniter with rod electrodes is placed in the connection for supplying the air and fuel mixture, the electrodes are made of graphite and placed along the entire length of the connection for supplying the air and fuel mixture, and the plasmatron-ignitor has two-flow nozzles and is installed with the possibility of longitudinal movement between the rod electrodes, whereby the plasmatron nozzles are oriented towards the ends of the electrodes.

[0009] In terms of the mode of operation, this device is characterized by a low reliability of ignition of powdered fuel, as well as a large specific electrical power of the burner and its bulky size. This, in turn, leads to high specific energy consumption during the operation process of this well-known device, which represents its significant disadvantage. In addition, due to the rapid wear of the rod electrodes, there is a necessity to replace them, which complicates this known device due to fuel combustion maintenance operations. As the closest state of the art, the known technical solution described in patent no. RU2410603C1 (IPC F23Q 5/00, F23Q 13/00; published 01/27/2011) which is a fuel burning device. This device contains a housing, rod electrodes connected to a source of high-frequency alternating current to generate an electric arc, a connection for the supply of air and fuel mixture and a secondary air connection, whereby according to the invention the housing is divided into an ignition chamber and a cooling chamber, where a secondary air passage is formed within the cooling chamber in which the rod electrodes are placed. The mentioned characteristics are common with the proposed technical solution.

[0010] The disadvantage of this device is its limited thermal power of the initiated torch and the impossibility of organizing the optimal process of burning the entire amount of fuel since the design of this known device is focused only on the generation of the torch flame. The supply of secondary air to the combustion chamber also limits the amount of combustible pulverized coal due to the need to increase the air volume, and as a consequence, the air-fuel mixture flow rates are unacceptable in terms of flare separation. The low reliability of ignition of low-reactive fuel (mixture of fuel and air with more air than fuel, ballast and wet fuel, for example when coal and water sludge is used) should also be counted as a disadvantage of this device. This is primarily due to the after-ignition of the main flare from the resulting flare. When burning fuel with a high degree of slag formation, slag deposits can occur on the surface of the combustion chamber, which requires persistent maintenance. This leads to a decrease in the reliability of the ignition system.

[0011] A known technical solution is described in small patent no. RU65177U1, which describes a burner intended for an electric power system, i.e. a burner for ignition, which can be used in thermal power plants, boiler houses, etc. for burning powdered fuel. The burner contains a feed line for the pulverized coal mixture, an ignition channel with ignition electrodes placed along its entire length, and a secondary air supply channel. The housing of the ignition channel is made in the form of a pipe with a diameter larger than the diameter of the pipe for supplying the powdered coal mixture. The ignition electrodes are made in the form of a coaxial anode formed by the housing of the ignition channel and the rod cathode. The outer surface of the ignition channel housing has a dielectric coating.

Presentation of the essence of the invention

[0012] The aim of the present invention is to provide a device and a procedure that would be able to ensure stable ignition and efficient combustion of the entire amount of powdered fuel that is fed to the boiler burners, with reduced requirements in terms of combustible fuel (ballasted, lean and water-soaked coals) as well as the temperature of the fuel and air that are fed to the burner, thus ensuring that the boiler is started from a cold state with cold components and with minimal consumption of electricity without the use of high reactive fuel. This ensures the reliability of the boiler operation and the safety of the ignition and fuel combustion process.

[0013] The technical result of the present invention is the possibility of burning fuel, including low-reactive fuel, and increasing the efficiency of its combustion.

[0014] The efficiency of fuel combustion implies the production of thermal energy with minimal losses (minimum air excess, ie close to the stoichiometric value, as well as minimal chemical and mechanical fuel combustion).

[0015] The reason for the impossibility of achieving the specified technical result using known technical solutions is that in the process of burning low-reactive fuel, for example coal dust, the intensity of the chemical ionization process can be reduced when changing its technical composition (moisture, ash, etc.) with the resulting decrease in the electrostatic potential of the pre-flame zone of the torch, which further leads to unstable fuel combustion and extinguishing of the torch.

[0016] Taking into account the characteristics and analysis of known technical solutions, it can be concluded that the problem of ensuring sustainable ignition and stabilization of the way of burning fuel in the process of its combustion is current to this day.

[0017] The technical result obtained by the invention is achieved by the fact that the fuel ignition device contains an ignition chamber, an alternating current source, at least two rod electrodes connected to the alternating current source, a connection for the supply of air and fuel mixture, a secondary connection for air and a cooling chamber, whereby the passages for placing the rod electrodes are formed between the ignition chamber and the cooling chamber. In the device for igniting fuel according to the invention, a source of constant voltage is connected to at least one of the rod electrodes, relative to the casing of the ignition chamber, while the flame forming chamber with the secondary air connection connected to it is placed at the exit of the ignition chamber. Such a design of the device enables the excitation of a diffuse electrical discharge between the electrodes, which produces ionization and ignition of the air-fuel mixture. Furthermore, as a result of the chemical ionization process, a highly ionized pre-flame zone of the igniter is formed, which is the main condition for ensuring heterogeneous chemical oxidation reactions of the air and fuel mixture, which enables efficient combustion of low-reactive fuel, i.e. an oxidation reaction that has a high rate of chemical reactions. The presence of at least one rod electrode with a source of constant voltage to which it is connected in relation to the ignition chamber envelope allows maintaining a highly ionized state of the pre-flame zone of the torch and ensures that the necessary condition for complete combustion of the fuel mixture in the process of its ignition is met. In addition, the presence of a secondary air port connected to the flare chamber ensures the formation and burning of the flare in the furnace by supplying secondary air to the flare chamber through the secondary air port. This creates opportunities for fuel combustion, and also increases the efficiency of low-reactive fuel combustion.

[0018] Stick electrodes are placed on thermally conductive and electrically conductive supports, the other end of which is fixed to the supporting plates placed inside the cooling chamber, isolated from the electrically conductive surfaces of the device. On the one hand, this enables reliable fixing of the rod electrodes, while on the other hand it enables the removal of excessive heat from the rod electrodes and the supporting plates. This leads to an increase in the service life of the rod electrodes, thus increasing the reliability of the device for efficient combustion of low-reactive fuel.

[0019] In addition, the cooling chamber has a sealing air supply port that supplies secondary air to the flare chamber. This allows heat to be removed from the rod electrodes by supplying sealing air to the cooling chamber, resulting in efficient heat removal from the electrodes in the device and increasing the reliability of the device for efficient low-reactive fuel combustion. Supplying secondary air to the flare chamber also ensures optimal flare formation and, as a result, low-reactive fuel combustion efficiency using the fuel ignition device of the invention.

[0020] The technical result is achieved by using the procedure for burning pulverized coal, which consists of the formation of an electric arc in the ignition zone inside the ignition chamber, bringing the mixture of air and fuel through the supply connection to the ignition zone, igniting the mixture of air and fuel in the ignition zone, creating a diffuse electric discharge, applying a diffuse electric discharge to the pre-flame zone and performing fuel combustion while adjusting the amplitude of the electrostatic potential of the pre-flame zone at a predetermined level by means of a source of constant voltage, which provides the necessary parameters for fuel combustion in the process of its ignition.

Description of the draft images

[0021] The implementation of the invention is described below in accordance with the attached figures which are presented to illustrate the essence of the invention and which in no way limit the scope of the invention.

[0022] The following images are attached to the application:

FIGURE 1 shows a basic schematic of a fuel ignition device;

FIGURE 2 shows the basic schematic of the ionization unit;

[0023] The mentioned images contain the following callsigns:

1: connection for air and fuel mixture supply;

2: ionization unit;

3: chamber for forming the torch;

4: alternating current source;

5: constant voltage source;

6: combustion chambers;

7: cooling chambers;

8: rod electrodes;

9: electrically conductive and thermally conductive supports;

10: insulators;

11: support plates;

12: fasteners;

13: passages for electric cable;

14: cooling air supply passage;

15: passage for carriers.

Detailed description of the invention

[0024] Numerous implementation details are set forth in the following detailed description of the invention in order to provide a clear understanding of the subject invention. However, it will be apparent to one skilled in the art how to practice the subject invention both with and without these implementation details. In other cases, well-known methods, procedures and components are not described in detail so as not to make it difficult to understand the features of the subject invention.

[0025] Furthermore, it is clear from the foregoing that the invention is not exclusively and only limited to the implementation described above. Numerous possible modifications, alterations, variations and substitutions will be apparent to those skilled in the art without departing from the scope of the subject invention.

[0026] The present invention is aimed at the development of devices and procedures that would be able to ensure stable ignition and efficient combustion of the entire amount of powdered coal fed to the boiler burners, with reduced requirements in terms of highly flammable fuel (ballasted, lean and water-soaked coal) and for the temperatures of fuel and air supplied to the burner, thus ensuring the start-up of the boiler from a cold state with cold components and with minimal consumption of electricity without the need to use reactive fuel.

[0027] Any known air/fuel mixture can be used as the fuel mixture. A fuel mixture is a mixture of fuel and air, or an oxidizing gas, such as oxygen. The fuel used can be in any aggregate state (solid, liquid or gaseous), however, a necessary condition is the size of the fuel particles or drops, if solid or liquid fuel is used as a component of the fuel mixture, respectively. The size of solid fuel particles should not exceed 60 microns. At the same time, the droplet size for liquid fuel should not exceed 10 microns. Examples of solid fuels that can be used as a component of the air-fuel mixture are coal, peat, wood processing waste, etc. Examples of liquid fuel that can be used as a component of the air-fuel mixture are petroleum products, water-coal fuel, etc.

[0028] As AC source 4, an AC source of any known design can be used, for example a commercially available IRBI9435-0.4 UHP3.1B plasma generator power supply converter. As the constant voltage source 5, a constant voltage source of any known design can be used, for example a commercially available high voltage source made according to the voltage multiplication scheme, IVNR-5/50. The ionization unit 2 contains an ignition chamber 6, a cooling chamber 7, electrodes 8 that are placed on electrically conductive and thermally conductive supports 9, supporting insulators 10 placed outside the ignition chamber 6 that serve as a support for a plate 11 that is connected to insulators 10 and supports 9 by fasteners 12. In the cooling chamber 7, which is hermetically sealed, a passage for an electric cable is formed 13, passage 14 for cooling air supply and passage 15 for supports 9.

[0029] The connection 1 for supplying the mixture of air and fuel can be made of any known construction material, for example of steel. The ionization unit 2 may be made of any known electrically conductive construction material, for example steel. The electrodes 8, supports 9 and support plate 11 can further be made of any known electrically conductive and thermally conductive material, for example copper or bronze. The torch forming chamber 3 may be made of any known heat-resistant material. For example, the chamber 3 for forming the torch can be made of a thermo-resistive steel alloy, for example steel class X20H35. In addition, the torch forming chamber 3 may have an internal high-temperature thermal insulation coating made using any known flame-resistant material, for example a material based on fireclay powder, fireclay clay, etc., which is temperature-resistant in a temperature range whose upper limit reaches 1500°C -1700°C.

[0030] The way the device works and the application of the plasma fuel ignition procedure are as follows: a discharge in the form of an electric arc is created in the ignition zone, a mixture of air and fuel is brought to the ignition zone, a mixture of air and fuel in the ignition zone is ignited, a diffuse electric discharge is created, a diffuse electric discharge is applied in the border zone of flame formation and the fuel is ignited, while maintaining the electrostatic potential of the border zone of flame formation at a given level.

[0031] It is known [Lauton D., Weinberg F. Electrical aspects of combustion. / Translation from English under the editorship of V. A. Popov. M.: Energy, 1976. - 296 pages] that the flame formation process, stability and burning intensity of the entire torch depend on the condition of the pre-flame zone, which is especially important when burning low-reactive fuel (coal dust, water coal as fuel) that cannot burn under normal conditions, so additional measures are required, for example, preheating of fuel and oxidizer.

[0032] The prepared mixture of air and fuel is supplied through connection 1 for supplying the mixture of air and fuel to the chamber 6 for ignition. From source 4 of alternating current, voltage of alternating current with a frequency in the range of 1 to 30 kHz is supplied to electrodes 8 and there is a breakdown of the inter-electrode space, as a result of which the electrical circuit is welded. As a result, a diffuse electrical discharge is excited that produces ionization and ignition of the air-fuel mixture. At the same time, as a result of the chemical ionization process, a highly ionized pre-flame zone of the torch is formed, which is the main condition for ensuring the occurrence of heterogeneous chemical reactions of oxidation of the entire amount of air and fuel mixture. Due to the relatively high electrical conductivity, the diffuse discharge acquires an equal electrostatic potential that provides the required electrostatic potential in the pre-flame zone of the torch. With a change in this potential, there is a change in the intensity of the ionic wind, which carries the combustion products into the ignition zone and supports fuel ignition processes along with chemical processes in the highly ionized parts of the diffuse discharge and the pre-flame zone of the igniter. As the voltage of the constant voltage source decreases, the potential of the pre-flame zone of the torch also decreases, whereby in the pre-flame zone of the torch, the concentration of charge, the amount of ion wind decreases and as a result, the burning intensity of the torch decreases to the point of its extinction. Ensuring the occurrence of heterogeneous chemical processes is the main condition for burning low-reactive fuels, including water coal as a fuel. In order to ensure a highly ionized state of the pre-flame zone of the igniter, at least one rod electrode 8 is supplied with an electrostatic potential from a constant voltage source 5, viewed relative to the electrically conductive surface of the ignition chamber 6. The ignition chamber 6 can be made as part of the air mixture supply port 1

1

and fuel. The ignited mixture of air and fuel enters the chamber 3 for the formation of the torch, where the main chemical processes take place. Further, the formed flare containing highly activated fuel and oxidizer components enters the furnace of the boiler where complete combustion of the fuel takes place. When changing the parameters of the fuel, its amount and the like, the value of the potential of the pre-flame zone is corrected, thus providing the necessary parameters for burning the torch. The range of electric potential variation is from 0.1 to 5 kV.

[0033] In order to ensure the formation and combustion of the torch in the furnace, secondary air is supplied to the chamber 3 for the formation of the torch through the connection for secondary air. The excessive amount of air in the chamber 3 for the formation of the torch is adjusted taking into account the fuel combustion mode in the furnace.

[0034] The heat generated on the rod electrodes 8 is conducted through the electrically conductive supports 9 to the support plate 11 which is cooled by the welding air entering under the casing of the ionization unit 2. After that, the heat is released into the torch ignition chamber 3 through the passages 15 for the electrically conductive supports 9 formed in the torch ignition chamber 3. Part of the thermal energy from the rod electrodes 8 and the support 9 is removed by the flow of the air and fuel mixture, which ensures the longevity of the rod electrodes 8.

[0035] At the exit from the chamber 3 for the formation of the torch, a fuel mixture is obtained with a temperature above 700°C and a content of combustible materials up to 50% in the gas phase. Such a mixture burns stably, which makes it possible to increase the reliability of burning the torch even in a cold furnace, which further makes it possible to use this device for igniting boilers without the use of highly reactive fuel, ensuring a high degree of fuel combustion.

[0036] The operating frequency of the AC source 4 is selected based on the conditions required to ensure a stable diffuse discharge and the technical limitations related to the technical realization and ranges from 3-50 kHz. In order to limit the erosion of the rod electrodes 8, the current amplitude should be in the range of 0.1-2 A, which ensures the durability of the rod electrodes 8 without their replacement.

[0037] The execution of the sequence of operations in the procedure and the device as described in the text of this application was confirmed through tests, but it is not exclusively the only possible variant and is presented for the purpose of the clearest description of the essence of the invention.

[0038] The invention applied for is technologically advanced and easy to use and manufacture.

Claims (4)

PATENT REQUESTS 1. A fuel ignition device consisting of an ignition chamber (6), a source (4) of alternating current, at least two electrodes (8) connected to the source (4) of alternating current, a connection (1) for supplying the air-fuel mixture, a secondary air connection and a cooling chamber (7), where passages for placing rod electrodes (8) are formed between the ignition chamber (6) and the cooling chamber (7), where a constant voltage source (5) is connected with at least one of the rod electrodes (8) relative to the casing of the ignition chamber (6), and the torch forming chamber (3) with associated secondary air connection is positioned at the outlet of the ignition chamber (6). 2. Fuel ignition device according to claim 1, where the rod electrodes (8) are attached to thermally conductive and electrically conductive supports (9), the other end of which is attached to support plates (11), are placed inside the cooling chamber (7) isolated from the electrically conductive surfaces of the device. 3. A fuel ignition device according to claim 1, wherein the cooling chamber (7) has a sealing air supply connection, and secondary air is supplied to the chamber (3) for forming the flare. 4. The method of fuel ignition using the device according to claim 1, which contains the steps of forming a discharge in the form of an electric arc in the ignition zone inside the ignition chamber (6), bringing the air and fuel mixture through the supply connection (1) into the ignition zone, igniting the air and fuel mixture in the ignition zone, creating a diffuse electric discharge, applying a diffuse electric discharge to the pre-flame zone and performing fuel ignition, whereby the electrostatic potential of the pre-flame zone is maintained at a given level using a source (5) of constant voltage.