RU229922U1 - Burner for combustion of low-calorie and waste gases - Google Patents

Abstract

The utility model relates to burner devices and can be used in organizing the combustion of various low-calorie gas fuels, including waste gases, together with natural gas in a wide range of ratios by heat fraction in combustion chambers of thermal power plants and industrial furnaces. The burner for burning low-calorie and waste gases comprises a central channel 2 for fuel supply with a gas-distributing nozzle 3 installed at the outlet, around which and coaxially with it, an internal annular air channel 4 with fuel tubes 13 of the peripheral gas manifold, an external annular air channel 5 and an annular channel 6 of low-calorie gas, in which axial vane swirlers 10, 11 and 12 are installed, are successively located. At the end of the outer shell of the annular channel 6 of low-calorie gas, a confuser 16 with a convergence angle from 10° to 30° can be installed. This design allows to increase the speed of mixing air with the low-calorie gas flow and to increase the stability of ignition and combustion of fuel due to the formation of two paraxial zones of reverse flows of hot combustion gases, and also, if necessary, to redistribute air to the area with a deficiency of oxidizer by feeding it to the burner through two air channels with installed axial blade swirlers. The utility model ensures an increase in the efficiency of combustion of various low-calorie gas fuels, including waste gases, together with natural gas in a wide range of ratios by heat fraction with ensuring the reliability of the design and combustion stability under various loads and operating modes of the burner device.

Description

The utility model relates to burner devices and can be used in organizing the combustion of various low-calorie gas fuels, including waste gases, together with natural gas in a wide range of ratios by heat fraction in combustion chambers of thermal power plants and industrial furnaces.

A burner device is known for burning and completely thermally rendering harmless various gas fuels, including ballasted gases, together with natural gas or without it (RU No. 77396 U1, IPC F23D 14/58, 2008), comprising an air supply box and a mixing chamber, a middle channel with swirler blades and a central channel located coaxially in it. Nozzles are installed axially-tangentially in the distributing air box, through which primary air enters the mixing chamber and mixes with a pre-swirled gas flow. Such an arrangement of nozzles allows for uniform distribution of primary air in the exhaust gas flow and for the fuel to be burned as quickly and completely as possible, as a result of which the combustion flame is shortened and the dimensions of the combustion chamber are reduced. The diameter of the middle channel is 0.55-0.65 of the diameter of the outlet nozzle of the burner device, which allows maintaining maximum productivity of the device and ensures combustion of exhaust gases outside the burner device, without the return of flue gases into the burner device and its damage due to overheating.

The disadvantage of this burner device is the lack of the ability to increase the proportion of natural gas when it is necessary to partially replace low-calorie fuel due to the presence of only one channel for supplying natural gas to the backlight, as well as the lack of the ability to adjust the torch when changing the composition and/or fuel consumption by adjusting the speed of mixing air with fuel, which reduces the efficiency of gas combustion. In addition, due to the supply of part of the air through the air nozzles and its subsequent complete mixing with the exhaust gas before exiting the burner, the reliability of the burner device is reduced due to the location of the torch in close proximity to the internal elements of the burner, such as air nozzles and axial swirler blades in the central air channel, which can lead to their overheating and damage.

The closest in technical essence is a burner device for burning low-calorie gas (RU No. 211642 U1, IPC F23D 14/22, 2022), containing an air duct, peripheral gas-distributing tubes coaxially located therein, a central pipe for supplying natural gas for illumination, on which an axial swirler is located, occupying 0.4-0.7 of the cross-section of the air duct, a barrel for a fuel oil nozzle is located inside the central pipe, a snail swirler located along the outer perimeter of the air duct for supplying low-calorie gas, a low-calorie gas channel, while the gas-distributing tubes are located along the perimeter of the axial swirler and are designed with the possibility of supplying natural gas. The technical result of ensuring the efficiency of combustion of low-calorie gas with a minimum amount of natural gas illumination is achieved by the fact that the flow of low-calorie gas is swirled by a snail swirler and supplied along the outer perimeter of the air flow, where the low-calorie gas is heated by high-temperature combustion products from the furnace, which, together with the axial zone of reverse currents, ensures its reliable ignition and burnout.

The disadvantage of this burner device is the low speed of mixing of low-calorie gas with air and, as a consequence, the reduced intensity of fuel combustion due to the fact that part of the air closest to the low-calorie gas supply area is supplied without swirling, which leads to a decrease in the efficiency of fuel combustion, protracted combustion and, as a consequence, an increase in the length of the torch of the burner device. Moreover, when burning low-calorie gas together with natural gas in a wide range of the ratio by heat fraction and/or a wide range of fuel characteristics, the efficiency of fuel combustion also decreases due to the supply of all air through one channel and the lack of the ability to redistribute air from the burner axis to the periphery and back to exclude areas with a rich mixture, which can lead to local deficiencies of the oxidizer and a significant prolongation of combustion. At the same time, in other areas, zones with high excess air may form, which leads to intense combustion of fuel and an increase in local temperatures of the gas mixture, thereby reducing the reliability of the burner device due to overheating and damage to internal elements.

The technical objective of this utility model is to increase the efficiency of combustion of various low-calorie gas fuels, including waste gases, together with natural gas in a wide range of ratios by heat fraction and a wide range of fuel characteristics, while ensuring the reliability of the design and combustion stability under various loads and operating modes of the burner device.

The technical result is achieved in that the burner for burning low-calorie and waste gases contains a central channel for feeding fuel along the burner axis, around which and coaxially with it, an annular air channel with fuel tubes of the peripheral gas manifold located at the same distance from the burner axis and a vane swirler installed at the outlet of the channel, an annular channel of low-calorie fuel are located. According to the utility model, the air channel is divided into an internal annular air channel with an axial vane swirler installed at the outlet of the channel and an external annular air channel, wherein the height h of the internal annular air channel and the diameter D of the outer shell of the external annular air channel have a certain ratio. In this case, the fuel tubes of the peripheral gas manifold are located in the outer part of the internal annular air channel, and axial vane swirlers with profiled blades are installed in the external annular air channel and in the low-calorie gas channel. A confuser can be installed at the end of the outer shell of the annular channel of low-calorie gas.

The design of the burner for burning low-calorie and waste gases is shown in the drawings:

Fig. 1 – longitudinal section of the burner;

in fig. 2 – view A in Fig. 1.

Fig. 1 additionally shows: A – the illumination zone due to combustion of high-calorie fuel of the central fuel supply channel; B – the zone of mixing of low-calorie gas with air and heating to its ignition temperature; B – the zone of afterburning of low-calorie fuel.

The burner for burning low-calorie and waste gases is mounted on the wall of the boiler furnace 1. It contains a central channel 2 for fuel supply with a gas-distributing nozzle 3 installed at the outlet. Around the central channel 2 and coaxially with it, an internal annular channel 4 of air, an external annular channel 5 of air and an annular channel 6 of low-calorie gas are sequentially located, which are equipped, respectively, with inlet pipes 7, 8 and 9. In the internal annular channel 4 of air, an axial vane swirler 10 is installed at the outlet, and in the external annular channel 5 of air and in the annular channel 6 of low-calorie gas, axial vane swirlers 11 and 12 with profiled vanes are installed, respectively. Through the internal annular air channel 4 at the outer wall of the channel, in the direction of the burner axis and uniformly around the circumference, the fuel tubes 13 of the peripheral gas manifold pass, at the outlet of which the fuel dispensing nozzles 14 and the ignition device 15 are installed. The recommended optimal number of fuel tubes 13 of the peripheral gas manifold is from 4 to 8.

The height h of the inner annular air channel 4 is related to the diameter D of the outer shell of the outer annular air channel 5 as follows:

,

where h is the height of the inner annular air channel 4;

D – diameter of the outer shell of the outer annular air channel 5.

At the end of the outer shell of the annular channel 6 of low-calorie gas, a confuser 16 with a convergence angle from 10° to 30° can be installed.

The burner for burning low-calorie and waste gases operates as follows.

When the burner is operating for burning low-calorific and waste gases in the nominal load mode and with the maximum thermal fraction of low-calorific gas, high-calorific fuel is supplied through the gas-distributing nozzle 3 of the central channel 2 of the fuel supply in the amount of 3% by thermal fraction and the burner is ignited by means of the igniter 15 installed in the internal annular air channel 4. For this purpose, air necessary for ignition and combustion of the fuel is supplied through the inlet pipe 7 into the annular channel 4. The axial blade swirler 10 at the outlet of the annular channel 4 swirls the air flow, thereby improving the mixing of high-calorific fuel with air and forming a near-axial zone of reverse flows of hot combustion gases, which makes it possible to increase the stability of fuel ignition in this area and create a zone of illumination A. The excess of oxidizer in zone A of combustion of high-calorific fuel of the central channel 2 of fuel supply leads to intensification of fuel combustion and an increase in local gas temperatures, which contributes to stable ignition and combustion of low-calorific fuel due to heating (illumination) to its ignition temperature.

After heating the furnace through the annular channel 6 of low-calorie gas, fuel is gradually supplied simultaneously with an increase in the air supply through the inlet pipe 8 into the outer annular channel 5. The air flow from the outer annular channel 5 passes through the axial vane swirler 11 and swirls, rushing to the periphery, which promotes intensive mixing with the low-calorie gas flow from the annular channel 6, as a result of which zone B is formed for preliminary mixing of the low-calorie gas with the oxidizer and heating of the mixture to the ignition temperature from high local temperatures in zone A. The direction of swirling of the flows in the inner annular channel 4 of air, the outer annular channel 5 of air and the annular channel 6 of low-calorie gas coincides. To increase the intensity of mixing of low-calorie fuel with the oxidizer, a confuser 16 with a constriction angle of 10° to 30° can be installed at the end of the outer shell of the annular channel 6 of low-calorie gas. This allows for an additional increase in the rate of mixing of low-calorie fuel with the oxidizer by deflecting the fuel flow directly into the air flow from the outer annular channel 5. After heating the mixture of low-calorie gas and air from the illumination of high-calorie gas and hot combustion gases, it ignites and burns intensively.

Due to the swirling of the low-calorie gas and air flows from the outer annular channel 5 after the start of ignition, a near-axial zone B of reverse flows of the mixture of hot reaction products and unburned low-calorie fuel is formed, which ensures the stability of the afterburning of the low-calorie fuel. Unspent air from the inner annular channel 4 enters zone B after the combustion of the high-calorie fuel in zone A, as a result of which complete afterburning of the low-calorie fuel occurs.

When the burner operates in the nominal load mode and with an increase in the thermal fraction of natural gas to 60%, high-calorific fuel is supplied through the gas-distributing nozzle 3 of the central channel 2 of the fuel supply in the amount of 5% by thermal fraction and the burner is ignited by means of the igniter 15 installed in the internal annular air channel 4. The air required for ignition and combustion is supplied to the annular channel 4 through the inlet branch pipe 7, where it is swirled by the axial blade swirler 10, as a result of which a paraxial zone of reverse currents of hot furnace gases is formed, and the stability of fuel ignition in this area is increased.

After the establishment of stable combustion of the fuel of the central channel 2 through the nozzles of distribution 14 of the fuel tubes 13 of the peripheral gas manifold and the annular channel 6 of low-calorie gas, fuel begins to be gradually supplied simultaneously with an increase in the air supply through the inlet pipe 8 into the outer annular channel 5. In this case, the excess air in the central axial region is significantly reduced due to the supply of additional high-calorie fuel to this zone through the fuel tubes 13 of the peripheral gas manifold. Therefore, some of the air from the outer annular channel 5 is transferred to the inner annular channel 4 to increase the excess air in the central axial region, which allows for stable ignition and combustion of the fuel in this zone.

The air flow from the outer annular channel 5 is swirled by the axial blade swirler 11, after which one part of the flow promotes intensive combustion of the fuel of the peripheral gas manifold, and the other part is mixed with the flow of low-calorie gas from the annular channel 6. The large thermal fraction of high-calorie fuel promotes the formation of a region with high local combustion temperatures, which ensures high stability of the afterburning of low-calorie fuel.

The optimum ratio of the height h of the inner annular channel 4 and the diameter D of the outer shell of the outer annular channel 5 is 0.20−0.35. Such a ratio ensures the optimum division of the air flow between the inner annular channel 4 and the outer annular channel 5 with the possibility of redistributing part of the air from one annular channel to the other. When the ratio of the height h of the inner annular channel 4 and the diameter D of the outer shell of the outer annular channel 5 is less than 0.20, the air flow rate may be insufficient to ensure stable ignition and combustion of the fuel in the near-axial region of the burner, especially in combustion modes with an increase in the thermal fraction of natural gas. Moreover, there is no possibility of transferring a significant portion of the air from the outer annular channel 5 to the inner annular channel 4 due to a significant increase in the aerodynamic resistance of the burner along the inner annular channel 4 of air. When the ratio of the height h of the inner annular channel 4 and the diameter D of the outer shell of the outer annular channel 5 is more than 0.35, the mixture of low-calorie gas and air in the initial section becomes richer in fuel, which leads to less stable ignition and combustion of the low-calorie gas, as a result of which the efficiency of burning low-calorie fuels decreases.

The use of the proposed burner for burning low-calorie and waste gases makes it possible to increase the efficiency of burning various low-calorie gas fuels together with natural gas in a wide range of heat fraction ratios and a wide range of fuel characteristics, ensuring the reliability of the design and combustion stability under various loads and operating modes of the burner device.

Claims (5)

1. A burner for burning low-calorie and waste gases, comprising a central channel for feeding fuel along the burner axis, around which and coaxially with it are located an annular air channel with fuel tubes of a peripheral gas manifold located at the same distance from the burner axis and an axial vane swirler installed at the outlet of the channel, an annular channel of low-calorie fuel, characterized in that the air channel is divided into an internal annular air channel with an axial vane swirler installed at the outlet of the channel and fuel tubes of a peripheral gas manifold located in the outer part of the channel and an external annular air channel, in the external annular air channel and in the low-calorie gas channel axial vane swirlers with profiled vanes are installed, wherein the height h of the internal annular air channel and the diameter D of the outer shell of the external annular air channel have a ratio h/D=0.20–0.35, where h is the height of the inner annular air channel; D – diameter of the outer shell of the outer annular air channel. 2. A burner according to item 1, characterized in that a confuser with a convergence angle of 10° to 30° is installed at the end of the outer shell of the annular channel of low-calorie gas.