RU226942U1 - Low emission vortex pulverized coal burner - Google Patents

Abstract

The utility model relates to the energy sector and can be used to organize the combustion of coal dust in the furnaces of boilers, combustion chambers and furnaces. A low-emission vortex pulverized coal burner contains a central channel 2 with a ignition device placed in it, around which and coaxially with it are located an annular channel 3 of the ignition air, an annular channel 4 of the air mixture and at least one annular channel 5 of secondary air, in which axial blade swirlers 9 are installed , 10, 11, along the circumference of the outer shell of the annular channel 4 of the air mixture, flame stabilizers 12 are evenly located, which are made in the form of flat teeth and are installed at an angle from 50 to 85° to the longitudinal axis of the burner in such a way that they direct the flow of the air mixture counter-twisting the axial blade swirler 10. The recommended number of flame stabilizers 12 is from 12 to 20. At the end of the outer shell of the annular channel 4 of the air mixture, a diffuser 13 can be installed with an opening angle from 15 to 45°. This design makes it possible to increase the efficiency of concentrating fuel particles on the wall of the flame stabilizer 12, while the movement of the air mixture in the area between the flame stabilizers 12 in counter-rotation to the remaining flows leads to increased stability of ignition and combustion of the fuel. Due to the increased efficiency of concentrating fuel particles in the active combustion area and the possibility of reducing the total excess air on the burner due to the high stability of fuel ignition, the level of NOx formation is further reduced. The useful model makes it possible to ensure high stability of ignition and combustion for fuels with different reactivity with a low level of NOx formation and reliable operation of the burner at various loads.

Description

The utility model relates to the energy sector and can be used to organize the combustion of coal dust in the furnaces of boilers, combustion chambers and furnaces.

A burner for fuel in the form of particles is known (RU No. 2587020 C2, IPC F23D 1/02, 2012), containing a primary pipe and a central pipe located in the primary pipe, wherein the primary pipe and the central pipe form a gap to ensure the direction of flow from the fuel in the form particles and gaseous combustion agent from the inlet side end to the outlet side opening of the primary tube, wherein the central tube in the longitudinal direction of the burner ends in front of the primary tube, wherein at least one device is provided for centering the flow within the primary tube in the region of the end of the primary tube from the exit side. The central pipe is made tapering towards its end from the outlet side. At the end of the primary pipe on the outlet side there is a flame stabilizer protruding inwards into the flow of the primary pipe, on the inner side of which there is a serrated edge facing radially inwards. This burner reduces NOx formation.

The disadvantages of this burner are the small size of the area with high turbulence intensity due to the low degree of overlap of the outlet section of the primary pipe with flame stabilizers, as a result of which the stability of ignition and combustion of the fuel is reduced, as well as the insufficient concentration of fuel in this area due to the entrainment of a fraction of particles deflected towards the burner axis flow, which does not significantly reduce the level of NOx formation.

The closest in technical essence is a vortex pulverized coal burner (RU No. 2716642 C1, IPC F23D 1/02, 2019), which contains a central channel with a kindling device located in it, around the central channel and coaxially with it there is an annular channel of kindling air, an annular an air mixture channel and at least one annular channel of secondary air, in which blade swirlers are installed; in the outlet part of the air mixture channel, aerodynamic air mixture flow converters are located evenly around the circumference. In this case, the aerodynamic converters of the air mixture flow are made in the form of flat teeth and are installed perpendicular to the longitudinal axis of the burner at the exit from the annular channel of the air mixture, and the height of the aerodynamic converters of the air mixture flow and the height of the annular channel of the air mixture have a certain ratio. The optimal number of aerodynamic air mixture flow converters is from 8 to 14.

The disadvantage of this burner is the breakthrough of the flow of the air mixture with dust particles in the area between adjacent aerodynamic flow converters without interacting with them, which leads to a decrease in the efficiency of fuel concentration, not allowing a significant reduction in the level of NOx formation, as well as insufficient intensity of turbulence in this area, resulting in a decrease stability of ignition and combustion of fuel.

The technical objective of this utility model is to increase the stability of ignition and combustion for fuels with different reactivity and reduce the level of NOx formation.

The technical result is achieved in that the low-emission vortex pulverized coal burner contains a central channel with a ignition device placed in it, around the central channel and coaxially with it there is an annular ignition air channel, an annular air mixture channel and at least one annular secondary air channel in which blades are installed. swirlers; in the outlet part of the air mixture channel, flame stabilizers in the form of flat teeth are located evenly around the circumference. According to the utility model, the flame stabilizers are installed at an angle from 50 to 85° to the longitudinal axis of the burner at the exit from the annular channel of the air mixture in counter-rotation to the movement of the air mixture after the swirler, and the height h of the flame stabilizers and the height H of the annular channel of the air mixture have a certain ratio, the width d of the flame stabilizer and the diameter D of the outer shell of the annular channel of the air mixture have a certain ratio, and at the end of the outer shell of the annular channel of the air mixture a diffuser with an opening angle of 15 to 45° can be installed.

In fig. Figure 1 shows a longitudinal section of a low-emission vortex pulverized coal burner.

In fig. 2 shows section A-A in Fig. 1.

In fig. 3 – location of the torch stabilizers in relation to the oncoming swirling flow of the air mixture.

In fig. 1, 3 additionally show: A – zone with an increased concentration of coal particles in front of the flame stabilizers; B – zone with increased intensity of turbulence, ensuring fuel ignition (stabilizing zone); B – zone of mixing and heating of the air mixture and combustion air; G – zone with air flow from the secondary air channel; D – zone of active combustion and afterburning of coal particles.

A low-emission vortex pulverized coal burner is installed on the wall 1 of the boiler furnace and contains a central channel 2 for placing an igniter and an oil burner (not shown). Around the central channel 2 and coaxially with it, an annular channel 3 of the ignition air, an annular channel 4 of the air mixture and at least one annular channel 5 of the secondary air are located in series, which are equipped, respectively, with inlet pipes 6, 7 and 8. In the annular channel 3 of the ignition air an axial blade swirler 9 is installed, an axial blade swirler 10 is installed in the annular channel 4 of the air mixture, and an axial blade swirler 11 with adjustable twist is installed in the annular channel 5 of the secondary air. At the exit from the annular channel 4 of the air mixture, flame stabilizers 12, made in the form of flat teeth, are installed evenly around the circumference of its outer shell. The torch stabilizers 12 are installed at an angle from 50 to 85° to the longitudinal axis of the burner at the exit from the annular channel 4 of the air mixture in counter-rotation to the axial blade swirler 10, and the height h of the stabilizers of the torch 12 and the height H of the annular channel 4 of the air mixture have the ratio:

,

where h is the height of the flame stabilizers 12;

H – height of the annular channel 4 of the air mixture.

The width d of the flame stabilizer 12 and the diameter D of the outer shell of the annular channel 4 of the air mixture have the ratio:

,

where d is the width of the torch stabilizers 12;

D – diameter of the outer shell of the annular channel 4 of the air mixture.

The recommended number of flame stabilizers 12 is from 12 to 20. At the end of the outer shell of the annular channel of the air mixture, a diffuser 13 can be installed with an opening angle from 15 to 45°.

A low-emission vortex pulverized coal burner operates as follows.

By means of an igniter and a liquid fuel burner (not shown), installed in the central channel 2, the kindling fuel in the firebox is ignited, for which the air necessary for intensive ignition and combustion of atomized fuel, for example, fuel oil, is supplied into the annular channel 3 through the inlet pipe 6 . With the help of an axial blade swirler 9 installed in the annular channel 3, the flow of ignition air and atomized fuel is swirled, which makes it possible to increase the intensity of their mixing and, accordingly, increase the rate of fuel burnout. Additionally, air supplied through ring channel 3 performs the function of cooling the igniter and liquid fuel burner (not shown).

After heating the furnace from the pilot fuel torch, the air mixture is supplied to the annular channel 4 through the inlet pipe 7. Passing through the swirler 10, the flow of the air mixture is twisted, as a result of which solid coal particles are thrown back through centrifugal forces to the outer wall of the annular channel 4 of the air mixture. This leads to the formation of zone A with an increased concentration of coal particles in the area of the outer wall before the air mixture leaves the annular channel 4. A swirling air mixture flow with an uneven distribution of fuel particle concentration along the channel height at the exit from the annular channel 4 meets the torch stabilizers 12, installed at an angle from 50 to 85° to the longitudinal axis of the burner and directing the air mixture flow counter-twisting the axial blade swirler 10. Obstacles along the way the flow of the air mixture in the form of flat teeth contributes to the formation of zone B with an increased intensity of turbulence, into which particles from zone A enter. The increased intensity of turbulence in zone B contributes to the intensive release of volatiles from fuel particles and their mixing with air for further ignition and combustion. An increase in the concentration of fuel particles in this area due to centrifugal forces creates a significant lack of air in zone B, which helps to reduce the intensity of NOx formation, as well as the reduction of formed NOx by hydrocarbon radicals due to the high concentration of volatile fuel components in this area, thereby reducing the overall level NOx formation. Thus, the formation of zone B with increased turbulence intensity makes it possible to increase the stability of ignition and combustion of solid fuel particles, ensure a high rate of fuel burnout due to intensive mixing of fuel with air, and also reduce the level of NOx formation. Installing the flame stabilizers 12 not perpendicular to the flow of the air mixture, but at an angle from 50 to 85° to the longitudinal axis of the burner so that they twist the flow of the air mixture counter-twisting the axial blade swirler 10, makes it possible to prevent some of the fuel from slipping between the flat teeth without interacting with them. In this case, the efficiency of concentrating fuel particles on the wall of the flame stabilizer 12 increases, and the possibility of passage for the air mixture in the area between the teeth remains. This leads to the fact that, firstly, due to the movement of the air mixture behind the flame stabilizers 12 in counter-rotation to the remaining flows, the intensity of turbulence at the boundaries of zone B increases, as a result of which the stability of ignition and combustion of fuel in this area increases. In turn, increasing combustion stability makes it possible to reduce the overall excess air on the burner, which has a beneficial effect on the overall level of NOx formation. Secondly, by increasing the efficiency of concentrating fuel particles, the local excess air in the area of ignition and initial combustion of “fuel” bundles drops even more, which also makes it possible to further reduce the level of NOx formation.

The optimal ratio of the height h of the torch stabilizers 12 and the height H of the annular channel 4 of the air mixture is 0.4÷0.7. This ratio provides the necessary degree of flow turbulization, while ensuring the speed characteristics of the air mixture flow at the exit from the annular channel 4, necessary for better mixing and ignition of the fuel. When the ratio of the height h of the torch stabilizers 12 and the height H of the annular channel 4 of the air mixture is less than 0.4, the stage of flow turbulization in zone B and the characteristic dimensions of this area become insufficient for the intensive release of volatile fuel components, their mixing with the oxidizer and stable ignition. When the ratio of the height h of the stabilizers of the torch 12 and the height H of the annular channel 4 of the air mixture is more than 0.7, the speed characteristics of the air mixture flow increase significantly, as a result of which the residence time of the fuel and the concentration of volatile components in the burner region are reduced, which leads to a decrease in the stability of fuel combustion.

The optimal ratio of the width d of the flame stabilizer 12 and the diameter D of the outer shell of the annular channel 4 of the air mixture is 0.15÷0.25. This ratio provides the necessary degree of overlap of the cross section in zone A of increased fuel concentration at the exit from the annular channel 4 of the air mixture to increase the efficiency of concentration of fuel particles, while the aerodynamic resistance of the area with flame stabilizers 12 remains moderate, which makes it possible to ensure through this zone the necessary flow of the air mixture transporting fuel particles. When the ratio of the width d of the stabilizer of the torch 12 and the diameter D of the outer shell of the annular channel 4 of the air mixture is less than 0.15, the concentration efficiency due to the breakthrough of fuel particles becomes insufficient, which does not significantly reduce the level of NOx formation. When the ratio of the width d of the stabilizer of the torch 12 and the diameter D of the outer shell of the annular channel 4 of the air mixture is more than 0.25, the aerodynamic resistance of the area with the stabilizers of the torch 12 increases significantly, which leads to a decrease in the flow rate of the air mixture between the teeth and a decrease in the efficiency of concentration in zone A due to the entrainment of fuel particles flow of air mixture deviating towards the burner axis.

The remaining part of the air mixture, depleted of fuel particles, passes through the internal region at the exit from the annular channel 4 of the air mixture and mixes with air from the annular channel 3, resulting in the formation of zone B, in which the mixture of gases and fuel particles is preheated to the temperature at which the volatile components are released and the start of ignition. This region is characterized by low temperatures of the gas mixture, a higher excess of air than in zone B, and a predominantly direct-flow nature of the flow. A mixture of gases and fuel particles from zone B can partially move into zone B with increased turbulence intensity.

Simultaneously with the air mixture, secondary air is supplied to the furnace through the inlet pipe 8 through the annular channel 5 of secondary air, which is swirled by an axial blade swirler 11 with adjustable twist. The direction of twisting of the flows in the annular channel 3, the annular channel 4 of the air mixture and the annular channel 5 of the secondary air coincides. At the exit from the annular channel 5, the main share of air, due to the large twist parameter of the swirler 11, is directed to the periphery, forming zone G, characterized by low temperatures and an increased concentration of the oxidizer. Part of the air from this area is drawn into zone B, maintaining stable ignition and combustion of fuel components in a zone of increased turbulence with low excess air. The degree of separation of secondary air from the main dust flow and combustion delay at the initial stage, as well as the speed of their subsequent mixing, depend on the twist of the axial blade swirler 11, which is adjusted during commissioning.

Gradually, zones B, C and D mix, forming zone D, where, due to an increase in the concentration of the oxidizer and the heating of fuel particles, active combustion and afterburning of coal particles occurs, which ensures horizontal staging of combustion and complete fuel burnout.

The use of the proposed low-emission vortex pulverized coal burner makes it possible to ensure high stability of ignition and combustion for fuels with different reactivity with a low level of NOx formation and reliable operation of the burner at various loads.

Claims (10)

1. Low-emission vortex pulverized coal burner containing a central channel with a ignition device placed in it, around which and coaxially with it there is an annular ignition air channel, an annular air mixture channel and at least one annular secondary air channel, in which axial blade swirlers are installed, according to around the outer shell of the annular channel of the air mixture, flame stabilizers are evenly located in the form of flat teeth, characterized in that the flame stabilizers are installed at an angle from 50 to 85° to the longitudinal axis of the burner in such a way that they direct the flow of the air mixture into counter-rotation of the axial blade swirler, and the height h of the stabilizers of the torch and the height H of the annular channel of the air mixture have the ratio: , where h is the height of the torch stabilizer; H – height of the annular channel of the air mixture; The width d of the flame stabilizer and the diameter D of the outer shell of the annular channel of the air mixture have the ratio: , where d is the width of the torch stabilizer; D – diameter of the outer shell of the annular channel of the air mixture; The recommended number of flame stabilizers is from 12 to 20. 2. The burner according to claim 1, characterized in that a diffuser with an opening angle of 15 to 45° is installed at the end of the outer shell of the annular channel of the air mixture.