RU2237218C2 - Method of control of sizes of gas torch and gas burner for realization of this method - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: proposed is used for control of gas torch in rotary furnace at constant flow rate of combustible gas; proposed method includes change of intensity of mixing of this gas with oxidizer due to re-distribution of consumption of gas among peripheral nozzles of gas burner and its central nozzle; part o fuel delivered through several peripheral nozzles is twisted and other part of fuel is fed in form of straight flow through central nozzle. Used as primary oxidizer is compressed air; part of compressed air is fed through external annular nozzle and other part of compressed air fed through internal annular nozzle. Used as primary oxidizer is oxygen; part of oxygen is fed through external annular nozzle and other part of oxygen is fed through internal annular nozzle. Re-distribution of consumption of primary oxidizer between external and internal annular nozzles is used as additional means for control of intensity of mixing and consequently, sizes of gas torch by increasing fraction of primary oxidizer fed through external annular nozzle for increase of intensity of mixing and decrease of torch length and vice versa, decreasing the fraction of primary oxidizer fed through external annular nozzle for decrease of intensity of mixing and increase of torch length at retained consumption of primary oxidizer through external annular nozzle no less than 20% of total consumption per burner.

EFFECT: possibility of change of torch configuration.

8 cl, 3 dwg

Description

One of the main requirements for burners of modern rotary kilns is the possibility of changing over a wide range of sizes of the torch, especially its length. This is necessary to change the firing regime under constant heat load, for example, to change the length of the sintering zone when changing the properties of the fired material, as well as to suppress the formation of nastily (rings) on the refractory lining of the furnace, i.e. sticking of the material to the lining as a result of its softening and partial melting. To combat this phenomenon, which significantly reduces the lining life, it is necessary to be able to move the high-temperature zone of the torch along the furnace, i.e. change the length of the torch.

At the same time, it is possible to change the geometric dimensions, in particular, the length of the flame under constant heat load, by affecting the nature of the mixing of combustible gas with an oxidizing agent (air or oxygen), i.e. on the intensity of this process.

Known methods for changing the intensity of mixing gas with an oxidizing agent using various moving elements located near the hot (output) end of the burner. For example, by moving in the axial direction a conical movable element located inside the confuser nozzle, the output section of the burner and thereby the speed of the gas or primary (forced into the burner) oxidizer at its outlet are changed. By varying the angle of inclination of the blades of the swirler installed near the outlet section, the degree of twist of the gas stream or primary oxidizer is changed.

A known method developed by UNITERM-CEMCON Gmbh (Austria) for changing the intensity of gas-air mixing is that the angle of inclination of the flexible armored hoses supplying gas to the outlet gas nozzles of the multi-nozzle burner is changed, and thereby the intensity of twisting of the gas jets is changed, and consequently the mixing intensity (UNITERM-CEMCON Gmbh. Burner for a rotary kiln. Type MAS / 3 / EC. Technical documentation).

However, the use of movable elements located in the high-temperature zone is a significant drawback of this method of controlling the size of a torch created by a multi-nozzle burner: exposure to high temperatures makes the operation of these devices unreliable, and the use of thermal protection from refractory concrete greatly complicates the design and operation of the burner.

Closest to the proposed invention, the technical solution is a method of changing the intensity of mixing gas with air and thereby changing the length of the flame as a result of redistribution of gas flow between the central and peripheral gas nozzles of a multi-nozzle burner (Vintovkin A.A., Ladygichev M.G., Gusovsky V. L., Usachev AB, Modern Burner Devices (Designs and Technical Specifications), Reference, Moscow: Mashinostroenie-1, 2001, pp. 105-107). The burner, designed to implement this method, contains peripheral gas nozzles mounted on the tips, equipped with blades, swirling flow of fan air, coaxially flowing around each tip.

A method for controlling the size of a torch in a rotary kiln at a constant flow of combustible gas by changing the intensity of mixing gas with an oxidizing agent as a result of the redistribution of the flow of combustible gas between the peripheral nozzles of the gas burner and its central nozzle is proposed, characterized in that a part of the flow of combustible gas supplied through a series of peripheral nozzles , twist, and the other part is served as a straight stream through a central nozzle. Thus, in contrast to the known method, it is not the air flow flowing around each peripheral nozzle that is swirling, but the flow of combustible gas flowing out of this nozzle, which increases the twisting efficiency due to the high speed of the combustible gas.

In contrast to the known method, in the proposed method, it is proposed to use compressed air supplied under high pressure (compressor rather than fan air that is supplied under low pressure) or oxygen as the primary oxidizing agent.

Another difference of the proposed method is the use of a burner having two annular nozzles - internal and external - for supplying the primary oxidizer, due to which, as an additional means of controlling the mixing intensity and, therefore, the size of the torch, redistribution of the primary oxidizer flow between the outer and inner ring nozzles is used, by increasing the proportion of primary oxidizing agent supplied through the outer annular nozzle to increase the mixing intensity (and reduce the length flare), and vice versa, by reducing the proportion of the primary oxidizing agent supplied through the outer annular nozzle to reduce the mixing intensity (and increase the length of the flare). In this case, the flow rate of the primary oxidizer through the outer annular nozzle providing cooling of the burner should be at least 20% of the total flow rate of the primary oxidizer to the burner.

Figure 1 shows a gas burner, a General view;

figure 2 is a view of figure 1;

figure 3 is a section bB in figure 2.

The gas burner housing for rotary kilns consists of a central channel 7 for supplying combustible gas (gaseous fuel), ending with a central nozzle 2, a channel for supplying a primary oxidizer 3, ending with an inner ring nozzle 4, and a peripheral channel for supplying gaseous fuel 5, ending with peripheral nozzles 6 located at an angle to the axis of the burner, as well as the external channel for supplying the primary oxidizing agent 7, ending with an external annular nozzle 8. Thus, the proposed design matrivaet separate supply of fuel gas to the main nozzle 2 and a number of peripheral nozzles 6, as well as a separate supply of primary oxidant to the inner 4 and outer ring 8 nozzles.

It is advisable to make the design of the burner from four coaxial pipes for supplying combustible gas and a primary oxidizer to the nozzles, and the peripheral nozzles for supplying combustible gas in the form of a Laval nozzle. Unlike the known burner, the peripheral nozzles are fixed in such a way that the axis of each of them makes a constant angle with the longitudinal axis of the burner, counted in the direction of the circle on which the centers of the peripheral nozzles are located, and in the range from 5 to 30 °. The selected range is explained by the fact that when the angle of inclination is less than 5 °, the flow practically does not twist and therefore good mixing of the combustible gas with the oxidizing agent is not achieved; when the angle of inclination is higher than 30 ° in the axial region of the torch, an extensive reverse current zone arises, which leads to the torch opening to the furnace walls and to burnout of the processed material.

It is advisable to make the nozzle part of the burner removable, which will allow you to install various options for peripheral nozzles, differing in angles of inclination to the axis of the burner in the specified range. The larger this angle, the smaller the lower limit of the length of the torch, adjustable as described above. The need to change this lower limit of the length of the torch may arise when changing the firing technology, or when changing the characteristics of the fuel used.

In the pipe supplying combustible gas to the central nozzle, a pilot burner or nozzle for burning other types of fuel can be installed, which will facilitate the operation of the burner and expand the possibilities of its use.

During operation of the burner, the combustible gas supplied to the central channel 1 exits a straight stream from the central nozzle 2, and the supplied to the peripheral channel 5 swirls through the peripheral nozzles 6. In this case, the combustible gas is intensively mixed with the primary oxidizer supplied to the channels 3 and 7 and coming out of the annular nozzles 4 and 8, as well as a secondary oxidizing agent - air sucked in from the environment or from the refrigerator through the discharge end of the furnace under vacuum. The configuration of the flame produced by gas combustion depends on the distribution of combustible gas between the central 2 and peripheral 6 nozzles, as well as on the distribution of the primary oxidizer between the inner 4 and outer 8 ring nozzles.

Mathematical modeling of the flare configuration was carried out depending on the fraction of gaseous fuel entering through peripheral nozzles. The simulation results for a burner with a central nozzle diameter d ₁ = 50 mm, operating on natural gas and using air as an oxidizing agent, are given in the table.

It was found that an increase in the proportion of the gas flow rate supplied through the peripheral nozzles, due to the twisting of the gas stream and the large contact surface with the primary and secondary air flows, intensifies mixing, which leads to a reduction in the length of the flame from 25 m (in the absence of supply through the peripheral gas nozzles) to 12 m (at 100% feed through peripheral gas nozzles). The width of the torch increases.

Additional control of the torch length can be achieved by changing the proportion of the primary oxidizer supplied through the outer ring nozzle 8 - its increase allows to further reduce the torch length, and a decrease leads to an increase in this value. Moreover, in all cases, the use of compressed (compressor) air provides a hard flame with intense intense combustion.

Thus, the proposed method of controlling the size of the gas torch and the device of the burner for its implementation allow you to change the configuration of the torch in a rotary kiln without the use of movable elements located in the high temperature region.

Claims (8)

1. The method of controlling the size of the torch in a rotary kiln at a constant flow of combustible gas by changing the intensity of mixing this gas with an oxidizing agent as a result of the redistribution of the flow of combustible gas between the peripheral nozzles of the gas burner and its central nozzle, characterized in that a portion of the flow of combustible gas supplied through a series peripheral nozzles, twist, and the other part is served as a straight stream through the Central nozzle. 2. The method according to claim 1, characterized in that compressed air is used as the primary oxidizing agent, part of the flow rate of which is supplied through the outer ring nozzle, and the other part through the inner ring nozzle. 3. The method according to claim 1, characterized in that oxygen is used as the primary oxidizing agent, part of the flow rate of which is supplied through the outer ring nozzle, and the other part through the inner ring nozzle. 4. The method according to one of claims 1 to 3, characterized in that as an additional means of controlling the mixing intensity and, consequently, the size of the torch, redistribution of the primary oxidizer flow rate between the outer and inner annular nozzles is used, increasing the proportion of the primary oxidizer supplied through the outer ring nozzle, to increase the mixing intensity and to reduce the length of the torch, and vice versa, by reducing the proportion of the primary oxidizing agent supplied through the outer ring nozzle, for reducing the intensity of mixing and increasing the flame length - while maintaining the primary oxidant flow through an outer annular nozzle is not less than 20% of the total flow rate to the burner. 5. A gas burner for rotary kilns, containing four coaxial pipes for supplying combustible gas and a primary oxidizer, as well as a central nozzle and a number of peripheral nozzles for exiting combustible gas with separate inlets of this gas to the central nozzle and to a number of peripheral nozzles, characterized in that peripheral nozzles for supplying combustible gas, made in the form of a Laval nozzle, are fixed in such a position that the axis of each of them makes a constant angle with the longitudinal axis of the burner, counted in the direction of the circle, to the centers of the peripheral nozzles are located, and are in the range from 5 to 30 °. 6. The gas burner according to claim 5, characterized in that it contains two annular nozzles for supplying the primary oxidizer - external and internal - with separate feeds of the primary oxidizer to each of them. 7. A gas burner according to claim 5 or 6, characterized in that inside the pipe supplying combustible gas to the central nozzle, a pilot burner or nozzle is installed for burning other types of fuel. 8. A gas burner according to one of claims 5 to 7, characterized in that its nozzle portion is removable.

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