RU2773999C1 - Furnace with an inclined-pushing grate for combustion of granulated and briquetted fuels - Google Patents

Abstract

FIELD: thermal power engineering.

SUBSTANCE: invention relates to devices for burning granular or briquetted biofuels, as well as granulated or briquetted peat, and can be used in thermal power engineering. Furnace with tilting-pushing grate contains a combustion chamber separated by an arched vault, equipped with fuel supply devices, zonal input of primary air under the second and third zones of the tilting-pushing grate and recirculation gases under the grate and nozzles for feeding recirculation gases into the above-layer volume of the combustion chamber, located on opposite walls above the first zone of the grate with a half-step offset relative to the nozzles of the opposite wall, and nozzles for supplying secondary air located on opposite walls in one inclined plane above the second zone of the grate with a half-step offset relative to the nozzles of the opposite wall, and an afterburning and cooling chamber connected to the combustion chamber by an exit window located in the arched vault at the rear wall of the combustion chamber , and equipped with nozzles for introducing tertiary air, located on opposite walls in the same horizontal plane with a half-step offset relative to the nozzles of the opposite wall, the rear wall of the combustion chamber and its front wall in the zone of the afterburning and cooling chamber and the revolving chamber, as well as the walls of the revolving chamber are closed with gas-tight water-cooled screen panels, and the recirculation gases are introduced under the first zone of the grate, and the arched ceiling of the arched vault is made gas-tight from steel water-cooled pipes connected to collectors.

EFFECT: invention allows to reduce the emission of harmful substances.

1 cl, 4 dwg

Description

The invention relates to devices for burning granular or briquetted biofuels, as well as granulated or briquetted peat, and can be used in thermal power engineering.

Known fireboxes with tilting-push grates, in which fuel from the bunker is supplied to the grate, which is formed from alternating rows of movable and fixed grates arranged in steps. The angle of inclination of the grate is less than the angle of repose of the combusted fuel, and the movement of fuel along the grate occurs due to the reciprocating motion of the movable grates, while the layer is skimmed. The air supply under the grate is carried out by zone. [Styrikovich M.A., Katkovskaya K.Ya., Serov E.P. boiler units. M.-L. Gosenergoizdat, 1959, p. 78].

To reduce heat losses with chemical incompleteness of combustion in furnaces with tilting-pushing grates, sharp blast nozzles installed on the front and rear walls began to be used, which made it possible to somewhat reduce the value of this loss to 2.5–3.0%. [Dumer A.B. Mechanisms of furnace devices. M.-L. Gosenergoizdat, 1963, p. 92-93].

Known are furnaces with tilting-pushing grates for burning wood waste with moderate humidity, in which waste is fed to the grate by screw feeders, primary air is supplied under the grate by zone (three zones), and secondary air is introduced into the furnace volume above the second and third zones of the grate. gratings from the side walls with the help of horizontal cylindrical nozzles located opposite in one vertical plane. The number of secondary blast nozzles is determined by the length of the grate and, accordingly, the heat output of the furnace. High-temperature combustion products in the above-layer region of the combustion chamber move to the first zone of the grate, intensifying the thermal preparation of fresh fuel for ignition, and through the outlet window of a rectangular section located in the arched vault, above the end section of the first zone of the grate, they are sent to the afterburning and cooling chamber, into which the combustion process is completed and the flue gases are cooled before they enter the gas-water heat exchanger. [Lyubov V.K., Lyubova N.V. Combustion of biofuels in boilers "Danstoker" // Actual problems of development of the forest complex: Proceedings of the international scientific and technical conference. Vologda: RIO VoGTU, 2009 p. 105-107].

Known combustion chambers with tilting-pushing grate for burning biofuels in the form of pellets, wood chips, plywood production waste, etc. with a particle size of not more than 50×50×15 mm, with a relative humidity of not more than 40%. [Lyubov V.K. Furnace with an inclined-pushing grate for burning biofuels / Patent for invention No. 2750588 of the Russian Federation according to application No. 2020140930, priority dated 12/11/2020; registered in the State image register RF 06/29/2021, published 06/29/2021, bul. No. 19]. These furnaces contain, separated by an arched vault, a combustion chamber equipped with devices for supplying fuel, zone input of primary air and recirculation gases under the grate, secondary air and recirculation gases into the above-layer volume of the combustion chamber through nozzles located on the side walls, and an afterburning and cooling chamber . The combustion chamber is connected to the afterburning and cooling chamber by an exit window located in the arched vault at the rear wall of the combustion chamber. Nozzles for supplying recirculation gases to the combustion chamber are located on opposite walls above the first zone of the grate with a half step offset relative to the nozzles of the opposite wall, secondary air nozzles are located on opposite walls of the combustion chamber in one inclined plane above the second zone of the grate with a half step offset relative to nozzles of the opposite wall. Primary air is introduced under the second and third zones of the tilt-and-push grate, and recirculation gases are introduced under the first and second zones of the grate. In these furnaces, tertiary air, which ensures the completion of the combustion process, is introduced into the afterburning and cooling chamber through nozzles located on the side walls in the same horizontal plane with a half-step offset relative to the nozzles of the opposite wall. The rear wall of the combustion chamber and its front wall in the zone of the afterburning and cooling chamber and the reversing chamber, as well as the walls of the reversing chamber, are closed with gas-tight water-cooled screen panels made of steel pipes, between which spacers (membranes) from a steel strip are welded.

However, these furnaces are sensitive to changes in the fractional composition of granulated or briquetted fuel and its thermal performance. When burning granulated or briquetted biofuels, as well as granulated or briquetted peat with a high content of fine fractions and low humidity, the ignition zone moves towards the front wall of the furnace. Early ignition of the fuel, accompanied by intense release and combustion of volatile substances, and the absence of heat-receiving heating surfaces in this zone cause a significant increase in temperatures in this area of the combustion chamber, which leads to melting of the side walls and especially the arched ceiling of the arched vault, made of refractory bricks, as well as to local burnout of the grate. The supply of recirculation gases taken from the gas duct after the main smoke exhauster under the first and second zones of the tilt-and-push grate and into the above-layer volume of the combustion chamber above the first zone of the grate makes it possible to reduce the intensity of these negative factors, but cannot eliminate them.

All this causes a decrease in the life cycle of the lining of the side walls and the arcuate ceiling of the arched vault, made of refractory materials, as well as the tilting-pushing grate. Recirculation gases increase the volume and velocity of combustion products, which causes an increased removal of solid particles separated on the upper surface of the arched roof and on the inner surface of the fire tubes. These phenomena lead to a complex decrease in the efficiency of boilers, to an increase in financial costs and the duration of repair work, and also require an increase in the installed capacity of boiler units.

This furnace device is taken by us as a prototype.

The problem to which the invention is directed is the creation of a highly efficient low-emission combustion device for burning granular or briquetted biofuels, as well as granulated or briquetted peat.

This is achieved by the fact that for a furnace with a tilting-pushing grate containing a combustion chamber separated by an arched vault, equipped with fuel supply devices, zone-wise input of primary air under the second and third zones of the tilting-pushing grate and recirculation gases under the grate, and supply nozzles into the overlayer volume of the combustion chamber of recirculation gases, located on opposite walls above the first zone of the grate with a shift of half a step relative to the nozzles of the opposite wall, and secondary air supply nozzles located on opposite walls in one inclined plane above the second zone of the grate with a shift of half a step relative to nozzles of the opposite wall, and an afterburning and cooling chamber connected to the combustion chamber by an exit window located in the arched vault at the rear wall of the combustion chamber, and equipped with tertiary air inlet nozzles located on opposite walls in one mountain isontal plane with a half-step offset relative to the nozzles of the opposite wall, the rear wall of the combustion chamber and its front wall in the zone of the afterburning and cooling chamber and the turning chamber, as well as the walls of the turning chamber are closed with gas-tight water-cooled screen panels, recirculation gases are introduced under the first zone of the grate and arcuate the ceiling of the arched vault is made gas-tight from steel water-cooled pipes connected to collectors.

In FIG. 1 shows the proposed firebox, longitudinal section; in fig. 2 is a cross section A-A of FIG. 1 in FIG. 3 - local section B-B of Fig. 1 in FIG. 4 is a local section B-B (the grate is conventionally not shown) FIG. one.

The furnace with an inclined-pushing grate contains combustion chambers 1 and afterburning and cooling chambers 2, separated by an arched vault 3, in which an outlet window 5 is located at the rear wall 4 of the combustion chamber, above which nozzles 6 are horizontally counter-shifted for introducing tertiary air. On the front wall 7 of the furnace, a fuel feeder 8 is installed, and on the side walls above the first zone of the tilting-pushing grate 9, counter-shifted nozzles for introducing recirculation gases 10 are installed, and above the second zone of the grate 9, nozzles for supplying secondary gas are counter-shifted in an inclined plane. air 11. Secondary air is supplied to the nozzles by means of air ducts 12 laid in the side walls of the combustion chamber 1. Fine ash, spilling through the gaps of the grate, is moved to the transverse conveyor 14 by means of a push rod 13, and coarse ash and slag enters it directly from the tilting-pushing grate 9. primary air is fed under the second and third zones of the tilting-pushing grate 9, and the recirculation gases taken after the main smoke exhauster are sent under the first zone of the grate 9. To reduce the temperature level in the combustion chamber 1, afterburning and cooling 2 to safe values, providing a long life the cycle of laying the walls of the furnace and the grate with the optimal proportions of recirculation gases from the point of view of ecology, in addition to gas-tight water-cooled screen panels made of steel pipes 16, between which spacers (membranes) 17 are welded, and installed on the rear wall 4 of the combustion chamber and its front wall 7 in the area of the afterburning and cooling chamber 2 and the reversing chamber 15, as well as on the walls of the reversing chamber 15, the arched ceiling of the arched vault 3 is gas-tight from steel water-cooled pipes 18 connected to collectors 19. All of the above heating surfaces are included in the circulation circuit of the boiler unit.

The operation of the furnace with an inclined-pushing grate for burning granular or briquetted biofuels, as well as granulated or briquetted peat, is carried out as follows.

The fuel from the bunker is fed by the feeder 8 to the tilting-pushing grate 9, in the area of the first zone of which thermal preparation and ignition of the fuel take place, in the second and third zones, respectively, active combustion and afterburning of combustible fuel components occur, primary air is supplied under the second and the third zone of the grate, in an amount less than theoretically necessary for fuel combustion. The ratio between primary and secondary air is determined by the thermophysical characteristics of the fuel being burned; with an increase in fuel moisture content, the proportion of primary air increases. The introduction of recirculation gases under and above the first zone of the inclined-pushing grate, the temperature of which is several times higher than the temperature of the supplied air, intensifies the thermal preparation of the fuel for ignition, reduces the emission of nitrogen oxides and expands the capabilities of the furnace in terms of the thermal characteristics of the combusted fuel, and also makes it possible to ensure optimal the share of recycling from the standpoint of ecology. The products of incomplete combustion coming out of the fuel layer enter the vortex flows formed during the interaction of counter-shifted jets of recirculation gases in the volume of the combustion chamber 1 above the first zone of the grate and vortex flows formed during the interaction of the counter-shifted jets of secondary air coming out of the nozzles 11 above the second grid zone. The vortex flows of hot flue gases also affect the layer of fuel located on the grate 9, increasing the uniformity of fuel distribution over its width and increasing its life cycle. Having passed the exit window 5, located at the rear wall 4 of the combustion chamber in the arched vault 3, made gas-tight from steel water-cooled pipes 18 connected to collectors 19 to ensure circulation of the working medium through them, high-temperature combustion products enter the vortex flows formed during the interaction of counter- displaced jets of tertiary air coming out of the nozzles 6. This ensures the oxidation of the remaining products of incomplete combustion. Execution of an arcuate overlap of the arched vault 3 in the form of a gas-tight water-cooled panel, as well as the presence of gas-tight water-cooled screen panels made of steel pipes 16, between which spacers (membranes) 17 are welded, on the rear wall 4 of the combustion chamber, its front wall 7 in the zone of the afterburning chamber and cooling 2 and the turning chamber 15, as well as on the walls of the turning chamber 15, can significantly reduce the level of maximum temperatures and ensure a long life cycle of lining the walls of the combustion chamber, the arcuate ceiling of the arched vault and the grate at optimal from the standpoint of ecology, the proportions of recirculation gases. The presence of a system of vortex flows in the above-layer region of the combustion chamber 1 and above the outlet window 5, as well as a decrease in the proportion of recirculation gases, reduce the removal of the solid phase from the combustion chamber 1 to the afterburning and cooling chamber 2, increasing the company of the boiler in terms of cleaning. Additional turbulence of the gas flow at the inlet to the afterburning and cooling chamber 2 intensifies heat transfer in the chamber and improves the operating conditions of the gas-water heat exchanger. Fine ash, waking up through the gaps of the grate, with the help of a push rod 13 moves to the transverse conveyor 14, and coarse ash and slag enter it directly from the tilting-pushing grate 9. Reducing the level of maximum temperatures in the combustion chamber and equalizing them over its volume eliminates the sintering of focal residues and ensures reliable operation of the ash and slag removal system.

The experience of research work on boilers burning various types of biofuels, as well as peat, and having different designs, makes it possible to predict highly efficient low-emission combustion of granular or briquetted biofuels, as well as granulated or briquetted peat in the proposed furnace device. In addition, the use of this furnace device creates the prerequisites for increasing the gross efficiency of the boiler by at least 1.0% by reducing heat losses with exhaust gases and chemical incompleteness of fuel combustion, will provide the ability to work with ultra-low excess air at the outlet of the furnace (α _m = 1.15-1.25), will reduce the emissions of nitrogen oxides by 20-40% and carbon monoxide by 20-30%, and will also extend the life cycle of the tilting-pushing grate, lining the walls of the combustion chamber and the arched ceiling of the arched vault.

Claims (1)

A furnace with a tilting-pushing grate, containing a combustion chamber separated by an arched vault, equipped with fuel supply devices, zone-by-zone input of primary air under the second and third zones of the tilting-pushing grate and recirculation gases under the grate and nozzles for feeding recirculation gases into the above-layer volume of the combustion chamber located on opposite walls above the first zone of the grate with an offset of half a step relative to the nozzles of the opposite wall, and secondary air supply nozzles located on opposite walls in one inclined plane above the second zone of the grate with an offset of half a step relative to the nozzles of the opposite wall, and an afterburner chamber and cooling, connected to the combustion chamber by an exit window located in the arched vault at the rear wall of the combustion chamber, and equipped with tertiary air inlet nozzles located on opposite walls in the same horizontal plane with by a half-step offset relative to the nozzles of the opposite wall, the rear wall of the combustion chamber and its front wall in the zone of the afterburning and cooling chamber and the reversing chamber, as well as the walls of the reversing chamber are closed with gas-tight water-cooled screen panels, characterized in that the recirculation gases are introduced under the first zone of the grate and the arched ceiling of the arched vault is made gas-tight from steel water-cooled pipes connected to collectors.

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