RU2518772C1 - Furnace with tilt-pushing furnace grate for combustion of wood wastes - Google Patents

Abstract

FIELD: energy industry.

SUBSTANCE: furnace with tilt-pushing furnace grate comprises a combustion chamber divided with a curved arch, equipped with the fuel supply devices, the devices of zoning input of primary air under the furnace grate and secondary air to the over-layer volume through the nozzles located on the side walls in one vertical plane, and a chamber of secondary combustion and cooling connected to the combustion chamber with the exit window located above the end part of the first area of the furnace grate. Supply nozzles of the secondary air located on the opposite wall from the entry chute of the primary air are inclined downwardly at an angle φ, and the nozzles of the secondary air of the other wall are inclined upwards at an angle φ, the exit window is equipped with a shoulder directed downwards of the furnace, under which two additional nozzles for inlet of the secondary air are mounted horizontally counter-staggered.

EFFECT: invention enables to improve the quality of wood fuel combustion, to reduce harmful emissions to the atmosphere.

3 dwg

Description

The invention relates to a device for burning waste wood biomass processing and may find application in the power system.

Known fire chambers with oblique-repulsive grids, in which fuel from the hopper enters 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 burned fuel and the movement of fuel along the grate is due to the reciprocating motion of the moving grate, while the layer is lined. The air supply under the grate is carried out zonewise. [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 oblique-repulsive grates, sharp blast nozzles installed on the front and rear walls began to be used, which made it possible to slightly reduce this loss to 2.5 ... 3%. [Dumer A.B. Mechanisms of combustion devices. M. - L. Gosenergoizdat, 1963, p. 92-93].

Known fire chambers with oblique-repulsive grate grates for burning wood waste with moderate humidity (up to 45 ... 50%), in which waste is fed to the grate with screw feeders, primary air is supplied under the grate zone (three zones), and secondary air is introduced into the furnace the volume above the second and third zones of the grate from the side of the side walls using horizontal cylindrical nozzles located in the opposite vertical plane. The number of secondary blast nozzles is determined by the length of the grate and, accordingly, the thermal power of the furnace. High-temperature combustion products in the superlayer 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 exit window of a rectangular section located in the arch type, above the end section of the first zone of the grate, are sent to the afterburning and cooling chamber, in 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. Burning biofuels in Danstoker boilers // Actual problems of the development of the forest complex: Materials of the International Scientific and Technical Conference. Vologda: RIO VOGTU, 2009, p.105-107]. This furnace device is accepted by us as a prototype.

However, these furnaces are very sensitive to the particle size distribution of the fuel burned and the change in its thermal characteristics. With an increase in the fine fractions in the composition of the combusted fuel, a decrease in its moisture content or the speed of movement along the grate, the ignition zone moves towards the front wall of the furnace. Early ignition of the fuel, accompanied by intensive release of volatile substances, in the absence of supply of secondary air to this area, causes a significant increase in heat loss with chemical underburning of fuel and a decrease in the efficiency and reliability of the furnace and boiler as a whole.

The problem to which the invention is directed, is the creation of a highly efficient low-emission furnace device for burning wood fuel with an extremely heterogeneous particle size distribution (with a particle size different by a thousand times) with a relative humidity per working mass of up to 50 ... 55%.

This is achieved by the fact that in a furnace with an oblique-repelling grate, containing a combustion chamber separated by an arch vault, equipped with fuel supply devices, devices for the primary input of primary air under the grate and secondary air into the superlayer volume through nozzles located on the side walls in one vertical planes, and the afterburning and cooling chamber connected to the combustion chamber by an exit window located above the end section of the first zone of the grate, the secondary nozzle of secondary air, located on the opposite wall from the primary air intake ducts, are inclined downward at an angle φ (depending on the width of the furnace and the thermophysical characteristics of the fuel), and the secondary air nozzles of the other wall are inclined upward at an angle φ, the outlet window is equipped with a shoulder directed downwards of the furnace, under which two additional nozzles for introducing secondary air are horizontally counter-offset.

Figure 1 shows the proposed firebox, a longitudinal section; figure 2 is a transverse section aa of figure 1, figure 3 is a local horizontal section bb of figure 1.

A furnace with an oblique-repelling grate contains combustion chambers 1 and afterburning and cooling 2, separated by an arch vault 3 made of refractory materials, over the end section of the first zone of the inclined-repulsive grating 4 in the vault there is an exit window 5 equipped with a shoulder 6 directed down a furnace, under which two additional nozzles 7 for introducing secondary air are horizontally counter-offset. On the front wall of the furnace, fuel feeders 8 are installed, and on the side walls above the second and third zones of the oblique-repulsive grate 4, the main nozzles of the secondary air supply 9 are installed, while the nozzles located on the opposite wall from the primary air intake ducts 10 are tilted down under angle φ, and the nozzles of the other wall are inclined upward at an angle φ. The supply of secondary air to the nozzles is carried out using air ducts 11, laid along the side walls of the combustion chamber 1. The screw conveyor 12, the axis of which is perpendicular to the longitudinal axis of the furnace, is located at the end of the oblique-repulsive grate 4.

The operation of the furnace with an inclined-repulsive grate for burning wood waste is as follows.

The multifractional wood waste from the bunkers is fed by feeders 8 to an inclined-repulsive grate 4, in the area of the first zone of which thermal preparation and ignition of the wood fuel takes place, in the second and third zones, respectively, active combustion and burning of combustible fuel components, primary air under the grate with the help of boxes 10 is supplied zonewise, in an amount less than theoretically necessary for the combustion of fuel. The ratio between primary and secondary air is determined by the thermophysical characteristics of the fuel burned; with increasing fuel humidity, the proportion of primary air increases. Incomplete combustion products leaving the fuel layer fall into a vortex stream generated by the interaction of multidirectional jets of secondary air emerging from the main nozzles 9. The downward inclination of nozzles located on the opposite wall from the primary air intake ducts 10 allows to reduce local burn-through of grates and burnout lining in this zone, which is typical for furnaces with one-way primary air supply. The swirling flow of hot flue gases affects the fuel layer located on the grate 4, increasing the uniformity of the distribution of fuel along its width and increasing its life cycle. Moving to the first zone of the inclined-repulsive lattice 4, the vortex flow of high-temperature gases intensifies the thermal preparation of wood fuel for ignition. In the area of the exit window 5, located in the arched vault 3 above the end section of the first zone of the grate 4 and equipped with a shoulder 6, an additional swirling of the gas stream is made when secondary air jets are introduced through horizontal counter-offset additional nozzles 7. This vortex flow allows the combustible components to burn out coming from the fuel layer from the site of the first grating zone, as well as in combination with the shoulder 6 of the exit window 5, reduces the removal of the solid phase from the combustion chamber 1 to the afterburner and 2. Additional turbulization of the gas stream at the outlet of the combustion chamber 1 intensifies heat transfer in the afterburner and cooling chamber 2 and improves the working conditions of the gas-water heat exchanger. Removing focal residues from the combustion chamber 1 during operation of the boiler is carried out using a screw conveyor 12.

Studies have shown that this furnace allows efficient burning of wood fuel of extremely heterogeneous particle size distribution (with a particle size different by a thousand times), increase the gross efficiency of the boiler by at least 2% by reducing heat loss with flue gases and with chemical incompleteness of combustion fuel, to ensure the ability to work with ultra-small excess air at the outlet of the furnace (α _t = 1.15), reduce emissions of nitrogen oxides ~ 20% and carbon monoxide by 30 ... 50%, and also extend the life cycle of oblique-repulsion grate and lining.

Claims (1)

A furnace with an inclined and repulsive grate, containing a combustion chamber separated by an arch vault, equipped with fuel supply devices, devices for the primary input of primary air under the grate and secondary air into the superlayer volume through nozzles located on the side walls in the same vertical plane, and an afterburner and cooling connected to the combustion chamber by an output window located above the end section of the first zone of the grate, characterized in that the secondary nozzle of air located on the opposite wall from the primary air intake ducts are tilted downward at an angle φ, and the secondary air nozzles of the other wall are tilted upward at an angle φ, the outlet window is equipped with a shoulder directed downwards of the furnace, under which two additional nozzles are installed horizontally counter-offset introducing secondary air.

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