RU2756712C1 - Combined bark-wood firing device - Google Patents

Abstract

FIELD: waste processing.

SUBSTANCE: invention relates to a device for the incineration of waste processing and processing of wood biomass and can be used in industrial heat power engineering. The combustion device for burning bark-wood fuel contains pre-furnaces separated by a front screen, equipped with fuel supply devices, fixed inclined and horizontal mechanical grates and devices for supplying primary air under the grates, illuminating gas-oil burners, and a main combustion chamber equipped with gas-oil burners. The outer surface of the wall tubes facing the pre-furnace is covered with a layer of refractory material, the main combustion chamber is equipped with the mouth of the "cold" funnel narrowed with the help of water-cooled panels, secondary blast input devices to which the slag removal system is connected, additional burners installed on the rear wall, inertial-gravitational devices located outside the exit window, and feeders with ash channels, providing the supply of the fuel-ash mixture from the bunkers of the inertial-gravitational devices to the ejectors for its transportation by hot air to additional burners.

EFFECT: invention allows increasing the technical, economic and environmental performance of the combustion device when burning bark-wood waste with a wide range of changes in the composition of the fuel mixture with a relative humidity per working mass up to 65% and to increase the efficiency of boilers when burning a fuel mixture of a heterogeneous particle size distribution without the use of high-calorific fuels (gas or fuel oil).

1 cl, 1 dwg

Description

The invention relates to a device for the incineration of waste processing and processing of wood biomass and can be used in industrial heat and power engineering.

Known high-speed combustion furnaces of the V.V. Pomerantsev, representing a vertical chamber bounded on three sides by brickwork, and on the side of the combustion chamber - by a clamping grate made of studded steel pipes included in the boiler circulation system and serving as a front screen. These furnaces have fixed and movable clamps, under which air is supplied, which ensures the combustion of fuel in the clamped vertical layer. For the afterburning of fine fuel fractions carried out from the vertical layer, the secondary air flow "sweeps" under the furnace, moving in a continuous stream from the rear wall of the furnace to the front wall [SI Golovkov, IF Koperin, VI Naydenov. Energy use of wood waste. - M .: Forest industry, 1987, p. 51-52].

To expand the range of energy use of wood waste with an increased content of mineral impurities, VO-110 furnaces with mechanized ash and slag removal are used, which also uses the principle of a clamped layer [SI Golovkov, IF Koperin, VI Naidenov. Energy use of wood waste. - M .: Forest industry, 1987, p. 52-54]. The principle of a clamped layer is also used in furnaces for burning wood waste [USSR Inventor's Certificate No. 1615463 A1, 5 F23В 5/04, 1990], where an autonomous supply and individual regulation of primary air along the width of the furnace are used to increase the efficiency of fuel combustion.

For the combustion of bark-wood fuel, high-speed combustion furnaces SevNIIP-TsKTI [Golovkov SI, Koperin IF, Naydenov VI are used. Energy use of wood waste. - M .: Forest industry, 1987, p. 94-95], layer-vortex furnace [RF Patent No. 2455561, author Lyubov VK, registered. in the State. the register of images RF 10.07.2012] and combined combustion devices containing a pre-furnace, in which there are fixed inclined and movable horizontal mechanical grate grates, and the main combustion chamber of a prismatic shape. [Golovkov S.I., Koperin I.F., Naydenov V.I. Energy use of wood waste. - M .: Forest industry, 1987, p. 95-96].

Multi-fuel boilers KM-75-40 were equipped with combined combustion devices. In these combustion devices, the forehearths and the main combustion chamber are separated from each other by a front screen having "windows" made by festooning the wall tubes to connect the forehearth and the main combustion chamber into a single device. The pre-furnace is equipped with a fixed inclined grate, to which bark-wood fuel flows through the chute, where it is dried, ignited and partially burned out. In the lower part of the pre-furnace there are mechanical horizontal grate grates of the forward stroke, on which the main process of combustion and afterburning of the combustible components of the fuel coming from the inclined grate takes place. Focal residues from the horizontal mechanical grates of the forward stroke are discharged into the slag chest of drawers of the combined combustion device. Hot primary air with a temperature of up to 450 ° C is supplied under the inclined grate, and under the mechanical grate with a temperature of up to 250 ° C. The pre-furnace is equipped with two gas-oil lighting burners, and on the side walls of the main combustion chamber there are two load burners with an oppositely displaced arrangement. Combustion products from the pre-furnace through the "windows" of the front screen enter the main combustion chamber, where the combustion process is completed and the flue gases are cooled. Due to the limited load of the boiler unit in cases of stopping the backlighting with the reserve fuel, the low efficiency of the combustion process and the reliability of the mechanical grate grates, as well as unsatisfactory environmental performance, these heat generating units were discontinued. However, they are still in operation at the enterprises of the Russian Federation. We have taken this combined combustion device as a prototype.

An energy survey of the KM-75-40 boiler unit when burning bark-wood fuel, consisting of the bark of coniferous and deciduous wood, substandard chips and sawdust with the gas burners off, showed that at a relative humidity of the burned biofuel 56.65%, its reduced steam capacity was no more than 53% of the nominal. The results of balance experiments showed that the design and technical condition of the combined combustion device and the boiler unit as a whole do not provide the required completeness of combustion of combustible fuel components and acceptable environmental performance. Thus, the concentration of carbon monoxide in the exhaust gases was 9790 mg / nm³ at an oxygen concentration of 6%, while the heat loss with chemical underburning of the fuel was 4.28%, the gross efficiency of the boiler unit was 71.74%, and the heat loss with exhaust gases was 21.13% [Lyubov V.K., Maryandyshev P. A., Popov A.N., Yarkov D.A. Analysis of the efficiency of energy use of wood fuel in medium-pressure boilers / Proceedings of the Seventh Russian National Conference on Heat Transfer (October 22-26, 2018, Moscow), vol. 1 - Moscow: MPEI Publishing House, 2018, p. 421-424].

The problem to be solved by the invention is to improve the technical, economic and environmental performance of the combined combustion device when burning bark-wood waste with a wide range of changes in the composition of the fuel mixture with relative humidity per working mass up to 65% and to increase the efficiency of boilers when burning a fuel mixture of inhomogeneous particle size distribution. composition without the use of high-energy fuels (gas or fuel oil).

This is achieved by the fact that a combined combustion device for burning bark-wood fuel, containing pre-furnaces separated by a front screen, equipped with fuel supply devices, fixed inclined and horizontal mechanical grates and devices for supplying primary air under the grate, illuminating gas-fuel oil burners, and the main furnace a chamber equipped with loading gas-oil burners; there are no windows in the forehearth, made by festooning the wall tubes, and the outer surface of the screen tubes facing the forehearth is covered with a layer of refractory material, the main combustion chamber is equipped with the mouth of the "cold" funnel narrowed with the help of water-cooled panels, secondary blast input devices to which the output system is connected slag, additional burners installed on the rear wall, inertial-gravity devices located outside the exit window, and feeders with ash channels, providing the supply of the fuel-ash mixture from the bunkers of the inertial-gravitational devices to the ejectors for its transportation by hot air to additional burners.

FIG. 1 shows the proposed combined combustion device, longitudinal section.

The combined combustion device contains a pre-furnace 1 with fuel chutes 2, separated from the main combustion chamber 3 by pipes of the front screen 4, the outer surface of which, facing the pre-furnace, is covered with a layer of refractory material 5. A fixed inclined grate 6 and mechanical grates 7 are installed in the pre-furnace 1 , under which the primary air supply is provided by means of ducts 8. To the mouth of the "cold" funnel of the main combustion chamber 3, narrowed by means of water-cooled panels 9, secondary blast input devices 10 are connected, providing its input along the rear slope 11 of the "cold" funnel. A slag removal system 12 is connected to the secondary blast input devices 10. On the rear wall of the main combustion chamber 3, additional burners 13 are installed, to which, with the help of ash channels 14 connected to ejectors 15 with hot air entering them, the fuel-ash mixture is supplied from bunkers 16 inertial-gravitational devices with the help of 17 feeders.

The operation of the combined combustion device for burning bark and wood fuel is carried out as follows.

Wood-based fuel through fuel chutes 2 is supplied to a fixed inclined grate 6 of the pre-furnace 1, on which the process of thermal preparation of fuel begins, the continuation of which and the ignition of the smallest and dry particles occurs on mechanical horizontal grates 7 of the forward stroke. To intensify the process of thermal preparation of bark-wood fuel, the outer surface of the pipes of the front screen 4, facing the pre-furnace, is covered with a layer of refractory material 5, and the side walls and ceiling of the pre-furnace 1 are made of refractory materials. For exothermic processes with fuel material, primary air is supplied under a fixed inclined grate 6 and mechanical grates 7 using ducts 8, while its total consumption is much less than the theoretically required fuel for combustion. To ensure reliable operation of the grate, hot primary air with a temperature of up to 450 ° C is supplied under the inclined grate, and under the mechanical grates with a temperature of up to 250 ° C. For kindling the combined combustion device, the pre-furnace is equipped with two gas-oil burners. The products of thermal decomposition and combustion of wood fuel, formed in the pre-furnace, enter the main combustion chamber 3 through the opening under the lower collector of pipes of the front screen 4 and by the flow of secondary air coming out of the secondary blast input device 10, are drawn into the vortex motion. Adjustable loading of the vortex zone with thermally prepared and burning bark-wood fuel is carried out using mechanical grates 7 of the forward stroke, which supply fuel to the secondary blast injection device 10. The vortex motion of the gas-fuel flow in the lower part of the main combustion chamber 3 is provided due to the torque arising from interaction two opposite streams: gas-fuel, leaving the secondary blast input device 10 and moving along the rear slope 11 of the "cold" funnel and streams of fuel-ash air mixture leaving additional burners 13 installed on the rear wall of the main combustion chamber 3. Fuel particles, making multiple forced circulation in a vortex flow with a horizontal axis of rotation, upon reaching a certain size, are carried out into the direct-flow part of the torch, where they are partially or completely burned out. When leaving the main combustion chamber 3, flue gases make a 90 ° turn at the entrance to a horizontal flue with convective heating surfaces 18, where due to an increase in the area of the "living" section, the gas flow rate decreases, which allows the inertial separation of fuel and ash particles to be supplemented with gravity. The separated solid particles are collected in bunkers 16 of inertial-gravitational devices, from where, with the help of feeders 17, they are directed into ash channels 14 and further into ejectors 15, into which hot air is supplied, controlled by means of dampers 19, providing transportation of the fuel-ash mixture to additional burners 13 and from them to the lower vortex zone of the main combustion chamber 3. In this case, as shown by aerodynamic studies, a vortex flow is also formed above the additional burners. The design of the secondary blast input devices 10, which ensures a gradual decrease in the flow rate, makes it possible to separate fuel particles by their mass and size, dry them and return them back to the vortex zone of the main combustion chamber 3, and slag and foreign inclusions allow them to be removed to the slag removal system 12 for subsequent removal. ... The hot gas-air flow coming out of the secondary blast input devices 10 and moving along the rear slope 11 of the "cold" funnel contributes to the creation of elements of a countercurrent layer of burning coke particles on it, which additionally stabilizes the process of ignition and combustion of high-moisture fuel and creates conditions for the reduction of oxides nitrogen. To regulate the performance of the boiler unit, load gas-oil burners 20, installed counter-displaced on the side walls of the boiler, can also be used.

The presence of vortex flows, both in the lower and in the upper parts of the main combustion chamber 3, intensifies heat and mass transfer processes and equalizes heat flows along its entire height, reduces screen fouling and increases their thermal efficiency, and also increases the residence time of coke particles, creating conditions for additional reduction of nitrogen oxides. The flow rate of hot air for the secondary blast input devices 10 and additional burners 13 depends on the load of the boiler unit, the particle size distribution of the bark-wood fuel and its moisture content.

Studies have shown that the combined combustion device allows combining the advantages of layer and vortex combustion technologies, while for thermal preparation and ignition of bark-wood fuel, a combination of inclined and horizontal layers, implemented in the pre-furnace, is used. In the main combustion chamber, thermally prepared and ignited fuel mainly burns out in the vortex zone located below the additional burners, while the elements of the counterflow layer appearing on the rear slope of the "cold" funnel are factors that stabilize the combustion process. Burnout of small particles occurs in the direct-flow part of the torch. The use of this combined combustion device will ensure an increase in the environmental and economic indicators of combustion of high-moisture bark-wood fuel with a wide range of particle size distribution, increase the performance of boiler units without "backlighting" with high-calorie fuel by at least 40%, and also significantly reduce emissions of nitrogen oxides and carbon monoxide.

Claims (1)

Combined combustion device for burning bark and wood fuel, containing pre-furnaces separated by a front screen, equipped with fuel supply devices, fixed inclined and horizontal mechanical grates and primary air supply devices under grate grates, illuminating gas-fuel oil burners, and a main combustion chamber equipped with loading gas fuel oil burners, characterized in that there are no windows in the forehearth, made by festooning the wall tubes, the outer surface of the wall tubes facing the forehearth is covered with a layer of refractory material, the main combustion chamber is equipped with the mouth of the "cold" funnel narrowed with the help of water-cooled panels, secondary input devices blast, to which the slag removal system is connected, additional burners mounted on the rear wall, inertial gravity devices located outside the exit window, and feeders with ash channels that provide fuel-ash mixture from bunkers of inertial-gravitational devices to ejectors for its transportation by hot air to additional burners.

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