RU2310123C1 - Boiler - Google Patents

Abstract

FIELD: heat and power engineering, possible use for heating water.

SUBSTANCE: boiler contains boiling layer furnace, moving fire bar flat part with blowing zones positioned below it, rotary screen, side screens, scalloped screen, convective block. On side screen, accelerating duct is mounted, inside which mobile plate is installed, and in its lower part pneumatic casting is built in. In frontal part of lower branch of mobile fire bar flat part, frontal thickened part is installed. In back part of upper branch of mobile fire bar flat part, back thickened part is installed. Rotary screen is made of pipes with metallic plates, attached to pipes along whole length. Between scalloped screen and convective block, in its lower part, water-cooled beam is installed, back part of boiler is connected to direct-flow cyclone. Boiler contains a recirculation system, which is made in form of a pipeline and positioned between smoke exhauster and air duct.

EFFECT: increased efficiency of boiler, reduced atmosphere pollution, improved labor conditions, reduced economic costs of boiler operation, increased reliability of boiler operation.

6 dwg

Description

The invention relates to a power system, namely to boilers for burning solid fuel in a fluidized bed, and can be used in the construction and reconstruction of industrial heating boilers.

A known boiler with a layer firebox (Boilers of small and medium power and furnace devices. Industry catalog. Section "Water boilers", M., 1992), in which the rotary screen is made of pipes, is inclined to the horizon up to 30 °, the upper plane of the rotary screen is lined refractory bricks. The rotary screen is designed for faster firing of fresh fuel, abandoned by the feeder onto the furnace.

A disadvantage of the known solution is the low efficiency of a layered furnace, underburning of fuel at loads of more than 70% of the nominal value, large emissions of ash and soot into the atmosphere, destruction of brickwork during operation leading to abrasive wear of the boiler pipes.

A boiler unit is known that contains tube screen and convective heating surfaces, a mechanical furnace of a high-temperature fluidized bed, a narrow inclined movable chain grate with direct flow with blown zones of primary air and removal of the entrainment failure, a pipe cooling panel, a mechanical coal feeder, secondary blast collectors, an ablation deposition hopper with by an air ejector of return of ablation, a boiler frame and a lattice frame (Utility Model Patent No. 38041, publ. 05.20.04, bull. No. 14).

A disadvantage of the known boiler unit is its low productivity and efficiency, lack of lateral refueling, and air pollution. During the reconstruction of the boiler room, it is difficult to get attached to the existing equipment, as reconstruction of the boiler room requires reworking the existing slag removal system.

The closest to the claimed boiler unit for the combination of essential features and the achieved effect is a boiler unit (RF patent No. 2231714, publ. June 27, 2004), consisting of a furnace for burning solid fuel in a fluidized bed, an inclined movable grate with side seals and blasting located under it zones, a rotary screen, a loading hopper for supplying fuel, an accelerating box with a fixed plate.

The disadvantages of the known boiler are its low efficiency, air pollution. A fixed stove in the booster box does not provide fuel in the optimal combustion zone. During the reconstruction of the boiler room, it is difficult to get attached to the existing equipment, as the capacity of the hopper for supplying fuel is not sufficient for continuous operation of the boiler (According to SNiP II-35-76 “Boiler installations”, the capacity of the hopper should provide continuous operation of the boiler for 7-8 hours without sending additional operating personnel to load coal during the shift), in connection with this reconstruction of the boiler room requires reworking the existing fuel supply system. In the known boiler, the rotary screen is made of vertical pipes and is lined with refractory bricks. During operation, the masonry is destroyed and the gases passing through the broken lining wear the pipes of the rotary screen with abrasive ash particles, while the functions of the rotary screen are to increase the residence time of small coal particles in the combustion zone, change the direction of the gas flow to clean them from small coal particles - not performed. In addition, flue gases from the rear of the boiler periodically enter the boiler room, creating gas contamination.

The objectives of the invention are to increase the efficiency of the boiler, reducing atmospheric pollution, improving working conditions, reducing the economic costs of operating the boiler, increasing the reliability of operation.

These tasks are achieved by the fact that in a boiler unit including an accelerating box, a fluidized bed furnace, a movable grate blade with blowing zones located below it, a rotary screen, side screens, a festoon screen, a convection unit, a smoke exhauster, an air box, according to the invention, is installed on the side screen an accelerating box, inside of which a movable plate is located, and in its lower part a pneumatic pick-up is mounted, in the front part of the lower branch of the moving grate the front seal is installed, made in the form of a curved plate, a rear seal is installed in the rear of the upper branch of the moving grate web, made in the form of a plate, under which there is a retaining blast zone, the rotary screen is installed vertically and made of pipes, the space between which is closed by metal plates attached to the pipes throughout in length, between the scallop screen and the convection unit, in its lower part, a water-cooled beam is installed, the back of the boiler is connected to a direct-flow cyclone, in addition, the boiler further comprising a recirculation system, which is configured as a pipe and is disposed between the exhaust fan and air duct.

The invention is illustrated by drawings, where in Fig.1 shows a General view of the boiler; figure 2 is a section aa in figure 1; figure 3 - direct-flow cyclone, figure 4 - design of the rotary screen; figure 5 is a view In figure 4; Fig.6 is a section aa in Fig.4.

The boiler unit contains a fluidized bed furnace 1, a boiler 2 and a once-through cyclone 3.

The fluidized bed furnace 1 contains a narrow movable grate blade 4 with front 5, rear 6 and side 7 seals and located inside the movable grate blade 4 in the sectionalized blast box blowing zones 8 and retaining zone 9, the duct 10 for supplying primary air and a recirculation system 11 for supply of flue gases to the blast zones 8.

The boiler 2 contains a loading hopper 12 with an accelerating box 13, in which a movable plate 14 and pneumatic inlet 15, lateral 16, front 17 and rotary 18 screens are installed, a rotary chamber 19 with an ablation return ejector 20, a convection unit 21 with a scallop 22 and a rear 23 screens and a water-cooled beam 24.

The in-line cyclone 3 contains a flue gas swirler 25, an outlet duct 26 and an ablation return ejector 27. Next to the in-line cyclone is an ablation return fan 28.

The boiler operates as follows.

Coal from the feed hopper 12 through the movable plate 14 of the booster box 13 and using pneumatic inlet 15 is fed into the furnace of the fluidized bed 1 to the blast zone 8.

In the furnace of the fluidized bed 1, inside a narrow movable grate sheet 4, there are blown zones 8, which are active, as they are used for burning fuel and are designed to supply primary air with an admixture of flue gases to organize the boiling regime and burning fuel in suspension. The blast zone 9 is passive, since it does not participate in the process of burning fuel, it is located in the rear of the furnace 1, next to the blast zones 8 and is designed to prevent the entry of flue gases from the rear of the boiler 2 into the boiler room. In the blast zone 9 from the return fan 28, air enters without flue gas impurities (clean). Above the upper part of the narrow movable grate sheet 4, above the blast zone 9, a metal plate (its thickness is at least 10 mm) is installed, which performs the function of the rear seal 6 of the furnace. A large part (70%) of the plate 6 is located outside the furnace space, therefore, the clean air coming from the blast zone 9 partially enters the combustion zone, and its main part enters the boiler room, preventing its gas contamination.

The front seal 5, made in the form of a curved plate, blocks the suction of external air into the combustion zone and directs the slag into the slag removal channel. Suction of outdoor air is harmful to the operation of the boiler, as does not participate in the combustion process and is a ballast, increasing the volume of gases, and by increasing the speed of gases increases the abrasive wear of the pipes.

The movable stove 14 is designed to control the accuracy of the fuel casting into the combustion zone with the aim of its most complete combustion. The wetter the coal, the closer its cast. The movable plate 14 allows you to send coal of any moisture in the zone of optimal combustion.

For casting a small fraction of coal into the optimal combustion zone and cleaning the space under the movable plate 14 from spills of the small fraction of coal, pneumatic inlet is intended 15. Air jets from the nozzles of pneumatic inlet 15 feed a small fraction of coal into the optimal combustion zone. The intake of primary air from the blast zones 8 through a narrow movable bed 4 provides for the boiling and combustion of coal in suspension, and the slag is then moved by a narrow movable grate sheet 4 into the slag removal channel (not shown).

Secondary air through the nozzle 29 enters the zone of maximum combustion temperature of the flame, cools it, thereby suppressing the reaction of the formation of nitrogen oxides. In addition, the secondary air flows coming from nozzles 29 swirl flue gases with small particles of “boiling coal”, preventing them from being removed from the combustion zone and increasing the residence time of these particles in the flare. The process of circulating torch twisting provides a more complete burnout of combustible substances in the fuel and increases the boiler efficiency up to 85-87%, and reduces emissions of nitrogen oxides by 2–3 times.

Further, the flue gas flows round the upper part of the rotary screen 18, pass along the scallop screen 22 and rotate 180 ° in the rotary chamber 19, while unburned coal particles are deposited in the hopper of the rotary chamber 19 and the ablation return ejector 20 are sent to the boiler for combustion, thereby the efficiency of the boiler increases and emissions into the atmosphere are reduced.

The rotary screen 18 is made of pipes, the annular space of which is closed by metal plates. The service life of the metal plates (see figure 3) is equal to the service life of the operation of the rotary screen. This allows you to reduce the economic costs of operating the boiler.

Further, the flue gases pass the convection unit 21, the rear screen 23 and enter the flue gas swirl 25 of the once-through cyclone 3. The once-through cyclone 3 is intended for additional purification of flue gases from unburned coal particles, which are then returned by the ejection return unit 27 to the boiler for afterburning, due to which increases the efficiency of the boiler, reduces the ash load on the battery ash collector and reduces harmful emissions into the atmosphere. The body of the direct-flow cyclone 3 is made in the form of a vertical metal cylinder, inside of which a flue gas swirl 25 is installed, designed to organize the rotational movement of gases in the cyclone. In the lower part of the once-through cyclone 3, flue gases are turned through 180 °, while they are freed from small particles of coal and ash and sent to the ash collector for final cleaning. The particles of coal deposited in the bunker of the once-through cyclone 3, using the ablation return ejector 27, are returned to the narrow movable grate sheet 4 for afterburning.

The recirculation system 11 provides the combustion of coal with a high content of volatile substances and coal with an ash content having a low melting point (up to 1000-1050 °). Flue gases entering the exhaust pipe 8 to the blast zone 8 (up to 30% of the volume) provide a decrease in the oxygen content in the blast air, thereby reducing the rate of the combustion reaction, lowering the temperature in the active zone of burning coal and preventing the melting of low-temperature rock contained in coal . Without a gas recirculation system, a rock having a low melting point, when coal is burned, turns into liquid slag, which floods a narrow mobile grate sheet 4, blocks the primary blast from the blast zones 8, and the coal combustion process stops.

The water-cooled beam 24 is a supporting structure for the refractory lining of the convection unit 21 of the boiler 2 and provides an overhaul period of operation of the lining of up to 7 years, which improves the reliability of operation of the boiler.

The claimed invention allows to increase the efficiency of the boiler when burning low-grade coal, including those containing ash with a low melting point, to reduce harmful emissions into the atmosphere, prevent gas contamination of the production room of the boiler house, and therefore, improve working conditions, increase the reliability of operation of the boiler and reduce its economic costs operation.

Claims (1)

A boiler unit including an accelerating box, a fluidized bed furnace, a moving grate with blowing zones located under it, a rotary screen, side screens, a festoon screen, a convection unit, a smoke exhaust, an air box, characterized in that an accelerating box is installed on the side screen, inside of which a movable plate is located, and pneumatic inlet is mounted in its lower part, a front seal made in the form of a curved plate is installed in the front part of the lower branch of the moving grate blade, in the rear part and the upper branch of the moving grate the back seal is installed, made in the form of a plate, under which there is a retaining blast zone, the rotary screen is installed vertically and made of pipes, the space between which is closed by metal plates attached to the pipes along the entire length, between the scallop screen and convection the unit, in its lower part, a water-cooled beam is installed, the back of the boiler is connected to a straight-through cyclone, in addition, the boiler unit additionally contains a recirculation system ventilation, which is made in the form of a pipeline and is located between the exhaust fan and the air duct.

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