JPS62123211A - Control of unburnt constituent in fluidized bed combustion boiler - Google Patents

Abstract

PURPOSE:To control the flow amount of gas in accordance with the fluctuation of a load and obtain a constant flow speed at all times by a method wherein an operation, in which particles including unburnt ash or the like dispersed from a fluidized bed are kept in a high temperature and the particles, having comparatively large grain sizes and collected by a cyclone, are returned to a free board under a high temperature condition through a circulating path, is repeated. CONSTITUTION:All or a part of the peripheral wall of a free board 4 is constituted by a heat insulating structure while all or a part of a contacting and heat transferring section until high-temperature cyclones 6a, 6b continued to the lower side of the free board 4 is lined by an insulating material 9. Further, the heat insulating structure is applied to circulating paths 7a, 7b. Unburnt constituent, flying out of a fluidized bed 2, is burnt in the free board section 4 and the unburnt constituent, corrected by the high-temperature cyclones 6a, 6b, returns to the free board section again and is burnt substantially perfectly while the free board section 4 is kept in a high- temperature condition by the heat insulating effects of the structure 8 of the furnace and the heat insulating material 9 whereby the reactions of denitrification and desulfurization may be effected effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling unburned matter in a fluidized bed combustion boiler.

[Background of the invention]

Generally, in this type of fluidized bed combustion boiler, when the load decreases, the temperature inside the flow rJhH decreases, and the gas temperature also decreases.
Furthermore, the problem arises that the gas flow through the freeboard, that is, the flow velocity is reduced, and the gas temperature is further reduced. This means a decrease in the amount of unburned matter that comes out when the load is low, and when the load is low, the efficiency of the cyclone deteriorates due to the flow velocity, making it impossible to ensure collection efficiency and reducing the amount of unburned matter circulating. This will further accelerate the process.

Therefore, in conventional fluidized bed combustion boilers, when the load changes, there is a problem that the combustion amount in the freeboard section and the heat exchange effect with the heat transfer surface become unbalanced, and the temperature of the freeboard section decreases. This will reduce the overall combustion efficiency of the boiler.

[Purpose of the invention]

The present invention has been developed in view of the above circumstances, and it solves the problems of the prior art by simple and rational means, and controls the gas flow rate in accordance with load fluctuations so that a constant flow rate can always be obtained. The purpose of the present invention is to provide a control method for maintaining the efficiency of either cyclone and maintaining the temperature of the freeboard section at the optimum temperature for desulfurization and denitration in accordance with the load.

[Structure of the invention]

The structure of the present invention, which solves the problems of the prior art, eliminates all contact heat transfer parts up to the cyclone of the fluidized bed combustion boiler, and eliminates the freeboard peripheral wall.

All or part of the exhaust gas duct and the high-temperature cyclone at the furnace outlet connected to it are made to have an insulated structure, and particles including unburned ash scattered from the fluidized bed are transferred from the freeboard to the cyclone through the exhaust gas duct. The relatively large particles captured by the cyclone are repeatedly returned to the freeboard via the circulation path in a high temperature state, and the unburned particles in the particles scattered from the fluidized bed are regenerated. A combustion means, a high-temperature cyclone at the outlet of the furnace, and a rear heat transfer surface are each connected to the freeboard through a plurality of exhaust gas ducts, and the amount of gas passing through the cyclone and the rear heat transfer surface is controlled by the amount of gas passing through the rear heat transfer surface. The gas flow rate in the freeboard section is controlled by a means for controlling the amount of passing gas separately by a damper for controlling the flow rate provided in the low temperature gas flow path connected to the lower side of the surface.

A method for controlling unburned matter in a fluidized bed combustion boiler, which is characterized by preventing large changes in the collection efficiency of the cyclone even at low loads, and controlling the temperature pattern of the freeboard section to a temperature suitable for desulfurization and denitrification. , and all or part of the contact heat transfer part up to the cyclone of the fluidized bed combustion boiler is eliminated, and all or part of the freeboard peripheral wall, the exhaust gas duct, and the high-temperature cyclone at the furnace outlet connected thereto are made into an insulated structure. Particles including unburned ash scattered from the fluidized bed are kept at high temperature until they pass from the freeboard through the exhaust gas duct and enter the cyclone, and relatively large particles captured by the cyclone are kept at high temperature. Repeatedly returning to the freeboard via the circulation path, the flow
A means for re-burning unburned matter in the particles scattered from the J layer, dividing the freeboard into a plurality of parts, and connecting each divided freeboard to a high-temperature cyclone at the furnace outlet via the exhaust gas duct; The rear heat transfer surfaces are connected separately, and the amount of gas passing through the cyclone and the rear heat transfer surface is controlled separately by a damper for flow rate control provided in the low temperature gas flow path connected to the lower side of the rear heat transfer surface. By means of controlling the amount of gas passing through, the gas flow velocity in the freeboard section and the collection efficiency of the cyclone are prevented from changing significantly even at low loads, and the temperature pattern of the freeboard section is made suitable for desulfurization and denitrification. It is characterized by temperature control.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

(a) By adding a system to the freeboard section that collects unburned ash scattered from the fluidized bed at a high temperature and circulates it to the freeboard section, effective combustion of unburned ash can be measured, and the freeboard section can be By maintaining the temperature at a high temperature, desulfurization and denitrification reactions are promoted, and the NOx generation value can be significantly controlled.
You can save on desulfurizing agent.

(b) At partial load, by reducing the number of cyclones used, the gas flow rate can be maintained within an appropriate range and collection efficiency can be ensured.

(e) The reliability of the flow control section is high because the damper is installed in the low-temperature section on the lower side of the rear heat transfer surface.

(d) When the load changes, even if the balance between the combustion amount and the heat transfer surface is lost, the use of the freeboard section corresponding to the damper can be interrupted by blocking any one of the multiple dampers. The remaining freeboard section can be used as is, and the humidity pattern of the freeboard section should be controlled to a temperature suitable for desulfurization and denitrification.

[Example IF　(Figures 1 and 2) Embodiments of the configuration of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a fluidized bed combustion boiler blunt for carrying out the method of the present invention, FIG. 2 is a perspective view of the same, FIG.
The figure is a perspective view of the same as above.

First, the embodiment shown in FIGS. 1 and 2 will be described. 1 is a fluidized bed combustion boiler (abbreviated as boiler) having a fluidized bed 2, and 4 is a freeboard section. The free board 4
High-temperature cyclones 6a, 6b are connected to the upper part of the exhaust gas pipes 5a, 5b.
It is connected to the freeboard section 4 through circulation paths 7a and 7b. All or part of the peripheral wall of the freeboard section 4 is made of an insulating structure that does not absorb heat, such as the furnace construction structure 8, and a contact heat transfer section is provided to the high temperature cyclones 6i and 6b continuing on the lower side of the freeboard section 4. All or ' are partially lined with a heat insulating material 9. In addition, the above circulation path 7m,
7b is also provided with a heat insulating structure as described above.

On the downstream side of each of the high-temperature cyclones 6a and 6b, a rear heat transfer surface 11 of a boiler such as an economizer and an air heater is connected via exhaust gas ducts 10a and 10b having a heat insulating structure.
a, 11b, and each rear heat transfer surface 11a, 11b
12 m of low-temperature exhaust gas flow path connected to the lower side of the 12
Flow rate control dampers 13a and 13b are respectively provided at 13b.

The exhaust gases flowing in the exhaust gas streams #12a and 12b pass through a second multi-cyclone and an air heater (not shown).

It reaches the chimney through a dust collector, etc. In addition, the above flow rate control damper 1
It goes without saying that 3a and 13b are configured so that fluctuations in the load are detected and the opening degree is automatically controlled based on this control signal.

[For production]

A method for controlling unburned content in a fluidized bed combustion boiler according to the present invention will be described based on the boiler blunt described above.

When the boiler 1 is operated and flowing VH bed combustion is started, fine particles containing unburned ash from the fluidized bed 2 are scattered in the direction of the free board section 4, and the fine particles are scattered on all or part of the peripheral wall of the 7 re-board section 4. Since the part has a furnace construction structure 8, after a part of the combustion occurs in the re-board part 4 without a temperature drop, the exhaust gas passes through the exhaust gas ducts 1-5a and 5b to the high-temperature cyclone 6a, 6b, where only relatively large particles are captured.

At this time, a 5 m exhaust gas duct connected to the 7 re-board part 4,
5b and the high-temperature cyclones (ia, Oh) are lined with a heat insulating material 9, so that the drop in temperature of the particles scattered in the exhaust gas is small.

The particles captured by the high temperature cyclones 6a and 6b are 80
Maintaining a high temperature of 0 to 1000℃, high temperature cyclone Oa, 6
b #) Circulate with vertical force! It passes through 87a and 7b and is returned to the lower part of the freeboard section 4, where it is reburned. Thereafter, this process is repeated, and the unburned matter that has flowed out from the fluid 2 is burned in the freeboard section 4, and the unburned matter that has been sent to and captured by the high-temperature cyclones 6a and 6b is returned to the freeboard section again. In addition to the heat insulating effect of the above-mentioned furnace structure 8° insulation material 9, the freeboard section 4 is maintained at a high temperature to effectively carry out desulfurization and denitrification reactions, and SOX in the exhaust gas is completely combusted.
, significantly reducing the Noχ emission value.

The exhaust gas with fine particles captured by the high-temperature cyclones 6m and 6b reaches the rear heat transfer surface 11a and Ilb of the boiler via exhaust gas ducts loa and 10b, which have an adiabatic structure, where they exchange heat and become low-temperature (approx. -400°C) passes through the exhaust gas channels 12a and 12bje and is treated in a known manner to continue operation.

During such operation, if the load decreases by 50%, for example, the temperature of the flow a layer decreases, the flow rate of exhaust gas and the amount of exhaust gas decrease by half, the amount of circulation by the high temperature cyclones 6a and 6b decreases, and the freeboard This causes a temperature drop in the rear part of the engine, causing an imbalance between the amount of combustion and the rear heat transfer surface.

Therefore, in the present invention, one of the dampers 13a or 13b is operated in response to a load detection signal, and one exhaust gas flow path 12
a or 12b to interrupt exhaust gas resulfurization.

This slows down the flow of exhaust gas, but if there is little heat absorption structure in the freeboard section 4, it will not be affected much and the high temperature cyclone 6m, 6b
Temperature control can be performed while ensuring the collection efficiency of .

[Example ■] (Figures 3 and 4) In this example, 1 is a fluidized bed combustion boiler (abbreviated as boiler) having a flow rIJJ layer 2, and the freeboard of the boiler 1 is a vertical partition wall. 3 into a plurality of freeboard parts 4a, 4b, and the following structure is the first part.
Since this is the same as the embodiment, detailed explanation will be omitted.

[For production]

A method for controlling unburned content in a fluidized bed combustion boiler according to the present invention will be described based on the boiler blunt described above.

When the boiler 1 is operated and combustion starts in the flow 111 layer, fine particles containing unburned ash from the fluidized bed 2 flow into the freeboard section 4a,
The particles scattered in the direction 4b are in the freeboard section 4a.
Since all or part of the peripheral walls of , 4b are the furnace structure 8, the freeboard portions 4c, 4b can be heated without temperature drop.
After some combustion occurs in the exhaust gas duct 1-5 along with the exhaust gas,
It passes through a and 5b and enters high-temperature cyclones 8m and 6b, where only relatively large particles are captured. At this time, since the exhaust gas ducts 5a, 5b and the high-temperature cyclones Oa, 6b connected to the freeboard parts 4a, 4b are lined with a heat insulating material 9, the temperature drop of particles scattered in the exhaust gas is small.

The particles captured by the high temperature cyclones 6'a and 6b are 80
A high temperature cyclone 6a that maintains a high temperature of 0 to 1000°C,
6b passes through the circulation paths 7a and 7b by gravity to the freeboard section 4a.

4b, and are reburned separately in freeboard sections 4a and 4b. Thereafter, this rise and fall is repeated, and the unburned matter that has jumped out of the fluidized bed 2 is transferred to the freeboard portions 4a, 4.
b, and a high temperature cyclone 6a.

The unburned matter sent to and captured by 6b is returned to the freeboard section and is almost completely combusted, resulting in the above-mentioned furnace construction structure 8. In combination with the insulation effect of the heat insulating material 9, the freeboard parts 4a and 4b are maintained at a high temperature to effectively carry out desulfurization and denitrification reactions, thereby converting SO in the exhaust gas.

110x emissions values are significantly reduced.

The exhaust gas in which fine particles have been captured by the high-temperature cyclones 6a and 6b is transferred to exhaust gas ducts l-10a and 10b with a heat-insulating structure.
The exhaust gas reaches the rear heat transfer surfaces 11a and 11b of the boiler via the boiler, and the exhaust gas is lowered in temperature (approximately 300 to 400 degrees Celsius) by heat exchange there. Continued.

During such operation, for example, if the round load decreases by 50%, the temperature of the flow m layer decreases, the flow rate of exhaust gas and the amount of exhaust gas decrease by half, and the amount of circulation by the high temperature cyclones 6a and Ob decreases. This causes a temperature drop (of the freeboard section), causing an imbalance between the amount of combustion and the rear heat transfer surface.

Therefore, in the present invention, one of the dampers 13a or 13b is operated in response to a load detection signal, and one exhaust gas flow path 12
Block a or 12b to interrupt the flow of exhaust gas.

As a result, the operation of the freeboard section 4a or 4b on the side where the flow of exhaust gas is interrupted is interrupted, and only the remaining freeboard section 4a or 4b continues to operate at 100%. Therefore, even if the use of one side is stopped, the other side continues to be used normally and the gas flow rate is maintained, so there is no overcooling in the freeboard section and the high temperature cyclone 6a
Alternatively, temperature control can be performed while ensuring the collection efficiency of 6b.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of a fluidized bed combustion boiler plant that implements the method of the present invention, FIG. 2 is a perspective view of the same as above, FIG. 3 is a schematic diagram showing a configuration in which a freeboard is divided by partition walls,
The figure is a perspective view of the same as above. 1. Fluidized bed combustion boiler, 2. Fluidized bed, 3. Partition wall. 4a, 4b-7 Lee board section, 5a, 5b-exhaust gas duct. 6a, 6b...high 1-item cyclone, 7a, 7b...
・Circulation path, 8...Furnace construction structure, 9...Insulation material, 10a
,]Ob...Exhaust gas duct. 11a, Ilb rear heat transfer surface, 12a, I2b・
Exhaust gas flow path. 13a, 13b flow rate control damper.

Claims (1)

[Claims] [Claim 1] (a) All or part of the contact heat transfer section up to the cyclone of the fluidized bed combustion boiler is eliminated, and the freeboard peripheral wall, the exhaust gas duct, and the high-temperature cyclone at the furnace outlet connected thereto are eliminated. A comparison in which all or part of the structure is made of an insulating structure, and the particles, including unburned ash, scattered from the fluidized bed are kept at high temperature until they enter the cyclone from the freeboard through the exhaust gas duct, and are captured by the cyclone. (b) means for re-burning the unburned components in the particles scattered from the fluidized bed by repeatedly returning particles with a large target particle size to the freeboard through a circulation path in a high temperature state; The high-temperature cyclone at the furnace outlet and the rear heat transfer surface are connected separately through the exhaust gas duct of the furnace, and the amount of gas passing through the cyclone and the rear heat transfer surface is connected to the lower side of the rear heat transfer surface. A means of controlling the amount of gas passing through each part using a damper for controlling the flow rate installed in the flow path, so that the gas flow velocity in the freeboard section and the collection efficiency of the cyclone do not change significantly even under low load, A method for controlling unburned content in a fluidized bed combustion boiler, characterized by controlling the temperature pattern of a freeboard section to a temperature suitable for desulfurization and denitrification. [Section 2] (a) Eliminate all or part of the contact heat transfer section up to the cyclone of the fluidized bed combustion boiler, and eliminate all or one of the freeboard peripheral wall, exhaust gas duct, and the high-temperature cyclone at the furnace outlet connected thereto. The part has an insulating structure to keep particles, including unburned ash, scattered from the fluidized bed at high temperature until they pass from the freeboard through the exhaust gas duct and enter the cyclone. (b) dividing the freeboard into a plurality of parts and dividing the freeboard into a plurality of parts; A high-temperature cyclone at the furnace outlet and a rear heat transfer surface are separately connected to each freeboard section via the exhaust gas duct, and the amount of gas passing through the cyclone and the rear heat transfer surface is determined by By means of controlling the amount of passing gas separately using flow rate control dampers installed in the low-temperature gas flow paths connected to the lower side of the surface, the gas flow velocity in the freeboard section and the collection efficiency of the cyclone can be adjusted even under low loads. A method for controlling unburned content in a fluidized bed combustion boiler, which is characterized by controlling the temperature pattern of the freeboard section to a temperature suitable for desulfurization and denitrification without causing wide changes.