JPH05196202A - Fluidized bed boiler - Google Patents

Abstract

PURPOSE:To desulfurize highly effectually by detecting temperature at a plurality of locations in a height direction in a furnace body, and issuing valve opening/closing instructions corresponding to the detected temperatures to a control valve. CONSTITUTION:Temperature at each location in a height direction in a furnace body 1 is detected by temperature detectors 28, 29 and is fed to a calculation control device 30. The calculation control device 30 issues valve opening/closing instructions corresponding to temperatures in the furnace body 1 to respective control valves 26, 27 to adjust the openings 26, 27 of the respective control valves 26, 27. Thereby, the flow rate of circulated exhaust gas G3 introduced into the furnace body 1 through exhaust gas pipe lines 10, 15 and through circulated exhaust gas pipe lines 21, 23, 24, 25, are regulated and hence the temperatures at the respective locations in the height direction in the furnace body 1 to desired once for promotion of desulfurization of combusted gas G1 are adjusted. Thus, the desulfurization of the combusted G1 is ensured highly efficiently.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fluidized bed boiler.

[0002]

2. Description of the Related Art In a circulating fluidized bed boiler, since desulfurization is performed in the furnace body, it is necessary to control the temperature in the furnace body to an optimum temperature for desulfurization. There is, for example, the one shown in FIG.

In FIG. 6, reference numeral 1 is a furnace body containing a bed material 2 fluidized by primary air A ₁ introduced from below, and 3 is arranged below the furnace body 1 and inside the furnace body 1. The supply ports 4 for supplying a fuel F such as coal and a desulfurizing agent such as CaCO ₃ separate the scattered particles in the combustion gas G ₁ sent from the upper part of the furnace body 1 through the pipe line 5 and separate the circulation. A cyclone for returning the particles to the lower part of the furnace body 1 through a pipe line 6 equipped with a J valve 6a, 7 is a rear heat transfer section into which the combustion gas G ₁ that has passed through the cyclone 4 is introduced, and 8 is inside the rear heat transfer section 7. The superheater 9 is disposed in the rear heat transfer unit 7, and the economizer 9 is disposed in the rear heat transfer unit 7 so as to be located below the superheater 8.

Reference numeral 10 denotes a pipe line connected to the lower end of the rear heat transfer unit 7 for feeding the boiler exhaust gas G ₂ discharged from the rear heat transfer unit 7, and 11 denotes air connected to a midway portion of the pipe line 10. A preheater, 12 is a dust collector connected to a midway portion of the pipeline 10 so as to be located downstream of the air preheater 11, 13 is an induction fan connected to the downstream end of the pipeline 10, and 14 is an induction fan. It is a chimney for discharging the boiler exhaust gas G ₂ discharged from the ventilator 13 and sent through the pipe line 15 to the atmosphere.

Reference numeral 16 denotes a primary air blower, 17 denotes a pipe line to which the air preheater 11 is connected in the middle, and the primary air blower 16 and the lower part of the furnace body 1 are connected by a pipe line 17. Thus, the primary air A ₁ from the primary fan 16 passes through the pipe 17, is preheated by the air preheater 11 and can be introduced from the pipe 17 to the lower part of the furnace body 1.

Reference numeral 18 denotes a secondary air blower, and 19 denotes a pipe line to which the air preheater 11 is connected in the middle thereof, and an over air port 19 provided at an intermediate position in the height direction between the secondary air blower 18 and the furnace body 1. Are connected by a conduit 20. Thus, the secondary air A ₂ from the secondary air blower 18 passes through the pipe 20, is preheated by the air preheater 11, and can be introduced into the furnace body 1 through the pipe 20 and the over air port 19. It has become.

During operation, the bed material 2 is fluidized by the primary air A ₁ introduced into the furnace body 1 from below, and the fuel F and the desulfurizing agent are supplied from the supply port 3 into the furnace body 1 and burned, The combustion gas G ₁ is generated, and the generated combustion gas G ₁ rises while heating water and steam flowing in the heat transfer tube forming the furnace body 1. Also the combustion gases G _1, the temperature of the combustion gas G ₁ is being adjusted to be optimal for desulfurization from the over Airport 19 secondary air A ₂ is introduced. As a result, the desulfurizing agent and the sulfur content in the combustion gas G ₁ are combined to desulfurize.

The combustion gas G ₁ further rises in the furnace body 1 while being desulfurized, and is fed to the cyclone 4 from the pipe line 5. In the cyclone 4, the bed material and the like entrained in the combustion gas G ₁ are separated. Separated and separated bed material is J valve 6
It is returned to the lower part of the furnace body 1 from the pipe line 6 provided with a.

On the other hand, the combustion gas G from which the bed material has been removed
₁ is introduced from the cyclone 4 to the rear heat transfer section 7, superheats the steam in the superheater 8 and heats the water in the economizer 9 to be discharged as boiler exhaust gas G ₂ into the pipeline 10, and passes through the pipeline 10. Meanwhile, the air preheater 11 preheats the primary air A ₁ and the secondary air A ₂ , and the dust is collected by the dust collector 12 and then attracted to the induced draft fan 13 to be pressurized and passed through the pipe line 15 and the chimney 14 Released into the atmosphere.

On the other hand, the primary fan 16 and the secondary fan 18
The primary air A ₁ and the secondary air A ₂ fed by the above are fed through the pipelines 17 and 20 and preheated by the air preheater 11, and further fed through the pipelines 17 and 20, the primary air A ₁ Is introduced from the lower part of the furnace body 1 into the furnace body 1 to fluidize the bed material 2 and to burn the fuel F, and the secondary air A ₂
From the side of the furnace body 1 through the over-Airport 19 is introduced into the top of the furnace body 1, it is mixed with the combustion gas G ₁ generated by the combustion of the fuel F of the combustion gas G ₁ to the optimum temperature for desulfurization adjust. The flow rate control of the primary air A ₁ and the secondary air A ₂ is performed, for example, by detecting the temperature of the combustion gas G ₁ at the lower position of the furnace body 1 and the position above the over air port 19 by a temperature detector (not shown). This is performed by adjusting the opening degrees of the dampers of the primary fan 16 and the secondary fan 18 so that the temperature at the position becomes a preset temperature.

[0011]

In the circulating fluidized bed boiler described above, the temperature of the combustion gas G ₁ in the furnace body 1 is controlled by adjusting the flow rates of the primary air A ₁ and the secondary air A ₂ . Therefore, the combustion state in the furnace body 1 changes depending on the air flow rate of each of the air A ₁ and A ₂ , and it is difficult to bring the temperature to a desired temperature over the entire height direction in the furnace body 1. Therefore, the region of the optimum temperature range for desulfurization formed in the furnace body 1 is narrow, and desulfurization cannot be performed with higher efficiency.

The present invention has been made in view of the above circumstances and has an object to widen the region of the optimum temperature range for desulfurization formed in the furnace body.

[0013]

DISCLOSURE OF THE INVENTION According to the present invention, there is provided a furnace body capable of accommodating a bed material therein, and a side portion provided with a supply port for supplying a desulfurizing agent and fuel, and combustion generated in the furnace body. An exhaust gas line for feeding gas as boiler exhaust gas, a primary air pipe that is connected to the lower part of the furnace body and allows primary air to be introduced into the furnace body, and a middle position in the height direction of the furnace body. And a secondary air pipeline adapted to introduce secondary air into the furnace main body, and a part of the boiler exhaust gas which is electrically connected to the exhaust gas pipeline and the lower part of the furnace main body and has a control valve in the middle Is introduced into the furnace main body, and a control valve is provided in the middle portion of the furnace main body while branching from the first circulation exhaust gas pipeline to be conducted to the middle position in the height direction of the furnace main body. In addition, some of the boiler exhaust gas can be introduced into the furnace body. The second circulating exhaust gas pipe, the temperature detector for detecting the temperature at a plurality of positions in the furnace body in the height direction, and the valve opening / closing command to the control valve corresponding to the temperature detected by each temperature detector. It is provided with an arithmetic and control unit for outputting.

[0014]

The temperature at each position in the height direction in the furnace body is detected by the temperature detector and given to the arithmetic and control unit. From the arithmetic and control unit, a valve opening / closing command corresponding to the temperature in the furnace body is sent. It is given to the control valve and the opening degree of the control valve is adjusted. Therefore, the flow rate of the circulating exhaust gas introduced into the furnace main body through the exhaust gas pipeline and the circulating exhaust gas pipeline is adjusted, and the temperature at each position in the height direction in the furnace main body is adjusted to a desired temperature. The desulfurization of combustion gas in the body can be promoted.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is an embodiment of the present invention, and the basic construction is substantially the same as that shown in FIG. 6, and in the figure, the same parts as those shown in FIG. is there.

In the figure, reference numeral 21 denotes a pipe line whose one end is connected to a pipe line 15 connecting the induction fan 13 and the chimney 14, and the suction side of the exhaust gas recirculation fan 22 is provided at the tip of the pipe line 21. It is connected. 23 is an exhaust gas recirculation fan 22
Is connected to the discharge side of the pipe, the tip of the pipe 23 branches into the pipes 24 and 25, and the ends of the pipes 24 and 25 are downstream of the air preheater 11 of the pipes 17 and 20. Connected to the position. Further, control valves 26 and 27 for controlling the flow rate of the circulating exhaust gas G ₃ flowing through the respective pipelines 24 and 25 are connected to the middle portions of the respective pipelines 24 and 25.

28 is the temperature T ₁ near the bottom of the furnace body 1.
A temperature detector 29 for detecting the temperature T is a temperature detector for detecting a temperature T ₂ slightly above the over-air port 19 in the furnace body 1, and the temperature T detected by the temperature detectors 28, 29 is T. ₁ and T ₂ are arithmetic and control units 3 as electric signals
0, and the arithmetic and control unit 30 deviates from the preset temperature T _{0 by} ΔT ₁ (= T ₀ −T ₁ ), ΔT ₂ (= T ₀ −).
T ₂ ) is obtained and the valve opening / closing commands X ₁ and X ₂ corresponding to the deviations ΔT ₁ and ΔT ₂ can be given to the control valves 26 and 27.

During operation, the primary air A ₁ mixed with the circulating exhaust gas G ₃ is introduced from below into the furnace body 1 to fluidize the bed material 2 and to supply the desulfurizing agent and the fuel F to the supply port 3
Is supplied to the inside of the furnace body 1 and combusted to generate combustion gas G _{1. The} generated combustion gas G ₁ rises while heating water and steam flowing in the heat transfer tube forming the furnace body 1. .. Further, the secondary air A ₂ mixed with the circulating exhaust gas G ₃ is introduced into the furnace main body 1 through the over-air port 19 and mixed into the combustion gas G ₁ , and the temperature of the combustion gas G ₁ is adjusted by the secondary air A _2. Is further raised in the furnace body 1 and is fed from the pipe 5 to the cyclone 4, where the combustion gas G
_The bed material and the like contained in ₁ are separated, and the separated bed material and the like is returned to the lower part of the furnace body 1 from the pipe line 6 equipped with the J valve 6a. The sulfur content contained in the combustion gas G ₁ is desulfurized by the desulfurizing agent when rising in the furnace body 1.

On the other hand, the combustion gas G from which the bed material has been removed
₁ is introduced from the cyclone 4 to the rear heat transfer section 7, superheats steam in the superheater 8 and heats water in the economizer 9, and is discharged to the pipeline 10 as the boiler exhaust gas G ₂ and passes through the pipeline 10. Meanwhile, the air preheater 11 preheats the primary air A ₁ and the secondary air A ₂ , and the dust is collected by the dust collector 12 and then attracted to the induced draft fan 13 to be pressurized and passed through the pipe line 15 and partially. Is discharged from the chimney 14 to the atmosphere, and part of it is circulated exhaust gas G ₃ in the pipeline 2
1, the circulating exhaust gas G ₃ introduced into the pipe line 21 is pressurized by the exhaust gas recirculation fan 22 and fed through the pipe line 23, and the flow rate is adjusted by the control valves 26 and 27. It is introduced into the pipelines 17, 20 through 24, 25.

On the other hand, the primary fan 16 and the secondary fan 18
The opening degree of the damper (not shown) is maintained within a constant opening degree corresponding to the boiler load. Thus, the primary air A ₁ and the secondary air A ₂ sent by the primary fan 16 and the secondary fan 18 are sent through the pipe lines 17 and 20 to the air preheater 1.
1, which is preheated at 1, and is further fed through the pipelines 17 and 20, and is mixed with the circulating exhaust gas G ₃ from the pipelines 24 and 25. The mixed primary air A ₁ from the circulating exhaust gas G ₃ is supplied from below to the furnace body. The secondary air A ₂ introduced into the furnace 1 and mixed with the circulating exhaust gas G ₃ is introduced from the over air port 19 to the upper portion of the furnace body 1.

In the above operation, the lower and upper T ₁ and T ₂ in the furnace body 1 are detected by the temperature detectors 28 and 29, and given to the arithmetic and control unit 30 as electric signals. Deviation ΔT ₁ (= T ₀ −T ₁ ) between the preset temperature T ₀ and the detected temperatures T ₁ and T ₂ ,
ΔT ₂ (= T ₀ −T ₂ ) is obtained, valve opening / closing commands X ₁ and X ₂ of the valves corresponding to the deviations ΔT ₁ and ΔT ₂ are given to the control valves 26 and 27, and the valve opening is adjusted. The flow rate of the circulating exhaust gas G ₃ flowing into the primary air A ₁ and the secondary air A ₂ in the pipes 17, 20 is adjusted, and as a result, the temperature in the furnace body 1 is the optimum temperature for desulfurization over a wide range. Adjusted to. When the boiler load does not change, the flow rates of the primary air A ₁ and the secondary air A ₂ do not change, so the temperature inside the furnace body 1 is adjusted only by adjusting the flow rate of the circulating exhaust gas G ₃ . Therefore, the combustion state inside the furnace body 1 does not change, the temperature inside the furnace body 1 can be finely adjusted, and efficient desulfurization can be performed.

For example, when the temperature distribution in the height direction in the furnace body 1 is high in the middle position in the height direction and high in the upper direction and at an appropriate temperature in the lower direction, the opening of the control valve 27 is increased. Then, the flow rate of the circulating exhaust gas G ₃ introduced into the furnace body 1 from below together with the primary air A ₁ does not change,
The flow rate of the circulating exhaust gas G ₃ introduced from the over air port 19 into the furnace body 1 along with the secondary air A ₂ increases.
Therefore, the temperature above the intermediate height in the furnace body 1 drops, and the inside of the furnace body 1 has an optimum temperature distribution for desulfurization as a whole as shown in FIG.

FIG. 4 shows the temperature distribution in the furnace body 1 in the height direction.
As shown in, when the temperature is high in the lower position and in the middle position in the height direction and the temperature is high in the upper position, the opening degree of the control valve 26 is increased. Then, the flow rate of the circulating exhaust gas G ₃ introduced into the furnace body 1 from the over air port 19 together with the secondary air A ₂ does not change, but the circulating exhaust gas G ₃ introduced from below into the furnace body 1 together with the primary air A ₁ is changed. Flow rate increases. Therefore, the temperature in the furnace body 1 from the lower side to the intermediate height is lowered, and the inside of the furnace body 1 has an optimum temperature distribution for desulfurization as a whole, as shown in FIG.

In the embodiment of the present invention, the case where two temperature detectors are provided in the upper and lower parts of the furnace body has been described. Although the case of using a circulating fluidized bed boiler as the boiler for adjusting the flow rate has been described, primary air,
A boiler that introduces secondary air can also be applied to a normal fluidized bed boiler, and circulating exhaust gas is not mixed with primary air and secondary air, but can be introduced directly into the furnace body. Needless to say, various changes can be made without departing from the gist of the present invention.

[0026]

According to the fluidized bed boiler of the present invention, the excellent effect that the desulfurization of combustion gas can be efficiently performed can be obtained.

[Brief description of drawings]

FIG. 1 is a flow system diagram of an embodiment of a fluidized bed boiler of the present invention.

FIG. 2 is a graph showing the temperature distribution in the height direction in the furnace body when the temperature in the middle position in the height direction and in the upper part of the furnace body is high.

FIG. 3 is a graph showing a temperature distribution in the height direction in the furnace body when the circulating exhaust gas is introduced into the furnace body in the upper direction.

FIG. 4 is a graph showing a temperature distribution in a height direction inside the furnace body when the temperature is lower in the furnace body and at an intermediate position in the height direction.

FIG. 5 is a graph showing the temperature distribution in the height direction in the furnace body when the circulating exhaust gas is introduced into the furnace body downward.

FIG. 6 is a flow system diagram of a conventional fluidized bed boiler.

[Explanation of symbols]

1 Furnace Main Body 2 Bed Material 3 Supply Port 10,15 Pipeline (Exhaust Gas Pipeline) 17 Pipeline (Primary Air Pipeline) 20 Pipeline (Secondary Air Pipeline) 21,23,24,25 Pipeline (Circulation Exhaust Gas) Pipe line) 26,27 Control valve 28,29 Temperature detector 30 Calculation control device F Fuel A ₁ Primary air A ₂ Secondary air G ₁ Fuel gas G ₂ Boiler exhaust gas G ₃ Circulating exhaust gas T ₁ , T ₂ Temperature X ₁ , X ₂ valve open / close command

Claims (1)

[Claims] 1. A furnace main body having a supply port for supplying a desulfurizing agent and a fuel, which can house a bed material inside, and a combustion gas generated in the furnace main body, which is fed as a boiler exhaust gas. An exhaust gas conduit, a primary air conduit that is conducted to the lower part of the furnace body and is capable of introducing primary air into the furnace body, and a primary air conduit that is conducted to an intermediate position in the height direction of the furnace body, and secondary air is introduced to the furnace body. So that it can be introduced into a secondary air pipeline, and the exhaust gas pipeline and a lower part of the furnace body are electrically connected to each other, and a control valve is provided in the middle part so that a part of the boiler exhaust gas can be introduced into the furnace body. With the first circulation exhaust gas pipe line, the first circulation exhaust gas pipe line is branched from the first circulation exhaust gas pipe and is conducted to the middle position in the height direction of the furnace main body, and has a control valve in the middle part and part of the boiler exhaust gas. A second circulation exhaust gas that can be introduced into the furnace body. A pipeline, a temperature detector for detecting temperatures at a plurality of positions in the furnace body in the height direction, and an arithmetic and control unit for outputting a valve opening / closing command to the control valve corresponding to the temperature detected by each temperature detector. A fluidized bed boiler characterized by being provided.