JP2000257807A - Fluidized layer heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluidized layer heat exchanger reducing the corrosion of a relatively high-temperature heat exchanger such as a super-heater or the like in a circulating fluidized bed boiler. SOLUTION: In a fluidized layer heat exchanger 140, separating particles from two-phase stream containing combustion gas and the particles produced in the furnace 110 of a circulating fluidized bed boiler 110 and recovering heat from at least one part of the separated particles, then, supplying the particles into the furnace 100 again after recovering heat, an upstream side first chamber and a downstream side second chamber are provided in the fluidized layer heat exchanger 140 in reference to the moving direction in the fluidized layer heat exchanger 140 of the particles running from the fluidized layer heat exchanger 140 toward the furnace 110 while a first heat exchanger 144, through which relatively low temperature operating fluid flows, is arranged in the first chamber and a second heat exchanger 146, through which relatively high temperature operating fluid flows, is arranged in the second chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed heat exchanger in which corrosion of a relatively high temperature heat exchanger such as a superheater in a circulating fluidized bed boiler or the like is reduced.

[0002]

2. Description of the Related Art Conventionally, a superheater in a fluidized-bed boiler,
The arrangement of a heat exchanger such as a reheater includes: (1) a configuration in which a superheater is provided in a furnace and a flue downstream of a cyclone. (2) a part or all of particles separated by a cyclone;
It is introduced into a fluidized bed heat exchanger provided independently of the furnace, and forms a fluidized bed in the fluidized bed heat exchanger using a part of the combustion air supplied to the boiler. A configuration in which a superheater and an evaporation tube are provided is known.

[0003] When burning fuel containing corrosive components, typically industrial waste, municipal waste, RDF, etc., corrosive gases such as hydrogen chloride gas and chlorine gas are generated in exhaust gas.
As in the configuration of (1), if a superheater that becomes hot inside a combustor or flue where corrosive gas exists at high temperature is installed,
This superheater is known to undergo severe hot corrosion. Therefore, it has been studied to adopt a configuration in which a relatively low-temperature superheater is provided in the flue and the high-temperature superheater is provided in a heat exchanger room independent of the furnace as in the configuration of (2). In particular, it has a general configuration for waste-fired fluidized-bed boilers.

Generally, it is said that particles are well mixed and diffused in a fluidized bed, and the temperature in the bed is kept uniform. Macroscopically, it can be said that the inside of the fluidized bed has a uniform temperature distribution, but when high-temperature particles are introduced into a specific portion inside the fluidized bed as in a fluidized bed heat exchanger, the heat exchanger A temperature distribution of the particles is formed in the chamber, and a portion where the high-temperature particles are supplied from the cyclone locally has a high temperature, and a portion from which the particles are discharged has a low temperature. Therefore, usually, a high-temperature superheater is arranged on the high-temperature side and an evaporator is arranged on the low-temperature side in consideration of efficient arrangement of the heat transfer surface.

FIG. 3 shows a conventional fluidized bed heat exchanger. In FIG. 3, the circulating fluidized bed boiler includes a furnace 10,
A cyclone 12 for separating particles from a gas-solid two-phase flow containing combustion gas and particles discharged from the furnace 10, and a flue for guiding the separated combustion gas to a chimney (not shown). 14 is provided. The stack 14 is provided with a low-temperature superheater 16 and a economizer 18.

The cyclone 12 is connected to a seal pot 22 via a conduit 20, and the seal pot 22 is connected to the furnace 10 via a conduit 24, and is connected via a ash removal control valve 26 and a conduit 26a. It is connected to a fluidized bed heat exchanger 28 provided independently of the furnace 10. The particles supplied to the fluidized bed heat exchanger 28 are cooled by performing heat exchange in the fluidized bed heat exchanger 28, and then returned to the furnace 10 via the conduit 34.

In the prior art, a high-temperature superheater 30 and an evaporator 32 are provided in a fluidized-bed heat exchanger 28.
More specifically, the high-temperature superheater 30 is connected to the fluidized-bed heat exchanger 28.
Is disposed in the high-temperature portion on the upstream side with respect to the flow of particles in the flow from the fluidized bed heat exchanger 28 to the furnace 10;
The evaporator 32 is disposed in the low temperature section on the downstream side.

[0008]

However, a part of the superheater 30 disposed on the high temperature side in the fluidized bed heat exchanger 28 directly contacts the high temperature particles of about 850 to 900 ° C. from the cyclone 12. Due to the contact, hot corrosion may be observed on the surface. Further, the fluidized bed heat exchanger 28
The particles supplied to the furnace 10 again through the furnace become low temperature by contact with the evaporator 32, and therefore, depending on the operating conditions of the fluidized bed boiler, the particle temperature circulating from the fluidized bed heat exchanger 28 to the furnace 10 Can become too cold, which can lead to a decrease in furnace firing temperature.

An object of the present invention is to solve the problems of the prior art. A fluidized bed heat exchanger in which corrosion of a relatively high temperature heat exchanger such as a superheater in a circulating fluidized bed boiler is reduced. It is intended to provide.

[0010]

According to the first aspect of the present invention, there is provided a fluidized bed heat exchanger for forming a fluidized bed and recovering heat by supplying high-temperature particles. A first chamber on the upstream side and a second chamber on the downstream side are provided in the fluidized-bed heat exchanger with respect to the moving direction of the particles discharged to the outside in the fluidized-bed heat exchanger; That a first heat exchanger through which a relatively low temperature working fluid flows is disposed in the chamber, and a second heat exchanger through which a relatively high temperature working fluid flows is disposed in the second chamber. Features.

The second heat exchanger can be either a superheater or a reheater, or both, and the first heat exchanger can be an evaporator, a economizer, or a low-temperature superheater. Any one or a combination thereof can be used.

[0012] Preferably, a fluidized bed and a stationary bed can be simultaneously formed in the first chamber so that the amount of heat exchange in the first heat exchanger provided in the first chamber can be adjusted. I do. More preferably, the steam inlet of the second heat exchanger is located upstream with respect to the moving direction of the particles.

The present invention separates particles from a two-phase flow containing combustion gas and particles generated in a furnace of a circulating fluidized bed boiler, and forms a fluidized bed with at least a part of the separated particles. The present invention can be applied to a fluidized bed heat exchanger in which heat recovery is performed and particles are supplied again into the furnace after the heat recovery. In this case, a first chamber is arranged on the upstream side and a second chamber is arranged on the downstream side with respect to the moving direction of the particles from the fluidized bed heat exchanger toward the furnace in the fluidized bed heat exchanger.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a circulating fluidized bed boiler 100 according to an embodiment of the present invention
And a cyclone 12 for separating particles from a gas-solid two-phase flow containing combustion gas and particles discharged from the furnace 110.
0 and a flue 130 for directing the separated combustion gases to a chimney (not shown). The flue 130 is provided with a low-temperature superheater 132 and a economizer 134.

The cyclone 120 is connected to a seal pot 126 via a conduit 122,
6 is connected to the furnace 110 via a conduit 124, and via an ash removal control valve 128 and a conduit 128a,
Fluidized bed heat exchanger 1 provided independently of furnace 110
40. The fluidized bed heat exchanger 140 is divided into a first chamber and a second chamber by a partition wall 142. More specifically, with respect to the moving direction of the particles in the fluidized bed heat exchanger 140 from the fluidized bed heat exchanger 140 to the furnace 110, a first chamber is provided on the upstream side and a second chamber is provided on the downstream side. Have been. In the present embodiment, an evaporator 144 as a first heat exchanger is provided in a first room, and a high-temperature superheater 146 as a second heat exchanger is provided in a second room.

The fluidized bed heat exchanger 140 is connected to an air supply source (not shown) such as a blower, a fan, and a compressor via a pipe 160, and combustion air is supplied from the air supply to the pipe 160, Fluidized bed heat exchanger 140, air supply line 1
It is supplied to the furnace 110 via 62. The combustion air is
As conventionally known, the air is divided into primary air and secondary air, and the primary air is supplied from the furnace bottom, and the secondary air is supplied from an intermediate portion in the furnace 110. Further, all of the combustion air to the furnace 110 may be supplied through the fluidized bed heat exchanger 140, or a part of the air may be directly supplied to the furnace 110,
The remainder may be supplied from the fluidized bed heat exchanger 140.

The operation of this embodiment will be described below. As is conventionally known, in a circulating fluidized-bed boiler, in a furnace 110, ash of fuel is a main component, and unburned char, calcium sulfate generated by a desulfurization reaction, and oxidation generated from limestone are used. The particles containing calcium and the like and air form a high-temperature, high-speed solid-gas two-phase flow and rise in the furnace 110. The solid-gas two-phase flow discharged from the furnace 110 is separated into particles and combustion gas in the cyclone 120.
The combustion gas separated in the cyclone 120 is supplied to the low-temperature superheater 132 and the economizer 134 disposed in the flue 130.
Cooled by heat exchange when passing through the chimney (not shown)
Emitted from the atmosphere. Although not shown in detail, waste as fuel is supplied to a lower primary combustion area inside the furnace.

The particles separated in the cyclone 120 are transferred by a conduit 122 to a seal pot 126,
A part thereof is supplied again from the seal pot 126 to the furnace 110 via the conduit 124, and the rest is supplied to the ash removal control valve 12.
8. It is supplied to the fluidized bed heat exchanger 140 via the conduit 128a. Thus, the particles supplied to the fluidized bed heat exchanger 140 accumulate in the fluidized bed heat exchanger 140, and
To form a fluidized bed.
Particles in the first chamber move across the partition 142 to the second chamber for this fluidization. The movement of the particles from the second chamber to the furnace 110 can be performed using, for example, a seal pot.

Here, as shown in FIG.
Are connected to one side in the fluidized bed heat exchanger 140, and the right side is the high temperature side and the left side is the low temperature side in FIG. That is, in the present embodiment, the upstream first chamber is on the high temperature side, and the downstream second chamber is on the low temperature side. More specifically, the particles fed into the first chamber of the fluidized bed heat exchanger 140 have a temperature of about 850-900 ° C,
It is cooled by heat exchange with a steam pipe arranged in the first chamber and moves to the second chamber at a temperature of about 750 ° C. Second
The particles moved to the chamber are further cooled there by heat exchange with the high-temperature superheater 146, and are again supplied to the furnace 110 via the air supply line 162 together with the combustion air.

Since the working fluid flowing through the high-temperature superheater 146 is relatively high-temperature steam, the high-temperature heater 146 is subjected to severe thermal conditions, and high-temperature corrosion is likely to occur on its surface. However, according to the present embodiment, since the high-temperature superheater 146 is disposed in the second room on the low-temperature side in the fluidized-bed heat exchanger 140, the high-temperature superheater 14
The surface temperature of No. 6 is lower than that in the case where it is disposed in the first room on the high temperature side, and a local high temperature portion which is a problem in the related art does not occur. In addition, the steam inlet of the high-temperature superheater is arranged on the upstream side in the moving direction of the particles in the fluidized bed heat exchanger, that is, the outlet side of the steam heated by the heat exchange is arranged on the downstream side in the moving direction of the particles. By doing so, it is possible to further prevent a local high-temperature portion from being formed on the surface of the high-temperature superheater.

On the other hand, since the evaporator 144 is disposed in the first chamber, the temperature of the particles supplied from the fluidized-bed heat exchanger to the furnace 110 is excessive depending on the operating conditions of the fluidized-bed boiler 100 as in the prior art. And the furnace temperature is prevented from lowering. Further, since the working fluid flowing inside the evaporator 144 is water having a relatively low temperature,
Even if the evaporator 144 is disposed in the first room on the high temperature side, the surface temperature is low and the problem of high temperature corrosion does not occur.

By the way, as long as the temperature in the furnace is kept constant, the amount of heat absorbed in the furnace is almost constant irrespective of the load of the fluidized-bed boiler 100 and cannot be controlled. Therefore, when reducing the load of the fluidized bed boiler 100,
It must be controlled by reducing the amount of heat exchange or heat absorption in the fluidized bed heat exchanger 140. In such a case, the amount of heat exchange in the fluidized bed heat exchanger 140 is conventionally reduced by reducing the amount of particles supplied to the fluidized bed heat exchanger 140.

This control method can be implemented also in the embodiment shown in FIG. However, the high-temperature superheater 14
In the configuration in which the fluid supply 6 is disposed in the second chamber on the low temperature side of the fluidized bed heat exchanger 140, when the supply amount of particles to the fluidized bed heat exchanger 140 is reduced, the temperature level in the second chamber becomes excessively high. There is a possibility that a problem may occur in which the temperature of the superheated steam decreases and sufficient superheated steam cannot be obtained.

Next, an embodiment which solves this problem will be described with reference to FIG. FIG. 2 shows a fluidized bed heat exchanger 140.
Is a schematic view of the wind box 150 as viewed from below. In FIG. 2, a wind box 150 includes a first wind box 152 for supplying combustion air to a first chamber of the fluidized bed heat exchanger 140 and a second wind box for supplying combustion air to a second chamber. 154 and
The first wind box 152 includes first to third small chambers 152a,
52b and 152c. More specifically, the first to third small chambers 152a, 152b, 152c are arranged in the direction of movement of particles from the first chamber to the second chamber in the fluidized bed heat exchanger 140 as indicated by arrows in FIG. It is defined by two partition walls 156a and 156b provided in parallel.

While the fluidized bed boiler 100 is operating at full load, all of the first to third small chambers 152a, 152
2b and 152c to supply combustion air, and while the fluidized-bed boiler 100 is operating at a partial load, the first
One or both of the first and second small chambers 152a and 152c are closed, and the combustion air is supplied to the fluidized bed heat exchanger 140. More specifically, the first and third compartments 152a,
By closing either one of 52c, the evaporator 144 disposed in the first chamber can use 66% of the heat transfer surface thereof, and both the first and third small chambers 152a and 152c are used. By closing, the evaporator 144 disposed in the first chamber has 33% of its heat transfer surface available.
In any case, the inventor of the present application opened the second small chamber 152b disposed in the middle and kept the central part of the first chamber fluidized at all times. From the second
Has been found to be advantageous from the viewpoint of moving to the room.

According to the embodiment of FIG. 2, forming a fluidized bed and a stationary bed in the first chamber of the fluidized bed heat exchanger 140 without reducing the particle flow rate to the fluidized bed heat exchanger 140. Accordingly, it is possible to reduce the load on the fluidized-bed boiler 100 by changing the amount of heat absorbed in the evaporator 144 in the first chamber. By appropriately selecting the arrangement and size of the heat transfer surface of the evaporator 144 in the first chamber, the particle temperature moving to the second chamber of the fluidized bed heat exchanger 140 can be adjusted to an appropriate temperature under a wide load condition. , For example, at 750 ° C.

In the embodiment described above, the fluidized bed heat exchanger 14
Although the example of the evaporator has been described as the first heat exchanger disposed in the first chamber in the chamber 0, the present invention is not limited to this, and even if a low-temperature superheater or a economizer is disposed. Good. Also, the second
The second heat exchanger provided in the room is not limited to the high-temperature superheater, and may be a reheater. Further, the first and second heat exchangers may be a combination of the above heat exchangers. In short, a heat exchanger through which a relatively low-temperature working fluid flows is disposed in the first chamber on the high-temperature side, thereby lowering the temperature of particles flowing into the second chamber, and It is only necessary to lower the surface of the second heat exchanger to prevent the occurrence of high-temperature corrosion.

Further, in the above-described embodiment, the inside of the fluidized bed heat exchanger 140 is divided into two by the partition wall 142, but the present invention is not limited to this, and may be divided into three or more chambers. Furthermore, the wind box 150 is not limited to three divisions, but may be divided into four or more small chambers. In short, the fluidized bed heat exchanger 140
It is sufficient that a fluidized bed and a stationary bed can be formed simultaneously in the first chamber. Thus, the amount of heat exchange in the first heat exchanger 144 is controlled, and the load of the fluidized-bed boiler 100 can be adjusted without lowering the particle temperature in the second chamber.

[0029]

According to the present invention, corrosion of a relatively high-temperature heat exchanger such as a superheater in a circulating fluidized bed boiler is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of a fluidized bed boiler according to an embodiment of the present invention.

FIG. 2 is a schematic view of a wind box viewed from below a fluidized bed heat exchanger according to another embodiment.

FIG. 3 is a conceptual diagram of a fluidized-bed boiler according to the related art.

[Explanation of symbols]

 Reference Signs List 100: fluidized bed boiler 110: furnace 120: cyclone 126: seal pot 130: flue 132: low temperature superheater 134: coal saving unit 140: fluidized bed heat exchanger 144: evaporator 146: high temperature superheater

[Procedure amendment]

[Submission date] April 23, 1999 (1999.4.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction contents]

The fluidized bed heat exchanger 140 is connected to an air supply source (not shown) such as a blower, a fan, and a compressor via a pipe 150, and combustion air is supplied from the air supply to the pipe 160, Fluidized bed heat exchanger 140, air supply line 1
It is supplied to the furnace 110 via 62. The combustion air is
As conventionally known, the air is divided into primary air and secondary air, and the primary air is supplied from the furnace bottom, and the secondary air is supplied from an intermediate portion in the furnace 110. In addition, the furnace 110
All of the secondary air may be supplied through the fluidized bed heat exchanger 140, or a part of the secondary air may be supplied directly to the furnace 110, and the remainder may be supplied from the fluidized bed heat exchanger 140.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction contents]

[0020] For the working fluid flowing in the high-temperature superheater 146 is a relatively high-temperature steam, hot overheating 146 becomes thermally severe conditions, high-temperature corrosion is liable to occur at the surface. However, according to the present embodiment, since the high-temperature superheater 146 is disposed in the second room on the low-temperature side in the fluidized-bed heat exchanger 140, the high-temperature superheater 14
The surface temperature of No. 6 is lower than that in the case where it is disposed in the first room on the high temperature side, and a local high temperature portion which is a problem in the related art does not occur. In addition, the steam inlet of the high-temperature superheater is arranged on the upstream side in the moving direction of the particles in the fluidized bed heat exchanger, that is, the outlet side of the steam heated by the heat exchange is arranged on the downstream side in the moving direction of the particles. By doing so, it is possible to further prevent a local high-temperature portion from being formed on the surface of the high-temperature superheater.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor: Manabu Miyamoto 1-1-1 Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo F-term in Kobe Shipyard, Mitsubishi Heavy Industries, Ltd. 3K064 AA06 AB01 AD05 AD08 AF10 BA07 BA15 BA17

Claims (5)

[Claims] 1. A fluidized bed heat exchanger for supplying a high-temperature particle to form a fluidized bed and recovering heat, wherein the fluidized bed heat exchanger of particles discharged from the fluidized bed heat exchanger after heat exchange. A first chamber on the upstream side and a second chamber on the downstream side are provided in the fluidized bed heat exchanger with respect to the moving direction in the first chamber, and the first chamber through which the relatively low-temperature working fluid flows is provided in the first chamber.
A fluidized bed heat exchanger, wherein a second heat exchanger through which a relatively high temperature working fluid flows is disposed in the second chamber. 2. The fluidized bed heat exchanger according to claim 1, wherein the second heat exchanger is one of a superheater and a reheater, or both of them. 3. The first heat exchanger is an evaporator, a economizer,
The fluidized bed heat exchanger according to claim 1, wherein the fluidized bed heat exchanger is any one of a low-temperature superheater or a combination thereof. 4. The fluidized bed heat exchanger according to claim 1, wherein a fluidized bed and a stationary bed can be simultaneously formed in the first chamber. 5. The fluidized bed heat exchanger according to claim 1, wherein a steam inlet of the second heat exchanger is arranged on an upstream side in a moving direction of the particles. .