JPH0972509A - Refuse derived fuel firing fluidized-bed boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the corrosion of a heat transfer tube in the layer of an external heat exchanger due to the contact with chlorine compound. SOLUTION: In a refuse derived fuel firing fluidized-bed boiler that the exhaust gas from a furnace 1 to which refuse derived fuel is supplied and burned is introduced to a cyclone 4, a bed material 3 is separated, then the exhaust gas is introduced to a rear heat transfer unit 18, and the material 3 separated by the cyclone 4 is circulated to an external heat exchanger 24 connected to and disposed at the lower part of the wall of the furnace 1 via a bed material dropping tube 4a and an ash recirculating unit 5, a blow bed material banker 28 charged with a no-chlorine containing bed material 27 is connected to and disposed at the tube 4a of the cyclone 4 via a bed material supply unit 26.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refuse-producing fuel burning fluidized bed boiler.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of effective utilization of unused energy, municipal waste is crushed and calcium 10 or the like is added.
Approximately 20 mm columnar chips are solidified and dried to generate dust-producing fuel RDF (Refuse derivated fuel)
The technology for producing l) has been developed, and it has become conceivable to utilize the above-mentioned waste fuel for a fluidized bed boiler.

As shown in FIG. 2, an example of the waste-producing fuel-fired fluidized bed boiler using the above-mentioned waste-producing fuel is that an air dispersion plate 2 is provided in the lower part of a furnace 1 formed in a rectangular shape by a water cooling wall 1a. The dust-producing fuel is supplied onto the air dispersion plate 2 through a fuel line W, and the dust-producing fuel flows with the bed material 3 made of ash, limestone or the like by the combustion air blown out from the air dispersion plate 2. The steam is generated and burned to generate steam to be supplied to a steam turbine for power generation (not shown).

A bed material 3 containing combustion ash and unburned components blown up by the exhaust gas burned in the furnace 1 is guided to and captured by a cyclone 4, and the bed material 3 captured by the cyclone 4 is captured. Is circulated from the vertical bed material falling pipe 4a below the cyclone 4 to the furnace 1 via an ash recirculation device (J-valve or the like) 5.

At the bottom of the furnace 1, there is a forced draft fan (FDF).
6, air line 9 with air preheater 7 and control valve 8
Auxiliary air line 11 connected to the ash recirculation device 5 having a control valve 10 in the air line 9
Are connected to prevent the particles of the circulating bed material 3 from clogging in the ash recirculation device 5. Also, the air line 9
A secondary air line 13 having a control valve 12 and connected to the central portion of the furnace 1 is connected to the
Also, the NOx is controlled by being supplied to the furnace 1 from the two systems of the secondary air line 13. A bed material discharge line 15 equipped with a cut-out valve 14 such as a rotary valve adapted to take out a part of the bed material 3 is connected to the bottom of the furnace 1.

The exhaust gas from which the bed material 3 has been separated by the cyclone 4 is cooled through a rear heat transfer section 18 having heat transfer surfaces such as a superheater 16 and a economizer 17, and then flows into an exhaust gas line 19. And is further cooled by the air preheater 7,
After the dust is removed by a dust collector (for example, a bag filter) 20, it is opened to the atmosphere from a chimney 22 via an induction draft fan (IDF) 21.

In the ash recirculation device 5, the pressure in the lower part of the furnace 1 is usually higher than the pressure in the lower part of the cyclone 4, but in this state, the exhaust gas in the furnace 1 is in the bed under the cyclone 4. The purpose is to prevent the material from falling toward the material falling pipe 4a, and to allow the bed material 3 separated by the cyclone 4 to flow back into the furnace 1 and return.

On the other hand, the dust, which is a raw material of the dust-producing fuel, contains chlorine-based plastic, and therefore the dust-producing fuel usually contains 0.5 to 1% of chlorine. When such a dust-producing fuel containing chlorine is burned, hydrogen chloride gas HCl having a very strong corrosive property is generated. It is generally known that this hydrogen chloride gas exhibits the strongest corrosiveness at around 400 ° C.

Therefore, conventionally, the temperature of the heat transfer surfaces of the superheater 16 and the economizer 17 of the rear heat transfer section 18 is 350 at the maximum.
It has been generally considered to control the temperature of the exhaust gas so that the upper limit is about ° C. At this time, since water or saturated water is flowing in the heat transfer tube of the furnace 1 and the metal temperature of the heat transfer surface is sufficiently low, there is no fear of corrosion due to the hydrogen chloride gas.

However, as described above, if the upper limit of the temperature of the rear heat transfer surface is limited to about 350 ° C.,
There is a problem that the steam temperature becomes low, the power generation efficiency by a steam turbine (not shown) is reduced, and the thermal efficiency of the entire plant becomes extremely low.

Therefore, in recent years, as shown in FIG.
An external heat exchanger 24 having an in-layer heat transfer tube 23 inside is connected and installed at the lower part of the wall surface of the furnace 1, and the bed material 3 flowing down from the ash recirculation device 5 is connected to the air dispersion plate of the furnace. Two
The combustion air ejected from the air dispersion plate 2a communicating with the fluidizing plate is fluidized to perform heat exchange with the in-layer heat transfer tube 23 of the external heat exchanger 24.

That is, after steam is superheated so that the temperature of the heat transfer surface of the superheater 16 which is a high temperature part of the rear heat transfer section 18 becomes 350 ° C. at the upper limit, the steam is further heated to the external heat exchanger. Heat is exchanged between the bed material 3 which is guided to the in-layer heat transfer tube 23 of 24 and flows down from the ash recirculation device 5 and which is usually at a high temperature of about 800 ° C. to obtain a steam of a high temperature of about 500 ° C. Is being considered.

According to this method, heat transfer surfaces such as the superheater 16 and the economizer 17 are installed at positions outside the temperature range of strong corrosiveness due to hydrogen chloride gas, and the ash recirculation device 5 and the bed material 3 are used. Since the in-layer heat transfer tube 23 is installed inside the external heat exchanger 24 in which hydrogen chloride gas is not circulated and supplied, it is possible to reduce the problem of corrosion of each heat transfer surface.
Moreover, since the final steam temperature can be raised to around 500 ° C., the power generation efficiency by the steam turbine can be increased.

[0014]

Most of the chlorine in the dust-producing fuel becomes hydrogen chloride gas during combustion in the furnace 1 and is guided to the rear heat transfer section 18 together with the exhaust gas.

However, the bed material 3 circulating through the furnace 1, the cyclone 4, the bed material falling pipe 4a, the ash recirculation device 5, and the external heat exchanger 24 contains metal such as iron and aluminum. However, since this metal reacts with chlorine in the refuse-producing fuel to form a chlorine compound (complex salt), the chlorine content of the circulating bed material 3 is concentrated by the operation and the concentration increases. There is a problem, and there is a concern that the in-layer heat transfer tube 23 of the external heat exchanger 24 may be corroded by the contact of the chlorine compound.

Therefore, the present invention has been made in view of such circumstances, and an object thereof is to reduce the problem that the in-layer heat transfer tube of the external heat exchanger is corroded by the contact with the chlorine compound. The purpose of the present invention is to provide a fluidized bed boiler that generates fuel for generating waste.

[0017]

The waste-producing fuel-fired fluidized bed boiler of the present invention guides the exhaust gas from a furnace that supplies and burns the waste-producing fuel to a cyclone to separate the bed material, and then transfers the exhaust gas to the rear part. A waste-generated fuel-fired fluidized-bed boiler that guides the heat to the cyclone and circulates the bed material separated by the cyclone to an external heat exchanger connected to the lower part of the furnace wall through a bed material drop pipe and an ash recirculation device. And
The bed material falling pipe of the cyclone is provided with a blower bed material bunker in which a bed material containing no chlorine is charged and connected through a bed material feeder.

Further, the invention is characterized in that a controller is provided for controlling the operation of the bed material feeder in accordance with the amount of the dust-producing fuel supplied.

In the present invention, the bed material bunker for blowing is connected and arranged to the bed material falling pipe of the cyclone through the bed material feeder, so that the bed material of the furnace is the cyclone, the bed material falling pipe, and the ash recycled. When the metal in the bed material reacts with chlorine to form a chlorine compound during the action of circulation returning to the furnace again through the circulation device and the external heat exchanger, and the chlorine content is concentrated, the blow is performed. By supplying the chlorine-free bed material containing no chlorine from the bed material bunker, it is possible to reduce the problem that the in-layer heat transfer tube of the external heat exchanger is corroded by contact with the chlorine compound.

Further, if a controller for controlling the operation of the bed material supply device is provided according to the amount of supplied dust-producing fuel, the bed material of the bed material is supplied according to the amount of chlorine brought into the furnace by the supply of the refuse-producing fuel. It is possible to adjust the amount of non-chlorine-containing bed material supplied from the blower bed material bunker by estimating the concentration of chlorine compound due to circulation, and to control the concentration of chlorine compound in the circulating bed material below a certain value. be able to.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an example of a circulating fluidized bed boiler. In the figure, the same parts as those in FIG. 2 are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 1, an inclined chute 25 is connected in the middle of a vertical bed material drop pipe 4a below the cyclone 4 which communicates with the ash recirculation device 5, and the chute 25 is connected to the chute 25.
Then, a blower bed material bunker 28 charged with a chlorine-free bed material 27 is connected and arranged via a bed material feeder 26 composed of a rotary valve or the like. The non-chlorine-containing bed material 27 is a bed material containing no chlorine, which is a mixture of sand and limestone.

Further, there is provided a controller 31 for inputting a fuel supply command 30 for controlling the fuel supply device 29 for supplying the dust producing fuel to the furnace 1 and controlling the supply by the bed material supplier 26. .

The dust producing fuel usually contains 0.5 to 1% of chlorine, and the chlorine in the refuse producing fuel is contained in the furnace 1.
Almost all of it becomes hydrogen chloride gas at the time of combustion at 1, and is guided to the rear heat transfer section 18 together with the exhaust gas.

However, since the bed material 3 in the furnace circulates through the cyclone 4, the bed material drop pipe 4a, the ash recirculation device 5, and the external heat exchanger 24, iron, aluminum, etc. in the bed material 3 are circulated. The metal reacts with a part of the chlorine to form a chlorine compound, whereby the chlorine content in the bed material 3 is concentrated by circulation, and the concentration gradually increases. Therefore, as described above, an apparatus designed to raise the steam temperature so that the temperature of the in-layer heat transfer tube 23 of the external heat exchanger 24 is in a temperature range (around 400 ° C.) in which strong corrosion due to chlorine is caused. In this case, there is a concern that the in-layer heat transfer tube 23 of the external heat exchanger 24 may be corroded by the contact with the chlorine compound.

At this time, the bed material feeder 26 is operated,
The chlorine-free bed material 27 filled in the blower bed material bunker 28 is supplied to the bed material drop pipe 4 a of the cyclone 4 via the chute 25. Then, the ash recirculation device 5
By mixing the non-chlorine-containing bed material 27 containing no chlorine with the bed material 3 supplied to the external heat exchanger 24 from the outside, the concentration of the chlorine compound in the bed material 3 is diluted and lowered. It is possible to prevent the in-layer heat transfer tube 23 of the heat exchanger 24 from being corroded.

Further, since the controller 31 is provided so as to control the operation of the bed material feeder 26 on the basis of the fuel supply command 30 which controls the supply amount of the dust producing fuel by the fuel supply device 29, The controller 31 calculates the amount of chlorine brought into the furnace 1 by supplying the dust-producing fuel, and further estimates the concentration of the chlorine compound due to the circulation of the bed material 3 in accordance with this amount of chlorine. Based on the estimated values, blow bed material bunker 28 to bed material drop pipe 4
The amount of the chlorine-free bed material 27 supplied to a is automatically adjusted. The non-chlorine-containing bed material 27 may be supplied continuously or intermittently.

As a result, the concentration of the chlorine compound in the circulating bed material 3 can always be controlled to a fixed value or less.

When the dust-producing fuel is supplied to the furnace 1 for combustion, the amount of the bed material 3 gradually increases.
The increased amount of the bed material 3 is discharged to the outside through the bed material discharge line 15 by opening the cut-out valve 14. However, when the chlorine-free bed material 27 is supplied, the chlorine-free bed is supplied. When the bed material 3 in an amount corresponding to the supply amount of the material 27 is extracted in advance and supplied, the non-chlorine-containing bed material 27 can be effectively used.

The blow bed material bunker 28 is also used.
Can also be used as a device for filling the bed material 3 into the furnace 1 after discharging all the bed material 3 in the furnace 1 and performing a periodical inspection.

[0032]

According to the present invention, the bed material bunker for blow is connected to the bed material falling pipe of the cyclone through the bed material feeder, so that the bed material of the furnace is the cyclone and the bed material falling. During the circulation back to the furnace through the pipe, ash recirculation device, and external heat exchanger, the metal in the bed material reacts with chlorine carried by the dust-producing fuel to form a chlorine compound, which is repeated. For the concern that the chlorine content will be concentrated, by supplying a non-chlorine-containing bed material that does not contain chlorine in the blower bed material bunker, the chlorine concentration of the bed material of the external heat exchanger section is reduced by dilution, It is possible to reduce the problem that the in-layer heat transfer tube is corroded by contact with a chlorine compound.

If a controller for controlling the operation of the bed material feeder is provided in accordance with the amount of the dust-producing fuel supplied, the blow bed can be provided in accordance with the amount of chlorine brought into the furnace by supplying the dust-producing fuel. The amount of non-chlorine-containing bed material supplied from the material bunker can be adjusted, so that the concentration of chlorine compounds in the circulating bed material can be automatically controlled to a certain value or less.

[Brief description of drawings]

FIG. 1 is an overall block diagram showing an exemplary embodiment of the present invention.

FIG. 2 is an overall block diagram showing an example of a conventional dust-generating fuel burning fluidized bed boiler.

[Explanation of symbols]

 1 Furnace 3 Bed material 4 Cyclone 4a Bed material drop pipe 5 Ash recirculation device (J-valve etc.) 18 Rear heat transfer part 24 External heat exchanger 26 Bed material feeder 27 Non-chlorine containing bed material 28 Blow bed material Bunker 31 Controller

Claims (2)

[Claims] 1. The exhaust gas from a furnace that supplies and burns dust-producing fuel is introduced into a cyclone to separate the bed material, and then the exhaust gas is introduced into a rear heat transfer section, and the bed material separated by the cyclone is dropped into the bed material. A waste-generated fuel-fired fluidized-bed boiler adapted to be circulated to an external heat exchanger connected to the lower part of the furnace wall through a pipe and an ash recirculation device,
A refuse-producing fuel-fired fluidized bed boiler, wherein a blow bed material bunker charged with a bed material containing no chlorine is connected to the bed material drop pipe of the cyclone through a bed material feeder. 2. The dust-generating fuel-fired fluidized bed boiler according to claim 1, further comprising a controller for controlling the operation of the bed material feeder according to the amount of the dust-generating fuel supplied.