JP3906175B2 - Cleaning system for convection heat transfer section in circulating fluidized bed boiler - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cleaning system for a circulating fluidized bed boiler convection heat transfer section that has low operating costs, provides a continuous cleaning effect, and provides a stable cleaning effect.
[0002]
[Prior art]
Waste power generation contributes greatly as a stable source of renewable energy to replace conventional fossil fuels, as a measure to prevent global warming, and as a measure to reduce the amount of landfill that leads to the extension of the life of final disposal sites. It is expected to contribute to the improvement of global energy problems, global environmental problems, and community problems.
[0003]
As a target for introducing waste power generation in FY2010 submitted in June 2001, a target of 4.17 million KW, which is 30% of all new energy, has been set. Since the actual result in 1999 is about 900,000 KW, it is said that it is necessary to increase the installed capacity five times.
[0004]
In addition, the legal system for building a recycling-oriented society has been steadily developed and reviewed, and since April 2003, the Special Measures Law (RPS system) concerning the use of new energy, etc. will be fully enforced. It is expected that new energy power generation will be promoted for waste such as garbage, sewage sludge, food waste, agriculture / forestry / fishery waste, papermaking black liquor, and building waste.
[0005]
In the promotion of new energy power generation, in recent years, circulating fluidized bed boilers that enable ultra-high efficiency power generation from waste combustion, which is the core of the waste power generation field, have attracted attention.
[0006]
As shown in FIG. 4, a conventional circulating fluidized bed boiler includes a combustor 50 having a fluidized bed, a cyclone 51, an external heat exchanger 52, a circulation line 53, a convection heat transfer section 54, a flue gas duct 55, a bug. A filter 56 is provided.
[0007]
When combustion is started in a state where fuel such as waste, auxiliary fuel, dense bed material such as gravel and sand, circulating solids, etc. supplied to the bottom of the combustor 50 is fluidized by the combustion air, high-temperature combustion gas is generated. The generated combustion gas is accompanied by some particles of the dense bed material and sent to the cyclone 51 to collect the particles.
[0008]
The particles collected by the cyclone 51 are discharged downward and sent to the external heat exchanger 52 for heat recovery. The particles that have passed through the external heat exchanger 52 become a cold solid and are sent as a circulating solid to the dense bed portion at the bottom of the combustor via the circulation line 53 for circulation. The separated gas and ash separated from the cyclone 51 are sent to the convection heat transfer section 54, and heat is recovered from the gas. Thereafter, the ash is sent to the bag filter 56 through the flue gas duct 55 and separated and collected. In such an apparatus, high-temperature and high-pressure steam is generated using heat recovered by the external heat exchanger 52 and the convection heat transfer section 54.
[0009]
However, when the alkali metal concentration in the waste, which is a fuel source, increases, problems of ash adhesion, clinker formation, and clogging become apparent from the cyclone to the convection heat transfer section. When it was remarkable, the boiler had to be stopped and cleaned. Further, when the contamination of the heat transfer tube in the convection heat transfer section increases, there is a problem that the exhaust gas temperature rises due to poor heat transfer and the thermal efficiency decreases.
[0010]
For this reason, the countermeasures for the site | part ranging from a cyclone to a convection heat-transfer part and the heat-transfer tube in a convection heat-transfer part were desired.
[0011]
Conventionally, a steam type soot blower is known as one of such cleaning means.
[0012]
However, the steam-type soot blower has a problem in that it has insufficient effects on sticky waste combustion ash, consumes expensive steam, has high exercise costs, and has many mechanical failures. .
[0013]
The steel ball shot method is also known, but since a metal ball of about 10 mm is dropped and collides with the tube, there is a problem of uneven cleaning effect on the part where the ball does not hit, and the ash adhering to the back side of the tube. There is a problem that the tube cannot be removed, and there is a problem that the tube may be damaged when used for a long time.
[0014]
There are also known methods of cleaning using sound waves and shock waves, but there are drawbacks that are less effective against sticky waste combustion ash, and there are cases where it is not effective even in general coal combustion. There's a problem.
[0015]
In Patent Document 1, a part of particles (solid) collected in the system is led to the upstream side of the convection heat transfer section and supplied to the surface of the heat transfer tube provided in the convection heat transfer section for collision. A particle cleaning method for peeling off surface deposits is disclosed.
[0016]
However, the components that make up the collected particles (solid) are composed of coal combustion ash, coal stone, gypsum, etc., but these particles are affected by changes in the fuel and the particle size and strength change. Therefore, there remains a problem that it is difficult to obtain a stable cleaning effect.
[0017]
In addition, when the cinnabar is supplied, the cinnabar has a crystal structure that changes at about 600 ° C., and the strength is reduced, so that it is easily worn.
[0018]
Patent Document 2 discloses a technique for reducing corrosion by increasing the amounts of oxides of Al ₂ O ₃ and SiO ₂ in ash.
[0019]
However, since the technique of Patent Document 2 is a technique of adding oxides of Al ₂ O ₃ and SiO ₂ , there is a problem that it is constantly consumed and needs to be added continuously, resulting in high running costs. Further, the technique of Patent Document 1 has a problem that a continuous cleaning effect cannot be obtained.
[0020]
[Patent Document 1]
Japanese Patent Laid-Open No. 4-48185 [Patent Document 2]
Japanese Patent Laid-Open No. 58-213882
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a cleaning system for a convection heat transfer section in a circulating fluidized bed boiler that has a low operating cost, provides a continuous cleaning effect, and provides a more stable cleaning effect.
[0022]
[Means for Solving the Problems]
The above problems are solved by the following inventions.
[0023]
(Claim 1) In a cleaning system for a convection heat transfer section in a circulating fluidized bed boiler that recovers heat by burning various wastes and generating steam,
On the upper inlet side of the convection heat transfer section into which the combustion gas flows, a ceramic particle reservoir is provided,
A ceramic particle feeder is provided at the bottom of the reservoir,
The feeder is connected to a particle supply pipe, and the particle supply pipe is connected to the inside of the convection heat transfer section so as to be able to supply the ceramic particles.
A ceramic particle return pipe is connected to the upper part of the reservoir,
A bag filter is provided downstream of the convection heat transfer section,
A lower part of the bag filter is provided with a separator for separating at least combustion ash and ceramic particles,
A cleaning system for a convection heat transfer section in a circulating fluidized bed boiler, wherein the ceramic particles separated by the separator are returned to the reservoir via the ceramic particle return pipe.
[0024]
(Claim 2) The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, wherein the separator is a mechanical vibration sieve.
[0025]
(Claim 3) The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, wherein the separator is an air classifier.
[0026]
(Claim 4) The ceramic particles are composed of Al ₂ O ₃ and SiO ₂ having Al ₂ O ₃ = 50 to 80% and SiO ₂ = 20 to 50% as composition materials, and at least a binder is mixed, fired and molded. 4. A cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, wherein the convection heat transfer section is a particle.
[0027]
(Claim 5) The convection heat transfer section in a circulating fluidized bed boiler according to claim 4, wherein the ceramic particles are mullite spherical ceramic particles of Al ₂ O ₃ = 61% and SiO ₂ = 37%. Cleaning system.
[0028]
(Claim 6) The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to any one of claims 1 to 5, wherein the particle size of the ceramic particles is in the range of 75 µm to 500 µm.
[0029]
(7) A means for controlling an interval for supplying the ceramic particles into the convection heat transfer section is provided, and the control means controls the ceramic particles to be supplied intermittently. A cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to any one of the above.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0031]
FIG. 1 is an explanatory view showing an example of a cleaning system for a convection heat transfer section in a circulating fluidized bed boiler preferably used in the present invention.
[0032]
In the figure, reference numeral 1 denotes a combustor having a fluidized bed (dense bed). The lower part of the combustor 1 is supplied with fuel, waste, auxiliary fuel, combustion air, circulating solids, dense bed material, etc., and when supplied with combustion air, these are vigorously fluidized and mixed and stirred. Is done. When ignited in a fluidized state, it burns violently at high temperatures, generating combustion gases and ash.
[0033]
Particles forming a fluidized bed (dense bed) accompany the combustion gas as a circulating solid (particles), and are guided to the particle collecting device 2 via the combustion gas duct 100.
[0034]
In the particle collecting device 2, the particles discharged accompanying the combustion gas are separated. For example, a cyclone capable of collecting particles can be used as the particle collecting device 2. Hereinafter, the particle collecting device 2 is referred to as a cyclone 2.
[0035]
The particles collected by the cyclone 2 are recovered by the external heat exchanger 3 and returned to the combustor 1 as a circulating solid.
[0036]
The separated gas and ash discharged from the cyclone 2 are introduced into the convection heat transfer unit 4.
[0037]
A heat transfer tube 40 is provided inside the convection heat transfer unit 4 and is configured to recover heat from the separated gas. The arrangement and the like of the heat transfer tubes 40 are not limited to those shown in the figure, and it is preferable that the heat transfer tubes 40 are designed so as to obtain efficient boiler steam from the recovered heat.
[0038]
The present invention uses ceramic particles with excellent wear resistance as cleaning particles, solves the problems of ash adhesion, clinker generation, and clogging, and further exhibits a cleaning effect with excellent sustainability by being used in circulation. A cleaning system suitable for a real device can be provided.
[0039]
In FIG. 1, reference numeral 400 denotes an inlet of the convection heat transfer section 4 into which a separated gas separated by the cyclone 2 (hereinafter sometimes referred to as combustion gas) flows, and a storage for storing ceramic particles at the upper portion of the inlet 400. A hopper 401 is provided.
[0040]
In the present invention, since it takes several minutes for the ceramic particles to return to the hopper 401 via the bag filter (BAG) described later, the amount used in the initial stage of operation is used in determining the hopper capacity. As a minimum, a capacity sufficient to hold a supply amount of ceramic particles of about 5 to 10 minutes is required. In addition, since it may be consumed during the operation process, it is necessary to consider the hopper capacity so that the consumed amount can be replenished.
[0041]
A ceramic particle feeder 402 is provided at the bottom of the hopper 401, and the feeder 402 is preferably a plurality of quantitative feeders that cut out a certain amount of ceramic particles. In the drawing, one quantitative feeder 402 is shown. The configuration of the quantitative feeder 402 is not particularly limited, but a rotary valve, a screw feeder, or the like can be used.
[0042]
The outlet of the fixed amount feeder 402 is branched into a plurality of particle supply pipes 403. In the drawing, two branch pipes 403 are exemplarily shown.
[0043]
The individual particle supply pipes 403 are connected to the inlet duct 404 of the convection heat transfer unit 4 and may be supplied to the inlet duct 404 by dropping or supplied to the inlet 400 of the convection heat transfer unit 4.
[0044]
The ceramic particles stored in the hopper 401 installed in the upper part of the convection heat transfer section 4 in this way are supplied into the convection heat transfer section 4 via the quantitative feeder 402 and the branch pipe 403.
[0045]
The supply amount of the ceramic particles into the convection heat transfer section 4 is preferably in the range of 1.0 to 4.0 kg / incineration ash amount Kg with respect to the incineration ash amount in order to exhibit a good cleaning effect. Preferably it is the range of 1.5-2.5 kg / incineration ash amount Kg.
[0046]
When adjusting the supply amount of the ceramic particles into the convection heat transfer section 4, it can be adjusted by the supply speed of the feeder 402 at the lower part of the hopper.
[0047]
Reference numeral 405 denotes a ceramic particle return pipe for returning to the hopper 401 via a bag filter (BAG) 5 described later.
[0048]
The ceramic particles used in the present invention are particles which are made of Al ₂ O ₃ and SiO ₂ as a composition raw material, mixed with a binder and the like, fired and molded, and have excellent wear resistance. Accordingly, since the ceramic particles are excellent in wear resistance and can be used until they become small, the present invention can exhibit a continuous cleaning effect. Further, since the ceramic particles are circulated and used, the operation cost is greatly reduced.
[0049]
Al ₂ O ₃ and a composition ratio of _Al 2 _{O 3} and SiO ₂ constituting the ceramic particles made of SiO _{2 is, Al 2 O 3 = 50~80%} , SiO 2 = 20~50% range is preferred.
[0050]
Further preferred ceramic particles in the present invention are mullite spherical ceramic particles having Al ₂ O ₃ = 61% and SiO ₂ = 37%. Although the crystal structure of cinnabar sand changes at about 600 ° C. and the strength decreases and becomes easy to wear, the ceramic particles have higher strength than cinnabar sand and are thermally stable. In addition, since it is spherical, it has wear resistance itself and has an effect of not wearing the boiler tube.
[0051]
In the present invention, by supplying ceramic particles into the convection heat transfer section 4, the ceramic particles contact and mix with the exhaust gas containing combustion ash in the convection heat transfer section 4, disperse, and collide with the heat transfer tube 40 group. The combustion ash adhering and depositing on the pipe can be cleaned by repeating the above.
[0052]
In order to exert such a cleaning effect, it is preferable to uniformly disperse the ceramic particles in the convection heat transfer section. This is because the ceramic particles can uniformly collide with the heat transfer tubes. From this point of view, in the present invention, as described above, it is preferable to provide the plurality of feeders 402 and the branch pipe 403 connected to the lower part thereof.
[0053]
As a preferred embodiment of the present invention, there is provided means for controlling the interval for supplying the ceramic particles into the convection heat transfer section, and the control means is controlled so as to supply the ceramic particles intermittently. Specifically, when supplying ceramic particles into the convection heat transfer section, as is clear in the embodiment, it is more efficient to supply ceramic particles intermittently even at the same supply amount, rather than supplying a constant amount of ceramic particles. Great effect and less uneven cleaning. For this reason, in this invention, it is preferable to make a supply system intermittent (1-2 minutes interval).
[0054]
The particle size of the ceramic particles used in the present invention is in the range of 75 μm to 500 μm, preferably 100 μm to 425 μm. Since the ceramic particles have such a relatively wide particle size distribution, the ash adhering to the back side of the heat transfer tube 40 due to gas disturbance can be cleaned, which is a preferable mode.
[0055]
The combustion ash and ceramic particles that have passed through the convection heat transfer section 4 flow into a bag filter (BAG) 5 and are collected.
[0056]
The bag filter 5 provided downstream of the convection heat transfer section 4 has a plurality of outlets 500 for discharging the combustion ash of each cell. The outlet 500 is provided with an open / close valve such as a damper. You may have. Reference numeral 503 denotes a suction blower for combustion exhaust gas.
[0057]
The plurality of discharge ports 500 are connected to the collective conveyor 502 via discharge pipes 501.
[0058]
Particles collected by the bag filter 5 are transported to a separator from the discharge port 500 provided at the lower part of each cell of the bag filter 5 and are collected on the collective conveyor 502.
[0059]
Since the ceramic particle size is about 75 to 500 μm (average 300 μm), preferably about 100 to 425 μm (average 300 μm), there is a considerable difference in the particle diameter, so that it can be easily separated by a separator.
[0060]
In the example of FIG. 1, the aspect which used the vibration sieve machine as an example of a separator is shown.
[0061]
Reference numeral 6 denotes a vibrating sieve 6 which is an example of a separator connected to the discharge port of the collective conveyor 502. In the illustrated example, two types of sieves 6A and 6B are provided, and the sieves are classified into three according to the particle diameter.
[0062]
The smallest particles passing through the sieve 6A and the sieve 6B are combustion ash (hereinafter also simply referred to as “ash”). The particle size of the combustion ash is in the range of 0 to 100 μm, and the average particle size is about 20 to 40 μm even in experiments.
[0063]
The ash is discharged from the ash discharge port 600, pneumatically transported by the transporter 601, sent to the ash silo 7, and stored. The transporter 601 has a structure in which powder can be pumped by external pressurized air.
[0064]
The second coarse particles (coarse particles) that pass through the sieve 6A but do not pass through the sieve 6B are ceramic particles of about 75 to 500 μm. The ceramic particles are discharged from the ceramic particle discharge port 602, pneumatically transported by the transporter 603, and sent to the hopper 401 through the ceramic particle return pipe 405.
[0065]
The ceramic particles thus separated are supplied from the hopper 401 to the convection heat transfer section 4 through the plurality of feeders 402 and the branch pipe 403, and are circulated for use.
[0066]
Ceramic particles are worn out by long-term operation due to circulation use, and long-term operation time can be secured until the particle diameter is refined to about 75 μm or less.
[0067]
The particles that are worn down to about 75 μm or less are separated together with the ash and sent to the ash silo 7.
[0068]
Coarse particles (having a size of 500 μm or more) that do not pass through the largest sieve 6A that is finally separated by the vibration sieve 6 are large clusters such as clinker struck by cleaning. In the example shown in the figure, a state where the material is discharged from the discharge port 604 and accumulated is shown.
[0069]
Next, another embodiment of the cleaning system of the present invention will be described with reference to FIG.
[0070]
The example shown in FIG. 2 is an example in which a pneumatic air classifier is used as a separator instead of a mechanical vibration sieve in the cleaning system shown in FIG.
[0071]
2, parts having the same reference numerals as those in FIG. 1 have the same configuration, and thus description thereof is omitted.
[0072]
In FIG. 2, reference numeral 60 denotes an air classifier that separates fine particles and coarse particles in the ash in the bag filter 5. Specifically, it separates into ash and ceramic particles. Separation by the air classifier 60 is performed by the difference in specific gravity and the difference in particle size.
[0073]
The ash containing the ceramic particles is transferred from the collective conveyor 502 to the transfer conveyor 61 and sent to the air classifier 60.
[0074]
The air classifier 60 is provided with an outlet 62 for air containing ash at the top, and the outlet 62 is connected to the ash silo 7.
[0075]
An air dispersion plate 63 is provided inside the air classifier 60, and the ceramic particles classified and dropped by the air blown from the air dispersion plate 63 are discharged from the particle discharge port 64.
[0076]
The particle discharge port 64 is connected to a transport facility 65 that transports particles. The ceramic particles discharged from the particle discharge port 64 are sent to the transporter 66 by the transport facility 65, transported by air from the transporter 66, and sent to the hopper 401 through the ceramic particle supply pipe 405. A blower 67 supplies air for classification into the air classifier 60. The air supplied from the blower 67 is preferably preheated by a heater in order to promote classification.
[0077]
As mentioned above, although embodiment of this invention was described, embodiment of this invention is not limited above, For example, the circulating fluidized bed boiler used for this invention burns various wastes, generate | occur | produces a vapor | steam. If it is a structure which performs heat recovery, it will not specifically limit. Various types of waste include building waste chips, sewage sludge, agricultural and forestry waste, food waste, renewable energy such as RDF (Rufuse Derived Fuel), and industrial waste such as RPF (Rufuse Paper & Plastic Fuel) and waste tires. Is mentioned.
[0078]
Moreover, although the above embodiment demonstrated the example which provided the heat exchanger tube 40 in the convective heat transfer part 4, you may provide the superheater, the evaporation pipe, the economizer, and the air preheater.
[0079]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this Example.
[0080]
Example 1
In the apparatus shown in FIG. 1, using a circulating fluidized bed boiler using RPF as fuel, the relationship between the amount of ceramic particles supplied to the convection heat transfer section (relative to combustion ash) and the BAG inlet temperature is investigated, and the ceramic particles are cleaned. The effect was confirmed.
[0081]
The results are shown in FIG.
[0082]
As shown in FIG. 3, the supply amount of ceramic particles into the convection heat transfer section can exhibit a cleaning effect in a range of 1.0 to 4.0 kg / incineration ash amount Kg with respect to the incineration ash amount. Recognize.
[0083]
In addition, as a method for supplying ceramic particles, the cleaning effect was examined for a continuous quantitative supply method and a 2-minute interval supply method.
[0084]
The results are shown in FIG.
[0085]
As shown in FIG. 3, it can be seen that the cleaning effect can be obtained with the interval supply method of 2 minutes.
[0086]
【The invention's effect】
According to the present invention, it is possible to provide a cleaning system for a convection heat transfer section of a circulating fluidized bed boiler that can be operated at low cost, has a continuous cleaning effect, and has a more stable cleaning effect.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an embodiment of the present invention. FIG. 2 is an explanatory diagram showing another embodiment of the present invention. FIG. 3 is a graph showing results of confirming the cleaning effect of the present invention. ] Diagram showing a conventional example [Explanation of symbols]
1: Combustor 100: Combustion gas duct 2: Particle collection device (cyclone)
3: External heat exchanger 4: Convective heat transfer section 40: Heat transfer pipe 400: Inlet 401: Hopper 402: Fixed amount feeder 403: Particle supply pipe (branch pipe)
404: Inlet duct 405: Ceramic particle return pipe 5: Bag filter (BAG)
500: Discharge port 501: Discharge pipe 502: Collective conveyor 503: Suction blower 6: Vibrating sieve 600: Ash discharge port 600
601: Transporter 602: Particle discharge port 603: Transporter 604: Discharge port 60: Wind classifier 61: Transfer conveyor 62: Outlet 63: Air dispersion plate 64: Particle discharge port 65: Transport facility 66: Transporter 67: Blower 7: Ash silo

Claims (7)

In the cleaning system of the convection heat transfer section in a circulating fluidized bed boiler that burns various wastes and generates steam to recover heat,
On the upper inlet side of the convection heat transfer section into which the combustion gas flows, a ceramic particle reservoir is provided,
A ceramic particle feeder is provided at the bottom of the reservoir,
The feeder is connected to a particle supply pipe, and the particle supply pipe is connected to the inside of the convection heat transfer section so as to be able to supply the ceramic particles.
A ceramic particle return pipe is connected to the upper part of the reservoir,
A bag filter is provided downstream of the convection heat transfer section,
A lower part of the bag filter is provided with a separator for separating at least combustion ash and ceramic particles,
A cleaning system for a convection heat transfer section in a circulating fluidized bed boiler, wherein the ceramic particles separated by the separator are returned to the reservoir via the ceramic particle return pipe. 2. The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, wherein the separator is a mechanical vibration sieve. 2. The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, wherein the separator is an air classifier. Ceramic particles are Al ₂ O ₃ = 50 to 80%, SiO ₂ = 20 to 50% Al ₂ O ₃ and SiO ₂ as composition materials, at least a binder mixed, fired and molded particles A cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to claim 1, 2 or 3. Ceramic _{particles, Al 2 O 3 = 61%} , the cleaning system of the convective heat transfer section in the circulating fluidized bed boiler according to claim 4 characterized in that the spherical ceramic particles _SiO 2 = 37% of mullite. The cleaning system for a convection heat transfer section in a circulating fluidized bed boiler according to any one of claims 1 to 5, wherein the particle size of the ceramic particles is in the range of 75 µm to 500 µm. A means for controlling an interval for supplying the ceramic particles into the convection heat transfer section is provided, and the control means controls the ceramic particles to be supplied intermittently. Cleaning system for convection heat transfer in circulating fluidized bed boiler.

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