JP4219312B2 - High temperature corrosion reduction device for circulating fluidized bed boiler - Google Patents

Description

  The present invention relates to a high-temperature corrosion reduction device for a circulating fluidized bed boiler having a wide range of fuel compatibility from gas to liquid to solid. Specifically, the problem of high-temperature corrosion in an external heat exchanger can be solved, and high efficiency of power generation can be realized. The present invention relates to a high temperature corrosion reduction device for a circulating fluidized bed boiler.

  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.

  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.

  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.

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.
Japanese Patent No. 3417952 JP 2003-207115 A

  The technique described in FIG. 1 of Patent Document 1 includes a furnace 20, a particle separator 14, a dilution chamber 16, an intermediate transfer chamber 42, and a heat transfer chamber 18. The particles discharged from the lower part of the particle separator 14 enter the dilution chamber 16 from the upper part and are discharged from the lower part. The particles discharged from the upper part of the dilution chamber 16 enter from the upper part of the intermediate transfer chamber 42 and are discharged from the lower part, and enter the heat transfer chamber 18 from the lower part.

  However, in this technique, the heat exchange chamber 18 is entered from the lower part and discharged to the upper part and returned to the furnace 20, and heat is exchanged by the heat exchanger, and the flow of fluidized air and particles are in the same direction (parallel). Therefore, there is a drawback that a large amount of corrosive components are brought in via the intermediate transfer chamber 42 and the problem of high-temperature corrosion of the heat exchanger is large and lacks practicality.

  The technique described in FIG. 1 of Patent Document 2 includes a furnace 2, a cyclone (particle collection device) 3, a desorption loop 13, and an external heat exchanger 6. The desorption loop 13 burns the circulating particles and returns them from the duct 14 to the furnace 2.

  However, the adhering unburned portion of the circulating particles that did not burn in the furnace 2 is merely a desire and has a problem of poor feasibility.

  Further, the fluidized bed provided with the external heat exchanger 6 has a disadvantage that the heat exchange efficiency is poor because the particles enter from the upper part of the adjacent layer and are discharged from the upper part.

  Further, when the particles are discharged from the upper part of the fluidized bed provided with the external heat exchanger 6, the flow is in the same direction as the fluidized air, so that the corrosion components are not sufficiently removed and the heat exchanger heat transfer tubes are corroded. There is a problem.

  Then, this invention is providing the high temperature corrosion reduction apparatus of the circulating fluidized bed boiler which can eliminate the problem of the high temperature corrosion in an external heat exchanger, and can implement | achieve the high efficiency of an electric power generation.

  As a result of intensive studies to solve the above problems, the present inventor has reached the present invention. That is, the said subject is solved by each following invention.

(Claim 1)
A furnace having a fluidized bed, a particle collection device that introduces particles discharged from the furnace accompanied by combustion gas, collects the particles and discharges them from below, and is collected by the particle collection device. In a circulating fluidized bed boiler equipped with a circulation system for circulating discharged particles to the furnace via an external heat exchanger,
The circulation system, the first fluidized bed common specifications particles sent from the particle collection device inside with partitioned by Setsukabe is to form a fluidized bed by fluidizing air from each other, the second fluidized bed and the 3 fluidized beds,
The first fluidized bed has a particle introduction pipe that introduces particles sent from the lower part of the particle collecting device and opens inside the fluidized bed, and has a fluidized air inlet for introducing fluidized air to the lower part, The lower part of the partition wall with the second fluidized bed has a first lower opening for introducing particles into the second fluidized bed, and the upper part of the partition wall has a first upper opening for introducing air from the second fluidized bed And the upper part of the side wall facing the partition wall has a structure having a circulation outlet that discharges the particles sent from the particle collector and the fluidized air and is connected to the furnace.
The second fluidized bed has a fluidized air inlet for introducing fluidized air at the bottom, introduces particles into the third fluidized bed at the upper part of the partition wall with the third fluidized bed, and the third fluidized bed. Having a second upper opening through which fluidized air flows into the second fluidized bed from
The third fluidized bed has an external heat exchanger in the fluidized bed of particles, has a fluidized air inlet for introducing fluidized air in the lower part, and discharges and circulates the heat-exchanged particles in the lower part. have a particle outlet being connected to the furnace via a line, the flow of the second lead to the particle discharge port is introduced from the second upper opening with the top of the partition wall of the fluidized bed particles, A circulating fluidized bed boiler characterized by having a structure in which a flow of fluidized air introduced from the fluidized air inlet at the lower part of the third fluidized bed and reaching the second upper opening forms a counterflow. High temperature corrosion reduction device.

(Claim 2)
2. The high-temperature corrosion reduction apparatus for a circulating fluidized bed boiler according to claim 1, wherein the external heat exchanger of the third fluidized bed has a configuration in which a superheater tube and an evaporator tube of a boiler are immersed.

  ADVANTAGE OF THE INVENTION According to this invention, the problem of the high temperature corrosion in an external heat exchanger can be eliminated, and the high temperature corrosion reduction apparatus of the circulating fluidized bed boiler which can implement | achieve the highly efficient electric power generation can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory view showing an example of a high-temperature corrosion reduction device for a circulating fluidized bed boiler according to the present invention, and FIG. 2 is a plan view showing an arrangement example of a plurality of fluidized beds.

  In the figure, reference numeral 1 denotes a furnace having a fluidized bed (dense bed). In the present invention, the structure of the furnace 1 is not particularly limited, but preferably, a dense bed portion 100 having a high superficial velocity is formed at the bottom of the furnace 1 and a furnace main body 101 having a low superficial velocity is formed at the top. Is preferably formed.

  The dense bed unit 100 has a structure capable of supplying waste, auxiliary fuel, combustion air, circulating particles (dense bed material), and the like as a fuel source. When the combustion air is supplied, the dense bed unit 100 The inside is vigorously fluidized and mixed and stirred. It is preferable that a combustion ash discharge part is provided at the lower part of the dense bed part 100.

  Wastes 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. Can be mentioned.

  As the auxiliary fuel, liquid fuels such as heavy oil and light oil, gaseous fuels such as city gas and propane gas, and solid fuels such as coal may be used, and these auxiliary fuels may use the above-mentioned one type. Two or more kinds can be used in combination. It is also preferable to prepare liquid fuel, gaseous fuel, and solid fuel, respectively, so that they can be switched.

  Combustion air is preferably preheated in order to increase the combustion rate.

  As the dense bed material, gravel, sand, ceramic particles and the like can be used, and mainly plays a role of retaining heat when burning in a fluid state.

  In the dense bed part 100, when the waste, auxiliary fuel, dense bed material, etc. are ignited in a state of being fluidized by the combustion air, they are violently burned, burned at a high temperature, and burned in the furnace 1 at about 900 ° C. Generate gas.

This combustion gas The combustion ash, lime, sand, etc. constituting the dense bed forming the fluidized bed (dense bed) are accompanied as circulating particles and guided to the particle collecting device 2 via the combustion gas duct 102.

  In the particle collecting device 2, 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 collection device 2 will be described as a cyclone 2.

  In the present invention, the first fluidized bed 3, the second fluidized bed 4 and the third fluidized bed 5 unique to the present invention are provided in the process in which the particles separated by the cyclone 2 are returned to the dense bed 100 via the circulation system. ing.

  The first fluidized bed 3, the second fluidized bed 4 and the third fluidized bed 5 are spaces partitioned by partition walls 300 and 400 common to each other, and the particles sent from the cyclone 2 flow into the space. The basic form is that the fluidized bed is formed by the chemical air. The upper surface DL of each fluidized bed is set to a height at which an air flow path can be formed in the upper portion. Here, the partition wall is preferably a water-cooled panel or a fireproof wall.

  The first fluidized bed 3 has a particle introduction tube 200 that introduces particles sent from the lower part of the cyclone 2 and opens inside the fluidized bed. Reference numeral 201 denotes an opening of the particle introduction tube 200. The reason why the particle introduction pipe 200 is opened inside the fluidized bed is that the fluidized air in the first fluidized bed does not flow backward in the direction of the cyclone 2 through the particle introduction pipe 200. The seal is done.

  A fluidized air inlet 301 for introducing fluidized air is provided below the first fluidized bed 3. The fluidized air introduction port 301 is preferably configured by a plurality of fluidized air introduction pipes that are evenly arranged so that air can be evenly supplied into the first fluidized bed 3.

  A first lower opening 302 for introducing particles into the second fluidized bed 4 is provided below the partition wall 300 with the second fluidized bed 4. In addition, a first upper opening 303 through which air flows from the second fluidized bed 4 to the first fluidized bed 3 is provided at the upper part of the partition wall 300.

  The first lower opening 302 and the first upper opening 303 of the partition wall 300 only need to have a structure capable of moving particles. For example, a water-cooled panel having only a water-cooled tube or a refractory wall having an opening is preferable. Further, there may be no particular structure.

  In the first fluidized bed 3, a circulation outlet 305 for discharging the particles sent from the cyclone 2 and the fluidized air is provided on the upper part of the side wall 304 facing the partition wall 300.

  The second fluidized bed 4 is provided with a fluidized air inlet 401 for introducing fluidized air at the bottom, and introduces particles into the third fluidized bed 5 at the upper part of the partition wall 400 with the third fluidized bed 5. A second upper opening 402 through which fluidized air flows from the third fluidized bed 5 to the second fluidized bed is provided.

  The second upper opening 402 of the partition wall 400 only needs to have a structure capable of moving particles. For example, a water-cooled panel having only a water-cooled tube or a fireproof wall having an opening is preferable. Further, there may be no particular structure.

  The third fluidized bed 5 includes an external heat exchanger 501 in a fluidized bed of particles. A fluidized air inlet 502 for introducing fluidized air is provided at the bottom, and a particle outlet 503 for heat-exchanged particles is provided at the bottom. The particles discharged from the particle discharge port 503 are returned to the furnace 1 through the circulation line 506. Reference numeral 504 denotes an inlet portion for steam to the external heat exchanger 501, and reference numeral 505 denotes an outlet portion.

  Next, the operation of the first fluidized bed 3, the second fluidized bed 4 and the third fluidized bed 5 having the above configuration will be described.

  The air supplied from the air inlet 301 into the first fluidized bed 3 causes gas and fine particles (having a small particle size and specific gravity) containing corrosive components flowing in from the opening 201 of the particle inlet pipe 200 to move upward. Purge, exhaust through the upper circulation outlet 305 and return to the furnace 1.

  For this reason, the gas and fine particles containing a corrosive component do not go to the external heat exchanger 501. Since the influence of high temperature corrosion is large due to fine particles, if the fine particles can be discharged together with fluidized air in front of the external heat exchanger, the effect of removing high temperature corrosion is great.

  In particular, in the present invention, the fluidized air containing the corrosive component is discharged to the outside without immediately contacting the external heat exchanger, and the purged corrosive component comes into contact with the fluidized bed portion again and returns to the fluidized bed. As such, the flow of air and particles is considered.

  Part of the particles purged with the corrosive component flows into the second fluidized bed 4 through the first lower opening 302 provided in the lower part of the partition wall 300.

  A first upper opening 303 is provided in the upper part of the partition wall 300, which is a flow path through which fluidized air from the second fluidized bed 4 and the third fluidized bed 5 flows. No. 3 fluidized air cannot flow through the first upper opening 303 to the second and third fluidized bed sides.

  The fluidizing gas flow rate of the first fluidized bed 3 is preferably set relatively large in order to blow up the fine particles among the particles collected by the cyclone 2, and specifically 0.3 to 0.6 m. A range of / sec is preferred. Moreover, the temperature in the 1st fluidized bed 3 has the preferable range of 850-900 degreeC.

  Since the first lower opening 302 is formed in the lower part of the partition wall 300 between the first fluidized bed 3 and the second fluidized bed 4, the particles sent from the first fluidized bed 3 to the second fluidized bed 4 are in the first fluidized bed. The fine particles that could not be removed by the layer 3 are contained, and these particles flow through the first upper opening 303 provided in the upper part of the partition wall 300 together with the air by the fluidized air supplied from the air introduction port 401. Carried to the top of layer 3; The particles purged by the second fluidized bed 4 are sent to the third fluidized bed 5 from the second upper opening 402 provided in the upper part of the partition wall 400.

  As described above, since the fine particles, which are corrosion components that could not be removed by the first fluidized bed 3, are purged by the second fluidized bed 4, the countermeasure against high temperature corrosion of the external heat exchanger is more effectively implemented. . That is, since the particles sent from the second fluidized bed 4 to the third fluidized bed 5 are purged with fine particles that cause high temperature corrosion, the factors causing the high temperature corrosion of the external heat exchanger are eliminated as described above.

  The fluidizing gas flow rate of the second fluidized bed 4 is preferably set in the range of 0.2 to 0.4 m / sec in order to form a normal developed fluidized bed. It is preferable that the temperature in the 2nd fluidized bed 4 is set to the range of 850-900 degreeC.

  In the third fluidized bed 5, fluidized air introduced from the air inlet 502 is configured to flow into the second fluidized bed 4 through the second upper opening 402. Using this air flow, the second fluidized bed 4 is purged and removed by the fine particles that are corrosive components in the third fluidized bed 5.

  In the structure in which the first fluidized bed 3, the second fluidized bed 4 and the third fluidized bed 5 are arranged in this way, when comparing the flow direction of particles and the flow direction of fluidized air in each fluidized bed, It is a feature of the present invention that the flow of fluidized air in the upper space after passing through the fluidized bed and the flow of particles to be purged are completely counterflow.

  Specifically, particles are sent from the second fluidized bed 4 to the third fluidized bed 5 through the second upper opening 402 at the top of the partition wall 400, and in the lower part of the third fluidized bed 5. Since the particle discharge port 503 is provided, the flow of particles inside the third fluidized bed 5 is a downward flow, and the flow of fluidized air is an upward flow. Therefore, the flow of particles and air is an opposite flow. Yes.

  Further, the particles are sent in the direction of the first fluidized bed 3 → the second fluidized bed 4 → the third fluidized bed 5, whereas the flow of air for purging the fine particles is the third fluidized bed 5 → the second fluidized bed. It is the direction of the layer 4 → the first fluidized bed 3, and the flow of particles and air is an opposite flow.

  That is, by adopting such a counter-flow structure, the fine particles containing the corrosive component once purged are prevented from returning to the original fluidized bed again, and are installed most downstream in the flow of particles. It is possible to keep the corrosive component concentration in the heat transfer tube portion of the external heat exchanger 501 at the lowest.

  As an example, when a high-temperature superheated air pipe is installed in a part of the external heat exchanger 501, when the steam inlet 504 is supplied from the upper part of the third fluidized bed 5 and the outlet 505 is provided at the lower part, the steam temperature is the highest. This is most effective because the concentration of the corrosive component is reduced on the outlet portion 505 side having a high value.

  In the third fluidized bed 5, the gas temperature is lowered to about 550 to 650 ° C. by the external heat exchanger 501, so the adhesion of fine particles containing corrosive components is lowered. For this reason, fine particles which are corrosive components and relatively large particles having a high specific gravity are easily separated, and this action can be effectively used in the present invention.

  Although this external heat exchanger 501 is not specifically limited, For example, it is preferable that it is the structure which immersed the superheater pipe | tube and evaporation pipe | tube of the boiler. In the present invention, high-temperature corrosion of these superheater tubes and evaporator tubes can be reduced.

  The fluidized gas flow rate of the third fluidized bed 5 is preferably set to a relatively slow flow rate in order to prevent wear of the submerged heat transfer tubes, and specifically the fluidized gas flow rate is 0.2 to It is preferably set to about 0.25 m / sec.

  In the present invention, the fine particle purge air in the upper part of the first fluidized bed 3 is structured to be discharged from the circulation discharge port 305 to the furnace 1 via the circulation line 306. The heat exchanger 501 has a great effect of removing the cause of high temperature corrosion because fine particles that cause high temperature corrosion can be discharged together with fluidized air in front of the external heat exchanger.

  In the cyclone 2, separated gas and ash that do not fall downward are introduced into the convection heat transfer section 6. In the convection heat transfer section 6, heat is recovered from the separated gas by a heat exchanger. The separated gas and ash are recovered from the heat and then sent from the convection heat transfer section 6 to the bag filter 7 through the combustion exhaust gas duct 700 to remove the ash. The separated gas is discharged out of the system from the bag filter 7 and, for example, exhaust gas treatment is performed.

  In the above embodiment, although the aspect provided with the three fluidized beds of the 1st fluidized bed 3, the 2nd fluidized bed 4, and the 3rd fluidized bed 5 was demonstrated exemplarily, you may add a 4th fluidized bed. it can.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by this Example.

Example 1
When the relationship between the corrosive component and the particle diameter was examined by a combustion test using RPF as the fuel, the results shown in Table 1 were obtained.

  From the results of Table 1, it can be seen that corrosion components such as Cl, S, and F have a large component ratio of a particle diameter of 53 μm or less.

(Example 2)
The corrosion rate of the superheater in waste combustion was investigated using the apparatus of the present invention (see FIG. 1).

  For comparison, the same corrosion rate was examined using the apparatus shown in FIG. 1 of Japanese Patent No. 3417952 and the apparatus shown in FIG. 1 of JP-A-2003-207115. The result is shown in FIG.

  In FIG. 3, the horizontal axis represents the chlorine concentration in the fuel, and the vertical axis represents the maximum corrosion depth (mm / year) of the superheater tube (material: SUS310S).

  As can be seen from FIG. 3, in the apparatus of the present invention, even when the chlorine concentration in the fuel is about 1%, the corrosion rate of the superheater tube is reduced to 0.5 mm / year or less.

  This is because in the apparatus of the present invention, the chlorine concentration in the external heat exchanger is maintained at a smaller value than in the conventional apparatus.

  In order to further confirm this, when the relationship between the chlorine concentration in the fuel and the chlorine concentration in the external heat exchanger was examined, the results shown in FIG. 4 were obtained.

(Example 3)
In the apparatus shown in FIG. 1, waste (mixed chlorine: An experiment was conducted to collect electric power using a fuel containing 1%.

The generated boiler steam was steam pressure: 130 Kg / cm ² G, steam temperature: 550 ° C., and power generation end efficiency: 38%.

  Moreover, the superheater corrosion rate was 0.5 mm / year or less, and when pollutant components in the exhaust gas were measured, the following results were obtained.

NO _x <100 ppm (O ₂ = 6%)
SO ₂ <100 ppm (O ₂ = 6%)
CO <50 ppm (O ₂ = 6%)
DXN 0.1 ng / Nm ³ or less

The figure which shows an example of the high temperature corrosion reduction apparatus of the circulating fluidized bed boiler which concerns on this invention Plan view showing an example of arrangement of multiple fluidized beds Graph showing the results of investigation of corrosion rate of superheater Graph showing the results of examining the relationship between the chlorine concentration in fuel and the chlorine concentration in the external heat exchanger

Explanation of symbols

1: Furnace 2: Particle collector (Cyclone)
3: 1st fluidized bed 4: 2nd fluidized bed 5: 3rd fluidized bed 6: Convective heat transfer part 7: Bag filter 100: Dense bed part 101: Furnace body 102: Combustion gas duct 200: Particle introduction pipe 201: Opening part 300, 400: Partition wall 301: Air inlet 302: First lower opening 303: First upper opening 304: Side wall 305: Circulation outlet 306: Circulation line 401: Air inlet 402: Second upper opening 501: External heat Exchanger 502: Air inlet 503: Particle outlet 504: Steam inlet 505: Steam outlet 506: Circulation line 700: Combustion exhaust gas duct

Claims (2)

A furnace having a fluidized bed, a particle collection device that introduces particles discharged from the furnace accompanied by combustion gas, collects the particles and discharges them from below, and is collected by the particle collection device. In a circulating fluidized bed boiler equipped with a circulation system for circulating discharged particles to the furnace via an external heat exchanger,
The circulation system, the first fluidized bed common specifications particles sent from the particle collection device inside with partitioned by Setsukabe is to form a fluidized bed by fluidizing air from each other, the second fluidized bed and the 3 fluidized beds,
The first fluidized bed has a particle introduction pipe that introduces particles sent from the lower part of the particle collecting device and opens inside the fluidized bed, and has a fluidized air inlet for introducing fluidized air to the lower part, The lower part of the partition wall with the second fluidized bed has a first lower opening for introducing particles into the second fluidized bed, and the upper part of the partition wall has a first upper opening for introducing air from the second fluidized bed And the upper part of the side wall facing the partition wall has a structure having a circulation outlet that discharges the particles sent from the particle collector and the fluidized air and is connected to the furnace.
The second fluidized bed has a fluidized air inlet for introducing fluidized air at the bottom, introduces particles into the third fluidized bed at the upper part of the partition wall with the third fluidized bed, and the third fluidized bed. Having a second upper opening through which fluidized air flows into the second fluidized bed from
The third fluidized bed has an external heat exchanger in the fluidized bed of particles, has a fluidized air inlet for introducing fluidized air in the lower part, and discharges and circulates the heat-exchanged particles in the lower part. have a particle outlet being connected to the furnace via a line, the flow of the second lead to the particle discharge port is introduced from the second upper opening with the top of the partition wall of the fluidized bed particles, A circulating fluidized bed boiler characterized by having a structure in which a flow of fluidized air introduced from the fluidized air inlet at the lower part of the third fluidized bed and reaching the second upper opening forms a counterflow. High temperature corrosion reduction device.   2. The high-temperature corrosion reduction apparatus for a circulating fluidized bed boiler according to claim 1, wherein the external heat exchanger of the third fluidized bed has a configuration in which a superheater tube and an evaporator tube of a boiler are immersed.

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