JP4014064B2 - Fluidized bed furnace and paste fuel supply nozzle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluidized bed boiler that burns coal in a fluidized bed, drives a turbine with generated steam, and further drives a gas turbine with high-pressure and high-temperature combustion gas to obtain electric power with high efficiency. The present invention relates to a nozzle for supplying a mixed paste of coal and water.
[0002]
[Prior art]
Since the pressurized fluidized bed boiler can obtain energy from the generated steam and high-pressure combustion gas, highly efficient power generation is possible. In a fluidized bed, coal of several millimeters is burned in a fluidized bed together with a fluid medium of limestone (hereinafter sometimes referred to as BM) of approximately the same size. However, it is important to supply the solid coal particles continuously and stably into the pressurized fluidized bed furnace. As a method of supplying coal to the pressurized fluidized bed combustion furnace, there are a so-called dry supply method and a wet supply method, and the wet supply method is excellent in operation. As a method of supplying coal to a fluidized bed furnace, there is a wet supply system (for example, Japanese Patent Laid-Open No. 62-155433).
[0003]
As shown in FIG. 13, the wet supply method mixes coal particles having a maximum diameter of about 6 mm, water, and limestone as a desulfurizing agent in the furnace with a kneader 10 to obtain a 25% moisture paste (CWP: Coal Water Paste, hereinafter referred to as CWP). The CWP is temporarily stored in the CWP tank 20 with the stirrer 25, and then the pressure is increased by the CWP pump 30, and the CWP supply nozzle 40 passes through the CWP piping 31 and the line 32 to the fluidized bed furnace 70. Pump. In the CWP supply nozzle 40, the CWP is dispersed by the dispersed air and supplied to the fluid medium 71 in the fluidized bed furnace 70.
[0004]
When stopping the supply of CWP into the fluidized bed furnace 70, the flow path is switched to the CWP circulation pipe 36 by the switching valve 35 disposed between the lines 31 and 32, and the CWP is recirculated into the CWP tank 20. Here, the fluidized bed furnace 70 is housed in a pressurized container 80 and is held under pressure by supplying pressurized air.
This CWP wet supply method is low in cost because it requires no pretreatment such as drying compared to the dry supply method, for example, the method of pneumatic transportation after increasing the pressure with a lock hopper, and the wear of the transport pipe is low. There is.
[0005]
The BM in the fluidized bed furnace 70 is fluidized together with CWP from below by the combustion air, and the water in the heat transfer tube 74 is heated by the combustion of CWP to generate steam. A dust removing device 90 for removing ash in the combustion gas is installed at the outlet of the fluidized bed furnace 70, and the dust-removed combustion gas is supplied to a gas turbine (not shown).
[0006]
FIG. 14 is a structural cross-sectional view of the CWP supply nozzle 40. The CWP supply nozzle 40 includes a cooling water pipe 44 provided on the outer periphery of the CWP supply pipe 43 and a dispersed air supply pipe 45 for CWP dispersion provided on the outer periphery thereof, and has an integral structure.
[0007]
The water injection conduit 61 is disposed in the cooling water pipe 44, and an opening 60 at the tip of the water injection conduit 61 is provided in the flow path of the CWP supply pipe 43 near the outlet of the dispersed air ejection slit 45 a at the tip of the CWP supply pipe 43. Further, when air is ejected from the purge air hole 42 into the CWP supply pipe 43, it collides with the CWP and the spray (dispersion) becomes good. The purge air is supplied into the CWP supply pipe 43 through the purge air hole 42, and the CWP and the purge air are sent into the fluidized bed furnace 70 while coexisting in the CWP supply pipe 43.
[0008]
The water injection conduit 61 has a small amount at the tip of the CWP supply pipe 43 to prevent the CWP remaining in the CWP supply pipe 43 from drying and solidifying due to radiant heat from the furnace 70 during an emergency stop of the plant. It supplies water.
[0009]
The CWP supply pipe 43 is inserted into the wall surface 71 (FIG. 14) of the fluidized bed furnace 70 and the opening of the wall surface 81 of the pressure vessel 80, and the flange 71 a of the furnace wall 71, the flange 81 a of the pressure vessel wall 81 and the dispersed air supply pipe 45. Are fixed by flanges 45b and 45c. The dispersion air supply pipe 45 is provided with an expansion 45d that absorbs thermal expansion. CWP is supplied from the dispersed air supply pipe 45 into the fluidized bed furnace 70 via the CWP supply line 32 (FIG. 13).
[0010]
The purge air supply pipe 37 (FIG. 13) that removes CWP remaining in the CWP supply pipe 43 has a structure that joins at the CWP supply pipe 43 that protrudes outside the pressurized container 80.
[0011]
In addition, the CWP dispersion air is guided into the dispersion air supply pipe 45, and the dispersion of the CWP in the fluidized bed furnace 70 is improved by the ejection from the dispersion air ejection slit 45a. The ejection slit 45a is disposed inside the CWP supply pipe 43 several mm upstream from the outlet, and the shape thereof is a nozzle structure that is open over the entire circumference or a structure that is open plurally along the circumference. In the case of a structure having a plurality of openings, the gap between each of the dispersed air ejection slits 45a is about 3 to 5 mm, and the air ejection speed from the dispersed air ejection slit 45a is operated in the range of 30 to 80 m / s. The CWP flowing from the CWP supply pipe 43 is dispersed by the dispersed air supplied from the dispersed air ejection slit 45a and continuously supplied into the fluidized bed.
[0012]
[Problems to be solved by the invention]
In the pressurized fluidized bed boiler using the above-described wet feed system, when the supply of CWP to the fluidized bed furnace 70 is stopped at normal time, the flow path is switched to the CWP circulation pipe 36 by the switching valve 35 shown in FIG. After performing the operation of returning the CWP into the tank 20, a predetermined amount of purge air and water are immediately supplied from the purge air pipe 37 provided downstream of the switching valve 35 from the line 38 and remain in the CWP supply pipe 43. The discharged CWP is discharged into the fluidized bed furnace 70.
[0013]
After the discharged CWP is combusted, the supply of combustion air is stopped. This operation does not leave CWP in the CWP supply pipe 43. However, there are cases where the plant must be stopped for some reason. At that time, the supply of combustion air is stopped and the supply of CWP is also stopped. The CWP whose supply is stopped remains in the CWP supply pipe 43 and is in the furnace 70 (FIG. 15A is a front view, FIG. 15B is a side sectional view of the nozzle 40) at a high temperature (860 ° C. or higher). A fluid medium (sometimes referred to as BM) enters from the dispersed air ejection slit 45 a of the CWP supply nozzle 40 and accumulates on the lower side in the passage of the horizontal portion of the dispersed air supply pipe 45.
[0014]
As shown in FIG. 15 (FIG. 15A is a front view of the nozzle 40 and FIG. 15B is a side sectional view of the nozzle 40), the fluid medium accumulated in the dispersed air supply pipe 45 is the front of the CWP supply nozzle 40. As seen from FIG. 16, 1/4 of the space in the vertical portion of the dispersed air supply pipe 45 is closed, and the passage of the horizontal portion of the dispersed air supply pipe 45 is viewed from the side of the CWP supply nozzle 40 as shown in FIG. There is a small amount of repose angle of the fluid medium (BM) in the medium. As shown in FIG. 16, the in-furnace fluid medium has entered the CWP supply pipe 43b by an angle of repose θ (30 to 40 degrees) reaching from the furnace 70 to the dispersed air ejection slit 45a.
[0015]
The angle of repose of the deposited fluid medium varies depending on the type of the fluid medium (the type depending on the location where the limestone is produced) and the particle diameter. The opening size of the dispersion air ejection slit 45a is designed so as to have a pressure loss larger than the pressure loss fluctuation value of the fluidized medium layer in the furnace during operation of the plant. However, if the opening size of the dispersed air ejection slit 45a is designed to be smaller than the particle size of the fluid medium, the ejection speed of the dispersed air from the dispersed air ejection slit 45a is increased, causing a problem of wear. Therefore, the opening diameter of the dispersed air ejection slit 45a is determined so as to satisfy the condition that the fluid medium does not enter from the dispersed air ejection slit 45a and the condition that the fluid medium does not wear during operation of the plant.
[0016]
When the plant is restarted, the amount of dispersed air ejected from the dispersed air ejection slit 45a in a state in which the fluid medium deposited on the lower side of the passage in the horizontal portion of the dispersed air supply pipe 45 of the CWP supply nozzle 40 does not scatter again Becomes non-uniform. The amount of dispersed air from the dispersed air ejection slit 45a of the CWP supply nozzle 40 is small on the lower side and larger on the upper side, and the jet flow to the lower side is strengthened to deteriorate the dispersion characteristics of CWP. When the CWP dispersion characteristic of the CWP supply nozzle 40 is poor, the CWP combustibility is lowered in the furnace, and agglomeration may occur.
[0017]
When the above-mentioned CWP wet supply method is used, the supply of the pressurized fluidized bed boiler is stopped in an emergency, and the CWP remaining in the CWP supply pipe evaporates the moisture in the CWP due to heat entering from the fluidized medium, and is solidified by drying. To do.
[0018]
Further, the CWP dried and solidified in the CWP flow path inhibits the activation of the CWP pump 30, and for restarting, the CWP supply pipe 43 is removed from the tip of the CWP supply pipe 43 as shown in FIG. 14 to remove the dried and solidified CWP. Is provided in a region where the opening 60 of the water injection conduit 61 is cooled by the cooling water pipe 44. When water is injected into the water injection conduit 61, the residual CWP is humidified to prevent evaporation of moisture. However, the CWP remaining in the CWP supply pipe 43 in the region not cooled by the cooling water pipe 44 is close to the furnace 70 side having a high temperature, and thus is easily dried. For this reason, there is a problem that the effect of water injection using the water injection conduit 61 is thin. In addition, when an operation of pouring water into the CWP supply pipe 43 is mistaken, for example, when the injected water enters the fluidized bed furnace 70, a calcium compound (for example, CaCO2) of the fluidized medium. ₃ , CaSO ₄ ) To form a hard lump. The large mass hinders fluidization and makes it impossible to restart the boiler.
[0019]
Moreover, the phenomenon that BM solidifies in the supply part of the dispersion | distribution air ejection slit 45a occurs by mixing of the fluidized medium into the dispersion | distribution air ejection slit 45a at the time of the emergency stop of a boiler. It takes about 24 hours or more to restart after the emergency stop of the boiler. During this time, the BM accumulated in the dispersed air ejection slit 45a reacts with the condensed water to produce hydrated solids, and the dispersed air ejection This is because the slit 45a is partially blocked. When dispersed air is re-supplied in a state where the dispersed air ejection slit is closed, the CWP dispersed particle size increases, and there is a problem that a coarse mass of CWP accumulates in the fluidized bed, resulting in poor flow.
[0020]
On the other hand, even during normal operation, there is a problem that BM is mixed into the dispersed air ejection slit 45a. In the fluidized bed, pressure fluctuations occur due to intense particle movement or bubble burst, and there is a problem that BM flows back into the dispersed air supply pipe as the pressure rises rapidly.
[0021]
Further, in the conventional CWP supply nozzle 40, since the dispersed air injection hole 60 is located at the tip of the nozzle 43, there is a problem that the dispersed air flow rate must be increased in order to obtain a predetermined CWP dispersed particle diameter. . As the dispersed air, the high-temperature air of about 300 ° C. supplied into the pressurized container is once cooled, and this is pressurized again and used as the dispersed air. Therefore, cooling causes the sensible heat of the air to be lost, leading to a decrease in boiler efficiency. In order to reduce wear on the inner wall surface of the CWP supply nozzle 40, it is desirable that the dispersed air flow rate be as small as possible.
[0022]
The first problem of the present invention is that when a plant such as a pressurized fluidized bed boiler is in an emergency stop, the fluid medium that has entered and accumulated in the passage of the horizontal portion of the dispersed air supply pipe of the CWP supply nozzle is re-entered into the furnace. By providing a CWP supply nozzle and a fluidized bed boiler equipped with the CWP supply nozzle that can disperse and uniformize the amount of dispersed air from the dispersed air nozzle, improve the dispersion characteristics of CWP, and eliminate the cause of agglomeration. is there.
[0023]
The second problem of the present invention is that the CWP remaining in the CWP supply nozzle is prevented from drying and solidifying, the CWP is kept in a flowable state, and the BM is provided in the dispersed air ejection slit at the time of emergency stop and normal operation of the boiler. Are provided, and a fluidized bed boiler provided with the CWP supply nozzle capable of facilitating restart of a fluidized bed boiler and the like.
[0024]
[Means for Solving the Problems]
In order to achieve the above first problem, in a fluidized bed furnace in which CWP produced by mixing coarse coal, pulverized coal slurry, water, limestone, etc. is supplied from the fuel supply nozzle into the fluidized bed and burned. The supply nozzle includes a CWP flow channel, a distributed air jet slit for air jet for dispersing the CWP provided in the vicinity of the furnace side outlet portion of the wall surface constituting the CWP flow channel, and the CWP flow channel A fuel dispersion air supply passage for supplying air to the dispersion air ejection slit on the outer periphery of the fuel, and the flow rate of the dispersion air in the fuel dispersion air supply passage is from the furnace through the dispersion air ejection slit. More than the penetration speed of solid particles entering the fuel dispersion air supply flow path (the air flow rate necessary to give a velocity component that returns the particles to the furnace side relatively before the solid particles enter) fuel The fluidized bed furnace provided with an air flow rate control device for controlling the capacity of the distributed air supply source for supplying the size and flow path of the diffuser air supply channel is used.
[0025]
When the fluidized bed boiler according to the present invention is urgently stopped, all the drive units are stopped. In particular, when the flow of the fluid medium in the furnace is stopped, the distance from the furnace of the dispersed air ejection slit of the CWP supply nozzle is very close (10 to 30 mm). Therefore, the repose angle (30 to 40 degrees) of the fluid medium in the furnace penetrates into the CWP supply nozzle hole and accumulates in the horizontal portion of the dispersion air supply channel from the dispersion air ejection slit. The removal of scattered BM deposited in the horizontal passage of the dispersed air supply channel is improved as the flow rate of the BM deposit increases. In other words, it has been found that it is sufficient to remove the scattered BM from the intrusion speed of the deposited BM.
[0026]
Therefore, for example, a throttle portion is provided on the entire circumference of the distributed air supply flow path so as to exceed the intrusion speed of the fluid medium accumulated in the horizontal passage of the distributed air supply flow path of the CWP supply nozzle. The throttle portion provided in the horizontal portion of the dispersed air supply flow path is a streamline with low pressure loss, and is composed of blades that provide a straight flow or a swirl flow. When the fluidized bed boiler plant is started, when dispersed air is supplied into the dispersed air supply flow path of the CWP supply nozzle,
[0027]
1) Since the constricted portion that provides a straight flow provided in the entire circumference of the horizontal portion of the dispersed air supply channel is a streamline with low pressure loss, the constricted portion suddenly increases beyond the intrusion speed of the fluid medium and accumulates. Disperse the fluid medium again and discharge it into the furnace.
2) The deposited fluid medium is re-scattered while being swirled by the blades that provide the swirl flow provided in the CWP dispersed air supply flow path and is discharged into the furnace.
[0028]
3) The purge nozzle provided on the lower side in the CWP dispersed air supply flow path advances to the fluid medium deposition part during operation of the plant and injects a constant time continuously or intermittently above the intrusion speed of the fluid deposition medium. The deposited fluid medium is re-scattered and discharged into the furnace. Thereafter, the purge nozzle is advanced to a predetermined position. The injection from the purge nozzle is performed when the dispersed air is ventilated. Furthermore, the purge nozzle can perform suction operation when the plant is stopped to suck and remove BM accumulated in the dispersed air supply flow path out of the system. Therefore, there is an effect due to the purge nozzle during operation of the plant. At this time, an independent air supply source or suction source and purge or suction air from the air supply source or suction source are continuously or intermittently supplied or suction controlled to the deposit purging or suction nozzle. It is desirable.
[0029]
As a result of diligent and experimental studies to solve the second problem of the present invention, solidification of CWP remaining in the CWP supply nozzle is prevented, the CWP is held in a flowable state, and the boiler is in an emergency stop state. In order to prevent solid particles such as BM from being mixed into the opening on the furnace side of the dispersion air supply channel during normal operation, the dispersion medium is jetted toward the outlet near the outlet of the CWP channel. A dispersed air ejection slit is provided to be joined to the CWP channel, and the slit is kept at a sufficient interval to form an angle of repose of the deposit when solid particles entering the CWP channel are deposited in the CWP channel. It has been found that it is necessary to arrange it upstream of the CWP supply flow path.
[0030]
When the pressurized fluidized bed boiler is urgently stopped, the supply of combustion air is stopped and the flow of the fluidized medium is stopped. At the same time, the CWP supply pump stops and the supply of the CWP slurry also stops. In this state, as shown in FIG. 7, the CWP slurry is almost 100% full in the CWP flow path upstream of the dispersed air ejection slit opening on the wall of the CWP flow path, but on the downstream side of the dispersed air ejection slit opening. Is in a state where there is almost no CWP. Furthermore, BM forms an angle of repose and stops at the tip of the CWP supply nozzle. Therefore, a space is formed between the dispersed air ejection slit opening and the CWP supply nozzle tip. The angle of repose of deposits such as BM varies depending on the properties of the deposits such as BM, but is 15 to 45 °. Even when the angle of repose is the smallest 15 °, BM or the like is in the dispersed air ejection slit opening. There is no invasion. Therefore, the BM accumulated at the tip of the CWP supply nozzle is not replaced with the BM in the fluidized bed, and the temperature of the BM is drastically lowered, and there is an effect of preventing heat from entering from the BM into the CWP accumulated in the CWP flow path. . Therefore, evaporation of CWP moisture accumulated in the CWP channel can be suppressed.
[0031]
Further, as shown in FIG. 9, since the dispersed air ejection slit is located inside the CWP flow path, a predetermined dispersed particle diameter can be obtained with a small gas-liquid ratio (dispersed air amount / CWP flow rate).
[0032]
In addition, the second problem of the present invention is that means for supplying water or gas to the tip of the CWP flow path is provided, and means for measuring the temperature from the location where water or gas is supplied to the fluidized bed furnace side Can be achieved with a configuration comprising
[0033]
When a fluidized bed boiler such as a pressurized fluidized bed boiler is urgently stopped, the supply of the primary dispersion air and the secondary dispersion air of the CWP is stopped, and CWP remains in the CWP supply flow path in that state. In order to prevent drying and solidification of the CWP remaining in the CWP supply flow path, water or gas is injected into the tip of the CWP supply flow path, the CWP is humidified, and a predetermined (initial) moisture is retained. Yes. Water injection or the like is performed by changing the water injection amount arbitrarily according to the fixed amount or the temperature in the bed as shown in FIG. The water injection stop of the CWP supply flow path is controlled so that, for example, the temperature at the tip of the CWP supply flow path is 60 ° C. or lower or the in-layer temperature is 200 ° C. or lower. Alternatively, simultaneously with the emergency stop of the boiler, air, preferably an inert gas (for example, nitrogen gas, carbon dioxide gas) is supplied to the water injection means, and water is injected after removing the residual CWP at the tip. During normal operation of the fluidized bed furnace, when the fluidized bed temperature reaches 200 ° C. to prevent the water injection hole provided at the tip of the CWP supply flow path from being clogged with CWP or the fluidized medium, the tip of the CWP nozzle Start pouring water. Stopping water injection at the tip of the CWP supply nozzle is performed after air and purging are completed in the CWP supply channel after the CWP supply is stopped.
[0034]
The position for supplying water or gas to the tip of the CWP supply channel is arranged at a location where the CWP supply channel is not cooled by the cooling water pipe. Moreover, you may provide the apparatus which controls the injection amount of the said water or gas arbitrarily according to the bed temperature of a fluidized bed.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1, FIG. 2 and FIG. 3 are sectional views showing the structure of a preferred CWP supply nozzle according to an embodiment of the present invention. FIG. 4 is a perspective view of a partially broken section inside the CWP supply nozzle shown in FIG.
FIG. 1 is a cross-sectional view of the tip of the CWP supply nozzle 40 shown in FIG. The CWP supply nozzle 40 is composed of concentric tubes in the order of a CWP supply tube 43, a cooling water tube 44, and a dispersed air supply tube 45. A water injection conduit 61 is disposed at the tip of the CWP supply pipe 43. The water injection conduit 61 is provided in the CWP supply pipe 43 in the vicinity of the outlet of the dispersed air ejection slit 45 a through the cooling water pipe 44. A water injection hole (opening) 60 at the tip of the water injection conduit 61 opens from the cooling water pipe 44 to the CWP supply pipe 43. The water temperature is adjusted so that the wall temperature of the CWP supply pipe 43 is 50 ° C. or less by passing cooling water through the cooling water pipe 44. The dispersed air ejection slit 45a is provided such that the ejection angle θ of the CWP dispersion air ejected from the slit 45a is directed to the nozzle central axis direction with an inclination of 45 degrees with respect to the horizontal direction.
[0036]
In the passage of the horizontal portion of the dispersion air supply pipe 45 upstream of the CWP flow at the location where the dispersion air ejection slit 45a is provided, there is provided a throttle portion 100 that narrows the flow area over the entire circumference of the passage. Yes. The throttle unit 100 shown in FIG. 1 has a structure that gives a streamlined straight flow, and the throttle unit 100 has a flat divergent shape in which the upstream side is streamlined and has a negative taper shape toward the downstream side (see FIG. 1). 4), the throttle part 100 is fixed to the outer wall of the cooling water pipe 44 by welding or bolt tightening.
[0037]
In FIG. 2, the shape of the throttle unit 100 shown in FIG. 1 is a semicircular cross section. FIG. 3 shows the squeezed portion 100 as a blade that provides a swirl flow. FIG. 4 shows a perspective view of a partially broken cross section. In this example, the squeezed portion 100 has a swirl angle of 30 to 60 degrees. Is provided.
[0038]
The dispersion air velocity that has passed near any throttle 100 shown in FIGS. 1, 2, and 3 is greater than the velocity at which the fluid medium particles (FIGS. 15 and 16) that accumulate in the dispersion air supply pipe 45 do not accumulate. It has become.
[0039]
FIG. 5 shows the arrangement of the purge nozzle 110 on the lower side in the passage of the horizontal portion of the dispersed air supply pipe 45 in the vicinity of the CWP dispersed air ejection slit 45a, instead of providing the throttle portion. Although not shown in FIG. 5, a compressed gas cylinder and a control device capable of arbitrarily controlling the forward / backward movement of the cylinder and the injection conditions are provided so that the purge nozzle 110 can be moved back and forth. The air source of the purge nozzle 110 is provided separately from the dispersed air source, and a device capable of sucking the fluid medium accumulated from the purge nozzle 110 may be provided. The front end of the purge nozzle 110 is cut obliquely. This is to open as close as possible to the surface of the fluidized medium particle deposit that forms an angle of repose in the dispersed air supply pipe 45 so that purge air or suction air can act effectively. .
[0040]
In the above structure, the CWP passes through the CWP supply pipe 43 shown in FIG. 1 and collides with the dispersed air ejected from the dispersed air nozzle ejection 45a at the front end portion at an angle θ of 45 degrees, and in the fluid medium layer in the furnace. Distributed. The cooling water is sent through the cooling water pipe 44 to cool the CWP supply nozzle 40.
[0041]
By the way, for some reason, the operation of a pressurized fluidized bed boiler, a normal pressure fluidized bed boiler, or the like is forced to stop, and the supply of combustion air and CWP must be cut off urgently. When the repose angle θ (30 to 40 degrees) of the flowing medium (BM) in the furnace enters into the CWP supply pipe 43, it accumulates in the passage of the horizontal portion of the dispersion air supply pipe 45 from the dispersion air ejection slit 45a. (See FIG. 16).
[0042]
According to the CWP supply nozzle 40 of the present invention, the throttle part 100 with a low pressure loss is provided inside the passage of the distributed air supply pipe 45, and the air flow rate of the throttle part 100 is the passage of the horizontal part of the distributed air supply pipe 45. It is set to be faster than the penetration speed of the fluid medium deposited inside. For this reason, when the dispersed air is ventilated through the dispersed air supply pipe 45 when the plant is restarted, the following phenomenon occurs.
[0043]
(1) As shown in FIG. 1, FIG. 2 and FIG. 3, the narrowed portion 100 having a streamlined cross-sectional shape or a semicircular cross-section provided on the entire circumference inside the passage of the horizontal portion of the distributed air supply pipe 45 causes a straight flow. By narrowing down, the flow velocity of the dispersed air is suddenly increased, and the accumulated BM is scattered and discharged from the dispersed air ejection slit 45a into the furnace.
The effect of the throttle unit 100 is that the distance L between the end of the passage in the vertical direction at the tip of the dispersed air supply pipe 45 and the throttle unit 100 is set closer to the region where the BM forms an angle of repose and accumulates. , The scattering removal rate of BM is improved.
(2) As shown in FIG. 4, in the throttle unit 100 provided with blades that give a swirling flow (30 to 60 degrees) to the entire circumference inside the passage of the horizontal portion of the dispersed air supply pipe 45, the accumulated BM is scattered while swirling. And discharge into the furnace.
[0044]
(3) A purge nozzle 110 is provided on the lower side in the passage of the horizontal portion of the dispersed air supply pipe 45 shown in FIG. 5 and is pulled upstream of the passage during normal operation, and forward when restarting. Then, the BM deposited by the air sprayed continuously or intermittently from the purge nozzle 110 together with the ventilation of the dispersed air is scattered and discharged into the furnace.
(4) In the purge nozzle 110 described in the above (3), the accumulated BM is sucked and removed out of the system by performing a suction operation with a suction device when the plant is stopped.
[0045]
When the fluidized bed boiler plant is restarted, the BM accumulated in the dispersed air supply pipe 45 is discharged into the furnace. Therefore, since the amount of dispersed air ejected from the dispersed air ejection slit 45a is uniform, stable operation can be performed without degrading the dispersion characteristics of CWP.
[0046]
In the example shown in the cross-sectional view of the CWP supply nozzle 40 shown in FIG. 6, the nozzle 40 is composed of a concentric tube from the center in the order of a CWP supply pipe 43, a double pipe cooling water pipe 44, and a dispersed air supply pipe 45. However, the dispersed air supply pipe 45 is formed with a dispersed air ejection slit 45a arranged in an annular shape.
[0047]
The dispersed air ejection slit 45a is located at a position 2 to 5 times the diameter D of the CWP supply pipe 43 from the pipe end plate 45d, and its opening is arranged toward the pipe end plate 45d. Further, the pipe end plate 44a of the cooling water pipe 44 cues downstream from the dispersed air ejection slit 45a, and the dispersed air flows around it. This is because the pipe end plate 45a and the dispersed air supply pipe 45 are exposed to a high temperature of 850 ° C. or higher, so that the pipe end plate 44a and the dispersed air supply pipe 45 are prevented from getting hot by bypassing the pipe end plate 44a. It serves a purpose.
[0048]
FIG. 7 shows a state of CWP and BM accumulation around the CWP supply nozzle 40 at the time of emergency stop of the boiler. At the time of an emergency stop of the boiler, the CWP pump 30 (FIG. 13) is stopped, and the supply of CWP is stopped, and at the same time, the ejection of dispersed air is stopped. As shown in FIG. 7, CWP remains in the CWP supply pipe 43 upstream from the opening of the dispersed air ejection slit 45a, but hardly exists in the CWP supply pipe 43 downstream of the opening position of the dispersed air ejection slit 45a. It becomes a state. Further, at the tip of the CWP supply pipe 43, the BM forms a repose angle θ and stops.
[0049]
Therefore, a space 102 is formed between the opening of the dispersed air ejection slit 45 a and the tip of the CWP supply pipe 43. The angle of repose θ of the BM varies depending on the properties of the BM, but is 15 ° to 45 °. When the BM is most likely to flow into the opening of the dispersed air ejection slit 45a, that is, the dispersed air ejection slit even at the angle of repose θ = 15 °. BM does not enter the opening 45a, and BM and CWP do not directly contact each other. Due to the formation of the space portion 102, the BM accumulated at the tip of the CWP supply pipe 43 is not replaced with the BM in the fluidized bed of the furnace, and the temperature of the BM is rapidly lowered to prevent heat from entering the CWP from the BM. In the point. Therefore, evaporation of moisture contained in CWP accumulated in the CWP flow path can be suppressed.
[0050]
FIG. 8 shows an example of test results for verifying the above characteristics. The CWP moisture concentration with respect to the distance from the tip of the CWP supply nozzle 40 when the CWP supply nozzle 40 at the time of emergency stop of the boiler is disassembled is shown by comparison between the prior art shown in FIG. 14 and the technique of the present invention shown in FIG. .
[0051]
It is shown that the water concentration at the tip of the CWP supply nozzle 40 of the prior art is 14% by weight, whereas the CWP supply nozzle 40 of the present invention is 22-23%, which is almost the same as the initial CWP water concentration. It was. The water concentration in CWP is usually 23 to 25% by weight. However, when the water content in CWP is 14% by weight, CWP has no fluidity and is completely solidified. In this case, it is impossible to push out and remove the CWP solidified by the CWP pump 30, and the work of disassembling and cleaning the CWP supply nozzle 40 occurs.
[0052]
Further, in the example of the present invention shown in FIGS. 6 and 7, a predetermined CWP dispersed particle size can be obtained with a small dispersed air flow rate. FIG. 9 shows, as an example, the CWP spray particle size when the gas-liquid ratio (dispersed air amount / CWP flow rate) is changed as compared with the conventional method. When the gas-liquid ratio is as large as 0.2 or more, the CWP dispersed particle diameter is almost the same, but when the gas-liquid ratio is 0.2 or less, the CWP supply nozzle 40 of the present invention has a larger particle size than that of the prior art nozzle. It became clear that the CWP dispersed particle size was reduced. This is because the CWP dispersed with the CWP dispersed air is further broken and split on the wall surface of the CWP supply pipe.
[0053]
However, it was confirmed that when the opening of the dispersed air ejection slit 45a on the wall surface of the CWP supply pipe 43 is located further upstream of the CWP supply pipe 43, the CWP dispersed particle size increases and the dispersion pulsates. It was estimated that this was because dispersed CWP increased in amount in the CWP supply pipe 43 and gathered and pulsated again in the CWP supply pipe 43.
[0054]
It shows in sectional drawing of the front-end | tip part of the CWP supply nozzle 40 shown in FIG.10 and FIG.11, and a water injection control system diagram. In this embodiment, water is poured into the tip of the CWP supply pipe 43 at the time of an emergency stop of the boiler, so that the remaining CWP moisture is retained and the nozzle is blocked.
As shown in FIG. 10, the CWP supply nozzle is composed of concentric tubes in the order of the CWP supply tube 43, the cooling water tube 44 and the dispersed air supply tube 45 from the center.
[0055]
The water injection conduit 61 (FIG. 14) includes a water injection hole 60 that opens into the CWP supply pipe 43 in the vicinity of the outlet of the dispersion air ejection slit 45 a of the dispersion air supply pipe 45 through the flow path of the cooling water pipe 44. The water injection hole 60 is provided in the downstream CWP supply pipe 43 portion that is not cooled by the cooling water pipe 44. The dispersed air ejection slit 45a has a dispersed air ejection angle of 45 degrees.
[0056]
FIG. 11 shows a control system diagram in which water is injected from the water injection conduit 61 to the tip of the CWP supply nozzle 40 via the water injection hole 60. The water injection device at the tip of the CWP supply nozzle 40 includes the water injection device 120, the fluidized bed. An in-layer temperature detector (thermocouple) 72 installed on the wall surface 71 of the furnace 70, a temperature detector (thermocouple) 65 installed at the tip of the CWP supply nozzle 40 shown in FIG. 10, the control device 130, and FIG. It consists of water injection pump, electromagnetic valve, flow meter, etc. not shown.
[0057]
In the nozzle structure shown in FIGS. 10 and 11, the CWP passes through the CWP supply pipe 43 shown in FIG. 10, and the purge air is supplied into the CWP supply pipe 43 through the purge air hole 42 (FIG. 14). The Accordingly, the CWP and the purge air 42 a are sent into the fluidized bed furnace 70 while coexisting in the CWP supply pipe 43.
[0058]
By the way, the pressurized fluidized bed boiler may be forced to stop for some reason, and the supply of combustion air and CWP may be urgently cut off. When the supply of CWP is stopped, the operation of the pressurized fluidized bed boiler is stopped, and the CWP remaining in the CWP supply pipe 43 is evaporated and dried and solidified by radiant heat from the fluidized bed furnace 70. According to the CWP supply nozzle 40 shown in FIG. 11, in order to prevent the CWP adhering to the inner wall of the CWP supply pipe 43 from being dried and solidified, water is injected from the water injection conduit 61 to the tip of the CWP supply pipe 43, and the remaining CWP Inject to retain moisture in this residual CWP. Alternatively, nitrogen gas or air gas is supplied to the water injection hole 60 for several seconds to remove residual CWP, and water is injected after separating the distance from the high temperature portion of the furnace 70 to avoid drying.
[0059]
Stopping of water injection at the tip of the CWP supply pipe 43 is performed when the temperature of the temperature detector 65 installed on the fluidized bed furnace 70 side is 60 ° C. or lower from the location where water is injected into the CWP supply pipe 43 or in the layer of the fluidized bed furnace 70. The temperature is 200 ° C. or lower. Thereby, the water | moisture content of CWP which remained in the state in which the cavity was formed in the CWP supply pipe | tube 43 can be hold | maintained, and since the fluidity | liquidity is acquired, the restart of a CWP pump can be performed easily.
[0060]
【The invention's effect】
According to the present invention, for example, in a coal / water mixed paste (CWP) supply nozzle to a pressurized fluidized bed furnace, the in-furnace fluid medium penetrates into the dispersed air supply pipe of the CWP supply nozzle at the time of emergency stop of the boiler. Although it accumulates, all of the fluid medium deposited at the time of restarting the plant is scattered again and discharged into the furnace. The amount of dispersed air ejected from the dispersed air ejection slit is uniform. Therefore, it is possible to provide a highly economical pressurized fluidized bed boiler that does not reduce the dispersion characteristics of CWP, does not generate agglomerates in the furnace, and can operate stably for a long period of time. In addition, the boiler can be easily restarted, and a highly reliable CWP nozzle can be provided. Furthermore, since the expense required for restart and the incidental equipment accompanying restart can be omitted, a low-cost boiler can be provided. At the same time, the efficiency of boiler air can be increased because the flow rate of dispersed air can be reduced.
[Brief description of the drawings]
FIG. 1 is a structural sectional view of a CWP supply nozzle according to an embodiment of the present invention.
FIG. 2 is a structural cross-sectional view of a CWP supply nozzle according to an embodiment of the present invention.
FIG. 3 is a structural cross-sectional view of a CWP supply nozzle according to an embodiment of the present invention.
FIG. 4 is a partially broken perspective view of the CWP supply nozzle according to the embodiment of the present invention.
FIG. 5 is a structural cross-sectional view of a CWP supply nozzle according to an embodiment of the present invention.
FIG. 6 is a cross-sectional view of a CWP supply nozzle structure according to the embodiment of the present invention.
7 is a CWP state diagram in the CWP supply nozzle of FIG. 6; FIG.
FIG. 8 is a diagram showing the relationship between the water content of CWP accumulated at the tip of the CWP nozzle according to the present invention and the prior art and the distance from the tip of the nozzle.
FIG. 9 is an explanatory diagram of moisture concentration characteristics in a CWP nozzle according to the present invention and the prior art.
FIG. 10 is a sectional view of a CWP supply nozzle structure according to the present invention.
11 is a partial cross-sectional view of the structure of the CWP supply nozzle of FIG. 10 and a water injection control system diagram.
FIG. 12 is a relationship diagram between the fluidized bed temperature and the amount of water injected.
FIG. 13 is a system diagram for supplying a CWP production apparatus in a pressurized fluidized bed and the obtained CWP to a fluidized bed boiler.
FIG. 14 is a structural sectional view of a conventional CWP supply nozzle.
15 is a ratio of a fluid medium accumulation amount in a dispersed air supply pipe in the CWP supply nozzle of FIG.
FIG. 16 is an enlarged view showing a fluid medium accumulation state in a CWP supply nozzle dispersed air supply pipe.
[Explanation of symbols]
10 Kneader 20 CWP tank
25 Stirrer 30 CWP pump
31 CWP piping 32 CWP line
35 Switching valve 36 CWP circulation piping
37 Purge air piping 40 CWP supply nozzle
42 Purge air hole 43 CWP supply pipe
44 Cooling water pipe 45 Dispersed air supply pipe
45a Dispersed air ejection slit 60 Water injection hole (opening)
61 Water injection conduit 70 Fluidized bed furnace
71 Fluidized bed furnace wall 72 In-bed temperature detector
74 Heat transfer tube 80 Pressure vessel
81 Pressure vessel wall 90 Dedusting device
100 Aperture part 102 Space part

Claims (14)

 In a fluidized bed furnace in which a paste-like fuel composed of a mixture containing coal and water is supplied from the fuel supply nozzle into a fluidized bed and combusted, the fuel supply nozzle includes a paste-like fuel channel and the paste-like fuel channel. Dispersion air ejection slits for air ejection for dispersing paste-like fuel provided in the vicinity of the furnace side outlet portion of the wall surface constituting the furnace, and the dispersed air ejection slits on the outer periphery of the fuel flow path A fuel dispersion air supply passage for supplying air, and the flow rate of the dispersion air in the fuel dispersion air supply passage enters the fuel dispersion air supply passage from the furnace through the dispersion air ejection slit A fluidized bed furnace provided with an air flow rate control device for controlling the size of the fuel dispersion air supply flow path and the capacity of the dispersion air supply source to supply the flow path so as to be higher than the particle penetration speed  2. The fluidized bed furnace according to claim 1, wherein a throttle portion for narrowing the fuel dispersion air passage is provided upstream of the dispersion air ejection slit in the fuel dispersion air supply passage.  The narrowing part that narrows the fuel dispersion air flow path is sufficient to form the angle of repose of the deposit when solid particles that enter from the furnace through the slit of the dispersion air jet accumulate at the tip of the fuel dispersion air supply flow path. The fluidized bed furnace according to claim 1, wherein the fluidized bed furnace is arranged on the upstream side of the fuel dispersion air supply flow path with a proper interval.  The fluidized bed furnace according to claim 1, wherein the outer shape of the throttle portion provided in the fuel dispersion air supply flow path is a shape that provides a streamlined or swirl flow.  A deposit purging or suction air nozzle is provided in the fuel dispersion air supply passage upstream of the dispersion air ejection slit, and the air nozzle is slidably disposed in the fuel dispersion air supply passage. The fluidized bed furnace according to claim 1, wherein  The air nozzle for purging or sucking deposits has an independent air supply source or suction source and purge for purge or suction air supplied or sucked from the air supply source or suction source continuously or intermittently. 6. A fluidized bed furnace according to claim 5, further comprising an air supply or suction control device.  The dispersed air ejection slit is provided with a sufficient interval to form an angle of repose of the deposit when solid particles that enter the paste-like fuel flow path from the furnace accumulate in the paste-like fuel flow path. 2. A fluidized bed furnace according to claim 1, wherein an opening is disposed on a wall surface constituting the pasty fuel flow channel on the upstream side of the passage.  A means for supplying water or gas to the furnace side outlet of the paste-like fuel flow path is provided, and a temperature measuring means is provided to the pace-like fuel flow path on the furnace side from the arrangement position of the means for supplying water or gas. The fluidized bed furnace according to claim 1.  9. A cooling water flow path for cooling the flow path is provided on the outer periphery of the paste-like fuel flow path, and means for supplying water or gas is installed at a location not cooled by the cooling water flow path. The fluidized bed furnace described. A paste-like fuel passage for supplying a paste-like fuel made of a mixture containing coal and water into the furnace, and a paste-like fuel provided in the vicinity of the furnace side outlet of the wall surface constituting the paste-like fuel passage. A distributed air ejection slit for air ejection for dispersion toward the fuel, a fuel dispersion air supply channel for supplying air to the dispersed air ejection slit on the outer periphery of the fuel supply channel, and a paste-like fuel flow Means for supplying water or gas provided at the furnace side outlet of the wall surface constituting the path, and temperature measuring means provided in the paste-like fuel flow path on the furnace side from the arrangement position of the means for supplying water or gas comprising the paste fuel to a fluidized bed from the paste fuel supply nozzle method of operating a fluidized bed furnace feeding and burning, from the means for supplying water or gas depending on the intralayer temperature of the fluidized bed The method of operating a fluidized bed furnace also is properly characterized by arbitrarily controlling the supply amount of the gas.  When the temperature in the fluidized bed furnace is 200 ° C. or higher, water or gas is supplied from the means for supplying water or gas, and the supply is stopped when the temperature at the furnace side outlet portion of the paste-like fuel flow path is 60. The operation method of a fluidized bed furnace according to claim 10, wherein the operation is performed at a temperature of not higher than ° C or an in-bed temperature of not higher than 200 ° C. A paste-like fuel passage for supplying paste-like fuel made of a mixture containing coal and water into the furnace, and a paste-like fuel provided in the vicinity of the furnace side outlet of the wall surface constituting the paste-like fuel passage is directed into the furnace. A dispersed air ejection slit for ejecting air for dispersion, a fuel dispersed air supply channel for supplying air to the dispersed air ejection slit on the outer periphery of the fuel supply channel, and a fuel dispersed air supply channel A paste-like fuel supply nozzle comprising: a throttle portion for narrowing a fuel dispersion air flow path provided upstream of the dispersion air ejection slit. A paste-like fuel passage for supplying a paste-like fuel made of a mixture containing coal and water into the furnace, and a paste-like fuel provided in the vicinity of the furnace side outlet of the wall surface constituting the paste-like fuel passage. Dispersed air ejection slits for air ejection for dispersion toward the fuel, a fuel dispersion air supply channel for supplying air to the dispersed air ejection slit on the outer periphery of the fuel supply channel, and a distributed air ejection slit A paste-like fuel supply nozzle, comprising: a deposit purging or suction air nozzle slidably provided in a fuel dispersion air supply flow path on the upstream side. A paste-like fuel flow path for supplying a paste-like fuel made of a mixture containing coal and water into the furnace, and solid particles that enter the paste-like fuel flow path from the furnace are deposited in the paste-like fuel flow path Air to disperse the paste-like fuel toward the furnace, with an opening provided on the upstream wall surface of the paste-like fuel supply channel with a sufficient interval to form the repose angle of the deposit A paste-like fuel comprising: a dispersed air jet slit for jetting; and a fuel dispersed air supply channel for supplying air to the dispersed air jet slit on an outer peripheral portion of the fuel supply channel Supply nozzle.

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