WO1990002293A1

WO1990002293A1 - Composite circulation fluidized bed boiler

Info

Publication number: WO1990002293A1
Application number: PCT/JP1989/000883
Authority: WO
Inventors: Takahiro Ohshita; Shuichi Nagato; Norihisa Miyoshi
Original assignee: Ebara Corporation
Priority date: 1988-08-31
Filing date: 1989-08-30
Publication date: 1990-03-08
Also published as: ATE131271T1; CN1041646A; MY104683A; DE68925033T2; EP0431163B1; KR100229691B1; EP0431163A1; DE68925033D1; EP0431163A4; CA1332685C; CN1017469B; AU4199889A; KR900700822A

Abstract

This invention relates to a composite circulation fluidized bed boiler. A fluidized bed portion of the fluidized bed boiler is divided by a partition into a main combustion chamber and a heat recovery chamber, and at least two kinds of air chambers, i.e. an air chamber for providing a large fluidizing speed to a fluidization medium and an air chamber for providing a small fluidizing speed are provided. The combination of air having different fluidization speeds and jetted from these air chambers generates a swirling circulation flow in the fluidization medium inside the main combustion chamber and a circulation flow of the fluidization medium is generated between the main combustion chamber and the heat recovery chamber. Inside the heat recovery chamber, heat recovery of an exhaust gas is made at a free board portion or downstream of the free board portion in an internal circulation fluidized bed boiler for lowering the fluidization medium in the form of the fluidized bed, and after the temperature of the exhaust gas is lowered, the exhaust gas thus cooled is led into a cyclone and the char in a fine particle form collected by the cyclone is returned to the portion immediately above, or into, the lowering moving layer of the fluidization medium in the main combustion chamber and/or the heat recovery chamber. Since the char is returned immediately above or into the lowering moving layer of the fluidization medium, it does not immediately scatter to the free board portion. Accordingly, though it is the fine particles, it sediments and diffuses sufficiently into the fluidized bed so that NOx generated by the combustion of coal or the like inside the layer can be reduced.

Description

Specification

Technical field of combined circulation and fluidized bed boiler

The present invention provides combustion of various kinds of coal, low-grade coal, coal-cleaning sludge, filco-tas, etc. by a so-called swirling type fluidized bed, and at the same time, a circulating fluidized bed and a free-flowing bed. This is an internal circulating fluidized bed boiler that recovers heat from the heat transfer section provided in one port and downstream of the free board section.

Background art

In recent years, coal has been spotlighted as an alternative energy to petroleum, but in order to expand the use of coal, which has poor physical and chemical properties as a fuel compared to oil, However, the development of technologies for promoting the processing, distribution, and utilization of coal has been urgently pursued, and research and development of pulverized coal-fired boilers and fluidized bed boilers have been actively conducted as combustion technologies. These combustion technologies still have restrictions on coal types in terms of combustion efficiency, low NOx, and low SOx, as well as the complexity of coal-fired guns and the difficulty of controlling load fluctuations. This tendency is particularly noticeable in small and medium-sized boilers.

In addition, there are two types of fluidized bed boilers, depending on the arrangement of the heat transfer section and the method that takes into account the burning of unburned particles protruding from the fluidized bed.

(1) Non-circulating fluidized bed boiler (conventional fluidized bed boiler or publishing type fluidized bed boiler α) (2) Circulating fluidized bed boiler

In the non-circulation type, a ripening tube is arranged in a fluidized bed, and heat exchange is performed with high heat transfer efficiency by physical contact between fuel and fluid medium burning at high temperature. Fine not :! A part of the distribution or the fluid medium (circulation solid) is placed in the flow of combustion gas and led to the heat exchange section, which is located separately from the combustion chamber, and is unburned. This is a method in which the combustion of particles is continued, and the circulating solid that has undergone heat exchange is returned to the combustion chamber. The solid circulates, so this name is given.

The non-circulating fluidized bed boiler and the circulating fluidized bed boiler will be described with reference to Figs. 4 and 5.

FIG. 4 shows a non-circulating flow-bed boiler, in which fluidizing air pumped from a blower (not shown) passes through a dispersion plate 72 from an air chamber 74 to be boiled. The fuel is ejected into 1 to form a fluidized bed 73, and the fuel, for example, granular coal, is supplied to the fluidized bed 73 and burned. Heat transfer tubes 76 and 7 in the fluidized bed 73 and at the exhaust gas outlet of the freeboard section? Is provided to recover heat.

The exhaust gas, which has become relatively low in temperature, is led from the exhaust gas outlet of the freeboard section to the convection heat transfer section 78, where heat is further recovered, and fine particles contained in the cycle port 79 are recovered. The ash that is discharged from the system through the convection heat transfer section is drawn out of the pipe 81, and is discharged through the pipe 82 together with the ash drawn out of the pipe 80. In addition to being drawn out, a part is returned to the fluidized bed 73 through the air chamber 74 or the fuel supply port 75 and recombusted. Fig. 5 shows a circulating fluidized-bed boiler. Fluidizing air pumped from a not-shown propellant is supplied from an air chamber 104 through a dispersing plate 102 to a furnace 10. The fine-grained coal containing lime as a desulfurizing agent that is blown into the furnace and supplied to the furnace is fluidized and burned as necessary.

Unlike a non-circulating fluidized-bed boiler, the mixing speed of the fluidizing air blown through the dispersion plate 102 is higher than the terminal speed of the fluidized particles, so that the mixing of particles and gas becomes more active. The particles are blown up together with the gas, and a fluidized bed and a spouted bed are formed in this order from below over the entire area of the combustion furnace. The particles and gas undergo heat exchange in the water-cooled reactor wall 107 on the way, and then are led to the cyclone 108. After the combustion gas leaves the cyclone 108, heat is exchanged in the convection heat transfer section 109 installed in the rear flue.

The particles collected in the cyclone 108 are returned to the combustion chamber again through the flow channel 113, and some of the particles are recovered in the flow channel 111 to control the furnace temperature. After passing through the external heat exchanger 115, it is cooled and returned to the combustion chamber again, but part of it is discharged to the outside as ash. The feature is that the particles circulate in the combustion chamber in this way. The circulating particles are mainly limestone flooded as a desulfurizing agent and the combustion ash and unburnt ash of the supplied coal.

In these fluidized-bed boilers, a wide range of objects to be combusted can be selected due to the characteristics of the combustion method, but on the other hand, disadvantages have been pointed out. Disadvantages of the bubbling fluidized bed boiler include problems such as load characteristics, complexity of the fuel supply system, and wear of the heat transfer tubes in the bed.

In order to solve these problems, the circulation type has been attracting attention.However, in order to maintain the temperature of the circulation system including the combustion furnace cycle at an appropriate value, it is necessary to use a circulation type. In addition to the factors that need to be developed, there is also a problem with the recycling solid ring, and the compactness of small and medium-sized products is difficult. It is said that there is.

Disclosure of the invention

The present inventors have made various studies to solve the above-described problems. As a result, a swirling flow is provided inside the fluidized bed at different fluidization speeds, and the swirling flow is used to generate heat. In an internal circulating fluidized bed boiler * that forms a circulating flow of fluidized medium between the recovery chamber and a freeboard section on the fluidized bed or a heat recovery section such as an evaporator tube downstream of the freeboard section. The low-temperature exhaust gas after heat recovery is guided to the cycle π, and the collected particles in the cycle port are returned to the descending moving bed of the rinsing medium in the fluidized bed, thereby reducing the boiler core. It has been found that it is possible to improve the compactness and combustion efficiency and to reduce NO x. Also, even with high fuel ratio coal, due to the swirling flow, there is no restriction on the type of coal because it is completely burned, and silica sand can be used as a fluid medium, and limestone is also used. By using the combined use, it is possible to solve all the problems in the conventional coal boiler by combining the effects such as the reduction of S0X. I found it.

The features of the present invention include: First, the fluidized bed section is largely divided into a main combustion chamber and a heat recovery chamber, and the main combustion chamber has a large fluidization rate at the lower part-an air chamber and a small fluidization rate. At least two types of air chambers are provided.A combination of these different fluidization speeds provides a swirling circulation flow to the fluid medium in the main combustion chamber, and A heat recovery circulating flow of the fluid medium is formed between the heat recovery chamber and the air chamber that provides a small fluidization rate to the lower part of the heat recovery chamber and the side of the main combustion chamber opposite to the heat recovery chamber. In an internal circulating fluidized-bed boiler equipped with a fin, the exhaust gas is guided to a cyclone, and the collected particles are returned to the downward moving bed of the main combustion chamber or the heat recovery chamber.

It is possible to return not only the collected particles but also the collected particles such as bag filters to the downward moving bed. By returning the trapped particles to the descending moving bed, the unburned matter (chars) in the trapped particles is uniformly diffused into the fluidized bed, and the entire bed is brought into a reducing atmosphere. However, N 0 X is reduced from the fluidized bed to the free board portion.

The effect of returning the char to the descending moving bed is that when returning to the fluidized bed, the char is fine particles, so it is immediately scattered to the free port area. The residence time is almost nil, and the combustion of the character itself and the function as a low NOx catalyst cannot be sufficiently performed.However, when it is used in a descending moving bed, even fine particles remain in the bed. Because of sedimentation and diffusion, the charcoal can sufficiently reach the place where NOx is generated by burning coal and the like in the formation, which is extremely effective in reducing NΰX. The reaction to this NQx reduction is

_{C + 2N0 → C0 2 + N} 2 ( Ji Ya - oxidation reactions) 2CQ + 2ND → 2C0 is 2 Tsugakangae of ₂ + N ₂ (catalysis Ji Ya I).

Both reactions are provided by charcoal, and their oxidation reactivity and catalyst birth are thought to dominate low NOx function.

The second feature is that heat transfer tubes are arranged on the freeboard part or downstream of the freeboard part on the fluidized bed, and heat is recovered mainly by convection heat transfer. It is.

Conventionally, the convection heat transfer section has been installed separately from the free board section, but in order to achieve compaction, the free board section volume necessary for secondary combustion is secured. After that, it is installed at the upper part of the freeboard or at the downstream side of the freeboard part integrally with the freeboard part. This simplifies conventional boiler image dusting and charging cycles, and also reduces the temperature of the gas entering the cycle from 250 to 400. Therefore, the cyclone does not need to have a castable lining, and can be made of steel to reduce the amount of S and the size.

Third, by installing the convection heat transfer section in the upper part of the freeboard, or because the furnace wall is composed of water-cooled tubes, In order to prevent the temperature of the combustion gas in the freeboard from lowering due to the radiation results, heat-insulating materials such as refractory materials are placed on the heat transfer section and the combustion chamber side of the ice-cooled furnace wall. is there. As a result, the combustion gas temperature is maintained and C0 is reduced.

When installing the convection heat transfer section downstream of the freeboard section, it is sufficient to put fire-resistant insulation only on the water cooling wall that composes the freeboard section.

In other words, the present invention relates to a swirling circulation flow of the main combustion chamber, a heat recovery circulation of the fluid medium performed between the main combustion chamber and the heat recovery chamber, and an unburned channel formed in the main combustion chamber or the heat recovery chamber. External circulation (char-circulation) to return to the descending moving bed of the fluidized medium, and o of a combined circulating fluidized-bed boiler that combines these three circulations.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1, 2, and 3 are schematic views of different types of the combined circulating fluidized bed boilers of the present invention in which a heat transfer tube such as an evaporator tube is disposed above the freeboard. Fig. 4 is a schematic diagram of the conventional fluidized bed boiler, Fig. 5 is a schematic diagram of the circulating fluidized bed boiler, and Fig. 6 is the amount of flowing air below the inclined partition wall and the amount of circulating fluid medium in the heat recovery chamber. Fig. 7 shows the relationship between the diffused air volume of the heat recovery chamber and the settling velocity of the descending moving bed, Fig. 8 shows the general mass transfer mass velocity and the overall heat transfer coefficient, Fig. 9 shows the diffused air volume and the overall heat transfer coefficient of the heat recovery chamber of the internal circulation type. Fig. 10 shows the relationship between the fluidization mass velocity and the wear rate of the heat transfer tubes. Outline of the composite circulating fluidized bed boiler of the present invention in which a heat transfer tube group such as an evaporator tube provided integrally with the freeboard portion is arranged downstream of the leadboard portion. Figure, first Fig. 2 A of the first 1 view - cross-sectional view your only that the A line, first 3 figures off rie When a heat transfer tube group such as a free board unit and an evaporator tube is provided on the downstream side of the board unit, relatively large particles are collected in the heat transfer tube group. Of a combined circulating fluidized-bed boiler constructed so that the heat flows into the left and right heat recovery chambers at both ends of the main combustion chamber. Fig. 14 shows a conveyor that returns particles containing fine particles collected by the cyclone and returns the particles collected by the heat transfer tube group to the fluidized bed. It is a figure showing an example which returns to a machine. BEST MODE FOR CARRYING OUT THE INVENTION

Next, the present invention will be schematically described with reference to the drawings. In FIG. 1, a dispersing plate 2 for fluidizing air introduced from a fluidizing air inlet pipe 15 by a blower 16 is provided at the inner bottom of the boiler body 1. Both sides of the boiler are higher than the center, and the bottom of the boiler body is formed to be concave.

Then, the fluidizing air sent by the blower 16 passes through the air chambers 12, 13 and 14 and is discharged upward from the air distribution plate 2. Therefore, the mass velocity of the fluidizing air ejected from the central air chamber 13 is a velocity sufficient to form a fluidized bed of the fluid medium in the boiler body, that is, 4 to 20 Gmf, Preferably, it is within the range of 6 to 12 Gmf, but the mass velocity of the fluidizing air ejected from the air chambers 12 and 14 on both sides is smaller than the former and is generally smaller than the former. The mass velocity is 0 to 2 Gmf from the air chamber 12 below the heat recovery chamber 4 in which the heat transfer tubes 5 are arranged, and the area below the main combustion chamber 3. It is preferable that the gas is ejected from the air chamber 14 forming the part at a mass velocity of 0.5 to 2 Gmf.

As a result, the mass velocity of the fluidizing air ejected from the air chamber 13 inside the main combustion chamber 3 is compared with the mass velocity of the fluidizing air ejected from the air chambers 12 and 14. Due to the size, the air and the fluid medium flow rapidly upward in the fluidized bed as a jet at the upper part of the air chamber 13, and diffuse around when leaving the fluidized bed surface. Air chambers 1 2, 1 4 Drop onto the upper surface of the fluidized bed.

On the other hand, in the upper fluidized bed of the air chamber 13, the gentle fluidized bed on both sides, that is, the upper part of the air chambers 12, 14, should be used to confirm that the fluid medium has moved upward. The fluid medium at the bottom of the fluidized bed moves to the center, that is, to the upper part of the air chamber 13. As a result, a strong updraft is formed in the central part of the fluidized bed, but a gentle downward moving bed is formed in the peripheral part.

The heat recovery chamber 4 uses this descending moving bed, but as shown in Fig. 8, as shown by the relation between the overall heat transfer coefficient of the baffling equation and the fluidized mass velocity, Without vigorous fluidization (typically 3 to 5 Gmf) as shown in the equation, as shown in Fig. 9, the fluidization mass velocity was 1 to 2 Gmf. A large overall heat transfer coefficient is obtained, and sufficient heat recovery is achieved by providing a vertical partition wall 18 inside the fluidized bed above the boundary between the air chambers 12 and 13. At the top, ie, the partition wall A ripening tube 5 was placed in the back of Fig. 18 and inside the fluidized bed of P on the wall of the ice-cooled furnace to form a ripening chamber. The height of the partition wall 18 is sufficient to allow the flowing medium to enter the heat recovery chamber 4 from the upper part of the air chamber 13 during operation, and the partition wall 18 and the bottom surface An opening 19 is provided to allow the fluid medium in the maturation recovery chamber 4 to return to the main fuel 3 in a simple manner in the air dispersion. Therefore, after rising violently as a jet in the main combustion chamber, the flow medium dispersed on the flow surface passes through the partition wall 18 and enters the heat recovery chamber, and the air chamber 12 The air that is blown from the air gradually descends while performing a gentle flow, and heat exchange is performed through the heat transfer tube 5 during that time.

The amount of sedimentation and circulation of the fluid medium in the maturation recovery chamber depends on the amount of air diffused from the air chamber 12 into the heat recovery chamber, and the amount of air flow for air circulation from the air chamber 13 of the main combustion chamber. Is controlled. That is, as shown in FIG. 6, the amount Gt of the fluid medium entering the heat recovery chamber 4 increases as the amount of fluidizing air blown out from the air chamber 13 increases. Also, as shown in Fig. 7, when the amount of air diffused into the heat recovery chamber 4 is changed in the range of 0 to lGraf, the amount of the fluid medium that settles in the heat recovery chamber is almost proportional. And becomes almost constant when the diffused air volume of the heat recovery chamber is 1 Gmf or more.

Is constant, the amount of flowing medium entering the maturation recovery chamber 4 is G! The amount of the flowing medium that settles in the heat recovery chamber is an amount corresponding to Gi. By adjusting the amount of rain and air flow, the settling amount of the medium that sinks in the heat recovery chamber 4 is controlled. Is controlled.

On the other hand, heat is recovered from the settling fluid medium through the heat transfer pipe 5, and the heat transfer coefficient is from 0 to When it is changed up to 2 Graf, it changes almost linearly as shown in Fig. 9, so the amount of heat recovery and the flow in the main combustion chamber 3 are changed by changing the amount of diffused air. It is possible to arbitrarily control the bed temperature.

That is, when the amount of fluidized air from the air chamber 13 in the main combustion chamber 3 is constant, increasing the amount of diffused air in the heat recovery chamber 4 increases the amount of fluidized medium circulated. At the same time, the heat transfer coefficient increases, and as a synergistic effect, the amount of heat recovery increases significantly. If this increase in heat recovery balances with the increase in the amount of heat generated in the main combustion chamber, the fluidized bed temperature will be kept constant ^ and the heat transfer tube in the fluidized bed will be maintained. It is said that the wear rate is proportional to the cube of the fluidization rate. Fig. 10 shows the relationship between the fluidization mass velocity and the wear rate. That is, by setting the amount of diffused air blown into the heat recovery chamber to be 0 to 3 Gmf, preferably 0 to 2 Gmf, wear of the heat transfer tube is extremely reduced, and durability is improved. It is possible.

On the other hand, the coal, which is the fuel, is also supplied to the start of the descending moving bed in the main combustion chamber 3. As a result, it is possible to swirl and circulate inside the high-temperature fluidized bed to completely burn even high-fuel-ratio coal and to perform high-load combustion. And there are no restrictions on coal types This contributes to the spread of boilers.

The exhaust gas leaves the boiler and is directed to cycle 7. On the other hand, the particles collected by the cyclone 7 are introduced into the hopper 10 together with the coal supplied in parallel through the lower double damper 8 in the boiler shown in FIG. The screw feeder 11 mixes and supplies the mixture to the descending moving bed of the main combustion chamber, twists the unburned matter (chars) in the trapped particles, and reduces NOx. Etc. Of course, the particles collected by Cyclone 7 are transported separately up to just before the main combustion chamber without mixing with the stones beforehand, and then put into the descending moving bed of the main combustion chamber. Are also mixed in the bed by the swirling circulation.

In the upper part of the freeboard, a confined heat transfer surface 6 is provided to recover the heat and function as an economizer and an evaporator tube. In order to maintain the combustion temperature at a constant temperature, preferably 900, as necessary, cut off fireproof material etc. at the lower part of the sealing heat transfer surface 6 and the twisting chamber side of the water cooling furnace wall. Install heating material 17. In the case of a convection heat transfer surface, install each heat transfer tube near the freeboard by wrapping it with heat insulating material, but do not obstruct the flow path of the scrubbing gas. It goes without saying that the pitch of the heat transfer tube should be considered.

In this way, the provision of the heat insulating material 17 makes it possible to maintain the temperature of the lower portion of the freeboard at a high temperature. The air blown from the air inlet boiler 20 for the next combustion has the effect of reducing CO, etc.

FIG. 2 shows another embodiment of the present invention. Basically, it has the same structure as the boiler shown in FIG. 1 and performs the same operation. The major difference is that the lower part of the partition wall 38 that separates the main combustion chamber 23 and the heat recovery chamber 24 prevents the upward flow of the air chamber 33 with a high fluidization velocity in the main combustion chamber. However, it is inclined so as to turn the flow toward the air chamber 34 where the fluidization speed is small, and the inclination angle is sealed horizontally and 10 degrees or less. 60 degrees, preferably 25 to 45 degrees. In addition, the projected length in the Eihei direction projected on the bottom of the inclined wall of the partition wall is the horizontal length L © 1/6 or 1/2, or preferably 1/4. It is formed to be half the length.

The bottom fluidized bed of the boiler body 21 is divided into a heat recovery chamber 24 and a main combustion chamber 23 by the partition wall 38, and a fluidizing air distribution plate 2 2 is provided at the bottom of the main combustion chamber 23. Is provided.

The fluidized air dispersion plate 22 has a lower portion at the center and a higher portion on the side opposite to the heat recovery chamber. In addition, two types of air chambers 33 and 34 are provided below the distribution plate 22.

The mass velocity of the fluidizing air ejected from the central air chamber 33 is a velocity necessary for the fluidized medium in the main combustion chamber to form a fluidized bed, that is, 4 to 20 Gmf, preferably. Is in the range of 6 to 12 Gmf, but the mass velocity of the fluidizing air ejected from the air chamber 34 is smaller than the former, and is in the range of 0 to 3 Gmf. The fluid medium above the chamber 34 does not move up and down sharply, but forms a moving bed that is moving downward and is in a weak fluid state. This moving bed expands below, and the air chamber 33 Since it has reached the upper side, it is blown up by the jet of fluidizing air with a large mass velocity from the air chamber 33. Then, a part of the fluidized medium below the moving bed is removed, and the moving bed descends by its own weight. On the other hand, the fluid medium blown up by the fluidizing air jet from the air chamber 33 is reflected and turned on the inclined partition wall 38, and mostly falls to the upper part of the transfer layer. It will replenish the fluid medium of the moving bed that has descended. As a result of this being carried out intermittently, the upper part of the air chamber 34 becomes a slowly descending moving bed, and the fluid medium in the main combustion chamber 23 as a whole forms a swirling flow. And On the other hand, a part of the fluid medium that is blown up by the fluidizing air from the air chamber 33 and turned by the inclined partition wall 38 passes over the inclined partition wall 38. Into the heat recovery chamber 24. The fluid medium that has entered the heat recovery chamber 24 forms a gentle downward moving bed by the air blown from the air diffuser 32.

When the descent speed is low, the flowing medium entering the heat recovery chamber forms an angle of repose at the top of the heat recovery chamber, and the surplus falls from the upper part of the inclined partition wall 38 into the main combustion chamber. Return.

In the heat recovery chamber, the flowing medium exchanges heat via the heat transfer tube 25 while slowly descending, and then returns to the main combustion chamber from the opening 39.

The amount of settling circulation of the fluid medium in the heat recovery chamber and the amount of heat recovered are controlled by the amount of diffused air blown into the heat recovery chamber, as in the embodiment shown in FIG. Boiler shown in Fig. 2 In the case of (1), it is controlled by the amount of air blown from the air diffuser 32, but its mass velocity is in the range of 0 to 3 Gmf, preferably in the range of 0 to 2 Gmf.

The coal, which is the fuel, is swirled and circulated in the fluidized bed of the main combustion chamber by being supplied to the upper part of the air chamber 34, which is the descending moving bed in the main combustion chamber 23, and very circulated. Good flammability.

On the other hand, the exhaust gas is led to Cyclone 27 after leaving the boiler. Particles collected in cyclone 27 are double damped

Through hops along with coal supplied in parallel

30 and is mixed and supplied by the screw feeder 31 to the descending moving layer of the main combustion chamber 23, that is, the upper part of the air chamber 34, and the trapped particles It contributes to the combustion of unburned components (chars) and the reduction of NOx. *

The particles collected by the cyclone 27 are not shown, but unlike the flooding equipment shown in Fig. 2, they may be supplied separately from the coal, or they may be supplied separately. Instead of a clean feeder, pneumatic transportation is also possible.

A convection heat transfer surface 26 is provided at the top of the freeboard to recover heat, but the combustion temperature on the freeboard is preferably set at a certain temperature or 90 ° C. In order to keep the temperature at 0 t, heat insulation materials 37 such as refractory materials are installed below the convection heat transfer surface 26 and the combustion chamber side of the ice-cooled furnace wall as necessary, and also for secondary combustion. Providing an air inlet 40 is effective in reducing C 0

FIG. 3 shows yet another embodiment. Basically, the maturation recovery chamber of the embodiment shown in Fig. 2 is integrated in a symmetrical position facing each other. As a result, the air chamber 53 with a low mass velocity of the blown air is located at the center, and the air chambers with a high mass velocity are 52 and 54. The flow of the fluid medium caused by the air blown out of the air chambers 53 and 54 is reversed by the inclined partition walls 58 and 58 ', and falls to the center, and forms a downward moving layer and is located above the air chamber 53. And then split right and left and blow up again. Therefore, there are two nominal swirling flows in the fluidized bed of the main combustion chamber.

Coal and particles collected in the cycle port are supplied to the central descent bed.

In Fig. 3, the supply position is indicated by an asterisk (*) in the main combustion chamber, and the supply direction is perpendicular to the paper. Fig. 3 shows an example in which the particles collected at the cycle inlet and the coal are mixed and supplied by the screw feeder 51, but they are not shown but may be supplied separately. Alternatively, pneumatic transportation is also possible.

When the flow of the moving medium caused by the air blown out of the air chambers 52, 54 is counter-tilted at the inclined partition walls 58, 58 ', the part passes over the partition walls. Enter the maturity collection room 4 4, 4 4 ¾ 'J' o

The 'settling and circulating amount' of the fluid medium in the heat recovery chamber is controlled by the amount of diffused air introduced from the diffusers 6Q, 60 'as in the device shown in FIG.

The heat transfer tubes 45, 45 'and after the ripening exchange, the medium is in the opening 59, Recirculates into the main combustion chamber through 5 9 '.

'On the other hand, a convection heat transfer surface 46 is provided at the top of the freeboard to recover heat, but the combustion temperature at the freeport is maintained at a constant temperature, preferably 90 Gt. If necessary, heat insulating material 57 such as refractory material is attached to the lower part of the heat transfer surface 46 and the combustion chamber side of the water-cooled reactor wall, and air is injected for secondary combustion as necessary. Providing the mouth 61 is effective in reducing C0 and the like.

Next, based on FIG. 11 to FIG. 14, heat recovery from the exhaust gas is performed by a heat transfer tube group provided integrally with the free board portion on the downstream side of the free board portion. A description will be given of another embodiment of the present invention.

FIG. 11 shows an embodiment of the present invention in which heat is recovered from exhaust gas by a heat transfer tube group provided integrally with the free board portion on the downstream side of the free board portion. FIG. 1 shows a longitudinal sectional view of a combined circulating fluidized bed boiler, and FIG. 12 shows a sectional view taken along line AA of FIG. In Fig. 11 and Fig. 12, reference numeral 201 denotes the main body of the coil, 2Q2 denotes a nozzle for dispersing air for fluidization, 203 denotes a main combustion chamber, 204 and 204. Is a heat recovery chamber, 205 and 205 'are heat transfer tubes, 2007 is a cyclone, 208 is a rotor valve, 2009 is a fuel supply tube, and 210 is a fuel supply tube. Hopper, 211 is screw feeder for feeding twisting material, 212, 213, and 214 are air chambers, 218, 218 'are partition walls , 219 and 219 'are openings at the bottom of the heat recovery chamber, 220 is a secondary air inlet pipe, 229 is an exhaust gas outlet, 230 is a steam drum, and 231 is water. Drum, 2 3 2 is a convection heat transfer chamber, 2 3 3, 2 3 4 and 2 3 5 are the partition walls in the convection heat transfer chamber, 2 3 6 is the evaporating pipe, 2 3 7 is the water pipe wall, 2 3 8 is the bottom of the convection heat transfer chamber, and 2 3 9 is the screw A compressor, 240 is the exhaust pipe of the high-temperature heat transfer chamber, and 242, 242 ', 243, 243' are of a different type from the air diffuser shown in Figs. 1 shows an air diffuser.

The operations of the main combustion chamber, heat recovery chamber, etc. in Figs. 11 and 12 are completely the same as those explained based on Fig. 3, but Figs. 11 and 12 In the boiler shown in Fig. 1, a heat transfer tube group for recovering heat from exhaust gas is not provided on the free board part, but is integrated with the free board part downstream of the free board part. It differs from the boiler shown in Fig. 3 in that it is provided in the convection heat transfer section provided in Fig. 3.

In other words, the exhaust gas discharged from the exhaust gas outlet 222 of the free board part is a group of evaporating pipes provided between the steam drum 330 and the water drum 230. The ice and heat in the evaporative tube group are introduced into the convection heat transfer chamber 2 3 2 having the After being exchanged and cooled at 25 Q to 400, it is guided to cyclone 207 via exhaust pipe 240, and fine particles including char in the cyclone. After being collected, it is released into the atmosphere. The fine particles, including the chars collected in the cyclone, pass through the mouth-tally valve 208, then the inlet 209, the phono. The fuel is returned from the same inlet as the fuel such as coal supplied to the boiler via the 210 and the skew feeder 211 just above the descending moving layer of the main combustion chamber 203. It is. On the other hand, the particles including the fluid medium having a relatively large particle size, the desulfurizing agent, and the channel separated in the convective heat transfer section 232 are collected at the V-shaped bottom below the convective heat transfer section. The screw conveyor 239 returns the main combustion chamber 203 to a position just above the descending moving layer opposite to the fuel supply side.

When the heat transfer section is installed downstream of the freeport section as shown in Figs. 11 and 12, the freeboard section is connected to the heat transfer section. By blowing secondary air in the direction opposite to the flow direction of the exhaust gas flowing in, a swirling flow is generated at the free board as shown in Fig. 11, and oxygen and exhaust gas are separated from each other. Highly efficient stirring and mixing, resulting in greater CO reduction o

Another embodiment will be described with reference to FIG.

Fig. 13 is a cross-sectional view corresponding to Fig. 12, and reference numerals 238 'and 239' also indicate the V-shaped bottom of the convection heat transfer section and the scutar Yukonya. In this embodiment, two V-shaped bottoms 238 and 238 '(W-shaped bottom) are provided below the convection heat transfer chamber. And a screw conveyor that collects relatively large channels collected at the V-shaped bottoms 238 and 238 '. 9 'at the point where it returns to the position just above the descending moving layers 204, 204' of the fluid medium in the heat recovery chambers provided on both sides of the combustion chamber, as shown in Figs. 11 and 12. It is different from La.

FIG. 14 shows still another embodiment of the present invention. In FIG. 14, reference numeral 241 indicates a conduit and other reference numerals. The symbols have the same meaning as the symbols in FIG. In the example shown in Fig. 14, the convective heat transfer part 23.2 To the screw feeder 2 39 at the lower part of the main combustion chamber, along with particles containing relatively large channels trapped in the convection heat transfer section. It differs from the embodiment shown in FIG. 11 only in that it is returned to the upper part.

Claims

The scope of the claims

1. The fluidized bed section of the fluidized bed boiler is divided into a main combustion chamber and a heat recovery chamber, and the lower part of the main combustion chamber is a small air chamber that gives a large fluidization speed to the fluidized medium. The main combustion chamber is provided with at least two types of air chambers that provide the fluidization speed, and the combination of the air with different fluidization speeds that are ejected from these air chambers. In the internal circulating fluidized bed boiler, in which a swirling circulation flow is provided to the fluidized medium and a circulation flow of the fluidized medium is formed between the main combustion chamber and the heat recovery chamber, the heat of the exhaust gas is recovered. After cooling the exhaust gas at the outlet of the ra, it is guided to the cyclone and the particles collected by the cyclone are returned to the main combustion chamber or the heat recovery chamber. The return port is located directly above or in the descending moving bed with a low fluidization rate inside the fluidized bed. A combined circulating fluidized bed boiler characterized in that:

2. A partition wall separating the main combustion chamber and the heat recovery chamber prevents upward flow of the fluidizing air ejected from the main combustion chamber above the air ejection portion having a high mass velocity. 2. The combined circulation according to claim 1, wherein the fluidizing air is inclined so as to be directed upward toward the air ejection portion having a low mass velocity. Fluid bed boiler.

3. The combined circulating fluidized bed boiler according to claim 1 or 2, characterized in that the desulfurizing agent is supplied to a downward moving bed of the main combustion chamber.

4. The method according to claim 1, wherein the exhaust gas is cooled to 250 to 400 ° C. and then guided to a cyclone. Combined fluidized bed boiler.

5. The combined circulating fluidized bed boiler according to claim 1, 2, 3 or 4, wherein heat recovery of the exhaust gas is performed by a heat transfer tube group provided on a freeboard section of the fluidized roof.

6. The combined circulation flow according to claim 1, 2, 3, or 4, wherein heat recovery of the exhaust gas is performed by a heat transfer tube group provided integrally with the free board portion downstream of the free board portion.勖 Floor boiler.

7. Flow medium, desulfurizing agent, and charcoal with relatively large particle size collected by the heat transfer tube group that is integrated with the free board downstream of the free board. One particle is mainly transported by a conveyor such as a screw conveyor! 7. The combined circulating fluidized bed boiler according to claim 6, wherein the boiler is returned to a position immediately above or in a descending moving bed of a fluidized bed of a firing chamber.

8. Relatively large fluid medium, desulfurizing agent and char particles collected by the heat transfer tube group provided integrally with the free board downstream of the free board. 7. The combined circulating fluidized bed boiler according to claim 6, wherein the fluid is returned to a position immediately above or in the descending moving bed of the fluid medium in the heat recovery chamber by a transfer device such as a screw conveyor. La.

9. The combined circulating fluidized bed according to claim 8, wherein the fluid medium, the desulfurizing agent, and the particles having a relatively large particle size are returned to the rain heat recovery chamber provided on both the left and right portions of the main combustion chamber. boiler .

10. Particles containing fine particles collected by the cyclone are collected by the heat transfer tube group provided integrally with the above-mentioned free board.

'' Conveyor that returns collected particles to fluidized bed or heat recovery section 10. The combined circulating fluidized-bed boiler according to claim 7, 8 or 9, wherein the boiler is returned to a transfer device such as the above.

1. By blowing secondary air in the opposite direction to the flow direction of the exhaust gas flowing from the freeboard to the upstream heat transfer section, a swirl flow of the exhaust gas is generated at the freeboard. The combined circulating fluidized bed boiler according to any one of claims 1 to 10, wherein the boiler is configured to be closed.

2. The fluidized bed portion of the fluidized bed boiler is divided into a main combustion chamber and a heat recovery chamber, and an air chamber and a small fluidizer are provided at the lower part of the main combustion chamber to give a large fluidizing speed to the fluidized medium. At least two types of air chambers are provided to provide the liquefaction speed, and the main combustion and the chamber are controlled by the combination of air with different fluidization speeds blown out of these air chambers. An internal circulating fluidized-bed boiler that provides a swirling circulating flow to the fluidized medium and forms a circulating flow of the fluidized medium between the main combustion chamber and the heat recovery chamber. The convection heat transfer section is provided integrally with the flyboard section on the downstream side of the airflow section, and the steam drum is located above the flyboard section and the convection heat transfer section. A water drum is provided at the lower part of the heat transfer part, and the main part of the steam drum is located above the free board part. The pipes that make up the water pipe wall of the room are drawn out, and the convection heat transfer section has an evaporative pipe that cools the exhaust gas and also recovers heat. Between the main combustion chamber and the heat recovery chamber, where the fluidization speed of the fluidized medium in the descending moving bed is low. Directly above or Combined circulating flow wheel configured to return into descending moving bed o

1 3. Collect particles trapped at the bottom of the V-shape provided at the bottom of the water drum and main-burn the particles by the screw conveyor provided at the bottom of the V-shape The combined circulation flow bed boiler according to claim 12, wherein the combined circulation flow bed boiler is configured so as to return to a position immediately above the moving bed or in the descending moving bed of the fluid medium in the chamber or the heat recovery chamber.

14. Collect the particles collected at the bottom of the W-shape provided at the bottom of the ice drum, and transfer the particles to two screw conveyors provided at the bottom of the W-shaped drawer. The combined circulating fluidized bed boiler according to claim 12, wherein the boiler is returned to a position immediately above or in a downwardly moving bed of the fluidized medium in the heat recovery chamber provided on both sides of the combustion chamber.