CA1332685C - Composite circulating fluidized bed boiler - Google Patents
Composite circulating fluidized bed boilerInfo
- Publication number
- CA1332685C CA1332685C CA000610057A CA610057A CA1332685C CA 1332685 C CA1332685 C CA 1332685C CA 000610057 A CA000610057 A CA 000610057A CA 610057 A CA610057 A CA 610057A CA 1332685 C CA1332685 C CA 1332685C
- Authority
- CA
- Canada
- Prior art keywords
- fluidized bed
- chamber
- fluidizing
- combustion chamber
- main combustion
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
- F23C—METHODS OR APPARATUS FOR COMBUSTION USING FLUID FUEL OR SOLID FUEL SUSPENDED IN A CARRIER GAS OR AIR
- F23C10/00—Fluidised bed combustion apparatus
- F23C10/02—Fluidised bed combustion apparatus with means specially adapted for achieving or promoting a circulating movement of particles within the bed or for a recirculation of particles entrained from the bed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F22—STEAM GENERATION
- F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
- F22B31/00—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus
- F22B31/0007—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed
- F22B31/0084—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed
- F22B31/0092—Modifications of boiler construction, or of tube systems, dependent on installation of combustion apparatus; Arrangements of dispositions of combustion apparatus with combustion in a fluidized bed with recirculation of separated solids or with cooling of the bed particles outside the combustion bed with a fluidized heat exchange bed and a fluidized combustion bed separated by a partition, the bed particles circulating around or through that partition
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention discloses an interior circulation fluidized bed boiler in which a fluidized bed portion of a fluidized bed boiler is divided by a partition into a main combustion chamber and a heat recovering chamber, the main combustion chamber being provided at the lower portion thereof with at least two air chambers, i.e., an air chamber for imparting a high fluidizing speed to a fluidiz-ing medium and an air chamber for imparting a low fluidizing speed thereto, a whirling and circulating flow is formed in the fluidizing medium in the main combustion chamber by a combination of air having different fluidizing speeds jetted out of these air chambers, a circulating flow of the fluidizing medium is formed between the main chamber and the heat recovering chamber, and the fluidizing medium is moved downward in the form of a moving layer in the heat recovering chamber, characterized in that heat recover-ing of exhaust gas is effected in a free board portion or downstream of the free board portion, a temperature of the exhaust gas is lowered and thereafter the thus cooled exhaust gas is guided to a cyclone, and fine parti-culate chars collected by the cyclone are returned to a portion directly above a descending moving layer of the fluidizing medium in the main combustion chamber and or the heat recovering chamber or into the descending moving layer. By returning the chars to the portion directly above the descending moving layer of the fluidizing medium or into the descending moving layer, the chars are not immediately scattered, and the chars even in the form of fine particles are sufficiently precipitated and scattered on the fluidized bed whereby NOx generated as the result of combustion of coals or the like in the bed can be reduced.
The present invention discloses an interior circulation fluidized bed boiler in which a fluidized bed portion of a fluidized bed boiler is divided by a partition into a main combustion chamber and a heat recovering chamber, the main combustion chamber being provided at the lower portion thereof with at least two air chambers, i.e., an air chamber for imparting a high fluidizing speed to a fluidiz-ing medium and an air chamber for imparting a low fluidizing speed thereto, a whirling and circulating flow is formed in the fluidizing medium in the main combustion chamber by a combination of air having different fluidizing speeds jetted out of these air chambers, a circulating flow of the fluidizing medium is formed between the main chamber and the heat recovering chamber, and the fluidizing medium is moved downward in the form of a moving layer in the heat recovering chamber, characterized in that heat recover-ing of exhaust gas is effected in a free board portion or downstream of the free board portion, a temperature of the exhaust gas is lowered and thereafter the thus cooled exhaust gas is guided to a cyclone, and fine parti-culate chars collected by the cyclone are returned to a portion directly above a descending moving layer of the fluidizing medium in the main combustion chamber and or the heat recovering chamber or into the descending moving layer. By returning the chars to the portion directly above the descending moving layer of the fluidizing medium or into the descending moving layer, the chars are not immediately scattered, and the chars even in the form of fine particles are sufficiently precipitated and scattered on the fluidized bed whereby NOx generated as the result of combustion of coals or the like in the bed can be reduced.
Description
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SPECI~ICATION
COMPOSITE CIRCULATING FLUIDIZED BED soILER
TECHNICAL FIELD
The present invention relates to an internally circulating fluidized bed boiler in which combustion materials such as various coals, low grade coals, dressing sludges, oil cokes and the like are burnt by a so-called whirl-flow fluidized bed and which recovers heat from the circulation fluidized bed, the interior of a free board and a lateral heat transfer portion provided downstream of the free board.
In the description that follows reference is made to Figures 4 and 5. For the sake of convenience all of the figures will be introduced briefly as follows:
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 are schematic views of different types of composite circulation fluidized bed boilers, respectively, according to the present invention, in which a heat transfer tube such as a vaporization tube is disposed at an upper part within a free board;
FIG. 4 is a schematic view of a conventional fluidized bed boiler;
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FIG. 5 is a schematic view of a circulation fluidized bed boiler;
FIG. 6 is a view showing the relationship between an amount of fluidizing air at the lower portion of an inclined partitioning wall and an amount of fluidizing medium in a heat recovery chamber;
FIG. 7 is a view showing the relationship between a gas flow into heat recovering chamber and precipitating rate of descending moving layer;
FIG. 8 is a view showing the general fluidized mass rate and the overall coefficient of heat transfer;
FIG. 9 is a view showing the gas flow into internal circulation heat recovering chamber and the overall coefficient of heat transfer;
FIG. 10 is a view showing the relationship between the fluidized mass rate and the abration rate of a heat transfer tube;
FIG. 11 is a schematic view of a composite circulation fluidized bed boiler according to the present invention in which a group of heat transfer tubes such as vaporization tubes provided integral with the free board portion are arranged downstream of the free board portion;
FIG. 12 is a sectional view taken on line A-A of FIG. 11;
FIG. 13 is a sectional view in a cutaway line corresponding to lines A-A of FIG. 11 of a composite circulation fluidized bed boiler designed so that a group of heat transfer tubes such a vaporization tubes provided ~- .
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~3~2~85 integral with a free board portion are disposed downstream of the free board portion and relatively large particles collected by said group of heat transfer tubes are returned to left and right heat recovering chambers disposed on opposite ends of the main combustion chamber;
and FIG. 14 is a view showing an embodiment in which particles containing fine char collected by cyclones are returned to a carrier such as a conveyor for returning particles collected by said group of heat transfer tubes to the fluidized bed portion.
BACKGROUND
Recently, coals as the energy in place of petroleum have been highlighted. In order to widely utilize coals inferior in physical and chemical properties as fuel to those of petroleum, developments of processing and circulation of coals and of technology for promoting use of coals have been demanded in a rapid manner.
Researchers and development of a pulverized coal firing boiler and a fluidized bed boiler as a combustion technology have been positively accomplished. In these combustion technologies, kinds of coals are restricted in view of the combustion efficiency, low NOx and low SOx, and ;3 . , .
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complexity of the coal feeding system and difficulty in control of load fluctuation have been evident, as particularly evidenced in small and medium boilers.
The fluidized bed boiler has two types as mentioned below according to the differenca in a system which considers the arrangement of a heat transfer portion and combustion of unburnt particles flied from the fluidized bed.
(1) ~on-circulation fluidized bed boiler (which is also called a conve~tional type fluidized bed boiler or a bubbling typa fluidized bed boiler) (2) Circulation fluidizing boiler In the non-circulation system, a heat transfer tube is arranged in the fluidized bed, and heat exchanging is carried out by physical contact between fuel being burned and a fluidizing medium with high heat transfer efficiency. On the other hand, in the circulation system, fine unburnt materials or ashes or a part of the fluidizing medium (circulating solid) are riddent on a flow of combustion gas and guided to a heat exchanging portion arranged independently from a combustion chamber where combustion of the unburnt particles is continued and the circulating solid having been heat exchanged is returned to the combustion chamber, the aforesaid title being named since the solid is circulated.
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The non-circulation fluidized bed boiler and the circulation fluidized bed boiler will be described with reference to FIGS. 4 and 5.
FIG. 4 shows the non-circulation fluidized bed boiler, in which air for fluidization fed under pressure from a blower not shown is jetted from an air chamber 74 into a boiler 71 through a diffusion plate 72 to form a fluidized bed 739 and fuel, for example, granular coals are supplied to the fluidized bed 73 for combustion.
Heat transfer tubes 76 and 77 are provided in the fluidized bed 73 and an exhaust gas outlet of a free board portion to recover heat.
The exhaust gas of a relatively low temperature is guided from the exhaust gas outlet of the free board portion to a convection heat transfer portion 78 to recover heat and therafter to recover particles contained in a cyclone 79, and thence discharged outside the system.
The ash recovered in the convection heat transfer portion is drawn out of a tube 81 and drawn outside the system together with ash drawn from a tube 80 via a tube 82, a part thereof being returned to the fluidized bed 73 through the air chamber 74 or a fuel inlet 75 for re-burning.
FIG. 5 shows the circulation fluidized bed boiler, in which air for fluidization fed under pressure from a blower not shown is blown from an air chamber 104 into ;-, ~_, ., ; ::
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a furnace 101 through a diffusion plate 102 to fluidize and burn small granular coals containing lime as a desulfurizing agent to be supplied into the furnace as - needed.
Unlike the non-circulation fluidized bed boiler, the air for fluidization blown through the diffusion plate 102 has the jetting speed higher than the end speed of the fluidizing particles, and therefore, the particles and gases are more actively mixed and the particles are blown upward together with the gases so that a fluidizing layer and a jetting layer are formed in that order from the bottom over the whole zone of the combustlon furnace.
The particles and gases are somewhat heat exchanged at a water cooling furnace wall 107 provided halfway and then guided to a cyclone 108. The combustion gas moved out of the cyclone 108 is heat exchanged at a convection heat transfer portion 109 arranged in a flue at the rear portion.
On the other hand, the partlcles collected in the cyclone 108 are again returned to the combustion chamber via a flowpassage 113, and a part of the particles is guided to an external heat exchanger 115 via a flowpassage 114 for control of the temperature in the furnace and cooled after which it is again returned to the combustion chamber, a part of which is discharged as ash outside the system. A feature lies in that the particles are .5 :, - ~;~Y~
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circulated into the combustion chamber in a manner as just mentioned. The circulating particles are mainly limestone supplied as a desulfurizing agent, burnt ash of supplied coal, unburnt ash, etc.
In these fluidized bed boilers, materials to be burnt can be widely selected in terms of characteristics of the combustion system thereof, but demerits thereof have been pointed out.
As the demerits of the bubbling type fluidized bed boiler, there are problems such as the load charact-eristics, complexity of the fuel supply system, abrasion resistance of the heat transfer tube in the bed, and the like.
Attention has been paid to the circulation type to settle these problems. However, elements to be developed in terms of technology remain unsolved to maintain the temperatures of the circulation system including a cyclone in a combustion furnace at a proper value. In addition, there remains a problem in handling of a circulating solid.
For small and medium types, there involves a difficulty in compactness.
DISCLOSURE OF THE INVENTION
After various studies in an attempt of solving the above-described problems, the present inventors have found that in an interior circulation fluidized bed boiler A
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in which a whirl flow is provided within a fluidized bed by different fluidizing speeds, and the whirl flow is utilized to form a circulating flow of a fluidizing medium relative to a heat recovering chamber, a heat recovering portion such as a vaporizing tube is provided in a free board portion on the fluidized bed or downstream of the free board portion to guide a low temperature exhaust gas after recovery of heat to a cyclone and particles collected by the cyclone are returned to a descending moving layer of the fluidizing medium of the fluidized bed portion thereby to make the boiler compact, enhance the combustion efficiency and reduce NOx. The inventors further found that even coals of high fuel ratio may be completely burned by the whirl flow and therefore the kind of coals is not limited, silica sand as the fluidizing medium can be used, and the limestone is used in combination therewith to reduce SOx, as a consequence of which all the problems encountered in the conventional coal boilers can be solved.
According to a first feature of the present invention, there is provided an interior circulation fluidizing boiler in which a fluidized bed is largely partitioned into a main combustion chamber and a heat recovering chamber, the main combustion chamber being provided with at least two kinds of air chambers, i.e., an air chamber for imparting a high fluidizing speed to the lower portion thereof and an air chamber for imparting a low fluidizing speed thereto, these different fluidizing ~: . .: .
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speeds being combined to thereby impart a whirl circulating flow to a fluidizing medium within the main combustion chamber by a combination of air having different fluidizing - speeds jetted out of the air chambers, and a heat recovering circulating flow of the fluidizing medium is formed between the main combustion chamber and the heat recovering chamber, that is, an air chamber is provided to impart a low fluidizing speed to the side opposite the lower portion of the heat recovering chamber and the heat recovering chamber of the main combustion chamber, whereby the exhaust gas is cooled and guided into a cyclone and the collected particles thereof are returned through a return opening to a descending moving layer of the main combustion chamber or the heat recovering chamber. The return opening is situated directly above a descending moving layer having a low fluidizing speed in the fluidized bed or in the descending moving layer.
The collected particles are not always from the cyclone but collected particles from a bag filter or the like can be also returned to the descending moving layer.
The collected particles are returned to the initiating portion of the descending moving layer whereby unburnt portions (char) within the collected particles are evenly scattered into the fluidized bed to make the whole portion in the bed a reduced atmosphere to thereby reduce NOx from the fluidized bed to the free board portion.
In returning the char to the descending moving layer, in case of returning the char to the fluidized . . .;
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~ ~ , - ~332~8~ -bed, since the char is microparticles, they become immedi-ately scattered in the bed so that there is rarely a staying time in the bed, failing to satisfactorily perform the combustion of the char itself and the function as a catalyst for low NOx. However, in case of returning it to the descending moving layer, even microparticles become preci-pitated and diffused into the layer, and therefore, the char is moved throughout to area of NOx generated as the result of combustion of coals or the like within the layer, thus advantageously reducing the NOx.
Reactions in connection with the reduction in NOx considered are two reactions below: -C + 2N0 ~ C02 + N2 (oxidization reaction of char) 2C0 + 2N0 ~ 2C02 + N2 (catalyst reaction of char) The char is participated in any of reactions.
It i8 considered that the low NOx function is governed by the oxidization ractivity and catalyst effect.
According to a second feature of the present invention, a heat transfer tube is aranged in a free board portion on a fluidized bed or downstream of the free board portion, and heat recovery is effected mainly by convection heat transfer.
In the past, the convection heat transfer portion is provided independently of the free board portion.
However, to provide compactness, a volume for the free . .,~.
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board portion necessary for the secondary combustion is secured and the convection heat transfer portion is provided at the upper portion within the free board or downstream of the free board portion. Thereby, the dust treatment and the char recycling around the boiler in the prior art can be facilitated. In addition, the temperature of gas entering the cyclone is 250 to 400C, and therefore, the cyclone need not be provided with castable lining, and the cyclone can be made of steel and light in weight and miniaturized.
According to a third feature, a convection heat transfer portion is provided at the upper part within the free board or a furnace wall is formed from a water cooling tube, from which arrangement, heat insulating material such as refractory material is lined on the convection heat transfer portion and the water cooling furnace wall on the side of the combustion chamber in order to prevent the temperature of the combustion gas within the free board from being lowered due to the radiation effect. Thereby, the temperature of the com-bustion gas is maintained to exhibit the effect of reducing C0 or the like.
In the case where the convection heat transfer portion is provided downstream of the free board portion, the refractory heat insulating material may be lined only ~ . , .... .
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on the water cooling wall constituting the free board portion.
That is, the present invention provides a composite circulation fluidized bed boiler comprising a combination of three circulations, i.e., a whirl flow circulation in the main combustion chamber, a heat recovering cir-culation of a fluidizing medium effected between the main combustion chamber and the heat recovering chamber, and an external circulation (char circulation) for returning unburnt char to the descending moving layer of a fluidizing medium within the main combustion chamber or the heat recovering chamber.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be schematically described hereinafter with reference to the drawings.
In FIG. 1, a boiler body 1 is internally provided on the bottom thereof with a diffusion plate 2 for an fluidizing air which is introduced from a fluidizing air introducing tube 15 by means of a blower 16, the diffusion plate 2 having opposite edges set to be higher than a central portion thereof, the bottom of the boiler body being formed into a recessed surface.
The fluidizing air fed by the blower 16 is jetted upwardly from the air diffusion plate 2 via air chambers 12, 13 and 14. The mass rate of the fluidizing air jetted out of the central air chamber 13 is the rate enough to form a fluidized bed of a fluidizing medium within the boilder body, that is, in the range of 4 to 20 Gmf, pre-ferably, in the range of 6 to 12 Gmf. The mass rate of the fluidizing air jetted out of the air chambers 12 and 14 on the opposite edges is smaller than the former, generally, in the range of 0 to 3 Gmf. It is preferable that the air is jetted out in the mass rate of 0 to 2 Gmf from the air chamber 12 located at the lower portion of the heat recovery chamber 4 provided with a heat transfer .-- . . : . , :
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tube 5, and the air is ~etted out in the mass rate of 0.5 to 2 Gmf from the air chamber which forms the lower portion of the main combustion chamber 3.
As the result, since the mass rate of the fluidizing air jetted out of the air chamber 13 interiorly of the main combustion chamber 3 is relatively higher than that - of the fluidizing air jetted out of the air chambers 12 and 14, the air and the fludizing medium in the upper portion of the air chamber 13 are rapidly moved as a jet flow upwardly within the fluidized bed, and when they are moved out of the surface of the fluidized bed, they are diffused and the fludizing medium falls onto the surface of the fluidizing layer at the upper portions of the air chambers 12 and 14.
On the other hand, in the upper fluidized bed of the air chamber 13, the fluidizing medium at the bottom `~ of the gentle fluidized beds on the opposite sides, that if, the upper fluidized beds of the air chambers 12 and 14 is moved to the central portion, that is, the upper portion of the air chamber 13. As the result, a violent up stream is formed in the central portion in the fluidized bed but a gentle descending moving layer is formed in the peripheral portion.
The heat recovery chamber 4 makes use of the afore-said descending moving layer. FIG. 8 shows the relation-,~ , . ...... . .
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ship between the overall coefficient of heat transferand the fluidized mass rate in the bubbling system. The large overall coefficient of heat transfer is obtained at the fluidiæed mass rate of 1 to 2 Gmf as show~ in FIG.
7 without effecting the severe fluidization (generally, 3 to 5 Gmf) as in the bubbling system to effect sufficient heat recovering.
A vertical partitioning wall 18 is provided inter-nally of the fluidiz ed bed at the upper portion of a boundary between the air chambers 12 and 13, and the heat transfer tube 5 is arranged at the upper portion of the air chamber 12, that is, internally of the fluidized bed between the back of the partitioning wall 18 and the water cooling furnace wall to form a heat recovering chamber.
The height of the partitioning wall 18 is designed so as to have a height at which the fluidizing medium may be moved from the top of the air chamber 13 into the heat recovering chamber 4 during operation, and an opening 19 is provided between the partitioning wall 18 and the air diffusion plate on the bottom so that the fluidizing medium within the heat recovering chamber 4 may be returned into the main combustion chamber 3. Accordingly, the fluidizing medium which has diffused on the surface of the fluidized bed after having been violently moved up as a jet flow within the main combustion chamber moves .. ~ .. .. . .
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13326~5 over the partitioning wall 18 into the heat recovering chamber, and is gradually moved down while being fluidized gently by the air blown from the air chamber 12, during which heat exchanging is carried out through the heat transfer tube 5.
The precipitating circulation amount of the fluidiz-ing medium in the heat recovering chamber is controlled by the gas flow from the air chamber 12 to the heat recover-ing chamber 4 and the fluidizing air flow from the air chamber 13 in the main combustion chamber. That is, the amount Gl of the fluidizing medium entering the heat recovering chamber 4 increases as the amount of the fluidi-zing air blown out of the air chamber 13 increases, as shown in FIG. 6. As shown in FIG. 7, when the gas flow into the heat recovering chamber 4 is varied in the range of O to 1 Gmf, the amount of the fluidizing medium precipitated into the heat recovery chamber varies substan-tially proportional thereto, and is substantially constant if the gas flow into the heat recovering chamber exceeds l Gmf.
The aforesaid constant amount of the fluidizing medium is substantially equal to the fluidizing medium amount Gl moved into the heat recovering chamber 4, and the fluidizing medium amount Gl precipitated into the heat recovering chamber is the amount corresponding to ~ . . .
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"' ` , .-1~3~685 the Gl. These two amounts are adjusted whereby theprecipitating amount of the fluidizing medium precipitated into the heat recovering chamber 4 is controlled.
On the other hand, the heat is recovered by the precipitating fluidizing medium through the heat ~ransfer tube 5. The coefficient of heat transfer substantially linearly changes as shown in FIG. 9 when the gas flow into the heat recovering chamber 4 from the air chamber 12 is changed from O to 2 Gmf, and therefore, the gas flow can be varied to thereby suitably control the heat recovering amount and the temperature of the fluidiz bed within the main combustion chamber 3.
That is, when the gas flow within the heat recovering chamber 4 is increased when the amount of the fluidizing air from the air chamber 13 in the main combustion chamber 3 is constant, the fluidizing medium circulating amount increases and at the same time the coefficient of heat transfer increases, and the heat recovering amount is considerably increased as a result of synergistic effect.
If an increment of the aforesaid heat recovering amount is balanced with an increment of the generated heat in the main combustion chamber, the temperature of the fluidiz-ed bed is maintained at constant.
It is said that the abrasion rate of the heat transfer tube in the fluidized bed is proportional to .;. . ~
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cube of the fluidization rate. FIG. 10 shows the relation-ship between the fluidization mass rate and the abrasion rate. That is, the gas flow blown into the heat recovering chamber is set to O to 3 Gmf, preferably, O to 2 Gmf, the abrasion of the heat transfer tube is extremely small, and the durability can be enhanced.
On the other hand, coals as fuel are supplied to the initiation portion of the descending moving layer within the main combustion chamber 3. Thereby, the coals are whirled and circulated within the high temperature fluidized bed, and even coals of high fuel ratio can be completely burned. Since the high load combustion can be made, the boiler can be miniaturized, and in addition, there is no restriction due to the kind of coal, contribut-ing to wide use of boilers.
The exhaust gas is moved out of the boiler and guided to the cyclone 7. On the other hand, particles collected by the cyclone passes through a lower double damper 8 in the boiler shown in FIG. 1 and is introduced into a hopper 10 together with coals supplied at the same time. The coals are then mixed and supplied to the descend-ing moving layer of the main combustion chamber by a screw feeder 11, distributing to combustion of unburnt (char) in the collected particles and reduction in NOx. It is of course that the particles collected by the cyclone ~ ..~.. .
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may not be mixed in advance but the particles may be separately carried before the main combustion chamber and moved into the descending moving layer of the main combustion chamber, in which case they are mixed in the layer by the whirling circulation.
On the other hand, in the upper portion of the free board, the convection heat transfer surface 6 is provided to effect heat recovering to function as an economizer and a vaporizing tube. However, a heat insulat-ing material 17 such as a refractory material is mountedon the lower portion of the convection heat transfer surface 6 and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintain the combustion temperature in the free board at a constant temperature, preferably, 900C. In case of the convection heat transfer surface, each heat transfer tube near the free board portion is mounted so as to be wound with a heat insulating material. Needless to say, a pitch of the heat transfer tube is taken into consideration so as not to impede a flowpassage of the exhaust gas.
By the provision of the heat insulating material 17 as described above, it becomes possible to maintain the temperature of the lower portion of the free board portion at a high temperature, and the effect of reducing CO is exhibited by air blown from an air blowing opening -`` 133268~
20 as the secondary combustion in the free board portion.
FIG. 2 shows a further embodiment of the present invention.
Basically, this emboidment has the structure similar to that of the boiler shown in FIG. 1 and performs the operation similar thereto. This embodiment is greatly different from the previous embodiment in that the lower portion of a partitioning wall 38 between the main com-bustion chamber 23 and the heat recovering chamber 24 is inclined so as to interrupt an upward flow of the air chamber 33 having a high fluidizing rate in the main com-bustion chamber and to turn the flow toward the air chamber 34 having a low fluidizing rate, the angle of inclination being 10 to 60 degrees to the horizon, preferably 25 to 45 degrees. The horizontal projection length Q with respect to the furnace bottom of the inclined portion of the partitioning wall is 1/6 to 1/2 of the horizontal length L of said furnace bottom, preferably 1/4 to 1/2.
The fluidized bed at the bottom of the boiler 20 body 21 is divided by the partitioning wall 38 into the ;
heat recovering chamber 24 and the main combustion chamber 23, and an air diffusion plate 22 for fluidization is provided on the bottom of the main combustion chamber 23.
The diffusion plate 22 is designed to be low in the central portion thereof and high on the side opposite . , . .
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the heat recovering chamber. Two air chambers 33 and 34 are provided below the diffusion plate 22.
The mass rate of the fluidizing air jetted out of the central air chamber 33 is the rate required for the fluidizing medium within the main combustion chamber to form the fluidized bed, that is, in the range of 4 to 20 Gmf, preferably, in the range of 6 to 12 Gmf, whereas the mass rate of the fluidizing air jetted out of the air chamber 34 is smaller than the former, in the range of O to 3 Gmf, at the time of which the fluidizing medium above the air chamber 34 is not accompanied by severe vertical movement but forms a descending moving layer in a weak fluidizing state. This moving layer is spread downwardly to reach the upper portion of the air chamber 33 and therefore receives the jetting of the fluidizing air having a large mass rate from the air chamber 33 and is blown up. Then, a part of the fluidizing medium at the lower portion of the moving layer is removed, and therefore, the moving layer is moved down by it own weight.
On the other hand, the fluidizing medium blown up by the jetting of the fluidizing air from the air chamber 33 impinges upon the inclined partitioning wall 38 and is reflected and turned, a majority of which fall on the upper portion of the moving layer to supplement the fluidiz-ing medium of the downwardly moved moving layer. As the ~. . . . .. ~ ... ......
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result of continuous operation as described above, the upper portion of the air chamber 34 is formed into a slow descending moving layer, and as a whole, the fluidizing medium within the main combustion chamber 23 is to form a whirling flow. On the other hand, a part of the fluidiz-ing medium blown up by the fluidizing air from the air chamber 33 and reflected and turned by the inclined partitioning wall 38 moves over the inclined partitioning wall 38 and enters the heat recovering chamber 24. The fluidizing medium moved into the heat recovering chamber 24 forms a gentle descending moving layer by the air blown by the gas flow device 32.
In the case where the descending rate is slow, the fluidizing medium moved into the heat recovering chamber forms an angle of repose at the upper portion of the heat recovering chamber, and a surplus portion thereof falls ~j;
from the upper portion of the inclined partitioning wall 38 to the main combustion chamber.
Within the heat recovering chamber, the fluidizing medium is subjected to heat exchanging through the heat transfer tube 25 while slowly moving down, after which the medium is cirulated from the opening 39 into the main combustion chamber.
The precipitating and circulation amount and the heat recovering amount of the fluidizing medium within ~ 133~685 the heat recovering chamber are controlled by the gas flow blown into the heat recovering chamber similarly to the embodiment shown in FIG. 1. In the case of the boiler shown in FIG. 2, the precipitating circulation amount or the like are controlled by the air amount blown from the gas flow device 32, and the mass rate thereof is in the range of O to 3 Gmf, preferably O to 2 Gmf.
Coals as fuel are supplied to the upper portion of the air chamber 34 which is the descending moving layer within the main combustion chamber 23 whereby the coals are whirled and circulated in the fluidized bed of the main combustion chamber and has an excellent combustibility.
On the other hand, the exhaust gas is guided to the cyclone 27 after having been moved out of the boiler.
The particles collected by the cyclone 27 pass through ~ ~;
the double damper 28 and are introduced into the hopper 30 together with coals supplied at the same time. They are mixed and supplied to the descending moving layer of the main combustion chamber 23, that is, the upper portion of the air chamber 34, contributing to the com-bustion of the unburnt (char) in the collected particles and the reduction in NOx.
Although not particularly shown, the particles collected by the cyclone 27 may be supplied separately of coals, unlike the supply device shown in FIG. 2, and , .. . . . .... .
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1332~8~
the particles may be airborne instead of the screw feeder.
On the other hand, in the upper portion of the free board, the convection heat transfer surface 26 is provided to effect heat recovering. A heat insulating material 37 such as a refractory material is mounted in the lower portion of the convection heat transfer surface 26 and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintain the combustion temperature of the free board at constant temperature, preferably 900C, and an air inlet 40 is provided for the secondary combustion to effectively reduce CO or the like.
FIG. 3 shows a still another embodiment of the present invention. Basicall~, the heat recovering chambers shown in ~IG. 2 are symmetrically opposed and integrated.
As a result, an air chamber 53 having a small mass rate of blown air is positioned centrally, and air chambers having a large mass rate. The flow of the fluidizing medium caused by air blown out of the air chambers 52 and 54 are inverted by inclined partitioning walls 58 and 58' and falls on the central portion. The flow is formed into a descending moving layer and reaches the upper portion of the air chamber 53, where it is divided into left and right portions, which are again blown up.
Accordingly, two symmetrical whirling flows are present r-~., .~:
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within the fluidized bed of the main combustion chamber.
The coals and the particlescollected by the cyclone are supplied to the central descending moving layer.
In FIG. 3, the supply device is indicated at *
within the main combustion chamber, and the supply direction is vertical to the paper surface. While in FIG. 3, an example has been shown in which the particles collected by the cyclone and coals are mixed and supplied by the screw feeder 51, it is to be noted that they may be supplied separately, though not shown, and the airborne supply may be employed.
On the other hand, when the flow of the fluidizing medium caused by air blown out of the air chambers 52 and 53 is inverted at the inclined partitioning walls 58 and 58', a part thereof moves over the partitining walls and moves into the heat recovering chambers 44 and 44'.
The precipitating circulation amount of the fluidiz-ing medium within the heat recovering chambers is controlled by the gas flow introduced from gas flow devices 60 and 60' similarly to the device shown in FIG. 2.
The fluidizing medium after being heat exchanged by the heat transfer tubes 45 and 45' passes through the openings 59 and 59' and circulates within the main combustion chamber.
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A convection heat transfer surface 46 is provided at the upper portion of the free board to effect heat exchanging. A heat insulating material 57 such as a refractory material is mounted on the convection heat transfer surface 4~ and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintin the combustion temperature in the free board at a constant temperature, preferably, 900C, and an air -inlet 61 is provided for the secondary combustion to effectively reduce C0 or the like.
Another embodiment will be described hereinafter with reference to FIGS. 11 to 14, in which the heat recover-ing from the exhaust gas is carried out by a group of heat transfer tubes provided integral with the free board downstream of the free board portion.
FIG. 1 is a longitudinal sectional view of a composite circulation fluidized bed boiler showing one embodiment of the present invention in which the heat recovering from the exhaust gas is carried out by a group of heat transfer tubes provided integral with the free board portion downstream of the free board portion. FIG.
12 is a sectional view taken on lines A-A of FIG. 11.
In FIGS. 11 and 12, reference numeral 201 designates a boiler body, 202 an air diffusion nozzle for fluidization, 203 a main combustion chamber, 204 and 204' heat recovering _.
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1332~8~
chambers, 205 and 205' heat transfer chambers, 207 a cyclone, 208 a rotary valve, 209 a fuel supply tube, 201 a hopper, 211 a screw feeder for supplying fuel, 212, 213 and 214 air chambers, 218 and 218' partitioning walls, 219 and 219' openings at the lower por~ion of the heat recovering chamber, 220 a secondary air introducing tube, 229 an outlet for exhaust gas, 230 a steam drum, 231 a water drum, 232 a convection heat transfer chamber, 233, 234, and 235 partitioning walls in the convection heat transfer chamber, 236 vaporization chamber, 237 a water pipe wall, 238 a bottom of the convection heat ~ransfer chamber, 239 a screw conveyor, 240 an exhaust pipe for the convection heat transfer chamber, and 247, 247', 243 and 243' gas flow chambers of the type different from those shown in FIGS. 1 and 2.
The functions of the main combustion chamber, the heat exchanging chambers and the like shown in FIGS. 11 and 12 are exactly the same as those explained in connection with FIG. 3, but the boiler shown in FIGS. 11 and 12 is different from that shown in FIG. 3 in that the group of heat transfer tubes for recovering heat from exhaust gas are not provided in the free board portion but the convection heat transfer portion integral with the free board portion is provided downstream of the free board portion.
`~'; ' ' '' ' " ' ~ ' ' '. ~ '. ' ' ' "' ' .. ,, , 133268~3 That is, the exhaust gas discharged out of the exhaust gas outlet 229 in the free board portion is introduced into the convection heat transfer chamber 232 having a group of vaporization tubes provided between the steam drum 330 and the water drum 231, heat-exchanged with water in the group of vaporization tubes during flowing toward the downstream of the convection chamber in a direction as indicated by the arrow by the action of the partitioning walls arranged within the convection heat transfer chamber, cooled to 250 to 400C and thereafter introduced into the. cyclone 207 via the exhaust pipe 240 to collect fine particles containing char in the cyclone and discharged into atmosphere. The fine particles contain-ing the char collected by the cyclone are returned via the rotary valve 208 to a portion directly above the descending moving layer of the main combustion chamber 203 from the same charging opening as that of fuel such as coals supplied to the boiler via teh charging opening 209, the hopper 210 and the screw feeder 211.
On the other hand, the fluidizing medium having a relatively large grain size separated in the convection heat transfer portion 232, the desulfurizer and the particles containing char are gathered a V-shaped bottom at the lower portion of the convection heat transfer portion and then returned by the screw conveyor 239 to the portion . .
,: , . ~. . ~ ' ' ' -- 1332~
directly above the descending moving layer on the side opposite the fuel supply side of the main combustion chamber.
In the case where the convection heat transfer portion is provided downstream of the free board portion as shown in FIGS. 11 and 12, the secondary air is blown in the direction reversed to the flowing direction of the exhaust gas flowing into the convection heat transfer portion from the free board portion to thereby give rise to a whirling flow at the free board portion so that oxygen and exhaust gas are efficiently stirred and mixed to ~:
greatly effective reduce C0.
Another embodiment will be described with reference to FIG. 13.
FIG. 13 is a sectional view corresponding to FIG. 12, and reference numerals in FIG. 13 has the same meaning as those shown in FIG. 12 except that 238' adn 239' denote the V-shaped bottom of the convection heat transfer portion and the screw conveyor, respectively.
This embodiment is different from the boilers shown in FIGS. 11 and 12 only in that two V-shaped bottoms 238 and 28' (W-shaped bottoms) are provided at the lower portion of the convection heat transfer chamber, and that the particles containing a relatively large char collected at the V-shaped bottoms 238 and 238' are returned by the r~
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screw conveyors 239 and 239' to the portion directly above the descending moving layers 204 and 204' for the fluidizing medium in the heat recovering chambers provided on opposite sides of the combustion chamber.
FIG. 14 sho~ a still another embodiment of the present invention.
Reference numerals used in FIG. 14 have the same meaning as those used in FIG. 11 except that the reference numeral 241 designates a conduit. The emodiment shown in FIG. 14 is merely different from that of FIG. 11 in that the fine particles containing char collected by the cyclone 207 are guided onto the screw feeder 239 at the lower portion of the convection heat transfer portion 232 by the conduit 241 and then returned together with the particles containing a relatively large char collected by the convection heat transfer portion to the portion directly above the descending moving layer of the main combustion chamber.
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SPECI~ICATION
COMPOSITE CIRCULATING FLUIDIZED BED soILER
TECHNICAL FIELD
The present invention relates to an internally circulating fluidized bed boiler in which combustion materials such as various coals, low grade coals, dressing sludges, oil cokes and the like are burnt by a so-called whirl-flow fluidized bed and which recovers heat from the circulation fluidized bed, the interior of a free board and a lateral heat transfer portion provided downstream of the free board.
In the description that follows reference is made to Figures 4 and 5. For the sake of convenience all of the figures will be introduced briefly as follows:
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 are schematic views of different types of composite circulation fluidized bed boilers, respectively, according to the present invention, in which a heat transfer tube such as a vaporization tube is disposed at an upper part within a free board;
FIG. 4 is a schematic view of a conventional fluidized bed boiler;
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FIG. 5 is a schematic view of a circulation fluidized bed boiler;
FIG. 6 is a view showing the relationship between an amount of fluidizing air at the lower portion of an inclined partitioning wall and an amount of fluidizing medium in a heat recovery chamber;
FIG. 7 is a view showing the relationship between a gas flow into heat recovering chamber and precipitating rate of descending moving layer;
FIG. 8 is a view showing the general fluidized mass rate and the overall coefficient of heat transfer;
FIG. 9 is a view showing the gas flow into internal circulation heat recovering chamber and the overall coefficient of heat transfer;
FIG. 10 is a view showing the relationship between the fluidized mass rate and the abration rate of a heat transfer tube;
FIG. 11 is a schematic view of a composite circulation fluidized bed boiler according to the present invention in which a group of heat transfer tubes such as vaporization tubes provided integral with the free board portion are arranged downstream of the free board portion;
FIG. 12 is a sectional view taken on line A-A of FIG. 11;
FIG. 13 is a sectional view in a cutaway line corresponding to lines A-A of FIG. 11 of a composite circulation fluidized bed boiler designed so that a group of heat transfer tubes such a vaporization tubes provided ~- .
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t ' . ' . ' ,, ~ - :
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~3~2~85 integral with a free board portion are disposed downstream of the free board portion and relatively large particles collected by said group of heat transfer tubes are returned to left and right heat recovering chambers disposed on opposite ends of the main combustion chamber;
and FIG. 14 is a view showing an embodiment in which particles containing fine char collected by cyclones are returned to a carrier such as a conveyor for returning particles collected by said group of heat transfer tubes to the fluidized bed portion.
BACKGROUND
Recently, coals as the energy in place of petroleum have been highlighted. In order to widely utilize coals inferior in physical and chemical properties as fuel to those of petroleum, developments of processing and circulation of coals and of technology for promoting use of coals have been demanded in a rapid manner.
Researchers and development of a pulverized coal firing boiler and a fluidized bed boiler as a combustion technology have been positively accomplished. In these combustion technologies, kinds of coals are restricted in view of the combustion efficiency, low NOx and low SOx, and ;3 . , .
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.
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1332~8~
complexity of the coal feeding system and difficulty in control of load fluctuation have been evident, as particularly evidenced in small and medium boilers.
The fluidized bed boiler has two types as mentioned below according to the differenca in a system which considers the arrangement of a heat transfer portion and combustion of unburnt particles flied from the fluidized bed.
(1) ~on-circulation fluidized bed boiler (which is also called a conve~tional type fluidized bed boiler or a bubbling typa fluidized bed boiler) (2) Circulation fluidizing boiler In the non-circulation system, a heat transfer tube is arranged in the fluidized bed, and heat exchanging is carried out by physical contact between fuel being burned and a fluidizing medium with high heat transfer efficiency. On the other hand, in the circulation system, fine unburnt materials or ashes or a part of the fluidizing medium (circulating solid) are riddent on a flow of combustion gas and guided to a heat exchanging portion arranged independently from a combustion chamber where combustion of the unburnt particles is continued and the circulating solid having been heat exchanged is returned to the combustion chamber, the aforesaid title being named since the solid is circulated.
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The non-circulation fluidized bed boiler and the circulation fluidized bed boiler will be described with reference to FIGS. 4 and 5.
FIG. 4 shows the non-circulation fluidized bed boiler, in which air for fluidization fed under pressure from a blower not shown is jetted from an air chamber 74 into a boiler 71 through a diffusion plate 72 to form a fluidized bed 739 and fuel, for example, granular coals are supplied to the fluidized bed 73 for combustion.
Heat transfer tubes 76 and 77 are provided in the fluidized bed 73 and an exhaust gas outlet of a free board portion to recover heat.
The exhaust gas of a relatively low temperature is guided from the exhaust gas outlet of the free board portion to a convection heat transfer portion 78 to recover heat and therafter to recover particles contained in a cyclone 79, and thence discharged outside the system.
The ash recovered in the convection heat transfer portion is drawn out of a tube 81 and drawn outside the system together with ash drawn from a tube 80 via a tube 82, a part thereof being returned to the fluidized bed 73 through the air chamber 74 or a fuel inlet 75 for re-burning.
FIG. 5 shows the circulation fluidized bed boiler, in which air for fluidization fed under pressure from a blower not shown is blown from an air chamber 104 into ;-, ~_, ., ; ::
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a furnace 101 through a diffusion plate 102 to fluidize and burn small granular coals containing lime as a desulfurizing agent to be supplied into the furnace as - needed.
Unlike the non-circulation fluidized bed boiler, the air for fluidization blown through the diffusion plate 102 has the jetting speed higher than the end speed of the fluidizing particles, and therefore, the particles and gases are more actively mixed and the particles are blown upward together with the gases so that a fluidizing layer and a jetting layer are formed in that order from the bottom over the whole zone of the combustlon furnace.
The particles and gases are somewhat heat exchanged at a water cooling furnace wall 107 provided halfway and then guided to a cyclone 108. The combustion gas moved out of the cyclone 108 is heat exchanged at a convection heat transfer portion 109 arranged in a flue at the rear portion.
On the other hand, the partlcles collected in the cyclone 108 are again returned to the combustion chamber via a flowpassage 113, and a part of the particles is guided to an external heat exchanger 115 via a flowpassage 114 for control of the temperature in the furnace and cooled after which it is again returned to the combustion chamber, a part of which is discharged as ash outside the system. A feature lies in that the particles are .5 :, - ~;~Y~
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circulated into the combustion chamber in a manner as just mentioned. The circulating particles are mainly limestone supplied as a desulfurizing agent, burnt ash of supplied coal, unburnt ash, etc.
In these fluidized bed boilers, materials to be burnt can be widely selected in terms of characteristics of the combustion system thereof, but demerits thereof have been pointed out.
As the demerits of the bubbling type fluidized bed boiler, there are problems such as the load charact-eristics, complexity of the fuel supply system, abrasion resistance of the heat transfer tube in the bed, and the like.
Attention has been paid to the circulation type to settle these problems. However, elements to be developed in terms of technology remain unsolved to maintain the temperatures of the circulation system including a cyclone in a combustion furnace at a proper value. In addition, there remains a problem in handling of a circulating solid.
For small and medium types, there involves a difficulty in compactness.
DISCLOSURE OF THE INVENTION
After various studies in an attempt of solving the above-described problems, the present inventors have found that in an interior circulation fluidized bed boiler A
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in which a whirl flow is provided within a fluidized bed by different fluidizing speeds, and the whirl flow is utilized to form a circulating flow of a fluidizing medium relative to a heat recovering chamber, a heat recovering portion such as a vaporizing tube is provided in a free board portion on the fluidized bed or downstream of the free board portion to guide a low temperature exhaust gas after recovery of heat to a cyclone and particles collected by the cyclone are returned to a descending moving layer of the fluidizing medium of the fluidized bed portion thereby to make the boiler compact, enhance the combustion efficiency and reduce NOx. The inventors further found that even coals of high fuel ratio may be completely burned by the whirl flow and therefore the kind of coals is not limited, silica sand as the fluidizing medium can be used, and the limestone is used in combination therewith to reduce SOx, as a consequence of which all the problems encountered in the conventional coal boilers can be solved.
According to a first feature of the present invention, there is provided an interior circulation fluidizing boiler in which a fluidized bed is largely partitioned into a main combustion chamber and a heat recovering chamber, the main combustion chamber being provided with at least two kinds of air chambers, i.e., an air chamber for imparting a high fluidizing speed to the lower portion thereof and an air chamber for imparting a low fluidizing speed thereto, these different fluidizing ~: . .: .
, . .
:. .. . : .
133268~
speeds being combined to thereby impart a whirl circulating flow to a fluidizing medium within the main combustion chamber by a combination of air having different fluidizing - speeds jetted out of the air chambers, and a heat recovering circulating flow of the fluidizing medium is formed between the main combustion chamber and the heat recovering chamber, that is, an air chamber is provided to impart a low fluidizing speed to the side opposite the lower portion of the heat recovering chamber and the heat recovering chamber of the main combustion chamber, whereby the exhaust gas is cooled and guided into a cyclone and the collected particles thereof are returned through a return opening to a descending moving layer of the main combustion chamber or the heat recovering chamber. The return opening is situated directly above a descending moving layer having a low fluidizing speed in the fluidized bed or in the descending moving layer.
The collected particles are not always from the cyclone but collected particles from a bag filter or the like can be also returned to the descending moving layer.
The collected particles are returned to the initiating portion of the descending moving layer whereby unburnt portions (char) within the collected particles are evenly scattered into the fluidized bed to make the whole portion in the bed a reduced atmosphere to thereby reduce NOx from the fluidized bed to the free board portion.
In returning the char to the descending moving layer, in case of returning the char to the fluidized . . .;
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~ ~ , - ~332~8~ -bed, since the char is microparticles, they become immedi-ately scattered in the bed so that there is rarely a staying time in the bed, failing to satisfactorily perform the combustion of the char itself and the function as a catalyst for low NOx. However, in case of returning it to the descending moving layer, even microparticles become preci-pitated and diffused into the layer, and therefore, the char is moved throughout to area of NOx generated as the result of combustion of coals or the like within the layer, thus advantageously reducing the NOx.
Reactions in connection with the reduction in NOx considered are two reactions below: -C + 2N0 ~ C02 + N2 (oxidization reaction of char) 2C0 + 2N0 ~ 2C02 + N2 (catalyst reaction of char) The char is participated in any of reactions.
It i8 considered that the low NOx function is governed by the oxidization ractivity and catalyst effect.
According to a second feature of the present invention, a heat transfer tube is aranged in a free board portion on a fluidized bed or downstream of the free board portion, and heat recovery is effected mainly by convection heat transfer.
In the past, the convection heat transfer portion is provided independently of the free board portion.
However, to provide compactness, a volume for the free . .,~.
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board portion necessary for the secondary combustion is secured and the convection heat transfer portion is provided at the upper portion within the free board or downstream of the free board portion. Thereby, the dust treatment and the char recycling around the boiler in the prior art can be facilitated. In addition, the temperature of gas entering the cyclone is 250 to 400C, and therefore, the cyclone need not be provided with castable lining, and the cyclone can be made of steel and light in weight and miniaturized.
According to a third feature, a convection heat transfer portion is provided at the upper part within the free board or a furnace wall is formed from a water cooling tube, from which arrangement, heat insulating material such as refractory material is lined on the convection heat transfer portion and the water cooling furnace wall on the side of the combustion chamber in order to prevent the temperature of the combustion gas within the free board from being lowered due to the radiation effect. Thereby, the temperature of the com-bustion gas is maintained to exhibit the effect of reducing C0 or the like.
In the case where the convection heat transfer portion is provided downstream of the free board portion, the refractory heat insulating material may be lined only ~ . , .... .
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` 1332~8~
on the water cooling wall constituting the free board portion.
That is, the present invention provides a composite circulation fluidized bed boiler comprising a combination of three circulations, i.e., a whirl flow circulation in the main combustion chamber, a heat recovering cir-culation of a fluidizing medium effected between the main combustion chamber and the heat recovering chamber, and an external circulation (char circulation) for returning unburnt char to the descending moving layer of a fluidizing medium within the main combustion chamber or the heat recovering chamber.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be schematically described hereinafter with reference to the drawings.
In FIG. 1, a boiler body 1 is internally provided on the bottom thereof with a diffusion plate 2 for an fluidizing air which is introduced from a fluidizing air introducing tube 15 by means of a blower 16, the diffusion plate 2 having opposite edges set to be higher than a central portion thereof, the bottom of the boiler body being formed into a recessed surface.
The fluidizing air fed by the blower 16 is jetted upwardly from the air diffusion plate 2 via air chambers 12, 13 and 14. The mass rate of the fluidizing air jetted out of the central air chamber 13 is the rate enough to form a fluidized bed of a fluidizing medium within the boilder body, that is, in the range of 4 to 20 Gmf, pre-ferably, in the range of 6 to 12 Gmf. The mass rate of the fluidizing air jetted out of the air chambers 12 and 14 on the opposite edges is smaller than the former, generally, in the range of 0 to 3 Gmf. It is preferable that the air is jetted out in the mass rate of 0 to 2 Gmf from the air chamber 12 located at the lower portion of the heat recovery chamber 4 provided with a heat transfer .-- . . : . , :
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1332~8~
tube 5, and the air is ~etted out in the mass rate of 0.5 to 2 Gmf from the air chamber which forms the lower portion of the main combustion chamber 3.
As the result, since the mass rate of the fluidizing air jetted out of the air chamber 13 interiorly of the main combustion chamber 3 is relatively higher than that - of the fluidizing air jetted out of the air chambers 12 and 14, the air and the fludizing medium in the upper portion of the air chamber 13 are rapidly moved as a jet flow upwardly within the fluidized bed, and when they are moved out of the surface of the fluidized bed, they are diffused and the fludizing medium falls onto the surface of the fluidizing layer at the upper portions of the air chambers 12 and 14.
On the other hand, in the upper fluidized bed of the air chamber 13, the fluidizing medium at the bottom `~ of the gentle fluidized beds on the opposite sides, that if, the upper fluidized beds of the air chambers 12 and 14 is moved to the central portion, that is, the upper portion of the air chamber 13. As the result, a violent up stream is formed in the central portion in the fluidized bed but a gentle descending moving layer is formed in the peripheral portion.
The heat recovery chamber 4 makes use of the afore-said descending moving layer. FIG. 8 shows the relation-,~ , . ...... . .
...... . .
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1332g~
ship between the overall coefficient of heat transferand the fluidized mass rate in the bubbling system. The large overall coefficient of heat transfer is obtained at the fluidiæed mass rate of 1 to 2 Gmf as show~ in FIG.
7 without effecting the severe fluidization (generally, 3 to 5 Gmf) as in the bubbling system to effect sufficient heat recovering.
A vertical partitioning wall 18 is provided inter-nally of the fluidiz ed bed at the upper portion of a boundary between the air chambers 12 and 13, and the heat transfer tube 5 is arranged at the upper portion of the air chamber 12, that is, internally of the fluidized bed between the back of the partitioning wall 18 and the water cooling furnace wall to form a heat recovering chamber.
The height of the partitioning wall 18 is designed so as to have a height at which the fluidizing medium may be moved from the top of the air chamber 13 into the heat recovering chamber 4 during operation, and an opening 19 is provided between the partitioning wall 18 and the air diffusion plate on the bottom so that the fluidizing medium within the heat recovering chamber 4 may be returned into the main combustion chamber 3. Accordingly, the fluidizing medium which has diffused on the surface of the fluidized bed after having been violently moved up as a jet flow within the main combustion chamber moves .. ~ .. .. . .
:, - - :, . :
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13326~5 over the partitioning wall 18 into the heat recovering chamber, and is gradually moved down while being fluidized gently by the air blown from the air chamber 12, during which heat exchanging is carried out through the heat transfer tube 5.
The precipitating circulation amount of the fluidiz-ing medium in the heat recovering chamber is controlled by the gas flow from the air chamber 12 to the heat recover-ing chamber 4 and the fluidizing air flow from the air chamber 13 in the main combustion chamber. That is, the amount Gl of the fluidizing medium entering the heat recovering chamber 4 increases as the amount of the fluidi-zing air blown out of the air chamber 13 increases, as shown in FIG. 6. As shown in FIG. 7, when the gas flow into the heat recovering chamber 4 is varied in the range of O to 1 Gmf, the amount of the fluidizing medium precipitated into the heat recovery chamber varies substan-tially proportional thereto, and is substantially constant if the gas flow into the heat recovering chamber exceeds l Gmf.
The aforesaid constant amount of the fluidizing medium is substantially equal to the fluidizing medium amount Gl moved into the heat recovering chamber 4, and the fluidizing medium amount Gl precipitated into the heat recovering chamber is the amount corresponding to ~ . . .
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"' ` , .-1~3~685 the Gl. These two amounts are adjusted whereby theprecipitating amount of the fluidizing medium precipitated into the heat recovering chamber 4 is controlled.
On the other hand, the heat is recovered by the precipitating fluidizing medium through the heat ~ransfer tube 5. The coefficient of heat transfer substantially linearly changes as shown in FIG. 9 when the gas flow into the heat recovering chamber 4 from the air chamber 12 is changed from O to 2 Gmf, and therefore, the gas flow can be varied to thereby suitably control the heat recovering amount and the temperature of the fluidiz bed within the main combustion chamber 3.
That is, when the gas flow within the heat recovering chamber 4 is increased when the amount of the fluidizing air from the air chamber 13 in the main combustion chamber 3 is constant, the fluidizing medium circulating amount increases and at the same time the coefficient of heat transfer increases, and the heat recovering amount is considerably increased as a result of synergistic effect.
If an increment of the aforesaid heat recovering amount is balanced with an increment of the generated heat in the main combustion chamber, the temperature of the fluidiz-ed bed is maintained at constant.
It is said that the abrasion rate of the heat transfer tube in the fluidized bed is proportional to .;. . ~
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cube of the fluidization rate. FIG. 10 shows the relation-ship between the fluidization mass rate and the abrasion rate. That is, the gas flow blown into the heat recovering chamber is set to O to 3 Gmf, preferably, O to 2 Gmf, the abrasion of the heat transfer tube is extremely small, and the durability can be enhanced.
On the other hand, coals as fuel are supplied to the initiation portion of the descending moving layer within the main combustion chamber 3. Thereby, the coals are whirled and circulated within the high temperature fluidized bed, and even coals of high fuel ratio can be completely burned. Since the high load combustion can be made, the boiler can be miniaturized, and in addition, there is no restriction due to the kind of coal, contribut-ing to wide use of boilers.
The exhaust gas is moved out of the boiler and guided to the cyclone 7. On the other hand, particles collected by the cyclone passes through a lower double damper 8 in the boiler shown in FIG. 1 and is introduced into a hopper 10 together with coals supplied at the same time. The coals are then mixed and supplied to the descend-ing moving layer of the main combustion chamber by a screw feeder 11, distributing to combustion of unburnt (char) in the collected particles and reduction in NOx. It is of course that the particles collected by the cyclone ~ ..~.. .
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may not be mixed in advance but the particles may be separately carried before the main combustion chamber and moved into the descending moving layer of the main combustion chamber, in which case they are mixed in the layer by the whirling circulation.
On the other hand, in the upper portion of the free board, the convection heat transfer surface 6 is provided to effect heat recovering to function as an economizer and a vaporizing tube. However, a heat insulat-ing material 17 such as a refractory material is mountedon the lower portion of the convection heat transfer surface 6 and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintain the combustion temperature in the free board at a constant temperature, preferably, 900C. In case of the convection heat transfer surface, each heat transfer tube near the free board portion is mounted so as to be wound with a heat insulating material. Needless to say, a pitch of the heat transfer tube is taken into consideration so as not to impede a flowpassage of the exhaust gas.
By the provision of the heat insulating material 17 as described above, it becomes possible to maintain the temperature of the lower portion of the free board portion at a high temperature, and the effect of reducing CO is exhibited by air blown from an air blowing opening -`` 133268~
20 as the secondary combustion in the free board portion.
FIG. 2 shows a further embodiment of the present invention.
Basically, this emboidment has the structure similar to that of the boiler shown in FIG. 1 and performs the operation similar thereto. This embodiment is greatly different from the previous embodiment in that the lower portion of a partitioning wall 38 between the main com-bustion chamber 23 and the heat recovering chamber 24 is inclined so as to interrupt an upward flow of the air chamber 33 having a high fluidizing rate in the main com-bustion chamber and to turn the flow toward the air chamber 34 having a low fluidizing rate, the angle of inclination being 10 to 60 degrees to the horizon, preferably 25 to 45 degrees. The horizontal projection length Q with respect to the furnace bottom of the inclined portion of the partitioning wall is 1/6 to 1/2 of the horizontal length L of said furnace bottom, preferably 1/4 to 1/2.
The fluidized bed at the bottom of the boiler 20 body 21 is divided by the partitioning wall 38 into the ;
heat recovering chamber 24 and the main combustion chamber 23, and an air diffusion plate 22 for fluidization is provided on the bottom of the main combustion chamber 23.
The diffusion plate 22 is designed to be low in the central portion thereof and high on the side opposite . , . .
.:
13~268~
the heat recovering chamber. Two air chambers 33 and 34 are provided below the diffusion plate 22.
The mass rate of the fluidizing air jetted out of the central air chamber 33 is the rate required for the fluidizing medium within the main combustion chamber to form the fluidized bed, that is, in the range of 4 to 20 Gmf, preferably, in the range of 6 to 12 Gmf, whereas the mass rate of the fluidizing air jetted out of the air chamber 34 is smaller than the former, in the range of O to 3 Gmf, at the time of which the fluidizing medium above the air chamber 34 is not accompanied by severe vertical movement but forms a descending moving layer in a weak fluidizing state. This moving layer is spread downwardly to reach the upper portion of the air chamber 33 and therefore receives the jetting of the fluidizing air having a large mass rate from the air chamber 33 and is blown up. Then, a part of the fluidizing medium at the lower portion of the moving layer is removed, and therefore, the moving layer is moved down by it own weight.
On the other hand, the fluidizing medium blown up by the jetting of the fluidizing air from the air chamber 33 impinges upon the inclined partitioning wall 38 and is reflected and turned, a majority of which fall on the upper portion of the moving layer to supplement the fluidiz-ing medium of the downwardly moved moving layer. As the ~. . . . .. ~ ... ......
. . .,,, . :
, - . ., ~ .
13~2~8~
result of continuous operation as described above, the upper portion of the air chamber 34 is formed into a slow descending moving layer, and as a whole, the fluidizing medium within the main combustion chamber 23 is to form a whirling flow. On the other hand, a part of the fluidiz-ing medium blown up by the fluidizing air from the air chamber 33 and reflected and turned by the inclined partitioning wall 38 moves over the inclined partitioning wall 38 and enters the heat recovering chamber 24. The fluidizing medium moved into the heat recovering chamber 24 forms a gentle descending moving layer by the air blown by the gas flow device 32.
In the case where the descending rate is slow, the fluidizing medium moved into the heat recovering chamber forms an angle of repose at the upper portion of the heat recovering chamber, and a surplus portion thereof falls ~j;
from the upper portion of the inclined partitioning wall 38 to the main combustion chamber.
Within the heat recovering chamber, the fluidizing medium is subjected to heat exchanging through the heat transfer tube 25 while slowly moving down, after which the medium is cirulated from the opening 39 into the main combustion chamber.
The precipitating and circulation amount and the heat recovering amount of the fluidizing medium within ~ 133~685 the heat recovering chamber are controlled by the gas flow blown into the heat recovering chamber similarly to the embodiment shown in FIG. 1. In the case of the boiler shown in FIG. 2, the precipitating circulation amount or the like are controlled by the air amount blown from the gas flow device 32, and the mass rate thereof is in the range of O to 3 Gmf, preferably O to 2 Gmf.
Coals as fuel are supplied to the upper portion of the air chamber 34 which is the descending moving layer within the main combustion chamber 23 whereby the coals are whirled and circulated in the fluidized bed of the main combustion chamber and has an excellent combustibility.
On the other hand, the exhaust gas is guided to the cyclone 27 after having been moved out of the boiler.
The particles collected by the cyclone 27 pass through ~ ~;
the double damper 28 and are introduced into the hopper 30 together with coals supplied at the same time. They are mixed and supplied to the descending moving layer of the main combustion chamber 23, that is, the upper portion of the air chamber 34, contributing to the com-bustion of the unburnt (char) in the collected particles and the reduction in NOx.
Although not particularly shown, the particles collected by the cyclone 27 may be supplied separately of coals, unlike the supply device shown in FIG. 2, and , .. . . . .... .
... ~ . . :. . : :: - .
1332~8~
the particles may be airborne instead of the screw feeder.
On the other hand, in the upper portion of the free board, the convection heat transfer surface 26 is provided to effect heat recovering. A heat insulating material 37 such as a refractory material is mounted in the lower portion of the convection heat transfer surface 26 and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintain the combustion temperature of the free board at constant temperature, preferably 900C, and an air inlet 40 is provided for the secondary combustion to effectively reduce CO or the like.
FIG. 3 shows a still another embodiment of the present invention. Basicall~, the heat recovering chambers shown in ~IG. 2 are symmetrically opposed and integrated.
As a result, an air chamber 53 having a small mass rate of blown air is positioned centrally, and air chambers having a large mass rate. The flow of the fluidizing medium caused by air blown out of the air chambers 52 and 54 are inverted by inclined partitioning walls 58 and 58' and falls on the central portion. The flow is formed into a descending moving layer and reaches the upper portion of the air chamber 53, where it is divided into left and right portions, which are again blown up.
Accordingly, two symmetrical whirling flows are present r-~., .~:
, ,. .
~2~8~
within the fluidized bed of the main combustion chamber.
The coals and the particlescollected by the cyclone are supplied to the central descending moving layer.
In FIG. 3, the supply device is indicated at *
within the main combustion chamber, and the supply direction is vertical to the paper surface. While in FIG. 3, an example has been shown in which the particles collected by the cyclone and coals are mixed and supplied by the screw feeder 51, it is to be noted that they may be supplied separately, though not shown, and the airborne supply may be employed.
On the other hand, when the flow of the fluidizing medium caused by air blown out of the air chambers 52 and 53 is inverted at the inclined partitioning walls 58 and 58', a part thereof moves over the partitining walls and moves into the heat recovering chambers 44 and 44'.
The precipitating circulation amount of the fluidiz-ing medium within the heat recovering chambers is controlled by the gas flow introduced from gas flow devices 60 and 60' similarly to the device shown in FIG. 2.
The fluidizing medium after being heat exchanged by the heat transfer tubes 45 and 45' passes through the openings 59 and 59' and circulates within the main combustion chamber.
.. . . . .
.. . . . .
! . . ~ :
. ,, , , : ' . .- . ' :
133~8~
A convection heat transfer surface 46 is provided at the upper portion of the free board to effect heat exchanging. A heat insulating material 57 such as a refractory material is mounted on the convection heat transfer surface 4~ and the water cooling furnace wall on the side of the combustion chamber as needed in order to maintin the combustion temperature in the free board at a constant temperature, preferably, 900C, and an air -inlet 61 is provided for the secondary combustion to effectively reduce C0 or the like.
Another embodiment will be described hereinafter with reference to FIGS. 11 to 14, in which the heat recover-ing from the exhaust gas is carried out by a group of heat transfer tubes provided integral with the free board downstream of the free board portion.
FIG. 1 is a longitudinal sectional view of a composite circulation fluidized bed boiler showing one embodiment of the present invention in which the heat recovering from the exhaust gas is carried out by a group of heat transfer tubes provided integral with the free board portion downstream of the free board portion. FIG.
12 is a sectional view taken on lines A-A of FIG. 11.
In FIGS. 11 and 12, reference numeral 201 designates a boiler body, 202 an air diffusion nozzle for fluidization, 203 a main combustion chamber, 204 and 204' heat recovering _.
,;
,: .
1332~8~
chambers, 205 and 205' heat transfer chambers, 207 a cyclone, 208 a rotary valve, 209 a fuel supply tube, 201 a hopper, 211 a screw feeder for supplying fuel, 212, 213 and 214 air chambers, 218 and 218' partitioning walls, 219 and 219' openings at the lower por~ion of the heat recovering chamber, 220 a secondary air introducing tube, 229 an outlet for exhaust gas, 230 a steam drum, 231 a water drum, 232 a convection heat transfer chamber, 233, 234, and 235 partitioning walls in the convection heat transfer chamber, 236 vaporization chamber, 237 a water pipe wall, 238 a bottom of the convection heat ~ransfer chamber, 239 a screw conveyor, 240 an exhaust pipe for the convection heat transfer chamber, and 247, 247', 243 and 243' gas flow chambers of the type different from those shown in FIGS. 1 and 2.
The functions of the main combustion chamber, the heat exchanging chambers and the like shown in FIGS. 11 and 12 are exactly the same as those explained in connection with FIG. 3, but the boiler shown in FIGS. 11 and 12 is different from that shown in FIG. 3 in that the group of heat transfer tubes for recovering heat from exhaust gas are not provided in the free board portion but the convection heat transfer portion integral with the free board portion is provided downstream of the free board portion.
`~'; ' ' '' ' " ' ~ ' ' '. ~ '. ' ' ' "' ' .. ,, , 133268~3 That is, the exhaust gas discharged out of the exhaust gas outlet 229 in the free board portion is introduced into the convection heat transfer chamber 232 having a group of vaporization tubes provided between the steam drum 330 and the water drum 231, heat-exchanged with water in the group of vaporization tubes during flowing toward the downstream of the convection chamber in a direction as indicated by the arrow by the action of the partitioning walls arranged within the convection heat transfer chamber, cooled to 250 to 400C and thereafter introduced into the. cyclone 207 via the exhaust pipe 240 to collect fine particles containing char in the cyclone and discharged into atmosphere. The fine particles contain-ing the char collected by the cyclone are returned via the rotary valve 208 to a portion directly above the descending moving layer of the main combustion chamber 203 from the same charging opening as that of fuel such as coals supplied to the boiler via teh charging opening 209, the hopper 210 and the screw feeder 211.
On the other hand, the fluidizing medium having a relatively large grain size separated in the convection heat transfer portion 232, the desulfurizer and the particles containing char are gathered a V-shaped bottom at the lower portion of the convection heat transfer portion and then returned by the screw conveyor 239 to the portion . .
,: , . ~. . ~ ' ' ' -- 1332~
directly above the descending moving layer on the side opposite the fuel supply side of the main combustion chamber.
In the case where the convection heat transfer portion is provided downstream of the free board portion as shown in FIGS. 11 and 12, the secondary air is blown in the direction reversed to the flowing direction of the exhaust gas flowing into the convection heat transfer portion from the free board portion to thereby give rise to a whirling flow at the free board portion so that oxygen and exhaust gas are efficiently stirred and mixed to ~:
greatly effective reduce C0.
Another embodiment will be described with reference to FIG. 13.
FIG. 13 is a sectional view corresponding to FIG. 12, and reference numerals in FIG. 13 has the same meaning as those shown in FIG. 12 except that 238' adn 239' denote the V-shaped bottom of the convection heat transfer portion and the screw conveyor, respectively.
This embodiment is different from the boilers shown in FIGS. 11 and 12 only in that two V-shaped bottoms 238 and 28' (W-shaped bottoms) are provided at the lower portion of the convection heat transfer chamber, and that the particles containing a relatively large char collected at the V-shaped bottoms 238 and 238' are returned by the r~
:" ' . . .
" . ~ . ' -- ~332~8~
screw conveyors 239 and 239' to the portion directly above the descending moving layers 204 and 204' for the fluidizing medium in the heat recovering chambers provided on opposite sides of the combustion chamber.
FIG. 14 sho~ a still another embodiment of the present invention.
Reference numerals used in FIG. 14 have the same meaning as those used in FIG. 11 except that the reference numeral 241 designates a conduit. The emodiment shown in FIG. 14 is merely different from that of FIG. 11 in that the fine particles containing char collected by the cyclone 207 are guided onto the screw feeder 239 at the lower portion of the convection heat transfer portion 232 by the conduit 241 and then returned together with the particles containing a relatively large char collected by the convection heat transfer portion to the portion directly above the descending moving layer of the main combustion chamber.
,. .. . , ~ - -,j: .
.. . . ~ .
.. : . " ~ ., ,
Claims (14)
1. In an interior circulation fluidized bed boiler in which a fluidized bed portion of a fluidized bed boiler is divided by a partition into a main combustion chamber and a heat recovering chamber, at least two air chambers, i.e., an air chamber for imparting a high fluidizing speed to a fluidizing medium and an air chamber for imparting a low fluidizing speed thereto are provided at a lower portion of the main combustion chamber, a whirling and circulating flow is applied to the fluidizing medium within the main combustion chamber by a combination of air having different fluidizing speeds jetted out of these air chambers, and a circulating flow of the fluidizing medium is formed between the main combustion chamber and the heat recovering chamber, a composite circulation fluidized bed boiler characterized in that the heat recovering of exhaust gas is carried out, the exhaust gas at a boiler outlet is cooled and thereafter guided to a cyclone and particles collected by said cyclone are returned through a return opening to said main combustion chamber or said heat recovering chamber, at which time the return opening is situated directly above a descending moving layer having a low fluidizing speed in the fluidized bed or in the descending moving layer.
2. The composite circulation fluidized bed boiler according to claim 1, wherein the partition between said main combustion chamber and said heat recovering chamber is inclined so as to interrupt an upward flow of fluidizing air jetted out of an air jetting portion having a large mass rate in the main combustion chamber and to reflect and turn said fluidizing air upwardly of an air jetting portion having a small mass rate.
3. The composite circulation fluidized bed boiler according to claim 1, wherein a desulfurizer is supplied to the descending moving layer of the main combustion chamber.
4. The composite circulation fluidized bed boiler according to claim 1, wherein the exhaust gas is guided to the cyclone after said exhaust gas has been cooled to 250°C to 400°C.
5. The composite circulation fluidized bed boiler according to claim 1, 2, 3 or 4, wherein the heat recovering of the exhaust gas is effected by a group of heat transfer tubes provided on a free board portion on the fluidized bed.
6. The composite circulation fluidized bed boiler according to claim 1, wherein the heat recovering of the exhaust gas is effected by a group of heat transfer tubes provided integral with a free board portion downstream of the free board portion.
7. The composite circulation fluidized bed boiler according to claim 6, wherein the fluidizing medium having a relatively large grain size collected by portions of the group of heat transfer tubes provided integral with the free board portion downstream of the free board portion, the desulfurizer and the char particles are returned by a carrier such as a screw conveyor to a portion directly above the descending moving layer of the fluidized bed of the main combustion chamber or into the descending moving layer.
8. The composite circulation fluidized bed boiler according to claim 6, wherein the fluidizing medium having a relatively large grain size collected by portions of the group of heat transfer tubes provided integral with the free board portion downstream of the free board portion, the desulfurizer and the char particles are returned by a carrier such as a screw conveyor to a portion directly above the descending moving layer of the fluidized medium in the heat recovering chamber or into the descending moving layer.
9. The composite circulation fluidized bed boiler according to claim 8, wherein the fluidizing medium having a relatively large grain size, the desulfurizer and the char particles are returned to both the air chambers provided on both left and right sides of the main combustion chamber.
10. The composite circulation fluidized bed boiler according to claim 7, 8 or 9, wherein the particles containing fine char collected by the cyclone are returned to a carrier such as a conveyor for returning the particles collected by the portions of the group of heat transfer tubes provided integral with said free board portion to the fluidized bed portion or the heat recovering portion.
11. The composite circulation fluidized bed boiler according to claim 1, wherein secondary air is blown in the direction reversed to the flowing direction of the exhaust gas flown from the free board portion to the convection heat transfer portion to thereby produce a whirling flow of the exhaust gas in the free board portion.
12. In an interior circulation fluidized bed boiler in which a fluidized bed portion of a fluidized bed boiler is divided by a partition into a main combustion chamber and a heat recovering chamber, at least two air chambers, i.e., an air chamber for imparting a high fluidizing speed to a fluidizing medium and an air chamber for imparting a low fluidizing speed thereto are provided at a lower portion of the main combustion chamber, a whirling and circulating flow is applied to the fluidizing medium within the main combustion chamber by a combination of air having different fluidizing speeds jetted out of these chambers, and a circulating flow of the fluidizing medium is formed between the main combustion chamber and the heat recovering chamber, a composite circulation fluidized bed boiler characterized in that a convection heat transfer portion provided integral with a free board portion is provided downstream of the free board of the main combustion chamber, a steam drum is provided at the upper portion of the free board portion and the convection heat transfer portion, a water drum is provided at the lower portion of the convection heat transfer portion, a pipe constituting a water pipe wall of the main combustion chamber is drawn from the upper portion of the free board of said steam drum, a vaporization tube for cooling the exhaust gas and recovering heat is provided between the steam drum and the water drum in the convection heat transfer portion, and particles collected at the convection heat transfer portion are returned to a portion directly above a descending moving layer having a small fluidizing rate of the fluidizing medium in the main combustion chamber or the heat recovering chamber or into the descending moving layer.
13. The composite circulation fluidized bed boiler according to claim 12, wherein the collected particles are gathered at a V-shaped bottom provided at the lower portion of the water drum, said particles being returned by a screw conveyor provided on the V-shaped bottom to the portion directly above the descending moving layer of the fluidizing medium in the main combustion chamber or the heat recovering chamber or into the descending moving layer.
14. The composite circulation fluidized bed boiler according to claim 12, wherein the collected particles are gathered at a W-shaped bottom provided at the lower portion of the water drum, said particles being returned by two screw conveyors provided on the W-shaped bottom to the portion directly above the descending moving layer of the fluidizing medium in the heat recovering chamber or into the descending moving layer.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21513588 | 1988-08-31 | ||
| JP215135/1988 | 1988-08-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1332685C true CA1332685C (en) | 1994-10-25 |
Family
ID=16667285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000610057A Expired - Fee Related CA1332685C (en) | 1988-08-31 | 1989-08-31 | Composite circulating fluidized bed boiler |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0431163B1 (en) |
| KR (1) | KR100229691B1 (en) |
| CN (1) | CN1017469B (en) |
| AT (1) | ATE131271T1 (en) |
| AU (1) | AU4199889A (en) |
| CA (1) | CA1332685C (en) |
| DE (1) | DE68925033T2 (en) |
| MY (1) | MY104683A (en) |
| WO (1) | WO1990002293A1 (en) |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2116745C (en) * | 1993-03-03 | 2007-05-15 | Shuichi Nagato | Pressurized internal circulating fluidized-bed boiler |
| CN100417862C (en) * | 2005-12-09 | 2008-09-10 | 清华大学 | Horizontal circulating fluidized bed burning equipment and its circulating burning method |
| FI122040B (en) * | 2009-11-10 | 2011-07-29 | Foster Wheeler Energia Oy | Process and arrangement for feeding fuel into a boiler with circulating fluidized beds |
| JP6085570B2 (en) * | 2012-02-13 | 2017-02-22 | 荏原環境プラント株式会社 | Heat transfer tube in a fluidized bed boiler |
| JP5992322B2 (en) * | 2012-12-28 | 2016-09-14 | 住友重機械工業株式会社 | Circulating fluidized bed boiler |
| CN103090397B (en) * | 2013-01-16 | 2015-09-09 | 河南科技大学 | A kind of mud and fluidized bed multifuel combustion reactor |
| FI126744B (en) | 2013-05-14 | 2017-04-28 | Valmet Technologies Oy | Arrangement and method of fluidization boiler |
| CN104279548A (en) * | 2013-07-12 | 2015-01-14 | 李雨田 | Energy-collecting heat exchange environment-friendly boiler |
| CN105444160B (en) * | 2014-08-29 | 2019-01-08 | 中国科学院工程热物理研究所 | Recirculating fluidized bed fine ash burner |
| CN106196124A (en) * | 2016-08-23 | 2016-12-07 | 苏州泰盛新绿节能环保科技有限公司 | A kind of coal-burning boiler assembly reducing smoke evacuation oxygen content |
| CN107631293A (en) * | 2017-10-27 | 2018-01-26 | 湘潭锅炉有限责任公司 | A kind of CFBB |
| JP7079627B2 (en) * | 2018-03-13 | 2022-06-02 | 荏原環境プラント株式会社 | Fluidized bed heat recovery device |
| CN114353049A (en) * | 2021-12-25 | 2022-04-15 | 江苏中科重工股份有限公司 | Method and equipment for recycling steam-water heat of boiler drain flash tank |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1517166A1 (en) * | 1963-12-03 | 1969-05-14 | Container Corp | Process for treating a waste liquor containing organic and inorganic substances |
| DE2449798C2 (en) * | 1974-10-19 | 1982-10-07 | Thyssen Industrie Ag, 4300 Essen | Fluidized bed furnace for the incineration of partially dewatered sludge |
| US4253425A (en) * | 1979-01-31 | 1981-03-03 | Foster Wheeler Energy Corporation | Internal dust recirculation system for a fluidized bed heat exchanger |
| JPS57139205A (en) * | 1981-02-23 | 1982-08-28 | Babcock Hitachi Kk | Fluidized bed furnace |
| GB2151503B (en) * | 1981-12-15 | 1986-08-20 | William Benedict Johnson | Fluidized bed combustion apparatus and method of carrying out fluidized bed combustion |
| CH659876A5 (en) * | 1983-05-10 | 1987-02-27 | Sulzer Ag | Fluid bed firing. |
| JPS62141408A (en) * | 1985-12-13 | 1987-06-24 | Mitsubishi Heavy Ind Ltd | Circulation type fluidized bed combustor |
| CA1285375C (en) * | 1986-01-21 | 1991-07-02 | Takahiro Ohshita | Thermal reactor |
| JPS63143409A (en) * | 1986-12-03 | 1988-06-15 | Mitsubishi Heavy Ind Ltd | Fluidized bed boiler of circulation type |
-
1989
- 1989-08-30 WO PCT/JP1989/000883 patent/WO1990002293A1/en active IP Right Grant
- 1989-08-30 AT AT89909857T patent/ATE131271T1/en not_active IP Right Cessation
- 1989-08-30 AU AU41998/89A patent/AU4199889A/en not_active Abandoned
- 1989-08-30 DE DE68925033T patent/DE68925033T2/en not_active Expired - Fee Related
- 1989-08-30 EP EP89909857A patent/EP0431163B1/en not_active Expired - Lifetime
- 1989-08-31 CA CA000610057A patent/CA1332685C/en not_active Expired - Fee Related
- 1989-08-31 CN CN89107888A patent/CN1017469B/en not_active Expired
- 1989-11-30 MY MYPI89001666A patent/MY104683A/en unknown
- 1989-12-29 KR KR1019890702496A patent/KR100229691B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| MY104683A (en) | 1994-05-31 |
| ATE131271T1 (en) | 1995-12-15 |
| WO1990002293A1 (en) | 1990-03-08 |
| KR900700822A (en) | 1990-08-17 |
| CN1041646A (en) | 1990-04-25 |
| DE68925033D1 (en) | 1996-01-18 |
| EP0431163A4 (en) | 1992-05-20 |
| AU4199889A (en) | 1990-03-23 |
| EP0431163A1 (en) | 1991-06-12 |
| KR100229691B1 (en) | 1999-11-15 |
| EP0431163B1 (en) | 1995-12-06 |
| DE68925033T2 (en) | 1996-05-15 |
| CN1017469B (en) | 1992-07-15 |
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