JP2014234935A - Circulating fluidized bed boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stable operation over a wide combustion range and to reduce material cost or installation cost even when various kinds of materials are combusted in a single or mixed state, by preventing fly ash or a fluid medium from being deposited within a duct by reduction of a gas flow velocity in the case of load fluctuation or fuel change.SOLUTION: A circulating fluidized bed boiler comprises: a furnace body 1 including a fluidized bed 1a and a combustion chamber 1b; a fluid medium collector 5 for separating exhaust gas G exhausted from the furnace body 1, a fluid medium S and fly ash into the exhaust gas G, the fly ash and the fluid medium S in accordance with gravity acceleration and centrifugal acceleration; and a loop seal part 7 for returning the separated fluid medium S to the fluidized bed 1a within the furnace body 1. A combustion chamber outlet 1c of the furnace body 1 and the fluid medium collector 5 are communicated by a combustion chamber outlet duct 2 and an inlet tilt duct 4. The combustion chamber outlet duct 2 is connected to the combustion chamber outlet 1c with a structurally minimum length and formed from a horizontal part 2a and a vertical part 2b. The inlet tilt duct 4 is connected to the combustion chamber outlet duct 2 in a downwards tilted attitude via an expansion joint 3 and connected to the fluid medium collector 5 in the tangential direction thereof.

Description

  The present invention relates to an improvement of a circulating fluidized bed boiler that uses biomass, coal, or the like as fuel, and is used as a steam boiler mainly for power generation, and in particular, connects a furnace body of a circulating fluidized bed furnace and a fluidized medium recovery device. By adding improvements to the duct, etc., it is possible to suppress the accumulation of fly ash and fluidized medium in the duct due to a decrease in the gas flow rate when the combustion load fluctuates or when the fuel changes. Even with single combustion or mixed combustion, stable operation is possible over a wide combustion range (high turndown), low-load operation is possible, and material and installation costs can be greatly reduced. The present invention relates to a circulating fluidized bed boiler.

  In general, circulating fluidized bed boilers have excellent combustion performance for fuels such as biomass, coal, RDF, wood waste, municipal waste, industrial waste, and sludge, and are used as steam boilers for power generation in waste incineration facilities. Has been.

  Conventionally, as this type of circulating fluidized bed boiler, for example, those disclosed in Japanese Patent Laid-Open No. 10-220708 (Patent Document 1) and Japanese Patent Laid-Open No. 2001-235101 (Patent Document 2) are known.

  FIG. 6 shows an example of a conventional circulating fluidized bed boiler. The circulating fluidized bed boiler is connected to a furnace body 20 having a fluidized bed 20a and a combustion chamber 20b, and a furnace body 20 via a duct 21, It is comprised from the cyclone 23 which has the inner cylinder 22, and the loop seal part 24 etc. which were connected to the cyclone 23 and the furnace main body 20, Constituent material (water pipe wall etc.), such as the furnace main body 20, the cyclone 23, and the loop seal part 24 ) And high-temperature and high-pressure superheated steam for power generation are generated by heat absorbed by a heat exchanger or the like disposed in a flue.

  That is, according to the circulating fluidized bed boiler, the fuel supplied into the furnace from the fuel supply port 20c is separated from the fluid medium S such as fluidized sand by the primary air ejected from the fluid nozzle (not shown) in the fluidized bed 20a. Combusts while being stirred and mixed.

  Incineration residues such as combustion gas and fly ash generated by combustion are blown up together with the fluidized medium S from the fluidized bed 20a to the combustion chamber 20b, where they are supplied to the combustion chamber 20b while being agitated and mixed with the fluidized medium S. After the combustion gas and unburned components are completely burned by the secondary air, they are introduced into the cyclone 23 through the duct 21.

  The exhaust gas G containing the fly ash and the like introduced into the cyclone 23 and the fluid medium S are separated into the fluid medium S and the exhaust gas G containing the fly ash by a centrifugal separation action.

  The separated fluid medium S is returned from the cyclone 23 to the fluidized bed 20a of the furnace body 20 through the downcomer 25, the loop seal portion 24, and the return port 20d of the fluid medium S, and the retained heat of the fluid medium S is retained. After being reused, the exhaust gas G containing fly ash and the like is recovered from the cyclone 23 through the flue through a heat exchanger and the like, and the fly ash and the like are removed by an exhaust gas treatment device such as a bag filter. Released from the chimney into the atmosphere.

  Since the circulating fluidized bed boiler has a large flow velocity difference between the combustion gas rising in the furnace body 20 and the fluid medium S, the fuel and the fluid medium S are vigorously stirred and mixed throughout the furnace, and the combustion reaction is performed. Progresses rapidly. As a result, the fuel can be completely burned with a low excess air ratio, and it has excellent effects such as improvement of boiler efficiency by reducing unburned material loss and low NOx combustion by a low excess air ratio. It is.

By the way, in the circulating fluidized bed boiler adopting a standard cyclone, the furnace body 20 and the cyclone 23 are usually connected in a continuous manner by a horizontal duct 21, but in this case, if low load combustion is performed, Since the gas flow rate in the gas chamber 21 becomes slow and the gas temperature also decreases, there is a problem that the fly ash and the fluid medium S are accumulated and solidified in the duct 21 and the duct 21 is easily blocked. This problem can also occur when the fuel introduced into the furnace is changed.
Moreover, when it transfers to high load combustion in the state in which the fly ash and the fluid medium S accumulated and solidified in the duct 21, since the opening area in the duct 21 is narrow, the gas flow velocity in the duct 21 rises rapidly, The fluid medium S contained in the exhaust gas G causes wear on the peripheral wall of the cyclone 23.

In some circulating fluidized bed boilers, in order to suppress the accumulation of fly ash and the like in the duct, there are some in which the duct is inclined as in JP-A-11-082968 and JP-A-2005-058872.
However, when the duct is simply tilted and connected to the cyclone, the structure of the boiler water pipe is difficult, and the furnace body and the cyclone forming the combustion chamber need to be integrated.
In addition, when the duct on the furnace body side and the duct on the cyclone side are connected by an expansion joint (not shown), fly ash and a fluid medium are likely to accumulate on the expansion joint portion, which may cause a reduction in the capacity and damage of the expansion joint. .

Furthermore, in the circulating fluidized bed boiler, when the combustion chamber and the cyclone boiler water pipe are configured integrally, in order to cope with the difference in the thermal expansion of the boiler, a strut is constructed to surround the entire circulating fluidized bed boiler, and the uppermost beam However, the circulating fluidized bed boiler itself is a heavy article having a height of 20 m to 40 m and requires a very large support.
In addition, when the circulating fluidized bed boiler is suspended, it is necessary to suspend the installation from the upper part after constructing the support that surrounds the entire circulating fluidized bed boiler, so an extra large crane is required for the installation work. The installation cost will be high.

JP-A-10-220708 JP 2001-235101 A JP 11-082968 A JP 2005-058872 A

  The present invention has the problems as described above in the conventional circulating fluidized bed boiler, that is, (1) fly ash and fluidized medium accumulate in the duct when the gas flow velocity in the duct decreases at the time of combustion load fluctuation or fuel change. -Solidifying and closing the duct (2) When an expansion joint is installed in the middle of the duct, fly ash and fluid medium accumulate on the expansion joint, (3) A structure that suspends the circulating fluidized bed boiler Therefore, it is intended to solve problems such as the need for very large struts and high material costs and installation work costs. By adding improvements to the duct that connects to the medium recovery unit, it is possible to suppress the accumulation of fly ash and fluid medium in the duct due to a decrease in the gas flow rate when the combustion load fluctuates or when the fuel changes. Switching between various types of fuel Even if single combustion or mixed combustion is used, stable operation can be performed over a wide combustion range (high turndown), low-load operation is also possible, and circulation that can significantly reduce material costs and installation work costs The purpose is to provide a fluidized bed boiler.

  The invention of claim 1 of the present invention combusts while stirring and mixing the fluidized bed in which the fuel is fluidized with the fluidized medium and combusted, and the combustion gas and unburned components generated by the combustion with the fluidized medium blown up from the fluidized bed. A combustion chamber having a combustion chamber, and exhaust gas, fluidized medium, and fly ash discharged from an outlet of the combustion chamber provided at the top of the furnace main body, and separating the exhaust gas, fly ash, and fluidized medium by gravity acceleration and centrifugal acceleration; A cylindrical fluid medium recovery unit that recovers the fluid medium from inside, and the fluid medium separated and recovered while sealing between the inside of the furnace body and the fluid medium recovery unit from the fluid medium recovery unit to the fluidized bed in the furnace body A circulating fluidized bed boiler having a loop seal portion to be returned, wherein the horizontal portion between the combustion chamber outlet of the furnace main body and the inlet of the fluid medium recovery unit is connected to the combustion chamber outlet and has a minimum length in terms of structure. And horizontally Combustion chamber outlet duct composed of vertical parts connected in a direction, and an inlet inclination connected to the vertical part of the combustion chamber outlet duct in a downward inclined posture via an expansion joint and connected in a tangential direction to the fluid recovery unit It is characterized in that it is configured to be connected in a continuous manner by a duct.

  The invention of claim 2 of the present invention is characterized in that, in the invention of claim 1, the inclination angle of the inlet inclined duct is set to 10 ° to 45 °.

  In the invention of claim 3 of the present invention, in the invention of claim 1 or claim 2, the exhaust gas outlet duct provided at the upper end portion of the fluid medium recovery device and the downcomer provided at the lower end portion of the fluid medium recovery device. It is characterized in that each of the joints is interposed, and the fluid medium recovery unit is self-supported by an intermediate support structure by a support column.

  The invention of claim 4 of the present invention is the invention of claim 1 or claim 2, wherein the flow rate of the exhaust gas flowing through the inlet inclined duct is 20 m / s or less at maximum load combustion, and the lower limit at low load combustion is set. It is characterized by not providing it.

  The invention of claim 5 of the present invention is the invention of claim 3, wherein the combustion chamber and the fluid recovery device are constituted by a water tube panel, and the combustion chamber outlet duct, the inlet inclined duct and the downcomer have a refractory structure. There is a special feature.

  According to a sixth aspect of the present invention, in the third aspect of the present invention, the combustion chamber, the fluid recovery device, the loop seal portion, the combustion chamber outlet duct, the downcomer, the inlet inclined duct, the loop seal portion and the furnace body are connected. It is characterized by the fact that each circulation duct is composed of water pipe panels.

  According to a seventh aspect of the present invention, in the third aspect of the present invention, the combustion chamber, the fluid recovery device, the loop seal portion, the combustion chamber outlet duct, the inlet inclined duct, the downcomer, the loop seal portion and the furnace body are connected. It is characterized by the fact that each circulation duct has a refractory structure.

  According to an eighth aspect of the present invention, in the first aspect of the present invention, an inlet for a replenishing fluid medium, a desulfurizing agent and a clinker inhibitor is formed at the upper end of the vertical portion of the combustion chamber outlet duct. It is characterized in that any one or two or more of a replenishing fluid medium, a desulfurizing agent, and a clinker inhibitor are added simultaneously by natural fall.

  According to a ninth aspect of the present invention, in the first or second aspect of the present invention, the inlet inclined duct is provided with an air inlet nozzle at a position parallel to and near the bottom surface of the inlet inclined duct, and the air inlet nozzle Is characterized in that air or a mixed fluid of air and at least one of a replenishing fluid medium, a desulfurizing agent and a clinker inhibitor is introduced.

  A circulating fluidized bed boiler according to the present invention includes a combustion chamber outlet duct connected between the combustion chamber outlet and a horizontal portion and a vertical portion between the combustion chamber outlet of the furnace body and the inlet of the fluid medium recovery unit, and a combustion chamber outlet. The length of the horizontal part of the combustion chamber outlet duct is connected to the vertical part of the duct in a downward inclined posture via an expansion joint and connected in a continuous manner to the fluid medium collector by the inlet inclined duct connected in the tangential direction. Is set to the minimum length in terms of structure, so that fly ash and fluidized medium can be prevented from accumulating and solidifying in the duct even when the gas flow velocity in the duct decreases during combustion load fluctuations or fuel changes. As a result, even when various types of fuels are switched to perform single combustion or mixed combustion, stable operation can be performed in a wide combustion range (high turndown), and low load operation is also possible.

  The circulating fluidized bed boiler of the present invention connects the inlet inclined duct to the fluid medium collector in a downward inclined posture and tangentially, and exhaust gas, fluid medium and fly ash from the inlet inclined duct to the fluid medium collector in a downward inclined posture. In addition, since it is introduced in the tangential direction, the fluid medium can be separated and collected by gravity acceleration and centrifugal acceleration in the fluid medium collector, and the inner cylinder used in the conventional general cyclone is unnecessary. Thus, it is possible to reduce equipment costs and avoid troubles such as deformation, dropout and blockage of the inner cylinder.

  In the circulating fluidized bed boiler of the present invention, since the inlet inclined duct is connected to the fluid medium recovery device in a downward inclined posture, the fluid medium is smoothly dropped even when extremely low load operation is performed, and the fluid medium recovery is performed. It is possible to avoid the blockage caused by the fluid medium gathering and dropping in the throttle part (cone part) at the lower part of the vessel.

  In the circulating fluidized bed boiler of the present invention, the inlet inclined duct is connected to the vertical portion of the combustion chamber outlet duct via an expansion joint, so even if the gas flow rate is slow due to low load operation, fly ash or The fluid medium does not accumulate, and troubles due to damage to the expansion joint can be avoided.

  The circulating fluidized bed boiler of the present invention has an inlet inclined duct connected to a vertical portion of a combustion chamber outlet duct via an expansion joint, and an exhaust gas outlet duct provided at an upper end portion of the fluidized medium recovery unit and a lower end of the fluidized medium recovery unit. Expansion joints are interposed in the downcomer provided in the section, and the fluid medium recovery unit is self-supporting by the intermediate support structure by the support column, so that the furnace body having the combustion chamber can also be self-supported by the intermediate support structure by the support column. This eliminates the need for supporting columns that surround the entire circulating fluidized bed boiler, simplifies the supporting columns, greatly reduces material costs and installation costs, and shortens the construction period.

In the circulating fluidized bed boiler of the present invention, a replenishment fluid medium, a desulfurizing agent, and a clinker inhibitor inlet are formed at the upper end of the vertical portion of the combustion chamber outlet duct. A desulfurization agent and a clinker inhibitor can be added by natural dropping.
Moreover, since the circulating fluidized bed boiler of the present invention is charged with a supplementary fluid medium, a desulfurizing agent, or the like in the combustion chamber outlet duct, it suppresses a decrease in furnace temperature due to direct injection of these into the combustion chamber. In addition, the inside of the combustion chamber outlet duct and the inside of the inlet inclined duct can be cleaned by the polishing effect of a replenishing fluid medium, a desulfurizing agent, and the like, and blockage of the combustion chamber outlet duct and the inlet inclined duct can be prevented.

In the circulating fluidized bed boiler according to the present invention, the inlet inclined duct is provided with an air inlet nozzle at a position parallel to and close to the bottom surface of the inlet inclined duct, and air is supplied from the air inlet nozzle. The fuel can be completely burned in the fluid medium collector, and the accumulation of fly ash and the like in the inlet inclined duct can be prevented.
In addition, the circulating fluidized bed boiler of the present invention is supplied with a replenishing fluid medium, a desulfurizing agent, and a clinker inhibitor together with air from an air charging nozzle, so that the temperature in the furnace is lowered by directly charging the combustion chamber. In addition, the inside of the inlet inclined duct can be cleaned by a polishing effect such as a replenishing fluid medium or a desulfurizing agent, and the inlet inclined duct can be prevented from being blocked.

It is a schematic front view of the circulating fluidized bed boiler which concerns on embodiment of this invention. It is a schematic plan view of a circulating fluidized bed boiler. It is a schematic front view of the circulating fluidized bed boiler which concerns on other embodiment of this invention. It is a schematic plan view of the circulating fluidized bed boiler shown in FIG. It is a schematic side view of the furnace main body of the circulating fluidized bed boiler shown in FIG. It is a schematic front view of the conventional circulating fluidized bed boiler.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1 and 2 show a relatively small circulating fluidized bed boiler according to an embodiment of the present invention. The circulating fluidized bed boiler combusts in a furnace body 1 having a fluidized bed 1a and a combustion chamber 1b, and in the furnace body 1. A cylindrical fluid medium collector 5 connected via the chamber outlet duct 2, the expansion joint 3 and the inlet inclined duct 4; a loop seal portion 7 connected to the fluid medium collector 5 via a downcomer 6; Consists of a circulation duct 11 that connects the loop seal 7 and the furnace body 1, and so on. Absorption heat by components (water pipe panels, etc.) of the furnace body 1 and the like, and absorption by a heat exchanger disposed in the flue It generates high-temperature and high-pressure superheated steam for power generation by heat.

Specifically, the furnace body 1 has a quadrangular cross-sectional shape formed by a water tube panel in which adjacent water tubes are connected in an airtight manner via fin plates, and the primary air is contained in the inside. Are provided with a fluidized bed 1a provided with a plurality of flow nozzles (not shown) for blowing air and a combustion chamber 1b for blowing secondary air. The outer surface of the water tube panel forming the furnace body 1 is covered with a heat insulating material and a casing made of a steel plate. Further, combustion gas in the furnace and blown fly ash blown up in the upper position of the side wall of the furnace body 1, A combustion chamber outlet 1 c for discharging the fluid medium S is formed, and a return port 1 d for the fluid medium S separated from the exhaust gas G is formed at a lower position of the side wall of the furnace body 1.

In addition, refractory materials such as refractory bricks and castable refractories are lined on the inner surface of the portion facing the fluidized bed 1a of the water tube panel, and wear of the water tube panel due to the fluidized fluid medium S is prevented. .
Further, the portion of the water tube panel facing the combustion chamber 1b may be in a bare tube state, or a protective coating is formed by spraying a wear-resistant metal, and the water tube panel is protected by this protective coating. good.

In the above embodiment, the furnace main body 1 has a water tube panel structure. However, in other embodiments, the furnace main body 1 may have a refractory wall structure in which a refractory is lined in a casing.
In the above-described embodiment, the cross-sectional shape of the furnace body 1 is a quadrangle. However, in other embodiments, the cross-sectional shape of the furnace body 1 may be a circle.

The combustion chamber outlet duct 2 is formed in a square tube shape and has a water tube panel structure or a refractory structure. The combustion chamber outlet duct 2 is connected to the combustion chamber outlet 1c of the furnace body 1 and has a rectangular tube shape having a minimum length in terms of structure. It consists of a horizontal portion 2a and a rectangular cylindrical vertical portion 2b that is connected to the horizontal portion 2a downward by 90 °.
The combustion chamber outlet duct 2 is connected to the combustion chamber outlet 1c of the furnace body 1 with the bottom wall of the horizontal portion 2a inclined downward with respect to the combustion chamber 1b, and the bottom of the horizontal portion 2a. The horizontal part of the wall is formed so as to have the minimum length in terms of structure.
Further, a replenishing fluid medium such as fluid sand, a desulfurizing agent (limestone, dolomite, etc.) and a powdery clinker inhibitor (Mg, Si, Ca, Al, etc.) are provided at the upper end of the vertical portion 2b of the combustion chamber outlet duct 2. The compound 2) is provided with an inlet 2c, and any one or two or more of a replenishing fluid medium, a desulfurizing agent, and a clinker inhibitor can be simultaneously introduced from the inlet 2c by natural fall. It is like that.

The inlet inclined duct 4 is formed in a rectangular tube shape and has a water tube panel structure or a refractory structure, and is connected to the vertical portion 2b of the combustion chamber outlet duct 2 in a downward inclined posture via an expansion joint 3. And connected to the fluid medium collector 5 in the tangential direction.
The inclination angle α of the inlet inclined duct 4 is appropriately determined from the flow rate of the exhaust gas G in the inlet inclined duct 4 and the required classifying performance of the fluid medium recovery unit 5.
Further, the cross-sectional area (height × width) of the inlet inclined duct 4 is set so that the flow velocity of the exhaust gas G flowing through the inlet inclined duct 4 becomes a predetermined value.
In this embodiment, the inclination angle α of the inlet inclined duct 4 is set to 10 ° to 45 °, and the flow rate of the exhaust gas G in the inlet inclined duct 4 is set to be equal to that of the circulating fluidized bed boiler. The maximum load combustion is set to 20 m / s or less, and the lower limit at low load combustion is not provided. These values are determined from test results using an actual machine.
Further, one or a plurality of air injection nozzles 8 are provided in the upstream portion of the inlet inclined duct 4, and air or air and a replenishing fluid medium, a desulfurization agent, and a clinker inhibitor are supplied from the air injection nozzle 8. A fluid mixture with at least one of them can be introduced. The air injection nozzle 8 is provided at a position parallel to the bottom surface of the inlet inclined duct 4 and as close as possible to the bottom surface of the inlet inclined duct 4, and fly ash and fluid medium deposited on the bottom surface of the inlet inclined duct 4. S can be blown away.

The fluid medium recovery unit 5 is formed in a cylindrical shape and has a water tube panel structure or a refractory structure, and has a relatively long cylindrical body 5a and an extremely short height that gradually decreases in diameter as it goes downward. And a conical portion 2b. The fluid medium recovery device 5 is configured such that the fluid medium S and the exhaust gas G are separated by a cylindrical body 5a having a relatively long length, and a member corresponding to an inner cylinder of a conventional cyclone is provided. Absent.
In addition, a cylindrical downcomer 6 having a water tube panel structure or a refractory structure is connected to the conical portion 2 b of the fluid medium collector 5, and an exhaust gas outlet is disposed at the center of the upper end surface of the fluid medium collector 5. A duct 9 is connected. These downcomers 6 and exhaust gas outlet ducts 9 are respectively provided with expansion joints 3.
Therefore, the fluid recovery device 5 is self-supporting with an intermediate support structure by a plurality of columns 10 separately from the furnace body 1 by providing the expansion joint 3 in the inlet inclined duct 4, the downcomer 6 and the exhaust gas outlet duct 9. Can be made. Along with this, the furnace body 1 can also be self-supporting with an intermediate support structure by a plurality of support columns 10.

The loop seal portion 7 has a trap-shaped box-like water tube wall structure or refractory wall structure having a partition wall 7a and an overflow portion 7b therein, and a conical portion of the fluid recovery unit 5 2b is connected to the return port 1d of the furnace body 1 through a circulation duct 11 having a water tube panel structure or a refractory structure, and the inside of the furnace body 1 and the fluid medium recovery device 5 are connected to the return port 1d of the furnace body 1. The fluid medium S separated and recovered while sealing the inside is returned to the fluidized bed 1 a in the furnace body 1.
In addition, fluidized air is supplied into the loop seal portion 7 from the bottom thereof, so that a fluidized bed 1 a is also formed in the loop seal portion 7.

  Thus, according to the circulating fluidized bed boiler described above, fuel such as biomass and coal supplied from the fuel supply port (not shown) into the furnace is disposed at the bottom of the furnace body 1 in the fluidized bed 1a. The primary air ejected from the fluidized nozzle (not shown) combusts while being agitated and mixed with the fluid medium S such as fluidized sand.

  Incineration residues such as combustion gas and fly ash generated by combustion are blown up together with the fluidized medium S from the fluidized bed 1a to the combustion chamber 1b, where they are supplied to the combustion chamber 1b while being agitated and mixed with the fluidized medium S. After the combustion gas and unburned components are completely burned by the secondary air, they are introduced into the fluid medium collector 5 through the combustion chamber outlet duct 2, the expansion joint 3 and the inlet inclined duct 4.

At this time, since the length of the horizontal portion 2a of the combustion chamber outlet duct 2 is set to the minimum length in terms of structure, even if the gas flow velocity in the combustion chamber outlet duct 2 decreases during combustion load fluctuation or fuel change The fly ash and the fluid medium S can be prevented from being deposited and solidified in the combustion chamber outlet duct 2.
In addition, since the inlet inclined duct 4 is connected to the fluid medium collector 5 in a downward inclined posture, the fluid medium S can be smoothly dropped even when an extremely low load operation is performed.
Furthermore, since the inlet inclined duct 4 is connected to the vertical portion 2b of the combustion chamber outlet duct 2 via the expansion joint 3, even if the gas flow rate is slow due to low load operation, fly ash or fluid medium is placed in the expansion joint 3 portion. S cannot be said to be deposited.

  The exhaust gas G containing the fly ash and the like introduced into the fluid medium recovery unit 5 and the fluid medium S are separated into the fluid medium S and the exhaust gas G containing the fly ash and the like. That is, in the fluid medium collector 5, the exhaust gas G, the fluid medium S, and the like are introduced into the fluid medium collector 5 in a downward inclined posture and in a tangential direction. Therefore, due to the gravitational acceleration and the centrifugal acceleration similar to the cyclone, The heavy fluid medium S having a large particle diameter is divided below the fluid medium collector 5, and the light exhaust gas G and the light fly ash having a small particle diameter are separated above the fluid medium collector 5.

  In this fluid medium collector 5, the fluid medium S can be separated and recovered by gravity acceleration and centrifugal acceleration, so that the inner cylinder used in the conventional general cyclone becomes unnecessary, and the equipment cost is reduced. And troubles such as deformation, dropout and blockage of the inner cylinder can be avoided.

The separated fluid medium S is returned from the fluid medium collector 5 to the fluidized bed 1a of the furnace body 1 through the downcomer 6, the loop seal portion 7, and the circulation duct 11, and the retained heat possessed by the fluid medium S. Will be reused.
Further, the separated exhaust gas G including fly ash is recovered from the heat through the flue from the exhaust gas outlet duct 9 of the fluid medium recovery device 5 by a heat exchanger, and is discharged by an exhaust gas processing device such as a bag filter. After the ash is removed, it is released from the chimney into the atmosphere.

  During the operation of the circulating fluidized bed boiler, any one of a supplementary fluid medium, a desulfurizing agent, or a clinker inhibitor is caused by natural fall from the inlet 2c provided at the upper end of the vertical portion 2b of the combustion chamber outlet duct 2. Two or more of them are put in at the same time. Further, air or a mixed fluid of air and at least one of a replenishing fluid medium, a desulfurizing agent, and a clinker inhibitor is also introduced from an air introduction nozzle 8 provided in the inlet inclined duct 4.

As a result, it is possible to suppress a decrease in the furnace temperature due to the direct introduction of the replenishing fluid medium, desulfurizing agent, etc. into the combustion chamber 1b, and the combustion chamber outlet due to the polishing effect of the supplementary fluid medium, desulfurizing agent, etc. The inside of the duct 2 and the inside of the inlet inclined duct 4 can be cleaned, and blockage of the combustion chamber outlet duct 2 and the inlet inclined duct 4 can be prevented.
Further, the unburned portion can be completely burned in the fluid medium recovery unit 5 by the air introduced from the air introduction nozzle 8 and the accumulation of fly ash or the like in the inlet inclined duct 4 can be prevented.

  As described above, in the circulating fluidized bed boiler described above, fly ash and fluid medium S in the duct (combustion outlet duct, expansion joint 3 and inlet inclined duct 4) due to gas flow rate decrease at the time of combustion load fluctuation or fuel change. As a result, stable operation can be performed over a wide combustion range (high turndown) and low-load operation is possible even when multiple types of fuels are switched for single combustion or mixed combustion. Become.

  Further, in this circulating fluidized bed boiler, expansion joints 3 are interposed between the combustion chamber outlet duct 2 and the inlet inclined duct 4, the exhaust gas outlet duct 9 of the fluid medium recovery unit 5, and the downcomer 6, respectively, Since the medium recovery unit 5 is self-supporting by the intermediate support structure by the support column 10, the furnace body 1 having the combustion chamber 1 b can also be self-supported by the intermediate support structure by the support column 10, and the support columns 10 that surround the entire circulating fluidized bed boiler. Is not necessary, and the columns 10 can be simplified, so that the material cost and the installation work cost can be greatly reduced, and the construction period can be shortened.

  3 to 5 show a large-scale circulating fluidized bed boiler according to another embodiment of the present invention. The circulating fluidized bed boiler burns in the furnace body 1 having a fluidized bed 1a and a combustion chamber 1b, and the furnace body 1. A cylindrical fluid medium collector 5 connected via the chamber outlet duct 2, the expansion joint 3 and the inlet inclined duct 4; a loop seal portion 7 connected to the fluid medium collector 5 via a downcomer 6; It is comprised from the duct 11 for circulation etc. which connects the loop seal part 7 and the furnace main body 1. FIG.

This large circulating fluidized bed boiler changes the position of the combustion chamber outlet 1c of the furnace body 1 and also changes the shape of the combustion chamber outlet duct 2, and the other configurations are the circulating flow shown in FIGS. Since the structure is the same as that of the bed boiler, the same reference numerals are assigned to the same parts and members as those of the circulating fluidized bed boiler shown in FIGS. 1 and 2, and the detailed description thereof is omitted.
This large circulating fluidized bed boiler can also achieve the same effects as the circulating fluidized bed boiler shown in FIGS.

  1 is a furnace body, 1a is a fluidized bed, 1b is a combustion chamber, 1c is a combustion chamber outlet, 1d is a return port, 2 is a combustion chamber outlet duct, 2a is a horizontal portion, 2b is a vertical portion, 2c is an inlet, 3 Expansion joint, 4 is an inlet inclined duct, 5 is a fluid medium collector, 5a is a cylindrical body, 5b is a conical part, 6 is a downcomer, 7 is a loop seal part, 7a is a partition wall, 7b is an overflow part, 8 Is an air injection nozzle, 9 is an exhaust gas outlet duct, 10 is a support column, 11 is a circulation duct, and α is an inclination angle of the inlet inclined duct.

Claims (9)

  A furnace body having a fluidized bed for combusting while fluidizing the fuel together with a fluidized medium, a combustion chamber for combusting while stirring and mixing the combustion gas and unburned components generated by combustion with the fluidized medium blown up from the fluidized bed, and a furnace A cylindrical shape that separates exhaust gas, fluidized ash, and fluidized ash discharged from the combustion chamber outlet provided at the top of the main body into exhaust gas, fly ash, and fluidized fluid by gravity acceleration and centrifugal acceleration, and recovers the fluidized medium from the exhaust gas. Circulating flow having a fluid medium recovery unit and a loop seal portion for returning the fluid medium separated and recovered while sealing between the inside of the furnace body and the fluid medium recovery unit from the fluid medium recovery unit to the fluidized bed in the furnace body It is a layer boiler, and the space between the combustion chamber outlet of the furnace main body and the inlet of the fluid recovery unit is connected to the combustion chamber outlet and connected to the horizontal portion and the horizontal portion, which is the minimum length in the structure. Vertical part The combustion chamber outlet duct is connected to the vertical portion of the combustion chamber outlet duct in a downward inclined posture through an expansion joint, and is connected in a communicating manner to the fluid medium collector in an inlet inclined duct connected in the tangential direction thereof. A circulating fluidized bed boiler characterized by that.   The circulating fluidized bed boiler according to claim 1, wherein an inclination angle α of the inlet inclined duct is set to 10 ° to 45 °.   Expansion joints are interposed between the exhaust gas outlet duct provided at the upper end of the fluid recovery device and the downcomer provided at the lower end of the fluid recovery device, respectively, and the fluid recovery device is self-supported by an intermediate support structure with a support. The circulating fluidized bed boiler according to claim 1 or 2, wherein the circulating fluidized bed boiler is provided.   The circulation according to claim 1 or 2, wherein the flow velocity of the exhaust gas flowing through the inlet inclined duct is set to 20 m / s or less at maximum load combustion, and no lower limit is set at low load combustion. Fluidized bed boiler.   The circulating fluidized bed boiler according to claim 3, wherein the combustion chamber and the fluid medium recovery unit are constituted by a water pipe panel, and the combustion chamber outlet duct, the inlet inclined duct, and the downcomer are each made of a refractory structure.   The combustion chamber, the fluid medium collector, the loop seal portion, the combustion chamber outlet duct, the inlet inclined duct, the downcomer, and the circulation duct connecting the loop seal portion and the furnace main body are each constituted by a water pipe panel. The circulating fluidized bed boiler according to 3.   The combustion chamber, the fluid medium recovery device, the loop seal portion, the combustion chamber outlet duct, the inlet inclined duct, the downcomer, and the circulation duct connecting the loop seal portion and the furnace body each have a refractory structure. The circulating fluidized bed boiler according to 3.   A replenishing fluid medium, desulfurizing agent and clinker inhibitor inlet is formed at the upper end of the vertical portion of the combustion chamber outlet duct, and the replenishing fluid medium, desulfurizing agent or clinker inhibitor is naturally dropped from the inlet. The circulating fluidized bed boiler according to claim 1, wherein any one or two or more of them are charged simultaneously.   The inlet inclined duct is provided with an air injection nozzle at a position parallel to and close to the bottom surface of the inlet inclined duct, and at least one of air or air, a supplementary fluid medium, a desulfurization agent, and a clinker inhibitor is provided from the air injection nozzle. The circulating fluidized bed boiler according to claim 1 or 2, wherein a mixed fluid with at least one of them is introduced.

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