JP2021071263A - Gas-gas heat exchanger - Google Patents

Abstract

To constitute a desired heat transfer pipe arrangement pattern on a gas circulation passage while suppressing increase of the number of rows of heat exchange bundles along a circulation direction of an exhaust gas.MEANS FOR SOLVING THE PROBLEM: A plurality of rows of heat exchange bundles 41 composed of heat transfer pipe groups in which a plurality of straight pipe portions 45 of heat transfer pipes 12 are arranged in a block shape while separating from each other, are disposed in series from an upstream side to a downstream side of an exhaust gas, and in each of the plurality of rows of the heat exchange bundles 41, the plurality of straight pipe portions 45 are disposed in a state of intersecting with an exhaust gas circulating direction. The plurality of heat exchange bundles 41 include a piping pattern hybrid bundle 41A in which a first arrangement pipe group 51 in which a piping pattern of the plurality of straight pipe portions 45 on a pipe orthogonal cross section substantially orthogonal to the straight pipe portions 45 has a first arrangement, and a second arrangement pipe group 52 which is disposed at a downstream side of the first arrangement pipe group 51 and in which a piping pattern of the plurality of straight pipe portions 45 has a second arrangement different from the first arrangement, are disposed in the same bundle and form the group of heat transfer pipes.SELECTED DRAWING: Figure 4

Description

The present invention relates to a gas gas heat exchanger that exchanges heat between a heat medium and exhaust gas.

In order to treat exhaust gas (smoke exhaust) from boilers used in thermal power plants, etc., air preheaters, GGH heat recovery devices, dust collectors, wet flue gas desulfurization devices, and GGH reheating are installed in the exhaust gas flow path. Exhaust gas treatment systems equipped with vessels are known. In the GGH heat recovery device, heat is recovered from the exhaust gas, and in the wet flue gas desulfurization device, a part of sulfur oxides and soot dust in the exhaust gas is removed by gas-liquid contact. The exhaust gas cooled to the saturated gas temperature in the wet flue gas desulfurization apparatus is heated in the GGH reheater using the heat recovered by the GGH heat recovery device, and then discharged from the chimney.

In Patent Document 1, in the exhaust gas treatment system, the gas flow passage of the GGH reheater is divided into an upstream region on the upstream side, a downstream region on the downstream side, and a middle basin region between the upstream region and the downstream region. A configuration is described in which heat exchange bundles (upstream bundle, midstream bundle, and downstream bundle) are arranged in the upstream region, the middle basin region, and the downstream region, respectively. A heat exchange bundle is a structure of a heat transfer tube group in which heat transfer tubes are combined and blocked (unitized) as a constituent unit of a heat transfer tube through which a heat medium flows. Patent Document 1 discloses an example in which each of the upstream bundle, the middle stream bundle, and the downstream bundle is composed of three stages of heat exchange bundles (upper stage bundle, middle stage bundle, and lower stage bundle) that are vertically stacked.

Further, in Patent Document 1, the heat transfer tube arrangement pattern of the upstream bundle of the GGH reheater is a staggered arrangement, the heat transfer tube arrangement pattern of the middle stream bundle and the downstream bundle is a square arrangement, and the heat medium passes from the upstream bundle to the downstream bundle. An example is described in which each bundle is configured to be connected so as to flow to the middle-stream bundle.

International Publication No. 2018/139669

In the GGH reheater of Patent Document 1, the upstream bundle, the middle stream bundle, and the downstream bundle function as a high temperature preheating section, a low temperature section, and a high temperature section, respectively, and the introduced exhaust gas is a staggered high temperature preheating section and a square low temperature section. Since the temperature is raised in the order of the part and the high temperature part, the efficiency of heat exchange in the GGH reheater can be improved. In addition, the efficiency with which the mist scattered from the wet flue gas desulfurization device collides with the heat transfer tube of the upstream bundle (mist evaporation efficiency in the high temperature preheating part) can be increased, and the mist adheres to the heat transfer tubes in the low temperature part and the high temperature part. It is possible to suppress an increase in pressure loss due to long-term use.

However, in the GGH reheater (gas gas heat exchanger) of Patent Document 1, three rows of heat transfer tube bundles (upstream bundle, middle flow bundle and downstream bundle) are provided along the flow direction of exhaust gas, and each row of heat transfer tube bundles is provided. Since the heat transfer tube arrangement pattern is set to the same arrangement pattern (staggered arrangement in the upstream bundle, square arrangement in the middle stream bundle and the downstream bundle), for example, two rows of heat transfer tube bundles are provided along the flow direction of the exhaust gas. In order to apply the configuration of Patent Document 1 to an existing gas gas heat exchanger, it is necessary to newly provide a one-row heat exchange bundle in addition to the existing two-row heat exchange bundle, which is a large scale. It needs to be repaired.

Therefore, an object of the present invention is to provide a gas gas heat exchanger capable of forming a desired heat transfer tube arrangement pattern in a gas flow passage while suppressing an increase in the number of rows of heat exchange bundles along the flow direction of exhaust gas. And.

In order to achieve the above object, the first aspect of the present invention is to provide a heat exchange bundle composed of a group of heat transfer tubes in which a plurality of linear tube portions of the heat transfer tubes are arranged in a block shape separated from each other on the upstream side of the exhaust gas. This is a gas gas heat exchanger in which a plurality of rows are arranged in series from the side to the downstream side, and a plurality of linear pipe portions are arranged so as to intersect the flow direction of exhaust gas in each of the plurality of rows of heat exchange bundles. The plurality of heat exchange bundles are provided in the first arrangement pipe group in which the piping pattern of the plurality of linear pipe portions in the pipe orthogonal cross section substantially orthogonal to the linear pipe portion is the first arrangement, and on the downstream side of the first arrangement pipe group. A second array tube group, which is a second array in which the piping patterns of the plurality of linear tube sections provided are different from the first array, includes a piping pattern mixed bundle provided in the same bundle to form a heat transfer tube group. ..

In the above configuration, since the first arrangement pipe group and the second arrangement pipe group having different piping patterns are provided in one heat exchange bundle, the number of rows of the heat exchange bundle along the flow direction of the exhaust gas can be increased. A desired heat transfer tube arrangement pattern can be formed in the gas flow passage while suppressing the heat transfer tube arrangement pattern.

A second aspect of the present invention is arranged as a reheater on the downstream side of the heat recovery device that recovers heat from the exhaust gas and on the downstream side of the desulfurization device that removes sulfur oxides in the exhaust gas by gas-liquid contact. In the gas gas heat exchanger of the first aspect, the plurality of heat exchange bundles include a pipe pattern mixed bundle and a downstream heat exchange bundle arranged on the downstream side of the pipe pattern mixed bundle. The first array tube group is a staggered array tube group in which a plurality of linear tube portions are arranged in a staggered manner. The second array tube group is a square array tube group in which a plurality of linear tube portions are arranged in a square grid pattern. A heat medium flows into the zigzag array tube group from the heat recovery device. The staggered arrangement tube group and the heat transfer tube group of the downstream heat exchange bundle are connected by the first connecting tube so that the heat medium flowing through the staggered arrangement tube group flows through the heat transfer tube group of the downstream side heat exchange bundle. .. The heat transfer tube group and the square array tube group of the downstream heat exchange bundle are connected by a second connecting tube so that the heat medium flowing through the heat transfer tube group of the downstream side heat exchange bundle flows through the square array tube group. ..

In the above configuration, the staggered arrangement tube group, the square arrangement tube group, and the downstream side heat exchange bundle (the heat transfer tube group constituting the downstream side heat exchange bundle) function as a high temperature preheating part, a low temperature part, and a high temperature part, respectively, and are introduced. Since the exhaust gas flows through the high-temperature preheating part in the staggered arrangement, the low-temperature part and the high-temperature part in the square arrangement in order to raise the temperature, the efficiency of heat exchange in the reheater (gas gas heat exchanger) can be improved. In addition, the efficiency at which the mist scattered from the desulfurization device collides with the linear tube portion of the staggered array tube group (mist evaporation efficiency in the high temperature preheating section) can be increased, and the mist to the heat transfer tube in the low temperature section and the high temperature section can be increased. Adhesion can be suppressed, and an increase in pressure loss due to long-term use can be suppressed.

The third aspect of the present invention is the gas gas heat exchanger of the second aspect, in which the linear tube portion of the staggered arrangement tube group is composed of the bare tube portion of the bare tube specification, and the straight tube portion of the square arrangement tube group. The shape tube portion and the linear tube portion of the downstream heat exchange bundle are composed of a finned pipe portion having a finned pipe specification.

In the above configuration, since the linear tube portion of the staggered array tube group is composed of the bare tube portion of the bare tube specification, the adhesion of mist to the heat transfer tube of the high temperature preheating section is suppressed and the increase in pressure loss due to aged use is suppressed. can do. In addition, since the linear tube part of the square array tube group and the linear tube part of the downstream heat exchange bundle are composed of the finned tube part of the finned tube specification, the efficiency of heat exchange in the low temperature part and the high temperature part can be improved. Can be enhanced.

A fourth aspect of the present invention is the gas gas heat exchanger of the third aspect, in which the fin pitch of the finned tube portion of the linear tube portion of the square array tube group is 5.0 mm or more and 10.0 mm or less. .. Further, the fifth aspect of the present invention is the gas gas heat exchanger of the third or fourth aspect, in which the fin pitch of the finned tube portion of the linear tube portion of the downstream heat exchange bundle is 5.0 mm or more. It is set to 10.0 mm or less.

With the above configuration, the problem that dust or the like is clogged between the adjacent pipes with fins over time is solved, so that the gas gas heat exchanger can be operated stably.

A sixth aspect of the present invention is the gas gas heat exchanger of any one of the second to fifth aspects, in which the flow velocity of the exhaust gas flowing between the linear pipe portions of the staggered arrangement pipe group is 8 m / s or more and 16 m or more. The staggered tube group is arranged so as to be less than / s.

In the above configuration, the mist removal rate (the removal rate of mist scattered from the desulfurization apparatus) can be increased in the first arrangement tube group (staggered arrangement tube group) on the upstream side in the reheater, and the mist removal performance can be improved. improves. For this reason, corrosion (corrosion due to mist) of the second array pipe group on the downstream side and the linear pipe part of the downstream heat exchange bundle (corrosion by the finned pipe part when the linear pipe part is composed of the finned pipe part). Can be reduced, and stable operation of the gas gas heat exchanger becomes possible.

According to the gas gas heat exchanger of the present invention, a desired heat transfer tube arrangement pattern can be formed in the gas flow passage while suppressing an increase in the number of rows of heat exchange bundles along the flow direction of exhaust gas.

It is a figure which shows typically the structural example of the exhaust gas treatment system provided with the gas gas heat exchanger which concerns on one Embodiment of this invention. It is a figure which shows typically the flow of the heat medium in the exhaust gas treatment system of FIG. It is a perspective view which shows typically the schematic structure of the GGH reheater of FIG. It is sectional drawing which shows the piping pattern of the linear tube part in the piping pattern mixed bundle of FIG. It is a figure which shows typically the structural example of the flue gas processing stem which divided into two systems of a GGH heat recovery device and a GGH reheater.

An embodiment of the present invention will be described with reference to the drawings. In the following description, the directions (sides) indicated by arrows X, -X, Y, -Y, Z, and -Z in the figure are forward (front side), rear (rear side), and right side (right side), respectively. , Left side (left side), upper side (upper side), lower side (lower side).

As shown in FIG. 1, an example of an air preheater (A / H) 3 and a gas gas heat exchanger (GGH: Gas Gas Heater) is provided in the exhaust gas flow path of the flue gas desulfurization stem (plant) S according to the present embodiment. GGH heat recovery device 4, Dust collector (EP: Electrostatic Precipitator) 5, Fan 6, Wet flue gas desulfurization device (FGD: Flue Gas Desulfurization) 7, GGH reheater 8 as an example of gas gas heat exchanger, And the chimneys 9 are provided in series, and the exhaust gas from the boiler 1 includes an air preheater 3, a GGH heat collector 4, a dust collector 5, a fan 6, a wet flue gas desulfurization device 7, and a GGH reheater 8. It is sequentially distributed and discharged from the chimney 9. In the present embodiment, the present invention is applied to the GGH reheater 8, but the present invention may be applied to the GGH heat recovery device 4. Further, the present invention may be applied to the GGH of another system. Further, a denitration device for removing nitrogen oxides in the exhaust gas may be installed between the boiler 1 and the air preheater 3.

In the air preheater 3, the exhaust gas is heat-exchanged with the combustion air to the boiler 1. The GGH heat recovery device 4 recovers heat from the exhaust gas, and the dust collector 5 removes most of the soot and dust in the exhaust gas. The fan 6 boosts the exhaust gas, and in the wet flue gas desulfurization apparatus 7, a part of sulfur oxides and soot dust in the exhaust gas is removed by gas-liquid contact. The exhaust gas cooled to the saturated gas temperature in the wet flue gas desulfurization apparatus 7 is heated (heat exchange, reheating) by using the heat recovered by the GGH heat recovery device 4 in the GGH reheater 8. , Is discharged from the chimney 9.

As shown in FIG. 2, in the smoke exhaust treatment system S of the present embodiment, the heat transfer tube 11 of the GGH heat recovery device 4 and the heat transfer tube 12 of the GGH reheater 8 are connected by a connecting pipe 13. The connecting pipe 13 is a connecting pipe 13A which is a flow path of the heat medium from the GGH heat recovery device 4 to the GGH reheater 8 and a flow path of the heat medium from the GGH reheater 8 to the GGH heat recovery device 4. It has a connecting pipe 13B. A heat medium circulation pump 14 is provided in the connecting pipe 13, and is a system (heat medium circulation system) in which the heat medium is circulated by the heat medium circulation pump 14. The heat medium circulation system is provided with a heat medium tank 15 for absorbing the expansion of the heat medium in the system. The heat medium temperature is controlled (above a predetermined temperature) in the connecting pipe 13A, which is the flow path of the heat medium from the GGH heat recovery device 4 to the GGH reheater 8, in order to enable stable operation under various conditions. A heat medium heater 16 for controlling) is provided.

As shown in FIG. 3, the GGH heat recovery device 4 and the GGH reheater 8 have a housing 31 as a housing. The housing 31 has a bottom plate (lower cover) 32, a back plate (back cover) 33, and a top plate (upper cover) 34. An inter-bundle cover 35 extending in the vertical direction is supported on the front portion of the housing 31. A plurality of bundle-to-bundle covers 35 extend in the vertical direction (vertical direction) and are arranged at a predetermined interval in the left-right direction (exhaust gas flow direction). The area covered by the inter-bundle cover 35 is a space that can be accessed by an operator during inspections, parts replacement, and the like.

A plurality of heat exchange bundles 41 are housed inside the housing 31. The heat exchange bundle 41 is a structure of a heat transfer tube group in which heat transfer tubes 11 and 12 are combined and blocked (unitized) as a constituent unit of the heat transfer tubes 11 and 12 through which the heat medium flows. Each heat exchange bundle 41 is composed of a group of heat transfer tubes in which a plurality of linear tube portions 45 of the heat transfer tubes 11 and 12 are arranged in a block shape so as to be separated from each other. A plurality of rows of heat exchange bundles 41 in the housing 31 are arranged in series from the upstream side to the downstream side of the exhaust gas, and in each of the plurality of rows of heat exchange bundles 41, a plurality of linear pipe portions 45 flow the exhaust gas. Arranged so as to intersect the direction. In the present embodiment, the exhaust gas flow direction is set to be substantially horizontal (right direction in the figure), and the linear pipe portion 45 is linear in the substantially horizontal direction (front-back direction in the figure) so as to be substantially orthogonal to the exhaust gas flow direction. It extends like a shape.

Each heat exchange bundle 41 has a first header 42 and a second header 43. The first and second headers 42 and 43 are formed in a columnar shape extending in the vertical direction. Each of the headers 42 and 43 is formed in a shape in which the inside is hollow and the upper and lower ends are closed, and a flowable space is formed inside. Further, mounting plates 44 projecting in the left-right direction are supported on the headers 42 and 43.

The linear tube portions 45 of the heat transfer tubes 11 and 12 extending rearward are supported on the rear surfaces of the headers 42 and 43. The heat transfer tubes 11 and 12 are configured to be curved at the rear end or the front end of the linear tube portion 45 so as to reciprocate in the front-rear direction a plurality of times inside the housing 31. A plurality of heat transfer tubes 11 and 12 are supported on the headers 42 and 43 at intervals in the vertical direction. Both ends of the heat transfer tubes 11 and 12 are supported by the headers 42 and 43, and the heat medium can be taken in and out of the heat transfer tubes 11 and 12 from the headers 42 and 43.

The linear tube portions 45 of the heat transfer tubes 11 and 12 are supported by the support member 47 at the central portion in the front-rear direction. The support member 47 is formed in a plate in which a plurality of holes through which the heat transfer tubes 11 and 12 pass are formed. Therefore, the heat transfer tubes 11 and 12 are not supported in the cantilever state only by the headers 42 and 43, but are held by the headers 42 and 43 and the support member 47. Although one support member 47 is shown in the front-rear direction and the left-right direction, a plurality of support members 47 may be provided in the front-rear direction or a plurality of support members 47 in the left-right direction depending on the lengths of the heat transfer tubes 11 and 12. Good.

A plug hole 48 is formed in each of the headers 42 and 43 at positions corresponding to the heat transfer tubes 11 and 12. The plug hole 48 is a hole that penetrates in the front-rear direction, and its rear end is connected to the inlet or outlet of the heat transfer tubes 11 and 12. Further, the front end of the plug hole 48 is closed with a plug (not shown) during normal use. If any of the heat transfer tubes 11 and 12 fails and the heat medium leaks out, remove the plug in the plug hole 48 and close the inlet or outlet of the heat transfer tubes 11 and 12 through the plug hole 48 (not shown). It is possible to stop the leakage of the heat medium by closing it.

A casing plate 49 is detachably supported between the headers 42 and 43. The casing plate 49 has a height corresponding to the height of the headers 42 and 43 in the vertical direction. The casing plate 49 is detachably supported on the mounting plate 44 by bolts (not shown). The method of detachably fixing the casing plate 49 to the mounting plate 44 is not limited to bolts. By attaching the casing plate 49, the headers 42 and 43 are connected, the headers 42 and 43 and the heat transfer tubes 11 and 12 are integrated in a state of having high rigidity, and the exhaust gas leaks from between the headers 42 and 43. Is suppressed.

The heat exchange bundle 41 is configured to be housed in the housing 31 as one unit. When the heat exchange bundle 41 is housed in the housing 31, exhaust gas flows inside the bottom plate 32, the back plate 33, the top plate 34, the inter-bundle cover 35, the headers 42, 43, and the casing plate 49. The road is constructed. Heat transfer tubes 11 and 12 are arranged in the gas flow passage so that heat can be exchanged with the exhaust gas flowing through the gas flow passage.

In each of the GGH heat recovery device 4 and the GGH reheater 8 of the present embodiment, the heat exchange bundles 41 are arranged in two rows along the flow direction of the exhaust gas, and the heat exchange bundles 41 are arranged in two rows in the vertical direction in each row. Four heat exchange bundles 41 are provided so as to be stacked in a tier. The two-stage heat exchange bundle 41 on the upstream side constitutes the upstream bundle (upstream heat exchange bundle) 41A, and the two-stage heat exchange bundle 41 on the downstream side each constitutes the downstream bundle (downstream heat exchange bundle). ) 41B is configured. In the present embodiment, in each row, the lower ends of the headers 42 and 43 of the upper heat exchange bundle 41 are directly stacked on the upper end of the lower heat exchange bundle 41 and fixed with bolts (not shown). In the following description, the two-stage heat exchange bundle 41 on the upstream side may be collectively referred to as the upstream bundle 41A, and the two-stage heat exchange bundle 41 on the downstream side may be collectively referred to as the downstream bundle 41B. Further, the number of rows of the heat exchange bundle 41 may be 3 or more, and the number of stages of the heat exchange bundle 41 in each row is 1 stage (1 row is composed of a single heat exchange bundle 41) or 3 or more stages. There may be.

As shown in FIG. 2, the upstream bundle 41A and the downstream bundle 41B of the GGH heat recovery device 4 are connected at each part by a connecting pipe 61, and a heat medium is provided between the upstream bundle 41A and the downstream bundle 41B. Is configured to be movable. Further, the GGH heat recovery device 4 of the present embodiment is configured so that the heat medium flows from the downstream bundle 41B to the upstream bundle 41A. When the heat medium flows from the upstream bundle 41A to the downstream bundle 41B, the temperature difference between the heat medium and the exhaust gas is maximized in the upstream bundle 41A, and the heat medium warmed by the upstream bundle 41A in the downstream bundle 41B. In this embodiment, the heat medium flows from the downstream bundle 41B to the upstream bundle 41A because the temperature difference from the exhaust gas cooled by heat exchange in the upstream bundle 41A becomes small and the efficiency of heat exchange decreases. It is configured as follows.

In the present embodiment, the upstream bundle 41A of the GGH reheater 8 is configured as a piping pattern mixed bundle. The pipe pattern mixed bundle is a heat exchange bundle 41 configured so that the pipe patterns of a plurality of linear pipe portions 45 in a pipe orthogonal cross section substantially orthogonal to the linear pipe portion 45 are different on the upstream side and the downstream side. In the example of the upstream bundle 41A shown in FIG. 4, of the 10 rows of linear pipes 45 arranged in the gas flow direction, the two rows on the upstream side are arranged in a staggered pattern (first array pipe group). The number is 51, and the group of square arrangement pipes (second arrangement pipe group having a piping pattern different from that of the first arrangement pipe group) 52 in which eight rows on the downstream side are arranged in a square grid pattern is used. In the present embodiment, the distance L1 between the rows of the linear tube portions 45 of the two adjacent rows in the staggered tube group 51 and the two rows adjacent to each other across the boundary between the staggered tube group 51 and the square array tube group 52. The inter-row distance L2 of the linear tube portion 45 and the inter-row distance L3 of the two adjacent linear tube portions 45 in the square array tube group 52 are set to substantially the same distance (L1 = L2 = L3). There is.

The downstream bundle 41B of the GGH reheater 8 of the present embodiment is configured as a piping pattern non-mixed bundle (pipe pattern single bundle). The pipe pattern non-mixed bundle is a heat transfer tube bundle 41 set in the same pipe pattern (square arrangement in this embodiment) in the entire area (all rows) from the upstream side to the downstream side. The upstream bundle 41A and the downstream bundle 41B of the GGH heat recovery device 4 of the present embodiment are all in the entire area (all rows) from the upstream side to the downstream side, similarly to the downstream bundle 41B of the GGH reheater 8. , A pipe pattern non-mixed bundle composed of the same pipe pattern (square arrangement in this embodiment).

In the square arrangement, the exhaust gas comes into contact with the linear pipe 45 in the most upstream row of the plurality of rows, but on the downstream side thereof, the linear pipes 45 in the second and subsequent rows are in the most upstream row with respect to the flow direction of the exhaust gas. Since it is hidden behind the linear pipe 45, the contact with the exhaust gas is reduced, and the contact is reduced, so that the exhaust gas easily flows. On the other hand, in the staggered arrangement, the linear pipes 45 in the second and subsequent rows (second row in this embodiment) are less likely to be behind the linear pipes 45 in the front row (first row in this embodiment), and the exhaust gas is generated. The number of contacts increases, but it becomes a resistance to the exhaust gas. In addition, the exhaust gas is rectified because it becomes a resistance to the exhaust gas.

In the GGH reheater 8 of the present embodiment, the heat medium flowing out from the GGH heat recovery device 4 flows through the connecting pipe 13A and flows into the heat medium inlet of the staggered arrangement pipe group 51. The heat medium outlet of the staggered arrangement tube group 51 and the heat medium inlet of the heat transfer tube group of the downstream bundle 41B are such that the heat medium flowing through the staggered arrangement tube group 51 flows through the heat transfer tube group of the downstream bundle 41B. It is connected by a first connecting pipe 62. The heat medium outlet of the heat transfer tube group of the downstream bundle 41B and the heat medium inlet of the square array tube group 52 are such that the heat medium flowing through the heat transfer tube group of the downstream bundle 41B flows through the square array tube group 52. It is connected by a second connecting pipe 63. The heat medium from the downstream bundle 41B flows into the heat medium inlet of the square array tube group 52. The heat medium flowing out of the square array tube group 52 and flowing out from the heat medium outlet of the square array tube group 52 passes through the connecting pipe 13B and returns to the GGH heat recovery device 4.

In this way, the staggered array tube group 51, the square array tube group 52, and the downstream bundle 41B (the heat transfer tube group constituting the downstream bundle 41B) function as a high temperature preheating section, a low temperature section, and a high temperature section, respectively, and are introduced. The exhaust gas flows through the high-temperature preheating part in a staggered arrangement, the low-temperature part in a square arrangement, and the high-temperature part in this order to raise the temperature. By first introducing the heat medium into the upstream staggered arrangement tube group 51, the heat medium flows into the staggered arrangement tube group 51 in the hottest state, and the mist from the wet flue gas desulfurization apparatus 7 easily evaporates quickly. .. Further, since the heat medium flows from the downstream bundle 41B on the downstream side to the square array tube group 52 in the middle flow, the temperature of the heat medium becomes higher in the downstream side than in the middle flow. When the temperature of the heat medium is lower in the downstream than in the middle stream, the exhaust gas is warmed by the high temperature middle stream and then passes through the low temperature downstream, so that the exhaust gas is hard to warm in the downstream stream and the heat exchange efficiency is low. On the other hand, when the temperature of the heat medium is higher in the downstream than in the middle stream as in the present embodiment, the exhaust gas is warmed in the order of the low temperature middle stream to the high temperature downstream, so that the efficiency of heat exchange is improved. ..

In the GGH heat recovery device 4 of the present embodiment, in both the upstream bundle 41A and the downstream bundle 41B, the linear tube portion 45 of the heat transfer tube 11 is provided with a fin having a large number of fold-shaped fins. It consists of a tube part. By forming the pipe portion with fins, the contact area with the exhaust gas becomes larger and the efficiency of heat exchange is improved as compared with the case where the pipe portion has a bare pipe specification without fins.

In the GGH reheater 8 of the present embodiment, the linear tube portion 45 of the staggered arrangement tube group 51 is composed of a bare tube portion, and the linear tube portion 45 of the square arrangement tube group 52 and the linear tube portion of the downstream bundle 41B. 45 is composed of a pipe portion with fins. When the linear pipe portion 45 of the staggered arrangement pipe group 51 is composed of a pipe portion with fins, mist from the wet flue gas desulfurization apparatus 7 adheres and is easily corroded. Since the linear tube portion 45 is composed of a bare tube portion, it is less likely to corrode than a case where the linear tube portion 45 is composed of a tube portion with fins.

In the GGH heat recovery device 4, the square arrangement reduces ash erosion (a phenomenon in which the surface of the heat transfer tube is roughened or scraped by coal ash in the exhaust gas). In the GGH heat recovery device 4, contact with the exhaust gas is ensured by forming the tube portion with fins. Further, in the staggered arrangement tube group 51 of the GGH reheater 8, mist from the wet flue gas desulfurization apparatus 7 easily flows in, and the staggered arrangement increases the contact probability with the mist and facilitates the removal of the mist. There is.

Further, in order to alleviate the corrosive environment in the finned pipe portion of the GGH reheater 8 and perform stable operation, the mist removal efficiency in the staggered arrangement pipe group 51 on the upstream side of the finned pipe portion is 60%. The above is desirable, and for that purpose, the gas flow velocity flowing between the linear pipe portions (bare pipe portions in this embodiment) 45 of the staggered arrangement tube group 51 is in the range of 8 m / s to 16 m / s. It is preferable to arrange the linear tube portion (bare tube portion) 45 of the staggered arrangement tube group 51.

Further, by setting the fin pitch of the finned pipe portion of the GGH reheater 8 (the finned pipe portion of at least one of the square array pipe group 52 and the downstream bundle 41B) to 5.0 mm to 10.0 mm, the fins are attached. The problem that the pipe part is clogged with dust over time is solved, and more stable operation becomes possible.

As described above, according to the present embodiment, in the GGH reheater 8, the first arrangement tube group (staggered arrangement tube group) having different piping patterns in one heat exchange bundle 41 (upstream side bundle 41A). ) 51 and the second arrangement tube group (square arrangement tube group) 52 are provided, so that a desired heat transfer tube arrangement pattern can be obtained while suppressing an increase in the number of rows of the heat exchange bundle 41 along the flow direction of the exhaust gas. It can be configured as a gas flow passage.

Further, the staggered tube group 51, the square tube group 52, and the downstream bundle 41B (the heat transfer tube group constituting the downstream bundle 41B) function as a high temperature preheating section, a low temperature section, and a high temperature section, respectively, and the introduced exhaust gas. Is able to improve the efficiency of heat exchange in the GGH reheater 8 because the high temperature preheating part in the staggered arrangement, the low temperature part and the high temperature part in the square arrangement are sequentially circulated to raise the temperature. In addition, the efficiency at which the mist scattered from the wet flue gas desulfurization apparatus 7 collides with the linear tube portion 45 of the staggered array tube group 51 (mist evaporation efficiency in the high temperature preheating section) can be increased, and the low temperature section and the high temperature section Adhesion of mist to the heat transfer tube 12 can be suppressed, and an increase in pressure loss due to long-term use can be suppressed.

Further, since the linear tube portion 45 of the staggered array tube group 51 is composed of a bare tube portion, it is possible to suppress the adhesion of mist to the heat transfer tube 12 of the high temperature preheating section and suppress the increase in pressure loss due to aged use. it can. Further, since the linear tube portion 45 of the square array tube group 52 and the linear tube portion 45 of the downstream bundle 41B are composed of the tube portion with fins, the efficiency of heat exchange in the low temperature portion and the high temperature portion can be improved. it can.

Further, by optimizing the gas flow velocity flowing through the linear pipe portion (bare pipe portion in this embodiment) 45 of the staggered arrangement pipe group 51 and optimizing the fin pitch of the finned pipe portion, corrosion of the finned pipe portion is prevented. It is possible to prevent clogging due to dust and dust, and stable operation is possible.

The present invention is not limited to the above-described embodiment and modification described as an example, and is not limited to the above-described embodiment and the like as long as it does not deviate from the technical idea of the present invention. , Various changes are possible depending on the design and the like.

For example, as shown in FIG. 5, the present invention is applied to a smoke exhaust treatment stem S in which the GGH heat recovery device 4 and the GGH reheater 8 are divided into a plurality of systems (two systems in the example of FIG. 5), and a plurality of GGH At least one of the heat recovery devices 4 and at least one of the plurality of reheaters 8 may be configured as in the above embodiment.

Further, in the above embodiment, the exhaust gas flow direction is set to a substantially horizontal direction, and the direction in which the linear pipe portion 45 extends (extension direction) is set to a substantially horizontal direction substantially orthogonal to the exhaust gas flow direction. And the extending direction of the linear pipe portion 45 is not limited to the above, and is set to another direction (the exhaust gas flow direction is set to be substantially horizontal, and the extending direction of the linear pipe portion 45 is set to the vertical direction (approximately vertical direction). ) May be set.

1: Boiler 3: Air preheater (A / H)
4: GGH heat recovery device (gas gas heat exchanger)
5: Dust collector (EP)
6: Fan 7: Wet flue gas desulfurization device 8: GGH reheater (gas gas heat exchanger)
9: Chimneys 11, 12: Heat transfer tubes 13, 13A, 13B: Connecting pipe 31: Housing 41: Heat exchange bundle 41A: Upstream bundle (upstream heat exchange bundle, piping pattern mixed bundle)
41B: Downstream bundle (downstream heat exchange bundle)
42: First header 43: Second header 45: Straight pipe portion 49: Casing plate 51: Staggered arrangement pipe group (first arrangement pipe group)
52: Square array tube group (second array tube group)
61: Connection pipe S: Smoke exhaust treatment system

Claims (6)

A plurality of rows of heat exchange bundles composed of a group of heat transfer tubes in which a plurality of linear tube portions of the heat transfer tubes are arranged in a block shape separated from each other are arranged in series from the upstream side to the downstream side of the exhaust gas, and the plurality of rows are arranged. A gas gas heat exchanger in which the plurality of linear pipe portions are arranged so as to intersect the flow direction of exhaust gas in each of the heat exchange bundles of the above.
The plurality of heat exchange bundles include a first arrangement pipe group in which the piping patterns of the plurality of linear pipe portions in a pipe orthogonal cross section substantially orthogonal to the linear pipe portion are the first arrangement, and the first arrangement pipe group. A second array tube group, which is provided on the downstream side of the above and has a second arrangement in which the piping patterns of the plurality of linear tube portions are different from the first arrangement, is provided in the same bundle to form the heat transfer tube group. A gas gas heat exchanger characterized by including a piping pattern mixed bundle. The gas-gas heat exchange according to claim 1, which is arranged as a reheater on the downstream side of the heat recovery device that recovers heat from the exhaust gas and on the downstream side of the desulfurization device that removes sulfur oxides in the exhaust gas by gas-liquid contact. It ’s a vessel,
The plurality of heat exchange bundles include the pipe pattern mixed bundle and a downstream heat exchange bundle arranged on the downstream side of the pipe pattern mixed bundle.
The first array tube group is a staggered array tube group in which the plurality of linear tube portions are arranged in a staggered manner.
The second array tube group is a square array tube group in which the plurality of linear tube portions are arranged in a square grid pattern.
A heat medium flows into the staggered tube group from the heat recovery device, and the heat medium flows into the staggered tube group.
The staggered arrangement tube group and the heat transfer tube group of the downstream side heat exchange bundle are first connected so that the heat medium flowing through the staggered arrangement tube group flows through the heat transfer tube group of the downstream side heat exchange bundle. Connected by a pipe,
The heat transfer tube group and the square array tube group of the downstream heat exchange bundle are secondly connected so that the heat medium flowing through the heat transfer tube group of the downstream side heat exchange bundle flows through the square array tube group. A gas-gas heat exchanger characterized by being connected by pipes. The gas gas heat exchanger according to claim 2.
The linear tube portion of the staggered array tube group is composed of a bare tube portion having a bare tube specification.
A gas gas heat exchanger characterized in that the linear tube portion of the square array tube group and the linear tube portion of the downstream side heat exchange bundle are composed of a finned tube portion of a finned tube specification. .. The gas gas heat exchanger according to claim 3.
A gas gas heat exchanger characterized in that the fin pitch of the finned tube portion of the linear tube portion of the square array tube group is 5.0 mm to 10.0 mm. The gas gas heat exchanger according to claim 3 or 4.
A gas gas heat exchanger characterized in that the fin pitch of the finned pipe portion of the linear pipe portion of the downstream side heat exchange bundle is 5.0 mm to 10.0 mm. The gas gas heat exchanger according to any one of claims 2 to 5.
A gas gas heat exchanger characterized in that the staggered pipe group is arranged so that the flow velocity of the exhaust gas flowing between the linear pipe portions of the staggered pipe group is 8 m / s to 16 m / s.

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