WO2022065082A1

WO2022065082A1 - Spray piping structure for flue gas desulfurization apparatus

Info

Publication number: WO2022065082A1
Application number: PCT/JP2021/033365
Authority: WO
Inventors: 佑一山根; 紀和稲葉; 晴佳木村; 晶寛上神; 一大倉
Original assignee: 三菱重工業株式会社
Priority date: 2020-09-25
Filing date: 2021-09-10
Publication date: 2022-03-31
Also published as: JP2022054258A

Abstract

A first spray pipe 12 extends from a first base end section 12A towards a first free end section 12B, with the ends being respectively on one side and the intermediate side along the direction 10 of extension of the piping, is secured to an absorbent tower at the side of the first base end section 12A, and feeds an absorbent to a first spray nozzle. A second spray pipe 13 extends from a second base end section 13A towards a second free end section 13B, with the ends being respectively on the other side and the intermediate side along the direction 10 of extension of the piping, is secured to the absorbent tower at the side of the second base end section 13A, and feeds an absorbent to a second spray nozzle. The first spray pipe 12 and the second spray pipe 13 are aligned in a colinear fashion. The first free end section 12B and the second free end section 13B are either proximate to or in contact with each other and are coupled in a mutually supporting manner restricting the sections from being relatively displaced in a direction traverse to the direction 10 of extension of the piping.

Description

Spray piping structure of flue gas desulfurization equipment

The present invention relates to a spray piping structure of a flue gas desulfurization apparatus.

A desulfurization device (wet limestone-plaster flue gas desulfurization device) has been put into practical use as a device for removing sulfur oxides from exhaust gas containing sulfur oxides generated in coal-fired boilers of thermal power plants. Some conventional desulfurization devices are provided with an absorption tower that divides the gas flow space, and a plurality of spray nozzles are arranged in the gas flow space. Sulfur oxides are removed from the exhaust gas by injecting and contacting the exhaust gas introduced into the absorption tower and flowing downward in the gas flow space from the lower side to the upper side by injecting the absorbing liquid downward from each spray nozzle.

In the desulfurization device that injects the absorption liquid from the spray nozzle, the spray pipe for supplying the absorption liquid to the spray nozzle is inserted into the gas flow space of the absorption tower. In the conventional piping structure of the spray pipe, the base end portion of both ends (base end portion and tip portion) of the spray pipe inserts the peripheral wall on one side of the absorption tower, and the tip portion is located in the gas flow space. A structure is known in which a spray tube is arranged so as to extend in a straight line substantially horizontally from the end to the tip, and an absorbent liquid is sent from the base end side to the tip side (for example, patented). Document 1). Since the absorbing liquid is sprayed over the entire cross section of the flow path of the gas flow space, the length of the spray pipe from the base end to the tip should be such that the tip approaches the inner surface of the peripheral wall on the other side of the absorption tower. Set.

Gazette No. 6-61423

In the plant that desulfurizes the exhaust gas from the boiler, there is a plant that installs one desulfurization device for the exhaust gas for one boiler, and there is a plant that treats the exhaust gas from multiple boilers with one desulfurization device. In a plant that treats exhaust gas from a plurality of boilers with one desulfurization device, the amount of exhaust gas (processed gas amount) treated by the desulfurization device is large. In addition, the amount of processing gas is also large in the case of a boiler that uses coal as fuel, which has a large amount of water and a small calorific value, such as lignite.

In order to optimize the desulfurization efficiency in the desulfurization equipment, the gas flow velocity passing through the gas flow space of the absorption tower must be within a certain range (range that does not exceed the predetermined upper limit flow velocity). Therefore, when the amount of treated gas increases, it is necessary to increase the cross-sectional area (flow path cross-sectional area) of the gas flow space so that the gas flow velocity does not exceed the upper limit flow velocity.

However, if the cross-sectional area of the flow path of the gas flow space is increased, the length of the spray pipe from the base end to the tip portion increases in the gas flow space, and the spray pipe becomes heavier. Further, the distance (liquid feeding distance) for feeding the absorbed liquid by one spray tube in the absorption tower increases, and the number of spray nozzles to be fed increases, so that the tube diameter of the spray tube increases. For example, in a spray tube whose diameter is reduced so as to taper from the proximal end portion toward the distal end portion, the tube diameter on the proximal end portion side increases and the spray tube becomes heavier. Therefore, the support structure for supporting the spray tube may be complicated.

In addition, since the liquid feeding distance of the spray pipe in the absorption tower increases, the required head (total length) of the pump (absorbent liquid circulation pump) for feeding the absorbed liquid becomes large. In addition, as the amount of processing gas increases, the required amount of absorbent liquid supplied (absorbent liquid circulation amount) also increases, and the pump capacity also increases. As a result, the size of the pump becomes large, and layout restrictions increase inside the pump chamber that houses the pump outside the collection tower.

Furthermore, even when the size of the pump is increased, there is a limit to suppressing the deterioration of the liquid feeding performance (variation in the liquid feeding amount) due to the increase in the liquid feeding distance, and the injection amount (spray amount) of the absorbed liquid from the spray nozzle is limited. ) Is relatively difficult to maintain uniformity.

Therefore, according to the present invention, even when the flow path cross section of the gas flow space is increased, the amount of the absorbed liquid injected from the spray nozzle is uniform while suppressing the complexity of the support structure of the spray pipe and the increase in the size of the pump. The purpose is to provide a spray piping structure that can maintain the properties.

In order to achieve the above object, the first aspect of the present invention is a spray piping structure of a flue gas desulfurization apparatus, which includes a first spray pipe and a second spray pipe. In the flue gas desulfurization apparatus, the peripheral wall of the absorption tower divides the gas flow space extending in the vertical direction, and the exhaust gas flows through the gas flow space from the bottom to the top, and a plurality of first spray nozzles and a plurality of second spray nozzles are included. The spray nozzle is placed in the gas flow space inside the absorption tower. An absorption liquid is supplied from the spray nozzle into the exhaust gas flowing through the gas distribution space, and the sulfur oxides in the exhaust gas are absorbed by the absorption liquid.

The first spray tube has a first base end portion and a first tip end portion. The first base end portion is arranged on one side in the pipe extending direction set linearly so as to cross the gas flow space substantially horizontally. The first tip portion is arranged on the central side in the pipe extension direction. The first spray pipe extends linearly from the first base end portion to the first tip portion along the pipe extending direction, and the first base end portion side is fixedly supported with respect to the absorption tower. The first spray tube sends the absorbing liquid from the first base end side to the first tip side and supplies the absorbing liquid to the first spray nozzle.

The second spray tube has a second base end portion and a second tip end portion. The second base end portion is arranged on the other side in the pipe extension direction. The second tip portion is arranged on the central side in the pipe extension direction. The second spray pipe extends linearly from the second base end portion toward the second tip portion along the pipe extending direction, and the second base end portion side is fixedly supported by the absorption tower. The second spray tube sends the absorbing liquid from the second base end side to the second tip side and supplies the absorbing liquid to the second spray nozzle.

The first spray pipe and the second spray pipe are lined up in a straight line. The first tip portion and the second tip portion are close to each other or in contact with each other, and are connected in a state of supporting each other so as to restrict relative movement in the direction crossing the pipe extension direction.

In the above configuration, in the gas flow space of the absorption tower, the first spray pipe is arranged in the region on one side in the pipe extension direction, the second spray pipe is arranged in the region on the other side, and the first spray pipe is used. It extends in a straight line with the second spray tube. That is, in the flow path cross section (horizontal cross section) of the gas flow space, the absorption liquid is supplied to substantially the entire area in the pipe extending direction by the first spray pipe and the second spray pipe. Therefore, the liquid feeding distance of the absorbed liquid by one spray pipe is shortened as compared with the case where the absorbed liquid is supplied by one spray pipe to substantially the entire area in the pipe extension direction (when a single spray pipe is used). It is possible to suppress an increase in the tube diameter of the spray tube. Further, the first spray tube is cantilevered and supported on the first base end side, the second spray tube is cantilevered and supported on the second base end side, and the first tip and the second tip are pipes. Since they are connected in a state of supporting each other so as to regulate the relative movement in the extending direction and the crossing direction, the spray pipe (connected spray pipe) composed of the first spray pipe and the second spray pipe is Both ends are supported. Therefore, it is possible to suppress the complexity of the support structure of the spray tube as compared with the case of using a single spray tube.

Since the liquid feeding distance of one spray pipe in the absorption tower can be shortened and the increase in the diameter of the spray pipe can be suppressed, it is possible to suppress the increase in size of the pump for feeding the absorbed liquid. can.

Since the liquid feeding distance of one spray tube can be shortened, the uniformity of the injection amount of the absorbed liquid from the spray nozzles (first spray nozzle and second spray nozzle) can be maintained.

Furthermore, the spray pipe that crosses the gas flow space becomes a flow resistance of the exhaust gas, but by providing a connected spray pipe instead of the single spray pipe, it is possible to suppress an increase in the pipe diameter of the spray pipe. As a result, the distribution resistance of the exhaust gas can be reduced, and an increase in the load of the fan that distributes the exhaust gas can be suppressed.

The second aspect of the present invention is the spray piping structure of the first aspect, in which the first tip portion and the second tip portion are separated so as to allow relative movement along the pipe extension direction. Connected in the state.

In the above configuration, the first tip portion and the second tip portion are connected in a separated state so as to allow relative movement along the pipe extension direction, so that the total length of the connecting spray pipe is not restricted. Therefore, even when the first spray tube and the second spray tube are made of a non-metal having a high linear expansion coefficient (for example, a resin material such as fiber reinforced plastic (FRP)), the first spray tube is formed. It is possible to prevent damage to the pipe, the second spray pipe, and the peripheral wall of the absorption tower.

A third aspect of the present invention is the spray piping structure of the first or second aspect, in which the end face opening of the first tip portion and the end face opening of the second tip portion are closed so that the absorbing liquid cannot flow out. ing.

In the above configuration, the end face opening of the first tip portion and the end face opening of the second tip portion are closed so that the absorbing liquid cannot flow out, so that the absorbing liquid can flow between the first tip portion and the second tip portion. Not distributed. That is, the absorption liquid is supplied to the first spray nozzle only from the first spray tube, and the absorption liquid is supplied to the second spray nozzle only from the second spray tube. Therefore, the uniformity of the injection amount of the absorbing liquid from each of the first spray nozzles and the second spray nozzles can be easily maintained.

A fourth aspect of the present invention is the spray piping structure of the first to third aspects, in which the liquid feeding distance of the first spray pipe from the first base end portion to the first tip end portion and the second base end portion. The liquid feeding distance of the second spray pipe from the portion to the second tip portion is set to be substantially equal.

With the above configuration, the liquid feeding distance of the absorbing liquid can be halved as compared with the case of using a single spray tube.

The fifth aspect of the present invention is the spray piping structure of the first to fourth aspects, which includes a third spray pipe and a fourth spray pipe. The plurality of spray nozzles includes a plurality of third spray nozzles and a plurality of fourth spray nozzles.

The third spray tube has a third base end portion and a third tip end portion. The third base end portion is arranged on one side of the second pipe extending direction, which is set linearly so as to cross the gas flow space substantially horizontally below the pipe extending direction. The third tip portion is arranged on the central side in the second pipe extension direction. The third spray pipe extends linearly from the third base end portion toward the third tip portion along the extension direction of the second pipe, and the third base end portion side is fixedly supported by the absorption tower. Will be done. The third spray tube sends the absorbing liquid from the third base end side to the third tip side and supplies the absorbing liquid to the third spray nozzle.

The 4th spray tube has a 4th base end portion and a 4th tip end portion. The fourth base end portion is arranged on the other side in the second pipe extension direction. The fourth tip portion is arranged on the central side in the second pipe extension direction. The fourth spray pipe extends linearly from the fourth base end portion toward the fourth tip portion along the extension direction of the second pipe, and the fourth base end portion side is fixedly supported by the absorption tower. Will be done. The 4th spray tube sends the absorbing liquid from the 4th base end side to the 4th tip side and supplies the absorbing liquid to the 4th spray nozzle.

The 3rd spray pipe and the 4th spray pipe are lined up in a straight line. The third tip portion and the fourth tip portion are close to each other or in contact with each other, and are connected in a state of supporting each other so as to restrict relative movement in the direction intersecting with the second pipe extension direction.

The first spray pipe and the second spray pipe constitute the upper connecting spray pipe. The third spray pipe and the fourth spray pipe form a lower connecting spray pipe. The upper connecting spray pipe and the lower connecting spray pipe are connected by a plurality of auxiliary members forming a truss structure.

In the above configuration, it is not necessary to install a spray pipe support beam that supports the spray pipes (first to fourth spray pipes) from below in the absorption tower, so that the support structure of the spray pipe can be simplified.

According to the present invention, even when the cross section of the flow path of the gas flow space is increased, the amount of the absorbed liquid injected from the spray nozzle can be reduced while suppressing the complexity of the support structure of the spray pipe and the increase in the size of the pump. Uniformity can be maintained.

It is a right side view schematically showing the flue gas desulfurization apparatus which concerns on 1st Embodiment of this invention. It is a front view of FIG. FIG. 3 is a plan view (cross-sectional view taken along the line III-III) of the spray piping structure of FIG. It is a side view of the spray piping structure of FIG. It is sectional drawing of the main part side of FIG. It is a main part side sectional view of the spray piping structure which concerns on 2nd Embodiment of this invention. It is a main part side sectional view of the spray piping structure which concerns on 3rd Embodiment of this invention. It is a main part side sectional view of the spray piping structure which concerns on 4th Embodiment of this invention.

The flue gas desulfurization apparatus according to the present invention will be described with reference to the drawings. In the following description, the front means the inflow side of the exhaust gas in the absorption tower 1, and the left and right means the left and right when the rear is viewed from the front. Further, in FIGS. 4, 5 and 6, the spray nozzle 5 is not shown.

(First Embodiment)
The flue gas desulfurization apparatus according to the first embodiment of the present invention is a wet limestone-gypsum method flue gas desulfurization apparatus that removes sulfur oxides from exhaust gas containing sulfur oxides generated in a thermal power plant or the like. It is provided with an absorption tower (desulfurization absorption tower) 1 into which the contained exhaust gas is introduced, and a separation device (not shown) for separating the absorption liquid flowing out from the absorption tower 1 into plaster and a dehydration filtrate.

As shown in FIGS. 1 to 3, the absorption tower 1 has a cylindrical peripheral wall 2 that stands up substantially vertically, and the inner peripheral surface of the peripheral wall 2 partitions a gas flow space 3 extending in the vertical direction. An inlet duct 4 is connected to the front side of the peripheral wall 2, and exhaust gas from a boiler (not shown) is introduced into the gas flow space 3 via the inlet duct 4. The introduced exhaust gas circulates in the gas distribution space 3 from the bottom to the top.

A large number of spray nozzles 5 are installed in the upper part of the gas flow space 3 in the absorption tower 1, and the absorption liquid is sprayed (sprayed) as fine droplets from the spray nozzles 5. When the sprayed absorption liquid comes into contact with the exhaust gas (gas-liquid contact), the sulfur oxides in the exhaust gas are chemically removed on the surface of the absorption droplets and discharged from the exhaust gas outlet 7 at the upper and rear sides. As described above, the spray nozzle 5 is a spray type in which the absorption liquid is sprayed as fine droplets and the sprayed droplets are brought into contact with the exhaust gas flowing upward, and the absorption liquid supplied from the spray nozzle 5 oxidizes sulfur in the exhaust gas. The thing is absorbed and removed. The minute droplets accompanying the exhaust gas flow are removed by a mist eliminator (not shown) installed on the gas outlet side of the absorption tower 1. The gas from which minute droplets have been removed by the mist eliminator is heated by a reheating facility (not shown) installed on the wake side of the absorption tower 1 as needed, and discharged from the chimney (not shown). To. Most of the droplets sprayed from the spray nozzle 5 absorb the sulfur oxides and then fall into the absorption tower tank 8 provided at the lower part of the absorption tower 1. The absorbed liquid staying in the absorption tower tank 8 is sent by the absorption liquid circulation pump 9 and supplied from the absorption liquid circulation pipe 6 to the spray nozzle 5. Further, the absorption tower tank 8 is provided with an air supply device (not shown) that supplies air to the accumulated absorption liquid.

The plurality of spray nozzles 5 includes a plurality of first spray nozzles 5A and a plurality of second spray nozzles 5B in the upper stage, and a plurality of third spray nozzles 5C and a plurality of fourth spray nozzles 5D in the lower stage (see FIG. 2). The number and arrangement of the spray nozzles 5 in each stage can be arbitrarily set. It is preferable that the plurality of spray nozzles 5 are arranged so that the absorbing liquid is evenly sprayed on the exhaust gas flowing through the gas flow space 3.

As shown in FIGS. 1 to 5, an upper pipe shaft arrangement line (pipe extension direction) 10 and a lower pipe shaft arrangement line (second pipe extension direction) 20 are located above the gas flow space 3. Multiple settings are made for each. The plurality of upper pipe shaft arrangement lines 10 extend linearly so as to cross the gas flow space 3 substantially horizontally, and are separated at substantially equal intervals in the flow path cross section (upper flow path cross section) of the gas flow space 3. Line up in parallel. Each of the plurality of lower pipe axis arrangement lines 20 extends linearly so as to cross the gas flow space 3 substantially horizontally below the upper pipe axis arrangement line 10, and the flow path cross section (downstream) below the upper flow path cross section. (Cross section of the road), they are lined up in parallel at approximately equal intervals. The upper pipe shaft arrangement line 10 and the lower pipe shaft arrangement line 20 of the present embodiment are set along the left-right direction. The directions of the upper pipe shaft arrangement line 10 and the lower pipe shaft arrangement line 20 are not limited to the left-right direction, and can be set to any direction (for example, the front-rear direction).

The upper connecting spray pipe 11 is arranged on the upper pipe shaft arrangement line 10, and the lower connecting spray pipe 21 is arranged on the lower pipe shaft arrangement line 20. The upper connecting spray pipe 11 is composed of a first spray pipe 12 and a second spray pipe 13, and the lower connecting spray pipe 21 is composed of a third spray pipe 22 and a fourth spray pipe 23.

The first spray tube 12 has a first base end portion 12A and a first tip portion 12B. The first base end portion 12A is arranged on one side (left side in the illustrated example) of the upper pipe shaft arrangement line 10, and the first tip end portion 12B is arranged on the center side of the upper pipe shaft arrangement line 10. The first spray pipe 12 extends linearly from the first base end portion 12A to the first tip portion 12B along the upper pipe shaft arrangement line 10, and the first base end portion 12A side is fixed to the absorption tower 1. Be supported. A plurality of first spray nozzles 5A are attached to the first spray tube 12.

The second spray tube 13 has a second base end portion 13A and a second tip portion 13B. The second base end portion 13A is arranged on the other side (right side in the illustrated example) of the upper pipe shaft arrangement line 10, and the second tip portion 13B is arranged on the center side of the upper pipe shaft arrangement line 10. The second spray pipe 13 extends linearly from the second base end portion 13A to the second tip portion 13B along the upper pipe shaft arrangement line 10, and the second base end portion 13A side is fixed to the absorption tower 1. Be supported. A plurality of second spray nozzles 5B are attached to the second spray tube 13.

The third spray tube 22 has a third base end portion 22A and a third tip portion 22B. The third base end portion 22A is arranged on one side (left side in the illustrated example) of the lower pipe shaft arrangement line 20, and the third tip portion 22B is arranged on the center side of the lower pipe shaft arrangement line 20. The third spray pipe 22 extends linearly from the third base end portion 22A to the third tip portion 22B along the lower pipe shaft arrangement line 20, and the third base end portion 22A side is fixed to the absorption tower 1. Be supported. A plurality of third spray nozzles 5C are attached to the third spray tube 22.

The fourth spray tube 23 has a fourth base end portion 23A and a fourth tip portion 23B. The fourth base end portion 23A is arranged on the other side (right side in the illustrated example) of the lower pipe shaft arrangement line 20, and the fourth tip end portion 23B is arranged on the center side of the lower pipe shaft arrangement line 20. The fourth spray pipe 23 extends linearly from the fourth base end portion 23A to the fourth tip portion 23B along the lower pipe shaft arrangement line 20, and the fourth base end portion 23A side is fixed to the absorption tower 1. Be supported. A plurality of fourth spray nozzles 5D are attached to the fourth spray tube 23.

As shown in FIG. 5, the first spray pipe 12 and the second spray pipe 13 are aligned in a straight line along the upper pipe shaft arrangement line 10, and the first tip portion 12B and the second tip portion 13B are in close proximity to each other. And face each other. A disk-shaped closing plate 30 is fixed to the end surface of the first tip portion 12B and the end face of the second tip portion 13B, respectively (see FIG. 5). The end face opening of the first tip portion 12B and the end face opening of the second tip portion 13B are sealed by the closing plate 30, and the outflow of the absorbing liquid from these end face openings is prevented.

The first tip portion 12B and the second tip portion 13B are connected via a cylindrical support ring 31. The outer diameter of the first tip portion 12B and the outer diameter of the second tip portion 13B are set to be substantially equal, and the inner diameter of the support ring 31 is set to be slightly larger than the outer diameters of the first tip portion 12B and the second tip portion 13B. Will be done. The tip of the first tip portion 12B is inserted into the inner diameter portion of the support ring 31 from one side, the tip of the second tip portion 13B is inserted into the inner diameter portion of the support ring 31 from the other side, and the support ring 31 is the first. It straddles the first tip portion 12B and the second tip portion 13B. The support ring 31 is fixed to one of the first tip portion 12B and the second tip portion 13B (for example, the first tip portion 12B), and the other of the first tip portion 12B and the second tip portion 13B (for example, the second tip portion 13B). ) And the support ring 31 are engaged with each other so as to be relatively movable along the upper pipe shaft arrangement line 10. That is, the first tip portion 12B and the second tip portion 13B are separated so as to allow relative movement along the upper pipe shaft arrangement line 10 and intersect with the upper pipe shaft arrangement line 10 (the present embodiment). Then, they are connected in a state of supporting each other so as to regulate the relative movement in the vertical direction and the front-back direction). The structure for connecting the first tip portion 12B and the second tip portion 13B is not limited to the above, and for example, both the first tip portion 12B and the second tip portion 13B are not fixed to the support ring 31 and are in the upper stage. The first tip portion 12B and the second tip portion 13B are engaged with the support ring 31 so as to be relatively movable along the pipe shaft arrangement line 10 to prevent the support ring 31 from falling off (for example, an annular member) 32. Other structures may be used, such as fixing to the outer periphery of each of the above.

The third spray pipe 22 and the fourth spray pipe 23 are aligned in a straight line along the lower pipe shaft arrangement line 20, and the third tip portion 22B and the fourth tip portion 23B are close to each other and face each other. Similar to the connecting spray pipe 11 in the upper stage, the closing plate 30 is fixed to the end surface of the third tip portion 22B and the end face of the fourth tip portion 23B, respectively. Further, the third end portion 22B and the fourth tip portion 23B are separated from each other so as to allow relative movement along the lower pipe shaft arrangement line 20 as in the upper connecting spray pipe 11, and the lower pipe shaft arrangement is allowed. They are connected via the support ring 31 in a state of supporting each other so as to restrict relative movement in the direction intersecting with the line 20.

The upper connecting spray pipe 11 (first spray pipe 12, second spray pipe 13), the lower connecting spray pipe 21 (third spray pipe 22, fourth spray pipe 23), the closing plate 30, and the support ring 31. Is made of a non-metal (for example, a resin material such as Fiber Reinforced Plastics (FRP)) having excellent corrosion resistance and slurry wear resistance and a high linear expansion coefficient. In this embodiment, considering the corrosive environment with a high chlorine concentration (for example, chlorine concentration of 20,000 to 35,000 ppm) in the absorption tower 1, it is not made of metal (for example, made of stainless steel), but has excellent corrosion resistance and slurry wear resistance, and is lightweight. It uses a cheap non-metal spray tube.

As shown in FIG. 3, in this embodiment, 10 upper pipe shaft arrangement lines 10 are set. Five upper pipe shaft arrangement lines 10 are set on the front side and the rear side of the center line (diameter) 33 extending in the left-right direction in the cross section of the flow path of the gas flow space 3. The first base end portion 12A of the first spray pipe 12 along the upper pipe shaft arrangement line 10 of the six upper pipe shaft arrangement lines 10 on the center side in the front-rear direction of the first spray pipe 12 is bolted to the peripheral wall 2 on the left side of the absorption tower 1. The tip of the first base end portion 12A on the central side extends to the left outer side of the absorption tower 1 and is connected to the header 35 on the left upper stage. Similar to the first spray pipe 12, the second base end portion 13A of the second spray pipe 13 along the upper pipe shaft arrangement line 10 of the six upper pipe shaft arrangement lines 10 on the center side in the front-rear direction of the second spray pipe 13 is the absorption tower 1. It is fixed to the peripheral wall 2 on the right side of the above by bolts or the like (double pipe seat not shown), and the tip of the second base end portion 13A on the center side extends to the right outer side of the absorption tower 1 and the header 35 on the upper right side. Connected to. The first base end portion 12A of the first spray pipe 12 along the upper pipe shaft arrangement line 10 of the two front sides and the two rear side of the first spray pipe 12 is the first base end of the adjacent first spray pipe 12. It is connected to and communicates with the unit 12A. Similarly, the second base end portion 13A of the second spray pipe 13 along the upper pipe shaft arrangement line 10 of the two front pipes and the two rear pipe pipes 13 of the second spray pipe 13 is the second of the adjacent second spray pipe 13. It is connected to and communicates with the two end portions 13A.

Although not shown, the lower pipe shaft arrangement line 20, the third spray pipe 22, and the fourth spray pipe 23 are set in the same manner as the upper pipe shaft arrangement line 10, the first spray pipe 12, and the second spray pipe 13. .. The third base end 22A on the center side is fixed to the peripheral wall 2 on the left side of the absorption tower 1 by bolts or the like (double pipe seat not shown), and its tip extends to the left outer side of the absorption tower 1 and is on the left side. Connected to the lower header. The fourth base end 23A on the center side is fixed to the peripheral wall 2 on the right side of the absorption tower 1 by bolts or the like (double pipe seat not shown), and its tip extends to the right outer side of the absorption tower 1 and is on the right side. Connected to the lower header. The two front side and two rear side third base end portions 22A are connected to and communicate with the adjacent third base end portion 22A, and the fourth base of the four front side and two rear side spray pipes 23. The end portion 23A is connected to and communicates with the adjacent fourth base end portion 23A.

Absorbent liquid circulation pipes 6 are connected to the headers 35 in the upper left, upper right, lower left, and lower right stages, and the absorbent liquid that has flowed through the absorbent liquid circulation pipe 6 is the first unit of the first spray pipe 12 from each header 35. It flows into the end portion 12A, the second base end portion 13A of the second spray pipe 13, the third base end portion 22A of the third spray pipe 22, and the fourth base end portion 23A of the fourth spray pipe 23. The absorbing liquid that has flowed into the first spray tube 12 is sent from the first base end portion 12A side to the first tip portion 12B side, and is supplied to the first spray nozzle 5A and sprayed. The absorbing liquid that has flowed into the second spray tube 13 is sent from the second base end portion 13A side to the second tip portion 13B side, is supplied to the second spray nozzle 5B, and is sprayed. The absorbing liquid that has flowed into the third spray tube 22 is sent from the third base end portion 22A side to the third tip portion 22B side, is supplied to the third spray nozzle 5C, and is sprayed. The absorbing liquid that has flowed into the fourth spray tube 23 is sent from the fourth base end portion 23A side to the fourth tip portion 23B side, is supplied to the fourth spray nozzle 5D, and is sprayed.

As shown in FIG. 3, the first tip portion 12B of the first spray pipe 12 and the second tip portion 13B of the second spray pipe 13 have a center line (diameter) extending in the front-rear direction in the cross section of the flow path of the gas flow space 3. ) 34 is placed in the vicinity. In each connecting spray pipe 11 in the upper stage, the liquid feeding distance from the first base end portion 12A to the first tip portion 12B of the first spray pipe 12 and the second base end portion 13A to the second tip of the second spray pipe 13 The liquid feeding distance to the portion 13B is set to be substantially equal. Although not shown, the third tip 22B of the third spray pipe 22 and the fourth tip 23B of the fourth spray pipe 23 are in the front-rear direction in the cross section of the flow path of the gas flow space 3, as in the upper stage. It is placed near the center line (diameter) extending to. In each connecting spray pipe 21 in the lower stage, the liquid feeding distance from the third base end 22A to the third tip 22B of the third spray pipe 22 and the fourth base end 23A to the fourth tip of the fourth spray pipe 23. The liquid feeding distance to the portion 23B is set to be substantially equal.

Further, the upper and lower connecting

spray pipes

11 and 21 are symmetrically configured around the center line 33 extending in the left-right direction in each of the upper and lower flow path cross sections of the gas flow space 3, and the center line extending back and forth. It is symmetrically configured around 34.

As shown in FIGS. 3 and 4, the first to

fourth spray tubes

12, 13, 22, 23 have inner and outer diameters from the

base end portions

12A, 13A, 22A, 23A to the

tip portions

12B, 13B, 22B, It has a circular tube shape that shrinks in diameter toward 23B (from the upstream side to the downstream side in the flow direction of the absorbing liquid). The diameters of the first to

fourth spray tubes

12, 13, 22, and 23 may be reduced stepwise or continuously (in FIGS. 3 and 4, the diameters are reduced stepwise). An example of diameter is shown).

As shown in FIGS. 4 and 5, between the upper connecting spray pipe 11 and the lower connecting spray pipe 21, the upper pipe shaft arrangement line 10 and the lower pipe shaft arrangement line 20 are separated from one side (left side). Brace (auxiliary member) 40A that inclines diagonally upward toward the side (right side) and brace (auxiliary member) 40B that incline diagonally downward are arranged alternately, and the upper connecting spray pipe 11 and the lower connecting spray pipe 11 are arranged alternately. The 21 is connected by a plurality of

braces

40A and 40B. The upper end and the lower end of each of the

braces

40A and 40B are fixed to the upper connecting spray pipe 11 and the lower connecting spray pipe 21, and are trussed by the upper and lower connecting

spray pipes

11 and 21 and the

braces

40A and 40B. The structure is formed. The

braces

40A and 40B of the present embodiment are made of a non-metal (for example, FRP) having excellent corrosion resistance and slurry wear resistance, similarly to the first to

fourth spray tubes

12, 13, 22, 23.

According to the present embodiment, the first spray pipe 12 is arranged in the region on the left side of the upper pipe shaft arrangement line 10, the second spray pipe 13 is arranged in the region on the right side, and the first spray pipe 12 and the second are arranged. It extends in a straight line with the spray tube 13. Further, the third spray pipe 22 is arranged in the area on the left side of the lower pipe shaft arrangement line 20, the fourth spray pipe 23 is arranged in the area on the right side, and the third spray pipe 22 and the fourth spray pipe 23 are It extends in a straight line. In the upper flow path cross section of the gas flow space 3, the absorption liquid is supplied to substantially the entire area of the upper pipe shaft arrangement line 10 by the first spray pipe 12 and the second spray pipe 13, and in the lower flow path cross section of the gas flow space 3, the third The absorption liquid is supplied to substantially the entire area of the lower pipe shaft arrangement line 20 by the spray pipe 22 and the fourth spray pipe 23. Therefore, as compared with the case where the absorption liquid is supplied by one spray pipe to substantially the entire area of the upper pipe shaft arrangement line 10 and the substantially entire area of the lower pipe shaft arrangement line 20 (when a single spray pipe is used). It is possible to shorten the liquid feeding distance of the absorbing liquid by one spray tube. Therefore, even when the cross section of the flow path of the gas flow space 3 is increased, the increase in the diameter of the spray pipe can be suppressed. In particular, in the present embodiment, in the upper connecting spray pipe 11, the liquid feeding distance of the first spray pipe 12 from the first base end portion 12A to the first tip portion 12B and the liquid feeding distance from the second base end portion 13A to the second tip portion The liquid feeding distance of the second spray pipe 13 up to 13B is set to be substantially equal, and in the lower connected spray pipe 21, the liquid feeding of the third spray pipe 22 from the third base end portion 22A to the third tip portion 22B is performed. The distance and the liquid feeding distance of the fourth spray pipe 23 from the fourth base end portion 23A to the fourth tip portion 23B are set to be substantially equal. Therefore, the liquid feeding distance of the absorbing liquid can be halved as compared with the case of using a single spray tube.

The first spray tube 12 is cantilevered and supported on the first base end portion 12A side, the second spray tube 13 is cantilevered and supported on the second base end portion 13A side, and the first tip portion 12B and the second tip portion 13B are supported. Is connected in a state of supporting each other so as to restrict relative movement in the direction intersecting with the upper pipe shaft arrangement line 10, so that both ends of the upper connecting spray pipe 11 are supported. Similarly, the third spray tube 22 is cantilevered on the third base end 22A side, the fourth spray tube 23 is cantilevered on the fourth base end 23A side, and the third tip 22B and the fourth. Since the tip portion 23B is connected to each other in a state of supporting each other so as to restrict relative movement in the direction intersecting with the lower pipe shaft arrangement line 20, the lower connecting spray pipe 21 is in a state where both ends are supported. become. Therefore, it is possible to suppress the complexity of the support structure of the spray pipe as compared with the case where a single spray pipe is used for each of the upper stage and the lower stage.

As described above, the liquid feeding distance of one spray pipe in the absorption tower 1 can be shortened, and the increase in the diameter of the spray pipe can be suppressed, so that the flow path cross section of the gas flow space 3 is increased. Even in this case, it is possible to suppress the increase in size of the absorbent liquid circulation pump 9 for feeding the absorbent liquid.

Since the liquid feeding distance of one spray pipe can be shortened, even when the cross section of the flow path of the gas flow space 3 is increased, the spray nozzle 5 (first spray nozzle 5A, second spray nozzle 5B, third spray nozzle) It is possible to maintain the uniformity of the injection amount of the absorbing liquid from 5C, the fourth spray nozzle 5D).

The spray pipe that crosses the gas flow space 3 becomes a flow resistance of the exhaust gas, but since the connected

spray pipes

11 and 21 are provided instead of the single spray pipe, it is possible to suppress an increase in the diameter of the spray pipe. As a result, the flow resistance of the exhaust gas can be reduced, and even when the cross section of the flow path of the gas flow space 3 is increased, the increase in the load of the fan (not shown) for passing the exhaust gas can be suppressed. can.

The upper and lower connecting

spray pipes

11 and 21 are symmetrically configured around the center line 33 extending in the left-right direction in each of the upper and lower flow path cross sections of the gas flow space 3, and the center line 34 extending in the front-rear direction is formed. It is symmetrically configured as the center. On the other hand, when a single spray tube that gradually or continuously tapers from the base end portion to the tip end portion is provided, it cannot be configured symmetrically. Therefore, regarding the deviation (variation) of the flow resistance of the exhaust gas in the cross section of the flow path, the deviation is less likely to occur in the present embodiment than in the case of providing the single spray pipe (the balance is less likely to be lost and the flow is less likely to be disturbed). It can be configured.

Since the first tip portion 12B and the second tip portion 13B are connected in a state of being separated so as to allow relative movement along the upper pipe shaft arrangement line 10, the total length of the upper connecting spray pipe 11 is not restricted. .. Similarly, since the third tip portion 22B and the fourth tip portion 23B are connected in a state of being separated so as to allow relative movement along the lower pipe shaft arrangement line 20, the total length of the lower connecting spray pipe 21 Is not restrained. Therefore, even when the first spray tube 12, the second spray tube 13, the third spray tube 22, and the fourth spray tube 23 are made of a non-metal having a high coefficient of linear expansion, the first to fourth spray tubes are formed. It is possible to prevent damage to 12, 13, 22, and 23 due to thermal expansion and damage to the peripheral wall 2 of the absorption tower 1 that fixedly supports them.

The end face opening of the first tip portion 12B and the end face opening of the second tip portion 13B are closed so that the absorption liquid cannot flow out, and the absorption liquid does not flow between the first tip portion 12B and the second tip portion 13B. Therefore, the absorption liquid is supplied to the first spray nozzle 5A only from the first spray pipe 12, and the absorption liquid is supplied to the second spray nozzle 5B only from the second spray pipe 13. Therefore, the uniformity of the injection amount of the absorbing liquid from each of the first spray nozzles 5A and each of the second spray nozzles 5B can be easily maintained. Similarly, the end face opening of the third tip portion 22B and the end face opening of the fourth tip portion 23B are closed so that the absorption liquid cannot flow out, and the absorption liquid is closed between the third tip portion 22B and the fourth tip portion 23B. Not distributed. Therefore, the absorption liquid is supplied to the third spray nozzle 5C only from the third spray pipe 22, and the absorption liquid is supplied to the fourth spray nozzle 5D only from the fourth spray pipe 23. Therefore, the uniformity of the injection amount of the absorbing liquid from each of the third spray nozzles 5C and each of the fourth spray nozzles 5D can be easily maintained. The state in which the absorbent liquid is closed so that it cannot flow out includes the case where the end face opening is closed and the case where the absorbent liquid is opened with a minute size that prevents the liquid from flowing out (air can enter and exit). ..

Further, since the upper connecting spray pipe 11 and the lower connecting spray pipe 21 are connected by a plurality of

braces

40A and 40B to form a truss structure, the spray pipe support for supporting the connecting

spray pipes

11 and 21 from below. It is not necessary to install the beam in the absorption tower 1, and the support structure of the spray pipe can be simplified.

The number of stages of the connected

spray pipes

11 and 21 is not limited to two, and may be one stage (only the connected spray pipe 11 in the upper stage of the present embodiment) or may be more than two stages. If the number of stages exceeds two, the number of stages connected by the truss structure is limited to two adjacent upper and lower stages (for example, in the case of four stages, the first and second stages from the top are connected by the truss structure, and the upper stage is used. It is preferable that the 3rd step surface and the 4th step surface are connected by a truss structure, and the 2nd step surface and the 3rd step surface are not connected).

(Second Embodiment)
In the second embodiment of the present invention, the materials of the connecting

spray pipes

11 and 21 and the closing plate 30, the mode of connecting the first tip portion 12B and the second tip portion 13B, and the third tip portion 22B and the fourth tip portion are described. The mode of connecting the 23B is different from that of the first embodiment, and the other configurations are common to the first embodiment. Therefore, the same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The connecting spray pipes 11 and 21 (first to

fourth spray pipes

12, 13, 22, 23) of the present embodiment are made of metal (for example, made of stainless steel or nickel-based alloy), which is harder to expand thermally than resin. Is. As shown in FIG. 6, the support ring 31 (see FIG. 5) is not provided, and the closing plate 30 of the first tip portion 12B and the closing plate 30 of the second tip portion 13B are both made of metal and are circular. It has a plate shape, is fixed by welding in a state of being in surface contact with each other, and does not move relative to the first tip portion 12B and the second tip portion 13B. Similarly, the closing plate 30 of the third tip 22B and the closing plate 30 of the fourth tip 23B are both made of metal and have a disk shape, are welded and fixed in a state of being in surface contact with each other, and the third tip 22B. And the fourth tip 23B do not move relative to each other. In this way, since the first spray pipe 12 and the second spray pipe 13 are integrated, the rigidity of the upper connecting spray pipe 11 can be increased. Further, since the third pre-tube 22 and the fourth pre-tube 23 are integrated, the rigidity of the lower connecting spray tube 21 can be increased. The

braces

40A and 40B may be made of metal or may be made of non-metal. Further, the outer diameter of the upper closing plate 30 is preferably the same as the outer diameter of the first tip portion 12B and the second tip portion 13B, and the outer diameter of the lower closing plate 30 is the third tip portion 22B and the first. 4 It is preferable that the size is the same as the outer diameter of the tip portion 23B.

(Third Embodiment)
The third embodiment of the present invention is different from the second embodiment in that the first tip portion 12B and the second tip portion 13B are connected and the third tip portion 22B and the fourth tip portion 23B are connected. However, other configurations are common to the second embodiment. Therefore, the same reference numerals are given to the same configurations as those of the second embodiment, and the description thereof will be omitted. A metal cylindrical connecting ring 36 is arranged between the closing plate 30 of the first tip portion 12B and the closing plate 30 of the second tip portion 13B. The connection ring 36 has an inner diameter smaller than the outer diameter of the first tip portion 12B and the outer diameter of the second tip portion 13B. One end surface of the connection ring 36 was welded and fixed in a state of being in surface contact with the outer surface of the closing plate 30 of the first tip portion 12B, and the other end surface of the connection ring 36 was in surface contact with the outer surface of the closing plate 30 of the second tip portion 13B. It is fixed by welding in the state. Similarly, a metal cylindrical connecting ring 36 is arranged between the closing plate 30 of the third tip 22B and the closing plate 30 of the fourth tip 23B. The connection ring 36 has an inner diameter smaller than the outer diameter of the third tip portion 22B and the outer diameter of the fourth tip portion 23B. One end surface of the connection ring 36 was welded and fixed in a state of being in surface contact with the outer surface of the closing plate 30 of the third tip portion 22B, and the other end surface of the connection ring 36 was in surface contact with the outer surface of the closing plate 30 of the fourth tip portion 23B. It is fixed by welding in the state. In this way, the first tip portion 12B and the second tip portion 13B are connected via the upper closing plate 30 and the connection ring 36, and the third tip portion 22B and the fourth tip portion 23B are closed at the lower stage. It is connected via the plate 30 and the connecting ring 36. The outer diameters of the upper closing plate 30 and the connecting ring 36 are preferably the same as the outer diameters of the first tip portion 12B and the second tip portion 13B, and the outer diameters of the lower closing plate 30 and the connecting ring 36 are the same. , The same size as the outer diameter of the third tip portion 22B and the fourth tip portion 23B is preferable.

(Fourth Embodiment)
In the fourth embodiment of the present invention, the second and third embodiments are a mode in which the first tip portion 12B and the second tip portion 13B are connected, and a mode in which the third tip portion 22B and the fourth tip portion 23B are connected. Unlike the embodiment, other configurations are common to the second and third embodiments. Therefore, the same reference numerals are given to the same configurations as those of the second and third embodiments, and the description thereof will be omitted. The first tip portion 12B and the second tip portion 13B are connected via a metal and cylindrical connecting ring 37. The inner diameter of the connecting ring 37 is set to be slightly larger than the outer diameter of the first tip portion 12B and the second tip portion 13B. The tip of the first tip portion 12B is inserted into the inner diameter portion of the connection ring 37 from one side, the tip of the second tip portion 13B is inserted into the inner diameter portion of the connection ring 37 from the other side, and the connection ring 37 is the first. It straddles the first tip portion 12B and the second tip portion 13B. The connection ring 37 is welded and fixed to the outer peripheral surface of the first tip portion 12B and the outer peripheral surface of the second tip portion 13B. Similarly, the third tip 22B and the fourth tip 23B are connected via a metal, cylindrical connecting ring 37. The inner diameter of the connecting ring 37 is set to be slightly larger than the outer diameter of the third tip portion 22B and the fourth tip portion 23B. The tip of the third tip 22B is inserted into the inner diameter of the connection ring 37 from one side, the tip of the fourth tip 23B is inserted into the inner diameter of the connection ring 37 from the other side, and the connection ring 37 is the first. It straddles the 3 tip portion 22B and the 4th tip portion 23B. The connection ring 37 is welded and fixed to the outer peripheral surface of the third tip portion 22B and the outer peripheral surface of the fourth tip portion 23B. In this way, the first tip portion 12B and the second tip portion 13B are connected via the upper connection ring 37, and the third tip portion 22B and the fourth tip portion 23B are connected via the lower connection ring 37. Will be connected. The material of the closing plate 30 of the present embodiment may be other than metal.

Also in the third and fourth embodiments, as in the second embodiment, the first spray pipe 12 and the second spray pipe 13 are integrated, so that the rigidity of the upper connecting spray pipe 11 can be increased. Further, since the third pre-tube 22 and the fourth pre-tube 23 are integrated, the rigidity of the lower connecting spray tube 21 can be increased.

It should be noted that the present invention is not limited to the above-described embodiments and modifications described as examples, and is not limited to the above-mentioned embodiments 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, the cylindrical shape of the peripheral wall 2 of the absorption tower 1 is not limited to a cylindrical shape, and other shapes (for example, the front wall and the rear wall separated in the front-rear direction and the left wall and the right wall separated in the left-right direction are substantially vertical. It may be a rectangular cylinder that stands upright.

1: Absorption tower (desulfurization absorption tower)
2: Peripheral wall 3: Gas flow space 4: Inlet duct 5: Spray nozzle 5A: 1st spray nozzle 5B: 2nd spray nozzle 5C: 3rd spray nozzle 5D: 4th spray nozzle 6: Absorbent liquid circulation pipe 9: Absorbent liquid circulation pump 10: Upper stage Pipe axis placement line (pipe extension direction)
11 and 21: Connected spray pipe 12: 1st spray pipe 12A: 1st base end 12B: 1st tip 13: 2nd spray pipe 13A: 2nd base end 13B: 2nd tip 20: lower pipe shaft Arrangement line (second pipe extension direction)
22: 3rd spray pipe 22A: 3rd base end 22B: 3rd tip 23: 4th spray pipe 23A: 4th base end 23B: 4th tip 30: Closing plate 31: Support ring 36, 37: Connection rings 40A, 40B: Brace (auxiliary member)

Claims

The peripheral wall of the absorption tower divides the gas flow space extending in the vertical direction, the exhaust gas flows from the bottom to the top in the gas flow space, and a plurality of spray nozzles including a plurality of first spray nozzles and a plurality of second spray nozzles are absorbed towers. It is a spray piping structure of a flue gas desulfurization device that is arranged in the gas flow space inside and supplies an absorption liquid from the spray nozzle into the exhaust gas flowing through the gas flow space and absorbs the sulfur oxides in the exhaust gas with the absorption liquid. hand,
The first base end portion arranged on one side of the pipe extending direction set linearly so as to cross the gas flow space substantially horizontally, and the first arranged on the center side of the pipe extending direction. It has a tip portion, extends linearly from the first base end portion to the first tip portion along the pipe extending direction, and the first base end portion side is fixedly supported by the absorption tower. A first spray tube that sends the absorbing liquid from the first base end side to the first tip side and supplies the absorbing liquid to the first spray nozzle.
It has a second base end portion arranged on the other side in the pipe extension direction and a second tip portion arranged on the center side in the pipe extension direction, and the second base end portion to the second base end portion. It extends linearly to the tip along the pipe extending direction, the second base end side is fixedly supported by the absorption tower, and the second base end side is moved to the second tip side. A second spray tube for sending the absorbing liquid and supplying the absorbing liquid to the second spray nozzle is provided.
The first spray tube and the second spray tube are aligned in a straight line.
The first tip portion and the second tip portion are close to each other or in contact with each other, and are connected to each other in a state of supporting each other so as to restrict relative movement in a direction intersecting with the pipe extension direction. Spray piping structure of flue gas desulfurization equipment.
The spray piping structure according to claim 1.
The spray piping structure of the flue gas desulfurization apparatus, characterized in that the first tip portion and the second tip portion are connected in a separated state so as to allow relative movement along the pipe extending direction.
The spray piping structure according to claim 1 or 2.
The end face opening of the first tip portion and the end face opening of the second tip portion are a spray piping structure of a flue gas desulfurization apparatus, characterized in that the absorbing liquid is closed so as not to flow out.
The spray piping structure according to any one of claims 1 to 3.
What is the liquid feeding distance of the first spray pipe from the first base end portion to the first tip portion and the liquid feeding distance of the second spray pipe from the second base end portion to the second tip portion? , The spray piping structure of the flue gas desulfurization device, which is characterized by being set almost equally.
The spray piping structure according to any one of claims 1 to 4, wherein the plurality of spray nozzles include a plurality of third spray nozzles and a plurality of fourth spray nozzles.
A third base end portion arranged on one side of the second pipe extension direction, which is set linearly so as to cross the gas flow space substantially horizontally below the pipe extension direction, and the second. It has a third tip portion arranged on the center side in the pipe extending direction of the pipe, and extends linearly from the third base end portion to the third tip portion along the second pipe extending direction. The third base end side is fixedly supported by the absorption tower, and the absorption liquid is sent from the third base end side to the third tip side to supply the absorption liquid to the third spray nozzle. 3rd spray tube and
It has a fourth base end portion arranged on the other side in the second pipe extension direction and a fourth tip portion arranged on the central side in the second pipe extension direction, and the fourth base portion. The fourth base end portion extends linearly from the end portion to the fourth tip portion along the extension direction of the second pipe, and the fourth base end portion side is fixedly supported by the absorption tower. A fourth spray tube for sending the absorbing liquid from the side to the fourth tip side and supplying the absorbing liquid to the fourth spray nozzle is provided.
The third spray tube and the fourth spray tube are arranged in a straight line, and the third spray tube and the fourth spray tube are arranged in a straight line.
The third tip portion and the fourth tip portion are connected in a state of being close to or in contact with each other and supporting each other so as to restrict relative movement in a direction intersecting with the second pipe extension direction.
The first spray pipe and the second spray pipe form an upper connecting spray pipe.
The third spray pipe and the fourth spray pipe form a lower connecting spray pipe.
The spray piping structure of the flue gas desulfurization apparatus, wherein the upper connecting spray pipe and the lower connecting spray pipe are connected by a plurality of auxiliary members forming a truss structure.