JPH09229300A - High-temperature gas piping system - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a path in which even when a high temperature gas extracted from two boilers has a temperature difference, it is mixed to a uniform temperature before flowing into a turbine and a large vibration of the entire piping system does not occur. To provide a hot gas piping system. In a high temperature gas piping system for supplying high temperature gas from two boilers to a turbine, the respective pipes drawn out from the two boilers A and B merge into one pipe and flow into the turbine. It was divided into two pipes again in front of it, and formed so as to have a route to flow into the turbine from two locations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a hot gas piping system, and more particularly to a piping system for supplying hot gas from a boiler of a pressurized fluidized bed plant to a turbine and the piping thereof.

[0002]

2. Description of the Related Art A pressurized fluidized bed (PFBC) plant, which is being developed as a next-generation high-efficiency thermal power plant,
It is formed so that pulverized coal is burned in a burner furnace, the high temperature gas obtained by this burning is sent to a gas turbine through a piping system, and power is generated by a generator connected to the gas turbine.

In this PFBC plant, two burner furnaces are installed as shown in the basic structure of FIG. 2, one for high-temperature heating of exhaust steam from a high-pressure steam turbine and the other for exhaust gas. It is formed to have the function of reheating the recirculated water from the heat recovery heat exchanger. By adopting such a configuration, the thermal efficiency of the entire plant is higher than that of the existing combined cycle, and because the size of one burner furnace is smaller, the construction cost can be suppressed, and a very effective plant configuration and evaluation Has been done.

However, in this PFBC plant, the temperature of the gas from the burner furnace to the turbine is very high, and in this gas piping system, the thermal expansion of the entire piping due to the high temperature gas is absorbed, so that the piping is supported by, for example, a hanger spring. It has a loose support structure. Since the pipe is a high temperature gas and supports pipes that absorb thermal expansion, the vibration of the entire pipe tends to occur when the fluctuation of the internal flow is large. In addition, various piping elements such as elbow, branch, confluence, diffuser and reducer are used in combination to reduce the fluctuation of internal flow.

Further, as shown in FIG. 5, the above-mentioned high temperature gas pipe is composed of a double pipe of an outer pipe and an inner pipe in order to prevent the outer pipe from being deformed. It has a structure in which a heat insulating material is filled in between. In this case, since the inner pipe that directly contacts the high-temperature fluid absorbs its thermal expansion, it is divided at regular intervals in the flow direction to form an integral structure with the outer pipe, and between the divided inner pipes, It is formed so that there are gaps at regular intervals (slide gaps during thermal expansion).

[0006] Examples of those related to this kind of high temperature gas piping include JP-A-59-6494 and JP-A-61-6498.

[0007]

[Problems to be Solved by the Invention]
In addition, the PFBC plant having such a piping system has a temperature and a steam of combustion gas as compared with a combined cycle thermal power plant which is conventionally adopted, that is, a combined cycle in which a gas turbine is disposed adjacent to a combustor. Since the temperature of the equipment greatly increases, not only the equipment but also the piping system is apt to be deformed due to thermal stress. Also, due to changes in plant start-up and operating conditions, two burners generate high-temperature gas with different temperatures. Although it may occur, in this case, if it flows into the turbine with a temperature difference, the turbine blade may be deformed and the rotation efficiency may be reduced.

Further, as described above, the pipe is composed of a double pipe including an outer pipe having a heat insulating material and an inner pipe, and the inner pipe is formed to have a gap in the longitudinal direction in order to absorb thermal expansion of the inner and outer pipes. Therefore, there is a risk that a high-temperature fluid may flow into the heat insulating material through the gap due to the separation vortex as shown in FIG. That is, this figure shows the situation where a separation vortex occurs and a backflow region occurs near the pipe wall in the downstream of the confluence and the branch.
This separation vortex could cause steam to be blown into the heat insulating material filling portion.

At the gaps at regular intervals in this inner pipe division structure, a pressure distribution is generated in the pipe circumferential direction in the process of changing the direction of the main flow in addition to the above-mentioned separation vortex at the elbow portion, the joining portion, and the branch portion. Blow-in and blow-out flows occur between the main flow section of the inner pipe and the filling area of the heat insulating section. When a blow-in flow is generated from the main flow part of the inner pipe through the gap to the heat insulating part filling region, when the flow velocity is high, the heat insulating material is compressed and at the same time thermal deterioration is caused. When the heat insulating material is significantly compressed and deteriorated, the flow blown from the main flow part of the inner pipe into the heat insulating part filling region may reach the inner surface of the outer pipe. In this case, since the outer pipe has a temperature higher than the set temperature, abnormal expansion occurs, and large thermal stress is applied to the entire pipe, which may cause large structural deformation.

The present invention has been made in view of the above, and an object of the present invention is, for example, in a piping system for supplying a high temperature gas from a boiler of a pressurized fluidized bed plant to a turbine, the high temperature gas drawn from two boilers. In order to provide a hot gas piping system of this type and a hot gas piping thereof, which has a path in which even if there is a temperature difference, the temperature is mixed to a uniform temperature before flowing into the turbine and large vibration of the entire piping system does not occur. is there.

Further, another object of the present invention is to provide a hot gas piping system of this kind in which the high temperature fluid is not spouted from the main stream to the heat insulating material filling portion downstream of the merging portion or the branching portion of the piping system.

[0012]

That is, according to the present invention, in a high temperature gas piping system for supplying high temperature gas from two boilers to a turbine, the respective pipes drawn out from the two boilers are combined into one pipe. In addition, the pipe is branched again into two pipes before flowing into the turbine so that the turbine has two paths to flow into the pipe from two locations to achieve the intended purpose.

Further, according to the present invention, in a portion where the two pipes drawn out from the two boilers merge into one pipe, the pipe which joins the main pipe is 90 ° from the side surface of the main pipe. It is formed so as to be connected at an angle of. Further, each of the pipes drawn out from the two boilers is formed so as to have a plurality of elbow parts before joining the one pipe. Further, in a portion where the pipe is branched into two pipes before flowing into the turbine, reducers each having the same pipe center axis and gradually decreasing in diameter are provided on the branched downstream side.

An elbow is installed between the merging portion and the branch portion and on the upstream side at a distance of 5 times or more the pipe diameter from the branch position. Further, in this case, the pipe is formed as a double pipe having an inner pipe and an outer pipe, and a heat insulating material is filled between the inner and outer pipes. In addition, the two pipes drawn out from the two boilers have a double pipe structure only in a portion where they merge into one pipe and a portion where they branch into two pipes again before they flow into the turbine. The tube is formed so that there is no gap leading to the heat insulating material filling portion.

Furthermore, the present invention has a merging portion where a plurality of pipes merge into a single pipe, or a branching portion where a single pipe branches into a plurality of pipes, and these pipes respectively include an inner pipe and an outer pipe. In a high temperature gas piping system that is formed in a heavy pipe and is filled with a heat insulating material between the inner and outer pipes, and the inner pipe is provided with thermal expansion and contraction slide gaps at predetermined intervals in the longitudinal direction, The slide gap of the inner pipe in the branch portion is formed so as to be located outside the reverse flow region of the fluid in the pipe generated at the merging portion or the branch portion.

In addition, a plurality of pipes have a merging portion that joins one pipe, or one pipe has a branch portion that branches into a plurality of pipes, and this pipe is formed into a double pipe of an inner pipe and an outer pipe, In a high temperature gas piping system in which a heat insulating material is filled between the inner and outer tubes, and the inner tubes are provided with thermal expansion / contraction slide gaps at predetermined intervals in the longitudinal direction, the inner tube slides at the merging portion or the branching portion. The gap
It is formed only at the position on the opposite side in the circumferential direction of the inner pipe corresponding to the reverse flow region of the fluid in the pipe generated at the merging portion or the branching portion.

Further, in the middle of the piping system, there is provided piping in which the diameter of the piping gradually increases, and this piping system is formed by a double pipe of an inner pipe and an outer pipe, and a heat insulating material is provided between the inner and outer pipes. In the high temperature gas pipe system filled with, the region of the pipe in which the diameter is gradually increased is arranged so that the flow of the fluid flowing in the pipe is in the vertical direction.

Further, in the middle of the piping system of the three-dimensional piping system, there is provided piping in which the diameter of the piping gradually increases, and this piping system is formed by a double piping of an inner pipe and an outer pipe, and In a high temperature gas piping system with insulation filled between
The region in which the pipe diameter of the pipe gradually increases is arranged such that the main flow of the internal fluid is always in the horizontal direction. Further, in this case, horizontal straight pipes are provided at regular intervals in the upstream portion of the region where the pipe diameter gradually increases, and the bent portion is formed so as not to be directly connected to this region.

That is, in the high temperature gas piping system formed in this way, the two drawn from the two boilers are used.
The two pipes merge once into one pipe, and then branch into two pipes again before they flow into the turbine. Even if the generated hot gas has a temperature difference, it can be mixed to a uniform temperature before entering the turbine.

Further, in the merging portion, the pipe merging with the mainstream pipe is connected at an angle of 90 ° from the side surface to the flow of the mainstream pipe. By providing reducers each having the same shaft and having a diameter that gradually decreases, it is possible to suppress fluctuations in the flow in the pipe and prevent large vibrations in the entire pipe system.

Further, in the high temperature gas piping from the boiler outlet to the turbine inlet, when various piping elements such as elbow, branching, merging, diffuser, reducer, etc. are used due to the layout of the building and equipment, the problematic flow It is known from the flow analysis result that the backflow region of (1) occurs in (1) the inner downstream portion of the T-shaped confluence portion, (2) the downstream portion of the branch portion, and (3) the elbow downstream portion having a small radius of curvature.
In these areas, since no gap is formed in the inner pipe, hot gas from the gap of the inner pipe to the heat-insulating material filling portion is not blown out by the backflow, and therefore the hot gas drawn from the two boilers is not blown out. Even if there is a temperature difference, it can be a path that mixes to a uniform temperature before flowing into the turbine and does not cause large vibrations in the entire piping system, and also in the downstream of the confluence or branch of the piping system. A high temperature gas piping system of this kind can be provided in which the high temperature fluid does not spout from the mainstream to the heat insulating material filling portion.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. FIG. 1 shows the hot gas piping system in a perspective view. The piping from the primary cyclone A reaches the confluence section 9 via the two elbow sections A1 and A2, and the piping from the secondary cyclone B passes through the three elbow sections B1, B2 and B3 to the confluence section 9. Reach These elbows are installed to absorb the thermal expansion of the pipe due to high temperature gas, but if these elbows are installed immediately before the confluence part, the separation vortex generated in the elbow part will flow in the confluence part. This greatly affects the pressure fluctuation and pressure loss at the confluence. Therefore, in this embodiment, the pipe coming out of the primary cyclone A is provided with a diffuser in which the pipe diameter gradually increases after leaving the last elbow so as to suppress the influence of the separation vortex generated in the elbow portion. ing.

When this diffuser is provided, if the mainstream flow direction in the diffuser is horizontal, dust in the fluid in the pipe, that is, ash in the case of a PFBC plant, accumulates in the retention area in the vertically lower part of the diffuser. there's a possibility that. Therefore, the diffuser in this embodiment is set so that the mainstream flow direction is the vertical direction.

FIG. 3 shows an enlarged shape of the merging portion. The pipe coming out of the secondary cyclone A is connected to the flow of the pipe coming out of the secondary cyclone B at an angle of 90 ° from the side surface. A cross-sectional view of the shape of the confluence of these two pipes is shown in FIG. Since a backflow region due to a separation vortex is generated downstream of the confluence, only the inner pipe immediately after the confluence has no gap so that the gap of the inner pipe is not located in this region.

As the shape of the merging portion, in addition to this embodiment,
A 180 ° counter type as shown in FIG. 10 can be considered. In this confluent shape, by shifting the opposing axes, a swirling flow is generated and the temperature mixing is promoted. On the other hand, since the flows are opposed to each other and merge, the pressure fluctuation width at the merge portion increases. As a result of the three-dimensional unsteady flow analysis, the maximum value of the pressure fluctuation is 1800 (pa) in the confluent shape of the present embodiment, whereas the maximum value of the pressure fluctuation is 6 in the counter confluent type of FIG.
It was 3.5 times that of 350 (pa).

Regarding the temperature mixing, the counter merging type mixes at a uniform temperature about 3D downstream from the merging (three times the pipe diameter), but in the merging shape of this embodiment, 5D to 6D.
Mix to a uniform temperature. But at the turbine entrance,
Both shapes have a uniform temperature. Therefore, the confluent shape of the present embodiment has a smaller potential for pipe vibration and can supply high-temperature gas having a uniform temperature to the turbine.

After the merging portion, as shown in FIG. 3, due to the layout of the plant and the arrangement of the equipment, it reaches the branch portion through two elbows. Even if the elbow is installed immediately before the branch part, the separation and drift in the same part affect the branch part, resulting in an increase in pressure fluctuation and pressure loss. Further, in the piping of the PFBC plant, it is necessary to set the flow rate after branching evenly on the left and right, and it is necessary to suppress the influence of the elbow before branching as much as possible. Therefore, a straight pipe portion having a constant length is provided immediately before the branch portion.

Immediately after branching, there is provided a reducer in which the pipe diameter gradually decreases in both left and right directions. This reducer suppresses separation vortices and fluctuations that occur at the bifurcation. After suppressing the turbulence with a reducer, an elbow is installed to allow it to flow into the gas turbine. FIG.
The branch portion is shown enlarged in FIG. The elbow after the reducer is bent downward due to the arrangement of the equipment. FIG. 9 shows the pipe cross-sectional shape of the branch portion.
Since a backflow region due to the separation vortex occurs downstream of the bifurcation,
In order not to locate the gap of the inner pipe in this portion, only the inner pipe immediately after the branching portion has no gap.

FIG. 11 shows a second hot gas piping system of the present invention.
The cross section of the confluence | merging part and branch part of the Example of FIG. In this embodiment, the thickness of the inner pipe is increased only at the merging portion and the branching portion. As in the first embodiment, if the interval between the inner pipe gaps is increased only in the confluence part and the branch part, the support interval is increased and the amount of deformation due to pressure fluctuation increases. Further, in these portions, the pressure fluctuation itself due to the turbulence of the flow becomes larger than that in the straight pipe portion. Therefore, increase the inner tube thickness only in the same part,
It suppresses the amount of deformation and maintains structural integrity.

FIG. 12 and FIG. 13 show the cross sections of the merging portion and the branch portion of the third embodiment of the hot gas piping system of the present invention. In this embodiment, the space between the inner pipe gaps only at the merging portion and the branching portion is set to be approximately the same as that of the straight pipe portion, and the inner pipe gap is closed only in the pipe circumferential direction where a reverse flow region occurs, and the portion from the same portion to the heat insulating material filling portion Suppress the gush. Since the converging part and the branching part have different regions of backflow generation, the regions that block the inner pipe gap also differ.

As described above, according to the hot gas piping system of the present invention, the hot gas drawn from the two boilers has a high temperature in the piping for supplying the hot gas from the boiler of the pressurized fluidized bed plant to the turbine. Even if there is a difference, it is possible to obtain a high temperature gas piping system having a path in which it is mixed to a uniform temperature before flowing into the turbine and at the same time a large vibration of the entire piping system does not occur.

Furthermore, an inner pipe gap is not provided in a region where backflow occurs in a downstream region of the elbow having a small radius of curvature, a pipe region to which the diffuser is connected immediately after the elbow, and a region downstream of the confluence position of the T-shaped merging portion. By
It is possible to prevent the high temperature gas from spouting into the heat insulating material filling portion, and improve the soundness of the entire plant.

[0033]

As described above, according to the present invention, in a piping system for supplying high temperature gas from a boiler to a turbine, even if the high temperature gas drawn from two boilers has a temperature difference, it flows into the turbine. It is possible to obtain a hot gas piping system of this kind that has a path in which it is mixed to a uniform temperature before it does not generate large vibrations in the entire piping system, and also downstream of the confluence or branch of the piping system.
It is possible to obtain this kind of high temperature gas piping system in which the high temperature gas is not spouted from the main stream to the heat insulating material filling portion.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a hot gas piping system of the present invention.

FIG. 2 is a basic configuration diagram of a conventional pressurized fluidized bed plant.

FIG. 3 is an enlarged perspective view showing an embodiment of a confluent portion of the hot gas piping system of the present invention.

FIG. 4 is an enlarged view of a branch portion of the embodiment of FIG.

FIG. 5 is a schematic diagram of a basic configuration of a cross section of a pipe.

FIG. 6 is a schematic diagram of a flow at a merging portion and a branching portion of a high temperature gas piping system.

FIG. 7 is a schematic diagram of a flow on the downstream side of the merging portion and a pressure distribution on the inner wall surface of the pipe.

FIG. 8 is a schematic configuration diagram of a merging portion of the first embodiment of the hot gas piping system of the present invention.

FIG. 9 is a schematic configuration diagram of a branch portion of the first embodiment of the hot gas piping system of the present invention.

FIG. 10 is a perspective view showing another embodiment of the shape of the confluent portion of the hot gas piping system of the present invention.

FIG. 11 is a schematic configuration diagram of a merging portion of a second embodiment of the hot gas piping system of the present invention.

FIG. 12 is a schematic configuration diagram of a branch portion of a second embodiment of the hot gas piping system of the present invention.

FIG. 13 is a schematic configuration diagram of a confluence portion of a third embodiment of the hot gas piping system of the present invention.

[Explanation of symbols]

1 ... High temperature gas piping, 2 ... Boiler, 3 ... Primary cyclone, 4 ... Secondary cyclone, 5 ... Gas turbine, 6 ... Compressor, 7 ... Generator, 8 ... Elbow, 9 ... Confluence section, 10
... Branching part, 11 ... Reducer, 12 ... Diffuser, 13
... Insulating material, 14 ... Outer tube, 16 ... Inner tube, 17 ... Inner tube support plate, 18 ... Backflow region, 19 ... Inner tube gap, 20 ... Gap closing ring.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masaki Suzuki 3-1-1, Saiwaicho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi factory (72) Inventor Ishii Constitution 7-chome, Omika-cho, Hitachi-shi, Ibaraki 2-1 Incorporated company Hitachi, Ltd. Electric Power & Electric Development Headquarters (72) Inventor Kikuo Umegaki 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi Electric Power & Electric Equipment Development Headquarters

Claims (13)

[Claims] 1. A merging portion in which a plurality of pipes merge into a single pipe, or a branch portion in which a single pipe branches into a plurality of pipes, and these pipes are double pipes of an inner pipe and an outer pipe, respectively. In a high temperature gas piping system that is formed and is filled with a heat insulating material between the inner and outer pipes, and the inner pipe is provided with thermal expansion and contraction slide gaps at predetermined intervals in the longitudinal direction, A high-temperature gas piping system, characterized in that the slide gap of the inner pipe is formed outside the reverse flow region of the fluid in the pipe generated at the confluence or branch. 2. A pipe having a merging portion where a plurality of pipes merge into one pipe, or a branch portion where one pipe branches into a plurality of pipes, and the pipe is formed into a double pipe of an inner pipe and an outer pipe. In a high temperature gas piping system in which a heat insulating material is filled between the inner and outer pipes, and the inner pipe is provided with thermal expansion and contraction slide gaps at predetermined intervals in the longitudinal direction, A high temperature gas piping system, characterized in that a slide gap is formed only at a position on the opposite side in the circumferential direction of the inner pipe corresponding to a reverse flow region of the fluid in the pipe generated at the merging portion or the branch portion. 3. A pipe having a pipe diameter of which gradually increases in the middle of the pipe system, and the pipe system is formed by a double pipe of an inner pipe and an outer pipe, and heat insulation is provided between the inner pipe and the outer pipe. In a high temperature gas piping system filled with a material, a region of the pipe in which the diameter is gradually increased is arranged such that a flow of a fluid flowing in the pipe is in a vertical direction. . 4. A three-dimensional piping system is provided with a pipe having a gradually increasing pipe diameter in the middle of the piping system, and the piping system is formed by a double pipe of an inner pipe and an outer pipe, and In a high temperature gas piping system in which a heat insulating material is filled between the pipes, a region where the pipe diameter of the pipe is gradually increased is arranged such that the main flow of the internal fluid is always arranged in a horizontal direction. Gas piping system. 5. A high-temperature gas pipe according to claim 5, wherein horizontal straight pipes are provided at regular intervals upstream of the region where the pipe diameter gradually increases, and the bent portion is formed so as not to be directly connected to this region. system. 6. In a high temperature gas piping system for supplying high temperature gas from two boilers to a turbine, the respective pipes drawn out from the two boilers are joined together into one pipe and before entering the turbine. A high-temperature gas piping system, characterized in that it is branched into two pipes again, and is formed so as to have a path to flow into the turbine from two locations. 7. The two drawn from the two boilers
In the portion where the two pipes merge into one pipe, the pipe that merges with the main pipe is 9 from the side surface of the main pipe.
The hot gas piping system according to claim 1, wherein the hot gas piping system is formed so as to be connected at an angle of 0 °. 8. The high temperature according to claim 6 or 7, wherein each of the pipes drawn out from the two boilers is formed to have a plurality of elbow parts before joining the one pipe. Gas piping system. 9. A reducer having the same pipe central axis and gradually decreasing diameter is provided on the branched downstream side in a portion branched into two pipes before flowing into the turbine. , 7 or 8 high temperature gas piping system. 10. The high temperature gas according to claim 6, 7, 8 or 9, wherein an elbow is installed between the merging portion and the branch portion and on the upstream side at a distance of 5 times or more the pipe diameter from the branch position. Piping system. 11. The high-temperature gas according to claim 6, wherein the pipe is formed as a double pipe of an inner pipe and an outer pipe, and a heat insulating material is filled between the inner pipe and the outer pipe. Piping system. 12. The high temperature gas pipe according to claim 11, wherein the inner pipe of the double pipe structure is connected to the outer pipe in such a manner that there is a gap leading to the heat insulating material filling portion at regular intervals in the flow direction. system. 13. A double pipe is provided only in a portion where two pipes drawn from the two boilers join together into one pipe and a portion where the two pipes are branched again before flowing into the turbine. 13. The hot gas piping system according to claim 12, wherein the inner pipe of the structure is formed in a shape in which there is no gap leading to the heat insulating material filling portion.