JP4404259B2 - Exhaust heat recovery boiler with auxiliary burner and its operation method - Google Patents

Description

  The present invention relates to an exhaust heat recovery boiler with an auxiliary burner, and more particularly to an exhaust heat recovery boiler with an auxiliary burner suitable for using a fuel with a low calorific value for the auxiliary burner and an operation method thereof.

  In an exhaust heat recovery boiler (hereinafter sometimes referred to as HRSG) that recovers heat of combustion exhaust gas from a gas turbine (GT) and generates steam, an auxiliary combustion burner is provided at the inlet duct portion, and the HRSG is generated by the combustion heat. In some cases, the form of increasing the amount of evaporation in is taken. This is mainly intended to increase the output of the steam turbine (ST) using steam generated by HRSG and maintain the output of the combined cycle power generation as a whole when the temperature is high and the gas turbine output decreases in summer. And

FIG. 7 is a side view showing a part of a conventional exhaust heat recovery boiler with an auxiliary burner, and FIG. 8 is a plan view of the exhaust heat recovery boiler with an auxiliary burner of FIG.
Exhaust gas passes through the inlet duct 3 of the exhaust gas duct 2 from a gas turbine (not shown) and is sent to the boiler body 7. In the boiler body 7, the heat energy of the exhaust gas is recovered by a heat exchanger (a economizer, an evaporator, a reheater, a superheater, etc.) including the heat transfer tube groups 13 to 15, and steam is generated from water. The exhaust gas heat recovered by the boiler body 7 passes through the outlet duct 8 and is discharged from the chimney 9 to the atmosphere. The obtained steam is used for a steam turbine.

The boiler main body 7 shown in FIG. 7 shows an example in which the auxiliary burner 4 is provided in the inlet duct 3 and the evaporator 13 is provided in the most upstream gas portion of the boiler main body 7. Here, the temperature of the exhaust gas leaving the gas turbine is about 600 ° C., but the fuel is supplied to the auxiliary burner 4 according to the amount of evaporation required in the boiler body 7, and the exhaust gas from the gas turbine is generated by the combustion heat. Raise the temperature. When the auxiliary burner 4 is ignited, ignition is performed using an igniter, and after reaching a predetermined temperature, the fuel is continuously supplied to keep the combustion.
JP 2001-82110 A

  When the gas turbine is operated at a constant output and the temperature and flow rate of the exhaust gas are constant, the amount of heat input from the auxiliary combustion burner 4 is determined by the required evaporation amount (steam turbine output request). Accordingly, in order to increase or decrease the flow rate of the fuel supplied to the auxiliary burner 4, in the above-described conventional technique, the combustion chamber R after the auxiliary combustion (the inlet duct 3 on the downstream side of the auxiliary combustion burner 4 is independent of the required evaporation amount. The exhaust gas temperature in the inner space) cannot be controlled.

  Here, when fuel with low calories (calorific value) such as blast furnace gas (BFG) is burned as auxiliary combustion fuel, gas phase combustion is performed using an igniter at the time of ignition, but the temperature of the combustion chamber R is set to a predetermined value during continuous operation It is necessary to keep the gas temperature above the above to maintain good combustibility. Specifically, it is necessary to maintain the gas temperature in the combustion chamber R at about 850 ° C. or higher.

  Therefore, in the above prior art, when the output demand of the steam turbine decreases, the temperature of the combustion chamber R cannot be maintained above a predetermined gas temperature, and the combustion of the blast furnace gas becomes unstable or misfires. There was a problem.

  An object of the present invention is to provide an exhaust heat recovery boiler with an auxiliary combustion burner that maintains the temperature of the combustion chamber at a predetermined gas temperature or higher so that the combustion of the blast furnace gas does not become unstable even when the output demand of the steam turbine decreases. It is to provide a driving method.

According to the first aspect of the present invention, a plurality of heat exchangers (heat transfer tube groups) that generate steam by collecting heat of the combustion exhaust gas from the gas turbine are arranged in the exhaust gas flow path, and the heat exchanger (heat transfer tube) In the exhaust heat recovery boiler with an auxiliary combustion burner in which an auxiliary combustion burner (4) using blast furnace gas as fuel is arranged in the inlet duct portion on the upstream side of the exhaust gas passage (2) in which the group) is disposed, the exhaust gas passage (2) , Branching from the exhaust gas flow path (2) on the upstream side of the auxiliary burner (4), and the heat exchanger (13) on the most upstream side in the plurality of heat exchangers (heat transfer tube group) A bypass passage (10) connected to the exhaust gas passage (2) on the downstream side is provided, and at least one of the upstream side of the auxiliary burner arrangement site in the exhaust gas passage and the bypass passage, or the exhaust gas Gas flow distribution adjustment at the branch of the flow path (2) and bypass flow path (10) Means (11a and 11b) are provided, and the heat exchanger (13 on the most upstream side in the plurality of heat exchangers (heat transfer tube group) on the downstream side of the auxiliary combustion burner arrangement portion in the exhaust gas passage. ) Is provided with a temperature measuring means (6a) on the upstream side (combustion chamber), and when the temperature measured by the temperature measuring means (6a) is a predetermined value or more, the temperature measuring means (6a) The gas flow rate in the provided exhaust gas flow path (2) is increased from the gas flow rate at the time when the temperature is above a certain value, and the gas flow rate in the bypass flow path (10) is increased at a time when the temperature is above a certain value. When the gas flow distribution adjusting means (11a and 11b) is adjusted to reduce the gas flow rate and the temperature measured by the temperature measuring means (6a) is less than a certain value, the temperature measuring means (6a) The gas flow rate in the provided exhaust gas flow path (2) The gas flow rate distribution adjusting means reduces the gas flow rate when the temperature is less than a certain value and increases the gas flow rate of the bypass passage (10) from the gas flow rate when the temperature is less than the certain value. It is a waste heat recovery boiler with an auxiliary burner provided with a control device that performs control to adjust (11a and 11b).

The invention according to claim 2 is characterized in that one or more mixing members (17) for mixing the gas in both of the flow paths into a connecting portion for introducing the branched exhaust gas from the bypass flow path (10) into the exhaust gas flow path (2). The exhaust heat recovery boiler with an auxiliary burner according to claim 1.

According to a third aspect of the invention, each mixing member (17) and the bypass flow path connecting portion between the (10) provided with a gas flow distribution adjusting hand stage, the mixing member (17) of the downstream side of the exhaust gas flow path The exhaust heat recovery boiler with an auxiliary combustion burner according to claim 2, wherein a temperature measuring means (6 b) is provided in the boiler.

According to a fourth aspect of the present invention, a plurality of heat exchangers (heat transfer tube groups) for recovering heat of the combustion exhaust gas from the gas turbine and generating steam are disposed in the exhaust gas flow path, and the heat exchanger (heat transfer tube) The auxiliary combustion burner (4) using blast furnace gas as a fuel is disposed in the inlet duct portion on the upstream side of the exhaust gas flow path (2) where the group) is disposed, bypassing the exhaust gas flow path (2), and the auxiliary combustion burner The exhaust gas flow path on the upstream side of the heat exchanger (13) on the most upstream side of the plurality of heat exchangers (heat transfer tube group) is branched from the exhaust gas flow path (2) on the upstream side of (4). A bypass flow path (10) connected to (2) is provided, and at least one of the upstream flow side of the auxiliary burner arrangement site in the exhaust gas flow path and the bypass flow path, or the exhaust gas flow path (2) and the bypass flow Gas flow distribution adjusting means (11a and 11b) is provided at a branch portion with the passage (10), Temperature measuring means (on the downstream side of the auxiliary burner arrangement site in the gas flow path, on the upstream side of the most upstream heat exchanger (13) in the plurality of heat exchangers (heat transfer tube group)) 6a), the temperature measuring means (6a) is provided when the temperature measured by the temperature measuring means (6a) is equal to or higher than a certain value. The gas flow rate in the exhaust gas flow path (2) is increased from the gas flow rate at the time when the temperature is above a certain value, and the gas flow rate in the bypass flow path is reduced from the gas flow rate at the time when the temperature is above a certain value. When the gas flow distribution adjusting means (11a and 11b) is adjusted as described above and the temperature measured by the temperature measuring means (6a) is less than a certain value, the exhaust gas flow provided with the temperature measuring means (6a) The temperature is constant at the gas flow rate in the passage (2) The gas flow distribution adjusting means (11a and 11b) is adjusted so as to reduce the gas flow rate at the time when the temperature is less than the gas flow rate and increase the gas flow rate of the bypass passage from the gas flow rate at the time when the temperature is less than a certain value. This is a method for operating a waste heat recovery boiler with an auxiliary burner.

The invention according to claim 5 further includes one or more mixing members that mix the gas in both of the flow paths into a connection part that introduces the branched exhaust gas from the bypass flow path (10) into the exhaust gas flow path (2). (17) is provided, a gas flow rate distribution adjusting means is provided at a connecting portion between each mixing member (17) and the bypass flow path, and a temperature measuring means is provided in the exhaust gas flow path on the downstream side of the mixing member (17). The exhaust heat recovery boiler with an auxiliary combustion burner is operated in such a manner that the temperature measured by the temperature measuring means (6b) provided in the exhaust gas passage on the downstream side of the mixing member (17) becomes a certain value or more. The flow rate of gas flowing from each mixing member (17) to the exhaust gas flow channel side is adjusted using a gas flow rate distribution adjusting means provided at the connecting portion between each mixing member (17) and the bypass flow channel (10). Characterize Motomeko a 4 auxiliary burner with heat recovery steam generator operating method of description.

According to the first and fourth aspects of the present invention, when the required evaporation amount is small, that is, when the auxiliary combustion amount is small, a part of the exhaust gas from the gas turbine is caused to flow to the bypass flow path side by the gas flow distribution adjusting means. The flow rate of the gas flowing through the exhaust gas flow path (inlet duct provided with the auxiliary burner on the main stream side) is reduced by the gas flow distribution adjusting means, and the exhaust gas temperature after the auxiliary combustion is maintained at a predetermined temperature even if the combustion load by the auxiliary burner is reduced. This can be maintained. In addition, if the exhaust gas temperature after the auxiliary combustion rises above the set temperature, the exhaust gas temperature after the auxiliary combustion is reduced to the set temperature or lower by increasing the gas flow rate flowing through the exhaust gas flow channel side and reducing the gas flow rate on the bypass flow channel side. can do.
Thus, even blast furnace gas (BFG) having a low calorific value can be effectively used as a fuel for auxiliary combustion, and the exhaust heat recovery boiler with an auxiliary combustion burner of the present invention can be used as a combined cycle plant at an ironworks. Moreover, the exhaust gas temperature after auxiliary combustion can be maintained at a predetermined temperature or higher.

According to the second aspect of the present invention, a mixing member is provided at the joining portion of the gas flowing in the bypass flow path and the gas flowing in the exhaust gas flow path to mix the gas flowing from both to eliminate the temperature difference, and The heat transfer amount of the tube group can be set accurately.

According to the third and fifth aspects of the invention, the gas in the connecting portion between each mixing member and the bypass flow path is based on the measured temperature of the temperature measuring means provided in the exhaust gas flow path on the downstream side of the mixing member. The gas distribution can be adjusted by independently operating the flow distribution adjusting means so that the temperature distribution does not occur in the gas flowing downstream thereof.

  Embodiments of the present invention will be described with reference to the drawings.

    1, 2, and 3 are a side view, a plan view, and a perspective view, respectively, showing a partial internal structure of the exhaust heat recovery boiler of this embodiment. In FIG. 1, the exhaust gas passes through the exhaust gas duct 2 and the inlet duct 3 and is sent to the boiler body 7. In the boiler body 7, the heat energy of the exhaust gas is used to heat the water flowing in the heat transfer tube groups 13, 14, and 15 such as an evaporator to generate steam. The exhaust gas heat recovered by the boiler body 7 passes through the outlet duct 8 and is discharged from the chimney 9 to the atmosphere. An auxiliary combustion burner 4 is provided inside the inlet duct 3 for the purpose of increasing the evaporation amount of the boiler body 7.

  Further, in addition to the exhaust gas main stream flowing from the exhaust gas duct 2 to the inlet duct 3, a bypass duct 10 is provided for branching from the exhaust gas duct 2 to flow a part of the exhaust gas to the boiler body 7. A bypass duct side damper 11 a is provided on the inlet side of the bypass duct 10, that is, on the connection portion side with the exhaust gas duct 2, and an auxiliary burner side damper 11 b is provided on the upstream side of the auxiliary burner 4 in the inlet duct 3. Further, a mixing member 17 is provided on the connection portion side between the bypass duct 10 and the boiler body 7. Further, an exhaust gas thermometer 6 a is provided at the upstream portion of the heat transfer tube group 13 disposed inside the boiler body 7 on the front side of the mixing member 17.

  Since blast furnace gas has a small calorific value and was not suitable as a fuel for supplementary combustion, it has conventionally been simply burned and discarded. When the blast furnace gas is used as a supplementary fuel, the gas temperature in the combustion chamber R in the inlet duct 3 needs to be maintained at about 850 ° C. or more because the combustibility is not so good. The auxiliary combustion amount is determined by the required evaporation amount in the steam turbine. When the required evaporation amount is small, that is, when the auxiliary combustion amount is small, the main flow gas flowing in the boiler body 7 and the blast furnace gas are mixed to form the combustion chamber R. The temperature does not rise to 850 ° C.

  Therefore, the measured value of the exhaust gas thermometer 6a provided in the combustion chamber R is read, and the auxiliary burner side damper 11b is squeezed and the bypass duct side damper 11a is opened so that 850 ° C. can be maintained. Adjust to reduce and increase gas flow on the bypass side.

On the other hand, when the temperature of the measured value of the exhaust gas thermometer 6a rises above the set temperature, the auxiliary combustion burner side damper 11b is opened, the bypass duct side damper 11a is throttled, and the main stream side gas flow rate flowing through the boiler body 7 is increased. Then, the gas flow rate on the bypass duct 10 side is reduced, or as a reference example, the auxiliary combustion amount is reduced so that the temperature becomes lower than the set temperature.

  The gas 5 obtained by mixing the hot gas obtained by the auxiliary burner 4 and the turbine exhaust gas is absorbed by heat when passing through the heat transfer tube group 13, and the temperature is lowered. In the exhaust gas, the gas 12 branched to the bypass duct 10 and the heat-absorbed gas group 16 that is absorbed when passing through the heat transfer tube group 13 are usually different in temperature. The inlet gas will produce a large temperature distribution. That is, the cross-sectional shape in the gas flow direction of the boiler body 7 is as large as, for example, a height of 20 m or more and a width of 6 m or more. Therefore, the bypass duct 10 can be connected to a part of the casing as it is or from the inlet duct 3. If the gas 16 and the flow of the gas 12 in the bypass duct 10 are separated, the heat transfer amounts of the heat transfer tube groups 14 and 15 cannot be accurately set due to the difference between the two gas temperatures before joining. Therefore, a mixing member 17 is provided at the connection portion between the boiler body 7 and the bypass duct 10 so that the mixed gas of the two gases 12 and 16 has a uniform gas temperature at the inlet of the tube group 14. Thereby, the temperature difference in the mixed region of the two gases 12 and 16 can be reduced.

  The heat transfer tube group 13 is desirably an evaporator having a large heat absorption amount because the gas temperature in the combustion chamber R becomes high. Thereby, the said material can be made into a thing with low heat resistance compared with the case where it is set as another heat exchanger (superheater, reheater).

  Here, the auxiliary burner 4 has a configuration in which, for example, several stages of pipes having a plurality of fuel supply ports are arranged in the vertical direction in the width direction of the cross section of the gas flow in the inlet duct 3. A shape that expands from upstream to downstream so that the flame from the auxiliary burner 4 does not reach the heat transfer tube group 13 locally and so that the heat transfer tube group 13 can receive radiant heat evenly. It is desirable to provide the auxiliary burner 4 on the upstream side of the inlet duct 3. A sufficient space is provided as a combustion chamber R between the auxiliary burner 4 and the heat transfer tube group 13 in which the cross-sectional area of the inlet duct 3 increases toward the downstream side and the gas flow velocity decreases.

  The mixing member 17 has a wing shape and is hollow inside, and the gas 12 flowing from the bypass duct 10 flows through the mixing member 17. In the boiler body 7, the gas 12 is introduced into the boiler body 7 from an opening on the surface of the mixing member 17. In addition, the wing | blade shape of the mixing member 17 is an example, and is not limited to this shape.

  The arrangement, number, and spacing of the mixing member 17 in the boiler body 7 and the shape, number, and spacing of the opening are selected for each plant. The mixing member 17 is arranged with its longitudinal direction oriented in the horizontal direction, but when the bypass duct 10 is provided above the inlet duct 3, the mixing member 17 may be arranged with its longitudinal direction oriented in the vertical direction. good.

  A plurality of exhaust gas thermometers 6 b may be provided in the upstream portion of the heat transfer tube group 14 in the boiler body 7 on the downstream side of the mixing member 17. In this case, instead of the damper 11a on the bypass duct 10 side, a gas flow rate adjusting means is provided for each mixing member 17 at the connecting portion between the bypass duct 10 and the mixing member 17 (not shown: for example, slide type), and a plurality of exhaust gases. The gas flow rate may be individually adjusted so that the temperature measured by the thermometer 6b is an appropriate condition. Thereby, for example, the distribution of the gas temperature passing through the heat transfer tube group 14 can be prevented.

  4, 5, and 6 are a side view, a plan view, and a perspective view showing a partial internal structure of an exhaust heat recovery boiler with a combustion burner provided with a bypass duct 10 according to the present invention. In the configuration of the present embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. When it is difficult to arrange the bypass duct due to an obstacle or the like, the bypass duct is arranged as shown in FIG.

  A damper 11 a is provided in a bypass duct 10 branched from the exhaust gas duct 2 and connected to the boiler body 7. During combustion of the auxiliary combustion burner 4, the flow rate of the exhaust gas flowing to the auxiliary combustion burner 4 side is controlled by adjusting the flow rate of the exhaust gas to the bypass duct 10 side by opening and closing the damper 11a. Thus, the temperature of the exhaust gas 5 after the auxiliary combustion can be controlled to be constant.

  Further, when the auxiliary burner 4 is not burned (when not used), the damper 11a is closed.

  In addition, instead of the damper 11a, a distribution valve-like one (not shown) may be provided at the branching portion of the duct to adjust the gas flow rates on the bypass side and the main flow side.

  In the present invention, the arrangement shape of the bypass duct 10 is not limited to the above.

  INDUSTRIAL APPLICABILITY The present invention is a combined cycle plant installed in an ironworks, and can be used for an exhaust heat recovery boiler with an auxiliary burner that burns while maintaining good combustibility of fuel with low calories (calorific value) such as blast furnace gas.

It is a side view which shows a partial inside of the waste heat recovery boiler with an auxiliary combustion burner of one Example of this invention. It is a top view of the waste heat recovery boiler with an auxiliary combustion burner of FIG. It is a perspective view of the waste heat recovery boiler with an auxiliary combustion burner of FIG. It is a side view which shows a partial inside of the waste heat recovery boiler with an auxiliary combustion burner of one Example of this invention. It is a top view of the waste heat recovery boiler with an auxiliary combustion burner of FIG. It is a perspective view of the waste heat recovery boiler with an auxiliary combustion burner of FIG. It is a side view which shows a partial inside of the waste heat recovery boiler with an auxiliary combustion burner of a prior art. It is a top view of the waste heat recovery boiler with an auxiliary combustion burner of FIG.

Explanation of symbols

2 Exhaust duct 3 Inlet duct 4 Auxiliary burner 6a, 6b Exhaust gas thermometer 7 Boiler body 8 Outlet duct 9 Chimney 10 Bypass duct 11a Bypass duct side damper 11b Auxiliary burner side dampers 13, 14, 15 Heat transfer tube group 17 Mixing members 5, 12 , 16 Gas R combustion chamber

Claims (5)

A plurality of heat exchangers for recovering the heat of the combustion exhaust gas from the gas turbine and generating steam are disposed in the exhaust gas flow path, and a blast furnace is provided at the inlet duct portion on the upstream side of the exhaust gas flow path where the heat exchanger is disposed. In an exhaust heat recovery boiler with an auxiliary burner in which an auxiliary burner that uses gas as fuel is arranged,
Bypassing the exhaust gas flow path, branching from the exhaust gas flow path on the upstream side of the auxiliary burner, and connecting to the exhaust gas flow path on the downstream side of the heat exchanger on the most upstream side of the plurality of heat exchangers Provided bypass flow path,
Gas flow distribution adjusting means is provided at a branch portion between the exhaust gas flow path and the bypass flow path or at least one of the auxiliary flow burner arrangement site in the exhaust gas flow path and at least one of the bypass flow path,
A temperature measuring means is provided on the upstream side of the heat exchanger on the most upstream side of the plurality of heat exchangers on the downstream side of the auxiliary combustion burner arrangement site in the exhaust gas flow path,
Further, when the temperature measured by the temperature measuring means is equal to or higher than a certain value, the gas flow rate of the exhaust gas passage provided with the temperature measuring means is increased from the gas flow rate at the time when the temperature is equal to or higher than the certain value. In addition, the gas flow distribution adjusting means is adjusted so as to reduce the gas flow rate in the bypass flow path from the gas flow rate at the time when the temperature is equal to or higher than a certain value, and the temperature measured by the temperature measuring means is less than a certain value. In some cases, the gas flow rate in the exhaust gas flow channel provided with temperature measuring means is reduced from the gas flow rate at the time when the temperature is less than a certain value, and the gas flow rate in the bypass flow channel is less than the certain value. An exhaust heat recovery boiler with an auxiliary burner, characterized in that a control device is provided for performing control to adjust the gas flow rate distribution adjusting means so as to increase from the gas flow rate at the time.   2. The exhaust with an auxiliary burner according to claim 1, wherein at least one mixing member for mixing the gas in both of the flow paths is provided at a connection portion for introducing the branched exhaust gas from the bypass flow path into the exhaust gas flow path. Heat recovery boiler.   The auxiliary combustion according to claim 2, wherein gas flow distribution adjusting means is provided at a connecting portion between each mixing member and the bypass flow path, and temperature measuring means is provided in an exhaust gas flow path on the downstream side of the mixing member. Exhaust heat recovery boiler with burner. A plurality of heat exchangers for recovering the heat of the combustion exhaust gas from the gas turbine and generating steam are disposed in the exhaust gas flow path, and a blast furnace is provided at the inlet duct portion on the upstream side of the exhaust gas flow path where the heat exchanger is disposed. An auxiliary burner that uses gas as fuel is placed,
Bypassing the exhaust gas flow path, branching from the exhaust gas flow path on the upstream side of the auxiliary burner, and connecting to the exhaust gas flow path on the downstream side of the heat exchanger on the most upstream side of the plurality of heat exchangers Provided bypass flow path,
Gas flow distribution adjusting means is provided at a branch portion between the exhaust gas flow path and the bypass flow path or at least one of the auxiliary flow burner arrangement site in the exhaust gas flow path and at least one of the bypass flow path,
Exhaust heat with an auxiliary burner provided with a temperature measuring means on the upstream side of the heat exchanger on the uppermost stream side of the plurality of heat exchangers, on the downstream side of the auxiliary burner arrangement site in the exhaust gas flow path A method for operating a recovery boiler,
When the temperature measured by the temperature measuring means is a certain value or more, the gas flow rate of the exhaust gas flow path provided with the temperature measuring means is increased from the gas flow rate at the time when the temperature is more than a certain value, When the gas flow distribution adjusting means is adjusted to reduce the gas flow rate of the bypass flow path from the gas flow rate at the time when the temperature is equal to or higher than a certain value, and the temperature measured by the temperature measuring device is less than a certain value Reduces the gas flow rate of the exhaust gas flow path provided with the temperature measuring means from the gas flow rate at the time when the temperature is less than a certain value, and reduces the gas flow rate of the bypass flow path at the time when the temperature is less than the certain value. A method of operating an exhaust heat recovery boiler with an auxiliary burner, characterized in that the gas flow distribution adjusting means is adjusted so as to increase from the gas flow rate. Further, at least one mixing member that mixes the gas in both of the flow paths is provided at a connection portion that introduces the branched exhaust gas from the bypass flow path into the exhaust gas flow path, and a connection portion between each mixing member and the bypass flow path Provided with a gas flow distribution adjusting means, and an operating method of the exhaust heat recovery boiler with a combustion burner provided with a temperature measuring means in the exhaust gas flow path on the downstream side of the mixing member,
Gas flow distribution adjustment provided at the connecting portion between each mixing member and the bypass flow path so that the temperature measured by the temperature measuring means provided in the exhaust gas flow path on the downstream side of the mixing member becomes a certain value or more. 4. auxiliary burner with heat recovery steam generator operating method of the wherein that you adjust the gas flow through the exhaust gas flow path from the mixing member using means.

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