EXHAUST GAS PURIFICATION DEVICE FOR GAS TURBINE ENGINE

Abstract

An exhaust gas purification device (26) for a gas turbine engine (10) comprises a catalyst chamber (64, 96) defined in an exhaust gas passage (22), a reduction agent container (32) containing a solid material that releases a reduction agent gas effective for NOx reduction when heated, a heating device (36, 38) for heating the solid material contained in the reduction agent container, and a reduction agent gas supply passage (48) for supplying the reduction agent gas released from the solid material into the catalyst chamber.

Claims

1. An exhaust gas purification device for a gas turbine engine, comprising: a catalyst chamber containing a reduction catalyst therein and defined in an exhaust gas passage conducting exhaust gas discharged from the gas turbine engine; a reduction agent container containing a solid material that releases a reduction agent gas effective for NOx reduction when heated; a heating device for heating the solid material contained in the reduction agent container; and a reduction agent gas supply passage for supplying the reduction agent gas released from the solid material into the catalyst chamber.

2. The exhaust gas purification device according to claim 1, wherein the reduction agent gas contains NH.sub.3.

3. The exhaust gas purification device according to claim 2, wherein the solid material contains a matrix retaining NH.sub.3 therein or urea.

4. The exhaust gas purification device according to claim 1, further comprising a hydrogen gas source and a hydrogen gas supply passage for supplying hydrogen gas from the hydrogen gas source into the catalyst chamber.

5. The exhaust gas purification device according to claim 4, wherein the hydrogen gas source comprises hydrogen compound in solid form that releases hydrogen gas by adding water or heating.

6. The exhaust gas purification device according to claim 5, wherein the hydrogen compound includes a member selected from a group consisting of MgH.sub.2 and CaH.sub.2.

7. The exhaust gas purification device according to claim 1, wherein the gas turbine includes a regenerator for heating intake air with exhaust gas, and the catalyst chamber is provided in an exhaust gas flow path in the regenerator.

8. The exhaust gas purification device according to claim 1, wherein the heating device includes a heat exchanger that exchanges heat between the solid material and a heat medium which acquires heat generated by operation of the gas turbine engine.

9. The exhaust gas purification device according to claim 1, wherein the heating device includes an electric heater for heating the solid material, and the electric heater is provided with a controller for controlling an amount of heat supplied to the solid material.

10. The exhaust gas purification device according to claim 8, wherein the heating device includes an electric heater for heating the solid material, and a controller for controlling an amount of heat supplied by the electric heater to the solid material.

11. The exhaust gas purification device according to claim 1, wherein the reduction agent container is provided with a pressure sensor for detecting a pressure in the reduction agent container, and the exhaust gas purification device is provided with a controller for controlling the heating device according to the pressure detected by the pressure sensor.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

[0026] FIG. 1 is a schematic diagram showing an overall structure of a gas turbine engine fitted with an exhaust gas purification device according to a first embodiment of the present invention;

[0027] FIG. 2 is a sectional side view of a regenerator used in the exhaust gas purification device of the first embodiment;

[0028] FIG. 3 is a view similar to FIG. 1 showing a second embodiment of the present invention; and

[0029] FIG. 4 is a view similar to FIG. 1 showing a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0030] An exhaust purification device for a gas turbine engine according to an embodiment of the present invention will be described in the following with reference to FIG. 1.

First Embodiment

[0031] FIG. 1 shows a gas turbine engine 10 equipped with an exhaust gas purification device 26 according to the first embodiment of the present invention. The gas turbine engine 10 is provided with a compressor 14 and a turbine 16 coaxially connected to each other by a rotating shaft 12, and a combustor 18. The compressor 14 compresses and pressurizes intake air, and supplies the pressurized intake air to the combustor 18 via an air supply passage 20. High pressure combustion gas is produced in the combustor 18 by the combustion of a mixture of intake air and fuel which is injected into the combustor 18 via a passage not shown in the drawings. The combustion gas rotationally drives the turbine 16. An output shaft 17 of the turbine 16 is connected to a generator (not shown in the drawings) or the like as an object to be rotationally driven by the gas turbine engine 10.

[0032] The combustion gas that has rotationally driven the turbine 16 is discharged to the atmosphere via an exhaust gas passage 22 as exhaust gas.

[0033] The gas turbine engine 10 is additionally provided with a regenerator 24 positioned between intermediate parts of the air supply passage 20 and the exhaust gas passage 22. The regenerator 24 heats the supply air (intake air) flowing through the supply passage 20 with the heat of the exhaust gas flowing through the exhaust gas passage 22. Thus, the charge air supplied to the combustor 18 is preheated so that the thermal efficiency of the Brayton cycle performed by the gas turbine engine 10 can be improved.

[0034] The exhaust gas purification device 26 is provided with an NH.sub.3 gas generator 30. The NH.sub.3 gas generator 30 is provided with an NH.sub.3 container 32 consisting of an enclosed container, and configured to accommodate a solid NH.sub.3 cartridge 34 therein in a removable manner. The solid NH.sub.3 cartridge 34 contains NH.sub.3 (ammonia) in solid form typically as a solid organic compound or as gas or molecules absorbed/adsorbed in a solid storage medium or a solid matrix. Solid NH.sub.3 may be maintained in a solid state such as powder, granules, and pellets, and is configured to release NH.sub.3 gas when heated.

[0035] The NH.sub.3 container 32 is internally provided with an electric heater 38 for heating the solid NH.sub.3 contained in the solid NH.sub.3 cartridge 34 as required.

[0036] The NH.sub.3 container 32 is additionally provided with a heat exchanger 36 through which lubricating oil for lubricating various parts of the gas turbine engine 10 is circulated. The oil which has lubricated various parts of the gas turbine engine 10, and is thereby heated is supplied to the heat exchanger 36 via an oil introduction passage 40, and after releasing heat in the heat exchanger 36, is forwarded to an oil tank 46 of the gas turbine engine 10 via an oil discharge passage 42. The heat released by the heat exchanger 36 is used for heating the solid NH.sub.3 contained in the solid NH.sub.3 cartridge 34.

[0037] The oil discharge passage 42 is provided with an oil flow control valve 44 which allows the flow of the oil into and out of the heat exchanger 36 to be quantitively controlled.

[0038] When the solid NH.sub.3 in the solid NH.sub.3 cartridge 34 is heated by the heat exchanger 36 or the electric heater 38, NH.sub.3 gas is generated in the NH.sub.3 container 32 by sublimation or other forms of gasification of the solid NH.sub.3.

[0039] The interior of the NH.sub.3 container 32 is communicated with a part of the exhaust gas passage 22 upstream of the regenerator 24 via an NH.sub.3 gas supply passage 48 so that the NH.sub.3 gas generated in the NH.sub.3 container 32 may be supplied to the part of the exhaust gas passage 22 upstream of the regenerator 24 via the NH.sub.3 gas supply passage 48. An NH.sub.3 gas flow rate control valve 50 is provided in the NH.sub.3 gas supply passage 48. The NH.sub.3 gas flow rate control valve 50 quantitatively controls the flow rate of the NH.sub.3 gas flowing through the NH.sub.3 gas supply passage 48 or, in other words, the amount of NH.sub.3 gas supplied to the exhaust gas passage 22.

[0040] The NH.sub.3 container 32A is provided with a pressure sensor 52 for detecting the internal pressure of the NH.sub.3 container 32. A NOx sensor 54 for detecting the concentration of NOx flowing through the exhaust gas passage 22 is provided in a part of the exhaust gas passage 22 upstream of the junction with the NH.sub.3 gas supply passage 48.

[0041] The exhaust gas purification device 26 is provided with an electronic control unit (ECU) 56 that controls the electric heater 38, the oil flow control valve 44 and the NH.sub.3 gas flow rate control valve 50.

[0042] The ECU 56 controls the heating of the solid NH.sub.3 in the solid NH.sub.3 cartridge 34 by using the heat obtained from the heat exchanger 36 and the electric heater 38 according to the internal pressure of the NH.sub.3 container 32 detected by the pressure sensor 52. The ECU 56 controls the NH.sub.3 gas flow rate control valve 50 according to the NOx concentration detected by the NOx sensor 54 so that the amount of NH.sub.3 gas supplied to the exhaust gas passage 22 is maintained at an optimum value as will be described hereinafter. The amount of NOx emission may also be estimated from the operating state of the gas turbine engine 10 instead of actually measuring the amount of NOx emission with the NOx sensor 54, and the NH.sub.3 gas supply amount may be determined based on this data.

[0043] The internal pressure of the NH.sub.3 container 32 can be increased by the NH.sub.3 gas produced by the sublimation or other modes of gasification of the solid NH.sub.3, and the internal pressure can be maintained at a designed value by the heat from the heat exchanger 36 and the electric heater 38 which is under the control of the ECU 56. Thus, the supply of NH.sub.3 gas can be performed without requiring a pump or the like. As a result, the cost of the exhaust gas purification device 26 can be reduced, and the space efficiency of the exhaust gas purification device 26 can be improved. By maintaining the pressure in the NH.sub.3 container 32 at a prescribed value, the quantitative control of the amount of NH.sub.3 gas supplied to the exhaust gas passage 22 by means of the NH.sub.3 gas flow rate control valve 50 is facilitated.

[0044] The ECU 56 turns on the electric heater 38 when the oil temperature falls short of the prescribed value only with the heat generated by the operation of the gas turbine engine 10. Typically, the electric heater 38 is turned on during the warm-up period of the gas turbine engine 10, and is kept turned on until the oil temperature has reached or exceeded the prescribed value. Therefore, even during the warm-up period following the initial starting of the gas turbine engine 10, the necessary amount of NH.sub.3 gas can be ensured by heating the solid NH.sub.3 cartridge 34 with the electric heater 38.

[0045] Normally, the electric heater 38 is required to be operated only for a short period of time immediately following the startup of the gas turbine engine 10 or until the oil of the gas turbine engine 10 reaches the temperature required for the gasification of the NH.sub.3 solid matter in the solid NH.sub.3 cartridge 34. Since this period is relatively short, even in the case of aircraft or the like using a gas turbine engine 10 as a power source, the existing onboard battery will be adequate as a power source for the electric heater 38, and no additional cost will be incurred.

[0046] As shown in FIG. 2, the regenerator 24 is provided with a regenerator housing 60 which is internally partitioned by a partition wall 62 between an exhaust gas channel 64 and an air supply channel 66. The exhaust gas channel 64 forms a part of the exhaust gas passage 22, and the air supply channel 66 forms a part of the air supply passage 20. Corrugated fins 68 and 70 are provided in the exhaust gas channel 64 and the air supply channel 66, respectively. These fins 68 and 70 are in contact with and/or attached to the adjoining walls of the housing 60 and the partition wall 62. The fins 68 and 70, the housing 60 and the partition wall 62 are all made of thermally conductive metal sheet members. Owing to the large surface areas provided by the corrugated or otherwise wavy configuration of the fins 68 and 70, heat exchange between the intake air flowing through the air supply channel 66 and the exhaust gas flowing through the exhaust gas channel 64 can be effected in an efficient manner.

[0047] A reduction catalyst layer 72 is formed on the surface of the fins 68 in the exhaust gas channel 64 so that the exhaust gas channel 64 forms a catalyst chamber. The catalyst material for the reduction catalyst layer 72 may be zeolite, which increases the efficiency of the NOx reduction reaction by NH.sub.3. The exhaust gas into which NH.sub.3 gas is supplied from the NH.sub.3 container 32 flows inside the exhaust gas channel 64. As a result, NOx in the exhaust gas is reduced under the catalytic action of the reduction catalyst layer 72 using the NH.sub.3 gas as a reducing agent. This reduction reaction can be representative by the following chemical formulas.

NO+NO.sub.2+2NH.sub.3.fwdarw.2N.sub.2+3H.sub.2O

4NO+4NH.sub.3+O.sub.2.fwdarw.4N.sub.2+6H.sub.2O

6NO.sub.2+8NH.sub.3.fwdarw.7N.sub.2+12H.sub.2O

[0048] In this way, the NOx in the exhaust gas is reduced and the exhaust gas is purified. In this reduction process, it is desirable that the amount of NH.sub.3 that is supplied corresponds to the flow rate of the exhaust gas and the concentration of NOx gas in the exhaust gas. In this embodiment, NH.sub.3 is obtained by the sublimation or gasification of NH.sub.3 in the solid NH.sub.3 cartridge 34, so the volume and weight of the NH.sub.3 supply source are minimized as compared to the case where NH.sub.3 is supplied as water solution of urea. As a result, the size and weight of the exhaust gas purification device 26 including the NH.sub.3 gas generator 30 can be reduced. In particular, since the NH.sub.3 supply source for the reduction process is in solid form, the storage space for the necessary amount of NH.sub.3 can be made smaller than when the NH.sub.3 supply source is in liquid form.

[0049] When the NH.sub.3 supply source is in liquid form such as water solution of urea, a leak-proof tank is required, but when the NH.sub.3 supply source is the solid NH.sub.3 cartridge 34, there is no risk of liquid leakage. When the NH.sub.3 supply source is in liquid form such as water solution of urea, a relatively large tank is required, and the sloshing of the liquid in the tank may also pose a problem in automobiles and aircraft. Further, since the NH.sub.3 supply source stored in the solid NH.sub.3 cartridge 34 is in solid form, the NH.sub.3 supply source NH is stable against external influences, and is easy to handle during the maintenance work such as replacing the cartridge.

[0050] The heat exchanger 36 heats the solid NH.sub.3 cartridge 34 by using the heat generated by the operation of the gas turbine engine 10 during the normal operation of the gas turbine engine 10 so that there is no need to separately prepare a heat source for gasification. As a result, the cost of the exhaust gas purification device can be reduced.

[0051] According to the first embodiment, a significant reduction in the size of the reducing agent storage unit can be accomplished owing to the use NH.sub.3 in solid form as compared to the case where hydrogen gas is used.

[0052] By providing the reduction catalyst layer 72 in the regenerator 24, there is no need to provide a separate housing to form the catalyst chamber. This also contributes to size and weight reduction of the exhaust gas purification device 26. Since the reduction catalyst layer 72 is formed on the surface of the fins 68 of the regenerator 24, the surface area of the reduction catalyst layer 72 can be maximized. Thus, owing to the effective use of the fins 68 of the regenerator 24, the surface area of the reduction catalyst layer 72 is increased. This improves the catalytic action of the reduction catalyst layer 72.

Second Embodiment

[0053] An exhaust gas purification device 26 according to a second embodiment of the present invention will be described in the following with reference to FIG. 3. In FIG. 3, parts corresponding to those in FIG. 1 are denoted with like numerals as in FIG. 1, and the description of such parts may be omitted in the following description to avoid redundancy.

[0054] The exhaust gas purification device 26 according to the second embodiment is provided with an H.sub.2 gas generator 80 in addition to the NH.sub.3 gas generator 30.

[0055] The H.sub.2 gas generator 80 is provided with a hydrogen compound container 82 having an enclosed structure. The hydrogen compound container 82 accommodates a solid H.sub.2 cartridge 84 in a removable manner. The solid H.sub.2 cartridge 84 contains MgH.sub.2 (magnesium hydride) as a solid hydrogen compound. MgH.sub.2 is stable in a solid state such as powder, granules, or pellets.

[0056] The hydrogen compound container 82 is provided with a hydration device 86 that hydrolyzes the solid MgH.sub.2 stored in the solid H.sub.2 cartridge 84.

[0057] The MgH.sub.2 in the solid H.sub.2 cartridge 84 releases H.sub.2 gas as a result of hydrolysis performed in the hydration device 86.

[0058] The hydrogen compound container 82 is connected to a part of the NH.sub.3 gas supply passage 48 downstream of the NH.sub.3 gas flow rate control valve 50 via a hydrogen gas supply passage 88. Thus, the H.sub.2 gas generated in the hydrogen compound container 82 is forwarded to the part of the exhaust gas passage 22 upstream of the regenerator 24 together with the NH.sub.3 gas. The hydrogen gas supply passage 88 may also be directly connected to a part of the NH.sub.3 gas supply passage 48 upstream of the regenerator 24.

[0059] An H.sub.2 gas flow rate control valve 90 is provided in an intermediate part of the hydrogen gas supply passage 88. The H.sub.2 gas flow rate control valve 90 quantitatively controls the flow rate of H.sub.2 gas flowing through the hydrogen gas supply passage 88, or in other words, the amount of H.sub.2 gas supplied to the exhaust gas passage 22.

[0060] The hydrogen compound container 82 is provided with a pressure sensor 52 for detecting the pressure inside the hydrogen compound container 82.

[0061] The ECU 56 controls the progress of the hydrolysis of MgH.sub.2 in the solid H.sub.2 cartridge 84 performed by the hydration device 86 according to the pressure inside the hydrogen compound container 82 detected by the pressure sensor 52. The ECU 56 controls the H.sub.2 gas flow rate control valve 90 so that the amount of H.sub.2 gas supplied to the exhaust gas passage 22 is maintained at a prescribed value. The H.sub.2 gas flow rate control valve 90 is controlled in relation with the control of the NH.sub.3 gas flow rate control valve 50 so that the amount of H.sub.2 gas supplied to the exhaust gas passage 22 is at a prescribed ratio to the amount of NH.sub.3 gas supplied to the exhaust gas passage 22.

[0062] The pressure inside the hydrogen compound container 82 increases as the H.sub.2 gas produced in the hydration device 86 increases so that the H.sub.2 gas can be supplied from the hydrogen compound container 82 to the exhaust gas passage 22 in a controllable manner and without requiring a pump or the like. This also contributes to the reduction in the size and cost of the exhaust gas purification device 26. By maintaining the pressure in the hydrogen compound container 82 at a prescribed value, the quantitative control the amount of H.sub.2 gas supplied to the exhaust gas passage 22 via the H.sub.2 gas flow rate control valve 90 is facilitated.

[0063] The reduction catalyst layer 72 (see FIG. 2) provided in the regenerator 24 may contain silver alumina (Ag/Al.sub.2O.sub.3) in the second embodiment. The activity of silver-alumina for NOx reduction by NH.sub.3 gas is enhanced by the addition of H.sub.2 gas. More specifically, the addition of H.sub.2 gas generates Ag clusters and O.sub.2, and a mechanism for promoting NOx reduction using these as free radicals is created. This improves the NOx reduction rate in the exhaust gas.

[0064] Since H.sub.2 gas is obtained from solid MgH.sub.2, the volume and weight of the H.sub.2 source can be reduced. As a result, the size and weight of the exhaust gas purification device 26 including the H.sub.2 gas generator 80 can be reduced. In other words, since the H.sub.2 gas supply source is in solid form, the installation space for the container of the H.sub.2 gas supply source can be reduced compared to the case where the H.sub.2 gas supply source is in gas form.

[0065] The present invention has been described in terms of specific embodiments thereof, but is not limited by such embodiments, and can be modified in various ways without departing from the scope of the present invention. Moreover, not all of the constituent elements shown in the above embodiments are essential to the broad concept of the present invention, and they can be appropriately selected, omitted and substituted without departing from the gist of the present invention. The contents of any cited references in this disclosure will be incorporated in the present application by reference.

[0066] For example, the solid material that releases a reduction agent gas effective for NOx reduction is not limited to NH.sub.3 retained in a solid material or solid matrix, but any solid compound that can exist in solid form such as CH.sub.4N.sub.2O (urea) may also be used for NOx reduction according to the present invention. Similarly as the solid material retaining NH.sub.3, CH.sub.4N.sub.2O can also maintain a solid state such as powder, granules, and pellets.

[0067] Solid hydrogen compounds suitable for generating H.sub.2 gas include CaH.sub.2 (calcium hydride) in addition to MgH.sub.2. Similarly as MgH.sub.2, CaH.sub.2 can also maintain a solid state such as powder, granules, and pellets. Since CaH.sub.2 generates H.sub.2 gas when heated, the hydrogen compound container 82 may be provided with a heating device (such as the heating device 94 shown in FIG. 3) in place of the hydration device 86. The H.sub.2 gas may also be fed to an upstream part of the exhaust gas passage 22 or the exhaust gas channel 64 of the regenerator 24, instead of an intermediate part of the NH.sub.3 gas supply passage 48. The heating device 94 may be a combination of a heat exchanger 36 and an electric heater 38 similar to the counterparts provided in the NH.sub.3 gas generator 30 of the first embodiment.

[0068] The regenerator 24 is optional for the present invention, and as shown in FIG. 4, the regenerator 24 may be replaced by a catalytic converter 96 defining a catalytic chamber therein, and provided separately from the air supply passage 20. In the case of the catalytic converter 96, a honeycomb structure containing a catalyst through which the exhaust gas flows may be used.