CA1329352C - Gas turbine plant system and gas pressure stabilizer thereof in emergency - Google Patents
Gas turbine plant system and gas pressure stabilizer thereof in emergencyInfo
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- CA1329352C CA1329352C CA000616329A CA616329A CA1329352C CA 1329352 C CA1329352 C CA 1329352C CA 000616329 A CA000616329 A CA 000616329A CA 616329 A CA616329 A CA 616329A CA 1329352 C CA1329352 C CA 1329352C
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- gas
- pressure
- water seal
- outer cylinder
- seal device
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Abstract
ABSTRACT OF THE DISCLOSURE:
Disclosed herein is a gas turbine system which is supplied with a low-pressure industrial by-product gas as a fuel and equipped coaxially with a gas compressor for compres-sing the fuel gas, the system providing a bypass pipeline for returning the gas in a high-pressure gas piping on the discharge side of the fuel gas compressor into a low-pressure gas piping on the inlet side of the compressor through a pressure reducing valve and a cooler, and an emergency gas pressure stabilizer having high responsive characteristics, the stabilizer being provided in the bypass pipeline on the outlet side of the cooler, and being constituted of a water seal device, the water seal device comprising a sealing water pipe, and an outer cylinder disposed at the water seal end of the sealing water pipe in a double tube form, the outer cylinder having such a height as to extend from a bottom portion of the water seal device to above the water level in the water seal device and being greater than the sealing water pipe in diameter.
Disclosed herein is a gas turbine system which is supplied with a low-pressure industrial by-product gas as a fuel and equipped coaxially with a gas compressor for compres-sing the fuel gas, the system providing a bypass pipeline for returning the gas in a high-pressure gas piping on the discharge side of the fuel gas compressor into a low-pressure gas piping on the inlet side of the compressor through a pressure reducing valve and a cooler, and an emergency gas pressure stabilizer having high responsive characteristics, the stabilizer being provided in the bypass pipeline on the outlet side of the cooler, and being constituted of a water seal device, the water seal device comprising a sealing water pipe, and an outer cylinder disposed at the water seal end of the sealing water pipe in a double tube form, the outer cylinder having such a height as to extend from a bottom portion of the water seal device to above the water level in the water seal device and being greater than the sealing water pipe in diameter.
Description
This is a division of Canadian patent application Serial No. 586,153, filed December 16, 19~8 for "C7AS TURBINE
PLANT SYSTEM AND GAS PRESSURE STABILIZER THEREOF IN EMERGENCY".
BACKGROUND OF THE INVENTION
(l) Field of the Invention This invention relates to a heat recovery gas turbine plant system supplied with a low-pressure industrial by-product gas, for instance, blast furnace gas, as a fuel, and more particularly to a gas pressure stabilizer for safely returning a high-pressure fuel gas on the discharge side of a fuel gas compressor into a low-pressure industrial by-product gas pipeline at the time of emergency shut-down of a gas turbine in such a system. Such gas turbine system can be employed in various process plant such as a paper manufacturing and pulp processing plant, a Portland cement manufacturing plant, a petroleum refinery plant or the like where a by-product gas is obtained.
PLANT SYSTEM AND GAS PRESSURE STABILIZER THEREOF IN EMERGENCY".
BACKGROUND OF THE INVENTION
(l) Field of the Invention This invention relates to a heat recovery gas turbine plant system supplied with a low-pressure industrial by-product gas, for instance, blast furnace gas, as a fuel, and more particularly to a gas pressure stabilizer for safely returning a high-pressure fuel gas on the discharge side of a fuel gas compressor into a low-pressure industrial by-product gas pipeline at the time of emergency shut-down of a gas turbine in such a system. Such gas turbine system can be employed in various process plant such as a paper manufacturing and pulp processing plant, a Portland cement manufacturing plant, a petroleum refinery plant or the like where a by-product gas is obtained.
(2) Description of the Prior Art As a power generation system employing a by-product gas fired gas turbine supplied with blast furnace gas as a fuel, 2~ there has recently been developed a large scale system in which, as disclosed in Japanese Patent Application Laid-Open No. 58-57012 (1983), the blast furnace gas i~ compressed to be a high-pressure gas, which is mixed with compressed air and burned, and the combustion gas is used to drive a gas turbine, thereby generating electric power.
In such a power generation system, when an emergency shut-down of the gas turbine is required, for example, when a power transmis~ion system is failed and a shut-down interlocking device is operated, it is nece~cary to cut off the supply of the fuel to the gas turbine, for the shut-down of the ga~ turbine.
For the purpose of the emergency shut-down of the gas turbine, it i~ necessary for a gas ~upply shut-off valve to be located as close as possible to the inlet to the ga~ turbine. It i~ also necessary that the shut-off operation can be performed at a sufficiently high speed.
The rapid clo~ing action (for in~tance, in 0.5 to 1 sec) of the ga~ supply shut-off valve closes the passage on the discharge side of a gas compressor continuously discharging the high-pressure ga~, resulting in a rapid increase in the discharge pressure.
In practice, therefore, a bypass pressure reducing valve for releasing the high-pressure gas into a bypass line must be rapidly opened simultaneously with the rapid closing action of the gas supply shut-off valve so that the passage on the discharge side of the gas compressor is not colsed.
The high-pressure gas on the discharge side of the gas compressor has, for instance, a pressure of about 12 kg/cm2G and a temperature of about 350C. The pressure of the high-pressure gas is lowered by the pressure reducing valve. Then, the gas is further lowered in pressure by a gas cooler disposed on the downstream side of the valve and is, simultaneously, cooled by a water Rpray, and the resultant low-pre~sure gas having a pressure of about 0.1 kg/cm2G and a temperature of about 50C i~ returned into the industrial by-product gas pipeline.
The pressure of the gas thus returned i8 not determined by only the characteristics of the gas compressor, bypass pressure reducing valve and gas cooler, but is further affected by the volume of the indu~trial by-product ga~ pipeline and the tide of the industrial by-product gas at the moment of the emergency ~hut-down. Moreover, the pre~ure of the ga~ is affected also by the in~tallation po~ition of a gasholder and by the volume absorption rate of the gasholder.
For instance, where the quantity of ga~
consumed at the gas turbine is greater than the quantity of blast furnace gas generated from the blast furnace, it is difficult to control the pressure at the outlet of the gas cooler to or below a predetermined value at any time, as upon the emergency shut-down of the gas turbine.
Upon the rapid closing action of the gas supply shut-off valve for the emergency shut-down of the gas turbine mentioned above, the gas turbine come~ to be stopped. The gas compressor, on the other hand, continues rotating due to inertia for a while;
therefore, until fully stopped, the compressor continues discharging the gas at a pressure matching the dishcarge resistance. particularly, at the moment (a few seconds) of the emergency shut-down of the gas turbine, the ga~
compressor continues discharging the gas at the same raté as immediately before the emergency shut-down.
Therefore, when the bypass pressure reducing valve is rapidly opened in conjunction with the rapid closlng of the gas ~upply shut-off valve for the gas turbine, both the high-pressure gas accumulated in the high-pressure gas piping on the discharge side of the compre~sor and the gas discharged continuou61y from the compressor are returned into the industrial by-product gas pipeline. In the industrial by-product gas pipeline, therefore, not only the flow of gas toward the gas turbine is shut off but the gas will be caused to flow backward.
This phenomenon makes it more difficult to recognize the condition of pressure setting in the industrial by-product ga~ system including the gasholder.
For in~tance, the gas absorption rate limit of the gasholder may be exceeded and the gasholder be broken. Further, ~ealing water contained in drain discharge seal pots disposed at several positions of the ~industrial by-product gas pipeline may be blown out, leading to a gas leakage accident.
For effective use of gases, it is practiced to perform calorific value control by appropriately mixing different by-product gases at positions in an indu~trial by-product gas piping. For instance, blast furnace gas having a lower calorific value is mixed with coke oven gas having a higher calorific value to get a proper calorific value of the mixed gas, thereby matching the 1 32~352 calorific value of the gas with the characteristics of the part at which the gas is used. Such a calorific value control through mixing of gases is performed by utilizing a low pressure difference of 500 to 1000 mm ~g, and is therefore heavily influenced by the above-mentioned disturbance in the gas pressure in the industrial by-product gas system.
In view of the above problems, it may be contemplated for such a gas turbine plant system to reduce the quantity of the gas returned at a lowered pressure into the low-pressure gas piping upon the closure of the gas supply shut-off valve, by reducing the internal volume of the high-pressure gas piping from the compressor to the gas turbine through shortening the piping or reducing the diameter of the piping. Such an approach, however, involve8 restrictions on layout or increase the flow resistance in the high-pressure gas piplng, and is therefore impracticable.
SUMMARY OF THE INVENTION
An object of this invention is to provide a ~ystem comprising an emergency gas pressure stabilizer effective for lowering the pressure of a high-pressure gas ~lowing backward upon emergency shut-down of a large . . .
1 32935~
gas turbine supplied with an industrial by-product gas as a fuel.
According to the invention there is provided an emergency gas pressure stabilizer for a gas turbine system sup-plied with a low-pressure industrial by-product gas as a fuel and equipped coaxially with a gas compressor for compressing the fuel gas, the stabilizer being constituted of a water seal device, the water seal device comprising a sealing water pipe, and an outer cylinder disposed at the water seal end of the sealing water pipe in a double tube form, the outer cylinder having such a height as to extend from a bottom portion of the water seal device to above the water level in the water seal de~ice and being greater than the sealing water pipe in diameter.
According to a preferred feature the outer cylinder is provided near a bottom portion thereof with slit holes for permitting communication between the interior and the exterior of the outer cylinder.
. BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a flow sheet of a gas turbine plant system according-to this invention, FIGURE 2 is a partially cutaway perspective view of a major portion of an embodiment of an emergency gas pressure stabilizer of this inventions FIGURES 3a, 3b and 3c are an illustration of the operation of a prior art water seal device;
FIGURES 4a, 4b and 4c are an illustration of the operation of the emergency gas pressure stabilizer according to this invention; and FIGURE 5 is a flow sheet showing an exemplary construction of a prior art gas turbine plant system.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIGURE 5 shows an example of a gas turbine system in which blast furnace gas is used as a fuel.
The gas generated from a blast furnace 14 is drawn out of a blast furnace gas main pipe 13 by a blast furnace gas inducting pipe 12. On the other hand, a coke oven gas supplied through a piping 15 is fed into the blast furnace gas inducting pipe 12 through a control valve 16, to form a mixed gas having a predetermined calorific value, for example, about 1000 Kcal/Nm3. The mixed gas is passed through a dust catcher 11, a piping 10 and a gas compressor 5, whereby the mixed gas is raised in pressure to about 12 kg/cm2 to be a high-pressure gas.
The high-pressure gas i8 mixed with compressed air supplied through an air compressor 2, and is burned, and the resultant combustion gas is supplied to a gas turbine 1. ~he gas turbine 1 drives a generator 6, which generates electric power.
In such a power generation system, when a power transmission system (not shown), for example, is failed, a gas supply shut-off valve 3 for the gas turbine 1 iR closed instantaneouly (for example, in 0.5 to 1 sec). Simultaneously, the high-pressure gas i9 reduced in pressure from 12 kg/cm2 to 0.1 kg/cm2 by a pressure reducing valve 7,-an~ the low-pressure gas is .. _ _ _ . , ._ . _. . ....__ _ ,_ . . .. . . _ _ . _ .
returned into a low-pressure.gas piping 8, The gas thus lowered in pressure is led-through the.gas-piping 8 into a gas cooler 9, where the gas is cooled from about 300C
to about.50C, and the cooled gas is returned into the.
blast furnace gas inducting pipe 12.
Normally, a.high-pressure gas supply pipe 5a supplies the high-pressure gas from the gas compressor 5 to the gas turbine 1. ~ut,.when the gas supply shut-off valve 3 is instantaneously closed due to, for instance, the above-mentioned failure in the power transmission system, the entire quantity of the high-pressure gas having been supplied to the gas turbine 1 is returned through the low-pressure gas piping 8 into the blast furnace gas inducting pipe 12. ~esides, in a low-load operation in which the gas turbine 1 is operated with a gas quantity below the proper operation range of the gas compressor 5, a portion of the high-pressure gas is decompressed and bypassed into the blast furnace gas inducting pipe 12 in order to prevent a surging phenomenon of the gas compressor 5.
The present inventors have made intensive studies of the system shown in FIGURE 1, before at~aining this invention. As a result of the studies, 1 32q3s2 it has been found that when a water seal device 20 is provided on the outlet side of the cooler 9, the high-pre~sure gas at a pressure of about 12 kg/cm2 blowing backward upon the instantaneous closure of the gas supply shut-off valve 3 is decompressed to 5 kg/cm2 by the pressure reducing valve 7, is then decompressed to 800 mm ~2 by the cooler 9 and further pressure relief i9 performed by the water seal device 20, whereby it is possible to lower the pressure in the bypass piping up to about 500 mm H20.
If the water seal device 20 comprises a sealing water pipe 21 simply water sealed, as shown in FIGURE 3(a), the construction being conventionally known in the gas suppliers, the instantaneous rise in the gas pressure results in a rising of the water surface 23, as shown in FIGURE 3(b). When the gas subsequently breaks the water sealing function, the pressure loss is so large (FIGURE 3(c)) that the gas cannot flow through and, therefore, the relief of the gas pressure i8 not achievedl ~hus, the gas pressure of 800 mm ~2 at the outlet of the cooler 9 at the time of emergency shut-down of the gas turbine cannot be lowered to a pressure not exerting a great effect on the low-pressure gas piping 8, the blast furnace ga~ inducting pipe 12 or the low-pressure gas piping 13, namely, to a pressure of about 500 mm H2O, which is higher than the pressure in low-pressure gas system by 150 to 200 mm H2O.
In view of the above, it may be contemplated to lower the height of the water surface 23 in the water seal device 20. This approach, however,.may lead to breakage of the water seal even under gas pressure variations during normal operation, resulting in gas leakage. Therefore, it is the usual practice to secure a predetermined water level, and it is impossible to lower the water level.
In consideration of the above, the present inventors made experiments with a double tube construction provided at a tip portion of a sealing water pipe 21, a~ shown in FIGURE 2. In the double tube construction, the sealing water pipe 21 constitutes an inner cylinder, and an outer cylinder 24 is constituted of an externally disposed pipe which is provided with a multipllci~y of notch grooves 2g located at the boundary of the water ~urface along the circumferential direction and 18 provided near bottom portion thereof with a multlplicity of lost portions, for instance, slit holes 2~ for communication between the interior and the exterlor of the external pipe. As a result of the 1 32935~
experiments, it has been found out that it is possible to instantaneously lower the gas pressure at the outlet of the cooler to 500 mm H20. This is due to a phenomenon in which, as shown FIGURE 4(a), a gap 30 defined by the sealing water pipe 21 and the outer cylinder 24 acts to cause water to be instantaneously blown out of the gap 30 as shown in FIGURE 4~b), whereby the water seal is broken and a passage being devoid of water is securely formed, so that the gas pressure is instantly released, as shown in FIGURE 4(c).
In FIGURE 2, an overflow pipe 25 is provided for controlling the water level in the water seal device, and a gas relief pipe 26 is provided for discharging the gas to a high position in the air upon the breakage of the water seal.
The outer cylinder 24 ia provided, near a bottom portion 22 o~ the water seal device, with the lost portions (slit holes for communication between the interior and the exterior of the outer cylinder) 28 which permit the sealing water to pass therethrough.
The designated numerals in FIGURE 1 are the same as those ln FIGURE 5.
The upper end notch grooves 29 and the alit holes 23 ~hown in FIGURE 2 are provided for restoring _ 13 -the water seal broken. The moment the gas pressure iB
relea~ed, the surrounding water is permitted to flow in through the upper end notch grooves 29 and the slit holes 28 to form a water seal again.
The upper end notch grooves 29 are provided for the following reason.
For a higher response to the instantaneous rise in the gas pressure, it is necessary for the small amount of sealing water sealing the Guter cylinder to be blown out. In addition, for restoration of the water seal upon the return of the pressure to a normal level it is neces~ary for the water thus blown out to be returned into the interior of the outer cylinder. The upper end notch grooves are provided for effective realization of the function to enhance the response.
The function of the slit holes 28 provided at a lower portlon of the outer cylinder is as follows.
~ y observation of the behavior of sealing water and the gas in the experiments (FIGURE 3), it has been revealed that the repon~ive characteristics is further raisable by providing slit holes in a lower portion of the outer cylinder. Of the intended function~ to prevent the instantaneous rise in the gas pressure and to restore the water seal under normal pressure, the function to restore the water seal is not satisfactorily ensured by providing the outer cylinder and providing the notch grooves at the upper end of the outer cylinder. Namely, once the gas pressure is raised, the water seal cannot be restored easily, and the gas is lePt blowing out. In consideration of this, the slit holes are provided in a lower portion of the outer cylinder so that the water pressure on the outer cylinder is exerted on the inner cylinder and the water seal is easily restorable.
According to the above considerations, when the water seal device 20 is provided on the downstream side of the cooler 9 as shown in PIGU~E 1, the gas discharged from the cooler 9 at 800 mm H2O breaks instantaneously the water seal with a pressure fall, Eor instance, to 500 mm H2O, and a portion of the gas iB
released into the atmosphere through the diffuser pipe 26, while the ma~or portion of the gas is returnable through the bypass piping ~ into the blast furnace gas lnductlng plpe 12, namely, the low-pressure gas piplng on the inlet side of the gas compressor 11.
Since the gas pressure has been lowered to about 500 mm H2O, in this case, it is possible to prevent the breakage of the gasholder 17 due to a rapid pressure increase in the gasholder and to prevent the gas leakage accident due to blow-out of sealing water from the seal pots.
The gas pressure of 500 mm H2O, mentioned by way of example in the above explanation, is not limitative. It i9 possible to select an appropriate value of the ga~ pressure by modifying the initial setting of the sealing water pressure through modification of the position of the overflow pipe 25 according to the actual situation of the plant to which the pre~ent sy~tem i~ applied.
This invention will now be explained more in detail while referring to a particular example.
The emergency gas pressure stabilizer shown in FIGURE 2 was fltted to a gas turbine power generation equipment shown in FIGURE 1, in which blast Eurnace gas and coke oven gas were mixed to have a calorific value of 1000 Kcal/Nm3, the mixed gas was compressed to a pressure of 12 kg/cm2 to produce a mixed gas at a rate of 250,000 Nm3/H, and the thus obtained gas was supplied to a 140 MW class gas turbine 1.
In an operation with a gas turbine load of 140 MWH (100%), an actual emergency shut-down test was carried out on the ga~ turbine. When the gas supply shut-off valve 3 shown in FIGURE 1 was closed, the gas pressure of 800 mm H2O on the outlet side of the cooler 9 was instantaneously lowered to 500 mm H2O, and it wa~
possible to return the high-pressure gas into the blast furnace gas inducting pipe 12 and the blast furnace gas main pipe 13 smoothly, without causing a rapid pressure rise in the gasholder or blow-out of sealing water from the seal pots.
The emergency gas pressure stabilizer according to this invention utilizes the properties of water and does not comprise mechanically moving component parts such as valves; therefore, the emergency gas pressure stabilizer operates securely, with only the water level control by overflow, and is extremely high in reliability.
In such a power generation system, when an emergency shut-down of the gas turbine is required, for example, when a power transmis~ion system is failed and a shut-down interlocking device is operated, it is nece~cary to cut off the supply of the fuel to the gas turbine, for the shut-down of the ga~ turbine.
For the purpose of the emergency shut-down of the gas turbine, it i~ necessary for a gas ~upply shut-off valve to be located as close as possible to the inlet to the ga~ turbine. It i~ also necessary that the shut-off operation can be performed at a sufficiently high speed.
The rapid clo~ing action (for in~tance, in 0.5 to 1 sec) of the ga~ supply shut-off valve closes the passage on the discharge side of a gas compressor continuously discharging the high-pressure ga~, resulting in a rapid increase in the discharge pressure.
In practice, therefore, a bypass pressure reducing valve for releasing the high-pressure gas into a bypass line must be rapidly opened simultaneously with the rapid closing action of the gas supply shut-off valve so that the passage on the discharge side of the gas compressor is not colsed.
The high-pressure gas on the discharge side of the gas compressor has, for instance, a pressure of about 12 kg/cm2G and a temperature of about 350C. The pressure of the high-pressure gas is lowered by the pressure reducing valve. Then, the gas is further lowered in pressure by a gas cooler disposed on the downstream side of the valve and is, simultaneously, cooled by a water Rpray, and the resultant low-pre~sure gas having a pressure of about 0.1 kg/cm2G and a temperature of about 50C i~ returned into the industrial by-product gas pipeline.
The pressure of the gas thus returned i8 not determined by only the characteristics of the gas compressor, bypass pressure reducing valve and gas cooler, but is further affected by the volume of the indu~trial by-product ga~ pipeline and the tide of the industrial by-product gas at the moment of the emergency ~hut-down. Moreover, the pre~ure of the ga~ is affected also by the in~tallation po~ition of a gasholder and by the volume absorption rate of the gasholder.
For instance, where the quantity of ga~
consumed at the gas turbine is greater than the quantity of blast furnace gas generated from the blast furnace, it is difficult to control the pressure at the outlet of the gas cooler to or below a predetermined value at any time, as upon the emergency shut-down of the gas turbine.
Upon the rapid closing action of the gas supply shut-off valve for the emergency shut-down of the gas turbine mentioned above, the gas turbine come~ to be stopped. The gas compressor, on the other hand, continues rotating due to inertia for a while;
therefore, until fully stopped, the compressor continues discharging the gas at a pressure matching the dishcarge resistance. particularly, at the moment (a few seconds) of the emergency shut-down of the gas turbine, the ga~
compressor continues discharging the gas at the same raté as immediately before the emergency shut-down.
Therefore, when the bypass pressure reducing valve is rapidly opened in conjunction with the rapid closlng of the gas ~upply shut-off valve for the gas turbine, both the high-pressure gas accumulated in the high-pressure gas piping on the discharge side of the compre~sor and the gas discharged continuou61y from the compressor are returned into the industrial by-product gas pipeline. In the industrial by-product gas pipeline, therefore, not only the flow of gas toward the gas turbine is shut off but the gas will be caused to flow backward.
This phenomenon makes it more difficult to recognize the condition of pressure setting in the industrial by-product ga~ system including the gasholder.
For in~tance, the gas absorption rate limit of the gasholder may be exceeded and the gasholder be broken. Further, ~ealing water contained in drain discharge seal pots disposed at several positions of the ~industrial by-product gas pipeline may be blown out, leading to a gas leakage accident.
For effective use of gases, it is practiced to perform calorific value control by appropriately mixing different by-product gases at positions in an indu~trial by-product gas piping. For instance, blast furnace gas having a lower calorific value is mixed with coke oven gas having a higher calorific value to get a proper calorific value of the mixed gas, thereby matching the 1 32~352 calorific value of the gas with the characteristics of the part at which the gas is used. Such a calorific value control through mixing of gases is performed by utilizing a low pressure difference of 500 to 1000 mm ~g, and is therefore heavily influenced by the above-mentioned disturbance in the gas pressure in the industrial by-product gas system.
In view of the above problems, it may be contemplated for such a gas turbine plant system to reduce the quantity of the gas returned at a lowered pressure into the low-pressure gas piping upon the closure of the gas supply shut-off valve, by reducing the internal volume of the high-pressure gas piping from the compressor to the gas turbine through shortening the piping or reducing the diameter of the piping. Such an approach, however, involve8 restrictions on layout or increase the flow resistance in the high-pressure gas piplng, and is therefore impracticable.
SUMMARY OF THE INVENTION
An object of this invention is to provide a ~ystem comprising an emergency gas pressure stabilizer effective for lowering the pressure of a high-pressure gas ~lowing backward upon emergency shut-down of a large . . .
1 32935~
gas turbine supplied with an industrial by-product gas as a fuel.
According to the invention there is provided an emergency gas pressure stabilizer for a gas turbine system sup-plied with a low-pressure industrial by-product gas as a fuel and equipped coaxially with a gas compressor for compressing the fuel gas, the stabilizer being constituted of a water seal device, the water seal device comprising a sealing water pipe, and an outer cylinder disposed at the water seal end of the sealing water pipe in a double tube form, the outer cylinder having such a height as to extend from a bottom portion of the water seal device to above the water level in the water seal de~ice and being greater than the sealing water pipe in diameter.
According to a preferred feature the outer cylinder is provided near a bottom portion thereof with slit holes for permitting communication between the interior and the exterior of the outer cylinder.
. BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a flow sheet of a gas turbine plant system according-to this invention, FIGURE 2 is a partially cutaway perspective view of a major portion of an embodiment of an emergency gas pressure stabilizer of this inventions FIGURES 3a, 3b and 3c are an illustration of the operation of a prior art water seal device;
FIGURES 4a, 4b and 4c are an illustration of the operation of the emergency gas pressure stabilizer according to this invention; and FIGURE 5 is a flow sheet showing an exemplary construction of a prior art gas turbine plant system.
DESCRIPTION OF PREFERRED EMBODIMENTS
FIGURE 5 shows an example of a gas turbine system in which blast furnace gas is used as a fuel.
The gas generated from a blast furnace 14 is drawn out of a blast furnace gas main pipe 13 by a blast furnace gas inducting pipe 12. On the other hand, a coke oven gas supplied through a piping 15 is fed into the blast furnace gas inducting pipe 12 through a control valve 16, to form a mixed gas having a predetermined calorific value, for example, about 1000 Kcal/Nm3. The mixed gas is passed through a dust catcher 11, a piping 10 and a gas compressor 5, whereby the mixed gas is raised in pressure to about 12 kg/cm2 to be a high-pressure gas.
The high-pressure gas i8 mixed with compressed air supplied through an air compressor 2, and is burned, and the resultant combustion gas is supplied to a gas turbine 1. ~he gas turbine 1 drives a generator 6, which generates electric power.
In such a power generation system, when a power transmission system (not shown), for example, is failed, a gas supply shut-off valve 3 for the gas turbine 1 iR closed instantaneouly (for example, in 0.5 to 1 sec). Simultaneously, the high-pressure gas i9 reduced in pressure from 12 kg/cm2 to 0.1 kg/cm2 by a pressure reducing valve 7,-an~ the low-pressure gas is .. _ _ _ . , ._ . _. . ....__ _ ,_ . . .. . . _ _ . _ .
returned into a low-pressure.gas piping 8, The gas thus lowered in pressure is led-through the.gas-piping 8 into a gas cooler 9, where the gas is cooled from about 300C
to about.50C, and the cooled gas is returned into the.
blast furnace gas inducting pipe 12.
Normally, a.high-pressure gas supply pipe 5a supplies the high-pressure gas from the gas compressor 5 to the gas turbine 1. ~ut,.when the gas supply shut-off valve 3 is instantaneously closed due to, for instance, the above-mentioned failure in the power transmission system, the entire quantity of the high-pressure gas having been supplied to the gas turbine 1 is returned through the low-pressure gas piping 8 into the blast furnace gas inducting pipe 12. ~esides, in a low-load operation in which the gas turbine 1 is operated with a gas quantity below the proper operation range of the gas compressor 5, a portion of the high-pressure gas is decompressed and bypassed into the blast furnace gas inducting pipe 12 in order to prevent a surging phenomenon of the gas compressor 5.
The present inventors have made intensive studies of the system shown in FIGURE 1, before at~aining this invention. As a result of the studies, 1 32q3s2 it has been found that when a water seal device 20 is provided on the outlet side of the cooler 9, the high-pre~sure gas at a pressure of about 12 kg/cm2 blowing backward upon the instantaneous closure of the gas supply shut-off valve 3 is decompressed to 5 kg/cm2 by the pressure reducing valve 7, is then decompressed to 800 mm ~2 by the cooler 9 and further pressure relief i9 performed by the water seal device 20, whereby it is possible to lower the pressure in the bypass piping up to about 500 mm H20.
If the water seal device 20 comprises a sealing water pipe 21 simply water sealed, as shown in FIGURE 3(a), the construction being conventionally known in the gas suppliers, the instantaneous rise in the gas pressure results in a rising of the water surface 23, as shown in FIGURE 3(b). When the gas subsequently breaks the water sealing function, the pressure loss is so large (FIGURE 3(c)) that the gas cannot flow through and, therefore, the relief of the gas pressure i8 not achievedl ~hus, the gas pressure of 800 mm ~2 at the outlet of the cooler 9 at the time of emergency shut-down of the gas turbine cannot be lowered to a pressure not exerting a great effect on the low-pressure gas piping 8, the blast furnace ga~ inducting pipe 12 or the low-pressure gas piping 13, namely, to a pressure of about 500 mm H2O, which is higher than the pressure in low-pressure gas system by 150 to 200 mm H2O.
In view of the above, it may be contemplated to lower the height of the water surface 23 in the water seal device 20. This approach, however,.may lead to breakage of the water seal even under gas pressure variations during normal operation, resulting in gas leakage. Therefore, it is the usual practice to secure a predetermined water level, and it is impossible to lower the water level.
In consideration of the above, the present inventors made experiments with a double tube construction provided at a tip portion of a sealing water pipe 21, a~ shown in FIGURE 2. In the double tube construction, the sealing water pipe 21 constitutes an inner cylinder, and an outer cylinder 24 is constituted of an externally disposed pipe which is provided with a multipllci~y of notch grooves 2g located at the boundary of the water ~urface along the circumferential direction and 18 provided near bottom portion thereof with a multlplicity of lost portions, for instance, slit holes 2~ for communication between the interior and the exterlor of the external pipe. As a result of the 1 32935~
experiments, it has been found out that it is possible to instantaneously lower the gas pressure at the outlet of the cooler to 500 mm H20. This is due to a phenomenon in which, as shown FIGURE 4(a), a gap 30 defined by the sealing water pipe 21 and the outer cylinder 24 acts to cause water to be instantaneously blown out of the gap 30 as shown in FIGURE 4~b), whereby the water seal is broken and a passage being devoid of water is securely formed, so that the gas pressure is instantly released, as shown in FIGURE 4(c).
In FIGURE 2, an overflow pipe 25 is provided for controlling the water level in the water seal device, and a gas relief pipe 26 is provided for discharging the gas to a high position in the air upon the breakage of the water seal.
The outer cylinder 24 ia provided, near a bottom portion 22 o~ the water seal device, with the lost portions (slit holes for communication between the interior and the exterior of the outer cylinder) 28 which permit the sealing water to pass therethrough.
The designated numerals in FIGURE 1 are the same as those ln FIGURE 5.
The upper end notch grooves 29 and the alit holes 23 ~hown in FIGURE 2 are provided for restoring _ 13 -the water seal broken. The moment the gas pressure iB
relea~ed, the surrounding water is permitted to flow in through the upper end notch grooves 29 and the slit holes 28 to form a water seal again.
The upper end notch grooves 29 are provided for the following reason.
For a higher response to the instantaneous rise in the gas pressure, it is necessary for the small amount of sealing water sealing the Guter cylinder to be blown out. In addition, for restoration of the water seal upon the return of the pressure to a normal level it is neces~ary for the water thus blown out to be returned into the interior of the outer cylinder. The upper end notch grooves are provided for effective realization of the function to enhance the response.
The function of the slit holes 28 provided at a lower portlon of the outer cylinder is as follows.
~ y observation of the behavior of sealing water and the gas in the experiments (FIGURE 3), it has been revealed that the repon~ive characteristics is further raisable by providing slit holes in a lower portion of the outer cylinder. Of the intended function~ to prevent the instantaneous rise in the gas pressure and to restore the water seal under normal pressure, the function to restore the water seal is not satisfactorily ensured by providing the outer cylinder and providing the notch grooves at the upper end of the outer cylinder. Namely, once the gas pressure is raised, the water seal cannot be restored easily, and the gas is lePt blowing out. In consideration of this, the slit holes are provided in a lower portion of the outer cylinder so that the water pressure on the outer cylinder is exerted on the inner cylinder and the water seal is easily restorable.
According to the above considerations, when the water seal device 20 is provided on the downstream side of the cooler 9 as shown in PIGU~E 1, the gas discharged from the cooler 9 at 800 mm H2O breaks instantaneously the water seal with a pressure fall, Eor instance, to 500 mm H2O, and a portion of the gas iB
released into the atmosphere through the diffuser pipe 26, while the ma~or portion of the gas is returnable through the bypass piping ~ into the blast furnace gas lnductlng plpe 12, namely, the low-pressure gas piplng on the inlet side of the gas compressor 11.
Since the gas pressure has been lowered to about 500 mm H2O, in this case, it is possible to prevent the breakage of the gasholder 17 due to a rapid pressure increase in the gasholder and to prevent the gas leakage accident due to blow-out of sealing water from the seal pots.
The gas pressure of 500 mm H2O, mentioned by way of example in the above explanation, is not limitative. It i9 possible to select an appropriate value of the ga~ pressure by modifying the initial setting of the sealing water pressure through modification of the position of the overflow pipe 25 according to the actual situation of the plant to which the pre~ent sy~tem i~ applied.
This invention will now be explained more in detail while referring to a particular example.
The emergency gas pressure stabilizer shown in FIGURE 2 was fltted to a gas turbine power generation equipment shown in FIGURE 1, in which blast Eurnace gas and coke oven gas were mixed to have a calorific value of 1000 Kcal/Nm3, the mixed gas was compressed to a pressure of 12 kg/cm2 to produce a mixed gas at a rate of 250,000 Nm3/H, and the thus obtained gas was supplied to a 140 MW class gas turbine 1.
In an operation with a gas turbine load of 140 MWH (100%), an actual emergency shut-down test was carried out on the ga~ turbine. When the gas supply shut-off valve 3 shown in FIGURE 1 was closed, the gas pressure of 800 mm H2O on the outlet side of the cooler 9 was instantaneously lowered to 500 mm H2O, and it wa~
possible to return the high-pressure gas into the blast furnace gas inducting pipe 12 and the blast furnace gas main pipe 13 smoothly, without causing a rapid pressure rise in the gasholder or blow-out of sealing water from the seal pots.
The emergency gas pressure stabilizer according to this invention utilizes the properties of water and does not comprise mechanically moving component parts such as valves; therefore, the emergency gas pressure stabilizer operates securely, with only the water level control by overflow, and is extremely high in reliability.
Claims (4)
1. An emergency gas pressure stabilizer for a gas turbine system supplied with a low-pressure industrial by-product gas as a fuel and equipped coaxially with a gas compressor for compressing the fuel gas, the stabilizer being constituted of a water seal device, the water seal device comprising a sealing water pipe, and an outer cylinder disposed at the water seal end of the sealing water pipe in a double tube form, the outer cylin-de having such a height as to extend from a bottom portion of the water seal device to above the water level in the water seal device and being greater than the sealing water pipe in diameter.
2. The emergency gas pressure stabilizer as set forth in claim 1, wherein the outer cylinder is provided near a bottom portion thereof with slit holes for permitting communication between the interior and the exterior of the outer cylinder.
3. The emergency gas pressure stabilizer as set forth in claim 1, wherein the outer cylinder is provided with a multi-plicity of notch grooves at the upper edge thereof.
4. The emergency gas pressure stabilizer as set forth in claim 3, wherein the outer cylinder is provided near a bottom portion thereof with slit holes for permitting communication between the interior and the exterior of the outer cylinder.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000616329A CA1329352C (en) | 1987-12-18 | 1992-03-25 | Gas turbine plant system and gas pressure stabilizer thereof in emergency |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP191461/1987 | 1987-12-18 | ||
| JP1987191461U JPH0439392Y2 (en) | 1987-12-18 | 1987-12-18 | |
| CA000586153A CA1325890C (en) | 1987-12-18 | 1988-12-16 | Gas turbine plant system and gas pressure stabilizer thereof in emergency |
| CA000616329A CA1329352C (en) | 1987-12-18 | 1992-03-25 | Gas turbine plant system and gas pressure stabilizer thereof in emergency |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000586153A Division CA1325890C (en) | 1987-12-18 | 1988-12-16 | Gas turbine plant system and gas pressure stabilizer thereof in emergency |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1329352C true CA1329352C (en) | 1994-05-10 |
Family
ID=25672310
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000616329A Expired - Fee Related CA1329352C (en) | 1987-12-18 | 1992-03-25 | Gas turbine plant system and gas pressure stabilizer thereof in emergency |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1329352C (en) |
-
1992
- 1992-03-25 CA CA000616329A patent/CA1329352C/en not_active Expired - Fee Related
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| MKLA | Lapsed |