JPS622650B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for increasing the safety of dispersing large amounts of residual gas into the atmosphere. As a variant, the invention relates to improvements in gas turbines. In particular, the present invention utilizes residual gas as a separate cooling flow in a gas turbine combustor, thereby increasing the overall efficiency of the gas turbine, and the present invention utilizes residual gas as a separate cooling flow in a gas turbine combustor, thereby increasing the overall efficiency of the gas turbine, and in which the residual gas is Concerning heating gas. Oil and gas processing facilities, refineries and other industrial operations often generate large amounts of residual gas of little or no value. Residual gas may occur naturally, such as carbon dioxide produced with natural gas from natural gas wells, or it may be a by-product of industrial operations. These residual gases must be disposed of independently of the gas source or the like.
Often the only real way to dispose of
This is to release residual gas into the atmosphere. Of course, even such releases into the atmosphere must comply with all environmental regulations. For example, the release of residual gases such as carbon monoxide (CO) or hydrogen sulfide ( _H2S ) is severely limited. However, in addition to the obvious environmental concerns, the release of large amounts of residual gas, even if environmentally acceptable, is dangerous to those living in the immediate vicinity of the release site. If the density of the emitted residual gas is greater than the surrounding air, the residual gas will displace the lighter air floating in the area of the emitted area. This poses a choking hazard to those living within the area. One example of this is the release of large amounts of _CO2 . Typically, the release of carbon dioxide is environmentally acceptable. However, due to the fact that CO ₂ is heavier than air,
The release of large amounts of CO ₂ is potentially dangerous to those living in the area of release. By heating the residual gas before releasing it, the above-mentioned risks can be reduced or eliminated. If the temperature of the gas is raised to such a temperature that the density of the gas is less than the density of the surrounding air, the gas will rise upon release and will disperse into the surrounding air rather than drifting into the area of the release point.
Thus, large amounts of residual gas can be safely released by preheating the residual gas. Unfortunately, the above solutions to the disposal problem are not economically desirable. Direct heating of residual gas consumes large amounts of energy and results in high disposal costs. Therefore, a more economical method of disposing of large amounts of residual gas is needed. One method that has been proposed to solve this problem is to mix the residual gas with the gas turbine exhaust stream. Gas turbines are often used in factories for operations requiring a rotating power source, such as generating electricity, for example. Gas turbines are widely used in the oil and gas industry. In oil refineries, gas turbines are used as drive units for compressors and pumps, and in oil and gas wells, gas turbines are used to maintain pressure. Typically,
The temperature of the exhaust gas of an industrial gas turbine is 500〓
It is within the range of 1000〓. Thus, introducing the residual gas to be disposed of into the exhaust stream of the gas turbine can help solve the disposal problem. Although this solution offers several benefits, disposal of any available residual gas is
Often inappropriate. In summary, the present invention uses large amounts of residual gas originating from industrial operations or similar gas sources as a separate cooling stream in a gas turbine to heat the residual gas, thereby Addresses the emission problem by reducing the tendency for particles to drift into the emission area. This significantly increases the residual gas that can be safely disposed of by the gas turbine, which in turn can increase the overall efficiency of the gas turbine. A gas turbine combustor consists of one or more separate combustion chambers known as combustion cans. These combustion cans typically have two main zones: a combustion zone where the fuel is mixed with compressed air and combusted, and a hot combustion zone to reduce the temperature of the combustion products to a temperature that does not harm the turbine. and a dilution or cooling zone in which the product is mixed with additional compressed air. Typically, only about 1/3 to 1/4 of the compressed air supplied by the turbine's compressor is used for combustion, with the remainder used to cool the hot combustion products. According to the invention, compressed residual gas replaces the air used in the dilution zone of the combustion can to cool the hot combustion products. Thus, reducing the amount of air that must be compressed by the turbine's compressor. Often, the residual gas is available at a pressure equal to or greater than the pressure of the combustion products of the combustor. In this case, residual gas can be introduced directly into the dilution zone of the combustor, increasing the overall efficiency of the gas turbine by reducing the amount of compressed air that has to be supplied by the compressor. . If only low pressure residual gas is available, compressing the residual gas can equal or even increase the beneficial effect of reducing the amount of compressed air required. In other cases, additional residual gas may be added to the gas turbine exhaust stream to increase the total amount disposed of. FIG. 1 diagrammatically shows the use of a gas turbine arrangement according to the invention for disposing of high pressure residual gas. FIG. 2 illustrates the invention for disposing of low pressure residual gas. Referring now to FIGS. 1 and 2, the gas turbine of the present invention consists essentially of a turbine 10 and
It consists of an air compressor 12 and a modified combustor 14. A gas turbine is used to drive the load 16, which can be anything that requires a source of rotary power. For example, load 16 may be a generator, pump, or compressor. Turbine 10 is mechanically coupled to load 16 by a drive shaft 18 including gears, reducers, clutches, transmissions, or the like (not shown). Turbine 10 and compressor 12 are mechanically coupled by a compressor drive shaft 20. Like the drive shaft, compressor drive shaft 20 may include additional intermediate power transmissions (not shown). Both drive shaft 18 and compressor drive shaft 20 are driven by turbine 10. Gas turbine combustors vary widely in design and configuration. For detailed information on combustor design, see Sawyer's Gas Turbine Technology Handbook, 2nd Edition (Gas Turbine Publishers 1976), especially Volume 1, pages 151-167, "Combustor Design" by Herbert Earl Hazzard. See especially Chapter 7 entitled ”. A gas turbine combustor consists of one or more separate combustion chambers, hereinafter referred to as combustion cans. Each combustion chamber consists of a main zone in which the fuel is combusted and a dilution zone in which the combustion products are cooled.
The combustor may be completely independent of the turbine and associated air compressor, or alternatively may be integral with the turbine and air compressor. Typically, a gas turbine combustor consists of several combustion cans arranged in a ring around a drive shaft connecting the turbine and air compressor. Regardless of type or configuration, all combustors perform the same basic function. Fuel is injected by a spray nozzle into the main zone of the combustion can, where it mixes with compressed air supplied by the compressor of the turbine and ignites. The hot combustion products are then mixed with additional compressed air in the secondary dilution zone of the combustion can.
The purpose of this dilution is to cool the combustion products to a temperature suitable for use in the turbine, and to cool the combustion can itself. Usually, about 1/3 to 1/3 of the compressed air supplied from the turbine compressor
Only 4 is used for combustion. remaining 2/ of compressed air
3 to 3/4 will be used for dilution and cooling. According to the invention, the compressed air used for dilution and cooling is replaced by pressurized residual gas. Referring again to FIGS. 1 and 2, a modified combustor 14 is schematically shown. As mentioned above, the modified combustor 14 typically consists of a number of individual combustion cans arranged to form a ring around the compressor drive shaft 20. However, for simplicity, it is assumed that the modified combustor 14 consists of only one combustion can. The dotted line indicates the transition between combustion zone 22 and dilution zone 24. Residual gas source 26 (shown as a block) may be any gas source that produces a significant amount of residual gas. The temperature of the residual gas in the residual gas source 26 is
Typically, it is equal to or less than the temperature.
Referring now to FIG. 1, it is assumed that the residual gas is available at a pressure equal to or greater than the pressure of the combustion products in the modified combustor 14. For example, _CO2 is produced as a residual gas at very high pressures from natural gas processing facilities. In this case, the residual gas flows directly from the residual gas source 26 through the pipeline 28 to the dilution zone 24 of the modified combustor 14 . Pipeline 28 includes additional pressure and/or fluid regulation devices (not shown). On the other hand, suppose
If the residual gas is only available at low pressure, it must be pressurized before entering the modified combustor 14. This pressurization is accomplished by a secondary compressor 30, as shown in FIG. 2
The secondary compressor 30 may be driven independently of the turbine 10. As a modification, as shown in Figure 2,
Secondary compressor 30 may be mechanically coupled to compressor 12 by a secondary compressor drive shaft 32. In this case, the secondary compressor 3
0 is generated by the turbine 10, and the compressor drive shaft 20,
It is transmitted to the secondary compressor 30 by the compressor 12 and the secondary compressor drive shaft 20. Other methods of driving secondary compressor 30 will be readily apparent to those skilled in the art. Residual gas is conveyed by pipeline 34 from residual gas source 26 to the inlet of secondary compressor 30 . After compression, the residual gas is transferred to the secondary compressor 30
from there to the dilution zone 24 of the modified combustor 14 via a pipeline 36 that includes additional pressure and/or fluid regulation devices (not shown). FIG. 3 shows one way to design the modified combustor 14. Fuel enters modified combustor 14 through fuel pipeline 38 and is atomized into combustion zone 22 by atomization nozzle 40 . Fuel enters compressor 12 through air intake 54 . After being compressed, the air is transferred to compressed air pipeline 42
to the combustion zone 22. Compressed air enters the combustion zone through swirl vanes 44 surrounding fuel pipeline 38. The purpose of the swirl vane, which is well known to those skilled in the art, is to create a turbulent flow pattern to better mix the fuel with the compressed air. This mixing promotes complete combustion. Pipeline 28 (Figure 1) or pipeline 36
The pressurized residual gas supplied by (FIG. 2) flows through a jacket 46 surrounding the combustion zone 22. Residual gas enters the interior of the combustor through port 48. The number of ports required depends on several factors such as flow rate, pressure and temperature. The hot combustion products and residual gases are mixed in dilution zone 24. This mixing creates the working fluid used to drive the turbine. Other ways to modify existing combustors or design new combustors for use with the present invention will be readily apparent to those skilled in the art of designing combustors. After combustion and dilution, the working fluid exits the modified combustor 14 and passes through the pipeline 50 to the turbine 10.
flows to the entrance of After the fluid has done work in the turbine, the used working fluid is exhausted to the atmosphere through exhaust pipe 52. Additional residual gas may be added to the exhaust pipe by pipeline 54. In carrying out the method of the invention, the compressed air normally used for cooling in the dilution zone of a gas turbine combustor is replaced by pressurized residual gas. This allows a corresponding reduction in the amount of air that has to be compressed in the air compressor of the turbine. If the residual gas is available at high pressure, as is often the case, the overall effectiveness of the turbine can be increased by reducing the amount of air that must be compressed. to accept pressurized residual gas as another cooling stream for use in dilution zone 24;
The gas turbine combustor 14 must be modified. This cooling flow must be separate from the pressurized air used for combustion in the combustion zone 22.
One method of modifying a typical gas turbine combustor according to the present invention is shown in FIG. Other ways to modify the gas turbine combustor used to practice the present invention will be readily apparent to those skilled in the art. As shown in Figure 1, the residual gas is
The residual gas can be passed directly to the dilution zone 24 of the modified combustor 14 if the pressure is kept high enough for use in the combustor 14. On the other hand, when only low pressure residual gas is available, a secondary compressor 30 is used to pressurize the residual gas before its use in the modified combustor 14, as shown in FIG.
must be used. In either case,
Additional residual gas may be added to the gas turbine exhaust stream 52 to increase the total amount disposed of. A computer study was conducted to compare the operating characteristics of a standard gas turbine engine (Case 1) and the characteristics of a gas turbine engine modified according to the present invention (Case 2). Details of the computer program used are not given here. However, the program is based on general laws of thermodynamics that are well known to those skilled in the art.
The results presented herein can be easily reproduced by one of ordinary skill in the art with or without the aid of a computer. In both cases, the gas turbine engine
It was assumed to have a nominal horsepower of 5000 horsepower. Fuel flow rate is 2268 tmol/day (5000 lbmol/day)
It was set to Fuel pressure is assumed to be 800 psia,
The fuel temperature was set at 4.4°C (40〓). The composition of the fuel used was as follows. Component Mol% Carbon dioxide 19.98 Methane 77.05 Ethane 1.17 Propane 0.26 N-butane 0.07 Nitrogen 1.47 100.00 To determine the amount of air required for combustion, it is necessary to determine whether all combustible components of the fuel gas are completely carbon dioxide (CO ₂ ) or not. It was assumed that it could be converted to water (H ₂ O). Based on this assumption, stoichiometric equilibrium was used to determine the amount of oxygen (O ₂ ) required to completely transform all combustible materials. Calculations show that 1,798,524 tonmoles (39,650 lbmoles) of air are required to provide enough oxygen to completely burn 2,268 tonmoles (5000 lbmoles) of the above fuel gas. Complete combustion of 2.268 tonmoles (5000 lbmol/day) of the above gas provides a total heat input of 8543.889 kcal/hour (57690000 BTU/hour) to the gas turbine engine. Thus, if the gas turbine engine were operated at 100% thermal efficiency, the output would be 22,668 horsepower. Typically, for dilution and cooling, the amount of compressed air used in a gas turbine combustor is two to three times the amount needed for complete combustion. For case 1, the amount of dilution air was assumed to be 21/2 times the amount of combustion air. Thus, the total compressed air used in Case 1 is 17.98524 tmol/day (39650 lbmol/day) required for combustion alone.
day) or 62.94834 tmol/day (138775
(pound mole/day). This air is 80 psia
Before being compressed to an operating pressure of 14 psia and 32.2
It was assumed that it could be obtained at a temperature of 90°C (90°C). Additionally, the air was assumed to be 100% saturated. In case 2, the residual gas was assumed to be carbon dioxide (CO ₂ ). It is assumed that CO ₂ is available at a pressure of 53 psia and a temperature of -15°C (5〓), and an additional 80.5 psia for use in a modified combustor.
compressed to a pressure of The composition of CO ₂ was assumed to be as follows. Component Mol % Carbon Dioxide 98.74 Methane 0.89 Ethane 0.09 Propower 0.10 N-Butane 0.17 Water 0.01 100.00 The above characteristics are typical of the CO ₂ stream often generated as residual gas in natural gas processing facilities. To ensure complete combustion, in case 2, 50%
It was assumed that excess compressed air was used. Thus, the total amount of compressed air used was 26.97786 tmol/day (59.475 lbmol/day). As in case 1, this air was assumed to be 100% saturated. The remainder of the compressed air used in Case 1 was replaced with 1.8144 tmol/day of 4000 lbmol/day of _CO2 . A comparison of the operating characteristics of the two devices is as follows.

[Table] In both cases, the efficiency of the compressor and expander was assumed to be 80% and 85%, respectively. For each case, the turbine exit temperature was determined by comparing the enthalpy of the exhaust stream and the enthalpy of the combined intake stream (compressed air, CO ₂ and fuel). The outlet temperature is varied until the enthalpy difference is exactly equal to the fuel flow rate multiplied by the net heat value of the fuel. In the example above, 18.144 tonmoles/day (40,000 lbmoles/day) of compressed CO ₂ was used in place of 35.97 tonmoles/day (79,300 lbmoles/day) of compressed air. As evidenced by the difference in turbine inlet temperatures, it is better to use less CO ₂ than to use more air.
can provide better cooling. In case 2, the total flow rate through the turbine is 17.8265 tmol/day (39300 lbmol/day), which is less than the total flow rate in case 1. The reduction in flow rate is the fundamental reason for the reduction in obtained turbine horsepower from Case 1 to Case 2. More importantly, however, even though the total horsepower available decreases from Case 1 to Case 2, the net horsepower available for work is significantly greater in Case 2 than in Case 1. This is due to a significant reduction in the amount of horsepower required for compression. Furthermore, the overall thermal efficiency in case 2 is better than case 1. In case 2, _CO2 was assumed to be available at 53 psia and was further compressed to 80.5 psia. This compression required 315 horsepower. If _CO2 were available at pressures above 80.5 psia, this 315 horsepower would not be needed, resulting in a further increase in available net horsepower and thermal efficiency. Conversely, if CO ₂ is only available at low pressure, more than 315 horsepower will be required for compression. This will negate some or all of the increases in horsepower and thermal efficiency. In addition to the main benefit of disposing of large amounts of _CO2 , the benefit of the present invention is that equal or greater net horsepower can be generated at lower flow rates when _CO2 is used for dilution. Since flow rate is one of the limiting factors in gas turbine design, smaller turbines can be used for specific tasks. A comparison of the dispersion ability of Case 1 and Case 2 is as follows. For this comparison, 4.536 tmol/day (10000 lbmol/day) for both cases.
The exhaust gas flow rate was assumed to be

[Table] In the above comparison, it appeared that a stack temperature of at least 204°C (400°C) was required to ensure proper dispersion in the atmosphere. In Case 1, the exhaust stream contains 1.583 tmol/day (3490 lbmol/day) of _CO2 produced during the combustion process. Furthermore, 37.8
By adding 64.411 tmol/day (142000 lbmol/day) of _CO2 to the exhaust stream at a temperature of 100°C, the final temperature of the exhaust stream is 208.3
It becomes ℃ (407〓). Thus, the total amount of _CO2 dispersed by a standard gas turbine with a flow rate of 45.360 tmol/day (100000 lbmol/day) is 65.994 tmol/day (145490 lbmol/day).
day). In Case 2, the exhaust stream contained 19.768 tmol/day (43580 lbmol/day) of _CO2 , with most of the _CO2 being added for dilution purposes. Furthermore, 37.8℃
By adding (100〓) of 83.008 tmol/day (183000 lbmol/day) of CO ₂ to the exhaust stream,
The exhaust temperature will be 213.9℃ (417〓). The total amount of _CO2 dispersed by a gas turbine engine modified according to the invention and having a flow rate of 45.36 tmol/day (100000 lbmol/day) is 102.777 tmol/day (226580 lbmol/day). The method and apparatus of the present invention and the best mode contemplated for applying the method have been described. The above description is for illustrative purposes only.
It is to be understood that other arrangements and obvious modifications may be employed without departing from the scope of the invention as specified in the claims. For example, any combustor design can be used as long as the combustion air is kept separate from the residual gases.
Also, residual gases other than CO ₂ may be used.

[Brief explanation of the drawing]

FIG. 1 is a flow diagram of a gas turbine apparatus of the present invention. FIG. 2 is a modified flow diagram of the gas turbine system of the present invention showing the use of a secondary compressor to compress low pressure residual gas. FIG. 3 is a cross-sectional side view of a typical gas turbine combustion can modified in accordance with the present invention. 10... Turbine, 12... Air compressor, 14... Modified combustor, 16... Drive load, 1
8... Drive shaft, 20... Compressor drive shaft, 22... Combustion zone, 24... Dilution zone, 26... Residual gas source, 28... Pipeline, 30... Secondary compressor.

Claims (1)

Claims: 1. Safety of the dispersion of large amounts of residual gas into the atmosphere by reducing the tendency for large amounts of residual gas originating from industrial operations or similar gas sources to drift into the discharge area. , wherein the gas source is located near a gas turbine engine, the gas turbine engine having a combustor having a combustion zone, a dilution zone, an inlet, and an outlet. , introducing the bulk residual gas as a cooling stream into a dilution zone of a gas turbine combustor and heating the residual gas to reduce the density of the residual gas; passing the heated residual gas through a gas turbine; venting the heated residual gas to the atmosphere without substantially removing heat therefrom, thereby reducing the tendency of the gas to drift to the discharge location. 2. The method of claim 1 further comprising the step of compressing the residual gas before introducing the residual gas into a dilution zone of the gas turbine combustor. 3. The method of claim 1 further comprising the step of introducing additional residual gas into the exhaust stream of the gas turbine engine. 4. Claim No. 4 characterized in that the residual gas is heated to a temperature such that when the residual gas is released into the atmosphere, the density of the residual gas is smaller than the density of the atmosphere into which the residual gas is released. The method described in Section 1. 5. The method of claim 4, wherein the temperature of the residual gas released into the atmosphere is at least about 400°C (204°C). 6. The method of claim 5 further comprising the step of introducing additional residual gas into the exhaust stream of the gas turbine engine to heat the additional residual gas. 7. Increasing the safety of the dispersion of large quantities of carbon dioxide gas into the atmosphere by reducing the tendency for large quantities of carbon dioxide gas originating from industrial operations or similar gas sources to drift to these points of release; , wherein the gas source of carbon dioxide is positioned near a gas turbine having a combustor;
The combustor has a combustion zone for mixing and combusting fuel with compressed air to form combustion products, and a dilution zone for cooling the combustion products to a temperature suitable for use in a turbine. introducing the bulk carbon dioxide as a cooling stream into a dilution zone of a combustor, thereby transferring heat from the combustion products to the carbon dioxide; and transferring the heated carbon dioxide and combustion products to a gas turbine. passing the heated carbon dioxide and combustion products into the atmosphere without substantially removing heat from the carbon dioxide, thereby transferring energy to the turbine. and increasing the safety of the dispersion of the heated carbon dioxide by reducing the tendency of the carbon dioxide to drift to the location where it is discharged. 8. The method of claim 7 further comprising the step of compressing the carbon dioxide before introducing it into the dilution zone of the combustor. 9. The method of claim 7 further comprising the step of introducing additional carbon dioxide into the exhaust stream of the gas turbine engine to heat the additional carbon dioxide. 10. The method according to claim 7, characterized in that the carbon dioxide is heated to a temperature such that when the carbon dioxide is released, the density of the carbon dioxide becomes smaller than the density of the atmosphere from which the carbon dioxide is released. Method. 11. The method of claim 10, wherein the temperature of the carbon dioxide released into the atmosphere is at least about 400°C (204°C).