AU607684B2 - Process for producing power - Google Patents

Description

Q

607 e; 4 St FORM 10 SPRUSON FERGUSON COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: This document contains the amendmecnts made under Seticn 49 and is correct for printing Class Int. Class Complete Specification Lodged: 0 00 0 0 0 000 4 o0 0 all Name of Applicant: Address of Applicant: Actual Inventor(s): Address for Service: FLUOR CORPORATION 3333 Michelson Drive, Irvine, California 92730, United States of America ASHOK DOMALPALLI RAC Spruson Ferguson, Patent Attorneys, Level 33 St Martins Tower, 31 Market Street, Sydney, New South Wales, 2000, .ustralia V J O 4t 0 4i 8 0 I I Complete Specification for the invention entitled: PROCESS FOR PRODUCING POWER The following statement is a full description of this invention, including the best method of performing it known to me/us f1 pk/23T L. -L K L -L KLN/9168M I I0, S 174/47 PROCESS FOR PRODUCING POWER BACKGROUND OF THE INVENTION This application is a continuation-in-part of Serial No.

707,673 filed March 4, 1985, which application is a continuation in part of Serial No. 576,038, filed February 1, 1984, both entitled "Process for Producing Power." 1. Field of the Invention This invention relates to a process for producing 0 ,4 0 0, 0 mechanical energy or electric power in which a combustion turbine o eo olOo is used for conversion of the chemical energy in a fuel.

0 0 000.

0 0 2. Description of Prior Art When a working fluid is used in an engine to produce o mechanical energy or electrical power from the chemical energy contained in a fuel, the working fluid is pressurized and, following combustion of the fuel, the energy thus released from o the fuel is absorbed into the working fluid as heat. The working o o fluid with the absorbed energy is then expanded to produce 00 mechanical energy which may in turn be used to drive a generator 0o o0 to produce electrical power. Unconverted energy is rejected in the exhaust in the form of heat, only a portion of which may be recovered and utilized. The efficiency of the engine is at a maximum when the temperature of the working fluid entering the expansion stage is also at a maximum.

In the case of combustion turbines, air compression is used for the pressurizaticn step and direct combustion of the SBR:eah 178M T~iu 174/47 fuel into the compressed air is the energy addition step.

Expansion in the turbine produces the mechanical energy and the unconverted heat is carried off by the turbine exhaust. The efficiency of the combustion turbine is a maximum when the combustion temperature itself is at a maximum, and this occurs when the fuel is burned in the presence of the pressurized air under stoichiometric conditions, enough air is present for complete combustion, but without any excess.

When fuel oil is burned with air under stoichiometric conditions, however, the resulting temperature is approximately 4000° F, which is in excess of the metallurgical limits of the turbine. As a result, it is necessary to atuil'i2~ a large excess 0000 of air in the combustion step, which acts as a thermal diluent oand reduces the temperature of the combustion products to approximately 2000° F. The necessity to use a large excess of o000 0o° air under pressure in turn creates a large parasitic load on the system, because compression of the air requires mechanical energy and thus reduces the net power produced from the system, as well 6 o as reducing the overall efficiency of the system.

Another disadvantage of existing combustion turbine cycles is that the pressurization step requires compression of air. Compression of a gas is very inefficient, since mechanical 0 energy is required, which is the highest form of en:rgy and o0 0 degrades into thermal energy. The mechanical energy required for air compression can be reduced by utilizing interstage cooling, that is, by cooling the temperature of the compressed air between successive stages of a multiple stage compression process.

However, from an overall cycle efficiency standpoint, interstage cooling can be utilized advantageously if the heat removed from the compressed air in the inter-cooler can be efficiently

I

174/47 recovered and utilized. If the entire heat is simply rejected to the atmosphere, the overall cycle efficiency is actually decreased, since it results in the consumption of more fuel to compensate for the energy lost through the inter-cooler.

Accordingly, rather than simply rejecting the heat, in commercial practice, the high compressor horsepower requirement has been tolerated while containing the heat in the compressed air stream.

Even in light of the foregoing limitations, it is very desirable to use a combustion turbine engine, because it is able to operate at the highest temperature of engines that use a working fluid to convert chemical energy in a fuel to mechanical energy. However, due to the high exhaust temperature that is inherent to a combustion turbine engine, the efficiency of the cycle is limited, and as a result, the exhaust from the engine is used as the heat source to operate another engine such as a steam S turbine to increase the overall efficiency of utilization of the i fuel. Such a system is called a combined cycle system and is lwidely used in the industry. Another use for the energy contained in the combustion turbine exhaust is to raise superheated steam which is injected back into the combustor of the combustion turbine, see, U.S. Patent No. 3,978,661. Yet another method is to preheat the air leaving the compressor against the engine exhaust and simultaneously use interstage cooling during compression (see Kent's Mechanical Engineers Handbook, 1950).

These systems show higher overall efficiencies with respect to the utilization of the chemical energy contained in a fuel, but as will be explained subsequently herein, are inherently less efficient than the process of the present invention.

A combined cycle cannot take full advantage of aircompressor inter-cooling, because the temperature of the -3- 174/47 heat rejected in the air compressor inter-cooler is too low to be recovered for efficient use such as steam generation. A small portion of this heat may be recovered for boiler feed water preheating as described in Agnet, U.S. Patent No. 3,335,565 but this res-lts in more heat being rejected with the stock gases and results in little, if any, net increase in either heat recovery or cycle efficiency. Recently, direct water injection into the air stream as a means of inter-cooling has been proposed.

However, there are two disadvantages with this. One is that the temperature of air leaving the inter-cooling step is limited by the dew point temperature of the saturated air. Also, by the direct injection of water into the air inl the intercooler, the added water vapor which serves as a thermal diluent needs to be compressed in the successive stages after the inter-cooler, which precludes realizing the full advantage of water vapor substitution as a means of saving compression power.

Foote, in U.S. Patent 2,869,324, describes evaporation S of water into the compressed air after preheating both the air S and the water. However, this means of evaporation requires a higher temperature level to achieve useful moisture loading of 0 1 44,.

the air because the air and water leave the evaporator in equilibrium with each other. This method of water evaporation is less efficient than the present invention which can take

I,

advantage of air entering the saturator at low temperatures.

The steam cycle has an inherent high irreversibility since the evaporation of water (steam generation) occurs at a constant temperature, whereas the heat release occurs at varying temperatures. The following diagram shows the heat release curve and the water evaporation line: 174/47 water evaporation (steam generation) line Cumulative Heat Duty *0 cr0 t t tt rrt 0 t 4 00 1 o I 0 0 0 0c 4004 0 1010 I t( 4 t Ct t i 1 1 i C &f- 1

JB''+

As can be seen from the diagram, with steam generation, a small temperature difference between the heat source and heat absorbing fluid cannot be maintained, and this leads to a high irreversibility in the system and hence a lower efficiency.

A combined cycle plant is also expensive since it requires an additional steam turbogenerator, steam drums, surface condenser for condensing steam turbine exhaust, and cooling towers to reject the heat from the surface condenser to the atmosphere.

A steam injected cycle cannot take full advantage of air-compressor inter-cooling for the same reasons as a combined cycle. Also this cycle involves the generation of steam and hence has the same irreversibility associated with it as described for a combined cycle, although eliminating the steam turbogenerator, surface condenser and cooling towers, and reducing the parasitic load of air compression by displacing some of the air with steam. This is an improvement over the water injected cycle described in NASA Report No. TR-981 titled "Theoretical Analysis of Various Thrust-Augumentation Cycles for Turbojet Engines", by B. L. Lundin, 1950, where liquid water is directly injected into the combustor. The injected water displaces some of the diluent air, but there is a tremendous irreversibility associated with this. The evaporation of the liquid water in the combustor uses energy from the fuel at the highest temperature, which results in an overall reduction of efficiency. Also with the water injected cycle, the heat available from the turbine exhaust still remains to be utilized.

The heat used for generation of steam in a steam injected cycle, is of a much higher quality, temperature level, than is desirable. For example, typically for a combustion turbine operating at a pressure ratio of 11, the steam pressure required for injection should be at least 200 psia. The corresponding saturation temperature of the steam is 3820 F.

0 ^l This requires that a heat source be available at much higher temperatures and heat down to only 420° F can be utilized without o 4, unreasonable temperature pinches.

I The inter-cooled regenerative cycle uses inter-cooling during the air-compression step, and compressed air preheated i against the turbine exhaust before the air enters the combustor. The optimum pressure ratio for this cycle is about 6 to 7. The heat released in the inter-cooler is all lost to atmosphere. Also the temperature of gas leaving the air pre-heater is around 500° F, and the heat contained in these gases is all i wasted. All the thermal diluent is compressed, leading to a large parasitic load, which results in poor overall efficiency for the system.

Martinka U.S. Patent 2,186,706, describes the replacement of a po:tion of the air for combustion with water vapor 174/47 derived by directly contacting the compressed air with heated water in a humidification operation. The heat required for this humidification operation is supplied by inter-coolers in the air compressor. Makeup water for the system picks up additional heat from the gas turbine exhaust. The net effect of such a system is a reduction in the parasitic load of air compression and, thus, an increase in cycle efficiency.

Nakamura et al., in U.S. Patent 4,537,023, describe a system similar to that of U.S. Patent 2,186,706, in which an after-cooler is used for the air compressor. The after-cooler reduces the temperature of the water leaving the humidifier, which in turn allows recovery of lower-level heat to a greater o0000 o 0 extent. The decrease in heat-rate resulting from the addition of 0 0 0 0 o 0 o the after-cooler is approximately 1.4 percent, based on the data 000 presented in the Nakamura et al. patent.

0 o. Both the Martinka and the Nakamura et al. systems reject 0oo heat from the cycle through the stack gases. Rejection of heat is a consequence of the second law of thermodynamics and any at power cycle converting heat to power must reject some heat. To Q0 improve the cycle efficiency, it is not only important to minimize the quantity of heat being rejected, but also, to minimize the temperature at which the heat is rejected. In both the Martinka and Nakamura et al. systems, the quality of heat being rejected is solely set by the stack temperature which constrains the cycle efficiency.

mom -8- It is the object of the present invention to overcome or substantially ameliorate the problems and/or disadvantages of the prior art.

There is disclosed herein a process for producing power utilizing a combustion turbine, comprising humidifying compressed air, in multistate counter-current flow prior to combustion, to provide water vapor as thermal dilutent for combustion in said turbine, water used to form said water vapor being at a temperature below its boiling point at the operating pressure when in contact with said compressed air, said compressed air being passed in heat exchange relationship with said water prior to humidification, whereby the temperature of said water is increased and the temperature of said compressed air is decreased and wherein heat is rejected from the process prior to said combustion.

There is further disclosed herein a gas combustion process for producing power using a compressed air, counter-current humidified, 15 wherein compressed air is used in the process being firstly cooled against °o water to heat said water and secondly humidified against said heated water 0 CO comprising the step of rejecting from the process heat contained in the 00 C° oo compressed air used in the process, wherein the heat is rejected from the process prior to combustion and prior to final heat rejection from the .o 20 process.

There is further disclosed herein a process for producing power in a gas turbine power system comprising the steps of: compressing air in a first air compressor; foioo, removing heat of compression from the air compressed in tW j first air compressor by collecting the removed heat in a circulating water I system; o oo, further compressing the air in a second air compressor; removing heat of compression from the air in the second air 1 compressor by further collecting the removed heat in the circulating water 30 system; 0 removing further heat from the air compressed in the second air compressor by rejecting heat from the process to precool air; l moisturizing the precooled air by feeding the precooled air and water from the circulating system containing the removed heat from the first and second air compressions into a counter-current two phase humidifier to produce water vapor; KLN/24781 L-i 8a feeding the water vapor and fuel into a combustion chamber to produce hot combustion gases; feeding the hot combustion gases to a gas turbine to convert thermal energy to mechanical work; coupling the gas turbine to a generator for converting mechanical work into the electric power; and coupling the gas turbine to the first and second air compressors for compressing air.

There is further disclosed herein a gas combustion process of producing power using a compressed air, counter-current humidifier, wherein compressed air is used in the process being firstly cooled against water to heat said water and secondly humidified against said heated water comprising the step of rejecting from the process heat contained in the circulating water system used in the process, wherein the heat is rejected 15 from the process prior co combustion.

There is further disclosed herein a process for producing power in a o 0o gas turbine power system comprising the steps of: 0 00 o o o00 o compressing air in a first air compressor; 0000 removing heat of compression from the air compressed in the oo 20 first air compressor by collecting the removed heat in the circulating water system; further compressing the air in a second air compressor; removing heat of compression from the air compressed in the second air compressor by further collecting the removed heat in the 25 circulating water system; removing the heat from the circulating water system by rejecting heat from the process to precool the air; moisturizing the precooled air by feeding the precooled air and water from the circulating system into the counter-current two phase humidifier to produce water vapor; feeding the water vapor and fuel into a combustion chamber to produce hot combustion gases; feeding the hot combustion gases to a gas turbine to convert thermal energy to mechanical work; coupling the gas turbine to a generator for converting A mechanical work into electric power; and 7 coupling the gas turbine to the first and second air compressors SLS for compressing air.

E r ti.

i KLN/24781 1. 8b There is further disclosed herein a process for producing mechanical power utilizing heat contained in process fluids within a system and heat from combusting in a combustionable fuel in a combustion chamber to turn a gas turbine comprising: providing combustible fuel; providing process fluids consisting of compressed air and water; providing a circulating water system which contains the water; providing a humidifier capable of creating a gaseous medium including water vapor; producing the gaseous medium by feeding the compressed air to.

i the humidifier and circulating the water through the humidifier; cooling the compressed air by rejecting from the process some heat from at least one of the process fluids prior to reducing the gaseous medium; feeding the gaseous medium and the combustible fuel to the combustion chamber; combusting the fuel in the presence of the gaseous medium within the combustion chamber to provide a working fluid at a first elevated temperature; ,20 feeding the working fluid to the gas turbine; expanding the working fluid in the gas turbine to produce mechanical power and turbine exhaust; extracting heat from the turbine exhaust for use within the process thereby producing a cooled turbine exhaust; and extracting heat from the turbine exhaust for use within the process thereby producing a cooled turbine exhaust; and rejecting the cooled turbine exhaust from the process.

There is further disclosed herein a process for producing power utilizing a combustion turbine, comprising humidifying a compressed gaseous medium, in multistage counter-current flow prior to combustion, to provide water vapor as thermal diluent from combustion in said turbine, water used to form said water vapor being at a temperature below its boiling point at operating pressure when in contact w'th said comoressed gaseous medium, passing said compressed gaseous medium in heat exchange relationship with water prior to humidification, whereby the temperature of said water is increased and the temperature of said compressed gaseous medium is 1 decreased, and rejecting heat from the power production cycle by KLN/24781 KLN/24781 ~~IXI iii:i i;;i i 8c additionally precoolirg said compressed gaseous medium prior to humidification.

There is further disclosed herein a process for producing power utitizing a combustion gas turbine, comprising: compressing a gaseous medium to a predetermined pressure; after-cooling the compressed gaseous medium against water, whereby the temperature of said water is increased and the temperature of said compressed air is decreased; contacting said compressed gasecus medium with said heated water in a multistage counter-current operation to humidify said compressed gaseous medium and provide water vapor as thermal diluent from combustion in said turbine; said step of contacting the compressed gaseous medium with heated water being preceded by heat rejection from the cycle by pre-cooling the gaseous medium.

There is further disclosed herein a process for producing power utilizing a combustion gas turbine, comprising: compressing a gaseous medium to a predetermined pressure; the said compression step being performed with inter-stage cooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with the heated water in a multistage counter-current operation of the humidification operation; said step of inter-cooling during the compression including heat 25 rejection from the cycle, using the compressed gaseous medium to drive a gas turbine for production of power.

There is further disclosed herein a process for producing power utilizing a combustion gas turbine, comprising: compressing a gaseous medium to a predetermined pressure; the said compression step being performed with inter-stage cooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with the heated water in a multistage counter-current operation for the humidification operation; burning fuel together with the humidified gaseous medium; driving a gas turbine for production of power; S said step of inter-cooling during compression including heat o rejection from the circulating water prior to its use for intercooling.

r-LN/24781 4 8d There is further disclosed herein a process for producing power utilizing a combustion gas turbine, comprising: compressing a gaseous medium to a predetermined pressure; the said compression step being performed with aftercooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with heated water in a multistage counter-current operation for the humidification operation; burning the fuel together with the humidified gaseous medium; driving a gas turbine for production of power; said step of after-cooling after compression including heat rejection of the circulating water prior to its use for after-cooling.

0 0r C o 0 00 0 0 0 S 900 o C O 6 o o i o V l R-KLNI247 I a LS...

A

r I- i 174/47 compressed air in a thermodynamically efficient manner, using direct contact of the compressed air in a saturator, which permits the air to be humidified with relatively cold water and without the requirement of a steam boiler.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic depiction of the process of the present invention in one preferred embodiment utilizing a twostage air compressor, axially coupled to a turbine.

Figure 2 is a schematic depiction of the process of the present invention, utilizing, variations in the mode of low level heat rejection.

Figures 3 and 4 are graphs of the effect of pressure ratio on cycle efficiency and the effect of air temperature to humidifier on cycle efficiency.

Description of Preferred Embodiments S1 *i g o I It Referring to Figure i, air through line 1 is introduced rrsJ into the first stage of the dual stage air compressor, 2 and 3, which are coupled together axially at 4. The compressed air exiting the first stage of the compressor 2 through line 5 is at a temperature of approximately 3000 to 4001F and passes through heat exchanger 6 where it undergoes heat exchange relationship with water passing through line 7. The temperature of the compressed air is thus reduced to approximately 400 to about 2500 F, typically about 700 to 1400 F, and thereafter is passed through line 8 to the second stage, 3, of the air compressor.

-9pk/23T 174/47 The compressed air exiting the air compressor through line 10 is at a temperature of approximately 300° to about 400° F and passes through heat exchanger 11 in which it experiences heat exchange with water passing through line 12. The temperature of the compressed air is thus reduced to approximately 40° to about 2500 F, typically about 115° to ,.bout 200 0

F.

Water in line 7, following heat exchange in heat QXr0i \C Ou on Vu> 0 e.c exchanger 6, is introduced into the top section of saturator at a temperature of about 3000 to about 400 0 F. Within the saturator, the air and water are contacted counter-currently in multi-stages, which improves the thermodynamic efficiency. The operating pressure of the saturator is about 200 psi to about 600 psi, and the water temperature is approximately 300 to about 400 0 F. The water remaining after vaporization is removed from the bottom of saturator 15 through line 16 and pu,;tped at 17 through exchanger 18 wherein heat is rejected and line 19 to either line 7 and heat exchanger 6 or line 13 and 12 to heat I exchanger 11, as desired. Low level heat from the intercooler and the aftercooler are thus rejected to the atmosphere.

The humidified air exits saturator 15 through line 20 as essentially saturated air at approximately 250 0 F to about 350°F and is passed through heat recovery unit 21 in heat exchange relationship with the exhaust from turbine 22 to preheat the saturated air prior to introduction to combustor 24. The fuel for combustion is introduced through line 25 and the combusted gaseous product exits through line 26 to drive turbine 22. The turbine is coupled axially, at 4, to the air compressor and also to generator 30 for the production of electrical power. While the compressor, turbine and generator are described and illustrated as coupled on a single axle, it will be appreciated T I I uo~'u JVJL L.SL- LYU-- -r 174/47 that other arrangements may be used, as will be readily understood by those skilled in the art.

Within heat recovery unit 21, the hot exhaust from the gas turbine is passed in heat exchange relationship with water to heat the water to the appropriate temperature for humidification within saturator 15, as illustrated. Thus, water through line 31 may be taken thereby to the heat recovery unit,kas illustrated.

Additionally, of course, makeup water may be added through line 32 by pump 33 as is necessary to maintain the necessary water inventory in the system.

Variations in the mode of low level heat rejection are, of cou:se, possible, and certain of these are depicted in Figure 2. Thus, in the embodiment here illustrated, heat rejection occurs in exchanger 35, wherein compressed air from the after- Scooler 11 undergoes heat exchange against water to increase the *oo temperature of the water, after which the cooled compressed air is introduced into the lower section of saturator 15. Provision Cc may also be made for heat rejection in exchanger 37 in which com- %t I pressed air from the inter-cooler is heat exchanged against cooling water or refrigerant prior to introduction into stage II of the multiple stage compressor. In this embodiment, makeup water Ii Sis heated by heat exchange is exchanger 38 before combining with S water in line 7 and passage through inter-cooler 6.

The process of this invention is shown as a stand alone I power generation cycle. This process may, if desired, be integrated with other process facilities for further optimization of energy conversion. In a cogeneration configuration, a portion of the hot turbine exhaust would be utilized to produce steam for other purposes. In a reverse manner, the cycle can be integrated with heat recovery in other processes to increase the supply of [I -11-

I

oi -ne cx -2- 'c I-I 'I 'I I -i I 4 174/47 Q ii OI ii it 44 4t 4144 I CC 4 tfIc.

14 4 0 4 0 4r 41(4 *14414 (0 4 4 heated water to the humidification operation. In this manner, the power cycle of the present invention can be used to a greater extent than other cycles in integration with a plant producing large quantities of low temperature level heat such as a coal gasification plant or a geothermal facility, because humidification can be achieved at such low temperatures while the work producing step of expansion in the turbine occurs at much higher pressure ratios. Also, the cycle may be used with reheat turbines more efficiently because this cycle optimizes at higher pressure ratios. In reheat turbines, the first turbine operates at a high pressure where partial expansion occurs, additional fuel is fired in a second combustor, and the hot gases are expanded to near atmospheric pressure in the second turbine. The results of rejecting heat to cooling water are presented in Figure 3 in the form of a plot of the pressure ratio versus cycle thermal efficiency. For comparison a similar plot for the Nakamura et al. system is also presented in the same Figure.

These efficiencies were calculated using a consistent set of design criteria established in the Nakamura et al. patent as follows: EXAMPLE 1: NAKAMURA PROCESS Conditions Efficiencies Compressor adiabetic efficiency Turbine adiabetic efficiency Mechanical efficiency Generator efficiency Combustion efficiency Ambient air conditions at compressor inlet Temperature Pressure Relative humidity Flow rate }dry air

}H

2 0 nC 0.89 nT 0.91 nM 0.99 nG 0.985 nB 0.999 150 C 1.033 ata.

1 Kg-mole/sec.

0.0101 Kg-mole/sec.

i -12- -3p_ t 1 I I' II- I IIeU 174/47 Fuel Kind Temperature High heating value (00 C.) Low heating value (00 C.) natural gas 150 C 245,200 Kral/Kg-mole 221,600 Kcal/Kg-mole Total pressure loss Replenishing water Temperature Flow rate 15.2% 150 C 0.132 Kg-mole/sec.

O00 o 00o 0 o 00 *0 0 0e,.

0.0.

0 60 o 00 00 0 o o0 0a 0 t O 00 0044 0500 4000- 00004 Turbine inlet conditions Pressure Temuerature Minimum temperature difference for heat-exchanger High temperature regenerator R 1 Low temperature regenerator R 2 Fuel preheater

R

3 Intercooler IC Miscellaneous The compressive forces of the fuel, replenishing water and water at the bottom of the exchanging tower are assumed to be negligible while the total auxiliary power is taken as 0.3 percent of the generator output.

Further, as to the cooling air for the turbine, the availability of low temperature compressed air in the regenerative gas turbine cycle is taken into account to determine its required amount.

(II) Results Waste gas Temperature Flow rate Compressor outlet temperature (AC 2 Sending end power output Sending end thermal efficiency (LHV) 6 ata.

1,0000 C 300 200 300 200 82.70 C 1.15 Kg-mole/sec.

1480 C 8690 KW 50.2% EXAMPLE 2: RAO PROCESS Conditions Efficiencies Compressor adiabetic efficiency Turbine adiabetic efficiency Mechanical efficiency Generator efficiency Combustion efficiency nC 0.89 nT 0.91 nM 0.99 nG 0.985 nB 0.999 -13- -4- III- 1

'Y

174/47 Ambient air conditions at compressor inlet Temperature Pressure Relative humidity Flow rate }dry air

}H

2 0 Fuel Kind Temperature High heating value (00 C.) Low heating value C.) Total pressure loss Replenishing Water Temperature Flow rate 150 C 1.033 ata.

1 Kg-mole/sec.

0.0101 Kg-mole sec.

natural gas 150 C 245,200 KCal/Kg-mole 221,600 Kcal/Kg-mole 15.2% 15 0

C

0.144 Kgmole/sec.

Turbine inlet conditions Pressure Temperature 6 ata.

1,0000 4 'fi Minimum temperature difference for heat exchanger and/or exchanger outlet condition High temperature regenerator

R

1 Low temperature regenerator

R

2 Fuel Preheater R 3 Inter Cooler IC Selfheat exchanger (SR) Intercooler Outlet IC 2 Rejecting Aftercooler RAC 30 0

C

20 0

C

30 0

C

20 0

C

20 0

C

35 0

C

48 0

C

I Ii It Miscellaneous The compressive forces of the fuel, replenishing water and water at the bottom of the exchanging tower are assumed to be negligible while the total auxiliary power is taken as 0.3 percent of the generator output. Further, as to the cooling air for the turbine, the availability of low temperature compressed air in the regenerative gas turbine cycle is taken into account to determine its required amount.

-14- W7i (II) Results (a) Waste Gas 3

E

ri

I~

.i ri r d; ii ,ii

~I

hI "i ;:i

:E

i i

B

a a Temperature 75.6 0

C

Flow Rate 1.18 kgmole/sec.

Compressor outlet Temperature (AC 2 157° Sending end power output 10947KW Sending end thermal efficiency (LHV) 51.06% The Nakamura et al. system shows a peak efficiency at a pressure ratio of approximately 6 for a gas turbine firing temperature of 1832 F.

The cycle of the present invention, however, shows a peak efficiency at a pressure ratio of approximately 10.5 for the same gas turbine firing temperature of 1832 F. Comparing the peak performance for the two systems, the heat-rate for the process of the present invention is approximately 1.6 percent lower than that for the N?.kamura et al. system. This improvement is actually higher than the improvement by Nakamura et al. from utilizing the after-cooler. Also, the process of the present invention makes it possible to take advantage of higher pressure ratios, for example in the range of 6:1 to 34:1, and thus increases the engine specific power.

20 Figure 4 is a plot of the cycle thermal efficiency drawn as a function of the temperature of the compressed air entering the humidification operation. The upper curve labeled "Air to Humidifier" shows air inlet temperatures with corresponding higher cycle efficiencies resulting from using heat rejection of the present invention in the Nakamura power cycle. An air inlet temperature and significantly lower cycle efficiency calculated from the example given in the Nakamura '023 patent is also shown in Figure 4. Also, the lower curve labeled "Resulting Temperatures of Water Leaving Humidifier" shows the temperature of the exit water in'the present invention, Figure 1 at 16, corresponding to the inlet fSAR/1025b 15 EE r- I-i- temperature. For example, when the inlet air temperature is about 150°F the corresponding exit water temperature is slightly less than 130 0 F. This plot shows that the cycle efficiency is not necessarily maximized when the inlet air temperature to the humidifier is minimized. The cycle efficiency drops off as inlet air temperatures, for this example, decreases below approximately 120 0 F, as shown by the downward sloping of the upper curve as temperature decreases from the point of maximum efficiency. The maximum efficiency is reached when the heat exchange in humidifier 15 is as close I as possible to reversible conditions, when the upper curve is closest to the lower curve. The optimum temperature depends on the simultaneous reduction of quality and quantity of heat rejected.

ooa According to U.S. Patent 4,537,023, precooling of the compressed air i 0 o 0o o' for the humidification operation is done to achieve the lowest possible 0 0.

o: e water temperature from the humidifier. This, however, does not result in 15 peak efficiency 01 oo1 4 t 1 LS SAR.

O-

-7- L 1' r r'l I r L~L~ I IC-r IC q~ C I~ 174/47 for the cycle as evidenced by Figure 4 which shows plots of temperature of air entering the humidifier and the resulting water leaving the humidifier versus cycle efficiency. The peak efficiency occurs when the quality and quantity of heat rejection are simultaneously minimized.

Another disadvantage with the system of U.S. Patent 4,537,023, is that the temperature difference between the air entering the humidifier and water leaving the humidifier is set by the temperature difference used in designing the aftercooler. This forces an added constraint on the system and fixes the temperature of the water leaving the saturator at a higher temperature than the corresponding temperature that results from the process of the present invention.

A major advantage of the process of the present invention is a significant improvement in thermal efficiency.

o' Appreciation for this improvement in thermal efficiency, compared to U.S. Patent 4,537,023 will be realized by the following. In a 500 MW power plant, with the Nakamura et al. process, the fuel required using a gas turbine with a firing temperature of 1832°F i 0 500n l00OKW x 6800 BTU x2h-ahi X KWH yr 2.98 x 107 MMBTU/year With the process of the present invention, the fuel required 500x10000 KW x 6700 BTU I mW KWH yr 2.93 x 107 MMBTU/year -16- KLN/24781 174/47 Hence, fuel savings with the Improved Power Cycle (2.98 x 107 2.93 x 107) MMBTU/year 0.05 x 107 MMBTU/year This corresponds to an annual saving (with fuel cost at $4/MMBTU) of 0.05 x 107 MMBTU x $4 $2 6 /year year MNBTU The process of the present invention may also be used to convert low level heat from another plant such as a gasification plant or refinery into mechanical energy or electrical power, at a much higher efficiency than other methods. The fuel used in the combustion engine serves to upgrade the recovered low level heat. Thus, for example, when the low level heat recovered by preheating the humidifier circulating water, in the range of 3000 Sto 1400 F from a gasification plant is converted to electric Soo power, the effective efficiency of conversion is as high as approximately 18%. The imported heat may be used to evaporate a a additional water to provide total water in the range of 0.26 to pounds per pound of dry air.

i The standard of efficiency of conversion of such low i ti Slevel heat may be calculated for U.S. Patent No. 4,085,591, "Continuous Flow, Evaporative-Type Thermal Energy Recovery Apparatus and Method for Energy Recovery", where a pressurized Sgas, e.g. air, is humidified in a spray chamber, and expanded through a gas turbine, to take advantage of the higher specific volume of humidified air. The resulting efficiency with this system is less than Also there are a number of inherent disadvantages. To produce appreciable amounts of power, very large equipmcnt is required sinc% the system pressure is limiting. This system cannot "upgrade" the recovered low level -17- KLN/24781 c I I 'Y r- i IC I

DI'

174/47 energy, since it cannot be used in conjunction with a combustion engine.

It will be appreciated from the foregoing description that, with the process of the present invention, chemical energy, or low level heat supplemented with chemical energy, may be converted to mechanical energy or electrical power at a very high efficiency. It will also be appreciated that significant environmental benefits will result from the process of the present invention, including conservation of energy resources and reduction in thermal pollution due to the higher efficiency, a reduction in water consumption, particularly as compared to either the combined cycle or the steam injected cycle, and a reduction in nitrogen oxide emissions. With combined cycle plants, steam must be injected into the combustor to reduce such emissions, which in turn leads to a decrease in efficiency, which °ooo is overcome by the present invention.

o 0In light of the foregoing description, certain variations and modifications of the process of the present invention may become apparent to those skilled in the art. Thus, for example, a plurality of inter-coolers may be used as well as more than two stages of air compression. Also, the inlet air to the compressor may be cooled using a refrigeration system to improve both the efficiency and capacity of the system. The air leaving the inter-cooler may also be further cooled using the refrigeration system and the saturator water may also be precooled, using a refrigeration system, before it enters the inter-cooler.

Additionally, saturators of designs other than that illustrated may be used, such as a design where the water would be introduced at a plurality of locations. It is accordingly to be understood that all such modifications and variations are to be considered within the scope of the present invention.

-18-

Claims (38)

1. A process for producing power utilizing a combustion turbine, comprising humidifying compressed air, in multistate counter-current flow prior to combustion, to provide water vapor as thermal dilutent for combustion in said turbine, water used to form said water vapor being at a temperature below Its boiling point at the operating pressure when In contact with said compressed air, said compressed air being passed in heat exchange relationship with said water prior to humidification, whereby the temperature of said water is increased and the temperature of said compressed air is decreased and wherein heat is rejected from the process prior to said combustion.

2. The process of claim 1 in which said compressed air is provided by a multiple state compression step and heat exchange between said compressed air and water occurs between the stages oc said multiple stage o compression. 0

3. The process of claim 1 in which the exhaust from said turbine is Lo passed in multistage counter-current flow heat exchange relationship with o 0 said lihmidified air to preheat the same prior to combustion.

4. The process of claim 1 in which the exhaust from said turbine is 0 *4 o-0 passed in heat exchange relationship with the water prior to humidification of said compressed air.

The process of claim 2 in which said compressed air, following compression, Is further cooled prior to humidification by passing said oO,, compressed air in heat exchange relationship with said water a second time.

6. The process of claim 2 in which the temperature of said compressed air is reduced from a range from 300° to 400°F to a range from o 40° to 250°F by said heat exchange occurring between stages of said 04A# multiple stage compression. i

7. The process of claim 2 in which the temperature of said A compressed air exiting said multiple state compression is in a range from 3000 to 400 0 F.

8. The process of claim 5 in which the temperature of said compressed air following said further cooling and prior to humidification is in a range from 40° to 250 0 F. LS4 _KLN/24781 L -r O'Z KLN/24781 L~ g ~LC1 1 C -r i q 099 9 0 b909 o 9 0, 0 20

9. The process of claim 1 wherein heat is rejected by means of an air-cooled heat exchanger.

The process of claim 5 in which the exhaust from said turbine is passed in heat exchange relationship with said humidified air to pre-heat said air prior to combustion.

11. The p.rocess of claim 10 in which the exhaust from said turbine is passed in heat exchange relationship with said water to increase the temperature of said water prior to humidification of said compressed air.

12. The process of claim 5 in which the temperature of said compressed air is reduced from a range from 3000 to 400°F to a range of from 40° to 2500 F by said heat exchange occurring between stages of said multiple stage compression.

13. The process of claim 10 in which the temperature of said compressed air exiting said multiple stage compression is in a range of 300° to 400°F,

14. The process of claim 6 in which said compressed air Is reduced in temperature to a range from 700 to 140 0 F.

15. The process of claim 12 in which the temperature of tile compressed air is reduced to a range from 70° to 140°C.

16. A gas combustion process for producing power using a compressed air, counter-current humidifier, wherein compressed air is used in the process being firstly cooled against water to heat said water and secondly humidified against said heated water comprising the step of rejecting from the process heat contained in the compressed air used in the process, wherein the heat is rejected from the process prior to combustion and prior to final heat rejection from the process.

17. A process for producing power in a gas turbine power system comprising the steps of: compressing air in a first air compressor; removing heat of compression from the air compressed in the first air compressor by collecting the removed heat in a circulating water system; further compressing the air in a second air compressor; removing heat of compression from the air in the second air compressor by further collecting the removed heat in the circulating water system; i I 4? _KLN/24781 -9- I" a 040 0 0 00A i o 0 n 0 0 0a 04 0 0 0l 0B 0 0 090 0 00 ft 000 0 00 *e 00 0 Q 0r r 21 removing further heat from the air compressed in the second air compressor by rejecting heat from the process to precool air; moisturizing the precooled air by feeding the precooled air and water from the circulating system containing the removed heat from the first and second air compressions into a counter-current two phase humidifier to produce water vapor; feeding the water vapor and fuel into a combustion chamber to produce hot combustion gases; feeding the hot combustion gases to a gas turbine to convert thermal energy to mechanical work; coupling the gas turbine to a generator for converting mechanical work into the electric power; and coupling the gas turbine to the first and second air compressors for compressing air.

18. A gas combustion process of producing power using a compressed air, counter-current humidifier, wherein compressed air is used in the process being firstly cooled against water to heat said water and secondly humidified against said heated water comprising the step of rejecting from the process heat contained in the circulating water system used in the process, wherein the heat is rejected from the process prior to combustion.

19. A process for producing power in a gas turbine power system comprising the steps of: compressing air in a first air compressor; removing heat of compression from the air compressed in the first air compressor by collecting the removed heat in the circulating water system; further compressing the air in a second air compressor; removing heat of compression from the air compressed in the second air compressor by further collecting the removed heat in the circulating water system; removing the heat from the circulating water system by rejecting heat from the process to precool the air; moisturizing the precooled air by feeding the precooled air and water from the circulating system into the counter-current two phase humidifier to produce water vapor; feeding the water vapor and fuel into a combustion chamber to produce hot combustion gases; i. t- f 0 84 000( 0 t KLN/24781 au ILlusutateu as coupieu on a sJ1iyq.tL d2it', .Lc WL.L.- -v 't T T C ;e II I 22 feeding the hot combustion gases to a gas turbine to convert thermal energy to mechanical work; coupling the gas turbine to a generator for converting mechanical work into electric power; and coupling the gas turbine to the first and second air compressors for compressing air.

The process of claim 1 or 5 wherein said heat rejection occurs at the location of the said heat exchangers.

21. The process of claim 1 or 5 wherein said heat rejection from the system prior to combustion is from the compressed air.

22. The process of claim 1 or 5 wherein the heat rejection from the system prior to combustion is from the water.

23. The process of claim 1 or 5 including refrigeration of air between the compression steps and after one or both hea *-'(changes with water.

24. The process of claim 1 or 5 wherein air is compressed in two compression steps and the compressed air is passed in heat exchange relationship with the water when the air has undergone the first of the two o said compression steps.

The process of claim 1 or 5 wherein heat is rejected from water issuing from the humidifier before being brought into heat exchange relationship with air to be humidified

26. The process of claim 1 or 5 wherein air is refrigerated prior to compression.

27. A process for producing mechanical power utilizing heat 4- contained in process fluids within a system and heat from combusting in a combustionable fuel in a combustion chamber to turn a gas turbine comprising: providing combustible fuel; S0 providing process fluids consisting of compressed air and water; providing a circulating water system which contains the water; providing a humidifier capable of creating a gaseous medium including wzter vapor; producing the gaseous medium by feeding the compressed air to the humidifier and circulating the water through the humidifier; _KLN/24781 -11- cooling the heat from at least one medium; 23 compressed air by rejecting from the process some of the process fluids prior to reducing the gaseous feeding the gaseous medium and the combustible fuel to the combustion chamber; combusting the fuel in the presence of the gaseous medium within the combustion chamber to provide a working fluid at a first elevated temperature; feeding the working fluid to the gas turbine; expanding the working fluid in the gas turbine to produce mechanical power and turbine exhaust; extracting heat from the turbine exhaust for use within the process thereby producing a cooled turbine exhaust; and extracting heat from the turbine exhaust for use within the process thereby producing a cooled turbine exhaust; and rejecting the cooled turbine exhaust from the process. S°

28. A process for producing power utilizing a combustion turbine, comprising humidifying a compressed gaseous medium, in multistage C 0o counter-current flow prior to combustion, to provide water vapor as thermal diluent for combustion in said turbine, water used to form said water vapor being at a temperature below its boiling point at operating pressure when In contact with said compressed gaseous medium, passing said compressed gaseous medium in heat exchange relationship with water prior to 0o. humidification, whereby the temperature of said water is increased and the temperature of said compressed gaseous medium is decreased, and rejecting heat from the power production cycle by additionally precooling said compressed gaseous medium prior to humidification.

29. A process for producing power utitizing a combustion gas turbine, comprising: o r compressing a gaseous medium to a predetermined pressure; after-cooling the compressed gaseous medium against water, whereby the temperature of said water is increased and the temperature of said compressed air is decreased; contacting said compressed gaseous medium with said heated water in a multistage counter-current operation to humidify said compressed gaseous medium and provide water vapor as thermal diluent from combustion Sin said turbine; 'I i. _KLN/24781 Kg-mole/sec. -12- ,I turbine, comprising- <-v 24 said step of contacting the compressed gaseous medium with heated water being preceded by heat rejection from the cycle by pre-cooling the gaseous medium.

30. A process for producing power utilizing a combustion gas turbine, comprising: S 0 compressing a gaseous medium to a predetermined pressure; the said compression step being performed with inter-stage cooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with the heated water in a multistage counter-current operation of the humidification operation; said step of inter-cooling during the compression including heat rejection from the cycle; n using the compressed gaseous medium to drive a gas turbine for e o production of power. o

31. A process for producing power utilizing a combustion gas turbine, comprising: as^ compressing a gaseous medium to a predetermined pressure; the said compression step being performed with inter-stage cooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with the heated water in a multistage counter-current operation for the humidification operation; I burning fuel together with the humidified gaseous medium; driving a gas turbine for production of power; said step of inter-cooling during compression including heat rejection from the circulating water prior to its use for intercooling.

KLN/32. A process for producing power utilizing a combustion gas S' turbine, comprising: compressing a gaseous medium to a predetermined pressure; BL I the said compression step being performed with aftercooling against water and using the heated water in the humidification of the compressed gaseous medium; contacting the compressed gaseous medium with heated water in a t multistage counter-current operation for the humidification operation; Cd) burning the fuel together with the humidified gaseous medium; driving a gas turbine for production of power; LS u said step of after-cooling after compression including heat rejection of the circulating water prior to its use for after-cooling, _KLN/24781 -13- 25

33. The processes of any one of claims 28 to 32, in which the humidified compressed medium is preheated against the gas turbine exhaust and then mixed with the fuel for combustion.

34. The processes of any one of claims 28 to 33 in which in addition to the water heated by heat exchange with the compressed gaseous medium, water heated In the gas turbine exhaust is used in the humidification operation.

The processes of any one of claims 28 to 34 in which in addition to the water heated by heat exchange with the compressed gaseous medium, water heated by sources external to the power cycle is used in the humidification operation.

36. The process of claims 34 or 35 in which the overall compression oo 7 0 ratio Is between 6:1 and 34:1.

37. The process of claim 35 In which the water vapor content of the humidified compressed gaseous medium is between 0.26 and 0.5 pounds per a pound of dry gaseous medium. o a

38. A process for producing power, the process being substantially as hereinbefore described with reference to the accompanying drawings. 0ooo DATED this TWENTY-SEVENTH day of JULY 1990 0o Fluor Corporation Patent Attorneys for the Applicant SPRUSON FERGUSON i KLN2LS 4781 KLN/24781 -14- 174/47 ABSTRACT OF THE DISCLOSURE A process is disclosed for producing mechanical energy or electric power from chemical energy contained in a fuel, utilizing a combustion turbine. The compressed air which is used for combustion of the fuel to drive the turbine is humidified prior to combustion in a multistage countercurrent saturator to replace some or all of the thermal diluent air with water sapor. Humidification is effected with the water at a temperature below its boiling point at the operating pressure. The compressed air 1, is cooled prior to humidification by passing in heat exchange relationship with the water used for humidification. Low level heat is rejected from the compressed air during intercooling and prior to humidification. This process provides a significant improvement in thermal efficiency, compared to combined cycle, steam injected cycle, intercooled regenerative cycle, and other air humidification based processes. Additionally, the entire steam cycle of a combined cycle process is eliminated, including the steam turbine generator, steam drums, surface condenser and cooling towers. Dated this THIRTY-FIRST day of OCTOBER 1986 FLUOR CORPORATION Patent Attorneys for the Applicant SPRUSON .FERGUSON