MXPA00000117A - Waste heat recovery in an organic energy converter using an intermediate liquid cycle - Google Patents

Abstract

A heat recovery method and system that extracts heat from the exhaust of a gas turbine unit in a waste heat, heat exchanger and transfers the heat to an intermediate fluid, which can be pressurized water. The intermediate fluid in-turn transfers the heat to an organic working fluid resulting in the vaporization thereof. The vaporized organic working fluid drives a series of turbines which in turn drive a generator that generates electricity.

Description

RECOVERY OF WASTE HEAT IN AN ORGANIC ENERGY CONVERTER USING A LIQUID CYCLE INTERMEDIARY TECHNICAL FIELD This invention is concerned with a waste heat recovery system and a method for using same. In particular, it is concerned with a waste heat recovery system for a gas turbine system and with a method for using a heat recovery cycle with the exhaust gases produced by a gas turbine system.

BACKGROUND OF THE INVENTION Gas turbines are used throughout the world that burn a fuel that can be combusted to generate power (or energy). This power can be used for example to drive fluid pumps, to start gas compressors, to start other equipment and to generate electricity. Frequently, these turbines are located in remote places around the world where extreme weather conditions, including freezing temperatures. When they are put into operation, the gas turbines produce exhaust gases that are usually extremely hot and so often, these hot gases are only REF: 32411 expelled into the atmosphere instead of being used to generate additional power. For example, high pressure natural gas transmission pipes are conventionally used to transport gas from the production fields to customers located far away from the fields. The gas compressors that feed such pipes are usually energized by a gas turbine and optionally a heat recovery cycle can be used to reduce the net power requirements by converting the waste heat into the hot exhaust gases of the turbine to electricity. An installation of this type is illustrated in the North American patent of Fisher et al 5,632,143 issued May 27, 1997, which is incorporated herein by reference. In summary, this patent describes a combined cycle power plant having a gas turbine system. In one embodiment, an anchor steam turbine power plant uses the heat contained in the exhaust gases leaving the gas turbine system, while in another embodiment an organic rankine anchor cycle power plant uses the heat contained in the exhaust gases of the gas turbine system. Commonly, the temperature of the exhaust gases is approximately 450 ° C. According to this patent, the temperature of the gases from which the heat is transferred to the anchor power plant is controlled using the ambient air added to the exhaust gases of the gas turbine system. During a cold time, ambient temperatures may drop below the freezing temperature causing the condensate to condense, adversely affecting the operation of the heat recovery system. On the other hand, organic fluids that function as the working fluid in such systems that have relatively high temperatures may not be stable. There is therefore a need for an improved heat recovery cycle for a gas turbine system that can be used in climates of extreme temperatures, on the one hand and still has an improved heat recovery cycle.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a heat recovery system for heat produced by a heat source, such as a gas turbine system. The heat recovery system uses an organic fluid as the working fluid, in such a way that the heat recovery system can be used in climates of extreme temperatures in which temperatures fall below the freezing point for water.

In addition, the present invention provides an increased safety factor by using an intermediate fluid to transfer heat from the hot exhaust gases to the organic working fluid. In a preferred embodiment of the present invention, four main systems are interconnected. The first system is a gas turbine system in which the gas turbine is a primary driving force for some particular application, such as for driving a gas compressor remotely located geographically and used in a natural gas line. The gas turbine system generates large amounts of heat that is usually lost to the atmosphere by means of gas exhaust chimneys. The second system is a waste heat recovery system that takes the exhaust gas from the turbine and deflects it from the exhaust chimneys to extract the heat contained in it and thus extracts energy from that heat that was previously wasted. The third system is an intermediate fluid system which in a preferred embodiment is a pressurized water system and to which the waste heat removed from the exhaust gas of the turbine is transferred. The fourth system is an organic working fluid system to which the heat of the intermediate fluid is transferred to generate an organic fluid vapor that is used to drive an organic fluid turbine to produce power, preferably by using an electrical generator connected to the turbine of the organic fluid. Thus, the present invention comprises a waste heat recovery system that transfers heat from primary heat source, such as exhaust heat from a gas turbine to an intermediate fluid, an intermediate fluid system that transfers heat to an organic working fluid to generate a steam and an organic working fluid system whose steam puts into operation an organic fluid turbine to generate additional power from the heat of waste.

BRIEF DESCRIPTION OF THE DRAWING Modalities of the present invention are described by way of example with reference to the accompanying drawing in which: Figure 1 is a schematic block diagram of a waste heat recovery system having an organic energy converter that uses an intermediate liquid cycle.

DETAILED DESCRIPTION Referring now to Figure 1, the reference numeral 10 designates a gas turbine system according to the present invention. The gas turbine unit drives a power device or mechanical power device such as an electric generator 14 to produce electric power or a gas compressor. Exhaust gases leaving the gas turbine 13 are fed to the waste heat recovery system 20. The waste heat recovery system 20 comprises heating coils 36 and 40 housed in the case 24 of the heat exchanger 22 to transfer the heat contained in the exhaust gases to the intermediate fluid system 60. When the heat is transferred to the system of intermediate fluid 60, the gas turbine exhaust gases in line 18 enter the waste heat recovery system 20 at the inlet 26 and flow to the coils 36 and 40 upon opening the valve 32 and closing the valve 30 After this, the expelled gases exhausted from heat leave the heat exchanger 22 via the outlet 52 and flow into the atmosphere via the chimney 56. If preferred, the route of the exhaust gases can be changed according to the site. specific. If for some reason, the heat exchanger 22 is to be omitted, the exhaust gases are fed to the atmosphere by closing the valve 32 and opening the valve 30 to feed the exhaust gases to the atmosphere. The heat transfer fluid, preferably water, flowing in the intermediate fluid system 60, which is a closed, pressurized liquid water flow system, receives the heat from the exhaust gases flowing in the heat exchanger 22. The heat transfer fluid flowing in the intermediate fluid system 60 leaves the heat exchanger 22 at 48 and transfers the heat to the organic fluid present in the organic Rankine cycle working fluid system designated by the number 90. by means of the use of the vaporizer 62. The portion of the heat-spent heat transfer fluid exiting the vaporizer 62 is fed by the pump 64 to the heat exchanger 22 at 44, while an additional portion of the heat transfer fluid Heat depleted is fed to the preheater 68 to preheat the organic working fluid in the system 90 of the organic cycle working fluid. In a preferred configuration, the pump 64 actually consists of two centrifugal pumps connected in parallel, each pump is capable of providing 100% of the pumping requirements, which at full operation at steady state is approximately 130 Kilograms per second (Kg. / s). The ratio of the amount of heat transfer fluid flow returned to heat exchanger 22 at 44 to the amount of heat transfer fluid fed to preheater 68 is determined by valve 66. Usually, the ratio is 70% flowing to heat exchanger 22 at 44 to 30% flowing to preheater 68 and preferably 72.5% to 27.5%. In addition, the heat-spent heat transfer fluid exiting the preheater 68 is fed to the heat exchanger 22 at the inlet 42 to receive more heat from the exhaust gases in the coil 36. In a preferred embodiment, the heat exchanger 22 has a capacity to transfer (that is, recover) approximately 33,000 Kilowatts (KW) of energy. When water is used, the pressure of the water or heat transfer fluid flowing in the intermediate fluid system 60 is maintained by the pressurizer 76. The lower side or side of the liquid, of pressurizer 76 is connected to line 70 in the intermediate fluid system 60 via line 78 and pump or pumps 80 together with valve 82. Valve 82 detects the fluid-transfer heat pressure flowing in the line 63 to maintain the desired pressure. Commonly, the pressure is maintained at approximately 3500 KPa with the range of 3000 to 4000 KPa in order to ensure that the water does not boil. The storage tank 72 is also connected to the duct 70 to accumulate the excess pressurized heat transfer fluid and from which the compensation fluid is fed when required. The compensating heat transfer fluid is transferred to the intermediate fluid system 60 according to the level of the liquid in the pressurizer 76 determined by the level detector 84. The detector 84 is also connected to the level controller 86 to control the operation of the pump 74. If required, the heat transfer liquid present in the system 60 of the intermediate fluid can be emptied into the storage tank 72. Such an operation can reduce the risk of the heat transfer fluid freezing. System 90 of the organic Rankine cycle working fluid comprises vaporizer 62 to produce steam from the organic working fluid that is fed to organic steam turbine 92. Pentane is the preferred organic working fluid. The organic steam turbine preferably comprises the turbine module 94 at high pressure which receives the vaporizer from the organic working fluid produced by the vaporizer 62 and the low pressure organic steam turbine module 96 which receives the steam from the working fluid expanded organic that leaves the turbine module 96 at high pressure. The high pressure turbine module 94 and the low pressure turbine module 96 produce power and preferably drive the electrical generator 98 which can be interposed between these turbine modules. The additional expanded organic vapor exiting the turbine module 96 at low pressure is fed to the condenser 102 via the recuperator 100, wherein the liquid organic working fluid exiting the condenser 102 cools the additional expanded organic vapor. Each turbine 92 and 94 can be a 3.75 MW turbine rotating at 1800 RPM. The hot liquid organic working fluid exiting the recuperator 100 is preferably fed to the preheater 68 to receive heat transferred from the heat transfer fluid flowing in the intermediate fluid system 60. The additional hot liquid organic working fluid that exits of the preheater 68 is fed to the vaporizer 62 thus completing the cycle of the organic working fluid. In the waste heat recovery system described above, sufficient heat is separated from the exhaust gases of the gas turbine to lower the temperature of the gas from a temperature of about 463 ° C to about 92 ° C. This separate waste heat results in the generation, by the generator 98 of a net electric power of approximately 5.8 MW and a gross power of 6.5 MW, the difference in power between the two power figures is necessary to put the components into operation of the system. In the modality described above, the heat recovery cycle is used to produce electricity. However, the power of the shaft produced by the organic gas turbines 94 and 96 can alternatively be used to directly drive equipment, such as gas compressors or to put into operation such machinery without converting the power of the tree into electricity. In addition, insofar as the description specifies a gas turbine, other heat sources may also be used, such as industrial heat, internal combustion engines such as diesel engines, reciprocating gas engines, etc. In addition, while the above description reveals a single heat recovery cycle of organic working fluid, the present invention includes the use of units operating in cascade or in parallel in a heat recovery cycle. If cascaded units are used, the turbine or higher pressure turbines can use water as a working fluid in closed cycles. In addition, while the above description discloses a power plant utilizing a simple closed-cycle organic Rankine cycle or cycles having an air-cooled condenser, the air can be added to the exhaust gases of the gas turbine for control the temperature of the gases from which the heat is extracted in the heat recovery cycle. By using a closed, organic Rankine cycle power plant for heat recovery instead of a steam turbine, the construction, operation and maintenance of the overall system is simplified allowing reliable and unattended systems to be in operation for long periods. periods of time in distant places. The advantages and improved results provided by the method and apparatus of the present invention are apparent from the foregoing description of the preferred embodiment of the invention. Various changes and modifications can be made without departing from the spirit and scope of the invention as described in the appended claims. It is noted that, with regard to this date, the best method known to the applicant, to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (22)

1. CLAIMS Having described the invention as above, the content of the following claims is claimed as property: 1. A method for generating power when using the exhaust gases of a gas turbine unit, characterized in that it comprises: heating an intermediate fluid with the exhaust gases; vaporizing an organic liquid working fluid with the intermediate fluid heated in a vaporizer to form a vaporized working fluid and an intermediate fluid exhausted from heat; expand the vaporized working fluid in an organic steam turbine to generate power and produce an expanded vaporized working fluid; condensing the expanded vaporized working fluid to produce a condensate; and transmit the condensate back to the vaporizer.
2. 2. The method of compliance with the claim 1, characterized in that it further includes preheating the condensate with the intermediate heat-spent fluid before the vaporization step.
3. 3. The method according to claim 2, characterized in that it also includes controlling the amount of the condensate that is preheated to a percentage of the total amount of the intermediate fluid. .
4. The method in accordance with the claim 2, characterized in that it also includes a further preheating step of the condensate by heating the condensate with the expanded vaporized working fluid before the condensate is preheated by the intermediate heat-spent fluid.
5. 5. The method of compliance with the claim 1, characterized in that the organic fluid is pentane.
6. 6. The method of compliance with the claim 1, characterized in that the intermediate fluid is pressurized water.
7. 7. A method for recovering energy from waste heat that is produced by a power generation system, characterized in that it comprises: providing a heated intermediate fluid heated by the waste heat; provide a vapor of gaseous organic working fluid that has been vaporized from a liquid by the hot intermediate fluid in a vaporizer in which an intermediate fluid exhausted from heat is produced, generating electrical power from the steam of working organic fluid gaseous with an electric generator driven by an organic steam turbine that is in turn driven by the vapor of gaseous working organic fluid that produces an expanded working fluid vapor; producing a condensate in a condenser from the steam of the working organic fluid after use thereof in the organic steam turbine and supplying the condensate to the vaporizer.
8. A method for recovering energy from waste heat according to claim 7, characterized in that it further includes producing a preheated condensate before the condensate is supplied to the vaporizer with the intermediate heat-spent fluid after the intermediate fluid - has vaporized the organic fluid.
9. 9. A method for recovering energy from waste heat according to claim 8, characterized in that it further includes producing a preheated condensate with the steam from the expanded vaporized working fluid before the condensate is preheated by the spent intermediate hot.
10. A method for recovering energy from waste heat according to claim 7, characterized in that the condensate is preheated with the expanded vaporized working fluid.
11. 11. A method for recovering energy from waste heat according to claim 7, characterized in that the intermediate fluid is pressurized water.
12. 12. A method for recovering energy from waste heat according to claim 7, characterized in that the working fluid is pentane.
13. 13. A heat recovery system utilizing heat produced by a power generation source such as a gas turbine unit, the heat recovery system being characterized in that it comprises: a heat supply from a generation source of power; a heat recovery heat exchanger that receives the heat supply and in which an intermediate fluid is heated by the heat supply; an intermediate fluid system containing an intermediate fluid and including an intermediate fluid pump having an inlet and a discharge and lines connected to the inlet of the pump and discharge to the heat exchanger, the lines contain and feed the intermediate fluid; a vaporizer in which a vaporized organic working fluid is produced from a liquid organic working fluid with heat contained in the intermediate fluid, the lines connect the heat recovery heat exchanger to the vaporizer and the intermediate heat exhausted fluid it is discharged from the vaporizer; an organic steam turbine that is driven by the vaporized organic working fluid and from which an expanded vaporized organic working fluid exits; a condenser in which the expanded vaporized organic working fluid condenses to a condensate; and a main pump of the condensate that is fed with the condenser of the condenser and in turn supplies the condensate to the vaporizer.
14. 14. A heat recovery system according to claim 13, characterized in that the organic working fluid is pentane.
15. 15. A method for recovering energy from waste heat according to claim 13, characterized in that the intermediate fluid is water.
16. 16. A heat recovery system according to claim 13, characterized in that the intermediate fluid is pressurized water having a pressure such that the water will not freeze at the temperatures found in cold climates in the earth.
17. 17. A heat recovery system according to claim 13, characterized in that it also includes a preheater in which the condensate is heated with the intermediate heat-exhausted fluid before entering the vaporizer.
18. 18. A heat recovery system according to claim 14, characterized in that the intermediate fluid system further includes a pressurizer connected to a first line located between the discharge of the intermediate fluid pump and the heat exchanger.
19. 19. A heat recovery system according to claim 16, characterized in that the intermediate fluid system further includes a storage tank having an inlet and an outlet and a compensation liquid pump connected with conduits between the storage tank and the first line.
20. 20. A heat recovery system according to claim 18, characterized in that it further includes a storage tank having an inlet and an outlet and a pump connected with lines between the storage tank and a first conduit located between the discharge of the intermediate fluid pump and the heat exchanger and where the pressurizer includes a vent connection that is connected to the storage tank.
21. 21. A heat recovery system according to claim 13, characterized in that it further includes a preheater having a primary side that contains a fluid that provides heat and a secondary side that contains a fluid that receives heat, the preheater is connected to the vaporizer to receive therefrom the intermediate exhausted heat fluid on the primary side and connected to the condensate pump to receive condensate thereof on the secondary side thereof and to provide an intermediate exhausted fluid of additional heat to the recovery heat exchanger of heat.
22. 22. A heat recovery system according to claim 13, characterized in that the heat recovery heat exchange comprises a first lower set of coils having an inlet and an outlet, a second upper set of coils having an inlet and an outlet. and an outlet and a cross connection line connecting the first coil outlet assembly to the inlet of the second set of coils and wherein the outlet of the intermediate fluid pump is connected to the cross connection conduit and wherein the pump Intermediate fluid discharges through a valve to the cross connection line.