WO2014165053A1

WO2014165053A1 - Turbine dry gas seal system and shutdown process

Info

Publication number: WO2014165053A1
Application number: PCT/US2014/024254
Authority: WO
Inventors: Jason Miller; Michael Louis Vermeersch
Original assignee: Echogen Power Systems, L.L.C.
Priority date: 2013-03-13
Filing date: 2014-03-12
Publication date: 2014-10-09

Abstract

Provided herein are heat engine systems and methods for cooling a power turbine while maintaining the dry gas seals (DGSs) free of contamination during shutdown procedures. One method includes activating a shutdown procedure by closing multiple valves coupled to the turbine to stop the working fluid passing therethrough and opening one or more turbine vent valves to provide seal gas to vent. The seal gas may flow from a seal gas conditioning system, through a DGS cavity, across a labyrinth seal, through a labyrinth seal cavity, the turbine, and the turbine vent line, and into a leak recapture storage vessel and/or the ambient atmosphere. One method further includes maintaining a storage tank pressure less than a reference pressure of the labyrinth seal cavity and maintaining a conditioning system pressure and a DGS cavity pressure greater than the reference pressure.

Description

Turbine Dry Gas Seal System and Shutdown Process Cross-Reference to Related Applications

[001] This application claims the benefit of U .S. Prov. Appl. No. 61 /779,310, filed on March 13, 2013, the contents of which are hereby incorporated by reference to the extent not inconsistent with the present disclosure. This application also claims the benefit of U .S. Prov. Appl. No. 61 /780,276, filed on March 13, 2013, the contents of which are hereby incorporated by reference to the extent not inconsistent with the present disclosure.

Background

[002] Waste heat is often created as a byproduct of industrial processes where flowing streams of high-temperature liquids, gases, or fluids must be exhausted into the environment or removed in some way in an effort to maintain the operating temperatures of the industrial process equipment. Some industrial processes utilize heat exchanger devices to capture and recycle waste heat back into the process via other process streams. However, the capturing and recycling of waste heat is generally infeasible by industrial processes that utilize high temperatures or have insufficient mass flow or other unfavorable conditions.

[003] Waste heat can be converted into useful energy by a variety of turbine generators or heat engine systems that employ thermodynamic methods, such as Rankine cycles. Rankine cycles and similar thermodynamic methods are typically steam-based processes that recover and utilize waste heat to generate steam for driving a turbine , turbo, or other expander connected to an electric generator/alternator a pump/compressor, or other device .

[004] An organic Rankine cycle utilizes a lower boiling-point working fluid, instead of water, during a traditional Rankine cycle. Exemplary lower boiling-point working fluids include hydrocarbons, such as light hydrocarbons (e.g. , propane or butane) and halogenated hydrocarbon, such as hydrochlorofluorocarbons (HCFCs) or hydrofluorocarbons (H FCs) (e.g., R245fa). More recently, in view of issues such as thermal instability, toxicity, flammability, and production cost of the lower boiling-point working fluids, some thermodynamic cycles have been modified to circulate no n- hydrocarbon working fluids, such as ammonia.

[005] A turbine generator is an example of a working fluid system that may be utilized to generate electrical energy throughout the world for both commercial and no n -commercial use. The turbine generator may supply electricity to an electrical bus or grid (e.g. , an alternating current bus) that usually has a varying load or demand over time. The general turbine generator has a turbine connected to a generator by a shaft.

[006] One problem that occurs is when dry gas seals, disposed around the shaft within the turbine generator, become contaminated due to unfiltered, unconditioned gas coming into contact with the dry gas seals. At system shutdown, the flow of cooling fluid and lubrication is stopped while the power turbine is usually still turning and thus generating heat. Once through the power turbine, the working fluid is heated to an elevated temperature while at a reduced pressure.

[007] The compact size and the high running temperature of the power turbine provide a situation called "heat soak back" during shutdown that may be problematic to the power turbine. The "heat soak back" issue occurs when hot working fluid is stopped from entering the power turbine and subsequently, the power turbine stops spinning. Immediately, the turbine housing, the shaft, the impeller, and other components of the power turbine become heated to elevated temperatures, such as to values of or greater than the temperature of the heated working fluid flowing into the inlet of the power turbine. If the heated working fluid is not cooled prior to entering the inlet, thermal energy may be conducted through the turbine housing and the shaft and therefore overheat areas that are not designed to be heated to elevated temperatures. The generated heat may lead to burning of the lube oil or the damaging of other temperature- sensitive components. In one example, lube oil or other lubricants may contact the heated metal surfaces of the power turbine and begin to degrade. Also, elastomer seals, such as labyrinth or dry gas seals are likely to fail since they are not designed to be heated to such high temperatures.

[008] Therefore, there is a need for a heat engine system and a method for transforming energy, whereby the power turbine within the heat engine system may be cooled and the dry gas seals are not contaminated during a shutdown procedure despite an elevated temperature and reduced pressure of the working fluid.

Summary

[009] Embodiments of the invention generally provide heat engine systems and methods for generating electricity, as well as methods for cooling a power turbine in the heat engine systems while maintaining the dry gas seals free or substantially free of contamination during a planned or emergency shutdown procedure. [010] In one or more embodiments described herein, a heat engine system with a turbine cooling system is provided and includes a working fluid circuit containing a working fluid and a heat exchanger. The working fluid circuit generally has a high pressure side and a low pressure side and at least a portion of the working fluid may be in a supercritical state. The heat exchanger may be fluidly coupled to and in thermal communication with the working fluid in the high pressure side of the working fluid circuit. The heat exchanger may be configured to transfer thermal energy from a heat source stream to the working fluid in the high pressure side. The heat engine system further contains a power turbine and a driveshaft. The power turbine may be fluidly coupled to and disposed between the high pressure side and the low pressure side of the working fluid circuit and configured to convert a pressure drop in the working fluid to mechanical energy. The driveshaft may be coupled to the power turbine and configured to drive a device with the mechanical energy. The driveshaft is at least partially, if not substantially, contained within a housing. The heat engine system further contains a seal gas conditioning system fluidly coupled to and disposed between the housing and a seal gas supply source. The seal gas conditioning system may be configured to dispense a seal gas.

[011] The heat engine system further contains a series of cavities, such as a labyrinth seal cavity, a dry gas seal cavity, and several segmented circumferential seal cavities. The labyrinth seal cavity may be formed between the power turbine and a labyrinth seal and between the driveshaft and the housing. The dry gas seal cavity may be formed between the labyrinth seal and a dry gas seal and between the driveshaft and the housing. The dry gas seal cavity may be configured to receive the seal gas from the seal gas conditioning system. A first segmented circumferential seal cavity may be formed between the dry gas seal and a first segmented circumferential seal and between the driveshaft and the housing. A second segmented circumferential seal cavity may be formed between the first segmented circumferential seal and a second segmented circumferential seal and between the driveshaft and the housing. The second segmented circumferential seal cavity may be configured to receive the seal gas from the seal gas conditioning system. The heat engine system further contains a leak recapture storage vessel fluidly coupled to the housing and in fluid communication with the first segmented circumferential seal cavity, a power turbine discharge line fluidly coupled to the power turbine on the low pressure side of the working fluid circuit, and a first power turbine vent line fluidly coupled to and between the power turbine discharge line and the leak recapture storage vessel. [012] The heat engine system further contains a first power turbine vent valve disposed on the first power turbine vent line and configured to release a portion of the seal gas flowing from the power turbine into the leak recapture storage vessel. The heat engine system may also have a second power turbine vent line fluidly coupled to the power turbine discharge line and extending into the ambient atmosphere. A second power turbine vent valve may be disposed on the second power turbine vent line and configured to release a portion of the seal gas flowing from the power turbine into the ambient atmosphere.

[013] The heat engine system generally contains at least one conditioned gas line, but in some examples, may contain two or more conditioned gas lines fluidly coupled to and disposed between the seal gas conditioning system and the housing. In one aspect, a conditioned gas valve may be fluidly coupled to the conditioned gas line and configured to control the seal gas passing through the conditioned gas line and into the dry gas seal cavity. In another aspect, a conditioned gas valve may be fluidly coupled to the conditioned gas line and configured to control the seal gas, utilized as a buffer gas, passing through the conditioned gas line and into the second segmented circumferential seal cavity. In other examples, the heat engine system further contains a buffer gas supply fluidly coupled to the housing and in fluid communication with the second segmented circumferential seal cavity. The buffer gas supply may contain a conditioned gas line fluidly coupled to and disposed between the seal gas conditioning system and the housing and in fluid communication with the second segmented circumferential seal cavity.

[014] In some embodiments, the heat engine system also contains a leak recapture line, a compressor, a condenser or a cooler, and/or combinations thereof. The leak recapture line may be fluidly coupled to and disposed between the leak recapture storage vessel and the housing. The leak capture compressor and/or the condenser may be fluidly coupled to the leak recapture line and disposed between the leak recapture storage vessel and the housing. In other embodiments, the heat engine system further contains a power turbine stop valve and a power turbine discharge valve. The power turbine stop valve may be fluidly coupled to a power turbine inlet line upstream of an inlet of the power turbine, the power turbine discharge valve may be fluidly coupled to the power turbine discharge line downstream of an outlet of the power turbine, and the power turbine stop valve and the power turbine discharge valve may be configured to control the flow of the working fluid through the power turbine. The heat engine system may also contain a power turbine bypass valve fluidly coupled to a power turbine bypass line. The power turbine bypass line may be fluidly coupled to the power turbine inlet line upstream of the power turbine stop valve and fluidly coupled to the power turbine discharge line upstream of the power turbine discharge valve.

[015] In some embodiments, the heat engine system further contains the labyrinth seal cavity configured to have a reference pressure within a reference pressure range, the leak recapture storage vessel may be configured to have a recapture storage vessel pressure within a recapture storage vessel pressure range, and the recapture storage vessel pressure is less than the reference pressure. The dry gas seal cavity may be configured to have a dry gas seal cavity pressure within a dry gas seal cavity pressure range, and the dry gas seal cavity pressure is greater than the reference pressure. The seal gas conditioning system may be configured to have a conditioning system pressure within a conditioning system pressure range, and the conditioning system pressure is greater than the dry gas seal cavity pressure.

[016] In some examples, the reference pressure may be within the reference pressure range from about 500 pounds per square inch gauge (psig) (about 3.45 MPa) to about 1 ,500 psig (about 10.34 MPa). The recapture storage vessel pressure may have a pressure differential within a range from about 50 pounds per square inch differential (psid) (about 345 kPa) to about 1 ,250 psid (about 8.62 MPa) less than the reference pressure. The recapture storage vessel pressure may be within a range from about 50 psig (about 345 kPa) to about 400 psig (about 2.76 MPa). The conditioning system pressure may have a pressure differential within a range from about 50 psid (about 345 kPa) to about 100 psid (about 689 kPa) greater than the reference pressure. The conditioning system pressure may be within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1 .0 MPa). The dry gas seal cavity pressure may have a pressure differential within a range from about 50 psid (about 345 kPa) to about 100 psid (about 689 kPa) greater than the reference pressure. The dry gas seal cavity pressure may be within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1 .0 MPa).

[017] In other embodiments, the heat engine system generally contains a seal gas supply source fluidly coupled to the seal gas conditioning system and configured to supply the seal gas to the seal gas conditioning system. The seal gas conditioning system may further be configured to form a conditioned or dried seal gas from an unconditioned seal gas received from the seal gas supply source. The seal gas supply source may have a seal gas source pressure within a seal gas source pressure range, and the seal gas source pressure is greater than the reference pressure. In many examples, the seal gas source pressure may have a pressure differential within a range from about 50 psid (about 345 kPa) to about 200 psid (about 1 .38 MPa) greater than the reference pressure. The seal gas source pressure may be within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1 .0 MPa).

[018] In one or more other embodiments described herein, a method for cooling a turbine in a heat engine during a shutdown is provided and includes circulating a working fluid within a working fluid circuit. The working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state. The method further includes transferring thermal energy from a heat source stream to the working fluid by a heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit, flowing the working fluid into a power turbine, and converting the thermal energy of the working fluid to mechanical energy of a driveshaft coupled to the power turbine. The method further includes activating a shutdown procedure by closing a power turbine stop valve and a power turbine discharge valve to stop the flow of the working fluid through the power turbine.

[019] The method also includes flowing a seal gas from a seal gas conditioning system, through a dry gas seal cavity, across a labyrinth seal, through a labyrinth seal cavity, through the power turbine, through a first power turbine vent line and a first power turbine vent valve disposed thereon, and to a leak recapture storage vessel. The labyrinth seal cavity and the dry gas seal cavity are generally separated by the labyrinth seal and are adjacent to and between the driveshaft within a housing. The method further includes flowing the seal gas from the seal gas conditioning system, through the dry gas seal cavity, across a dry gas seal, through a first segmented circumferential seal cavity, through a leak recapture line, and to the leak recapture storage vessel. The first segmented circumferential seal cavity and the dry gas seal cavity are separated by the dry gas seal and are adjacent the driveshaft within the housing. Generally, the labyrinth seal cavity may have the reference pressure within the reference pressure range, the dry gas seal cavity may have the dry gas seal cavity pressure within the dry gas seal cavity pressure range, and the dry gas seal cavity pressure is greater than the reference pressure. The leak recapture storage vessel may be at the recapture storage vessel pressure within the recapture storage vessel pressure range, and the recapture storage vessel pressure may be less than the reference pressure.

[020] The method further includes opening a second power turbine vent valve to release a portion of the seal gas flowing from the power turbine into the ambient atmosphere. The second power turbine vent valve may be fluidly coupled to a second power turbine vent line disposed fluidly coupled to the power turbine discharge line and extending into the ambient atmosphere. The second power turbine vent valve may be fluidly coupled to the second power turbine vent line and configured to control the portion of the seal gas flowing through the second power turbine vent line. The seal gas supply source may have a seal gas source pressure within a seal gas source pressure range, and the seal gas source pressure is greater than the reference pressure. The seal gas conditioning system may have a conditioning system pressure within a conditioning system pressure range, and the conditioning system pressure is greater than the reference pressure. The method may further include flowing the seal gas from the seal gas conditioning system, through a conditioned gas line, and into the dry gas seal cavity. The conditioned gas line may be fluidly coupled to and disposed between the seal gas conditioning system and the housing. In another embodiment, the method may further include flowing the seal gas from the seal gas conditioning system, through a second segmented circumferential seal cavity, across a segmented circumferential seal, through the first segmented circumferential seal cavity, through the leak recapture line, and to the leak recapture storage vessel. The second segmented circumferential seal cavity and the first segmented circumferential seal cavity are separated by the segmented circumferential seal and are adjacent the driveshaft within the housing. The method may further include flowing the seal gas from the seal gas conditioning system, through a conditioned gas line, and into the second segmented circumferential seal cavity. The conditioned gas line may be fluidly coupled to and disposed between the seal gas conditioning system and the housing.

[021] The method may further include closing a power turbine bypass valve while stopping the flow of the working fluid from the primary heat exchanger through the power turbine during the shutdown procedure. The power turbine stop valve may be fluidly coupled to the working fluid circuit upstream of an inlet of the power turbine, and the power turbine discharge valve may be fluidly coupled to the working fluid circuit downstream of an outlet of the power turbine. The power turbine bypass valve may be fluidly coupled to the working fluid circuit by a power turbine bypass line extending between the inlet and the outlet of the power turbine. The shutdown procedure may be a planned shutdown, an emergency shutdown, a loss of power, a process upset, or a process trip of the power turbine.

Brief Description of the Drawings

[022] The present disclosure is best understood from the following detailed description when read with the accompanying Figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. [023] Figure 1 A illustrates an exemplary heat engine system, according to one or more embodiments disclosed herein.

[024] Figures 1 B-1 D illustrate more detailed views of portions of the heat engine system depicted in Figure 1 A, according to multiple embodiments disclosed herein.

[025] Figure 2 illustrates another exemplary heat engine system, according to one or more embodiments disclosed herein.

[026] Figure 3 is a flow chart illustrating a method for cooling a turbine in a heat engine during shutdown, in accordance with one or more embodiments disclosed herein.

Detailed Description

[027] Embodiments of the invention generally provide heat engine systems and turbine case venting systems, as well as methods for generating electricity, cooling a power turbine in the heat engine system while maintaining the dry gas seals free or substantially free of contamination during a planned or emergency shutdown procedure , and venting a turbine case containing the power turbine. Figures 1 A-1 D depict an exemplary heat engine system 90, which may also be referred to as a thermal engine system, an electrical generation system, a waste heat or other heat recovery system, and/or a thermal to electrical energy system, as described in one of more embodiments herein. In the embodiment shown in Figure 1 A, the heat engine system 90 includes a turbine case venting system 190. The turbine case venting system 190 includes a turbine case vent line 1 92, a turbine case vent valve 194, and an optional sound suppressing device 196.

[028] The heat engine system 90 further contains a waste heat system 100 and a power generation system 220 coupled to and in thermal communication with each other via a working fluid circuit 202. The working fluid circuit 202 contains the working fluid (e.g., sc-C0₂) and has a high pressure side and a low pressure side. A heat source stream 1 10 flows through heat exchangers 120, 130, and/or 150 disposed within the waste heat system 100. The heat exchangers 120, 130, and/or 150 are fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202, configured to be fluidly coupled to and in thermal communication with a heat source stream 1 10, and configured to transfer thermal energy from the heat source stream 1 10 to the working fluid. Thermal energy is absorbed by the working fluid within the working fluid circuit 202 and the heated working fluid is circulated through a power turbine 228 within the power generation system 220. [029] The power turbine 228 may be disposed between the high pressure side and the low pressure side of the working fluid circuit 202 and fluidly coupled to and in thermal communication with the working fluid. The power turbine 228 may be configured to convert thermal energy to mechanical energy by a pressure drop in the working fluid flowing between the high and low pressure sides of the working fluid circuit 202. A power generator 240 may be coupled to the power turbine 228 and configured to convert the mechanical energy into electrical energy. As depicted in Figure 1A, a power outlet 242 may be electrically coupled to the power generator 240 and configured to transfer the electrical energy from the power generator 240 to an electrical grid 244. The power generation system 220 generally contains a driveshaft 230 and a gearbox 232 coupled between the power turbine 228 and the power generator 240.

[030] Figures 1 B-1 D further depict portions of the power generation system 220 containing a housing 238, which may be a case, a chamber, a container, or any other housing for the components of the power generation system 220. The housing 238 may contain or be composed of one or multiple segments or pieces. Similarly, as depicted in Figures 1 B-1 D, a turbine case 128 may be a housing, a chamber, a container, or other casing components containing the power turbine 228. The turbine case 128 may also contain or be composed of one or multiple segments or pieces. The turbine case 128 is generally coupled to and in fluid communication with the housing 238. In some configurations, the turbine case 128 and the housing 238 may be the same housing or casing for containing the components of the power generation system 220.

[031] The turbine case venting system 190 is operatively connected to the turbine case 128 for venting gases and fluids from within the turbine case 128 in order to reduce the internal pressure of the turbine case 128, as well as to reduce the internal pressure of the housing 238. One end of the turbine case vent line 192 may be fluidly coupled to the turbine case 128, and the other end of the turbine case vent line 192 extends away from the turbine case 128, such as into the ambient atmosphere. The turbine case vent valve 194 is operatively and fluidly connected to the turbine case vent line 192 and may be configured to control or adjust the passage of gases and/or fluids (e.g., seal gas) from the turbine case 128, through the turbine case vent line 192, and into the ambient atmosphere. In some configurations of the turbine case venting system 190, the sound suppressing device 196 may be optionally coupled to the turbine case vent line 192. [032] The housing 238 may include a gas manifold (not shown), as well as all, a portion of, or none of the power turbine 228, the gearbox 232, and/or the power generator 240. The gas manifold may have multiple passageways or branched connections for flowing gas, liquid, or fluid that may be integrated within the housing 238 or contained within conduits or piping extending along and/or through the housing 238. In multiple configurations, the heat engine system 90 provides for the delivery of one or more gases and/or fluids, such as seal gas, conditioned seal gas, dry seal gas, bearing gas, a portion of the working fluid, air, other gases, or combinations thereof into the housing 238 within the power generation system 220. The gas may be utilized for cooling and purging one or more parts of the power turbine 228, the driveshaft 230, the gearbox 232, and other components within the power generation system 220.

[033] The housing 238 includes a seal assembly containing multiple dry gas seals along the driveshaft 230 and cavities disposed between the dry gas seals and the driveshaft 230. In some embodiments, as depicted in Figures 1 B-1 C, the seal assembly contains a labyrinth seal (LABY) 153, a dry gas seal (DGS) 155, one or multiple segmented circumferential seals (seg cs or SCS) - such as a first segmented circumferential seal (SCS) 157 and a second segmented circumferential seal (SCS) 159, one or multiple oil bearings 161 , a bearing seal 163, and optionally other seals and bearings disposed between the power turbine 228 and the gearbox 232, as well as between the driveshaft 230 and the housing 238. The seal assembly of the housing 238 also contains multiple cavities formed adjacent or between the seals and/or bearings and along and between the driveshaft 230 and the housing 238. Figures 1 C-1 D depict that the seal assembly contains a labyrinth seal (LABY) cavity 143 disposed between the power turbine 228 and the labyrinth seal 153, a dry gas seal (DGS) cavity 145 disposed between the labyrinth seal 153 and the dry gas seal 155, a first segmented circumferential seal (SCS) cavity 147 disposed between the dry gas seal 155 and the first SCS 157, a second segmented circumferential seal (SCS) cavity 149 disposed between the first and second SCSs 157, 159, as well as other cavities.

[034] The heat engine system 90 generally contains several pumps, such as the turbopump 260 and the start pump 280, disposed within the working fluid circuit 202 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202, as depicted in Figure 1A. The turbopump 260 and the start pump 280 may be operative to circulate the working fluid throughout the working fluid circuit 202. The start pump 280 has a pump portion 282 and a motor-drive portion 284. The start pump 280 is generally an electric motorized pump or a mechanical motorized pump, and may be a variable frequency motor- driven pump.

[035] The turbopump 260 has a pump portion 262 and a drive turbine 264. The pump portion 262 of the turbopump 260 may be disposed between the high pressure side and the low pressure side of the working fluid circuit 202. The pump inlet of the pump portion 262 is generally disposed in the low pressure side and the pump outlet on the pump portion 262 is generally disposed in the high pressure side. The drive turbine 264 of the turbopump 260 may be fluidly coupled to the working fluid circuit 202 at a point downstream of the heat exchanger 150, and the pump portion 262 of the turbopump 260 may be fluidly coupled to the working fluid circuit 202 upstream of the heat exchanger 120. In some embodiments, a secondary heat exchanger, such as heat exchanger 150, may be fluidly coupled to and in thermal communication with the heat source stream 1 10 and independently fluidly coupled to and in thermal communication with the working fluid in the working fluid circuit 202. The heated and pressurized working fluid may be utilized to move or otherwise power the drive turbine 264.

[036] Figure 2 depicts an exemplary heat engine system 200 that contains the process system 210 and the power generation system 220 fluidly coupled to and in thermal communication with the waste heat system 100 via the working fluid circuit 202, as described in one of more embodiments herein. The heat engine system 200 may be referred to as a thermal engine system, an electrical generation system, a waste heat or other heat recovery system, and/or a thermal to electrical energy system, as described in one or more embodiments herein. The heat engine system 200 is generally configured to encompass one or more elements of a Rankine cycle, a derivative of a Rankine cycle, or another thermodynamic cycle for generating electrical energy from a wide range of thermal sources.

[037] The heat engine system 200 depicted in Figure 2 and the heat engine system 90 depicted in Figures 1A-1 D share many common components. It should be noted that like numerals shown in the Figures and discussed herein represent like components throughout the multiple embodiments disclosed herein. For example, in one or more embodiments disclosed herein, the heat engine system 90 depicted in Figure 1A and the heat engine system 200 depicted in Figure 2 have a power turbine bypass line 208 and a power turbine bypass valve 219 fluidly coupled to the working fluid circuit 202 and disposed upstream of a turbine inlet of a power turbine 228 of a power generation system 220.

[038] In other embodiments, the working fluid circuit 202 contains the power turbine bypass line 208 extending between the inlet and the outlet of the power turbine 228. The power turbine bypass line 208 may be fluidly coupled to the working fluid circuit 202 at a point upstream of the inlet of the power turbine 228 and may also be fluidly coupled to the working fluid circuit 202 at a point downstream of the outlet of the power turbine 228. The power turbine bypass valve 219 may be fluidly coupled to the power turbine bypass line 208 and configured to be operative for controlling the flow of the working fluid therethrough. Also, the power turbine stop valve 217 may be fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the power turbine 228, and the power turbine discharge valve 221 may be fluidly coupled to the working fluid circuit 202 at a point downstream of an outlet of the power turbine 228. In some embodiments, a disclosed method includes closing the power turbine bypass valve 219 while stopping the flow of the working fluid from the heat exchanger 120 through the power turbine 228 during the shutdown procedure.

[039] In one or more embodiments described herein, the heat engine systems 90, 200 with a turbine cooling system are provided and include the working fluid circuit 202 containing a working fluid and at least one heat exchanger, such as the heat exchangers 120, 130, and/or 150. The working fluid circuit 202 generally has a high pressure side and a low pressure side and at least a portion of the working fluid may be in a supercritical state. The heat exchanger 120 may be fluidly coupled to and in thermal communication with the working fluid in the high pressure side of the working fluid circuit 202. The heat exchanger 120 may be configured to transfer thermal energy from the heat source stream 1 10 to the working fluid in the high pressure side.

[040] The heat engine systems 90, 200 further contain at least one expander, such as the power turbine 228 and/or the drive turbine 264 and the driveshaft 230. The power turbine 228 may be fluidly coupled to and disposed between the high pressure side and the low pressure side of the working fluid circuit 202 and configured to convert a pressure drop in the working fluid to mechanical energy. The driveshaft 230 may be coupled to the power turbine 228 and configured to drive a device with the mechanical energy. The driveshaft 230 is at least partially, if not substantially, contained within the housing 238. The heat engine systems 90, 200 further contain the seal gas conditioning system 174 fluidly coupled to and disposed between the housing 238 and the seal gas supply source 170. The seal gas conditioning system 174 may be configured to receive a seal gas from the seal gas supply source 170 and to dispense a seal gas into the housing 238.

[041] The heat engine systems 90, 200 further contain a series of cavities, such as the labyrinth seal cavity 143, the dry gas seal cavity 145, and several segmented circumferential seal cavities, such as the first segmented circumferential seal cavity 147 and the second segmented circumferential seal cavity 149. The labyrinth seal cavity 143 may be formed between the power turbine 228 and a labyrinth seal (LABY) 153 and between the driveshaft 230 and the housing 238. The dry gas seal cavity 145 may be formed between the labyrinth seal 153 and the dry gas seal 155 and between the driveshaft 230 and the housing 238. The dry gas seal cavity 145 may be configured to receive the seal gas from the seal gas conditioning system 174, such as through a conditioned gas line 176a fluidly coupled therebetween. The first segmented circumferential seal cavity 147 may be formed between the dry gas seal (DGS) 155 and the first segmented circumferential seal 157 and between the driveshaft 230 and the housing 238. The second segmented circumferential seal cavity 149 may be formed between the first segmented circumferential seal 157 and the second segmented circumferential seal 159 and between the driveshaft 230 and the housing 238. The second segmented circumferential seal cavity 149 may be configured to receive the seal gas from the seal gas conditioning system 174. The heat engine systems 90, 200 further contain the leak recapture storage vessel 184 fluidly coupled to the housing 238 and in fluid communication with the first segmented circumferential seal cavity 147, the power turbine discharge line 233 fluidly coupled to the power turbine 228 on the low pressure side of the working fluid circuit 202, and the first power turbine vent line 236 fluidly coupled to and between the power turbine discharge line 233 and the leak recapture storage vessel 184.

[042] The heat engine systems 90, 200 further contain the first power turbine vent valve 234 disposed on the first power turbine vent line 236 and configured to release a portion of the seal gas flowing from the power turbine 228 into the leak recapture storage vessel 184. The heat engine systems 90, 200 also contain the second power turbine vent line 166 fluidly coupled to the power turbine discharge line 233 and extending into the ambient atmosphere. The second power turbine vent valve 164 may be disposed on the second power turbine vent line 166 and configured to release a portion of the seal gas flowing from the power turbine 228 into the ambient atmosphere. Additionally, in some embodiments, the power turbine vent line 166 may be equipped with a valve, such as the power turbine vent valve 164, and/or a muffler, a resonator, or other sound suppressing device 167.

[043] The heat engine systems 90, 200 further contain at least one conditioned gas line, but in some examples, may contain two or more conditioned gas lines fluidly coupled to and disposed between the seal gas conditioning system 174 and the housing 238. In one aspect, a conditioned gas valve 178a may be fluidly coupled to the conditioned gas line 176a and configured to control the seal gas flowing from the seal gas conditioning system 174, through the conditioned gas line 176a, through the housing 238, and into the dry gas seal cavity 145. In another aspect, a conditioned gas valve 178b may be fluidly coupled to the conditioned gas line 176b and configured to control the seal gas, utilized as a buffer gas, flowing from the seal gas conditioning system 174, through the conditioned gas line 176b, through the housing 238, and into the second segmented circumferential seal cavity 149. In other examples, the heat engine systems 90, 200 also contain a buffer gas supply 179 fluidly coupled to the housing 238 and in fluid communication with the second segmented circumferential seal cavity 149. In some examples, the buffer gas supply 179 may include the conditioned gas line 176b and the conditioned gas valve 178b fluidly coupled to and disposed between the seal gas conditioning system 174 and the housing 238 and in fluid communication with the second segmented circumferential seal cavity 149.

[044] In some embodiments, the heat engine systems 90, 200 also contain the leak recapture line 182, the compressor 180, a cooler, such as the condenser 272, and/or combinations thereof. The leak recapture line 182 may be fluidly coupled to and disposed between the leak recapture storage vessel 184 and the housing 238. The leak capture compressor 180 and/or the condenser 272 may be fluidly coupled to the leak recapture line 182 and disposed between the leak recapture storage vessel 184 and the housing 238. In other embodiments, the heat engine systems 90, 200 further contain the power turbine stop valve 217 and the power turbine discharge valve 221 . The power turbine stop valve 217 may be fluidly coupled to the power turbine inlet line 205 upstream of an inlet of the power turbine 228. The power turbine discharge valve 221 may be fluidly coupled to the power turbine discharge line 233 downstream of an outlet of the power turbine 228. For example, the power turbine discharge valve 221 may be coupled to the power turbine discharge line 233 at a first location 300 shown in Figure 1 D downstream of the power turbine bypass line 208. However, in other embodiments, the power turbine discharge valve 221 may be located at a second position 302 between the power turbine bypass line 208 and the second power turbine vent line 166, at a third position 304 between the second power turbine vent line 166 and the first power turbine vent line 236, or at a fourth position 306 between the outlet of the power turbine 228 and the first power turbine vent line 236. The power turbine stop valve 217 and the power turbine discharge valve 221 may be configured to control the flow of the working fluid through the power turbine 228. The heat engine systems 90, 200 also contain the power turbine bypass valve 219 fluidly coupled to the power turbine bypass line 208. The power turbine bypass line 208 may be fluidly coupled to the power turbine inlet line 205 upstream of the power turbine stop valve 217 and fluidly coupled to the power turbine discharge line 233 upstream of the power turbine discharge valve 221 .

[045] In some embodiments, the heat engine systems 90, 200 further contain the labyrinth seal cavity 143 configured to have a reference pressure within a reference pressure range . The leak recapture storage vessel 184 may be configured to have a recapture storage vessel pressure within a recapture storage vessel pressure range and the recapture storage vessel pressure is less than the reference pressure. The dry gas seal cavity 145 may be configured to have the dry gas seal cavity pressure within the dry gas seal cavity pressure range , and the dry gas seal cavity pressure is greater than the reference pressure. The seal gas conditioning system 174 may be configured to have a conditioning system pressure within a conditioning system pressure range and the conditioning system pressure is greater than the dry gas seal cavity pressure.

[046] To prevent unfiltered/unconditioned gas from entering the dry gas seal cavity 145, the seal gas supply source 170 may be kept at a minimum pressure of 25 psid (about 172 kPa) greater than a reference pressure (RP). Therefore, the gas flow that has not been through the seal gas conditioning system 174 is kept from entering the dry gas seal cavity 145. The supplied gas flow also provides cooling for the driveshaft 230, the housing of the power turbine 228, and/or the housing 238 of the power generation system 220 during a shutdown procedure. During the shutdown procedure, when the working fluid is not flowing through the power turbine 228, the system may be configured to provide a pressure differential according to the method described herein. The shutdown procedure may include starting or experiencing a planned/anticipated shutdown, an unplanned/unanticipated shutdown, an emergency shutdown, a loss of power or surge, and/or other disruption. Generally, in some exemplary processes, the reference pressure (RP) may be maintained , adjusted, controlled, or otherwise provided within a range from about 100 pounds per square inch gauge (psig) (about 689 kPa) to about 1 ,500 psig (about 10.34 MPa) , more narrowly within a range from about 500 psig (about 3.45 MPa) to about 1 ,500 psig (about 10.34 MPa), more narrowly within a range from about 500 psig (about 3.45 MPa) to about 1 ,300 psig (about 8.96 MPa), and more narrowly within a range from about 700 psig (about 4.83 MPa) to about 1 ,200 psig (about 8.27 MPa), such as about 1 ,000 psig (about 6.89 MPa).

[047] Thereafter, in some examples, the seal gas may be flowed from the dry gas seal cavity 145, across the labyrinth seal 153, through the labyrinth seal cavity 143, through the power turbine 228, through the power turbine vent line 236 and the power turbine vent valve 234, and to a leak recapture storage vessel 184. In other examples, the seal gas may be flowed from the dry gas seal cavity 145, across the dry gas seal 155, into the first SCS cavity 147, through a leak recapture line 182 extending between from the dry gas seal cavity 145 and the leak recapture storage vessel 184. The leak recapture line 182 may be fluidly coupled to the housing 238 of the power generation system 220. A leak recapture compressor 180 and a condenser 272 may be fluidly coupled along the leak recapture line 182. The condenser 272 may be utilized to condense and the leak recapture compressor 180 may be utilized to compress the recaptured gas before flowing into the leak recapture storage vessel 184.

[048] The recapture storage vessel pressure of the leak recapture storage vessel 184 may have a pressure differential within a range from about 50 pounds per square inch differential (psid) (about 345 kPa) to about 1 ,250 psid (about 8,62 MPa) less than the reference pressure, more narrowly within a range from about 200 psid (about 1 ,38 MPa) to about 1 ,100 psid (about 7.58 kPa) less than the reference pressure, more narrowly within a range from about 500 psid (about 3.45 MPa) to about 1 ,000 psid (about 6.89 MPa) less than the reference pressure, and more narrowly within a range from about 600 psid (about 4.14 MPa) to about 900 psid (about 6.21 MPa), such as about 750 psid (about 5.17 MPa) less than the reference pressure. The recapture storage vessel pressure of the leak recapture storage vessel 184 may be within a range from about 50 psig (about 345 kPa) to about 400 psig (about 2.76 MPa), more narrowly within a range from about 100 psig (about 689 kPa) to about 325 psig (about 2.24 MPa), and more narrowly within a range from about 200 psig (about 1.38 MPa) to about 300 psig (about 2.07 MPa), such as about 250 psig (about 1 .72 MPa).

[049] The conditioning system pressure of the seal gas conditioning system 174 may have a pressure differential within a range from about 25 psid (about 172 kPa) to about 200 psid (about 1 .38 MPa) greater than the reference pressure, more narrowly within a range from about 40 psid (about 276 kPa) to about 150 psid (about 1.03 MPa) greater than the reference pressure, and more narrowly within a range from about 50 psid (about 345 k Pa) to about 100 psid (about 689 kPa) greater than the reference pressure. The conditioning system pressure may be within a range from about 100 psig (about 689 kPa) to about 1 ,800 psig (about 12.41 MPa), more na rowly within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1.03 MPa), and more narrowly within a range from about 750 psig (about 5.17 MPa) to about 1 ,300 psig (about 8.96 MPa), such as about 1 ,050 psig (about 7.24 MPa).

[050] The dry gas seal cavity pressure of the dry gas seal cavity 145 may have a pressure differential within a range from about 25 psid (about 172 kPa) to about 200 psid (about 1.38 MPa) greater than the reference pressure, more narrowly within a range from about 40 psid (about 276 kPa) to about 150 psid (about 1.03 MPa) greater than the reference pressure, and more narrowly within a range from about 50 psid (about 345 kPa) to about 100 psid (about 689 kPa) greater than the reference pressure. The dry gas seal cavity pressure of the dry gas seal cavity 145 may be within a range from about 100 psig (about 689 kPa) to about 1 ,800 psig (about 12.41 MPa), more narrowly within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1 .03 MPa), and more narrowly within a range from about 750 psig (about 5.17 MPa) to about 1 ,300 psig (about 8.96 MPa), such as about 1 ,050 psig (about 7.24 MPa).

[051] In other embodiments, the heat engine systems 90, 200 generally contain the seal gas supply source 170 fluidly coupled to the seal gas conditioning system 174 and configured to supply the seal gas to the seal gas conditioning system 174. The seal gas conditioning system 174 may further be configured to form a conditioned or dried seal gas from an unconditioned seal gas received from the seal gas supply source 170. The seal gas supply source 170 may have a seal gas source pressure within a seal gas source pressure range and the seal gas source pressure is greater than the reference pressure. In some examples, the seal gas source pressure may also be greater than the conditioning system pressure. The seal gas source pressure of the seal gas supply source 170 may have a pressure differential within a range from about 25 psid (about 172 kPa) to about 300 psid (about 2.07 MPa) greater than the reference pressure, more narrowly within a range from about 40 psid (about 276 kPa) to about 250 psid (about 1 .72 MPa) greater than the reference pressure, and more narrowly within a range from about 50 psid (about 345 kPa) to about 200 psid (about 1 .38 MPa) greater than the reference pressure. In many examples, the seal gas source pressure of the seal gas supply source 170 may be within a range from about 350 psig (about 2.41 MPa) to about 2,000 psig (about 13.79 MPa), more narrowly within a range from about 550 psig (about 3.79 MPa) to about 1 ,600 psig (about 1 1 .03 MPa), and more narrowly within a range from about 750 psig (about 5.17 MPa) to about 1 ,500 psig (about 10.34 MPa), such as about 1 ,200 psig (about 8.27 MPa).

[052] In one or more other embodiments described herein, a method 20 illustrated in Figure 3 is provided for cooling a turbine in a heat engine during a shutdown. The method 20 includes circulating a working fluid within the working fluid circuit 202 (block 22) and transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 120 (block 24). The working fluid circuit 202 has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state. The heat exchanger 120 is fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202. The method 20 further includes flowing the working fluid into the power turbine 228 and converting the thermal energy of the working fluid to mechanical energy of the driveshaft 230 coupled to the power turbine 228 (block 26). The method 20 further includes activating a shutdown procedure by closing the power turbine stop valve 217 and the power turbine discharge valve 221 to stop the flow of the working fluid through the power turbine 228, such as from the heat exchanger 120 (block 28).

[053] In some embodiments, the method 20 also includes flowing a seal gas from the seal gas conditioning system 174 to the leak recapture storage vessel 184 via one or more pathways (block 30). For example, the method 20 may include flowing a seal gas from the seal gas conditioning system 174, through the dry gas seal cavity 145, across the labyrinth seal 153, through the labyrinth seal cavity 143, through the power turbine 228, through the first power turbine vent line 236 and the first power turbine vent valve 234 disposed thereon, and to the leak recapture storage vessel 184. The labyrinth seal cavity 143 and the dry gas seal cavity 145 are generally separated by the labyrinth seal 153 and adjacent to and formed between the driveshaft 230 within the housing 238. The method 20 may also include flowing the seal gas from the seal gas conditioning system 174, through the dry gas seal cavity 145, across the dry gas seal 155, through the first segmented circumferential seal cavity 147, through the leak recapture line 182, and to the leak recapture storage vessel 184. The first segmented circumferential seal cavity 147 and the dry gas seal cavity 145 are generally separated by the dry gas seal 155 and adjacent to and formed between the driveshaft 230 within the housing 238. Generally, the labyrinth seal cavity 143 may have a reference pressure (Rp) - designated as "RP" in Figures 1 C-1 D - within a reference pressure range. The dry gas seal cavity 145 may have the dry gas seal cavity pressure within the dry gas seal cavity pressure range and the dry gas seal cavity pressure is greater than the reference pressure, and the leak recapture storage vessel 184 may have a recapture storage vessel pressure within a recapture storage vessel pressure range and the recapture storage vessel pressure is less than the reference pressure.

[054] The method further includes opening the second power turbine vent valve 164 to release a portion of the seal gas flowing from the power turbine 228 into the ambient atmosphere. The second power turbine vent valve 164 may be fluidly coupled to the second power turbine vent line 166 fluidly coupled to the power turbine 228 and extending into the ambient atmosphere. The seal gas supply source 170 may have a seal gas source pressure within a seal gas source pressure range, and the seal gas source pressure is greater than the reference pressure. The seal gas conditioning system 174 may have a conditioning system pressure within a conditioning system pressure range, and the conditioning system pressure is greater than the reference pressure. The method may further include flowing the seal gas from the seal gas conditioning system 174, through at least one conditioned gas line 176a, 176b and conditioned gas valve 178a, 178b, and into the dry gas seal cavity 145. The conditioned gas lines 176a, 176b may be fluidly coupled to and disposed between the seal gas conditioning system 174 and the housing 238. In one example, the conditioned gas valve 178a may be fluidly coupled to the conditioned gas line 176a and may be configured to control the flow of the conditioned seal gas passing through the conditioned gas line 176a and into the dry gas seal cavity 145.

[055] In another embodiment, the method may further include flowing the seal gas from the seal gas conditioning system 174, through the second segmented circumferential seal cavity 149, across a segmented circumferential seal, through the first segmented circumferential seal cavity 147, through the leak recapture line 182, and to the leak recapture storage vessel 184. The second segmented circumferential seal cavity 149 and the first segmented circumferential seal cavity 147 are separated by the first segmented circumferential seal 157 and are adjacent the driveshaft 230 within the housing 238. The method may further include flowing the seal gas from the seal gas conditioning system 174, through the second conditioned gas line 176b and the second conditioned gas valve 178b, and into the second segmented circumferential seal cavity 149. The second conditioned gas line 176b may be fluidly coupled to and disposed between the seal gas conditioning system 174 and the housing 238. In some embodiments, the buffer gas supply 179 may include the conditioned gas line 176b and the conditioned gas valve 178b. The conditioned gas valve 178b may be fluidly coupled to the conditioned gas line 176b and may be configured to control the flow of the conditioned seal gas passing through the conditioned gas line 176b and into the second segmented circumferential seal cavity 149.

[056] In other embodiments, the method may further include closing the power turbine bypass valve 219 while stopping the flow of the working fluid from the primary heat exchanger through the power turbine 228 during the shutdown procedure. The power turbine stop valve 217 may be fluidly coupled to the working fluid circuit 202 upstream of an inlet of the power turbine 228 and the power turbine discharge valve 221 may be fluidly coupled to the working fluid circuit 202 downstream of an outlet of the power turbine 228. The power turbine bypass valve 219 may be fluidly coupled to the working fluid circuit 202 by the power turbine bypass line 208 extending between the inlet and the outlet of the power turbine 228. The shutdown procedure may be a planned shutdown, an emergency shutdown, a loss of power, a process upset, or a process trip of the power turbine 228.

[057] In some embodiments, the heat engine systems 90, 200 further contain the power generator 240 and at least one pump, such as the turbopump 260 and/or the start pump 280. The power generator 240 may be coupled to the power turbine 228 by the driveshaft 230, such that the mechanical energy may be converted into electrical energy. The pump may be fluidly coupled to the working fluid circuit 202 between the low pressure side and the high pressure side of the working fluid circuit 202 and configured to circulate the working fluid through the working fluid circuit 202. The heat engine systems 90, 200 further contain at least one recuperator, such as the recuperators 216, 218, and/or a cooler, such as the condenser 274. The recuperators 216, 218 may be fluidly coupled and in thermal communication with the working fluid circuit 202. The recuperators 216, 218 are generally operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. The cooler or the condenser 274 may be in thermal communication with the working fluid in the low pressure side of the working fluid circuit 202 and configured to remove thermal energy from the working fluid in the low pressure side of the working fluid circuit 202. The heat engine systems 90, 200 further contain the mass management system 270 fluidly coupled to the working fluid circuit 202 and configured to increase or decrease the amount of the working fluid within the working fluid circuit 202. A working fluid storage vessel 292 may be fluidly coupled to the mass management system 270 by a working fluid supply/return line 289. The working fluid storage vessel 292 may be configured to receive the working fluid, store a supply of the working fluid, and distribute the working fluid into the working fluid circuit 202 via the mass management system 270.

[058] In another embodiment, the method for cooling the power turbine 228 in the heat engine systems 90, 200 includes maintaining the dry gas seals (e.g. , the labyrinth seal (LABY) 153 and the dry gas seal (DGS) 1 55) free or substantially free of contamination during the shutdown procedure, such as a planned or unplanned shutdown , an emergency shutdown, a power loss or trip, and/or other issues or procedures. The method further includes circulating a working fluid within a working fluid circuit 202, such that the working fluid circuit 202 has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state. The method also includes transferring thermal energy from the heat source stream 1 10 to the working fluid by at least a primary heat exchanger, such as the heat exchanger 120, fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202. In addition, the method includes feeding or otherwise flowing the working fluid into a power turbine 228 and converting the thermal energy from the working fluid to mechanical energy of the power turbine 228. A driveshaft 230 is generally coupled to the power turbine and the mechanical energy of the power turbine 228 is transferred to mechanical energy, such as rotational energy, of the driveshaft 230. The method further includes converting the mechanical energy into electrical energy by a power generator 240 coupled to the power turbine 228 by the driveshaft 230.

[059] The method further includes activating a shutdown procedure that includes closing a power turbine stop valve 217, a power turbine discharge valve 221 , and optionally a power turbine bypass valve 219 to stop or prohibit the flow of the working fluid from the heat exchanger 120 through the power turbine 228 or otherwise to a power turbine discharge line 233, as depicted in Figure 1 D. The shutdown procedure may be a planned/routine shutdown, an unplanned shutdown, an emergency shutdown, a loss of power, a process upset, a process trip of the power turbine 228, or derivatives thereof.

[060] In one embodiment, the method also includes - generally - opening a power turbine vent valve 234 and flowing the seal gas from a seal gas supply source 170, through the power turbine 228, and to a leak recapture storage vessel 184 and/or a power turbine vent line 166. For example, the seal gas may flow from the seal gas supply source 170, through a seal gas line 172 and a seal gas valve 168, into and through a dry gas seal (DGS) or seal gas conditioning system 174, through one or more sets of conditioned gas lines and valves, such as the conditioned gas lines 176a and 176b and the conditioned gas valves 178a and 178b, and into and through the housing 238 of the power generation system 220.

[061] In one aspect, the seal gas may flow from the conditioned gas line 176a, into and through the dry gas seal cavity 145, across the labyrinth seal 153, into and through the labyrinth seal cavity 143, into and through the power turbine 228, and into the power turbine discharge line 233. In another aspect, the seal gas may flow from the conditioned gas line 176a, into and through the dry gas seal cavity 145, across the dry gas seal 155, into and through the first SCS cavity 147, into and through the leak recapture line 182, and into the leak recapture storage vessel 184. In another aspect, the seal gas - being utilized as a buffer gas - may flow from the conditioned gas line 176b, into and through the second SCS cavity 149, across the first SCS 157, into and through the first SCS cavity 147, into and through the leak recapture line 182, and into the leak recapture storage vessel 184. [062] The power turbine discharge line 233 may be fluidly coupled to and disposed between the outlet of the power turbine 228 and a power turbine vent line 236, which further extends to the leak recapture storage vessel 184 via the leak recapture line 182. Also, a power turbine vent line 166 may extend from the power turbine discharge line 233 to vent into the ambient atmosphere. Therefore, the method may further include flowing the seal gas through the power turbine discharge line 233, through the power turbine vent line 236 and the power turbine vent valve 234, through the leak recapture line 182, and into the leak recapture storage vessel 184.

[063] In another embodiment, the method further includes opening a power turbine vent valve 164 to release a portion of the seal gas flowing from the power turbine 228 into the ambient atmosphere outside of the heat engine system 200. The power turbine vent valve 164 may be disposed on a power turbine vent line 166, extending between and in fluid communication with the power turbine 228 and the atmosphere, as depicted in Figure 1 D. The method may further include flowing the seal gas through the power turbine discharge line 233, through the power turbine vent line 166 and the power turbine vent valve 164, and into the ambient atmosphere.

[064] In one example, the power turbine vent line 236 and the power turbine vent valve 234 may be utilized together along with the power turbine vent line 166 and the power turbine vent valve 164 to vent the seal gas from the power turbine 228. The seal gas may be flowed from the power turbine 228, through the power turbine discharge line 233, and subsequently a portion of the seal gas may be delivered to the leak recapture storage vessel 184 via the power turbine vent line 236, and another portion of the seal gas may be delivered to the atmosphere via the power turbine vent line 166. In another example, the power turbine vent line 236 along with the power turbine vent valve 234 may be solely used to vent the seal gas from the power turbine 228. The seal gas may be flowed from the power turbine 228, through the power turbine discharge line 233, through the power turbine vent line 236, and into the leak recapture storage vessel 184. In another example, the power turbine vent line 166 along with the power turbine vent valve 164 may be solely used to vent the seal gas from the power turbine 228. The seal gas may be flowed from the power turbine 228, through the power turbine discharge line 233, through the power turbine vent line 166, and into the ambient atmosphere.

[065] The power turbine vent line 236 may be fluidly coupled to and between the power turbine discharge line 233 and the leak recapture line 182, while power turbine vent valve 234 may be fluidly coupled to the power turbine vent line 236 and operable to control the flow of the gaseous fluid passing through the power turbine vent line 236. The power turbine vent line 236 may be fluidly coupled to the power turbine discharge line 233 at a point along the power turbine discharge line 233 disposed between the power turbine 228 and the power turbine discharge valve 221 . Also, the power turbine vent line 236 may be fluidly coupled to the leak recapture line 182 at a point along the leak recapture line 182 disposed between the leak recapture storage vessel 184 and the leak recapture compressor 1 80.

[066] Contamination of dry gas seals, such as the labyrinth seal 153 and the dry gas seal 155, may be avoided by minimizing or prohibiting unfiltered, unconditioned gas contained within the labyrinth seal (LABY) cavity 143 from coming into contact with the dry gas seals, such as passing over the labyrinth seal 153 into the dry gas seal cavity 145. Therefore, disclosed methods described herein may be utilized to keep unfiltered, unconditioned gas (e.g. , contaminated gas) from entering the dry gas seal cavity 145, even during a shutdown procedure of the heat engine systems 90, 200, without the need to vent the system or without the use of a pressure boosting device.

[067] In one embodiment described herein, a method for cooling a power turbine 228 during a shutdown procedure of the heat engine systems 90, 200, as well as minimizing or prohibiting unfiltered, unconditioned gas contained within the labyrinth seal (LABY) cavity 143 from entering into the dry gas seal cavity 145 during the shutdown procedure. The method further includes maintaining, adjusting, controlling, or otherwise providing a recapture storage vessel pressure of the leak recapture storage vessel 184 within a recapture storage vessel pressure range less than the reference pressure. In addition, the method includes maintaining, adjusting, controlling, or otherwise providing the dry gas seal cavity pressure of the dry gas seal cavity 1 5 within the dry gas seal cavity pressure range greater than the reference pressure. Also, the method includes maintaining , adjusting, controlling, or otherwise providing a conditioning system pressure of the seal gas conditioning system 174 within a conditioning system pressure range greater than the reference pressure. The reference pressure, the recapture storage vessel pressure, the dry gas seal cavity pressure, and the conditioning system pressure may be independently maintained, adjusted, or otherwise controlled by a shutdown procedure.

[068] In some embodiments, during the shutdown, the method includes closing the power turbine stop valve 217, the power turbine discharge valve 221 , and optionally the power turbine bypass valve 219 to stop the flow of the working fluid from the heat exchanger 120 through the power turbine 228. The method also includes opening the power turbine vent valve 234 and/or the power turbine vent valve 164 to flow the seal gas away from the dry gas seal cavity 145. The method further includes flowing the seal gas (e.g., dried and/or conditioned) from the seal gas conditioning system 174, through the dry gas seal cavity 1 45, over the labyrinth seal 153, through the labyrinth seal cavity 143, through the power turbine 228, and through the power turbine discharge line 233. From the power turbine discharge line 233, the seal gas may flow through the power turbine vent valve 234 and the power turbine vent line 236 to the leak recapture storage vessel 184 and/or flow through the power turbine vent valve 164 and the power turbine vent line 166 to the ambient atmosphere.

[069] In one or more embodiments described herein, Figure 2 depicts the working fluid circuit 202 containing the working fluid and having a high pressure side and a low pressure side, wherein at least a portion of the working fluid contains carbon dioxide in a supercritical state. In many examples, the working fluid contains carbon dioxide, and at least a portion of the carbon dioxide is in a supercritical state. The heat engine system 200 also has the heat exchanger 120 fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202, configured to be fluidly coupled to and in thermal communication with the heat source stream 1 10, and configured to transfer thermal energy from the heat source stream 1 10 to the working fluid within the working fluid circuit 202. The heat exchanger 120 may be fluidly coupled to the working fluid circuit 202 at a point upstream of the power turbine 228 and at another point downstream of the recuperator 216.

[070] The heat engine system 200 further contains the power turbine 228 disposed between the high pressure side and the low pressure side of the working fluid circuit 202, fluidly coupled to and in thermal communication with the working fluid, and configured to convert thermal energy to mechanical energy by a pressure drop in the working fluid flowing between the high and the low pressure sides of the working fluid circuit 202. The heat engine system 200 also contains a power generator 240 coupled to the power turbine 228 and configured to convert the mechanical energy into electrical energy. As depicted in Figure 2, a power outlet 242 may be electrically coupled to the power generator 240 and configured to transfer the electrical energy from the power generator 240 to the electrical grid 244.

[071] The heat engine system 200 further contains a turbopump 260, which has a drive turbine 264 and a pump portion 262. The pump portion 262 of the turbopump 260 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the low pressure side of the working fluid circuit 202, fluidly coupled to the high pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the high pressure side of the working fluid circuit 202, and configured to circulate the working fluid within the working fluid circuit 202. The drive turbine 264 of the turbopump 260 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the high pressure side of the working fluid circuit 202, fluidly coupled to the low pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the low pressure side of the working fluid circuit 202, and configured to rotate the pump portion 262 of the turbopump 260.

[072] In some embodiments, the heat engine system 200 further contains the heat exchanger 150, which is generally fluidly coupled to and in thermal communication with the heat source stream 1 10 and independently fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202, such that thermal energy may be transferred from the heat source stream 1 10 to the working fluid. The heat exchanger 150 may be fluidly coupled to the working fluid circuit 202 downstream of the outlet of the pump portion 262 of the turbopump 260 and upstream of the inlet of the drive turbine 264 of the turbopump 260. The drive turbine throttle valve 263 may be fluidly coupled to the working fluid circuit 202 at a point downstream of the heat exchanger 150 and upstream of the inlet of the drive turbine 264 of the turbopump 260. The working fluid containing the absorbed thermal energy flows from the heat exchanger 150 to the drive turbine 264 of the turbopump 260 via the drive turbine throttle valve 263. Therefore, in some embodiments, the drive turbine throttle valve 263 may be utilized to control the flowrate of the heated working fluid flowing from the heat exchanger 150 to the drive turbine 264 of the turbopump 260.

[073] In some embodiments, the recuperator 216 may be fluidly coupled to the working fluid circuit 202 and configured to transfer thermal energy from the working fluid within the low pressure side to the working fluid within the high pressure side of the working fluid circuit 202. In other embodiments, a recuperator 218 may be fluidly coupled to the working fluid circuit 202 at a point downstream of the outlet of the pump portion 262 of the turbopump 260 and upstream of the heat exchanger 150 and configured to transfer thermal energy from the working fluid within the low pressure side to the working fluid within the high pressure side of the working fluid circuit 202.

[074] Figure 2 further depicts the waste heat system 100 of the heat engine system 200 containing three heat exchangers (e.g., the heat exchangers 120, 130, and 150) fluidly coupled to the high pressure side of the working fluid circuit 202 and in thermal communication with the heat source stream 1 10. Such thermal communication provides the transfer of thermal energy from the heat source stream 1 10 to the working fluid flowing throughout the working fluid circuit 202. In one or more embodiments disclosed herein, two, three, or more heat exchangers may be fluidly coupled to and in thermal communication with the working fluid circuit 202, such as a primary heat exchanger, a secondary heat exchanger, a tertiary heat exchanger, respectively the heat exchangers 120, 150, and 130, and/or an optional quaternary heat exchanger (not shown). For example, the heat exchanger 120 may be the primary heat exchanger fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the power turbine 228, the heat exchanger 150 may be the secondary heat exchanger fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the drive turbine 264 of the turbine pump 260, and the heat exchanger 130 may be the tertiary heat exchanger fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the heat exchanger 120.

[075] The waste heat system 100 also contains an inlet 104 for receiving the heat source stream 1 10 and an outlet 106 for passing the heat source stream 1 10 out of the waste heat system 100. The heat source stream 1 10 flows through and from the inlet 104, through the heat exchanger 120, through one or more additional heat exchangers, if fluidly coupled to the heat source stream 1 10, and to and through the outlet 106. In some examples, the heat source stream 1 10 flows through and from the inlet 104, through the heat exchangers 120, 150, and 130, respectively, and to and through the outlet 106. The heat source stream 1 10 may be routed to flow through the heat exchangers 120, 130, 150, and/or additional heat exchangers in other desired orders.

[076] The heat source stream 1 10 may be a waste heat stream such as, but not limited to, gas turbine exhaust stream, industrial process exhaust stream, or other combustion product exhaust streams, such as furnace or boiler exhaust streams. The heat source stream 1 10 may be at a temperature within a range from about 100°C to about 1 ,000°C, or greater than 1 ,000°C, and in some examples, within a range from about 200°C to about 800°C, more narrowly within a range from about 300°C to about 600°C. The heat source stream 1 10 may contain air, carbon dioxide, carbon monoxide, water or steam, nitrogen, oxygen, argon, derivatives thereof, or mixtures thereof. In some embodiments, the heat source stream 1 10 may derive thermal energy from renewable sources of thermal energy, such as solar or geothermal sources.

[077] In some embodiments, the types of working fluid that may be circulated, flowed, or otherwise utilized in the working fluid circuit 202 of the heat engine system 200 include carbon oxides, hydrocarbons, alcohols, ketones, halogenated hydrocarbons, ammonia, amines, aqueous, or combinations thereof. Exemplary working fluids that may be utilized in the heat engine system 200 include carbon dioxide, ammonia, methane, ethane, propane, butane, ethylene, propylene, butylene, acetylene, methanol, ethanol, acetone, methyl ethyl ketone, water, derivatives thereof, or mixtures thereof. Halogenated hydrocarbons may include hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (H FCs) (e.g. , 1 ,1 , 1 ,3,3- pentafluoropropane (R245fa)) , fluorocarbons, derivatives thereof, or mixtures thereof.

[078] In many embodiments described herein , the working fluid circulated, flowed, or otherwise utilized in the working fluid circuit 202 of the heat engine system 200, and the other exemplary circuits disclosed herein, may be or may contain carbon dioxide (CO2) and mixtures containing carbon dioxide. Generally, at least a portion of the working fluid circuit 202 contains the working fluid in a supercritical state (e.g. , sc-C0₂). Carbon dioxide utilized as the working fluid or contained in the working fluid for power generation cycles has many advantages over other compounds typically used as working fluids, since carbon dioxide has the properties of being non-toxic and non-flammable and is also easily available and relatively inexpensive. Due in part to a relatively high working pressure of carbon dioxide, a carbon dioxide system may be much more compact than systems using other working fluids. The high density and volumetric heat capacity of carbon dioxide with respect to other working fluids makes carbon dioxide more "energy dense" meaning that the size of all system components can be considerably reduced without losing performance. It should be noted that use of the terms carbon dioxide (C0₂) , supercritical carbon dioxide (SC-CO2), or subcritical carbon dioxide (sub-CC>2) is not intended to be limited to carbon dioxide of any particular type, source, purity, or grade. For example, industrial grade carbon dioxide may be contained in and/or used as the working fluid without departing from the scope of the disclosure.

[079] In other exemplary embodiments, the working fluid in the working fluid circuit 202 may be a binary, ternary, or other working fluid blend. The working fluid blend or combination can be selected for the unique attributes possessed by the fluid combination within a heat recovery system, as described herein. For example, one such fluid combination includes a liquid absorbent and carbon dioxide mixture enabling the combined fluid to be pumped in a liquid state to high pressure with less energy input than required to compress carbon dioxide. In another exemplary embodiment, the working fluid may be a combination of carbon dioxide (e.g., sub- CO2 or SC-CO2) and one or more other miscible fluids or chemical compounds. In yet other exemplary embodiments, the working fluid may be a combination of carbon dioxide and propane, or carbon dioxide and ammonia, without departing from the scope of the disclosure .

[080] The working fluid circuit 202 generally has a high pressure side and a low pressure side and contains a working fluid circulated within the working fluid circuit 202. The use of the term "working fluid" is not intended to limit the state or phase of matter of the working fluid. For instance, the working fluid or portions of the working fluid may be in a liquid phase, a gas phase, a fluid phase, a subcritical state, a supercritical state, or any other phase or state at any one or more points within the working fluid circuit 202, the heat engine system 200, or thermodynamic cycle. In one or more embodiments, the working fluid is in a supercritical state over certain portions of the working fluid circuit 202 of the heat engine system 200 (e.g. , a high pressure side) and in a subcritical state over other portions of the working fluid circuit 202 of the heat engine system 200 (e.g. , a low pressure side) . Figure 2 depicts the high and low pressure sides of the working fluid circuit 202 of the heat engine system 200 by representing the high pressure side with " " and the low pressure side with " " - as described in one or more embodiments. In other embodiments, the entire thermodynamic cycle may be operated such that the working fluid is maintained in either a supercritical or subcritical state throughout the entire working fluid circuit 202 of the heat engine system 200.

[081] Generally, the high pressure side of the working fluid circuit 202 contains the working fluid (e.g. , sc-C0₂) at a pressure of about 15 MPa or greater, such as about 17 MPa or greater or about 20 MPa or greater. In some examples, the high pressure side of the working fluid circuit 202 may have a pressure within a range from about 15 MPa to about 30 MPa, more narrowly within a range from about 16 MPa to about 26 MPa, more narrowly within a range from about 17 MPa to about 25 MPa, and more narrowly within a range from about 17 MPa to about 24 MPa, such as about 23.3 MPa. In other examples, the high pressure side of the working fluid circuit 202 may have a pressure within a range from about 20 MPa to about 30 MPa, more narrowly within a range from about 21 MPa to about 25 M Pa, and more narrowly within a range from about 22 MPa to about 24 MPa, such as about 23 MPa.

[082] The low pressure side of the working fluid circuit 202 contains the working fluid (e.g. , C0₂ or sub-C0₂) at a pressure of less than 15 MPa, such as about 12 MPa or less or about 10 MPa or less. In some examples, the low pressure side of the working fluid circuit 202 may have a pressure within a range from about 4 MPa to about 14 MPa, more narrowly within a range from about 6 MPa to about 13 MPa, more narrowly within a range from about 8 MPa to about 12 MPa, and more narrowly within a range from about 10 MPa to about 1 1 MPa, such as about 10.3 MPa. In other examples, the low pressure side of the working fluid circuit 202 may have a pressure within a range from about 2 MPa to about 10 MPa, more narrowly within a range from about 4 MPa to about 8 MPa, and more narrowly within a range from about 5 MPa to about 7 MPa, such as about 6 M Pa.

[083] In some examples, the high pressure side of the working fluid circuit 202 may have a pressure within a range from about 17 MPa to about 23.5 MPa, and more narrowly within a range from about 23 MPa to about 23.3 MPa while the low pressure side of the working fluid circuit 202 may have a pressure within a range from about 8 MPa to about 1 1 MPa, and more narrowly within a range from about 1 0.3 MPa to about 1 1 MPa .

[084] The heat engine system 200 further contains the power turbine 228 disposed between the high pressure side and the low pressure side of the working fluid circuit 202, disposed downstream of the heat exchanger 120, and fluidly coupled to and in thermal communication with the working fluid . The power turbine 228 may be configured to convert a pressure drop in the working fluid to mechanical energy whereby the absorbed thermal energy of the working fluid is transformed to mechanical energy of the driveshaft 230 coupled to the power turbine 228. Therefore, the power turbine 228 is an expansion device capable of transforming a pressurized fluid into mechanical energy, generally, transforming high temperature and pressure fluid into mechanical energy, such as rotating a shaft (e.g. , the driveshaft 230).

[085] The power turbine 228 may contain or be a turbine, a turbo, an expander, or another device for receiving and expanding the working fluid discharged from the heat exchanger 120. The power turbine 228 may have an axial construction or radial construction and may be a single-staged device or a multi-staged device. Exemplary turbine devices that may be utilized in the power turbine 228 include an expansion device, a geroler, a gerotor, a valve, other types of positive displacement devices such as a pressure swing , a turbine, a turbo, or any other device capable of transforming a pressure or pressure/enthalpy drop in a working fluid into mechanical energy. A variety of expanding devices are capable of working within the inventive system and achieving different performance properties that may be utilized as the power turbine 228.

[086] The power turbine 228 is generally coupled to the power generator 240 by the driveshaft 230. A gearbox 232 is generally disposed between the power turbine 228 and the power generator 240 and adjacent or encompassing the driveshaft 230. The driveshaft 230 may be a single piece or may contain two or more pieces coupled together. In one example, a first segment of the driveshaft 230 extends from the power turbine 228 to the gearbox 232, a second segment of the driveshaft 230 extends from the gearbox 232 to the power generator 240, and multiple gears are disposed between and couple the two segments of the driveshaft 230 within the gearbox 232.

[087] The power generator 240 may be a generator, an alternator (e.g., permanent magnet alternator), or other device for generating electrical energy, such as transforming mechanical energy from the driveshaft 230 and the power turbine 228 to electrical energy. A power outlet 242 may be electrically coupled to the power generator 240 and configured to transfer the generated electrical energy from the power generator 240 to an electrical grid 244. The electrical grid 244 may be or include an electrical grid, an electrical bus (e.g. , plant bus) , power electronics, other electric circuits, or combinations thereof. The electrical grid 244 generally contains at least one alternating current bus, alternating current grid, alternating current circuit, or combinations thereof. In one example, the power generator 240 is a generator and is electrically and operably connected to the electrical grid 244 via the power outlet 242. In another example, the power generator 240 is an alternator and is electrically and operably connected to power electronics (not shown) via the power outlet 242. In another example, the power generator 240 is electrically connected to power electronics, which are electrically connected to the power outlet 242.

[088] The power electronics may be configured to convert the electrical power into desirable forms of electricity by modifying electrical properties, such as voltage, current, or frequency. The power electronics may include converters or rectifiers, inverters, transformers, regulators, controllers, switches, resistors, storage devices, and other power electronic components and devices. In other embodiments, the power generator 240 may contain, be coupled with, or be other types of load receiving equipment, such as other types of electrical generation equipment, rotating equipment, a gearbox (e.g., gearbox 232) , or other device configured to modify or convert the shaft work created by the power turbine 228. In one embodiment, the power generator 240 is in fluid communication with a cooling loop having a radiator and a pump for circulating a cooling fluid, such as water, thermal oils, and/or other suitable refrigerants. The cooling loop may be configured to regulate the temperature of the power generator 240 and power electronics by circulating the cooling fluid to draw away generated heat.

[089] The heat engine system 200 also provides for the delivery of a portion of the working fluid into a chamber or housing of the power turbine 228 for purposes of cooling one or more parts of the power turbine 228. In one embodiment, due to the potential need for dynamic pressure balancing within the power generator 240, the selection of the site within the heat engine system 200 from which to obtain a portion of the working fluid is critical because introduction of this portion of the working fluid into the power generator 240 should respect or not disturb the pressure balance and stability of the power generator 240 during operation. Therefore, the pressure of the working fluid delivered into the power generator 240 for purposes of cooling is the same or substantially the same as the pressure of the working fluid at an inlet of the power turbine 228. The working fluid may be conditioned to be at a desired temperature and pressure prior to being introduced into the power turbine 228. A portion of the working fluid , such as the spent working fluid, exits the power turbine 228 at an outlet of the power turbine 228 and may be directed to one or more heat exchangers or recuperators, such as recuperators 216 and 218. The recuperators 216 and 218 may be fluidly coupled to the working fluid circuit 202 in series with each other. The recuperators 216 and 218 may be operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202.

[090] In one embodiment, the recuperator 216 may be fluidly coupled to the low pressure side of the working fluid circuit 202, disposed downstream of a working fluid outlet on the power turbine 228, and disposed upstream of the recuperator 218 and/or the condenser 274. The recuperator 216 may be configured to remove at least a portion of thermal energy from the working fluid discharged from the power turbine 228. In addition, the recuperator 216 may also be fluidly coupled to the high pressure side of the working fluid circuit 202, disposed upstream of the heat exchanger 120 and/or a working fluid inlet of the power turbine 228, and disposed downstream of the heat exchanger 130. The recuperator 216 may be configured to increase the amount of thermal energy in the working fluid prior to flowing into the heat exchanger 120 and/or the power turbine 228. Therefore, the recuperator 216 may be operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. In some examples, the recuperator 216 may be a heat exchanger configured to cool the low pressurized working fluid discharged or downstream of the power turbine 228 while heating the high pressurized working fluid entering into or upstream of the heat exchanger 120 and/or the power turbine 228.

[091] Similarly, in another embodiment, the recuperator 218 may be fluidly coupled to the low pressure side of the working fluid circuit 202, disposed downstream of a working fluid outlet on the power turbine 228 and/or the recuperator 216, and disposed upstream of the condenser 274. The recuperator 218 may be configured to remove at least a portion of thermal energy from the working fluid discharged from the power turbine 228 and/or the recuperator 216. In addition, the recuperator 218 may also be fluidly coupled to the high pressure side of the working fluid circuit 202, disposed upstream of the heat exchanger 150 and/or a working fluid inlet of a drive turbine 264 of turbopump 260, and disposed downstream of a working fluid outlet on a pump portion 262 of turbopump 260. The recuperator 218 may be configured to increase the amount of thermal energy in the working fluid prior to flowing into the heat exchanger 150 and/or the drive turbine 264. Therefore, the recuperator 218 may be operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. In some examples, the recuperator 218 may be a heat exchanger configured to cool the low pressurized working fluid discharged or downstream of the power turbine 228 and/or the recuperator 216 while heating the high pressurized working fluid entering into or upstream of the heat exchanger 150 and/or the drive turbine 264.

[092] A cooler or a condenser 274 may be fluidly coupled to and in thermal communication with the low pressure side of the working fluid circuit 202 and may be configured or operative to control a temperature of the working fluid in the low pressure side of the working fluid circuit 202. The condenser 274 may be disposed downstream of the recuperators 216 and 218 and upstream of the start pump 280 and the turbopump 260. The condenser 274 receives the cooled working fluid from the recuperator 218 and further cools and/or condenses the working fluid which may be recirculated throughout the working fluid circuit 202. In many examples, the condenser 274 is a cooler and may be configured to control a temperature of the working fluid in the low pressure side of the working fluid circuit 202 by transferring thermal energy from the working fluid in the low pressure side to a cooling loop or system outside of the working fluid circuit 202.

[093] A cooling media or fluid is generally utilized in the cooling loop or system by the condenser 274 for cooling the working fluid and removing thermal energy outside of the working fluid circuit 202. The cooling media or fluid flows through, over, or around while in thermal communication with the condenser 274. Thermal energy in the working fluid is transferred to the cooling fluid via the condenser 274. Therefore, the cooling fluid is in thermal communication with the working fluid circuit 202, but not fluidly coupled to the working fluid circuit 202. The condenser 274 may be fluidly coupled to the working fluid circuit 202 and independently fluidly coupled to the cooling fluid. The cooling fluid may contain one or multiple compounds and may be in one or multiple states of matter. The cooling fluid may be a media or fluid in a gaseous state, a liquid state, a subcritical state, a supercritical state, a suspension, a solution, derivatives thereof, or combinations thereof.

[094] In many examples, the condenser 274 is generally fluidly coupled to a cooling loop or system (not shown) that receives the cooling fluid from a cooling fluid return 278a and returns the warmed cooling fluid to the cooling loop or system via a cooling fluid supply 278b. The cooling fluid may be water, carbon dioxide, or other aqueous and/or organic fluids (e.g., alcohols and/or glycols), air or other gases, or various mixtures thereof that are maintained at a lower temperature than the temperature of the working fluid. In other examples, the cooling media or fluid contains air or another gas exposed to the condenser 274, such as an air steam blown by a motorized fan or blower. A filter 276 may be disposed along and in fluid communication with the cooling fluid line at a point downstream of the cooling fluid supply 278b and upstream of the condenser 274. In some examples, the filter 276 may be fluidly coupled to the cooling fluid line within the process system 210.

[095] In another embodiment, the condenser 272 or another cooler may be fluidly coupled to and in thermal communication with the leak recapture line 182 and disposed between the housing 238 of the power generation system 220 and extending to the leak recapture compressor 180. The captured seal gas may flow through the condenser 272 and then through the leak recapture compressor 180, as depicted in Figures 1A, 1 D, and 2.

[096] A cooling media or cooling fluid is generally utilized by the condenser 272 for cooling the captured seal gas. The cooling media or fluid flows through, over, or around while in thermal communication with the condenser 272. Thermal energy in the working fluid is transferred to the cooling fluid via the condenser 272. The condenser 274 may be fluidly coupled to the leak recapture line 182 and independently fluidly coupled to the captured seal gas. The cooling fluid may contain one or multiple compounds and may be in one or multiple states of matter. The cooling fluid passing through the condenser 272 may be a media or fluid in a gaseous state, a liquid state, a subcritical state, a supercritical state, a suspension, a solution, derivatives thereof, or combinations thereof. The cooling fluid may be water, carbon dioxide, or other aqueous and/or organic fluids, air or other gases, or various mixtures thereof that are maintained at a lower temperature than the temperature of the working fluid. In other examples, the cooling media or fluid contains air or another gas exposed to the condenser 272, such as an air steam blown by a motorized fan or blower.

[097] The heat engine system 200 further contains several pumps, such as a turbopump 260 and a start pump 280, disposed within the working fluid circuit 202 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202. The turbopump 260 and the start pump 280 may be operative to circulate the working fluid throughout the working fluid circuit 202. The start pump 280 is generally a motorized pump and may be utilized to initially pressurize and circulate the working fluid in the working fluid circuit 202. Once a predetermined pressure, temperature, and/or flowrate of the working fluid is obtained within the working fluid circuit 202, the start pump 280 may be taken off line, idled, or turned off and the turbopump 260 is utilized to circulate the working fluid during the electricity generation process. The working fluid enters each of the turbopump 260 and the start pump 280 from the low pressure side of the working fluid circuit 202 and exits each of the turbopump 260 and the start pump 280 from the high pressure side of the working fluid circuit 202.

[098] The start pump 280 may be a motorized pump, such as an electric motorized pump, a mechanical motorized pump, or other type of pump. Generally, the start pump 280 may be a variable frequency motorized drive pump and contains a pump portion 282 and a motor-drive portion 284. The motor-drive portion 284 of the start pump 280 contains a motor and a drive including a driveshaft and gears. In some examples, the motor-drive portion 284 has a variable frequency drive, such that the speed of the motor may be regulated by the drive. The pump portion 282 of the start pump 280 is driven by the motor-drive portion 284 coupled thereto. The pump portion 282 has an inlet for receiving the working fluid from the low pressure side of the working fluid circuit 202, such as from the condenser 274 and/or the working fluid storage system 290. The pump portion 282 has an outlet for releasing the working fluid into the high pressure side of the working fluid circuit 202.

[099] Start pump inlet valve 283 and start pump outlet valve 285 may be utilized to control the flow of the working fluid passing through the start pump 280. Start pump inlet valve 283 may be fluidly coupled to the low pressure side of the working fluid circuit 202 upstream of the pump portion 282 of the start pump 280 and may be utilized to control the flowrate of the working fluid entering the inlet of the pump portion 282. Start pump outlet valve 285 may be fluidly coupled to the high pressure side of the working fluid circuit 202 downstream of the pump portion 282 of the start pump 280 and may be utilized to control the flowrate of the working fluid exiting the outlet of the pump portion 282.

[0100] The turbopump 260 is generally a turbo-drive pump or a turbine-drive pump and utilized to pressurize and circulate the working fluid throughout the working fluid circuit 202. The turbopump 260 contains a pump portion 262 and a drive turbine 264 coupled together by a driveshaft 267 and an optional gearbox (not shown). The drive turbine 264 may be configured to rotate the pump portion 262, and the pump portion 262 may be configured to circulate the working fluid within the working fluid circuit 202.

[0101] The driveshaft 267 may be a single piece or may contain two or more pieces coupled together. In one example, a first segment of the driveshaft 267 extends from the drive turbine 264 to the gearbox, a second segment of the driveshaft 230 extends from the gearbox to the pump portion 262, and multiple gears are disposed between and coupled to the two segments of the driveshaft 267 within the gearbox. [0102] The drive turbine 264 of the turbopump 260 is driven by heated working fluid, such as the working fluid flowing from the heat exchanger 150. The drive turbine 264 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the high pressure side of the working fluid circuit 202, such as flowing from the heat exchanger 150. The drive turbine 264 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the low pressure side of the working fluid circuit 202.

[0103] The pump portion 262 of the turbopump 260 is driven by the driveshaft 267 coupled to the drive turbine 264. The pump portion 262 of the turbopump 260 may be fluidly coupled to the low pressure side of the working fluid circuit 202 by an inlet configured to receive the working fluid from the low pressure side of the working fluid circuit 202. The inlet of the pump portion 262 may be configured to receive the working fluid from the low pressure side of the working fluid circuit 202, such as from the condenser 274 and/or the working fluid storage system 290. Also, the pump portion 262 may be fluidly coupled to the high pressure side of the working fluid circuit 202 by an outlet configured to release the working fluid into the high pressure side of the working fluid circuit 202 and circulate the working fluid within the working fluid circuit 202.

[0104] In one configuration, the working fluid released from the outlet on the drive turbine 264 is returned into the working fluid circuit 202 downstream of the recuperator 216 and upstream of the recuperator 218. In one or more embodiments, the turbopump 260, including piping and valves, is optionally disposed on a turbopump skid 266, as depicted in Figure 2. The turbopump skid 266 may be disposed on or adjacent the main process skid 212.

[0105] A drive turbine bypass valve 265 is generally coupled between and in fluid communication with a fluid line extending from the inlet of the drive turbine 264 with a fluid line extending from the outlet on the drive turbine 264. The drive turbine bypass valve 265 is generally opened to bypass the turbopump 260 while using the start pump 280 during the initial stages of generating electricity with the heat engine system 200. Once a predetermined pressure and temperature of the working fluid is obtained within the working fluid circuit 202, the drive turbine bypass valve 265 is closed and the heated working fluid is flowed through the drive turbine 264 to start the turbopump 260.

[0106] A drive turbine throttle valve 263 may be coupled between and in fluid communication with a fluid line extending from the heat exchanger 150 to the inlet of the drive turbine 264 of the turbopump 260. The drive turbine throttle valve 263 may be configured to modulate the flow of the heated working fluid into the drive turbine 264, which in turn may be utilized to adjust the flow of the working fluid throughout the working fluid circuit 202. Additionally, valve 293 may be utilized to provide back pressure for the drive turbine 264 of the turbopump 260.

[0107] A drive turbine attemperator valve 295 may be fluidly coupled to the working fluid circuit 202 via an attemperator bypass line 291 disposed between the outlet on the pump portion 262 of the turbopump 260 and the inlet of the drive turbine 264 and/or disposed between the outlet on the pump portion 282 of the start pump 280 and the inlet of the drive turbine 264. The attemperator bypass line 291 and the drive turbine attemperator valve 295 may be configured to flow the working fluid from the pump portion 262 or 282, around and circumvent the recuperator 218 and the heat exchanger 150, and to the drive turbine 264, such as during a warm-up or cool-down step of the turbopump 260. The attemperator bypass line 291 and the drive turbine attemperator valve 295 may be utilized to warm the working fluid with the drive turbine 264 while avoiding the thermal heat from the heat source stream 1 10 via the heat exchangers, such as the heat exchanger 150.

[0108] A control valve 261 may be disposed downstream of the outlet of the pump portion 262 of the turbopump 260, and the control valve 281 may be disposed downstream of the outlet of the pump portion 282 of the start pump 280. Control valves 261 and 281 are flow control safety valves and generally utilized to regulate the directional flow or to prohibit backflow of the working fluid within the working fluid circuit 202. Control valve 261 may be configured to prevent the working fluid from flowing upstream towards or into the outlet of the pump portion 262 of the turbopump 260. Similarly, control valve 281 may be configured to prevent the working fluid from flowing upstream towards or into the outlet of the pump portion 282 of the start pump 280.

[0109] The drive turbine throttle valve 263 may be fluidly coupled to the working fluid circuit 202 upstream of the inlet of the drive turbine 264 of the turbopump 260 and configured to control a flow of the working fluid flowing into the drive turbine 264. The power turbine bypass valve 219 may be fluidly coupled to the power turbine bypass line 208 and configured to modulate, adjust, or otherwise control the working fluid flowing through the power turbine bypass line 208 for controlling the flowrate of the working fluid entering the power turbine 228.

[0110] The power turbine bypass line 208 may be fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the power turbine 228 and at a point downstream of an outlet of the power turbine 228. The power turbine bypass line 208 may be configured to flow the working fluid around and circumvent the power turbine 228 when the power turbine bypass valve 219 is in an opened position. The flowrate and the pressure of the working fluid flowing into the power turbine 228 may be reduced or stopped by adjusting the power turbine bypass valve 219 to the opened position. Alternatively, the flowrate and the pressure of the working fluid flowing into the power turbine 228 may be increased or started by adjusting the power turbine bypass valve 219 to the closed position due to the backpressure formed through the power turbine bypass line 208.

[0111] The power turbine bypass valve 219 and the drive turbine throttle valve 263 may be independently controlled by the process control system 204 that is communicably connected, wired and/or wirelessly, with the power turbine bypass valve 219, the drive turbine throttle valve 263, and other parts of the heat engine system 200. The process control system 204 may be operatively connected to the working fluid circuit 202 and a mass management system 270 and is enabled to monitor and control multiple process operation parameters of the heat engine system 200.

[0112] In one or more embodiments, the working fluid circuit 202 provides a bypass flowpath for the start pump 280 via the start pump bypass line 224 and a start pump bypass valve 254, as well as a bypass flowpath for the turbopump 260 via the turbopump bypass line 226 and a turbopump bypass valve 256. One end of the start pump bypass line 224 may be fluidly coupled to an outlet of the pump portion 282 of the start pump 280, and the other end of the start pump bypass line 224 may be fluidly coupled to a fluid line 229. Similarly, one end of a turbopump bypass line 226 may be fluidly coupled to an outlet of the pump portion 262 of the turbopump 260, and the other end of the turbopump bypass line 226 is coupled to the start pump bypass line 224. In some configurations, the start pump bypass line 224 and the turbopump bypass line 226 may merge to form a single line coupled to a fluid line 229 extending between and fluidly coupled to the recuperator 218 and the condenser 274. The start pump bypass valve 254 is fluidly coupled to the start pump bypass line 224. When the start pump bypass valve 254 is in a closed position, the start pump bypass valve 254 may separate the low and high pressure sides at one portion of the working fluid circuit 202. Similarly, the turbopump bypass valve 256 is fluidly coupled to the turbopump bypass line 226. When the turbopump bypass line 226 is in a closed position, the turbopump bypass line 226 may separate the low and high pressure sides at another portion of the working fluid circuit 202.

[0113] Figure 2 further depicts a power turbine throttle valve 250 fluidly coupled to a bypass line 246 on the high pressure side of the working fluid circuit 202 and upstream of the heat exchanger 120, as disclosed by at least one embodiment described herein. The power turbine throttle valve 250 may be fluidly coupled to the bypass line 246 and configured to modulate, adjust, or otherwise control the working fluid flowing through the bypass line 246 for controlling a coarse or high volume flowrate of the working fluid within the working fluid circuit 202. The bypass line 246 may be fluidly coupled to the working fluid circuit 202 at a point upstream of the valve 293 and at a point downstream of the pump portion 282 of the start pump 280 and/or the pump portion 262 of the turbopump 260. Additionally, a power turbine trim valve 252 may be fluidly coupled to a bypass line 248 on the high pressure side of the working fluid circuit 202 and upstream of the heat exchanger 150, as disclosed by another embodiment described herein. The power turbine trim valve 252 may be fluidly coupled to the bypass line 248 and configured to modulate, adjust, or otherwise control the working fluid flowing through the bypass line 248 for controlling a fine flowrate of the working fluid within the working fluid circuit 202. The bypass line 248 may be fluidly coupled to the bypass line 246 at a point upstream of the power turbine throttle valve 250 and at a point downstream of the power turbine throttle valve 250.

[0114] The heat engine system 200 further contains a drive turbine throttle valve 263 fluidly coupled to the working fluid circuit 202 upstream of the inlet of the drive turbine 264 of the turbopump 260 and configured to modulate a flow of the working fluid flowing into the drive turbine 264, a power turbine bypass line 208 fluidly coupled to the working fluid circuit 202 at a point upstream of an inlet of the power turbine 228, fluidly coupled to the working fluid circuit 202 at a point downstream of an outlet of the power turbine 228, and configured to flow the working fluid around and circumvent the power turbine 228, a power turbine bypass valve 219 fluidly coupled to the power turbine bypass line 208 and configured to modulate a flow of the working fluid flowing through the power turbine bypass line 208 for controlling the flowrate of the working fluid entering the power turbine 228, and a process control system 204 operatively connected to the heat engine systems 90, 200. The process control system 204 may be configured to adjust the drive turbine throttle valve 263 and the power turbine bypass valve 219.

[0115] A heat exchanger bypass line 160 may be fluidly coupled to a fluid line 131 of the working fluid circuit 202 upstream of the heat exchangers 120, 130, and/or 150 by a heat exchanger bypass valve 162, as illustrated in Figure 2. The heat exchanger bypass valve 162 may be a solenoid valve, a hydraulic valve, an electric valve, a manual valve, or derivatives thereof. In many examples, the heat exchanger bypass valve 162 is a solenoid valve and configured to be controlled by the process control system 204.

[0116] In one or more embodiments, the working fluid circuit 202 provides release valves 213a, 213b, 213c, and 213d, as well as release outlets 214a, 214b, 214c, and 214d, respectively in fluid communication with each other. Generally, the release valves 213a, 213b, 213c, and 213d remain closed during the electricity generation process, but may be configured to automatically open to release an over-pressure at a predetermined value within the working fluid. Once the working fluid flows through the valve 213a, 213b, 213c, or 213d, the working fluid is vented through the respective release outlet 214a, 214b, 214c, or 214d. The release outlets 214a, 214b, 214c, and 214d may provide passage of the working fluid into the ambient surrounding atmosphere. Alternatively, the release outlets 214a, 214b, 214c, and 214d may provide passage of the working fluid into a recycling or reclamation step that generally includes capturing, condensing, and storing the working fluid.

[0117] The release valve 213a and the release outlet 214a are fluidly coupled to the working fluid circuit 202 at a point disposed between the heat exchanger 120 and the power turbine 228. The release valve 213b and the release outlet 214b are fluidly coupled to the working fluid circuit 202 at a point disposed between the heat exchanger 150 and the drive turbine 264 of the turbopump 260. The release valve 213c and the release outlet 214c are fluidly coupled to the working fluid circuit 202 via a bypass line that extends from a point between the valve 293 and the pump portion 262 of the turbopump 260 to a point on the turbopump bypass line 226 between the turbopump bypass valve 256 and the fluid line 229. The release valve 213d and the release outlet 214d are fluidly coupled to the working fluid circuit 202 at a point disposed between the recuperator 218 and the condenser 274.

[0118] A computer system 206, as part of the process control system 204, contains a multi- controller algorithm utilized to control the drive turbine throttle valve 263, the power turbine bypass valve 219, the heat exchanger bypass valve 162, the power turbine throttle valve 250, the power turbine trim valve 252, as well as other valves, pumps, and sensors within the heat engine system 200. In one embodiment, the process control system 204 is enabled to move, adjust, manipulate, or otherwise control the heat exchanger bypass valve 162, the power turbine throttle valve 250, and/or the power turbine trim valve 252 for adjusting or controlling the flow of the working fluid throughout the working fluid circuit 202. By controlling the flow of the working fluid, the process control system 204 is also operable to regulate the temperatures and pressures throughout the working fluid circuit 202.

[0119] In some embodiments, the overall efficiency of the heat engine system 200 and the amount of power ultimately generated can be influenced by the inlet or suction pressure at the pump when the working fluid contains supercritical carbon dioxide. In order to minimize or otherwise regulate the suction pressure of the pump, the heat engine system 200 may incorporate the use of a mass management system ("MMS") 270. The mass management system 270 controls the inlet pressure of the start pump 280 by regulating the amount of working fluid entering and/or exiting the heat engine system 200 at strategic locations in the working fluid circuit 202, such as at tie-in points, inlets/outlets, valves, or conduits throughout the heat engine system 200. Consequently, the heat engine system 200 becomes more efficient by increasing the pressure ratio for the start pump 280 to a maximum possible extent.

[0120] The mass management system 270 contains at least one vessel or tank, such as a storage vessel (e.g. , working fluid storage vessel 292), a fill vessel, and/or a mass control tank (e.g., mass control tank 286), fluidly coupled to the low pressure side of the working fluid circuit 202 via one or more valves, such as stop valve 287. The valves are moveable - as being partially opened, fully opened, and/or closed - to either remove working fluid from the working fluid circuit 202 or add working fluid to the working fluid circuit 202. Exemplary embodiments of the mass management system 270, and a range of variations thereof, are found in U .S. Appl. No. 13/278,705, filed October 21 , 201 1 , published as U .S. Pub. No. 2012-0047892, and issued as U .S. Patent No. 8,613, 195, the contents of which are incorporated herein by reference to the extent consistent with the present disclosure. Briefly, however, the mass management system 270 may include a plurality of valves and/or connection points, each in fluid communication with the mass control tank 286. The valves may be characterized as termination points where the mass management system 270 may be operatively connected to the heat engine system 200. The connection points and valves may be configured to provide the mass management system 270 with an outlet for flaring excess working fluid or pressure, or to provide the mass management system 270 with additional/supplemental working fluid from an external source , such as a fluid fill system.

[0121] In some embodiments, the mass control tank 286 may be configured as a localized storage tank for additional/supplemental working fluid that may be added to the heat engine system 200 when needed in order to regulate the pressure or temperature of the working fluid within the working fluid circuit 202 or otherwise supplement escaped working fluid. By controlling the valves, the mass management system 270 adds and/or removes working fluid mass to/from the heat engine system 200 with or without the need of a pump, thereby reducing system cost, complexity, and maintenance.

[0122] In some examples, a working fluid storage vessel 292 is part of a working fluid storage system 290 and may be fluidly coupled to the working fluid circuit 202. At least one connection point, such as a working fluid feed 288, may be a fluid fill port for the working fluid storage vessel 292 of the working fluid storage system 290 and/or the mass management system 270. Additional or supplemental working fluid may be added to the mass management system 270 from an external source, such as a fluid fill system via the working fluid feed 288. Exemplary fluid fill systems are described and illustrated in U.S. Pat. No. 8,281 ,593, the contents of which are incorporated herein by reference to the extent consistent with the present disclosure.

[0123] In another embodiment described herein, bearing gas and seal gas may be supplied to the turbopump 260 or other devices contained within and/or utilized along with the heat engine system 200. One or multiple streams of bearing gas and/or seal gas may be derived from the working fluid within the working fluid circuit 202 and contain carbon dioxide in a gaseous, subcritical, or supercritical state. In some examples, the bearing gas or fluid is flowed by the start pump 280, from a bearing gas supply 296a and/or a bearing gas supply 296b, into the working fluid circuit 202, through a bearing gas supply line (not shown), and to the bearings within the power generation system 220. In other examples, the bearing gas or fluid is flowed by the start pump 280, from the working fluid circuit 202, through a bearing gas supply line (not shown), and to the bearings within the turbopump 260. In some examples, the gas return 298 is a connection point or valve that feeds into a gas system, such as a bearing gas, dry gas, seal gas, or other system. A gas return 294 is generally coupled to a discharge, recapture, or return of bearing gas, seal gas, and other gases. The gas return 294 provides a feed stream into the working fluid circuit 202 of recycled, recaptured, or otherwise returned gases - generally derived from the working fluid. The gas return is generally fluidly coupled to the working fluid circuit 202 upstream of the condenser 274 and downstream of the recuperator 218.

[0124] The heat engine system 200 contains a process control system 204 communicably connected, wired and/or wirelessly, with numerous sets of sensors, valves, and pumps, in order to process the measured and reported temperatures, pressures, and mass flowrates of the working fluid at the designated points within the working fluid circuit 202. In response to these measured and/or reported parameters, the process control system 204 may be operable to selectively adjust the valves in accordance with a control program or algorithm, thereby maximizing operation of the heat engine system 200.

[0125] The process control system 204 may operate with the heat engine system 200 semi- passively with the aid of several sets of sensors. The first set of sensors is arranged at or adjacent the suction inlet of the turbopump 260 and the start pump 280 and the second set of sensors is arranged at or adjacent the outlet of the turbopump 260 and the start pump 280. The first and second sets of sensors monitor and report the pressure, temperature, mass flowrate, or other properties of the working fluid within the low and high pressure sides of the working fluid circuit 202 adjacent the turbopump 260 and the start pump 280. The third set of sensors is arranged either inside or adjacent the working fluid storage vessel 292 of the working fluid storage system 290 to measure and report the pressure, temperature, mass flowrate, or other properties of the working fluid within the working fluid storage vessel 292. Additionally, an instrument air supply (not shown) may be coupled to sensors, devices, or other instruments within the heat engine system 200 including the mass management system 270 and/or other system components that may utilize a gaseous supply, such as nitrogen or air.

[0126] In some embodiments described herein, the waste heat system 100 is disposed on or in a waste heat skid 102 fluidly coupled to the working fluid circuit 202, as well as other portions, sub-systems, or devices of the heat engine system 200. The waste heat skid 102 may be fluidly coupled to a source of and an exhaust for the heat source stream 1 10, a main process skid 212, a power generation skid 222, and/or other portions, sub-systems, or devices of the heat engine system 200.

[0127] In one or more configurations, the waste heat system 100 disposed on or in the waste heat skid 102 generally contains inlets 122, 132, and 152 and outlets 124, 134, and 154 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlet 122 is disposed upstream of the heat exchanger 120 and the outlet 124 is disposed downstream of the heat exchanger 120. The working fluid circuit 202 may be configured to flow the working fluid from the inlet 122, through the heat exchanger 120, and to the outlet 124 while transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 120. The inlet 152 is disposed upstream of the heat exchanger 150 and the outlet 154 is disposed downstream of the heat exchanger 150. The working fluid circuit 202 may be configured to flow the working fluid from the inlet 152, through the heat exchanger 150, and to the outlet 154 while transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 150. The inlet 132 is disposed upstream of the heat exchanger 130 and the outlet 134 is disposed downstream of the heat exchanger 130. The working fluid circuit 202 may be configured to flow the working fluid from the inlet 132, through the heat exchanger 130, and to the outlet 134 while transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 130.

[0128] In one or more configurations, the power generation system 220 is disposed on or in the power generation skid 222. The power generation system 220 contains inlets 225a, 225b and an outlet 227 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlets 225a, 225b are upstream of the power turbine 228 within the high pressure side of the working fluid circuit 202 and are configured to receive the heated and high pressure working fluid. In some examples, the inlet 225a may be fluidly coupled to the outlet 124 of the waste heat system 100 and configured to receive the working fluid flowing from the heat exchanger 120 and the inlet 225b may be fluidly coupled to the outlet 241 of the process system 210 and configured to receive the working fluid flowing from the turbopump 260 and/or the start pump 280. The outlet 227 is disposed downstream of the power turbine 228 within the low pressure side of the working fluid circuit 202 and may be configured to provide the low pressure working fluid. In some examples, the outlet 227 may be fluidly coupled to the inlet 239 of the process system 210 and configured to flow the working fluid to the recuperator 216.

[0129] A filter 215a may be disposed along and in fluid communication with the fluid line at a point downstream of the heat exchanger 120 and upstream of the power turbine 228. In some examples, the filter 215a may be fluidly coupled to the working fluid circuit 202 between the outlet 124 of the waste heat system 100 and the inlet 225a of the process system 210.

[0130] The inlets 225a and 225b may be utilized to flow the working fluid into the portion of the working fluid circuit 202 contained within the power generation system 220. A power turbine stop valve 217 may be fluidly coupled to the working fluid circuit 202 between the inlet 225a and the power turbine 228. The power turbine stop valve 217 may be configured to control the working fluid flowing from the heat exchanger 120, through the inlet 225a, and into the power turbine 228 while in an opened position. Alternatively, the power turbine stop valve 217 may be configured to cease the flow of working fluid from entering into the power turbine 228 while in a closed position.

[0131] A power turbine attemperator valve 223 may be fluidly coupled to the working fluid circuit 202 via an attemperator bypass line 21 1 disposed between the outlet on the pump portion 262 of the turbopump 260 and the inlet of the power turbine 228 and/or disposed between the outlet on the pump portion 282 of the start pump 280 and the inlet of the power turbine 228. The attemperator bypass line 21 1 and the power turbine attemperator valve 223 may be configured to flow the working fluid from the pump portion 262 or 282, around and circumvent the recuperator 216 and the heat exchangers 120 and 130, and to the power turbine 228, such as during a warm-up or cool-down step. The attemperator bypass line 21 1 and the power turbine attemperator valve 223 may be utilized to warm the working fluid with heat coming from the power turbine 228 while avoiding the thermal heat from the heat source stream 1 10 flowing through the heat exchangers, such as the heat exchangers 120 and 130. In some examples, the power turbine attemperator valve 223 may be fluidly coupled to the working fluid circuit 202 between the inlet 225b and the power turbine stop valve 217 upstream of a point on the fluid line that intersects the incoming stream from the inlet 225a. The power turbine attemperator valve 223 may be configured to control the working fluid flowing from the start pump 280 and/or the turbopump 260, through the inlet 225b, and to a power turbine stop valve 217, the power turbine bypass valve 219, and/or the power turbine 228.

[0132] The power turbine bypass valve 219 may be fluidly coupled to a turbine bypass line that extends from a point of the working fluid circuit 202 upstream of the power turbine stop valve 217 and downstream of the power turbine 228. Therefore, the bypass line and the power turbine bypass valve 219 are configured to direct the working fluid around and circumvent the power turbine 228. If the power turbine stop valve 217 is in a closed position, the power turbine bypass valve 219 may be configured to flow the working fluid around and circumvent the power turbine 228 while in an opened position. In one embodiment, the power turbine bypass valve 219 may be utilized while warming up the working fluid during a start-up operation of the electricity generating process. An outlet valve 221 may be fluidly coupled to the working fluid circuit 202 between the outlet on the power turbine 228 and the outlet 227 of the power generation system 220.

[0133] In one or more configurations, the process system 210 is disposed on or in the main process skid 212. The main process skid 212 contains inlets 235, 239, and 255 and outlets 231 , 237, 241 , 251 , and 253 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlet 235 is upstream of the recuperator 216 and the outlet 154 is downstream of the recuperator 216. The working fluid circuit 202 may be configured to flow the working fluid from the inlet 235, through the recuperator 216, and to the outlet 237 while transferring thermal energy from the working fluid in the low pressure side of the working fluid circuit 202 to the working fluid in the high pressure side of the working fluid circuit 202 by the recuperator 216. The outlet 241 of the process system 210 is downstream of the turbopump 260 and/or the start pump 280, upstream of the power turbine 228, and configured to provide a flow of the high pressure working fluid to the power generation system 220, such as to the power turbine 228. The inlet 239 is upstream of the recuperator 216, downstream of the power turbine 228, and configured to receive the low pressure working fluid flowing from the power generation system 220, such as to the power turbine 228. The outlet 251 of the process system 210 is downstream of the recuperator 218, upstream of the heat exchanger 150, and configured to provide a flow of working fluid to the heat exchanger 150. The inlet 255 is downstream of the heat exchanger 150, upstream of the drive turbine 264 of the turbopump 260, and configured to provide the heated high pressure working fluid flowing from the heat exchanger 150 to the drive turbine 264 of the turbopump 260. The outlet 253 of the process system 210 is downstream of the pump portion 262 of the turbopump 260 and/or the pump portion 282 of the start pump 280, couples a bypass line disposed downstream of the heat exchanger 150 and upstream of the drive turbine 264 of the turbopump 260, and is configured to provide a flow of working fluid to the drive turbine 264 of the turbopump 260.

[0134] Additionally, a filter 215c may be disposed along and in fluid communication with the fluid line at a point downstream of the heat exchanger 150 and upstream of the drive turbine 264 of the turbopump 260. In some examples, the filter 215c may be fluidly coupled to the working fluid circuit 202 between the outlet 154 of the waste heat system 100 and the inlet 255 of the process system 210.

[0135] In another embodiment described herein, as illustrated in Figure 2, the heat engine system 200 contains the process system 210 disposed on or in a main process skid 212, the power generation system 220 disposed on or in a power generation skid 222, and the waste heat system 100 disposed on or in a waste heat skid 102. The working fluid circuit 202 extends throughout the inside, the outside, and between the main process skid 212, the power generation skid 222, and the waste heat skid 102, as well as other systems and portions of the heat engine system 200. In some embodiments, the heat engine system 200 contains the heat exchanger bypass line 160 and the heat exchanger bypass valve 162 disposed between the waste heat skid 102 and the main process skid 212. A filter 215b may be disposed along and in fluid communication with the fluid line 135 at a point downstream of the heat exchanger 130 and upstream of the recuperator 216. In some examples, the filter 215b may be fluidly coupled to the working fluid circuit 202 between the outlet 134 of the waste heat system 100 and the inlet 235 of the process system 210.

[0136] It is to be understood that the present disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described herein to simplify the present disclosure, however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the present disclosure may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments described herein may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment without departing from the scope of the disclosure.

[0137] Additionally, certain terms are used throughout the present disclosure and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Further, in the present disclosure and in the claims, the terms "including", "containing", and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to". All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term "or" is intended to encompass both exclusive and inclusive cases, i.e., "A or B" is intended to be synonymous with "at least one of A and B", unless otherwise expressly specified herein.

[0138] The foregoing has outlined features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the present disclosure.

Claims

Claims:

1 . A heat engine system with a turbine cooling system, comprising:

a working fluid circuit containing a working fluid, wherein the working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state;

a heat exchanger fluidly coupled to and in thermal communication with the working fluid in the high pressure side of the working fluid circuit, wherein the heat exchanger is configured to transfer thermal energy from a heat source stream to the working fluid in the high pressure side; a power turbine fluidly coupled to and disposed between the high pressure side and the low pressure side of the working fluid circuit and configured to convert a pressure drop in the working fluid to mechanical energy;

a driveshaft coupled to the power turbine and configured to drive a device with the mechanical energy, wherein the driveshaft is at least partially contained within a housing;

a seal gas conditioning system fluidly coupled to and disposed between the housing and a seal gas supply source, wherein the seal gas conditioning system is configured to dispense a seal gas;

a labyrinth seal cavity formed between the power turbine and a labyrinth seal and between the driveshaft and the housing;

a dry gas seal cavity formed between the labyrinth seal and a dry gas seal and between the driveshaft and the housing, wherein the dry gas seal cavity is configured to receive the seal gas from the seal gas conditioning system;

a first segmented circumferential seal cavity formed between the dry gas seal and a first segmented circumferential seal and between the driveshaft and the housing;

a second segmented circumferential seal cavity formed between the first segmented circumferential seal and a second segmented circumferential seal and between the driveshaft and the housing, wherein the second segmented circumferential seal cavity is configured to receive the seal gas from the seal gas conditioning system;

a leak recapture storage vessel fluidly coupled to the housing and in fluid communication with the first segmented circumferential seal cavity;

a power turbine discharge line fluidly coupled to the power turbine on the low pressure side of the working fluid circuit; and

a first power turbine vent line fluidly coupled to and between the power turbine discharge line and the leak recapture storage vessel.

2. The heat engine system of claim 1 , further comprising a first power turbine vent valve disposed on the first power turbine vent line and configured to release a portion of the seal gas flowing from the power turbine into the leak recapture storage vessel.

3. The heat engine system of claim 1 , further comprising a second power turbine vent line fluidly coupled to the power turbine discharge line and extending into the ambient atmosphere.

4. The heat engine system of claim 3, further comprising a second power turbine vent valve disposed on the second power turbine vent line and configured to release a portion of the seal gas flowing from the power turbine into the ambient atmosphere.

5. The heat engine system of claim 1 , further comprising a conditioned gas line fluidly coupled to and disposed between the seal gas conditioning system and the housing.

6. The heat engine system of claim 5, further comprising a conditioned gas valve fluidly coupled to the conditioned gas line and configured to control the seal gas passing through the conditioned gas line and into the dry gas seal cavity.

7. The heat engine system of claim 5, further comprising a conditioned gas valve fluidly coupled to the conditioned gas line and configured to control the seal gas passing through the conditioned gas line and into the second segmented circumferential seal cavity.

8. The heat engine system of claim 1 , further comprising a buffer gas supply fluidly coupled to the housing and in fluid communication with the second segmented circumferential seal cavity.

9. The heat engine system of claim 8, wherein the buffer gas supply comprises a conditioned gas line fluidly coupled to and disposed between the seal gas conditioning system and the housing and in fluid communication with the second segmented circumferential seal cavity.

10. The heat engine system of claim 1 , further comprising a leak recapture line fluidly coupled to and disposed between the leak recapture storage vessel and the housing.

1 1 . The heat engine system of claim 10, further comprising a compressor, a condenser, or both the compressor and the condenser, wherein the compressor and the condenser are fluidly coupled to the leak recapture line and disposed between the leak recapture storage vessel and the housing.

12. The heat engine system of claim 1 , further comprising a power turbine stop valve and a power turbine discharge valve, wherein the power turbine stop valve is fluidly coupled to a power turbine inlet line upstream of an inlet of the power turbine, the power turbine discharge valve is fluidly coupled to the power turbine discharge line downstream of an outlet of the power turbine, and the power turbine stop valve and the power turbine discharge valve are configured to control the flow of the working fluid through the power turbine.

13. The heat engine system of claim 12, further comprising a power turbine bypass valve fluidly coupled to a power turbine bypass line, wherein the power turbine bypass line is fluidly coupled to the power turbine inlet line upstream of the power turbine stop valve and fluidly coupled to the power turbine discharge line downstream of the power turbine.

14. The heat engine system of claim 1 , wherein:

the labyrinth seal cavity is configured to have a reference pressure within a reference pressure range;

the leak recapture storage vessel is configured to have a recapture storage vessel pressure within a recapture storage vessel pressure range and the recapture storage vessel pressure is less than the reference pressure;

the dry gas seal cavity is configured to have a dry gas seal cavity pressure within a dry gas seal cavity pressure range and the dry gas seal cavity pressure is greater than the reference pressure; and

the seal gas conditioning system is configured to have a conditioning system pressure within a conditioning system pressure range and the conditioning system pressure is greater than the dry gas seal cavity pressure.

15. The heat engine system of claim 14, wherein the reference pressure is within the reference pressure range from about 3.45 MPa to about 10.34 MPa.

16. The heat engine system of claim 14, wherein the recapture storage vessel pressure has a pressure differential within a range from about 345 kPa to about 8.62 MPa less than the reference pressure.

17. The heat engine system of claim 14, wherein the recapture storage vessel pressure is within the recapture storage vessel pressure range from about 345 kPa to about 2.76 MPa.

18. The heat engine system of claim 14, wherein the conditioning system pressure has a pressure differential within a range from about 345 kPa to about 689 kPa greater than the reference pressure.

19. The heat engine system of claim 14, wherein the conditioning system pressure is within the conditioning system pressure range from about 3.79 MPa to about 1 1 .03 MPa.

20. The heat engine system of claim 14, wherein the dry gas seal cavity pressure has a pressure differential within a range from about 345 kPa to about 689 kPa greater than the reference pressure.

21 . The heat engine system of claim 20, wherein the dry gas seal cavity pressure is within the dry gas seal cavity pressure range from about 3.79 MPa to about 1 1 .03 MPa.

22. The heat engine system of claim 14, further comprising a seal gas supply source having a seal gas source pressure within a seal gas source pressure range and the seal gas source pressure is greater than the reference pressure.

23. The heat engine system of claim 22, wherein the seal gas source pressure has a pressure differential within a range from about 345 kPa to about 1.38 MPa greater than the reference pressure.

24. The heat engine system of claim 22, wherein the seal gas source pressure is within the seal gas source pressure range from about 3.79 MPa to about 1 1 .0 MPa.

25. A method for cooling a turbine in a heat engine during a shutdown, comprising: circulating a working fluid within a working fluid circuit, wherein the working fluid circuit has a high pressure side and a low pressure side and at least a portion of the working fluid is in a supercritical state;

transferring thermal energy from a heat source stream to the working fluid by a heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit;

flowing the working fluid into a power turbine and converting the thermal energy of the working fluid to mechanical energy of a driveshaft coupled to the power turbine; and

activating a shutdown procedure, comprising:

closing a power turbine stop valve and a power turbine discharge valve to stop the flow of the working fluid through the power turbine;

flowing a seal gas from a seal gas conditioning system, through a dry gas seal cavity, across a labyrinth seal, through a labyrinth seal cavity, through the power turbine, through a first power turbine vent line and a first power turbine vent valve, and to a leak recapture storage vessel, wherein the labyrinth seal cavity and the dry gas seal cavity are separated by the labyrinth seal and are adjacent the driveshaft within a housing; and

flowing the seal gas from the seal gas conditioning system, through the dry gas seal cavity, across a dry gas seal, through a first segmented circumferential seal cavity, through a leak recapture line, and to the leak recapture storage vessel, wherein the first segmented circumferential seal cavity and the dry gas seal cavity are separated by the dry gas seal and are adjacent the driveshaft within the housing; wherein:

the labyrinth seal cavity has a reference pressure within a reference pressure range; the dry gas seal cavity has a dry gas seal cavity pressure within a dry gas seal cavity pressure range and the dry gas seal cavity pressure is greater than the reference pressure; and the leak recapture storage vessel has a recapture storage vessel pressure within a recapture storage vessel pressure range and the recapture storage vessel pressure is less than the reference pressure.

26. The method of claim 25, further comprising opening a second power turbine vent valve to release a portion of the seal gas flowing from the power turbine into the ambient atmosphere.

27. The method of claim 26, further comprising a second power turbine vent line fluidly coupled to the power turbine discharge line and extending into the ambient atmosphere, wherein the second power turbine vent valve is fluidly coupled to the second power turbine vent line and is configured to control the portion of the seal gas flowing through the second power turbine vent line.

28. The method of claim 25, wherein the seal gas supply source has a seal gas source pressure within a seal gas source pressure range and the seal gas source pressure is greater than the reference pressure.

29. The method of claim 25, wherein the seal gas conditioning system has a conditioning system pressure within a conditioning system pressure range and the conditioning system pressure is greater than the reference pressure.

30. The method of claim 25, further comprising flowing the seal gas from the seal gas conditioning system, through a conditioned gas line, and into the dry gas seal cavity, wherein the conditioned gas line is fluidly coupled to and disposed between the seal gas conditioning system and the housing.

31 . The method of claim 25, further comprising flowing the seal gas from the seal gas conditioning system, through a second segmented circumferential seal cavity, across a segmented circumferential seal, through the first segmented circumferential seal cavity, through the leak recapture line, and to the leak recapture storage vessel, wherein the second segmented circumferential seal cavity and the first segmented circumferential seal cavity are separated by the segmented circumferential seal and are adjacent the driveshaft within the housing.

32. The method of claim 31 , further comprising flowing the seal gas from the seal gas conditioning system, through a conditioned gas line, and into the second segmented circumferential seal cavity, wherein the conditioned gas line is fluidly coupled to and disposed between the seal gas conditioning system and the housing.

33. The method of claim 25, wherein the reference pressure is within the reference pressure range from about 3.45 MPa to about 10.34 MPa.

34. The method of claim 25, wherein the recapture storage vessel pressure has a pressure differential within a range from about 345 kPa to about 8.62 MPa less than the reference pressure.

35. The method of claim 25, wherein the recapture storage vessel pressure is within the recapture storage vessel pressure range from about 345 kPa to about 2.76 MPa.

36. The method of claim 29, wherein the conditioning system pressure has a pressure differential within a range from about 345 kPa to about 689 kPa greater than the reference pressure.

37. The method of claim 29, wherein the conditioning system pressure is within the conditioning system pressure range from about 3.79 MPa to about 1 1 .0 MPa.

38. The method of claim 25, wherein the dry gas seal cavity pressure has a pressure differential within a range from about 345 kPa to about 689 kPa greater than the reference pressure.

39. The method of claim 38, wherein the dry gas seal cavity pressure is within the dry gas seal cavity pressure range from about 3.79 MPa to about 1 1 .0 MPa.

40. The method of claim 25, further comprising a seal gas supply source fluidly coupled to the seal gas conditioning system and configured to supply the seal gas to the seal gas conditioning system, wherein the seal gas supply source has a seal gas source pressure within a seal gas source pressure range and the seal gas source pressure is greater than the reference pressure.

41 . The method of claim 40, wherein the seal gas source pressure has a pressure differential within a range from about 345 kPa to about 1 .38 MPa greater than the reference pressure.

42. The method of claim 40, wherein the conditioning system pressure is within the conditioning system pressure range from about 3.79 MPa to about 1 1 .0 MPa.