[0001] This application claims benefit of U.S. Util. Appl. No. 14/051 ,435, entitled "Bypass and Throttle Valves for a Supercritical Working Fluid Circuit," and filed October 1 0, 201 3 and of U.S. Prov. Appl. No. 61 /71 2,91 4, entitled "Bypass and Throttle Valves for a Supercritical Working Fluid Circuit," and filed October 1 2, 2012, which are both incorporated herein by reference in their entirety to the extent consistent with the present application.

Background

[0002] 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.

[0003] Waste heat can be converted into useful energy by a variety of turbine generator 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.

[0004] 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 (HFCs) (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 non- hydrocarbon working fluids, such as ammonia.

[0005] A synchronous power generator is a commonly employed heat engine utilized for generating electrical energy in large scales (e.g., megawatt scale) throughout the world for both commercial and non-commercial use. The synchronous power generator generally supplies electricity to an electrical grid or bus (e.g., an alternating current bus) that usually has a varying load or demand over time. In order to be properly connected, the frequency of the synchronous power generator must be tuned and maintained to match the frequency of the electrical grid or bus. Severe damage may occur to the synchronous power generator as well as the electrical grid or bus should the frequency of the synchronous power generator become un synchronized with the frequency of the electrical grid or bus.

[0006] Turbine generator systems also may suffer an overspeed condition during the generation of electricity - generally - due to high electrical demands during peak usage times. Turbine generator systems may be damaged due to an increasing rotational speed of the moving parts, such as a turbine, a generator, a shaft, and a gearbox. The overspeed condition often rapidly progresses out of control without immediate intervention to reduce the rotational speed of the turbine generator. The overspeed condition causes the temperatures and pressures of the working fluid to increase and the system to overheat. Once overheated, the turbine generator system may incur multiple problems that lead to catastrophic failures of the turbine generator system. The working fluid with an excess of absorbed heat may change to a different state of matter that is outside of the system design, such as a supercritical working fluid transitioning to a fluid in a subcritical state, gaseous state, or other state. The overheated working fluid may escape from the closed system causing further damage.

[0007] Mechanical governor controls have been utilized to provide control - or at least partial control - of the system and to prevent or reduce overspeed conditions in analogous steam-powered generators. The classic flyball governor and the Watt governor were introduced on the earliest steam engines and utilized a rotating assembly of weights (e.g., steel balls) mounted on arms to determine and to regulate the shaft rotational speed. The Gibbs governor - also used on the steam engine - was an improved version of the original flyball governor that was designed to respect the then recently discovery of thermodynamic principals. However, similar mechanical controls are unknown or not common for preventing or reducing overspeed conditions in turbine generator systems utilizing supercritical fluids.

[0008] Therefore, there is a need for a heat engine system and a method for generating electrical energy, whereby generator frequency and rotational speed are precisely and accurately controlled while maximizing the efficiency of the heat engine system to generate electricity.

Summary

[0009] Embodiments of the disclosure generally provide heat engine systems and methods for generating electricity with such systems. In some configurations, the heat engine system may have a turbo pump throttle valve, a power turbine bypass valve, and a power turbine bypass line. In other configurations, the heat engine system may have a turbo pump bypass valve, the turbo pump throttle valve, the power turbine bypass valve, and the power turbine bypass line. The method for generating electricity includes synchronizing a generator frequency of a power generator to a grid frequency of an electrical grid by modulating the turbo pump throttle valve and the power turbine bypass valve during a synchronization process. The heat engine system and the method for generating electricity are configured to efficiently generate valuable electrical energy from thermal energy, such as a heated stream (e.g., a waste heat stream). The heat engine system utilizes a working fluid in a supercritical state (e.g., sc-C0 ₂ ) and/or a subcritical state (e.g., sub-C0 ₂ ) contained within a working fluid circuit for capturing or otherwise absorbing thermal energy of the waste heat stream with one or more heat exchangers. The thermal energy is transformed to mechanical energy by a power turbine and subsequently transformed to electrical energy by the power generator coupled to the power turbine. The heat engine system contains several integrated subsystems managed by a process control system for maximizing the efficiency of the heat engine system while generating electricity. [0010] In one or more embodiments described herein, a method for generating electricity with a heat engine system includes circulating a working fluid within a working fluid circuit by a turbo pump, transferring thermal energy from a heat source stream to the working fluid by at least one heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit, flowing the working fluid through a power turbine and converting the thermal energy in the working fluid to mechanical energy in the power turbine, and converting the mechanical energy into electrical energy by a power generator coupled to the power turbine. The method further includes transferring the electrical energy from the power generator to an electrical grid electrically coupled to the power generator and synchronizing a generator frequency of the power generator to a grid frequency of the electrical grid by modulating a turbo pump throttle valve and a power turbine bypass valve during a synchronization process.

[0011] In some examples, the synchronization process may further include adjusting a flowrate of the working fluid entering the power turbine by modulating the turbo pump throttle valve and the power turbine bypass valve and adjusting the rotational speed of the power turbine by adjusting the flowrate of the working fluid entering the power turbine. The synchronization process may further include adjusting the rotational speed of the power generator by adjusting the rotational speed of the power turbine and adjusting the generator frequency to be synchronized with the grid frequency by adjusting the rotational speed of the power generator.

[0012] In an alternative embodiment, the method may further include controlling the power turbine by modulating the turbo pump throttle valve, the power turbine bypass valve, and a turbo pump bypass valve in order to adjust or otherwise control the flowrate of the working fluid entering the power turbine. The process control system may be configured to synchronize the power generator to the electrical grid by controlling the power turbine while operating the turbo pump throttle valve, the turbo pump bypass valve, and the power turbine bypass valve to adjust the flow of the working fluid.

[0013] In another alternative embodiment, the method may further include controlling the power turbine by modulating one or more valves in order to adjust or otherwise control the flowrate of the working fluid entering the power turbine. The one or more valves may be selected from the turbo pump throttle valve, the power turbine bypass valve, the turbo pump bypass valve, the power turbine throttle valve, the power turbine trim valve, or combinations thereof. The process control system may be operatively connected to the heat engine system and configured to individually adjust one or more valves during the synchronization process.

[0014] In one or more embodiments described herein, the heat engine system for generating electricity has a working fluid circuit with a high pressure side and a low pressure side and containing a working fluid, wherein at least a portion of the working fluid circuit contains the working fluid in a supercritical state. In some exemplary embodiments, the working fluid contains carbon dioxide and at least a portion of the working fluid circuit contains the working fluid in a supercritical state. The heat engine system also has a primary heat exchanger fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit, configured to be fluidly coupled to and in thermal communication with the heat source stream, and configured to transfer thermal energy from the heat source stream to the working fluid. The primary heat exchanger may be fluidly coupled to the working fluid circuit upstream of the power turbine and downstream of a recuperator.

[0015] The heat engine system further contains a power turbine disposed between the high pressure side and the low pressure side of the working fluid circuit, 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. The heat engine system also contains a power generator coupled to the power turbine and configured to convert the mechanical energy into electrical energy and a power outlet electrically coupled to the power generator and configured to transfer the electrical energy from the power generator to power electronics and/or and the electrical grid.

[0016] The heat engine system further contains a turbo pump which has a drive turbine and a pump portion. The pump portion of the turbo pump is configured to pressurize and/or circulate, or otherwise flow or move, the working fluid within the working fluid circuit. The pump portion may be fluidly coupled to the low pressure side of the working fluid circuit by an inlet configured to receive the working fluid from the low pressure side of the working fluid circuit and fluidly coupled to the high pressure side of the working fluid circuit by an outlet configured to release the working fluid into the high pressure side of the working fluid circuit. The drive turbine of the turbo pump is configured to rotate the pump portion and may be fluidly coupled to the high pressure side of the working fluid circuit by an inlet configured to receive the working fluid from the high pressure side of the working fluid circuit and fluidly coupled to the low pressure side of the working fluid circuit by an outlet configured to release the working fluid into the low pressure side of the working fluid circuit.

[0017] The heat engine system further contains a turbo pump throttle valve, a power turbine bypass valve, and a power turbine bypass line. The turbo pump throttle valve and the power turbine bypass valve may be modulated or otherwise adjusted by the process control system which is configured to synchronize a generator frequency of the power generator to a grid frequency of the electrical grid during a synchronization process. The turbo pump throttle valve may be fluidly coupled to the working fluid circuit upstream of the inlet of the drive turbine of the turbo pump and configured to modulate a flow of the working fluid flowing into the drive turbine. The power turbine bypass line may be fluidly coupled to the working fluid circuit at a point disposed upstream of an inlet of the power turbine and at a point disposed downstream of an outlet of the power turbine. The power turbine bypass line is configured to flow the working fluid around and avoid the power turbine. The power turbine bypass valve may be fluidly coupled to the power turbine bypass line and configured to modulate, adjust, or otherwise control a flow of the working fluid flowing through the power turbine bypass line for controlling the flowrate of the working fluid entering the power turbine.

[0018] In some embodiments, the heat engine system further contains a secondary heat exchanger which is generally fluidly coupled to and in thermal communication with the heat source stream and independently fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit, such that thermal energy may be transferred from the heat source stream to the working fluid. The secondary heat exchanger may be fluidly coupled to the working fluid circuit upstream of the outlet of the pump portion of the turbo pump and downstream of the inlet of the drive turbine of the turbo pump. The turbo pump throttle valve may be fluidly coupled to the working fluid circuit downstream of the secondary heat exchanger and upstream of the inlet of the drive turbine of the turbo pump. The working fluid containing the absorbed thermal energy flows from the secondary heat exchanger to the drive turbine of the turbo pump via the turbo pump throttle valve. Therefore, the turbo pump throttle valve may be utilized to control the flowrate of the heated working fluid flowing from the secondary heat exchanger to the drive turbine of the turbo pump.

[0019] In some embodiments, a primary recuperator may be fluidly coupled to the working fluid circuit 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. In other embodiments, a secondary recuperator may be fluidly coupled to the working fluid circuit downstream of the outlet of the pump portion of the turbo pump and upstream of the secondary heat exchanger 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.

Brief Description of the Drawings

[0020] 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.

[0021] Figure 1 illustrates an exemplary heat engine system, according to one or more embodiments disclosed herein.

[0022] Figure 2 illustrates the heat engine system depicted in Figure 1 , including additional components and details, according to one or more embodiments disclosed herein.

Detailed Description [0023] Embodiments of the disclosure generally provide a heat engine system and a method for generating electricity. The heat engine system contains a turbo pump throttle valve, a power turbine bypass valve, and a power turbine bypass line and the method for generating electricity includes modulating the turbo pump throttle valve and the power turbine bypass valve to synchronize a generator frequency of the power generator to a grid frequency of the electrical grid during a synchronization process. The heat engine system and the method for generating electricity are configured to efficiently transform thermal energy of a heated stream (e.g., a waste heat stream) into valuable electrical energy. The heat engine system utilizes a working fluid in a supercritical state (e.g., sc-C0 ₂ ) and/or a subcritical state (e.g., sub-C0 ₂ ) contained within a working fluid circuit for capturing or otherwise absorbing thermal energy of the waste heat stream with one or more heat exchangers. The thermal energy is transformed to mechanical energy by a power turbine and subsequently transformed to electrical energy by the power generator coupled to the power turbine. The heat engine system contains several integrated sub-systems managed by a process control system for maximizing the efficiency of the heat engine system while generating electricity.

[0024] Figures 1 and 2 depict exemplary embodiments of a heat engine system 200 that may be utilized to convert thermal energy into mechanical energy and/or electrical energy. The heat engine system 200 may be referred to as a thermal engine system, a power cycle 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. 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. The illustration of the heat engine system 200 in Figure 2 contains the components and details of the heat engine system 200 in Figure 1 , as well as additional components and details that are not shown in Figure 1 . These additional components and details of the heat engine system 200 in Figure 2 were not depicted in the heat engine system 200 in Figure 1 in order to provide a simplified illustration of the heat engine system 200.

[0025] The heat engine system 200 contains a process system 21 0 and a power generation system 220 that may be fluidly coupled to and in thermal communication with a waste heat system 100 via a working fluid circuit 202, as described in one of more embodiments herein. The working fluid circuit 202 contains a working fluid (e.g., sc-C0 ₂ ) that may be utilized to transfer thermal energy throughout the heat engine system 200. The working fluid circuit 202 has a high pressure side and a low pressure side, as depicted in Figure 2. In some exemplary embodiments, the working fluid contains carbon dioxide and at least a portion of the working fluid circuit 202 contains the working fluid in a supercritical state. The heat engine system 200 also contains a turbo pump 260 coupled to the working fluid circuit 202.

[0026] A heat source stream 1 10 may be flowed or otherwise passed through heat exchangers 120, 130, and/or 150 disposed within the waste heat system 1 00. Each of the heat exchangers 1 20, 130, and/or 150 may be fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202. Also, each of the heat exchangers 1 20, 130, and/or 150 may be configured to be fluidly coupled to and in thermal communication with the heat source stream 1 1 0 so to transfer thermal energy from the heat source stream 1 1 0 to the working fluid within the working fluid circuit 202. The thermal energy is absorbed or otherwise captured by the working fluid to form a heated and pressurized working fluid that may be circulated through the working fluid circuit 202 to deliver or otherwise transfer the captured energy to components of the heat engine system 200, such as a power turbine 228 of the power generation system 220 or a drive turbine 264 of the turbo pump 260.

[0027] The power turbine 228 may be disposed between the high pressure side and the low pressure side of the working fluid circuit 202 and may be fluidly coupled to and in thermal communication with the working fluid flowing through the working fluid circuit 202. The power turbine 228 is 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. A power outlet 236 may be electrically coupled to the power generator 240, power electronics 242, and/or and an electrical grid. The power outlet 236 may be configured to transfer the electrical energy from the power generator 240, optionally through the power electronics 242, to the electrical grid 244.

[0028] The turbo pump 260 may be utilized to circulate and/or pressurize the working fluid throughout the working fluid circuit 202. The turbo pump 260 generally contains at least the drive turbine 264 coupled to a pump portion 262. The pump portion 262 of the turbo pump 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 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. The pump portion 262 may be configured to pressurize and/or circulate, or otherwise flow or move, the working fluid within the working fluid circuit 202. The drive turbine 264 of the turbo pump 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. Also, 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. The drive turbine 264 may be coupled with and configured to rotate the pump portion 262 of the turbo pump 260. In one exemplary embodiment, the drive turbine 264 and the pump portion 262 are coupled together by a shaft 268. The shaft 268 may be a single or common shaft coupled to the drive turbine 264 and the pump portion 262. Alternatively, the shaft 268 may be multiple shafts, such that the drive turbine 264 is coupled to one shaft and the pump portion 262 is coupled to another shaft and the two shafts are coupled together to form the shaft 268.

[0029] The heat engine system 200 further contains a turbo pump throttle valve 263, a power turbine bypass line 208 and a power turbine bypass valve 21 9, and a turbo pump bypass valve 256 and a bypass line 226 operatively connected to the heat engine system 200. Each of the turbo pump throttle valve 263, the power turbine bypass valve 219, and the turbo pump bypass valve 256 may individually be modulated or otherwise adjusted by a process control system 204 operatively connected to the heat engine system 200 and configured to synchronize the generator frequency of the power generator 240 to the grid frequency of the electrical grid 244 during a synchronization process. The turbo pump throttle valve 263 may be fluidly coupled to the working fluid circuit 202, disposed upstream of the inlet of the drive turbine 264 of the turbo pump 260, and configured to modulate a flow of the working fluid flowing into the drive turbine 264. The power turbine bypass line 208 may be fluidly coupled to the working fluid circuit 202 at a point disposed upstream of an inlet of the power turbine 228 and at a point disposed 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 avoid the power turbine 228. 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 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. The turbo pump bypass valve 256 and the bypass line 226 may be configured to control the flowrate of the working fluid exiting the pump portion 262 to divert the working fluid to the condenser 274.

[0030] In some exemplary embodiments, the process control system 204 may be communicably connected to (e.g., wired and/or wirelessly) sensors, valves, pumps, and other components of the working fluid circuit 202 for controlling and managing the heat engine system 200. Sets of sensors may be utilized to measure and report temperatures, pressures, and/or 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, pumps, and/or other components in accordance with a control program or algorithm, thereby maximizing operation of the heat engine system 200.

[0031] At least one computer or processor, such as a computer system 206, as part of the process control system 204 may be utilized for controlling the heat engine system 200. The computer system 206 generally has a multi-controller algorithm utilized to control the bypass valve 1 62, the power turbine bypass valve 21 9, the turbo pump bypass valve 256, and/or the turbo pump throttle valve 263, 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 bypass valve 1 62, the power turbine throttle valve 250, and/or 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.

[0032] The heat engine system 200 also contains a recuperator 21 6, a recuperator 218, and a condenser 274 fluidly coupled to the working fluid circuit 202. The recuperators 216 and 218 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 one exemplary embodiment, the recuperator 216, the recuperator 21 8, and the condenser 274 are disposed in series on the low pressure side of the working fluid circuit 202. In another exemplary embodiment, the recuperator 216 and the recuperator 218 are disposed in parallel on the high pressure side of the working fluid circuit 202.

[0033] Each of the recuperators 21 6 and 21 8 and the condenser 274 may independently be a heat exchanger, such as a recuperator or a cooler/condenser. The recuperators 216 and 21 8 and the condenser 274 may be utilized to remove or otherwise transfer thermal energy from the working fluid flowing through the low pressure side of the working fluid circuit 202, such as the working fluid released from the outlet of the power turbine 228 and/or the outlet of the drive turbine 264. In addition, the recuperator 21 6 may be configured to heat the working fluid flowing downstream of the heat exchanger 1 30, a power turbine throttle valve 250, and/or a power turbine trim valve 252 and upstream of the heat exchanger 120 and/or the inlet of the power turbine 228 in the high pressure side of the working fluid circuit 202. The recuperator 21 8 may be configured to heat the working fluid flowing downstream of a valve 293, the pump portion 262, and/or the pump portion 282 and upstream of the heat exchanger 1 50 and/or the inlet of the drive turbine 264 in the high pressure side of the working fluid circuit 202.

[0034] In another exemplary embodiment described herein, a method for generating electricity with a heat engine system, such as the heat engine system 200, is provided and includes circulating or otherwise flowing a working fluid within the working fluid circuit 202 by the turbo pump 260 and transferring thermal energy from the heat source stream 1 10 to the working fluid by at least one heat exchanger, such as the heat exchanger 1 20, fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202. The method further includes flowing the working fluid through the power turbine 228 and converting the thermal energy in the working fluid to mechanical energy in the power turbine 228, and converting the mechanical energy into electrical energy by the power generator 240 coupled to the power turbine 228. The method further includes transferring the electrical energy from the power generator 240 to the electrical grid 244 electrically coupled to the power generator 240 and synchronizing a generator frequency of the power generator 240 to a grid frequency of the electrical grid 244. In some examples, the generator frequency of the power generator 240 may be synchronized to a grid frequency of the electrical grid 244 by modulating the turbo pump throttle valve 263 and the power turbine bypass valve 219, or alternatively, by modulating the turbo pump throttle valve 263, the turbo pump bypass valve 256, and the power turbine bypass valve 21 9 during a synchronization process.

[0035] Broadly, the method may include controlling the power turbine 228 by modulating one or more valves in order to adjust or otherwise control the flowrate of the working fluid entering the power turbine 228. The one or more valves may be selected from the turbo pump throttle valve 263, the power turbine bypass valve 21 9, the turbo pump bypass valve 256, the power turbine throttle valve 250, the power turbine trim valve 252, or combinations thereof. The process control system 204 may be operatively connected to the heat engine system 200 and configured to individually adjust one or more valves during the synchronization process. The process control system 204 may be configured to synchronize the generator frequency of the power generator 240 to the grid frequency of the electrical grid 244 by controlling the power turbine 228 while operating the turbo pump throttle valve 263, the power turbine bypass valve 21 9, and optionally the turbo pump bypass valve 256 to adjust the flow of the working fluid within the working fluid circuit 202.

[0036] In some exemplary embodiments, the synchronization process may include adjusting the flowrate of the working fluid entering the power turbine 228 by modulating the turbo pump throttle valve 263 and the power turbine bypass valve 219 in order to adjust or otherwise control the rotational speed of the power turbine 228 by adjusting the flowrate of the working fluid entering the power turbine 228. Therefore, the rotational speed of the power turbine 228 may be controlled by modulating the turbo pump throttle valve 263 and the power turbine bypass valve 219 in order to adjust or otherwise control the flowrate of the working fluid entering the power turbine 228.

[0037] In other exemplary embodiments, the synchronization process may include adjusting the flowrate of the working fluid entering the power turbine 228 by modulating the turbo pump throttle valve 263, the turbo pump bypass valve 256, and the power turbine bypass valve 219 in order to adjust or otherwise control the rotational speed of the power turbine 228 by adjusting the flowrate of the working fluid entering the power turbine 228. Therefore, the rotational speed of the power turbine 228 may be controlled by modulating the turbo pump throttle valve 263, the turbo pump bypass valve 256, and the power turbine bypass valve 21 9 in order to adjust or otherwise control the flowrate of the working fluid entering the power turbine 228. The synchronization process may further include adjusting the rotational speed of the power generator 240 by adjusting the rotational speed of the power turbine 228 and adjusting the generator frequency to be synchronized with the grid frequency by adjusting the rotational speed of the power generator 240.

[0038] In another embodiment, as depicted in Figure 2, the waste heat system 100 of the heat engine system 200 contains the heat exchangers 1 20, 1 30, and 1 50 fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit 202 and the heat source stream 1 1 0. 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, 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) may be fluidly coupled to and in thermal communication with the working fluid circuit 202. In one exemplary configuration, the heat exchanger 120 may be the primary heat exchanger fluidly coupled to the high pressure side of the working fluid circuit 202 downstream of the recuperator 216 and upstream of an inlet on the power turbine 228, the heat exchanger 150 may be the secondary heat exchanger fluidly coupled to the high pressure side of the working fluid circuit 202 downstream of the recuperator 218 and upstream of an inlet on the drive turbine 264 of the turbine pump 260, and the heat exchanger 130 may be the tertiary heat exchanger fluidly coupled to the high pressure side of the working fluid circuit 202 downstream of the power turbine throttle valve 250 and upstream of the recuperator 216.

[0039] 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 1 04, 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 1 0 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, 1 50, and/or additional heat exchangers in other desired orders.

[0040] The heat source stream 1 10 may be a waste heat stream such as, but not limited to, gas turbine exhaust streams, industrial process exhaust streams, 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, and 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.

[0041] 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 (HFCs) (e.g., 1 ,1 ,1 ,3,3-pentafluoropropane (R245fa)), fluorocarbons, derivatives thereof, or mixtures thereof.

[0042] 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 (C0 ₂ ) 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-C0 ₂ ). Carbon dioxide utilized as the working fluid or contained in the working fluid for power generation cycles has many advantages over other compounds typical 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 (C0 ₂ ), supercritical carbon dioxide (sc-C0 ₂ ), or subcritical carbon dioxide (sub-C0 ₂ ) is not intended to limit 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.

[0043] 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-C0 ₂ or sc-C0 ₂ ) 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.

[0044] 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.

[0045] Generally, the high pressure side of the working fluid circuit 202 contains the working fluid (e.g., sc-C0 ₂ ) at a pressure of about 1 5 MPa or greater, such as about 1 7 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 1 5 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 1 7 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 MPa, and more narrowly within a range from about 22 MPa to about 24 MPa, such as about 23 MPa.

[0046] The low pressure side of the working fluid circuit 202 contains the working fluid (e.g., C0 ₂ or sub-C0 ₂ ) at a pressure of less than 1 5 MPa, such as about 12 MPa or less or about 1 0 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 1 2 MPa, and more narrowly within a range from about 1 0 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 1 0 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 MPa.

[0047] The power turbine 228 of the heat engine system 200 may be 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 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.

[0048] 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 1 20. 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 turbines 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.

[0049] The power turbine 228 is generally coupled to the power generator 240 by a shaft 230. A gearbox 232 is generally disposed between the power turbine 228 and the power generator 240 and adjacent or encompassing the shaft 230. The shaft 230 may be a single piece or contain two or more pieces coupled together. In one example, a first segment of the shaft 230 extends from the power turbine 228 to the gearbox 232, a second segment of the shaft 230 extends from the gearbox 232 to the power generator 240, and multiple gears are disposed between and coupled to the two segments of the shaft 230 within the gearbox 232.

[0050] In some configurations, the heat engine system 200 also provides for the delivery of a portion of the working fluid, seal gas, bearing gas, air, or other gas into a chamber or housing 238 of the power generator 240 for purposes of cooling one or more parts of the power turbine 228. In other configurations, the shaft 230 includes a seal assembly (not shown) designed to prevent or capture any working fluid leakage from the power turbine 228. Additionally, a working fluid recycle system may be implemented along with the seal assembly to recycle seal gas back into the working fluid circuit 202 of the heat engine system 200.

[0051] 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 shaft 230 and the power turbine 228 to electrical energy. Generally, the power generator 240 may be electrically coupled to the electrical grid 244 by the power outlet 236 and optionally through the power electronics 242. The power outlet 236 may be configured to transfer the generated electrical energy from the power generator 240, through the power electronics 242, and to the electrical grid 244. The electrical grid 244 may be or include an electrical grid, an electrical bus (e.g., plant bus), power/electronic equipment, 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 an exemplary embodiment, the power generator 240 is a generator or an alternator and may be electrically and operably connected to the power electronics 242 and/or the electrical grid 244 via the power outlet 236. Figures 1 and 2 depict the power generator 240, the power outlet 236, the power electronics 242, and the electrical grid 244 electrically connected in series. However, in other embodiments, the power generator 240 may be electrically and operably connected to the electrical grid 244 with or without the power outlet 236 and/or the power electronics 242.

[0052] The power electronics 242 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 242 may include converters or rectifiers, inverters, transformers, regulators, controllers, switches, resisters, storage devices, electrical contacts, 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 (not shown) 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/or the power electronics 242 by circulating the cooling fluid to draw away generated heat.

[0053] In another exemplary embodiment, the heat engine system 200 may be configured to deliver 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 is 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 is directed to one or more heat exchangers or recuperators, such as recuperators 21 6 and 218. The recuperators 21 6 and 218 may be fluidly coupled to the working fluid circuit 202 in series with each other. The recuperators 216 and 218 are operative to transfer thermal energy between the low and high pressure sides of the working fluid circuit 202, such as from the low pressure side to the high pressure side.

[0054] In one embodiment, the recuperator 21 6 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 21 6 is configured to remove at least a portion of thermal energy from the working fluid discharged from the power turbine 228. In addition, the recuperator 21 6 is also 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 on the power turbine 228, and disposed downstream of the heat exchanger 1 30. The recuperator 216 may be configured to increase the amount of thermal energy absorbed by the working fluid prior to the working fluid flowing through the heat exchanger 120 and/or the power turbine 228. Therefore, the recuperator 21 6 is operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. For example, the recuperator 21 6 may be configured to transfer thermal energy from the working fluid contained in the low pressure side to the working fluid contained in the high 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 from or downstream of the power turbine 228 while heating the high pressurized working fluid entering into or upstream of the heat exchanger 1 20 and/or the power turbine 228.

[0055] 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 21 6, and disposed upstream of the condenser 274. The recuperator 21 8 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 21 6. In addition, the recuperator 21 8 is also fluidly coupled to the high pressure side of the working fluid circuit 202, disposed upstream of the heat exchanger 1 50 and/or a working fluid inlet on the drive turbine 264 of the turbo pump 260, and disposed downstream of a working fluid outlet on the pump portion 262 of turbo pump 260. The recuperator 21 8 is configured to increase the amount of thermal energy in the working fluid prior to flowing into the heat exchanger 1 50 and/or the drive turbine 264. Therefore, the recuperator 218 is operative to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit 202. For example, the recuperator 21 8 may be configured to transfer thermal energy from the low pressure side to the high pressure side. In some examples, the recuperator 218 may be a heat exchanger configured to cool the low pressurized working fluid discharged from 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 1 50 and/or the drive turbine 264.

[0056] The 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 21 6 and 21 8 and upstream of the start pump 280 and the turbo pump 260. The condenser 274 receives the cooled working fluid from the recuperator 21 8 and further cools and/or condenses the working fluid which may be recirculated throughout the working fluid circuit 202. In some exemplary embodiments, 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.

[0057] 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 compound or multiple compounds and may be in a single state of matter or multiple states of matter throughout the working fluid circuit 202. 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.

[0058] In some exemplary embodiments, 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 is 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 (not shown). A filter 276 may be disposed along and in fluid communication with the cooling fluid line at a point disposed 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.

[0059] The heat engine system 200 further contains several pumps, such as the turbo pump 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. The turbo pump 260 and the start pump 280 are operatively configured to circulate the working fluid throughout the working fluid circuit 202. The start pump 280 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 turbo pump 260 may be utilized to circulate the working fluid during the electricity generation process. The working fluid enters each of the turbo pump 260 and the start pump 280 from the low pressure side of the working fluid circuit 202 and exits each of the turbo pump 260 and the start pump 280 from the high pressure side of the working fluid circuit 202.

[0060] 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 drive shaft 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/supply 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.

[0061] Valves 283 and 285 may be utilized to isolate the pump portion 282 of the start pump 280 from the working fluid circuit 202 and/or to control the flow of the working fluid passing through the start pump 280. Valves 283 and 285 may be utilized to prevent leakage of the working fluid via the pump seals. Valve 285 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. Valve 283 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.

[0062] The turbo pump 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 turbo pump 260 contains the pump portion 262 and the drive turbine 264 coupled together by a drive shaft 268 and optional gearbox (not shown). The pump portion 262 of the turbo pump 260 is driven by the drive shaft 268 coupled to the drive turbine 264. The pump portion 262 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/supply system 290. Also, the pump portion 262 has an outlet for releasing the working fluid into the high pressure side of the working fluid circuit 202.

[0063] The drive turbine 264 of the turbo pump 260 is driven by heated working fluid, such as the working fluid heated by the heat exchanger 1 50. The drive turbine 264 has an inlet for receiving the working fluid flowing from the heat exchanger 1 50 in the high pressure side of the working fluid circuit 202. The drive turbine 264 has an outlet for releasing the working fluid into the low pressure side of the working fluid circuit 202. 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 turbo pump 260, including piping and valves, is optionally disposed on a turbo pump skid 266, as depicted in Figure 2. The turbo pump skid 266 may be disposed on or adjacent to the main process skid 212.

[0064] A bypass valve 265 is generally coupled between and in fluid communication with a fluid line extending from the inlet on the drive turbine 264 with a fluid line extending from the outlet on the drive turbine 264. The bypass valve 265 is generally opened to bypass the turbo pump 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 bypass valve 265 is closed and the heated working fluid is flowed through the drive turbine 264 to start the turbo pump 260.

[0065] The turbo pump throttle valve 263 may be coupled between and in fluid communication with a fluid line extending from the heat exchanger 1 50 to the inlet on the drive turbine 264 of the turbo pump 260. The turbo pump throttle valve 263 is 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, the valve 293 fluid coupled to a fluid line 291 may be utilized to provide back-pressure at point 289 along the fluid line 291 downstream of the pump portion 262 of the turbo pump 260 and upstream of the drive turbine 264 of the turbo pump 260. The valve 295 is generally an attemperator valve utilized by the turbo pump 260.

[0066] A control valve 261 may be disposed downstream of the outlet of the pump portion 262 of the turbo pump 260 and a control valve 281 may be disposed downstream of the outlet of the pump portion 282 of the start pump 280. The control valves 261 and 281 are flow control safety valves and are generally utilized to regulate the directional flow or to prohibit backflow of the working fluid within the working fluid circuit 202. The 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 turbo pump 260. Similarly, the 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.

[0067] In one or multiple embodiments described herein, the turbo pump throttle valve 263 and the power turbine bypass valve 21 9 may be modulated or otherwise adjusted to change the flow of the working fluid while synchronizing the generator frequency of the power generator 240 to the grid frequency of the electrical grid 244 during the synchronization process. Alternatively, the turbo pump throttle valve 263, the turbo pump bypass valve 256, and the power turbine bypass valve 21 9 may be modulated or otherwise adjusted to change the flow of the working fluid during the synchronization process. In one embodiment, the turbo pump throttle valve 263 may be utilized as a course adjuster and the power turbine bypass valve 219 may be utilized as a fine adjuster of flowrate of the working fluid entering the power turbine 228 and the tuning of the generator frequency of the power generator 240 during the synchronization process.

[0068] The turbo pump throttle valve 263 may be fluidly coupled to the working fluid circuit 202 upstream of the inlet of the drive turbine 264 of the turbo pump 260 and configured to modulate a flow of the working fluid flowing into the drive turbine 264. The power turbine bypass valve 21 9 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.

[0069] The power turbine bypass line 208 may be fluidly coupled to the working fluid circuit 202 at a point disposed upstream of an inlet of the power turbine 228 and at a point disposed downstream of an outlet of the power turbine 228. The power turbine bypass line 208 is configured to flow the working fluid around and avoid 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 21 9 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.

[0070] The power turbine bypass valve 219, the turbo pump bypass valve 256, and/or the turbo pump 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 21 9, the turbo pump 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 may be enabled to monitor and control multiple process operation parameters of the heat engine system 200.

[0071] In one embodiment, the working fluid circuit 202 contains a bypass flowpath for the working fluid exiting the pump portion 282 of the start pump 280 via the bypass line 224 and a bypass valve 254. Also, in another embodiment, the working fluid circuit 202 contains a bypass flowpath for the working fluid exiting the pump portion 262 of the turbo pump 260 via the bypass line 226 and the bypass valve 256. During various operations periods of the heat engine system 200, such as at startup, shutdown, or an emergency, the working fluid may be directed from the pump portion 282 of the start pump 280 and/or the pump portion 262 of the turbo pump 280 directly to the condenser 274 while circumventing or otherwise bypassing major components of the heat engine system 200, such as the heat exchangers 1 20, 130, and/or 1 50, the power turbine 228, the drive turbine 264, and other components.

[0072] One end of the bypass line 224 may be fluidly coupled to the working fluid circuit 202 downstream of an outlet of the pump portion 282 of the start pump 280, and the other end of the bypass line 224 may be fluidly coupled to the bypass line 226 or a fluid line 229. Similarly, one end of the bypass line 226 may be fluidly coupled to the working fluid circuit 202 downstream of an outlet of the pump portion 262 of the turbo pump 260 and the other end of the bypass line 226 is coupled to the bypass line 224. In one exemplary configuration, as depicted in Figure 2, the bypass lines 224 and 226 merge together downstream as a single line that is fluidly coupled to the fluid line 229. The fluid line 229 may be fluidly coupled to the recuperator 21 8 and the condenser 274 on the low pressure side, such that the working fluid exits the recuperator 218 and flows to the condenser 274. The bypass valve 254 may be disposed along the bypass line 224 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202 when in a closed position. Similarly, the bypass valve 256 may be disposed along the bypass line 226 and fluidly coupled between the low pressure side and the high pressure side of the working fluid circuit 202 when in a closed position.

[0073] Figure 2 further depicts the 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 1 20, as disclosed by at least one embodiment described herein. The power turbine throttle valve 250 may be used to modulate the circulation of the working fluid throughout the working fluid circuit 202. The power turbine throttle valve 250 may be fluidly coupled to the bypass line 246 and configured to modulate, adjust, or otherwise control the flowrate of the working fluid passing through the bypass line 246 which provides control and adjustability of a general coarse 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 disposed upstream of the valve 293 and at a point disposed downstream of the pump portion 282 of the start pump 280 and/or the pump portion 262 of the turbo pump 260. Additionally, the 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 1 50, 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 disposed upstream of the power turbine throttle valve 250 and at a point disposed downstream of the power turbine throttle valve 250.

[0074] The fluid line 291 may be fluidly coupled to the working fluid circuit 202 downstream of both the pump portion 262 of the turbo pump 260 and the pump portion 282 of the start 280. Also, the fluid line 291 may be fluidly coupled to the working fluid circuit 202 upstream of the valve 293, the bypass lines 246, 248, the power turbine throttle valve 250, and the power turbine trim valve 252. In one exemplary embodiment, the working fluid may be flowed from the pump portion 262 and/or the pump portion 282, through the fluid line 291 , through the bypass line 246 and the power turbine throttle valve 250 and/or the bypass line 248 and the power turbine trim valve 252, through a fluid line 1 31 , optionally through the heat exchanger 1 30, through the recuperator 21 6 on the high pressure side, through the heat exchanger 120, and to the power turbine 228.

[0075] In an alternative embodiment, the power turbine throttle valve 250 and the power turbine trim valve 252 are configured to control a flow of the working fluid throughout the working fluid circuit 202 during a synchronization process. In one or multiple embodiments described herein, the power turbine throttle valve 250 and the power turbine trim valve 252 may be modulated or otherwise adjusted to change the flow of the working fluid while synchronizing the generator frequency of the power generator 240 to the grid frequency of the electrical grid 244 during the synchronization process. In one embodiment, the power turbine throttle valve 250 may be utilized as a course adjuster and the power turbine trim valve 252 may be utilized as a fine adjuster of flowrate of the working fluid entering the power turbine 228 and the tuning of the generator frequency of the power generator 240 during the synchronization process. The power turbine throttle valve 250 and the power turbine trim valve 252 may be independently controlled by the process control system 204 that is communicably connected, wired and/or wirelessly, with the power turbine throttle valve 250, the power turbine trim valve 252, and other parts of the heat engine system 200.

[0076] In one exemplary embodiment, a bypass line 160 may be fluidly coupled to a fluid line 1 31 of the working fluid circuit 202 upstream of the heat exchangers 1 20, 130, and/or 1 50 by a bypass valve 1 62, as illustrated in Figure 2. The bypass valve 1 62 may be a solenoid valve, a hydraulic valve, an electric valve, a manual valve, or derivatives thereof. In some exemplary embodiments, the bypass valve 1 62 is a solenoid valve and configured to be controlled by the process control system 204. The bypass valve 1 62 may have multiple positions for allowing, stopping, and/or redirecting the passage of the working fluid within the working fluid circuit 202. The bypass valve 162 may be positioned in multiple positions to control the flow of the working fluid within the working fluid circuit 202 during various segments of the electricity generation processes described herein. In a first position, the bypass valve 1 62 is configured to flow the working fluid from the power turbine throttle valve 250, through the fluid line 131 , through the bypass valve 162, through the bypass line 1 60 while avoiding the heat exchanger 1 30 and the fluid line 1 33, through the fluid line 1 35, and then through the recuperator 216, the heat exchanger 120, the inlet of the power turbine 228, and the fluid lines therebetween. In a second position, the bypass valve 162 is configured to flow the working fluid from the power turbine throttle valve 250, through the fluid line 1 31 , through the bypass valve 162, through the heat exchanger 130 and the fluid line 1 33 while avoiding the bypass line 1 60, through the fluid line 1 35, and then through the recuperator 216, the heat exchanger 120, the inlet of the power turbine 228, and the fluid lines therebetween. In a third position, the bypass valve 1 62 is configured to stop the flow the working fluid at the bypass valve 1 62 while avoiding the bypass line 160 and avoiding the heat exchanger 1 30 and the fluid line 1 33.

[0077] In one or more embodiments, the working fluid circuit 202 contains release valves 213a, 21 3b, 21 3c, and 21 3d, as well as release outlets 21 4a, 214b, 214c, and 214d, respectively in fluid communication with each other. Generally, the release valves 213a, 213b, 213c, and 21 3d 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 21 3d, the working fluid may be vented through the respective release outlet 21 4a, 214b, 214c, or 21 4d. The release outlets 214a, 214b, 214c, and 21 4d may provide passage of the working fluid into the ambient surrounding atmosphere, such as to reduce pressure in the working fluid circuit 202 if over- pressurized or during an emergency shut-down process. Alternatively, the release outlets 21 4a, 21 4b, 21 4c, and 21 4d may provide passage of the working fluid into a recycling or reclamation step that generally includes capturing, condensing, and storing the working fluid.

[0078] The release valve 21 3a and the release outlet 21 4a 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 21 3b and the release outlet 21 4b are fluidly coupled to the working fluid circuit 202 at a point disposed between the heat exchanger 1 50 and the turbo portion 264 of the turbo pump 260. The release valve 213c and the release outlet 21 4c 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 turbo pump 260 to a point on the bypass line 226 between the bypass valve 256 and the fluid line 229. The release valve 213d and the release outlet 21 4d are fluidly coupled to the working fluid circuit 202 at a point disposed between the recuperator 218 and the condenser 274.

[0079] 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 may be utilized to control 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. [0080] The mass management system 270 contains at least one or more vessels or tanks, such as a mass control tank 286 and at least one or more valves, such as a control valve 287 fluidly coupled to the low pressure side of the working fluid circuit 202. 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 working fluid circuit 202 when needed in order to regulate the pressure and/or temperature of the working fluid within the working fluid circuit 202 or otherwise supplement escaped working fluid. The control valve 287 is 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. 1 3/278,705, filed October 21 , 201 1 , and published as U.S. Pub. No. 201 2- 0047892, which is incorporated herein by reference in its entirety to the extent consistent with the present application. 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. In one exemplary embodiment, by adjusting the control valve 287, the mass management system 270 may add and/or remove 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. In some configurations, multiple connection points and valves may be configured to provide the mass management system 270 with one or more outlets 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.

[0081] In another exemplary embodiment, the mass management system 270 may further contain a working fluid storage/supply system 290 that includes a working fluid storage vessel 292 and a working fluid feed 288. The working fluid storage vessel 292 may be a storage vessel/tank or a fill vessel/tank. The working fluid feed 288 and/or other connection points, may be utilized as a fluid fill port for the working fluid storage vessel 292 of the working fluid storage/supply 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, which is incorporated herein by reference in its entirety to the extent consistent with the present application.

[0082] In embodiments described herein, bearing gas and/or seal gas may be supplied to the power turbine 228 or other devices contained within and/or utilized along with the heat engine system 200. Also, the turbo pump 260 may be supplied bearing gas or a portion of the working fluid from the mass management system 270, the bearing gas supply 296, and/or a fluid line (not shown) extending from the pump discharge of the turbo pump 260. 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 supply 296 and the seal gas supply 298 are connection points that feed into a bearing gas system or a seal gas 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 for the power turbine 228 is generally fluidly coupled to the working fluid circuit 202 upstream of the condenser 274 and downstream of the recuperator 218.

[0083] In one exemplary configuration, 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 may be arranged at or adjacent the suction inlet of the turbo pump 260 and the start pump 280 and the second set of sensors may be arranged at or adjacent the outlet of the turbo pump 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 turbo pump 260 and the start pump 280. The third set of sensors may be arranged either inside or adjacent the working fluid storage vessel 292 of the working fluid storage/supply 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 and/or the mass management system 270 that may utilize a gaseous source, such as nitrogen or air.

[0084] In some embodiments described herein, the waste heat system 1 00 may be disposed on and/or within a waste heat skid 1 02 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.

[0085] In one or more configurations, the waste heat system 1 00 disposed on or in the waste heat skid 1 02 generally contains inlets 1 22, 1 32, and 1 52 and outlets 1 24, 1 34, and 1 54 fluidly coupled to and in thermal communication with the working fluid within the working fluid circuit 202. The inlet 1 22 may be disposed upstream of the heat exchanger 1 20 and the outlet 124 may be disposed downstream of the heat exchanger 1 20. The working fluid circuit 202 is configured to flow the working fluid from the inlet 1 22, through the heat exchanger 1 20, and to the outlet 1 24 while transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 1 20. The inlet 152 may be disposed upstream of the heat exchanger 150 and the outlet 154 may be disposed downstream of the heat exchanger 1 50. The working fluid circuit 202 is configured to flow the working fluid from the inlet 152, through the heat exchanger 1 50, and to the outlet 1 54 while transferring thermal energy from the heat source stream 1 10 to the working fluid by the heat exchanger 1 50. The inlet 132 may be disposed upstream of the heat exchanger 1 30 and the outlet 134 may be disposed downstream of the heat exchanger 130. The working fluid circuit 202 is configured to flow the working fluid from the inlet 1 32, 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 1 30.

[0086] In one or more configurations, the power generation system 220 may be disposed on or in the power generation skid 222 and generally 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 disposed 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 1 24 of the waste heat system 1 00 and configured to receive the working fluid flowing from the heat exchanger 1 20 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 turbo pump 260 and/or the start pump 280. The outlet 227 may be disposed downstream of the power turbine 228 within the low pressure side of the working fluid circuit 202 and is 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 21 6.

[0087] A filter 21 5a may be disposed along and in fluid communication with the fluid line at a point disposed downstream of the heat exchanger 1 20 and upstream of the power turbine 228. In some examples, the filter 21 5a 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 21 0.

[0088] The portion of the working fluid circuit 202 within the power generation system 220 is fed the working fluid by the inlets 225a and 225b. A stop valve 21 7 may be fluidly coupled to the working fluid circuit 202 between the inlet 225a and the power turbine 228. The stop valve 217 is configured to control the flow of heated working fluid flowing from the heat exchanger 1 20, through the inlet 225a, and into the power turbine 228 while in an opened position. Alternatively, the stop valve 21 7 may be configured to cease the flow of working fluid from entering into the power turbine 228 while in a closed position.

[0089] An attemperator valve 223 may be fluidly coupled to the working fluid circuit 202 between the inlet 225b and the stop valve 217 upstream of a point on the fluid line that intersects the incoming stream from the inlet 225a. The attemperator valve 223 is configured to control the flow of heated working fluid flowing from the start pump 280 and/or the turbo pump 260, through the inlet 225b, and to a stop valve 21 7, the power turbine bypass valve 219, and/or the power turbine 228.

[0090] 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 stop valve 217 and downstream of the power turbine 228. Therefore, the bypass line and the power turbine bypass valve 21 9 are configured to direct the working fluid around and avoid the power turbine 228. If the stop valve 21 7 is in a closed position, the power turbine bypass valve 21 9 may be configured to flow the working fluid around and avoid the power turbine 228 while in an opened position. In one embodiment, the power turbine bypass valve 21 9 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.

[0091] In one or more configurations, the process system 210 may be disposed on or in the main process skid 21 2 generally 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 1 54 is downstream of the recuperator 216. The working fluid circuit 202 is configured to flow the working fluid from the inlet 235, through the recuperator 21 6, 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 21 6. The outlet 241 of the process system 210 is downstream of the turbo pump 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 21 6, 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 21 0 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 1 50. The inlet 255 is downstream of the heat exchanger 150, upstream of the drive turbine 264 of the turbo pump 260, and configured to provide the heated high pressure working fluid flowing from the heat exchanger 1 50 to the drive turbine 264 of the turbo pump 260. The outlet 253 of the process system 21 0 is downstream of the pump portion 262 of the turbo pump 260 and/or the pump portion 282 of the start pump 280, couples a bypass line disposed downstream of the heat exchanger 1 50 and upstream of the drive turbine 264 of the turbo pump 260, and configured to provide a flow of working fluid to the drive turbine 264 of the turbo pump 260.

[0092] Additionally, a filter 21 5c may be disposed along and in fluid communication with the fluid line at a point disposed downstream of the heat exchanger 1 50 and upstream of the drive turbine 264 of the turbo pump 260. In some examples, the filter 21 5c may be fluidly coupled to the working fluid circuit 202 between the outlet 154 of the waste heat system 1 00 and the inlet 255 of the process system 210.

[0093] In another embodiment described herein, as depicted in Figure 2, the heat engine system 200 contains the process system 21 0 disposed on or in a main process skid 21 2, the power generation system 220 disposed on or in a power generation skid 222, 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 21 2, the power generation skid 222, the waste heat skid 102, as well as other skids, systems, and portions of the heat engine system 200. In some embodiments, the heat engine system 200 contains the bypass line 160 and the bypass valve 1 62 disposed between the waste heat skid 102 and the main process skid 21 2. A filter 215b may be disposed along and in fluid communication with the fluid line 1 35 at a point disposed downstream of the heat exchanger 1 30 and upstream of the recuperator 216. In some examples, the filter 21 5b 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.

[0094] In one or more embodiments described herein, power generation onto the electrical grid 244 may be achieved with precise and accurate control of the rotational speed of turbo machinery and related components, such as the power turbine 228, the shaft 230, the gearbox 232, and/or the power generator 240. In one exemplary embodiment, the power turbine trim valve 252 and the bypass line 248 may be utilized by the heat engine system 200 to provide precise and accurate control of the rotational speed of the power turbine 228 and the power generator 240. However, the power turbine trim valve 252 is a sophisticated electro-hydraulic valve that is expensive, provides additional complexity to the heat engine system 200, and is prone to failure.

[0095] Therefore, in another embodiment, the turbo pump throttle valve 263 and the power turbine bypass valve 21 9 may be modulated or otherwise adjusted to change the flow of the working fluid while synchronizing the generator frequency of the power generator 240 to the grid frequency of the electrical grid 244 during a synchronization process. The power turbine bypass valve 219 controls the flowrate of the working fluid through the power turbine bypass line 208. The power turbine trim valve 252 and the bypass line 248 may be removed from the heat engine system 200 or alternatively, the power turbine trim valve 252 may be left in an opened position while utilizing the turbo pump throttle valve 263, the power turbine bypass valve 219, and the power turbine bypass line 208 during the synchronization process. In some examples, the same or greater flow control sensitivity of the working fluid is provided by the power turbine bypass valve 219 and the turbo pump throttle valve 263 as obtained by the power turbine trim valve 252.

[0096] The turbo pump throttle valve 263 essentially builds the pressure within the working fluid circuit 202 at point 289 which provides the system energy, such as a backpressure. The turbo pump bypass valve 256 diverts flow of the working fluid from the high pressure side, provided by the turbo pump 262 to the low pressure side 229 also affecting pressure. Such energy may be converted to mechanical energy and the backpressure may be modulated to synchronize the generator frequency to the grid frequency. The power turbine bypass valve 21 9 and the power turbine bypass line 208 redirect a portion of the working fluid around the power turbine 228 thus reducing or increasing the effect of system pressure (point 289) on the turbo machinery, the power turbine 228, the shaft 230, the gearbox 232, and/or the power generator 240.

[0097] It is to be understood that the present disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the disclosure. 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, e.g., any element from one exemplary embodiment may be used in any other exemplary embodiment without departing from the scope of the disclosure.

[0098] Additionally, certain terms are used throughout the written description and claims for referring 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 disclosure, 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 written description and 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. [0099] 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.