Patent ID: 12253024

DETAILED DESCRIPTION

Embodiments of the present disclosure are described below in detail with reference to the accompanying figures. Like elements in the various figures may be denoted by like reference numerals for consistency. Further, in the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the claimed subject matter. However, it will be apparent to one having ordinary skill in the art that the embodiments described may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description. As used herein, the term “coupled” or “coupled to” or “connected” or “connected to” may indicate establishing either a direct or indirect connection and is not limited to either unless expressly referenced as such. As used herein, fluids may refer to slurries, liquids, gases, and/or mixtures thereof. Wherever possible, like or identical reference numerals are used in the figures to identify common or the same elements. The figures are not necessarily to scale, and certain features and certain views of the figures may be shown exaggerated in scale for purposes of clarification.

In one aspect, embodiments disclosed herein relate to a power generation system for electricity generation, petrochemical plants, waste heat recovery, and other industrial applications. The power generation system may also be interchangeably referred to as a recuperative heat exchanger system as a network or assembly of heat exchangers in the present disclosure. Additionally, the recuperative heat exchanger system may incorporate a precooling section to reduce turbine exhaust gas temperature. The recuperative heat exchanger system may minimize life cycle cost of heat exchangers that are critical to efficient recuperative thermal energy exchange at high pressure and with high thermal effectiveness. In some embodiments, the recuperative heat exchanger system may be used for Supercritical Carbon Dioxide (SCCO2) power cycles, such as an Allam cycle.

Recuperative heat exchanger systems, according to embodiments herein, may include a combination of Printed Circuit type (PCHE) and Shell and Tube type (STHE) heat exchangers. For example, the recuperative heat exchanger system may include a precool section, a major heating section (recycle heating), and a minor heating section (oxidant heating). In some embodiments, a heat recovery section may be optionally connected to the major heating section and/or the minor heating section.

In one or more embodiments, the recuperative heat exchanger system may use a heat exchanger network that incorporates parallel sections for heating of a minor portion of a high-pressure gas and a major portion of the high-pressure gas. The minor portion may consist of the oxygen containing CO2 (Oxidant) and the major portion may consist of the balance of the recirculated CO2 (Recycle CO2). The two parallel sections may have substantially different temperature profiles. In a non-limiting example, the major portion (about 75% of a total flow, in a range 51-90%) may be heated to a lower temperature than the minor portion. The minor portion may be first heated to an intermediate temperature of approximately 440° C. (in a range of 350-550° C.) before being used to precool the entire high temperature exhaust stream from a high temperature approximate 600° C. (in a range of 550-850° C.) to a temperature low enough to avoid a significant mechanical design constraint, and in particular to a temperature below 575° C. The 575° C. limit may represent a mechanical design constraint when diffusion bonded PCHE are employed and are fabricated from austenitic stainless steel and in particular alloy 316/316L. PCHE Alloy 316 blocks may require allowable stresses that are determined from time dependent (creep) properties at temperatures above 575° C. Further, a heat recovery section may be provided in the recuperative heat exchanger system. The heat recovery section may add heat at a temperature below the combustion temperature, e.g. low-grade heat.

Conventional power generation systems in industrial applications are typically exceptionally large and heavy. Conventional power generation systems may include an extensive layout and arrangement of pipes that require a large space and weigh several tons each. In some instances, large heat exchangers connected in series and may include complicated bends or changes in orientation. Additionally, large manifolds are needed to introduce fluids into the heat exchanges as well as when the fluids exit the heat exchanges. Such power generation systems may be both heavier in weight and may also be more expensive to manufacture because of the higher number of parts and components. For example, stress loops are used to accommodate an expansion of the pipework within the system. This additional pipework of stress loops needed to connect the various manifolds and heat exchangers together adds to the weight, installation costs, and overall cost of power generation systems.

Accordingly, one or more embodiments in the present disclosure may be used to overcome such challenges as well as provide additional advantages over conventional power generation systems, as will be apparent to one of ordinary skill. In one or more embodiments, a recuperative heat exchanger system may be lighter in weight and lower in cost as compared with conventional power generation systems due, in part, minimizing creep fatigue/damage, independent oxidant and recycle sections such that exhaust fluid flow split may be controlled with one or more low temperature valves, and exhaust fluid leaving the turbine does not require a balancing vessel to be placed between the turbine and recuperative heat exchanger. Additionally, the recuperative heat exchanger system may increase reliability and performance for thousands of hours where some components of the recuperative heat exchanger system are subject to high pressures, high temperatures and cycles of operation. Overall, the recuperative heat exchanger system may minimize product engineering, risk associated with flow loops manufacture, reduction of assembly time, hardware cost reduction, and weight and envelope reduction.

Turning toFIG.1A,FIG.1Ashows a schematic view of a power generation system100in accordance with one or more embodiments of the present disclosure. In one or more embodiments, a turbine101may be powered by fuel source102via a combustor103. As known in the art, a turbine, such as the turbine101may be a structure useful for extracting energy from a fluid flow and converting the fluid flow into useful work, such as to drive a generator to produce electricity, and is often a rotary device with other components (i.e., rotor, stator, and/or turbine blades) having various functions relevant to producing or converting mechanical energy. It is noted that the turbine101in one or more embodiments may be configured as a gas or steam turbine. The combustor103may be a component of the turbine101where combustion takes place, such as a chamber. Additionally, an oxygen supply112may be provided to feed oxygen into the combustor103. As known to those of ordinary skill in the art, the turbine101may produce exhaust gases104. The exhaust gases104may be fed into a recuperative heat exchanger system105(see dotted square) to form a turbine exhaust gas stream.

In one or more embodiments, the recuperative heat exchanger system105may include a precool section200, a major heating section301, and a minor heating section302. In some embodiments, the major heating section301may be a recycle heating section and the minor heating section302may be an oxidant heating section. The precool section200may be high-temperature pre-coolers having shell and tube type construction wherein the shell that may be combined with an annular distributor. Both the major section301and the minor section302may include at least two heat exchangers vertically stacked on top of each other to form a vertically modular heat exchanger stack.

Still referring toFIG.1A, all the exhaust gas104leaving the turbine may be fed into the precool section200. The precool section200may cool the exhaust gas104against a minor portion of a high-pressure gas to be heated, and preferably against an oxidant stream before redistribution to independent parallel trains (e.g., the major section301and the minor section302). In this way, the exhaust gas104may be directly cooled prior to entering the major section301and the minor section302, with a significant saving in cost and increase in reliability. Additionally, a manifold205may be optionally used to split the cooled exhaust gas104into streams entering the major section301and the minor section302. The cooled exhaust gas104may split to a major flow path131feeding into the major section301and a minor flow path130feeding into the minor section302. Further, one or more valves (not shown) may be used to balance a split of the exhaust gas flow104flowing from the major section301and into the minor section302. Further, flow resistances may be provided in both the major section301and the minor section302to balance the flow of the exhaust gas104. Furthermore, a flow may exit the major section301via flow lines133while a flow may exit the minor section302via flow lines132. In some embodiments, one or more valves106may be provided on the flow lines133.

In some embodiments, heat recovery systems may be operationally coupled to the recuperative heat exchanger system105. The heat recovery systems may add heat at a temperature below the combustion temperature. Further examples of the heat recovery systems include, but are not limited to, directly or indirectly adding heat (via a low-grade heat source108) to the turbine exhaust gas stream, recovering heat from an Air Separation Unit (ASU) coupled to a compressor (not illustrated), or recovering heat from a recycle gas compressor discharge from the compressor (not illustrated). In a non-limiting example, a flow line134from a pump111may feed into the minor section302while a flow line135from the pump111may feed into the major section301. In addition, a separator109may separate liquid condensate from exhaust gas such that liquid condensates109amay be collected. Further, a compressor110may be coupled to the separator109. Additionally, from the pump111, a discharge flow line138may be provided for product Carbon Dioxide (CO2) to exit the power generation system100. In some embodiments, the heat recovery systems may be incorporated into the major section301. It is further envisioned that a series of manifolds within the recycle and heat recovery sections may be used to redistribute the recycled high-pressure carbon dioxide and to provide draw points for the various turbine cooling flows that may be required. Further, a first flow back line136from the major section301and a second flow back line137from the minor section302may be used to provide the combustor103with fluid flow from the major section301and the minor section302.

Referring now toFIG.1B, another embodiment of a power generation system100according to embodiments herein is illustrated, where like numerals represent like parts. The embodiment ofFIG.1Bis similar to that of the embodiment ofFIG.1A. However, in place of just one heat exchanger, the major section301and the minor section302may both include two or more vertically modular heat exchanger stacks in series. The PCHE blocks may have a maximum size based on a plate size that can be accommodated within a diffusion bonding furnace, and thus, it may be beneficial to have more than one vertically modular heat exchanger stack. In some embodiments, there may be a need to re-distribute the high-pressure stream between the major section301and the heat recovery section, and thus, it may be beneficial to have more than one vertically modular heat exchanger stack.

FIG.2illustrates a close-up schematic view of a recuperative heat exchanger system105according to embodiments herein is illustrated, where like numerals represent like parts. As shown by arrows104, exhaust gas leaving a turbine may enter a precool section200via one or more transfer pipes. In a non-limiting example, four nominally identical transfer pipes may be used to transfer the exhaust gas (arrows104) to the precool section200. It is noted that any number of transfer pipes may be used without departing from the scope of the present disclosure.

In one or more embodiments, the precool section200may include one or more shell and tube heat exchangers (“STHE”)201. The STHE201of the precool section200may be made from a material selected from an INCONEL material (e.g. Alloy 625 or Alloy 617) or a similar material that is not subject to time dependent properties at a highest temperature. The one or more transfer pipes may be connected a shell-side202of the STHE201. In a non-limiting example, each STHE201may have one transfer pipe connected thereof. On a tube-side203of the STHE201, the STHE201may receive a fluid flow (e.g., oxidant fluid) from a minor section (302a,302b). In some embodiments, a mass heat capacity (e.g., mass flow x specific heat capacity) of a tube-side fluid of the STHE201may be lower than the mass heat capacity of the exhaust gas (arrows104) entering the STHE201on the shell-side202. Based on the lower mass heat capacity of an oxidant fluid on the tube-side, a temperature change of the exhaust gas may be small (e.g., 15-50° C.) whilst a temperature change of an oxidant stream may be large (e.g., 100-200° C.). It is further envisioned that the STHE201may include a heated oxidant outlet204for the oxidant stream to exit. From the STHE201, the exhaust gas may enter a manifold205to split the exhaust gas flow.

In some embodiments, the manifold205may split the exhaust gas along various flow paths. In a non-limiting example, the manifold205splits the exhaust gas into two flow paths, namely the minor flow path130(which may also be referred to herein as an exhaust gas minor stream130) and the major flow path131(which may also be referred to herein as an exhaust gas major stream131)

In the exhaust gas minor stream130, the exhaust gas flows through the minor section having a first minor heat exchanger302aand a second minor heat exchanger302b. Both the first minor heat exchanger302aand the second minor heat exchanger302bmay be a printed circuit type heat exchanger (“PCHE”), a coil wound type heat exchanger, a micro-tube heat exchanger, a diffusion bonded exchanger using stamped fins in addition to etched plates or any other type heat exchanger. In addition, both the first minor heat exchanger302aand the second minor heat exchanger302bmay be constructed from a suitable material, such as of dual certified stainless steel 316/316L. Additionally, the first minor heat exchanger302amay be operated at a higher temperature than the second minor heat exchanger302b. Further, the exhaust gas may be used to preheat the minor stream134to 350-500° C. In some embodiments, both the first minor heat exchanger302aand the second minor heat exchanger302bmay be used for oxidant heating.

In the exhaust gas major stream131, the exhaust gas flows through the major section having a first major heat exchanger301a, a second major heat exchanger301b, and a third major heat exchanger301c. Each of the major heat exchangers301a,301b,301cmay be a printed circuit type heat exchanger (“PCHE”), a coil wound type heat exchanger, a micro-tube heat exchanger, a diffusion bonded exchanger using stamped fins in addition to etched plates or any other type heat exchanger. Additionally, the first major heat exchanger301amay be operated at a highest temperature in the major section while the third major heat exchanger301cmay operate a lowest temperature in the major section. The second major heat exchanger301bmay operate at a temperature between the first major heat exchanger301aand the third major heat exchanger301c. In addition, each of the major heat exchangers301a,301b,301cmay be constructed from a material of dual certified stainless steel 316/316L. Further, the exhaust gas major stream131may be used to preheat the major stream135to 520-650° C. In some embodiments, each of the major heat exchangers301a,301b,301cmay be used for heating recycle CO2 along line303. Additionally, a second flow line304may be used to provide the turbine with a cooling flow. In a non-limiting example, the cooling flow may be a recycle gas leaving107aor301b. In some cases, a temperature of the cooling flow may not match a required turbine coolant temperature. In order to match the required turbine coolant temperature, hot gas or cold gas may be added to the cooling flow to raise or lower the temperature to match the required turbine coolant temperature. In some embodiments, the cooling flow may be a blended mixture from the recycle stream leaving107aor301band the higher temperature recycle stream leaving301a.

In some embodiments, a flow balance of the gas exhaust between the minor section (302a,302b) and the major section (301a,301b,301c) may be controlled by flow resistances in the minor section (302a,302b) and the major section (301a,301b,301c). In a non-limiting example, one or more valves at an outlet (i.e., a cold end) of the minor section (302a,302b) may be used for flow balance.

In the heat recovery stream108, recycled exhaust gas or a separate low-grade heat stream may be used to add heat at a temperature below a combustion temperature via a first recovery heat exchanger107aand a second recovery heat exchanger107b. In some embodiments, the recycled exhaust gas may be exhaust gas that is reheated and recycled back through the heat recovery sections107aand107b. Both the first recovery heat exchanger107aand the second recovery heat exchanger107bmay be a printed circuit type heat exchanger (“PCHE”), a coil wound type heat exchanger, a micro-tube heat exchanger, a diffusion bonded exchanger using stamped fins in addition to etched plates or any other type heat exchanger. In addition, both the first recovery heat exchanger107aand the second recovery heat exchanger107bmay be constructed from a suitable material, such as dual certified stainless steel 316/316L. Further, the first recovery heat exchanger107amay be at a higher temperature than the second recovery heat exchanger107b. In some embodiments, the first recovery heat exchanger107aand the second recovery heat exchanger107bmay be integrated into the second major heat exchanger301band the third major heat exchanger301c, respectively.

In one or more embodiments, the precool section200may cool the exhaust gas. In a non-limiting example, the exhaust gas104may be precooled to a temperature of 575° C. By precooling the exhaust gas104to 575° C., an available temperature difference for first major heat exchanger301amay be reduced. This may be compensated for by using additional heat transfer surface area, or by increasing the overall heat transfer coefficient. The product of the overall heat transfer coefficient and the heat transfer surface area may be called UA which is equivalent to the heat duty divided by the mean temperature difference LMTD which may be calculated from the inlet and outlet temperatures of the hot stream and cold stream. The UA value of a heat exchanger may be related to the cost of the heat exchanger. By including the precool section200in the recuperative heat exchanger system105, the required UA may increase overall by about 15%. However, a difference in cost (e.g., a value of cost/UA) between the high temperature sections and low temperature sections may lower an overall cost of the recuperative heat exchanger system105. In a non-limiting example, the value of cost/UA of systems above 575° C. may be more than 30% higher than the value of cost/UA of systems below 575° C. The recuperative heat exchanger system105may provide a lower value of cost/UA by increasing an expected life of equipment and reduced material use owing to a higher allowable stress for heat exchangers below 575° C. Although the INCONEL material of the precool section200may be a more expensive material, the amount of material required is relatively small because of the higher LMTD in the precool section200, which reduces the required UA.

Embodiments herein for operating the recuperative heat exchanger system105may be implemented on a computing system. Any combination of mobile, desktop, server, router, switch, embedded device, or other types of hardware may be used with the recuperative heat exchanger system105. For example, the computing system may include one or more computer processors, non-persistent storage (e.g., volatile memory, such as random access memory (RAM), cache memory), persistent storage (e.g., a hard disk, an optical drive such as a compact disk (CD) drive or digital versatile disk (DVD) drive, a flash memory, etc.), a communication interface (e.g., Bluetooth interface, infrared interface, network interface, optical interface, etc.), and numerous other elements and functionalities. It is further envisioned that software instructions in a form of computer readable program code to perform embodiments of the disclosure may be stored, in whole or in part, temporarily or permanently, on a non-transitory computer readable medium such as a CD, DVD, storage device, a diskette, a tape, flash memory, physical memory, or any other computer readable storage medium. For example, the software instructions may correspond to computer readable program code that, when executed by a processor(s), is configured to perform one or more embodiments of the disclosure.

In one or more embodiments, a precool heat exchanger may be used in recuperative heat exchanger system. The precool heat exchanger may be a shell and tube heat exchanger (“STHE”) for distributing exhaust gas from a turbine. In some embodiments, instead of being a STHE, the precool heat exchanger may be a printed circuit type heat exchanger (“PCHE”), a coil wound type heat exchanger, a micro-tube heat exchanger, a diffusion bonded exchanger using stamped fins in addition to etched plates or any other type heat exchanger. The precool heat exchanger may in turn fed the exhaust gas directly into heat exchangers thereby eliminating a need for a large high temperature exhaust manifold. In a non-limiting example, the STHE may replace a large high temperature exhaust manifold such that turbine exhaust gases could be directly cooled prior to entering a minor (oxidant stream) section and a major (recycled stream) section of a recuperative heat exchanger system. In some embodiments, pressure components of the precool heat exchanger may be made from a material selected from an INCONEL material (e.g. Alloy 625 or Alloy 617) or a similar material that is not subject to time dependent properties at a highest temperature. Internal components of the precool heat exchanger500, which are non-pressure parts, may be made from a stainless steel or similar materials.

In one or more embodiments, a fluid may enter at a center and split into two streams (one going right and the other left). The fluid may leave the heat exchanger through two or more separate outlets. The streams may be combined again outside the heat exchanger through a system of pipes. In some embodiments, the fluid may enter at two or more points, combine and ultimately leave in a single outlet nozzle. Large pressure drops may cause tube vibration, which may damage to the tubes and shell. Because of this, splitting the flow in the heat exchanger may be useful for reducing the risk of damage due to vibrations and may reduce the pressured drops associated with the heat exchange system.

In some embodiments, the heat exchanger may be a double-split flow exchanger. This means the heat exchanger may have two areas where the flow is divided and then reunited, as well as two support plates. When the pressure drop needs to be kept low, a split-shell design may be employed. Further, there may be no baffle plates in the split-shell design exchanger and a single support plate is installed in the center of the shell.

Referring toFIG.3, in one or more embodiments,FIG.3illustrates a precool heat exchanger500may have two annular shells501,502and a distributor section513. A first annular shell501may be an outer shell forming a pressure boundary. Additionally, the first annular shell501may include an exhaust gas inlet503may be provided on a shell-side504to receive exhaust gases from a turbine. A transfer pipe may be connected to the exhaust gas inlet503from the turbine. Further, at an end of the precool heat exchanger500, a stationary head channel505with an inlet506and an outlet507may be provided. A pass partition508may be provided within the stationary head channel505to split flow between the inlet506and the outlet507. The inlet506may be used to receive oxidant from the minor section. It is further envisioned that one or more exhaust outlets515may be provided on the shell-side504for the exhaust stream to exit.

Still referring toFIG.3, a second annular shell502may be an inner shell or shroud around a tube bundle509with two or more tube-side passes. The tube bundle509may be a U-tube bundle. A support plate511is provided to support the weight of the tube bundle509and prevent overloading of the tube to tubesheet and channel505assembly connection. In some embodiments, a large difference between the shell-side504and a tube-side509flowrates mean that multiple passes may be used to maintain a reasonable tube-side509velocity and heat transfer coefficient. Additionally, an annular distribution device513may replace the function of an exhaust manifold by stepwise decelerating the exhaust gas flow and providing a controlled entrance to the tube bundle509. The annular distribution device may be provided with slots that are rectangular or oval and with an open area that decreases with distance from the inlet503. Further, the tube bundle509may have rods or grid type baffles to support the tubes and arranged on a baffle ring514rather than conventional segmental plate type baffles. It is further envisioned that insulation517may be provided within the precool heat exchanger500between various internal components.

While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.