RECOVERY FOR THERMAL CYCLES
A gas burner system may include a first burner configured to burn gas to produce burned gas in a first portion of the waste gas burner system and a second burner configured to burn gas to produce burned gas in a second portion of the waste gas burner system. A heat exchanger may reside out of the first portion and may be configured to receive heat from the burned gas in the second portion and heat a working fluid of a thermal cycle system. A valve may be configured to control an amount of gas provided to the second burner. The gas may be a waste gas from a process. The thermal cycle system may include an organic Rankine cycle.
This application claims priority to U.S. Provisional Patent Application having Ser. No. 61/569,177, filed Dec. 9, 2011 and U.S. Provisional Patent Application having Ser. No. 61/569,702, filed Dec. 12, 2011, the entire contents of the forgoing are incorporated by reference herein.
FIELDThis disclosure pertains to heat recovery for thermal cycles, and more particularly, to heat recovery from flares and/or incinerators for a Rankine Cycle.
BACKGROUNDDuring the production of oil and gas, either in the field or at processing plants, natural gas and/or other flammable process gases are often consumed using a flare or incinerator. Heat may be dissipated as a result of combustion through hot gases in the stack vented out to the environment.
SUMMARYThis disclosure describes systems, methods, and apparatuses whereby this heat can be safely and effectively captured without impacting the underlying oil and gas production and used by way of a thermal cycle to produce electric power in a safe manner, and/or use the excess heat for other processes.
By providing a bypass some or all of the hot gas can exchange heat with the thermal cycle heat exchanger. This allows heat recovery without impacting the gas combustion process or burn rate. Furthermore, a failure of the thermal cycle system does not impact the flare gas process.
For high flow applications or applications that allow large pressure drops across the valves, the use of butterfly valves enables rapid equalization of pressure across the valve. Therefore, the power required to actuate the valve is decreased, and control of the valve is more readily established.
Control of the transfer of heat to the thermal cycle heat exchanger is realized by controlling the exposure of heat exchanger surface to hot gas. This method can be used alone or in conjunction with valves and fans and by controllably changing the position of the heat exchanger within the heating chamber. The valves and/or the fans can be controlled by the thermal cycle system to control the heat transferred to the working fluid.
The flue stack may be designed in such a way to allow natural convection to exhaust the gases through the bypass.
Integrating the ORC heat exchanger within the stack allows for more effective heat transfer, simpler plant and less obstruction to flue gases. A heat exchanger may reside in direct path of flue gases. In such an arrangement a fan may be used to assist the flue gas through the heat exchanger. The ORC system working fluid may be heated in conjunction with another process liquid reduces overall cost and provides electric power to be used on site or to supply to the grid. A heat source may be used to elevate the temperature of a process fluid as well as an ORC system fluid by means of transferring heat through the process fluid.
The disclosure describes arrangements for capturing waste heat generated from a burning waste gas either in a flare burner, or incinerator. The captured waste heat may be used as heat input to a thermal cycle, such as a (Organic) Rankine Cycle. References made to Rankine Cycles or Organic Rankine Cycles (ORC) are examples. Other thermal cycles within the scope of this disclosure include, but are not limited to, Sterling cycles, Brayton cycles, Kalina cycles, etc. The principles of invention apply to all thermal cycles where capturing heat from a heat source is required. Similarly fuel used for generating heat may be waste natural gas, or other fuel sources such as biogas, oil etc.
In certain instances, the turbine generator apparatus 102 includes a turbine 120 and a generator 160. The turbine generator apparatus 102 can be used to convert heat energy from a heat source into kinetic energy (e.g., rotation of the rotor), which is then converted into electrical energy. The turbine 120 is configured to receive heated and pressurized gas, which causes the turbine 120 to rotate (and expand/cool the gas passing through the turbine 120). Turbine 120 is coupled to a rotor of generator 160 using, for example, a common shaft or a shaft connected by a gear box. The rotation of the turbine 120 causes the shaft to rotate, which in-turn, causes the rotor of generator 160 to rotate. The rotor rotates within a stator to generate electrical power. For example, the turbine generator apparatus 102 may output electrical power that is configured by a power electronics package to be in form of 3-phase 60 Hz power at a voltage of about 400 VAC to about 480 VAC. Alternative embodiments may output electrical power at different power and/or voltages. Such electrical power can be transferred to a power electronics system 140, other electrical driven components within or outside the engine compressor system and, in certain instances, to an electrical power grid system. Turbine may be an axial, radial, screw or other type turbine. The gas outlet from the turbine 120 may be coupled to the generator 160, which may receive the gas from the turbine 120 to cool the generator components.
The power electronics 140 can operate in conjunction with the generator 160 to provide power at fixed and/or variable voltages and fixed and/or variable frequencies. Such power can be delivered to a power conversion device configured to provide power at fixed and/or variable voltages and/or frequencies to be used in the system, distributed externally, or sent to a grid.
Rankine Cycle 100 may include a pump device 30 that pumps the working fluid. The pump device 30 may be coupled to a liquid reservoir 20 that contains the working fluid, and a pump motor 35 can be used to operate the pump. The pump device 30 may be used to convey the working fluid to a heat exchanger 65 (the term “heat exchanger” will be understood to mean one or both of an evaporator or a heat exchanger). The heat exchanger 65 may receive heat from a heat source 60, such as a waste heat source from one or more heat sources associated with a waste gas burner. In such circumstances, the working fluid may be directly heated or may be heated in a heat exchanger in which the working fluid receives heat from a byproduct fluid of the process. In certain instances, the working fluid can cycle through the heat source 60 so that at least a substantial portion of the fluid is converted into gaseous state. Heat source 60 may also indirectly heat the working fluid with a thermal fluid that carries heat from the heat source 60 to the evaporator 65. Some examples of a thermal fluid include water, steam, thermal oil, etc.
Typically, working fluid at a low temperature and high pressure liquid phase from the pump device 30 is circulated into one side of the economizer 50, while working fluid that has been expanded by a turbine upstream of a condenser is at a high temperature and low pressure vapor phase and is circulated into another side of the economizer 50 with the two sides being thermally coupled to facilitate heat transfer there between. Although illustrated as separate components, the economizer 50 (if used) may be any type of heat exchange device, such as, for example, a plate and frame heat exchanger, a shell and tube heat exchanger or other device.
The evaporator/preheater heat exchanger 65 may receive the working fluid from the economizer 50 at one side and receive a supply of thermal fluid (that is (or is from) the heat source 60) at another side, with the two sides of the evaporator/preheater heat exchanger 65 being thermally coupled to facilitate heat exchange between the thermal fluid and working fluid. For instance, the working fluid enters the evaporator/preheater heat exchanger 65 from the economizer 50 in liquid phase and is changed to a vapor phase by heat exchange with the thermal fluid supply. The evaporator/preheater heat exchanger 65 may be any type of heat exchange device, such as, for example, a plate and frame heat exchanger, a shell and tube heat exchanger or other device.
In certain instances of the Rankine Cycle 100, the working fluid may flow from the outlet conduit of the turbine generator apparatus 102 to a condenser heat exchanger 85. The condenser heat exchanger 85 is used to remove heat from the working fluid so that all or a substantial portion of the working fluid is converted to a liquid state. In certain instances, a forced cooling airflow or water flow is provided over the working fluid conduit or the condenser heat exchanger 85 to facilitate heat removal. After the working fluid exits the condenser heat exchanger 85, the fluid may return to the liquid reservoir 20 where it is prepared to flow again though the Rankine Cycle 100. In certain instances, the working fluid exits the generator 160 (or in some instances, exits a turbine 120) and enters the economizer 50 before entering the condenser heat exchanger 85.
Liquid separator 40 (if used) may be arranged upstream of the turbine generator apparatus 102 so as to separate and remove a substantial portion of any liquid state droplets or slugs of working fluid that might otherwise pass into the turbine generator apparatus 102. Accordingly, in certain instances of the embodiments, the gaseous state working fluid can be passed to the turbine generator apparatus 102, while a substantial portion of any liquid-state droplets or slugs are removed and returned to the liquid reservoir 20. In certain instances of the embodiments, a liquid separator may be located between turbine stages (e.g., between the first turbine wheel and the second turbine wheel, for multi-stage expanders) to remove liquid state droplets or slugs that may form from the expansion of the working fluid from the first turbine stage. This liquid separator may be in addition to the liquid separator located upstream of the turbine apparatus.
Controller 180 may provide operational controls for the various cycle components, including the heat exchangers and the turbine generator.
Waste gas 204 is burned via the burner 202 which can be in various configurations to suit the application. Gas combustion may be controlled by a fan 204 that directs the air flow toward the burner 202. In addition to providing the necessary air for combustion, the combustor fan 206 provides a flow stream that normally directs the flue gases to the stack or to the heat exchanger 208. Heat exchanger 208 may be a heat exchanger for a thermal cycle that directly heats the thermal cycle working fluid. Heat exchanger 208 may alternatively be a heat exchanger that heats a thermal fluid that subsequently heats the working fluid. For example, the flow stream may assist in directing the heated gas into a heat exchanger chamber 210 that houses the heat exchanger 208. Valves, such as valve A 212 and valve B 214 may controllably opened and closed to control the gas flow into the heat exchanger chamber 210. By modulating valves A and B, some or all of the hot gas can be directed to the heat exchanger chamber 210 that houses the heat exchanger 208. Valve A 212 proportionally controls the flow between the flue stack 218 and heat exchanger chamber 210. Valve B 214 controls the flow of hot gas from the heat exchanger chamber 210 to the flue stack 218. If the thermal cycle system is shut down, valves A 121 and B 214 can close, closing off the heat exchanger chamber 210 to the hot gas, thereby protecting the working fluid from high temperatures and subsequent decomposition. The valves 212 and 214 can be operated independently or mechanically interconnected and driven by one motor/controller. The valves would be normally closed so that the fail safe position is to always allow the gas to be burned and bypass the heat exchanger 208 until heat is required by the thermal cycle system. The thermal cycle system, through its control logic, can control valves A 212 and B 214 as well as the fan to ensure maximum system operation and generation of electric power. A portion of the electric power produced by the thermal cycle system can be used to operate the valves and fan shown in
The combined waste gas burner and thermal cycle heat exchanger 200 described above can include an air fan 216 that can introduce air into the heat exchange chamber. The addition of air allows full modulation of temperature as well as flow control across the heat exchanger 208. Tempering air can be used to control the heat in the heat exchanger chamber 210.
As described above, the heat exchanger 208 can be used as either a direct evaporator for the working fluid or can indirectly heat the working fluid: a second thermal fluid can be used to absorb the heat energy in the heat exchanger and carry that heat energy to a second heat exchanger located separately acting as the evaporator in the ORC system. Indirect heating facilitates protection of the thermal cycle system working fluid from high temperatures. The direct heating of the working fluid is an efficient heat transfer process that is low in cost and more reliable due to the lower complexity.
The thermal cycle system 720 includes a heat exchanger 708 that directly or indirectly heats a working fluid. The heated working fluid is directed to an expander 722. The heated working fluid causes the expander to rotate, which rotates a rotor of the generator 724. The rotor can be magnetically suspended to rotate within a stator. Rotation of the rotor within the stator can generate electric power, which is output to power electronics (PE) 726. The power can be inverted in an inverter 728. Power can be output to a grid or consumed, either internally or externally. For example, power from the generator may be used to power electrical systems that are part of the thermal cycle or part of the burner system, such as combustor fan 706 and air fan 716 and/or the refraction mechanism shown in
In addition, the PE can provide inverter function without the need for a dedicated inverter unit. In certain instances, the PE can also provide power conditioning (e.g., rectification, AC to DC conversion, DC to AC conversion, amplification, filtering, etc.) to power one or more electronic components of the thermal cycle system 720 or the burner system 701.
Power electronics 726 can operate in conjunction with the generator 724 to provide power at fixed and/or variable voltages and fixed and/or variable frequencies. Such power can be delivered to a power conversion device configured to provide power at fixed and/or variable voltages and/or frequencies to be used in the system, external, or to the grid. The output of the electric power system provides power at a variable voltage or frequency to drive with adjustable speed a fan motor on the burner 701 or to an electric motor or to another electric device driven by a variable speed drive. The output of the electric power system can provide fixed voltage and frequency for ancillary equipment such as a fan motor, an oil pump, an electrically driven compressor, or other electric device driven by a fixed voltage and/or frequency.
As mentioned above, the working fluid is expanded by expander 722 and directed to fluid heater 736 prior to being directed to a condenser 730. The fluid heater 736 can use residual heat from the working fluid after expansion to heat another fluid 738 and to cool the working fluid. An example fluid is crude oil. As crude oil emerges from the well or other process, it can be heated from 60-70 degrees F. to 100-120 degrees F. for processing or final dispatch using the expanded working fluid. The heated fluid can be stored in a tank 740.
Thermal cycle systems may use a condenser to cool the working fluid from a gaseous to liquid state. Condenser heat rejection is a major component of parasitic loads associated with an thermal cycle system. In plants where a stream of cold fluid requires heating, the thermal cycle condenser can be partially or wholly replaced by allowing the thermal cycle working fluid to exchange heat with the cold fluid stream. Specifically, flare gas applications are generally part of crude oil production. Often the oil emerging from the well at 60-70 F needs to be heated to 100-120 F for further processing or transport. Using the thermal cycle system to recover the waste heat from flare and heating the produced oil, using expanded thermal cycle working fluid, adds two distinct and simultaneous benefits to overall production whilst reducing the parasitic load on the thermal cycle system.
The working fluid can be directed from the fluid heater 736 to a condenser 730 where it is cooled. It can then be stored in a receiver tank 732. Pump 734 can pump the cooled working fluid from the receiver tank 732 into the heat exchanger 708.
Heat exchanger 914 resides outside of the first portion 901a of system 900. Heat exchanger 914 is out (substantially or entirely) of the convective heat flow from burner A 902. In other words, heat exchanger 914 receives heat from burned gas from burner B 904 in the second portion 901b. Heat exchanger 914 can directly heat a thermal cycle working fluid or may indirectly heat a thermal cycle working fluid by heating a thermal fluid that heats the working fluid of a thermal cycle. The heat exchanger chamber outlet 918 allows hot gases from burner A 902 to aid the flow of gases from burner B 904 through the flue stack 912, thereby eliminating a need for an exhaust fan. Furthermore design of the heat exchanger chamber outlet 918 can be elected so that hot gases from burner A 902 cannot enter the heat exchanger chamber 916.
Fans 910 and 920 can aid in controlling the temperature within each respective chamber. Additionally, the fans 910 and 920 can be controlled by the thermal cycle system to control the heating of the working fluid. For example, the thermal cycle system controller 180 can send control signals to fans 910 and/or 920. Valve 908 can likewise be controlled by the thermal cycle system to control the heating of the working fluid. That is, the thermal cycle system can control valve 908 to adjust the amount of waste gas burned in each chamber, thereby controlling the heat applied to the heat exchanger 914 in chamber 901b.
One or both of fan 944 or valve 946 can be controlled by the thermal cycle system (e.g., through thermal cycle system controller 180). For example, the thermal cycle system can send control signals to the fan 944 so that the fan 944 can aid in adjusting the temperature in the heat exchanger chamber 940. By controlling the fan, the amount of heat transferred to the thermal cycle working fluid through the heat exchanger 938 can be adjusted. Likewise, the temperature in the heat exchanger chamber 940 can be controlled by operating the valve 946 to change the amount of waste gas burned.
The waste gas burner and thermal cycle heat exchanger system 1000 can include a housing 1002 that defines a flue 1004. In certain instances, the housing 1002 can be that of an incinerator, a furnace, a burner, a flare, a thermal oxidizer, and/or another system for burning or destroying waste gas. To this end, waste gas is introduced into and burned with a burner 206 within the housing 1002, which can be in various configurations to suit the application. In certain instances, the burner 1006 is a burner configured to output its heat substantially as radiant heat, for example, outputting more radiant heat than convective heat. In one example, the burner 1006 is an infrared burner having a high radiance emitter heated by the burning waste gas, such as metal alloy foam emitter, a ceramic emitter and/or another configuration of emitter. The burner 1006 can have heat shields or be otherwise configured to direct and focus the radiant heat in a primary heating direction. The burner 1006 can be more than one burner.
In certain instances, the burner 206 can include multiple types of burners. For example, the burner 1006 shown in
A heat exchanger 1008 is positioned in the housing 1002 adjacent to and out (substantially or entirely) of the upward convective heat flow from the burner 1006. The burner's primary heating direction is oriented toward the heat exchanger 1008 (i.e., down) and the heat exchanger 1008 is in line of sight of the burner 1006. Thus, the combustion byproducts and burnt impurities flow upward and exit through the flue 1004, as does a substantial amount of the convective heat, and the radiant heat is directed downward toward the heat exchanger 208. The heat exchanger 1008 may be associated with a thermal cycle in that it directly heats the thermal cycle working fluid and/or heats a heat exchange fluid that subsequently heats the working fluid, for example, via another heat exchanger outside of the housing 1002. The burner 1006 thus can be the heat source to the thermal cycle (e.g., heat source 60 of
In certain instances, the heat exchanger 1008 can include a radiant heat collector 1014 thermally coupled to coils 1016. The coils 1016 contain the thermal cycle working fluid or the heat transfer fluid that is used in transferring heat to the thermal cycle working fluid. The coils 1016 can be coils of a tube type heat exchanger and/or another configuration. In certain instances, the coils 1016 can be thermally bonded to the radiant heat collector 1014 to achieve conductive heat transfer and/or can be thermally coupled in another manner.
In certain instances, the radiant heat collector 1014 is conical to correspond with a cylindrical burner 1006 and/or housing 1002 or a triangular cross-section trough to correspond with a rectangular burner 1006 and/or housing 1002. Other shapes of collector 1014, burner 1006 and housing 1002 exist and the shape of the collector 1014 need not correspond with the shape of the housing 1002. In a conical or trough style heat collector 1014, the angle of the radiant heat collector 1014 surfaces to the burner 1006 can be selected in connection with the surface area and emissivity based on the desired of heat transfer. One or more surfaces of the heat collector 1014 and/or coils 1016 can have a specified emissivity selected based on the desired heat transfer. Further, the coils 1016 can be sized in connection with the radiant heat collector 1014. For example, in certain instances, the waste gas may burn at a temperature of five to ten times the operating temperature of the working fluid, and the burner 1006, heat collector 1014 and coils 1016 can be sized or configured to maintain that ratio without overheating the working fluid.
A number of embodiments have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other embodiments are within the scope of the following claims:
Claims
1. A gas burner system comprising:
- a first burner configured to burn gas to produce burned gas in a first portion of the waste gas burner system;
- a second burner configured to burn gas to produce burned gas in a second portion of the waste gas burner system;
- a heat exchanger residing out of the first portion, the heat exchanger configured to receive heat from the burned gas in the second portion and heat a working fluid of a thermal cycle system; and
- a valve configured to control an amount of gas provided to the second burner.
2. The waste gas burner system of claim 1, wherein the first portion of the waste gas burner system is a first chamber and the second portion of the gas burner system is a second chamber, the first chamber separated from the second chamber by a thermal barrier.
3. The gas burner system of claim 2, wherein the thermal barrier comprises an insulated wall configured to keep heat generated in the first chamber isolated from the second chamber.
4. The gas burner system of claim 2, wherein the thermal barrier comprises an aperture configured to allow burned gas from the first chamber to aid in exhausting burned gas from the second chamber.
5. The gas burner system of claim 2, wherein the thermal barrier comprises an aperture configured to prevent burned gas from the first chamber from entering the second chamber.
6. The gas burner system of claim 1, further comprising an air fan configured to provide air to the first chamber.
7. The gas burner system of claim 1, further comprising:
- an air fan configured to provide air to both the first chamber and second chamber; and
- a diverter valve configured to receive a signal from the thermal cycle system and control an amount of air provided to one or both of the first chamber or the second chamber.
8. The gas burner system of claim 1, further comprising:
- a first air fan configured to provide air to the first chamber; and
- a second air fan configured to provide air to the second chamber, wherein the first air fan and the second air fan can each be controlled separately by the thermal cycle system.
9. The gas burner system of claim 1, wherein the heat exchanger resides in the second portion of the gas burner system, and wherein the working fluid of the thermal cycle system passes through at least a portion of the heat exchanger.
10. The gas burner system of claim 1, wherein the burned gas heats a thermal fluid that heats the working fluid.
11. The gas burner system of claim 1, wherein the thermal cycle system comprises an organic Rankine cycle.
12. The gas burner system of claim 1, further comprising a flue stack configured to received burned gas from the first and second chambers and direct the burned gas to one or both of a gas destruction process or another process.
13. The gas burner system of claim 1, wherein the gas burner system comprises an incinerator.
14. The gas burner system of claim 1, wherein the gas burner system comprises a flare.
15. The gas burner system of claim 1, wherein the first burner resides at a position above the heat exchanger and the second burner resides at a position below the heat exchanger.
16. The gas burner system of claim 1, wherein the valve is configured to receive gas and to control the amount of gas directed to the second burner and to direct a remainder of the received gas to the first burner.
17. The gas burner system of claim 16, wherein the valve is controlled by the thermal cycle system.
18. The gas burner system of claim 1, wherein the gas comprises a waste gas.
19. A method comprising:
- burning a first portion of a gas in a gas burner device;
- burning a second portion of a gas in a gas burner device;
- heating a thermal cycle working fluid with the burning of the second portion of the gas; and
- directing the burned gas out of the chamber.
20. The method of claim 19, wherein heating the thermal cycle working fluid comprises heating a thermal fluid.
21. The method of claim 19, wherein directing the burned gas out of the chamber comprises directing the burned gas to another process.
22. The method of claim 19, wherein a heat exchanger of a thermal cycle resides in the second portion, and the thermal cycle working fluid is heated by the burning of the second portion of the gas.
23. A system comprising:
- a gas burner device comprising: a first burner configured to burn gas to produce burned gas in a first portion of the gas burner device, a second burner configured to burn gas to produce burned gas in a second portion of the gas burner device, and a valve configured to control an amount of gas provided to the second burner; and
- a thermal cycle system comprising: a heat exchanger configured to receive heat from the burned gas in the second portion of the gas burner device and heat a thermal cycle working fluid, and an electric machine apparatus configured to receive the heated working fluid and generate electric power based on receiving the heated working fluid.
24. The system of claim 23, wherein the heat exchanger resides in the second portion of the gas burner device and receives heat from the burned gas in the second portion of the gas burner device, and wherein the working fluid of the thermal cycle passes through at least a portion of the heat exchanger.
25. The system of claim 23, wherein the first portion of the gas burner system is a first chamber and the second portion of the gas burner system is a second chamber, the first chamber separated from the second chamber by a thermal barrier, wherein the thermal barrier comprises an aperture configured to allow burned gas from the first chamber to aid in exhausting burned gas from the second chamber.
26. The system of claim 23, wherein the thermal cycle system comprises an organic Rankine cycle.
27. The system of claim 23, wherein the gas comprises a waste gas.
Type: Application
Filed: Dec 7, 2012
Publication Date: Jun 13, 2013
Inventors: Parsa Mirmobin (La Mirada, CA), Dennis Strouse (Anaheim, CA), Herman Artinian (Huntington Beach, CA)
Application Number: 13/707,956
International Classification: F22B 1/18 (20060101); F01K 25/08 (20060101);