CLAIM OF PRIORITY

This application claims priority to U.S. Provisional Patent Application No. 61/569, 177, filed December 9, 201 1 and U.S. Provisional Patent Application No. 61/569,702, filed December 12, 2011, the entire contents of the forgoing are incorporated by reference herein.

FIELD

This disclosure pertains to heat recovery for thermal cycles, and more particularly, to heat recovery from flares and/or incinerators for a Rankine Cycle. BACKGROUND

During 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. SUMMARY

This 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.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram of an example thermal cycle.

FIG. IB is a schematic diagram of an example Rankine Cycle system illustrating example Rankine Cycle system components.

FIG. 2A is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger.

FIG. 2B is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger.

FIG. 2C is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger.

FIG. 3 is a schematic illustration of an example waste gas burner and heat exchanger system.

FIG. 4 is a schematic illustration of an example waste gas burner and heat exchanger system.

FIG. 5 is a schematic illustration of an integrated spiral heat exchanger embedded within the structure of the flue stack.

FIG. 6 is a schematic illustration of an example waste gas burner and heat exchanger system.

FIG. 7 is a schematic of an example burner and thermal cycle system.

FIG. 8A is a schematic illustration of an example heat transfer system. FIG. 8B is a schematic illustration of another example heat transfer system. FIG. 9A is a schematic illustration of an example dual waste gas burner and heat exchanger system.

FIG. 9B is a schematic illustration of another example dual waste gas burner and heat exchanger system.

FIG. 10 is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger system.

DETAILED DESCRIPTION

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,

011 etc.

FIG. 1A is a schematic diagram of a an example thermal cycle 10. The cycle consists of a heat source 12 and a heat sink 14. The heat source temperature is greater than heat sink temperature. Flow of heat from the heat source 12 to heat sink 14 is accompanied by extraction of heat and/or work 16 from the system. Conversely, flow of heat from heat sink 14 to heat source 12 is achieved by application of heat and/or work 16 to the system. Extraction of heat from the heat source 12 or application of heat to heat sink 14 is achieved through a heat exchanging mechanism. Systems and apparatus described in this disclosure are applicable to any heat sink 14 or heat source

12 irrespective of the thermal cycle. For descriptive purposes, a Rankine Cycle (or Organic Rankine Cycle) is described by way of illustration, though it is understood that the Rankine Cycle is an example thermal cycle, and this disclosure contemplates other thermal cycles. Other thermal cycles within the scope of this disclosure include, but are not limited to, Sterling cycles, Brayton cycles, Kalina cycles, etc.

FIG. IB is a schematic diagram of an example Rankine Cycle system 100 illustrating example Rankine Cycle system components. Elements of the Rankine Cycle 100 may be integrated into a waste gas burner system and recover waste heat therefrom. The Rankine Cycle 100 may be an Organic Rankine Cycle ("Rankine Cycle"), which uses an engineered working fluid to receive waste heat from another process, such as, for example, from the waste gas burner that the Rankine Cycle system components are integrated into. In certain instances, the working fluid may be a refrigerant (e.g., an HFC, CFC, HCFC, ammonia, water, R245fa, or other refrigerant). In some circumstances, the working fluid in cycle 100 may include a high molecular mass organic fluid that is selected to efficiently receive heat from relatively low temperature heat sources. As such, the turbine generator apparatus 102 can be used to recover waste heat and to convert the recovered waste heat into electrical energy.

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.

FIG. 2A is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger 200. The combined waste gas burner and thermal cycle heat exchanger 200 is operable to capture the heat produced by burning waste gas 204. This heat energy is converted into other forms of energy using the thermal cycle. In the case of a Rankine Cycle, the heat energy is converted into mechanical energy, which in turn can be converted to electrical power using a 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 FIG. 2A-C and in other figures.

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.

FIG. 2B is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger 220. Gas combustion is controlled by a fan as in FIG. 2A. In FIG. 2B, the combined waste gas burner and thermal cycle heat exchanger 220 includes three butterfly valves: valve A 222, valve B 224, and valve C 226. The valves modulate the gas flow between the flue stack 218 and the heat exchanger chamber 210. Valve A 222 modulates the flow of hot gases through the stack 218. Valves B 224 and C 226 control the flow of gases through the heat exchanger 208. For high flow applications, butterfly valves provide pressure balancing.

FIG. 2C is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger 230. The combined waste gas burner and thermal cycle heat exchanger 230 includes a retractable heat exchanger 232. A bellows 234 and an expanding seal can be used around the heat exchanger 232 to insert or detract it from direct heat flow of the heat exchange chamber 236. By modulating the position of the heat exchanger 232, heat transfer to the heat exchanger 232 is controlled.

FIG. 3 is a schematic illustration of an example waste gas burner and heat exchanger system 300. The system 300 is a bypass scheme in which waste gas is burned in a burner 302 (e.g., a flare or incinerator), and the hot gas is passed through a thermal cycle system heat exchanger 320. The burner 302 includes a gas inlet 308. Gas to be burned flows through the burner 302 through a gas riser 306 to gas discharge ports 304. A flare burner 310 may burn the gas. The burned waste gas is directed through the flue stack 330. By modulating valve A 326, some or all of the available hot gas can be diverted from the flue stack 330 and into the heat exchanger chamber 322, which houses the heat exchanger 320. Heat exchanger 320 can directly heat a thermal cycle working fluid or may heat a thermal fluid that indirectly heats a working fluid of a thermal cycle. A fan 324 can be used to assist the flow of gas through the heat exchanger 320. By varying the speed of the fan 324 and/or opening and closing valve A 326, control of heat from the burned gas is achieved. The bypass can be mounted within the stack 330 or at top of the stack 330. In addition to valve A, a second valve B 328 can be added so that during thermal cycle system shut down, hot gas does not pass through the heat exchanger chamber 322. The system 300 of FIG. 3 also includes a low pressure air riser 312, a vaneaxial low-pressure air burner unit 314. A two-speed motor 316 is also connected to the burner 302. Air can input by an inlet bell 318.

FIG. 4 is a schematic illustration of an example waste gas burner and heat exchanger system 400. System 400 includes a bypass layout similar to that shown in FIG. 3, but uses natural convection rather than a fan to assist the flow of hot gases through the heat exchanger 408. System 400 includes a waste gas burner 404 that burns a waste gas 406. The burned waste gas can be selectively directed to a heat exchange chamber 410 and/or the flue vent 414 by controlling the position of valve A 412. Bypassing in FIG. 4 is achieved using convection created by the structure of the chamber 410 and the flue stack vent 414. A single fan and valve may be used.

FIG. 5 is a schematic illustration of an example integrated spiral heat exchanger 504 embedded within the structure of the flue stack 502. Spiral heat exchanger 504 resides within a heat exchanger chamber 505 and includes a thermal cycle fluid inlet 506 and a thermal cycle fluid outlet 508. The hot gas 510 passes through the flue stack 502 and heats the thermal cycle working fluid as it passes across the spiral heat exchanger 504. The gas 512 is then vented out. A fan 514 can aid in directing the fluid across the spiral heat exchanger 504. Alternatively, the fan 515 can be located below the heat exchanger 504 to blow the burned gas across the heat exchanger 504.

FIG. 6 is a schematic illustration of an example waste gas burner and heat exchanger system 600. System 600 includes a flue stack 602 housing a heat exchanger 604 within the flue stack 602 such that hot gas 606 exchanges heat with the heat exchanger 604 surface while the thermal cycle working fluid is passed within the heat exchanger 604. The system 600 of FIG. 6 may include a flue stack 602 that houses the heat exchanger 604 in the wall of the flare or incinerator so that it is not directly exposed to the hot gas 606. The coiled heat exchanger 604 can be sandwiched between an inner and outer shell that make up the flue stack 602. A thermal fluid or gel may be used in conjunction with this approach to enhance the heat transfer from the hot gas 606 to the working fluid. The system 600 may be a modular system that can connect to existing flue stacks. To that end, it includes joints 606 and 607 to link the modular system to an existing flue stack. The embedded heat exchanger allows for the heat exchange to take place without impeding the flow of the burned gas 606. Heat exchanger 604 can be of any practical design, and in some implementations, the heat exchanger 604 may be a spiral-shaped heat exchanger.

FIG. 7 is a schematic of an example burner and thermal cycle system 700.

System 700 includes a burner 701, which may be a flare or incinerator burner or other type of waste gas burner, and a thermal cycle 720. System 700 uses a heated working fluid to heat or evaporate another fluid (e.g., oil or other process liquid) after the working fluid has been expanded by an expander 722 of the thermal cycle. Specifically, thermal cycle expanded working fluid may be partially or wholly cooled by another fluid, which in turn would be heated by the expanded working fluid. The working fluid can then be further cooled by a condenser 730.

FIG. 7 shows a burner system 701 that includes a heat exchanger 708 housed in a heat exchanger chamber 710. Waste gas 704 is directed into a burner 702 that burns the waste gas. The burned waste gas is directed into the flue stack 718. In some implementations, the burned gas is directed by a combustor fan 706 can be used to direct the burned gas into the flue stack 718. The position of valves, such as valve 712 and valve 714, can be controlled to direct burned gas into the heat exchanger chamber 710. In the heat exchanger chamber 710, the burned gas interacts with a heat exchanger 708, which can either directly or indirectly heat a working fluid. The burned gas is vented out of the flue stack 718. Another air fan 716 can be used to control the heat in the heat exchanger chamber 710. The burner system 701 shown in FIG. 7 may include one or more alternative implementations as shown in FIGS. 2A-C. For example, butterfly valves may be used, or a retractable heat exchanger may be used. Similarly, one or more of fans 706 and 716 may be optionally omitted.

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 retraction mechanism shown in FIG. 2C. Similarly, the burner system could incorporate some or all of the aspects described in conjunction with FIGS. 2-6.

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 60-70F needs to be heated to 100-120F 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.

FIG. 8A is a schematic illustration of an example heat transfer system 800. In system 800, the heat transfer takes place in one common chamber 802 with a fire tube- type burner 806, heat exchanger 808, and other process liquid heat exchanger 814. In system 800, heat from burned gas is directed through a fire tube 810 and out of a flue stack 812. The fire tube 810 resides within a thermal bath 802 that is filled with a thermal fluid 804. The thermal fluid (e.g., glycol) can transfer heat from the fire tube 810 to thermal cycle heat exchanger 808 and process heat exchanger 814. The heated thermal cycle working fluid can be used to produce electric power. The thermal cycle heat exchanger 808 can heat the working fluid directly or indirectly via another fluid transferring the heat to another external heat exchanger (not shown). The thermal bath may be an oil/gas/water separator tank.

FIG. 8B is a schematic illustration of an example heat transfer system 820. System 820 is similar to that shown in FIG. 8A, except that in system 820, the second process fluid 822 to be heated acts as the thermal transfer fluid between the fire tube 810 and the thermal cycle heat exchanger 808. The process fluid 822 enters the thermal bath 821 through a process fluid inlet 824. It fills the thermal bath 821 to the extent that it can transfer heat between the fire tube 810 and the thermal cycle heat exchanger 808. It can then be directed out of the thermal bath 821 by a process fluid outlet 826.

FIG. 9A is a schematic illustration of an example of dual waste gas burner and heat exchanger system 900. The system 900 includes two portions: a first portion 901a and a second portion 901b, each portion separated by a thermal barrier 903. In the example shown in FIG. 9A, the first portion 901a is a first chamber and the second portion 901b is a second chamber. The system 900 includes two burners: burner A 902 and burner B 904. Waste gas 906 enters the burners 902 and/or 904 via a modulating valve 908 where the proportion of gas to each burner can be controlled. Burner A 902 facilitates combustion of waste gas 906 with or without the aid of combustor fan A 910. Hot gases may then be exhausted through the flue stack 912. In the case of incinerator applications, the hot gases may be directed elsewhere, such as to another process. Similarly burner B 904 facilitates combustion of waste gas 906. Hot gases are passed through a heat exchanger 914 housed in the second chamber, which is referred to here as a heat exchanger chamber 916, and are then admitted to the flue stack 912 from the heat exchanger chamber 916 via an aperture, referred to here as a heat exchanger chamber outlet 918. Burner B 904 facilitates combustion of waste gas 906 with or without the aid of combustor fan B 920. The heat exchanger chamber outlet 918 can be structured or configured to restrict the flow of burned waste gas from the first portion 901a into the second portion 901b, the result being that the temperature of the second portion 901b is not affected when the burner 904 is not burning waste gas. In some implementations, the thermal barrier 903 is an insulated wall, which also aids in controlling the temperature in each chamber.

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. FIG. 9B is a schematic illustration of another example dual waste gas burner and heat exchanger system 930. System 930 includes a first portion 931a residing above a second portion 931b. In the implementation shown in FIG. 9B, the first portion 93 la is separated from the second portion 93 lb by a thermal barrier 933. The system 930 includes two burners: burner A 932 and burner B 936. Waste gas 948 enters chambers in which burners 932 and/or 936 reside via a modulating valve 946. Modulating valve 946 controls the proportion of gas to each burner. Valve 946 may be controlled by the thermal cycle system to control the amount of heating of the working fluid. Burner A 932 facilitates combustion of waste gas 948 with or without the aid of a fan 944. Hot gases are then exhausted through the flue stack 942. Similarly burner B 936 facilitates combustion of waste gas 948. Burned gas is passed from the burner B 936 to a heat exchanger 938 housed in a heat exchanger chamber 940 (in this case, heat exchanger chamber 940 is the second portion 931b). The burned gas is then passed to the burner A chamber 934 housing burner A 932 via an aperture, heat exchanger chamber outlet 950, and out through the flue stack 942. Burner B 936 facilitates combustion of waste gas 948 with or without the aid of the fan 944. Heat exchanger 938 can directly heat a thermal cycle working fluid or may indirectly heat a thermal cycle working fluid by heating a thermal fluid that indirectly heats the working fluid of a thermal cycle. The aperture heat exchanger chamber outlet 950 allows hot gases from burner A 932 to aid the flow of gases from burner B 936 through the flue stack 942 through the Venturi effect. Furthermore, design of the heat exchanger chamber outlet 918 can be elected so that hot gases from burner A 932 cannot enter the heat exchanger chamber 938. Accordingly, heat exchanger 938 receives heat from burned gas in the second portion 93 lb from burner B 936.

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. FIG. 10 is a schematic illustration of an example combined waste gas burner and thermal cycle heat exchanger system 1000. The combined waste gas burner and thermal cycle heat exchanger system 1000 is operable to capture the heat produced by burning waste gas. This heat energy is converted into other forms of energy using the thermal cycle (e.g., thermal cycle generator system 100). In the case of a Rankine cycle, the waste gas burner and thermal cycle heat exchanger system 1000 is used as or with the Rankine cycle's evaporator and heat source (e.g., evaporator 65 and heat source 60 of FIG. IB).

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 FIG. 10 is a burner configuration having a burner 1006a configured primarily for efficient destruction of the waste gas, regardless of the type of heat output by the burner, and a burner 1006b configured to output its heat substantially as radiant heat. In other instances, the burners 1006a can be of the same configuration.

[0001]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 FIG. IB) and the heat exchanger 1008 can be the evaporator to the thermal cycle (e.g., evaporator 65) or used in heating the evaporator to the thermal cycle. With the heat exchanger out (substantially or entirely) of the upward convective heat flow from the burner 1006, the combustion byproducts and impurities in the waste gas are carried up the flue 1004 and away from the heat exchanger 1008. Therefore, this reduces deposition of these combustion byproducts and impurities on the heat exchanger 1008, and enables the system 1000 to burn high impurity waste gas. In FIG. 10, the heat exchanger 1008 is shown below the burner 1006. In other instances, the heat exchanger 1008 can be positioned differently relative to the burner 1006. For example, the heat exchanger 1008 can be positioned to a side of the burner 1006 and the burner's primary heating direction oriented to the side. Still other configurations exist.

[0002]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.

[0003]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: