Combined heat and power system and method of operation

Abstract

The present invention provides a combined heat and power system and operating method. The system includes a combustion chamber configured to directly combust solid organic material. A compressor turbine is fluidly coupled to the combustion chamber. An expansion turbine is fluidly coupled to the combustion chamber. In one embodiment, the system has a low turbine pressure ratio.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of U.S. Application No. 16 / 538,144, filed on August 12, 2019, which is incorporated herein by reference in its entirety.

[0003] The subject matter described herein relates to a cogeneration system, and specifically to a thermal system that utilizes waste, organic, and plastic resources and converts them into thermal energy, which is used to drive a gas turbine coupled to the thermal system to produce electricity and high levels of usable waste heat that can be used for both low temperature and high temperature thermal applications. Background Art

[0004] Combined heat and power (CHP) systems have been used in various forms for more than 100 years. The most common are fossil fuel combustion systems that use, for example, steam turbines, gas turbines and internal combustion engines to generate electricity. Waste heat from these systems can be used for a wide range of applications such as heating, cooling, and in some cases where the waste heat temperature is high enough, the waste heat can be used to drive the second cycle. Traditionally, most of the emphasis of traditional CHP systems has been on large fossil fuel combustion systems connected to regional heating networks. Recently, the focus has shifted to smaller distributed CHP systems, in which the heat or electricity generated can be better utilized by end users. These smaller CHP systems are also fossil fuel combustion systems that usually use small gas turbines or reciprocating engines to generate electricity and available waste heat from the cycle. Other systems using organic Rankine cycles have also been used, even if the quality of the waste heat is relatively low, which limits thermal applications.

[0005] Recently, the focus of using renewable organic waste streams for fuel has dominated and made technology progress. Large biomass and municipal solid waste energy conversion systems have been in operation for decades. The ability to utilize multiple organic sources in small CHP systems (e.g., less than 1MW electricity) has always been challenging for many reasons. There have been many small organic power conversion technologies that have been used for varying degrees of success. In traditional power systems, gasification of organic matter into synthesis gas has been a method of converting solid fuels into hydrocarbon gas for combustion. Unfortunately, these systems may be expensive, especially when scaled to smaller-scale applications. In addition, there may be specific challenges in the application of organic raw materials. For example, depending on the gasification method and conversion efficiency, the potential energy that can be obtained in some organic matter suffers losses, which has an economic impact on the cost of electricity and heat. For many gasification systems, the gasification of mixed organic residues is particularly problematic.

[0006] Another method applied to small CHP applications has been used to directly burn organic matter through appropriate burners and use heat to drive external combustion engines through heat exchangers. Traditional external combustion systems include Stirling cycle, Steam Rankine, Organic Rankine and supercritical CO2 circulation. In all these systems, the temperature of waste heat affects the cycle efficiency. The higher the temperature of waste heat, the lower the power efficiency. Except for steam cycle, other thermodynamic cycles usually fail when producing uniform hot water at 90 ℃. However, in the case of steam cycle, the defect is the complexity and cost associated with the high pressure steam loop in small applications.

[0007] Another method that has been adopted recently is to use an open Brayton cycle gas turbine and introduce heat indirectly through a heat exchanger. Several systems have been tested in which small turbines have been connected to organic combustion systems. In these systems, ambient air is compressed in the compressor of the turbine and then directed to a heat exchanger to preheat the compressor air. Then, the compressed and preheated air is directed to a high heat exchanger to be heated by the organic combustion system. The highly heated air is then expanded in the turbine to produce work in order to turn the generator and generate electricity. Continuous circulation, hot turbine gas is used for preheating in a heat exchanger as described above. The turbine waste heat gas can then be discharged or directed to another heat exchanger, where the combustion air is heated with the discharged combustion gas and directed to the combustion process. In the configuration disclosed by the prior art, the turbine uses a heat exchanger to preheat the compressed ambient air. In addition, most existing systems use a combustion air preheater to recover heat from the combustion gas and the remaining heat in the turbine exhaust gas. Although these approaches improve thermoelectric conversion efficiency, they still require multiple heat exchangers and complex piping to route the gas in the loop, which can reduce overall system efficiency.

[0008] The role of the heat exchanger is to increase the temperature of the compressor air before the high heat exchanger. Heat is extracted from the expansion turbine to preheat the compressor air. The compressor air is further heated by the high heat exchanger, where heat is extracted from the combustion gases. The use of a heat exchanger reduces the size of the high heat exchanger. However, this also reduces the amount of thermal energy extracted from the combustion gases. In order to achieve high thermoelectric efficiency, it is desirable to recover as much heat as practicable from the exhaust combustion gases. Since it is not possible to feed the combustion exhaust gases directly back into the combustion system, a combustion air preheater is used to recover heat from the exhaust gases. These losses can be reduced by using the turbine exhaust as the combustion air, but this still uses an air preheater.

[0009] Another challenge of existing systems involves controlling the temperature of the combustion gases entering the high heat exchanger. For applications using Brayton cycle gas turbines, it is desirable to be able to deliver compressor (or expander) air at the design inlet temperature of the turbine. In many cases, this temperature can be as high as 950°C. In order to achieve this inlet air temperature, the heat exchanger is operated close to the maximum design temperature limit. In addition, it is desirable to be able to maintain a constant temperature at the heat exchanger. Overheating and temperature variations may cause stress on the heat exchanger and the expansion turbine, while insufficient heating will cause a lower inlet temperature, thereby reducing power and efficiency. Temperature variations may be an important issue when burning mixed fuels that may have greatly different calorific values.

[0010] Existing systems also typically use a constant volume feed system to deliver solid fuel into the combustion chamber. However, there is no system to determine the calorific value of the mixed solid fuel as it is fed into the combustion chamber. As the fuel burns, a higher calorific value fuel will cause the temperature of the exhaust gas to increase, while a lower calorific value fuel will have the opposite effect. Therefore, the mixed solid fuel produces a variable gas temperature flow that cannot be easily corrected by adjusting the feed system.

[0011] Another method that has been adopted in recent years is to use an open Brayton cycle gas turbine and directly introduce heat through a pressurized combustion system. Several systems have been developed in which large turbines have been connected to organic combustion systems. In these systems, ambient air is compressed in the compressor of the turbine and then directed into a combustion chamber where solid organic fuel is fed under pressure and combustion and heating gases are produced. The heated combustion exhaust gases are then passed through the turbine and expanded in the turbine to produce work in order to turn a generator and generate electricity. Large turbines are usually operated at high pressure ratios, where heat exchangers are usually not used. The turbine waste heat gases can then be discharged or directed to another heat exchanger, where additional heat can be extracted to generate heat, cool or process heat requirements. This system has not yet been used for smaller turbine systems, mainly for economic reasons.

[0012] Still another challenge of direct-fired turbine systems is to reduce the amount of particulates leaving the combustion chamber, which may cause erosion of the turbine blades and deposit and contaminate the heat exchanger and other heat exchangers. To reduce this particulate, various methods including high-temperature ceramic filters, electrostatic precipitators and cyclone separators of different configurations have been used. The challenge is to provide appropriate particulate removal at an acceptable cost without introducing a large pressure drop. Ceramic filters are efficient but require continuous cleaning to reduce the pressure drop, and the automated system is expensive. Counter-flow cyclone separators have been used, and the counter-flow cyclone separators provide appropriate particle removal, even with the disadvantages of high pressure drop at high gas velocities and decreased efficiency as the gas velocity decreases and stops operating at less than 50% of the maximum design velocity. Single-flow cyclone separators can also be used for particulate removal and have the advantage of maintaining higher efficiency down to 25% of the maximum design velocity. Single-flow cyclone separators also have a much shorter gas residence time, which reduces the amount of heat loss through the cyclone separator wall.

[0013] Another challenge of organic fuel direct-fired turbine systems is the need for a pressurized fuel feed system to introduce fuel into the pressurized combustion chamber. Several methods including rotary valves, dual rotary valves, dual gate valves, dual flapper valves, and various types of plug-in feeders have been used. All of these systems have a common defect in that the hot gas from the combustion chamber can flow through these valves in the reverse direction toward the feed supply. This introduces both efficiency losses and potential thermal risks. Backflow is caused by leakage around the rotary valve or from the dead space between the dual airlocks, where high pressure, hot gas flows into the space and is then released to the lower pressure inlet side when the inlet airlock is opened.

[0014] Still another challenge of organic fuel direct combustion turbine system is to provide combustion chamber and system that meet both physical and economic parameters expected by power system. It is expected that solid fuel combustion system can withstand high temperature exceeding 1000 ℃. In addition, solid fuel can contain many different inorganic materials, such as small metals, rocks and sands, as well as salts and other minerals. With regard to sand and rocks, these inorganic materials may cause wear and tear, and may produce slagging with salts and other minerals or chemically interact with combustion chamber materials. Traditional solid fuel combustion chamber uses castable refractory or fired ceramic components. Refractory can cope with high temperature, even with several defects. One defect is that refractory is not very strong and is susceptible to wear. In addition, refractory casting requires thick walls to achieve structural stability, thereby increasing a lot of weight. In addition, refractory needs to be wrapped in steel to maintain compression force on refractory when material is heated. Refractory is also brittle and susceptible to thermal stress, which causes cracks in refractory over time and in the case of thermal cycle. The large thermal mass of the refractory material has a large thermal mass that causes start-up times to be very lengthy and also causes changes in operating temperature to take longer times due to the need for the refractory to reject or absorb heat.

[0015] Another material used for the combustion chamber is silicon carbide, which is a fired ceramic. Silicon carbide can also handle very high temperatures and is extremely hard and wear-resistant. Due to the strength of fired ceramics, silicon carbide components can also be made with thinner walls than refractory materials. There are some drawbacks to using silicon carbide. One drawback is that silicon carbide is brittle and susceptible to thermal stress. As with refractory materials, it is very difficult to connect with ceramics, specifically to fit tightly with metals. Making high-temperature connections in the case of pressurized systems becomes very expensive. Both refractory materials and silicon carbide components are also susceptible to transportation damage, where impact vibrations can cause cracks in the ceramic. Another drawback is the high cost of firing silicon carbide.

[0016] Thus, while existing CHP systems are suitable for their intended purposes, there remains a need for improvement, and in particular for providing CHP systems having the features described herein. Summary of the invention

[0017] According to one aspect of the present disclosure, a combined heat and power system is provided, comprising: a combustion chamber configured to directly combust solid organic material; a compressor turbine fluidly coupled to the combustion chamber; and an expansion turbine fluidly coupled to the combustion chamber, wherein a turbine pressure ratio is less than 8.

[0018] In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a turbine pressure ratio of less than 4. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a single-flow cyclone separator fluidly coupled between the combustion chamber and the expansion turbine. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a generator operably coupled to the expansion turbine. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a fuel feed system fluidly coupled to the combustion chamber, the fuel feed system having a hopper configured to receive the solid organic material and a feed pipe disposed between the hopper and the combustion chamber.

[0019] In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a metering device, such as a rotary valve, disposed between the hopper and the feed pipe, the metering device being configured to selectively cause pressurized gas to flow from the combustion chamber to the hopper. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include the hopper being sized to provide fuel to the combustion chamber for 1 to 6 hours of operation. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include an ash bin operably coupled to the single-flow cyclone separator and fluidly coupled to the hopper via a flow control valve, wherein the flow control valve is configured to cause pressurized air to flow from the hopper to the ash bin before the hopper is refilled with solid organic fuel.

[0020] In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a second cycle system thermally coupled to the output of the expansion turbine. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include the second cycle system being one of the following: an organic Rankine cycle, a closed regenerative Brayton, a Stirling, or a supercritical carbon dioxide (CO2) engine.

[0021] According to another aspect of the present disclosure, a combustion system is provided. The system includes: a pressure vessel; a combustion chamber disposed within the pressure vessel, the combustion chamber being configured to burn solid organic material, wherein the combustion chamber and the pressure vessel are arranged to define a space therebetween; a conical plenum disposed within the combustion chamber, the conical plenum being configured to distribute fuel to the periphery of the combustion chamber; a plurality of plenum tubes extending from the conical plenum and oriented tangentially to the radius of the combustion chamber, the plurality of plenum tubes being configured to lift and suspend the solid organic material and induce cyclonic flow within the combustion chamber; and a port fluidly coupled between an air source and the space, wherein during operation, air flows from the air source through the port and into the space to provide a thermal break between the combustion chamber and the pressure vessel.

[0022] In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a particle separator pressure vessel that is fluidly coupled to receive an airflow from the space. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a single-flow cyclone separator that is fluidly coupled to receive combustion gases from the combustion chamber. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a first insulation layer that is disposed around the combustion chamber.

[0023] In addition or as an alternative to one or more of the features described herein, further embodiments of the system can include a second insulation layer, the second insulation layer surrounding the single flow cyclone separator. In addition or as an alternative to one or more of the features described herein, further embodiments of the system can include the first insulation layer and the second insulation layer being a sprayed refractory or blanket insulation material.

[0024] According to another aspect of the present disclosure, a particle separator is provided. The particle separator comprises: a pressure vessel; at least one single-flow cyclone separator disposed in the pressure vessel, the at least one single-flow cyclone separator being configured to remove particles larger than 10 microns; a plenum disposed in the pressure vessel around the at least one single-flow cyclone separator, the plenum defining a thermal insulation layer between the at least one single-flow cyclone separator and the pressure vessel; and an ash bin disposed in the pressure vessel adjacent to an outlet of the at least one single-flow cyclone separator.

[0025] In addition to or as an alternative to one or more of the features described herein, further embodiments of the particle separator may include a cyclone discharge valve operably coupled to an ash bin outlet, the cyclone discharge valve being configured to pneumatically isolate the plurality of single-flow cyclones. In addition to or as an alternative to one or more of the features described herein, further embodiments of the particle separator may include a water-cooled jacket disposed around the outlet of the ash bin. In addition to or as an alternative to one or more of the features described herein, further embodiments of the particle separator may include a conduit coupled between the cyclone discharge valve and the ash bin.

[0026] According to yet another aspect of the present disclosure, a pressurized feed system is provided. The pressurized feed system includes: a fuel hopper having a hollow interior and configured to hold a material under pressure; a gas valve configured to seal the pressurized feed system; a metering device configured to meter the material flowing therethrough; a pressurized auger operatively coupled between the fuel hopper and a rotary feed valve; and a feed pipe operatively coupled to the metering device, opposite the pressurized auger.

[0027] In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a solenoid air valve fluidly coupled to the fuel hopper, the solenoid air valve being configured to selectively release pressurized air from the fuel hopper. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include a cyclone separator ash discharge valve fluidly coupled to the solenoid air valve. In addition to or as an alternative to one or more of the features described herein, further embodiments of the system may include the metering device being a rotary feed valve.

[0028] These and other advantages and features of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The subject matter regarded as the present disclosure is particularly pointed out and distinctly claimed in the claims at the end of the specification. The foregoing and other features and advantages of the present disclosure will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0030] Figure 1 is a schematic diagram of a cogeneration system according to an embodiment;

[0031] Figure 2 yes Figure 1 A schematic diagram of a portion of a combined heat and power system;

[0032] Figure 3 yes Figure 1 Schematic diagram of a rotary feed valve of a combined heat and power system;

[0033] Figure 4 yes Figure 1 a schematic diagram of the combustor and particle separator portions of a combined heat and power system; and

[0034] Figure 5 is a flow chart of a method of operating a combined heat and power system.

[0035] The detailed description explains embodiments of the disclosure, together with advantages and features, by way of example with reference to the drawings. DETAILED DESCRIPTION

[0036] A cogeneration system is described in one or more embodiments herein that utilizes waste organic resources and converts them into thermal energy that is used to drive a gas turbine coupled to a thermal system to produce electricity and high levels of usable waste heat that can be used for both low temperature and high temperature thermal applications.

[0037] One or more embodiments herein provide a system and method for a solid fuel, direct-fired, open Brayton cycle. This method uses a low pressure ratio gas turbine, which includes a compressor for compressing air and a turbine for expanding exhaust gas and producing useful work. In one embodiment, the pressure ratio is less than 8. In another embodiment, the pressure ratio is less than 4. In this system, filtered ambient air is compressed in the compressor of the turbine and then directed to a pressure vessel covering a combustion chamber. The compressor air is used to cool the combustion chamber components made of metal. The cooling air also creates a thermal insulation layer between the combustion chamber and the external pressure vessel wall. The compressor air is then passed into a second pressure vessel covering a multi-single-flow cyclone separator. The cooling air is used to cool the metal cyclone separator and provide a thermal insulation layer to the external container. The air leaving the second container then enters the high-pressure side of the heat exchanger, where the gas is heated by heat transfer from the exhaust gas leaving the turbine. The heated high-pressure air is directed to the combustion chamber, where solid organic fuel is fed under pressure and combustion is generated to add heat to the gas. The heated combustion exhaust gas is then directed through a channel to a multiple single flow cyclone separator where particulates are removed from the hot gas. The hot gas leaving the cyclone separator then enters an expansion turbine to produce work in order to turn a generator and generate electricity. Continuing the cycle, the hot gas leaving the turbine enters the low pressure inlet of the heat exchanger where it transfers heat to the compressor air. The turbine waste hot gas can then be exhausted or directed to another heat exchanger where additional heat can be extracted to produce additional work, heat, cooling or process heat requirements.

[0038] The advantage of an efficient, low-power, solid fuel CHP system is the ability to use waste organic fuel inventories that are too expensive to transport to the centralized locations required for large systems. In other words, the embodiments of the CHP system provided herein allow the use of waste organic fuel inventories close to their sources of generation. Utilizing these resources in situ provides low-cost fuels, which produces low-cost electricity. Distributed generation also reduces the infrastructure costs associated with using turbine waste heat for heating and cooling.

[0039] A feature of the described embodiment is to configure a low pressure ratio turbine system with a combustion chamber capable of burning solid organic materials, the system being used to heat the compressor air from the discharge temperature to the maximum temperature required at the turbine inlet after the compressor air leaves the heat exchanger. The combustion chamber contains a mechanical device to introduce solid fuel into the combustion zone under pressure. The material in contact with the hot gas mixed with the compressor air ignites the material in a continuous process. The direct combustion of organic materials has the advantage of eliminating the high heat exchanger used in indirect combustion systems, where heat is transferred to the working gas through the heat exchanger. This improves thermal power efficiency and reduces capital and maintenance costs.

[0040] Another feature of the described embodiment of the combustion system includes a temperature sensor such as a thermocouple to measure the temperature of the combustion exhaust gas leaving the combustion chamber. In one embodiment, a high temperature cyclone separator particle separation system is used to remove about 99% of particles larger than about 10 microns in size from the combustion gas to reduce damage to the expansion turbine and pollution to the heat exchanger. In order to obtain the desired combustion level, it is expected to achieve a combustion gas temperature of at least 1000°C. Higher temperatures are expected until NOx formation can become an emission limit. In some embodiments, the combustion gas temperature is generally higher than the maximum temperature limit of the turbine inlet. The hot gas entering the cyclone separator flows through a conduit having a port for introducing a secondary gas. This gas can be any available gas stream with a lower temperature than the combustion gas. One source will be compressor air flowing through a pressure vessel covering the cyclone separator. Another gas stream that can also be used is compressor air leaving the heat exchanger, the temperature of the air stream being higher than the temperature of the air leaving the compressor but lower than the turbine inlet temperature. A flow regulating valve is attached to the port to control the quality and amount of heat energy entering the combustion air stream. The secondary gas stream provides a way to reduce the combustion gas temperature to the desired turbine inlet temperature and regulate fluctuations in the gas temperature. A second thermocouple measuring the temperature of the combustion gases exiting the cyclone separator sends a signal to the flow control valve to increase or decrease the flow of gas into the system and regulate the temperature of the combustion gases entering the turbine.

[0041] Yet another feature of the described embodiment is a combustion chamber made of nickel alloy steel and capable of withstanding temperatures up to 1100°C. Advantages of a metal combustion chamber are lower cost, lower weight, and higher resistance to heat and mechanical shock compared to refractory or ceramic components. Another feature of the described embodiment includes coating the inner surface of the metal combustion chamber with a ceramic coating to improve wear resistance, chemical corrosion resistance, and oxidation resistance. These coatings include yttrium / zirconium or aluminum oxide and other coatings. Another feature of the described embodiment includes a combustion chamber enclosed in a pressure vessel, wherein secondary cooling air passes through an open plenum around the combustion chamber. The pressure vessel provides isolation of the combustion process within the combustion chamber under pressure while eliminating the force of pressure on the combustion chamber components. An external pressure vessel is used to maintain pressure at a lower temperature, which has the effect of creating a substantially zero pressure difference between the outside and inside of the combustion chamber. The pressure vessel is pressurized by compressor air that flows from the turbine into the pressure vessel enclosing the combustion chamber and then flows through a connecting channel to the cyclone separator pressure vessel. The purpose of the cooling air is to reduce the isolation requirements around the combustion chamber by 80%. Adding heat to the cooling air is kept to a minimum because heat addition reduces the efficiency of the heat exchanger and the overall thermoelectric efficiency. Yet another feature of the described embodiment is a combustion chamber comprising a conical combustion chamber bottom. The conical shape is used to distribute organic feed material from a central feed pipe to the outer edge of the combustion chamber. There are multiple combustion air ports at the base of the conical form, and the multiple combustion air ports are oriented approximately tangential to the outer radius of the combustion chamber. The ports are used to create turbulent cyclonic flow within the combustion chamber and lift organic material into suspension within the combustion zone. Another feature of the described embodiment is a combustion chamber that maintains organic material in suspension during combustion and moves all ash material out of the combustion chamber and into a cyclonic particle separator.

[0042] Another feature of the described embodiment is a combustion chamber comprising a mechanical feed system to deliver solid fuel to the chamber under pressure. A feature of the described embodiment comprises a metering device such as a rotary valve to, for example, produce a pressure seal and meter fuel into the combustion chamber, a pressurized rotary feed auger, a pressurized feed hopper, and a dome valve. The rotary valve does not produce a perfect seal because there is a gas leak around the inner barrel and a gas backflow caused by an empty impeller cavity after the release material is delivered to the feed side of the valve. In operation, with the dome valve open and at atmospheric pressure, the organic material fills the hopper. When the hopper is full, a level sensor in the hopper sends a signal to close the dome valve. Once the valve is closed, the hopper, the feed auger, and the connecting assembly begin to pressurize through the leak around the rotary valve. Depending on the size of the hopper, the system may take 5 to 15 minutes to pressurize. Once the pressure in the feed system is equal to the pressure in the combustion chamber, there is almost no additional backflow (e.g., about 2 cubic feet per hour), thereby preventing hot gases from continuing to flow to the fuel. The advantage of this system is that it does not require a separate compressor to pressurize the feed system and greatly reduces effective leakage, thereby improving efficiency. The feed auger delivers the feed fuel to the top of the rotary valve that feeds under gravity. When the fuel level is low and needs to be filled again, a second level sensor in the hopper sends a signal. Another feature of the pressurized feed system is that when the system is ready to be refilled, the gas from the feed system needs to be depressurized, after which the dome valve is opened. The compressed air from the feed system can be used as a power to transport the ash from the particle separator to the ash bin. The advantage of this is that the pneumatic system can transport ash over long distances and does not require a separate separator to supply pressurized air. Once the system has been depressurized, the dome valve opens and the organic material is allowed to fill the hopper and repeat the cycle. The size of the hopper depends on how often the ash system needs to be cleaned of ash. The ash removal cycle time depends on the feed material and can vary from 1 hour for high ash content materials to 6 or more hours for low ash content.

[0043] Another feature of the described embodiment includes multiple high temperature single flow cyclone particle separators that are coupled to the combustion chamber to clean the exhaust gas. An ash removal system is provided and includes an isolation valve to close the bottom of the cyclone separator when the pneumatic system removes particles from the cyclone separator. The multiple cyclone separators are enclosed in a pressure vessel where secondary cooling air passes through an open plenum around the cyclone separators. The pressure vessel is pressurized by compressor air that flows from the turbine into the pressure vessel enclosing the combustion chamber and then flows through a connecting channel to the cyclone separator pressure vessel. The cooling air reduces the isolation requirements around the cyclone separator by 80%. Heat addition to the cooling air is kept to a minimum because heat addition reduces the efficiency of the heat exchanger and the overall thermal and electrical efficiency. In one embodiment, the multiple single flow cyclone separators include multiple small diameter bodies of about 4 inches. The cutoff diameter of the particles in the cyclone separator is a function of the diameter of the cyclone separator body. The small cyclone separator body diameter allows for high removal efficiency of particles as low as 10 microns. Multiple clones are combined in parallel to meet the total airflow requirements.

[0044] Further aspects of the described embodiments include an exhaust plenum coupled to a provided cyclone separator. A secondary gas port is coupled to the exhaust plenum to allow for the introduction of secondary gas. An electronically controlled proportional valve coupled to the gas port is provided to control the mass flow of the secondary gas. A mixing zone is provided in the plenum for the gas to achieve temperature equilibrium. After the mixing zone, a thermocouple is coupled to the plenum to measure the gas temperature. A thermocouple coupled to the secondary port is provided to measure the gas temperature of the secondary gas. An electronic controller is provided to automatically control the proportional valve.

[0045] In addition, additional features of the described embodiments include a heat exchanger coupled to a low pressure, exhaust plenum of the gas turbine. A fluid connection from the cyclone pressure vessel is coupled to the high pressure, low temperature side of the heat exchanger. A fluid connection from the high pressure, hot side of the heat exchanger is coupled to the inlet of the combustion chamber. A fluid connection from the heat exchanger to the low pressure, cold side of the low temperature heat exchanger is provided to remove residual heat from the combustion gases.

[0046] For exemplary purposes and without being bound by any theory, the principles of the present disclosure are described herein and will now refer to the embodiments shown in the accompanying drawings, and specific language will be used to describe these embodiments. Nevertheless, it should be understood that it is not intended to limit the scope of the present disclosure. The following description is merely illustrative in nature and is not intended to limit the present disclosure, its application or use. It should be understood that throughout the accompanying drawings, corresponding reference numerals indicate similar or corresponding parts or features. As used herein, the term controller refers to an electronic processor (shared, dedicated or group) and memory, combinational logic circuits and / or other processing circuit systems that provide suitable interfaces and components for the functions that may include an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a digital signal processor (DSP), an electronic circuit, an electronic processor (shared, dedicated or group) and memory that executes one or more software or firmware programs, a combinational logic circuit and / or other suitable interfaces and components that provide the functions.

[0047] As shown and described herein, various features of the present disclosure will be presented. Various embodiments may have the same or similar features, and therefore the same or similar features may be labeled with the same reference numerals, but preceded by a different first numeral indicating the drawings in which the features are shown. Thus, for example, component "a" shown in Figure X may be labeled "Xa" and similar features in Figure Z may be labeled "Za". Although similar reference numerals may be used in a general sense, various embodiments will be described and various features may include changes, alterations, modifications, etc., as understood by those skilled in the art, whether explicitly described or otherwise understood by those skilled in the art.

[0048] Figure 1 A combined heat and power system (CHP) 100 is depicted according to an embodiment. The CHP system 100 utilizes a combustion system 21, an open cycle Brayton gas turbine 22, a high temperature cyclone particle separator 23, a high temperature heat exchanger 24 for transferring heat from the exhaust gas of the turbine 22 to the combustion system 21, and optionally a low temperature heat exchanger 25. In some embodiments, as described below with respect to Figure 5 As discussed, high temperature heat exchanger 24 is optional.

[0049] All indirect combustion power systems utilize at least one heat exchanger to transfer heat from the combustion process to the working gases of the engine. Depending on the type of engine cycle, the heat transfer will occur at different temperatures. For cycles such as Organic Rankine (ORC), the temperature delivered to the engine is rarely above 500°C and more typically below 250°C. The advantage of using ORC is that it can utilize lower temperature heat and subsequently lower cost heat exchangers. The disadvantages are low efficiency, higher overall cost, and low temperature waste heat discharged from the cycle, typically below 90°C, which is not easily achieved elsewhere.

[0050] Therefore, it is generally desirable to use a higher temperature cycle such as an open Brayton cycle to more directly and efficiently utilize the high temperatures available from the combustion system 21. Currently, low pressure ratio, Brayton turbine engines are designed to utilize heat at about 950° C. The advantages of a high temperature cycle are high efficiency, low cost, and high temperature waste heat that may be as high as 650° C. discharged from the cycle. The disadvantage is the use of higher temperature components in the combustion gas path as will be discussed further herein.

[0051] In one embodiment, for example, the pressurized feed system 20 further includes, but is not limited to, an air valve 60 for airtightly sealing the fuel feed system, such as a dome valve, a disc valve, a double disc valve, or a flapper valve. An electromagnetic flow control valve 61 depressurizes the feed system for refilling and allows the exhausted pressurized air to be used as a motive force to remove ash from the ash system. The pressurized feed hopper 63 holds the organic solid fuel under pressure, and the pressurized feed auger 64 then delivers the fuel from the hopper 63 to the rotary valve 65. The pressurized rotary feed valve 65 meters the fuel under pressure and creates an airlock between the combustion chamber 26 and the fuel above the rotary valve 65. The vertical fuel feed pipe 47 delivers the fuel from the rotary valve 65 to the bottom of the combustion chamber 26. During operation, the rotary valve 65 does not create a perfect seal or airlock because gas may leak around the inner barrel of the valve and the open void space between the impellers, which delivers pressurized gas to the low pressure area above the valve. In prior art systems, this would result in a loss of efficiency as the compressed air would not be able to reach the turbine to produce work. Additionally, these gases may be hot and may cause thermal risks as the gases travel towards the fuel.

[0052] Embodiments of the present invention utilize the leak to pressurize the feed system, which may take 5 to 15 minutes in some embodiments. It should be understood that as the feed system is equalized with the combustion chamber under pressure, no more backflow occurs. The hopper volume can be sized to hold enough fuel to operate for 1 to 6 hours without having to be refilled, which effectively reduces the gas loss caused by the leak by an average of 90%. Another advantage of the feed system is that when the fuel hopper needs to be refilled, the feed system is depressurized by opening the gas valve and allowing the gas to be discharged through the ash system 45 and the ash is pneumatically removed into the ash bin 46. This system and method also reduces or eliminates the need for a secondary compressor to pressurize the feed system and the need for a pressurized air source for the ash system 45.

[0053] like Figure 2-Figure 4 Continue to refer Figure 1As shown, in one embodiment, the combustion system 21 further includes, but is not limited to, a combustion chamber or housing 26 for burning organic fuel to generate heat, a pressure vessel 28 for accommodating the combustion chamber 26 and providing pressurized cooling air to flow around the combustion chamber 26. The pressure vessel 28 is additionally used to eliminate the pressure difference on the combustion chamber 26 components. Biomass fuel (that is, organic material produced in a renewable manner) includes, for example, wood fuels such as sawdust, seaweed, agricultural waste, saw grass, animal manure (i.e., manure) or even municipal solid waste (MSW). The organic material may also include plastic material. The combustion chamber 26 also includes a feed pipe 47 for delivering fuel to the combustion chamber 26 and an electric heater 51 for delivering heat to start.

[0054] The combustion system 21 also includes a rotary valve 65 for metering the mass of solid fuel introduced into the combustion chamber 26, a port 35 for delivering combustion air from the heat exchanger 24, an optional proportional valve 41 for metering the combustion air from the heat exchanger 24, a temperature sensor (e.g., a thermocouple 52) for measuring the temperature of the combustion gases in the combustion chamber 26, a temperature sensor (e.g., a thermocouple 53) for measuring the temperature of the combustion exhaust gases entering the turbine 22, and a controller 90 for receiving various sensor inputs (e.g., temperature, valve position, speed, etc.) and for controlling various valves and motors in the system 100. The combustion chamber 26 is configured to operate at combustion gas temperatures up to 1100°C and is constructed of nickel alloy steels such as Hastalloy X and is able to withstand high thermal and mechanical stresses compared to refractory or ceramic components. Nickel alloys are also resistant to the wear and corrosion effects of combustion gases. In one embodiment, the interior surfaces of the combustion chamber are coated with a ceramic composite coating to provide high wear and corrosion resistance and thermal insulation properties. Some examples of coatings are yttria / zirconia or alumina. In one embodiment, the exterior surface of the combustion chamber 26 is coated with an insulation layer to reduce heat loss from the combustion chamber 26 to the cooling air flowing through the pressure vessel 28. The thermal insulation material can be a sprayed refractory or a blanket insulation material.

[0055] In one embodiment, the particle separator 23 further comprises a pressure vessel 29 ( Figure 4), a separation hopper 71 for particulate collection, a cyclone ash discharge valve 68 for pneumatically isolating the cyclone during ash removal, an electromagnetic flow control valve 70 for pneumatically removing particles from the hopper 71 by pressurized air from the fuel hopper, and an electromagnetic flow control valve 69 for allowing particles to enter the ash bin 46. The particle separator 23 is configured to operate at combustion gas temperatures up to 1100°C and is constructed of nickel alloy steel such as Hastelloy X or other nickel alloy steels and can withstand high thermal and mechanical stresses compared to refractory or ceramic components. Nickel alloys are also resistant to the abrasive and corrosive effects of combustion gases. In one embodiment, the interior surface of the cyclone is coated with a ceramic composite coating to provide high wear resistance and thermal insulation properties. Some examples of coatings are yttria / zirconia or aluminum oxide.

[0056] In one embodiment, the outer surface of the single-flow cyclone particle separator 27 is coated with an insulation layer to reduce heat loss from the single-flow cyclone particle separator 27 to the cooling air flowing through the pressure vessel 29. The thermal insulation material can be a spray-on refractory substance or a blanket insulation material. The cyclone particle separator 23 also includes an exhaust gas plenum 49, a secondary gas port 42, a motorized proportional gas flow valve 41 connected to the port 42 to automatically control the amount of secondary air mixed with the combustion exhaust gas, and a temperature sensor, such as a thermocouple 53, for measuring the temperature of the gas entering the turbine inlet port 72.

[0057] The CHP system 100 also uses a high temperature heat exchanger 24, which includes a first port 55 for directing hot exhaust gas from the turbine 38 into the heat exchanger 24, a port 56 for directing cold exhaust gas from the heat exchanger 24 to an optional secondary heat exchanger for useful secondary heat use, an input port 57 for directing cold, high pressure, compressor air into the heat exchanger 24, and a port 58 for directing hot, high pressure, compressor air from the heat exchanger 24 into the combustion chamber 26. The high temperature heat exchanger 24 is configured to operate at temperatures up to about 700°C. Heat exchangers capable of operating within the high temperature and high pressure range required for this application operate near the structural limits of the metals employed, which are typically made of stainless steel or nickel alloys. Therefore, it is desirable to precisely control the temperature of the combustion gases to ensure that the temperature limits of the high temperature heat exchanger 24 materials are not exceeded. It should be understood that such temperatures are at the end of the structural capabilities of metal heat exchangers, and it is desirable to provide precise and accurate control of the temperature of the combustion gases delivered to the high temperature heat exchanger 24.

[0058] In one embodiment, a single countercurrent heat exchanger is used to improve the thermoelectric efficiency of the CHP system 100. It should be understood that other heat exchanger configurations are possible. In one embodiment, stainless steel or nickel alloy, single countercurrent plate or tubular heat exchangers are used, but other types can also be used, including but not limited to tube and shell, microtube, microchannel, plate type, etc. In one embodiment, the high temperature heat exchanger can be constructed of ceramic or nickel alloy steel. The control of the combustion gas temperature entering the high temperature heat exchanger 24 reduces the cost in two aspects. The first is to strictly control the temperature of the combustion shell to the high temperature heat exchanger 24 so that a stainless steel heat exchanger is used instead of a significantly more expensive nickel alloy. The second cost saving is to extend the life of the heat exchanger, thereby reducing the maintenance cost over time. Power generation equipment generally has an expected service cycle of twenty years. Operating a high temperature heat exchanger at high pressure may experience higher thermal stresses that may result in component replacement as short as 5 years. Reducing thermal stress at a well-controlled combustion gas temperature will extend the service life, which may result in a maintenance cost reduction of up to 25%. The advantage of using a heat exchanger is to recover heat energy from the turbine exhaust gas to preheat the combustion air after compression.

[0059] The open cycle Brayton gas turbine system 22 further comprises a turbine compressor 31 for compressing ambient air, a fluid connection 32 ( Figure 1 ), which fluid connection carries compressed ambient air to the combustor pressure vessel 28. The gas turbine system 22 also includes a fluid connection 37 from the cyclone separator outlet port 49 to the expansion turbine inlet port 72. The turbine expander 38 operates to expand the working gas and produce useful work, such as turning the generator 50 to generate electricity. The turbine system 22 also includes a fluid connection 39 from the outlet port 73 of the expansion turbine 38 to the inlet port 55 of the heat exchanger 24. The turbine system also includes a generator 50 connected to the shaft of the turbine to generate electricity.

[0060] In one embodiment, the combustion gases exiting the high temperature heat exchanger 24 at port 56 may be passed through the low temperature heat exchanger 25 to recover additional heat from the cooled combustion gases for use as in optional process step 250 ( Figure 5 ) is used in low temperature thermal applications as depicted in FIG. 1 . For example, in one embodiment, the cooled combustion gases may be at a temperature of about 200° C. and may be used in low temperature applications including, but not limited to, hot water, low pressure steam, bottoming cycle power generation, absorption refrigeration, etc. Additional cooled combustion gases exit the low temperature heat exchanger 25 and may be exhausted or recycled if desired.

[0061] refer to Figure 2 , continue to refer to Figure 1, depicting a pressurized solid fuel feed and ash removal system. In one embodiment, the pressurized feed system 20 further includes, but is not limited to, an air valve 60 for hermetically sealing the fuel feed system. An electromagnetic flow control valve 61 depressurizes the feed system during refilling and allows the exhausted pressurized air to be used as power to remove ash from the ash system. A pressurized feed hopper 63 holds the organic solid fuel under pressure, a pressurized feed auger 64 delivers the fuel from the hopper 63 to a rotary valve 65, a pressurized rotary feed valve 65 meters the fuel under pressure and creates an airlock between the combustion chamber 26 and the fuel above the rotary valve 65, and a vertical fuel feed pipe 47 delivers the fuel to the bottom of the combustion chamber 26. During operation, the rotary valve does not create a complete or perfect seal or airlock because gas may leak around the inner barrel of the valve and the open void space between the impellers, which delivers pressurized gas to the low pressure area above the valve. This will generally result in a loss of efficiency since the compressed air cannot reach the turbine to produce work. Additionally, these gases may be hot and may cause fires as the gases propagate toward the fuel. Embodiments of the present invention utilize the leak to pressurize the feed system, which in one embodiment may take 5 to 15 minutes, and as the feed system equalizes with the combustion chamber under pressure, no further backflow occurs. The hopper volume can be sized to hold enough fuel to operate for 1 to 6 hours without having to be refilled, which effectively reduces gas losses caused by leaks by an average of 90%. Another advantage of the feed system is that when the fuel hopper is refilled, the system is depressurized by opening the gas valve and exhausting the gas through the ash system and pneumatically removing the ash into the ash bin. This method also reduces or eliminates the need for a secondary compressor to pressurize the feed system and the need for a pressurized air source for the ash system.

[0062] Figure 3 The gas leakage path through the rotary feed valve is shown. In one embodiment, the rotary valve 65 further includes, but is not limited to, a rotary barrel 89 for metering the fuel into the combustion chamber 26 and a barrel housing 87 for preventing the pressure across the valve from leaking from the system. In operation, solid organic fuel is fed to the top of the rotary valve through the inlet port 85 under gravity. As the barrel rotates, the fuel fills the rotary valve barrel cavity 86. The fuel in the cavity 86 is delivered to the bottom side of the rotary valve 65 and falls through the combustion chamber feed pipe 47 under gravity. The cavity 88 in the barrel contains pressurized gas from the combustion chamber, and this gas is delivered to the top side of the rotary valve 65 as the barrel rotates. The rotary barrel in all rotary valves has a gap between the tip of the impeller and the barrel housing 87. The rotary valve experiences gas leakage around both the tip of the impeller and the gas volume delivered by the empty barrel cavity.

[0063] Reference now Figure 4 , continue to refer to Figure 1-Figure 3, which describes the combustion and cyclone separator system in detail. In one embodiment, the combustion system 21 further includes, but is not limited to, a combustion chamber or housing 26 for burning organic fuel to generate heat, a fuel feed pipe 47 for delivering fuel to the bottom of the combustion chamber 26, at least one electric heater 51 for delivering heat to start, a tapered inlet plenum 80 for admitting hot combustion air into the combustion chamber and distributing solid organic fuel from the center feed pipe to the outer radius of the combustion chamber, and a plurality of air plenum tubes 81 positioned approximately tangential to the outer radius of the combustion chamber. The plenum tubes 81 promote high velocity, turbulence, and cyclonic action within the combustion chamber 26.

[0064] The combustion further includes a pressure vessel 28 that houses the combustion chamber 26 and provides pressurized cooling air flowing around the combustion chamber 26. The pressure vessel 28 is further used to reduce or eliminate pressure differentials across the components of the combustion chamber 26. The pressure vessel 28 receives compressed air from the turbine 22 and allows the compressed air to enter the pressure vessel 28 through the port 82. The compressed air flows around the combustion chamber 26 to provide a thermal break between the combustion chamber 26 and the wall of the pressure vessel 28. The compressed air then flows out of the pressure vessel 28 and enters the particle separator pressure vessel 29. The combustion system 21 also includes a rotary valve 65 fluidly coupled to the combustion chamber 26 through a feed pipe 47, a port 35 for delivering combustion air from the heat exchanger 24, an optional proportional valve 41 for metering the combustion air from the heat exchanger 24, a temperature sensor (e.g., a thermocouple 52) for measuring the temperature of the combustion gases in the combustion chamber 26, and a controller 90 for receiving various sensor inputs (such as temperature, valve position, speed, etc.) and controlling various valves and motors in the system 100.

[0065] The combustion chamber 26 is designed to operate at combustion gas temperatures up to 1100°C and is constructed of nickel alloy steels such as Hastelloy X and can withstand higher thermal and mechanical stresses relative to refractory or ceramic components. Nickel alloys are also resistant to the wear and corrosion effects of combustion gases. In one embodiment, the interior surface of the combustion chamber is coated with a ceramic composite coating to provide high wear and corrosion resistance and thermal insulation properties. Some examples of coatings are yttria / zirconia or alumina. In one embodiment, the exterior surface of the combustion chamber 26 is coated with an insulating material to reduce heat loss from the combustion chamber 26 to the cooling air flowing through the pressure vessel 28. The thermal insulation material can be a sprayed refractory or a blanket insulation material. During system startup, the electric heater 51 is energized and heated until 1000°C, while the turbine rotates at a low speed to provide air flow. Allow solid organic fuel to fall (e.g., by gravity) to the bottom of the burner, where at least some of the fuel contacts the heater and begins to burn. In one embodiment, the turbine air flow is not enough to lift the material into suspension during startup but promotes rapid combustion of the fuel. Once combustion occurs, the temperature sensor 52 will register a rise in temperature at which time the turbine 22 will be accelerated to accelerate the combustion air and lift the fuel into suspension.

[0066] In one embodiment, the particle separator 23 further comprises a pressure vessel 29 for housing a plurality of single-flow cyclone particle separators 27, a separation hopper 71 for particulate collection, a cyclone separator ash discharge valve 68 for pneumatically isolating the plurality of single-flow cyclone particle separators during ash removal, a water-cooled jacket 84 around the ash outlet for cooling the particles, an electromagnetic flow control valve 70 for allowing pressurized air from the fuel hopper to pneumatically remove particles from the hopper 71, and an electromagnetic flow control valve 69 for allowing particles to enter the ash bin 46. The particle separator 23 is designed to operate at combustion gas temperatures up to 1100°C and is constructed of nickel alloy steels such as Hastelloy X and is able to withstand high thermal and mechanical stresses compared to refractory or ceramic components. Nickel alloys are also resistant to the wear and corrosion effects of combustion gases. In one embodiment, the internal surfaces of the cyclone separators are coated with a ceramic composite coating to provide high wear resistance and thermal insulation properties. Some examples of coatings are yttria / zirconia or alumina. In one embodiment, the outer surface of the single-flow cyclone particle separator 27 is coated with an insulating material to reduce heat loss from the single-flow cyclone particle separator 27 to the cooling air flowing through the pressure vessel 29. The thermal insulating material can be a sprayed refractory substance or a blanket-type insulating material. The cyclone particle separator 23 also includes an exhaust gas plenum 49, a secondary gas port 42, a motorized proportional gas flow valve 41 fluidly connected to the port 42 to automatically control the amount of secondary air mixed with the combustion exhaust gas, and a temperature sensor, such as a thermocouple 52, for measuring the temperature of the gas entering the turbine inlet port 72. The pressure vessel 29 provides pressurized cooling air flowing around the single-flow cyclone particle separator 27. The pressure vessel 29 is also used to reduce or eliminate the pressure difference on the components of the single-flow cyclone particle separator 27. The pressure vessel 29 receives compressed air from the combustion chamber pressure vessel 28 and flows the compressed air around the single-flow cyclone particle separator 27 to provide a thermal break between the single-flow cyclone particle separator 27 and the wall of the pressure vessel 29. The compressed air then flows out of the pressure vessel 29 through port 83 to enter the heat exchanger 24 .

[0067] Now continue to Figure 5 , continue to refer to Figure 1-Figure 4, an embodiment of a method 199 for controlling combustion of a CHP system 100 is shown. In operation, the method 199 includes starting the CHP system 100 by turning on the turbine 22 and the electric heater 51. Ambient air is delivered to the combustion chamber 26, as depicted at box 200. In one embodiment, in box 210, solid organic fuel is fed into the bottom of the combustion chamber 26 by the fuel feed system 20 through the feed pipe 47. In box 205, combustion air is provided by the turbine compressor 31, which passes through the pressure vessels 28, 29 through the fluid connection 32 and then passes through the heat exchanger 24 and is delivered to the combustion chamber 26 through the fluid connection 35. The solid fuel is introduced through the valve 65, thereby delivering the fuel to the bottom of the combustion chamber 26. The fuel is deposited on the electric heater at a temperature of up to 1000C, in which the material begins to burn. In one embodiment, a rotary valve 65 is used to control the feed rate of the fuel into the combustion chamber 26. When the temperature sensor 52 reaches 350°C, the speed of the turbine 22 is increased to promote a higher firing rate and further increase the temperature. The valve 65 also increases the fuel feed in proportion to the combustion gas flow until the desired operating temperature set point is reached and then the heater 51 is turned off. In one embodiment, the rotary valve 65 may contain multiple chambers and rotate to meter the amount of solid fuel entering the combustion chamber 26. The rotary valve also acts as an airlock to prevent the hot combustion gases from flowing back into the fuel feed and organic fuel reservoir.

[0068] For operations where the fuel is an organic material, the materials may be mixed and exhibit different heating values ​​as well as different moisture contents. In the case of such fuels, it is desirable to control the air / fuel ratio to maintain a more constant output temperature. Determining the moisture and heating value of the fuel stream entering the combustion chamber 26 is difficult and generally not very practical. Furthermore, due to these inconsistencies, fluctuations in the exhaust gas temperature may be significant. Therefore, in block 220, control of the post-combustion exhaust gas temperature is used to control the desired set point temperature of the turbine inlet port 72.

[0069] In one embodiment, the target operating temperature of the combustion process is about 1050 ℃, which depends on the fuel type adopted. It should be understood that other combustion operating temperatures in the combustion process are possible and can be selected based on several factors. It is usually expected that higher temperatures are used to burn fuel more completely, and reduce the amount of particulate emissions, hydrocarbon emissions (e.g., carbon monoxide (CO) emissions), although higher combustion temperatures will increase nitrous oxide (NOx) emissions. In one embodiment, this makes the desired operating temperature of the combustion chamber between 1000 ℃ and 1100 ℃. This temperature range provides a desired combustion level while minimizing NOx formation.

[0070] The combustion gas temperature at the outlet of the combustion chamber 26 is measured by a temperature sensor 52 (e.g., a thermocouple, an IR sensor semiconductor sensor, etc.), which is used to control the feed rate of the rotary valve 65 and the auger 64 feeding fuel to the combustion chamber 26 and the high temperature gas to be directed to the downstream process. When the gas leaves the combustion chamber 26, the temperature is measured by the temperature sensor 52. The controller 90 has a set point temperature of a defined average combustion temperature. In one embodiment, the controller 90 uses a time-averaged temperature measurement to control the speed of the solid fuel rotary valve 65 to control the feed rate of the fuel. The rotary valve is configured to feed solid fuel into the combustion chamber 26 while also providing an airlock to minimize the backflow of the combustion gas. Using the time-averaged temperature measurement to control the rotary valve allows the rotary valve 65 to maintain a more constant speed, rather than responding to fluctuations in the output temperature of the combustion gas. The gas temperature leaving the combustion chamber 26 can be as high as 1100°C, which exceeds the maximum temperature of the turbine 22. High temperatures are desired to achieve complete combustion and eliminate unburned hydrocarbon emissions.

[0071] The temperature sensor 52 is used to control the temperature of the combustion gases leaving the combustion chamber 26. The temperature sensor measures the instantaneous temperature of the gases and sends it to the controller 90. The time average is used to compare with the set point value of the combustion chamber 26 and control the amount of fuel and air required to maintain the set point temperature. The instantaneous value is compared with the set point value to determine the magnitude of the deviation from the set point value. The temperature sensor 53 ( Figure 1 ) is used to sense the temperature of the exhaust gas entering the expansion turbine 38. The temperature of the gas instructs the controller 90 to increase or decrease the gas flow from the proportional valve 41 into the fluid connection 37 to adjust the turbine inlet gas temperature to the desired set point as depicted in process step 220. When the sensor 53 measures the deviation from the set point temperature, the controller 90 begins to adjust the valve 41 in anticipation of the exhaust gas arriving at the turbine port 72. The first control process will open or close the valve to a predetermined position based on the temperature of the secondary gas. Once the combustion gases in the combustion system 21 and the gases at the expansion turbine 38 reach the desired set point temperature, the system 100 can begin to produce useful work.

[0072] In one embodiment, the compression turbine draws filtered ambient air and compresses the air to a desired pressure ratio relative to the power output, as depicted in box 200. The compressor turbine 31 and the expansion turbine 38 are mechanically coupled by a common shaft and rotate at equal speeds. The speed and pressure ratio are controlled by the controller 90 in response to the power demand for the turbine 22. The compressed air flows through the combustion system 21 as depicted in process step 200 and then flows to the heat exchanger 24 as depicted in process step 225.

[0073] Advantageously, in one embodiment, in box 225, the turbine 22 is connected to the high temperature heat exchanger 24 through an independent gas loop that allows a method of transferring heat from the exhaust gas of the expansion turbine 38 to the combustion air from the turbine compressor 31. As depicted at process step 225, the turbine 22 pulls clean working gas (e.g., ambient air from the environment) into the inlet of the compressor 31, where the working gas is compressed. The compressed gas is fed to the combustion pressure vessel 28 through the fluid connection 32 and flows through the plenum around the combustion chamber 26 and then enters the particle separator pressure vessel 29, where the compressed gas leaves, flows through the plenum around the particle separator. The air then flows to the high pressure cold side inlet port 57 of the high temperature heat exchanger 24 through the fluid connection 33.

[0074] The compressed working gas is heated by the exhaust gas leaving the expansion turbine 38 by extracting heat from the combustion gases flowing through a separate channel in the heat exchanger 24. The low pressure hot exhaust gas leaving the expansion turbine 38 flows to the inlet port 55 of the heat exchanger 24 through the fluid connection 39. The heat from the exhaust gas is transferred to the compressed air, enters the combustion chamber and leaves the heat exchanger 24 through the port 56. The remaining heat can be used for further purposes, as described in the optional blocks 240 and 250. The heated compressed air travels from the heat exchanger port 58 through the fluid connection 35 to the inlet plenum 80 of the combustion chamber 26. The hot compressed air then flows through a plurality of tubes 81 into the hot combustion chamber 26 to induce cyclonic action and combust with the solid fuel as depicted in block 200.

[0075] Advantageously, in one embodiment, as depicted in box 210, the combustion gases exiting the combustion chamber 26 flow through fluid connection 36 into a plurality of single flow cyclone particle separators 27 where particles above 10 microns are removed from the combustion gases. Ash is collected in an ash hopper 71 and periodically removed through fluid connection / conduit 45. The ash bin valve 69 opens to allow pressurized air from the fuel hopper 63 to pneumatically convey the ash into the ash bin 46. The cyclone separator also has a valve that isolates the cyclone separator during ash removal to maintain a higher cyclone pressure during operation. The cleaned combustion gases then exit the cyclone separator through outlet port 49 to the turbine inlet port 72.

[0076] In one embodiment, the exhaust gas exiting the outlet port 49 is at a temperature above 1000° C. and exceeds the turbine inlet temperature limit. As depicted in box 220, the proportional valve 41 is fluidly coupled from the heat exchanger 24 to the fluid connection 35. The hot compressed air from the heat exchanger 24 is allowed to flow through the port 42 and mix with the combustion gases in the fluid connection 37. The temperature sensor 53 is used to control the proportional valve 41 to reduce the temperature of the combustion gases to the desired turbine inlet temperature set point.

[0077] The combustion gases then pass through the expansion turbine 38 where useful work is produced in the form of shaft powering depicted at box 230. In one embodiment, the turbine shaft is connected to a generator 50 to convert this work into electricity. In another embodiment, the useful work is used to perform a manufacturing process. For example, the useful work can be used to operate a pump or other mechanical process, such as a mechanical refrigerator, compressor, vapor compression distillation, conveying equipment, etc.

[0078] In one embodiment, after expansion, the hot turbine working gas is then used to improve the efficiency and effectiveness of the CHP system 100 for several reasons. The first is that the hot working gas is used to provide high temperature combustion air to the combustion system 21 as depicted at box 225. Another reason is to provide high temperature (700°C), clean exhaust gas to generate additional shaft power by using a second cycle as depicted in optional box 240. The turbine exhaust working gas can be used for second cycle power generation, such as in a second cycle ORC system to generate additional work or electricity. In one embodiment, about 80% of the combustion input heat energy present in the exhaust gas is available for secondary cycle use. In one embodiment, for example, the secondary cycle can be used for power generation as described herein or for other purposes, such as but not limited to water purification, desalination, and drying materials. For example, although the main function of the heated expanded working gas from the expansion turbine 38 is to provide combustion air preheating through the heat exchanger 24 as described in box 225, the hot turbine gas can be used for additional heat transfer or work generation. In one embodiment, the working gas temperature at fluid connection 39 is about 700°C and will not utilize heat exchanger 24 but will flow to the heat exchanger for use in the second cycle. The second cycle can be arranged in series or in parallel.

[0079] Advantageously, for a system 100 sized to produce 75 kW of electrical power, an additional 40 kW - 150 kW of additional power can be generated from the second cycle process. For example, a low temperature ORC utilizing available waste heat can generate an additional 40 kW, while a high temperature ORC can generate an additional 75 kW. More efficient cycles, such as closed regenerative Brayton, Stirling, or supercritical CO2 engines, can generate over 100 kW of additional power. The further cooled working gas exiting the second cycle process may be exhausted. Furthermore, in some embodiments, after the second cycle process, the cooled working gas can be used in any additional lower temperature process to recover any residual heat as depicted in process step 250, and can even be recovered to restart the process.

[0080] In one embodiment, the hot working gas leaves the expansion turbine 38 through fluid connection 39. Fluid connection 39 can also be coupled to an external thermal system to utilize the hot gas as depicted in process step 250. Thermal applications can use the turbine exhaust gas with the heat exchanger 24 for lower temperature (250°C) applications, or without the heat exchanger 24 for high temperature (700°C) applications. In one embodiment, the turbine exhaust gas flows to a high temperature application through fluid connection 39, which may or may not include a heat exchanger. Applications include high temperature drying applications, sludge drying, hot water purification, and space heating and cooling. In another embodiment, the turbine exhaust gas leaving the heat exchanger 24 at port 56 can pass through a low temperature heat exchanger 25 to recover additional heat from the cooled combustion gas for a lower temperature thermal application as depicted at optional box 250. For example, in one embodiment, the cooled exhaust gas can be at a temperature below 250°C and can be used for low temperature applications, including but not limited to hot water, low pressure steam, bottom cycle power generation, absorption refrigeration, etc. Additional cooled combustion gases exit the low temperature heat exchanger 25 and may be vented or recycled if desired.

[0081] The term "about" is intended to encompass the degree of error associated with the measurement of a particular quantity based on the equipment available at the time the application was filed. For example, "about" may encompass a range of ±8%, or 5%, or 2% of a given value.

[0082] In addition, the term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as "exemplary" is not necessarily to be construed as being preferred or advantageous over other embodiments or designs. The terms "at least one" and "one or more" are understood to include any integer greater than or equal to one, i.e., one, two, three, four, etc. The term "plurality" is understood to include any integer greater than or equal to two, i.e., two, three, four, five, etc. The term "connected" may include both indirect "connected" and direct "connected."

[0083] The terms used herein are only used to describe specific embodiments and are not intended to limit the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular forms "a / an" and "the" are also intended to include the plural forms. It should be further understood that when used in this specification, the terms "comprises" and / or "comprising" specify the presence of stated features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups thereof.

[0084] Although the present disclosure is only specified in detail with respect to a limited number of embodiments, it should be readily understood that the present disclosure is not limited to such disclosed embodiments. On the contrary, the present disclosure may be modified to incorporate any number of changes, modifications, substitutions, or equivalent arrangements that are not previously described but are commensurate with the spirit and scope of the present disclosure. In addition, although various embodiments of the present disclosure have been described, it should be understood that exemplary embodiments may include only some of the exemplary aspects described. Therefore, the present disclosure should not be considered to be limited by the foregoing description, but only by the scope of the appended claims.

Claims

1. A cogeneration system, comprising: a combustion chamber configured to directly combust solid organic material; a compressor turbine fluidly coupled to the combustion chamber; as well as an expansion turbine fluidly coupled to the combustion chamber, The turbine pressure ratio is less than 8. Wherein, the system further comprises: a single-flow cyclone separator fluidly coupled between the combustion chamber and the expansion turbine; a fuel feed system fluidly coupled to the combustion chamber, the fuel feed system having a hopper configured to receive the solid organic material and a feed tube disposed between the hopper and the combustion chamber, wherein the hopper is sized to provide fuel to the combustion chamber for operation for 1 to 6 hours; a metering device disposed between the hopper and the feed pipe, the metering device being configured to selectively cause pressurized gas to flow from the combustion chamber to the hopper; An ash bin is operably coupled to the single flow cyclone separator and fluidly coupled to the hopper through a flow control valve, wherein the flow control valve is configured to flow pressurized air from the hopper to the ash bin before the hopper is refilled with solid organic fuel. 2 . The system of claim 1 , wherein the turbine pressure ratio is less than 4. 3 .

3. The system of claim 1, further comprising a generator operably coupled to the expansion turbine.

4. The system of claim 1, further comprising a second circulation system thermally coupled to an output of the expansion turbine.

5. The system of claim 4, wherein the second cycle system is one of an organic Rankine cycle, a closed regenerative Brayton, a Stirling, or a supercritical carbon dioxide (CO2) engine.

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