Combined heat and power generation device taking LNG (Liquefied Natural Gas) as fuel

Abstract

The invention discloses a combined heat and power generation device with LNG as fuel, and relates to the technical field of energy technology and thermoelectric conversion. Comprising a fuel inlet (1), an air inlet (2), an ignition needle (3), a porous medium premixing cavity (4), a combustion area (5), a first combustion section (6), a second combustion section (7), a third combustion section (8), a flue gas outlet (9), a flue gas heat exchange device (10), a combustor outer wall (11), a thermoelectric module (12), an LNG gasification runner (13), a heat preservation layer (14), an LNG storage tank (15), a regulating valve (16) and an auxiliary gasification device (17). The gradient porosity design is adopted in the combustion area, flame oscillation is effectively restrained, the combustion temperature uniformity is improved, local overheating or uneven temperature of the hot end of the thermoelectric module is avoided, the thermoelectric conversion efficiency is improved, and the service life of the module is prolonged.

Description

Technical Field

[0001] This invention relates to the fields of energy technology and thermoelectric conversion technology, and more specifically to a combined heat and power (CHP) device using LNG as fuel. Background Technology

[0002] In remote, off-grid areas such as isolated islands and polar regions, a highly reliable supply of electricity and heat is essential for human activities. Photovoltaic and wind power are the primary power generation methods in these areas, but their output often depends on natural conditions, their performance is unstable, and they require battery storage, making long-term reliable operation impossible in cold conditions like polar regions. Small diesel generators can also provide electricity, but their complex system structure and high maintenance requirements make them unsuitable. Thermoelectric generators, as solid-state energy conversion devices, can directly convert heat energy into electrical energy. They offer advantages such as no moving parts, no working medium, and a long service life. Combining a burner with a thermoelectric generator to construct a fuel combustion-based thermoelectric power generation device is a highly reliable power reserve device with significant application potential. Chinese patent CN111678124B, "A Thermoelectric Generator and Its Heat Collection Structure and Burner," utilizes a heat collection structure to enhance heat exchange at the hot end of the thermoelectric generator, but the cold end of the thermoelectric generator uses conventional coolant for cooling, limiting the improvement in power generation efficiency. The Chinese patent with authorization number CN104595899B, "A micro-sized catalytic burner using foamed metal as the catalyst structural matrix", uses foamed metal to improve the heat transfer effect and catalytic reaction intensity of the burner. At the same time, the heat generated by combustion is used for thermoelectric power generation and fuel preheating, but it is difficult to meet the large power and heat supply needs of off-grid areas such as isolated islands and polar regions.

[0003] Existing technologies face the following challenges: First, the fuel combustion is intense, resulting in uneven flame temperature distribution and a large temperature gradient at the hot end of the thermoelectric module along the flue gas flow direction, causing significant local thermal stress that is detrimental to the safe and efficient operation of the thermoelectric module. Second, thermoelectric materials have optimal operating temperatures, and thermoelectric modules using a single thermoelectric material cannot maintain efficient and stable operation over a wide temperature range (-160℃ to above 800℃). Third, there is a lack of thermoelectric power generation structures using LNG as fuel. Due to the special low-temperature characteristics of LNG, it needs to be vaporized before combustion. How to rationally utilize the cold energy of LNG vaporization while ensuring efficient LNG vaporization is the key to realizing the thermoelectric conversion of LNG combustion flue gas.

[0004] Therefore, a combined heat and power (CHP) device using LNG as fuel is proposed, which can efficiently utilize the cold energy and combustion heat energy of LNG, achieve uniform temperature distribution and optimized matching of thermoelectric materials, and provide combined power generation for both electricity and heat supply. Summary of the Invention

[0005] In view of this, the present invention provides a cogeneration device using LNG as fuel. By combining porous media combustion technology, gradient porosity thermal equilibrium structure and segmented cogeneration modules, it achieves synergistic and efficient utilization of LNG gasification cold energy and combustion heat energy, and can provide electricity and heat energy at the same time. It has the advantages of simple structure and high reliability.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A combined heat and power (CHP) unit using LNG as fuel includes: a fuel inlet, an air inlet, an ignition needle, a porous media premixing chamber, a combustion zone, a first combustion section, a second combustion section, a third combustion section, a flue gas outlet, a flue gas heat exchanger, a burner outer wall, a CHP module, an LNG vaporization channel, an insulation layer, an LNG storage tank, a regulating valve, and an auxiliary vaporization device; wherein... The LNG vaporization channel and the outer wall of the burner constitute the cold end and hot end of the thermoelectric module, respectively. The auxiliary vaporization device and the inlet of the LNG vaporization channel are connected to the LNG storage tank, and the outlet is connected to the fuel inlet. The insulation layer is wrapped around the outside of the LNG vaporization channel. The regulating valve is located at the branch node between the auxiliary gasification unit and the LNG gasification channel to regulate the flow and pressure of the LNG branch. The fuel inlet and air inlet are located at the front end of the burner. The burner is equipped with a porous media premixing chamber, a combustion zone, and a flue gas outlet. The porous media premixing chamber premixes and rectifies the incoming natural gas and air, and is separated from the combustion zone by a gap to prevent backfire. The combustion zone is divided into a first combustion section, a second combustion section, and a third combustion section along the axial direction from the fuel inlet, and is filled with porous media materials with increasing porosity, which can enhance combustion heat transfer in a gradient and achieve uniform temperature inside the burner. The ignition needle is located in the combustion zone, and the flue gas outlet is located at the tail end of the burner and connected to the flue gas heat exchange device.

[0007] Optionally, the porosities of the first combustion section, the second combustion section, and the third combustion section are 90%-99%, 70%-90%, and 50%-70%, respectively, to achieve flame stability and temperature uniformity within the burner.

[0008] Optionally, the thermoelectric module uses three thermoelectric materials arranged in sections, from the hot end to the cold end: cobaltite, bismuth telluride, and bismuth-antimony alloy, with the proportions of the three thermoelectric materials ranging from 10%-25%, 20%-50%, and 20%-40%, respectively.

[0009] Optionally, the auxiliary gasification unit is activated by a regulating valve during startup to supply gaseous natural gas to the porous media premixing chamber. After the combustion in the burner stabilizes, the supply gradually switches to the LNG gasification channel.

[0010] Optionally, the shape and arrangement of the thermoelectric module and the LNG vaporization channel can be achieved by plate bonding or serpentine winding.

[0011] Optionally, the type and ratio of porous media in the burner can be made of high-temperature resistant silicon carbide or foam metal.

[0012] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a cogeneration device using LNG as fuel, the beneficial effects of which are: 1) Wide temperature range high-efficiency power generation: By combining the cold energy of LNG vaporization (-162℃) with the heat energy of natural gas combustion (>800℃), a temperature difference of more than 900℃ is constructed, which greatly improves the thermoelectric conversion efficiency. The thermoelectric modules composed of segmented thermoelectric materials (cobaltite, bismuth telluride, bismuth-antimony alloy) are used to achieve high-efficiency power generation under extreme temperature differences. 2) Maintain stable temperature difference: By adopting a gradient porosity design in the combustion zone (90%-99% in the first combustion section, 70%-90% in the second combustion section, and 50%-70% in the third combustion section), flame oscillation is effectively suppressed, the uniformity of combustion temperature is improved, local overheating or uneven temperature at the hot end of the thermoelectric module is avoided, and the thermoelectric conversion efficiency and module life are improved. 3) High reliability and wide applicability: Equipped with an auxiliary gasification device and regulating valve, it provides gaseous natural gas during the startup phase to quickly establish combustion; after combustion stabilizes, it switches to LNG gasification channel for gas supply, achieving self-sustaining system operation. The flue gas generated by combustion can be used for heating needs after heat exchange. Operation is not dependent on the environment and does not require additional equipment such as batteries, resulting in high reliability and wide applicability. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0014] Figure 1 This invention provides a structural diagram of a combined heat and power (CHP) unit using LNG as fuel. Figure 2 A schematic diagram of the material composition of the thermoelectric module provided by the present invention; Among them, 1-fuel inlet, 2-air inlet, 3-ignition needle, 4-porous medium premixing chamber, 5-combustion zone, 6-first combustion section, 7-second combustion section, 8-third combustion section, 9-flue gas outlet, 10-flue gas heat exchange device, 11-burner outer wall, 12-thermal power module, 13-LNG vaporization channel, 14-insulation layer, 15-LNG storage tank, 16-regulating valve, 17-auxiliary vaporization device. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0016] See Figure 1 As shown, this invention discloses a combined heat and power (CHP) device using LNG as fuel, comprising: a fuel inlet 1, an air inlet 2, an ignition needle 3, a porous media premixing chamber 4, a combustion zone 5, a first combustion section 6, a second combustion section 7, a third combustion section 8, a flue gas outlet 9, a flue gas heat exchange device 10, a burner outer wall 11, a CHP module 12, an LNG vaporization channel 13, an insulation layer 14, an LNG storage tank 15, a regulating valve 16, and an auxiliary vaporization device 17; wherein... The LNG vaporization channel 13 and the outer wall 11 of the burner respectively constitute the cold end and hot end of the thermoelectric module 12. The auxiliary vaporization device 17 and the inlet of the LNG vaporization channel 13 are respectively connected to the LNG storage tank 15, and the outlet is respectively connected to the fuel inlet 1. The insulation layer 14 is wrapped around the outside of the LNG vaporization channel 13. The regulating valve 16 is located at the branch node between the auxiliary gasification device 17 and the LNG gasification channel 13, and is used to regulate the flow and pressure of the LNG branch. The fuel inlet 1 and the air inlet 2 are located at the front end of the burner. The burner is equipped with a porous media premixing chamber 4, a combustion zone 5, and a flue gas outlet 9. The porous media premixing chamber 4 premixes and rectifies the incoming natural gas and air, and is separated from the combustion zone 5 by a gap to prevent backfire. The combustion zone 5 is divided into a first combustion section 6, a second combustion section 7, and a third combustion section 8 along the axial direction from the fuel inlet 1, and is filled with porous media materials with increasing porosity, which can gradient enhance combustion heat transfer and achieve uniform temperature inside the burner. Specifically, the burner is equipped with a porous media premixing chamber 4, a combustion zone 5, and a flue gas outlet 9. The three zones are coaxially designed to ensure smooth airflow.

[0017] The ignition needle 3 is located in the combustion zone 5, and the flue gas outlet 9 is located at the tail end of the burner and is connected to the flue gas heat exchange device 10.

[0018] Specifically, the ignition needle 3 is located in the combustion zone 5 at one end near the fuel inlet 1.

[0019] Specifically, the enhanced heat transfer method in combustion zone 5 is not limited to filling porous media materials with gradient porosity; gradient enhanced heat transfer can be achieved by using fins with different arrangements.

[0020] Specifically, the LNG vaporization channel 13 and the burner outer wall 11 constitute the cold and hot ends of the thermoelectric module 12, respectively, and the three are tightly fitted together. The thermoelectric module 12 is composed of three different types of thermoelectric materials in segments, such as... Figure 2 As shown.

[0021] Fuel inlet 1 and air inlet 2 are located at the front end of the burner.

[0022] Furthermore, the porosities of the first combustion section 6, the second combustion section 7, and the third combustion section 8 are 90%-99%, 70%-90%, and 50%-70%, respectively, to achieve flame stability and temperature uniformity within the burner.

[0023] Furthermore, the thermoelectric module 12 is arranged in sections using three thermoelectric materials, namely squardite material, bismuth telluride material and bismuth-antimony alloy material from the hot end to the cold end, with the proportions of the three thermoelectric materials ranging from 10-25%, 20-50% and 20-40%.

[0024] Specifically, from the hot end to the cold end, the materials are: cobaltite suitable for high temperature, bismuth telluride suitable for medium temperature, and bismuth-antimony alloy suitable for low temperature. The proportions of the three types of thermoelectric materials suitable for high temperature, medium temperature, and low temperature are 10%-25%, 20%-50%, and 20%-40%, respectively.

[0025] Furthermore, the auxiliary gasification device 17 is opened by the regulating valve 16 during startup to supply gaseous natural gas to the porous medium premixing chamber 4. After the combustion in the burner stabilizes, it is gradually switched to supply LNG to the gasification channel 13.

[0026] Furthermore, the shape and arrangement of the thermoelectric module 12 and the LNG vaporization channel 13 adopt a plate-type bonding or serpentine winding method.

[0027] Furthermore, the porous media inside the burner are made of high-temperature resistant silicon carbide or foam metal.

[0028] In one specific embodiment, the operation process of a combined heat and power (CHP) unit using LNG as fuel provided by the present invention is as follows: When the system starts, the regulating valve 16 controls the auxiliary gasification device 17 to open. LNG in the LNG storage tank 15 enters the auxiliary gasification device 17 and is gasified into gaseous natural gas, which enters the burner through the fuel inlet 1. At the same time, air enters through the air inlet 2. The fuel and air are mixed in the porous media premixing chamber 4 to form a combustible mixture. The porous media structure in the porous media premixing chamber 4 plays a role in rectifying the combustible mixture and preventing backfire. The premixed combustible gas enters the combustion zone 5 and is ignited by the ignition needle 3. The combustion process passes through the first combustion section 6, the second combustion section 7, and the third combustion section 8 in sequence.

[0029] The porous media material features an increasing porosity gradient, achieving stable combustion, suppressing oscillations, and promoting uniform temperature distribution. The high-temperature heat generated during combustion is transferred through the burner's outer wall 11, becoming the hot end of the thermoelectric module 12. When the internal combustion temperature reaches a predetermined threshold, the regulating valve 16 controls the LNG from the LNG storage tank 15 to enter the LNG vaporization channel 13, where it is vaporized into gaseous natural gas for combustion. Simultaneously, the cold energy released during LNG vaporization keeps the channel at a low temperature, becoming the cold end of the thermoelectric module 12. The thermoelectric module 12 is tightly fitted between the burner's outer wall 11 and the LNG vaporization channel 13, with thermally conductive silicone grease applied between them to reduce thermal resistance. The thermoelectric module 12 employs a segmented design using thermoelectric materials suitable for both high and low temperatures, enabling efficient thermoelectric power generation over a wide temperature range. The high-temperature flue gas after combustion enters the flue gas heat exchange device 10 through the flue gas outlet 9, where waste heat is recovered and utilized before being cooled and discharged. After combustion stabilizes, regulating valve 16 gradually closes the passage of auxiliary gasification device 17, and opens or increases the LNG flow to LNG gasification channel 13, switching the system to a self-sustaining operation mode where fuel is entirely supplied by LNG gasification channel 13. In this mode, LNG gasification channel 13 continuously supplies natural gas fuel, the heat generated by combustion maintains the high temperature at the hot end of thermoelectric module 12, and the LNG gasification process maintains the low temperature at the cold end, allowing thermoelectric module 12 to maintain stable power generation and enabling the unit to continuously perform combined heat and power (CHP). Insulation layer 14 is wrapped around the outside of LNG gasification channel to reduce energy loss.

[0030] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0031] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A combined heat and power plant fueled by LNG, characterized in that, The application relates to a LNG gasifier, which comprises a fuel inlet (1), an air inlet (2), an ignition needle (3), a porous medium premixing cavity (4), a combustion zone (5), a first combustion section (6), a second combustion section (7), a third combustion section (8), a flue gas outlet (9), a flue gas heat exchange device (10), a combustor outer wall (11), a thermoelectric module (12), a LNG gasification flow channel (13), a thermal insulation layer (14), a LNG storage tank (15), an adjusting valve (16) and an auxiliary gasification device (17), wherein the LNG gasification flow channel (13) and the combustor outer wall (11) respectively form a cold end and a hot end of the thermoelectric module (12), the auxiliary gasification device (17) and the LNG gasification flow channel (13) are respectively connected with the LNG storage tank (15) and the fuel inlet (1), and the thermal insulation layer (14) is wrapped outside the LNG gasification flow channel (13). The adjusting valve (16) is arranged at a flow distribution node of the auxiliary gasification device (17) and the LNG gasification flow channel (13) and is used for adjusting the flow and pressure of an LNG distribution branch, and the fuel inlet (1) and the air inlet (2) are located at the front end of the combustor. The combustor is internally provided with the porous medium premixing cavity (4), the combustion zone (5) and the flue gas outlet (9), the porous medium premixing cavity (4) is used for premixing and rectifying the incoming natural gas and air and is spaced apart from the combustion zone (5) by a gap to prevent backfire, the combustion zone (5) is sequentially divided into the first combustion section (6), the second combustion section (7) and the third combustion section (8) from the fuel inlet (1) along an axial direction and is respectively filled with porous medium materials with increasing porosities, so that the combustion heat exchange is gradiently strengthened and the temperature in the combustor is uniform. The ignition needle (3) is located in the combustion zone (5), and the flue gas outlet (9) is located at the tail end of the combustor and is connected with the flue gas heat exchange device (10). The porosities of the first combustion section (6), the second combustion section (7) and the third combustion section (8) are 90%-99%, 70%-90% and 50%-70% respectively, so that the flame in the combustor is stable and the temperature is uniform. The thermoelectric module (12) is arranged in sections by using three kinds of thermoelectric materials, and the materials are cobaltite material, bismuth telluride material and bismuth-antimony alloy material from the hot end to the cold end, and the proportion of the three kinds of thermoelectric materials ranges from 10% to 25%, from 20% to 50% and from 20% to 40%.

2. The combined heat and power plant using LNG as fuel according to claim 1, characterized in that, The auxiliary gasification device (17) is controlled to be opened by the adjusting valve (16) at the start and provides gaseous natural gas to the porous medium premixing cavity (4), and is gradually switched to the LNG gasification flow channel (13) for supply after the combustion in the combustor is stable.

3. The LNG-fueled combined heat and power plant according to claim 1, characterized in that, The shapes and arrangement modes of the thermoelectric module (12) and the LNG gasification flow channel (13) adopt a plate type adhesion or a serpentine winding mode.

4. The LNG-fueled combined heat and power plant according to claim 1, characterized in that, The types and proportion of the porous medium in the combustor adopt a high-temperature-resistant silicon carbide or a foam metal structure.

5. The LNG-fueled combined heat and power plant according to claim 1, characterized in that, ​ 6. The combined heat and power plant using LNG as fuel according to claim 1, characterized in that, ​

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