Waste heat power generation system based on organic liquid hydrogen storage medium

Abstract

The invention relates to a waste heat power generation system based on an organic liquid hydrogen storage medium, and the system comprises a dehydrogenation reactor which enables the organic liquid hydrogen storage medium to be subjected to a dehydrogenation reaction to generate hydrogen; the heat source is arranged in the dehydrogenation reactor; the conversion device is communicated with the dehydrogenation reactor and is used for converting the internal energy of the hydrogen into electric energy; the cooling device is communicated with the conversion device and is used for reducing the temperature of the hydrogen flowing out of the conversion device; and the hydrogenation reactor is communicated with the cooling device and is used for carrying out hydrogenation reaction on the hydrogen and the organic liquid hydrogen storage medium in the hydrogenation reactor. Wherein the dehydrogenation reactor and the hydrogenation reactor are communicated with each other and are used for maintaining circulation of the organic liquid hydrogen storage medium.

Description

Technical Field

[0001] The invention relates to a waste heat power generation system based on an organic liquid hydrogen storage medium, belonging to the technical field of waste heat recovery and utilization. Background Art

[0002] As the global energy crisis and environmental pollution become increasingly severe, energy conservation and emission reduction have become a global consensus. In the industrial production process, a large amount of low-temperature waste heat resources have not been effectively recycled, which not only causes a huge waste of energy, but also causes serious thermal pollution problems. Therefore, the development and utilization of these low-temperature waste heat resources is of great significance to achieve sustainable utilization of energy and environmental protection.

[0003] The traditional organic Rankine cycle (ORC) system uses low-boiling-point organic working fluids to achieve low-temperature waste heat power generation by matching the temperature of the low-temperature heat source. This system can effectively convert low-grade thermal energy into electrical energy, but it has certain limitations in improving the thermal efficiency of the system.

[0004] In the prior art, in order to improve the thermal efficiency of the Rankine cycle, the initial steam pressure can be increased. However, the increase in the initial steam pressure will lead to an increase in the exhaust steam humidity, and the gas-liquid mixture will cause impact damage to the turbine blades. In addition, in order to ensure that the working fluid is still in a superheated state at the outlet of the turbine expander and to prevent the organic working fluid vapor from condensing into a gas-liquid phase under high-speed movement, the ORC system adopts a steam intermediate reheating method. However, this method also increases the requirements for the performance of metal materials, and in the case of temperature and pressure fluctuations in the system, the superheated organic steam still has the risk of condensation before entering the turbine.

[0005] Therefore, improving ORC system design and innovating system integration methods are crucial to promoting the development of this field.

[0006] The inventors have found that by combining organic liquid hydrogen storage technology with low-temperature waste heat recovery power generation, a new energy system can be developed that can not only effectively utilize low-temperature waste heat resources, but also achieve efficient hydrogen storage and power generation. In the field of hydrogen storage, organic liquid hydrogen storage technology has attracted attention due to its high hydrogen storage density and safety. This system combines organic liquid hydrogen storage technology with low-temperature waste heat power generation, aiming to improve energy utilization efficiency, reduce environmental pollution, and provide technical support for achieving sustainable development of energy. Summary of the invention

[0007] The main purpose of the present invention is to provide a waste heat power generation system based on an organic liquid hydrogen storage medium to solve the problems of low energy conversion efficiency, short equipment life and high system cost in the prior art.

[0008] In order to achieve the above-mentioned purpose, according to one aspect of the present invention, a waste heat power generation system based on an organic liquid hydrogen storage medium is provided, which includes: a dehydrogenation reactor, which causes the organic liquid hydrogen storage medium to undergo a dehydrogenation reaction through heat provided by a heat source to produce hydrogen; a conversion device, which is connected to the dehydrogenation reactor and is used to convert the internal energy of the hydrogen into electrical energy; a cooling device, which is connected to the conversion device and is used to reduce the temperature of the hydrogen flowing out of the conversion device; and a hydrogenation reactor, which is connected to the cooling device and is used to cause the hydrogen to undergo a hydrogenation reaction with the organic liquid hydrogen storage medium in the hydrogenation reactor. The dehydrogenation reactor and the hydrogenation reactor are interconnected to maintain the circulation of the organic liquid hydrogen storage medium.

[0009] Further, the organic liquid hydrogen storage medium includes one or more of N-methylcarbazole, N-ethylcarbazole, N-acetylcarbazole, N-benzoylcarbazole and N-phenylcarbazole. Preferably, the organic liquid hydrogen storage medium is selected from one or more of N-methylcarbazole, N-ethylcarbazole and N-phenylcarbazole. Preferably, the boiling point of the organic liquid hydrogen storage medium is 310°C to 450°C, the hydrogen release temperature is 170°C to 220°C, and the mass hydrogen storage density is 2wt% to 8wt%.

[0010] Furthermore, the catalyst used in the dehydrogenation reactor is a molecular sieve-supported noble metal catalyst, and preferably the noble metal is selected from one or more of Pt, Pd and Rh.

[0011] Furthermore, the catalyst used in the hydrogenation reactor is a molecular sieve-supported noble metal catalyst or a molecular sieve-supported non-noble metal catalyst, preferably the noble metal is selected from one or more of Pt, Pd and Ru, and preferably the non-noble metal is selected from one or more of Fe, Cu and Ni.

[0012] Further, the conversion device comprises an expansion device and a generator, wherein the expansion device is connected to the generator, preferably the expansion device is a turbine expander, a screw expander or a piston expander, and more preferably the expansion device is a turbine expander.

[0013] Furthermore, the surface of the turbine blades of the turboexpander is coated with an anti-hydrogen embrittlement coating material. Preferably, the anti-hydrogen embrittlement coating material is an anti-hydrogen embrittlement ceramic coating material of oxide, nitride or nitrogen oxide, and more preferably is selected from one or more of titanium nitride, titanium oxide, aluminum nitride, aluminum oxide or aluminum oxynitride.

[0014] Further, the temperature in the dehydrogenation reactor is 250° C. to 300° C., and the pressure is 5 MPa to 10 MPa, preferably the temperature is 260° C. to 275° C., and the pressure is 6 MPa to 8 MPa.

[0015] Furthermore, the temperature of the hydrogenation reactor is 100°C to 200°C; preferably, the workload of the cooling device is interlocked with the temperature control of the hydrogenation reactor; more preferably, the hydrogenation reactor further includes a temperature regulating device, and the workloads of both the temperature regulating device and the cooling device are interlocked with the system temperature control mechanism.

[0016] Further, the dehydrogenation reactor is a fixed bed reactor; the cooler is a plate heat exchanger; and the hydrogenation reactor is a fixed bed reactor.

[0017] According to another aspect of the present invention, a method for waste heat power generation is provided, which comprises the following steps: S1: a heat source provides heat, a dehydrogenation reactor causes an organic liquid hydrogen storage medium to undergo a dehydrogenation reaction to generate hydrogen, and the dehydrogenated organic liquid hydrogen storage medium enters a hydrogenation reactor; S2: the hydrogen enters a conversion device to convert internal energy into electrical energy; S3: the hydrogen flowing out of the conversion device is cooled in a cooling device; S4: the cooled hydrogen enters a hydrogenation reactor, undergoes a hydrogenation reaction with the dehydrogenated organic liquid hydrogen storage medium in the hydrogenation reactor, and the hydrogenated organic liquid hydrogen storage medium enters a dehydrogenation reactor.

[0018] The waste heat power generation system of the present invention realizes efficient storage and release of hydrogen by adopting an organic liquid hydrogen storage medium, using high-temperature waste heat for dehydrogenation reaction and low-temperature waste heat for hydrogenation reaction, effectively recovering waste heat and improving energy utilization efficiency. The precise temperature control of the cooling device and the maintenance of gas-liquid circulation ensure the continuity and controllability of the system operation and improve the power generation efficiency. The system is not only suitable for the recovery and utilization of industrial waste heat, but also provides a new idea for the utilization of hydrogen energy, with significant economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0020] Figure 1 A schematic diagram showing an embodiment of a waste heat power generation system based on an organic liquid hydrogen storage medium according to the present invention.

[0021] right Figure 1 The reference numerals in the figures are described as follows:

[0022] 1. Dehydrogenation reactor; 2. Heat source; 3. Heat exchanger; 4. Turbine expander; 5. Generator; 6. Cold source; 7. Cooling device; 8. Air pump; 9. Hydrogenation reactor; 10. First liquid pump; 11. Second liquid pump. DETAILED DESCRIPTION

[0023] The present application is further described in detail below in conjunction with examples. These examples are intended to better further understand the present invention, are not limited to the best mode of implementation, and do not limit the content and protection scope of the present invention. Any product that is the same or similar to the present invention and is obtained by anyone under the inspiration of the present invention or by combining the present invention with the features of other prior arts falls within the protection scope of the present invention.

[0024] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The experimental methods used in the following embodiments are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments, unless otherwise specified, can all be obtained from commercial sources. The present invention will be described in detail below in conjunction with the embodiments.

[0025] In traditional ORC, the reversible phase change principle of low-boiling-point organic working fluid is used to generate high-temperature and high-pressure gaseous working fluid to drive the turbine to do work, while recovering the waste heat in the low-temperature heat source. In contrast, the present invention uses the principle of reversible hydrogen storage and release of organic media to generate high-temperature and high-pressure hydrogen to drive the turbine to do work, while using reversible chemical reactions to absorb and release heat to recover the waste heat in the heat source. The system of the present invention not only improves the comprehensive utilization rate of energy by efficiently utilizing waste heat, but also reduces the cost of power generation. It is particularly suitable for waste heat recovery in high-energy-consuming industries such as steel and chemical industries, and provides an effective solution for energy conservation and emission reduction.

[0026] Compared with the traditional ORC, the working fluid of the present invention is hydrogen. Hydrogen has high thermal conductivity, which is conducive to recovering more heat from the heat source in the dehydrogenation reactor and is more efficient in cooling in the cooling device.

[0027] A specific embodiment of the present invention provides a waste heat power generation system based on an organic liquid hydrogen storage medium, the system comprising: a dehydrogenation reactor, the dehydrogenation reactor causes the organic liquid hydrogen storage medium to undergo a dehydrogenation reaction through heat provided by a heat source to produce hydrogen; a conversion device, the conversion device is connected to the dehydrogenation reactor, and is used to convert the internal energy of the hydrogen into electrical energy; a cooling device, the cooling device is connected to the conversion device, and is used to reduce the temperature of the hydrogen flowing out of the conversion device, recover the waste heat and control the temperature of the system; and a hydrogenation reactor, the hydrogenation reactor is connected to the cooling device, and is used to cause the hydrogen to undergo a hydrogenation reaction with the organic liquid hydrogen storage medium in the hydrogenation reactor. The dehydrogenation reactor and the hydrogenation reactor are interconnected to maintain the circulation of the organic liquid hydrogen storage medium.

[0028] The specific principle and process are as follows: a heat exchanger connected to a heat source is set in the dehydrogenation reactor, and the organic liquid hydrogen storage medium releases hydrogen under the heating action of the heat exchanger, so that the temperature and pressure of the hydrogen in the dehydrogenation reactor increase. Since the boiling point of the organic hydrogen storage medium selected in the present invention is much higher than the working temperature of the dehydrogenation reactor, and increasing the pressure of the dehydrogenation reactor is conducive to the condensation of a small part of the volatile organic hydrogen storage medium, the stage from the dehydrogenation reactor to the conversion device is a single-phase high-temperature and high-pressure hydrogen. Compared with the traditional ORC, the present invention improves the work efficiency of the expansion device (such as a turbine) in the conversion device by increasing the initial pressure of the working fluid (hydrogen) without using a steam superheater to reheat the steam, and effectively reduces the liquid content in the gas phase working fluid. At the same time, the organic hydrogen storage medium after hydrogen release enters the hydrogenation reactor. The high-temperature and high-pressure hydrogen enters the conversion device and performs work externally through reversible adiabatic expansion, and then reversible isobaric cooling occurs in the cooling device, but no condensation occurs. Therefore, compared with the traditional ORC, the stage from the cooling device to the hydrogenation reactor is still a gas phase rather than a liquid phase. After that, the gaseous hydrogen enters the hydrogenation reactor. The organic hydrogen storage medium after releasing hydrogen in the hydrogenation reactor enters the hydrogenation reactor from the dehydrogenation reactor, and in the hydrogenation reactor, it undergoes a hydrogenation reaction with the cooled hydrogen entering the hydrogenation reactor from the cooling device, and the temperature and pressure in the system decrease. Then, the liquid organic hydrogen storage medium saturated with hydrogen in the hydrogenation reactor enters the dehydrogenation reactor from the hydrogenation reactor.

[0029] Preferably, in the dehydrogenation reactor, the organic liquid hydrogen storage medium after dehydrogenation enters the hydrogenation reactor from the dehydrogenation reactor through a liquid pump connected to the hydrogenation reactor; in the hydrogenation reactor, the organic liquid hydrogen storage medium saturated with hydrogen gas enters the dehydrogenation reactor from the hydrogenation reactor through another liquid pump connected to the dehydrogenation reactor. That is to say, the organic liquid hydrogen storage medium for dehydrogenation and hydrogenation is circulated by two liquid pumps operating in opposite directions arranged between the dehydrogenation reactor and the hydrogenation reactor. The liquid pump can be, for example, a diaphragm pump, a plunger pump, a gear pump, a screw pump or a peristaltic pump. In the present invention, the liquid pump can be replaced by a device that realizes the same function, and can be determined according to the specific circumstances such as the operating conditions and application scenarios of the system.

[0030] Preferably, after cooling by a cooling device, the hydrogen enters the hydrogenation reactor after being pressurized by an air pump. The pressure after pressurization by the air pump can be in the range of 1MPa to 2MPa. In the present invention, the air pump can be replaced by a device that achieves the same function, such as a diaphragm compressor, a screw compressor, a centrifugal compressor, a piston compressor, a scroll compressor or a Roots blower, etc., which can be determined according to the specific circumstances of the operating conditions and application scenarios of the system, and the safety and efficiency when handling hydrogen need to be considered.

[0031] The gas pump and the liquid pump can be used to maintain the circulation of hydrogen gas and the circulation of the organic liquid hydrogen storage medium in the system to control the pressure balance.

[0032] In a specific embodiment of the present invention, the organic liquid hydrogen storage medium includes one or more of N-methylcarbazole, N-ethylcarbazole, N-acetylcarbazole, N-benzoylcarbazole and N-phenylcarbazole. Preferably, the organic liquid hydrogen storage medium is selected from one or more of N-methylcarbazole, N-ethylcarbazole and N-phenylcarbazole. Preferably, the boiling point of the organic liquid hydrogen storage medium is 310°C to 450°C, the hydrogen release temperature is 170°C to 220°C, and the mass hydrogen storage density is 2wt% to 8wt%.

[0033] These organic liquid hydrogen storage media remain in liquid form at the dehydrogenation temperature, which can avoid unnecessary gas-liquid two-phase mixing during the dehydrogenation process, thereby improving the gas-liquid phase separation efficiency and hydrogen purity of the dehydrogenation process. At the same time, the difference between the higher boiling point and the lower dehydrogenation temperature provides sufficient temperature margin, so that hydrogen can be effectively released in the dehydrogenation reactor without affecting the operation due to premature evaporation or boiling. Moreover, the higher hydrogen storage density can store more hydrogen, which is beneficial to the overall design of the system. As organic liquid hydrogen storage media, carbazoles and their derivatives are safer during storage and transportation than high-pressure hydrogen or metal hydrides. In addition, their chemical reactions are usually carried out under mild conditions, which reduces operational risks, and these organic media have less impact on the environment during cyclic use. Organic liquid hydrogen storage media such as N-methylcarbazole, N-ethylcarbazole and N-phenylcarbazole can maintain good performance in multiple cycles due to their stable chemical structure and reversibility during dehydrogenation and storage. After releasing hydrogen, these media can still reabsorb hydrogen through the hydrogenation process and restore their initial state, thus ensuring the long-term stable operation and recycling efficiency of the system.

[0034] In a specific embodiment of the present invention, a molecular sieve-supported catalyst is disposed in a dehydrogenation reactor and a hydrogenation reactor to catalyze a reversible chemical reaction of an organic liquid hydrogen storage medium. The catalyst used in the dehydrogenation reactor is a molecular sieve-supported noble metal catalyst, preferably the noble metal is selected from one or more of Pt, Pd and Rh. The catalyst used in the hydrogenation reactor is a molecular sieve-supported noble metal catalyst or a molecular sieve-supported non-noble metal catalyst, preferably the noble metal is selected from one or more of Pt, Pd and Ru, preferably the non-noble metal is selected from one or more of Fe, Cu and Ni.

[0035] In the dehydrogenation reactor, especially the dehydrogenation reaction of organic liquid hydrogen storage media such as N-methylcarbazole, N-ethylcarbazole, and N-phenylcarbazole, the use of molecular sieve-supported precious metal catalysts (such as Pt, Pd, and Rh) can significantly improve the reaction rate and efficiency. These precious metal catalysts have high catalytic activity and selectivity, and can promote the dehydrogenation reaction of organic media at lower temperatures and higher pressures to produce high-temperature and high-pressure hydrogen. In the hydrogenation reactor, molecular sieve-supported precious metal catalysts (such as Pt, Pd, and Ru) or non-precious metal catalysts (such as Fe, Cu, and Ni) are used to catalyze the hydrogenation reaction of organic liquid hydrogen storage media and hydrogen. Due to its efficient catalytic activity, precious metal catalysts can promote hydrogenation reactions under milder conditions, effectively absorb hydrogen, and restore the initial state of the organic medium to prepare for the next dehydrogenation cycle. Although the catalytic activity of non-precious metal catalysts may be slightly lower, the cost is lower, which has economic advantages for large-scale applications.

[0036] In a specific embodiment of the present invention, the conversion device comprises an expansion device and a generator, wherein the expansion device is connected to the generator, preferably the expansion device is a turbine expander, a screw expander or a piston expander, and more preferably the expansion device is a turbine expander.

[0037] The conversion device is a key component that converts thermal energy into mechanical energy and then into electrical energy. It can be replaced with a device that achieves the same function according to specific needs. The selection of the conversion device should take into account factors such as system performance, operating environment, economy and maintenance convenience to ensure that the system can operate in the most efficient and economical way.

[0038] In a specific embodiment of the present invention, the surface of the turbine blade of the turboexpander is coated with an anti-hydrogen embrittlement coating material. Preferably, the anti-hydrogen embrittlement coating material is an anti-hydrogen embrittlement ceramic coating material of an oxide, nitride or oxynitride, and more preferably is selected from one or more of titanium nitride, titanium oxide, aluminum nitride, aluminum oxide or aluminum oxynitride.

[0039] Since hydrogen gas contacts metal under high pressure, it may cause hydrogen embrittlement, that is, hydrogen atoms penetrate into the metal lattice, resulting in a decrease in the mechanical properties of the metal material, including a decrease in strength and ductility, thereby increasing the risk of turbine blade fracture. In order to prevent this problem, the surface of the turbine blade is coated with an anti-hydrogen embrittlement coating material, which can enhance the stability and safety of the system and avoid damage to the metal material by hydrogen. Anti-hydrogen embrittlement coating materials, such as ceramic coatings such as titanium nitride, titanium oxide, aluminum nitride, aluminum oxide or aluminum oxynitride, can form a dense protective layer that effectively prevents hydrogen molecules from penetrating into the metal matrix. These coatings usually have a low hydrogen diffusion coefficient, which can avoid the occurrence of hydrogen embrittlement. Moreover, the anti-hydrogen embrittlement coating material has good high temperature resistance and can remain stable at the operating temperature of the turbine blade. Under high temperature conditions, these coatings can resist oxidation and thermal degradation and protect the substrate from damage.

[0040] In one embodiment of the present invention, the temperature in the dehydrogenation reactor is 250° C. to 300° C., and the pressure is 5 MPa to 10 MPa.

[0041] The temperature range and pressure range of the present invention are optimized based on the characteristics of the organic liquid hydrogen storage medium, which can effectively activate the chemical reaction in the organic liquid hydrogen storage medium, promote the release of hydrogen, and avoid the side reactions that may be caused by excessively high temperatures, while maintaining the activity and stability of the catalyst.

[0042] In a specific embodiment of the present invention, the temperature of the hydrogenation reactor is 100°C to 200°C; preferably, the workload of the cooling device is interlocked with the temperature control of the hydrogenation reactor; more preferably, the hydrogenation reactor further includes a temperature regulating device, and the workloads of both the temperature regulating device and the cooling device are interlocked with the system temperature control mechanism.

[0043] The present invention can achieve efficient and stable hydrogen absorption by the organic liquid hydrogen storage medium by accurately controlling the temperature of the hydrogenation reactor, thereby improving the energy conversion efficiency and operational reliability of the entire system. The interlocking mechanism is mainly used to ensure coordination between various parts of the system, maintain stable operation of the entire system and optimize energy utilization efficiency. The interlocking can be a signal-based automatic control or a logic-based control strategy.

[0044] In one embodiment of the present invention, the dehydrogenation reactor is a fixed bed reactor; the cooler is a plate heat exchanger; and the hydrogenation reactor is a fixed bed reactor.

[0045] In a fixed bed reactor, the catalyst is loaded in the reactor in the form of a fixed bed, and the reactants flow through the catalyst bed to react. Fixed bed reactors can provide stable reaction conditions and are relatively simple in design, which is conducive to the integration and maintenance of the entire system. A plate heat exchanger is an efficient heat exchange device that achieves heat exchange by alternating the flow of hot fluids between multiple layers of parallel thin plates. In the present invention, the plate heat exchanger is used as a cooler to cool the spent gas (hydrogen) produced after turbine expansion, so that its temperature drops to a suitable level for further processing or direct entry into a hydrogenation reactor.

[0046] According to another specific embodiment of the present invention, a method for waste heat power generation is provided, which includes the following steps: S1: heat is provided by a heat source, and a dehydrogenation reactor causes an organic liquid hydrogen storage medium to undergo a dehydrogenation reaction to generate hydrogen, and the dehydrogenated organic liquid hydrogen storage medium enters a hydrogenation reactor; S2: the hydrogen enters a conversion device to convert internal energy into electrical energy; S3: the hydrogen flowing out of the conversion device is cooled in a cooling device; S4: the cooled hydrogen enters a hydrogenation reactor, undergoes a hydrogenation reaction with the dehydrogenated organic liquid hydrogen storage medium in the hydrogenation reactor, and the hydrogenated organic liquid hydrogen storage medium enters a dehydrogenation reactor.

[0047] The present invention has the following beneficial effects:

[0048] (1) Compared with the traditional ORC, the present invention can improve the power generation efficiency by increasing the pressure of the gas working fluid before the turbine, without using the method of superheating the working fluid steam to eliminate the steam condensation caused by pressurization. Therefore, the steam superheater and the corresponding high-temperature heat source or energy input can be omitted in the cycle, thereby reducing the system cost while improving the working life of the turbine and the upper limit of the working efficiency.

[0049] (2) Hydrogen as a working fluid has strong fluidity and fast heat conduction, which can improve the heat transfer efficiency of the cooler. Its high specific heat capacity can enable the system to have high energy conversion efficiency over a wider temperature range.

[0050] (3) The present invention utilizes the reversible hydrogen charging and discharging chemical reaction and the reversible heat absorption and release process of organic liquid hydrogen storage to replace the reversible phase change of the working fluid in ORC, providing a new idea for the design and development of efficient thermodynamic cycles.

[0051] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0052] Embodiment 1:

[0053] according to Figure 1Schematic diagram of the waste heat power generation system based on organic liquid hydrogen storage medium of the present invention includes: a dehydrogenation reactor 1, a heat source 2, a heat exchanger 3, a turbine expander 4, a generator 5, a cold source 6, a cooling device 7, an air pump 8, a hydrogenation reactor 9, a first liquid pump 10 and a second liquid pump 11.

[0054] A heat exchanger 3 connected to a heat source 2 is arranged in the dehydrogenation reactor 1. The dehydrogenation reactor 1 is a fixed bed reactor, wherein the catalyst is a noble metal catalyst supported by a molecular sieve, and the noble metal component is Pt; the organic liquid hydrogen storage medium used in the dehydrogenation reactor 1 is N-phenylcarbazole, which has a boiling point of 415°C, a hydrogen release temperature of 210°C, and a mass hydrogen storage density of 6.9wt%.

[0055] In the dehydrogenation reactor 1, the organic liquid hydrogen storage medium undergoes a chemical reaction to release hydrogen, thereby increasing the temperature and pressure of the hydrogen in the dehydrogenation reactor; the temperature of the dehydrogenation reactor is 273°C and the pressure is 7.7 MPa; the dehydrogenated organic liquid hydrogen storage medium enters the hydrogenation reactor 9 through the first liquid pump 10;

[0056] The high-temperature and high-pressure hydrogen released in the dehydrogenation reactor 1 enters the turbine expander 4 to perform work and drive the generator 5 to generate electricity. At the outlet of the turbine expander 4, the temperature and pressure of the hydrogen are reduced; the blade surface of the turbine expander 4 is coated with an anti-hydrogen embrittlement ceramic coating, and the coating component is titanium nitride.

[0057] The hydrogen flowing out of the turbo expander is cooled in a cooling device 7 connected to a cooling source 6 for lowering the temperature; the cooling device 7 is a plate heat exchanger, and the working load of the cooling device 7 is interlocked with the temperature control of the hydrogenation reactor 9;

[0058] The cooled hydrogen is pressurized by the air pump 8 and enters the hydrogenation reactor 9; the pressure of the hydrogen after being pressurized by the air pump 8 is 1.6 MPa; the hydrogenation reactor 9 is a fixed bed reactor; the catalyst used in the hydrogenation reactor 9 is a molecular sieve-supported noble metal catalyst Pt; the temperature of the hydrogenation reactor 9 is 180°C;

[0059] The dehydrogenated organic liquid hydrogen storage medium in the hydrogenation reactor 9 undergoes a chemical reaction with the hydrogen gas pressurized into the hydrogenation reactor 9, and the hydrogen gas is absorbed by the dehydrogenated organic liquid hydrogen storage medium;

[0060] The hydrogenated organic liquid hydrogen storage medium is pressurized by the second liquid pump 11 and enters the dehydrogenation reactor 1 .

[0061] Example 2

[0062] The configuration is carried out in the same manner as in Example 1, except that the organic liquid hydrogen storage medium is N-acetylcarbazole, with a boiling point of 315°C, a hydrogen release temperature of 175°C, and a mass hydrogen storage density of 6.3wt%. The temperature of the dehydrogenation reactor is 262°C and the pressure is 6.7MPa. The blade surface of the turboexpander 4 is coated with a hydrogen embrittlement-proof ceramic coating, and the coating component is alumina. The pressure of hydrogen after pressurization by the air pump is 1.5MPa; the catalyst used in the hydrogenation reactor is a non-precious metal catalyst Fe loaded with a molecular sieve; the temperature of the hydrogenation reactor 9 is 170°C; a temperature regulating device is built into the hydrogenation reactor 9, and is controlled and interlocked with the temperature control of the cooling device 7 before the air pump 8 and the hydrogenation reactor 9.

[0063] Example 3

[0064] The same configuration as in Example 1 was performed, except that the dehydrogenation reactor temperature was 295°C and the pressure was 9.5 MPa.

[0065] Comparative Example 1

[0066] The configuration was the same as in Example 1, except that the temperature of the dehydrogenation reactor was 450°C.

[0067] Comparative Example 2

[0068] The configuration is carried out in the same manner as in Example 1, except that the blade surface of the turbo expander 4 is not coated with the anti-hydrogen embrittlement ceramic coating.

[0069] Comparative Example 3

[0070] Take the organic Rankine cycle (ORC) system with R245fa as the working fluid as an example, where the critical temperature of R245fa is 154°C and the critical pressure is 4.059MPa. First, in the heating stage, the working fluid R245fa absorbs heat from the external heat source through the heat exchanger, heats it to 200°C, evaporates it into high-temperature steam, and the evaporation pressure is 2.5MPa. Then, the steam enters the expansion stage, expands through the expander (turbine), expands to do work and reduces the pressure, the steam temperature drops to about 40°C, and the pressure drops to 0.5MPa. During the expansion process, mechanical energy is converted into electrical energy or other forms of output work. After that, the working fluid enters the cooling stage, and heat is exchanged with the cooling medium (such as water or air) through the condenser. The working fluid releases heat during the condensation process and is converted into liquid. At this time, the temperature of the working fluid is about 40°C. Finally, in the compression stage, the liquid working fluid is compressed to a higher pressure (2.5MPa) by a pump and returns to the heat exchanger to start a new cycle.

[0071] The thermal efficiencies of Examples 1 and 2 are 27.5% and 24.4%, respectively, proving that a high thermal efficiency can be achieved by using an organic liquid hydrogen storage carrier with a boiling point higher than the dehydrogenation temperature, and proving the versatility of the system and method of the present invention. In contrast, the thermal efficiency of Example 3 is 20.1%. Although increasing the Rankine cycle heat source temperature (dehydrogenation reactor temperature) can theoretically increase the dehydrogenation rate and cycle thermal efficiency, high dehydrogenation temperature will reduce the life of organic matter in the cycle of hydrogen absorption and dehydrogenation, and high temperature will also cause a small amount of organic matter to volatilize, and steam is also easy to condense again at a higher working pressure, which will lead to a decrease in system life and efficiency. Therefore, there is an optimal range for the temperature and pressure of the dehydrogenation reactor. Although the thermal efficiency of Example 3 is lower than that of Examples 1 and 2, the thermal efficiency is improved compared to the traditional ORC system. In Comparative Example 1, the temperature of the dehydrogenation reactor is higher than the boiling point of the organic liquid hydrogen storage carrier, and N-phenylcarbazole volatilizes or decomposes, which affects the efficiency of the working fluid on the one hand, and on the other hand, the volatilized high-boiling point organic matter may condense into droplets again before entering the turbine, which seriously reduces the life of the system. In Comparative Example 2, because the turbine blades were not coated with anti-hydrogen embrittlement coating, the blades broke, which seriously reduced the life of the system. In Comparative Example 3, the overall thermal efficiency of the conventional ORC system was low, about 18%.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A waste heat power generation system based on organic liquid hydrogen storage medium, characterized in that: The system comprises: A dehydrogenation reactor, wherein the dehydrogenation reactor uses heat provided by a heat source to cause an organic liquid hydrogen storage medium to undergo a dehydrogenation reaction to generate hydrogen; A conversion device, the conversion device is connected to the dehydrogenation reactor and is used to convert the internal energy of the hydrogen into electrical energy; a cooling device, the cooling device being in communication with the conversion device and configured to reduce the temperature of the hydrogen flowing out of the conversion device; and A hydrogenation reactor, the hydrogenation reactor being in communication with the cooling device and configured to cause a hydrogenation reaction between the hydrogen gas and the organic liquid hydrogen storage medium in the hydrogenation reactor; Wherein, the dehydrogenation reactor and the hydrogenation reactor are interconnected to maintain the circulation of the organic liquid hydrogen storage medium.

2. The waste heat power generation system according to claim 1, characterized in that: The organic liquid hydrogen storage medium includes one or more of N-methylcarbazole, N-ethylcarbazole, N-acetylcarbazole, N-benzoylcarbazole and N-phenylcarbazole. Preferably, the organic liquid hydrogen storage medium is selected from one or more of N-methylcarbazole, N-ethylcarbazole and N-phenylcarbazole. Preferably, the boiling point of the organic liquid hydrogen storage medium is 310°C to 450°C, the hydrogen release temperature is 170°C to 220°C, and the mass hydrogen storage density is 2wt% to 8wt%.

3. The waste heat power generation system according to claim 1 or 2, characterized in that: The catalyst used in the dehydrogenation reactor is a noble metal catalyst supported by a molecular sieve, and preferably the noble metal is selected from one or more of Pt, Pd and Rh.

4. The waste heat power generation system according to claim 1 or 2, characterized in that: The catalyst used in the hydrogenation reactor is a molecular sieve-supported noble metal catalyst or a molecular sieve-supported non-noble metal catalyst, preferably the noble metal is selected from one or more of Pt, Pd and Ru, and preferably the non-noble metal is selected from one or more of Fe, Cu and Ni.

5. The waste heat power generation system according to claim 1 or 2, characterized in that: The conversion device comprises an expansion device and a generator, wherein the expansion device is connected to the generator. Preferably, the expansion device is a turbine expander, a screw expander or a piston expander, and more preferably, the expansion device is a turbine expander.

6. The waste heat power generation system according to claim 5, characterized in that: The surface of the turbine blade of the turboexpander is coated with an anti-hydrogen embrittlement coating material. Preferably, the anti-hydrogen embrittlement coating material is an anti-hydrogen embrittlement ceramic coating material of oxide, nitride or oxynitride, and more preferably is selected from one or more of titanium nitride, titanium oxide, aluminum nitride, aluminum oxide or aluminum oxynitride.

7. The waste heat power generation system according to claim 1 or 2, characterized in that: The temperature in the dehydrogenation reactor is 250° C. to 300° C., and the pressure is 5 MPa to 10 MPa, preferably the temperature is 260° C. to 275° C., and the pressure is 6 MPa to 8 MPa.

8. The waste heat power generation system according to claim 1 or 2, characterized in that: The temperature of the hydrogenation reactor is 100°C to 200°C; preferably, the workload of the cooling device is interlocked with the temperature control of the hydrogenation reactor; more preferably, the hydrogenation reactor further includes a temperature regulating device, and the workloads of both the temperature regulating device and the cooling device are interlocked with the system temperature control mechanism.

9. The waste heat power generation system according to claim 1 or 2, characterized in that: The dehydrogenation reactor is a fixed bed reactor; the cooler is a plate heat exchanger; and the hydrogenation reactor is a fixed bed reactor.

10. A method for waste heat power generation using the waste heat power generation system according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: S1: The heat source provides heat, and the dehydrogenation reactor causes the organic liquid hydrogen storage medium to undergo a dehydrogenation reaction to generate hydrogen, and the dehydrogenated organic liquid hydrogen storage medium enters the hydrogenation reactor; S2: The hydrogen enters the conversion device to convert internal energy into electrical energy; S3: cooling the hydrogen flowing out of the conversion device in a cooling device; S4: The hydrogen after cooling enters the hydrogenation reactor, and undergoes a hydrogenation reaction with the organic liquid hydrogen storage medium after dehydrogenation in the hydrogenation reactor, and the hydrogenated organic liquid hydrogen storage medium enters the dehydrogenation reactor.

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