A chemical energy storage system and method based on a nitric acid-ammonia water system

Abstract

The present invention relates to the technical field of chemical energy storage, and in particular, to a chemical energy storage system and method based on a nitric acid-ammonia water system. The electrolytic water device of the system is respectively connected to an ammonia production device and a nitric acid production device, and the ammonia production device is connected to the nitric acid production device; it further includes a nitric acid storage separation and decomposition device, an ammonia water storage separation and decomposition device, and a reaction heat recovery device; the nitric acid storage separation and decomposition device is connected to the reaction heat recovery device, and the ammonia water storage separation and decomposition device is connected to the reaction heat recovery device; the nitric acid production device is connected to the nitric acid storage separation and decomposition device. This system can produce ammonia water and nitric acid, convert electrical energy into chemical energy, and also enable the reaction of the decomposition products of nitric acid with NH3 generated by ammonia water, converting chemical energy into heat energy or electrical energy; this system can achieve chemical energy storage under normal temperature and pressure with large capacity and long cycle, does not depend on meteorological or geological conditions, has a wide application range, and is simple to maintain.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical energy storage, and in particular, to a chemical energy storage system and method based on a nitric acid-ammonia water system. Background Art

[0002] With the rapid development of green power such as wind power, photovoltaic power, and solar thermal power, green power has become the main source of electric energy supply in China. In 2020, the total installed load ratio of green power has reached 46.33%, and the proportion of newly installed load of only wind-solar green power in the total newly installed load is as high as 63%. Statistical data in 2021 shows that the power supply of green power has accounted for as high as 36.30% in the total electricity consumption of the whole society.

[0003] Since the power generation efficiency and power generation of green power such as wind power, photovoltaic power, and solar thermal power are seriously affected by meteorological conditions, the state has paid attention to the related supporting energy storage issues regarding the safety and stability of the power grid at the initial stage of the development of green power. In 2021, it was even clearly stated in the green power policy that new green power projects such as wind power, photovoltaic power, and solar thermal power must be equipped with corresponding energy storage facilities.

[0004] Currently, the energy storage facilities on the market include the following categories: electrochemical energy storage, chemical energy storage, kinetic energy storage, potential energy storage, and heat storage. Electrochemical energy storage is the most widely used. A typical application is lithium-ion battery energy storage. Its advantages are fast response, long energy storage cycle, and low loss. The disadvantages are high cost and small capacity. The representative of kinetic energy storage is flywheel energy storage. Its actual industrial applications are mainly concentrated in the transportation system. The advantage is energy recovery, and the disadvantages are high cost, short energy storage cycle, and small capacity. The typical of heat storage technology is molten salt heat storage. Its advantages are high energy storage capacity and low cost. The disadvantages are short energy storage cycle, high operation and maintenance requirements, and low energy conversion efficiency. The representative technologies of potential energy storage are pumped storage and compressed air energy storage. Among them, pumped storage, as a representative of large-capacity and long-cycle energy storage at normal temperature and pressure, can achieve an energy storage efficiency of 80%, and also has the ability of large-capacity energy storage at normal temperature and pressure. It is the best-known energy storage technology currently. However, the disadvantages of potential energy storage are also very obvious. Whether it is pumped storage or compressed air energy storage technology, both rely on the geographical environment. Pumped storage requires a large-capacity water body lake resource with a suitable head at normal temperature and pressure, and compressed air depends on a specific geological structure of underground rock formations. The actual applicable scenarios are few.

[0005] The typical representative of chemical energy storage is the combination of electrolytic water hydrogen production + hydrogen-oxygen fuel cell, which meets all the technical advantages required by energy storage technologies, such as large capacity, long cycle, high efficiency, etc. at normal temperature and pressure. However, its disadvantages are also fatal. The proton exchange membrane technology of hydrogen-oxygen fuel cells is still some distance from large-scale industrial application, with high costs and short lifespan. At the same time, as the intermediate medium for energy storage, the large-scale high-pressure storage tanks required for storing hydrogen and oxygen, and the requirements for their operating safety impose strict restrictions on the site layout, significantly reducing the actual applicable scenarios. However, it is certain that chemical energy storage is an important direction for achieving large-capacity, long-cycle, and high-efficiency energy storage at normal temperature and pressure.

[0006] The process route for synthesizing ammonia from hydrogen and nitrogen has been gradually developed and improved since the establishment of a large-scale industrial ammonia plant by Badische Anilin- und Soda-Fabrik in 1913; the large-scale industrial application of producing nitric acid by reacting ammonia with oxygen was successfully implemented by DuPont in the United States in 1920. Both ammonia synthesis technology and nitric acid preparation technology are mature industrial technology products that have undergone a century of technological development and innovation, and are also one of the most widely used and safe basic chemical process technologies in the current market.

[0007] However, there has not yet been a chemical energy storage system that uses the conversion of ammonia to nitric acid to achieve large-capacity and long-cycle energy storage at normal temperature and pressure. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a chemical energy storage system and method based on a nitric acid-ammonia water system.

[0009] The technical solution of the present invention to solve the above technical problems is as follows:

[0010] The present invention provides a chemical energy storage system based on a nitric acid-ammonia water system, including a chemical energy storage device and a chemical energy release device;

[0011] The chemical energy storage device includes an electrolytic water device, an ammonia preparation device, and a nitric acid preparation device; wherein, the electrolytic water device is respectively connected to the ammonia preparation device and the nitric acid preparation device through a hydrogen gas pipeline and an oxygen gas pipeline, and the ammonia preparation device is connected to the nitric acid preparation device through an ammonia pipeline;

[0012] The chemical energy release device includes a nitric acid storage separation and decomposition device, an ammonia water storage separation and decomposition device, and a reaction heat recovery device; wherein, the nitric acid storage separation and decomposition device is connected to the reaction heat recovery device through a nitrogen oxide pipeline, and the ammonia water storage separation and decomposition device is connected to the reaction heat recovery device through an ammonia gas mixing pipeline;

[0013] The nitric acid preparation device is connected to the nitric acid storage separation and decomposition device through a nitric acid pipeline.

[0014] Furthermore, the chemical energy storage device further includes a process water preparation and storage device and a nitrogen preparation and storage device;

[0015] The process water preparation and storage device is respectively connected to the reaction heat recovery device, the nitrogen preparation and storage device, and the electrolytic water device through a reaction heat recovery tail gas pipeline, a low-temperature drying reaction tail gas pipeline, and a process water pipeline;

[0016] The nitrogen preparation and storage device is connected to the ammonia preparation device through a nitrogen pipeline.

[0017] Furthermore, it further includes a tail gas treatment device; the ammonia preparation device, the nitric acid preparation device, and the nitrogen preparation and storage device are respectively connected to the tail gas treatment device.

[0018] Furthermore, the nitric acid preparation device and the nitric acid storage, separation, and decomposition device are also connected through a dilute nitric acid pipeline.

[0019] Furthermore, the ammonia preparation device and the ammonia water storage, separation, and decomposition device are connected through an ammonia water pipeline.

[0020] Furthermore, the ammonia preparation device and the ammonia water storage, separation, and decomposition device are also connected through a dilute ammonia water pipeline.

[0021] The present invention also provides a chemical energy storage method based on a nitric acid - ammonia water system, including a chemical energy storage process and a chemical energy release process;

[0022] The chemical energy storage process is as follows: electrolyze electrolytic water to prepare hydrogen and oxygen; use the prepared hydrogen and nitrogen to continue preparing ammonia, and then convert the ammonia into an ammonia water solution; use the prepared oxygen and the prepared ammonia to continue preparing nitric acid;

[0023] The chemical energy release process is as follows: mix nitrogen with the ammonia water solution and perform high-temperature stripping to separate and release an unsaturated high-temperature ammonia mixed gas from the ammonia water; concentrate the nitric acid into a concentrated nitric acid solution to release an unsaturated high-temperature nitrogen oxide gas from the concentrated nitric acid solution; react the unsaturated high-temperature ammonia mixed gas and the unsaturated high-temperature nitrogen oxide gas, and the energy generated by the reaction can be utilized, and the tail gas generated by the reaction can be used to prepare the electrolytic water and the nitrogen.

[0024] Furthermore, the components of the unsaturated high-temperature ammonia mixed gas include NH3 and water vapor; the components of the unsaturated high-temperature nitrogen oxide gas are NO2, NO, O2, water vapor, and N2; the components of the tail gas include N2 and water vapor.

[0025] Further, in the aqueous ammonia solution, the mass percentage of ammonia is 20% - 25%; in the nitric acid solution, the mass percentage of nitric acid is 55% - 60%; in the concentrated nitric acid solution, the mass percentage of nitric acid is greater than or equal to 90%.

[0026] Further, during the chemical energy release process, the energy generated by the reaction is utilized in the form of heat energy or potential energy; when it is utilized as heat energy, a waste heat boiler is used to recover the heat energy, and when it is utilized as potential energy, a steam turbine or an expander is used for power recovery.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) The chemical energy storage system based on the nitric acid - aqueous ammonia system of the present invention combines an electrolyzed water device, an ammonia preparation device, and a nitric acid preparation device, enabling the preparation process of aqueous ammonia and nitric acid, thereby realizing the chemical energy storage process of converting electrical energy into chemical energy. Moreover, the obtained aqueous ammonia and nitric acid have stable properties, are easy to store in large quantities for a long period under normal temperature and pressure, and have good safety.

[0029] (2) The chemical energy storage system based on the nitric acid - aqueous ammonia system of the present invention realizes the release of chemical energy by setting up a reaction heat recovery device, enabling the reaction of the decomposition products of nitric acid, namely NO2, NO, and O2, with NH3 generated after the stripping of aqueous ammonia. Through the recovery of the reaction heat release, the process of converting chemical energy into heat energy or electrical energy is achieved; there are many reaction process control measures, and the operation is safe; for energy recovery, mature heat and power recovery equipment is used, with stable recovery efficiency and reliable operation.

[0030] (3) The chemical energy storage system based on the nitric acid - aqueous ammonia system of the present invention can realize the recovery of reaction tail gas by setting up a process water preparation and storage device and a nitrogen preparation and storage device, enabling the reuse of process water and nitrogen to form a cycle and reducing the total energy consumption of the system.

[0031] (4) The chemical energy storage method based on the nitric acid - aqueous ammonia system of the present invention adopts a mature inorganic chemical synthesis process for the chemical energy storage process, does not depend on meteorological or geological conditions, and has a wide application range.

[0032] (5) The chemical energy storage method based on the nitric acid - aqueous ammonia system of the present invention constructs a complete cycle of nitrogen source, hydrogen source, and oxygen source based on water and nitrogen, realizing the material cycle system during the chemical energy storage process, thereby ensuring the operation economy of the chemical energy storage system of the present invention. Description of the Drawings

[0033] Figure 1 It is a schematic structural diagram of the chemical energy storage system based on the nitric acid - aqueous ammonia system of the present invention;

[0034] Figure 2In the chemical energy storage system based on the nitric acid - ammonia water system of the present invention, it is a schematic diagram of the chemical energy storage process;

[0035] Figure 3 In the chemical energy storage system based on the nitric acid - ammonia water system of the present invention, it is a schematic diagram of the chemical energy release process.

[0036] In the attached drawings, the list of components represented by each reference numeral is as follows:

[0037] 1. Electrolytic water device; 2. Ammonia preparation device; 3. Nitric acid preparation device; 4. Nitric acid storage, separation and decomposition device; 5. Ammonia water storage, separation and decomposition device; 6. Reaction heat recovery device; 7. Process water preparation and storage device; 8. Nitrogen preparation and storage device; 9. Tail gas treatment device;

[0038] 11. Hydrogen gas pipeline; 12. Oxygen gas pipeline; 13. Ammonia gas pipeline; 14. Nitrogen oxide pipeline; 15. Ammonia gas mixing pipeline; 16. Reaction heat recovery tail gas pipeline; 17. Low - temperature drying reaction tail gas pipeline; 18. Nitrogen gas pipeline; 19. Tail gas treatment pipeline;

[0039] 21. Process water pipeline; 22. Nitric acid pipeline; 23. Dilute nitric acid pipeline; 24. Ammonia water pipeline; 25. Dilute ammonia water pipeline. Detailed implementation manners

[0040] The principles and features of the present invention will be described below with reference to the attached drawings. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention.

[0041] As Figure 1 shown, the chemical energy storage system based on the nitric acid - ammonia water system of the present invention includes a chemical energy storage device and a chemical energy release device; the chemical energy storage device includes an electrolytic water device 1, an ammonia preparation device 2, and a nitric acid preparation device 3; among them, the electrolytic water device 1 is respectively connected to the ammonia preparation device 2 and the nitric acid preparation device 3 through a hydrogen gas pipeline 11 and an oxygen gas pipeline 12, and the ammonia preparation device 2 is connected to the nitric acid preparation device 3 through an ammonia gas pipeline 13; the chemical energy release device includes a nitric acid storage, separation and decomposition device 4, an ammonia water storage, separation and decomposition device 5, and a reaction heat recovery device 6; among them, the nitric acid storage, separation and decomposition device 4 is connected to the reaction heat recovery device 6 through a nitrogen oxide pipeline 14, and the ammonia water storage, separation and decomposition device 5 is connected to the reaction heat recovery device 6 through an ammonia gas mixing pipeline 15; the nitric acid preparation device 3 is connected to the nitric acid storage, separation and decomposition device 4 through a nitric acid pipeline 22.

[0042] The chemical energy storage system based on the nitric acid - ammonia water system of the present invention can achieve large - capacity and long - cycle chemical energy storage under normal temperature and pressure. This system can store energy, that is, convert electrical energy or thermal energy into chemical energy for storage, and can store it in large capacity, long cycle and high efficiency under normal temperature and pressure; at the same time, it can also release chemical energy, that is, release the stored chemical energy in the form of electrical energy or thermal energy again.

[0043] Specifically, the system of the present invention converts ammonia to nitric acid, realizes the combination of oxygen and ammonia to produce nitric acid, and realizes the safe and stable solidification of oxygen. At the same time, the decomposition products NO2 / NO of nitric acid are used as oxidants instead of oxygen to realize the combustion process of ammonia.

[0044] In addition, the electrolytic water device 1, ammonia preparation device 2 and nitric acid preparation device 3 adopted by the system of the present invention all belong to mature and reliable large - scale industrial process systems. Their construction and operation are not affected by meteorological and geographical environments, their operation modes and operation management measures are perfect, and they have wide applicability and promotion value. At the same time, the specific process technologies and operation pressures of the above - mentioned devices can be comprehensively selected according to the overall energy consumption during combined operation, ensuring that the energy consumption during the chemical energy storage process is small and realizing the improvement of the energy utilization rate during the chemical energy storage process.

[0045] As Figure 1 and 2 shown, the specific working process of the chemical energy storage device of the present invention is as follows:

[0046] Preferably, the chemical energy storage device further includes a process water preparation and storage device 7 and a nitrogen preparation and storage device 8; the process water preparation and storage device 7 is respectively connected to the reaction heat recovery device 6, the nitrogen preparation and storage device 8 and the electrolytic water device 1 through a reaction heat recovery tail gas pipeline 16, a low - temperature drying reaction tail gas pipeline 17 and a process water pipeline 21; the nitrogen preparation and storage device 8 is connected to the ammonia preparation device 2 through a nitrogen pipeline 18.

[0047] External input energy is respectively connected to the electrolytic water device 1 and the ammonia preparation device 2 to provide the required energy for both. It should be noted that the nitric acid preparation device 3 also needs external input energy to provide some energy in the initial startup stage. However, the energy required by the nitric acid preparation device 3 is less and can be ignored, Figure 2 and is not shown in

[0048] The electrolytic water device 1 decomposes process water into hydrogen and oxygen through externally input energy (electrical energy). The process water consumed in the electrolysis process is provided by the process water preparation and storage device 7. The operating pressure of the electrolytic water device 1 is determined according to the working pressures and temperatures of the subsequent ammonia - making process device and nitric - acid - making process device for its economic operation.

[0049] The ammonia preparation device 2 uses the hydrogen produced by the electrolytic water device 1 and the nitrogen provided by the nitrogen preparation and storage device 8 to produce ammonia. A part of the produced ammonia is sent as a raw material to the nitric acid preparation device 3; the other part of the ammonia is prepared into finished ammonia water and stored in the ammonia water storage, separation and decomposition device 5. The ammonia concentration of the finished ammonia water is determined comprehensively according to the on-site layout, surrounding environmental conditions, designed long-term storage time and safety requirements.

[0050] For the preparation of ammonia water, further preferably, the ammonia preparation device 2 and the ammonia water storage, separation and decomposition device 5 are connected through an ammonia pipeline 24; the ammonia preparation device 2 and the ammonia water storage, separation and decomposition device 5 are also connected through a dilute ammonia pipeline 25; the other part of the ammonia is mixed with the dilute ammonia water refluxed from the ammonia water storage, separation and decomposition device 5 to prepare commercial ammonia water. The refluxed dilute ammonia water is mixed with the ammonia water generated in the ammonia preparation device 2 and is prepared into commercial ammonia water with a volume percentage of 20% in the washing and absorption device in the ammonia preparation device 2.

[0051] Preferably, the concentration of the commercial ammonia water is less than or equal to 20% by volume percentage. This concentration has the advantages of safety and can be stored at normal temperature and pressure for a long time; the concentration of the dilute ammonia water is 1% by volume percentage.

[0052] The nitric acid preparation device 3 uses the ammonia produced by the ammonia preparation device 2 and the oxygen produced by the electrolytic water device 1 to prepare commercial nitric acid, and the commercial nitric acid is stored in the nitric acid storage, separation and decomposition device 4.

[0053] For the preparation of commercial nitric acid, further preferably, the nitric acid preparation device 3 and the nitric acid storage, separation and decomposition device 4 are also connected through a dilute nitric acid pipeline 23; the nitric acid prepared from ammonia and oxygen is mixed with the dilute nitric acid refluxed from the nitric acid storage, separation and decomposition device 4 to obtain commercial nitric acid. The concentration of the commercial nitric acid is determined comprehensively according to the on-site layout, surrounding environmental conditions, designed long-term storage time and safety requirements.

[0054] Preferably, the concentration of the commercial nitric acid is 55% by volume percentage, and the concentration of the dilute nitric acid is 5% by volume percentage.

[0055] After the above process, the commercial ammonia water and commercial nitric acid are stored in the ammonia water storage, separation and decomposition device 5 and the nitric acid storage, separation and decomposition device 4 respectively as storage media; due to the advantages of safety and stability of the two solutions, they are particularly suitable for long-term and large-scale storage at normal temperature and pressure, realizing the chemical medium storage of energy (electric energy, heat energy), and at the same time realizing the unity of the safety and economy of chemical energy storage.

[0056] The working pressure and temperature of the above-mentioned devices during operation and storage can be specifically adjusted and set according to actual conditions and specific requirements.

[0057] Such as Figure 1 andFigure 3 As shown in the figure, the specific working process of the chemical energy release device of the present invention is as follows:

[0058] The unsaturated high-temperature ammonia mixed gas generated in the ammonia storage separation and decomposition device 5 and the unsaturated high-temperature nitrogen oxide gas generated in the nitric acid storage separation and decomposition device 4 respectively enter the reaction heat recovery device 6 for reaction, and the heat released by the reaction can be recovered as electric energy to realize the release of chemical energy.

[0059] The main components of the unsaturated high-temperature nitrogen oxide gas are a mixed gas of NO2, NO, O2, water vapor, and N2, and the main component of the unsaturated high-temperature ammonia mixed gas is an NH3 / water vapor mixed gas. In the reaction heat recovery device 6, the mixed gas of NO2, O2, water vapor, and N2 is the main body, and the NH3 / water vapor mixed gas is slowly injected. The specific reaction process occurring in the reaction heat recovery device 6 is as follows: NO2 first undergoes a disproportionation reaction with NH3, releasing a large amount of heat, which causes the temperature of the mixed gas in the reaction heat recovery device 6 to rise. When the temperature rises, NO2 begins to decompose, releasing NO and O2; then, as the temperature continues to rise, NH3 and O2 begin to undergo a reduction reaction to form N2; at high temperatures, NO and NH3 undergo a reduction reaction to form N2.

[0060] In the above reaction process, there is not only a temperature rise process with heat release, but also a volume expansion process of the reaction gas. The energy recovery of the chemical energy release process can be achieved by directly converting it into mechanical energy / electric energy using a steam turbine or other means, or by converting it into heat energy / electric energy using a boiler or other means.

[0061] Preferably, in the above reaction process, the role of the inert gas N2 is to act as a diluent gas to control the intensity of the reaction process and ensure the controllability and safety of the reaction. The source of N2 can be added additionally or can be from the nitrogen preparation and storage device 8.

[0062] Preferably, in the above reaction process, the intensity and rate of the reaction are controlled by controlling the dosage of the NH3 / water vapor mixed gas, and the controllability and safety of the reaction are enhanced.

[0063] Preferably, in the above reaction process, at the end of the disproportionation reaction, since the concentrations of NO2, NO, and O2 decrease and the reaction can no longer proceed efficiently, at this time, an SCR denitration catalyst is used to catalyze the denitration reaction of the reaction gas. Under the catalytic action of the denitration catalyst, NOx and NH3 are promoted to react fully and thoroughly, and the remaining concentrations of NO, O2, and NH3 are all reduced to the ppm level. After the catalytic denitration reaction, the temperature of the reaction gas rises and enters the waste heat boiler for waste heat recovery; in the cooled reaction gas, only ppm-level NO, O2, and NH3 remain, and the rest are N2 and H2O.

[0064] The process water preparation and storage device 7 receives the low-temperature tail gas after the waste heat recovery from the reaction heat recovery device 6. The low-temperature tail gas is cooled and condensed in the process water preparation and storage device 7 to obtain condensed water, and the condensed water is stored in the process water preparation and storage device 7. The condensed water in the process water preparation and storage device 7 can be transferred to the electrolytic water device 1 as process water and continue to participate in the electrolysis reaction.

[0065] Preferably, in the process water preparation and storage device 7, along with the condensation and cooling process, most of the residual NH3 in the tail gas is removed together with the condensed water and collected together with the condensed water; the condensed water is further deammoniated and then stored as process water.

[0066] Preferably, the process water preparation and storage device 7 can be connected to the ammonia water storage, separation and decomposition device 5 through an independent pipeline. The ammonia gas removed in the process water preparation and storage device 7 can be directly recovered or sent to the ammonia water storage, separation and decomposition device 5 to be absorbed and stored as dilute ammonia water. Of course, the ammonia gas required by the ammonia water storage, separation and decomposition device 5 can also be provided by other external devices.

[0067] The process water preparation and storage device 7 is a circulation / storage device for the hydrogen source and oxygen source (in the form of process water H2O). During the chemical energy storage process, it undertakes the task of providing process water for the electrolytic water process; during the chemical energy release process, it undertakes the tasks of recovering condensed water and preparing the condensed water into qualified process water.

[0068] In the process of the process water preparation and storage device 7 preparing process water, only the condensed water to be recovered from the tail gas of the NOx and NH3 reaction (high-purity nitrogen source) needs to be prepared into process water, and the energy consumption and cost are greatly reduced; the process water preparation and storage device 7 needs to prepare a small amount of process water from an external water source to supplement the inevitable small amount of process water loss and escape during the chemical energy storage process and the chemical energy release process, and maintain the water balance of the entire chemical energy storage system.

[0069] The components in the low-temperature tail exhaust gas after cooling, condensing and dehydrating are mainly N2, and there are only trace amounts of NO, O2 and NH3 at the ppm level of low-temperature saturated water vapor remaining. These tail gases continue to enter the nitrogen preparation and storage device 8, and the nitrogen in the nitrogen preparation and storage device 8 is transported to the ammonia preparation device 2 through the nitrogen pipeline 18.

[0070] For the nitrogen preparation and storage device 8, it undertakes the task of providing nitrogen during the chemical energy storage process and undertakes the tasks of recovering nitrogen and controlling the reaction intensity during the chemical energy release process. During the chemical energy release process, nitrogen recovery only needs to recover nitrogen from the tail gas of the reaction between NOx and NH3 (high-purity nitrogen source), and the energy consumption and cost are greatly reduced. At the same time, for the nitrogen preparation and storage device 8, a small amount of nitrogen also needs to be produced from the outside, such as directly from the air, to supplement the inevitable loss and escape of a small amount of nitrogen source (including nitrogen) during the chemical energy storage process and the chemical energy release process, and maintain the nitrogen balance of the entire chemical energy storage system.

[0071] It should be noted that the nitrogen preparation and storage device 8 can also be connected to the nitric acid storage separation and decomposition device 4 and the ammonia water storage separation and decomposition device 5 through independent pipelines respectively to provide a small amount of nitrogen for both. Of course, the nitrogen required by the nitric acid storage separation and decomposition device 4 and the ammonia water storage separation and decomposition device 5 can also be provided separately by other external devices.

[0072] Preferably, it further includes a tail gas treatment device 9; the ammonia preparation device 2, the nitric acid preparation device 3, and the nitrogen preparation and storage device 8 are respectively connected to the tail gas treatment device 9 through tail gas treatment pipelines 19. After the N2 separation and purification in the nitrogen preparation and storage device 8, a very small amount of residual NO, O2, and NH3 are sent to the tail gas treatment device 9 for terminal purification treatment. A very small amount of tail gas generated in the ammonia preparation device 2 and the nitric acid preparation device 3 also enters the tail gas treatment device 9 for treatment.

[0073] For the chemical energy storage system of the nitric acid-ammonia water system of the present invention, the heat balance mechanism is shown in Table 1, where l represents liquid, g represents gas, and △ represents heat; the total heat is the rounded value, and the positive value of heat represents endothermic, and the negative value represents exothermic.

[0074] Table 1

[0075]

[0076] It can be seen from the above table that, overall, from the perspective of endothermic and exothermic, theoretically, the heat of the endothermic process is 14745 KJ / 48 mol, the heat of the exothermic process is -12174 KJ / 48 mol, the deviation value is 2570 KJ / 48 mol, and the theoretical energy utilization rate is 82.57%.

[0077] Analyzing separately from the two processes of chemical energy storage and chemical energy release, theoretically, during the chemical energy storage process, the stored heat is 8275 KJ / 48 mol, and during the chemical energy release process, the heat that can be released is 5705 KJ / 48 mol, the deviation value is 2570 KJ / 48 mol, and the theoretical energy utilization rate is 68.94%.

[0078] In the actual process, considering the low-temperature heat loss in the processes of ammonia water preparation, ammonia stripping, nitric acid preparation and nitric acid decomposition, as well as the energy consumption in the circulation process, the actual energy utilization rate is slightly lower than the above theoretical value. However, the above analysis can still prove that the system of the present invention has good conversion efficiency.

[0079] Example

[0080] This example takes a specific chemical energy storage system based on the nitric acid-ammonia water system as an example to illustrate the specific implementation process of the present invention and the conversion of energy.

[0081] The chemical energy storage process of this example is specifically as follows:

[0082] The electrolytic water device 1 electrolyzes process water through externally input energy to generate hydrogen and oxygen. In this example, the specific structure of the electrolytic water device 1 is a common alkaline electrolytic cell. In the industrial production process, the power consumption per unit hydrogen production of the alkaline electrolytic cell is 4.5 KWh / Nm 3 (H2). An electrolytic water device 1 with a hydrogen production capacity of 10,000 Nm 3 / h can consume 45 MWh of electric energy per unit hour, produce 10,000 Nm of hydrogen 3 / h, 5,000 Nm of oxygen 3 / h, with an operating pressure of 1.5 MPa, and consume about 8.0 t / h of process water.

[0083] The electrolytic water device 1 is not provided with a hydrogen storage device, and the hydrogen electrolytically prepared is directly sent to the ammonia preparation device 2 after pressurization to participate in the ammonia production process. The flow rate of hydrogen is 10,000 Nm 3 / h. The nitrogen raw material is directly supplied from the nitrogen storage tank in the nitrogen preparation and storage device 8 to the ammonia synthesis device 2, and the flow rate of nitrogen is 3,333 Nm 3 / h.

[0084] The ammonia preparation device 2 is specifically an ammonia synthesis tower in the ammonia production process system. In the ammonia synthesis tower of the ammonia production process system, nitrogen and hydrogen are mixed, and under the action of a catalyst in the synthesis tower, the synthesis process of ammonia is completed. The specific type of this process and the catalyst used are both conventional choices in this field. The output of the synthesized ammonia is approximately 5.1 t / h (calculated as 100% pure NH₃). The synthesized ammonia is condensed and separated into liquid ammonia. Then, it is directly depressurized, evaporated, and reheated. Approximately 1.9 t / h of a part of the ammonia directly enters the nitric acid preparation device 3 to participate in the preparation of nitric acid. Approximately 3.2 t / h of a part of the ammonia is mixed with approximately 13.3 t / h of dilute ammonia water (generally less than 1%, calculated as 1%) refluxed from the ammonia water storage, separation, and decomposition device 5, and is prepared into commercial ammonia water with a volume percentage of 20% in the washing and absorption device in the ammonia preparation device 2. The above ratio can produce 16.5 t / h of commercial ammonia water. The commercial ammonia water then flows back into the ammonia water storage, separation, and decomposition device 5 for long-term storage. The ammonia preparation process uses nitrogen and hydrogen as raw materials, with a nitrogen pressure of 15 MPa and a hydrogen pressure of 1.5 MPa. The unit ammonia energy consumption is 21.28 GJ / t (NH₃), which is converted to 5911 KWh / t (NH₃), and the electric energy that can be consumed per unit hour is 30 MWh.

[0085] After 1.9 t / h of ammonia produced by the ammonia preparation device 2 enters the nitric acid preparation device 3, it reacts with 5000 Nm 3 / h of oxygen electrolytically prepared by the electrolytic water device 1 to prepare nitric acid, and the amount of nitric acid obtained is 7.0 t / h (calculated as 100% pure HNO₃). The nitric acid preparation device 3 uses dilute nitric acid (generally less than 5%, calculated as 5%) refluxed from the nitric acid storage, separation, and decomposition device 4 as an absorbent to prepare finished nitric acid. The required dilute nitric acid is 4.1 t / h, the concentration of the prepared finished nitric acid is 55%, and the preparation amount is 13.2 t / h. The prepared finished nitric acid then enters the nitric acid storage, separation, and decomposition device 4 for long-term storage. There are many specific process routes available for the nitric acid production process. Generally, the energy consumption is 12 KWh / t (calculated as 100% pure HNO₃), and the by-product steam output is 0.17 t / t (calculated as 100% pure HNO₃). Its external input energy consumption is extremely small and can be ignored.

[0086] In the above ammonia preparation process and nitric acid preparation process, a very small amount of reaction tail gas will be generated, and the tail gas is sent to the tail gas treatment device 9 for treatment and then discharged.

[0087] In summary, in the chemical energy storage process of the system in this embodiment, an electrolytic water device with a hydrogen production capacity of 10000 Nm 3 / h is equipped with an ammonia production process system with an ammonia production capacity of 5.1 t / h and a nitric acid production process system with a nitric acid production capacity of 7.0 t / h (calculated as 100% pure HNO₃), which can consume 75 MW of external input energy; consume 8.0 t / h of process water and 3333 Nm of nitrogen3 / h; Produce chemical energy storage media with large capacity and long cycle, including 16.5 t / h of 20% commercial ammonia water and 13.2 t / h of 55% concentration finished nitric acid.

[0088] Taking the total energy storage of 3000 MWh in the chemical energy storage process as an example, the total storage of 20% commercial ammonia water in the chemical energy storage medium is 659 t, and only an atmospheric storage tank with an effective storage capacity of 721 m 3 is required to meet long-term storage; the total storage of 55% finished nitric acid in the chemical energy storage medium is 526 t, and only an atmospheric storage tank with an effective storage capacity of 393 m 3 is required to meet long-term storage; the process water consumption is 320 t, and an atmospheric storage tank with an effective storage capacity of 320 m 3 is required to meet the process consumption during the energy storage process; the nitrogen consumption is 133333 Nm 3 . Taking the working pressure of the ammonia synthesis tower in the ammonia production process system as 15 MPa, an atmospheric storage tank with an effective storage capacity of 889 m 3 with a working pressure not lower than 15 MPa is required to meet the process consumption during the energy storage process.

[0089] The specific process of chemical energy release in this embodiment is as follows:

[0090] The nitrogen preparation and storage device 8 can supply a small amount of nitrogen into the ammonia water storage, separation and decomposition device 5 through a separate pipeline to blow off the 20% ammonia water therein, so as to separate a mixed gas composed of ammonia gas, water vapor and nitrogen. The temperature of the above ammonia water evaporation and blow-off operation is 120 °C, and the operating pressure is 0.2 MPa. In addition to the inert blowing gas nitrogen in the blowing gas, the volume ratio of ammonia gas to water vapor is about 49% and 51%, and the gas volume of nitrogen can be determined according to the evaporation and blow-off efficiency and the temperature control requirements of the chemical energy release process. The supplementary heat in the ammonia water evaporation and blow-off process comes from the heat recovery of the chemical energy release process.

[0091] Specifically, taking the pure ammonia gas release flow rate of 3.2 t / h of the nitrogen preparation and storage device 8 as an example, the inlet flow rate of 20% commercial ammonia water is 16.3 t / h, and 9.7 t / h of 1% dilute ammonia water is refluxed to the ammonia gas preparation device 2 after evaporation and blow-off. The ammonia water evaporation and blow-off process produces a mixed gas composed of about 49% (volume concentration) ammonia gas / water vapor of 8470 Nm 3 / h, which is sent to the reaction heat recovery device 6 to participate in the reaction under its own pressure. The supplementary heat required for the ammonia water evaporation and blow-off process is about 5.9 GJ / h of low-level heat, with a temperature of about 150 °C. This supplementary heat is used for the endothermic evaporation process in the ammonia water evaporation and blow-off process and is provided by the waste heat of the tail gas after chemical energy release. Continuously supplementing a small amount of inert gas N2 can ensure the non-saturated state of ammonia gas / water vapor and prevent the problem of ammonia water condensation during transportation. In this process, the nitrogen consumption is small and can be ignored.

[0092] The finished nitric acid with a concentration of 55% in the nitric acid preparation device 3 is concentrated by the superazeotropic acid rectification method into concentrated nitric acid with a concentration greater than or equal to 90% (calculated based on 90% concentrated nitric acid). These concentrated nitric acids and dilute nitric acid with a concentration of 5% are stored in the nitric acid storage separation and decomposition device 4, and the concentrated nitric acid further undergoes a decomposition reaction to generate NO2 and H2O gases.

[0093] Specifically, the temperature of the superazeotropic acid rectification method concentration operation is about 120 °C, which is the highest constant boiling point. The unit energy consumption during the concentration process is about 116 MJ / t (calculated based on 100% HNO3); the decomposition temperature for the 90% concentrated nitric acid to decompose into NO2, O2, and H2O gases is 150 °C, and the unit energy consumption is about 1465 MJ / t (calculated based on 100% HNO3). The mixed gas obtained by decomposition is specifically a mixture of NO2, O2, and water vapor. A certain amount of nitrogen is proportioned during the decomposition process of concentrated nitric acid to dilute the decomposition gas, control the concentrations of NO2 and O2, reduce the partial pressure of NO2, and promote the decomposition of gaseous HNO3. The nitrogen can be sourced from the nitrogen preparation and storage device 8. The mixture of NO2, O2, N2, and water vapor after decomposition is sent to the reaction heat recovery device 6 to participate in the reaction under its own pressure.

[0094] Specifically, taking the separation and decomposition of 7.0 t / h of pure HNO3 as an example, the flow rate of the 55% concentration finished nitric acid is 13.3 t / h, and after concentration, 7.8 t / h of 90% concentrated nitric acid and 5.5 t / h of dilute nitric acid are obtained; 7.8 t / h of 90% concentrated nitric acid is heated and decomposed, and the volume flow rate of the mixed gas of NO2, O2, and water vapor is 5347 Nm 3 / h, and the volume fractions of each component are 46.8%, 11.7%, and 41.6%. In addition to promoting the decomposition of gaseous HNO3, the dosing amount of the dilution nitrogen also serves as an inert gas to control the reaction temperature of the NOx and NH3 reaction heat recovery device. Here, it is calculated according to the dosing amount of 500 Nm 3 / h; about 11.1 GJ / h of low-level heat (about 150 °C) needs to be supplemented during the nitric acid separation and decomposition process, which is provided by the waste heat of the tail gas after the release of chemical energy.

[0095] In the reaction heat recovery device 6, the mixed gas of NO2, O2, water vapor, and N2 is the main body, and the NH3 / water vapor mixed gas from the ammonia water storage separation and decomposition device 5 is slowly injected. The specific reaction process occurring in the reaction heat recovery device 6 is as follows: NO2 first undergoes a disproportionation reaction with NH3, releasing a large amount of heat, which causes the temperature of the mixed gas in the reaction heat recovery device 6 to rise. When the temperature rises, NO2 begins to undergo a decomposition reaction, releasing NO and O2; then, as the temperature continues to rise, NH3 and O2 begin to undergo a reduction reaction to generate N2; at high temperatures, NO and NH3 undergo a reduction reaction to generate N2.

[0096] The NH3 / steam mixed gas is injected at different flow rates in different temperature ranges, stably controlling the reaction temperature and reaction intensity. This control process uses a mature control system to control according to the reaction temperature. Additionally, in the area of about 320 °C at the end of the reaction, an SCR denitration reaction layer is set up to ensure that only a very small amount of NO and O2 remain at the end of the reaction process.

[0097] When the reaction heat of NOx and NH3 is calculated based on the volume of NH3, 15.0 MJ / Nm 3 of heat can be released, and the theoretical volume of the gas under standard conditions expands by 1.26 times after the reaction. Taking the mixed gas of 5847 Nm 3 / h of NO2, O2, steam, and N2 transported by the nitric acid storage, separation, and decomposition device 4 as an example, in the heat recovery process, an NH3 / steam mixed gas with a flow rate of 8470 Nm 3 / h is added. During the reaction process, 62.6 GJ / h of heat is released, and the total volume expands from 14317 Nm 3 / h to 16609 Nm 3 / h, expanding 1.16 times.

[0098] When a steam turbine is used as the heat recovery device, the recoverable electric power can reach about 18 MW; the temperature of the tail gas at the end of the reaction drops to about 150 °C, and the tail gas flow rate is 16609 Nm 3 / h, of which 12775 Nm 3 / h of steam accounts for 76.9%, and 3833 Nm 3 / h of nitrogen accounts for 23.1%. Among them, 5.9 GJ / h of high-temperature flue gas returns to the nitric acid storage, separation, and decomposition device 4 as supplementary heat, and 11.1 GJ / h of high-temperature flue gas returns to the ammonia water storage, separation, and decomposition device 5 as supplementary heat. The remaining tail gas at the end of the reaction continues to be cooled and condensed for waste heat recovery through an organic Rankine cycle system, with a recovery amount of 8.5 GJ / h; calculated according to the conventional power generation efficiency of 12% of the organic Rankine cycle, the recoverable electric power is 0.3 MW. The total electric power recovered by the reaction heat recovery device 6 can reach 18.3 MW.

[0099] In the tail gas discharged from the reaction heat recovery device 6, N2 is the main component, and it also contains saturated water vapor and a small amount of residual NO and O2. These tail gases first enter the process water preparation and storage device 7 for condensate recovery, then continue to enter the nitrogen preparation and storage device 8 for nitrogen recovery, and finally enter the tail gas treatment device 9. A very small amount of NO and O2 are purified and discharged in the tail gas treatment device 9.

[0100] Taking the tail gas at the end of the reaction as an example, the tail gas at the end of the reaction is 16609 Nm 3 / h, 10.3 t / h of water can be recovered, and 3833 Nm 3 / h. After the process water preparation and storage device recovers 10.3 t / h of condensate water, 8.0 t / h of it is stored as process water for the electrolytic water device 1, and the remaining part can be returned to the ammonia water storage, separation and decomposition device 5 and the nitric acid storage, separation and decomposition device 4 as dilution and makeup water. In the nitrogen preparation and storage device 8, 3833 Nm 3 / h of clean and dry nitrogen is pressurized to 15 MPa and stored in the nitrogen storage tank.

[0101] In summary, in the process of chemical energy release of the system in this embodiment, taking one set of ammonia water storage / separation device releasing pure ammonia at a flow rate of 3.2 t / h and one set of nitric acid storage / separation and decomposition device separating and decomposing 7.0 t / h of pure HNO3 as an example, 18.3 MW of electric energy can be recovered in the reaction heat recovery device 6, and the energy storage recovery rate is 24.4%; 10.3 t / h of process water is recovered, 3833 Nm 3 / h of nitrogen is recovered, and 500 Nm 3 / h of nitrogen is consumed.

[0102] It should be noted that the above examples are only for describing the specific energy storage and release processes of the present invention, and the process selections and technical parameters involved therein all adopt the relevant data of the conventional chemical synthesis process route, and these data are at the average level in actual use. In fact, when putting the present invention into use, the technical route of the existing synthesis or decomposition process can be more specifically adjusted according to the specific actual situation, so as to obtain a higher energy storage recovery rate.

[0103] However, this embodiment has been able to prove that the energy recovery efficiency of the large-capacity and long-cycle chemical energy storage system based on the nitric acid-ammonia water system of the present invention can reach 82%, and the recoverable rate of electric energy can reach 68%.

[0104] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0105] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0106] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "below" and "beneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the horizontal height of the first feature is less than that of the second feature.

[0107] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0108] In the description of the present invention, it should be noted that, unless otherwise clearly specified and defined, the terms "mounted", "connected" and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention may be understood according to specific circumstances.

[0109] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A chemical energy storage system based on a nitric acid - ammonia water system, characterized in that, It includes a chemical energy storage device and a chemical energy release device; The chemical energy storage device includes an electrolytic water device (1), an ammonia preparation device (2), and a nitric acid preparation device (3); wherein, the electrolytic water device (1) is respectively connected to the ammonia preparation device (2) and the nitric acid preparation device (3) through a hydrogen gas pipeline (11) and an oxygen gas pipeline (12), and the ammonia preparation device (2) is connected to the nitric acid preparation device (3) through an ammonia pipeline (13); The chemical energy release device includes a nitric acid storage, separation and decomposition device (4), an ammonia water storage, separation and decomposition device (5), and a reaction heat recovery device (6); wherein, the nitric acid storage, separation and decomposition device (4) is connected to the reaction heat recovery device (6) through a nitrogen oxide pipeline (14), and the ammonia water storage, separation and decomposition device (5) is connected to the reaction heat recovery device (6) through an ammonia gas mixing pipeline (15); The nitric acid preparation device (3) is connected to the nitric acid storage, separation and decomposition device (4) through a nitric acid pipeline (22); The chemical energy storage device further includes a process water preparation and storage device (7) and a nitrogen preparation and storage device (8); The process water preparation and storage device (7) is respectively connected to the reaction heat recovery device (6), the nitrogen preparation and storage device (8), and the electrolytic water device (1) through a reaction heat recovery tail gas pipeline (16), a low-temperature drying reaction tail gas pipeline (17), and a process water pipeline (21); The nitrogen preparation and storage device (8) is connected to the ammonia preparation device (2) through a nitrogen pipeline (18); It further includes a tail gas treatment device (9); the ammonia preparation device (2), the nitric acid preparation device (3), and the nitrogen preparation and storage device (8) are respectively connected to the tail gas treatment device (9).

2. The chemical energy storage system based on a nitric acid - ammonia water system according to claim 1, wherein The nitric acid preparation device (3) and the nitric acid storage, separation and decomposition device (4) are also connected through a dilute nitric acid pipeline (23).

3. The chemical energy storage system based on the nitric acid-ammonia water system according to claim 1, wherein The ammonia preparation device (2) is connected to the ammonia water storage, separation and decomposition device (5) through an ammonia water pipeline (24).

4. The chemical energy storage system based on a nitric acid-ammonia water system according to claim 3, wherein The ammonia preparation device (2) and the ammonia water storage, separation and decomposition device (5) are also connected through a dilute ammonia water pipeline (25).

5. A chemical energy storage method based on a nitric acid - ammonia water system, characterized in that, Using the chemical energy storage system according to any one of claims 1-4, including a chemical energy storage process and a chemical energy release process; The chemical energy storage process is: electrolyzing electrolytic water to prepare hydrogen and oxygen; using the prepared hydrogen and nitrogen to continue preparing ammonia, and then converting the ammonia into an ammonia water solution; using the prepared oxygen and the prepared ammonia to continue preparing a nitric acid solution; The chemical energy release process is: mixing nitrogen with the ammonia water solution and performing high-temperature stripping to separate and release an unsaturated high-temperature ammonia mixed gas from the ammonia water solution; concentrating the nitric acid solution into a concentrated nitric acid solution to release an unsaturated high-temperature nitrogen oxide gas from the concentrated nitric acid solution; reacting the unsaturated high-temperature ammonia mixed gas and the unsaturated high-temperature nitrogen oxide gas, the energy generated by the reaction can be utilized, and the tail gas generated by the reaction can be used to prepare the electrolytic water and nitrogen.

6. The chemical energy storage method based on a nitric acid - ammonia water system according to claim 5, characterized in that, The components of the unsaturated high-temperature ammonia mixed gas include NH3 and water vapor; the components of the unsaturated high-temperature nitrogen oxide gas are NO2, NO, O2, water vapor, and N2; the components of the tail gas include N2 and water vapor.

7. The chemical energy storage method based on the nitric acid-ammonia water system according to claim 5, characterized in that, In the ammonia aqueous solution, the mass percentage of ammonia is 20% - 25%; in the nitric acid solution, the mass percentage of nitric acid is 55% - 60%; in the concentrated nitric acid solution, the mass percentage of nitric acid is greater than or equal to 90%.

8. A chemical energy storage method based on a nitric acid-ammonia water system according to claim 5, characterized in that, During the process of chemical energy release, the energy generated by the reaction is utilized in the form of heat energy or potential energy; when it is utilized as heat energy, a waste heat boiler is used to recover the heat energy, and when it is utilized as potential energy, a steam turbine or an expander is used for power recovery.

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