Carbon dioxide recovery system for purifying lithium carbonate by hydrogenolysis method

Abstract

An outlet of a liquid carbon dioxide storage tank is connected with a tube pass inlet of a carbon dioxide cooler, a tube pass outlet of the carbon dioxide cooler is connected with a carbon dioxide gasification tank, and an outlet of the carbon dioxide gasification tank is connected with a first carbon dioxide buffer tank. The outlet of the carbon dioxide buffer tank is connected with the inlet of the carbon dioxide filter; the filtered outlet II is connected with an inlet of a carbonization bubble tower, and an outlet of the carbonization bubble tower is connected with a second carbon dioxide buffer tank; the filtered outlet III is connected with an inlet of a pyrolysis crystallizer, an outlet of the pyrolysis crystallizer is connected with a shell pass inlet of a carbon dioxide cooler, and a shell pass outlet of the carbon dioxide cooler is connected with a second carbon dioxide buffer tank; the top centers of the first carbon dioxide buffer tank and the second carbon dioxide buffer tank are respectively connected with emptying pipes. The system can realize efficient recycling of carbon dioxide in the lithium carbonate purification industry, and the purification cost is reduced.

Description

Technical Field

[0001] The utility model relates to a carbon dioxide recovery system, in particular to a carbon dioxide recovery system for purifying lithium carbonate by a hydrogenation decomposition method, and belongs to the technical field of resource recycling. Background Art

[0002] Lithium carbonate is a commonly used industrial inorganic compound that can be used in ceramics, medicines and chemical catalysts. It is also used as a positive electrode material for lithium batteries. It has the advantages of high energy density, long service life and good stability. It has great application prospects and market demand. The hydrogenation decomposition method is currently the most commonly used process for industrial purification of lithium carbonate. How to more efficiently recycle the carbon dioxide produced by the lithium carbonate hydrogenation decomposition method has become a hot topic in market research.

[0003] At present, the commonly used methods for recovering carbon dioxide include physical adsorption, chemical absorption and membrane separation, but these traditional methods have their own limitations and are difficult to be put into industrial use on a large scale. The purity of lithium carbonate produced by the lithium carbonate purification industry needs to reach more than 99.5%, which requires a high purity of carbon dioxide involved in production. At the same time, the amount of carbon dioxide processed for recovery fluctuates greatly, and the downstream demand for carbon dioxide will also change with the number of devices opened, posing a challenge to the long-term stable operation of the carbon dioxide recovery system. Utility Model Content

[0004] The purpose of this section is to summarize some aspects of the embodiments of the utility model and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract of the specification of this application and the name of the utility model, and such simplifications or omissions cannot be used to limit the scope of the utility model.

[0005] In view of the above problems and / or the problems existing in the prior art, the present utility model is proposed.

[0006] The purpose of the utility model is to overcome the problems existing in the prior art and provide a carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method, which can realize the efficient recovery and utilization of carbon dioxide in the lithium carbonate purification industry, improve the carbon dioxide utilization rate, system stability and lithium carbonate product purity, and reduce the cost of industrial purification of lithium carbonate.

[0007] In order to solve the above technical problems, the utility model discloses a carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method, comprising a liquid carbon dioxide storage tank, the outlet of the liquid carbon dioxide storage tank is connected to the pipe-side inlet of a carbon dioxide cooler, the pipe-side outlet of the carbon dioxide cooler is connected to the inlet of a carbon dioxide gasification tank, a heating coil is wound around the outer circumference of the carbon dioxide gasification tank, the outlet of the carbon dioxide gasification tank is connected to the lower inlet of a first carbon dioxide buffer tank, the upper outlet of the first carbon dioxide buffer tank is connected to the inlet of a carbon dioxide filter, and the post-filtration outlet of the carbon dioxide filter is connected to a carbon dioxide recoil pipe;

[0008] The second post-filtration outlet of the carbon dioxide filter is connected to the inlet of the carbonization bubbling tower, and the outlet of the carbonization bubbling tower is connected to the inlet of the second carbon dioxide buffer tank;

[0009] The post-filtration outlet three of the carbon dioxide filter is connected to the lower inlet of the pyrolysis crystallizer, the upper outlet of the pyrolysis crystallizer is connected to the shell-side inlet of the carbon dioxide cooler, and the shell-side outlet of the carbon dioxide cooler is connected to the reflux port of the second carbon dioxide buffer tank;

[0010] The top centers of the first carbon dioxide buffer tank and the second carbon dioxide buffer tank are respectively connected with exhaust pipes for exhausting impurity gases.

[0011] As an improvement of the present invention, the lower outlet of the second carbon dioxide buffer tank is connected to the inlets of two parallel V-shaped double-acting piston compressors, and the outlets of the two V-shaped double-acting piston compressors are both connected to the lower inlet of the first carbon dioxide buffer tank.

[0012] As a further improvement of the present invention, the outlet pipeline of the V-type double-acting piston compressor is connected to the inlet pipeline of the V-type double-acting piston compressor through a carbon dioxide compressor bypass pipe, and a flow regulating valve is provided in the carbon dioxide compressor bypass pipe.

[0013] As a further improvement of the present invention, the V-shaped double-acting piston compressor includes two groups of compressor cylinders arranged in a V shape, the two ends of the two compressor cylinders are closed, the compressor piston is located in the middle of the compressor cylinder so that the inner cavity of the cylinder forms two compression chambers, and the side walls of the two compression chambers away from the compressor piston are respectively connected to the compressor inlet nozzle and the compressor outlet nozzle; the centers of the two compressor pistons are respectively fixedly connected to one end of the compressor piston rod, the other ends of the two compressor piston rods respectively pass through the corresponding cylinder heads and are respectively hinged to the outer ends of the compressor connecting rods, and the inner ends of the two compressor connecting rods are driven by the compressor crankshaft.

[0014] Compared with the prior art, the utility model has achieved the following beneficial effects: 1. The system is suitable for the efficient purification of wet industrial-grade lithium carbonate, which increases the utilization rate of carbon dioxide in the system to more than 98%, making the produced lithium carbonate products purer and in line with the qualified product requirements of YS / T 582-2013 "Battery-grade lithium carbonate".

[0015] 2. The upstream carbon dioxide is successively transported to the pyrolysis crystallizer, carbonization bubbling tower and transmission pipeline and other lithium carbonate purification processes through liquid carbon dioxide tank trucks, liquid carbon dioxide storage tanks, carbon dioxide gasification tanks and carbon dioxide filters; the carbon dioxide after the reaction returns to the second carbon dioxide buffer tank for collection and separation, and returns to the original first carbon dioxide buffer tank after being pressurized by a V-type double-acting piston compressor to participate in the next round of lithium carbonate purification reaction. The system process is simple and efficient, and the carbon dioxide has a very high utilization rate.

[0016] 3. This system is designed with a carbon dioxide cooler, which makes full use of the high temperature of carbon dioxide after the reaction in the pyrolysis crystallizer to preheat the liquid carbon dioxide added to the system, saving the subsequent consumption of heating steam; at the same time, the low-temperature liquid carbon dioxide will also reduce the temperature of carbon dioxide discharged from the pyrolysis crystallizer, so that the carbon dioxide entering the compressor is maintained at an appropriate temperature, thereby improving the operating efficiency of the compressor.

[0017] 4. This system is designed with a carbon dioxide compressor pressurization system. Two piston compressors are connected in parallel. When the upstream processing gas volume is large, both compressors are turned on, and when the upstream volume is small, only one compressor is turned on. When the processing gas volume continues to decrease, the compressor bypass pipeline can also be activated to effectively ensure the long-term stable operation of the carbon dioxide treatment system.

[0018] 5. This system is designed with a V-shaped double-acting piston compressor. Carbon dioxide enters the compressor through four compressor inlet nozzles for pressurization. When intake, the air pressure outside the compressor is relatively high, pushing the compression spring inward, the intake valve core opens inward, and the gas enters the compressor; similarly, when exhausting, the air pressure in the piston cavity is relatively high, pushing the compression spring outward, the exhaust valve core opens outward, and the gas is discharged outward through four compressor outlet nozzles; every time the piston in the compressor cylinder moves a complete stroke, the compressor cylinder inhales and exhausts twice, and the compression efficiency is nearly doubled. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. The drawings are only provided for reference and explanation, not for limiting the present utility model. Among them:

[0020] Figure 1 This is a flow chart of a carbon dioxide recovery system for purifying lithium carbonate by the hydrogenation decomposition method of the utility model;

[0021] Figure 2 This is a structural diagram of a V-shaped double-acting piston compressor in the utility model;

[0022] Figure 3 It is a partial enlarged view of the inlet and outlet of the compressor in the utility model;

[0023] In the figure: 1. Liquid carbon dioxide tanker; 2. Liquid carbon dioxide storage tank; 3. Carbon dioxide gasification tank; 4. First carbon dioxide buffer tank; 5. V-type double-acting piston compressor; 5-1. Compressor inlet nozzle; 5-2. Compressor outlet nozzle; 5-3. Compressor piston; 5-4. Compressor piston rod; 5-5. Piston rod sealing packing; 5-6. Piston sealing ring; 5-7. Compressor crankcase; 5-8. Compressor connecting rod; 5-9. Compressor cylinder; 5-10. Compression spring; 5-11. Valve sealing seat; 5-12. Intake valve core; 5-13. Exhaust valve core; 6. Carbon dioxide cooler; 7. Second carbon dioxide buffer tank; 8. Carbonization bubbling tower; 9. Carbon dioxide filter; 10. Pyrolysis crystallizer;

[0024] G1. Liquid carbon dioxide inlet pipe; G2. Liquid carbon dioxide preheating inlet pipe; G3. Liquid carbon dioxide preheating outlet pipe; G4. Heating steam replenishment pipe; G5. Steam condensate discharge pipe; G6. Carbon dioxide delivery pipe; G7. Carbon dioxide compressor inlet pipe; G8. Carbon dioxide compressor outlet pipe; G9. Carbon dioxide compressor bypass pipe; G10. Pyrolysis crystallizer carbon dioxide outlet pipe; G11. Second top drain pipe; G12. Bubble tower gas phase outlet pipe; G13. Bubble tower gas phase inlet pipe; G14. Carbon dioxide recoil pipe; G15. Buffer tank outlet pipe; G16. Pyrolysis crystallizer gas phase inlet pipe; G17. First top drain pipe. DETAILED DESCRIPTION

[0025] In the following description of the utility model, the terms "upper", "lower", "front", "back", "left", "right", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the utility model and simplifying the description, and do not mean that the device must have a specific direction.

[0026] In order to make the technical means, creative features, objectives and effects of the present invention easier to understand, the present invention is further described below with reference to specific figures. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0028] like Figure 1 As shown, the carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method of the utility model comprises a liquid carbon dioxide storage tank 2, a carbon dioxide gasification tank 3, a first carbon dioxide buffer tank 4, a V-shaped double-acting piston compressor 5, a carbon dioxide cooler 6, a second carbon dioxide buffer tank 7, a carbonization bubbling tower 8, a carbon dioxide filter 9 and a pyrolysis crystallizer 10. The outlet of the liquid carbon dioxide tanker 1 is connected to the inlet of the liquid carbon dioxide storage tank 2 through a liquid carbon dioxide inlet pipe G1, the outlet of the liquid carbon dioxide storage tank 2 is connected to the pipe side inlet of the carbon dioxide cooler 6 through a liquid carbon dioxide preheating inlet pipe G2, the pipe side outlet of the carbon dioxide cooler 6 is connected to the carbon dioxide inlet of the carbon dioxide gasification tank 3 through a liquid carbon dioxide preheating outlet pipe G3, the outer periphery of the carbon dioxide gasification tank 3 is wrapped with a heating coil, the upper end inlet of the heating coil is connected to the heating steam replenishment pipe G4, and the bottom outlet of the heating coil is connected to the steam condensate discharge pipe G5. The outlet of the carbon dioxide gasification tank 3 is connected to the lower inlet of the first carbon dioxide buffer tank 4 through the carbon dioxide delivery pipe G6, the top center of the first carbon dioxide buffer tank 4 is connected to the first top exhaust pipe G17, the upper outlet of the first carbon dioxide buffer tank 4 is connected to the inlet of the carbon dioxide filter 9 through the buffer tank outlet pipe G15, and the post-filtration outlet of the carbon dioxide filter 9 is connected to the carbonization flushing port of the main pipeline of the lithium carbonate hydrogenation decomposition device through the carbon dioxide backwash pipe G14.

[0029] The second post-filtration outlet of the carbon dioxide filter 9 is connected to the inlet of the carbonization bubbling tower 8 through the bubbling tower gas phase inlet pipe G13, and the outlet of the carbonization bubbling tower 8 is connected to the inlet of the second carbon dioxide buffer tank 7 through the bubbling tower gas phase outlet pipe G12.

[0030] The post-filtration outlet three of the carbon dioxide filter 9 is connected to the lower inlet of the pyrolysis crystallizer 10 through the pyrolysis crystallizer gas phase inlet pipe G16, the upper outlet of the pyrolysis crystallizer 10 is connected to the shell side inlet of the carbon dioxide cooler 6 through the pyrolysis crystallizer carbon dioxide outlet pipe G10, the shell side outlet of the carbon dioxide cooler 6 is connected to the reflux port of the second carbon dioxide buffer tank 7, and the second top exhaust pipe G11 is connected to the top center of the second carbon dioxide buffer tank 7.

[0031] The lower outlet of the second carbon dioxide buffer tank 7 is connected to the inlet of the V-type double-acting piston compressor 5 through the carbon dioxide compressor inlet pipe G7. Two V-type double-acting piston compressors 5 are connected in parallel, and the outlets are connected to the lower inlet of the first carbon dioxide buffer tank 4 through the carbon dioxide compressor outlet pipe G8.

[0032] The carbon dioxide compressor outlet pipe G8 is also connected to the carbon dioxide compressor inlet pipe G7 through the carbon dioxide compressor bypass pipe G9.

[0033] Liquid carbon dioxide is transported to the production plant by a liquid carbon dioxide tanker 1, and then transported to a liquid carbon dioxide storage tank 2 for storage via a liquid carbon dioxide inlet pipe G1; liquid carbon dioxide is regularly transported to the cold side of a carbon dioxide cooler 6 via a liquid carbon dioxide preheating inlet pipe G2 for preheating, and after the temperature rises, it enters a carbon dioxide gasification tank 3 via a liquid carbon dioxide preheating outlet pipe G3 for gasification. The heating steam enters the heating coil via a heating steam replenishment pipe G4 to heat the liquid carbon dioxide, and the condensed steam water is discharged via a steam condensate discharge pipe G5. A safety valve is provided at the top of the carbon dioxide gasification tank 3 to maintain the pressure of the gasification tank at no more than 2.2MPa, thus ensuring the safety of the gasification tank.

[0034] Qualified clean carbon dioxide is transported to the first carbon dioxide buffer tank 4 through the carbon dioxide delivery pipe G6 for buffering, and the impurities are regularly discharged through the first top exhaust pipe G17 to ensure the purity of carbon dioxide; the pressure in the buffer tank is maintained at 0.15MPa, and the carbon dioxide enters the carbon dioxide filter 9 through the buffer tank outlet pipe G15 for filtration and liquid separation. The clean carbon dioxide is divided into three streams, the first stream is carbonized and flushed for the main pipelines of the lithium carbonate hydrogenation decomposition device through the carbon dioxide recoil pipe G14, the second stream enters the carbonization bubbling tower 8 through the bubbling tower gas phase inlet pipe G13, and the third stream enters the pyrolysis crystallizer 10 through the pyrolysis crystallizer gas phase inlet pipe G16 for carbon washing.

[0035] Lithium carbonate reacts with carbon dioxide in the carbonization bubbling tower 8 to generate more soluble lithium bicarbonate, and the remaining carbon dioxide from the reaction enters the second carbon dioxide buffer tank 7 through the bubbling tower gas phase outlet pipe G12 for buffering.

[0036] In the lithium carbonate purification process, lithium bicarbonate is heated and pyrolyzed in the pyrolysis crystallizer 10 to generate carbon dioxide, which is returned to the second carbon dioxide buffer tank 7 through the pyrolysis crystallizer carbon dioxide outlet pipe G10, and is cooled by the hot side of the carbon dioxide cooler 6 before returning to the buffer tank to ensure that the temperature in the buffer tank is maintained within 40°C; the second carbon dioxide buffer tank 7 regularly discharges impurity gases through the second top exhaust pipe G11 to ensure the purity of the carbon dioxide.

[0037] The carbon dioxide buffered and separated by the second carbon dioxide buffer tank 7 enters the two parallel V-type double-acting piston compressors 5 through the carbon dioxide compressor inlet pipe G7 for compression and pressure boosting. The pressurized carbon dioxide returns to the first carbon dioxide buffer tank 4 through the carbon dioxide compressor outlet pipe G8. In order to ensure the continuous operation of the compressor, the flow of the compressor is regulated through the carbon dioxide compressor bypass pipe G9.

[0038] Regarding the internal structure of the V-type double-acting piston compressor, such as Figure 2 As shown, two groups of compressor cylinders 5-9 are symmetrically distributed, and the compressor inlet nozzle 5-1 and the compressor outlet nozzle 5-2 are connected to the two sides of one end of the compressor cylinder 5-9. The compressor inlet nozzle 5-1 and the compressor outlet nozzle 5-2 are also connected to the two sides of the other end of the compressor cylinder 5-9. The carbon dioxide in the cylinder is compressed or decompressed by the compressor piston 5-3.

[0039] There are five annular grooves on the outer circumference of the compressor piston 5-3, in which the piston sealing ring 5-6 and the matching piston expansion ring are embedded, wherein the piston sealing ring 5-6 is on the outer layer and the matching piston expansion ring is on the inner layer. The piston expansion ring and the piston sealing ring 5-6 in the five annular grooves realize the sealing of the compressor piston 5-3 running up and down in the cylinder body.

[0040] The compressor piston rod 5-4 passes through the center of the compressor piston 5-3, and the compressor piston rod 5-4 is connected to the compressor piston 5-3 through the piston locking nut at the bottom, and an elastic gasket is arranged in the middle to prevent loosening. Three annular grooves are arranged on the outer circumference of the compressor piston rod 5-4 inside the compressor piston 5-3, and the annular grooves are equipped with piston rod sealing packing to ensure the sealing performance between the piston and the piston rod; the center hole of the cylinder head is sealed with the compressor piston rod 5-4 through the piston rod sealing packing 5-5. The driving end of the compressor piston rod 5-4 is driven by the compressor connecting rod 5-8, and the root of the compressor connecting rod 5-8 is hinged to the corresponding crankshaft in the compressor crankcase 5-7.

[0041] Regarding the compression process of V-type double-acting piston compressor, such as Figure 3 As shown, carbon dioxide enters the cylinder of the compressor through each compressor inlet nozzle 5-1 for pressurization. In the compressor inlet nozzle 5-1, the intake valve core abuts against the inner port of the valve seal seat 5-11, and the compression spring 5-10 presses against the inner end face of the intake valve core. In the compressor outlet nozzle 5-2, the valve seal seat 5-11 is close to the cylinder, the exhaust valve core abuts against the outer port of the valve seal seat 5-11, and the compression spring 5-10 presses against the outer end face of the exhaust valve core.

[0042] When taking in air, the air pressure outside the compressor is relatively high, pushing the compression spring 5-10 inward, causing the intake valve core to push the compression spring 5-10 inward and open, allowing gas to enter the cylinder body; similarly, when exhausting air, the air pressure inside the piston chamber is relatively high, causing the exhaust valve core to push the compression spring 5-10 outward and open, allowing gas to be discharged outward through the compressor outlet nozzle 5-2.

[0043] When the compressor piston 5-3 moves outward along the compressor cylinder body 5-9, the outer chamber compresses and exhausts, and the inner chamber inhales air; when the compressor piston 5-3 moves inward along the compressor cylinder body 5-9, the outer chamber inhales air, and the inner chamber compresses and exhausts air; every time the compressor piston 5-3 in the compressor cylinder moves a complete stroke, the cylinder bodies at both ends each complete an intake and exhaust process, that is, completes two compressions, thereby improving the compression efficiency.

[0044] According to the demand law of carbon dioxide required for the production of lithium carbonate purification industry, combined with the physical and chemical properties of carbon dioxide itself, this system has designed a complete carbon dioxide recovery process. The required carbon dioxide is successively transported to the pyrolysis crystallizer, carbonization bubbling tower and transmission pipeline and other lithium carbonate purification processes through liquid carbon dioxide tank trucks, liquid carbon dioxide storage tanks, carbon dioxide gasification tanks and carbon dioxide filters; the carbon dioxide after the reaction returns to the second carbon dioxide buffer tank 7 for collection and separation, and returns to the original first carbon dioxide buffer tank 4 after being pressurized by a V-type double-acting piston compressor, and re-participates in the next round of lithium carbonate purification reaction; the system process is simple and efficient, and the carbon dioxide has extremely high purity and utilization rate.

[0045] The carbon dioxide cooler in this system makes full use of the high temperature of the carbon dioxide after the reaction in the pyrolysis crystallizer to preheat the liquid carbon dioxide added to the system, saving the subsequent consumption of heating steam; at the same time, the low-temperature liquid carbon dioxide will also reduce the temperature of the carbon dioxide discharged from the pyrolysis crystallizer and improve the operating efficiency of the compressor.

[0046] The CO2 compressor pressurization system and bipolar buffer tank system reasonably change the number of compressors on and off according to the changes in the upstream and downstream CO2 demand, effectively ensuring the long-term stable operation of the CO2 treatment system. The V-type double-acting piston compressor has flexible and variable processing capacity, simple structure and high efficiency, which reasonably meets the relevant needs of CO2 recovery and utilization in the lithium carbonate industry.

[0047] The above description is only the preferred feasible embodiment of the utility model, which shows and describes the basic principle, main features and advantages of the utility model, but does not limit the scope of patent protection of the utility model. The technicians in this industry should understand that the utility model is not limited by the above embodiments. In addition to the above embodiments, the utility model can also have other implementation modes without departing from the spirit and scope of the utility model. The utility model will also have various changes and improvements. All technical solutions formed by equivalent replacement or equivalent transformation fall within the scope of protection required by the utility model. The scope of protection required by the utility model is defined by the attached claims and their equivalents. The technical features not described in the utility model can be achieved by or using existing technologies, which will not be repeated here.

Claims

1. A carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method, comprising a liquid carbon dioxide storage tank, characterized in that: The outlet of the liquid carbon dioxide storage tank is connected to the pipe-side inlet of the carbon dioxide cooler, the pipe-side outlet of the carbon dioxide cooler is connected to the inlet of the carbon dioxide gasification tank, a heating coil is wound around the outer circumference of the carbon dioxide gasification tank, the outlet of the carbon dioxide gasification tank is connected to the lower inlet of the first carbon dioxide buffer tank, the upper outlet of the first carbon dioxide buffer tank is connected to the inlet of the carbon dioxide filter, and the post-filtration outlet of the carbon dioxide filter is connected to the carbon dioxide recoil pipe; The second post-filtration outlet of the carbon dioxide filter is connected to the inlet of the carbonization bubbling tower, and the outlet of the carbonization bubbling tower is connected to the inlet of the second carbon dioxide buffer tank; The post-filtration outlet three of the carbon dioxide filter is connected to the lower inlet of the pyrolysis crystallizer, the upper outlet of the pyrolysis crystallizer is connected to the shell-side inlet of the carbon dioxide cooler, and the shell-side outlet of the carbon dioxide cooler is connected to the reflux port of the second carbon dioxide buffer tank; The top centers of the first carbon dioxide buffer tank and the second carbon dioxide buffer tank are respectively connected with exhaust pipes for exhausting impurity gases.

2. The carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method according to claim 1, characterized in that: The lower outlet of the second carbon dioxide buffer tank is connected to the inlets of two parallel V-shaped double-acting piston compressors, and the outlets of the two V-shaped double-acting piston compressors are both connected to the lower inlet of the first carbon dioxide buffer tank.

3. The carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method according to claim 2, characterized in that: The outlet pipeline of the V-shaped double-acting piston compressor is connected to the inlet pipeline of the V-shaped double-acting piston compressor through a carbon dioxide compressor bypass pipe, and a flow regulating valve is provided in the carbon dioxide compressor bypass pipe.

4. The carbon dioxide recovery system for purifying lithium carbonate by hydrogenation decomposition method according to claim 2 or 3, characterized in that: The V-shaped double-acting piston compressor comprises two groups of compressor cylinder bodies arranged in a V shape, both ends of the two compressor cylinder bodies are closed, the compressor piston is located in the middle of the compressor cylinder body so that the inner cavity of the cylinder body forms two compression chambers, and the side walls of the two compression chambers away from the compressor piston are respectively connected to the compressor inlet nozzle and the compressor outlet nozzle; the centers of the two compressor pistons are respectively fixedly connected to one end of the compressor piston rod, the other ends of the two compressor piston rods respectively pass through the corresponding cylinder heads and are respectively hinged to the outer ends of the compressor connecting rods, and the inner ends of the two compressor connecting rods are driven by the compressor crankshaft.

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