System and method for recycling exhaust gas in liquid carbon dioxide production process

Abstract

The invention discloses a system and a method for recycling exhaust gas in a liquid carbon dioxide production process. The system comprises a CO2 spherical tank, a CO2 filling pump, a CO2 tank car, a liquid pump drainage pipeline, a liquid phase pipeline, a gas phase pipeline, a reciprocating compressor, a drying unit, a residual gas recycling device and a connecting pipeline. And the residual gas recovery device comprises a decompression buffering unit, a filtering unit and a blending unit. The method comprises the following steps: firstly, collecting CO2 spherical tank flash steam, and cooling exhaust gas of a tank car and a CO2 filling pump to the residual gas recovery device; sequentially decompressing and filtering in the device, and blending according to the inlet pressure requirement of a compressor; and finally, the treated gas is merged into an inlet pipeline of a reciprocating compressor to participate in liquid carbon dioxide production. Exhaust gas in each link is recycled, the yield of carbon dioxide is increased, and resource waste is reduced; the feed gas concentration is improved, and the energy consumption and cost are reduced; quality of recycled gas is guaranteed, and reliability and stability of a production system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide recovery and utilization, and in particular to a system and method for recovering and utilizing exhaust gas during the production of liquid carbon dioxide. Background Art

[0002] In the production process of liquid carbon dioxide, the raw gas undergoes a series of treatments such as pressurization, desulfurization, drying, and cryogenic distillation to obtain liquid carbon dioxide. However, in the subsequent storage and transportation links, there are many problems with exhaust gas. For example, when liquid carbon dioxide enters the spherical tank, because the tank pressure is slightly lower than the system pressure, some liquid carbon dioxide and trace light components flash vaporize, causing the tank pressure to increase. To maintain the tank pressure, a discharge operation is required; when liquid carbon dioxide is loaded, the tank truck needs to be cooled. After the liquid carbon dioxide enters the tank truck, it vaporizes due to the high temperature of the tank body. The vaporized carbon dioxide also needs to be discharged to continue cooling. In addition, the CO2 filling pump needs to be cooled before loading, and this process also produces exhaust gas. If these exhaust gases are discharged directly, it will not only waste carbon dioxide resources, but also increase production energy consumption and have a serious impact on the environment.

[0003] With global warming and increasing pressure to reduce carbon emissions, carbon dioxide capture, utilization, and storage (CCUS) technology has become a key tool. Existing technologies only achieve a 79% CO2 recovery rate, and the recovery process consumes 33.24 kgce / t of energy per unit of product, increasing production costs.

[0004] Therefore, it is necessary to develop a system and method for recycling exhaust gas during the production of liquid carbon dioxide to solve the above problems. Summary of the Invention

[0005] The object of the present invention is to provide a system and method for recycling exhaust gas in the production process of liquid carbon dioxide.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A system for recycling exhaust gas during the production of liquid carbon dioxide, comprising a CO2 spherical tank, a CO2 filling pump, a CO2 tank truck, a liquid pump discharge pipeline, a liquid phase pipeline, a gas phase pipeline, a reciprocating compressor, a desiccant unit, a residual gas recovery device, and connecting pipelines; The CO2 spherical tank 1 is provided with an exhaust gas outlet on the top, which is connected to the residual gas recovery device through a connecting pipe; the CO2 filling pump is connected to the connecting pipe through a liquid pump discharge pipeline; at the same time, the CO2 filling pump is connected to the CO2 tanker through a liquid phase pipeline; the CO2 tanker is connected to the connecting pipe through a gas phase pipeline, and can enter the residual gas recovery device through this gas phase pipeline through the connecting pipe; the recycling system is also provided with a pipeline that is only connected to the inlet pipe of the reciprocating compressor, so that the gas processed by the residual gas recovery device can be incorporated into the inlet pipe of the reciprocating compressor.

[0007] Specifically, the residual gas recovery device is provided with a pressure reducing buffer unit, a filtering unit, and a mixing unit.

[0008] A method for recycling exhaust gas in a liquid carbon dioxide production process comprises the following steps: S1. Exhaust gas collection: The flash gas inside the CO2 spherical tank, the exhaust gas from the CO2 tank truck, and the exhaust gas from the cooling and cooling of the CO2 filling pump are collected and sent to the residual gas recovery device through the connecting pipe; the flash gas from the CO2 spherical tank flows into the connecting pipe through the exhaust gas pipe at the top of the CO2 spherical tank and then enters the residual gas recovery device; the exhaust gas from the cooling and cooling of the CO2 filling pump is connected to the connecting pipe through the liquid pump discharge line and then enters the residual gas recovery device 9; the exhaust gas from the CO2 tank truck is connected to the connecting pipe through the gas phase pipeline and then enters the residual gas recovery device; S2. Treatment of residual gas recovery device: After the exhaust gas enters the residual gas recovery device, it is first decompressed by the decompression buffer unit to stabilize the gas pressure; then it passes through the filtration unit to remove impurities in the gas; finally, the gas pressure is adjusted by the mixing unit according to the pressure requirement of the reciprocating compressor inlet pipeline; S3. Gas incorporation: The gas processed by the residual gas recovery device is incorporated into the inlet pipe of the reciprocating compressor through a connecting pipe and participates in the subsequent liquid carbon dioxide production process as raw gas, while reducing carbon dioxide emissions.

[0009] The beneficial effects of the present invention are: 1. The present invention significantly increases the output of carbon dioxide and reduces resource waste by collecting and recycling the exhaust gas in each link of the liquid carbon dioxide production process. 2. The recovered high-purity gas is introduced into the raw gas pipeline, which increases the concentration of the raw gas, optimizes the production process, greatly reduces energy consumption and reduces production costs. 3. The design of the residual gas recovery device can effectively handle exhaust gases of different pressures, ensuring the quality and stability of the recovered gas, ensuring the normal operation of the compressor, and improving the reliability and stability of the entire production system.

[0010] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a structural schematic diagram of a system for recycling exhaust gas in a liquid carbon dioxide production process according to the present invention. DETAILED DESCRIPTION

[0012] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0013] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0014] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0015] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0016] See Figure 1 , which is a system for recycling exhaust gas during the production of liquid carbon dioxide according to the present invention, comprising a CO2 spherical tank 1, a CO2 filling pump 2, a CO2 tanker 3, a liquid pump discharge pipeline 4, a liquid phase pipeline 5, a gas phase pipeline 6, a reciprocating compressor 7, a desiccant unit 8, a residual gas recovery device 9, and a connecting pipeline 10; The exhaust gas outlet at the top of the CO2 spherical tank 1 is connected to the residual gas recovery device 9 through a connecting pipe 10; the CO2 filling pump 2 is connected to the connecting pipe 10 through a liquid pump discharge line 4, and the exhaust gas generated during the cooling process can enter the residual gas recovery device 9 from there; at the same time, the CO2 filling pump 2 is connected to the CO2 tanker 3 through a liquid phase line 5, which is used to pressurize and transport liquid carbon dioxide to the CO2 tanker 3; the CO2 tanker 3 is connected to the connecting pipe 10 through a gas phase line 6, and the exhaust gas generated by the vaporization of liquid carbon dioxide due to temperature problems during the loading process of the CO2 tanker 3 can enter the residual gas recovery device 9 through this gas phase line 6 and the connecting pipe 10. In addition, a pipeline specifically connected to the inlet pipeline of the reciprocating compressor 7 is provided to allow the gas processed by the residual gas recovery device 9 to be incorporated into the inlet pipeline of the reciprocating compressor 7. The other end of the pipeline of the reciprocating compressor 7 is connected to a desiccant unit 8, which is used to remove moisture from the raw gas.

[0017] Specifically, the residual gas recovery device 9 is provided with a pressure reducing buffer unit, which is used to reduce the pressure of the flash gas from the CO2 spherical tank 1, the exhaust gas from the CO2 tanker 3, and the cooling exhaust gas from the CO2 filling pump 2, so that the pressure of gases of different pressures tends to be stable; the filtering unit can filter impurities carried in the gas to ensure the purity of the recovered gas; the blending unit can adjust the gas pressure according to the pressure requirement of the inlet pipe of the reciprocating compressor 7 to ensure that the recovered gas can be smoothly incorporated into the inlet pipe of the reciprocating compressor 7 to maintain the normal operation of the reciprocating compressor 7.

[0018] A method for recycling exhaust gas during the production of liquid carbon dioxide comprises the following steps: S1. Exhaust gas collection: The flash gas inside the CO2 spherical tank 1, the exhaust gas from the CO2 tank truck 3, and the exhaust gas from the cooling and cooling of the CO2 filling pump 2 are collected and sent to the residual gas recovery device 9 through the connecting pipe 10. Specifically, the flash gas from the CO2 spherical tank 1 flows through the exhaust gas pipe at the top of the CO2 spherical tank 1 into the connecting pipe 10 and then into the residual gas recovery device 9; the exhaust gas from the cooling and cooling of the CO2 filling pump 2 enters the residual gas recovery device 9 after being connected to the connecting pipe 10 through the liquid pump discharge line 4; and the exhaust gas from the CO2 tank truck 3 enters the residual gas recovery device 9 after being connected to the connecting pipe 10 through the gas phase pipeline 6. S2. Treatment of residual gas recovery device 9: After the exhaust gas enters the residual gas recovery device 9, it is first decompressed by the decompression buffer unit to stabilize the gas pressure; then it passes through the filtration unit to remove impurities in the gas; finally, the gas pressure is adjusted by the mixing unit according to the pressure requirement of the inlet pipe of the reciprocating compressor 7; S3. Gas incorporation: The gas processed by the residual gas recovery device 9 is incorporated into the inlet pipe of the reciprocating compressor 7 through the connecting pipe 10 and participates in the subsequent liquid carbon dioxide production process as raw gas.

[0019] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0020] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A system for recycling exhaust gas during the production of liquid carbon dioxide, characterized in that: Including CO2 spherical tank, CO2 filling pump, CO2 tank truck, liquid pump discharge pipeline, liquid phase pipeline, gas phase pipeline, reciprocating compressor, desiccant unit, residual gas recovery device and connecting pipelines; The CO2 spherical tank 1 is provided with an exhaust gas outlet on the top, which is connected to the residual gas recovery device through a connecting pipe; the CO2 filling pump is connected to the connecting pipe through a liquid pump discharge pipeline; at the same time, the CO2 filling pump is connected to the CO2 tanker through a liquid phase pipeline; the CO2 tanker is connected to the connecting pipe through a gas phase pipeline, and can enter the residual gas recovery device through this gas phase pipeline through the connecting pipe; the recycling system is also provided with a pipeline that is only connected to the inlet pipe of the reciprocating compressor, so that the gas processed by the residual gas recovery device can be incorporated into the inlet pipe of the reciprocating compressor.

2. The system for recycling exhaust gas during the production of liquid carbon dioxide according to claim 1, characterized in that: The residual gas recovery device is provided with a pressure reducing buffer unit, a filtering unit and a mixing unit.

3. A method for recycling exhaust gas during the production of liquid carbon dioxide, characterized in that: The following steps are involved: S1. Exhaust gas collection: The flash gas inside the CO2 spherical tank, the exhaust gas from the CO2 tank truck, and the exhaust gas from the cooling and cooling of the CO2 filling pump are collected and sent to the residual gas recovery device through the connecting pipe. The flash steam from the CO2 spherical tank flows into the connecting pipe through the exhaust gas pipe on the top of the CO2 spherical tank and then enters the residual gas recovery device. The exhaust gas from the cooling and cooling of the CO2 filling pump enters the residual gas recovery device after being connected to the connecting pipe through the liquid pump discharge pipeline. The exhaust gas from the CO2 tank truck enters the residual gas recovery device after being connected to the connecting pipe through the gas phase pipeline. S2. Treatment of residual gas recovery device: After the exhaust gas enters the residual gas recovery device, it is first decompressed by the decompression buffer unit to stabilize the gas pressure; then it passes through the filtration unit to remove impurities in the gas; finally, the gas pressure is adjusted by the mixing unit according to the pressure requirement of the reciprocating compressor inlet pipeline; S3. Gas incorporation: The gas processed by the residual gas recovery device is incorporated into the inlet pipe of the reciprocating compressor through a connecting pipe and participates in the subsequent liquid carbon dioxide production process as raw gas, while reducing carbon dioxide emissions.

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