Liquid carbon dioxide refueling system and refueling method

Abstract

The application discloses a liquid carbon dioxide filling system and a filling method. The system comprises a storage tank subsystem, a conveying and metering subsystem and a filling nozzle. The storage tank subsystem is used for storing liquid carbon dioxide and comprises a double-layer vacuum insulation storage tank and a refrigerating unit. The conveying and metering subsystem comprises a filling pipeline which is communicated with the bottom of the storage tank. The filling pipeline is provided with an insulation layer so that the heat input from the outside is less than the refrigerating capacity of the refrigerating unit when the carbon dioxide is filled. The filling pipeline is provided with a conveying pump and a metering pump. The conveying pump is used for conveying excessive liquid carbon dioxide to the metering pump. The metering pump is used for metering and conveying the liquid carbon dioxide according to the required amount of the formula. The filling nozzle is used for filling the accurately metered liquid carbon dioxide into a foaming component. The application can maintain the storage temperature of the liquid carbon dioxide by regulating and controlling the pressure of the storage tank, and can maintain the liquid carbon dioxide in a liquid state by the filling pipeline to be metered and filled into the foaming component, so that a porous material with uniform and dense pores can be obtained.

Description

Technical Field

[0001] This invention belongs to the field of liquid carbon dioxide storage and refueling technology, specifically relating to a liquid carbon dioxide refueling system and refueling method. Background Technology

[0002] In the field of sponge foaming, liquid carbon dioxide is used as a physical foaming agent. It is crucial to ensure that the carbon dioxide remains in a liquid phase throughout the transportation, metering, and addition of other components. If partial vaporization of the liquid carbon dioxide occurs during this process, it can lead to inaccurate carbon dioxide metering, gas blockage and cavitation in the pump, prematurely released carbon dioxide gas affecting the sponge's nucleation timing, causing uneven foam cell formation and pore closure, and further, heat retention during the foaming reaction can lead to core burning or even fire. The most common industrial applications of liquid carbon dioxide currently involve pressurizing and storing it in tanks, then converting it into gaseous carbon dioxide via a vaporizer for further application; or heating and pressurizing the liquid carbon dioxide to a supercritical state, utilizing the properties of supercritical fluids for material extraction and purification. In these known liquid carbon dioxide storage and usage processes, carbon dioxide exists in a gaseous or supercritical state in addition to the liquid phase, which does not meet the requirements of continuous sponge foaming processes. Therefore, there is an urgent need to provide a liquid carbon dioxide storage and addition system for sponge foaming that ensures the liquid carbon dioxide remains in a liquid phase throughout the transportation, metering, and addition process. Summary of the Invention

[0003] In one aspect, the present invention provides a liquid carbon dioxide filling system that maintains the storage temperature of liquid carbon dioxide by regulating the pressure of the storage tank and keeps the carbon dioxide metered and added to the foaming component in a liquid state through the filling pipeline, thereby obtaining a porous material with uniform and dense pores.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A liquid carbon dioxide dispensing system, comprising:

[0006] A storage tank subsystem for storing liquid carbon dioxide includes a storage tank, a refrigeration unit installed inside the storage tank, and a liquid level and pressure measuring unit electrically connected to the refrigeration unit. The liquid level and pressure measuring unit is used to monitor the liquid level and pressure inside the storage tank in real time. The refrigeration unit is controlled to start and stop according to the pressure inside the storage tank to control the pressure of the storage tank.

[0007] The delivery and metering subsystem includes a filling pipeline connected to the bottom outlet of the storage tank. The filling pipeline is equipped with a heat insulation layer to ensure that the external heat input during carbon dioxide filling is less than the cooling capacity of the refrigeration unit. The filling pipeline is also equipped with a delivery pump and a metering pump. The delivery pump is used to deliver excess liquid carbon dioxide to the metering pump, and the metering pump is used to meter and deliver the required amount of liquid carbon dioxide according to the formula.

[0008] The filling nozzle, connected to the filling pipeline, is used to add accurately measured liquid carbon dioxide into the foaming component.

[0009] In some technical solutions, the storage tank includes an inner cylinder and an outer cylinder, with insulation material filling the interlayer between the inner and outer cylinders. A vacuum pumping device and a vacuum measuring gauge are connected by a pipeline to maintain the vacuum level of the interlayer to ensure the insulation capability of the storage tank.

[0010] In some technical solutions, the storage tank is equipped with a safety device, which includes a pressure relief device installed at the top outlet of the storage tank and two connected safety venting pipelines. A three-way valve A and a safety valve assembly are installed on the safety venting pipelines. The three-way valve A is used to control the switching between the two safety venting pipelines. The safety valve assembly is equipped with a safety valve with a rupture disc, which is used to release the excess pressure when the pressure in the storage tank exceeds the working pressure, or to rupture when the safety valve is damaged or fails, so as to ensure the safety of equipment and personnel.

[0011] In some technical solutions, the filling pipeline includes a delivery pipeline, a metering pipeline, and a return pipeline connected in sequence.

[0012] The delivery pump is installed on the delivery pipeline, and an outlet valve is installed on the connecting pipeline between the inlet of the delivery pump and the bottom outlet of the storage tank.

[0013] The metering pipeline is equipped with a delivery pipeline output valve at the inlet end, the metering pump is installed on the metering pipeline, a pressure detection element is installed on the metering pipeline at the inlet end of the metering pump, and a mass flow meter is installed on the metering pipeline at the outlet end of the metering pump.

[0014] A reflux valve is installed on the reflux pipeline, and the reflux valve is used to control the reflux of liquid carbon dioxide back to the storage tank;

[0015] The metering pipeline, return pipeline, and filling nozzle are switched via a three-way valve B.

[0016] In some technical solutions, the conveying and metering subsystem includes a gas circulation loop and a liquid circulation loop.

[0017] The gas circulation loop includes a return gas pipe connecting the gas outlet of the delivery pump to the return gas port at the top of the storage tank. A pump return gas valve is installed on the front section of the return gas pipe, and a return gas valve is installed on the middle section of the pipe.

[0018] The liquid circulation loop includes a return pipe connecting the delivery pipe and the return port at the top of the storage tank. A pre-cooling valve is installed on the front section of the return pipe, and a return valve is installed on the middle section of the return pipe.

[0019] In some technical solutions, the conveying and metering subsystem includes a back pressure circuit.

[0020] The back pressure circuit includes a back pressure pipeline connecting the delivery pipeline and the return port at the top of the storage tank. The back pressure pipeline includes a first back pressure branch and a second back pressure branch arranged in parallel. A back pressure valve is installed on the first back pressure branch, and a spare valve is installed on the second back pressure branch.

[0021] On the other hand, the present invention further provides a method for adding liquid carbon dioxide, wherein the refrigeration unit is started and stopped according to the pressure inside the storage tank to maintain the pressure of the storage tank; the adding pipeline is pre-cooled so that the temperature of the adding pipeline is close to the storage temperature of liquid carbon dioxide; and the accurately measured liquid carbon dioxide is added to the foaming component using the adding nozzle. By implementing this step, the vaporization caused by external heat transfer during the storage and transportation of liquid carbon dioxide can be minimized, and prematurely released carbon dioxide gas can be avoided from affecting the nucleation time of sponge foaming and the inaccuracy of carbon dioxide measurement, thus affecting the continuous foaming process.

[0022] In some technical solutions, the specific steps for maintaining the pressure in the storage tank are as follows:

[0023] When the liquid level and pressure measuring unit detects the upper limit of the tank pressure, it starts the refrigeration unit to cool the gas inside the tank. When the tank pressure drops to the lower limit, it controls the refrigeration unit to stop running.

[0024] In some technical solutions, the specific steps for precooling the injection pipeline are as follows:

[0025] Close the precooling valve and the output valve of the delivery pipeline, open the return gas valve, and use the low-temperature carbon dioxide gas at the top of the storage tank to precool the delivery pump.

[0026] Open the liquid outlet valve and use the low-temperature carbon dioxide liquid at the bottom of the storage tank to pre-cool the transfer pump and the outlet pipe of the transfer pump.

[0027] Open the precooling valve and return valve and start the transfer pump to establish a liquid circulation loop and precool the pipeline of the liquid circulation loop;

[0028] Close the precooling valve and open the back pressure valve to precool the pipeline in the back pressure circuit.

[0029] Open the output valve and return valve of the delivery pipeline, and switch the three-way valve B to the return state. When the pressure detection element shows pressure, start the metering pump to pre-cool the metering pipeline and return pipeline.

[0030] In some technical solutions, the precooling time for the metering pipeline is determined based on the fluid density displayed by the mass flow meter. The precooling time is determined when the mass flow meter stably displays a carbon dioxide density greater than 1 g / cm³. 3 At that time, switch the three-way valve B to the filling position to add liquid carbon dioxide; and / or,

[0031] The filling method further includes the steps of: controlling the circulation pressure of liquid carbon dioxide in each pipeline to be higher than the storage pressure of liquid carbon dioxide, and controlling the filling pressure of liquid carbon dioxide to be higher than the circulation pressure of liquid carbon dioxide in each pipeline.

[0032] The present invention, by employing the above technical solution, has at least the following beneficial effects:

[0033] 1. The present invention proposes a liquid carbon dioxide filling system, which regulates the pressure of the storage tank by a refrigeration unit to maintain it at 13-22 bar. Under this pressure, the storage temperature of the liquid carbon dioxide is maintained below -24°C for a long time. The filling pipeline connected to the bottom outlet of the storage tank is equipped with a heat insulation layer, which can ensure that the external heat input during carbon dioxide filling is less than the cooling capacity of the refrigeration unit, thereby maintaining the carbon dioxide in a liquid state when it is added to the foaming component. This allows for continuous foaming process to obtain a porous material with uniform and dense pores.

[0034] 2. The liquid carbon dioxide filling system proposed in this invention adopts a double-layer vacuum insulated storage tank, with the interlayer filled with high-vacuum perlite, and uses a vacuum pumping device and vacuum measuring gauge connected by pipeline to control the vacuum pressure of the interlayer at 5-10 Pa to ensure the heat insulation capacity of the storage tank.

[0035] 3. The liquid carbon dioxide filling system proposed in this invention includes a delivery and metering subsystem comprising a delivery pipeline, a metering pipeline and a return pipeline connected in sequence, and simultaneously constructs a gas circulation loop, a liquid circulation loop and a back pressure loop. It can accurately meter the liquid carbon dioxide used for foaming according to the formula, and at the same time return excess liquid carbon dioxide and carbon dioxide vaporized during the delivery process to the storage tank, reducing gas discharge loss.

[0036] 4. The present invention proposes a method for adding liquid carbon dioxide, which involves pre-cooling the delivery pump, delivery pipeline, gas circulation loop, liquid circulation loop, back pressure loop, metering pipeline and return pipeline in sequence to make the pipeline system temperature close to the storage temperature of liquid carbon dioxide. At the same time, combined with the thermal insulation design of the pipeline, it can maintain the carbon dioxide in a liquid state when added to the foaming component, so as to ensure accurate metering and uniform and dense foam cells, which is suitable for continuous foaming process.

[0037] 5. The present invention proposes a method for adding liquid carbon dioxide. In order to reduce the vaporization of carbon dioxide during the adding process, the pressure of carbon dioxide circulating in the pipeline is made to be about 5 bar higher than the storage pressure, that is, the pipeline circulation pressure is taken as 30 bar; the adding pressure of liquid carbon dioxide is made to be about 5 bar higher than the circulation pressure by adjusting the adding nozzle, that is, the adding pressure is taken as 35 bar. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings and their markings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of a liquid carbon dioxide dispensing system according to an embodiment of the present invention.

[0040] The meanings of the symbols marked in the figure are as follows:

[0041] 1—Storage tank subsystem, 11—Double-walled vacuum insulated storage tank, 13—Vacuum measuring gauge, 14—Pressure relief device, 15—Liquid level and pressure measuring unit, 16—Refrigeration unit, 17—Liquid outlet valve, 18—Liquid filling valve, 19—Pressure booster and return valve, 110—Safety valve assembly, 111—Exhaust valve, 112—Liquid return valve, 113—Return valve, 114—Full test valve, 115—Purge valve;

[0042] 2—Transportation and metering subsystem; 21—Transportation pump; 22—Pump return valve; 23—Pre-cooling valve; 24—Transportation pipeline output valve; 25—Pressure sensor; 26—Metering pump; 27—Mass flow meter; 29—Return valve; 210—Check valve; 211—Back pressure valve; 212—Standby valve; 213—Heat insulation layer;

[0043] 3—Refill nozzle. Detailed Implementation

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0045] To keep the drawings concise, each figure only schematically shows the parts relevant to the invention, and these do not represent the actual structure of the product. Furthermore, to facilitate understanding, in some figures, only one of components with the same structure or function is schematically depicted, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one."

[0046] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0047] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0048] According to a specific embodiment of the present invention, a liquid carbon dioxide dispensing system is proposed, see reference. Figure 1 As shown, it includes a storage tank subsystem 1, a conveying and metering subsystem 2, and a filling nozzle 3. The storage tank subsystem 1 is used for storing liquid carbon dioxide, the conveying and metering subsystem 2 is used for metering and conveying liquid carbon dioxide according to the required amount of the formula, and the filling nozzle 3 is used for adding accurately metered liquid carbon dioxide to the foaming components.

[0049] In the above embodiments, the storage tank subsystem 1 includes a storage tank, a refrigeration unit 16 installed inside the storage tank, and a liquid level and pressure measuring unit 15 electrically connected to the refrigeration unit 16. The liquid level and pressure measuring unit 15 is used to monitor the liquid level and pressure inside the storage tank in real time. The refrigeration unit 16 controls its start and stop according to the pressure inside the storage tank to control the pressure of the storage tank. The refrigeration unit 16 is used to cool the storage tank by the heat input from the outside, ensuring that the pressure of the storage tank is maintained at 13-22 bar. Under this pressure, the storage temperature of liquid carbon dioxide is maintained below -24°C for a long period of time.

[0050] In a preferred embodiment, the aforementioned storage tank is a double-layered vacuum insulated storage tank 11, comprising an inner cylinder and an outer cylinder. Insulating material is filled in the space between the inner and outer cylinders, and a vacuum pumping device and a vacuum measuring gauge 13 are connected via pipelines to maintain the vacuum level of the space and ensure the storage tank's insulation capability. Specifically, the inner cylinder is made of 16MnDr alloy steel or 304 stainless steel, the outer cylinder is made of Q235B or 16MnDr, the insulating material is high-vacuum perlite, and the vacuum pressure of the storage tank space is controlled at 5-10 Pa.

[0051] In one specific embodiment, the storage tank is equipped with a safety device, which includes a pressure relief device 14 located at the top outlet of the tank and two connected safety venting pipelines. The pressure relief device 14 can rupture to release pressure when a leak occurs in the inner cylinder of the tank, ensuring the safety of equipment and personnel. The safety venting pipelines are equipped with a three-way valve A and two sets of safety valve groups 110. Under normal use, one set of safety valve groups 110 is in operation while the other is on standby. When one set of safety valve groups 110 is damaged or requires maintenance, the three-way valve A can be switched to the other set of safety valve groups 110, allowing the safety valve group 110 requiring maintenance to be removed for repair. Each safety valve group 110 is equipped with a safety valve featuring a rupture disc. The rupture pressure of the rupture disc is slightly higher than the safety valve's opening pressure. When the safety valve fails, the rupture disc ensures the safety of equipment and personnel.

[0052] In addition, a liquid filling pipeline is connected to the bottom of the storage tank, and a liquid filling valve 18 is installed on the liquid filling pipeline for connecting to a liquid carbon dioxide tank truck for filling with liquid carbon dioxide; a pressurization return gas pipeline is connected to the top of the storage tank, and a pressurization return gas valve 19 is installed on the pressurization return gas pipeline for connecting to the corresponding pipeline of the liquid carbon dioxide tank truck to replenish the storage tank; a measuring pipeline is also connected to the corresponding liquid level of the storage tank, and a full-level valve 114 is installed on the measuring pipeline; an exhaust pipeline is also connected to the top of the storage tank, and an exhaust valve 111 is installed on the exhaust pipeline for venting some of the gas in the storage tank to reduce the pressure. Overfilling is not allowed when filling the storage tank with liquid to avoid the safety valve from tripping.

[0053] In the above embodiment, the delivery and metering subsystem 2 includes a filling pipeline connected to the bottom outlet of the storage tank. The filling pipeline is provided with a heat insulation layer 213 so that the external heat input during carbon dioxide filling is less than the cooling capacity of the refrigeration unit 16. The filling pipeline is also equipped with a delivery pump 21 and a metering pump 26. The delivery pump 21 is used to deliver excess liquid carbon dioxide to the metering pump 26, and the metering pump 26 is used to meter and deliver liquid carbon dioxide according to the required amount of the formula.

[0054] In one specific embodiment, the filling pipeline includes a delivery pipeline, a metering pipeline, and a return pipeline connected in sequence. A delivery pump 21 is installed on the delivery pipeline, and an outlet valve 17 is installed on the connecting pipeline between the inlet of the delivery pump 21 and the bottom outlet of the storage tank. A delivery pipeline output valve 24 is installed at the inlet end of the metering pipeline. A metering pump 26 is installed on the metering pipeline. A pressure sensor 25 is installed on the metering pipeline at the inlet end of the metering pump 26, and a mass flow meter 27 is installed on the metering pipeline at the outlet end of the metering pump 26. A return valve 29 and a check valve 210 are installed on the return pipeline. The return valve 29 is used to control the return of liquid carbon dioxide to the storage tank. The metering pipeline, the return pipeline, and the filling nozzle 3 are switched through a three-way valve B.

[0055] In a preferred embodiment, the delivery metering subsystem 2 includes a gas circulation loop, a liquid circulation loop, and a back pressure loop. The gas circulation loop includes a return gas pipe connecting the outlet of the delivery pump 21 to the return gas port at the top of the storage tank. A pump return gas valve 22 is installed on the first section of the return gas pipe, and a return gas valve 113 is installed on the middle section of the pipe. The liquid circulation loop includes a return liquid pipe connecting the delivery pipe to the return liquid port at the top of the storage tank. A pre-cooling valve 23 is installed on the first section of the return liquid pipe, and a return liquid valve 112 is installed on the middle section of the return liquid pipe. The back pressure loop includes a back pressure pipe connecting the delivery pipe to the return liquid port at the top of the storage tank. The back pressure pipe includes a first back pressure branch and a second back pressure branch arranged in parallel. A back pressure valve 211 is installed on the first back pressure branch, and a spare valve 212 is installed on the second back pressure branch.

[0056] Additionally, purge valves 115 are installed on the inlet sections of the aforementioned liquid outlet valve 17, liquid filling valve 18, pressurized return gas valve 19, return liquid valve 112, and return gas valve 113 to release some carbon dioxide gas and accelerate the process.

[0057] In this embodiment, the conveying and metering subsystem 2 includes a conveying pipeline, a metering pipeline and a return pipeline connected in sequence, and simultaneously constructs a gas circulation loop, a liquid circulation loop and a back pressure loop. It can accurately measure the liquid carbon dioxide used for foaming according to the formula, and at the same time return the excess liquid carbon dioxide and the carbon dioxide vaporized during the conveying process to the storage tank to reduce gas discharge loss.

[0058] According to another specific embodiment of the present invention, a method for adding liquid carbon dioxide is provided, comprising the following steps:

[0059] The refrigeration unit 16 is started and stopped according to the pressure inside the storage tank to maintain the pressure in the storage tank.

[0060] The filling pipeline is pre-cooled to bring its temperature close to the storage temperature of liquid carbon dioxide.

[0061] Accurately metered liquid carbon dioxide is added to the foaming component using the filling nozzle 3.

[0062] Specifically, the process of controlling the start and stop of the refrigeration unit 16 to maintain the pressure of the storage tank based on the internal pressure of the storage tank is as follows: During the storage and use of carbon dioxide, the input of external heat will cause carbon dioxide to vaporize, and the internal pressure of the storage tank will increase. When the pressure sensor 25 of the refrigeration unit 16 detects the upper limit of the pressure, the refrigeration unit 16 will start. The refrigeration unit 16 will cool the gas in the tank, so that the gas cools down and liquefies, and the internal pressure of the storage tank will decrease. When the pressure drops to the lower limit, the refrigeration will stop.

[0063] Because liquid carbon dioxide is stored in tanks at temperatures below -24°C, ambient heat inevitably enters the transfer pump 21, metering pump 26, and pipelines from the tank. This causes the carbon dioxide to heat up and vaporize. If a large amount of carbon dioxide gas remains in the pipelines, it will inevitably lead to increased tank pressure, cavitation in the transfer pump 21 and metering pump 26, and inaccurate measurement by the mass flow meter 27. To prevent the vaporization of liquid carbon dioxide, the pipelines and valves must be insulated. The insulation work must ultimately ensure that the external heat input during carbon dioxide filling is less than the cooling capacity of the refrigeration unit 16, thus maintaining the carbon dioxide in a liquid state during filling into the foaming component. Although the external heat input during carbon dioxide refueling is less than the cooling capacity of the refrigeration unit 16 after the insulation measures are taken, the rate of external heat input is very high when the liquid carbon dioxide is just output from the storage tank to the refueling pipeline. This is because the room temperature of the pipeline system is much higher than the temperature of the liquid carbon dioxide. If the external heat input is still less than the cooling capacity of the refrigeration unit 16 under this situation, the cooling power of the refrigeration unit 16 will be very large and the heat exchange area will also need to be very large, which is very uneconomical and difficult to achieve. Therefore, the filling pipeline needs to be pre-cooled before adding carbon dioxide to bring the pipeline system temperature close to the storage temperature of liquid carbon dioxide. In order to reduce carbon dioxide vaporization, the pressure of carbon dioxide circulating in the pipeline can be about 5 bar higher than the storage pressure, that is, the pipeline circulation pressure is 30 bar. Low temperature liquid carbon dioxide (-30℃) is added to the foaming component at room temperature (about 20℃) through the nozzle, and it still needs to be stirred, mixed and reacted. If the temperature rises too high or the pressure drops too quickly before the foam is formed, it is easy to cause premature carbon dioxide vaporization, which will affect the foaming quality. Therefore, the liquid carbon dioxide filling pressure is adjusted by adjusting the filling nozzle 3 to be about 5 bar higher than the circulation pressure, that is, the filling pressure is 35 bar.

[0064] The above-mentioned pre-cooling of the injection pipeline to bring its temperature close to the storage temperature of liquid carbon dioxide; and the specific process of adding accurately measured liquid carbon dioxide into the foaming component using injection nozzle 3 are as follows:

[0065] First, close the precooling valve 23 and the delivery pipeline output valve 24. Then, open the storage tank return valve to precool the delivery pump 21 using the low-temperature carbon dioxide gas at the top of the storage tank. After about 5-10 minutes (the specific time is determined by the actual pipeline in the embodiment), open the storage tank outlet valve 17 to precool the delivery pump 21 and its outlet pipeline using the low-temperature carbon dioxide liquid. At this time, the purge valve 115 before the storage tank return valve 113 can be slightly opened to release some gas and accelerate the cooling speed of this section of the pipeline. When liquid flows out of the purge valve 115, close the purge valve 115, manually open the precooling valve 23 and the return valve 112, and start the delivery pump 21. After the delivery pump 21 starts, the liquid carbon dioxide flows out of the storage tank and is pumped by the delivery pump 21 (liquid and gas) before flowing back to the storage tank through the storage tank return valve, establishing a circulation loop. After the circulation loop is established for about 5-10 minutes, manually close the precooling valve 23 and simultaneously open the back pressure valve 211. The liquid carbon dioxide flows through the back pressure valve. Valve 211 then returns the liquid to the storage tank via return valve 112. After the pre-cooling time of this part of the pipeline is about 5 minutes, open the output valve of the delivery pipeline, the return valve 29 of the metering pipeline, and open the three-way valve B to the return state. When the pressure sensor 25 before the metering pump 26 shows pressure, start the metering pump 26. After the metering pump 26 is started, excess liquid carbon dioxide flows directly through the back pressure valve 211 and return valve 112 before the output valve 24 of the delivery pipeline and returns to the storage tank. The liquid carbon dioxide required for the formula is pressurized by the metering pump 26 and flows through the mass flow meter 27, three-way valve B, return valve 29, back pressure valve 211, and return valve 112 back to the storage tank. The pre-cooling time of the metering pipeline is determined by the fluid density displayed by the mass flow meter 27. When the mass flow meter 27 stably displays a carbon dioxide density greater than 1 g / cm3, there is no gaseous carbon dioxide in the liquid. At this time, the three-way valve B can be switched to the filling position to add liquid carbon dioxide.

[0066] In this embodiment, by sequentially pre-cooling the delivery pump 21, delivery pipeline, gas circulation loop, liquid circulation loop, back pressure loop, metering pipeline and return pipeline, the temperature of the pipeline system is brought close to the storage temperature of liquid carbon dioxide. At the same time, combined with the heat insulation design of the pipeline, carbon dioxide can be kept in a liquid state and added to the foaming component, so that the metering is accurate and the resulting foam cells are uniform and dense, which is suitable for continuous foaming process.

[0067] The above-described filling process of the metering and conveying subsystem 2 is based on a manual control method. In practice, the manual valve can be replaced with a pneumatic or electric valve, pressure and temperature sensors can be added for detection, and automatic control can be achieved. In a filling system with added pressure and temperature sensors, when the filling system pressure exceeds the limit, the electric vent valve added to the overpressure pipeline can be controlled to release pressure, protecting the pipeline and personnel safety. Regarding the setting of carbon dioxide circulation and filling pressure, in specific embodiments, adjustments can be made based on the density of the foam and the product characteristics; this does not mean that the circulation and filling pressure and temperature must be limited to the pressures and temperatures mentioned above.

[0068] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A liquid carbon dioxide dispensing system, characterized in that, The system comprises: a storage tank system for storing liquid carbon dioxide, which comprises a storage tank, a refrigeration unit installed in the storage tank, and a liquid level and pressure measuring unit electrically connected to the refrigeration unit, the liquid level and pressure measuring unit being used to monitor the liquid level and pressure inside the storage tank in real time, and the refrigeration unit being controlled to start and stop according to the pressure inside the storage tank to control the pressure of the storage tank; the storage tank comprises an inner cylinder and an outer cylinder, and the interlayer of the inner cylinder and the outer cylinder is filled with insulation material, and a pipe is connected to a vacuum measuring gauge and a vacuum pumping device to maintain the vacuum degree of the interlayer to ensure the heat insulation capacity of the storage tank; a delivery and metering system, which comprises a filling pipe connected to the outlet at the bottom of the storage tank, the filling pipe being provided with a heat insulation layer to ensure that the heat input from the outside during carbon dioxide filling is less than the refrigeration capacity of the refrigeration unit; the filling pipe is further provided with a delivery pump and a metering pump, the delivery pump being used to deliver excess liquid carbon dioxide to the metering pump, and the metering pump being used to deliver the liquid carbon dioxide according to the required amount in the formula; and a filling nozzle connected to the filling pipe and used to fill the accurately metered liquid carbon dioxide into the foaming component; the filling pipe comprises a delivery pipe, a metering pipe and a return pipe connected in sequence, the delivery pump is arranged on the delivery pipe, a liquid outlet valve is arranged on the connecting pipe between the liquid inlet of the delivery pump and the outlet at the bottom of the storage tank, the inlet end of the metering pipe is provided with a delivery pipe outlet valve, the metering pump is arranged on the metering pipe, a pressure detection element is arranged on the metering pipe at the inlet end of the metering pump, and a mass flow meter is arranged on the metering pipe at the outlet end of the metering pump, a return valve is arranged on the return pipe, and the return valve is used to control the return of the liquid carbon dioxide to the storage tank; the metering pipe, the return pipe and the filling nozzle are switched by a three-way valve B; the delivery and metering system further comprises a gas circulation loop and a liquid circulation loop, the gas circulation loop comprises a gas return pipe connected to the gas outlet of the delivery pump and the gas return port at the top of the storage tank, a pump gas return valve is arranged on the front section of the gas return pipe, and a gas return valve is arranged on the middle section of the gas return pipe; the liquid circulation loop comprises a liquid return pipe connected to the delivery pipe and the liquid return port at the top of the storage tank, a pre-cooling valve is arranged on the front section of the liquid return pipe, and a liquid return valve is arranged on the middle section of the liquid return pipe; the delivery and metering system further comprises a back pressure loop, the back pressure loop comprises a back pressure pipe connected to the delivery pipe and the liquid return port at the top of the storage tank, the back pressure pipe comprises a first back pressure branch and a second back pressure branch arranged in parallel, a back pressure valve is arranged on the first back pressure branch, and a standby valve is arranged on the second back pressure branch.

2. The filling system according to claim 1, wherein The safety device is provided with a pressure relief device arranged at the top outlet of the tank and connected to two-way safety venting pipelines, a three-way valve A and a safety valve group arranged on the safety venting pipelines, the three-way valve A is used for controlling switching between the two-way safety venting pipelines, and the safety valve group is provided with a safety valve provided with a bursting disc, which is used for discharging the excess pressure when the pressure of the tank exceeds the working pressure or is used for blasting when the safety valve is damaged to ensure the safety of the equipment and personnel.

3. A method of filling liquid carbon dioxide, characterized in that, The filling system according to claim 1 or 2 comprises the following steps: The refrigerating unit is started and stopped according to the pressure inside the tank to maintain the pressure of the tank; The filling pipeline is pre-cooled to make the temperature of the filling pipeline close to the storage temperature of the liquid carbon dioxide; The accurately metered liquid carbon dioxide is filled into the foaming component by using the filling nozzle.

4. The filling method according to claim 3, characterized in that, The specific steps of maintaining the pressure of the tank are as follows: When the upper limit of the tank pressure is detected by the liquid level pressure measuring unit, the refrigerating unit is started to cool the gas inside the tank, and the refrigerating unit is stopped when the pressure of the tank is reduced to the lower limit.

5. The filling method according to claim 3, characterized in that, The specific steps of pre-cooling the filling pipeline are as follows: The pre-cooling valve and the output valve of the conveying pipeline are closed, the back gas valve is opened, and the conveying pump is pre-cooled by using the low-temperature carbon dioxide gas at the top of the tank; The liquid outlet valve is opened, and the conveying pump and the outlet pipeline of the conveying pump are pre-cooled by using the low-temperature carbon dioxide liquid at the bottom of the tank; The pre-cooling valve and the liquid return valve are opened, and the conveying pump is started to establish a liquid circulation loop, and the pipeline of the liquid circulation loop is pre-cooled; The pre-cooling valve is closed and the back pressure valve is opened to pre-cool the pipeline of the back pressure loop; The output valve of the conveying pipeline and the back flow valve are opened, and the three-way valve B is switched to the back flow state, and the metering pump is opened when the pressure detecting element shows pressure to pre-cool the metering pipeline and the back flow pipeline.

6. The filling method according to claim 5, characterized in that, The time for pre-cooling the metering pipeline is judged according to the fluid density displayed by the mass flowmeter, when the mass flowmeter stably displays the density of carbon dioxide greater than 1 g / cm 3 When the mass flowmeter stably displays the density of carbon dioxide greater than 1 g / cm 3 , the three-way valve B is switched to the filling position to fill the liquid carbon dioxide; and / or, The filling method further comprises the steps of controlling the circulating pressure of the liquid carbon dioxide in the pipelines to be higher than the storage pressure of the liquid carbon dioxide, and controlling the filling pressure of the liquid carbon dioxide to be higher than the circulating pressure of the liquid carbon dioxide in the pipelines.

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