Method for recovering residues from walnut protein powder extracted by supercritical CO2 fluid

Abstract

The invention provides a supercritical CO2 fluid extraction walnut protein powder residue recovery method, which comprises: pretreating a walnut raw material, carrying out walnut supercritical CO2 fluid circulation extraction on the pretreated walnut, after extraction for 30 min, putting the extracted walnut oil and the walnut protein powder residue into a separation kettle, and carrying out separation, after the weight of the received walnut oil is less than or equal to 0.5 kg, when the pressure of the extraction kettle is reduced to a specified value, starting supercritical CO2 fluid circulation heating, after heating is completed, performing shutdown flat pressing, when the pressure of the extraction kettle is consistent with the pressure of a middle storage tank, completing shutdown flat pressing operation, starting CO2 recovery, and when the pressure of the extraction kettle is displayed as' 0 'MPa, closing an inlet valve and an outlet valve of the extraction kettle; discharging after residual gas in the extraction kettle is emptied; on the premise of improving the recovery efficiency of the walnut protein powder residues, residual CO2 in the materials can be effectively reduced, the moisture content of the walnut protein powder residues is controlled, the quality of the walnut protein powder residues is better improved, and the storage life of the walnut protein powder residues is better prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of walnut oil preparation, and particularly relates to a method for recovering walnut protein powder residue by extracting it with supercritical CO2 fluid. Background Art

[0002] With the continuous innovation of oil extraction technology, supercritical extraction technology has stood out in the field of oil extraction, and has been included in the encouraged technologies of the National "Guiding Catalogue of Industrial Structure Adjustment (2019 Edition)", and continues to be included in the encouraged technologies of the National "Guiding Catalogue of Industrial Structure Adjustment (2024 Edition)". The technology of supercritical extraction of oils and fats has become more and more widespread. As the frequency of use increases, many problems have gradually been exposed in the extraction process. For example, after the extraction is completed, the pressure of the extraction kettle needs to be leveled and recovered. The cover can only be opened and unloaded when the pressure reaches zero. During these operations, as the pressure drops rapidly, the CO2 temperature drops, the slag becomes compacted, and it is difficult to recover the remaining CO2. After depressurization, the material is very compact and frozen, which increases the difficulty of unloading. The CO2 in the material is not completely released. After loading, the CO2 releases pressure again, and a large amount of condensed water is generated around it, which affects the quality of the slag and its subsequent preservation, resulting in low production efficiency. Summary of the Invention

[0003] In view of the above problems, the purpose of the present invention is to provide a method for recovering walnut protein powder residue by supercritical CO2 fluid extraction, which can improve CO2 recovery efficiency, reduce CO2 consumption, and make the residue looser after pressure relief.

[0004] The present invention is achieved through the following technical solutions: A method for recovering walnut protein powder residue by extracting it with supercritical CO2 fluid comprises the following steps: pre-treating walnut raw materials, subjecting the pre-treated walnuts to walnut supercritical CO2 fluid circulation extraction, and after 30 minutes of extraction, placing the extracted walnut oil and walnut protein powder residue into a separation kettle for separation until the weight of the extracted walnut oil is less than or equal to 0.5 kg. When the pressure of the extraction kettle drops to a specified value, supercritical CO2 fluid circulation heating is started, and after heating is completed, the extraction kettle is shut down for pressure equalization. When the pressure of the extraction kettle is consistent with the pressure of an intermediate storage tank, the shutdown and pressure equalization operation are completed, and CO2 recovery is started. When the pressure of the extraction kettle is displayed as "0" MPa, the inlet and outlet valves of the extraction kettle are closed, and the residual gas in the extraction kettle is emptied before unloading.

[0005] The walnut raw material pretreatment includes vibration screening, microwave drying and three-roller crushing. The temperature of the microwave drying is 70° C., the belt speed in the microwave drying is 4 m / min, and the crushing particle size of the three-roller crusher is 30-40 mesh.

[0006] The steps of the supercritical CO2 fluid circulation extraction of walnuts include: an extraction kettle used for extraction comprises an upper and lower material barrel, the crushed walnuts are loaded, during loading, the loading amount of the lower material barrel is 70-85%, and the loading amount of the upper material barrel is 65-75%, the upper material barrel cover of the extraction kettle is covered with steel wool and the steel wool is fixed on the extraction kettle cover, the hot water temperature is set to 50-65°C, the cold water temperature is set to 6-10°C, the extraction pressure is set to 32-50MPa, the extraction temperature is set to 35-55°C, the extraction flow rate is set to 2500-2700L / h, and the extraction time is set to 3-8h.

[0007] The separation pressure of the walnut oil and the walnut protein powder residue is 5-16 MPa and the separation temperature is 40-50° C., and the machine is stopped after the weight of the walnut oil discharged from the separation kettle outlet is ≤0.5 kg / h.

[0008] When the pressure of the extraction kettle is reduced from 32-55 MPa to 7-10 MPa during the shutdown and pressure reduction, the extraction temperature is also reduced to 20-30°C.

[0009] During the supercritical CO2 fluid circulation heating process, the extraction kettle pressure is 7-10 MPa, the extraction kettle temperature is 35-45°C, the CO2 flow rate is 1000-1800 L / h, and the heating time is 10-30 min.

[0010] The shutdown and pressure leveling step includes: slowly adjusting the frequency of the CO2 booster pump to 0HZ, adjusting the valve from the separation kettle to the intermediate storage tank, controlling the pressure leveling rate of the extraction kettle to 0.001-0.10MPa / s, and completing the shutdown and pressure leveling operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 25-40°C.

[0011] Adjust the system gas line to the tail gas recovery state, open the valve connecting the extraction kettle to the CO2 recovery pump, start the tail gas recovery pump, open the tail gas recovery automatic valve, control the pressure recovery speed of the extraction kettle to 0.001-0.10MPa / s, until the pressure of the extraction kettle is displayed as "0"MPa, close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 15-25℃.

[0012] The unloading step includes an automatic unloading device; the automatic unloading device is a scattering machine and a pumping machine; the unloading step includes: after the residual air is emptied, the scattering device is opened to scatter the material, and after the material is loosened, the scattering device is closed and the pumping system is started to pump the scattered material.

[0013] Beneficial effects of the present invention: Under the premise of improving the recovery efficiency of walnut protein powder residue, the present invention can effectively reduce the residual CO2 in the material, control the moisture content of the walnut protein powder residue, and better improve the quality and storage period of the walnut protein powder residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will be further described in detail below with reference to the accompanying drawings.

[0015] Figure 1 This is a diagram showing the effect of slag recovery by circulating and heating supercritical CO2 fluid according to the present invention.

[0016] Figure 2 The conventional method of slag recovery effect Figure 1 .

[0017] Figure 3 The conventional method of slag recovery effect Figure 2 . DETAILED DESCRIPTION

[0018] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Example 1

[0019] The pretreated walnuts are loaded, with the upper material barrel loading amount being 65% and the lower material barrel loading amount being 75%. The upper material barrel lid of the extraction kettle is covered with steel wool and fixed on the extraction kettle lid. The hot water temperature is set to 60°C and the cold water temperature is 6°C. The equipment is adjusted to the start state, the CO2 pressure pump is started, the extraction pressure is adjusted to 35MPa, the extraction temperature is 35°C, the extraction flow rate is 2500L / h, and the extraction time is 6h. After the temperature and pressure are reached, the CO2 circulation is started. After 30 minutes, the extracted walnut oil and walnut protein powder residue are placed in the separation kettle for separation. The separation pressure is 12MPa and the separation temperature is 40°C. The oil is collected in separation kettle No. 1 and separation kettle No. 2, and collected every 30 minutes until the weight of the collected walnut oil is ≤0.5kg. Then, the frequency modulation of the CO2 pressure pump is slowly reduced to stop, the CO2 circulation is stopped, the pressure is reduced, and the valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure reduction rate of the extraction kettle to 0 .01~0.10MPa / s, close the valve from the separation kettle to the intermediate storage tank, when the pressure of the extraction kettle drops from 35MPa to 7MPa, the extraction temperature also drops to 25℃, start supercritical CO2 fluid circulation and heating, slowly open the valve from the separation kettle to the intermediate storage tank, adjust the frequency modulation of the CO2 booster pump to 15HZ, set the supercritical CO2 fluid circulation and heating parameters to extraction kettle pressure 7MPa, extraction kettle temperature 35℃, CO2 flow rate 1000L / h, heating time 20min, after heating is completed, start to stop and equalize the pressure, slowly reduce the frequency modulation of the CO2 booster pump to stop, adjust the valve from the separation kettle to the intermediate storage tank, and control the pressure equalization rate of the extraction kettle to 0.001~0 .10MPa / s, and when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank, the shutdown and pressure equalization operation are completed. At this time, the temperature of the extraction kettle is 30℃, and CO2 recovery is started. The system gas line is adjusted to the CO2 recovery state, and the valve connecting the extraction kettle to the CO2 recovery pump is opened. The tail gas recovery pump is started, and the tail gas recovery automatic valve is opened. The pressure recovery speed of the extraction kettle is controlled to 0.001~0.10MPa / s until the pressure of the extraction kettle is displayed as "0" MPa. Close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 23℃. Open the extraction kettle cover for unloading. The material is loose, without compaction or ice. There is no need to break it up, and the material can be directly extracted. Example 2

[0020] The pretreated walnuts are loaded, with the upper material barrel loading volume being 70% and the lower material barrel loading volume being 80%. The upper material barrel lid of the extraction kettle is covered with steel wool and fixed on the extraction kettle lid. The hot water temperature is set to 60°C and the cold water temperature is set to 6°C. The equipment is adjusted to the start state, the CO2 pressure pump is started, the extraction pressure is adjusted to 40MPa, the extraction temperature is 45°C, the extraction flow rate is 2600L / h, and the extraction time is 7h. After the temperature and pressure are reached, the CO2 circulation is started. After 30 minutes, the extracted walnut oil and walnut protein powder residue are placed in the separation kettle for separation. The separation pressure is 12MPa and the separation temperature is 40°C. The oil is collected in separation kettle No. 1 and separation kettle No. 2, and collected every 30 minutes until the weight of the collected walnut oil is ≤0.5kg. Then, the frequency modulation of the CO2 pressure pump is slowly reduced to stop, the CO2 circulation is stopped, the pressure is reduced, and the valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure reduction rate of the extraction kettle to 0 .01~0.10MPa / s, close the valve from the separation kettle to the intermediate storage tank, when the pressure of the extraction kettle is flattened from 40MPa to 8MPa, the extraction temperature is also reduced to 29℃, and the supercritical CO2 fluid circulation and heating is started. Slowly open the valve from the separation kettle to the intermediate storage tank, adjust the frequency modulation of the CO2 booster pump to 15HZ, set the supercritical CO2 fluid circulation and heating parameters to the extraction kettle pressure of 8MPa, the extraction kettle temperature of 40℃, the CO2 flow rate of 1500L / h, and the heating time of 25min. After the heating is completed, start the first shutdown and pressure equalization, slowly reduce the frequency modulation of the CO2 booster pump to shutdown, adjust the valve from the separation kettle to the intermediate storage tank, and control the pressure equalization rate of the extraction kettle to 0.001~0 .10MPa / s, and complete the pressure equalization operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 34℃, and CO2 recovery starts. The system gas line is adjusted to the CO2 recovery state, and the valve connecting the extraction kettle to the CO2 recovery pump is opened. The tail gas recovery pump is started, and the tail gas recovery automatic valve is opened. The pressure recovery speed of the extraction kettle is controlled to 0.001~0.10MPa / s until the pressure of the extraction kettle is displayed as "0" MPa. Close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 25℃. Open the extraction kettle cover for unloading. The material is loose, without compaction or ice. There is no need to break it up, and the material can be directly extracted. Example 3

[0021] The pretreated walnuts are loaded, with the upper material barrel loading volume being 70% and the lower material barrel loading volume being 80%. The upper material barrel lid of the extraction kettle is covered with steel wool and fixed on the extraction kettle lid. The hot water temperature is set to 60°C, the cold water temperature is 6°C, the equipment is adjusted to the start state, the CO2 pressure pump is started, the extraction pressure is adjusted to 40MPa, the extraction temperature is 50°C, the extraction flow rate is 2700L / h, and the extraction time is 7h. After the temperature and pressure are reached, the CO2 circulation is started. After 30 minutes, the extracted walnut oil and walnut protein powder residue are placed in the separation kettle for separation. The separation pressure is 12MPa and the separation temperature is 40°C. The oil is collected in separation kettle No. 1 and separation kettle No. 2, and collected every 30 minutes until the weight of the collected walnut oil is ≤0.5kg. Then, the frequency modulation of the CO2 pressure pump is slowly reduced to stop, the CO2 circulation is stopped, the pressure is reduced, and the valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure reduction rate of the extraction kettle to 0 .01~0.10MPa / s, close the valve from the separation kettle to the intermediate storage tank, when the pressure of the extraction kettle is flattened from 40MPa to 9MPa, the extraction temperature is also reduced to 38℃, and the supercritical CO2 fluid circulation and heating is started. Slowly open the valve from the separation kettle to the intermediate storage tank, adjust the frequency modulation of the CO2 booster pump to 15HZ, set the supercritical CO2 fluid circulation and heating parameters to the extraction kettle pressure of 9MPa, the extraction kettle temperature of 50℃, the CO2 flow rate of 1800L / h, and the heating time of 20min. After the heating is completed, start to stop and equalize the pressure, slowly reduce the frequency modulation of the CO2 booster pump to stop, adjust the valve from the separation kettle to the intermediate storage tank, and control the pressure equalization rate of the extraction kettle to 0.001~0 .10MPa / s, and complete the shutdown and pressure equalization operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 43℃, and CO2 recovery starts. The system gas line is adjusted to the CO2 recovery state, and the valve connecting the extraction kettle to the CO2 recovery pump is opened. The tail gas recovery pump is started, and the tail gas recovery automatic valve is opened. The pressure recovery speed of the extraction kettle is controlled to 0.001~0.10MPa / s until the pressure of the extraction kettle is displayed as "0" MPa. Close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 32℃. Open the extraction kettle cover for unloading. The material is loose, without compaction or ice. There is no need to break it up, and the material can be directly extracted.

[0022] Comparative Example 1 The pretreated walnuts are loaded, the loading amount of the upper material barrel is 65%, and the loading amount of the lower material barrel is 75%. The upper material barrel cover of the extraction kettle is covered with steel wool and fixed on the extraction kettle cover. The hot water temperature is set to 60℃, the cold water temperature is 6℃, the equipment is adjusted to the start state, the CO2 pressure pump is started, the extraction pressure is adjusted to 35MPa, the extraction temperature is 35℃, the extraction flow rate is 2500L / h, the separation pressure is 12MPa, the separation temperature is 40℃, and the extraction time is 6h. After the temperature and pressure are reached, the CO2 circulation is started. After 30min, the oil is connected to the separation kettle No. 1 and the separation kettle No. 2, and it is connected every 30min until the weight of the walnut oil connected is ≤0.5kg. Then, the frequency modulation of the CO2 pressure pump is slowly reduced to stop, the CO2 circulation is stopped, and the pressure is leveled. The valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure leveling rate of the extraction kettle to be 0.01~0 .10MPa / s, and complete the pressure equalization operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 27℃, and CO2 recovery is started. The system gas line is adjusted to the CO2 recovery state, and the valve connecting the extraction kettle to the CO2 recovery pump is opened. The tail gas recovery pump is started, and the tail gas recovery automatic valve is opened. The pressure recovery speed of the extraction kettle is controlled to 0.001~0.10MPa / s until the pressure of the extraction kettle is displayed as "0" MPa. Close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 14℃. Open the extraction kettle cover for unloading. The material is not loose, and there is compaction and ice. It needs to be broken up before extraction.

[0023] Comparative Example 2 The pretreated walnuts are loaded, with the upper material barrel being loaded at 70% and the lower material barrel being loaded at 80%. The upper material barrel cover of the extraction kettle is covered with steel wool and fixed on the extraction kettle cover. The hot water temperature is set to 60°C, the cold water temperature is set to 6°C, the equipment is adjusted to the start state, the CO2 booster pump is started, the extraction pressure is adjusted to 40MPa, the extraction temperature is 45°C, the extraction flow rate is 2600L / h, the separation pressure is 14MPa, the separation temperature is 40°C, and the extraction time is 7h. After the temperature and pressure are reached, the CO2 circulation is started. After 30 minutes, the oil is connected to the separation kettle No. 1 and the separation kettle No. 2, and it is connected every 30 minutes until the weight of the walnut oil connected is ≤0.5kg. Then, the frequency modulation of the CO2 booster pump is slowly reduced to stop, the CO2 circulation is stopped, and the pressure is leveled. The valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure leveling rate of the extraction kettle to be 0.01~0 .10MPa / s, and complete the pressure equalization operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 30℃, start CO2 recovery, adjust the system gas line to CO2 recovery state, open the valve connecting the extraction kettle to the CO2 recovery pump, start the tail gas recovery pump, open the tail gas recovery automatic valve, control the pressure recovery speed of the extraction kettle to 0.001~0.10MPa / s, until the pressure of the extraction kettle is displayed as "0" MPa, close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 18℃, open the extraction kettle cover for unloading, the material is not loose, and there is compaction and ice phenomenon, which needs to be broken up before extraction.

[0024] Comparative Example 3 The pretreated walnuts are loaded, the loading amount of the upper material barrel is 70%, and the loading amount of the upper material barrel is 80%. The upper material barrel cover of the extraction kettle is covered with steel wool and fixed on the extraction kettle cover. The hot water temperature is set to 60℃, the cold water temperature is 6℃, the equipment is adjusted to the start state, the CO2 pressure pump is started, the extraction pressure is adjusted to 40MPa, the extraction temperature is 50℃, the extraction flow rate is 2700L / h, the separation pressure is 14MPa, the separation temperature is 45℃, and the extraction time is 7h. After the temperature and pressure are reached, the CO2 circulation is started. After 30min, the oil is connected to the separation kettle No. 1 and the separation kettle No. 2, and it is connected every 30min until the weight of the walnut oil connected is ≤0.5kg. Then, the frequency modulation of the CO2 pressure pump is slowly reduced to stop, the CO2 circulation is stopped, and the pressure is leveled. The valve from the separation kettle to the intermediate storage tank is adjusted to control the pressure leveling rate of the extraction kettle to be 0.01~0 .10MPa / s, and complete the pressure equalization operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 37℃, and CO2 recovery starts. The system gas line is adjusted to the CO2 recovery state, and the valve connecting the extraction kettle to the CO2 recovery pump is opened. The tail gas recovery pump is started, and the tail gas recovery automatic valve is opened. The pressure recovery speed of the extraction kettle is controlled to 0.001~0.10MPa / s until the pressure of the extraction kettle is displayed as "0" MPa. Close the inlet and outlet valves of the extraction kettle, empty the residual gas in the extraction kettle and then unload. At this time, the temperature of the extraction kettle is 20℃. Open the extraction kettle cover for unloading. The material is not loose, and there is compaction and ice. It needs to be broken up before extraction.

[0025] The above-mentioned extraction kettle, separation kettle, dispersing machine and material extraction machine are all existing technologies and are conventional models in this field.

[0026] The following is a comparison table of embodiments and comparative examples:

[0027] Table 1 It can be concluded from Table 1 that the difference between the embodiment and the comparative example is that after the walnut oil is taken out and reaches the specified value, the pressure inside the extraction kettle will be reduced first. After the pressure is reduced to the specified value, the CO2 inside it is heated, and finally the CO2 is recovered and unloaded at equal pressure. A large number of experiments have shown that this may effectively reduce the residual CO2 in the material. There is no need to further break up the material during unloading, while the conventional methods in the comparative examples all require further breaking up, which increases manpower, material and financial resources. The walnut protein powder residue produced by the present invention is of higher quality and has a longer storage period than that produced by the conventional method.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for recovering walnut protein powder residue by supercritical CO2 fluid extraction, characterized in that the steps include: The walnut raw materials are pretreated, and the pretreated walnuts are subjected to walnut supercritical CO2 fluid circulation extraction. After 30 minutes of extraction, the extracted walnut oil and walnut protein powder residue are placed in a separation kettle for separation until the weight of the walnut oil collected is ≤0.5kg. When the pressure of the extraction kettle drops to a specified value, the supercritical CO2 fluid circulation heating is started. After the heating is completed, the machine is shut down for pressure equalization. When the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank, the shutdown and pressure equalization operation are completed, and CO2 recovery is started. When the pressure of the extraction kettle is displayed as "0" MPa, the inlet and outlet valves of the extraction kettle are closed, and the residual gas in the extraction kettle is emptied before unloading.

2. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, wherein: The walnut raw material pretreatment includes vibration screening, microwave drying and three-roller crushing. The temperature of the microwave drying is 70° C., the belt speed in the microwave drying is 4 m / min, and the crushing particle size of the three-roller crusher is 30-40 mesh.

3. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: The steps of the supercritical CO2 fluid circulation extraction of walnuts include: an extraction kettle used for extraction comprises an upper and lower material barrel, the crushed walnuts are loaded, during loading, the loading amount of the lower material barrel is 70-85%, and the loading amount of the upper material barrel is 65-75%, the upper material barrel cover of the extraction kettle is covered with steel wool and the steel wool is fixed on the extraction kettle cover, the hot water temperature is set to 50-65°C, the cold water temperature is set to 6-10°C, the extraction pressure is set to 32-50MPa, the extraction temperature is set to 35-55°C, the extraction flow rate is set to 2500-2700L / h, and the extraction time is set to 3-8h.

4. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, wherein: The separation pressure of the walnut oil and the walnut protein powder residue is 5-16 MPa and the separation temperature is 40-50° C., and the machine is stopped after the weight of the walnut oil discharged from the separation kettle outlet is ≤0.5 kg / h.

5. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: When the pressure of the extraction kettle is reduced from 32-55 MPa to 7-10 MPa during the shutdown and pressure reduction, the extraction temperature is also reduced to 20-30°C.

6. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: During the supercritical CO2 fluid circulation heating process, the extraction kettle pressure is 7-10 MPa, the extraction kettle temperature is 35-45°C, the CO2 flow rate is 1000-1800 L / h, and the heating time is 10-30 min.

7. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: The shutdown and pressure leveling step includes: slowly adjusting the frequency of the CO2 booster pump to 0HZ, adjusting the valve from the separation kettle to the intermediate storage tank, controlling the pressure leveling rate of the extraction kettle to 0.001-0.10MPa / s, and completing the shutdown and pressure leveling operation when the pressure of the extraction kettle is consistent with the pressure of the intermediate storage tank. At this time, the temperature of the extraction kettle is 25-40°C.

8. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: The CO2 recovery step includes: adjusting the system gas line to the tail gas recovery state, opening the valve connecting the extraction kettle to the CO2 recovery pump, starting the tail gas recovery pump, opening the tail gas recovery automatic valve, controlling the pressure recovery rate of the extraction kettle to 0.001-0.10MPa / s until the pressure of the extraction kettle displays "0" MPa, closing the inlet and outlet valves of the extraction kettle, emptying the residual gas in the extraction kettle and then unloading. At this time, the temperature of the extraction kettle is 15-25°C.

9. The method for recovering walnut protein powder residue by supercritical CO2 fluid extraction according to claim 1, characterized in that: The unloading step includes an automatic unloading device; the automatic unloading device is a scattering machine and a pumping machine; the unloading step includes: after the residual air is emptied, the scattering device is opened to scatter the material, and after the material is loosened, the scattering device is closed and the pumping system is started to pump the scattered material.

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