Low-temperature rectification extraction process for high-purity liquid oxygen
By using multi-layer polyethylene microporous body-based corrugated plates as fillers in the air-part distillation process, the problem of insufficient purity of high purity oxygen in the prior art is solved, high purity extraction of liquid oxygen is achieved, and cost is reduced and corrosion resistance is improved.
Patent Information
- Application Number
- CN202411975151.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-03-14
AI Technical Summary
The high-purity oxygen obtained by the existing air-part distillation process is insufficient, making it difficult to effectively remove impurities from industrial oxygen.
Multi-layer polyethylene microporous body based corrugated plates are used as regular fillers to provide a sufficient gas-liquid contact surface in the distillation tower, and the purity of liquid oxygen is significantly improved through the heat and mass transfer process.
Through the use of polyethylene microporous body-based corrugated plates, the impurity content in purified liquid oxygen is significantly reduced, the purity of liquid oxygen is improved, and the cost is reduced, while excellent corrosion resistance is obtained.
Smart Images
Figure SMS_1 
Figure SMS_2
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of cryogenic distillation gas, and more specifically, to a cryogenic distillation extraction process for high-purity liquid oxygen. Background Art
[0002] The raw materials used in the production of high-purity oxygen by cryogenic distillation are basically industrial oxygen, which contains impurities such as nitrogen, argon, methane, carbon dioxide, carbon monoxide and water. Therefore, in the process of cryogenic distillation of industrial oxygen, these impurities usually need to be further processed to effectively increase the oxygen content of pure oxygen.
[0003] At present, there are two main processes for producing high-purity oxygen. One is to produce industrial oxygen by water electrolysis, and then catalytically dehydrogenate it, cool it, remove water and dry it, and the other is to produce industrial oxygen by air separation equipment and then obtain it by low-temperature distillation. Among them, air separation refers to the process of separating components from air by low-temperature freezing principle. Generally, the air is compressed and cooled to a very low temperature, or the air is liquefied by expansion method, and then separated in a distillation tower. For example, when the liquid air boils, the nitrogen that is more volatile will be vaporized first, and the oxygen will be vaporized later.
[0004] At present, common nitrogen and oxygen air separation equipment is mainly composed of a distillation tower system. In the lower tower of the distillation tower, the rising gas is fully in contact with the downstream gas. After heat and mass transfer, pure nitrogen is obtained at the top. The pure nitrogen enters the main condenser evaporator at the top of the lower tower and exchanges heat with liquid oxygen to be condensed. Part of the liquid nitrogen flows downstream as the reflux liquid of the lower tower, and another part of the liquid nitrogen is supercooled through the heat exchanger and enters the upper tower after throttling to participate in distillation; the liquid air in the lower tower enters the upper tower through the heat exchanger to participate in distillation; after further distillation in the upper tower, nitrogen is generated at the top of the upper tower and liquid oxygen is generated at the bottom of the lower tower. However, the purity of pure oxygen obtained by the above air separation distillation process is still insufficient. Summary of the invention
[0005] In order to improve the defect that the pure oxygen obtained by the conventional air separation and distillation process is insufficient in purity, the present application provides a high-purity liquid oxygen cryogenic distillation extraction process.
[0006] The present application provides a high-purity liquid oxygen cryogenic distillation extraction process, which adopts the following technical solution: A high-purity liquid oxygen cryogenic distillation extraction process comprises the following steps: S1. The liquid nitrogen stored in the liquid nitrogen storage tank is sent to the upper tower of the distillation tower through the liquid nitrogen delivery pipe to provide cooling capacity for the upper tower. The oxygen generated after the liquid oxygen in the distillation tower is vaporized absorbs the cooling capacity and is finally condensed again to obtain purified liquid oxygen. S2, sending the purified liquid oxygen into the high oxygen tower 1 for primary distillation, and then transferring it to the high oxygen tower 2 for secondary distillation, and finally obtaining high-purity liquid oxygen; S3, transporting high-purity liquid oxygen to a liquid oxygen storage tank; Wherein, a filler is arranged in the lower tower of the distillation tower, and the filler is a structured filler with multi-layer polyethylene microporous body-based corrugated plate as a basic component unit.
[0007] The packing can provide sufficient contact surface for the gas-liquid two phases and enhance the mass transfer and heat transfer process between the two phases. The formation mechanism of purified liquid oxygen lies in that in the lower tower of the distillation tower, the rising gas is in full contact with the downstream gas. After heat and mass transfer, pure nitrogen is obtained at the top and liquid oxygen is formed at the bottom. Therefore, the packing can promote heat and mass transfer, thereby effectively reducing the impurity content in the purified liquid oxygen.
[0008] Commonly used packings can be broadly divided into random packings and structured packings. Among them, structured packings are beneficial to promote heat and mass transfer between countercurrent flowing liquids and steam. Compared with random packings or tower plates, structured packings have higher heat and mass transfer efficiency, lower pressure drop, and more predictable performance.
[0009] At present, the commonly used structured packing is BX packing made of metal corrugated wire mesh stacked at a certain angle, but the cost of metal corrugated wire mesh packing is too high and its corrosion resistance is poor. The present application adopts polyethylene material, which reduces the cost while also obtaining extremely good corrosion resistance.
[0010] In addition, in order to ensure that the polyethylene filler has excellent heat and mass transfer properties, it is necessary to expand the specific surface area of the polyethylene filler, thereby expanding the gas-liquid contact surface. The microporation of polyethylene can form a large number of holes, thereby effectively increasing the specific surface area of the polyethylene filler and improving the purity of liquid oxygen.
[0011] Preferably, the multi-layer polyethylene microporous body-based corrugated board comprises the following raw materials in parts by weight: 30-36 parts of polyethylene, 50-60 parts of hexadecanol and 15-20 parts of benzhydrol.
[0012] Preferably, the preparation method of the multilayer polyethylene microporous body-based corrugated board is: first, polyethylene, hexadecanol and benzhydrol are mixed, and then the mixture is added to a screw extruder for melt mixing, the melting temperature is 120-140°C, and then extruded, cooled and solidified, and finally the product is immersed in ethanol for 20-30h, and finally transferred to deionized water at 90-100°C for heat treatment for 60-100min to obtain a polyethylene microporous body-based corrugated board.
[0013] The mixture of hexadecanol and benzhydrol is a temperature-variable diluent, which is a polyethylene solvent at high temperature, that is, at high temperature, polyethylene and the temperature-variable diluent will form a uniform liquid phase; but at low temperature, it is converted into a non-polyethylene solvent due to the loss of heat energy, that is, at low temperature, polyethylene is converted into a solid state, while the temperature-variable diluent is still in a liquid state, which leads to the separation of the two phases.
[0014] Ethanol is a solvent for the variable temperature diluent, but it has no effect on polyethylene. Therefore, after the polyethylene is cooled and solidified, the product is immersed in ethanol, and the variable temperature diluent will be extracted, thereby producing a large number of uniform and stable micropores, thereby increasing the specific surface area of the polyethylene, thereby expanding the gas-liquid contact area, and promoting a significant improvement in the heat and mass transfer performance of the polyethylene filler.
[0015] Preferably, the polyethylene microporous body-based corrugated board is treated with O2 and N2 plasma.
[0016] Preferably, the specific steps of the plasma treatment are: first, immerse the polyethylene microporous body-based corrugated plate in ethanol for ultrasonic cleaning to remove impurities, then transfer the polyethylene microporous body-based corrugated plate to the center of the sample processing chamber of the low-temperature plasma modification equipment, the plasma equipment model is PG-3000K, and then O2 and N2 are introduced in sequence, during which the equipment is turned on to excite plasma, and finally a plasma-treated polyethylene microporous body-based corrugated plate is obtained.
[0017] Preferably, in plasma treatment, O2 parameters are: power 1000W, time 10s, flow rate 1.5L / min; N2 parameters are: power 800W, time 15s, flow rate 2.5L / min.
[0018] In the process of heat and mass transfer, the wettability of the filler also plays a vital role. However, since polyethylene is a non-polar polymer, the surface energy of polyethylene is extremely low, which ultimately shows poor wettability. When the polyethylene microporous body-based corrugated sheet is treated with O2 and N2 plasma, oxygen-containing functional groups C—O, C=O, O—C=O and nitrogen-containing functional groups -C—NH2, -C—NH— will be introduced to the surface of the polyethylene microporous body-based corrugated sheet, thereby significantly improving the wettability of the polyethylene microporous body-based corrugated sheet, further improving the heat and mass transfer performance of the polyethylene microporous body-based corrugated sheet, and improving the purity of liquid oxygen.
[0019] Preferably, the distillation tower, high oxygen tower 1 and high oxygen tower 2 are all provided with condensers, and the cold sources of the condensers of the high oxygen tower 1 and high oxygen tower 2 are provided by the liquid nitrogen in the condensers of the distillation tower; The distillation tower, high oxygen tower 1 and high oxygen tower 2 are all provided with evaporators, and the heat sources of the evaporators of the high oxygen tower 1 and high oxygen tower 2 are provided by the nitrogen in the evaporators of the distillation tower.
[0020] Preferably, the liquid-gas ratio in the high oxygen tower 1 is 0.5-0.7; the liquid-gas ratio in the high oxygen tower 2 is 1.3-1.4.
[0021] Preferably, the polyethylene microporous body-based corrugated plates are stacked, the channels of the packing unit plates of the odd-numbered layers are in the same direction, the channels of the packing unit plates of the even-numbered layers are in the same direction, an angle is set between the channels of the odd-numbered layers and the even-numbered layers, and the angle is 30°-170°; there is a corrugation inclination angle between the parallel direction of the corrugation and the vertical direction of the packing disk, and the corrugation inclination angle is 15°-85°, and the corrugation inclination angles of adjacent polyethylene microporous body-based corrugated plates are the same and in opposite directions.
[0022] In summary, this application has the following beneficial effects: 1. The packing can provide sufficient contact surface for the gas-liquid two phases, and strengthen the mass transfer and heat transfer overshoot between the two phases. The formation mechanism of purified liquid oxygen is that in the lower tower of the distillation tower, the rising gas is fully in contact with the downstream gas. After heat and mass transfer, pure nitrogen is obtained at the top and liquid oxygen is formed at the bottom. Therefore, the packing can promote heat and mass transfer, thereby effectively reducing the impurity content in the purified liquid oxygen; Commonly used packings can be broadly divided into random packings and structured packings. Structured packings are beneficial to promoting heat and mass transfer between countercurrent flowing liquids and steam. Compared with random packings or trays, structured packings have higher heat and mass transfer efficiency, lower pressure drop, and more predictable performance. At present, the commonly used structured packing is a BX packing obtained by stacking metal corrugated wire mesh at a certain angle, but the cost of metal corrugated wire mesh packing is too high and the corrosion resistance is poor. The present application adopts polyethylene material, which reduces the cost and obtains extremely good corrosion resistance. In addition, in order to ensure that the polyethylene filler has excellent heat and mass transfer performance, it is necessary to expand the specific surface area of the polyethylene filler, thereby expanding the gas-liquid contact surface, and the microporation of polyethylene can form a large number of holes, thereby effectively increasing the specific surface area of the polyethylene filler and improving the purity of liquid oxygen.
[0023] 2. The mixture of hexadecanol and benzhydrol is a temperature-variable diluent, which is a polyethylene solvent at high temperature, that is, at high temperature, polyethylene and the temperature-variable diluent will form a uniform liquid phase; but at low temperature, it will be converted into a non-polyethylene solvent due to the loss of heat energy, that is, at low temperature, polyethylene will be converted into a solid state, while the temperature-variable diluent will remain in a liquid state, which will lead to the separation of the two phases; Ethanol is a solvent for the variable temperature diluent, but it has no effect on polyethylene. Therefore, after the polyethylene is cooled and solidified, the product is immersed in ethanol, and the variable temperature diluent will be extracted, thereby producing a large number of uniform and stable micropores, thereby increasing the specific surface area of the polyethylene, thereby expanding the gas-liquid contact area, and promoting a significant improvement in the heat and mass transfer performance of the polyethylene filler.
[0024] 3. In the process of heat and mass transfer, the wettability of the filler also plays a vital role. However, since polyethylene is a non-polar polymer, the surface energy of polyethylene is extremely low, which ultimately shows poor wettability. When the polyethylene microporous body-based corrugated sheet is treated with O2 and N2 plasma, oxygen-containing functional groups C—O, C=O, O—C=O and nitrogen-containing functional groups -C—NH2, -C—NH— will be introduced to the surface of the polyethylene microporous body-based corrugated sheet, thereby significantly improving the wettability of the polyethylene microporous body-based corrugated sheet, further improving the heat and mass transfer performance of the polyethylene microporous body-based corrugated sheet, and improving the purity of liquid oxygen. DETAILED DESCRIPTION
[0025] The present application is further described in detail below in conjunction with Examples 1-4 and Comparative Examples 1-3. raw material
[0026] Polyethylene GUR-4120; Hexadecanol CAS: 36653-82-4; Benzhydrol CAS: 91-01-0; Ethanol CAS: 64-17-5. Example Example 1
[0027] S1. The liquid nitrogen stored in the liquid nitrogen storage tank is sent to the upper tower of the distillation tower through the liquid nitrogen delivery pipe to provide cooling capacity for the upper tower. The oxygen generated after the liquid oxygen in the distillation tower is vaporized absorbs the cooling capacity and is finally condensed again to obtain purified liquid oxygen. S2, sending the purified liquid oxygen into the high oxygen tower 1 for primary distillation, and then transferring it to the high oxygen tower 2 for secondary distillation, and finally obtaining high-purity liquid oxygen; S3. Transport high-purity liquid oxygen to the liquid oxygen storage tank.
[0028] Among them, the lower tower of the distillation tower is provided with packing, which is a regular packing with multiple layers of polyethylene microporous body-based corrugated plates as the basic component units, and the polyethylene microporous body-based corrugated plates are stacked. The channels of the packing unit plates of the odd-numbered layers are in the same direction, and the channels of the packing unit plates of the even-numbered layers are in the same direction. An angle is set between the channels of the odd-numbered layers and the even-numbered layers, and the angle is 100°; there is a corrugation inclination angle between the parallel direction of the corrugation and the vertical direction of the packing plate, and the angle of the corrugation inclination angle is 50°. The corrugation inclination angles of adjacent polyethylene microporous body-based corrugated plates are the same and in opposite directions.
[0029] The multilayer polyethylene microporous body-based corrugated board includes the following raw materials: 33 kg polyethylene, 55 kg hexadecanol and 18 kg benzhydrol; The preparation method of the multilayer polyethylene microporous body-based corrugated board is as follows: first, polyethylene, hexadecanol and benzhydrol are mixed, and then the mixture is added to a screw extruder for melt mixing at a melting temperature of 130°C, followed by extrusion molding, cooling and solidification, and finally the product is immersed in ethanol for 24 hours, and finally transferred to deionized water at 95°C for heat treatment for 80 minutes to obtain a polyethylene microporous body-based corrugated board.
[0030] The distillation tower consists of a lower tower and an upper tower base condenser evaporator. The working pressure of the lower tower is 0.6Mpa. The raw air in the lower tower is initially separated, and pure liquid nitrogen is obtained at the top of the lower tower, while oxygen-rich liquid air is at the bottom of the lower tower. The working pressure of the upper tower is 0.06Mpa. The oxygen-rich liquid air in the lower tower is discharged into the upper tower for separation, and liquid oxygen and nitrogen are finally obtained.
[0031] The condenser evaporator is arranged between the upper tower and the lower tower. The air is distilled from bottom to top with the condensed liquid. Finally, the nitrogen with a lower boiling point gathers at the top of the lower tower to obtain high-purity nitrogen. It then exchanges heat with the liquid oxygen in the condenser evaporator to obtain coldness and form liquid nitrogen. A part of it is used as the reflux liquid to maintain the distillation condition of the lower tower, and exchanges heat and mass with the gas from bottom to top. Finally, oxygen-rich liquid air can be obtained at the bottom of the tower. The remaining liquid nitrogen is depressurized and cooled by the liquid nitrogen throttle valve, and a part of it is sent to the liquid nitrogen storage tank, and a part of it enters the top of the upper tower as the reflux liquid of the upper tower.
[0032] The liquid air condensed in the lower tower is sent to the middle position of the upper tower after being reduced in pressure by a throttling regulating valve, and then gradually flows downward along the packing, exchanging heat and mass with the rising steam from the bottom of the upper tower during the process, and finally obtaining high-purity liquid oxygen at the bottom of the upper tower.
[0033] Condensers are provided in the distillation tower, high oxygen tower one and high oxygen tower two, and the cold sources of the condensers of the high oxygen tower one and high oxygen tower two are provided by the liquid nitrogen in the condensers of the distillation tower; evaporators are provided in the distillation tower, high oxygen tower one and high oxygen tower two, and the heat sources of the evaporators of the high oxygen tower one and high oxygen tower two are provided by the nitrogen in the evaporators of the distillation tower, and the liquid-to-gas ratio in the high oxygen tower one is 0.6; the liquid-to-gas ratio in the high oxygen tower two is 1.35.
[0034] Example 2-3 The difference from Example 1 is that the addition amounts of the components of the polyethylene microporous body-based corrugated board are different, as shown in Table 1.
[0035] Table 1 Addition amount of each component of the multilayer polyethylene microporous body-based corrugated board in Examples 1-3 / kg Example 4
[0036] The difference from Example 1 is that the polyethylene microporous body-based corrugated sheet is treated with O2 and N2 plasma; The specific steps of plasma treatment are: first, immerse the polyethylene microporous body-based corrugated plate in ethanol for ultrasonic cleaning to remove impurities, then transfer the polyethylene microporous body-based corrugated plate to the center of the sample processing chamber of the low-temperature plasma modification equipment, the plasma equipment model is PG-3000K, then introduce O2 and N2 in sequence, during which the equipment is turned on to excite plasma, and finally obtain the plasma-treated polyethylene microporous body-based corrugated plate; During the plasma treatment, the O2 parameters were: power 1000 W, time 10 s, flow rate 1.5 L / min; the N2 parameters were: power 800 W, time 15 s, flow rate 2.5 L / min.
[0037] Comparative Example 1 A high-purity liquid oxygen cryogenic distillation extraction process comprises the following steps: S1. The liquid nitrogen stored in the liquid nitrogen storage tank is sent to the upper tower of the distillation tower through the liquid nitrogen delivery pipe to provide cooling capacity for the upper tower. The oxygen generated after the liquid oxygen in the distillation tower is vaporized absorbs the cooling capacity and is finally condensed again to obtain purified liquid oxygen. S2, sending the purified liquid oxygen into the high oxygen tower 1 for primary distillation, and then transferring it to the high oxygen tower 2 for secondary distillation, and finally obtaining high-purity liquid oxygen; S3. Transport high-purity liquid oxygen to the liquid oxygen storage tank.
[0038] Among them, the distillation tower consists of a lower tower and an upper tower base condenser evaporator. The working pressure of the lower tower is 0.6Mpa. The raw air in the lower tower is initially separated, and pure liquid nitrogen is obtained at the top of the lower tower, and oxygen-rich liquid air is at the bottom of the lower tower. The working pressure of the upper tower is 0.06Mpa. The oxygen-rich liquid air in the lower tower is discharged into the upper tower for separation, and finally liquid oxygen and nitrogen are obtained.
[0039] The condenser evaporator is arranged between the upper tower and the lower tower. The air is distilled from bottom to top with the condensed liquid. Finally, the nitrogen with a lower boiling point gathers at the top of the lower tower to obtain high-purity nitrogen. It then exchanges heat with the liquid oxygen in the condenser evaporator to obtain coldness and form liquid nitrogen. A part of it is used as the reflux liquid to maintain the distillation condition of the lower tower, and exchanges heat and mass with the gas from bottom to top. Finally, oxygen-rich liquid air can be obtained at the bottom of the tower. The remaining liquid nitrogen is depressurized and cooled by the liquid nitrogen throttle valve, and a part of it is sent to the liquid nitrogen storage tank, and a part of it enters the top of the upper tower as the reflux liquid of the upper tower.
[0040] The liquid air condensed in the lower tower is sent to the middle position of the upper tower after being reduced in pressure by a throttling regulating valve, and then gradually flows downward, exchanging heat and mass with the rising steam from the bottom of the upper tower during the process, and finally obtaining high-purity liquid oxygen at the bottom of the upper tower.
[0041] Condensers are provided in the distillation tower, high oxygen tower one and high oxygen tower two, and the cold sources of the condensers of the high oxygen tower one and high oxygen tower two are provided by the liquid nitrogen in the condensers of the distillation tower; evaporators are provided in the distillation tower, high oxygen tower one and high oxygen tower two, and the heat sources of the evaporators of the high oxygen tower one and high oxygen tower two are provided by the nitrogen in the evaporators of the distillation tower, and the liquid-to-gas ratio in the high oxygen tower one is 0.6; the liquid-to-gas ratio in the high oxygen tower two is 1.35.
[0042] Comparative Example 2 The difference from Example 1 is that the polyethylene microporous body-based corrugated board is replaced by BX filler, and the BX filler is purchased from Hebei Wojun, model 500BX.
[0043] Comparative Example 3 The difference from Example 1 is that hexadecanol and benzhydrol are no longer added to the multi-layer polyethylene microporous body-based corrugated board.
[0044] Performance testing Liquid oxygen product purity test The purity of the purified liquid oxygen produced by the distillation tower in Examples 1-4 and Comparative Examples 1-3 was tested respectively, and the data are shown in Table 2.
[0045] Table 2 Purity test table of purified liquid oxygen in Examples 1-4 and Comparative Examples 1-3
[0046] Referring to Example 1 and Comparative Examples 1-2 and in combination with Table 2, it can be seen that, relative to Comparative Example 1, the oxygen purity of Example 1 and Comparative Example 2 is significantly improved, which indicates that the use of fillers can effectively improve the purity of liquid oxygen distillation.
[0047] The reason is that the filler can provide sufficient contact surface for the gas-liquid two phases and enhance the mass transfer, heat transfer and overshoot between the two phases. The formation mechanism of purified liquid oxygen is that in the lower tower of the distillation tower, the rising gas is in full contact with the downstream gas. After heat and mass transfer, pure nitrogen is obtained at the top and liquid oxygen is formed at the bottom. Therefore, the filler can promote heat and mass transfer, thereby effectively reducing the impurity content in the purified liquid oxygen.
[0048] Commonly used packings can be broadly divided into random packings and structured packings. Among them, structured packings are beneficial to promote heat and mass transfer between countercurrent flowing liquids and steam. Compared with random packings or tower plates, structured packings have higher heat and mass transfer efficiency, lower pressure drop, and more predictable performance.
[0049] BX filler is a structured filler obtained by stacking metal corrugated wire mesh at a certain angle, but the cost of metal corrugated wire mesh filler is too high and its corrosion resistance is poor. Example 1 is a structured filler with multi-layer polyethylene microporous body-based corrugated board as the basic component unit. While reducing the cost, it also obtains extremely good corrosion resistance. At the same time, it has a similar effect to BX filler and can be a perfect substitute.
[0050] Referring to Example 1 and Comparative Example 3 and in combination with Table 2, it can be seen that the purity of liquid oxygen in Comparative Example 3 is significantly reduced compared with that in Example 1, which indicates that the addition of hexadecanol and benzhydrol can effectively improve the purity of liquid oxygen.
[0051] The reason is that specific surface area is one of the important characteristics that affect the heat and mass transfer performance of liquid oxygen. The increase in specific surface area can effectively expand the gas-liquid contact area, and the microporation of polyethylene can form a large number of pores, thereby effectively increasing the specific surface area of polyethylene filler and improving the purity of liquid oxygen.
[0052] The mixture of hexadecanol and benzhydrol is a temperature-variable diluent, which is a polyethylene solvent at high temperature, that is, at high temperature, polyethylene and the temperature-variable diluent will form a uniform liquid phase; but at low temperature, it is converted into a non-polyethylene solvent due to the loss of heat energy, that is, at low temperature, polyethylene is converted into a solid state, while the temperature-variable diluent is still in a liquid state, which leads to the separation of the two phases.
[0053] Ethanol is a solvent for the variable temperature diluent, but it has no effect on polyethylene. Therefore, after the polyethylene is cooled and solidified, the product is immersed in ethanol, and the variable temperature diluent will be extracted, thereby producing a large number of uniform and stable micropores, thereby increasing the specific surface area of the polyethylene, thereby expanding the gas-liquid contact area, and promoting a significant improvement in the heat and mass transfer performance of the polyethylene filler.
[0054] With reference to Examples 1-3 and in combination with Table 2, it can be seen that the purity of liquid oxygen in Examples 2-3 is slightly lower than that in Example 1, which indicates that when the components of the polyethylene microporous body-based corrugated board are added in the amounts of Example 1, the prepared polyethylene microporous body-based corrugated board will have better heat and mass transfer properties.
[0055] Referring to Example 1 and Example 4 and combining with Table 2, it can be seen that compared with Example 1, the purity of liquid oxygen in Example 4 is significantly improved, which shows that the purity of liquid oxygen can be further improved after the polyethylene microporous body-based corrugated plate is treated with O2 and N2 plasma.
[0056] The reason is that the wettability of the filler also plays a vital role in the heat and mass transfer process. However, since polyethylene is a non-polar polymer, the surface energy of polyethylene is extremely low, which ultimately shows poor wettability. When the polyethylene microporous body-based corrugated sheet is treated with O2 and N2 plasma, oxygen-containing functional groups C—O, C=O, O—C=O and nitrogen-containing functional groups -C—NH2, -C—NH— will be introduced to the surface of the polyethylene microporous body-based corrugated sheet, thereby significantly improving the wettability of the polyethylene microporous body-based corrugated sheet, further improving the heat and mass transfer performance of the polyethylene microporous body-based corrugated sheet, and improving the purity of liquid oxygen.
[0057] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed, but such modifications are protected by the patent law as long as they are within the scope of the claims of the present application.
Claims
1. A high-purity liquid oxygen cryogenic distillation extraction process, characterized in that: The following steps are involved: S1. The liquid nitrogen stored in the liquid nitrogen storage tank is sent to the upper tower of the distillation tower through the liquid nitrogen delivery pipe to provide cooling capacity for the upper tower. The oxygen generated after the liquid oxygen in the distillation tower is vaporized absorbs the cooling capacity and is finally condensed again to obtain purified liquid oxygen. S2, sending the purified liquid oxygen into the high oxygen tower 1 for primary distillation, and then transferring it to the high oxygen tower 2 for secondary distillation, and finally obtaining high-purity liquid oxygen; S3, transporting high-purity liquid oxygen to a liquid oxygen storage tank; Wherein, a filler is arranged in the lower tower of the distillation tower, and the filler is a structured filler with multi-layer polyethylene microporous body-based corrugated plate as a basic component unit.
2. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 1, characterized in that: The multi-layer polyethylene microporous body-based corrugated board comprises the following raw materials in parts by weight: 30-36 parts of polyethylene, 50-60 parts of hexadecanol and 15-20 parts of benzhydrol.
3. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 2, characterized in that: The preparation method of the multilayer polyethylene microporous body-based corrugated board is as follows: polyethylene, hexadecanol and benzhydrol are first mixed, and then the mixture is added to a screw extruder for melt mixing, the melting temperature is 120-140°C, and then extruded, cooled and solidified, and finally the product is immersed in ethanol for 20-30 hours, and finally transferred to deionized water at 90-100°C for heat treatment for 60-100 minutes to obtain the polyethylene microporous body-based corrugated board.
4. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 2, characterized in that: The polyethylene microporous body-based corrugated board is treated with O2 and N2 plasma.
5. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 4, characterized in that: The specific steps of the plasma treatment are: first, immerse the polyethylene microporous body-based corrugated plate in ethanol for ultrasonic cleaning to remove impurities, then transfer the polyethylene microporous body-based corrugated plate to the center of the sample processing chamber of the low-temperature plasma modification equipment, the plasma equipment model is PG-3000K, and then O2 and N2 are introduced in sequence, during which the equipment is turned on to excite plasma, and finally a plasma-treated polyethylene microporous body-based corrugated plate is obtained.
6. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 5, characterized in that: During the plasma treatment, the O2 parameters were: power 1000 W, time 10 s, flow rate 1.5 L / min; the N2 parameters were: power 800 W, time 15 s, flow rate 2.5 L / min.
7. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 1, characterized in that: The distillation tower, the high oxygen tower one and the high oxygen tower two are all provided with condensers, and the cold sources of the condensers of the high oxygen tower one and the high oxygen tower two are provided by the liquid nitrogen in the condensers of the distillation tower; The distillation tower, high oxygen tower 1 and high oxygen tower 2 are all provided with evaporators, and the heat sources of the evaporators of the high oxygen tower 1 and high oxygen tower 2 are provided by the nitrogen in the evaporators of the distillation tower.
8. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 1, characterized in that: The liquid-to-gas ratio in the high oxygen tower 1 is 0.5-0.7; the liquid-to-gas ratio in the high oxygen tower 2 is 1.3-1.
4.
9. The high-purity liquid oxygen cryogenic distillation extraction process according to claim 1, characterized in that: The polyethylene microporous body-based corrugated plates are stacked, the channels of the packing unit plates of the odd-numbered layers are in the same direction, the channels of the packing unit plates of the even-numbered layers are in the same direction, an angle is set between the channels of the odd-numbered layers and the even-numbered layers, and the angle of the angle is 30°-170°; there is a corrugation inclination angle between the parallel direction of the corrugation and the vertical direction of the packing disk, and the angle of the corrugation inclination angle is 15°-85°, and the corrugation inclination angles of adjacent polyethylene microporous body-based corrugated plates are the same and in opposite directions.