A gas purification method

Abstract

The present invention provides a gas purification method, belonging to the field of purification technology. The gas purification method provided by the present invention comprises the following steps: using a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated to obtain a purified gas; the preparation method of the recrystallized silicon carbide gas filtration membrane comprises the following steps: mixing silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and performing kneading treatment to obtain a kneaded material; successively extruding, drying and degumming the kneaded material to obtain a degummed blank; performing sintering-coating treatment on the degummed blank to obtain the recrystallized silicon carbide gas filtration membrane. The present invention uses a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated, which is acid and alkali resistant and high temperature resistant, and is convenient for directly purifying corrosive high temperature gases.

Description

Technical Field

[0001] The present invention relates to the field of purification technologies, and particularly to a gas purification method. Background Art

[0002] With the development of industry, gases generated in many production processes contain certain toxic and harmful components, and the gases need to be purified for subsequent processes or emissions. Using a filtration membrane to purify gases is convenient to operate and has a wide application range.

[0003] Currently, the filtration membranes used for gas purification are mainly organic polymer gas filtration membranes, such as polytetrafluoroethylene (PTFE) membranes or polyvinylidene fluoride (PVDF) membranes. Organic polymer gas filtration membranes have good acid and alkali resistance but are not resistant to high temperatures. Usually, the gas needs to be rapidly cooled before treatment, wasting energy. Summary of the Invention

[0004] The purpose of the present invention is to provide a gas purification method. The present invention uses a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated, which is acid and alkali resistant and high temperature resistant, facilitating the direct purification of corrosive high-temperature gases.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a gas purification method, including the following steps:

[0007] Using a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated to obtain a purified gas;

[0008] The preparation method of the recrystallized silicon carbide gas filtration membrane includes the following steps:

[0009] Mixing silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and performing kneading treatment to obtain a kneaded material;

[0010] Successively extruding, drying and degumming the kneaded material to obtain a degummed blank;

[0011] Performing sintering-coating treatment on the degummed blank to obtain the recrystallized silicon carbide gas filtration membrane.

[0012] Preferably, the recrystallized silicon carbide gas filtration membrane is a single-channel tubular membrane or a multi-channel tubular membrane; the inner diameter of the single-channel tubular membrane is 15 - 25 mm, the outer diameter is 30 - 40 mm, and the length is 1000 - 1500 mm; the inner diameter of each channel of the multi-channel tubular membrane is 2 - 25 mm, and the length of the multi-channel tubular membrane is 1000 - 1500 mm.

[0013] Preferably, the pH value of the gas to be treated is 0 to 14, the temperature is room temperature to 800 °C, and the volume content of impurities is ≤ 5%.

[0014] Preferably, the gas to be treated includes nitrogen and ammonia. The pH value of the gas to be treated is 11.5 to 12.5, the temperature is 50 to 60 °C, and the volume content of impurities is 1 to 2.5%.

[0015] Preferably, the gas to be treated includes hydrogen chloride. The pH value of the gas to be treated is 3.5 to 4.5, the temperature is 300 to 350 °C, and the volume content of impurities is 1 to 5%.

[0016] Preferably, the purification conditions include: the flow rate of the gas to be treated is ≤ 30 m / s, the pressure is ≤ 1 kPa, the ambient temperature is ≤ 50 °C, and the relative humidity is ≤ 45%.

[0017] Preferably, the mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water is 70:8 - 10:3 - 5:5 - 7:1 - 3:8 - 10.

[0018] Preferably, the temperature of the kneading treatment is 15 to 35 °C, the time is 6 to 10 h, and the rotation speed is 15 to 45 rpm; the temperature of the degumming treatment is 115 to 125 °C, and the time is 2 to 4 h.

[0019] Preferably, the sintering - coating treatment includes sintering and coating treatments carried out in sequence, and the number of times of the sintering - coating treatment is 3 to 4 times.

[0020] Preferably, the temperature of each sintering is independently 2400 to 2500 °C, and the heat preservation time of each sintering is independently 3 to 5 h;

[0021] Each coating treatment uses a coating reagent including silicon carbide, cellulose, dextran, vegetable oil, glycerol and water. The mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water in the coating reagent is independently 70:8 - 10:3 - 5:5 - 7:1 - 3:8 - 10; each coating treatment is independently carried out under the condition of a pressure of 0.0005 to 0.0015 MPa.

[0022] The present invention provides a gas purification method, which includes the following steps: using a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated to obtain a purified gas; the preparation method of the recrystallized silicon carbide gas filtration membrane includes the following steps: mixing silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and performing kneading treatment to obtain a kneaded material; successively extruding, drying and degumming the kneaded material to obtain a degummed blank; performing sintering-coating treatment on the degummed blank to obtain the recrystallized silicon carbide gas filtration membrane. The present invention uses a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated, which is acid and alkali resistant and high temperature resistant, and is convenient for directly purifying corrosive high temperature gases.

[0023] Furthermore, the organic polymer gas filtration membrane has a high damage rate, a short service life, is prone to causing secondary pollution, and the quality of the purified gas is unstable. In the present invention, the recrystallized silicon carbide gas filtration membrane has a long service life, no secondary pollution, and the quality of the purified gas is stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of the recrystallized silicon carbide gas filtration membrane in the embodiment of the present invention;

[0025] Figure 2 It is a physical diagram of the recrystallized silicon carbide gas filtration membrane used in Application Example 1;

[0026] Figure 3 It is a physical diagram of the recrystallized silicon carbide gas filtration membrane used in Application Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention provides a gas purification method, which includes the following steps:

[0028] Using a recrystallized silicon carbide gas filtration membrane to purify the gas to be treated to obtain a purified gas;

[0029] The preparation method of the recrystallized silicon carbide gas filtration membrane includes the following steps:

[0030] Mixing silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and performing kneading treatment to obtain a kneaded material;

[0031] Successively extruding, drying and degumming the kneaded material to obtain a degummed blank;

[0032] Performing sintering-coating treatment on the degummed blank to obtain the recrystallized silicon carbide gas filtration membrane.

[0033] The present invention uses a recrystallized silicon carbide gas filtration membrane to purify gases. It is acid and alkali resistant and high temperature resistant, facilitating the direct purification of corrosive high-temperature gases and having excellent purification effects. First, the recrystallized silicon carbide gas filtration membrane of the present invention will be described in detail below.

[0034] As an embodiment of the present invention, the recrystallized silicon carbide gas filtration membrane can be a single-channel tubular membrane or a multi-channel tubular membrane; the inner diameter of the single-channel tubular membrane can be 15-25 mm, specifically 21 mm; the outer diameter can be 30-40 mm, specifically 35 mm; the length can be 1000-1500 mm, specifically 1200 mm; the number of channels of the multi-channel tubular membrane can be customized according to customer requirements. For example, the number of channels of the multi-channel tubular membrane can be 19 holes, and the inner diameter of each channel can be 2-25 mm, specifically 2 mm, 4 mm, 21 mm or 25 mm; the length of the multi-channel tubular membrane can be 1000-1500 mm, specifically 1200 mm; the specific dimensions of the recrystallized silicon carbide gas filtration membrane can be customized according to actual needs.

[0035] As an embodiment of the present invention, the preparation method of the recrystallized silicon carbide gas filtration membrane includes the following steps:

[0036] Mix silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and perform kneading treatment to obtain a kneaded material;

[0037] Extrude, dry and degum the kneaded material in sequence to obtain a degummed blank;

[0038] Perform sintering-coating treatment on the degummed blank to obtain the recrystallized silicon carbide gas filtration membrane.

[0039] In the present invention, unless otherwise specified, the raw materials used are commercially available products well-known to those skilled in the art or are prepared by methods well-known to those skilled in the art.

[0040] The present invention mixes silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and performs kneading treatment to obtain a kneaded material. As an embodiment of the present invention, the mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water can be 70:8-10:3-5:5-7:1-3:8-10, specifically 70:9:6:2:9. In the embodiments of the present invention, the purity of the silicon carbide is 99.8 wt%, the particle size of the silicon carbide is 0.7-1.2 μm, and the silicon carbide with a particle size of ≥1 μm accounts for more than 50% of the total mass of the silicon carbide; the glycerol is food-grade glycerol with a purity of 98%; the dextran is dextran xt300; the water is pure water. In the present invention, silicon carbide is used as a matrix material to construct the main body of the gas filtration membrane. Using silicon carbide with the above dosage and particle size is beneficial to improving the strength of the gas filtration membrane and the membrane body throughput (i.e., membrane flux). In the present invention, glycerol and dextran are used as binders. Using the above dosage of glycerol and dextran in combination can fill the gaps between silicon carbide particles, bond the silicon carbide particles together, ensure the smooth progress of extrusion and subsequent processes, and finally prepare a gas filtration membrane with excellent performance. In the present invention, cellulose can form a binding force to ensure that the membrane body will not be loose or cracked. In the present invention, vegetable oil and water are used as dispersants to make each raw material disperse and mix evenly, facilitating the preparation of a gas filtration membrane with excellent homogeneity.

[0041] As an embodiment of the present invention, the mixing method of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water can be: mixing silicon carbide, cellulose and dextran, and mixing the obtained mixed material with water, vegetable oil and glycerol. As an embodiment of the present invention, the temperature of the kneading treatment can be 15-35 °C, specifically 15 °C, 20 °C, 25 °C, 30 °C or 35 °C; the time can be 6-10 h, specifically 6 h, 7 h, 8 h, 9 h or 10 h; the rotation speed can be 15-45 rpm, specifically 15 rpm, 20 rpm, 25 rpm, 30 rpm, 35 rpm, 40 rpm or 45 rpm. In the embodiments of the present invention, the kneading treatment is specifically carried out in a kneader. In the embodiments of the present invention, mixing and kneading treatment are carried out under the above conditions, which is beneficial to obtaining a kneaded material with uniform texture and stable performance.

[0042] After obtaining the kneaded material, the present invention successively extrudes, dries, and degums the kneaded material to obtain a degummed green body. The present invention performs extrusion molding according to the specific shape of the recrystallized silicon carbide gas filtration membrane to obtain a green body; for example, when the recrystallized silicon carbide gas filtration membrane is a single-channel tubular membrane, a single-channel tubular membrane green body is obtained through extrusion molding; the present invention has no special limitation on the operating conditions of the extrusion molding, and the conditions well-known to those skilled in the art can be adopted. In the embodiments of the present invention, the extrusion molding is specifically carried out in an extruder. The present invention adopts wet material extrusion molding, which has at least the following advantages: 1. Production continuity and high efficiency: Wet material extrusion molding can achieve continuous production, greatly improving production efficiency; 2. Wide applicability: By replacing the mold, different models of filtration membranes and customized membranes can be extruded; 3. Simple equipment and less investment: Compared with injection molding machines and calendering machines, the equipment structure of wet material extrusion molding is simple, with less investment, convenient installation and commissioning, small floor area, and lower requirements for workshops and supporting facilities, etc.

[0043] After obtaining the green body, the present invention dries the green body to obtain a dried green body. The present invention has no special limitation on the drying, as long as the moisture in the green body can be removed. In the embodiments of the present invention, the drying is specifically carried out in an oven.

[0044] After obtaining the dried green body, the present invention degums the dried green body to obtain a degummed green body. As an embodiment of the present invention, the temperature of the degumming can be 115-125°C, specifically 115°C, 118°C, 120°C, 122°C, or 125°C; the time can be 2-4 h, specifically 2 h, 2.5 h, 3 h, 3.5 h, or 4 h. Degumming is carried out under the above conditions in the embodiments of the present invention, which can effectively remove vegetable oil and glycerol, and finally prepare a gas filtration membrane with excellent performance.

[0045] After obtaining the degummed green body, the present invention performs sintering-coating treatment on the degummed green body to obtain the recrystallized silicon carbide gas filtration membrane. As an embodiment of the present invention, the sintering-coating treatment includes successively performing sintering and coating treatment, and the number of times of the sintering-coating treatment is 3-4 times.

[0046] As an embodiment of the present invention, the temperature of each sintering can be independently 2400 - 2500 °C, specifically it can be 2410 °C, 2420 °C, 2430 °C, 2440 °C, 2450 °C, 2460 °C, 2470 °C, 2480 °C, 2490 °C or 2500 °C; the heat preservation time of each sintering can be independently 3 - 5 h, specifically it can be 3 h, 3.5 h, 4 h, 4.5 h or 5 h. As an embodiment of the present invention, taking the sintering temperature of 2450 °C as an example, the heating program for heating to the required sintering temperature can be: uniformly heating from room temperature to 200 °C in 30 min; uniformly heating from 200 °C to 900 °C in 60 min; uniformly heating from 900 °C to 1100 °C in 30 min; uniformly heating from 1100 °C to 2000 °C in 45 min; uniformly heating from 2000 °C to 2410 °C in 20 min; uniformly heating from 2410 °C to 2450 °C in 10 min. As an embodiment of the present invention, after each sintering, it further includes cooling, and the cooling can specifically be natural cooling, and the temperature after each cooling can specifically be room temperature.

[0047] As an embodiment of the present invention, the coating reagent used for each coating treatment can include silicon carbide, cellulose, dextran, vegetable oil, glycerol and water, and the mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water in the coating reagent can be independently 70:8 - 10:3 - 5:5 - 7:1 - 3:8 - 10, specifically it can be 70:9:6:2:9; each coating treatment can be independently carried out under the condition of a pressure of 0.0005 - 0.0015 MPa, specifically it can be 0.001 MPa.

[0048] Through sintering, the present invention can make silicon carbide recrystallize, and pore structures will be formed during the recrystallization process. Through the coating treatment, the pore diameter can be reduced; in the examples of the present invention, sintering and coating treatment are carried out under the above conditions, so that the recrystallized silicon carbide gas filtration membrane can have a suitable pore diameter and porosity, which is beneficial to ensuring a good purification effect on the gas while improving the purification efficiency.

[0049] After the sintering - coating treatment, the present invention preferably further includes detection, and the product is qualified after passing the detection. As an embodiment of the present invention, the specific detection requirements are as follows:

[0050] 1 General requirements and health and safety requirements

[0051] 1.1 Components should be made of non - toxic, harmless and non - radioactive materials.

[0052] 1.3 Components should comply with the "Hygienic and Safety Evaluation Specification for Drinking Water Distribution Equipment and Protective Materials".

[0053] 2 Appearance quality

[0054] The overall color of the component should be uniform, and there should be no cracks, pits, notches or peeling when observed with the naked eye. The cross-section should be flat.

[0055] 3 Requirements for external dimensions

[0056] 3.1 The allowable deviations of the component diameter and the inner diameter of the flow channel shall comply with the provisions of Table 1.

[0057] 3.2 The camber of the component shall comply with the provisions of Table 2.

[0058] 3.3 The allowable tolerance of the actual channel diameter of the component shall not be greater than 5% of the nominal channel diameter.

[0059] 3.4 The minimum length of the component is 200 mm, and the maximum length is 1500 mm.

[0060] Table 1 Allowable deviation of diameter

[0061]

[0062] Table 2 Camber

[0063]

[0064] 4 Performance requirements

[0065] 4.1 The pure water flux, overall bubble point pressure and membrane porosity of the component shall comply with the provisions of Table 3.

[0066] Table 3 Performance requirements

[0067]

[0068] 4.2 The flexural strength of the component shall comply with the provisions of Table 4.

[0069] Table 4 Flexural strength

[0070]

[0071] 4.3 The acid and alkali corrosion resistance of the component shall comply with the provisions of Table 5.

[0072] Table 5 Acid and alkali corrosion resistance

[0073]

[0074] 4.4 The defect rate of the component shall comply with the provisions of Table 6 (for all product specifications).

[0075] Table 6 Defect rate

[0076]

[0077] 4.5 The aperture range of the component shall comply with the provisions of Table 7.

[0078] Table 7 Aperture Range

[0079]

[0080] The recrystallized silicon carbide gas filtration membrane prepared by the method of the present invention has good thermal stability, and the service temperature can be higher than 400 °C, even up to 800 °C; it has good chemical stability, is resistant to acids and alkalis, and organic solvents, is applicable to a wide pH range, can be used in strongly corrosive media, and can be cleaned with chemical reagents; it has high mechanical strength and can be used under higher pressures; it has strong anti-microbial ability, does not interact with microorganisms, is non-toxic itself, and does not contaminate the separated system. Therefore, it has unique advantages in the food and biochemical fields.

[0081] After obtaining the recrystallized silicon carbide gas filtration membrane, the present invention uses the recrystallized silicon carbide gas filtration membrane to purify the gas to be treated, and obtains the purified gas.

[0082] As an embodiment of the present invention, the pH value of the gas to be treated can be 0-14, further can be 4-12, specifically can be 4, 5, 6, 7, 8, 9, 10, 11 or 12, that is, the recrystallized silicon carbide gas filtration membrane of the present invention can purify neutral gases, acidic gases, and alkaline gases. As an embodiment of the present invention, the temperature of the gas to be treated can be room temperature - 800 °C, further can be 30 - 650 °C, still further can be 50 - 350 °C, specifically can be 50 °C, 60 °C, 80 °C, 100 °C, 150 °C, 200 °C, 250 °C, 300 °C or 350 °C, that is, the recrystallized silicon carbide gas filtration membrane of the present invention can purify room temperature gases and high temperature gases. As an embodiment of the present invention, the volume content of impurities in the gas to be treated ≤ 5%, further can be 1 - 5%, specifically can be 1%, 2%, 3%, 4% or 5%. As an embodiment of the present invention, the gas to be treated can be a single gas or a mixed gas, and can be processed according to actual needs.

[0083] As an embodiment of the present invention, the gas to be treated can include nitrogen and ammonia, the pH value of the gas to be treated can be 11.5 - 12.5 (specifically can be 12), the temperature can be 50 - 60 °C, and the volume content of impurities can be 1 - 2.5%, specifically can be 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2% or 2.5%.

[0084] As an embodiment of the present invention, the pH value of the gas to be treated can be 3.5 to 4.5 (specifically, it can be 4), the temperature can be 300 to 350 °C, and the volume content of impurities can be 1 to 5%, specifically, it can be 1%, 1.2%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0085] As an embodiment of the present invention, the purification conditions can include: the flow rate of the gas to be treated ≤ 30 m / s, further it can be 15 to 30 m / s, specifically, it can be 15 m / s, 20 m / s, 25 m / s or 30 m / s; the pressure ≤ 1 kPa, further it can be 0.45 to 1 kPa, specifically, it can be 0.45 kPa, 0.6 kPa, 0.8 kPa or 1 kPa; the ambient temperature ≤ 50 °C, further it can be 25 to 40 °C, specifically, it can be 25 °C, 30 °C, 35 °C or 40 °C; the relative humidity ≤ 45%, further it can be 30 to 45%, specifically, it can be 30%, 35%, 40% or 45%.

[0086] As an embodiment of the present invention, the volume content of impurities in the purified gas can ≤ 0.5%, further it can be 0.1 to 0.5%, specifically, it can be 0.1%, 0.2%, 0.3%, 0.4% or 0.5%.

[0087] The recrystallized silicon carbide gas filtration membrane prepared by the method of the present invention has appropriate pore size and porosity. In addition to meeting the requirements of purification accuracy, pressure and flux, its working temperature can be increased to 800 °C, filling the shortcoming that other filtration media are not resistant to high temperature. It can be used in the purification of acidic or alkaline gases without the risk of secondary pollution of other media. Due to the high hardness and corrosion resistance of recrystallized silicon carbide, the service life of the recrystallized silicon carbide gas filtration membrane is greatly improved, the maintenance cycle is extended, and the operation cost is reduced.

[0088] Figure 1 This is the flow chart of the recrystallized silicon carbide gas filtration membrane in the embodiments of the present invention. Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the embodiments in the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0089] The purity of the silicon carbide used in the following experiments is 99.8%, the particle size of the silicon carbide is 0.7 - 1.2 μm, where the silicon carbide with a particle size of ≥1 μm accounts for more than 50% of the total amount of the silicon carbide, and the silicon carbide powder comes from Shenyang Changxin New Materials Co., Ltd.; the glycerol used is food-grade glycerol with a purity of 98%; the dextran used is dextran xt300; the water used is purified water.

[0090] Example 1

[0091] Mix silicon carbide, cellulose and dextran, and place the obtained mixed material together with water, vegetable oil and glycerol in a kneader, and perform kneading treatment for 6 h at room temperature with a stirring speed of 30 rpm to obtain a kneaded material; where the mass ratio of the silicon carbide, cellulose, dextran, vegetable oil, glycerol and water is 70:9:4:6:2:9;

[0092] Place the kneaded material in an extruder for extrusion to obtain a single-channel tubular membrane blank;

[0093] Place the single-channel tubular membrane blank in an oven for drying to remove moisture, and obtain a dried single-channel tubular membrane blank;

[0094] Place the dried single-channel tubular membrane blank in a degumming furnace, and perform degumming at 120 °C for 3 h to remove vegetable oil and glycerol, and obtain a degummed single-channel tubular membrane blank;

[0095] Place the degummed single-channel tubular membrane blank in a vacuum induction sintering furnace, and uniformly heat from room temperature to 200 °C at a constant speed in 30 min, uniformly heat from 200 °C to 900 °C at a constant speed in 60 min, uniformly heat from 900 °C to 1100 °C at a constant speed in 30 min, uniformly heat from 1100 °C to 2000 °C at a constant speed in 45 min, uniformly heat from 2000 °C to 2410 °C at a constant speed in 20 min, uniformly heat from 2410 °C to 2450 °C at a constant speed in 10 min, perform sintering at 2450 °C for 4 h, and then naturally cool to room temperature to obtain a sintered single-channel tubular membrane blank; under the pressure condition of 0.001 MPa, use a coating machine to perform coating treatment on the inner wall of the sintered single-channel tubular membrane blank to obtain a coated single-channel tubular membrane blank; where the coating reagent used for the coating treatment is a mixed material with a mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water of 70:9:4:6:2:9; then sequentially repeat the sintering-coating treatment process, and perform the sintering-coating treatment process 3 times in total to obtain a recrystallized silicon carbide gas filtration membrane (specifically a single-channel tubular membrane), and then use a bubble press and a flux machine for detection (detect according to the aforementioned detection requirements 1 - 4, which will not be elaborated here), and the qualified products are stored in the finished product warehouse; where the length of the recrystallized silicon carbide gas filtration membrane is 80 mm, the inner diameter is 21 mm, and the outer diameter is 35 mm.

[0096] Example 2

[0097] The recrystallized silicon carbide gas filtration membrane was prepared by referring to the method of Example 1, except that the size of the recrystallized silicon carbide gas filtration membrane was different. In this example, the length of the recrystallized silicon carbide gas filtration membrane was 1200 mm, the inner diameter was 21 mm, and the outer diameter was 35 mm.

[0098] Application Example 1

[0099] The recrystallized silicon carbide gas filtration membrane was prepared according to the method of Example 1. The physical diagram is as Figure 2 shown. Its length was 80 mm, the inner diameter was 21 mm, and the outer diameter was 35 mm. The above-mentioned recrystallized silicon carbide gas filtration membrane was used to purify the alkaline mixed gas to be treated of Wuhan Zhisheng Environmental Protection Technology Co., Ltd. to obtain a purified alkaline mixed gas. Among them, the pH value of the alkaline mixed gas to be treated was 12, the temperature was 50 - 60 °C, the main components were nitrogen and ammonia, and it also contained impurities such as dust, and the volume content of the impurities was 2.5%. The purification conditions included: the flow rate of the alkaline mixed gas to be treated was 15 m / s, the pressure was 0.45 kPa, the ambient temperature was 25 °C, and the relative humidity was 35%. The volume content of the impurities in the purified alkaline mixed gas was 0.5%. It shows that the recrystallized silicon carbide gas filtration membrane prepared by the present invention can realize the purification of the alkaline mixed gas to be treated.

[0100] Application Example 2

[0101] The recrystallized silicon carbide gas filtration membrane was prepared according to the method of Example 2. The physical diagram is as Figure 3 shown. Its length was 1200 mm, the inner diameter was 21 mm, and the outer diameter was 35 mm. The above-mentioned recrystallized silicon carbide gas filtration membrane was used to purify the acidic gas to be treated of Sichuan Sidaneng Environmental Protection Technology Co., Ltd. to obtain a purified acidic gas. Among them, the pH value of the acidic gas to be treated was 4, the temperature was 300 - 350 °C, the main component was hydrogen chloride, and it also contained impurities such as dust, and the volume content of the impurities was 1%. The purification conditions included: the flow rate of the acidic gas to be treated was 25 m / s, the pressure was 1 kPa, the ambient temperature was 40 °C, and the relative humidity was 40%. The mass content of the impurities in the purified acidic gas was 0.3%. It shows that the recrystallized silicon carbide gas filtration membrane prepared by the present invention can realize the purification of the acidic gas to be treated.

[0102] As can be seen from the above results, the recrystallized silicon carbide gas filtration membrane of the present invention is used to purify the gas to be treated, which has stronger acid and alkali corrosion resistance and can be widely used for the purification of special gases such as acidic gases or alkaline gases. At the same time, the recrystallized silicon carbide gas filtration membrane has the characteristic of high temperature resistance. When purifying the high temperature gas in the special industry, it is not necessary to pre-cool in advance, and the high temperature treatment can be directly purified. Moreover, the Mohs hardness of silicon carbide is as high as 9.2-9.5, second only to diamond, and it is one of the very hard substances in nature. Its superior hardness can ensure a long service life on the basis of a good purification effect, reducing the operating cost.

[0103] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A gas purification method, characterized in that: The following steps are involved: A recrystallized silicon carbide gas filter membrane is used to purify the gas to be treated to obtain a purified gas; the pH value of the gas to be treated is 0-5 or 9-14, and the temperature is 50-800°C; the purification conditions include: the flow rate of the gas to be treated is ≤30m / s, the pressure is ≤1kPa, the ambient temperature is ≤50°C, and the relative humidity is ≤45%; The method for preparing the recrystallized silicon carbide gas filtration membrane comprises the following steps: Silicon carbide, cellulose, dextran, vegetable oil, glycerol and water are mixed and kneaded to obtain a kneaded material; The kneaded material is sequentially subjected to extrusion molding, drying and degumming to obtain a degummed green body; The degummed green body is subjected to sintering-coating treatment to obtain the recrystallized silicon carbide gas filtration membrane; The sintering-coating treatment includes sintering and coating treatment in sequence, and the number of sintering-coating treatments is 3 to 4 times; the sintering temperature each time is independently 2450 to 2500°C, and the insulation time each time is independently 3 to 4 hours; the coating reagents used in each coating treatment include silicon carbide, cellulose, dextran, vegetable oil, glycerol and water.

2. The gas purification method according to claim 1, characterized in that: The recrystallized silicon carbide gas filtration membrane is a single-channel tubular membrane or a multi-channel tubular membrane; the inner diameter of the single-channel tubular membrane is 15-25 mm, the outer diameter is 30-40 mm, and the length is 1000-1500 mm; the inner diameter of each channel in the multi-channel tubular membrane is 2-25 mm, and the length of the multi-channel tubular membrane is 1000-1500 mm.

3. The gas purification method according to claim 1, characterized in that: The volume content of impurities in the gas to be treated is ≤5%.

4. The gas purification method according to claim 3, characterized in that: The gas to be treated includes nitrogen and ammonia, the pH value of the gas to be treated is 11.5-12.5, the temperature is 50-60° C., and the volume content of impurities is 1-2.5%.

5. The gas purification method according to claim 3, characterized in that: The gas to be treated includes hydrogen chloride, the pH value of the gas to be treated is 3.5-4.5, the temperature is 300-350° C., and the volume content of impurities is 1-5%.

6. The gas purification method according to claim 1, characterized in that: The mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water is 70:8-10:3-5:5-7:1-3:8-10.

7. The gas purification method according to claim 1 or 6, characterized in that: The kneading treatment is performed at a temperature of 15-35° C., a time of 6-10 hours, and a rotation speed of 15-45 rpm; the degumming treatment is performed at a temperature of 115-125° C., and a time of 2-4 hours.

8. The gas purification method according to claim 1, characterized in that: The mass ratio of silicon carbide, cellulose, dextran, vegetable oil, glycerol and water in the coating reagent used for each coating treatment is independently 70:8~10:3~5:5~7:1~3:8~10; and each coating treatment is independently carried out under a pressure of 0.0005~0.0015MPa.

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