A method for cleaning ceramic membrane and its application

Abstract

The present invention provides a cleaning method and application of a ceramic membrane, belonging to the technical field of water treatment, wherein the cleaning method comprises the following steps: (1) preparing a cleaning agent: the cleaning agent comprises the following components by mass: 20-25 parts of formic acid, 16-21 parts of phytic acid aqueous solution, 4-8 parts of citric acid, 9-14 parts of glycolic acid, 2-5 parts of softener, 3-6 parts of surfactant, 15-20 parts of isopropanol, and 40-45 parts of water; (2) preparing a solution of the cleaning agent, heating the solution to 25-30°C, performing non-permeation cycle cleaning, permeation cycle cleaning, and stopping cleaning; (3) inputting ozone into the system from the water production end of the ceramic membrane system in reverse, draining the ozone, rinsing with water until the drainage is neutral, and the cleaning process ends. The cleaning method of the present invention has a good cleaning effect on the ceramic membrane for treating cold rolling oily wastewater and the ceramic membrane for treating oilfield wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a ceramic membrane cleaning method and application thereof. Background Art

[0002] In the water treatment process, ceramic membranes are widely used in various filtration scenarios due to their high temperature resistance, corrosion resistance, high mechanical strength and long service life. However, over time, ceramic membranes may be contaminated, resulting in decreased membrane flux and deterioration of separation performance. Therefore, regular cleaning of ceramic membranes is essential to maintain their efficiency and extend their service life.

[0003] Ceramic membrane treatment of oily wastewater from cold rolling is a very effective technology in the field of modern industrial wastewater treatment, especially in the steel industry. Oily wastewater generated during cold rolling is quite difficult to treat due to its high organic content, complex chemical composition and high oil content. Ceramic membranes are ideal for treating this type of wastewater due to their unique properties, such as high temperature resistance, corrosion resistance, wear resistance and high porosity.

[0004] Some oil fields in my country are in the middle and late stages of development. A large amount of produced water needs to be treated. The produced water has complex and variable components, often containing a large amount of emulsified oil or hydrocarbons, soluble organic matter, solid particles, inorganic ions, bacteria, etc. It is difficult to separate them using general physical or chemical methods, and it is difficult to meet the requirements of discharge water quality and reinjection water. The pollutants on the membrane surface can be divided into two layers: the dirt layer and the gel layer. Ceramic membrane treatment of oilfield wastewater is an advanced wastewater treatment technology, especially suitable for treating oilfield wastewater containing high concentrations of oil, suspended matter, soluble organic matter and inorganic salts.

[0005] At present, most ceramic membrane cleaning agents on the market have the problems of single use field, incomplete cleaning, difficulty in penetrating into the membrane pores, low flux recovery rate of ceramic membranes, and unsatisfactory cleaning effect. The Chinese invention patent with application number 202111096888.X discloses a ceramic membrane cleaning agent, which is composed of ozone and liquid enhancer, and has a good cleaning effect on deposited stubborn scale. However, the cleaning agent of this patent cannot simultaneously have a good cleaning effect on ceramic membranes for treating cold-rolled oily wastewater and ceramic membranes after treating oilfield wastewater.

[0006] Therefore, there is an urgent need for a ceramic membrane cleaning method with good cleaning effect and lower cost. Summary of the invention

[0007] The purpose of the present invention is to provide a ceramic membrane cleaning method and application thereof.

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for cleaning a ceramic membrane, the cleaning method comprising the following steps:

[0010] (1) Preparation of cleaning agent: The cleaning agent comprises the following components in parts by weight: 20-25 parts of formic acid, 16-21 parts of phytic acid aqueous solution, 4-8 parts of citric acid, 9-14 parts of glycolic acid, 2-5 parts of softener, 3-6 parts of surfactant, 15-20 parts of isopropyl alcohol, and 40-45 parts of water; the surfactant comprises a non-ionic surfactant, cocoamidopropyl betaine, and a zwitterionic surfactant in a mass ratio of 1: (1.3-1.6): (0.5-0.8):

[0011] (2) Prepare a cleaning agent solution and heat it to 25-30°C. Perform non-permeation cycle cleaning for 3-5 minutes, permeation cycle cleaning for 2-3 minutes, and then stop cleaning.

[0012] (3) Reversely input ozone into the system from the water production end of the ceramic membrane system; utilize the microporous structure of the ceramic membrane to allow ozone to pass through the membrane pores and form nano-scale bubbles in the membrane tube. Input ozone for 10-15 minutes, drain the ozone, rinse with water until the drainage is neutral, and the cleaning process is completed.

[0013] In the prior art, inorganic acids, such as hydrochloric acid or nitric acid, are added to the cleaning agent, which is not only highly corrosive to the pipeline, but also has an unsatisfactory cleaning effect on the permeable membrane for treating cold-rolled oily wastewater. The present invention reduces the corrosiveness to the pipeline by compounding formic acid, phytic acid aqueous solution, citric acid, and glycolic acid in a specific ratio, and at the same time improves the cleaning effect on the permeable membrane for treating cold-rolled oily wastewater. These acids have different mechanisms of action and can work synergistically to effectively remove various pollutants on the membrane. Formic acid and glycolic acid can act together on organic matter and inorganic salt scale, while phytic acid aqueous solution and citric acid focus on the control of metal ions and biofilms. This multi-acid mixture can comprehensively cover various types of pollution that may occur in the process of treating cold-rolled oily wastewater, improve cleaning efficiency, and restore the flux and selectivity of the membrane. However, under this condition, the cleaning effect of the ceramic membrane after treating oilfield sewage is unsatisfactory.

[0014] Furthermore, in step 2, the cleaning agent is prepared into an aqueous solution with a mass concentration of 0.2-5%.

[0015] Furthermore, the preparation method of the zwitterionic surfactant is:

[0016] S1: dissolving 13-15 parts by weight of 4-amino-3-hydroxybenzoic acid and 18-20 parts by weight of a three-membered cyclic chlorine-containing compound in 50 parts by weight of ethanol, adding 4-6 parts by weight of a 0.1-0.3 mol / L aqueous solution of sodium hydroxide, heating to 82-85° C., reacting for 10-15 hours, to obtain an intermediate product;

[0017] S2: Mix the intermediate product, 50-55 parts by weight of hexadecyldimethyl tertiary amine, 80-85 parts by weight of ethanol and 60-65 parts by weight of water, heat to 82-85° C., react for 25-30 hours, and remove the ethanol by rotary evaporation to obtain a zwitterionic surfactant.

[0018] Furthermore, the three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin, and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of (1.5-1.7):1:(0.3-0.6).

[0019] Furthermore, in parts by mass, the preparation method of the nonionic surfactant is:

[0020] S1: Add 150-155 parts of mixed alcohol and 4-6 parts of potassium hydroxide to a stainless steel reactor, maintain the temperature at 32-35°C, evacuate the reactor, raise the temperature to 112-115°C, add 1720-1750 parts of alkylene oxide, add it within 7-9 hours, control the pressure at 0.1-0.3MPa, the temperature at 110-115°C, react for 3-5 hours, and obtain polyether polyol;

[0021] S2: Add 900-920 parts of polyether polyol and 1200-1230 parts of glycerol into a stainless steel reactor. After nitrogen substitution, heat the reactor to 140-145°C and pressurize the reactor to 0.2-0.3MPa. When the pressure in the reactor drops, control the temperature to 110-113°C and the pressure to 0.3-0.4MPa. React for 6-8h to obtain a nonionic surfactant.

[0022] Furthermore, the alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of (1.3-1.6):1:(0.2-0.5).

[0023] Furthermore, the mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of (0.3-0.5):(1.5-1.7):1.

[0024] In order to improve the cleaning effect of ceramic membrane after treating oilfield sewage, the present invention attempts to add commercially available surfactants to the cleaning agent, but the effect is not ideal. The surfactant obtained by mixing nonionic surfactant, cocoamidopropyl betaine and zwitterionic surfactant can improve the cleaning effect of ceramic membrane after treating oilfield sewage. Nonionic surfactants retain part of the hydroxyl group and have repeated alkane groups, which can emulsify oil pollutants, reduce the oil-water interfacial tension, and make it easier for oil droplets to detach from the membrane surface and disperse in the cleaning solution. Zwitterionic surfactants contain both positive and negative charges, which can neutralize the charges on the membrane surface or pollutants, reduce the pollution caused by charge attraction, and large steric hindered space groups can prevent pollutants from being re-adsorbed on the membrane surface, reducing secondary pollution. Cocoamidopropyl betaine can produce stable foam, which helps the cleaning agent to better contact and decompose pollutants. Cocoamidopropyl betaine has certain antibacterial properties, and glycolic acid contains a special structure of hydroxyl and carboxyl groups, which has a significant inhibitory effect on the growth of iron-oxidizing bacteria and can be used as a bactericide. Microbial contamination on the membrane surface can be reduced. When these three surfactants are used in combination, the synergistic effect between them can further enhance the cleaning effect. When nonionic surfactants, cocamidopropyl betaine and zwitterionic surfactants are mixed in a specific ratio, the storage stability of the cleaning agent can be improved.

[0025] Furthermore, the concentration of the phytic acid aqueous solution is 60-70% by mass.

[0026] Furthermore, the softener is selected from one or more of methyl cellulose, hydroxyethyl cellulose and sodium carboxymethyl cellulose.

[0027] Furthermore, the softener is a mixture of methyl cellulose, hydroxyethyl cellulose and sodium carboxymethyl cellulose in a mass ratio of (1.5-1.8):1:(0.3-0.5).

[0028] Furthermore, ozone flow rate: 0.2-0.3L / min, ozone pressure 0.1-0.3Mpa.

[0029] The invention also provides an application of a ceramic membrane cleaning method.

[0030] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0031] 1. The present invention provides a method for cleaning a ceramic membrane, which has a good cleaning effect on ceramic membranes used to treat cold-rolled oily wastewater and ceramic membranes used to treat oilfield wastewater.

[0032] 2. The present invention reduces the corrosion to the pipeline by compounding formic acid, phytic acid aqueous solution, citric acid and glycolic acid in specific proportions, and at the same time improves the cleaning effect of the permeable membrane for treating cold rolling oily wastewater.

[0033] 3. The surfactant obtained by mixing the nonionic surfactant, cocoamidopropyl betaine and the zwitterionic surfactant in the present invention can improve the cleaning effect of the ceramic membrane after treating oilfield wastewater.

[0034] 4. When nonionic surfactants, cocoamidopropyl betaine and zwitterionic surfactants are mixed in a specific proportion, the storage stability of the cleaning agent can be improved. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] This embodiment provides a method for cleaning a ceramic membrane, the cleaning method comprising the following steps:

[0038] (1) Preparation of a cleaning agent: The cleaning agent comprises the following components in parts by weight: 23 parts of formic acid, 18 parts of phytic acid aqueous solution, 6 parts of citric acid, 12 parts of glycolic acid, 3 parts of softener, 5 parts of surfactant, 17 parts of isopropyl alcohol, and 42 parts of water; the surfactant comprises a non-ionic surfactant, cocoamidopropyl betaine, and a zwitterionic surfactant in a mass ratio of 1:1.5:0.6; the softener is a mixture of methyl cellulose, hydroxyethyl cellulose, and sodium carboxymethyl cellulose in a mass ratio of 1.7:1:0.4; the concentration of the phytic acid aqueous solution is 65% by mass.

[0039] (2) Prepare a 1% aqueous solution of the cleaning agent and heat it to 27°C. Perform non-permeation cycle cleaning for 4 minutes and permeation cycle cleaning for 3 minutes, then stop cleaning.

[0040] (3) Reversely input ozone into the system from the water production end of the ceramic membrane system; utilize the microporous structure of the ceramic membrane to allow ozone to pass through the membrane pores and form nano-scale bubbles in the membrane tube. Input ozone for 10 minutes, ozone flow rate: 0.2L / min, ozone pressure 0.3Mpa, drain the ozone, rinse with water until the drainage is neutral, and the cleaning process is completed.

[0041] The preparation method of the zwitterionic surfactant is:

[0042] S1: 14 parts by mass of 4-amino-3-hydroxybenzoic acid and 19 parts by mass of a three-membered cyclic chlorine-containing compound are dissolved in 50 parts by mass of ethanol, 5 parts by mass of a 0.2 mol / L aqueous solution of sodium hydroxide are added, and the mixture is heated to 84° C. and reacted for 12 hours to obtain an intermediate product;

[0043] S2: The intermediate product, 52 parts by mass of hexadecyldimethyl tertiary amine, 83 parts by mass of ethanol and 62 parts by mass of water were mixed, heated to 84° C., reacted for 28 hours, and the ethanol was removed by rotary evaporation to obtain a zwitterionic surfactant.

[0044] The three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of 1.6:1:0.5.

[0045] In parts by mass, the preparation method of the nonionic surfactant is:

[0046] S1: Add 152 parts of mixed alcohol and 5 parts of potassium hydroxide to a stainless steel reactor, keep the temperature at 33°C, evacuate the reactor, raise the temperature to 114°C, add 1740 parts of alkylene oxide, add it within 8 hours, control the pressure at 0.2MPa and the temperature at 112°C, react for 4 hours, and obtain polyether polyol;

[0047] S2: Add 910 parts of polyether polyol and 1215 parts of glycerol to a stainless steel reactor. After nitrogen substitution in the reactor, heat it to 142°C and pressurize the reactor to 0.2 MPa. When the pressure in the reactor drops, control the temperature to 112°C and the pressure to 0.3 MPa. React for 7 hours to obtain a nonionic surfactant.

[0048] The alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of 1.5:1:0.4.

[0049] The mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of 0.4:1.6:1.

[0050] Example 2

[0051] This embodiment provides a method for cleaning a ceramic membrane, the cleaning method comprising the following steps:

[0052] (1) Preparation of a cleaning agent: The cleaning agent comprises the following components in parts by weight: 20 parts of formic acid, 16 parts of phytic acid aqueous solution, 4 parts of citric acid, 9 parts of glycolic acid, 2 parts of a softener, 3 parts of a surfactant, 15 parts of isopropyl alcohol, and 40 parts of water; the surfactant comprises a non-ionic surfactant, cocoamidopropyl betaine, and a zwitterionic surfactant in a mass ratio of 1:1.3:0.5; the softener is a mixture of methyl cellulose, hydroxyethyl cellulose, and sodium carboxymethyl cellulose in a mass ratio of 1.5:1:0.3; the concentration of the phytic acid aqueous solution is 60% by mass.

[0053] (2) Prepare a 1% aqueous solution of the cleaning agent and heat it to 25°C. Perform non-permeation cycle cleaning for 3 minutes and permeation cycle cleaning for 2 minutes, then stop cleaning.

[0054] (3) Reversely input ozone into the system from the water production end of the ceramic membrane system; utilize the microporous structure of the ceramic membrane to allow ozone to pass through the membrane pores and form nano-scale bubbles in the membrane tube. Input ozone for 10 minutes, ozone flow rate: 0.2L / min, ozone pressure 0.1Mpa, drain the ozone, rinse with water until the drainage is neutral, and the cleaning process is completed.

[0055] The preparation method of the zwitterionic surfactant is:

[0056] S1: 13 parts by mass of 4-amino-3-hydroxybenzoic acid and 18 parts by mass of a three-membered cyclic chlorine-containing compound are dissolved in 50 parts by mass of ethanol, 4 parts by mass of a 0.1 mol / L aqueous solution of sodium hydroxide are added, and the mixture is heated to 82° C. and reacted for 10 hours to obtain an intermediate product;

[0057] S2: The intermediate product, 50 parts by mass of hexadecyldimethyl tertiary amine, 80 parts by mass of ethanol and 60 parts by mass of water were mixed, heated to 82° C., reacted for 25 hours, and the ethanol was removed by rotary evaporation to obtain a zwitterionic surfactant.

[0058] The three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of 1.5:1:0.3.

[0059] In parts by mass, the preparation method of the nonionic surfactant is:

[0060] S1: Add 150 parts of mixed alcohol and 4 parts of potassium hydroxide to a stainless steel reactor, keep the temperature at 32°C, evacuate the reactor, raise the temperature to 112°C, add 1720-1750 parts of alkylene oxide, add it within 7 hours, control the pressure at 0.1 MPa and the temperature at 110°C, react for 3 hours, and obtain polyether polyol;

[0061] S2: Add 900 parts of polyether polyol and 1200 parts of glycerol to a stainless steel reactor. After nitrogen substitution, heat the reactor to 140°C and pressurize the reactor to 0.2MPa. When the pressure in the reactor drops, control the temperature to 110°C and the pressure to 0.3MPa. React for 6 hours to obtain a nonionic surfactant.

[0062] The alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of 1.3:1:0.2.

[0063] The mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of 0.3:1.5:1.

[0064] Example 3

[0065] This embodiment provides a method for cleaning a ceramic membrane, the cleaning method comprising the following steps:

[0066] (1) Preparation of a cleaning agent: The cleaning agent comprises the following components in parts by weight: 25 parts of formic acid, 21 parts of a phytic acid aqueous solution, 8 parts of citric acid, 14 parts of glycolic acid, 5 parts of a softener, 6 parts of a surfactant, 20 parts of isopropyl alcohol, and 45 parts of water; the surfactant comprises a non-ionic surfactant, cocoamidopropyl betaine, and a zwitterionic surfactant in a mass ratio of 1:1.6:0.8; the softener is a mixture of methyl cellulose, hydroxyethyl cellulose, and sodium carboxymethyl cellulose in a mass ratio of 1.8:1:0.5; the concentration of the phytic acid aqueous solution is 70% by mass.

[0067] (2) Prepare a 1% aqueous solution of the cleaning agent and heat it to 30°C. Perform non-permeation cycle cleaning for 5 minutes and permeation cycle cleaning for 3 minutes, then stop cleaning.

[0068] (3) Reversely input ozone into the system from the water production end of the ceramic membrane system; utilize the microporous structure of the ceramic membrane to allow ozone to pass through the membrane pores and form nano-scale bubbles in the membrane tube. Input ozone for 15 minutes, ozone flow rate: 0.3L / min, ozone pressure 0.3Mpa, drain the ozone, rinse with water until the drainage is neutral, and the cleaning process is completed.

[0069] The preparation method of the zwitterionic surfactant is:

[0070] S1: 15 parts by mass of 4-amino-3-hydroxybenzoic acid and 20 parts by mass of a three-membered cyclic chlorine-containing compound are dissolved in 50 parts by mass of ethanol, 6 parts by mass of a 0.3 mol / L aqueous solution of sodium hydroxide are added, and the mixture is heated to 85° C. and reacted for 15 hours to obtain an intermediate product;

[0071] S2: The intermediate product, 55 parts by mass of hexadecyldimethyl tertiary amine, 85 parts by mass of ethanol and 65 parts by mass of water were mixed, heated to 85° C., reacted for 30 hours, and the ethanol was removed by rotary evaporation to obtain a zwitterionic surfactant.

[0072] The three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of 1.7:1:0.6.

[0073] In parts by mass, the preparation method of the nonionic surfactant is:

[0074] S1: Add 155 parts of mixed alcohol and 6 parts of potassium hydroxide to a stainless steel reactor, keep the temperature at 35°C, evacuate the reactor, raise the temperature to 115°C, add 1750 parts of alkylene oxide, add it over 9 hours, control the pressure at 0.3MPa, the temperature at 115°C, react for 5 hours, and obtain polyether polyol;

[0075] S2: Add 920 parts of polyether polyol and 1230 parts of glycerol to a stainless steel reactor. After nitrogen substitution in the reactor, heat it to 145°C and pressurize the reactor to 0.3MPa. When the pressure in the reactor drops, control the temperature to 113°C and the pressure to 0.4MPa. React for 6-8h to obtain a nonionic surfactant.

[0076] The alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of 1.6:1:0.6.

[0077] The mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of 0.5:1.7:1.

[0078] Comparative Example 1

[0079] The difference between this comparative example and Example 1 is that: 20 parts of formic acid, 16 parts of phytic acid aqueous solution, 4 parts of citric acid, and 9 parts of glycolic acid are replaced by: 4 parts of formic acid, 9 parts of phytic acid aqueous solution, 20 parts of citric acid, and 16 parts of glycolic acid.

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that 20 parts of formic acid, 16 parts of phytic acid aqueous solution, 4 parts of citric acid, and 9 parts of glycolic acid are replaced by: 10 parts of formic acid, 26 parts of phytic acid aqueous solution, 11 parts of citric acid, and 2 parts of glycolic acid.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 1 is that the surfactant includes sodium dodecylbenzene sulfonate, sodium lauryl sulfate, and cocoamidopropyl betaine in a mass ratio of 1:1.5:0.6.

[0084] Comparative Example 4

[0085] The difference between this comparative example and Example 1 is that the three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of 1:1:1.

[0086] Comparative Example 5

[0087] The difference between this comparative example and Example 1 is that the alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of 1:1:1.

[0088] Comparative Example 6

[0089] The difference between this comparative example and Example 1 is that the mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of 1:1:1.

[0090] Comparative Example 7

[0091] The difference between this comparative example and Example 1 is that the surfactant includes a nonionic surfactant, cocoamidopropyl betaine and a zwitterionic surfactant in a mass ratio of 1:1:1.

[0092] Performance Testing

[0093] 1. Simulation of the preparation of cold rolling emulsion oily wastewater and membrane fouling process: According to the analysis results of the composition and properties of cold rolling oily wastewater in a certain factory, a high shear dispersing emulsifier was used to disperse 20# engine oil and emulsifier in water at a certain ratio at high speed to prepare an oil-water emulsion with an oil concentration of 5 parts by mass / L. The ceramic membrane used was a 19-channel Al2O3 ceramic microfiltration membrane with a membrane pore size of 50nm. A 0.24m2 ceramic membrane filtration device was used to treat the oily wastewater by cross-flow filtration, and the operation (membrane fouling process) time was 48h. The operating conditions were: the transmembrane pressure difference ΔP was 0.05MPa, the membrane surface flow rate was 4.2m / s, and the feed liquid temperature T was about 50℃.

[0094] The cleaning methods prepared by Examples 1-3 and Comparative Examples 1-7 were used respectively, and the pure water flux recovery rate (FRw) and oil-water permeation flux recovery rate (FRo) of the membrane after cleaning are shown in Table 1.

[0095] Table 1 Performance test results

[0096]

[0097] 2. The cleaning methods prepared in Examples 1-3 and Comparative Examples 1-7 were used to clean the ceramic membrane used to treat wastewater in an oil field. The pure water flux recovery rate (FRw) and oil-water permeation flux recovery rate (FRo) of the membrane after cleaning are shown in Table 2.

[0098] Table 2 Performance test results

[0099]

[0100] 3. The cleaning agents prepared in Examples 1-3 and Comparative Examples 1-7 were stored at room temperature (25° C.) for three months to observe whether stratification occurred. The results are shown in Table 3.

[0101] Table 3 Performance test results

[0102]

[0103] It can be seen from the above performance test results that the cleaning effects of Examples 1-3 are good, especially the comprehensive performance of Example 1 is the most outstanding, which is mainly due to the synergistic effect of each component.

[0104] However, the comparative examples did not adopt the necessary technical solutions, resulting in that the corresponding performance tests were significantly worse than those of the embodiments. In comparative examples 1-2, the ratios of the four acids were changed, and it can be seen that the cleaning effect of the permeable membrane for treating cold rolling oily wastewater was reduced. Comparative examples 2-6 did not use the solution of applying the present invention to prepare non-ionic surfactants and zwitterionic surfactants. From the results, it can be seen that the cleaning effect of the ceramic membrane after treating oilfield wastewater was affected. The above experimental results further prove the importance of the technical solution defined in the present invention for its technical effect.

[0105] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for cleaning a ceramic membrane, characterized in that: The cleaning method comprises the following steps: (1) Preparation of cleaning agent: The cleaning agent is composed of the following components in parts by weight: 20-25 parts of formic acid, 16-21 parts of phytic acid aqueous solution, 4-8 parts of citric acid, 9-14 parts of glycolic acid, 2-5 parts of softener, 3-6 parts of surfactant, 15-20 parts of isopropyl alcohol, and 40-45 parts of water; the surfactant includes a non-ionic surfactant, cocoamidopropyl betaine, and a zwitterionic surfactant in a mass ratio of 1: (1.3-1.6): (0.5-0.8): The preparation method of the zwitterionic surfactant is: S1: dissolving 13-15 parts by weight of 4-amino-3-hydroxybenzoic acid and 18-20 parts by weight of a three-membered cyclic chlorine-containing compound in 50 parts by weight of ethanol, adding 4-6 parts by weight of a 0.1-0.3 mol / L aqueous solution of sodium hydroxide, heating to 82-85° C., reacting for 10-15 hours, to obtain an intermediate product; S2: mixing the intermediate product, 50-55 parts by weight of hexadecyl dimethyl tertiary amine, 80-85 parts by weight of ethanol and 60-65 parts by weight of water, heating to 82-85° C., reacting for 25-30 hours, and removing the ethanol by rotary evaporation to obtain a zwitterionic surfactant; (2) Prepare a cleaning agent solution and heat it to 25-30°C. Perform non-permeation cycle cleaning for 3-5 minutes, permeation cycle cleaning for 2-3 minutes, and then stop cleaning. (3) Reversely input ozone from the water production end of the ceramic membrane system into the system; utilize the microporous structure of the ceramic membrane to allow ozone to pass through the membrane pores and form nano-scale bubbles in the membrane tube. Input ozone for 10-15 minutes, drain the ozone, rinse with water until the drainage is neutral, and the cleaning process is completed; The three-membered cyclic chlorine-containing compound is a mixture of 1,2-epoxychlorobutane, epichlorohydrin, and 2-(chloromethyl)-1,2-epoxybutane in a mass ratio of (1.5-1.7):1:(0.3-0.6); In parts by mass, the preparation method of the nonionic surfactant is: S1: Add 150-155 parts of mixed alcohol and 4-6 parts of potassium hydroxide to a stainless steel reactor, maintain the temperature at 32-35°C, evacuate the reactor, raise the temperature to 112-115°C, add 1720-1750 parts of alkylene oxide, add it within 7-9 hours, control the pressure at 0.1-0.3MPa, the temperature at 110-115°C, react for 3-5 hours, and obtain polyether polyol; S2: Add 900-920 parts of polyether polyol and 1200-1230 parts of glycerol into a stainless steel reactor. After nitrogen substitution, heat the reactor to 140-145°C and pressurize the reactor to 0.2-0.3MPa. When the pressure in the reactor drops, control the temperature to 110-113°C and the pressure to 0.3-0.4MPa. React for 6-8h to obtain a nonionic surfactant.

2. The method for cleaning a ceramic membrane according to claim 1, characterized in that: The alkylene oxide is a mixture of ethylene oxide, propylene oxide and 2,3-butylene oxide in a mass ratio of (1.3-1.6):1:(0.2-0.5).

3. The method for cleaning a ceramic membrane according to claim 1, characterized in that: The mixed alcohol is a mixture of lauryl alcohol, ethylene glycol monomethyl ether and isomeric tridecanol in a mass ratio of (0.3-0.5):(1.5-1.7):

1.

4. The method for cleaning a ceramic membrane according to claim 1, characterized in that: The concentration of the phytic acid aqueous solution is 60-70% by mass.

5. The method for cleaning a ceramic membrane according to claim 1, characterized in that: The softener is selected from one or more of methyl cellulose, hydroxyethyl cellulose and sodium carboxymethyl cellulose.

6. The method for cleaning a ceramic membrane according to claim 1, characterized in that: The softener is a mixture of methyl cellulose, hydroxyethyl cellulose and sodium carboxymethyl cellulose in a mass ratio of (1.5-1.8):1:(0.3-0.5).

7. The method for cleaning a ceramic membrane according to claim 1, characterized in that: Ozone flow rate 0.2-0.3L / min, ozone pressure 0.1-0.3Mpa.

8. An application of the method for cleaning a ceramic membrane according to any one of claims 1 to 7, characterized in that: The cleaning method is used for cleaning the ceramic membrane after treating cold rolling oily wastewater and / or the ceramic membrane after treating oilfield sewage.

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