An integrated membrane treatment process for industrial alkaline water of canned peaches

Abstract

The present invention belongs to the technical field of sewage treatment, and particularly relates to an integrated membrane treatment process for industrial alkaline water in canned peach production. The present invention targets the industrial alkaline water generated in different technological processes of canned peaches for targeted treatment. For the highly contaminated and highly concentrated alkaline sewage generated in the lye peeling process, a composite flocculant is first added for sedimentation, and then ultrafiltration - nanofiltration membranes are used for treatment; for the relatively low - concentration alkaline sewage generated in the rinsing process of peach segments after lye peeling, an ultrafiltration - nanofiltration - reverse osmosis integrated membrane system is directly used for treatment. The industrial alkaline water treatment process for canned peaches of the present invention is not only simple to operate, but also after the alkaline sewage is treated by the process of the present invention, the recovery rate of the highly concentrated alkaline water reaches more than 90%, and the clear water recovery rate of the rinsing water reaches 91.6%. The recovered highly concentrated alkaline water and clear water can be reused in the rinsing process, greatly reducing the cost of sewage treatment and further reducing the processing cost of canned peaches.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment, and particularly relates to an integrated membrane treatment process for industrial alkaline water of peach cans. Background Art

[0002] The canning industry is a traditional food processing industry, and peach cans are deeply loved by people for their unique taste.

[0003] At present, in the industrial production process of peach cans, in order to achieve continuous production, the alkali spraying method is mostly used for peeling separation. That is, after peaches are cleaned, cut into pieces, and pitted, hot alkaline solution is sprayed on the peach pieces on the conveyor belt. Usually, alkaline solution with high concentration (generally 12%-18% by mass fraction) and high temperature (above 90°C) is used to rinse the peach pieces, so that the epidermis is corroded and degraded. The fruits and vegetables rinsed with alkali enter the rotating drum, and are peeled by rolling and rubbing against the edge of the rotating drum under the condition of flushing water; the alkali concentration of this part of the rinsing alkaline water is relatively high. Generally, after rough filtration through a filter screen, it is recycled for 3-5 days, and solid caustic soda needs to be continuously added to ensure better peeling efficiency. As the number of recycling times increases, the content of sugar, suspended pectin and other particulate matters in the alkaline water also increases, and the peeling effect of the alkaline water decreases. Finally, the high-concentration alkaline water is discharged to the sewage treatment station.

[0004] This part of the high-concentration alkaline water not only contains more alkali, but also contains more substances such as sugar and pectin, and the COD Mn content is relatively high, and the treatment is difficult, which brings a great burden to the sewage treatment station.

[0005] In addition, after the alkali spraying and peeling process of peach pieces is completed, the surface of the peeled peach pieces will adhere to alkaline solution. The residual alkaline solution is likely to cause the discrete of the pulp tissue of the peach pieces and affect the quality of the cans. In order to remove the residual alkaline solution, a large amount of citric acid needs to be added in the subsequent process for neutralization, which not only increases the content of Na + in the cans, but also increases the production cost of the enterprises processing peach cans.

[0006] In order to further achieve energy conservation and emission reduction in the peach canning industry, a peach piece rinsing process is added after the alkali spraying process, that is, 1-1.2 times of the total amount of high-concentration alkaline water of clear water is used to rinse the peach pieces, and the rinsed peach pieces then enter the next acid adjustment and neutralization process section. The pollutants contained in this part of the obtained rinsing water are only less, and are accompanied by a small amount of sugar, pectin and alkali, and the treatment difficulty is greatly reduced.

[0007] All in all, a large amount of industrial alkaline water generated in the production process of peach cans has high treatment cost and high pollution. Therefore, it is urgent to develop an efficient green treatment process for industrial alkaline water of cans. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides an integrated membrane treatment process for industrial alkaline water of canned peaches, aiming at the industrial alkaline water with different characteristics generated in different production process stages of canned peaches.

[0009] Among them, the industrial alkaline water described in the present invention specifically includes: high-concentration alkaline water generated by the alkali peeling process and low-concentration alkaline water generated by the rinsing process of peach petals after alkali peeling.

[0010] For the sake of simplicity, in the following description of the specification, the present invention directly omits the process source of alkaline sewage, and the high-concentration alkaline water generated by the alkali peeling process is simplified to "high-concentration alkaline water", and the low-concentration alkaline water generated by the rinsing process of peach petals after alkali peeling is simplified to "low-concentration alkaline water".

[0011] The treatment process for high-concentration alkaline water provided by the present invention specifically includes the following steps:

[0012] (1) Pretreatment of high-concentration alkaline water: Use a composite flocculant to carry out flocculation sedimentation on the high-concentration alkaline water, separate the alkaline water after flocculation sedimentation by a spiral press filter, and measure the alkaline water parameters;

[0013] (2) Treat the alkaline water pretreated in step (1) with an integrated membrane to recover the alkaline water;

[0014] The treatment process for low-concentration alkaline water directly uses an integrated membrane system for treatment.

[0015] In the above step (1), the flocculant is a composite flocculant, which includes the following raw materials in parts by weight: 6-12 parts of sucrose ester, 3-8 parts of sodium styrene sulfonate, 20-52 parts of polyacrylamide, 5-15 parts of diatomite, and 15-30 parts of chitosan.

[0016] Preferably, the flocculant in step (1) includes the following raw materials in parts by weight: 8-10 parts of sucrose ester, 5-8 parts of sodium styrene sulfonate, 20-45 parts of polyacrylamide, 5-13 parts of diatomite, and 18-27 parts of chitosan.

[0017] In the above step (2), the integrated membrane includes at least one of an ultrafiltration membrane, a nanofiltration membrane, and a reverse osmosis membrane.

[0018] Preferably, the integrated membrane in step (2) is an ultrafiltration membrane and a nanofiltration membrane.

[0019] Since the alkaline water generated in the alkaline peeling process of canned peaches is not only highly concentrated but also contains a large number of biological macromolecular components, such as macromolecular proteins, pectins, polysaccharides, etc. Among them, pectin has strong viscosity, and its conventional molecular weight is about 10,000 - 300,000 Da, which significantly affects the flux decline of the nanofiltration membrane. Therefore, in the present invention, after the flocculation separation of the high-concentration alkaline water, in order to ensure the stability and continuity of the process system operation and avoid the too-fast flux decline of the nanofiltration membrane, ultrafiltration membrane is first used for primary separation to remove all pectins, most proteins and some macromolecular polysaccharides, and then a nanofiltration membrane system is used for secondary removal.

[0020] In the integrated membrane treatment process of the above high-concentration alkaline water, the integrated membrane includes at least one of ultrafiltration membrane, nanofiltration membrane, and reverse osmosis membrane.

[0021] Preferably, in the treatment process of high-concentration alkaline water, the integrated membrane used is ultrafiltration membrane, nanofiltration membrane, and reverse osmosis membrane.

[0022] Since the low-concentration alkaline water generated in the rinsing process contains fewer pollutants and is accompanied by a small amount of sugar, pectin, and alkali, the present invention uses an ultrafiltration-nanofiltration membrane system for purification and further adds a reverse osmosis membrane element to the membrane system for treatment. This can not only concentrate the alkali solution in the low-concentration alkaline water but also recover most of the rinsing water for reuse, further achieving energy conservation and emission reduction.

[0023] Preferably, the ultrafiltration membrane is selected from any one of the spiral-wound ultrafiltration membrane with bionic tubular structure (UF 3), tubular ultrafiltration membrane (UF1), cross-linked spiral-wound membrane (UF 2), PVDF hollow fiber membrane (UF 4), and PTFE hollow fiber membrane (UF 5).

[0024] Preferably, the ultrafiltration membrane is any one of UF 1, UF 2, and UF 3.

[0025] Preferably, the ultrafiltration membrane is UF 3.

[0026] The aperture specification of the nanofiltration membrane is any one of 100 - 200 Da (NF 1), 200 - 300 Da (NF 2), 300 - 500 Da (NF3), 500 - 1000 Da (NF 4), and 2000 - 5000 Da (NF 5).

[0027] Preferably, the aperture specification of the nanofiltration membrane is any one of NF 1, NF 2, and NF 3.

[0028] Preferably, the aperture specification of the nanofiltration membrane is NF 2.

[0029] The reverse osmosis membrane is any one of TSOC(RO 1), CTROC 40(RO 2), CTROC 46(RO 3), CTROC 48(RO4), and CTROC 50(RO 5).

[0030] Preferably, the reverse osmosis membrane is any one of RO 4 and RO 5.

[0031] Preferably, the reverse osmosis membrane is RO 5.

[0032] The lye to be treated in the present invention has a relatively high pH. To ensure the service life of the membrane tubes, all membrane tubes need to select alkali-resistant ultrafiltration membranes, and the applicable pH range is pH > 13.

[0033] Currently, common organic ultrafiltration membranes can be mainly divided into three categories according to their flow channel structures: tubular membranes, spiral wound membranes, and hollow fiber membranes. Among them, compared with tubular and spiral wound membranes, hollow fiber membranes have the characteristics of high strength, good retention performance, and easy recovery of cleaning flux, but their cost is relatively high and the requirements for the use environmental conditions are relatively harsh;

[0034] The difference between tubular membranes and spiral wound membranes is that spiral wound membranes have a larger effective filtration area under the same unit volume condition, and the overall cost is lower. Spiral wound membranes have obvious advantages in terms of cost and treatment capacity. However, the flow channel structure of conventional spiral wound membranes is relatively narrow, and it is easy to have the situation of flow channel blockage. Therefore, the present invention adopts a spiral wound ultrafiltration membrane with a bionic tubular structure, and all the membrane elements in this research are screened and provided by Chengdu Lianjie Fluid Separation Technology Co., Ltd.

[0035] More specifically, for the integrated membrane treatment process of industrial lye for peach cans provided by the present invention, among them, the treatment process of the high-concentration lye generated by the lye peeling process is as follows:

[0036] (1) Pretreatment of high-concentration lye: Use a composite flocculant to carry out flocculation sedimentation on the high-concentration lye, and separate the lye after flocculation sedimentation through a spiral press, and measure the lye parameters to make the treated lye meet the conditions for entering the membrane system;

[0037] (2) Treat the lye pretreated in step (1) with ultrafiltration membrane UF 3 and nanofiltration membrane NF 2 to recover the lye;

[0038] The treatment process of the low-concentration lye generated by the peach petal rinsing process is: Use an integrated membrane system of ultrafiltration membrane UF 3, nanofiltration membrane NF 2, and reverse osmosis membrane RO 5 for treatment.

[0039] In addition, for the low-concentration lye generated by the rinsing of peach petals after nanofiltration treatment, since there is only a small amount of monosaccharide and OH in the lye -, which is relatively clean, but the amount of water is large, and the low-concentration alkaline water that needs to be rinsed is recycled.

[0040] In addition, since the wastewater discharged during the processing of canned peaches contains a mixture of various substances such as peel, pulp, sugar, pectin, etc., and pectin becomes viscous after dissolving in water, it is relatively troublesome to precipitate the wastewater. When precipitating the wastewater containing pectin, the present invention needs to use a coagulant to pre-treat the wastewater by flocculation. However, most of the existing wastewater sedimentation devices do not have a good material storage function. It is easy for the wastewater to be treated to be unable to undergo normal flocculation and sedimentation treatment due to the lack of coagulant due to untimely addition of the flocculant, which seriously affects the use function of the wastewater sedimentation device.

[0041] Therefore, in order to better achieve the treatment effect, the integrated membrane treatment process for canned peach industrial alkaline water provided by the present invention is specifically realized by combining with a canned peach processing wastewater stirring and sedimentation device with a storage function.

[0042] The device comprises a sedimentation tank, the top of which is fixedly connected with a top frame, a stirring rod extending into the sedimentation tank is vertically arranged in the middle of the top frame, and material storage mechanisms are respectively arranged on both sides of the stirring rod on the top frame.

[0043] The material storage mechanism comprises a material storage barrel located inside the sedimentation tank and a cover plate located inside the top frame, and a material discharge mechanism is provided at the bottom of the material storage barrel.

[0044] In the above device, parallel pull rods are provided on both sides of the cover plate, a pull plate perpendicular to the pull rods is fixedly provided on one side of the cover plate, the pull plate is arranged on the outer side of the top frame, one end of the pull rod passes through the top frame and is fixedly connected to the pull plate, and the other end is fixedly connected to the limiting plate, and an elastic device is provided on the outer surface of the pull rod.

[0045] Preferably, the discharging mechanism includes a pull frame arranged on one side of the storage barrel, one side of the pull frame is fixedly connected to a bottom plate, one side of the top frame is fixedly connected to a side plate, one side of the side plate is fixedly connected to a guide rod, the outer surface of the guide rod is sleeved with a tension spring, and the outer surface of the bottom plate is sleeved with a sealing sleeve.

[0046] Preferably, a slot compatible with the bottom plate is opened on one side of the storage barrel, the outer surface of the sealing sleeve contacts the inner wall of the slot, a guide hole compatible with the guide rod is opened on one side of the pull frame, one end of the tension spring is welded to one side of the side plate, and the other end of the tension spring is welded to one side of the pull frame.

[0047] Preferably, a stirring rod is movably penetrated through one side of the top frame via a bearing, and a motor is fixedly installed on the other side of the top frame, and the output end of the motor is fixedly connected to one end of the stirring rod.

[0048] Preferably, one end of the pull rod slidably penetrates through one side of the top frame, and a limiting groove adapted to the limiting disc is formed inside the top frame.

[0049] Preferably, one end of the elastic device is welded to one side of the inner wall of the limiting groove inside the top frame, and the other end of the elastic device is welded to one side of the limiting disc.

[0050] Preferably, a sealing gasket is adhered to one side of the cover plate.

[0051] The beneficial effects of the present invention are as follows:

[0052] (1) The present invention provides a treatment process for industrial alkaline water generated by the alkali peeling process in the production of peach canned food. A composite flocculant is used and combined with a peach canned food processing wastewater stirring and precipitation device with a storage function to perform flocculation and precipitation treatment on impurities in the wastewater. With the storage and discharging mechanisms provided by the equipment, the coagulant is pre-stored and discharged reasonably, avoiding the phenomenon that the existing device fails to treat the wastewater in time due to the inability to discharge the flocculant in time during the working process. At the same time, the efficiency of the device for flocculation and precipitation treatment of wastewater is improved, and after further combination with a spiral press, it is beneficial for the wastewater to meet the conditions for membrane treatment.

[0053] (2) The present invention also provides a composite flocculant for the high-organic matter content and high-concentration alkaline sewage generated by the peach canned food preparation process, which contains components such as sucrose esters and styrene sulfonate surfactants. It can emulsify most of the ester substances contained in the peach canned food sewage well. On this basis, acrylamide, chitosan, etc. are combined to flocculate impurities, achieving a good flocculation effect.

[0054] (3) The pretreated high-concentration alkaline water is purified and recycled by an integrated membrane system. A bionic flow channel spiral wound membrane with a pore size of 10 nm and a nanofiltration membrane with a rejection of 200 - 300 Da are selected, realizing the effective recovery of high-concentration alkaline water. The alkali recovery rate is 92.6%, and the recovered high-concentration alkaline liquid meets the reuse conditions and can be reused for the alkali peeling process.

[0055] (4) The low-concentration alkaline water generated by the peach petal rinsing process, after being treated by the membrane combination system, realizes the recovery of more than 90% of the rinsing water and can be reused for rinsing water. At the same time, in the alkaline liquid concentrated by the reverse osmosis membrane, after adding caustic soda, it can make up for the alkali water loss in the recovery process of the high-concentration alkaline liquid, greatly reducing the production cost and improving the economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is the flocculation effect of different coagulants;

[0057] Figure 2 is the influence of the coagulant addition amount on the flocculation rate;

[0058] Figure 3 Effect of flocculation temperature on flocculation rate;

[0059] Figure 4 Effect of flocculation time on flocculation rate;

[0060] Figure 5 Effect of different membrane pore sizes on pectin retention rate;

[0061] Figure 6 Attenuation rate curves of different membrane materials;

[0062] Figure 7 Spiral ultrafiltration membrane with bionic tube structure adopted in the present invention;

[0063] Figure 8 Effect of different nanofiltration membrane materials on total sugar retention;

[0064] Figure 9 Effect of different types of reverse osmosis membrane elements on NaOH retention;

[0065] Figure 10 Stereogram of a stirring and sedimentation device for peach canning processing wastewater with a storage function adopted in the process of the present invention;

[0066] Figure 11 Stereogram of the discharging mechanism of a stirring and sedimentation device for peach canning processing wastewater with a storage function adopted in the process of the present invention;

[0067] Figure 12 Partially sectional stereogram of the top frame of a stirring and sedimentation device for peach canning processing wastewater with a storage function adopted in the process of the present invention;

[0068] Figure 13 Developed stereogram of the bottom plate of a stirring and sedimentation device for peach canning processing wastewater with a storage function adopted in the process of the present invention.

[0069] Legend:

[0070] 1. Sedimentation tank; 2. Top frame; 3. Storage mechanism; 4. Stirring rod; 5. Motor;

[0071] 31. Cover plate; 32. Storage barrel; 33. Discharging mechanism; 34. Sealing gasket; 35. Pulling plate; 36. Pulling rod; 37. Elastic device; 38. Limiting disc;

[0072] 331. Pulling frame; 332. Bottom plate; 333. Side plate; 334. Guide rod; 335. Pulling spring; 336. Sealing sleeve. Detailed implementation manners

[0073] To enable those skilled in the art to better understand the present invention, the present invention will be further elaborated below in conjunction with specific embodiments.

[0074] Example 1 (Screening of Optimal Flocculant)

[0075] S1, Selection of Flocculant

[0076] Since the pH of the alkaline water is relatively high and the alkaline water needs to be recycled, three coagulants, namely composite flocculant, bentonite, and chitosan, are selected. Under the flocculation conditions of an addition amount of 300 mg / L, a temperature of 50 °C, and a flocculation sedimentation time of 180 min, the high-concentration alkaline water obtained by alkali peeling is subjected to flocculation sedimentation. Then, after separation by a spiral press, the COD, SS, and turbidity indexes are measured respectively to evaluate the influence of the type of flocculant on the flocculation effect. The results are shown in Figure 1 .

[0077] From Figure 1 it is not difficult to see that the composite flocculant has the best flocculation effect. The main reason is that the composite flocculant contains organic polymer flocculants, which are easily in a semi-network structure under alkaline conditions, can reduce the frictional resistance of the fluid, play a coagulation aid effect, and contain surfactant components, which can emulsify the oil components contained in the peach cans, reduce the smoothness of the surface of the impurities, make the impurities have better adhesiveness, and further neutralize the charge with the suspended matter, thus achieving a better flocculation effect.

[0078] S2, Influence of Flocculant Dosage on the Flocculation Effect of Alkaline Water

[0079] Accurately weigh 5 portions of 500 mL of high-concentration alkaline water into beakers. With the addition amounts of the composite flocculant being 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, and 250 mg / L, a flocculation temperature of 40 °C, and a flocculation time of 120 min, and then after separation by a spiral press, the COD, SS, and turbidity indexes are measured respectively to evaluate the influence of the flocculant dosage on the flocculation effect. The results are shown in Figure 2 .

[0080] From Figure 2 it can be seen that when the flocculant dosage is between 50 - 200 mg / L, the flocculation rate of the alkaline water increases from 37.08% to 75.72%, showing an obvious upward trend. When it is greater than 200 mg / L, the change range is not large, indicating that the coagulant has fully combined with the pollutants in the alkaline water and the flocculation effect has approached the limit.

[0081] S3, Influence of Flocculation Temperature on the Flocculation Effect of Alkaline Water

[0082] Accurately weigh 5 portions of 500 mL of high-concentration alkaline water into beakers. With the addition amount of the composite flocculant being 150 mg / L, the flocculation temperatures being 30 °C, 40 °C, 50 °C, 60 °C, and 70 °C respectively, and the flocculation time being 120 min. Then, after separation using a spiral press, measure the COD, SS, and turbidity indicators respectively to evaluate the influence of the flocculation temperature on the flocculation effect. The results are shown in Figure 3 .

[0083] Figure 3 As can be seen in

[0084] When the temperature is higher than 50 °C, the flocculation rate shows an obvious downward trend. The main reason is that under high-temperature conditions, the stability of the composite flocculant decreases and decomposition occurs, and the pollutant particles in the alkaline water move violently and are not easily flocculated. Therefore, if the temperature of the discharged alkaline water is too high, it should be fully statically cooled in the sedimentation tank before adding the composite flocculant as a coagulant for flocculation.

[0085] Accurately weigh 5 portions of 500 mL of high-concentration alkaline water into beakers. With the addition amount of the composite flocculant being 150 mg / L, the flocculation temperature being 40 °C, and the flocculation times being 60 min, 90 min, 120 min, 150 min, and 180 min respectively. Then, after separation using a spiral press, measure the COD, SS, and turbidity indicators respectively to evaluate the influence of the flocculation time on the flocculation effect. The results are shown in Figure 4 .

[0086] From Figure 4 it can be known that with the addition amount of the composite flocculant being 150 mg / L, the flocculation temperature being 40 °C, and the flocculation time being 50 - 150 min, the flocculation rate of the alkaline water increases from 46.18% to 75.19%, showing an obvious upward trend. When the flocculation time exceeds 150 min, the increase in the flocculation rate tends to level off.

[0087] After the alkaline water after the above S1 - S4 has been flocculated and precipitated, separate it using a spiral press, and then measure the COD, SS, and turbidity indicators respectively to evaluate the flocculation effect of the coagulant and its removal effect on the pollutants in the alkaline water.

[0088] S5, Orthogonal experiment of coagulant

[0089] According to the results of the above single-factor experiments, select the addition amount of the flocculant, the flocculation temperature, and the flocculation time to conduct a three-factor and three-level experiment to obtain the optimal conditions for the flocculant process. The results are shown in Table 1.

[0090] Table 1 Results of the orthogonal experiment on flocculation effect

[0091]

[0092] It can be concluded from the table that the addition amount of flocculant, flocculation temperature, and flocculation time all have an impact on the flocculation effect of alkaline water, and the order of influence from large to small is A > B > C, that is, the addition amount of coagulant > flocculation temperature > flocculation time.

[0093] The results show that the optimal scheme is when the addition amount of coagulant is 200 mg / L, the flocculation temperature is 50 °C, and the flocculation time is 120 min. Since A2B2C2 is not in the orthogonal design scheme, a comparative verification test was carried out between A2B2C2 and the orthogonal optimal design value A2B2C1 this time. It was found that the flocculation rate of A2B2C2 was 77.23%, and the flocculation rate of A2B2C1 was 76.19%; A2B2C2 > A2B2C1, that is, the verification test was successful. The best coagulant flocculation parameters are the addition amount of coagulant 200 mg / L, flocculation temperature 50 °C, and flocculation time 150 min.

[0094] Example 2 Screening of integrated membranes

[0095] S1, Screening of ultrafiltration membranes

[0096] (1) Screening of the pore size of ultrafiltration membranes

[0097] In this study, the pore sizes of the ultrafiltration membranes selected were 10 nm, 30 nm, 50 nm, 70 nm, and 90 nm. The pectin content on the concentrated solution side was measured, and the pectin rejection rate was calculated to screen the optimal ultrafiltration membrane pore size. The results are shown in Figure 5 .

[0098] As Figure 5 can be seen, with the increase of the ultrafiltration membrane pore size, the pectin rejection rate shows an obvious decreasing trend. According to the molecular weight range of conventional pectin of about 10,000 - 300,000 Da, in order to minimize the pectin content on the permeate side, when the ultrafiltration membrane pore size is 10 nm, no pectin was detected on the permeate side, and the pectin rejection rate reached 100%. The rejection molecular weight corresponding to the 10 nm pore size is about 3000 Da, which can effectively achieve the retention and separation of pectin and avoid the attenuation of the nanofiltration membrane flux caused by pectin adhesion.

[0099] (2) Screening of the fouling resistance of ultrafiltration membranes with different channel designs;

[0100] All the membrane elements in this study were screened and provided by Chengdu Lianjie Fluid Separation Technology Co., Ltd. Five kinds of ultrafiltration membranes, namely tubular ultrafiltration membranes with an ultrafiltration pore size of 10 nm, cross-linked wound membranes, wound ultrafiltration membranes with a bionic tubular structure, PVDF hollow fiber membranes, and PTFE hollow fiber membranes, were selected as the test objects. Under the condition of a treatment temperature of 50 °C, the membrane flux decay was measured for 24 h continuously, and the membrane flux decay at 0, 3, 6, 9, 12, 15, 18, 21, and 24 h was calculated respectively to compare and select the ultrafiltration membrane element with the best fouling resistance. The results are shown in Figure 6 .

[0101] After continuous operation for 24 hours, the membrane fluxes of all kinds decreased to varying degrees. The flux decay rates of the membrane materials with different channel structures were calculated respectively to compare their anti-fouling performances.

[0102] It can be Figure 6 seen that the flux decay rates from low to high are: UF3 > UF1 > UF2 > UF4 > UF5. Among them, the flux decays of the two hollow fiber membranes UF4 and UF5 are the most obvious, indicating that the anti-fouling ability of the hollow fiber membrane is poor when treating this high-concentration alkaline water.

[0103] In addition, the tubular membrane has good anti-fouling property, so the flux decay rate of UF1 is lower than that of the traditional UF2. In order to give full play to the advantages of the spiral wound membrane, the patented membrane of Chengdu Connect Fluid Separation Technology Co., Ltd. was used in this experiment: a spiral wound ultrafiltration membrane with a bionic tubular structure was used for the purification and recovery of alkali during the ultrafiltration process. The structure of the flow channel of this membrane was improved by adding an isolation layer and a support body, so that the high-concentration material on the membrane surface can be easily washed away by the newly entering feed liquid at high speed and leave the membrane surface, reducing the deposition of impurities or materials on the membrane surface and the probability of membrane element fouling, making the membrane flux more stable. Therefore, UF3 was selected as the ultrafiltration membrane for high-concentration alkaline solution.

[0104] The structure of the ultrafiltration membrane finally selected in the present invention is as Figure 7 shown.

[0105] S2. Screening experiment of nanofiltration membrane

[0106] All the membrane elements in this study were screened and provided by Chengdu Connect Fluid Separation Technology Co., Ltd. Five kinds of nanofiltration membrane elements with strong alkali resistance and pore size specifications of 100 - 200 Da, 200 - 300 Da, 300 - 500 Da, 500 - 1000 Da, and 2000 - 5000 Da were respectively selected as the test objects. Under the conditions of a treatment temperature of 50 °C and an operating pressure of 3.0 MPa, their total sugar rejection rates were measured, and the nanofiltration membrane element with a high total sugar rejection rate was selected by comparison. The test results are shown in Figure 8 .

[0107] It can be Figure 8 seen that the interception effects of the five kinds of nanofiltration membranes on total sugar are significantly different.

[0108] The interception rates of NF1 and NF2 are 98.7% and 98.5% respectively, and the difference in the interception rates is not significant. The interception of monosaccharides such as glucose, fructose, and xylose is about 30% - 40% or so; however, as the pore size of the nanofiltration membrane increases, the interception rate of the nanofiltration membrane for sugar shows a downward trend, and the interception rate of total sugar gradually decreases starting from NF3; the interception effect of NF5 is the worst, only 86%, mainly because the passing rates of disaccharides, oligosaccharides, and small molecular polysaccharides in it increase, resulting in a decrease in the interception efficiency.

[0109] Since the alkaline water needs to be effectively recycled, the maximum total sugar rejection rate should be preferably selected to achieve the purification of high-concentration alkaline liquor, reduce the sugar residue in the alkaline water, and at the same time take into account the flux. NF2 is preferably selected as the optimal pore size screening of the nanofiltration membrane.

[0110] S3. According to the experiments of S1-S2, a spiral wound ultrafiltration membrane with a bionic tubular structure with a pore size of 10 nm and a nanofiltration membrane with a pore size range of 200-300 Da integrated membrane system are selected for the recovery of high-concentration alkaline water after pretreatment. According to the membrane system treatment capacity of 2.5 m 3 / h and a daily treatment of 50 m 3 / d of high-concentration alkaline water, the membrane system is designed. Since the entire pretreatment and membrane system basically do not cause the loss and retention of alkaline liquor, the results are shown in Table 2;

[0111] Table 2 Basic physical and chemical indicators of high-concentration alkaline water after membrane system recovery

[0112] Item pH value SS (mg / L) Turbidity (NTU) Pectin content (g / L) Membrane system for recycling highly concentrated alkaline water 14.18±0.01 0 0 0

[0113] It can be seen from Table 2 above that SS and pectin in high-concentration alkaline water have been completely removed and can be recycled. 50 m 3 After the alkaline water is pretreated and recovered by the membrane system, excluding the process loss, 46.3 m of high-concentration alkaline water is recovered 3 , and the alkali recovery rate is 92.6%. Pump this part of the alkaline water into the storage tank, which can realize circular use, greatly reduce the discharge of high-concentration alkaline water, and achieve energy conservation and emission reduction.

[0114] Example 3

[0115] S1. Reverse osmosis membrane screening

[0116] All RO membrane elements in this study were screened and provided by Chengdu Lianjie Fluid Separation Technology Co., Ltd. Five RO membrane elements were selected, namely TSOC, CTROC40, CTROC46, CTROC48, CTROC50 and other five reverse osmosis membrane elements as test objects. Under the conditions of a treatment temperature of 30 °C and an operating pressure of 4.0 MPa, the rejection rate of NaOH was measured, and the reverse osmosis membrane element with a high NaOH rejection rate was selected by comparison. The results are shown in Figure 9 .

[0117] As Figure 9 can be seen, the interception effects of the five RO membranes on NaOH are different. Among them, the interception rate of RO5 is 81.67%, and the interception effect is the best; the interception rate of conventional RO membranes (RO1-RO3) on NaOH is about 60%, mainly because the characteristics of RO membranes are mainly to retain Cl - , and the interception rate of acids and alkalis is also limited.

[0118] From the experiments, it can be seen that when choosing a membrane with high salt rejection, the rejection rate of NaOH is also relatively high. Therefore, the CTROC50 reverse osmosis membrane element is selected as the optimal membrane element for the reverse osmosis process.

[0119] S2. Analysis of the water recovery effect of the membrane system in treating the alkaline water for peach petal rinsing

[0120] According to the above-mentioned membrane system design, the ultrafiltration - nanofiltration membrane system is shared with the membrane system for high-concentration alkaline water to treat the alkaline water for peach petal rinsing. It can treat 60 m 3 / d of rinsing alkaline water, and the CTROC50 reverse osmosis membrane is selected for fresh water recovery. Considering the process loss of about 5 m 3 of rinsing alkaline water in the whole membrane system, the fresh water recovery efficiency is 91.6%. On the concentrate side of the RO membrane, the alkaline water is concentrated by the RO membrane interception. The indexes on both sides of the RO membrane are shown in Table 3. This part of the concentrated alkaline water can be continuously added with caustic soda to supplement the loss of high-concentration alkaline liquid in the alkaline peeling process.

[0121] Table 3 Basic physical and chemical indexes of the liquids on both sides after the reverse osmosis membrane recovery treatment

[0122] Item pH value NaOH% SS (mg / L) Turbidity (NTU) Alkaline water on the concentrate side of the reverse osmosis membrane 13.72±0.01 2.2±0.1 0 1 Clean water on the permeate side of the reverse osmosis membrane 11.82±0.01 0.03 0 0

[0123] Example 4 (Economic accounting of the integrated membrane system treatment process)

[0124] S1. Economic accounting of the traditional alkaline spraying process

[0125] (1) Production costs of the traditional alkaline spraying process

[0126] Water cost: 3 yuan / m 3 ×12.5 m 3 / d = 37.5 yuan / d;

[0127] Alkaline spraying water cost: 4000 yuan / t × (15% × 12.5 m 3 / d + 0.25 t) = 8500 yuan / d;

[0128] Cost of neutralizing residual alkaline liquid: 10000 yuan / t × 0.33 t = 3300 yuan / d;

[0129] (2) Sewage treatment costs of the traditional alkaline spraying process

[0130] Cost of industrial hydrochloric acid for neutralization: 2500 yuan / t × 5.18 t = 12950 yuan / d;

[0131] Operation cost of sewage treatment station equipment: 50 kwh × 24 h / d × 0.8 yuan / kwh = 960 yuan / d;

[0132] Sewage treatment labor cost: 5000 yuan / person × 5 persons / 30 days = 833 yuan;

[0133] Coagulant usage cost: 0.08% × (12.5 + 5.18) m 3 / d × 4000 yuan / t + 0.01% × (12.5 + 5.18) m 3 / d × 20000 yuan / t = 92 yuan;

[0134] (3) Total cost of traditional alkali leaching process

[0135] 37.5 + 8500 + 3300 + 12950 + 960 + 833 + 92 = 26672.5 yuan / d.

[0136] S2, Economic accounting of integrated membrane system

[0137] (1) Production cost of alkali leaching by integrated membrane system recovery technology

[0138] Water usage cost: 3 yuan / m 3 × 1.2 m 3 / d = 3.6 yuan / d;

[0139] Alkali leaching water cost: 4000 yuan / t × (15% × 1.2 m 3 / d + 0.14 t) = 1280 yuan / d;

[0140] Rinsing pure water cost: 4 yuan / m 3 × 5 m 3 / d = 20 yuan / d;

[0141] Cost of neutralizing residual alkali solution: 10000 yuan / t × 0.165 t = 1650 yuan / d;

[0142] (2) Sewage treatment cost of integrated membrane system for treating and recovering alkali leaching process

[0143] Cost of industrial hydrochloric acid for neutralization: 2500 yuan / t × 0.5 t = 1250 yuan / d;

[0144] Operation cost of sewage treatment station equipment: 30 kwh × 24 h / d × 0.8 yuan / kwh = 576 yuan / d;

[0145] Sewage treatment labor cost: 5000 yuan / person × 5 persons / 30 days = 833 yuan;

[0146] Coagulant usage cost: 0.08% × (1.2 + 0.5) m 3 / d × 4000 yuan / t + 0.01% × (1.2 + 0.5) m 3 / d × 20000 yuan / t + 0.02% × 12.5 m 3 / d × 20000 yuan / t = 58.8 yuan;

[0147] Operation cost of the integrated membrane system: 85 kwh × 24 h / d × 0.8 yuan / kwh = 1632 yuan / d;

[0148] Material loss cost of the integrated membrane system: 15.3 yuan / m 3 × 60 m 3 / d = 918 yuan / d;

[0149] Cleaning cost of the integrated membrane system: 150 yuan / d;

[0150] Total cost of the alkali spraying process in the integrated membrane system for treatment and recycling technology

[0151] (3) Total cost:

[0152] 3.6 + 1280 + 20 + 1650 + 1250 + 576 + 833 + 58.8 + 1632 + 918 + 150 = 8371.4 yuan / d.

[0153] Moreover, this system has been actually measured and verified in a 30 t / d peach can processing production line. Through the calculation of the operating costs of the original alkali spraying process and the new process in the factory, the new process system can save about 18,000 yuan / d in production costs. Calculated according to the average production cycle of 80 days / year in the peach can factory, it can save about 1.4 million yuan in production and sewage treatment costs every year.

[0154] In the present invention, the total investment of the integrated membrane system equipment designed according to the factory capacity and sewage volume is about 1.2 million yuan. Excluding the equipment investment, the net income in the first year can be 200,000 yuan, and it can significantly reduce sewage discharge and acid-base consumption, effectively contributing to the energy conservation, emission reduction, and green and low-carbon processing upgrade of the traditional canning industry.

[0155] Example 5

[0156] The integrated membrane treatment process for peach can industrial alkaline water provided by the present invention is realized in combination with the following peach can processing wastewater stirring and sedimentation device with a material storage function.

[0157] A peach can processing wastewater stirring and sedimentation device with a material storage function includes: a sedimentation tank 1, a top frame 2 is fixedly connected to the top of the sedimentation tank 1, a material storage mechanism 3 is arranged on one side of the top frame 2, a stirring rod 4 passes through the top frame 2 on one side through a bearing, and a motor 5 is fixedly installed on the other side of the top frame 2, and the output end of the motor 5 is fixedly connected to one side of the stirring rod 4.

[0158] The storage mechanism 3 includes a cover plate 31 that slides through one side of the top frame 2. On the other side of the top frame 2, a storage barrel 32 is fixedly connected. On one side of the storage barrel 32, a discharging mechanism 33 is provided. On one side of the cover plate 31, a sealing gasket 34 is adhered. On the other side of the cover plate 31, a pulling plate 35 is fixedly connected. On one side of the pulling plate 35, a pulling rod 36 is fixedly connected. One end of the pulling rod 36 slides through one side of the top frame 2. Inside the top frame 2, a limiting groove adapted to the limiting disk 38 is opened. By opening the limiting groove, the limiting disk 38 can move normally inside the top frame 2, avoiding the phenomenon that the limiting disk 38 cannot move. An elastic device 37 is sleeved on the outer surface of the pulling rod 36. One end of the elastic device 37 is welded to one side of the inner wall of the limiting groove inside the top frame 2, and the other end of the elastic device 37 is welded to one side of the limiting disk 38. By setting the elastic device 37, the elastic device 37 provides sufficient elastic force so that the limiting disk 38 can actively restore its position by means of the elastic force of the elastic device 37 after moving. One end of the pulling rod 36 is fixedly connected to the limiting disk 38.

[0159] As Figure 11 and Figure 13 shown, the discharging mechanism 33 includes a pulling frame 331 provided on one side of the storage barrel 32. On one side of the pulling frame 331, a bottom plate 332 is fixedly connected. On one side of the top frame 2, a side plate 333 is fixedly connected. On one side of the side plate 333, a guiding rod 334 is fixedly connected. A pulling spring 335 is sleeved on the outer surface of the guiding rod 334. A sealing sleeve 336 is sleeved on the outer surface of the bottom plate 332. On one side of the storage barrel 32, a slot adapted to the bottom plate 332 is opened. By opening the slot, the bottom plate 332 can be normally inserted into the inside of the storage barrel 32. The outer surface of the sealing sleeve 336 is in contact with the inner wall of the slot. By setting the sealing sleeve 336, good sealing measures are provided between the bottom plate 332 and the storage barrel 32. On one side of the pulling frame 331, a guiding hole adapted to the guiding rod 334 is opened. By opening the guiding hole, good moving guiding measures are provided during the movement of the pulling frame 331. One end of the pulling spring 335 is welded to one side of the side plate 333, and the other end of the pulling spring 335 is welded to one side of the pulling frame 331. By setting the pulling spring 335, the pulling spring 335 provides sufficient pulling force so that the pulling frame 331 can maintain good stability by means of the pulling force of the pulling spring 335.

[0160] The working principle of the above equipment provided by the present invention is as follows: When in use, the peach canning wastewater generated during the processing of peach cans is discharged into the sedimentation tank 1. Before the wastewater is discharged into the sedimentation tank 1 and the device is in an idle state, the pulling plate 35 is pulled to move. The pulling plate 35 drives the pulling rod 36 to move. The pulling rod 36 gradually moves out of the inside of the top frame 2, and the shape of the elastic device 37 gradually changes under the influence of the pulling force.

[0161] During the movement of the draw plate 35, the cover plate 31 moves along with the movement of the draw plate 35 and gradually opens until the draw plate 35 is pulled to the point where it can no longer move, at which point the cover plate 31 is fully open and remains in the position after the draw plate 35 is pulled without moving.

[0162] Place the flocculant required for wastewater precipitation in the storage bucket 32 with the cover plate 31 open. After the addition of the flocculant is completed, release the draw plate 35 that remains stationary. The elastic device 37 will then gradually resume its original shape without being affected by the large tensile force, and drive the limit disc 38 to move. When the limit disc 38 moves, it drives the pull rod 36 to move. The pull rod 36 gradually retracts into the interior of the top frame 2 and drives the draw plate 35 to move. During the movement of the draw plate 35, it drives the cover plate 31 to gradually close.

[0163] When the wastewater is discharged into the sedimentation tank 1, pull the draw frame 331 to move. The draw frame 331 drives the bottom plate 332 to move, and the bottom plate 332 gradually moves out of the interior of the storage bucket 32. When the draw frame 331 moves, it gradually slides on the outer surface of the guide rod 334, and the tension spring 335 gradually changes its shape under the influence of the tensile force until the draw frame 331 is pulled to the point where the bottom plate 332 is completely open with the storage bucket 32, and the position of the draw frame 331 is maintained without moving. After the bottom plate 332 is opened, the flocculant stored inside the storage bucket 32 falls into the interior of the sedimentation tank 1 and comes into contact with the wastewater until all the coagulants have fallen, then release the draw frame 331 that remains stationary, and the bottom plate 332 actively closes by means of the tensile force of the tension spring 335.

[0164] Start the motor 5 to run. The motor 5 drives the stirring rod 4 to rotate by means of its output end, and the stirring rod 4 stirs and precipitates the wastewater with coagulants inside the sedimentation tank 1.

Claims

1. An integrated membrane treatment process for industrial alkaline water of canned peaches, characterized in that, The industrial alkaline water mentioned above includes the high-concentration alkaline water generated in the process of alkali spraying and peeling, and the low-concentration alkaline water generated in the process of rinsing the peach petals after alkali spraying and peeling; Among them, for the high-concentration alkaline water generated in the alkali spraying and peeling process, the treatment process is as follows: (1) Pretreatment of high-concentration alkaline water: A composite flocculant is used to flocculate and sediment the high-concentration alkaline water generated in the alkali spraying and peeling process, and the flocculated and sedimented alkaline water is separated by a spiral press filter, and the parameters of the alkaline water are measured to meet the conditions for entering the membrane system; The composite flocculant mentioned above includes the following raw materials in parts by weight: 6-12 parts of sucrose ester, 3-8 parts of sodium styrene sulfonate, 20-52 parts of polyacrylamide, 5-15 parts of diatomite, and 15-30 parts of chitosan; (2) The pretreated alkaline water in step (1) is treated by an ultrafiltration membrane and a nanofiltration membrane to recover the high-concentration alkaline water; For the low-concentration alkaline water generated in the process of rinsing the peach petals after alkali spraying and peeling, it is directly treated by an integrated membrane system of an ultrafiltration membrane, a nanofiltration membrane and a reverse osmosis membrane; The ultrafiltration membrane mentioned above is a spiral wound ultrafiltration membrane with a bionic tubular structure, and the pore size specification of the nanofiltration membrane is 200-300 Da.

2. The integrated membrane treatment process of industrial alkaline water for canned peaches according to claim 1, characterized in that, The above process is realized by combining the use of a peach can processing wastewater stirring and sedimentation device with a material storage function; The device mentioned above includes: a sedimentation tank (1), a top frame (2) is fixedly connected to the top of the sedimentation tank (1), a stirring rod (4) extending vertically into the interior of the sedimentation tank (1) is provided in the middle of the top frame (2), and material storage mechanisms (3) are respectively provided on both sides of the stirring rod (4) on the top frame (2); The material storage mechanism (3) includes a material storage bucket (32) located inside the sedimentation tank (1) and a cover plate (31) located inside the top frame (2), and a discharge mechanism (33) is provided at the bottom of the material storage bucket (32); On both sides of the cover plate (31), there are parallel pull rods (36). On one side of the cover plate (31), a pull plate (35) perpendicular to the pull rod (36) is fixedly provided. The pull plate (35) is arranged outside the top frame (2). One end of the pull rod (36) passes through the top frame (2) and is fixedly connected to the pull plate (35), and the other end is fixedly connected to a limit disc (38). An elastic device (37) is sleeved on the outer surface of the pull rod (36).

3. An integrated membrane treatment process for industrial alkaline water of canned peaches according to claim 2, characterized in that, In the peach can processing wastewater stirring and sedimentation device with a material storage function mentioned above, the discharge mechanism (33) includes a pull frame (331) provided on one side of the material storage bucket (32). On one side of the pull frame (331), a bottom plate (332) is fixedly connected. On one side of the top frame (2), a side plate (333) is fixedly connected. On one side of the side plate (333), a guide rod (334) is fixedly connected. A tension spring (335) is sleeved on the outer surface of the guide rod (334), and a sealing sleeve (336) is sleeved on the outer surface of the bottom plate (332); One side of the storage bucket (32) is provided with a slot adapted to the bottom plate (332), the outer surface of the sealing sleeve (336) is in contact with the inner wall of the slot, one side of the pulling frame (331) is provided with a guiding hole adapted to the guiding rod (334), one end of the pulling spring (335) is welded to one side of the side plate (333), and the other end of the pulling spring (335) is welded to one side of the pulling frame (331); One side of the top frame (2) is movably penetrated by a stirring rod (4) through a bearing, the other side of the top frame (2) is fixedly provided with a motor (5), and the output end of the motor (5) is fixedly connected to one end of the stirring rod (4); One end of the pull rod (36) slidably penetrates one side of the top frame (2), and a limiting groove adapted to the limiting disc (38) is provided inside the top frame (2); One end of the elastic device (37) is welded to one side of the inner wall of the limiting groove inside the top frame (2), and the other end of the elastic device (37) is welded to one side of the limiting disc (38); A sealing gasket (34) is adhered to one side of the cover plate (31).

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