KR100301607B1 - Recycling Method of Water-Soluble Cleaner Solutions Using Hydrophilic Membranes - Google Patents

Abstract

The present invention removes suspended solids by passing an oil-soluble aqueous detergent solution through a cartridge type pretreatment filter having a size of 1 to 30 μm, and thereafter, a molecular weight (Molecular Weight Cut-off) of 10,000 to 100,000 Daltons of polyacrylonitrile ( PAN) copolymer hydrophilic ultrafiltration membrane or fractional molecular weight 100,000 to 300,000 Dalton polyvinylidene fluoride (PVDF) copolymer hydrophilic ultrafiltration membranes are used to selectively pass water-soluble active ingredients such as surfactants and various additives The oil relates to a method of recycling a water soluble detergent solution which comprises excluding the reuse of the permeate solution.

According to the method of the present invention, since the water-soluble detergent solution treated with the hydrophilic or hydrophilized membrane can be reused in the process, the amount of the water-soluble detergent can be minimized, and the amount of the water-soluble detergent solution discarded can be drastically reduced. In addition, the membrane can be periodically backwashed to reduce pore fouling of the membrane, thereby improving permeation performance, thereby enabling the treatment of an economical and efficient water-soluble detergent solution.

Description

Recycling Method of Water-Soluble Cleaner Solutions Using Hydrophilic Membranes}

The present invention relates to a method capable of minimizing the drainage of the detergent solution by treating the water-soluble detergent solution containing the metal surface processing oil with a hydrophilic or hydrophilized separator to reuse the permeate solution passed through the separator in a washing process.

More specifically, the present invention removes suspended solids by passing an oil-soluble aqueous detergent solution through a cartridge type pretreatment filter having a size of 1 to 30 μm, and thereafter, a molecular weight (Molecular Weight Cut-off) of 10,000 to 100,000 Dalton poly Water-soluble active ingredients such as surfactants and various additives using acrylonitrile (PAN) copolymer hydrophilic ultrafiltration membranes or polyvinylidene fluoride (PVDF) copolymer hydrophilized ultrafiltration membranes having a molecular weight of 100,000 to 300,000 Daltons A method of reusing a water soluble detergent solution comprising selectively passing through and excluding oil to reuse the permeate solution.

The water-soluble detergent solution is used to remove greases such as wax, grease, and rust preventive oil applied to the metal surface, and grease to remove oily substances such as cutting oil and abrasive oil used during metal processing from the metal surface and to remove various contaminants on the metal surface. It has excellent cleaning power.

However, as the operation time of the washing tank becomes longer, the oil is saturated in the water-soluble detergent solution and the cleaning ability is reduced. Therefore, the detergent solution must be replaced. The detergent solution used here contains a large amount of various oils, surfactants and various additives. Treatment for drainage is essential because it does not meet the criteria.

In general, the treatment of waste oil-containing water-soluble detergents includes physical separation as an oil-water separation method using a difference in specific gravity between oil and water, sludge addition of a chemical flocculant, and treatment of biologically active sludge. Not only is it impossible to reuse, but there is a problem of not reaching the water quality satisfying the discharge standard or generating a large amount of sludge.

Therefore, the research to solve the above problems and to introduce a membrane process for reuse of the water-soluble detergent solution as an active ingredient has been recently conducted, some of which have been introduced into the actual process.

Korean Unexamined Patent Publication No. 96-30985 [Inventive name: Ultrafiltration Technology for Recycling Alkaline Cleaner Solution] describes a method of recycling an alkaline wash solution using a hydrophobic polysulfone ultrafiltration membrane. However, hydrophobic membranes such as polysulfones are not suitable for separation of oils from oil-containing aqueous solutions, because oils present in emulsions in aqueous solutions maintain strong affinity with hydrophobic membranes. Therefore, it is because the pores of the membrane is easily closed to rapidly reduce the permeation flow rate.

The present inventors, unlike the hydrophobic membrane as described above, in the case of a hydrophilic membrane or a surface-hydrophilized membrane, since the permeability of the surfactant having a hydrophilic group and various water-soluble additives and water is maintained while forming a mutual repulsion with oil, the oil in the solution It was found that the removal rate of oil in the permeate can be kept high by limiting the transmittance of.

An object of the present invention is to solve the problems of the prior art and to introduce a process using a hydrophilic or hydrophilized membrane to reuse the water-soluble detergent solution as an active ingredient to extend the life cycle of the water-soluble detergent solution and also discharged water-soluble detergent It is to propose an economical and environmentally friendly way to minimize waste.

1 is a diagram schematically showing a hydrophilic or hydrophilized membrane system manufactured and used in the present invention.

FIG. 2 is an alkaline detergent solution containing 0.1 wt% of Cindol 3401 VNS (Hauton Korea), which is a non-aqueous cutting oil, when separating a 3 wt% aqueous solution of Cerfa Kleen 5380D (Haupton, Korea) from the membrane system of FIG. , Which shows the membrane permeation velocity and the cutting oil rejection rate according to the operating pressure.

3 is an alkaline detergent solution containing 0.1% by weight of Hocut SSK (Hauton, Korea), which is a water-soluble cutting oil (3% by weight of Cerfa Kleen 5380D aqueous solution, Houghton, Korea) is operated when separating the membrane system of FIG. Figure showing the membrane permeation rate and the cutting oil rejection rate according to the pressure.

Figure 4 is a comparison of the permeation flow rate of the alkaline detergent solution according to the permeation time when backwashing and not backwashing the hydrophilic or hydrophilized ultrafiltration membrane using nitrogen.

<Explanation of symbols for the main parts of the drawings>

11: Raw water (oil-containing alkaline cleaner solution)

12: raw water supply tank

13: feed pump

14: pretreatment filter

15: Membrane Module

16: permeate

17: concentrated water

18: high pressure nitrogen

19: By-pass

20: multiple

V1, V2: operating pressure and flow regulating valve

V3: drain valve

SV1: backwash solenoid valve

SV2: Permeate Drain Solenoid Valve

SV3: Membrane Bypass Solenoid Valve

FI1: Membrane Influent Flow Meter

FI2: Permeate Flow Meter

PG1: Membrane Inlet Pressure Gauge

PG2: Membrane Outlet Flow Meter

PG3: backwash pressure gauge

Such an object of the present invention is achieved by a method of recycling a water-soluble detergent solution using a hydrophilic or hydrophilized membrane.

Accordingly, it is an object of the present invention to remove suspended solids by passing a water-soluble aqueous detergent solution through a cartridge type pretreatment filter having a size of 1 to 30 μm, and then to a polyacrylonitrile (PAN) copolymer having a fractional molecular weight of 10,000 to 100,000. A hydrophilic ultrafiltration membrane or a polyvinylidene fluoride (PVDF) copolymer having a fractional molecular weight of 100,000 to 300,000 is used to selectively pass water-soluble active ingredients such as surfactants and various additives, and to exclude metal processing oils. A method of recycling a water soluble detergent solution comprising reusing the permeated solution.

The present invention further relates to a method for reusing a water-soluble detergent solution further comprising backwashing with a gas such as nitrogen or air in order to suppress a decrease in the permeation flow rate according to the permeation time of the ultrafiltration membrane.

The water-soluble detergent solution that can be used in the method of the present invention is used for degreasing and metal surfaces to remove oils such as wax, grease, rust preventive oil, and oil-retaining substances such as cutting oil and abrasive oil used during metal processing from metal surfaces. It is a solution containing various contaminants.

In particular, the water soluble detergent solutions used in the process of the invention are those containing from 0.1 to 1.0% by weight of water soluble or non-aqueous cutting oil.

The polyacrylonitrile hollow fiber type ultrafiltration separator that may be used in the present invention may preferably be used with an inner diameter of 1.1 mm, a diameter of 2.5 cm of the membrane module, and a length of 26 cm, and the polyvinylidene fluoride tubular ultrafiltration membrane may have an inner diameter of 2.5. cm, a length of 146 cm can be preferably used.

In the method of recycling the water-soluble detergent solution of the present invention, a continuous membrane system as shown in FIG. 1 is used.

In the continuous membrane system of the present invention, the oil-containing water soluble detergent solution 11 is stored in the feed tank 12 and moved to the membrane pretreatment filter 14 by the feed pump 13 where it is sized as a metal scrap. Large foreign matter is removed. Thereafter, the oil particles introduced into the membrane module 15 and contained in the aqueous detergent solution are removed, and the permeate 16 passed through the membrane is circulated to the washing process and reused. The concentrated liquid 17 in which the oil component is concentrated in the separator is recycled to the feed tank 12, concentrated, and then removed from the feed tank as effluent 20. A flow meter FI1 is installed to measure the flow rate into the membrane module, and pressure gauges PG1 and PG2 are installed at the inlet and outlet of the membrane to measure the pressure difference in the membrane. Install (PG3) to measure transmembrane pressure and backwash pressure. Adjust valves (V1, V2) are installed to adjust the flow rate through the membrane and the membrane operating pressure.

In addition, in order to reduce the so-called concentration polarization phenomenon in which the oil removed in the detergent solution accumulates on the surface of the separator, a backwash apparatus using high pressure nitrogen is installed. The backwasher is equipped with solenoid valves (SV1, SV2) at the permeate outlet and the nitrogen inlet, respectively, and the solenoid valve (SV3) is also provided at the membrane bypass to maintain a constant membrane pressure during backwash regardless of the operating pressure. Mount it. All three solenoid valves are connected to one time control system so that the opening and closing of the valve can be operated simultaneously.

Acceptance criteria of the water-soluble detergent solution reused according to the present invention applies the management criteria of the 3% by weight aqueous detergent solution of Hawthorne Korea currently supplying metal working oil and water-soluble detergent solution in Korea, Table 1 shows the reference value.

Control Criteria for 3% by weight Aqueous Cleaner Solution Brix concentration (%) 0.4 or more pH 9.5 or more Total alkalinity (% KOH) 0.1 or more Surface tension (dyne / cm) 65 or less Foreign substance content (ppm) below 10 Antirust (hr) over 10

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example 1>

Separating the cutting oil from the alkaline detergent solution (3% by weight aqueous solution of Cerfa Kleen 5380D, Houghton Korea) containing 0.1 wt% of non-aqueous cutting oil Shindol 3401 VNS (Hautton Korea) using a membrane system as shown in FIG. The operation results are shown in FIG. 2. Cutting oil rejection rate in Figure 2 was measured using a turbidimeter (HACH 2100N). Permeate flow rate increased almost linearly with increasing operating pressure and the coolant rejection rate was over 90%.

In order to determine the reusability of the permeated alkali cleaner solution, items related to the cleaning performance of the 3 wt% alkaline cleaner solution are shown in Table 2. In addition, the alkaline detergent solution containing 0.1% by weight of water-insoluble cutting oil was removed using a hydrophilic or hydrophilized ultrafiltration membrane near the meter pressure of 2 bar, and the items related to the cleaning performance of the alkaline detergent solution that penetrated the membrane were analyzed. Indicated.

Transmembrane Alkaline Washing Water Alkaline wash water stock solution (3% by weight) Brix concentration 0.55 0.6 pH 10.7 10.5 Total alkalinity (% KOH) 0.18 0.32 Surface tension (dyne / cm) 61.2 52.2 Foreign substance content (ppm) One 0 Antirust (hr) 20 70

As can be seen from Table 2, the brix concentration and surface tension of the alkaline detergent solution that has passed through the separator is slightly lower than the 3% by weight stock solution of the alkaline cleaner solution, but is suitable for use in the table 1, which is a standard for use of an aqueous detergent solution. It is possible. However, if the alkaline cleaner solution is repeatedly recycled, the rust preventive property may be slightly reduced.

<Example 2>

Cutting oil was separated according to the method of Example 1 from an alkali detergent solution (1.0% by weight of a water-insoluble cutting oil, Sindol 3401 VNS (Hauton Corporation), 3% by weight aqueous solution of Cerfa Kleen 5380D).

Table 3 below analyzes the items related to the cleaning performance of the alkaline detergent solution that permeated the membrane.

Transmembrane Alkaline Washing Water Brix concentration 0.55 pH 10.5 Total alkalinity (% KOH) 0.28 Surface tension (dyne / cm) 64.3 Foreign substance content (ppm) 0 Antirust (hr) 36

As can be seen from Table 3 above, the alkaline detergent solution that penetrated the membrane was in accordance with Table 1, which is the standard of use of the aqueous detergent solution.

<Example 3>

Cutting oil was separated according to the method of Example 1 from an alkaline detergent solution containing 0.1% by weight of Hocut SSK (Hawton, Korea), a water-soluble cutting oil (3% by weight aqueous solution of Cerfa Kleen 5380D, Houghton, Korea). Indicated. Cutting oil rejection rate in Figure 3 was measured using a turbidimeter (HACH 2100N).

The cleaning performance-related items of the alkaline detergent solution that passed through the membrane are analyzed and shown in Table 4 below.

Transmembrane Alkaline Washing Water Brix concentration 0.64 pH 10.4 Total alkalinity (% KOH) 0.31 Surface tension (dyne / cm) 42.3 Foreign substance content (ppm) 3 Antirust (hr) 30

As can be seen from Table 4 above, the alkaline detergent solution that permeated the membrane was in accordance with Table 1, which is the standard of use of the aqueous detergent solution.

<Example 4>

Cutting oil was separated from the alkaline detergent solution containing 1.0% by weight of Hocut SSK (Hawton, Korea), a water-soluble cutting oil (3% by weight of Cerfa Kleen 5380D aqueous solution, Houghton, Korea) according to the method of Example 1.

The cleaning performance-related items of the membrane-permeable alkaline detergent solution are analyzed and shown in Table 5 below.

Transmembrane Alkaline Washing Water Brix concentration 0.65 pH 10.5 Total alkalinity (% KOH) 0.32 Surface tension (dyne / cm) 42.3 Foreign substance content (ppm) 3 Antirust (hr) 30

As can be seen from Table 5, the alkaline cleaner solution that has passed through the membrane is in accordance with Table 1, which is the standard of use of the aqueous detergent solution.

Example 5

Separating the cutting oil from the alkaline detergent solution (3% by weight aqueous solution of Cerfa Kleen 5380D, Houghton Korea) containing 0.1 wt% of non-aqueous cutting oil Shindol 3401 VNS (Hautton Korea) using a membrane system as shown in FIG. In order to improve the membrane permeation flow rate of the alkaline detergent solution, the membrane was backwashed periodically with nitrogen or air.

4 shows the improvement of the permeation flow rate according to the permeation time when the alkaline detergent solution is passed through the separator for about 200 seconds and backwashed for about 40 seconds using nitrogen or air. In the case of backwashing, the permeation flux increased more than two times after 30 minutes of permeation time.

Comparative Example 1

A polysulfone copolymer hydrophobic ultrafiltration membrane module having a fractional molecular weight of 100,000 was mounted in a membrane system as shown in FIG. 1, and an alkaline detergent solution containing 0.1 wt% of a water-soluble cutting oil, Hocut SSK (Hawthorne Korea), was used. The cutting oil was separated from Cerfa Kleen 5380D 3 wt% aqueous solution).

The results are shown in Table 6 below.

Operating pressure (bar) 0.5 1.0 1.5 2.0 Polyacrylonitrile membrane Permeate Flow Rate (L / ㎡ · hr) 71.9 73.7 70.0 61.5 Exclusion rate (%) 99.8 99.5 99.0 98.3 Polysulfone membrane Permeate Flow Rate (L / ㎡ · hr) 38.7 48.3 52.6 56.9 Exclusion rate (%) 98.6 99.4 97.9 96.1 Excellence of Polyacrylonitrile Membrane Compared to Polysulfone Membrane Permeate flow rate increase rate (%) 85.8 52.6 33.1 8.1 Exclusion rate growth rate (%) 1.2 - 1.1 2.3

As can be seen from Table 6, the hydrophobic polysulfone membrane used in this comparative example has a large permeation flow rate in the case of the hydrophilic or hydrophilized ultrafiltration membrane of the present invention, despite the fractional molecular weight is twice as large, In particular, when backwashing under the same conditions, the effect of backwashing did not appear in the hydrophobic membrane, but in the case of hydrophilic or hydrophilized ultrafiltration membranes, the permeation flow rate was greatly improved by the backwashing effect as shown in FIG.

As such, the permeability of the hydrophilic or hydrophilized ultrafiltration membranes used in the present invention is much better than the hydrophobic polysulfone ultrafiltration membranes mentioned in Korean Patent Publication No. 96-30985.

Comparative Example 2

Alkaline detergent solution containing 0.1% by weight of the non-aqueous cutting oil Shindol 3401 VNS (Korea Houghton), equipped with a hydrophobic ceramic ultrafiltration membrane having a fractional molecular weight of 50,000 in a separator system as shown in FIG. 1 (Korea Houghton, Cerfa Kleen) 5380D 3 wt% aqueous solution) was separated from the cutting oil.

The results are shown in Table 7 below in comparison with the experimental results of the polyacrylonitrile separation membrane which is a hydrophilic ultrafiltration membrane.

Operating pressure (bar) 0.5 1.0 1.5 2.0 Polyacrylonitrile membrane Permeate Flow Rate (L / ㎡ · hr) 62.4 79.3 85.7 101.8 Exclusion rate (%) 92.5 96.5 97.7 97.4 Ceramic film Permeate Flow Rate (L / ㎡ · hr) 5.9 11.2 13.4 17.4 Exclusion rate (%) 91.0 88.4 84.5 87.7 Superiority of Polyacrylonitrile Membranes over Ceramic Membranes Permeate flow rate increase rate (%) 958 608 540 485 Exclusion rate growth rate (%) 1.6 9.2 15.6 11.1

As can be seen from Table 7, the permeation flux of the polyacrylonitrile copolymer ultrafiltration membrane, which is a hydrophilic membrane, is 4.8 times higher.

Comparative Example 3

Alkaline detergent containing 0.1 wt% of non-aqueous cutting oil Shindol 3401 VNS (Hawthorne Korea) equipped with a hydrophobic stainless steel (SS) microfiltration membrane having a 0.2 μm pore size in the membrane system as shown in FIG. The cutting oil was separated from the solution (3% by weight aqueous solution of Cerfa Kleen 5380D, Houghton Korea).

The results are shown in Table 8 below in comparison with the experimental results of the polyacrylonitrile separation membrane which is a hydrophilic ultrafiltration membrane.

Driving time (minutes) 0.5 1.0 1.5 2.0 Polyacrylonitrile membrane Permeate Flow Rate (L / ㎡ · hr) 62.4 79.3 85.7 101.8 Exclusion rate (%) 92.5 96.5 97.7 97.4 Stainless steel film Permeate Flow Rate (L / ㎡ · hr) 653 738 956 1211 Exclusion rate (%) 40.2 34.3 34.1 21.0

As can be seen from Table 8, in the case of the microfiltration membrane, the permeate flow rate was maintained high, but the cutting oil and the rejection rate were very low at 20 to 40%, which was not suitable for the recycling process of the aqueous detergent solution.

According to the method of the present invention, since the water-soluble detergent solution can be reused, the amount of the water-soluble detergent solution can be minimized, as well as the amount of the water-soluble detergent solution discarded is drastically reduced, thereby reducing the treatment cost thereof.

In addition, since the membrane can be periodically backwashed to reduce pore fouling of the membrane, the permeation performance can be improved, thereby enabling economical and efficient treatment of the aqueous detergent solution.

Claims (4)

The oil-containing aqueous detergent solution was passed through a cartridge type pretreatment filter of 1 to 30 μm in order to remove suspended solids, followed by a molecular weight cut-off of 10,000 to 100,000 Daltons of polyacrylonitrile (PAN) air. Water-soluble active ingredients such as surfactants and various additives are selectively passed and oil is eliminated using a copolymerized hydrophilic ultrafiltration membrane or a polyvinylidene fluoride (PVDF) copolymer having a fractional molecular weight of 100,000 to 300,000 Daltons. A method of reusing a water-soluble detergent solution comprising the reuse of the permeated solution. The method according to claim 1, wherein the oil is water-insoluble cutting oil, which is contained in an aqueous solution of 0.1 to 1.0% by weight. The method of claim 1, wherein the oil is a water-soluble cutting oil, 0.1 to 1.0% by weight in a water-soluble detergent solution. The method of claim 1, further comprising backwashing with a gas such as nitrogen or air to suppress a decrease in permeation flow rate with the permeation time of the ultrafiltration membrane.