KR100256532B1 - Method for reusing wasted mercerizing liquid - Google Patents

Abstract

PURPOSE: A reuse method of mercer wastewater is provided, which can recover the whole amount of sodium hydroxide from mercer wastewater and reuse as padding liquid of mercer processing, so that a complete reuse system of mercer wastewater is achieved. The main reason of pH problem of dying wastewater is sodium hydroxide delivered from mercer process and most of dying plant costs to buy sulfuric acid and pay the amount imposed for pH to treatment plant, thereby the method of reuse can save much and invest the saved money to install this membrane. CONSTITUTION: The method is as follows: (i) separating step of sodium hydroxide solution by passing through a nanofilter separating membrane the mercer wastewater that is disposed after used as padding liquid at a mercer process of fiber industry; (ii) concentrating step of the separated sodium hydroxide to 20-25 %; and (iii) a reusing step of the recovered sodium hydroxide as water for producing the mercer padding liquid that is adjusted to 50 % concentration.

Description

Mercer Wastewater Reuse Method

The present invention relates to a method for reusing useful materials from the textile industry wastewater, and in particular, by using a nanofiltration (NF) membrane from the mercer wastewater which is discarded after mercerizing the yarn, fabric or knitted fabric with a padding liquid. A method for recovering sodium and reusing it for the next mercerization process.

Mercerization processing refers to processing that imparts performance, such as dipping yarns or fabrics in a sodium hydroxide solution to swell and shrink the fibers to give gloss or dyeability to the yarns or fabrics. Mercerization is generally carried out at temperatures of up to 20 ° C. with 20 to 25% sodium hydroxide solution.

Membrane technology is a leading technology, the general recognition that it is still premature to be applied to wastewater treatment or reuse in the textile industry, and it was introduced in some factories before the technology was fully reviewed and failed. It is true. For example, U.S. Patent No. 4,270,914 describes a method for reusing mercer wastewater using Ultrafiltration (UF) membranes. Since UF membranes can only separate substances with molecular weights ranging from 1,00 to 10,000, all of the substances below the fractional molecular weight, together with NaOH, are permeated to remove the chromaticity of the permeate. There is a problem with reuse.

Therefore, an object of the present invention is to make practical use of the membrane technology in the wastewater reuse of the textile industry.

The inventors of the present invention to solve the above problems can be seen from the confirmation of the following fact that the NF separation membrane process can be practical and very usefully applied to recover and reuse sodium hydroxide in mercer wastewater.

◎ It is possible to design 10-20 tons of treatment capacity per day because it is a process that only deals with Mercer wastewater, not large-scale installation such as reuse of industrial water in stages.

◎ It is a technology that recovers sodium hydroxide, not simplification, so it can reduce the amount of sodium hydroxide to be purchased as much as sodium hydroxide is recovered.

◎ Currently, the source of dye wastewater pH problem is mostly from sodium hydroxide in Mercer wastewater in Banwol Industrial Complex, and each dyeing plant spends pH charge according to the sulfuric acid cost for neutralization and the pH when discharged to the joint wastewater treatment plant. This cost can therefore be invested in membrane installation costs.

◎ Pretreatment and membrane cleaning are simple and there is almost no burden on concentrate treatment. : Mercer wastewater is a relatively clean sodium hydroxide solution in the range of 1 to 10%, which contains only a small amount of fiber, scouring agent, refining agent, or humectant, which is economical and simple to prevent membrane contamination. (Sodium hydroxide solution itself can be generally used as a cleaning solution for contaminated membranes.) Since there is little burden on concentrate treatment, it is a very suitable waste water for recovery using membranes.

◎ If an NF separator is installed by an environmental company that collects existing alkali, it will increase to NF separator capacity while carrying out the business according to the existing method, and then recover the reagent grade sodium hydroxide to recover the initial fee for the installation cost. There is an advantage that can be divided.

1 is an explanatory diagram schematically showing a method for recovering sodium hydroxide solution in mercerized wastewater with NF separator according to a preferred embodiment of the present invention and reusing it in the next step.

FIG. 2 is a graph illustrating a change in flux according to the operating time of the NF separator in Example 7. FIG.

Therefore, according to the present invention, the mercer wastewater, which is used as a padding liquid in mercerization processing, is passed through an NF separator to separate an aqueous sodium hydroxide solution, and the reused method of mercer wastewater is reused. Is provided.

Hereinafter, the present invention will be described in more detail.

Mercer wastewater discharged after mercerizing to give gloss or dyeability to yarns or fabrics is relatively clean, ranging from 1 to 10%, containing only a small amount of fiber, scouring agents or humectants remaining after washing. Sodium solution.

According to the present invention, an NF separator is used to recover a clean sodium hydroxide solution from such mercer wastewater. Nanofiltration (NF) is a membrane separation process that separates molecules or ions in a dissolved state with a size of 0.3 to 2 nm (3 to 20 μs), and the fractional molecular weight of NF membrane (Nano Filtration mem brane) is between RO membrane and UF membrane. . While UF membrane is permeable to organic material, it is difficult to remove chromaticity, COD, and BOD, whereas NF membrane has more than 97-98% of rejection rate of dye (rejection%: amount that solute does not penetrate the membrane and remains in the concentrate). Thus, almost clear permeate can be obtained. Compared with RO membranes, NF membranes have larger flux (permeate permeate per unit area of membrane per unit time) than RO membranes, so they have a higher treatment capacity and monovalent salts such as NaCl or NAOH, unlike RO membranes. It selectively passes through water and can be used for special applications such as desalination or salt and alkali recovery.

In the present invention, the NF separator is preferably a type in which a tubular NF separator is embedded in a module. Commercially available examples of tubular modular NF separators include module codes TM 203, TM 410 and TM 1228, which are manufactured and sold by Membrane Products, Israel. The TM 203 is a monomodule containing one membrane tube and is mainly used for experimentation. The TM 410 and TM 1228 can be used for industrial purposes with 18 membrane tubes in one module.

According to the present invention, mercurized wastewater is passed through an NF separator to recover an aqueous solution having a sodium hydroxide concentration of 1 to 10% with almost no impurities. The clean aqueous sodium hydroxide solution thus recovered may be reused as a mercerized padding liquid in the following process, or used for refining and alkali reduction. Particularly preferred among these uses is the reuse as mercerized padding liquid.

For example, according to one aspect of the present invention, there is provided a method for recovering an aqueous sodium hydroxide solution by passing a mercer wastewater through an NF separator, and concentrating the recovered aqueous sodium hydroxide solution and reusing it as a mercuring process liquid.

In the concentration process, for example, a vacuum evaporator may be used. Applying this concentration method, the total amount of aqueous sodium hydroxide solution can be recovered and reused from the mercerized wastewater, but there are disadvantages in that the initial installation and operating costs are high. In order to reduce the installation cost, the membrane is preferably installed in each plant at a capacity suitable for the size of each plant, and it is preferable to collect the aqueous sodium hydroxide solution collected at each plant in one place and to concentrate it in one concentrator. Concentration is advantageously performed until the concentration of the padding liquid (about 20-25%) is reached.

According to another aspect of the present invention, the mercurized wastewater is passed through an NF separator to recover a clean aqueous sodium hydroxide solution, and dissolved or mixed with sodium hydroxide or concentrated sodium hydroxide in the recovered sodium hydroxide solution to a sodium hydroxide concentration of 20 to 25%. A method of making an aqueous sodium hydroxide solution and reusing it as a mercuring process liquid is provided.

In general, mercerized padding solution is prepared by the automatic control of 50% aqueous sodium hydroxide solution and water to 20-25% aqueous sodium hydroxide solution. Therefore, in the case of applying the non-concentrated reuse method described above, by using the 1-10% sodium hydroxide solution recovered through the separator instead of water and reducing the amount of 50% sodium hydroxide solution, the concentration of 20-25% sodium hydroxide is reduced. The mercerized padding liquid can be easily produced. This method has the limitation that the installation cost is small but the capacity to be recovered cannot be used up, and the use of recovered sodium hydroxide solution should be secured to reduce the processing scale or recover the total amount. For example, the joint wastewater treatment plant of Banwol Industrial Complex consumes approximately (50% sodium hydroxide 50 tons / day) of sodium hydroxide to neutralize the discharged water after the Fenton treatment method. 10% sodium hydroxide can be used for this purpose. The environmental company's Alchemie plant in India collects mercury wastewater from several textile mills and recovers alkalis for redistribution.The process can be arbitrarily scaled at the expense of additional costs (tankraw, labor, etc.). The advantage of being able to resell the recovered alkali by adding sodium hydroxide (50%) to a concentration suitable for the purpose of other industries (eg 5, 7, 10, 15, 20, 25, 30%), not for mercerization. have.

In either case, the higher the alkali concentration of the mercer wastewater, the greater the economic benefit from the recovery of sodium hydroxide, so the higher the concentration of the wash, the more the padding will be collected.

In addition, in the present invention, it is preferable to perform a pretreatment step of removing suspended matter in the mercer wastewater before treatment with the NF separator. For this pretreatment, a filter, a nonwoven filter, a centrifuge, or the like can be used. When using a filter or a nonwoven fabric filter, it is good to use about 10-500 micrometers. Performing such pretreatment prevents membrane fouling and thus facilitates membrane cleaning.

If the NF membrane is not soiled much, it is sufficient to clean it with water.If the membrane is not used for several months or the flux cannot be recovered by washing with water alone, increase the cleaning time or recover the sodium hydroxide recovered from the membrane separation. It can be recovered to its original state by washing with liquid, EDTA-4Na hot water, etc. The cleaning cycle of the NF separator is preferably at the point where the flux drops in half, usually 4 to 5 hours, but in practical terms, the cleaning cycle is preferably performed for 12 hours or 20 hours a day.

As mentioned above, features of the present invention and other advantages will become more apparent from the embodiments described below.

Some definitions of terms shown in the following examples are as follows.

◎ Feed volum: Volume of feed solution supplied to membrane device (Vo)

◎ permeate volum: volume of liquid permeated through the membrane (Vp)

◎ Flux: The amount of soybean curd that passes through the unit area of the membrane per unit time. The unit is LMH (ℓ / ㎡ · hr).

◎ Membrane area: Area per membrane module × number of modules used

◎ Exclusion rate: A measure of the amount of solute not permeable to the membrane but circulated to remain in the concentrate. For example, the exclusion rate of NaCl of 5% indicates that only 5% of permeation cannot be permeated.

◎ volumetric recovery (volumemetric recovery): Vp is divided by the volume (Vf) of the remaining liquid that is continuously circulated without permeating through the membrane.

◎ Alkali recovery rate: Volume recovery rate (%) × (100-% NaOH exclusion rate) / 100

[Examples 1 to 6]

Using NF separator membrane module TM 203 (monomodule, 0.60m) and TM 410 (18 membrane tubes in one module, 1.22m) manufactured and manufactured by Membrane Products, Israel The membrane separation was performed by supplying Mercer wastewater with sodium hydroxide concentration of 1 to 4.5%. The operating conditions and treatment results of each example are shown in Table 1 below.

Example 7

Mercer wastewater having a sodium hydroxide concentration of 1 to 4.5% was pretreated with a 10 μm filter, or was supplied to the TM 203 module at a flow rate of 9-10 l / min without pretreatment to measure the change in flux according to the membrane operation time.

The operating pressure was 20 to 26 gf / cm 2 r, and the operating temperature was 26 to 66 ° C. For Mercer wastewater with 1% sodium hydroxide, starting at flux 80LMH (L / m 2 · hr) and driving for 3 to 5 hours, the flux was reduced in half to 40LMH and gradually decreased to 12LM to 20LMH. The flux decreased as the mercury wastewater sodium hydroxide concentration increased. These measurement results are shown in the graph of FIG.

As described above, according to the present invention, it is possible to recover the entire amount of NaOH in the mercer wastewater, and thus, the NaOH recovered in this way can be reused as a padding liquid for mercerization of the next process, thereby enabling the implementation of an almost complete wastewater reuse system. do.

Claims (5)

Reuse of Mercer wastewater, characterized in that the aqueous solution of sodium hydroxide is separated by passing the Mercer wastewater, which is used as a padding liquid during mercerization processing in a fiber industry, through a nanofiltration (NF) membrane, and the separated sodium hydroxide solution is reused. Way. The method according to claim 1, wherein the recovered aqueous sodium hydroxide solution is concentrated to a concentration of 20 to 25% and reused as a mercerized padding liquid. The method of claim 1, wherein the recovered aqueous sodium hydroxide solution is used in place of the water used in preparing the mercerized padding liquid, and the padding liquid concentration is adjusted to 50% fresh sodium hydroxide solution to be reused as the mercerized padding liquid. How to reuse Mercer wastewater. The method for reusing mercer wastewater according to claim 1, wherein the recovered sodium hydroxide aqueous solution is reused by adjusting to a concentration suitable for use of other industries other than the textile industry. The method of any one of claims 1 to 4, wherein the suspended matter in the Mercer wastewater is removed before the Mercer wastewater is treated with the NF separator.

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