Method for treating mercerizing waste alkali liquor

Abstract

The invention discloses a mercerizing waste alkali liquor treatment method, and belongs to the technical field of wastewater treatment, the mercerizing waste alkali liquor treatment method adopts the following technical scheme: the mercerizing waste alkali liquor treatment method comprises the following steps: S1, preheating waste alkali liquor, and then carrying out wet catalytic oxidation to remove COD (Chemical Oxygen Demand); s2, carrying out gas-liquid separation on the waste alkali liquid treated in the step S1, feeding the waste alkali liquid into a preheater, and then feeding the waste alkali liquid into a heat exchanger for cooling; s3, the cooled waste alkali liquor is subjected to diffusion dialysis treatment, NaOH is recycled and then discharged, and light alkali liquor is recycled; s4, the light alkali liquor recycled through diffusion dialysis enters a heat exchanger to be heated and then is subjected to membrane distillation concentration recycling. According to the combined treatment technology, through cooperative use of all stages, the problems that alkali liquor recycling does not reach the standard, waste liquor treatment does not reach the standard, and an existing method is not suitable for treating high-concentration COD waste liquor are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wastewater treatment, in particular to a treatment method of mercerizing waste lye. BACKGROUND

[0002] Mercerizing is a key process in cotton fabric production, which makes the fiber swell and obtain a silk-like luster through immersion in concentrated lye, and is crucial in the textile and dyeing industry. With the development of the industry, mercerizing is increasingly widely used, greatly improving the quality and aesthetics of cotton fabrics and promoting the progress of the textile and dyeing industry. However, a large amount of mercerizing waste lye is generated during the mercerizing process, which has gradually become a constraint factor for the development of the industry. The mercerizing waste lye not only has a large quantity, but also has complex composition, which is difficult to treat. If not properly treated, it will cause serious environmental pollution and waste of resources. How to efficiently and environmentally treat mercerizing waste lye has become an important problem to be solved in the textile and dyeing industry.

[0003] At present, the industry mainly uses the following methods to treat mercerizing waste lye. Neutralization is one of the common treatment methods, which uses acid to neutralize the waste lye, so that the pH of the waste lye reaches the standard for discharge or further treatment. Biological treatment is also a commonly used method, which uses the metabolic action of microorganisms to decompose organic matter in the waste lye, and has the characteristics of high efficiency and low cost. Membrane separation separates the waste lye through special membranes to separate the lye and other impurities, realizing the recovery of the lye. Evaporation and concentration evaporates the waste lye to remove water, thereby increasing the concentration of the lye for subsequent recycling.

[0004] The existing treatment methods have obvious defects. Although the neutralization method is relatively simple to operate, it wastes a large amount of alkali resources in the mercerizing waste lye, and produces a large amount of salt precipitate during the neutralization process, which not only increases the difficulty of subsequent treatment, but also may cause secondary pollution to the environment. The biological treatment method has strict requirements for the pH and COD concentration of the influent, while the composition of the mercerizing waste lye is complex, and the pH and COD concentration fluctuate greatly, which makes it difficult to meet the requirements of the biological treatment method, resulting in poor treatment effect. The membrane separation method and the evaporation and concentration method mainly focus on the recovery of the lye, ignoring the subsequent treatment of the waste liquid, and cannot fundamentally solve the pollution problem of the mercerizing waste lye. At present, there is a lack of a complete process for treating mercerizing waste lye. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a treatment method of mercerizing waste lye, which sets up a combined treatment process, which solves the problems of non-compliance of lye recycling, non-compliance of waste liquid treatment and non-applicability of existing methods to high-concentration COD waste liquid through the cooperation of each stage.

[0006] The application provides a treatment method for spent mercerizing lye. A treatment method for spent mercerizing lye comprises the following steps: S1, wet catalytic oxidation is performed on the preheated spent lye to remove COD; S2, after the spent lye treated in step S1 is subjected to gas-liquid separation, the spent lye is introduced into a preheater and then into a heat exchanger to reduce the temperature; S3, the spent lye after temperature reduction is subjected to diffusion dialysis treatment, and the recovered NaOH is discharged, and the dilute lye is recovered; S4, the dilute lye recovered through diffusion dialysis is introduced into the heat exchanger to increase the temperature and then subjected to membrane distillation concentration for recycling.

[0007] By adopting the above technical scheme, the special combined treatment process is provided, the spent lye is first introduced into the wet catalytic oxidation to reduce the COD value of the spent lye, so that the burden of subsequent membrane treatment is reduced, the service life of the diffusion dialysis treatment and the membrane of the membrane distillation system is increased, the diffusion dialysis device is arranged before the membrane distillation, the corrosion and pollution risk of the membrane caused by high pH is reduced, the membrane pollution and membrane poisoning risk of the whole combined treatment process are reduced, the service life of the membrane can be effectively prolonged to 2-5 years, the spent lye can reach the standard, in addition, the temperature of the waste liquid generated in the wet catalytic oxidation process can be used as part of the heat source of the dilute lye in the membrane distillation process, and the treatment cost of the spent lye is effectively reduced.

[0008] In a preferred embodiment, the COD concentration in the spent lye in step S1 is not higher than 80000 mg / L, and the alkali concentration in the spent lye is not higher than 6%. When the COD concentration in the spent lye is not higher than 80000 mg / L, the combined treatment method of the application can achieve the treatment effect, and the COD removal rate can be at least 80%.

[0009] In a preferred embodiment, the operating pressure in the wet catalytic oxidation in step S1 is 2-8 MPa, and the preferred pressure is 4-6 MPa.

[0010] In a preferred embodiment, the oxygen amount in the wet catalytic oxidation in step S1 is 1-2 times the theoretical gas amount, and the preferred oxygen amount is 1.5-1.7 times the theoretical gas amount. When the oxygen amount is 1-2 times the theoretical gas amount, the removal rate of the COD amount in the spent lye can be ensured.

[0011] In a preferred embodiment, the catalyst in the wet catalytic oxidation in step S1 is a heterogeneous catalyst.

[0012] In a preferred embodiment, the addition amount of the heterogeneous catalyst is 3-5 g / L.

[0013] In a preferred embodiment, the heterogeneous catalyst is one or more of a ruthenium system, a cerium system, a titanium system, and a platinum system.

[0014] In a preferred embodiment, the flow ratio of the waste lye solution pump to the dilute lye solution pump in the diffusion dialysis treatment of step S3 is 1:(1-1.3), and preferably the flow ratio is 1:(1.1-1.2). When the flow ratio of the waste lye solution pump to the dilute lye solution pump is set within this range, the recovery rate of the lye can be effectively ensured. If the flow ratio of the waste lye solution pump is too high, the recovery rate of the lye will decrease.

[0015] In a preferred embodiment, when the lye recovery rate decreases by 10-15% in step S3, the device is cleaned with distilled water.

[0016] In a preferred embodiment, the COD removal rate in step S1 is greater than 80%.

[0017] In summary, the present application has the following beneficial effects: 1. By combining wet catalytic oxidation with diffusion dialysis treatment, the present application can significantly reduce the COD value of the waste lye solution, so that the COD removal rate of the waste lye solution in the wet catalytic oxidation treatment process can be at least 80%, effectively reducing the risk of pollution of the diffusion dialysis treatment and the membrane distillation process by the waste lye solution, and reducing the corrosion and pollution risk of high pH on the membrane by placing the diffusion dialysis before the membrane distillation process, thereby reducing the processing burden. Therefore, the continuous use of this treatment system not only reduces the COD amount in the waste lye solution, but also separates and processes the lye resource, so that the discharge of the waste lye solution meets the national standards.

[0018] 2. The waste lye solution with a higher temperature obtained after wet catalytic oxidation treatment can preheat the untreated waste lye solution after entering the preheater, and can heat the single lye after entering the heat exchanger, thereby providing a certain amount of heat for the membrane distillation system. Therefore, the entire treatment system can effectively improve the recovery and utilization of heat, reduce the processing cost, and achieve the effect of energy saving and emission reduction.

[0019] 3. The distilled water produced by the membrane distillation is used as the water inlet of the diffusion dialysis, fully utilizing the water resources produced in the system, and achieving the effect of resource recovery.

[0020] 4. No new reagent is added in the treatment process of the present application, so no new substance is produced, and therefore there is no secondary pollution, making the entire treatment process more efficient and simple. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is the waste lye treatment flowchart of the present application. DETAILED DESCRIPTION

[0022] The following description will be made in conjunction with Figure 1 The application will be further described. All reagents not specified by the manufacturer are conventional reagent products that can be obtained commercially.

[0023] The existing conventional waste lye treatment methods include single treatment methods and combined treatment processes, wherein the single treatment methods include: Neutralization method: waste lye is commonly neutralized by hydrochloric acid to make the pH of the waste water reach the discharge standard, but reagents need to be added, which not only wastes the alkali resources in the waste lye but also produces a large amount of salts to increase the difficulty of subsequent treatment.

[0024] Evaporation concentration recovery: the evaporation concentration process can increase the concentration of the recovered waste lye to reach the recycling standard, but it has high energy consumption and certain corrosiveness to the equipment.

[0025] Wet catalytic oxidation: wet catalytic oxidation is a kind of advanced oxidation method, which realizes high-efficiency oxidation by using oxygen or air as an oxidant under the conditions of 2-8 MPa pressure and 200°C temperature. This technology uses a catalyst to accelerate the reaction process and significantly reduces the reaction activation energy, and is suitable for treating high-concentration organic waste water, difficult-to-degrade pollutants and industrial waste water containing harmful substances. It has the advantages of high oxidation efficiency, less secondary pollution and recyclable energy, and shows a wide application prospect in the environmental governance of chemical, pharmaceutical, printing and dyeing industries. Wet catalytic oxidation equipment can significantly reduce the COD in waste lye, but as a single treatment method, it needs to be combined with other treatment methods to make the waste water reach the discharge standard, or the waste lye is treated as a resource.

[0026] Diffusion dialysis: diffusion dialysis uses the concentration difference of solutions on both sides of an ion exchange membrane and the selectivity of the ion exchange membrane to realize the separation of substances. Diffusion dialysis is commonly used for the separation and recovery of acids and bases, as well as the removal of heavy metal ions. Diffusion dialysis is simple to operate and the system is simple, and acids, bases and other substances can be recovered. However, high COD concentration of the influent and excessively high acid and alkalinity will reduce the performance of the membrane and shorten the service life of the membrane.

[0027] Membrane distillation: membrane distillation is a kind of heat-driven membrane separation technology, which uses the vapor pressure difference on both sides of the membrane to realize the separation and concentration of substances. It is commonly used for high-salinity waste water treatment, seawater desalination, waste lye resourceization, concentration of industrial waste acid and waste lye, etc. However, like diffusion dialysis, high-concentration COD waste lye will also adversely affect the performance of the membrane.

[0028] The combined treatment process methods include: Neutralization and biological treatment: the waste lye is first treated by neutralization to reduce the pH of the solution, and then microorganisms are used to decompose the organic matter in the waste lye. The disadvantage is that a large amount of salt is generated in the neutralization process, and the microorganism decomposition process has certain requirements for the COD value of the incoming water. Water is often used to dilute and reduce the COD concentration before entering the microorganism decomposition process to reduce the processing complexity. This not only wastes water resources, but also cannot handle high-concentration COD waste liquid.

[0029] Membrane separation and evaporation crystallization: first use the selective permeability of ion exchange membrane to separate NaOH, and then evaporate to crystallize NaOH to realize the recovery and utilization of high-purity alkali. However, the COD tolerance of ion exchange membrane stack is low, which shortens the service life of ion exchange membrane, leading to a decrease in membrane flux, and the COD-containing waste liquid after separation of alkali still needs further treatment.

[0030] Therefore, in view of the problems of the existing method, a new treatment process for mercerizing waste lye is designed. The COD content in the waste lye is effectively removed by wet catalytic oxidation, avoiding the pollution of the waste lye to the membrane treatment in the later stage. At the same time, the waste lye with high temperature obtained after wet catalytic oxidation can preheat the untreated waste lye when passing through the preheater, and the dilute lye obtained by diffusion dialysis membrane stack treatment can also be preheated in the entire circulation system. The heat generated by wet catalytic oxidation can be further recovered, reducing the processing cost (for example, in the heat saving situation of step S3 of the embodiment of the present application: for example, in the process of concentrating 4.17 kg of sodium hydroxide solution with a content of 6% to 1 kg of reusable sodium hydroxide with a content of 25%, the heat required to heat the sodium hydroxide solution with a content of 6% from 25°C to 85°C is Q=m×c×ΔT=4.17*4.18*(85-25)=1045kJ energy, that is, 1 kg of reusable sodium hydroxide is generated, and 1045kJ of energy is saved). It also improves the processing efficiency and enables the sodium hydroxide in the waste lye to be reused. No new reagent is added in the entire treatment process, so no new substances are generated, and there is no secondary pollution. Therefore, the entire treatment process is more efficient and simple. Embodiment

[0031] A treatment method for mercerizing waste lye, comprising the following steps: The NaOH concentration in a certain mercerizing waste lye is 5%, and the COD concentration is 20000mg / L. S1, the waste lye is preheated by a preheater and then enters a wet catalytic oxidation tower with air or oxygen, under the conditions of a temperature of 260°C and a pressure of 6 MPa, for 1 h, the gas amount is 1.7 times of the theoretical gas amount, the usage amount of the heterogeneous catalyst ruthenium system is 4 g / L, the COD of the waste lye after oxidation treatment is 198 mg / L, the NaOH content is 6%, and the COD removal rate is 99.01%; S2, the waste lye after step S1 treatment enters a gas-liquid separator for gas-liquid separation, the separated gas enters a tail gas centralized treatment system, and the waste lye with a higher temperature enters a preheater and then a heat exchanger to be cooled to 30°C; S3, the cooled waste lye enters a diffusion dialysis membrane stack for treatment to recover NaOH, wherein the flow ratio of the waste lye entering the diffusion dialysis membrane stack to the flow of the flow pump of the dilute lye out of the diffusion dialysis membrane stack is 1:1.1, specifically, the optimal flow of the flow pump of the waste lye entering the diffusion dialysis membrane stack is 10 mL / min; the final alkali recovery rate is 95% (if the alkali recovery rate decreases by 10-15% in this process, the diffusion dialysis membrane stack needs to be flushed and cleaned), the NaOH concentration in the alkali-removed lye is 0.03%, the NaCl concentration in the diluted lye after neutralization is 423 mg / L, the COD concentration is 195 mg / L, and the pH is 7.5, so the diluted lye can be directly discharged, and the dilute lye is recovered; S4, the dilute lye recovered by diffusion dialysis enters a heat exchanger to be heated to 85°C and then enters a membrane distillation system for concentration, and concentrated lye is obtained after membrane distillation treatment, the NaOH concentration in the concentrated lye is 25%, reaching the reuse standard, and the distilled water produced in the distillation process is cooled and then enters the diffusion dialysis membrane stack as a solvent for recovering the dilute lye. Embodiment

[0032] A treatment method of a mercerizing waste lye, comprising the following steps: The NaOH concentration in a certain mercerizing waste lye is 3%, and the COD concentration is 10,000 mg / L; S1, the waste lye is preheated by a preheater and then enters a wet catalytic oxidation tower with air or oxygen, under the conditions of a temperature of 245°C and a pressure of 5 MPa, for 1.3 h, the gas amount is 1.5 times of the theoretical gas amount, the usage amount of the heterogeneous catalyst ruthenium system is 3 g / L, the COD of the waste lye after oxidation treatment is 266 mg / L, the NaOH content is 3%, and the COD removal rate is 97.34%; S2, the waste lye after step S1 treatment enters a gas-liquid separator for gas-liquid separation, the separated gas enters a tail gas centralized treatment system, and the waste lye with a higher temperature enters a preheater and then a heat exchanger to be cooled to 25°C; S3, the waste lye after cooling enters the diffusion dialysis membrane stack for treatment, and NaOH is recovered, wherein the flow ratio of the waste lye entering the diffusion dialysis membrane stack to the flow of the flow pump of the dilute lye out of the diffusion dialysis membrane stack is 1:1.2, and specifically, the flow of the flow pump of the waste lye entering the diffusion dialysis membrane stack is best 10 mL / min; the final alkali recovery rate is 91% (if the alkali recovery rate decreases by 10-15% in the process, the diffusion dialysis membrane stack needs to be flushed and cleaned), the concentration of sodium hydroxide in the alkali-removed lye is 0.03%, the concentration of sodium chloride in the alkali-removed lye after neutralization is 394 mg / L, the COD concentration is 266 mg / L, and the pH is 7.5, so the dilute lye can be directly discharged, and the dilute lye is recovered; S4, the dilute lye recovered by diffusion dialysis enters the heat exchanger and is heated to 85°C, and then enters the membrane distillation system for concentration, and concentrated lye is obtained after membrane distillation treatment, the concentration of NaOH in the concentrated lye is 25%, reaching the reuse standard, and the distilled water produced in the distillation process is cooled and then enters the diffusion dialysis membrane stack as a solvent for recovering dilute lye. Embodiment

[0033] A treatment method of mercerizing waste lye, comprising the following steps: The concentration of NaOH in the waste lye is 4%, and the COD concentration is 80000 mg / L; S1, the waste lye after preheating by the preheater enters the wet catalytic oxidation reaction tower with air or oxygen, and is treated at a temperature of 270°C and a pressure of 6.2 MPa for 1.6 h, the amount of gas introduced is 1.8 times the theoretical amount, and the amount of non-homogeneous catalyst ruthenium is 5 g / L, after oxidation treatment, the COD in the waste lye is 136 mg / L, and the NaOH content is 5%, and the COD removal rate is 99.83%; S2, the waste lye after step S1 treatment enters the gas-liquid separator for gas-liquid separation, the separated gas enters the tail gas centralized treatment system, and the waste lye at a higher temperature enters the preheater and then enters the heat exchanger to be cooled to 30°C; S3, the waste lye after cooling enters the diffusion dialysis membrane stack for treatment, and NaOH is recovered, wherein the flow ratio of the waste lye entering the diffusion dialysis membrane stack to the flow of the flow pump of the dilute lye out of the diffusion dialysis membrane stack is 1:1.2, and specifically, the flow of the flow pump of the waste lye entering the diffusion dialysis membrane stack is best 10 mL / min; the final alkali recovery rate is 88% (if the alkali recovery rate decreases by 10-15% in the process, the diffusion dialysis membrane stack needs to be flushed and cleaned), the concentration of sodium hydroxide in the alkali-removed lye is 0.03%, the concentration of sodium chloride in the alkali-removed lye after neutralization is 394 mg / L, the COD concentration is 288 mg / L, and the pH is 7.5, so the dilute lye can be directly discharged, and the dilute lye is recovered; S4, the recovered dilute lye solution is heated to 85°C in a heat exchanger and then fed into a membrane distillation system for concentration. The concentrated lye solution obtained after membrane distillation treatment has a NaOH concentration of 24%, reaching the reuse standard. Distilled water produced in the distillation process is cooled and then fed into the diffusion dialysis membrane stack as the solvent for the recovered dilute lye solution.

[0034] The embodiments of the present application are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Any equivalent changes made on the basis of the structure, shape, and principle of the present application should be covered by the protection scope of the present application.

Claims

1. A method for treating spent mercerizing lye, characterized by, It comprises the following steps: S1, removing COD of waste lye after preheating by wet catalytic oxidation; S2, after gas-liquid separation of waste lye treated in step S1, the waste lye enters a preheater and then a heat exchanger for cooling; S3, after cooling, the waste lye is treated by diffusion dialysis, and after recovering NaOH, it is discharged, and the dilute lye is recovered; S4, the dilute lye recovered by diffusion dialysis is heated in a heat exchanger and then concentrated by membrane distillation for recycling.

2. A process for the treatment of spent sulphite lye according to claim 1, characterized in that: The COD concentration of the waste lye in step S1 is not higher than 80000 mg / L.

3. The method for treating the spent sulphite lye according to claim 1, characterized in that: The operation pressure of the wet catalytic oxidation in step S1 is 2-8 Mpa.

4. The method for treating the spent sulphite lye according to claim 1, characterized in that: The oxygen amount in the wet catalytic oxidation in step S1 is 1-2 times of the theoretical gas amount.

5. The method for treating the spent sulphite lye according to claim 1, characterized in that: The catalyst in the wet catalytic oxidation in step S1 is a heterogeneous catalyst.

6. The method for treating spent sulphite lye according to claim 5, characterized in that: The addition amount of the heterogeneous catalyst is 3-5 g / L.

7. The method of claim 5, wherein the spent sulphite lye is treated with a mixture of calcium hydroxide and calcium carbonate. The heterogeneous catalyst is one or more of ruthenium system, cerium system, titanium system and platinum system.

8. The method for treating waste alkaline solution from mercerizing according to claim 1, characterized in that: The flow ratio of the waste lye pump to the dilute lye pump in the diffusion dialysis treatment of step S3 is 1: (1-1.3).

9. The method for treating waste alkaline solution from mercerizing according to claim 1, characterized in that: If the lye recovery rate decreases by 10-15% in step S3, the device is cleaned with distilled water.

10. The method for treating waste alkaline solution from mercerizing according to claim 1, characterized in that: The COD removal rate in step S1 is greater than 80%.

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