Wastewater recycling method for dyeing and finishing process of high-elastic denim fabric

Abstract

According to the technical scheme, the waste water recycling method is characterized by comprising the following steps that S1, printing and dyeing waste water discharged from a dye vat is discharged into a raw water ditch through a dye vat blow-off pipe for heat dissipation, and meanwhile the PH value of raw water is detected and recorded; s2, lifting the printing and dyeing wastewater in the raw water ditch into a primary sedimentation tank through a water pump, adding waste acid and / or waste alkali, fully mixing, adjusting the pH value of the printing and dyeing wastewater to make the printing and dyeing wastewater be alkalescent, putting aerobic bacteria into the sedimentation tank, performing aerobic treatment on the purified wastewater to degrade organic matters in the wastewater, and discharging the wastewater into the primary sedimentation tank; and reacting for 1.5-2.5 hours to obtain a precipitate. The method effectively solves the problems of high treatment cost and large investment of the printing and dyeing wastewater, realizes resource utilization of the printing and dyeing wastewater, and avoids waste of water resources and salt resources.

Description

Technical Field

[0001] This invention relates to the field of wastewater utilization technology, and more specifically, to a method for reusing wastewater from the dyeing and finishing process of high-elastic denim fabric. Background Technology

[0002] Dyeing and printing wastewater (hereinafter referred to as dyeing and printing wastewater) refers to the wastewater discharged from dyeing and printing factories, wool dyeing and finishing factories, and silk factories that mainly process cotton, linen, chemical fibers and their blended products, and silk. Dyeing and printing wastewater contains a large amount of dyes, sizing agents, inorganic salts, etc., and is characterized by large volume, high salinity, high content of organic pollutants, complex composition, high color, and poor biodegradability, making it one of the most difficult industrial wastewaters to treat.

[0003] However, during the dyeing process, to ensure the dyeing effect on the fabric later, a portion of the water used for dyeing needs to be pure water (i.e., natural water or river water); the other portion can be mixed with dyeing wastewater (i.e., raw water) that has undergone dehydration and impurity removal treatment. Therefore, in order to maintain the rated water usage within the factory area, a portion of the pre-treated dyeing wastewater needs to be transported through the municipal pipeline network to a combined wastewater treatment plant for further purification treatment, and then discharged in a unified manner after passing the test.

[0004] Currently, the treatment of existing dyeing and printing wastewater requires significant costs, and the reuse rate of this wastewater is relatively low.

[0005] Therefore, a solution needs to be proposed to address this problem. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a wastewater reuse method for the dyeing and finishing process of high-elastic denim fabric, which effectively solves the problems of high cost and large investment in dyeing and printing wastewater treatment, and makes resource utilization of dyeing and printing wastewater, avoiding the waste of water and salt resources.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a method for wastewater reuse in the dyeing and finishing process of high-elastic denim fabric, comprising the following steps: Step S1: the dyeing wastewater discharged from the dyeing vat is discharged into the raw water ditch through the dyeing vat drain pipe for heat dissipation, and the pH value of the raw water is detected and recorded at the same time; Step S2: the dyeing wastewater located in the raw water ditch is pumped to the primary sedimentation tank, and waste acid and / or waste alkali are added and fully mixed to adjust the pH value of the dyeing wastewater to make it weakly alkaline, and aerobic bacteria are introduced into the sedimentation tank. After the above-mentioned purified wastewater is aerobically treated, the organic matter in it is degraded, and the precipitate is obtained after reacting for 1.5-2.5 hours;

[0008] Step S3: The water obtained after sedimentation in step S2 is discharged into the flotation tank through a conduit, and polyacrylamide and polyaluminum chloride are added and mixed thoroughly for decolorization treatment.

[0009] Step S4: The sludge in the flotation tank is collected by a scraper and then pumped into the sludge thickening tank for thickening treatment.

[0010] The water in the flotation tank is discharged into the oxidation ditch through water pipes. Multiple aeration heads are installed in the S-shaped oxidation ditch to carry out aeration treatment at the same time.

[0011] Step S5: The water treated by the oxidation ditch is pumped into a storage tank for temporary storage; then the water in the storage tank is pumped into an aerobic biological treatment tank, and after continuous aeration, the organic matter in the water is removed by activated sludge process.

[0012] Step S6: The water from step S5 is pumped into the aerobic biological treatment tank. After continuous aeration, the organic matter in the water is decomposed, adsorbed and coagulated by aerobic bacteria.

[0013] Step S7: The water obtained in Step S6 is pumped into a secondary sedimentation tank for further sedimentation. The settled water is then filtered, and the filtrate is subjected to resin adsorption to obtain a salt solution and post-adsorption resin. The salt solution is then concentrated using a membrane to obtain a high-salt concentrate and fresh water. The high-salt concentrate is split into two streams, one of which is crystallized to obtain solid salt and fresh water. The post-adsorption resin is then regenerated to obtain organic dye and regenerated resin. The regenerated resin and the resin are used for resin adsorption.

[0014] Step S8: The other part of the high-salt concentrate, solid salt, is recycled for the printing and dyeing process. Organic dyes are pumped into the workshop and used as water for the water-jet loom. Another part of the fresh water is introduced into the bleaching tank, where bleaching agent is used to perform secondary bleaching and decolorization treatment on the wastewater. Small samples are taken to test its COD content. When the COD is below 200, it is discharged into the municipal pipe network.

[0015] Step S9: The water discharged from the water-jet loom in step S8 is pumped back into the dyeing vat and reused as dyeing water.

[0016] The present invention is further configured such that the filter used for filtration in step S7 is an ultrafiltration membrane module.

[0017] The present invention is further configured such that: the ultrafiltration membrane module is a ceramic tubular membrane module or a PTFE tubular membrane module; the inner diameter of the ceramic tubular membrane module or the PTFE tubular membrane module is 8 mm, and the average pore size of the membrane fibers is 0.76 μm.

[0018] In summary, the present invention has the following beneficial effects:

[0019] 1. This invention effectively solves the problems of high cost and large investment in the treatment of dyeing and printing wastewater, and makes resource utilization of dyeing and printing wastewater, avoiding the waste of water and salt resources;

[0020] 2. This invention reduces the organic content in water bodies, improves the reuse rate of dyeing and printing wastewater, and further saves the cost of subsequent treatment; at the same time, it also helps to improve the strength of the connection between fibers, and improves the tensile strength and firmness of the fabric. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this application can be combined with each other.

[0022] In the description of this invention, it should be noted that the terms "upper", "lower", "inner", "outer", "top / bottom", etc., indicate the orientation or positional relationship based on the shown orientation or positional relationship, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed," "equipped with," "set up / connected," "connected," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The present invention will now be described in detail.

[0025] A method for wastewater reuse in the dyeing and finishing process of high-elastic denim fabric includes the following steps: Step S1: The dyeing wastewater discharged from the dyeing vat is discharged into the raw water ditch through the dyeing vat drain pipe for heat dissipation, while the pH value of the raw water is detected and recorded.

[0026] Step S2: The dyeing wastewater located in the raw water ditch is pumped to the primary sedimentation tank. At the same time, waste acid and / or waste alkali are added and thoroughly mixed to adjust the pH value of the dyeing wastewater to make it weakly alkaline. Aerobic bacteria are introduced into the sedimentation tank. After the above-mentioned purified wastewater is aerobically treated, the organic matter in it is degraded. After reacting for 1.5-2.5 hours, sediment is obtained.

[0027] Step S3: The water obtained after sedimentation in step S2 is discharged into the flotation tank through a conduit, and polyacrylamide and polyaluminum chloride are added and mixed thoroughly for decolorization treatment.

[0028] Step S4: The sludge in the flotation tank is collected by a scraper and then pumped into the sludge thickening tank for thickening treatment.

[0029] The water in the flotation tank is discharged into the oxidation ditch through water pipes. Multiple aeration heads are installed in the S-shaped oxidation ditch to carry out aeration treatment at the same time.

[0030] Step S5: The water treated by the oxidation ditch is pumped into a storage tank for temporary storage; then the water in the storage tank is pumped into an aerobic biological treatment tank, and after continuous aeration, the organic matter in the water is removed by activated sludge process.

[0031] Step S6: The water from step S5 is pumped into the aerobic biological treatment tank. After continuous aeration, the organic matter in the water is decomposed, adsorbed and coagulated by aerobic bacteria.

[0032] Step S7: The water obtained in step S6 is pumped into a secondary sedimentation tank for further sedimentation. The settled water is then filtered, and the filtrate is subjected to resin adsorption to obtain a salt solution and the adsorbed resin. The salt solution is then concentrated using a membrane to obtain a high-salt concentrate and fresh water. The high-salt concentrate is split into two streams, one of which is crystallized to obtain solid salt and fresh water. The adsorbed resin is then regenerated to obtain an organic dye and regenerated resin. The regenerated resin and the resin are then used for resin adsorption.

[0033] The resin used for resin adsorption is preferably macroporous resin D210. The filtrate is decolorized, and the decolorized liquid (salt solution) is passed through the bottom of the column at a flow rate of 6 BV / h. The flow rate and color of the water entering and leaving the resin adsorption column are measured.

[0034] Macroporous resin D210 has an adsorption capacity of over 99% for organic dyes. After adsorption saturation, the resin can be regenerated in a distillation column using ethanol (or methanol), a low-boiling-point volatile organic solvent, at a regeneration flow rate of 1.5 BV / h. After the regeneration process is completed, the volume and color of the regenerated liquid are measured to obtain the organic dye and the regenerated resin.

[0035] Step S8: The other part of the high-salt concentrate, solid salt, is recycled for the printing and dyeing process. Organic dyes are pumped into the workshop and used as water for the water-jet loom. Another part of the fresh water is introduced into the bleaching tank, where bleaching agent is used to perform secondary bleaching and decolorization treatment on the wastewater. Small samples are taken to test its COD content. When the COD is below 200, it is discharged into the municipal pipe network.

[0036] Step S9: The water discharged from the water-jet loom in step S8 is pumped back into the dyeing vat and reused as dyeing water.

[0037] The filter used in step S7 is an ultrafiltration membrane module, which is either a ceramic tubular membrane module or a PTFE tubular membrane module; the inner diameter of the ceramic tubular membrane module or the PTFE tubular membrane module is 8 mm, and the average pore size of the membrane fibers is 0.76 μm.

[0038] The organic solvent ethanol (or methanol) after resin regeneration is heated to 70°C with organic dye, and the ethanol (or methanol) is recovered through a condenser for use in the next batch of resin regeneration; at the same time, the organic dye is recovered for use in the printing and dyeing process; during this process, the concentration and volume of the recovered ethanol or methanol are measured; the color and volume of the recovered organic dye are measured.

[0039] After the filtrate is adsorbed by resin to remove the dye, it becomes a low-concentration salt solution. The low-concentration salt solution is then concentrated to a high-salt concentrate of more than 4% through membrane concentration and returned to the printing and dyeing process as a dyeing auxiliary agent, or it enters the crystallization process to be made into solid salt for reuse. At the same time, the fresh water generated is used as supplementary water in the printing and dyeing process or other production processes, depending on the needs of the production process.

[0040] Reverse osmosis membranes are preferred for concentrating salt solutions. The feed water salt content is 8000 mg / L, the water recovery rate is 87.5% (feed water to concentrate ratio 8:1), the operating pressure is 55 bar, and the concentrate is nearly 8 times concentrated. The feed and effluent volumes and salt content are measured separately (nanofiltration membranes or high-efficiency, low-energy homogeneous electrodialysis membranes can also be used).

[0041] The dyeing and printing wastewater is discharged into the raw water ditch through the dyeing vat drain pipe to dissipate heat. Then, the wastewater is pumped to the primary sedimentation tank, where it reacts with waste acid (such as organic acids like acetic acid or sulfuric acid) or waste alkali (such as limestone or sodium hydroxide) to form a precipitate. This precipitate is an organic precipitate formed after the dye molecules react with the organic acid or waste alkali. Under the influence of its own gravity, the precipitate moves downward, while the water remains above the primary sedimentation tank. At this point, the dewatering treatment of the water body is completed. At the same time, during the sedimentation process in the sedimentation tank, the organic matter in the wastewater is effectively degraded by aerobic bacteria.

[0042] The water from the top layer of the primary sedimentation tank is then discharged through a conduit into an air flotation tank where polyacrylamide and polyaluminum chloride are added and thoroughly mixed for decolorization. Afterward, it is piped into an oxidation ditch, fully aerated, and pumped into a storage tank for temporary storage. It is then discharged into an aerobic biological treatment tank for purification. A portion of the water treated in the secondary sedimentation tank is discharged back into the workshop and used as water for the water-jet loom. After the water-jet loom is completed, the water can be reused for dyeing. The remaining water, after passing COD testing, is transported through the municipal pipeline to a combined wastewater treatment plant for unified treatment before being discharged again.

[0043] Subsequently, since water jet looms utilize water as the weft insertion medium during operation, the frictional traction force generated by the jetting water on the weft yarn guides the weft yarn from the fixed bobbin into the shed. At this point, pre-treated dyeing wastewater (also known as treated water) is used for weaving. The water jet loom uses treated water as the weft insertion medium, ensuring full contact between the yarn and the treated water. Organic matter in the water can fully interact with the fibers; some fills the gaps between fibers, while a small amount penetrates the fibers and binds to the fiber molecules. This further reduces the organic matter content in the water, increases the reuse rate of dyeing wastewater, and further saves on subsequent treatment costs. Simultaneously, it also helps improve the strength of the fiber bonds, enhancing the tensile strength and durability of the fabric.

[0044] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A method for wastewater reuse in the dyeing and finishing process of high-elastic denim fabric, characterized in that: Including the following Steps: Step S1: The dyeing wastewater discharged from the dyeing vat is discharged into the raw water ditch through the dyeing vat drain pipe for heat dissipation, and the pH value of the raw water is measured and recorded at the same time. Step S2: The dyeing wastewater located in the raw water ditch is pumped to the primary sedimentation tank. At the same time, waste acid and / or waste alkali are added and thoroughly mixed to adjust the pH value of the dyeing wastewater to make it weakly alkaline. Aerobic bacteria are introduced into the sedimentation tank. After the above-mentioned purified wastewater is aerobically treated, the organic matter in it is degraded. After reacting for 1.5-2.5 hours, sediment is obtained. Step S3: The water obtained after sedimentation in step S2 is discharged into the flotation tank through a conduit, and polyacrylamide and polyaluminum chloride are added and mixed thoroughly for decolorization treatment. Step S4: The sludge in the flotation tank is collected by a scraper and then pumped into the sludge thickening tank for thickening treatment. The water in the flotation tank is discharged into the oxidation ditch through water pipes. Multiple aeration heads are installed in the S-shaped oxidation ditch to carry out aeration treatment at the same time. Step S5: The water treated by the oxidation ditch is pumped into a storage tank for temporary storage; then the water in the storage tank is pumped into an aerobic biological treatment tank, and after continuous aeration, the organic matter in the water is removed by activated sludge process. Step S6: The water from step S5 is pumped into the aerobic biological treatment tank. After continuous aeration, the organic matter in the water is decomposed, adsorbed and coagulated by aerobic bacteria. Step S7: The water obtained in Step S6 is pumped into a secondary sedimentation tank for further sedimentation. The settled water is then filtered, and the filtrate is subjected to resin adsorption to obtain a salt solution and post-adsorption resin. The salt solution is then concentrated using a membrane to obtain a high-salt concentrate and fresh water. The high-salt concentrate is split into two streams, one of which is crystallized to obtain solid salt and fresh water. The post-adsorption resin is then regenerated to obtain organic dye and regenerated resin. The regenerated resin and the resin are used for resin adsorption. Step S8: The other part of the high-salt concentrate, solid salt, is recycled for the printing and dyeing process. Organic dyes are pumped into the workshop and used as water for the water-jet loom. Another part of the fresh water is introduced into the bleaching tank, where bleaching agent is used to perform secondary bleaching and decolorization treatment on the wastewater. Small samples are taken to test its COD content. When the COD is below 200, it is discharged into the municipal pipe network. Step S9: The water discharged from the water-jet loom in step S8 is pumped back into the dyeing vat and reused as dyeing water.

2. The wastewater reuse method for the dyeing and finishing process of high-elastic denim fabric according to claim 1, characterized in that: The filter used in step S7 is an ultrafiltration membrane module.

3. The wastewater reuse method for dyeing and finishing high-elastic denim fabric according to claim 2, characterized in that: The ultrafiltration membrane module is a ceramic tubular membrane module or a PTFE tubular membrane module; the inner diameter of the ceramic tubular membrane module or the PTFE tubular membrane module is 8 mm, and the average pore size of the membrane fibers is 0.76 μm.