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WO2013035123A1 - Plant and procedure for recovering used brine from dyeing vats - Google Patents

Plant and procedure for recovering used brine from dyeing vats Download PDF

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Publication number
WO2013035123A1
WO2013035123A1 PCT/IT2012/000275 IT2012000275W WO2013035123A1 WO 2013035123 A1 WO2013035123 A1 WO 2013035123A1 IT 2012000275 W IT2012000275 W IT 2012000275W WO 2013035123 A1 WO2013035123 A1 WO 2013035123A1
Authority
WO
WIPO (PCT)
Prior art keywords
station
liquid
stainless steel
tank
dyeing
Prior art date
Application number
PCT/IT2012/000275
Other languages
French (fr)
Inventor
Alberto Zanetti
Original Assignee
EURO MEC S.r.L
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by EURO MEC S.r.L filed Critical EURO MEC S.r.L
Priority to EP12773403.6A priority Critical patent/EP2753584A1/en
Publication of WO2013035123A1 publication Critical patent/WO2013035123A1/en

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/442—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/16—Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/58—Multistep processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D65/00—Accessories or auxiliary operations, in general, for separation processes or apparatus using semi-permeable membranes
    • B01D65/02—Membrane cleaning or sterilisation ; Membrane regeneration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/44—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis
    • C02F1/444—Treatment of water, waste water, or sewage by dialysis, osmosis or reverse osmosis by ultrafiltration or microfiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/04—Specific process operations in the feed stream; Feed pretreatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/06—Specific process operations in the permeate stream
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/08—Specific process operations in the concentrate stream
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/10—Temperature control
    • B01D2311/106—Cooling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/18—Details relating to membrane separation process operations and control pH control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2649—Filtration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2311/00—Details relating to membrane separation process operations and control
    • B01D2311/26—Further operations combined with membrane separation processes
    • B01D2311/2673—Evaporation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2321/00—Details relating to membrane cleaning, regeneration, sterilization or to the prevention of fouling
    • B01D2321/16—Use of chemical agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/02—Reverse osmosis; Hyperfiltration ; Nanofiltration
    • B01D61/027—Nanofiltration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/30—Nature of the water, waste water, sewage or sludge to be treated from the textile industry
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2209/00—Controlling or monitoring parameters in water treatment
    • C02F2209/06—Controlling or monitoring parameters in water treatment pH
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2301/00—General aspects of water treatment
    • C02F2301/08—Multistage treatments, e.g. repetition of the same process step under different conditions
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters

Definitions

  • the present invention refers to a plant and procedure for recovering used salts from dyeing vats that is particularly suitable for reducing the quantity of salts in discharges from dyeing plants in the textile industry and for enabling the brine to be reused.
  • the most commonly used technologies recover the waste water from the dyeing vat downstream of the active-sludge biological treatment, where, however, the most limiting factor for the use of these technologies is the concentration of dissolved salts.
  • the technological solutions that are currently used and which ensure good results from a qualitative, quantitative and environmental impact point of view are the separating procedures with semipermeable membranes, which are sometimes preceded by oxidation with ozone, by means of which, in some cases, over 90% completely decoloured water with a low saline content is obtained that can be reused in the dying process.
  • the residual concentration of the membrane separating procedures is treated by expensive evaporating plants that on the one hand enable a condensate to be obtained that can in turn be recovered and on the other hand a reduced volume of sludge to be disposed of that contains all the polluting substances, including salts.
  • the percentage incidence of used salt in the dyeing vat varies with respect to the total used quantity and depends on the formula for dyeing the fabric, on the so-called liquor ratio, i.e. on the water kg/product kg ratio, and on the quantity of liquor discharged, or similarly, on the quantity of liquor retained in the fibres, which is about three litres for every kilo of fibre, also the quantity discharged with the liquor with respect to the total quantity of water discharged from the dyeing plant varies and depends on the liquor ratio and on total water consumption in relation to the weight of the treated product.
  • the discharged liquor contains 50% of the salt used for the process in 5-10% of the total discharges. If also the first rinse is considered, the quantity of salt increases to 75% of the total, so it would be interesting to be able to recover the greatest possible quantity of salt.
  • the object of the present invention is substantially to solve the prior art problems by overcoming the difficulties disclosed above by means of a plant and procedure for recovering used brine from dyeing vats, that is able to send waste water to the centralised treatment plant that has a considerably lighter load of polluting substances, with lower plant and operating costs.
  • a second object of the present invention is to have a plant and procedure for recovering used brine from dyeing vats that is able to allow the recovery, downstream of the centralised treatment plant, of a greater quantity of water at lower costs.
  • a third object of the present invention is to have a plant and procedure for recovering used brine from dyeing vats that enables a clear and colourless saline solution to be recovered that is reusable in the dyeing process and/or for other purposes.
  • Another object of the present invention is to have a plant for recovering used brine from dyeing vats that enables the salinity of the discharge to be noticeably reduced, allowing greater recovery and recycle of the water.
  • a further object of the present invention arises from the fact that the plant and the process for recovering used brine from dyeing vats are usable in plants for dyeing cotton yarn or fabric.
  • the last object of the present invention is to make a plant for recovering used brine from dyeing vats that is simple and efficient.
  • figure 1 shows schematically a plant for recovering used brine from dyeing vats that is the object of the present invention for performing the procedure of recovering sodium chloride brine ;
  • FIG. 1 shows the procedure diagram for recovering sodium chloride brine performed by the plant in figure 1.
  • 1 indicates the overall diagram of a plant for recovering used brine from dyeing vats, according to the present invention.
  • the plant 1 according to the present invention is intended for recovering used sodium chloride brine from dyeing vats so as to send, to the centralised treatment plant, waste water that contains considerably fewer polluting substances, for recovering a greater quantity of water downstream of the centralised treatment plant and for recovering a clear and colourless saline solution that is reusable in the dyeing procedure and/or for other purposes such as, for example, regenerating the ion exchange resins of the waste water desalinisation plant.
  • the plant and the process made with the plant according to the present invention enable lower costs to be obtained for the centralised plant but above all lower operating costs in addition to another considerable saving on the water used in the dyeing vats.
  • the plant 1 substantially consists of a plurality of stations in which the first station 2 comprises an ultrafiltration section, the second station 3 a nanofiltration section and the third station 4 a membrane washing section.
  • the plant 1 consists of the first station 2 consisting of the ultrafiltration section, which comprises a storage tank 20 designed to collect the liquids coming from the dyeing vat, a first pumping station 21 provided for sending the liquids to be treated to the next drum safety filtering unit 22 that removes fibres and other possible solids suspended in the liquid, a second pumping station 23 for making the liquid recirculate, ultrafiltration modules 24 consisting of tubular ceramic membrane elements with the task of conducting a first filtration of the liquid so as to separate the suspended solids from the liquor and a cooling unit 25 consisting of a heat exchanger that lowers the temperature of the partially treated liquid, which will then be sent to the second station 3.
  • the first station 2 consisting of the ultrafiltration section, which comprises a storage tank 20 designed to collect the liquids coming from the dyeing vat, a first pumping station 21 provided for sending the liquids to be treated to the next drum safety filtering unit 22 that removes fibres and other possible solids suspended in the liquid, a second pumping station 23 for making the liquid re
  • the repumping action performed by the second pumping station 23 is performed to maintain a high tangential speed of the liquid on the membranes and thus obtain constant cleaning thereof and protect the membranes from sudden dirtying.
  • a flow of filtered liquid is generated that is sent to the next station 3 and on the other side there is a concentrate that is partially recirculated in the ultrafiltration modules and is partially discharged and treated separately.
  • the tank 20 is made of concrete and has a plastic or epoxy or glass fibre or stainless steel protection.
  • the first pumping station 21 is made of stainless steel or marine bronze for supplying the ultrafiltration section. Further, the drum safety filtering unit 22 is made of plastics or stainless steel with a 250 ⁇ filtration grade. According to this embodiment, the second pumping station 23 is made of stainless steel or marine bronze for circulation of the liquid on the membrane elements.
  • the ultrafiltration modules 24 are located in stainless steel containers and comprise tubular ceramic membrane elements that ensure removal of all the suspended solids, many macromolecules such as some auxiliary dyeing auxiliaries and enable the liquids to be filtered at a high temperature and with a high load of pollutants.
  • the ultrafiltration modules 24 work at high temperature, so the permeate is passed through the cooling unit 25 consisting of the heat exchanger that lowers the temperature thereof to 35°, after which it is sent to an intermediate tank of the second station 3.
  • the heat exchanger is of the stainless steel or titanium plate type and has a cooling water regulating valve.
  • the plant in question 1 comprises the second station 3 constituted by the nanofiltration section that consists of a storage tank 30 for the filtered liquor, of a first pumping station 31 provided for supplying the drum safety filtering unit 32 that has the task of removing other possible particles that may have entered the tank 30 from a second pumping station 33 that is provided for performing liquid repumping and pressurizing action to promote high tangential speed of the liquid in a similar manner to what occurs in the first station, of nanofiltration modules 34 consisting of polymer membrane elements the task of which is to perform a second filtration of the liquid to remove completely the colouring substances, all the organic molecules and almost all the bivalent salts.
  • the storage tank 30 is made of concrete with a plastic or epoxy or glass fibre or plastic material or stainless steel protection.
  • the pumping station 31 is made of stainless steel or marine bronze and the drum safety filtering unit 32 is made of plastic or stainless steel with a 250 ⁇ filtering grade.
  • the nanofiltration modules 34 are located in glass fibre or stainless steel containers containing polymer membrane elements that are designed to obtain a perfectly clear, colourless sodium chloride brine that has a high degree of purity and is completely reusable.
  • the plant that is the object of the present invention has between the first 2 and the second station 3 an intermediate pH control station 5 consisting of one or more dosing pumps and of a plastic tank for acid.
  • the pH measured in the intermediate tank is regulated by a dedicated proportional- action pump and regulates the pH by dosing hydrochloric acid.
  • the plant has the third station 4 which comprises a membrane washing section that consists of a plastic or stainless steel washing tank provided for washing the membranes in which the dedicated pumps or supply pumps of the respective sections are used.
  • a membrane washing section that consists of a plastic or stainless steel washing tank provided for washing the membranes in which the dedicated pumps or supply pumps of the respective sections are used.
  • the membranes are washed by chemical substances that have been appropriately diluted in the appropriate tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning with the elimination, by removal, of the substances deposited thereupon.
  • the plant 1 is provided with a series of instruments such as gauges of the flowrate of the permeate and concentrate and optionally also supply gauges located on the lines of both the first and second station, gauges of the inlet and outlet pressure of the membranes, temperature gauges in each tank and a pH gauge of the ultrafiltrated liquor.
  • instruments such as gauges of the flowrate of the permeate and concentrate and optionally also supply gauges located on the lines of both the first and second station, gauges of the inlet and outlet pressure of the membranes, temperature gauges in each tank and a pH gauge of the ultrafiltrated liquor.
  • a further feature of the plant according to the present invention is to have all plumbing connections and the valves made of stainless steel and, alternatively, for the plastic low-pressure lines, withstanding high temperatures (up to 90 °C).
  • the plant according to the present invention enables the following procedure to be performed to recover the brine from the dyeing vats as shown schematically in figure 2.
  • the recovery procedure comprises the following operating steps:
  • the flowrate of the permeate is provided for, managed and regulated by the backpressure generated by the pumps 21 and 23 and by a valve installed on the repumping line of the concentrate.
  • One part of the concentrate is discontinuously tapped from the supply tank or directly from the supply pipe of the membranes by a discharge valve located either on the tank 20 or on the line.
  • the recovery process comprises the following intermediate step: regulating the PH of the brine by dosing hydrochloric acid.
  • the recovery procedure continues with the following steps:
  • the brine has to be delivered to a storage tank of suitable dimensions where, for reuse thereof, it mi sdJ ⁇ mfli ⁇ atned3 ⁇ 4 ⁇
  • This can occur by injection of desalinated or demineralised water, regulated by the feedback of a massive flowrate gauge that regulates an automatic valve located downstream of the plant.
  • the discharged liquor has to be treated so as to recover the sodium chloride contained therein so as to be able to reuse the sodium chloride for subsequent processing.
  • the present invention thus achieves the proposed objectives.
  • the plant for recovering used brine from dyeing vats in question offers the possibility of sending to the centralised treatment plant waste water that contains considerably fewer polluting substances, with lower plant and operating costs.
  • the plant according to the present invention is able to permit a greater quantity of water to be recovered at lower cost than occurred with prior-art plants.
  • the plant enables a clear and colourless saline solution to be obtained that is reusable in the dyeing procedure and/or for other purposes such as, for example, for regenerating the ionic exchange resins of the water desalinisation plant of the process water.
  • Another advantage stems from the fact that the plant in question enables the salts to be recovered correctly as well, which leads to a noticeable reduction in discharge procedure uses, at lower costs, or enables it to be used for agricultural purposes and for irrigation, thus without altering the basic conditions for water life.
  • a further advantage of the plant is that it enables to meet an increasing demand to recover brine by means of efficient and reliable procedures. Further, the plant enables dyeing management costs to be saved over time inasmuch as the recovery of salts by evaporation that occurred in prior-art plants and had exorbitant costs is drastically reduced.
  • the plant in question can be applied in all cotton yarn or fabric dyeing plants but can also be used in dyeing vats of other types of natural or synthetic fibres with the same adjustments due to the different quantities of salt used.
  • the procedure in question enables a solution to be obtained with a high degree of purity compared with prior-art plants.
  • the procedure is also applicable to mixed discharges that combine dyeing with both sulphate and with sodium chloride, making the system for managing discharges in dyeing plants much simpler.
  • the step of final refinement with macroporous resins for the total removal of the colour is not necessary, the colour being removed with the sole membrane process, unlike what occurred with prior art processes where to eliminate the colour it was necessary to refine with resins and active carbons at high cost and with production of waste water that was difficult to manage.
  • the sodium chloride is recovered with nanofiltration membranes that permit exclusively the passage of monovalent ions and so the solution is almost completely devoid of hardness, which can be practically absent from the dyeing process water.
  • the overall saline recovery solution with the procedure in question is between 80 and 85%, with a concentration that is equal to that of the used liquor. This enables a quantity of sodium chloride brine to be recovered that is equal to 80% - 85% of the used liquor from the dyeing vat.
  • the plant and the procedure in question enable an energy saving and savings in both plant and running costs to be achieved.
  • a further advantage of the present invention is the significant ease of use, simple manufacture and efficiency thereof.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Nanotechnology (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Coloring (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

A plant and a procedure is disclosed for recovering used brine from dyeing vats and in particular sodium chloride brine used in dyeing cotton yarn and fabrics. The plant is of the type comprising a plurality of stations in which the first station (2) comprises an ultrafiltration section, the second station (3) a nanofiltration section, the third station (4) a membrane washing section and an intermediate pH control station (5).

Description

"PLANT AND PROCEDURE FOR RECOVERING USED BRINE FROM DYEING VATS".
DESCRIPTION
The present invention refers to a plant and procedure for recovering used salts from dyeing vats that is particularly suitable for reducing the quantity of salts in discharges from dyeing plants in the textile industry and for enabling the brine to be reused.
As is known, in recent years the growing rationalisation of industrial processes, the use of increasingly efficient plants and the recovery and reuse of waste water have significantly reduced specific water consumption (consumption per product unit) but, in many cases, it has unfortunately caused a deterioration in the waste water because of the high concentration of polluting substances.
In the textile industry, the most apparent aspect of this deterioration is the increase in the concentration of colouring substances, which has an immediate visual impact and on the other hand the dissolved salts, mainly chloride and sodium sulphate, that, even if they are harmless, have a significant environmental impact and cannot be eliminated.
Currently, legal regulations are becoming increasingly restrictive in the environmental field and require ever more efficient water treatment and recovery plants, even as far as "zero discharge" systems.
The most commonly used technologies recover the waste water from the dyeing vat downstream of the active-sludge biological treatment, where, however, the most limiting factor for the use of these technologies is the concentration of dissolved salts. The technological solutions that are currently used and which ensure good results from a qualitative, quantitative and environmental impact point of view are the separating procedures with semipermeable membranes, which are sometimes preceded by oxidation with ozone, by means of which, in some cases, over 90% completely decoloured water with a low saline content is obtained that can be reused in the dying process.
These systems imply, given the peculiar features of semipermeable membranes (ultrafiltration, nanofiltration and reverse osmosis), the production of residual waste water with a very high concentration of salts, dyes and other polluting substances that cannot be discharged as such or be disposed of at sustainable cost.
In fact, the residual concentration of the membrane separating procedures, especially in "zero discharge" plants, is treated by expensive evaporating plants that on the one hand enable a condensate to be obtained that can in turn be recovered and on the other hand a reduced volume of sludge to be disposed of that contains all the polluting substances, including salts.
The plant and operating costs per volume of water treated, both by membrane separating procedures and by evaporation, are higher the greater the concentration of salts in the waste water.
Today, the need is strongly felt to be able to reduce the quantity of salt discharged with the dyeing liquor to be able to also reuse it and obtain more concentrated discharges to be treated separately upstream of the purification plant to which all the dyeing waste water is conveyed. In fact, most of the concentration of salts is contained in the dyeing liquor. In order to be able to reuse the salts, it must be possible to extract the salts from the water solution directly from the discharge from the machines for dyeing for example cotton fabrics.
As the percentage incidence of used salt in the dyeing vat varies with respect to the total used quantity and depends on the formula for dyeing the fabric, on the so-called liquor ratio, i.e. on the water kg/product kg ratio, and on the quantity of liquor discharged, or similarly, on the quantity of liquor retained in the fibres, which is about three litres for every kilo of fibre, also the quantity discharged with the liquor with respect to the total quantity of water discharged from the dyeing plant varies and depends on the liquor ratio and on total water consumption in relation to the weight of the treated product.
It is calculated in theory that for production in which dyeing machines are used with a liquor ratio of 1 :10, 70% of the salts used is contained in the first dyeing vat discharge, and the volume of these discharges is about 10-15% of the water used in the dyeing plant.
With the 1 :5 liquor ratio that is used in the most recent dyeing machines, the discharged liquor contains 50% of the salt used for the process in 5-10% of the total discharges. If also the first rinse is considered, the quantity of salt increases to 75% of the total, so it would be interesting to be able to recover the greatest possible quantity of salt.
In addition, current legislative and market conditions have led the recovery of sodium chloride brine to be evaluated with increasing attention, which is generally less expensive but much more used than sulphate, with the aim of recycling all the water used in the dyeing plant at lower costs. The object of the present invention is substantially to solve the prior art problems by overcoming the difficulties disclosed above by means of a plant and procedure for recovering used brine from dyeing vats, that is able to send waste water to the centralised treatment plant that has a considerably lighter load of polluting substances, with lower plant and operating costs.
A second object of the present invention is to have a plant and procedure for recovering used brine from dyeing vats that is able to allow the recovery, downstream of the centralised treatment plant, of a greater quantity of water at lower costs.
A third object of the present invention is to have a plant and procedure for recovering used brine from dyeing vats that enables a clear and colourless saline solution to be recovered that is reusable in the dyeing process and/or for other purposes.
Another object of the present invention is to have a plant for recovering used brine from dyeing vats that enables the salinity of the discharge to be noticeably reduced, allowing greater recovery and recycle of the water.
A further object of the present invention arises from the fact that the plant and the process for recovering used brine from dyeing vats are usable in plants for dyeing cotton yarn or fabric.
Not the last object of the present invention is to make a plant for recovering used brine from dyeing vats that is simple and efficient.
These and still other objects that will appear more closely in the course of this description are substantially achieved by a plant for recovering used brine from dyeing vats, as claimed below. Further characteristics and advantages will become clearer from the detailed description of a plant for recovering used brine from dyeing vats, according to the present invention, which description follows with reference to the attached drawings that are provided merely by way of example and are not therefore limiting, in which: figure 1 shows schematically a plant for recovering used brine from dyeing vats that is the object of the present invention for performing the procedure of recovering sodium chloride brine ;
- figure 2 shows the procedure diagram for recovering sodium chloride brine performed by the plant in figure 1.
With reference to the figures mentioned, and in particular to figure 1 , 1 indicates the overall diagram of a plant for recovering used brine from dyeing vats, according to the present invention.
In fact, the plant 1 according to the present invention is intended for recovering used sodium chloride brine from dyeing vats so as to send, to the centralised treatment plant, waste water that contains considerably fewer polluting substances, for recovering a greater quantity of water downstream of the centralised treatment plant and for recovering a clear and colourless saline solution that is reusable in the dyeing procedure and/or for other purposes such as, for example, regenerating the ion exchange resins of the waste water desalinisation plant.
The plant and the process made with the plant according to the present invention enable lower costs to be obtained for the centralised plant but above all lower operating costs in addition to another considerable saving on the water used in the dyeing vats. The plant 1 substantially consists of a plurality of stations in which the first station 2 comprises an ultrafiltration section, the second station 3 a nanofiltration section and the third station 4 a membrane washing section.
As already indicated, the plant 1 consists of the first station 2 consisting of the ultrafiltration section, which comprises a storage tank 20 designed to collect the liquids coming from the dyeing vat, a first pumping station 21 provided for sending the liquids to be treated to the next drum safety filtering unit 22 that removes fibres and other possible solids suspended in the liquid, a second pumping station 23 for making the liquid recirculate, ultrafiltration modules 24 consisting of tubular ceramic membrane elements with the task of conducting a first filtration of the liquid so as to separate the suspended solids from the liquor and a cooling unit 25 consisting of a heat exchanger that lowers the temperature of the partially treated liquid, which will then be sent to the second station 3.
In particular, the repumping action performed by the second pumping station 23 is performed to maintain a high tangential speed of the liquid on the membranes and thus obtain constant cleaning thereof and protect the membranes from sudden dirtying. With the passage into these membranes on the one hand a flow of filtered liquid is generated that is sent to the next station 3 and on the other side there is a concentrate that is partially recirculated in the ultrafiltration modules and is partially discharged and treated separately.
More in detail, the tank 20 is made of concrete and has a plastic or epoxy or glass fibre or stainless steel protection.
The first pumping station 21 is made of stainless steel or marine bronze for supplying the ultrafiltration section. Further, the drum safety filtering unit 22 is made of plastics or stainless steel with a 250 μ filtration grade. According to this embodiment, the second pumping station 23 is made of stainless steel or marine bronze for circulation of the liquid on the membrane elements.
Further, the ultrafiltration modules 24 are located in stainless steel containers and comprise tubular ceramic membrane elements that ensure removal of all the suspended solids, many macromolecules such as some auxiliary dyeing auxiliaries and enable the liquids to be filtered at a high temperature and with a high load of pollutants.
As just mentioned, the ultrafiltration modules 24 work at high temperature, so the permeate is passed through the cooling unit 25 consisting of the heat exchanger that lowers the temperature thereof to 35°, after which it is sent to an intermediate tank of the second station 3.
More in detail, the heat exchanger is of the stainless steel or titanium plate type and has a cooling water regulating valve.
The plant in question 1, as already anticipated, comprises the second station 3 constituted by the nanofiltration section that consists of a storage tank 30 for the filtered liquor, of a first pumping station 31 provided for supplying the drum safety filtering unit 32 that has the task of removing other possible particles that may have entered the tank 30 from a second pumping station 33 that is provided for performing liquid repumping and pressurizing action to promote high tangential speed of the liquid in a similar manner to what occurs in the first station, of nanofiltration modules 34 consisting of polymer membrane elements the task of which is to perform a second filtration of the liquid to remove completely the colouring substances, all the organic molecules and almost all the bivalent salts. According to this embodiment, the storage tank 30 is made of concrete with a plastic or epoxy or glass fibre or plastic material or stainless steel protection. Further, the pumping station 31 is made of stainless steel or marine bronze and the drum safety filtering unit 32 is made of plastic or stainless steel with a 250 μ filtering grade.
In particular, the nanofiltration modules 34 are located in glass fibre or stainless steel containers containing polymer membrane elements that are designed to obtain a perfectly clear, colourless sodium chloride brine that has a high degree of purity and is completely reusable.
The plant that is the object of the present invention has between the first 2 and the second station 3 an intermediate pH control station 5 consisting of one or more dosing pumps and of a plastic tank for acid.
As is known, dyeing vats for cellulose fibres are very alkaline, so the ultrafiltration permeate is taken to neutral before being sent for further treatment of the second station with the polymer membranes, which would be damaged if the pH was very alkaline (or acid). Further, the recovered brine has to be neutralised to be able to be reused.
The pH measured in the intermediate tank is regulated by a dedicated proportional- action pump and regulates the pH by dosing hydrochloric acid.
In addition to what has been illustrated so far and as already mentioned, the plant has the third station 4 which comprises a membrane washing section that consists of a plastic or stainless steel washing tank provided for washing the membranes in which the dedicated pumps or supply pumps of the respective sections are used.
More in detail, the membranes are washed by chemical substances that have been appropriately diluted in the appropriate tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning with the elimination, by removal, of the substances deposited thereupon.
Moreover, the plant 1 is provided with a series of instruments such as gauges of the flowrate of the permeate and concentrate and optionally also supply gauges located on the lines of both the first and second station, gauges of the inlet and outlet pressure of the membranes, temperature gauges in each tank and a pH gauge of the ultrafiltrated liquor.
A further feature of the plant according to the present invention is to have all plumbing connections and the valves made of stainless steel and, alternatively, for the plastic low-pressure lines, withstanding high temperatures (up to 90 °C).
The plant according to the present invention enables the following procedure to be performed to recover the brine from the dyeing vats as shown schematically in figure 2.
The recovery procedure comprises the following operating steps:
collecting the used liquid of the dyeing vat in the tank 20,
- moving the liquid by the first pumping station 21,
- passage of the liquid into the drum filter 22 to remove fibres and other possible suspended solids that could clog the channels of the membranes,
- passage of the liquid into the ceramic modules that enable all the suspended solids and many macromolecules to be removed, and enable liquids to be filtered at a high temperature and with a high load of pollutants,
- repumping of the liquid by a second pumping station through ceramic membranes at a flowrate that is 10 - 12 times greater than the supply flowrate in order to maintain a high speed, thus obtaining constant cleaning of the filtering surface, filtering of the liquid via repumping of the concentrate in the supply tank 20 or directly in the supply lines of the membranes,
- passage of the permeate through a heat exchanger that lowers the temperature thereof to 35 °C, with the delivery of the permeate to an intermediate tank.
In particular, the flowrate of the permeate is provided for, managed and regulated by the backpressure generated by the pumps 21 and 23 and by a valve installed on the repumping line of the concentrate.
One part of the concentrate is discontinuously tapped from the supply tank or directly from the supply pipe of the membranes by a discharge valve located either on the tank 20 or on the line.
The recovery process comprises the following intermediate step: regulating the PH of the brine by dosing hydrochloric acid.
According to the present invention, the recovery procedure continues with the following steps:
- delivery of the permeate coming from the first station by the first pumping station 31 to a safety filter 32 and then to the second pumping station 33 for repumping and pressurising,
- repumping of the liquid in a nano filtration system with polymer membranes, delivery of the permeate (sodium chloride brine) to a storage tank35,
- repumping of the concentrate in the intermediate tank 30.
More in detail, the brine has to be delivered to a storage tank of suitable dimensions where, for reuse thereof, it mi sdJ^mfli^atned¾ ^^ This can occur by injection of desalinated or demineralised water, regulated by the feedback of a massive flowrate gauge that regulates an automatic valve located downstream of the plant.
From what has been disclosed in a mainly structural manner, the operation of the invention in question is as follows.
When the fabric dyeing operations have finished, the discharged liquor has to be treated so as to recover the sodium chloride contained therein so as to be able to reuse the sodium chloride for subsequent processing.
Once the previously disclosed steps have been performed, a purified sodium chloride brine that is reused in the dyeing process is obtained as well as a small quantity of concentrate that is stored to be subsequently treated or delivered directly to the centralised treatment plant.
The present invention thus achieves the proposed objectives.
The plant for recovering used brine from dyeing vats in question offers the possibility of sending to the centralised treatment plant waste water that contains considerably fewer polluting substances, with lower plant and operating costs.
Further, the plant according to the present invention is able to permit a greater quantity of water to be recovered at lower cost than occurred with prior-art plants. Advantageously, the plant enables a clear and colourless saline solution to be obtained that is reusable in the dyeing procedure and/or for other purposes such as, for example, for regenerating the ionic exchange resins of the water desalinisation plant of the process water.
Another advantage stems from the fact that the plant in question enables the salts to be recovered correctly as well, which leads to a noticeable reduction in discharge procedure uses, at lower costs, or enables it to be used for agricultural purposes and for irrigation, thus without altering the basic conditions for water life.
A further advantage of the plant is that it enables to meet an increasing demand to recover brine by means of efficient and reliable procedures. Further, the plant enables dyeing management costs to be saved over time inasmuch as the recovery of salts by evaporation that occurred in prior-art plants and had exorbitant costs is drastically reduced.
In particular, the plant in question can be applied in all cotton yarn or fabric dyeing plants but can also be used in dyeing vats of other types of natural or synthetic fibres with the same adjustments due to the different quantities of salt used. Advantageously, the procedure in question enables a solution to be obtained with a high degree of purity compared with prior-art plants.
In addition, the procedure enables a greater quantity of both sodium chloride and water to be recovered than with prior-art methods.
In particular, the procedure is also applicable to mixed discharges that combine dyeing with both sulphate and with sodium chloride, making the system for managing discharges in dyeing plants much simpler.
In the process according to the invention, the step of final refinement with macroporous resins for the total removal of the colour is not necessary, the colour being removed with the sole membrane process, unlike what occurred with prior art processes where to eliminate the colour it was necessary to refine with resins and active carbons at high cost and with production of waste water that was difficult to manage.
With the procedure in question, the sodium chloride is recovered with nanofiltration membranes that permit exclusively the passage of monovalent ions and so the solution is almost completely devoid of hardness, which can be practically absent from the dyeing process water. The overall saline recovery solution with the procedure in question is between 80 and 85%, with a concentration that is equal to that of the used liquor. This enables a quantity of sodium chloride brine to be recovered that is equal to 80% - 85% of the used liquor from the dyeing vat.
The plant and the procedure in question enable an energy saving and savings in both plant and running costs to be achieved.
A further advantage of the present invention is the significant ease of use, simple manufacture and efficiency thereof.
Naturally, various modifications to and variations on the present invention can be made that are all part of the inventive concept characterizing the invention.

Claims

Plant for recovering used brine from dyeing vats, characterised in that it comprises a plurality of stations in which the first station (2) comprises an ultrafiltration section, the second station (3) a nanofiltration section, the third station (4) a membrane washing station and an intermediate pH control station (5).
Plant according to claim 1, characterised in that said first station (2) is comprised of the ultrafiltration section, which comprises a storage tank (20) designed to collect liquids coming from the dyeing vat, a first pumping station (21) provided for sending the liquids to be treated to the subsequent drum safety filtering unit (22) that has the task of removing fibres and other possible suspended solids present in the liquid, a second pumping station (23) provided for repumping the liquid, ultrafiltration modules (24) consisting of tubular ceramic membrane elements whose task is to perform initial liquid filtration such as to separate the suspended solids of the liquor and a cooling unit (25) consisting of a heat exchanger that lowers the temperature of the partially treated liquid that will then be sent to the second station (3).
Plant according to claim 1, characterised in that said second station (3) is comprised of the nanofiltration section, which consists of a storage tank (30) for the filtered liquor, of a first pumping station (31 ) provided for supplying the subsequent drum safety filtering unit (32) the task of which is to remove other possible particles that may have entered the tank (30), of a second pumping station (33) provided for repumping and pressurising the liquid so as to promote high tangential speed of the liquid, of nanofiltration modules (34) consisting of polymer membrane elements the task of which is to perform a second filtration of the liquid to remove completely the colouring substances, all the organic molecules and almost all the bivalent salts.
4. Plant according to claim 1 , characterised in that said intermediate stage (5) consists of one or more proportional-action dosing pumps and regulates the pH by dosing hydrochloric acid contained in a plastic tank for hydrochloric acid.
5. Plant according to claim 1 , characterised in that said third station (4) that comprises the membrane washing station consists of a plastic or stainless steel washing tank provided for washing the membranes in which dedicated pumps or the pumps supplying the respective sections are used and for said washing chemical substances are used that have been appropriately diluted in the appropriate tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning with the elimination by removal of the substances deposited thereupon.
6. Plant according to claim 1, characterised in that in said ultrafiltration section the tank (20) is made of concrete and has a plastic or epoxy or glass fibre or plastic or stainless steel protection, the first pumping station (21) is made of stainless steel or marine bronze to supply the ultrafiltration section, the drum safety filtering unit (22) is made of plastic or stainless steel with a 250 μ filtering grade, the second pumping station (23) is made of stainless steel or marine bronze for circulation of the liquid on the membrane elements, the ultrafiltration modules (24) are located in stainless steel containers and comprise tubular ceramic membrane elements that ensure removal of all the suspended solids, many macromolecules such as some auxiliary dyeing auxiliaries and enable the liquids to be filtered at a high temperature and with a high load of pollutants and the cooling unit (25) consists of the stainless steel or titanium plate heat exchanger and has a cooling water regulating valve.
7. Plant according to claim 1, characterised in that in said nano filtration section the storage tank (30) is made of concrete with a plastic or epoxy protection or of glass fibre or plastic, or stainless steel, the pumping station (31) is made of stainless steel or marine bronze and the drum safety filtering unit (32) is made of plastic or stainless steel with a 250 μ filtration grade, the nanofiltration modules (34) are located in glass fibre or stainless steel containers containing polymer membrane elements that are designed to obtain a perfectly clear, colourless sodium chloride brine that has a high degree of purity and is completely reusable.
8. Plant according to claim 1 , characterised in that it comprises a series of instruments such as gauges of the flowrate of the permeate and concentrate and optionally also supply gauges located on the lines of both the first and second station, gauges of the inlet and outlet pressure of the membranes, temperature gauges in each tank and a pH gauge of the ultrafiltrated liquor and has all plumbing connections and the valves made of stainless steel, and, alternatively, for the plastic low-pressure lines withstanding high temperatures (up to 90 °C).
9. Procedure for recovering used brines from the dyeing vats performed with the plant according to claims 1 to 8, characterised in that it comprises a plurality of operating steps conducted in the first station (2), in the second station (3), in the intermediate station (5) and in the third station (4) in which in the first station (2) the following steps are conducted:
- collecting the used liquid of the dyeing vat in the tank (20),
- moving the liquid by the first pumping station (21 ), - passage of the liquid into the drum filter (22) to remove fibres and other possible suspended solids that could clog the channels of the membranes,
- passage of the liquid into the ultrafiltration modules (24) that enable all the all the suspended solids and many macromolecules to be removed, and enable liquids to be filtered at a high temperature and with a high load of pollutants,
- repumping of the liquid by a second pumping station through ceramic membranes at a flowrate that is 10 - 12 times greater than the supply flowrate in order to maintain a high speed, thus obtaining constant cleaning of the filtering surface,
filtering of the liquid via repumping of the concentrate in the supply tank (20) or directly in the supply lines of the membranes,
- passage of the permeate through a heat exchanger that lowers the temperature thereof to 35 °C, with the delivery of the permeate to an intermediate tank, and in the intermediate stage the step is performed of:
- regulating the PH of the brine by dosing hydrochloric acid, in the second station the following steps are performed: delivery of the permeate coming from the first station by the first pumping station (31) to a safety filter (32) and then to the second pumping station (33) for repumping and pressurising,
- repumping of the liquid in a nanofiltration system with polymer membranes,
- delivery of the permeate (sodium chloride brine) to a storage tank (35), and in the third station (4) membrane washing is performed by appropriately diluted chemical substances that are fluxed through the membranes to remove the substances deposited on the membranes.
PCT/IT2012/000275 2011-09-07 2012-09-07 Plant and procedure for recovering used brine from dyeing vats WO2013035123A1 (en)

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IT000019A ITMN20110019A1 (en) 2011-09-07 2011-09-07 PLANT AND PROCESS FOR THE RECOVERY OF BRIARES FROM EXHAUSTED DYE BATHS.
ITMN2011A000019 2011-09-07

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