EP2986569A1 - Plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry - Google Patents

Plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry

Info

Publication number
EP2986569A1
EP2986569A1 EP14739953.9A EP14739953A EP2986569A1 EP 2986569 A1 EP2986569 A1 EP 2986569A1 EP 14739953 A EP14739953 A EP 14739953A EP 2986569 A1 EP2986569 A1 EP 2986569A1
Authority
EP
European Patent Office
Prior art keywords
station
pva
liquid
filtering
plant
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP14739953.9A
Other languages
German (de)
French (fr)
Inventor
Massimiliano PREVIDI
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Euro Mec Srl
Original Assignee
Euro Mec Srl
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 Srl filed Critical Euro Mec Srl
Publication of EP2986569A1 publication Critical patent/EP2986569A1/en
Withdrawn legal-status Critical Current

Links

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
    • C02F1/001—Processes for the treatment of water whereby the filtration technique is of importance
    • 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
    • B01D61/149—Multistep processes comprising different kinds of membrane processes selected from ultrafiltration or microfiltration
    • 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
    • C02F1/22—Treatment of water, waste water, or sewage by freezing
    • 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
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F9/00—Multistage treatment of water, waste water or sewage
    • 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
    • B01D61/14—Ultrafiltration; Microfiltration
    • B01D61/145—Ultrafiltration
    • 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
    • B01D61/147—Microfiltration
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/34—Organic compounds containing oxygen
    • 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
    • C02F2303/00—Specific treatment goals
    • C02F2303/16—Regeneration of sorbents, filters
    • 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
    • C02F2303/24—Separation of coarse particles, e.g. by using sieves or screens

Definitions

  • the present invention relates to a plant and procedure for the recovery of Polyvinyl Alcohol from the washing bath in the textile industry particularly suitable to separate the Polyvinyl Alcohol (PVA) from the wastewater in the thread washing bath.
  • PVA Polyvinyl Alcohol
  • PVA is used in the textile industry to make the thread more compact so that the different strands, of which it is made up, are grouped together making the thread more resistant and easier to use in the spinning process.
  • the PVA is discharged together with the other waste into the water, which is then conveyed to the treatment process.
  • the washing bath containing PVA is generally discharged in the wastewater treatment plants and the presence of this substance considerably worsens the chemical-physical characteristics and often makes the water difficult to treat or even makes it unbeatable, since PVA is poorly biodegradable and is not compatible with the treatment plants that are generally of the biological type.
  • PVA has a very high COD (chemical oxygen demand) level therefore it is considered a major pollutant and its presence in processing waste has always generated serious plant management problems as it causes, for example in biological plants, the growth of filamentous bacteria that are difficult to separate; this results in a significant increase in plant management operating costs.
  • COD chemical oxygen demand
  • PVA undermines the treatment plants as the waste must be chemically treated before being discharged into the environment, but such treatments do not give the expected results and moreover they create many problems.
  • the technologies mainly adopted concern the recovery of dyeing wastewater, downstream of the activated sludge biological treatment; the most limiting factor however for the use of these technologies is the concentration of PVA that makes biological systems difficult to manage, also due to the high operating costs resulting from the considerable consumption of electricity. Furthermore, the presence of PVA makes it difficult to adopt processes that employ membrane filtration downstream of biological treatment systems.
  • the object of the present invention is substantially to solve the problems of the known technique overcoming the above mentioned difficulties by means of a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry, which enables the recovery of water in order to obtain hot clean water at a temperature of 70-80° C.
  • a second object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry, which enables the separation of the PVA from the water and its gelification, to take it to a solid state so that it can be reused in other industrial processes.
  • Another object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry that enables wastewater, with a considerably lower concentration of pollutants, to be sent to the centralised treatment plant, with a reduction in management and plant costs.
  • a further object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry that enables the recovery, upstream of the centralised treatment plant, of hot water, resulting in a substantial recovery in energy and consequently in lower plant and operating costs.
  • FIG. 1 shows a diagram of a plant for the recovery of polyvinyl alcohol from the washing bath in the textile industry that is the object of the present invention for the development of the PVA recovery process.
  • the plant 1 substantially consists of a number of stations, of which the first station 2 comprises a screening and accumulation section, the second station 3 comprises a filtering section and the third station 4 comprises a gelification section.
  • the plant 1 of which the first station 2 consists of the screening and accumulation section comprises a series of grilles 20 foreseen to carry out a first filtering phase to prevent suspended solids, such as threads, from entering and passing into the following stations of the system creating mechanical problems to the system, and comprises an accumulation tank 21 with the task of collecting the liquids from the thread washing bath. More in detail, the tank 21 is made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel with the task of maintaining a constant flow of water to the following filtering station.
  • the material collected by the grilles 20 is conveyed towards the waste and disposed of.
  • the second station 3 consisting of the filtering section comprises a first pumping station 30, envisaged to send the liquids to be treated to a first filtering unit 31, of the microfiltration type, which has the task of removing any fibres or any suspended solids present in the liquid, with a more accurate filtering action with respect to the grilles 20 and to a second filtering unit 32 of the ultrafiltration type.
  • the second filtering unit 32 consists of at least one module comprising an ultrafiltration apparatus 32 and a second pumping station 33 envisaged for the recirculation of the liquid.
  • the ultrafiltration apparatus 32 consists of tubular ceramic membrane elements with the task of removing the P VA and separating it from the water through different phases until a permeate of clean water is obtained.
  • the recirculation of the liquid is carried out to maintain a high tangential velocity of the liquid on the membranes and therefore to constantly clean them and the filtering surface to prevent them from getting dirty quickly.
  • the various recirculations are determined according to the features of the membranes used.
  • the passage through the ceramic membrane elements generates on one side a flow of clean water (permeate) which is sent to a tank 26 for reuse and, on the other side, a flow (concentrate) that is sent to the following gelification station 4.
  • the first pumping station 30 is made of stainless steel or marine bronze and supplies the filtering section.
  • the first filtering unit 31 is made of plastic or stainless steel and has a filtering level of 250 ⁇ .
  • the second pumping station 33 is made of stainless steel or marine bronze and makes the liquid circulate on the membrane elements.
  • the ultrafiltration apparatuses 32 are located in stainless steel containers and include tubular ceramic membrane elements that guarantee the separation of the PVA from the water through high temperature filtering. As previously mentioned, the ultrafiltration modules operate at a high temperature and the permeate is sent at a temperature of 70-80° C to an insulated storage tank 26 to avoid heat dispersion.
  • the plant in question 1 features a filtering unit 32 consisting of a series of ultrafiltration modules 32, shown in figure 1, each of which features its own pumping station 33.
  • the said plurality of modules and the different passages of the liquid through the ceramic membrane have the task of further separating the PVA from the water, concentrating it in an increasingly smaller amount of liquid.
  • the number of elements varies according to the quantity of clean water and of PVA separated from the water to be obtained and according to the size and capacity that the plant must have.
  • clean water is discharged from the various stages and passages, which is sent to the tank 26, while the remaining water is increasingly loaded with PVA.
  • second pumping station 33 is envisaged for the recirculation and pressurisation of the liquid, to favour a high tangential velocity of the liquid, similarly to what occurs in the pumping station 30.
  • the plant features the third station 4 that comprises a PVA gelification section that consists of a PH control device 40 made up of one or more dosing pumps and of a tank for acid made of plastic material.
  • the adjustments of the PH of the concentrate is carried out by a dedicated pump of the proportional type which adjusts the PH by dosing the sulphuric acid to bring the concentrate to a neutral state.
  • the gelification section includes a concentrate collection tank 41 made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel, a pumping station 42 to supply a gelification device 43 that comprises gelification cylinders in which the PVA is cooled and passes from a liquid to a solid state.
  • the cleaning of the membranes is carried out using chemical substances duly diluted in the special tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning thereof through the elimination by removal of the substances deposited on them.
  • the plant 1 features a series of instruments such as flow meters of the permeate and concentrate, also according to the supply, located on the lines in the first and second station, pressure gauges at the input and output of the membranes, temperature gauges in each tank and a concentrate pH meter.
  • instruments such as flow meters of the permeate and concentrate, also according to the supply, located on the lines in the first and second station, pressure gauges at the input and output of the membranes, temperature gauges in each tank and a concentrate pH meter.
  • a further characteristic of the plant according to the present invention is a particular system that allows the plant to be completely emptied if there is a sudden power cut, avoiding that the PVA, cooling down, clogs the ceramic membrane elements and the pumping stations and filtering stations in general.
  • the plant 1 has the task of separating the PVA present in the thread washing baths from the water, to recover clean water and energy and to recover the PVA for other uses in a variety of other production processes, such as, for example, paper production, asphalt production, etc.. and / or for other purposes.
  • the plant does not overload and put a strain on discharge treatment plants since the effluent sent to the centralised treatment plant has a considerably lower load of highly polluting substances.
  • the plant and the procedure developed with the plant according to the present invention allow the costs of the centralised treatment plant to be contained but, above all, the operating costs are reduced and considerable savings are obtained on the consumption of water used in the various processes.
  • the plant according to the present invention allows the following process to be performed to recover the PVA molecules from the thread washing baths as schematically shown in figure 1.
  • the PVA recovery procedure includes the following operational phases:
  • the flow rate of the permeate is guaranteed, managed and controlled by the back pressure generated by the pump 30 and by a valve installed on the concentrate recirculation line.
  • a part of the permeate (clean water) is continuously tapped and sent to the tank 26, while the concentrate continues into the ultrafiltration unit.
  • the separation and recovery procedure continues with the following stages: adjustment of the PH of the liquid by dosing of sulphuric acid, sending of the concentrate to a storage tank 41 , - pumping of the concentrate through a cooling and gelification system in which the PVA passes from a liquid state to gel through the reduction of temperature recovery and reuse of the PVA.
  • the liquid When washing operations of the threads for textiles are complete and the bath is drained, the liquid must be treated to eliminate and recover the PVA it contains, so the water can be reused in subsequent stages and the PVA can be used in other industrial processes.
  • a high temperature treated water is obtained that is reused in subsequent processes, as well as a quantity of concentrate composed of PVA gel that is stored to be subsequently used in other sectors such as, for example, paper production, asphalt production, etc.
  • the effluent sent to the centralised treatment plant has a considerably lower load of polluting substances.
  • the plant for the separation and recovery of PVA in the thread bleaching process in question allows a recovery of over 90% of water perfectly free from PVA, decolorized and with a low salt content and still at a high temperature (70-80 0 C), which can be reused in the production process.
  • the plant offers the possibility to send to the centralised treatment plant an effluent with a considerably lower load of polluting substances, with lower system and operating costs.
  • the plant according to the present invention allows the recovery, downstream of the centralised treatment plant, of a greater amount of water at lower costs.
  • the plant and procedure allow the polyvinyl alcohol to be separated and recovered in gel form, upstream of the treatment plants, which was not previously possible.
  • the overall PVA recovery factor is between 90-100 % and what is recovered can be reused in various manufacturing processes in other sectors.
  • the residual wastewater obtained has a high concentration of PVA which cannot be discharged in wastewater treatment plants or disposed of, so it is recovered or even sold at an affordable cost.
  • Another advantage of the plant derives from the fact that the system in question can be used at high temperatures, avoiding the risk of gelification of PVA that would clog every type of membrane making it unusable, hot-separates the PVA molecules making them available in a concentrated state and then obtains a solid product that can be reused both in the textile industry and in other industrial processes.
  • the plant and procedure in question prevent the problems that effluent treatment plants previously had; in fact, previously, when the PVA was discharged there was an immediate and sudden increase of COD, which was difficult to manage and forced the workers to close down the plants to clean them.
  • the plant and procedure provide greater recovery and recycling of water, which can then be used in the process at lower cost.
  • a further advantage of the plant is that it meets a growing need, which is the increasing demand for the recovery of substances through efficient and reliable processes. Furthermore, over time, the plant offers savings on the management costs of the bleaching process because the cost of the recovery of PVA from the wastewater, which was exorbitant, is drastically reduced.
  • a further but not final advantage of the present invention is that it proves remarkably easy to use and to manufacture and works well.

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  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Hydrology & Water Resources (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Detergent Compositions (AREA)

Abstract

The present invention relates to a plant and procedure for the recovery of Polyvinyl Alcohol (PVA) from the washing bath in the textile industry. The system is of the type that comprises a plurality of stations, of which the first station (2) comprises a screening and accumulation section, the second station (3) comprises a filtering section that generates on one side a flow of clean water (permeate) which is sent to a an insulated tank (26) and on the other side a flow (concentrate) that is sent to a third station (4) which comprises a PVA gelification section, where the PVA passes from a liquid to a solid state by lowering the temperature.

Description

DESCRIPTION
"PLANT AND PROCEDURE FOR THE RECOVERY OF POLYVINYL ALCOHOL FROM THE WASHING BATH IN THE TEXTILE
INDUSTRY"
Technical field
The present invention relates to a plant and procedure for the recovery of Polyvinyl Alcohol from the washing bath in the textile industry particularly suitable to separate the Polyvinyl Alcohol (PVA) from the wastewater in the thread washing bath.
Background Art
As is known, PVA is used in the textile industry to make the thread more compact so that the different strands, of which it is made up, are grouped together making the thread more resistant and easier to use in the spinning process.
When the thread is then washed in the subsequent process, also called bleaching, the PVA is discharged together with the other waste into the water, which is then conveyed to the treatment process.
As previously mentioned, the washing bath containing PVA is generally discharged in the wastewater treatment plants and the presence of this substance considerably worsens the chemical-physical characteristics and often makes the water difficult to treat or even makes it unbeatable, since PVA is poorly biodegradable and is not compatible with the treatment plants that are generally of the biological type.
In fact, PVA has a very high COD (chemical oxygen demand) level therefore it is considered a major pollutant and its presence in processing waste has always generated serious plant management problems as it causes, for example in biological plants, the growth of filamentous bacteria that are difficult to separate; this results in a significant increase in plant management operating costs. As previously mentioned, PVA undermines the treatment plants as the waste must be chemically treated before being discharged into the environment, but such treatments do not give the expected results and moreover they create many problems.
In fact, with the systems used, it is very difficult to treat the wastewater and the small results that are obtained have a high cost.
Nowadays there is a strong need to separate PVA from the discharges of the bleaching process, given that the highest concentration of PVA is contained in the thread washing bath before dyeing of the thread, in order to reuse them and eliminate the most concentrated discharges, which are then treated separately upstream of the treatment plant in which all the dyeing wastewater is conveyed.
In particular, nowadays, there are not any plants that separate and recover the PVA found in the thread washing baths upstream of the wastewater treatment plants.
In recent years, the increasing rationalisation of industrial processes, the use of increasingly efficient systems and the recovery and reuse of wastewater, has led to a substantial reduction of specific water consumption (consumption per unit of product) but, in many cases, this has also caused a deterioration of wastewater due to a high concentration of pollutants.
Alongside the deterioration of the characteristics of this type of waste, the laws, which are increasingly strict in the environmental field, require increasingly efficient water treatment and recovery plants, up to the so-called "zero discharge" systems.
The technologies mainly adopted concern the recovery of dyeing wastewater, downstream of the activated sludge biological treatment; the most limiting factor however for the use of these technologies is the concentration of PVA that makes biological systems difficult to manage, also due to the high operating costs resulting from the considerable consumption of electricity. Furthermore, the presence of PVA makes it difficult to adopt processes that employ membrane filtration downstream of biological treatment systems.
Disclosure of Invention
The object of the present invention is substantially to solve the problems of the known technique overcoming the above mentioned difficulties by means of a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry, which enables the recovery of water in order to obtain hot clean water at a temperature of 70-80° C.
A second object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry, which enables the separation of the PVA from the water and its gelification, to take it to a solid state so that it can be reused in other industrial processes.
Another object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry that enables wastewater, with a considerably lower concentration of pollutants, to be sent to the centralised treatment plant, with a reduction in management and plant costs.
A further object of the present invention is to achieve a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry that enables the recovery, upstream of the centralised treatment plant, of hot water, resulting in a substantial recovery in energy and consequently in lower plant and operating costs.
Not the least object of the present invention is to develop a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry that is easy to manufacture and works well. These objects and still others that will appear more clearly in the course of this description are substantially achieved by a plant and procedure for the recovery of polyvinyl alcohol by washing bath in the textile industry, as hereinafter claimed.
Brief Description of Drawings
Further features and advantages will appear more clearly from the detailed description of a plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry, according to the present invention, made below with reference to the attached drawings, provided merely for illustrative and thus non-limiting purposes, in which:
- figure 1 shows a diagram of a plant for the recovery of polyvinyl alcohol from the washing bath in the textile industry that is the object of the present invention for the development of the PVA recovery process.
With reference to the cited figure, with 1 a diagram of a plant for the recovery of polyvinyl alcohol from the washing bath in the textile industry has been indicated overall, according to the present invention.
Best Mode for Carrying Out the Invention
The plant 1 substantially consists of a number of stations, of which the first station 2 comprises a screening and accumulation section, the second station 3 comprises a filtering section and the third station 4 comprises a gelification section.
As mentioned above, the plant 1 , of which the first station 2 consists of the screening and accumulation section comprises a series of grilles 20 foreseen to carry out a first filtering phase to prevent suspended solids, such as threads, from entering and passing into the following stations of the system creating mechanical problems to the system, and comprises an accumulation tank 21 with the task of collecting the liquids from the thread washing bath. More in detail, the tank 21 is made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel with the task of maintaining a constant flow of water to the following filtering station.
In particular, the material collected by the grilles 20 is conveyed towards the waste and disposed of.
The second station 3 consisting of the filtering section comprises a first pumping station 30, envisaged to send the liquids to be treated to a first filtering unit 31, of the microfiltration type, which has the task of removing any fibres or any suspended solids present in the liquid, with a more accurate filtering action with respect to the grilles 20 and to a second filtering unit 32 of the ultrafiltration type.
More in detail, the second filtering unit 32 consists of at least one module comprising an ultrafiltration apparatus 32 and a second pumping station 33 envisaged for the recirculation of the liquid. In particular, the ultrafiltration apparatus 32 consists of tubular ceramic membrane elements with the task of removing the P VA and separating it from the water through different phases until a permeate of clean water is obtained. In particular, the recirculation of the liquid is carried out to maintain a high tangential velocity of the liquid on the membranes and therefore to constantly clean them and the filtering surface to prevent them from getting dirty quickly. The various recirculations are determined according to the features of the membranes used.
As mentioned, the passage through the ceramic membrane elements generates on one side a flow of clean water (permeate) which is sent to a tank 26 for reuse and, on the other side, a flow (concentrate) that is sent to the following gelification station 4. According to the present embodiment, the first pumping station 30 is made of stainless steel or marine bronze and supplies the filtering section. Furthermore, the first filtering unit 31 is made of plastic or stainless steel and has a filtering level of 250 μ. In addition the second pumping station 33 is made of stainless steel or marine bronze and makes the liquid circulate on the membrane elements. More in detail, the ultrafiltration apparatuses 32 are located in stainless steel containers and include tubular ceramic membrane elements that guarantee the separation of the PVA from the water through high temperature filtering. As previously mentioned, the ultrafiltration modules operate at a high temperature and the permeate is sent at a temperature of 70-80° C to an insulated storage tank 26 to avoid heat dispersion.
In particular, the plant in question 1 , as previously mentioned, features a filtering unit 32 consisting of a series of ultrafiltration modules 32, shown in figure 1, each of which features its own pumping station 33.
The said plurality of modules and the different passages of the liquid through the ceramic membrane have the task of further separating the PVA from the water, concentrating it in an increasingly smaller amount of liquid.
The number of elements varies according to the quantity of clean water and of PVA separated from the water to be obtained and according to the size and capacity that the plant must have.
More in detail, clean water is discharged from the various stages and passages, which is sent to the tank 26, while the remaining water is increasingly loaded with PVA.
In particular, second pumping station 33 is envisaged for the recirculation and pressurisation of the liquid, to favour a high tangential velocity of the liquid, similarly to what occurs in the pumping station 30.
In addition to what has been illustrated so far and as previously mentioned, the plant features the third station 4 that comprises a PVA gelification section that consists of a PH control device 40 made up of one or more dosing pumps and of a tank for acid made of plastic material. The adjustments of the PH of the concentrate, obtained after the passages in the ultrafiltration station, is carried out by a dedicated pump of the proportional type which adjusts the PH by dosing the sulphuric acid to bring the concentrate to a neutral state.
Furthermore, the gelification section includes a concentrate collection tank 41 made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel, a pumping station 42 to supply a gelification device 43 that comprises gelification cylinders in which the PVA is cooled and passes from a liquid to a solid state.
According to the present invention, the plant comprises a fourth station that is the membrane cleaning section that features a washing tank, which is the tank 26 made of plastic or stainless steel, foreseen to clean the membranes, in which dedicated pumps are used, or the supply pumps of the respective sections.
More in detail, the cleaning of the membranes is carried out using chemical substances duly diluted in the special tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning thereof through the elimination by removal of the substances deposited on them.
Furthermore, the plant 1 features a series of instruments such as flow meters of the permeate and concentrate, also according to the supply, located on the lines in the first and second station, pressure gauges at the input and output of the membranes, temperature gauges in each tank and a concentrate pH meter.
A further characteristic of the plant according to the present invention is a particular system that allows the plant to be completely emptied if there is a sudden power cut, avoiding that the PVA, cooling down, clogs the ceramic membrane elements and the pumping stations and filtering stations in general. According to the present invention, the plant 1 has the task of separating the PVA present in the thread washing baths from the water, to recover clean water and energy and to recover the PVA for other uses in a variety of other production processes, such as, for example, paper production, asphalt production, etc.. and / or for other purposes. In addition, the plant does not overload and put a strain on discharge treatment plants since the effluent sent to the centralised treatment plant has a considerably lower load of highly polluting substances.
The plant and the procedure developed with the plant according to the present invention allow the costs of the centralised treatment plant to be contained but, above all, the operating costs are reduced and considerable savings are obtained on the consumption of water used in the various processes.
The plant according to the present invention allows the following process to be performed to recover the PVA molecules from the thread washing baths as schematically shown in figure 1.
The PVA recovery procedure includes the following operational phases:
- passage of the liquid though a series of grilles 20 to carry out a first filtering phase,
- removal of the material collected by the grilles which is disposed of in the waste, collection of the liquid of the washing bath in a tank 21 ,
- movement of the liquid by means of the first pumping station 30,
passage of the liquid through a first filtering unit 31 , of the microfiltration type 31 to remove any fibres or any suspended solids present in the liquid, with a more accurate filtering action compared to the grilles,
- passage of the liquid in ultrafiltration modules 32 that separate the PVA molecules, - recirculation of the concentrate by means of a second pumping station 33 through ceramic membranes with a flow 10-12 times greater than the supply with the aim of maintaining a high velocity to obtain constant cleaning of the filtering surface, sending of the permeate (clean water) at high temperature to an insulated storage tank 26 to avoid heat dispersion.
In particular, the flow rate of the permeate is guaranteed, managed and controlled by the back pressure generated by the pump 30 and by a valve installed on the concentrate recirculation line.
A part of the permeate (clean water) is continuously tapped and sent to the tank 26, while the concentrate continues into the ultrafiltration unit.
According to the present invention, the separation and recovery procedure continues with the following stages: adjustment of the PH of the liquid by dosing of sulphuric acid, sending of the concentrate to a storage tank 41 , - pumping of the concentrate through a cooling and gelification system in which the PVA passes from a liquid state to gel through the reduction of temperature recovery and reuse of the PVA.
After the predominantly structural description above, the operation of the invention in question will now be outlined.
When washing operations of the threads for textiles are complete and the bath is drained, the liquid must be treated to eliminate and recover the PVA it contains, so the water can be reused in subsequent stages and the PVA can be used in other industrial processes. Once the steps described above have been performed, a high temperature treated water is obtained that is reused in subsequent processes, as well as a quantity of concentrate composed of PVA gel that is stored to be subsequently used in other sectors such as, for example, paper production, asphalt production, etc.
In particular, after the steps of the process in question, the effluent sent to the centralised treatment plant has a considerably lower load of polluting substances.
Thus the present invention achieves the aims set.
The plant for the separation and recovery of PVA in the thread bleaching process in question allows a recovery of over 90% of water perfectly free from PVA, decolorized and with a low salt content and still at a high temperature (70-80 0 C), which can be reused in the production process.
In addition, the plant offers the possibility to send to the centralised treatment plant an effluent with a considerably lower load of polluting substances, with lower system and operating costs.
Furthermore, the plant according to the present invention allows the recovery, downstream of the centralised treatment plant, of a greater amount of water at lower costs.
Advantageously, the plant and procedure allow the polyvinyl alcohol to be separated and recovered in gel form, upstream of the treatment plants, which was not previously possible. In addition, the overall PVA recovery factor is between 90-100 % and what is recovered can be reused in various manufacturing processes in other sectors.
In fact, given the characteristics of the semipermeable membranes used in the microfiltration and ultra filtration, the residual wastewater obtained has a high concentration of PVA which cannot be discharged in wastewater treatment plants or disposed of, so it is recovered or even sold at an affordable cost. Another advantage of the plant derives from the fact that the system in question can be used at high temperatures, avoiding the risk of gelification of PVA that would clog every type of membrane making it unusable, hot-separates the PVA molecules making them available in a concentrated state and then obtains a solid product that can be reused both in the textile industry and in other industrial processes.
Advantageously, the plant and procedure in question prevent the problems that effluent treatment plants previously had; in fact, previously, when the PVA was discharged there was an immediate and sudden increase of COD, which was difficult to manage and forced the workers to close down the plants to clean them.
In addition, the plant and procedure provide greater recovery and recycling of water, which can then be used in the process at lower cost.
A further advantage of the plant is that it meets a growing need, which is the increasing demand for the recovery of substances through efficient and reliable processes. Furthermore, over time, the plant offers savings on the management costs of the bleaching process because the cost of the recovery of PVA from the wastewater, which was exorbitant, is drastically reduced.
In particular, the procedure makes the discharge management system in textile plants much simpler.
The plant and procedure in question lead to energy savings and savings in both system and operating costs.
A further but not final advantage of the present invention is that it proves remarkably easy to use and to manufacture and works well.
Naturally, further modifications or variants may be applied to the present invention while remaining within the scope of the invention that characterises it.

Claims

Plant for the recovery of Polyvinyl Alcohol (PVA) from the washing bath in the textile industry characterised by the fact that it includes a plurality of stations, of which the first station
(2) comprises a screening and accumulation section, the second station
(3) comprises a filtering section that generates on one side a flow of clean water (permeate) which is sent to a an insulated tank (26) and on the other side a flow (concentrate) that is sent to a third station
(4) which consists of a PVA gelification section.
Plant for the recovery of Polyvinyl Alcohol from the washing bath in the textile industry characterised by the fact that it includes a fourth station which consists of a membrane cleaning section.
Plant according to claim 1 , characterised by the fact that the said first station (2) consisting of the screening and accumulation section comprises a series of grilles (20) foreseen to carry out a first filtering phase to prevent suspended solids, such as threads, from entering and passing into the following stations of the system creating mechanical problems, and comprises an accumulation tank (21) with the task of collecting the liquids from the thread washing bath and maintaining a constant flow of water to the following filtering stations.
Plant according to claim 1, characterised by the fact that the said second station (3) consisting of the filtering section comprises a first pumping station (30) envisaged to send the liquids to be treated to a first filtering unit (31 ), of the micro filtration type, which has the task of removing any fibres or any suspended solids present in the liquid, with a more accurate filtering action compared to the grilles (20) and to a second filtering unit of the ultrafiltration type.
5. Plant according to claim 4, characterised by the fact that the said second filtering unit consists of at least one module comprising and ultrafiltration apparatus (32) which includes tubular ceramic membrane elements with the task of removing the PVA and separating it from the water through different phases until a permeate of clean water is obtained; the said second filtering unit consists of a second pumping station (33) envisaged for the recirculation of the liquid, carried out to maintain a high tangential velocity of the liquid on the membranes and therefore to constantly clean them and the filtering surface.
6. Plant according to claim 1, characterised by the fact that the said third station consisting of the PVA gelification section comprises:
- a PH control device (40) made up of one or more dosing pumps and of a tank for acid made of plastic material; the adjustments of the PH of the concentrate is carried out by a dedicated pump of the proportional type which adjusts the PH by dosing the sulphuric acid to bring the concentrate to a neutral state,
a concentrate collection tank (41) made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel, a pumping station (42) to supply a gelification device (43) that comprises gelification cylinders in which the PVA is cooled and passes from a liquid to a solid state.
7. Plant according to claim 4, characterised by the fact that the said second filtering unit is composed of a series of ultrafiltration apparatuses (32) each of which features its own pumping station (33) and the said plurality of apparatuses varies according to the quantity of clean water to be obtained and of PVA separated from water and to the size and capacity that the system must have.
8. Plant according to claim 2, characterised by the fact that the said fourth station consisting of the membrane cleaning section features a washing tank made of plastic or stainless steel foreseen to clean the membranes, in which dedicated pumps are used, or the supply pumps of the respective sections, and the said cleaning is carried out using chemical substances duly diluted in the special tank and fluxed according to a particular procedure through the membranes to obtain complete cleaning thereof through the elimination by removal of the substances deposited on them.
9. Plant according to claim 4, characterised by the fact that in the said screening and accumulation section, the tank (21) is made of concrete with plastic or epoxy protection or made of fibreglass or plastic material or stainless steel, the first pumping station (30) is made of stainless steel or marine bronze and supplies the filtering section, the first filtering unit (31) is made of plastic or stainless steel and has a filtering level of 250 μ, the second pumping station (33) is made of stainless steel or marine bronze and makes the liquid circulate on the membrane elements, the ultrafiltration apparatuses (32) are located in stainless steel containers and include tubular ceramic membrane elements that guarantee the separation of the PVA from the water through high temperature filtering.
10. Plant according to claim 1, characterized by the fact that it comprises a series of instruments such as flow meters of the permeate and concentrate, also according to the supply, located on the lines in the first and second station, pressure gauges at the input and output of the membranes, temperature gauges in each tank and a concentrate pH meter.
1 1. Procedur of recovery of PVA from the washing bath in the textile industry carried out with the system according to claims from 1 to 10, characterised by the fact that it comprises a plurality of operational phases whereby: in the first station (2) the following phases are carried out:
passage of the liquid though a series of grilles (20) to carry out a first filtering phase,
- removal of the material collected by the grilles which is disposed of in the waste, collection of the liquid of the washing bath in a tank (21),
in the second station (3), the following phases are carried out:
- movement of the liquid by means of the first pumping station (30),
- passage of the liquid through a first filtering unit (31 ), of the microfiltration type, to remove any fibres or any suspended solids present in the liquid, with a more accurate filtering action compared to the grilles,
- passage of the liquid in ultrafiltration modules (32) that separate the PVA molecules,
- recirculation of the concentrate by means of a second pumping station (33) through ceramic membranes with a flow 10-12 times greater than the supply with the aim of maintaining a high velocity to obtain constant cleaning of the filtering surface,
continuous tapping of a part of the permeate (clean water) at high temperature and sending of the liquid to an insulated storage tank (26) to avoid heat dispersion, in the third station (4) the following phases are carried out: adjustment of the PH of the liquid by dosing of sulphuric acid, sending of the concentrate to a storage tank (41), pumping of the concentrate through a cooling and gelification system in which the PVA passes from a liquid state to gel through the reduction of temperature, recovery and reuse of the PVA and in the fourth station the membranes are cleaned with chemical substances duly diluted and fluxed through the ceramic membrane elements to remove the substances deposited on them.
EP14739953.9A 2013-04-15 2014-04-15 Plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry Withdrawn EP2986569A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT000004A ITMN20130004A1 (en) 2013-04-15 2013-04-15 PLANT AND PROCESS FOR THE RECOVERY OF POLI VINIL ALCOOL FROM THE WASHING BATHROOM IN THE TEXTILE INDUSTRY.
PCT/IT2014/000110 WO2014170924A1 (en) 2013-04-15 2014-04-15 Plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry

Publications (1)

Publication Number Publication Date
EP2986569A1 true EP2986569A1 (en) 2016-02-24

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EP14739953.9A Withdrawn EP2986569A1 (en) 2013-04-15 2014-04-15 Plant and procedure for the recovery of polyvinyl alcohol from the washing bath in the textile industry

Country Status (3)

Country Link
EP (1) EP2986569A1 (en)
IT (1) ITMN20130004A1 (en)
WO (1) WO2014170924A1 (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL179546C (en) * 1973-05-10 Union Carbide Corp MODULE FOR USE IN AN ULTRAFILTRATION DEVICE.
US4200533A (en) * 1978-06-28 1980-04-29 Brandon Craig A Hyperfiltration apparatus and method of fluid treatment
US4734097A (en) * 1981-09-25 1988-03-29 Nippon Oil Company, Ltd. Medical material of polyvinyl alcohol and process of making
ITMN20110019A1 (en) * 2011-09-07 2013-03-08 Euro Mec S R L PLANT AND PROCESS FOR THE RECOVERY OF BRIARES FROM EXHAUSTED DYE BATHS.

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2014170924A1 *

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ITMN20130004A1 (en) 2014-10-16

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