RU2367623C2 - Method for purification of dimethylamide-containing process water - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention can be used for purification of dimethylamide-containing process water and for recycling of valuable components used in synthetic fibers production. For method implementation the initial waste water is beforehand divided by baromembrane separation to purified water (permeate) and concentrate. The purified water is returned to production line and the concentrate is filtered through active charcoal with following active charcoal regeneration by the flow of desorbent (hot nitrogen with temperature 150-200°C) and separation of concentrated dimethylamide.

EFFECT: pure water recycling, economical efficiency enhancing of the process of dimethylamide sorption with active charcoal including its following extraction by desorbent flow.

1 ex, 1 dwg, 1 tbl

Description

The invention relates to methods for treating industrial wastewater from dimethylacetamide and can be used to treat wastewater and returning purified water and dimethylacetamide to the process in the production of synthetic fibers.

A known method of processing wastewater containing dimethylacetamide, including their biological treatment in aeration tanks (Sat. New methods and facilities for wastewater and wastewater treatment. L., 1981, p. 86-92).

The disadvantages of this method are:

- loss of a valuable component (dimethylacetamide);

- water pollution by microorganisms, products of their metabolism, as well as substances added to provide the necessary living conditions of microorganisms;

- the difficulty of practical implementation for large volumes of effluent associated with the action of a large number of physicochemical factors and associated chemical contaminants that affect the efficiency of the process.

The features of the method common with the proposed:

- the method is intended for the treatment of technological wastewater contaminated with dimethylacetamide.

Closest to the proposed technical solution is a method of treating wastewater containing dimethylacetamide, including filtering wastewater through activated carbon to obtain purified water, regenerating activated carbon with chloroform, distilling spent chloroform with desorbed substances into dimethylacetamide, isobutyl alcohol and chloroform returned to regeneration of activated carbon coal (AS No. 1599312, class С02F 1/28, published on October 15, 1990).

The disadvantages of this method of cleaning include:

- the environmental hazard of using the selected desorbent (chloroform) with such a high hazard class on an industrial scale;

- high weight and size characteristics of the equipment associated with the need to use a large volume of sorption coal columns in the treatment of large volumes of effluents with a low concentration of organic impurities;

- high consumption of expensive desorbent (chloroform) associated with the need to regenerate a large amount of activated carbon;

- low concentration of the released dimethylacetamide in the stream of spent chloroform, causing significant costs for its dispersal;

- pollution of the purified water with chloroform and the inability to remove inorganic impurities by this method, which does not allow to use purified water again in the production cycle without additional purification by other methods.

Signs of an analogue common with the proposed:

- the method is intended for the treatment of industrial wastewater contaminated with dimethylacetamide;

- the method allows not only to purify the waste water, but also to allocate for reuse the valuable components contained therein (dimethylacetamide and isobutyl alcohol);

- to isolate dimethylacetamide, the activated carbon sorption method is used, followed by the regeneration of activated carbon by a desorbent stream (chloroform).

The technical result achieved in the proposed method is characterized by:

reducing the overall dimensions of the equipment for treating technological wastewater from dimethylacetamide and mineral impurities while simultaneously recovering the extracted dimethylacetamide for reuse in the form of a solution with a concentration of at least 250 g / l using an environmentally friendly method and ensuring a high degree of purification of technological wastewater from dimethylacetamide and mineral impurities.

To achieve the specified technical result, the treated water is preliminarily divided into purified water (permeate) and concentrate by the method of baromembrane separation, followed by filtering of one concentrate through activated carbon with further regeneration of activated carbon by a desorbent stream and the separation of dimethylacetamide and / or other organic impurities in a concentrated form. As a desorbent, hot nitrogen is used.

Preliminary separation of the entire volume of the treated effluent by means of a baromembrane separation unit allows one to repeatedly reduce the required amount of activated carbon and desorbent for the separation of dimethylacetamide and / or other organic impurities and increase the concentration of emitted impurities in the spent desorbent stream sent for distillation, and water purified by the baromembrane method is freed all contaminants, including inorganic compounds, and can be reused in production no additional cleaning. The use of such an environmentally friendly desorbent as nitrogen greatly simplifies the acceleration, in addition, in a nitrogen environment, organic substances practically do not undergo degradation, which is important if the substances are used again in production.

The distinguishing features that determine the proposed method meets the “novelty” criterion are as follows: a preliminary stage of separation of the treated water into concentrate and permeate by means of a baromembrane separation, filtration through activated carbon to extract dimethylacetamide already only one concentrate, use of hot activated carbon as a desorbent nitrogen followed by distillation of spent nitrogen and the separation of dimethylacetamide in concentrated form. Since the totality of these distinguishing features has not been previously described and its effect on the achievement of the specified technical result for a specialist does not explicitly follow from the prior art, the proposed method, according to the authors, meets the criterion of "inventive step".

The drawing shows a diagram of the method.

Source water is supplied to the installation of baromembrane separation 1, which includes the required number of stages of separation. The obtained permeate, which is water purified from dimethylacetamide, as well as associated inorganic contaminants, and constituting 80-90% of the initial volume of treated water, is returned to production, and a concentrate of 10-20% of the initial volume of runoff is fed to the coal column 2 for sorption of dimethylacetamide. After the life of the coal column 2 has expired, hot nitrogen is supplied to the column inlet to regenerate it, and spent nitrogen containing extracted components is discharged through the outlet, which is then fed to the input of distillation column 3. In distillation column 3, dimethylacetamide and nitrogen are returned to the coal recovery columns 2 after re-heating in the heater 4. The selected dimethylacetamide goes to the warehouse for further use. The bottoms are returned to the original stream of treated water or disposed of as waste.

Example 1. Purification was subjected to water containing dimethylacetamide and isopropyl alcohol in amounts of from 20 mg / l to 2.0 g / l. HYDRONAUTICS reverse osmosis membranes were used. The selection of the concentrate was 10%. Analyzes of purified water and concentrate were carried out at various time intervals after the installation was turned on. The results are shown in table 1.

Table 1
The content of dimethylacetamide in water after purification by the baromembrane method, depending on the initial concentration. Original conc. DMAA, mg / L The content of DMAA in purified water, mg / l, after different times 24 hours 48 hours 56 hours 112 hours 224 hours 448 hours 2000 145 140 151 142 139 148 200 12 fourteen 12 eleven fifteen 13 twenty <1 <1 <1 <1 <1 <1

As can be seen from the table, the content of dimethylacetamide in purified water is about 25 times lower than in the original, which allows two or three steps to almost completely purify the water to return it to the process.

The sorption and desorption conditions of dimethylacetamide and isobutyl alcohol were evaluated on a coal column with BAU at a linear flow velocity of 5 m / h. The dynamic exchange capacity of the column was 45 g / kg for DMAA and 35 g / kg for IHD. The column was regenerated with steam from a laboratory steam generator and hot nitrogen (150-200 ° С). In the first case, the concentration of DMAA and IHD in the condensate was about 10 g / l, in the second case, about 300 g / l.

Thus, on the basis of laboratory tests, we can conclude that the use of the proposed method for the treatment of industrial wastewater from dimethylacetamide gives the following advantages:

- a high degree of purification of wastewater from dimethylacetamide and inorganic compounds, which allows reuse of purified water in production without additional purification;

- low weight and size characteristics of the sorption equipment;

- environmental safety of the used desorbent while ensuring a concentration of emitted dimethylacetamide of at least 250 g / l.

Claims (1)

A method of purifying process wastewater containing dimethylacetamide, comprising filtering the treated water through activated carbon and regenerating the activated carbon by a desorbent stream, characterized in that the treated water is first divided into purified water — permeate and concentrate by a baromembrane separation method, followed by filtration of the concentrate through activated carbon, followed by regeneration of activated carbon by a desorbent stream - hot nitrogen with a temperature of 150-200 ° C and the release of dimethyl acetate amide in concentrated form.

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