FI62852C - FOERFARANDE FOER RENING AV AVFALLSLOESNINGSMEDEL - Google Patents

Description

χ 62852

This invention relates to a method for purifying waste solvents.

Waste solvents currently pose a considerable environmental problem. In Finland alone, waste solvents are generated, including paint waste.

20,000 t / y.

This amount of solvent is economically considerable because they are expensive petrochemical products. In the case of highly processed products, such as polar solvents, their incineration is a waste of the national economy.

Waste solvents can be purified from solids and water by distillation. If it is also desired to fractionate them, the distillation method must be too expensive in practice and in many cases impossible.

When using the distillation method, the solid of the waste solvent also causes great inconveniences in the form of fouling of the heat exchange surfaces. Distillation can no longer be performed when the solids content exceeds 20%. There are methods for removing solids, e.g.

DOS 1,924,831 and U.S. Patent 2,552,351, as well as Dutch Patent Application 6,716,214, which are based on the treatment of a waste solvent with dilute NaOH solution and subsequent distillation. In this case, however, the ester portion of the solvents is hydrolyzed. Moreover, in these methods the yield is worse than in the process of the present invention.

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It has now surprisingly been found that by treating the waste solvent with an aqueous solution or suspension containing so much alkali metal or alkaline earth metal hydroxide that the mixture of organic phase and aqueous phase contains at least 50 g of hydroxide per liter of mixture, the waste resin waste can be insoluble. Organic matter can be removed from the aqueous phase by filtration and the aqueous phase recycled. If the waste solvent contains pigment, this is effectively separated in the alkali treatment.

If the waste solvent contains components that decompose upon contact with the alkali solution, such as esters, they are removed according to the present invention prior to alkali treatment.

In a preferred embodiment of the invention according to this method, polar solvents such as alcohols, esters and ketones are removed by extracting the waste solvent before alkali treatment with water which dissolves the above-mentioned polar compounds. When this extraction is carried out at an elevated temperature, at a temperature of at least 50 ° C and at most 100 ° C, the lowest boiling component or azeotrope is simultaneously distilled from the solution. The aqueous phase containing the remaining polar compounds can then be separated from the organic phase, after which the aqueous phase is liberated from the polar compounds it contains, e.g. by distillation or salting out. The salting-out substance can be removed from the circulation, e.g. by ion exchange. Because small amounts of salt are removed from the solution, ion exchange can be used for this.

If desired, the aromatic hydrocarbons contained in the solvents can be extracted from the remaining mixture of aromatic and aliphatic hydrocarbons after removal of the solid by known extraction methods. The remaining part, which contains not more than 10% of aromatics in addition to aliphatic hydrocarbons, can be used as such for the production of solvent-based paints.

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The fractionation method has the advantage that the components thus separated can be used for the production of paints, varnishes, etc., in which the solvent base must have a certain composition.

The following examples further illustrate the process of the invention.

Example 1

A liter of washing solvent was taken, the composition of which was as follows:

Aliphatic white spirit 60%

Aromatic white spirit 27% Waste 13%

To the above was added 1 liter of a solution of 200 g NaOH + 100 g NaCl / 1 H 2 O and stirred for 15 minutes. The product was allowed to clear for 30 minutes. The upper clear organic phase was decanted and was 850 ml. The aqueous phase containing the resulting slurry was centrifuged and the phases were separated. The volume of the aqueous phase was 920 ml and its NaOH content was 195 g / l. The evaporation residue from the organic phase (1 h at 190 ° C) was 1.2%.

Example 2

1 liter of washing solvent was taken as follows:

Petroleum 30%

Ethyl acetate 20%

Toluene 20%

Ethanol 10%

Xylene 5% Waste 15% 4 62852

1 liter of a solution of 100 g CaCl 2 / l H 2 O was prepared. To this were added 100 g of Ca (OH) 2 and 100 g of CaO. The resulting slurry was combined with the washing solvent, and stirred for 2 hours. The mixture thus obtained was filtered and the filtrate was allowed to clear. The solids content of the organic phase had decreased by 36%.

Example 3 A waste solvent having the following composition was treated:

Polar solvents, ethyl acetate and ethanol 15%

Aromatic solvents, toluene and xylene 31%

White spirit 36%

Solids (pigments, various binders) 18%

The solution was stirred with 1 liter of water for five minutes, after which the phases were separated. The volume of the organic phase was 910 ml and that of the aqueous phase 1090 ml.

The resulting aqueous phase was distilled to give 98 ml of a solvent containing a mixture of 92% ethyl acetate and ethanol, and 8% water and traces of other solvents as an impurity.

Example 4

1 liter of washing solvent was taken as follows:

Petroleum 30%

Ethyl acetate 20%

Toluene 20 20%

Ethanol 10 10%

Xylene 5% Waste 15% 5 62852

50 ml of water was added to the solvent and distilled at 71 ° C until 250 g of excess was obtained, of which 80% ethyl acetate, 9% ethanol and 10% water and 1% other solvents. The alite was allowed to clear and the aqueous phase was passed to a second distillation to give 30 g of an aqueous ethanol solution. The submerged water was contacted with the distillate obtained in the first step, the phases were separated and the ethyl acetate content of the organic phase was found to be 95%.

Example 5

A continuous test process according to the flow chart of the attached figure was performed. A solvent having the following composition was used in the experiment:

Petroleum 30%

Ethyl acetate 2Q%

Ethyl alcohol 10%

Toluene 20% Waste 20%

The density of the solution was 0.84 kg / l. The waste solvent was fed through the preheater 1, whereupon it was heated to 71 ° C. The feed rate was 10 1 / h. From the preheater, the solution was passed to a thermostatically controlled distillation extraction column 2, which was heated with an electric heater of 3 kW. The circulating water flow (1.03 l / h) was connected to the feed. At 70.2 ° C, an azeotrope of 2.27 l / h was distilled from the top of the column. Its composition was 82.6% ethyl acetate, 8.4% ethanol and 9% water. This stream was cooled 3 and a circulating water stream was connected to it. The solution thus obtained was passed to clarifier 4 and an organic phase consisting of 97% ethyl acetate and 3% water was recovered at 1.92 l / h. The aqueous phase was returned to circulation. The alite from the distillation extraction column 2 (8.4 l / h) was passed to a clarifier 5 where the aqueous phase was separated and

Claims (1)

6 62852 was pumped (1.7 l / h) to distillation column 6. The excess (0.9 1 / h) from column 6 was cooled 7 and had a composition of 95% ethanol and 5% water. Water was added to the slurry at 0.23 l / h and directed to the excess obtained from the first distillation. From the clarifier 5, the organic phase was introduced at 6.7 l / h into a saponification reactor 8 with a volume of 30 liters. Sodium hydroxide solution (100 g / l NaOH) 6.7 l / h was fed to the same reactor 8 with stirring. The mixture was passed to a clarifier 10 with a volume of 30 liters. The organic phase was discarded (5.36 l / h) and the aqueous phase was filtered 11 and recycled after the addition of NaOH (130 g / h).