CS273887B1 - Method of utilized oil emulsions deemulsifying - Google Patents

Abstract

The method concerns treatment of wastewater containing emulsified petroleum substances. It has wide application, particularly in the machine engineering industry. It particularly concerns demulsifying oils from used oil emulsions used when working metals, which is problematic when using existing methods, particularly for demulsifying used oil emulsions of higher concentrations. Adequate effectiveness is often not achieved in the first phase, when quantitative isolation of the oil share should occur. Cleaning in the proposed method is based on the fact that the used oil emulsion is acidified to pH 1.5 to 2.3 by means of spent mordant hydrochloric acid, which, per litre, contains 25 to 30 g soluble bivalent iron and therefore, at the same time as acidification, bivalent iron is added in a quantity of 0.63 to 1.00 g/l and, after subsequent mixing and oxidation of the bivalent iron to trivalent by means of 0.6 to 0.9 g potassium permanganate per 1 litre of demulsified used oil emulsion, the actual demulsifying reaction occurs while mixing with pressurised air with subsequent separation of the oil fraction. After calm flotation, contracture of the free oil fraction occurs and the water is neutralised by sodium or calcium hydroxide to pH 8.5.

Description

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Process for deemulsifying spent oil emulsions

CS 273887 Bl

The process belongs to the field of waste water treatment containing emulsified petroleum substances. It is widely used mainly in the engineering industry. In particular, it is the deemulsification of oils from spent oil emulsions used in metal machining, which is problematic using the prior art processes, in particular when deemulsifying spent oil emulsions of higher concentrations. Sufficient efficiency is often not achieved mainly in phase 1, when the quantitative separation of the oil fraction is to take place.

Purification by the proposed method consists in acidifying the spent oil emulsion to a pH of 1.5 to 2.3 with depleted pickling hydrochloric acid, which contains 25 to 30 g of dissolved bivalent iron per liter, and therefore the bivalent iron is metered in with the acidification. amounts of 0.63 to 1.00 g / L and thereafter; mixing and oxidation of divalent iron to trivalent with 0.6 to 0.9 g of potassium permanganate per liter of deemulsified spent oil emulsion takes place during the air-pressure mixing process, the actual deemulsification reaction followed by separation of the oil fraction. After quiescent flotation, the free oil fraction is withdrawn and the water is neutralized to pH 8.5 with sodium or calcium hydroxide.

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CS 273887 Bl

BACKGROUND OF THE INVENTION The present invention relates to a process for deemulsifying spent oil emulsions which are used as cutting fluids in metal machining and are produced primarily in the engineering industry.

By its content, the invention belongs to the group of chemical processes for the treatment of industrial waste water containing extractable substances.

Current known methods of deemulsifying spent oil emulsions are based on the following most commonly used principles:

- chemical destruction: addition of precipitating salts in an acid medium

- thermal destruction: heating to different temperatures in the range of 50 to 100 c in an acidic environment

- a combination of the two previous methods.

These processes do not always guarantee perfect purification of waste water containing emulsified petroleum substances, especially at higher concentrations. The thermal source for implementing the thermal method is problematic. Pressure steam has proved its best, but it is not always achievable. Installation and heating by an electric body is a costly solution and often also unavailable due to the unavailability of suitable electrically heated bodies resistant to virtually the entire pH range.

The disadvantages of these processes are eliminated by the process of deemulsifying spent oil emulsions using depleted pickling hydrochloric acid containing dissolved ferric iron and subsequent oxidation with potassium permanganate. Said hydrochloric acid is used diluted 1: 1 to remove iron oxides from the surfaces of iron and cast iron parts before surface treatment (= pickling). After exhaustion of its activity, it contains 25 to 30 g of dissolved bivalent iron per liter and is discarded as a waste product.

The invention advantageously utilizes the aforementioned spent hydrochloric acid pickling acid to acidify the spent oil emulsion to a pH of 1.5 to 2.3, and at the same time to introduce a sufficient amount of ferric iron necessary for the actual demulsification reaction. After intensive stirring of the spent hydrochloric acid to the spent oil emulsion for one hour, this reaction is carried out by adding 0.58 to 0.92 kg of potassium permanganate per m ^{3 of} acidified spent oil emulsion. Stirring is continued for one hour. Compressed air is best used for mixing. After cleavage of the emulsifying substances and after the oxidation is complete, the free oil fraction is separated and separated at the surface during rest flotation and then quantitatively withdrawn. Sodium or calcium hydroxide is used to adjust the pH of the remaining water to 8.5. For better sedimentation, flocculant is recommended. The resulting sludge then settles better and faster. The necessary optimum doses of spent hydrochloric acid spent to achieve the indicated pH values as well as the required amounts of potassium permanganate and sodium or calcium hydroxide, respectively, are determined by laboratory tests.

The advantage of this method is above all the elimination of the necessity of heat supply, which is necessary in the realization of thermal destruction, and the achievement of very low residual content of oil substances in the purified water.

Exemplary embodiment

Oil emulsions are used in mechanical machining. The spent oil emulsions, together with contaminated water from machine and floor washing, are collected to form a 57 g / l oil mixture, of which 2/3 are emulsified. The mixture has a pH of 9.2. The laboratory assay has determined that the optimum amount of reagents is as follows:

- to acidify 1 m ^{3 of the} de-emulsified mixture from pH 9,2 to 1,7, 26,7 liters of spent hydrochloric acid pickling with a concentration of 26,5 g / l of bivalent dissolved iron are required.

This will add 707.55 g of dissolved bivalent iron to 1 m ^{3 of the} mixture together with the acidification;

- 0.78 kg of solid potassium permanganate per m ^{3 of} de-emulsified mixture is required for quantitative oxidation, after which the spent oil emulsion is completely de-emulsified;

CS 273887 Bl

- to neutralize to pH 8,5, 3,4 liters of 40% sodium hydroxide per m ^{3 of} de-emulsified mixture should be used.

It was uniformly determined (in the trial operation) that after the addition of 9 to 10 g of flocculant (flocculant) per 1 m ^{3 of the} de-emulsified mixture, the sedimentation of the resulting sludge would be faster and more perfect. However, the use of this flocculant does not affect the resulting residual oil content.

After acidifying the de-emulsified mixture to pH 1.7 with spent hydrochloric acid pickling, stirring under compressed air was performed for one hour. Potassium permanganate was then metered in and compressed air stirred again for one hour.

After quiescent flotation, the free oil fraction was withdrawn from the surface and the water neutralized by the addition of a predetermined dose of sodium hydroxide. of which the petroleum substances were 0.07 mg / l. Deemulsification was carried out in a universal deemulsification reactor of 6.3 m ³ .

The invention can be used in particular in the engineering industry and wherever the previously known methods of deemulsifying spent oil emulsions and their mixtures with waste water containing free petroleum substances have not proved useful.

Claims (1)

OBJECT OF THE INVENTION Process for the deemulsification of spent oil emulsions, characterized in that the spent oil emulsion is acidified to pH 1.5 to 2.3 with spent hydrochloric acid pickling containing 25 to 30 g of dissolved bivalent iron per liter at the same time in a reaction of 0.63 to 1. 0 g of divalent iron per liter of deemulsified spent oil emulsion and after stirring for an hour, the acidified spent oil emulsion is oxidized by the addition of 0,6 to 0,9 g of potassium permanganate per liter of deemulsified spent oil emulsion, after which the free oil fraction is withdrawn and the remaining water is neutralized to pH 8.5 with sodium or calcium hydroxide.