RU2237648C1 - Method of refining and isolating water-glycol solution from exhausted antifreezes - Google Patents

Abstract

FIELD: special-destination fluids.

SUBSTANCE: improved method of refining and isolating water-glycol solution from exhausted antifreezes for preparing cooling fluids and low-freezing heat carriers comprising addition of coagulant followed by filtration on sand filter and refining on activated carbon, is characterized by that, after addition of coagulant, additional separator-assistant centrifugation stage is included and coagulant is selected from alkali metal hydroxide, 75% orthophosphoric acid, alkali metal carbonate, and sodium sulfate with following proportions of components utilized, wt %: sodium or potassium hydroxide 0.01-1.0, 75% orthophosphoric acid 0.02-1.6, sodium or potassium carbonate 0.05-0.5, sodium sulfate 0.01-0.07, glycols 40.0-90.0, water and oxidation products - the balance.

EFFECT: increased degree of purification to 100% regarding suspended impurities and to 95-100% regarding chief part of ethylene glycol oxidation products and corrosion products.

3 tbl, 11 ex

Description

The invention relates to the allocation of aqueous solutions of glycols, in particular to a method for the purification of 40-90% glycol solutions of spent antifreeze used to cool internal combustion engines.

A known method of regenerating a working fluid from a water-glycol mixture by filtration and passing through a complexing ion-exchange resin (JP application 62-23040, class C 10 M 175/04, 1987).

A known method of producing ethylene glycol from a spent antifreeze solution, carried out at the first stage on reverse osmosis membranes, at the second stage - passing through ion-exchange resins (JP application 7-108141, CL 01 D 61/02, 1995).

A known method of glycol regeneration by distillation on columns at a temperature of 160-220 ° C and a pressure of 100-350 mm Hg (SU copyright certificate 816099, IPC C 07 C 31/20, 1994).

A known method of obtaining a solution of ethylene glycol from spent antifreeze on ion-exchange membranes in a three-chamber electrodialyzer (RU patent 2109556, CL 6 B 01 D 61/44, 1998).

A known method for the separation of ethylene glycols of high purity by evaporation of an aqueous solution of ethylene glycols, followed by alkalization of this solution and distillation under reduced pressure (JP patent 224399, IPC C 07 C 31/20, 1968).

These methods are laborious, require large energy costs, although they make it possible to obtain solutions of ethylene glycols of a sufficiently high degree of purification, which is not a prerequisite for the preparation of antifreezes and low-freezing coolants. To prepare these coolants, it is sufficient to obtain a water-glycol solution purified from the products of the oxidation of ethylene glycol and corrosion products formed during the operation of antifreeze.

Closest to the proposed solution regeneration method is a method for cleaning glycol solutions by introducing a coagulant followed by passing the mixture through a sand filter and adsorber (SU copyright 1685910, С 07 С 31/20, 1991). The purification of glycol solutions used in water recycling systems during compressor cooling is achieved by introducing a coagulant into the glycol solution in the following ratio of components, wt.%:

Coagulant 0.05-0.1

Glycol 50-99

Water Else

As a coagulant, sodium phosphoric acid monosubstituted or soda ash is used in the form of a 0.1-1% solution in glycol or water.

The method of purification of such aqueous solutions, according to the prototype, gives good results in the case of purification of the same substances - water and glycol. However, substances possessing different physical and chemical properties must be extracted from the spent antifreeze, depending on the formulation, therefore this cleaning method cannot be considered universal. Its use leads to incomplete and poor-quality cleaning.

The proposed method for the regeneration of aqueous solutions of ethylene glycol from spent antifreeze used to cool internal combustion engines, allows you to clean the spent antifreeze based on glycols from additives, oxidation products and corrosion.

The aim of the invention is to increase the purity of the target product and reduce the energy intensity of the process.

This goal is achieved by the method of regenerating an aqueous solution of ethylene glycol from spent antifreezes by treating them with alkali metal hydroxide, 75% phosphoric acid, alkali metal carbonate, sodium sulfate and subsequent centrifugation of the resulting suspension on a separator (to remove mechanical impurities, precipitate of corrosion products and additives due to the action of coagulants), the introduction of additional filtering through a sand filter (to remove traces of technical oil) and the last blowing passage through an adsorber filled with activated charcoal (to remove the oxidation products of glycols), with the following component ratio, wt.%:

Sodium hydroxide (caustic soda)

or potassium 0.01-1.0

Phosphoric acid 75% 0.02-1.6

Sodium or potassium carbonate (potash) 0.05-0.5

Sodium Sulfate 0.01-0.07

Glycols 40.0-90.0

Water, oxidation and corrosion products

In this case, activated carbon brand BAU, AG-3, Ckt-6A.

Comparative analysis with the prototype shows that the coagulant used to clean spent antifreeze differs from the known one by the introduction of four new components: alkali metal hydroxide, phosphoric acid, alkali metal carbonate, sodium sulfate to increase the content of strong electrolytes, providing a more complete precipitation present in the spent antifreeze additives, and to remove impurities of technical oil and additional purification filtering is introduced on a sand filter.

Thus, the claimed technical solution meets the criterion of "novelty."

The use of new components as a coagulant in this method for purifying ethylene glycol solutions and the found ratio of all ingredients provide the maximum degree of purification of spent antifreeze from mechanical impurities up to 100%, ethylene glycol oxidation products and corrosion products formed during antifreeze operation, up to 95-100%.

Example 1. In a container equipped with a stirrer or pump, 99.91 g of spent antifreeze is placed, with stirring at ambient temperature, 0.01 g of sodium hydroxide, 0.02 g of 75% phosphoric acid, 0.05 g of sodium carbonate are loaded and 0.01 g of sodium sulfate. The mixture is stirred until the components dissolve, left for 2-3 hours to form a gel-like precipitate (coagel) caused by the coagulation process. The resulting suspension is centrifuged on a separator and passed through a filter filled with washed river sand. Next, the filtrate is passed through an adsorber filled with activated carbon at a speed of 300 l / h.

The degree of purification of water-glycol solutions is controlled by the content of mechanical impurities, by the content of glycols, water and anticorrosion additives present in the spent antifreeze.

Example 2. Purification of 98.45 g of spent antifreeze is carried out in the same way as in example 1, but the coagulant contains 0.5 g of sodium hydroxide, 0.8 g of 75% phosphoric acid, 0.2 g of sodium carbonate and 0, 05 g of sodium sulfate.

Example 3. Purification of 96.83 g of spent antifreeze is carried out in the same way as in example 1, but the coagulant contains 1.0 g of sodium hydroxide, 1.6 g of 75% phosphoric acid, 0.5 g of potash and 0.07 g of sodium sulfate.

The compositions of the coagulants of examples 1-11 and the prototype are presented in table 1.

The degree of purification of an aqueous solution of glycols in spent antifreezes is presented in table 2.

The mass fraction of water of mono-, di- and triethylene glycols is determined using the gas chromatographic method (internal normalization method) on a Tsvet-500 series chromatograph, LHM-8 MD or a similar device with a thermal conductivity detector. As nozzles for the chromatographic column using polysorb 1.

A decrease in the concentration of sodium or potassium hydroxide below 0.01 wt.% Does not cause coagulation and the formation of a precipitate in the spent antifreeze due to the insufficient amount of coagulant (example 4), and an increase above 1.0 wt.% Does not increase the positive effect ( example 5).

A decrease in the content of orthophosphoric acid in the composition of the coagulant below 0.02 wt.% Significantly reduces the amount of sediment in the spent antifreeze (example 6), an increase in its concentration above 1.6 wt.% Leads to a decrease in pH of the medium, which negatively affects the formation of sediment of oxidation products ethylene glycol and corrosion products (example 7).

A decrease in the concentration of sodium or potassium carbonate below 0.05 wt.% Significantly affects the formation of sediment, which leads to insufficient purification of spent antifreeze (example 8), an increase in its concentration above 0.5 wt.% Causes a strong alkalization of the medium and a decrease in the amount of sediment ( example 9).

A decrease in the concentration of sodium sulfate in the composition of the coagulant below 0.01 wt.% Significantly affects the cleaning of spent antifreeze, since it reduces the mass content of all electrolytes that contribute to the sedimentation of the formed gel in the form of a dense precipitate (example 10); the increase in its concentration above 0.07 wt.% does not positively affect the cleaning (example 11).

Subject to the indicated values of the coagulation process of spent antifreeze, the regenerated aqueous solution of ethylene glycol practically does not contain any impurities by the end of the treatment.

A small amount of additives remaining after cleaning play only a positive role as an additional set of corrosion inhibitors in the preparation of coolants or coolant based on purified spent antifreeze.

The main physicochemical properties of the coolant obtained on the basis of the regenerated spent antifreeze with the additional introduction of the necessary quantities of anticorrosive, stabilizing additives and monoethylene glycol are presented in table 3.

Thus, the proposed method of purification of spent antifreeze allows you to get a fairly clean water-glycol solution, devoid of oxidation products of ethylene glycol and corrosion products formed during the operation of antifreeze.

Based on the antifreeze regenerated in this way, high-quality coolants can be obtained that are used to cool internal combustion engines and as heat carriers. In this regard, the issue of protecting the environment is being addressed, since so far the spent antifreeze has often been poured into the ground. The application of the proposed method for cleaning spent antifreeze will save significant amounts of expensive ethylene glycol used in coolants.

Claims (1)

The method of purification and separation of a water-glycol solution from spent antifreeze, including adding a coagulant to the spent antifreeze, then filtering through a sand filter, then cleaning it with activated carbon adsorbent, characterized in that after the coagulant is added, the centrifugation step is additionally carried out on a separator, and as a coagulant oxidation and corrosion products in the spent antifreeze use alkali metal hydroxide, 75% phosphoric acid, alkali metal carbonate and sodium Ulfat the following component ratio, wt.%: Sodium hydroxide (caustic soda) or potassium 0.01-1.0 Phosphoric acid 75% 0.02-1.6 Sodium or potassium carbonate (potash) 0.05-0.5 Sodium Sulfate 0.01-0.07 Glycols 40.0-90.0 Water, oxidation and corrosion products