CS259521B2 - Method of used oil regeneration - Google Patents

Abstract

After the removal of water and volatile constituents, the spent oil is subjected to an alkali treatment and, if necessary after separating off a gas oil fraction, distilled. In this distillation, pure oil is separated off as distillate in one step from a tar fraction which contains the impurities.

Description

The invention relates to a process for regenerating used oil and oil-like materials.

The regeneration of used oil, especially lubricating oil, is of increasing economic and environmental importance. Much and great effort has been made to develop a satisfactory method of regenerating the oil used. Such a process must be satisfactory with regard to the ecology, economy and quality of the regenerated oil. The solids which form a stable suspension with the oil used must be separated and the dissolved impurities removed.

The known processes each comprise a plurality of distillation steps until a purified oil is obtained, which are always associated with further processing steps, for example by addition of acid, coagulation, adsorption and filtration, and optionally treatment with metallic sodium or sodium hydride for dehalogenation. These workflows are costly for equipment and energy consumption, or are associated with voluminous, ecologically burdensome residues and / or using highly reactive, particularly chemical-safety, security operations.

In order to avoid the use of highly reactive chemicals and the formation of voluminous residues, DE-OS 30 42 094 proposes a process in which used oil is passed through a sedimentation tank in which coarse impurities and some of the water present are removed to remove acidic oil components and additive residues treated at 120 to 150 ° C with alkaline lye, at the first thin-film distillation it is freed of additional water and volatile components, at the next thin-film distillation the suspension is broken and the resulting condensate, which still contains entrained solid suspended parts, is fed to a third distillation thin layer, self refining to obtain purified oil. This known process requires, after breaking the suspension by distillation, an additional distillation step to obtain a purified product, which is very expensive both in terms of equipment and energy balance. In addition, the purified oil obtained cannot fully satisfy the purity, and in particular the odor and color, so that its use is limited.

It is an object of the present invention to provide a process of the kind mentioned above which is economical in its embodiment and provides a perfectly regenerated oil as a product.

According to the invention, the object is achieved by treating the oil used after the removal of water and volatile fractions and before separating the tar fraction by adding 0.2 to 5% by weight of an alkaline solution such as sodium or potassium in the form of an aqueous solution of 30%. up to 50% by weight, and the purified oil is separated by thin-layer distillation from a tar fraction containing alkali and solid and non-distillate impurities.

By the step of the process according to the invention, i.e. by treating the pre-dried and easily volatile fractions free of the used oil with an alkaline lye, a stable suspension, which also contains dissolved and / or emulsified impurities, is rendered labile so that suspended solids are perfectly and thus a single step is sufficient to completely separate the suspended solids and to obtain a perfectly regenerated oil.

It is believed that the treatment of alkali, in addition to neutralizing the acidic components and possibly saponification of the saponifiable impurities, simultaneously causes a change in the interface area of the suspended particles due to the prior removal of volatile components acting as a type of protective colloid. This change allows the suspended parts to be separated off simultaneously with the distillation of the oil suspension medium, which is free of already solid particles, thereby leaving, for example, saponified impurities in the tar fraction. In other words, the alkali treatment following the separation of water and volatiles according to the invention makes it possible to separate the solid and dissolved impurities and obtain a perfect oil in one single distillation step without separate disruption of the slurry preceding the final distillation.

The adkaline treatment is generally carried out at 180 to 300 ° C, preferably 230 to 260 ° C, in a closed reactor with an aqueous alkali solution. Higher processing temperatures within this range generally provide a lower acid number and lower chloride content in the purified oil. Preferred as alkali are water-soluble alkali metal hydroxides, alkali metal carbonates, alkali metal bicarbonates and alkali metal alcoholates, although insoluble and sparingly soluble alkaline earth compounds may also be used.

The alkali treatment can also be carried out at the same time as the distillation of the gas oil, for example by adding the alkali before the circulation pump of the forced-circulation evaporator for distilling the gas oil.

After the alkali treatment, the used oil is preferably fed to a gas oil distillation stage and then generally passes through a relief valve to an evaporator, such as a film evaporator with a run-off or upstream layer, which works in co-current or countercurrent to draw pitch or tar. a residue comprising particles suspended in the oil used and further imparted and / or non-distillate impurities. This residue can be used as a tar substitute, for example in road construction.

Vapors containing pure oil vapors as well as readily volatile components are fed to a liquid separator for the separation of the possibly guided liquid parts, where they can be simultaneously treated with stripping steam or flowing steam or liquid water, which immediately evaporates at given temperatures. With steam treatment, both the color of the recovered oil is improved and 1 odor nuisance agents are removed. Interestingly, the phosphorus content of the purified oil is also reduced after steam treatment. It is believed that this unexpected result is made possible by the use of dry steam after prior treatment with alkali. In addition to the known liquid separating devices, a correspondingly arranged vapor guiding section can assume this function.

After the steam treatment, the pure oil vapors are gradually condensed, the highest boiling fraction being obtained first and the lower boiling fraction in each subsequent step. Successive condensation is an inverted fractional distillation in which the fraction separation is carried out by several consecutive condensation steps instead of multiple consecutive evaporation steps. Fractional condensation is not only more energy-efficient with respect to fractional distillation, but has the additional great advantage of being carried out at high temperatures that low-boiling impurities do not condense with the low-boiling oil fractions and cannot be contaminated, but are possible after. Condensate the low-boiling oil fractions separately in the cold sump.

The invention is illustrated by the drawing which schematically illustrates an apparatus for carrying out the method according to the invention.

The homogenized and coarse impurities used oil are fed to a circulating evaporator 1 where it is freed of water and easily volatile components, i.e. petrol and solvents. The run-in evaporator 1 operates at normal pressure or slight vacuum and the temperature of the products at the outlet 2 of the evaporator 1 is 140 to 180 ° C, corresponding to a residual water content of <0.1%.

This is advantageous for the subsequent alkali treatment since less foam formation is observed at a low water content. The vapors from the outlet 2 of the evaporator 1 are fed to a separation column 3 where they are separated into fractions with a different boiling range. The distillate 5 can be separated into a heavy aqueous and light organic phase in the decanter after the condenser 4.

The used oil, free of water and volatile matter, is fed to the heated reactor 8, where it is replenished at a temperature of 180 to 300 degrees Celsius, preferably 230 to 260 ° C. from an alkali storage tank 7, for example 50% NaOH. Depending on the quality of the oil used and based on it, 0.1: 1 is used; 1.5; 3 and 5% NaOH (dry). The spent oil may be heated to the reaction temperature in a pre-heat exchanger with the already used spent oil or in a reactor.

6. The residence time in reactor 6 is about 1 to 5 minutes.

The used alkali-treated oil is recovered from the reactor β in another circulating evaporator 8, where a fraction 9 of the gas oil is distilled off at an average vacuum of 5-10 ³ to 5.10 ⁴ Pa and about 330 ° C. The temperature necessary for this distillation is preferably adjusted by cooling after treatment with alkali and heating in a circulating evaporator 8. The heat exchanger used for cooling can simultaneously serve to preheat the used oil before treating the alkali. Fraction column 10 allows separation of the gas oil fraction with the desired flash point temperature and the desired viscosity.

The oil-free gas oil used is subjected to vacuum total distillation in a thin-film evaporator 11. The thin-film evaporator 11 can be driven statically or mechanically and can be a film-like evaporator with a run-off or a wicking layer. Vacuum distillation, ie; distillation under reduced pressure at 1. 10 ² to 5. 10 ² Pa, which is carried out in countercurrent, at a heating temperature from 350 to 380 ° C, the suspension of oil © divides the product 13 taken from the bottom of the column 13 or tar fraction and steam frakoi lubricating oil. The product 13, taken from the bottom of the column, is drawn off at about 300 ° C and can be used as a tar substitute.

Vapors from the vapor receiving head 12 having a temperature of about 270 ^C C separator 14 into a liquid which is separated entrained droplets and fed again to the thin film evaporator eleventh

In the embodiment shown, in the case of ¹ metering of the spent oil slurry, this is effected from the distillation of the gas oil to the liquid separator 14, from where they are fed together with the separated liquid to a thin-film evaporator 11. This procedure has the advantage 14 liquid. Of course, the used oil suspension can also be injected directly into the thin-film evaporator 11.

The liquid separator 14 is preferably fed with stripping steam, thereby improving the color and odor of the condensate and reducing the phosphorus content of the products.

The liquid-free vapors then enter the first mixed condenser 15 where they condense together with the condensate in the circuit through a heat exchanger at a temperature about 10 ° C below the boiling point of the desired condensate fraction and withdraw as the first heavy oil Fraction 16. The next mixed condenser 17 is operated in the same manner but at a lower temperature to provide a second light oil fraction 18. Due to the strong turbulence in the mixed capacitors 15, 17, a good degree of efficiency is achieved and the sedimentation and sedimentation observed on the cooling surfaces of other types of capacitors is reduced. The vapors exiting the second condenser 17 still have a temperature of about 200 DEG C. and contain small amounts of readily volatile substances which are trapped in the freezer sump 19 so that they are trapped in the condenser. no impurities can get through the vacuum pump.

By using a two-stage mixed condensation system, as well as the stages operating only just below the boiling point of the condensation fraction, the ratio of both oil fractions and their boiling point can be varied within a wide range, both of which can be adjusted practically multiple times.

The following table shows the results of oils recovered by the process of the invention.

Table

Analysis

Color (ASTM D 1500) Flash point (ASTM D 92/93) ° C viscosity (ASTM D 445) 40 ° C mm ³ / s

100 ° C mmVs viscosity index (ASTM D 2270) total acid number (ASTM D 664) mg KOH / g total alkalinity number (ASTM D 2896) mg KOH / g ash content of the oxide (ASTM D 482) g / 100 g pour point ( ASTM D 97) ° C specific gravity at 15 ° C kg / m ³ aging process (DIN 51 352) g / 100 g sulfur content g / 100 g chlorine content g / 100 g silver content mg / kg aluminum content mg / kg content mg / kg barium content mg / kg calcium content mg / kg

Cadmium content mg / kg Chromium content mg / kg Copper content mg / kg Iron content mg / kg Magnesium content mg / kg Manganese content mg / kg Molybdenum content mg / kg Nickel content mg / kg Phosphorus content mg / kg Lead content mg / kg silicon content mg / kg

> 10 2 1.5 183 110 180 52.1 +13,71 + 9.97 8.65 - - 143 - - 1.52 - - 2.98 - • - 066 <0.001 <0.001 - 33 - - 0.888 865 857 0.72 0.65 0.45 0.12 0,1137 0,0468 .nn nn nn 16 nn nn 23 ~ 12 nn 130 nn nn 1200 nn 0.4 3.1 nn nn 4.2 nn nn 32 nn nn 160 nn nn 170 nn nn 3.4 nn nn 2.1 nn nn 2.8 nn nn 730 230 27 Mar: 960 nn 0.8 32 11 nn

5

1.5 6.5 1.0 167 32.6 - 13.33 218 15.2 3.09 5.39 3.36 84 98 87 0.03 0.69 0.04 0.21 0.24 0.19 0 0 0 - - 6 —18 - 877 868 0.53 0.42 0.53 0.42 0,045 0,033 0.007 nn nn nn nn nn nn nn 2 nn nn nn nn nn nn he nn nn he nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn nn 22nd 100 ALIGN! 5.5 nn nn nn 1.5 4.7 0.7

Analysis 0 1 2 3 4 5 tin content 3.9 nn nn nn nn nn titanium content 3.9 nn nn nn nn nn vanadium content 0.4 nn nn nn nn nn mg / kg zinc content 510 nn nn nn nn nn mg / kg Table - continued Analysis 6 7 8 9 10 11 Paint (ASTM D 1500) 4,5 2,0 6 4 2 ___ Flash point (ASTM D 92/93) ° C ’ viscosity 193 226 236 223 (ASTM D 445) 40 ° C mm ² / s 24.1 30.7 52, .6 82.4 33.1 100 ° C mm'7s viscosity index 4.49 5.2 7.32 9.69 5.49 - ASTM D 2270 95 98 98 95 101 - total acidity number 0.06 0.03 0.12 0.01 0.02 - (ASTM D 664) mg KOH / g _ total alkali number 0.41 0.25 0.26 0.61 0.23 (ASTM D 2896) mg / KOH / g ash content 0 0 0 0 0 8 (ASTM D 482) g / 100 g pour point (ASTM D 97) ° C —6 ~ 3 —6 —6 —6 - density at 15 ° C kg / m ³ 873 875 880 885 875 - ’ aging process - 0.43 0.58 0.27 - (DIN 51 532) g / 100 g sulfur content g / 100 g - 0.48 0.58 0.61 0.48 1.65 chlorine content g / 100 g 0.01 0.01 0.017 nn nn 0.3 silver content nn nn nn mn nn nn mg / kg aluminum content nn nn nn nn nn 70 mg / kg boron content nn nn nn nn nn 66 mg / kg barium content 0.5 nn nn nn nn 440 calcium content mg / kg 0.4 nn nn 0.1 nn 4600 cadmium content mg / kg nn nn nn nn nn 8.8 chromium content nn nn nn nn nn 17 mg / kg copper content nn nn nn nn nn 94 mg / kg iron content 1.8 nn nn nn nn 540 mg / kg magnesium content • nn nn nn nn nn 460 mg / kg manganese content nn nn nn nn nn 10 mg / kg molybdenum content mg / kg nn nn nn nn nn 7.2

7

Analysis

10 11 nickel content nn mg / kg phosphorus content 7,5 mg / kg lead content nn mg / kg silicon content nn mg / kg tin content nn mg / kg titanium content nn mg / kg vanadium content nn mg / kg zinc content 0, 9 mg / kg

П1П nn nn nn 8.6 6.4 71 nn 3.6 2 200 nn nn nn nn 3 000 1Д 4,5 nn nn 162 nn nn nn nn 15 Dec nn nn nn nn 20 May nn nn nn nn 2.8 nn nn nn nn 3 000

Individual sample numbers represent:

gas oil supply, without alkali processing, cold condensation, pilot plant gas oil, with alkali processing, hot condensation, pilot plant gas oil, with alkali processing, hot condensation, steam processing, pilot plant light oil fraction, without alkali processing , pilot plant light oil fraction, with alkali processing, glass evaporator light oil fraction, with alkali processing, pilot plant light oil fraction, with alkali processing, steam processing, pilot plant heavy oil fraction, without alkali processing, pilot plant heavy oil fraction with alkali treatment, glass evaporator heavy oil fraction, alkali treatment, pilot plant, values given for the tar fraction, i.e. the fraction which is no longer usable as an oil and which at point 13 schematically shows This leaves the thin-film device

Meaning of symbols in the table:

^ь viscosity measured at 20 ° C —- unknown not detectable

According to the method described, an excellent gas oil fraction and a light and heavy lubricating oil fraction are obtained using an economically advantageous NaOH treatment agent and with a minimum of process steps, as shown in the previous analysis results.

Minimizing the working steps, in particular distillation, reduces the risk of thermal cracking and the resulting reduction in yield, which in the process according to the invention makes at least 90% of the distilled portion of the oil used and thus increases the economy.

Claims (10)

SUBJECT OF THE INVENTION A process for recovering used oil by treating with alkali, removing water and easily volatile fractions, separating the tar fraction and distilling the purified oil, characterized in that the used oil is treated by addition of 0.2 after the removal of water and volatile fractions and before separating the tar fraction up to 5% by weight of an alkaline liquor, for example sodium or potassium, in the form of an aqueous solution having a concentration of 30 to 50% by weight, and the purified oil is separated by thin-layer distillation from the tar-containing fraction containing alkali and solid non-distillate impurities. Method according to claim 1, characterized in that the treatment with alkaline lye is carried out at a temperature of 180 to 300 ° C, preferably 2 to 50 to 280 ° C. 3. The process according to claim 1, wherein the gas oil fraction is distilled off simultaneously with the alkali treatment. Method according to one of the preceding claims, characterized in that, after the treatment with alkaline lye, the gas oil fraction distills off. 5. Method according to one of the preceding claims, characterized in that the separation of the tarry distillation fraction and the oil in a thin layer is carried out at a temperature of 350 to 380 ° C under reduced pressure 1.10 ^{2-5 2} .10 Pa. Method according to any one of the preceding claims, characterized in that water vapor is blown into the oil vapors resulting from the distillation to reduce their partial pressure. Method according to one of the preceding claims, characterized in that, in the distillation of the entrained liquid part, it is separated before condensation. Method according to one of the preceding claims, characterized in that the oil vapors resulting from its distillation are treated after the steam-distillation. Method according to one of the preceding claims, characterized in that the condensation is achieved by introducing liquid and cooled products. Method according to one of the preceding claims, characterized in that the condensation of the oil vapors is carried out at temperatures about 10 ° C lower than the boiling point of the fraction to be recovered.