JP3122180B2 - Organic solvent recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering an organic solvent, and more particularly to a method for recovering an organic solvent in a waste liquid in a washing process of a mechanical part, a precision tool, a heat exchanger part, a rocket part, etc. with an organic solvent, a petrochemical process. The present invention relates to a method which can be advantageously applied to the recovery of an organic solvent in a high-boiling oil produced in the above process.

[0002]

2. Description of the Related Art Conventionally, heat exchange parts, compressor parts,
In cleaning metal parts such as cutting tools, dirt (machining oil, cutting oil, cutting powder, etc.) attached to the surface of the parts is washed away with an organic solvent (trichloroethane, trichloroethylene, methylene chloride, chlorofluorocarbon, etc.) as a cleaning liquid. . Therefore, since the dirt gradually accumulates in the solvent, the solid content is usually separated and discarded by filtering out the solid content and the oil content by driving out the organic solvent by a distillation operation.

[0003] There are two methods for distilling and recovering an organic solvent from a mixed liquid of an oil / organic solvent, a normal pressure distillation method and a reduced pressure distillation method.

[0004] In the former, the organic solvent which is a volatile component is driven out by distillation, and the distillation temperature rises as the oil is concentrated. When the temperature becomes high, the organic solvent is decomposed and degraded.
As a result, the impurities contained in the apparatus material or the solvent at the time of reuse cause corrosion of the object to be cleaned or the cleaning apparatus, which is not preferable.

The distillation characteristics of an oil / methylene chloride mixed system will be described. Pure boiling methylene chloride has a boiling point of about 40 ° C., but the boiling point (distillation temperature) sharply rises due to mixing of oil. For the above reasons, the distillation temperature is 70-80 ° C.
It is usually managed as follows. Therefore, although it differs depending on the type of the contaminated oil, it can be distilled only up to an oil concentration of about 70 to 80% by weight, and about 30 to 20% by weight of methylene chloride as an active ingredient is contained in the oil and discarded.

[0006] In the latter case, the degree of concentration of the oil is 90 wt% or more, but equipment and auxiliary equipment for decompression are required in addition to installation of a distillation column, equipment cost and running cost are high, and economical in small amount processing. It is not practical because it cannot be expected to have any merit.

[0007]

The normal pressure distillation method conventionally used for recovering the organic solvent contained in the waste oil,
Each of the vacuum distillation methods has the disadvantages described above.
Accordingly, the present invention has been made in view of the above-mentioned state of the art, and has as its object to provide a method capable of recovering this kind of organic solvent for the purpose.

[0008]

Means for Solving the Problems To solve the above-mentioned problems, the present inventors have proposed an azeotropic distillation method in which a third component is added to a binary mixture which is difficult to separate by distillation and the two components are separated. Attention was paid, and as a result of earnest research, the present invention was completed.

That is, the present invention is characterized in that (1) when recovering an organic solvent from an oil-containing organic solvent by a batch atmospheric distillation method, methanol is added to the oil-containing organic solvent and distillation is performed. To recover organic solvents.

(2) When recovering an organic solvent from an organic solvent containing oil by a batch atmospheric distillation method, when the distillation proceeds and the oil content in the organic solvent becomes 50 wt% or more, the organic solvent at that time is recovered. A method for recovering an organic solvent, comprising adding 4 to 40% by weight of methanol based on the amount of the solvent and continuing the distillation.

(3) The amount of organic solvent contained is about 30
3. The method for recovering an organic solvent according to claim 2, wherein methanol having a ratio of not more than wt% is dividedly added plural times over time. It is.

The organic solvent to be used in the present invention includes methylene chloride, trichloroethane, trichloroethylene, perchloroethylene, etc. Examples of the oil include a processing oil mainly containing a mineral oil-based substance (for example, containing about 98% paraffin); Cutting oil mainly composed of mineral oil-based substances (for example, about 95%)
９８98% kerosene) and other fats and oils.

[0013]

The effect of adding methanol (boiling point: 64.7 ° C.) in atmospheric distillation of oil and an organic solvent is that the distillation temperature is lower than in the case of a two-component system of oil-organic solvent, while the organic solvent having a low boiling point is added. Separation is promoted. That is, the oil can be concentrated while the distillation temperature is kept low, in other words, the recovery of the organic solvent proceeds.

The added methanol evaporates together with the organic solvent, and the content ratio of methanol to the organic solvent gradually decreases, and the effect of promoting the evaporation of the organic solvent by the addition of methanol gradually disappears. For this reason, this evaporation promoting effect can be restored by dividing and adding methanol a plurality of times.

Although the recovery amount of the organic solvent increases as the amount of methanol added increases, the increase amount of the recovery amount decreases with respect to the addition amount, and the energy for distillation increases. Although it should be judged from the viewpoint, the amount of methanol to be added is preferably about 40 wt% or less of the recovered amount of the organic solvent.

[0016]

【Example】

Example 1 A simple distillation test was carried out using the apparatus shown in FIG. 2, and an oil obtained by adding methanol (Cosmo Oil: Cosmo Punch 401, mineral oil consisting of 98% paraffin) / methylene chloride (manufactured by Asahi Glass) : Industrial methylene chloride,
The result of determining the distillation characteristics of Super M) is shown in FIG.

FIG. 3 shows a curve without methanol.
The oil / methylene chloride = 250 g / 300 g mixture was distilled.
The value is as high as 0, 70, and 80 wt%, but at the same time, the temperature gradually rises from about 47 ° C, indicating that when the oil content reaches about 90 wt%, it exceeds 100 ° C.

The curve is in accordance with the distillation curve. Methanol is added to a mixture of oil / methylene chloride / 250 g / 205 g which is distilled at a distillation temperature of about 47 ° C. and oil / methylene chloride = 55/45 (wt%). It can be seen that when 5 g was added and distillation was continued, oil concentration at a low temperature, that is, distillation of methylene chloride proceeded.

Along the curve and the distillation curve, distillation temperature: 67 ° C., oil / methylene chloride @ 80/20 (wt.
%), Oil / methylene chloride = 400 g /
8 g of methanol and 12 g of methanol were added to 100 g of the mixture.
This shows the case where distillation was continued after adding g and 32 g. In each of the curves, similarly to the curves, it can be seen that the addition of methanol promotes the distillation of methylene chloride and lowers the distillation temperature (the liquid temperature in the distillation flask in FIG. 2). It can also be seen that this tendency becomes more pronounced as the concentration of methanol is higher.

For example, when methanol is not added (curve), the oil content is 81.6 even when the distillation temperature is increased to 70 ° C.
wt%, but only 32 g of methanol (3
2%) as indicated by the curve
The oil was concentrated to 94% by weight, and 75 g of methylene chloride was distilled off.

From the above, it was confirmed that by adding an appropriate amount of methanol, the distillation temperature causing deterioration of methylene chloride was lowered, separation of methylene chloride in oil was promoted, and methylene chloride could be efficiently recovered.

FIG. 4 is obtained by rearranging the data using the above experimental data. That is, FIG.
In the experiment shown in the above, the mixture of oil / methylene chloride was distilled without addition of methanol. When the mixture reached a predetermined temperature (here, 47 ° C. and 67 ° C.), methanol was added, and the above-mentioned predetermined temperature was again obtained. The horizontal axis shows the ratio of the amount of methanol added to the amount of residual methylene chloride at the time of adding methanol, and the vertical axis shows the ratio of residual chlorine at the time of adding methanol. It is the ratio of the amount distilled off until the same temperature is reached again, relative to the amount of methylene. The slope of this curve gradually becomes gradually to the right, and the more the amount of methanol added,
Although the recovery amount of the organic solvent increases, when the methanol addition ratio exceeds about 15 wt%, the increase ratio of the recovery amount decreases with respect to the addition amount, so it can be seen from an economic viewpoint that the methanol addition ratio has an upper limit. .

(Example 2) Table 1 shows the results of a simple distillation test conducted using the experimental apparatus shown in FIG. Test No. 1
The initial charge of the distillation flask is oil = 400 g and methylene chloride = 200 g. Distillation was 70 in both experiments.
Performed within the range not exceeding ° C.

Test No. 1 is data obtained when heating was started from room temperature without adding methanol and distillation was stopped when the liquid temperature (distillation temperature) in the distillation flask reached 70 ° C. Only methylene chloride is distilled off, and the oil concentration rate is 8
It was 1.6 wt%.

Test No. 2 was completed at the end of distillation of Test No. 1, that is, in a bottom at 70 ° C., a bottom oil content of 400 g and a bottom methylene chloride content of 90 g, the amount of methylene chloride remaining in the bottom was 3%.
The data are obtained when 28.8 g of methanol corresponding to 2 wt% was added, distillation was further continued, and the temperature of the distillate was increased to 70 ° C. again. This indicates that 61.6 g of methylene chloride was further distilled and recovered at the same distillation temperature by adding 28.8 g of methanol.

In Test No. 3, as in Test No. 2, methanol equivalent to 8 wt% of the amount of methylene chloride in the bottom was added to the bottom at the end of distillation in Test No. 1, and distillation was continued. The data are obtained when methanol is repeatedly (divisionally) added three times in such a manner that when the distillation temperature reaches 70 ° C., about 8 wt% of the remaining methylene chloride is added again. Methanol was added in a weight ratio of about 7: 5: 3, and the total amount of addition was 15.6 g. Test N
Compared to O.2, the amount of methanol added was about half less, but the amount of methylene chloride distilled / recovered was almost equivalent to 60.4 g, and the addition of methanol was effective for the recovery of methylene chloride. You can see that.

Tests Nos. 4 and 5 are data obtained by the divisional addition in which the methanol addition conditions were changed in the same manner. For example, Test No. 4 shows that the recovery amount of methylene chloride was 70.0 g with respect to the total addition amount of methanol of 18.0 g, and that about 4 times the methylene chloride was recovered with respect to the addition amount of methanol. . The oil concentration was also 95% by weight or more.

Most of the added methanol is distilled off together with methylene chloride. Therefore, it is recycled again as a washing solution together with the recovered methylene chloride. However, since methanol is originally used as a stabilizer for organic solvents (methylene chloride, trichloroethane, etc.),
It is thought that there is no problem even if it increases slightly. However, the addition of a small amount at the end of oil concentration (80 wt% or more), loss in waste oil and loss in the solvent recovery process actually occur, and increase in the content of methanol in the solvent From the fact that the amount of methanol to be added can be suppressed by that amount, the amount of increase in methanol is small, and it is considered that there is no problem.

[Table 1]

(Embodiment 3) An example of application to an actual machine will be described with reference to FIG. A predetermined amount of methylene chloride 1 containing several% to several tens% of oil is supplied to the solvent recovery unit 2 and distillation is performed in a batch operation. First, the solvent is heated by the heater 4 while being stirred by the stirrer 3.

Methylene chloride begins to distill at about 30 ° C.
This vapor is cooled and condensed by the cooling water 6 in the condensing section 5, and is recovered as liquid methylene chloride in the recovery tank 7.

When the liquid temperature of the recovery unit 2 reaches about 60 to 70 ° C., a predetermined amount of methanol 8 is added. The liquid temperature of the recovery unit 2 temporarily drops to about 50 to 60 ° C., but the distillation is continued. When the liquid temperature rises again to about 60 to 70 ° C., a predetermined amount of methanol 8 is added again. This is repeated about 2 to 5 times. The distillation is terminated when the decrease in the amount of distillate becomes remarkable or when the operation at a liquid temperature in the recovery unit 2 of 70 ° C. or less becomes difficult.

The waste oil 9 from which methylene chloride has been recovered is discharged from the recovery unit 2 to the outside of the system. The recovered methylene chloride 10 is appropriately taken out of the system from the recovery tank 7 and reused.

In this way, methylene chloride 1 containing oil is again supplied to the solvent recovery unit 2 to repeatedly recover methylene chloride.

The method of separating an organic solvent from a mixture using methylene chloride as an organic solvent and processing oil as an oil has been described above. Similar effects have been confirmed with trichloroethane and trichloroethylene. The same holds true for other synthetic oils and mineral oils.

[0035]

According to the present invention, the organic solvent is separated from the oil by performing distillation in a low temperature range (for example, 70 to 80 ° C. or less for a methylene chloride solvent) which can prevent the deterioration of the solvent and the corrosion of the apparatus material and the object to be cleaned. The concentration of oil that can be recovered and could not be achieved by conventional low-temperature distillation can be increased to 90 wt% or more, and can be increased to 95 wt% or more by changing operation conditions, and the solvent loss can be reduced to 10 to 5 wt% or less. Can be suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of an actual machine according to the present invention.

FIG. 2 is an explanatory view of a simple distillation apparatus used for an experimental test.

FIG. 3 is a chart of distillation characteristics of oil / methylene chloride by adding methanol.

FIG. 4 is a graph showing the relationship between the methanol addition rate and the methylene chloride recovery rate.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-88501 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 3/00-3/42 C10G 7 / 08

Claims (3)

(57) [Claims] 1. A method for recovering an organic solvent comprising recovering an organic solvent from an oil-containing organic solvent by batchwise atmospheric distillation, wherein methanol is added to the oil-containing organic solvent and distillation is performed. . 2. When recovering an organic solvent from an organic solvent containing oil by a batch-type atmospheric distillation method, when the distillation proceeds and the oil content in the organic solvent becomes 50 wt% or more, the organic solvent at that time is recovered. A method for recovering an organic solvent, comprising adding 4 to 40% by weight of methanol based on the amount and continuing distillation. 3. About 30% by weight based on the amount of organic solvent contained
3. The method for recovering an organic solvent according to claim 2, wherein the following ratio of methanol is added a plurality of times over time.