JPS585682B2 - How to recover solvents - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering a solvent from an organic solvent treatment solution such as chlorinated hydrocarbons or light hydrocarbons.

Chlorides of lower hydrocarbons or light hydrocarbons are widely used as solvents, extractants or cleaning agents because of their ability to dissolve organic matter.

In particular, chlorides of lower hydrocarbons such as trichlorethylene and trichloroethane are not only highly effective in degreasing and deoiling, but also pose no risk of ignition when handled.
The equipment is simplified and the scale can be reduced relatively easily, and the amount of circulating solvent for cleaning, degreasing, deoiling, etc. is also economical, so it is widely used.

Various impurities are mixed into and accumulate in processing solvents used for degreasing, deoiling, cleaning, etc. Therefore, it is necessary to remove impurities from the processing solvents and regenerate them into pure solvents.

Regarding recycling, high purity is generally required when the solvent is used for chemical processing, etc., but depending on the purpose of use, high purity is not necessarily required and contamination with impurities up to the allowable distillate may be a hindrance. Therefore, the ability to obtain high yields at low cost is more important than purity.

This is because, for example, when cleaning metals, the contamination of other light oils does not pose much of a problem.

Therefore, the present invention aims to recover the solvent at low cost and in high yield by setting the maximum distillation limit of the processing solvent, and also to avoid the contamination of obstacles caused by thermal decomposition of chlorides and unstable hydrocarbons. The aim is to provide a collection method.

The method of the present invention will be explained in more detail below with reference to the illustrated embodiments.

1 is a distillation can of a distillation apparatus, and a rectification column 2 is provided on the distillation can.

A branch pipe 3 for normal pressure and a branch pipe 4 for reduced pressure are connected to this rectification column. A branch pipe 3 having an inverted U-shaped pipe 3' to prevent residual oil from flowing into the branch pipe 3.
The liquid enters the liquid receiving tank 8 through the condenser γ.

The branch pipe 4 is arranged at a higher position than the branch pipe 3, and is connected to the ejector 11 via a vacuum pressure regulator 5 and a check valve 6'. The pressure is reduced by the cold solvent fed and injected through the driving liquid circulation pipe 9, and the solvent vapor is cooled and mixed.

The reverse valves 6, 6', the condenser 7, and the pump 10 are controlled by a control device 16 so that the vacuum pressure regulator 5, heater 12, temperature indicating regulator 13 in the liquid to be treated, etc. are driven in a related manner. It is automatically controlled by

In addition, the reference numeral 15 in the figure is a waste liquid supply tank that is to be treated.

To explain the method of the present invention using the recovery device configured as described above, a liquid containing a solvent to be treated is introduced into the distillation can 1 from the waste liquid supply tank 15, and heated by the heater 12. A high-purity fraction of the solvent is recovered from the rectification column 2 through the branch pipe 3 and the condenser 7 into the liquid receiving tank 8 .

When the low boiling point solvent content in the distiller decreases, the solvent proportion of heavy oil content increases, and accordingly, the boiling point gradually rises, and when the temperature reaches a predetermined value, it is linked with the temperature indicating controller 13. As a result, the liquid pump 10 is driven, the ejector 11 is activated, and the inside of the branch pipe 4 for pressure reduction is suctioned to keep the inside of the apparatus at a reduced pressure.At the same time, the reverse valve 6 of the branch pipe 3 for atmospheric distillation is closed to reduce the pressure. Branch pipes 4 of the system are connected, and the distilled steam flows out from the upper part of the rectification column 2 into the ejector 11, is cooled and condensed by the fraction injected from the nozzle, and is recovered into the liquid receiving tank 8.

In this case, the degree of vacuum is changed in two stages by a pressure regulator 5 to prevent dry boiling of the liquid.

Since the total pressure within the system consisting of the still and branch pipes is reduced in this way, the boiling point of the solvent in the liquid to be treated is reduced, and the solvent can be recovered quickly and easily even at low temperatures.

When the temperature of the residual liquid in the distillation can 1, the predetermined degree of pressure reduction, and the predetermined time reach predetermined set values, the heater 12 and the pump 10 are stopped in conjunction with each other, and the distillation operation is stopped. Collection work will be discontinued.

Specific examples of the method of the present invention are shown below.

The results obtained in the above examples are as follows.

Specific gravity of recovered solvent: 20/4℃ 1.340 Solvent in residual oil in pot: 0.80 As explained above, the method for recovering solvents according to the present invention is as follows:
One distillation device is equipped with a branch pipe for atmospheric distillation and a branch pipe for vacuum distillation, and the solvent is recovered by heating at normal pressure, and the boiling point of the solvent at low temperatures is lowered by further reducing the pressure. Because it uses a two-stage recovery method, the recovery process is faster and the recovery rate is extremely high.

(Recovery rate is 70-80% under normal pressure, 98% or higher under reduced pressure.

) In addition, since the boiling point of the solvent is lowered and recovered by reducing the pressure, the distillation temperature is low (50-60℃), preventing chloride and other thermal decomposition in the liquid to be treated, and improving the purity of the recovered solvent. Because of the high CO2, the cleaning tank and other circulation systems are kept clean during reuse, and maintenance and inspection of the entire device becomes extremely easy, which is an excellent effect.

[Brief explanation of the drawing]

FIG. 1 is a schematic plan view of an apparatus for carrying out the method of the invention, and FIG. 2 is a schematic side view of the same apparatus. 1... Distillation can, 2... Rectification tower, 3...
... Branch pipe for atmospheric distillation, 4 ... Branch pipe for reduced pressure distillation, 5 ... Vacuum pressure regulator, 6.6'
...Check valve, 7...Condenser, 8...
...Liquid receiving tank, 9...Driving liquid circulation pump, 10
... Lifting pump, 11 ... Ejector, 12
... Heater, 13 ... Liquid temperature indicator controller, 14 ... Stirring pump, 15 ...
Waste liquid supply tank, 16...control device.

Claims (1)

[Claims] 1 A branch pipe for normal pressure distillation and a branch pipe for reduced pressure distillation are provided for one rectification column of the distillation apparatus, and the branch pipe for normal pressure distillation is connected to a liquid receiving tank via a condenser. The branch pipe for vacuum distillation is connected to a liquid receiving tank via an ejector,
A driving liquid circulation pipe is connected between the ejector and the liquid receiving tank via a liquid pump, and the temperature of the liquid to be distilled stored in the rectification column is heated to a predetermined value, and a branch pipe for atmospheric distillation is connected to the ejector. Then, in the temperature state, the pump is driven and the collected liquid in the liquid receiving tank is spouted out from the ejector, thereby performing vacuum distillation. A method for recovering solvents, which consists of the step of taking out the distillate through a branch pipe.