JPS60209202A - Apparatus for distillation of contaminated solvent or analogue substance - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION It relates to a device for distillation purification, preferably for distilling dirty solvents coming from a dry cleaning device. The distillation apparatus includes a forced circulation evaporator, which includes:
A tube for supplying heated dirty solvent in a heat exchanger is connected to the tube, which has a throttle valve adjacent to the evaporator. the evaporator is connected in its upper part to a tube for conducting vapor through a vapor compressor to a condenser, and in its lower part to draw liquid solvent from the evaporator and said liquid connected to pipes for delivering the solvent by means of a pump to the heat exchanger, and also includes a water trap, a pipe for supplying the dirty solvent and a pipe for drawing off the distillate. .

Known distillation equipment must be operated at temperatures above the boiling point of the solvent. If the solvent consists of, for example, chloroethylene, which has a boiling point of /C/'C, conventional distillation requires heating the solvent to at least that temperature. Moreover, the hydrostatic head of the liquid sump must be overcome to allow vapor bubbles to form and the change in boiling point resulting from condensation of the residue. If foaming is to be maintained during distillation, heating to higher temperatures is required. However, heating the solvent to high temperatures in dry cleaning equipment is not permissible, as perchlorethylene degrades at about 0°C. Heating to such high temperatures results, for example, in the decomposition of amino compounds, causing the distillate to emit an unpleasant odor. Moreover, the remainder of lIO% to 60% of the solvent cannot be extracted from the residue even if the residue is heated to about /SO<0>C. During this process, oil, wax.

Distillation residues consisting of resins and the like are decomposed and polymerized, solidifying and sticking to heated surfaces. Removal of polymerized distillation residues with a solvent content of approximately Sθ% is expensive and hazardous to health. If the solvent to be distilled, such as perchlorethylene, is mixed with water, strong foaming will occur, which will adversely affect the distillation process.

Moreover, adding just 10% by weight of water to the mixed solvent doubles the operating cost.

Some improvements can be achieved by using known distillation plants of the type mentioned at the outset. In this plant, dirty solvent is heated in a heat exchanger by external steam and then fed to a surface evaporator. In this case, the heat exchange surface area can be made as large as desired. / square cm
Thermal degradation of the residue is reduced because the heat transfer coefficient of the 'AF) is reduced and residence time on the heat exchange surface is reduced. However, the solvent to be distilled must still be heated above its boiling point. Since this method cannot substantially reduce the solvent content of the residue, it requires a conventional primary distillation system to distill the solvent from the residue, which has known drawbacks and problems. have.

Known distillation plants involve the supply of heating energy to evaporate the solvent and the supply of round cooling energy to condense and cool the vapor, ie to dissipate the previously supplied energy. Published German patent application no. Ig3
．． 2721. No. 6 dry compression (d
discloses the use of a ``ry-compressing'' vacuum pump. However, this known pump is not suitable for oil-tree
) The vacuum pump disclosed in the published German patent application No. 3 Core JA, which is not a vacuum pump, is oil-sealed.

Oil-sealed vacuum pumps cannot be used in the apparatus according to the invention. In the vacuum distillation of the solvent according to the published German patent application no. Cannot be used in conjunction with dry cleaning equipment.

The published German patent application no. 32'1l1099 is
We disclose a vacuum pump comprising λ stages, one stage of which consists of a Northey vane pump; the vacuum pump disclosed in published German patent application no. It was not possible to set it up. The reason is that the lack of temperature control causes the pump to overheat.

The object of the invention is to provide a distillation apparatus of the initially mentioned type in order to be able to carry out the distillation at much lower temperatures and to reduce the solvent content of the sludge-like distillation residue to low values. It is about improving.

This objective is achieved according to the invention. That is, in the present invention, the vapor compressor is not an oilless vacuum pump having no mouth valve and no outlet valve and having internal compression; The pump includes an equal non-contacting rotor that rotates, the housing has an overlapping cylindrical profile, and the pump has an injection nozzle for injecting distillate to the discharge side of the rotor to cool the rotor. The crystallizing distillate is injected by said nozzle at such a rate that the distillate evaporates during compression.

The distillation apparatus according to the invention comprises a vacuum distillation plant with a surface evaporator, preferably a cyclone evaporator.

The solvent contained and to be evaporated is withdrawn and fed to the heat exchanger and recycled from the heat exchanger to the evaporator. The evaporator may be designed for use as a foaming evaporator. The vapor drawn from the evaporator and compressed and heated by the oilless vacuum ring is condensed in the other flow path of the heat exchanger. A counterflow heat exchanger may be used in conjunction with the system to heat the incoming solvent to its boiling point and recool the outgoing distillate.

In the distillation apparatus according to the invention, the energy required to evaporate the solvent is recovered by condensing the vapor, so that no additional energy for cooling is required. No additional energy is required for the distillation of water-soluble azeotropes either. Distillation can be carried out at lower temperatures so that degradation of the residue and solvent is prevented, yet the solvent in the residue can be depleted to a greater extent than is possible in conventional systems. can. ``Evaporation of the solvent in vacuum significantly lowers the evaporation temperature of the solvent and improves the efficiency with which the components of the solvent can be separated. The temperature of the solvent vapor used for heating provides a balance with the evaporation temperature, which changes as the residue is concentrated. As a result, there is no overheating and due to the lower temperatures there is no thermal decomposition.

The vacuum distillation of solvents or solvent mixtures by compressing steam in order to provide the heat for evaporation is known per se. However, this concept could not be used for many solvents, especially for dry cleaning equipment. This is because the solvent attacks and partially dissolves the lubricants and sealants required in conventional vacuum pumps.

For this reason, inventive lines, all-tre without oil
e) teaching to carry out vacuum distillation with the aid of a vacuum pump, which provides internal compression and does not contain solvents or lubricants that can be affected by solvent vapors; . FWi-required cooling of the vacuum pump is accomplished by injection of liquid solvent during compression.

According to the invention, the vacuum pump includes λ non-contacting lobe-shaped rotors having λ overlapping cylindrical profiles and rotating relative to each other in the housing, which has an outlet valve and an outlet valve. Not worth it. Pumps of this type are available, for example, from Mannesmann Demark under the designation D/1O-2R5.
Made by nn oernag). This known pump is used as a compressor. This compressor is also known as a North@y lobe rotor pump. However, other than being used as a vacuum pump in the design proposed by the present invention, the rotor of said pump may have a different radius if the dynamic sealing problems occurring in the steam engine are to be addressed. The rotor must rotate at a higher surface speed than the rotor of known pumps. Additionally, the pump must be cooled to avoid overheating of the solvent vapor.

According to the invention, the pump f1d is equipped with an injection nozzle for injecting distillate to the discharge side of the rotor for cooling the rotor during compression, so that this distillate is completely evaporated. It is injected at a certain rate. This cooling prevents overheating of the steam; as a result, the quality of the solvent is not degraded and there is no need for cooling zones in the condenser. This cooling system also eliminates the risk of the formation of vapor defects due to overheating of the rotor.The zero distillate is completely evaporated during compression so that the rotor remains dry on the suction side. sprayed in a manner.

It is clear that the vacuum distillation according to the invention is carried out using an oil-free vacuum pump that does not contain lubricants and seals that can be pumped by liquid solvents or solvent vapors.

According to another feature of the invention, the /stage Norsi rope rotor pump can be used as a vacuum pump within the scope of the invention, since it is cooled by the injected distillate. The condenser also constitutes a heat exchanger and, for this purpose, incorporates a pipe coil for conducting the dirty solvent. This design allows the heat of evaporation to be replaced by the heat released as a result of condensation. The dissipation within the system is compensated by the compression work of the vacuum pump, which is often supplied, eliminating the need for extra heating of the dirty solvent to be distilled. The power required to drive the vacuum pump is only a fraction of the power that would otherwise be required for evaporation. As a result, the use of the distillation apparatus according to the invention is accompanied by great power savings, such that the investments required, especially for pumps, are recovered in a relatively short time.

According to a further feature of the invention, the solvent being supplied is sprayed directly into the film of solvent in the evaporator. The result is flash evaporation such that even solvent-water azeotropes can be distilled. Azeotropes are difficult to distill in conventional distillation plants due to foam formation.

In the distillation of an azeotropic mixture of a suitable solvent and water, this mixture has a lower boiling point than each component of the mixture! It is possible to take advantage of the fact that

For example, glI% solvent and 76% water by weight form an azeotrope that boils at g7°C under normal pressure.

As the mixture approaches the composition of the azeotrope, the evaporation temperature decreases and with it the heat input of the residue.

Preferably, the evaporator comprises a cyclone evaporator,
The recycled liquid solvent is injected into the evaporator through a choke so that the liquid forms a thin film that swirls at high velocity.

According to another feature of the invention, the forced circulation evaporator comprises:
It is connected to the condenser by a tube for conducting the entrained air. The entrained air heats the supplied solvent to the evaporation temperature, maintaining a total pressure in the evaporator that is higher than the pressure at which the solvent boils, so that a much lower vacuum is sufficient for evaporation. Additional energy is saved because the solvent feed and the distillate effluent are passed through a counterflow heat exchanger so that the energy required for the distillate effluent is recovered from the distillate effluent. can.

The vessel housing the forced circulation evaporator is suitably equipped with an additional heating device. This is not only advantageous when operating the plant, but also improves the distillation of the solvent from the sludge. For this purpose, the circulation of the solvent is interrupted and an additional heating device is operated, so that the solvent can be distilled from the solvent sludge by means of a vacuum pump, except for a small residue content. Since the distillation takes place in a vacuum,
Since the solvent sludge is unfractionated and unpolymerized and is in a flowable state up to t, it can be easily removed from the evaporator.

Exemplary embodiments of the invention will be described in detail with reference to the accompanying drawings.

The distillation purifier line, schematically shown in FIG. 1, includes a forced circulation evaporator 1 having a cyclone-like housing, the evaporator 1 being connected at its upper end to a vacuum pump by a tube 2. . The vacuum pump 3 sucks steam from the forced circulation evaporator l and discharges it to the heat exchanger 4. A tube 5 for conducting the dirty solvent runs through the heat exchanger 4. The pre-distilled liquid solvent is sucked out from the lower part of the forced circulation evaporator l by means of bomb f6 through pipe 7.8 and v9
is discharged through the heat exchanger 4. Through tube 10, the liquid solvent is recirculated above the liquid solvent level into the vessel of the forced circulation evaporator.

The distillate in tubes 11 leaving heat exchanger 4 is cooled in cooler 12 and air is discharged from cooler 12 through tubes 13 . Water is separated from the solvent in the water tray 7'14,
This solvent is then fed through pipe 15 to a tank for pure solvent.

Alternatively, the distillate from heat exchanger 4 may be fed to cooler 12 via tube 17, heat exchanger 16 and tube 18. The heat exchanger 16 serves to heat the dirty solvent that enters the tube 8 before the bong 7''6 and is fed to the heat exchanger 16.

Distillate is fed to the vacuum pump through line 19 to cool it and is sprayed onto its discharge side on the rotor at such a rate that the fed distillate is completely evaporated.

The rate at which dirty solvent is supplied can be controlled by valve 20.

When a solvent sludge with a suitable concentration has formed in the vessel of forced circulation evaporator l, valve 2 t ; 22 is closed, while operation of vacuum bomb f3 continues and additional heat is supplied. Next, the solvent is distilled from the sludge to a small residual content. The sludge is then withdrawn through valve 23 and the entrained air for disposal is fed through pipe 24 to the forced circulation evaporator.

Distillation can be carried out under the following conditions, for example: In forced circulation evaporators consisting of surface evaporators.

A vacuum bong 76 maintains a pressure of approximately 50 .theta. millimeters/4-liters. The temperature is maintained at approximately 700°C.

The solvent vapor is pumped through a vacuum pump in a heat exchanger 4 where an internal temperature of 720°C is maintained.
．． It is compressed to the pressure of t repar. It leaves heat exchanger 4 through tube 17 with a temperature of 720°C. The dirty solvent is fed to heat exchanger 16 at a temperature of approximately 100°C. The distillate leaving the heat exchanger 16 is at about 4 to C. The general design of the vacuum pump 3 is clear from FIGS. 1-j. Rotor 2.

They are interconnected by cars 27, 28. Rotor 215
．． The shape with 26 teeth is evident from FIG.

The distillate is fed through tube 29.30 (FIG. 1) to the discharge side of rotor 25.26 for evaporative cooling.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a distillation apparatus. Figures 1, 3 and 9 show a vertical sectional view, a horizontal sectional view and an end elevation view, respectively, of the vacuum pump. FIG. S is a schematic cross-sectional view showing the pump housing and the rotor therein. l...Forced circulation evaporator 3...Vacuum pump 4.16...Heat exchanger 25.26...Rotor 6... pump

Claims (1)

Claims: l An apparatus for distilling dirty solvents and dirty mixed solvents, preferably for distilling dirty solvents from a dry cleaning apparatus, said distillation apparatus comprising a forced circulation evaporator. a tube for supplying the heated dirty solvent in the heat exchanger to the bulk evaporator, the tube incorporating a throttle valve adjacent to the evaporator; is connected in its upper part to a tube for conducting the vapor through the vapor compressor to the condenser, and in the lower part of the evaporator for drawing liquid solvent from the evaporator and delivering said liquid solvent by means of a pump to a heat exchanger. In a distillation apparatus, the distillation apparatus includes a water trap, a tube for supplying dirty solvent, and a tube for withdrawing distillate: a vapor compressor; It consists of an oil-free vacuum pump with no mouth or outlet valve and with internal compression, the vacuum fyf rotating in a housing with an overlapping cylindrical profile and with one equal non-contacting rotor with toothed lobes. The pump includes an injection nozzle for injecting distillate to the discharge side of the rotor for cooling the rotor, and the distillate is evaporated during compression. An apparatus for distilling a dirty solvent, characterized in that: when injected through said nozzle at a rate such that: Apparatus according to claim 1, characterized in that a -9-ib coil for conducting dirty solvent extends through the condenser so that the condenser also constitutes a heat exchanger. 3. Claim 7, characterized in that the tube for conducting the dirty solvent opens into a suction tube connected to a pump for sucking liquid solvent from the forced circulation evaporator.
Equipment described in Section. A patent claim characterized in that the tube for conducting the solvent to be atomized into the forced circulation evaporator opens into the evaporator above the level of the liquid solvent in the evaporator. A patent characterized in that the tube for conducting the liquid solvent to be atomized into the device 0 according to item 1 opens tangentially into the cyclone-shaped vessel of the forced circulation evaporator. The device according to claim 1, characterized in that the forced circulation evaporator is connected to the condenser by a pipe for introducing entrained air. Device 07 according to claims 1 to 6, characterized in that a heat exchanger is provided for heat transfer between the dirty solvent being fed and the distillate. The equipment according to any one of the items. g. Device 0 according to any one of claims 1 to 7, characterized in that the vessel of the forced circulation evaporator is equipped with an additional heating device.