JPH0239281B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an evaporative distillation method using an inert gas, and more specifically, the present invention relates to an evaporative distillation method using an inert gas. Relating to a method for evaporative distillation.

When handling substances with high boiling points during evaporation or distillation operations, use a high vacuum to lower the boiling point of the distillate, or blow steam into the liquid in the pot to lower the boiling point of the system to efficiently reach the desired temperature. It is common practice to separate and extract the fraction.

However, when performing evaporative distillation operations in high vacuum, vacuum pumps are special and expensive, and oil vacuum pumps mix distillates into the oil, so industrially they are not suitable for use as vacuum pumps. Since a water jet or a steam jet is used, a large amount of water or steam is consumed and most of the extracted fraction is mixed with water.

In addition, in the latter steam distillation or evaporation, a large amount of water vapor is cooled and condensed together with the fraction in a condenser, so the fraction must be separated from water. Naturally, the remaining liquid in the pot also contains water.

Furthermore, if the target liquid is, for example, a mixture of fats and oils and an aromatic solvent, there is a strong affinity between the two, so even if the above-mentioned method is used, the aromatic solvent cannot be used. It is generally difficult to efficiently separate the

Therefore, an object of the present invention is to provide an evaporative distillation method for efficiently separating and recovering a low-boiling fraction from a liquid containing a plurality of components using an inert gas.

Another object of the present invention is to provide an evaporative distillation method capable of recovering a desired fraction within a short time with high thermal efficiency and without causing thermal deterioration or oxidative deterioration of each component in a liquid. be.

Still another object of the present invention is to perform the above-mentioned evaporative distillation operation in a closed circuit;
An object of the present invention is to provide an evaporative distillation method that does not cause loss of fractions to the outside.

According to the present invention, in an evaporative distillation method for recovering a low boiling point fraction from a liquid containing a plurality of components, the inside of the system is closed with an inert gas, and the inert gas is circulated by a vacuum pump. , the distilled low boiling point fraction is partially condensed on the suction side of the vacuum pump, and the uncondensed fraction remaining in the pressurized circulating inert gas whose partial pressure has been increased is removed on the discharge side of the vacuum pump. The majority of the inert gas is condensed, and the inert gas is then reduced to the internal pressure of the evaporative distillation column through a pressure reducing valve to further reduce the partial pressure of the remaining trace low-boiling fraction, which is then recycled into the evaporative distillation column as an inert gas. A vacuum evaporative distillation method is provided.

In the present invention, an inert gas such as nitrogen or carbon dioxide is used instead of steam in the steam distillation operation, and this inert gas is blown into the liquid in the pot.
By lowering the partial pressure of the vapor pressure of the fraction, the boiling point of the liquid is lowered, and low boiling point components in the liquid are evaporated and separated together with an inert gas at a low temperature.

Further, in order to further lower the boiling point of the fraction, the inert gas is circulated and supplied using a vacuum pump to perform vacuum evaporation or vacuum distillation.

The inert gas mixture containing the evaporated fraction is removed from the evaporative distillation apparatus under reduced pressure and cooled on the suction side of the vacuum pump to condense and recover a portion of the fraction vapor.

The remaining inert gas mixture is compressed from the vacuum suction side to the normal pressure to high pressure discharge side, and by cooling this compressed gas, most of the contained distillate vapor is condensed and liquefied.

In this case, since an inert gas containing a large amount of solvent fraction is compressed in the vacuum pump, much of the fraction is condensed in the vacuum pump. Therefore, it is more convenient to use a liquid ring type (Natsushi type) vacuum pump as the type of vacuum pump. Also, when creating a high vacuum, use a booster in front of the liquid-ring vacuum pump. In this case, since the fraction remains in the liquid ring pump, the condensed fraction is used as the sealing liquid. The fraction condensing in the pump overflows and is collected in a storage tank. Thus, according to the present invention, unlike steam distillation, water is prevented from being mixed into the distillate components. When an oil vacuum pump is used, distillate components are mixed into the oil and the degree of vacuum is lowered, so old oil needs to be taken out and new oil needs to be constantly injected, which is not very preferable.

Further, most of the distillate vapor is condensed and liquefied, and the inert gas containing a small amount of the distillate vapor is further reduced in pressure to the internal pressure of the evaporative distillation column, and the partial pressure of the distillate vapor is significantly lowered.

This makes the inert gas as close to pure inert gas as possible, and by supplying it to the evaporative distillation column, the concentration of the residual boiling point component in the residual liquid can be reduced as much as possible. It becomes possible.

According to the present invention, by performing the evaporative distillation operation in an inert gas, it is possible to effectively prevent oxidation and deterioration of each component due to heating of the liquid. In addition, by blowing inert gas into the liquid, the boiling point can be lowered to a temperature considerably lower than that of the desired fraction, and the fraction can be evaporated or distilled at a low temperature. The degree of oxidation and deterioration will be lower.

Moreover, according to the present invention, in connection with the use of an inert gas, the latent heat of vaporization of water during evaporation and the latent heat of liquefaction of water during cooling condensation are completely unnecessary as in the case of steam distillation, and the latent heat of liquefaction of water during cooling condensation is completely unnecessary. By simply imparting the latent heat of vaporization of the distillate components and removing this latent heat during cooling, an evaporative distillation operation becomes possible, achieving numerous advantages in terms of thermal economy.

Furthermore, the inert gas blown into the liquid lowers the boiling point of the distillate component, and even if this component is present in minute amounts, it acts as a carrier gas to entrain it into the gas phase, so it can be used for a short period of time. It also has the advantage that a minute amount of the desired fraction can be separated and evaporated during the process.

The present invention will be explained below based on the accompanying drawings.

In FIG. 1, the evaporator main body 1 includes a liquid storage section (pot section) 2 and a thin film evaporation section 3 above it.
Each of them has a steam jacket 4 for heating the liquid,
4' is provided. The steam jackets 4, 4' include inlet pipes 5, 5', valves 6,
6' and drain extraction pipes 7, 7' are provided, respectively, to heat each part of the apparatus to a predetermined temperature.

A supply pipe 8, a valve 9, and a pipe 10 for supplying the liquid to be treated are provided above the thin film evaporator 3. A liquid extraction pipe 1 is provided at the lower end of the liquid reservoir 2.
1 is provided, and a valve 1 is connected from this extraction pipe 11.
2, circulation pump 13, circulation pipe 14, valve 1
5 and a liquid circulation path leading to the supply pipe 10 is formed.

The liquid reservoir section 2 is provided with an inert gas blowing pipe 16, and the top of the evaporator main body 1 is provided with a pipe 17 for extracting the fraction-containing inert gas. From this extraction pipe 17 to the condenser 18 and pipe 1
9 to the first condensate tank 20, pipe 21 to the low pressure side of the liquid ring vacuum pump 22, the high pressure side of this pump 22 to the cooler 23 to the second condensate tank 24, and from the tank 24 to the pipe 25. Inert gas circulation paths are formed which reach the blowing pipe 16 via the pressure reducing valve 26 and the blowing pipe 16, respectively.

In FIG. 1, 27 and 28 are pipes and valves for gas discharge, 29 and 30 are pipes and valves for supplying inert gas, and 31
is an operation switching valve.

First, the valve 15 is closed, the valve 9 is opened, and a predetermined amount of processing liquid is introduced into the apparatus main body 1 through the pipes 8 and 10. Steam is supplied to the steam jackets 4 and 4' to heat the main body of the device, and
The valve 9 is closed, the valves 12 and 15 are opened, and the pump 13 is operated to supply the thin film evaporator 3 through the liquid pipes 11, 14 and 10 in the liquid reservoir 2.
Continue heating while circulating.

Prior to this, or at the same time, the valve 31 is closed and the valve 30 is opened to blow inert gas into the liquid through the pipe 29 from an inert gas source (not shown) such as a nitrogen cylinder through the blowing pipe 16. It's crowded. Open the valve 28, operate the liquid ring vacuum pump 22, purge the air in the system with inert gas, then close the valves 29 and 30, and operate the liquid ring vacuum pump 22.
Open 1. The pressure of the inert gas to be blown is controlled by the pressure reducing valve 26.
The pressure is reduced by reducing the partial pressure of the trace low boiling point fraction, and the fraction is supplied into the distillation column.

The liquid is stirred by the inert gas blown in, and low-boiling fractions in the liquid are evaporated. The inert gas containing this distilled vapor is extracted from the apparatus through a pipe 17, cooled in a condenser 18,
An amount of steam corresponding to the temperature difference is condensed and collected in the first condensate tank 20. The remaining gas is compressed by a liquid ring vacuum pump 22, and most of the vapor is condensed and collected and separated in a second condensate tank 24. The inert gas after separation is adjusted to the internal pressure of the distillation column by the pressure reducing valve 26, and is blown into the liquid through the blowing pipe 16 to continue the evaporation operation.

According to the present invention, by the above-described inert gas circulation operation, low boiling point fractions can be efficiently separated and recovered.
Moreover, it can be completed almost completely within a short period of time.

As an example, an example in which the present invention is applied to a liquid mixture containing vegetable oil and toluene will be shown.

The evaporator main body 1 used has a pot 2 with a volume of 100
The thin film evaporation section 3 had a height of 100 mm x 1000 mm. A mixed solution of 50 kg of vegetable oil and 40 kg of toluene was supplied into this device, the atmosphere was set to a nitrogen pressure of 100 Torr (mmHg), and the steam temperature supplied to the jackets 4 and 4' was set to 130°C, and an evaporation operation was performed by blowing nitrogen. Summer. The temperature of the liquid at the start
30℃, 129℃ at the end, operating time is 5
It was time.

As a result, the amount of toluene recovered was 40 kg, and the amount of toluene in the residual vegetable oil was 500 ppm.

For comparison, an experiment was conducted using the apparatus shown in FIG. 2 instead of the apparatus shown in FIG. In the apparatus of FIG. 2, common parts are indicated by common reference numerals, and in this apparatus only the blowing pipe 1 of FIG.
6 is not used, and a steam ejector 32 is used instead of the circulation system shown in FIG. Uncondensed gas from the first condensate tank 20 is transferred to pipe 3
3 and is led to the ejector 32. The ejector 32 is operated by steam introduced via a steam inlet pipe 34 and the steam and distillate drain mixture is discharged via a pipe 35 into a tank 36.

The dimensions of the evaporator used and the composition of the stock solution are the same as in the previous example, and the steam temperature for the jacket is also the same.
The temperature is 130℃. The atmospheric pressure was 3 Torr (mmHg), and the liquid temperature was 30℃ at the start and 120℃ at the end.
I drove for 10 hours.

The amount of toluene recovered was approximately 30 kg, and the amount of toluene remaining in the residual vegetable oil was approximately 5500 ppm.

The following is clear from the above results.

It is clear that even if an oil containing 44% of low-boiling point toluene (boiling point 110°C) is evaporated in a high vacuum such as 3 torr, the evaporative separation of this fraction will not be sufficient. . That is, raise the temperature to 3 Torr and 120℃.
Even after 10 hours of distillation, about 5000 ppm of distillate still remains in the residual solution.

In other words, when the content of low boiling point components in the liquid mixture becomes minute, even if this liquid mixture is heated to a temperature equal to or higher than the boiling point of the fraction, the fraction does not easily distill out. . This is thought to be because minute components such as toluene exist in the oil in an adsorbed state.

However, when blowing nitrogen gas according to the present invention, even when the degree of vacuum is as low as 100 Torr,
Compared to ordinary vacuum evaporation, the amount of residual toluene can be reduced to an order of magnitude lower in about half the time, and without the need for troublesome separation from water.
It can be separated in its pure form.

Although the present invention has been described using the case of evaporation as an example, the present invention can of course also be applied to distillative separation of liquids containing two or more components with similar boiling points.
In this case, a distillation column such as a bubble column, plate column, or packed column may be provided above the pot, and the same treatment may be performed.

[Brief explanation of drawings]

FIG. 1 is a layout diagram showing an example of an apparatus for suitably carrying out the method of the present invention, and FIG. 2 is a layout diagram of an apparatus used in a comparative experiment. Reference number 1 is the main body of the device, 2 is the liquid reservoir, 4 is the heating mechanism, 16 is the inert gas blowing mechanism, 17 and 2
2 is an inert gas circulation mechanism, 18, 20 and 2
3 and 24 are cooling condensation recovery mechanisms.

Claims (1)

[Claims] 1. In an evaporative distillation method for recovering a low-boiling fraction from a liquid containing multiple components, the system is sealed with an inert gas, and the inert gas is circulated by a vacuum pump. At the same time, a portion of the distilled low boiling point fraction is condensed on the suction side of the vacuum pump, and on the discharge side of the vacuum pump, the uncondensed fraction remaining in the pressurized circulating inert gas whose partial pressure has increased is Most of the inert gas is condensed, and the pressure of the inert gas is reduced to the internal pressure of the evaporative distillation column through a pressure reducing valve to further reduce the partial pressure of the remaining trace low-boiling fraction, which is then introduced into the evaporative distillation column as an inert gas. A vacuum evaporation distillation method characterized by circulating supply.