JPS58124578A - Distillation - Google Patents

Abstract

PURPOSE:To perform energy-saving distillation, by withdrawing the concentrated vapor of low-boiling point components from the top of a concentration column, using it as a heat source for the reboiler of a distilling column, and then introducing it into the distilling column to obtain the fraction of the low-boiling point components from the top of the distilling column. CONSTITUTION:An aqueous ethanol solution F as a raw material for instance is made to flow through heat exchangers C, D, preheated by vapor obtained from the top of a distilling column B and a waste liquid obtained from the bottom of a thickening column A, respectively, supplied to the upper part of the column A, and brought into countercurrent contact with steam S introduced through the lower part of the column. Thereafter, the concentrated vapor of low-boiling point components is withdrawn from the top of the column A, used as a heat source for a reboiler R at the bottom of the column B and then supplied to the column B to obtain the fraction of the low- boiling point components from the top of the column B. The top vapor from the column B is introduced into the heat exchanger C, etc. and condensed therein, to recover a part of the vapor as a product P and to circulate the remainder to the upper part of the column B. Since a liquid contg. unrefined SAKE does not flow through the reboiler R at the bottom of the column B, throubles such as pollution and corrosion are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for separating and recovering low-boiling components by distillation from an aqueous solution containing components with a lower boiling point than water.

The conventional distillation method is to feed an aqueous raw material solution to the middle stage of a distillation column, and then release steam of low-boiling components from the top of the column. This is taken out, condensed in a condenser, a part is taken out of the system as a distillate, and the rest is all refluxed to the top of the distillation column, and a waste liquid corresponding to the amount of distillate is taken out from the bottom of the column. In such methods, steam is generally used as a heat source for the distillation column, and its consumption is large. In order to completely reduce this, it is common practice to preheat the raw material aqueous solution by heat-exchanging the raw material aqueous solution with the steam taken out from the top of the tower or the waste liquid taken out from the bottom of the tower. However, this method does not reduce the amount of water vapor consumed, and cannot be said to be an energy-saving distillation method.

For example, an aqueous solution containing mash obtained by alcoholic fermentation generally contains 4 to 12 parts by weight of alcohol, and such a dilute alcohol solution contains 90 to 95 parts by weight of alcohol.
In order to obtain 6 parts by weight of alcohol by the method described above, a large amount of steam is required as a heat source, and the thermal energy input for distillation is quite large. Recently, a distillation method using overhead steam as a heat source has been proposed to save energy. One of them is the two-column co-current multiple effect distillation method shown in Figure 2 (Biomass and New Energy Development Conference Abstracts, pages 2-5-1 to 2-5-15, 1981).
The Japan Management Association (Japan Management Association) introduced a method in which the steam from the top of the first column was used as a heat source for the IJ Thaler unit in the second column by supplying all the raw materials to each of the two distillation columns to obtain separate distillation columns. Afterwards, a portion is refluxed to the first column, and the remainder is taken out as a tg product. However, in this method, effective heat exchange is not performed because scale adheres to the surface of the heating tube of the boiler due to the decomposition of the mash components under high temperature and high pressure. Furthermore, the surface of the heating tube of the resailor corrodes, making long-term operation impossible. The other method is the overhead vapor self-compression distillation method (fermentation and industry 39) as shown in Figure 3.
651. <1981)), the top vapor of the distillation column is pressurized with a compression material O, and the condensation heat is used as a heat source for the 21Jz irrer, but this method also +)N iller is contaminated with mash, There are also other problems, such as the need for a large-capacity compressor. Furthermore, JP-A-56-
In ``113717, the top vapor of the distillation column is pressurized using a compressor.

This is used as a heat source to generate some of the steam that is blown into the tower.

Since this method also requires a large-capacity compressor, it is difficult to expect an effective reduction in processing costs.

An object of the present invention is to provide an energy-saving method for distilling an aqueous solution containing a component having a boiling point lower than that of water, which is expected to reduce energy consumption and processing costs, and which is free from the risk of contamination or corrosion of the resailor due to scale adhesion, etc. It is.

In order to achieve all of these objectives, the inventors of the present application have conducted intensive research and found that the invention consists of one or more concentration columns and the same number of distillation columns, and an aqueous solution containing components with a lower boiling point than water is placed in the upper part of the concentration column. It is brought into countercurrent contact with the water vapor introduced from the bottom of the concentrating column, and the concentrated vapor of low-boiling components is extracted from the top of the concentrating column.

1. After being used as a heat source to generate steam sound for blowing into other concentrating columns and/or as a heat source for a distillation column boiler, it is introduced into a distillation column and a low-boiling point fraction is obtained from the top of the distillation column. This led to the invention of a distinctive distillation method.

Next, the method of the present invention will be specifically explained with reference to one drawing as an example in which an alcohol-containing aqueous solution is used as a raw material.

Figure 4 shows downstream multiple effect (two towers) in the method of the present invention.
This is a flow sheet for the case. Raw material ethanol aqueous solution F
The vapors are passed through heat exchangers C and D and obtained from the top of the second column (distillation column) B, respectively.

After being preheated by the waste liquid obtained from the bottom of the first column (concentration column) A, it is supplied to the upper part of the first column (condensation column) A, and brought into countercurrent contact with the steam S introduced from the bottom of the column. 1st Tower (
Concentration tower] Ethanol from the top of A
The top vapor containing approximately t% is taken out, and this top vapor is used as a heat source for the +1yf error at the bottom of the second column (distillation column) B, and then supplied to the second column (distillation column) B. and concentrate to desired concentration. The top vapor from the second column (distillation column) B is guided to a heat exchanger C etc. and condensed, a part of which is recovered as product ethanol P, and the remainder is refluxed to the upper part of the second column (distillation column) B. . The reflux ratio of the second column (distillation column) B is 2.4
That's about it. II ziller R on the bottom of the second column (distillation column) B? There is no need to worry about contamination or corrosion because the liquid it contains does not flow out.

Figure 5 shows a combination of forward flow and parallel flow type (4 towers) in the method of the present invention.
70-sheets in case of . The raw material ethanol aqueous solution F is transferred to the heat exchanger C and the respective (heat exchangers) DI and (
After passing through B2 (heat exchanger) and preheating by exchanging heat with the top vapor of the distillation column and the waste liquid from the bottom of the column, the first column (concentrating column)
Both A1 and the second column (concentration column) Ax are supplied to the upper part and brought into countercurrent contact with the steam introduced from the lower part of the column. The first column (concentration column) A+ and the second column (concentration column) A+ contain about 50ωt% of ethanol and completely remove all mash.
The top vapor of No. 2 is transferred to No. 2 of the third tower B and fourth tower B2, respectively.
At this time, the first column (concentration column) is fed to the main distillation column.
The top vapor of A+ is introduced into steam generator E [introduced into the second column (concentration column) A2 before being supplied to the third column (distillation column) Bt.
It is used as a heat source to generate all the steam that is blown into the water.

If a column bottom liquid 1 which does not contain mash and is obtained from within the system is used as the steam source, for example, a column bottom liquid such as the fourth column (distillation column) B2, a further energy saving effect can be expected. Second
The top vapor of column (concentration column) A2 is transferred to fourth column (distillation column) B2
Before being supplied to the third column (distillation column), it is used as a heat source in the BI resiler R8. Third column (distillation column) B1
The vapor obtained from the top of the column is transferred to the fourth column (distillation column) B2.
After using it as a heat source for the IJ Niller R2, a portion is taken out as product ethanol P1, and the remainder is refluxed to the column B.

After passing the top vapor of the fourth column (distillation column) B2 through a suitable heat exchanger, a portion is taken out of the system as product ethanol P2, and the remainder is refluxed to the column B2. R1 and R
2 may be a side reboiler as shown in the figure. Furthermore, if the heat source of the distillation column is insufficient, the vapor at the top of the distillation column can be pressurized by a compressor, and the latent heat of the vapor can all be used to heat and evaporate the bottom liquid to compensate. Specifically, in the case of a downflow type multiple effect (two columns), as shown in FIG. 6, part or all of the top vapor of the second column (distillation column) B is pressurized by a compressor GK.

This vapor is passed through the IJ yi Ilar R3 of the column and used as a heating source for the bottom liquid, and then the condensed liquid is further cooled by passing through a heat exchanger, a part of which is recovered as product ethanol P, and the remainder is Reflux to the tower. Also, instead of the reboiler type, it is also possible to adopt a type that blows steam. In this case, as described above, pressurized overhead steam is introduced into a steam generator to heat water.

This can be done by directly feeding the obtained steam to the total distillation column.

In the case of the forward flow/cocurrent flow type, the vapor at the top of the distillation column is similarly pressurized by the compressor G, as shown in FIG. 7, and this heat is used for heating and evaporation of the bottom liquid. In addition, although Figures 6 and 7 show an example in which the top vapor pressurized by a compressor is used as a heat source for the bottom liquid of the distillation column, it is not limited to this and can be used as a heat source for other distillation columns or concentration columns. It is also possible to use

However, when compressed steam is used in a column at a higher pressure than the distillation column, the power required for the compressor and the cost of equipment are large, so it is not preferable to use it in a column with a large pressure difference.

Further, the concentration column and the distillation column in the present invention do not necessarily need to be separate columns. The entire distillation column may be installed above the concentration column and integrated to form a composite single-column type. In this case, it can be expected that the space and equipment costs required for device construction will be reduced.

Example 1.2 An aqueous ethanol solution 17-6 with an ethanol concentration of 11.9 #t% was prepared using the apparatuses shown in FIGS. 4 and 5, respectively.
Product ethanol with an ethanol concentration of 93 wt% was obtained using 100 ton/Hr as a raw material. Table 1 shows the operating conditions and utility usage at this time.

Comparative Example 1 Using the apparatus shown in FIG. 1, it was operated using the same raw materials as in Example 1 to obtain product ethanol with an ethanol concentration of 93 vt%. The operating conditions and amount of utilities used at this time are shown in Table 1.

Example 3 Using the apparatus shown in FIG. 6, it was operated to obtain product ethanol with the raw material empty ethanol concentration of 93 ωt% as in Example 1. However, +1.7 Ton of the top steam of the second tower
/ Hr k compressor with 0.5 Kf/i ()
The pressure was increased to 5-2 Kg/cJG and used as the IJz iller heat source for the second column. Table 2 shows the amount of stripping steam and the amount of utility used at this time.

Example 4 The apparatus shown in FIG. 7 was operated to obtain product ethanol having the same raw material empty ethanol concentration of 93 ωt% as in Example 1. However, 1.5 of the steam at the top of the fourth tower is ton
/ Hr with compressor 22 +1NxlI? From 115
The pressure was increased to 0txxHt and used as the IJyg heater heat source for the fourth column. The total amounts of stripping steam and utilities used at this time are shown in Table 2.

The results of calculations regarding the cost required for energy used, the cost required for equipment, and the processing cost for the product ethanol unit Dogata Shi in each of the above Examples and Comparative Examples, as well as the processing cost for the product ethanol unit, are shown in Table 3, assuming Comparative Example 1 as 1. It was as follows. It was assumed that the equipment would be depreciated over four years.

As described above, although the method of the present invention requires more expensive equipment than the conventional method, it can significantly reduce the energy used and the processing cost for each child's picture product. In addition, there is no reduction in heat conduction or corrosion caused by the resailor's mash, so energy can be used more effectively.

The device also has the advantage of being able to be used for a longer period of time.

In addition, the target of the method of the present invention is not limited to alcohol-containing aqueous solutions, but also components with a lower boiling point than water. It is effective when concentrating a dilute aqueous solution of a target low-boiling point component to a low-boiling point component of less than 1%. This method is suitable for handling the aqueous solution containing substances that may cause scale to adhere to the surface of the heating tube of the resailor, hindering effective heating, or causing corrosion.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet of a conventional distillation method, and FIGS. 2, 3, and 3 are flow sheets of a distillation method recently proposed for energy saving. Figure 4 shows a forward flow type multiple effect system (2
Figure 6 shows the flow sheet for the self-compressing type. FIG. 5 is a flow sheet for a forward flow parallel flow type (four columns), which is another embodiment of the present invention, and FIG. 7 is a flow sheet for the self-compression type, showing only the fourth column. Patent Applicant: JGC Corporation

Claims (1)

[Claims] (1) l''! In a system consisting of several concentration columns and the same number of distillation columns, an aqueous solution containing all components with a lower boiling point than water is introduced into the upper part of the concentration column and brought into countercurrent contact with the water vapor introduced into the lower part of the concentration column, One concentrated vapor of low-boiling components is extracted from the top of the concentrating column and used as a heat source for generating steam for blowing into other concentrating columns and/or as a heat source for the IJ of the distillation column.
A distillation method characterized in that after being used as a heat source for an iller, it is introduced into a distillation column and a low boiling point component fraction is recovered from the top of the distillation column.・(2) After using the low-boiling point component fraction 1 obtained from the top of the distillation column in a system consisting of a plurality of concentrating columns and the same number of distillation columns as a heat source for the IJ yy iller of another lower pressure distillation column,
1. The method of claim 1, wherein a part of the fraction is refluxed to the upper part of the distillation column and the remainder is recovered as a product of low-boiling components. (3) The method of item 1, wherein each of the concentration column and the distillation column is two columns. (4) The method of item 1, in which at least a portion of the bottom liquid of the distillation column is completely evaporated and used as steam for blowing into the concentration column. (5) After pressurizing a part or all of the steam at the top of one of the distillation columns in the system, the heat source of the sailor of the distillation column and/or the steam blown into the distillation column is The method of item 1, which is used as a heat source for generating electricity.