JPS6174568A - Purification of ethanol - Google Patents

Abstract

PURPOSE:To enable the recovery of ethanol in high purity, by adding an alkali to a concentration column, and precipitating the impurities. CONSTITUTION:An alkali metal hydroxide or alkaline earth metal hydroxide, etc. is added to a concentration column between the refluxing position and the fusel oil extraction position. The amount of the alkali is 1-0.3% based on ethanol. Since the impurities having low boiling point or high boiling point are removed by this process, a high-purity ethanol can be produced without repeating the fractionation process.

Description

[Detailed Description of the Invention] The present invention relates to a method for purifying ethanol, and more specifically, when recovering ethanol from an ethanol-containing liquid by distillation, alkali is added to a condensation column in the middle to precipitate impurities, This invention relates to a method for recovering ethanol with high purity.

Prior Art To recover ethanol from an ethanol-containing liquid, such as an ethanol fermentation liquid, by distillation, for example, steam is added to the fermentation liquid, ethanol is evaporated together with the steam, condensed in a concentrating tower, and dehydrated if necessary in a dehydration tower. A necessary third component is added to generate an azeotropic mixture to recover highly pure ethanol.

On the other hand, the ethanol fermentation liquor contains impurities with low or high boiling points, and these must be removed to obtain ethanol of higher purity.

For example, fermentation liquid made from blackstrap molasses contains approximately 8% ethanol (
V/V), methanol, inacyl alcohol, isobutanol, n-propanol, acetaldehyde, etc. are contained in an amount of 22-150 pp.

High-boiling impurities are usually removed from the concentrator by returning it to the mortar with the fusel oil or from the bottom of the column, and low-boiling impurities are removed from the concentrator downstream of the overhead condenser. However, these methods do not completely remove it, and in order to further increase the purity, the number of losses in the distillation column is increased and rectification is repeated.

Although there is always a demand for ethanol with higher purity than the problem that the invention aims to solve, repeating rectification consumes a large amount of energy and increases costs. There is a need for the development of a simpler method for removing impurities.

Means for Solving the Problems According to the present invention, impurities can be removed as precipitates by adding steam to the ethanol-containing liquid in the mortar tower and sending the ethanol to the concentrating tower where it is a-condensed by adding alkali. This is because impurities are thought to react with alkali to form precipitates.

The alkali used is a hydroxide of an alkali metal such as sodium, calcium, or potassium or an alkaline earth metal such as KOH, NaOH, Ca (OH)=, etc. These alkalis are added to the AWI column, preferably between its reflux point and fusel oil withdrawal point, at less than 1% (V/V), preferably from 0.3 to 0.01%, relative to ethanol.

The alkali used usually has a concentration of 50% by weight or less.

The present invention will be explained in more detail with reference to FIG. Figure 1 shows an example of a process diagram for obtaining ethanol from an ethanol-containing liquid. The ethanol-containing liquid is supplied to an acid group 2 through a heat exchanger 1, heated by steam, becomes steam, and is sent to a concentrating column 3 together with steam. Sent. From the top of the concentration column 3, 95% to 96% ethanol is discharged.

A fusel oil outlet 4 is provided at the bottom of the ate tower 3, and the fusel oil is appropriately extracted. The alkali supply port 5 is provided between the reflux port 6 and the fusel oil outlet.

The ethanol concentrate from the top of the column passes through a heat exchanger 7 and is transferred to a receiver 8.
A part of it is refluxed to the concentration column 3 and the remainder is supplied to the dehydration column 9.

If necessary, a third component such as cyclohexane, benzene, etc. is added to the dehydration tower to form a ternary azeotrope. Purified ethanol is obtained from the bottom of the dehydration tower.

The precipitate resulting from the reaction with the alkali is returned to the acid group through the concentrator drain outlet.

aW by a modification of the above method or a method other than the above.
By adding alkali to the r column, low or high boiling point impurities can be removed.

The method of the present invention is applicable not only to ethanol fermentation liquid but also to any solution containing ethanol, and by applying it when recovering ethanol, it can be recovered with high purity and at low cost.

Aspects of the present invention will be explained below using examples.

Example 16 m of ethanol-containing culture solution (containing 8% ethanol)
”/H to supply acid groups (atmospheric pressure) and steam at the same time.
2'00 kg/H is supplied, the column is operated at 78° C., and ethanol is sent to the a condensation column. The reflux ratio of the l1itf column is 5.0.
95% (V/V) ethanol was added from the top of the column at 1
Discharge at 315L/H. Fusel oil is taken out at 50 L/H from a fusel oil cut nozzle, and 10 L/H of low boiling point impurities are taken out in liquid or gas form from a heat exchange group 10 downstream of the heat exchanger 7.

Ethanol leaving the concentration tower is sent to a dehydration tower.

The dehydration tower was supplied with 1,600 kg/H of cyclohexane and 2,000 tons of steam to form an azeotropic mixture;
After adding H, the top of the column was operated at 64°C and atmospheric pressure, and 99.5% (V/V) or more of ethanol was produced from the bottom of the column.
OL/H humiliates. The obtained ethanol contains acetaldehyde (120 ppm) and ketone (25 ppm).

5 between the fusel oil cut position and the reflux position of the concentrator
When carrying out the same procedure as above except adding 2.5 L/H of 0% (W/W) NaOH (0.2% (V/V) to the product ethanol), there were no traces of both acetaldehyde and ketone. only was recognized.

Effects of the Invention Impurities with low or high boiling points can be easily removed as precipitates in a concentration column by adding alkali, and high purity ethanol can be obtained at low cost without repeating rectification.

[Brief explanation of the drawing]

FIG. 1 shows an example of the ethanol production process according to the present invention. Each symbol indicates the following equipment. 1: Heat exchanger, 2: Acid group, 3: Concentration column.

Claims (1)

[Claims] A method for purifying ethanol, which comprises adding an alkali to a concentrating column when recovering ethanol from an ethanol-containing liquid by a distillation method using a concentrating column.