JPS6065702A - Continuous production of bromine - Google Patents

Abstract

PURPOSE:The feed of chlorine is controlled so that the oxidation-reduction potential of the cleaning solution for the exhaust gas, as a starting material, is kept constant to effect effective recovery of excess chlorine and enable continuous production of bromine in high yield. CONSTITUTION:An aqueous solution containing bromine ion B and chlorine A are fed from the column top and the intermediate point or bottom of the reactive distillation column 1, respectively, and steam C is continuously inctroduced from the column bottom and the steam from the top is condensed in the condenser 2 to separated into the condensate containing bromine and uncondensing gas. The exhausted gas is led into the cleaning column 4 in which the gas is brought into contact with a part of the aqueous solution B to allow the unreacting Cl in the gas to react with Br ion, then, the feed of chlorine is controlled so that the oxidation-reduction potential according to the meter 5 becomes constant. In the meantime, the condensate is led into the dechlorination column 3 to contact with a part of the aqueous solution B to remove Cl and Br ion in the Br condensate by allowing them to react with each other, then the separated Br solution is recovered into the tank 6 and the aqueous solution B is recycled to the column 1.

Description

Detailed Description of the Invention The present invention involves applying chlorine to an aqueous solution containing bromine ions such as bromate or hydrobromic acid (hereinafter referred to as a bromide ion-containing aqueous solution), and distilling and recovering the liberated bromine. The present invention relates to a method for continuously producing bromine.

Conventionally, as a method for producing bromine, an aqueous solution containing bromine ions is supplied from the top of a reactive distillation column, and the bromine liberated by reaction with chlorine supplied from the bottom of the column is distilled from the top of the column by blowing steam from the bottom of the column. The method of cooling and condensing and recovering this is well known.

By the way, in this method, chlorine is usually used in an excess amount than is chemically theoretically necessary in order to increase the reaction rate of raw material bromine ions. For this reason, an excess amount of chlorine is mixed into the recovered bromine and the exhaust gas after condensation, and such chlorine is usually removed by dechlorination treatment such as distillation.
In addition, chlorine in the exhaust gas is disposed of through exhaust gas abatement treatment, etc.

Therefore, in such a method, not only chlorine is lost, but also bromine accompanying the waste chlorine is lost, reducing the bromine recovery rate. It is difficult to adjust the amount of chlorine supplied as the concentration changes, and the operation becomes complicated, which tends to cause excess or deficiency in the amount of chlorine supplied, resulting in an increase in the amount of waste chlorine or a decrease in the bromine recovery rate.

Therefore, the present inventors have conducted studies to overcome these drawbacks, supply chlorine stably with simple normal pressure operation, effectively recover excess chlorine, and produce bromine with high yield. As a result, the present invention was completed.

That is, in the present invention, a bromide ion-containing aqueous solution is extracted from the top of a reactive distillation column! In a method for continuously producing bromine by introducing chlorine from the #rm section or the middle part of the column and steam from the bottom of the column, and recovering the liberated bromine by distillation,
@The distilled vapor from the top is condensed and separated into uncondensed m exhaust gas and condensed liquid containing condensed bromine, and a part of the raw material bromide ion-containing aqueous solution is brought into contact with the uncondensed exhaust gas to remove unreacted components contained in the exhaust gas. After reacting with chlorine and bromide ions, the chlorine is introduced into the reactive distillation column, and the amount of chlorine supplied to the reactive distillation column is adjusted so that the redox potential of the bromide ion-containing aqueous solution after the contact treatment is constant. On the other hand, part or all of the remainder of the raw material bromine ion-containing aqueous solution is brought into contact with the condensed liquid to remove dissolved chlorine in the condensed bromine by reacting with the bromine ions, and then the bromine liquid is separated. The present invention provides a method for continuous production of bromine, characterized in that each of the above operations of introducing a bromide ion-containing water bath into a reactive distillation column is performed continuously.

The present invention will be explained below based on a flow sheet shown in FIG. 841 as an example.

Basically, in the present invention, a raw material bromide ion-containing aqueous solution B is introduced from the top of the reactive distillation column 1, chlorine A is introduced from the bottom or the middle of the column, and steam C is introduced from the bottom of the column. Bromine liberated by reaction with chlorine in
& It is carried out by continuously distilling from the top.

In carrying out the present invention, the raw material bromide ion-containing aqueous solution is divided into two parts, each of which is supplied into the tower via an exhaust gas cleaning tower 4 and a dechlorination tower 3, which will be described later.

The bromine vapor distilled from the top of the reactive distillation column is led to the condenser 2 together with unreacted chlorine and water vapor, where the bromine vapor and water vapor are condensed into a 6M liquid containing °Cs @ Ha bromine and mainly unreacted chlorine. It is separated into uncondensed waste, which consists of reactive chlorine and partially contains bromine.

The uncondensed waste is led to the waste waste cleaning tower, where it is brought into contact with a portion of the raw material bromide ion-containing aqueous solution.

Although there are no particular restrictions on the contact method itself, packed columns are often used in terms of contact efficiency, and a countercurrent method in which uncondensed waste is introduced from the bottom and a bromide ion-containing bath liquid is introduced from the top of the column is suitable. .

In the waste sludge cleaning tower, unreacted chlorine in the waste sludge reacts with a part of the bromine ions in the bromine-containing saliva to liberate bromine, and the liberated bromine and waste sludge are The bromine entrained in the filtrate is dissolved in the flowing bromide ion-containing aqueous bath liquid, and the aqueous solution is supplied as is to the reactive distillation column, so the unreacted chlorine in the waste is consumed in reaction with bromide ions. , it will be effectively recovered and used in the first stage of bromine production.

Incidentally, the oxidation-reduction potential of the effluent from the exhaust gas cleaning tower is related to the amount of dissolved bromine, and the amount of dissolved η' bromine is related to the amount of unreacted chlorine in the exhaust gas.

Furthermore, the amount of unreacted chlorine in the exhaust gas is influenced by the amount of chlorine supplied into the reactive distillation column. Therefore, excess or deficiency in the amount of chlorine supplied to the reactive distillation column will result in a change in the amount of unreacted chlorine in the antagonistic gas led to the scum cleaning column and the amount of bromine entrained therein.
The change can be detected by the redox potential of the effluent flowing out from the exhaust gas cleaning tower. Therefore, the redox potential of this effluent is measured and monitored, and the redox potential of the effluent is measured and transferred to the reactive distillation tower so that the redox potential is constant. By adjusting the amount of chlorine supplied, the ratio between the amount of chlorine and bromine ions in the reactive distillation column becomes constant, and bromine can be produced stably and continuously.

Here, the oxidation-reduction potential is measured by a normal method, and the amount of chlorine supplied is generally adjusted so that the oxidation-reduction potential is 1100 to 1250 mV (this corresponds to a bromine concentration of about 0.5 to 2 g). Although the voltage is adjusted, it is of course not limited to this, and the redox potential to be kept constant is determined depending on each condition.

However, in the present invention, the oxidation-reduction potential being constant does not necessarily mean that it is at one specific point, but may have a range within an allowable range under each operating condition. Needless to say.

This redox potential measurement is performed at any step before the effluent from the exhaust gas cleaning tower is introduced into the reactive distillation tower.

On the other hand, the condensate condensed in the condenser 2 consists of condensed bromine and condensed water, but since unreacted chlorine is dissolved in the condensed bromine, condensed bromine is mixed with the condensed water in order to remove the dissolved chlorine. Introduced to dechlorination 83 [7. Contact with raw material bromide ion-containing aqueous solution.

The dechlorination tower used here may be a packed tower type or a simple pipe type (vertical type), and the treatment method is to allow the condensate to flow down from the top of the tower, and introduce the remainder of the raw material bromide ion-containing aqueous solution upward from the lower part. While taking out the bromine liquid from the bottom of the tower,
The bromide ion-containing aqueous solution and condensed water flowing out from the top of the column are introduced into the top of the reactive distillation column.

Through this process, the condensed bromine in the condensate that has flowed down from the top of the tower falls through the tower due to the difference in ratio. During this time, the condensed bromine comes into contact with the rising aqueous solution containing bromide ions, converting dissolved chlorine into bromine ions. During the reaction, bromine is liberated and dechlorinated. The condensed water is mixed with an aqueous solution containing bromide ions in the tower, and part of the unreacted chlorine in the condensed water reacts with the bromide ions here, but the rest is contained in the effluent from the top of the dechlorination tower and is sent to the reactive distillation tower. It is recycled inside.

The bromine removal is adjusted so that the bromine solution forms a high bromine layer at the bottom of this dechlorination tower, and the bromine ion-containing aqueous solution is introduced so as to pass through this bromine layer, thereby removing chlorine from the bromine. The effect is further improved.

In the exhaust gas cleaning treatment and dechlorination treatment described above, the effluent after these treatments becomes the raw material liquid for bromine production, so it is necessary to continuously supply the raw material liquid together with chlorine and steam to the reactive distillation column. are carried out simultaneously and consecutively.

In the above explanation, we have described the case where the bromide ion-containing aqueous solution that is the raw material is divided into two parts: one that passes through the exhaust gas cleaning tower and one that passes through the dechlorination tower. It is determined as appropriate depending on the treatment efficiency of chlorine contained in the chlorine, and in some cases, it is divided into three parts within the range where the above chlorine treatment is possible, and one divided part is directly introduced as it is into the reactive distillation column, and the remaining part is 2
The above processing may be performed on the divided portions.

Thus, according to the method of the present invention, the amount of chlorine supplied is adjusted safely and easily so that the oxidation-reduction potential of the raw material exhaust gas cleaning liquid becomes constant, and even when the amount of bromine in the raw material changes, Correspondingly, chlorine can be supplied stably, excess chlorine can be effectively reused without any particular difficulty, and bromine with a low chlorine content can be produced at a good yield.

The present invention will be explained below with reference to Examples.

Example 1 Bromine ion concentration [10
% of hydrobromic acid and l-'Jium bromide mixed aqueous solution 11
Q Q 1 (When recovering bromine from vH, exhaust gas cleaning #!ir(!-
inch porcelain pilling) and inner diameter 0.1 m tower height 2
．． A 5 m tubular dechlorination tower was installed as shown in FIG. 1, and the raw material bromine ion-containing liquid was supplied from the upper part of the former tower and the lower part of the latter tower at a rate of 550 Kf/H, respectively. The liquid passing through the exhaust gas cleaning tower is allowed to flow down from the bottom of the exhaust gas cleaning tower, and then the redox potential is measured with an oxidation-reduction potentiometer and supplied to the reactive distillation tower.The liquid at the bottom of the dechlorination tower is condensed in a heat transfer area of 15m2. It was brought into countercurrent contact with the bromine condensed in the reactor and fed to the reactive distillation column. Chlorine 49Kg/El, steam 820Kg/H from the bottom of the reaction distillation column (pressure 8.5Kg/Mei 2 (gauge))
When bromine was supplied in steady state, 109 Kf/■
(Recovery rate: 99cm) was recovered, and the amount of chlorine in the bromine was 0.
It was an office worker. At this time, the chlorine flow rate was controlled so that the potential of the oxidation-reduction potentiometer was kept constant at about 1150 mV.

Example 2 A glass tube with an inner diameter of 19 mm and a height of 600 mm was filled with glass packing to make a reactive distillation column, and a glass condenser was installed in this, and a glass tube with an inner diameter of 191111 B and a height of 200 mm was filled with glass packing. The exhaust gas cleaning tower filled with
a. A glass tube dechlorination tower with a height of 590 B was connected as shown in FIG. 1 using glass tubes. The liquid flowing from the bottom of the exhaust gas cleaning tower is received by a 150-bar glass container with a redox potential meter electrode inserted, and the overflow is supplied to the reactive distillation tower, so that the redox potential is approximately 1150 m
The amount of chlorine supplied was adjusted to be constant at V. An average of 18 ff of hydrobromic acid aqueous solution with a bromide ion concentration of 9.8%
/m to the upper part of the exhaust gas cleaning tower, and the average t 2 Si'
/I+i was supplied to the lower part of the dechlorination tower. Chlorine was blown into the bottom of the reactive distillation column at a rate of about 1.3 mol, and water vapor was blown into the bottom of the reactive distillation column at a rate of about 1OV so that the top temperature was 90°C. In a steady state, the amount of recovered bromine was 2.9 volts (recovery rate 99 inches) and the amount of chlorine in the recovered bromine was 0.01 inches. The amount of chlorine was adjusted to keep the potential of the oxidation-reduction potentiometer constant, but it was controllable even if the amount of the hydrobromic acid aqueous solution was changed, and there was no increase in either the recovery rate or the amount of chlorine in the recovered bromine.

Comparative Example A glass tube with an inner diameter of 19 tm and a height of 760 m is filled with glass packing to form a reactive distillation column, and a glass condenser and a bromine and condensed water separation tank are installed on the condensate side to recover bromine. I did it.

A mixed aqueous solution of hydrobromic acid and sodium bromide with a bromide ion concentration of 5.2's (bromine ion ratio of hydrobromic acid and sodium bromide of 2:l) was heated at an average of 48.6 V from the top of the reaction distillation column.
Chlorine was introduced from the bottom of the reactive distillation column in about 1 minute, and the bottom of the reactive distillation column was heated with a heater so that the temperature at the top of the column reached 90°C. Bromine recovered in steady state 2.2P/e,
The chlorine in bromine was 1.7%, and the bromine recovery rate was 97%. The amount of chlorine was adjusted by calculating the amount of bromide ion-containing liquid in the raw material, but there was an excess or deficiency, resulting in a considerable loss of chlorine and bromine as uncondensed gas, and the bromine recovery rate including the shortage was 92. - It was about -. Further, even when bromine obtained by absorbing uncondensed gas with a 10% caustic soda aqueous solution was added to the recovered bromine, the recovery rate was 96%.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a typical example of carrying out the method of the present invention. In the figure, 1 is a reactive distillation column, 2 is a condenser, 3 is a dechlorination column, 4 is an exhaust gas cleaning column, 5 is a redox electrometer, 6 is a bromine storage tank, A is chlorine, and B is an aqueous solution containing bromine ions. , C is water vapor, and D is drain.

Claims (1)

[Claims] In a method for continuously producing bromine by introducing a bromide ion-containing aqueous solution from the top of a reactive distillation column, introducing chlorine from the bottom or middle part of the column, and introducing steam from the bottom of the column, and recovering liberated bromine by distillation, Distilled vapor from the top of the column is condensed and separated from uncondensed flue gas containing condensed bromine, and a portion of the raw material bromine-containing water bath liquid is brought into contact with the uncondensed flue gas to remove uncondensed waste gas contained in the flue gas. The reactive chlorine is reacted with bromide ions and then introduced into the reactive distillation column, and the amount of chlorine supplied to the reactive distillation column is adjusted so that the redox potential of the bromide ion-containing aqueous solution after the contact treatment is constant. On the other hand, the raw material bromine ions are removed by contacting some or all of the remainder of the water bath solution with the condensate to react the dissolved chlorine in the condensed bromine with the bromine ions, and then the bromine solution is separated, and after the contact treatment. A method for continuous production of bromine, characterized in that each of the above operations of introducing an aqueous solution containing bromide ions into a reactive distillation column is performed continuously.