JPS5941922B2 - Bromine recovery method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering bromine from a bromine-containing gas source.

Details (7) A step in which a gas containing bromine is brought into contact with a strongly basic anion exchange resin to adsorb bromine, and the resin that has adsorbed bromine is heated to 60 to 130°C to desorb bromine from the resin. The present invention provides a method for recovering bromine, which comprises the steps of:

Methods for producing bromine are divided into (1) the bittern method, (2) the seawater method, and (3) natural can washing, depending on the raw material.In Japan, the seawater method is mainly used.

The seawater method includes the sulfur dioxide gas method and the hydric soda absorption method.

In the sulfur dioxide gas method, sulfuric acid is added to seawater to adjust p)I to about 3, and then chlorine is blown in to liberate bromine.

(1 set). 2NaBr+C1-+Br2+2NaCV
(1) This is allowed to flow down from the top of the generation tower, and air is blown from the bottom to drive out bromine from the seawater (referred to as generated gas).Next, sulfur dioxide gas is blown into this generated gas to convert the odor into hydrogen bromide. Reduce and absorb into water together with sulfuric acid (2 formulas).

B r 2 +802 + 2H2()” 2HB r
+H2804 (2) Next, when this is allowed to flow down from the top of the distillation column and steam and chlorine are blown into the bottom, hydrogen bromide is oxidized by chlorine, and the liberated bromine is distilled out together with the steam (Equation 3).

2HBr+C1-)Br2+2HCl (3) After this is cooled and condensed, water is separated to obtain Japanese bromine, which is purified by redistillation to produce a product.

The hydric soda absorption method is a method in which the generated gas is absorbed into an aqueous hydric soda solution (Formula 4), then sulfuric acid is added to liberate bromine (Formula 5), and the bromine is recovered by steam distillation.

3Br +6NaOH-+5NaB'r+NaBrO3
+3HO(4) 5NaBr+NaBrO3-t-3H2804→3Br
2+3Na2S04+3H20 (5) The bromine concentration in seawater is as low as 60 to 651119/l, so in the method described above, in which chlorine is blown in and freed bromine is expelled with air, the bromine concentration in the generated gas varies depending on the generation conditions, but at most It is 0.7-0.8-/l.

Therefore, in order to recover bromine from this generated gas, the sulfur dioxide gas method requires sulfur dioxide gas and chlorine for distillation, and the hydric soda absorption method requires hydric soda and sulfuric acid. be.

Since these drugs are required in large quantities as shown in formulas (2) to (5), they currently account for a large portion of the manufacturing cost.

The present invention was discovered as a result of intensive research in consideration of these problems and in order to find a method for efficiently recovering bromine from gas with a low bromine concentration.

That is, according to the method of the present invention, (1) no chemicals such as hydrolytic soda or sulfur dioxide gas are used, so raw material costs can be greatly reduced.

(2) It is advantageous in terms of materials because it does not use highly corrosive sulfuric acid.

It is well known that bromine in an aqueous solution is adsorbed by a strongly basic anion exchange resin, and methods that form polyhalides and perform ion exchange as shown in formulas (6) to (9) are old.

J. Aveston measured the amount of bromine adsorbed using saturated bromine water.

According to it, the exchange capacity is 3.74 eq/kg dry.
27. with resin's strongly basic anion exchange resin Amberlite IRA-400. Oeq/kg-dry ree
It is sin.

(Chemistry and Industry, Se
p, 14, 1238 (1957')).

Additionally, there is Japanese Patent No. 212,506 which attempts to utilize this property to directly recover bromine from seawater using a strongly basic anion exchange resin.

This is done by adding an oxidizing agent to seawater to liberate bromine, adsorbing it to a strongly basic anion exchange resin such as Amberlite IRA-400, and then desorbing it with a mixed aqueous solution of sodium hydroxide and sodium sulfite. be.

In addition, a solution containing liberated bromine is treated with a continuous fluidized bed method,
Adsorption of bromine onto strongly basic anion exchange resins was initiated by US Pat. No. 307'5830.

Further, US Pat. No. 3,037,845 discloses a method for efficiently desorbing sulfite using an aqueous sulfite solution.

However, these known methods involve adsorbing bromine in an aqueous solution onto a strongly basic anion exchange resin, and all of the methods use agents reactive with bromine to desorb the adsorbed bromine. There is nothing to suggest that.

As a result of the research conducted by the present inventors, bromine in the gas is easily adsorbed on a strongly basic anion exchange resin even if it is diluted, and the adsorbed bromine is
It was found that it can be easily desorbed by heating above ℃.

In an attempt, an aqueous solution in which bromine was released by blowing chlorine into seawater with a bromine concentration of 65/Q/7 under acid conditions was passed through a column packed with strong basic anion exchange resin Amberlite I RA400. When the amount of adsorption was measured,
It was only 0.7 eq/l-wet resin.

Further, this resin was exposed to steam and heated to 100°C, but almost no bromine was desorbed.

The present invention will be explained in more detail below.

The resin necessary for the present invention is a quaternary ammonium anion resin, which is usually called the most basic or strongly basic anion exchange resin.

Weakly basic anion exchange resins have a low adsorption amount and do not desorb even when heated, and in some cases the resin deteriorates.

Examples of strong basic resins include Amberlyte IRA-400 series and Amberlye 1- manufactured by Rohm and Haas Co., Ltd.
-900 series, Amberlist A-26, Amberlist A-27, Amberlist A-29, etc.

These strong basic resins are usually commercially available in the chlorine form, so if it is undesirable for the recovered bromine to be contaminated with chlorine, it is best to convert it into the bromine form in advance with an aqueous solution of a bromine compound such as sodium bromide.

If contamination with chlorine is not a problem, use -C as it is commercially available.

Moreover, since commercially available resins and resins made into brominated form in aqueous solutions contain water, they can be dried before use if necessary.

When a gas containing bromine contains moisture in the form of steam or mist, the adsorption amount decreases.

If the bromine concentration in the gas is 5 In9/1 or higher, the effect is small, but if it is lower than that, for example, in the case of so-called generated gas, where it is 1 to 1/l or less, the effect of moisture contained in the gas is likely. It's thick.

When dealing with such a gas containing moisture, a porous, strongly basic anion exchange resin with good desorption properties is desirable.

Particularly desirable are resins with a high exchange capacity and high porosity, such as Amberlyst A-26.

Since the generated gas contains some mist in addition to water vapor corresponding to the vapor pressure, it is more effective to contact the resin after removing the water.

The method of contacting the strongly basic anion exchange resin with the gas is not particularly limited, but in order to make the most of the adsorption capacity of the resin, it may be brought into contact continuously in a fixed bed, or the gas may be brought into contact with the gas from the bottom of a packed column. It is preferable to supply and give an upward flow to form a fluidized bed and bring them into contact.

In the latter case, it is best to repeat it two or more times.

If the temperature exceeds 40°C, the amount of adsorption decreases, so it is desirable that the temperature is lower than that.

When desorbing adsorbed bromine from the resin, adsorption tower power)
A part or all of the resin may be extracted and desorbed, or the resin may be desorbed while being filled in the adsorption tower.

Bromine adsorption amount is 6.7eq/1-dry-resin
Strong basic salt ion exchange resin Amberlite 40
The desorption rate of 0 changes depending on the temperature as shown in table 60.
It showed a remarkable desorption rate above ℃.

Desorption was carried out by blowing in a very small amount of air and then heating the external cutting edge using an oil bath.

Note that ion exchange resins have incomplete heat resistance, so 13
It is desirable to desorb at temperatures below 0°C.

Furthermore, it has been found that when heated steam is used in direct contact with the resin for heating during desorption, the desorption rate increases even at the same temperature.

This is thought to be because the resin swells slightly due to the thermal steam, making it easier to desorb.

In addition, when heated steam is used, it is convenient because the steam also serves as a carrier for the desorbed bromine.

The desorbed resin can be reused for adsorption.

Bromine recovered in this way can be condensed by cooling to obtain liquid bromine.

This will be explained below using examples.

Example 1 Amberlite IRA-400 manufactured by 01 M&Haas Co., Ltd.
was made into a bromine form and dried under vacuum at 40°C.

This resin was packed into a 100rrll column, and the bromine concentration was 2.
0 m9/l! of bromine air mixed gas 100m from the top.
The flow rate was 17 sec.

After 7.5 hours, the adsorption zone that changed color moved to the bottom, so ventilation was stopped.

After measuring the adsorption amount, 6.7eq/1-dry re
sin, and the adsorption was almost complete.

When this resin was transferred to another container and exposed to steam at 100° C., 66 was detached.

The yield of bromine was 35 g.

Also, when the desorption resin was transferred to the adsorption ram again and the same test was conducted, only the amount that was desorbed the first time was adsorbed again, and almost the entire amount was desorbed.

Example 2 A porous strongly basic anion exchange resin Amberlyst A-26 manufactured by Munich & Haas was converted into a bromine form, vacuum dried at 40°C, and 200 ml of the resultant was packed into a column.

Seawater containing bromide at a concentration of 65 m9/l was pH adjusted with sulfuric acid.
The temperature was adjusted to 3.0 and chlorine gas was blown in to liberate bromine.

Bromine was expelled with air to obtain a generated gas containing water at a saturated vapor pressure at 20° C. and having a bromine concentration of 0.8 to 1/l.

This gas is fed into the above column from the top at 100ml/sec.
Aerated at a flow rate of .

After 240 hours, the adsorption zone that changed color reached the bottom, so the ventilation was stopped.

The adsorption amount was measured and was 4.2 eq/A'-dry.
It was resin, and the adsorption was almost complete.

One half of this resin was transferred to another container, and one half was heated externally to 100°C while 100°C water vapor was blown in, and the other was heated to 100°C while blowing a very small amount of air.

The desorption rate of the former was 42% and the yield of bromine was 14.1 g, and the desorption rate of the latter was 37% and the yield of bromine was 12.4.9 g.

Next, the same test was repeated once again using the desorbing resin, and only the amount that had been desorbed was adsorbed again.

When water vapor at 100° C. was applied, the desorption rate was over 100% of the adsorption amount in the second time.

Claims (1)

[Claims] 1. When recovering bromine from a bromine-containing gas, a step of bringing the bromine-containing gas into contact with a strongly basic anion exchange resin, and heating the bromine-adsorbed resin to 60 to 130°C. A method for recovering bromine comprising the step of desorbing bromine by heating. 2. The method according to claim 1, characterized in that a porous strong basic anion exchange resin is used as the strong basic anion exchange resin. 3. The method according to claim 1 or 2, characterized in that the resin is heated by direct contact with water vapor.