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Bromine is a very reactive material and therefore finds widespread use in many parts of the chemical industry. For example, it is used in the production of a wide range of organic intermediates, dyestuffs, agrochmicals and fire retardants.

The reactions to form the chemicals usually generate hydrogen bromide as a by-product as in the following example:

R - H + Br2 -> R - Br + HBr

Cleanly, no more than half the bromine added ends up in the product -

the rest being rejected as hydrogen bromide gas and as dissolved bromides(often rejected in washing solutions). But bromine is an expensive raw material and economic good sense suggests that it should be recovered.hydrogen bromide in water and then recover the bromine from this solution as well as from other aqueous waste streams. We can then purify the bromine to give a product (typically better than 99.5% bromine) to re-use in the reactors.

process Description

The system shown in figure 1 is designed to recover 26 tonnes/day of bromine from two waste solutions; on of hydrobromic acid from an absorber an the other of sodium bromide.

The two feeds are mixed in a bulk storage before being pumped (1) to the vent scrubber (2) as a 12% HBr, 5% NaBr solution The feed then passes to the reaction column (3) where it is reacted with chlorine vapour. The chlorine liberates elemental bromine from the dissolved bromides. This is then stripped out by the live steam fed near the column base.

The bottom product leaving this column, stripped of bromide, is then cooled (4) before passing for effluent treatment, while at the column head, steam and bromine are condensed (5) and separated (6). The water layer returns to the reaction column (3) while the bromine, contaminated with chlorine and water, passes to the purification column (7) for further treatment.

The purification column distils the bromine to remove water from it (as bromine/water azeotrope), which is then condensed and separated in items 5 and 6. It also removes chlorine, which passes out to the vent scrubber. At the column base, purified bromine leaves the reboiler (11) - fitted with tantalum bayonets - passing to storage via a cooler (8). Transfer from the storages (10) is normally carried out by blowing using air or nithrogen pressure.