Module:5
Lecture:25 Bromine
Dr. N. K. Patel
Module: 5
Lecture: 25
BROMINE
INTRODUCTION
The bromine name derived from Greek word brómos, which means
"strong-smelling" or "stench". Bromine (Br2) atom is belongs to the halogen
group having atomic number 35. It was first isolated by, Carl Jacob Löwig
and Antoine Jerome Balard, in 1825 – 1826. Elemental bromine is a red-brown
liquid at room temperature. It is a corrosive and toxic in nature and having
properties between those of chlorine and iodine. Free bromine occurs as
colourless soluble crystalline mineral halide salts as it does not occur in nature.
The bromine element is easily extracted from brine pools due to its high
solubility. Organo bromine compounds were readily converted to free
bromine at high temperatures; this process has the effect of stopping free
radical chemical chain reactions. This effect makes organo bromine
compounds useful as fire retardants and more than half of the bromine
produced industrially worldwide each year is used for the same.
Unfortunately, a volatile organo bromine compound was converted into the
free bromine atoms in the atmosphere and leads to the ozone depletion. As
a result, many organo bromide compounds that were in common use
formerly the pesticide methyl bromide have been abandoned.
MANUFACTURE
1. From sea water
Raw material
Basis: 1000kg of bromine from sea water (95% yield)
Sea water
1250kg
Chlorine gas
445kg
Sulfurous acid
625kg
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Module:5
Lecture:25 Bromine
Dr. N. K. Patel
Reaction
Manufacture process
H2O and Cl2
Br2(g), Cl2(g)and H2O(g)
H2SO4
Water
Water
Condenser
Condenser
Cl2
Purified brine
Water
Absorption
tower
Bromine
Br2 and
H2O
Steam
Br2
Water
NaOH or
NH3
Separator
Neutralizer
Distillation
Waste brine to other use or
well disposal
Figure: Manufacture of Bromine from sea water and brine
Block diagram of manufacturing process
Diagram with process equipment
Animation
Bromine was extracted from seawater, which typically containing
bromide ions at 65 – 70mg/l concentration.
Brine from sea water was first chlorinated using chlorine gas, so that
bromide was oxidized to the free bromine. The free bromine was then treated
with sulfurous acid which converted free bromine into the hydrobromic acid.
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Module:5
Lecture:25 Bromine
Dr. N. K. Patel
Then acid solution was treated with recycle chlorine gas from separator
which reoxidized the bromide back to free bromine. While unconverted acid
solution was neutralized with caustic or ammonia and sent back to other
uses.
After the second chlorine oxidation, the vapours which containing
bromines and water were condensed and run to the separator where water
vapour and chlorine gas were separated out and recycled to the process.
The crude bromine was purified in the distillation column. The bromine vapour
was condensed, stored and packaged.
Other method
Bromine can be produced from well brines where only one oxidation
by chlorine is required. Crude bromine was condensed, separated from the
water present using distillation.
2. By steaming out process
Raw material
Basis: 1000kg of bromine by steaming out process (95% yield)
Raw brine
1250kg
Chlorine
445kg
Reaction
Manufacture process
Generally the concentration of bromine in ocean water is relatively
dilute. Air proved as the best economical blowing out agent, treatment of
rich bromine sources brine, steaming out the bromine vapour is the more
suitable processes.
Brine was first pre-heated in heat exchanger at 900C then the hot brine
was run into the chlorinator. Partial chlorination of brine was carried out. Then
sent to steaming out tower where brine was contacted with steam and
chlorine counter currently and waste gases was discharged form chlorinator.
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Module:5
Lecture:25 Bromine
Dr. N. K. Patel
Halogen containing vapour in steaming out tower was passed to the
condenser. The vapour was condensed and then enters into gravity
separator where upper layer containing water, Cl 2 and Br2 layer was returned
to steaming out tower and partially recycled to chlorinator.
Waste
gases
Chlorinator
Chlorine
Br2 + Cl2 + H2O
Condenser
Steaming-out
tower
Brine
H2O + Cl2 + Br2
Chlorine &
Steam
Cl2
CaO
Condenser
Crude
Br2
Neutralizer
Raw
brine
Gravity
separator
Cl2
Heat
exchanger
Distilling
column
Waste
brine
Bromine
fractionating
column
Br2
Steam
Residue
Steam
Bromine
Figure: Manufacture of Bromine by steaming-out process
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Lecture:25 Bromine
Dr. N. K. Patel
Block diagram of manufacturing process
Diagram with process equipment
Animation
The bottom layer containing bromine and chlorine was separated out,
which was then run into the column where residue separated from bottom
and vapour condensed in condenser where chlorine was recycled and
bromine purification was carried out in fractionating column where a trace of
chlorine vapour was recycled.
Raw waste loads
In the bromine extraction process, the raw wastes include all of the
spent brines as well as minor amounts of materials which were added to the
process stream.
Waste Material
Kilograms per 1000kg of Product
Plant (I)
Plant (II)
Spent brine solids
113570
76500
Bromine (from leaks)
Not given
Nil
Brine solids (from leaks and Not given
0.5
spills)
In the both plant, the brine solids contains the chlorides of calcium,
sodium, magnesium and potassium. The exact compositions are dependent
on the composition of the incoming brine raw material. The input brine at
Plant I and Plant II are 0.3% and 0.4% bromine. The total amount of the brine
solids raw waste was depended on the amount of bromide in the brine
relative to the other dissolved solids.
Plant water use
Pump seals, noncontact cooling and boiler feed water was used for
the dilution of brine.
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Lecture:25 Bromine
Dr. N. K. Patel
The consumption pattern of water is as follow
Consumption
Brine dilution
Other process water
Boiler feed
Noncontract cooling
Liters per 1000kg of Product
Plant (I)
14700
370
1770
Plant (II)
9740
13210
57030
Between the two plants, the different volume of water was used. But
still the total process contact water is similar in plants.
Wastewater treatment
At Plant I, all brine process waters were returned to the brine cavity
while noncontact cooling water was discharged. Then the waste brines were
treated with lime to effect neutralization before they were returned to their
source.
In the Plant II, the cooling water was discharged without treatment. The
neutralization of spent brine and process wastewater using different agents
were carried out with ammonia and then settled in ponds prior to return to
the brine cavity.
Effluent
The neutralized brine and process water wastes were returned to the
brine cavity in both the plants. While cooling water and boiler blow down
were discharged or used for the noncontact applications.
Engineering aspects
 Kinetics and thermodynamic
The steaming-out process for bromine formerly carried out at sub
atmospheric pressure. In the double-stage process the tail brines from the first
stripping were stripped again under greater vacuum. In the steaming-out
process it was further heated to the boiling point by steam. Additional brine
was required to strip the bromine from the brine. In the modified process
vacuum was applied, which eliminates the need for the steam to heat the
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Lecture:25 Bromine
Dr. N. K. Patel
brine by matching the vapour pressure of the brine. The capacity of a given
size of contact towers was increased by using lower volume of steam in the
vacuum process. A further benefit of vacuum process operating at lower
temperature, chlorine undergoes fewer side reactions and less hydrolysis so
chlorine use can be reduced. A second stripping of the tail brine was done in
two-stage process. Other advantages of vacuum process were less amount
of lime required to treat the spent brine, plant maintenance costs was lower
and decreased waste gases.
PROPERTIES
 Molecular formula
 Molecular weight
 Appearance




Odour
Boiling point
Melting point
Density
 Refractive index
 Vapour density
 Solubility
: Br
: 79.90gm/mole
: Red-brown (gas or liquid), metallic
luster (solid)
: Sharp and penetrating odour
: 58.80C
: -7.20C
: 3.12gm/cm3 at 200C, 2.93gm/ml at
590C
: 1.647 at 200C,
: 5.5
: Soluble in water
USES
 In manufacturing of bromine compounds
 In cooling towers for controlling the bacteria and algae
 In desizing of cotton, in bleaching of pulp and paper, hair waving
compositions and air conditioning absorption fluids
 In the manufacturing of brominated vegetable oil which is used as an
emulsifier in many soft drinks
 For maintenance of swimming pool
 For reduction of mercury pollution from coal-fired power plants,
poisonous methyl bromide and ethylene bromide were widely used as
pesticide to fumigate soil and housing by tenting method
 In well-drilling fluids
 In film photography
 As an intermediate in the manufacture of organic chemicals
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Lecture:25 Bromine
Dr. N. K. Patel
 Used over chlorine by one anti-parasitic enzyme in the human immune
system
 Organo bromides are produced enzymatically from bromide by some
lower life forms in the sea, particularly algae and the ash of seaweed
was one source of bromine's discovery
 As a pharmaceutical, the simple bromide ion, Br-, has inhibitory effects
on the central nervous system and bromide salts were once a major
medical sedative, before being replaced by shorter-acting drugs
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