Recommendations of the GRP
for the caustic-chlorine industry
The economic and social benefits provided by the causticchlorine sector is being
eclipsed by the environment damages caused by chlorine and chlorinated products and by the
use of mercury cell technology. This places a question mark over the future of the
industry. While it must be acknowledged that the sector has improved a lot in areas like
energy and water, it has failed miserably in mercury pollution and pollution being caused
by its products (product stewardship). There is large scope for improvement in the indian
caustic-chlorine sector and the sector will have to work very hard for its future
survival.
8.1 FOR THE
CAUSTIC-CHLORINE INDUSTRY
8.1.1 Input sourcing phase
 The quality of salt needs to be substantially upgraded in India. In
Western countries, general preference is given for using evaporated salt. This is a major
reason responsible for reduction in sludge and hence, mercury emission. Though it might
not be economically viable to go for evaporated salt in India, nevertheless, Indian
companies will have to improve their input salt quality by other means, for instance by
undertaking salt upgradation process before salt brine purification.
The amount of water
consumed by caustic-chlorinecompanies is rather small compared to other industrial
sectors. It is the assessment of GRP that rainwater harvesting in the plant alone will
enable companies to meet a substantial portion of their annual water requirement.
Therefore, it makes economic as well as ecological sense for the caustic-chlorine
companies to undertake rainwater harvesting at their plant.
At present, the practice of
sourcing energy from renewable sources is very poor. Given the potential of sourcing
energy from hydrogen, which is one of the outputs of the industry, effort should be made
to utilise the entire hydrogen for energy generation.
8.1.2 Production and conversion phase
To avoid another disaster like Minamata in Japan, mercury cell
companies must either regulate mercury emissions or move to membrane cell technology.
There are certain practices
that need to be followed and certain technology that needs to be installed for reducing
the mercury pollution from the existing mercury cells.
Housekeeping in mercury
cell plants needs to be upgraded substantially and detailed operation and maintenance
guideline for mercury cell need to be put in place and followed religiously.
Companies need to improve the awareness of the employees regarding
mercury pollution.
All streams, gaseous, liquid and solid should be properly treated for
mercury contaminant’s, including the ventilation from cell room.
Existing mercury cell companies need to retort entire mercury released
through solid waste stream, including those that are generated during maintenance.
Existing mercury cell companies need to remove mercury from each and
every product they produce by installing suitable recovery technology.
The current utilisation
pattern of hydrogen is both environmentally and economically unsustainable in the Indian
industry. Hydrogen is one of the cleanest fuels and an ideal candidate for generating
energy in a stationary power plant. With the new generation fuel cells achieving a energy
conversion efficiency of 90 per cent, the use of hydrogen in fuel cells for generating
power in caustic-chlorine industry has the potential to save as much as 30 per cent of the
power cost of the industry. This will also significantly reduce the air emissions from
plant. Therefore, the caustic-chlorine industry needs to move towards the use of hydrogen
in fuel cells for generating energy.
The approach of Indian
companies towards resource and energy conservation as well as environmental pollution is
fragmented. It is important that an integrated and longterm strategy is adopted by the
companies to make their operations environmentally sustainable.
Chlorine destruction unit based on lime (calcium hypo) should be
immediately replaced by sodium hypo plant.
The quality of sodium hypo produced from the chlorine destruction unit
should be such that the entire hypo is sold. No discharge of hypochlorite to water should
take place from the chlorine destruction unit.
Indian companies should minimise the consumption of sulphuric acid by
means of one or more of the following options:
On-site re-concentration in closed loop evaporators
Using the spent acid in other processes in the plant
Returning the spent acid to a sulphuric acid manufacturer for
re-concentration.
Maximum focus should
be paid on recycling the wastewater within the process rather than discharging it after
treatment.
Mercury bearing brine sludge should be stabilised before being
put in the secured landfill site.
In the case of non-mercury bearing brine sludge, instead of its
disposal, companies should try to make products like barium sulphate.
Existing mercury cell companies are not able to account for more
than 50 per cent of the total input mercury in various output and waste streams. It is
recommended that a detailed study be taken by each company to account their entire mercury
consumption. l Storage of large amount of chlorine should be avoided from safety point of
view. The best option for companies is to use chlorine on the site as soon as it is
produced.
Indian companies should upgrade their chlorine, HCl and hydrogen
safety systems to meet the global best performance.
The off-site emergency plan for accidents is almost absent in
Indian caustic-chlorine companies. Considering the safety hazards associated with the
production process and the storage of products, off-site emergency plan should be
implemented by each and every company.
8.2 FOR THE GOVERNMENT
The onus for improving the environment performance of the caustic-chlorine sector
also lies on the government. The authorities can play a major role by ensuring that its
policies support and promote environment friendly trends. In order to control and
eliminate the pollution from caustic-chlorine sector, the government needs to take
following measures:
8.2.1 Phase out mercury cell plants
The government should develop and implement a time-table for phasing-out the mercury cell
plants. The mercury pollution from existing mercury cell plants are very high and poses
serious threat to the public health. In this context, it is recommended that:
Mercury cell
companies should be asked to close down or the plants should only be allowed on the basis
of revised emissions norms for mercury. By doing this, the mercury pollution in India can
be straightaway reduced by 40 per cent
8.2.2 Revise the existing pollution control norms
The government needs to revise pollution control norms to reflect the impact of the
pollution on environment. In this regard, it is recommended that:
The total mercury emissions from existing mercury cell plants be
restricted to 10 gm per tonne caustic soda produced. This should be verified with the
input mercury data. Mercury cell companies should be asked to give a full break-up of
input and output mercury. Currently, companies are not able to account even 50 per cent of
the input of mercury.
Restrictions on water consumption should be put on the industry
and be regularly monitored. For membrane cell
8.1.3 Product use and disposal phase
Long distance transportation of chlorine and caustic soda lye
should be discouraged. Ideally, companies should use the products at the plant only.
Companies should utilise their entire products. The disposal of
the products has a high environmental cost that the society has to pay.
Spent sulphuric acid should not be sold to the informal sector
where it is likely to cause pollution during use. Companies should sell spent sulphuric
acid only for those uses where it is likely to cause least pollution during use.
The use of chlorine is declining and is going to decline further
due to environmental pressures. In India, the paper industry, which is the major user of
chlorine, is slowly shifting towards chlorine dioxide and other nonchlorine based
bleaching chemicals. Similarly, chlorine use in pesticide industry is going to decrease
substantially due to POP convention. It is important, therefore, for the industry, if it
plans to stay in this business to find alternatives for the sound use of chlorine, if they
exists. Industry should also work to delink the production of caustic soda with chlorine.
With increasing pressure on chlorine from environment front, industry will have to think
in terms of producing caustic soda on stand alone basis to meet the requirement of caustic
soda. plants be restricted to 10 gm per tonne caustic soda produced. This should be
verified with the input mercury data.
Mercury cell companies should be asked to give a full break-up of input and output
mercury. Currently, companies are not able to account even 50 per cent of the input of
mercury.
Restrictions on water
consumption should be put on the industry and be regularly monitored. For membrane cell
companies, process water consumption should be restricted to 2.5 tonne per tonne caustic
soda produced and for mercury cell companies, the process water consumption should be
restricted to 4 tonne per tonne caustic soda produced. companies, process water
consumption should be restricted to 2.5 tonne per tonne caustic soda produced and for
mercury cell companies, the process water consumption should be restricted to 4 tonne per
tonne caustic soda produced.
Companies should be asked to dispose mercury bearing brine sludge
only after stabilisation. If the leachate during the TCLP test of brine sludge solids
contains less than 0.02 mg per litre mercury, it can be considered as stabilised brine
sludge.
The standard for concentration of chlorine in ambient air should
be reduced to 1 mg/Nm3 from its current level of 3.0 mg/Nm3 and the standard for the
concentration of mercury in cell room should be reduced to 0.01 mg/Nm3 from its current
level of 0.3 mg/Nm3.
Government should make it mandatory for companies to put in place
offsite disaster management plan.
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