Integrated management: the art of doing two things at once
If the handling of exhausts and effluents are looked at simultaneously, and combined with the opportunities for recycling and recovery, not only will a manufacturing process be more environmentally responsible, it can also be made more profitable.
The final aim of any waste treatment strategy is to find the most cost-effective
technology for discharging the minimum volume of waste into the environment.
All too often the subject of waste treatment, which includes air pollution,
is handled piecemeal, whereas taking an overall, integrated approach is much
more efficient financially and effective technically.
There are five distinct areas that can be defined within an integrated waste
i. minimisation of waste produced,
ii. gas abatement,
iii. liquid effluent
iv. chemical recovery,
v. final disposal.
The need to minimise waste in the first place may seem self evident, but IEM
Technologies Ltd was recently asked to look at the treatment of an exhaust stream
with a very high SO2 content resulting from H2S incineration.
Simply asking the question, ‘Can emissions be decreased by reducing the levels
of H2S being sent into the system?’ lead to an internal audit of usage that
may cause an improvement in output levels. Though this is quite a dramatic example,
it is not an isolated case.
Waste gas abatement
Abatement of industrial waste gases employs various technologies, one of the
most commonly used is wet scrubbing, particularly where the exhaust stream is
At its simplest, this will be a water system, though water alone is unlikely
to provide adequate removal levels. IEM Technologies has been a specialist provider
of chemical scrubbing systems for use by compound semiconductor fabricators
for over a decade. The waste streams from these fabricators contain high levels
of arsine and phosphine and are some of the most technically challenging to
be found in any industry.
In IEM Technologies’ experience, the key to the effective use of scrubbing
technology is the careful design of the scrubbing regime and the accurate and
precise control of its delivery. Continuous, computer aided monitoring of key
operating parameters ensures that removal levels are maximised and that the
cost of the scrubbing chemicals is minimised.
Continuous monitoring also provides advance indication of impending maintenance
issues, which reduces unplanned downtime and aids planned maintenance programmes.
Remote monitoring is possible with IEM Technologies’ systems using an Ethernet
connection, which is invaluable in fault diagnosis.
Liquid effluent may be produced directly from the industrial process itself
or as a by-product of toxic gas abatement. But whatever its origin, the aim
is always the same – to remove the toxic content and to discharge clean air
and water with the minimum volume of waste needing to be disposed of and the
maximum sent for chemical recovery and recycling.
Water is perhaps the most obvious candidate for recycling, either within the
process itself or in a symbiotic relationship with another activity. IEM Technologies
is currently advising on a water treatment system in India in which water from
the treatment of animal slurry is used for irrigation.
This is part of a larger system providing potable water from a bore hole. In
Taiwan, where water is a much scarcer resource than in the UK, the level of
water recovery has been crucial in IEM Technologies winning a number of contracts
to install toxic gas abatement systems at semiconductor wafer fabrication plants.
In an ideal world, the best waste treatment solution would be one that removes
all contaminants but in the real world, the best solution will always balance
environmental responsibility with what is commercially acceptable. An overall
approach to costs is imperative. Initial outlay must be considered alongside
running costs, and cheapest is not always best. Reliability is the result of
both good initial build quality and commissioning and a well implemented maintenance
programme and saves one of the biggest costs of all: that of system failure
and consequential production downtime.
It is easy to overlook the value of investment in initial plant commissioning
in ensuring that the treatment system is operating at optimum performance. IEM
Technologies is currently advising on improvements to the acid removal system
at a plating plant.
Initially upgrading the system was under discussion but as soon as on-site inspections
started, it became evident that the scrubbing system had not been properly commissioned,
and together with other problems, the scrubbing tower packing was inadequate.
This, unsurprisingly, has resulted in the plant not operating very effectively
and running costs being higher than necessary.
Costs take many forms, some of which are not numerical. Public image and profile
may be difficult to put a price on but can be of major importance. Public appearance
was certainly imperative at De Montford University in Leicestershire.
A gas removal system was needed by the electronics department but on a building
of architectural importance. Discharge stacks are not noted for their beauty
but IEM Technologies’ design team was able to design and build an aesthetically
acceptable stack that met local planning restrictions.
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