Are you MCERT-ain about air pollution?

There are several factors to consider with the control of emissions to air including process optimisation and abatement. Dr Tony Smith of Envirocare reports on the need for MCERTS.

Manufacturing industry in the UK and Europe is being constantly bombarded with new environmental legislation to cover every aspect of its existence, from the control of emissions under PPC to the Emissions trading scheme. Almost all of these new controls are being brought about by the implementation of European directives, which have been produced in order to meet our commitments to global environmental issues. This means that there will be no slackening of the pace of the introduction of new legislation, so industry has got to learn to live with it – or die. In some cases this is exactly what will happen; where some companies will not or cannot evolve, they will perish and new technologies will arise to take their place. This is the way of the business world.

And this is true about emissions to air. For about 50 years in the UK there has been a gradual tightening of controls on the emissions of pollutants to the air, from the Clean Air Act in the 1950’s to the recent phased introduction of PPC. This has seen a corresponding development of combustion technologies and abatement and has also been a driving force for process improvements.

Types of Air Pollution Control

Air pollution control can take many forms and there is a recognised hierarchy of control which includes:

  • Elimination or substitution of the substance causing the emission problem;
  • If this is not possible then reduction of the emission by process change/optimisation;
  • Finally, if the above are not possible, abatement of the pollutant.

The first two controls require a complete understanding of the process but are often successful as they lead to lower environmental impact without resource implications. The latter, abatement route, often referred to as ‘end-of-pipe’ technology, can lead to the replacement of one emission by another (as in incineration) or create another effluent stream (as in scrubber liquor), except where some form of recovery/recycling of the pollutant is practised (solvent recovery). As a result of this, process modification/optimisation is always the preferred initial approach to reduction of emissions followed by abatement options including recovery and finally other abatement options.

Fundamental to all of this control is measurement – “if you cannot measure it, you cannot control it”.

Emission Monitoring

At the start of any project to reduce pollutant emissions to air, must be the requirement to understand the process and to profile the current emissions to air. This can be undertaken utilising a multitude of techniques, including on-line sampling and grab sampling, but in all cases great care must be taken in choosing the correct methodology and protocol, otherwise time, effort and money may be wasted. Indeed if an incorrect monitoring technique is chosen then any data produced may be suspect and may lead to inappropriate decisions regarding process optimisation or abatement equipment procurement.

These could be very expensive mistakes!!

To ensure the quality of the data produced, it is important that the manufacturing industries utilise the expertise of environmental consultancies with stack sampling skills. The recent introduction of MCERTS, the Environment Agency’s monitoring certification scheme, has led to an upsurge in the numbers of companies in the stack sampling field, who have undertaken UKAS accreditation to ISO 17025. This is good news for everyone concerned, as it has improved the quality of the data for compliance sampling but also recognises the expertise of the stack sampling engineers and the quality of the operations of the stack sampling companies.

MCERTS Accreditation

Choosing an MCERTS accredited company to undertake compliance sampling is recommended by the Environment Agency and is likely to improve the Operator Monitoring Assessment score (OMA). However a similar choice should be made for process optimisation or abatement sizing studies. It is likely that any stack sampling company which possesses MCERTS accreditation, will have the competence and expertise within its staff and organisation to assist with developing an appropriate investigative study.

When choosing a supplier, it is important that the stack testing company can demonstrate a thorough understanding of the specific industrial process. Not all emissions are simply one pollutant or a small number of discrete pollutants and an understanding of the chemistry of the process is vitally important. In this case “what goes in, must come out” is not necessarily true, as it may come out changed chemically or in a different form.

As an example, many textile processes involve additions of chemicals to fabric substrates followed by direct gas-fired heat treatment. The emissions from such processes are often very complex and can contain high levels of VOC and ‘blue fume’ as well as formaldehyde. Many of the emissions are not derived from the added chemicals but are artefacts of the process chemicals on the textile substrate or the substrate itself. Similarly, apparently high levels of VOC may in fact be from unburned methane from the direct gas-fired process and not from true VOC. Finally
‘blue fume’ is often semi-volatile VOC in aerosol form, which must be sampled isokinetically to derive the correct data.

If the emissions from such a textile process were not sampled correctly, then decisions about abatement control may be made, which will not solve the problem. This would indeed be a potentially very expensive mistake.

Continuous Emission Monitoring Systems

Once a process is optimised, control may still be required in the form of periodic compliance sampling or there may be the requirement to install some form of continuous emission monitoring system (CEMS), also known as automated measuring system (AMS) in Europe. During 2004 a new European standard (EN 14181) will be published and this will have far reaching consequences for process operators and stack testing companies.

The new standard specifies procedures for establishing quality assurance levels for validation at selection, commissioning and periodic surveillance testing of AMS. Once again MCERTS becomes very important here, as only MCERTS accredited companies may undertake this type of testing.

In conclusion, there are a number of factors to bear in mind when considering the control of emissions to atmosphere. A complete understanding of the process concerned is extremely important, so that any changes made can be properly quantified in terms of their influence on emissions to atmosphere. This may be undertaken by the process operator, in conjunction with an appropriately qualified and experienced stack sampling company, ideally MCERTS accredited. Following this, if there is a requirement to install abatement equipment, then the choice of the most appropriate equipment can be made using good quality, relevant data and its efficiency can be determined after installation, by an MCERTS accredited company. Finally, if an AMS is to be installed, the initial testing and surveillance testing must be undertaken by an MCERTS accredited company.

So in terms of air pollution control, the future is MCERTS shaped!

By Dr Tony Smith, Envirocare.

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