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 Following publications by the Expert Panel on Air Quality Standards (EPAQS) in 1995 and the UK Committee on the Medical Effects of Air Pollutants (COMEAP) in 1997, documenting the relationship between measured concentrations of PM10 (particles with an aerodynamic diameter less then 10 mm) and increases in levels of mortality/morbidity, the Air Quality Regulations (1997) have been made. These implement air quality objectives for a range of pollutants, including PM10 and form part of a comprehensive UK National Air Quality Strategy. The many pieces of air pollution control equipment which have successfully reduced mass emissions of particulate matter from the steel industry's processes probably result in a residual release of predominantly PM10 material. Furthermore, hitherto uncontrolled or incompletely contained, fugitive releases from iron and steelmaking processes are known to be comprised mainly of fine particulates - these are essentially from non-stack sources such as roof vents. Stack emissions are measured using conventional standard techniques. The measurement of fugitive, non-stack emissions, however, has presented a considerable challenge In order to quantify and characterise the mass emission of particulates from an area source, it is necessary to quantify particulate concentration, volume flow and the particle size distribution of released dusts. If a building has several roof vents and apertures, it is necessary to identify the area sources that contribute to emissions and carry out representative measurements at these locations. In contrast to stacks and ducts, roof vents and apertures have relatively large cross-sectional areas with velocity profiles dependant upon atmospheric and localised aerodynamic conditions. In addition, vents typically emit non-uniform concentrations of particulates across an area. Hence standard methods cannot be applied and even carefully selected sampling points may not represent emissions for the sampling duration. To overcome this, Corus’ Swinden Technology Centre developed a technique to quantify non-stack emissions, combining point gravimetric sampling with visual observations in an attempt to describe emissions across a total vent relative to the measurement location. In order to validate results and evaluate practical constraints, the technique has been employed to quantify fugitive emissions from various Corus plants housing a variety of iron and steelmaking processes. At each plant, sampling exercises were taken over at least three separate days and a mass emission estimation was made together with an estimate of error. The technique provides reasonably reproducible results, taking into account the variation in mass emission caused by fluctuations in plant activity, process output, etc. Providing that an adequate number of exercises are undertaken to reduce any error owing to non-representative activity, then it is believed that the technique provides a result that is sufficiently accurate to identify areas of concern and to assist in planning remedial action. It is important for the steel industry to identify at an early stage new environmental concerns to which it may contribute. The accumulation of specific data on releases and impacts allows the industry to develop an understanding of issues and thus it can debate these with the authorities, media, customers, etc. from a position of knowledge. If there are justified pressures to reduce emissions, then the data accumulated allow cost-effective decisions to be made on targeting any environmental control investment | |
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