High quality additives derived from fly ash could be used as money-saving fillers in a number of industrial applications, including advanced coatings for the aircraft and automotive industries. Bill Lavers reports

An environmentally friendly waste remediation project that has recently started up at a coal-fired power generation plant in the UK has the potential to produce thousands of tonnes per year of high quality additives for coatings, polymer composites and other applications for large-scale industrial end-users.

There are more than 15Mt of fly ash that have been accumulated in lagoons over the past 40 years at the Fiddler’s Ferry plant, near Warrington. It is a waste product common to all coal-fired power stations and so more is being added every year. In fact, in Britain as a whole, coal-fired power stations generate an estimated 6Mt each year. About half of this has been used in cement product formulations by the construction industry, and there has been no alternative to dumping the rest. Until now, that is.

Recycling fly ash

Fly ash recycling specialist, RockTron, based at Keynsham, near Bristol, has recently started up a large-scale waste remediation facility at Fiddler’s Ferry – the first of its kind in the world – that is set to change all that. Using what the company calls “standard mineral beneficiation techniques,” the new facility will process 800,000t of fly ash a year – otherwise known as pulverised fuel ash (PFA) – to remove undesirable impurities. The rest will be separated into a range of five minerals that can serve as high-grade additives for use as money-saving fillers in a number of industrial applications from cement and concrete through to advanced coatings for aircraft and automobiles. When fully operational, the plant will take newly produced fly ash, together with stockpiled waste from the lagoons and – using reagents and water, with settlers and separators – will produce some 650,000t/a of solid glass (alumino-silicate) micro-spheres, together with smaller volumes of hollow glass spheres, spherical magnetite (iron oxide) and high purity carbon. In particular, the process will generate more than 350,000t/a of MinTron 7 micron glass spheres and a further 300,000t/a of MinTron 70 micron glass spheres. The company says that all of the glass micro-sphere particles and the spherical magnetite are potentially suitable for use in polymers and the carbon can be returned to the power station for burning, or used as reductants, or in its purest form could be used in water filters.

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