Renewable Energy
Fly ash recycled into high performance products
Philip Michael describes the process that recycles the waste from coal-fired power stations into valuable industrial minerals.
Philip Michael describe el proceso de reciclado de residuos de centrales eléctricas de carbón en valiosos minerales industriales.
Philip Michael beschreibt den Prozess, mit dem Abfälle aus Kohlekraftwerken in wertvolle Industriemineralien umgewandelt werden.
U
sing a proven mining technique, the RockTron Beneficiation Process separates the waste fly ash components into 100 per cent recycled high performance
products. RockTron has developed advanced mineral
processing technologies that enable greater sustainable sourcing of minerals from waste fly ash that, up until now, has been discarded and land-filled. Tis technology could enable billions of tonnes of stored fly ash to be recovered, beneficiated and sold to industries worldwide, thus reducing the mining and energy intensive processing of billions of tonnes of virgin minerals. As a result, it can make an incremental and effective contribution towards reducing the carbon intensity of cement production and carbon emissions, while conserving natural resources through recycling waste fly ash material currently consigned to long term landfill.
carbon in the form of char. All fly ashes vary in their percentage of these three components but together these three account for 100 per cent of fly ash residues. Approximately 1-2 per cent of the alumino-silicates are hollow glass spheres known as cenospheres. Te utilisation of fly ash by the construction
industry is regulated by technical standards, such as the EN450 standards in Europe, the ASTM C-618 standards in the USA and their equivalents in Asia. Various methods have been attempted to improve the quality of fly ash in an effort to make it more suitable for industrial applications. Te most simple and commonly applied process is to grade the fly ash by particle size, which categorises it for a range of cementitious applications. Tis is referred to as Classified Ash. Additional improvements are made by the removal of some carbon in an effort to bring the overall Loss on Ignition (LOI) content below the 7 per cent demanded by BS EN450 Category A & B for use as a CEM I replacement in ready-mixed concrete. Most technologies to date have employed
Fig. 1. The first plant in the UK licensed to use RockTron’s Technology.
Fly ash is the waste product generated from burning hard coal at coal-fired power stations. It comprises the heat-treated constituents of coal itself, the major ones being alumino-silicates, iron oxides in the form of maghemite and
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dry fly ash beneficiation techniques, fractioning the finer particles of fly ash captured in either electrostatic precipitators or bag filters, while other systems aim to remove some of the deleterious carbon fraction from the fly ash. However, none of these approaches provide a holistic solution that deals with 100 per cent of all fresh fly ash produced by power stations each year. Moreover, no dry ash beneficiation system can even attempt to recycle, recover and beneficiate the billions of tonnes of fly ash in long term storage around the world. Te RockTron Beneficiation process is the first of its kind to provide a total processing solution for both fresh and stockpiled fly ash. RockTron plants do not require a working coal-fired power station to operate effectively, as they can work on legacy ash deposits as well as fresh ash from power stations’ electrostatic precipitators. Despite the obvious commercial and environmental opportunities of this technology, it has taken almost 20 years for the founders to secure funding for the first large scale beneficiation plant. Tis was due in part to the
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