Analysis: Urban mining
Slag, ash and dusts as the residues of incineration plants fired by solid fuels, reflect the minor chemical constituents which are contained in the fuel.
As a mass flow, slag, ash and dusts often represent a compound containing several or many metals “worth mining”, thus being of equal value to a natural ore – if not of higher value in many cases.
Similar to natural ore deposits in the Earth’s upper crust, the metals contained in slag, ash and dusts do not occur as pure metals, but are chemically bonded as minerals or form part of alloys, and mostly are just minor constituents of the mass-flow.
Natural ores, first a minor constituent of the mass flow, need to be processed in order to form a major constituent of a partial mass flow (Teilmassenstrom). Corresponding steps need to be taken in the case of slag, ash and dusts.
These “artificial ores” are, in contrast to natural ores, bonding types which rarely occur in nature. They include chlorides, among others. Hence, specific processing procedures are required.
Our senior CheMin staff have a geo-scientific background with a special focus on economic geology. This background combined with our numerous investigations regarding the properties and behaviour of slag, ash and dusts (keywords: formation of hydrogen, heavy metal mobility, ageing, processing, formation of phosphine) have led to our wealth of knowledge in this field which is summarised under the headword “urban mining”.
In addition to this, CheMin has also acquired extensive experience on the chemical processes in power plants with regard to soiling, emissions, the transport and storage of dusts and ash, and with regard to the local enrichments of mass flows in certain sections of the process chain.
In our capacity as consultants and developers we are well-equipped drivers
of innovation in order to support and further develop the recycling of reusable
substances out of slag, ash and dusts.