Tarmac Limited’s 480tph lignite removal plant at its Snabe Quarry in South Ayrshire, Scotland is showing how a new approach to the processing of lignite contaminated materials can bring significant advantages.
As a result of the small island that we live on everyone working in the quarrying sector in the UK is aware of the growing requirement to tackle materials that would not have previously been considered for processing. As we approach the time when the majority of clean and easily processed material has been exhausted the attention turns to how we can effectively process these ‘difficult’ materials to allow for the production of high quality sand and aggregates.
The contamination of sand and gravel deposits with lignite and the development of processing systems to deal with this contamination is evidence that there is increasing pressure to process materials that were previously overlooked. Lignite in itself can be a very useful commodity being a soft brown fuel, the characteristics of which put it somewhere between coal and peat. In Greece over 50 per cent of electricity comes from lignite fuelled power plants. In Germany deposits of lignite are concentrated around the Cologne area and stocks are believed to be over 50 billion tonnes. These are currently being exploited and generate some 25 per cent of the electricity produced by Germany.
Tried & Tested system
However, when lignite is present in deposits of sand and gravel it presents a significant problem for companies such as Tarmac as it will compromise the final quality of the sand and aggregate products. In seeking to process this material effectively the specification of a system that is tried and tested in the effective removal of this lignite material is key.
Since this CDE plant was fully commissioned at Snabe Quarry it has exceeded the requirements as detailed in extensive performance guarantees drafted by Tarmac. Firstly, and most significantly, lignite is being effectively removed – final lignite content was required by the performance guarantees to be 0.05 per cent by mass. This is being comfortably beaten with Tarmac reporting levels of 0.03 per cent by mass from the regular testing that they undertake on the final products.
In addition to this the requirements relating to capacity and moisture content of the final products have never been called into question. With almost 12 months continuous production now achieved at Snabe Quarry the plant has allowed Tarmac to deliver significant volumes of material to the local market that would otherwise not have been available.