THE CUSTOMER: Our customer is a leading composter in the UK with a proactive approach to investing in new technology, as well as having an excellent reputation in the industry for quality of service.
THE CHALLENGE: The company was suffering with an issue that many other composters experience – that being having to deal with contamination in compost oversize material. Typical contamination consists of stone, metals, film and rigid plastics, these materials can be difficult to separate away from the desired wood fraction due to the varied nature of the materials.
THE SOLUTION: Blue Group had the perfect solution for this problem, with the Doppstadt range of Washing Equipment and their HDS-M washing system. The system is comprised of a trommel for the removal of fines, prior to feeding the oversize material in to a Westeria Windsifter for true density separation and removal of the light films, foils and other super-light materials. The resulting heavy material is fed into the Doppstadt HDS-M Washing System where the heavy stone is cleaned and separated, along with any other high-density materials such as metals. The remaining wood fraction is conveyed out of the end of the washing system, where it is further dried and shredded before being used as a boiler fuel in energy plants. Any remaining rigid plastics are currently removed by hand. However, as part of this customer’s ongoing commitment to investing in automated technology, they will soon be removing all remaining rigid plastic and contaminants with Optical Sorting technology that Blue will install during Q4 of 2019.
Plant Overview
The Process
• The oversize compost material is fed in to a Doppstadt SM518F trommel with integral hopper feeder at a rate in the region of 20 tonnes per hour. The trommel removes the <10mm fines.
• The >10mm material moves into a Westeria Windsifter, here all light materials such as plastic film, foils and any super-light organic materials are blown-out of the material stream. These light materials are a suitable refuse derived fuel (RDF)
• The remaining heavy fraction from the windsifter is conveyed into the feed zone of the Doppstadt HDS-M Washing System. Fast jets of water push materials down into the water separation tank, where the stone, metal and any other heavy materials move out the bottom via screw conveyor. The resulting stone fraction passes through a magnet drum to separate ferrous metals from the aggregate material.
• Once the heavy stones are removed in the washing process, the wood fraction passes through an integral trommel drum for final washing and fines removal. Any resulting fines are put back in to the composting process whilst process water is in a closed-loop system, with a Lamellar Clarifier being used for cleaning sediment out of the water
• The separated wood fraction can contain rigid plastics, which are removed on a hand-picking line. However, this will be upgraded to a fully-automated, Optical Sorting line to efficiently achieve an end product suitable for waste-to-energy plants as a fuel. The clean wood product is then dried and shredded to suit the size requirement of its end user.
