With the volume of sludge that needs to be dried likely to continue growing over the next few years, Birkenmayer, in association with Eirich, offers a sophisticated range of direct drying systems that provides lower energy costs, better environmental practices and maximum operational efficiency.
According to Birkenmayer, a number of recent trials have proven Eirich industrial mixers to be exceptionally efficient at drying municipal sewage sludge, industrial sludge and lacquer-containing sludge by using super-heated steam and exact process parameters such as temperature, pressure, speed and mixing time, among various others. Key to the range’s success is the mixers’ ability to accommodate vacuum drying, superheated steam drying, exceptional wear and abrasion resistance and the ability to operate in extreme operating conditions.
“Eirich mixers are capable of granulating, homogenising and heating within a single batch cycle, which simplifies process engineering and reduces setup costs – as well as operational expenses,” says Birkenmayer’s Business Development Manager, Louis Eksteen. “Maintenance is minimal, and thanks to the purpose-developed intensive mixing principle, whereby maximum energy is directed into the mix using minimal energy input, results are predictable, highly repeatable and granulates are remarkably dense.”
Direct Drying of Municipal Sewage
Sewage sludge is typically reduced to a solids content of approximately 20 to 35 % with a centrifuge, belt filter or chamber filter, but Eirich machines that are configured to drying sewage sludge have demonstrated enormous cost benefits by reducing solids content by up to 95 %, as it is significantly cheaper to dispose of smaller volumes.
Any vapours from the steam drying process can be condensed and returned to the sewage works for reprocessing, while the heat output is available for other uses such as energy generation and biological waste digestion.
Industrial Sludge Drying
A recent experiment reduced the moisture content of electrolysis sludges from 20 % down to just 5 %, making the residue suitable for sintering at high temperature without flaking. “The advanced homogenisation afforded by the mixer is the main condition that prevents flaking – a result of greater stability and compressive strength than, for example, pelletised granules made from a more powdery material,” says Eksteen.
Eirich mixers are suitable for drying lacquer-containing sludge with a relatively high amount of solvent and a low amount of binding agent. Like many other types of sludge, lacquer-containing sludge is occasionally contaminated with significant foreign particles, such as plastic films, plastic pieces, etc., but thanks to the high temperatures achieved within Eirich mixers, these impurities simply melt and blend homogenously into the sludge mixture.
“This means that batches with lower plastic levels are suitable for re-use within the lacquer industry, while high plastic levels render sludge suitable for landfill or incineration,” concludes Eksteen.