Sludge dryers for gasification process of sewage sludge
Downer and Eliquo Water & Energy signed a contract for the design and supply of two low temperature EloDry sludge dryers for Australian’s first full scale gasification process at waste water treatment plant Loganholme near Brisbane.
High energy efficiency
The two large EloDry NT-48 belt dryers will support the Pyrocal CCT gasification process that is to produce biochar from the surplus active sludge.
The process was successfully tested at wwtp Loganholme with the surplus sludge being dried and gasified. Now a full scale installation will be build and the start up is foreseen by end of 2021.
The low temperature dryers contribute to the high energy efficiency of the full sludge treatment process. By drying the dewatered sludge with recovered thermal energy from the gasification process, the system will work on a 70 percent energy autonomous basis. The remaining 30 percent of required energy is sourced from an onsite solar power system that is under construction.
Increasing costs
Wwtp Loganholme services about 300,000 people in the region of Logan City and produces 34,000 tonnes of sewage sludge per year. Currently this sludge is used as a soil improver in agriculture about 300 kilometres away from the city.
The transport costs are currently around 30 percent of the total operating costs. The Logan City Council expects the costs will further increase and foresees tighter regulations on greenhouse gas emissions and on the disposal of sewage sludge on land.
The new gasification installation at wwtp Loganholme will reduce the volume of produced sludge by 90 percent. The remaining biochar can be used as a sustainable harmless soil conditioner.
Proven performance
According to Matt Thomson, Operations Manager at Downer, the EloDry low temperature sludge dryers were selected based on their high energy efficiency and proven performance with other systems that also includes thermal heat recovery.
Thomson: ‘By working with Eliquo we have secured both dedicated knowledge about heat recovery and delivery of a proven drying concept.’
