Improving the heat transfer properties of waste activated sludge by advanced oxidation processes
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3)
Keywords: waste activated sludge, drying, heat transfer, biosolids
The Waste Activated Sludge (WAS) process has the inherent drawback of producing large amounts of sludge, which should be disposed of. The drying of excess sludge presents an interesting intermediate stage in sludge handling since it stabilises and hygienises the sludge and reduces its volume. Dried sludge can moreover readily be used as a secondary fuel in energy plants.
Recently much attention has been focussed on the use of advanced oxidation processes (AOP) in wastewater and sludge treatment. These methods have the potential to enhance the mechanical dewaterability of the sludge and to reduce the total amount of produced sludge. Since the AOPs affect the consistency of the sludge to a large extent, the heat transfer properties of the sludge are also changed. This paper studies and quantifies the influence of some AOP methods on the thermal conductivity of the sludge. These results are then used for calculating the heat transfer coefficient which is needed in the design of sludge dryers.
The AOPs which were used in the experiments include the traditional Fenton peroxidation and the peroxidation with peroxymonosulphate. The use of the latter in sludge treatment is novel. It was seen that the application of both oxidation methods significantly increase the thermal conductivity of the sludge, resulting in a higher heat transfer coefficient. To assess the impact on the design of a sludge dryer, a multiple hearth and a fluidized bed dryer were taken as an example. The calculations show that the application of the treatment results in reduced dryer dimensions or a higher capacity for an existing dryer of given dimensions. The economy of the combined process and design will moreover be illustrated.
See the full pdf manuscript of the abstract.
Presented Tuesday 18, 16:00 to 16:20, in session Environmental Engineering & Management (T1-3).
