OPERATIONS MANAGEMENT
PERFORMANCE OF DEWATERING
Dr Alexis Speck, Bernhard Salbaum and Uwe Gradl compare mechanical and thermal cake drying
W
ithin solid-liquid separation with filter presses there is quite often a special task to
gain a certain purity of the filtrate and the cake. In many cases, a very low residual moisture content is required. With the existing filtration methods often, an additional dryer must be used to achieve solid concentrations above 40%. Different efficient processes in a filter press are available to increase the dry solids content.
1. MECHANICAL HIGH PRESSURE DRYING IN A FILTER PRESS (DHC- PROCESS) This process works with membrane and combination plates, squeezing the filter cake with high pressure and displacing liquid from the filter cake. The limitation of this process is the compressibility of the cake to a maximum of 40-50% dry solids content.
2. THERMAL VACUUM DRYING IN A FILTER PRESS (DHV- PROCESS) This process uses the mechanical drying according to item 1. above, but with low pressure. The additional application of temperature and vacuum evaporates the remaining liquid in the heated cake. The limitation mentioned above does not exist anymore and a dry solid content close to 100% can be achieved.
ABOVE RIGHT: Thermal controlled filter plates RIGHT: Anode sludge filter cake
Dr Alexis Speck, Bernhard Salbaum and Uwe Gradl are with JVK Filtration
Systems.www.jvk.de
16
www.engineerlive.com
Area
TYPICAL DRYING SOLID CONCENTRATION Product
Sewage treatment works
Purification of waste gases
Glass industry Waste slurry
Metallurgical industry
Paper industry Oxides
Leather industry Food industry Water treatment Digested sludge
Cement slurry Waste slurry
Waste slurry
Hydroxid slurry Silver powder Venturi sludge
Electrolysis sludge Anode sludge
Production sludge Titanium Dioxide Tannery sludge
Corn (Polenta) Protein Apple
Contrasting sludge 60-95%
91-96% 90-95%
98% 65-78%
96-100% 98%
96-99% 97%
92-97% 83%
90-94% 92-97% 70-90% 91-93% 92%
Solid Concentration
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