Volute® System for dewatering of sediments
Résumé
The sludge-dryer VOLUTE® , a Japanese patented machine, looks like a continuous filter press, able to operate a continuous work system, it allows to dehydrate sludge and/or mud without stopping the machine. This machine has been conceived on the combination of physical actions: gravity, filtration, compression and shear forces. It allows the dehydration of sludge by a specific system and a characteristic drying design. The VOLUTE® dewatering machine consists of a conical cylinder composed by a screw which rotates at a constant speed within a succession of fixed and moving rings and spacers. This conical cylinder is usually divided into two main parts. A first part concerns the thickening zone where the rings are gradually tightening from 0.5 – 0.3 mm. The second part corresponds to the dewatering zone where the rings are separated gradually between 0.3 and 0.15 mm. The process used by this machine is simple: the sludge is introduced into a feed chamber. Flocculants/polymers are injected into the material to be dehydrated (sludge, muds...). This mixture is carried by the screw to the thickening and dewatering zones. In fact, dehydration of sludge begins in the first zone, solid-liquid mixes are separated by filtration process. In the second zone, the solid-liquid mixes are separated by applying compression and shear forces. Furthermore, this machine offers several advantages: it allows highly efficient dewatering (the rate of throughput can vary from 0.5 to 780 kg - DMS /h and the sludge thickeners capacity can be selected from 1 - 90 m3/h). The protocol to be followed for the use of this machine is easy and do not require any specific formation for users. This work system can be installed in small and compact areas in comparison with other dewatering machines. It has a low operating cost. In the design of this machine, environmental aspects have been considered so as to reduce them. The power consumption required by a machine of 30 kg- DMS/h throughput is about 6 times smaller than of belt press. The principle of water-saving has been developed. The amount of water required is about 12 times lower than the conventional screw press. The self-cleaning mechanism and the clog-free do not need large amounts of water because the machine’s filter mesh does not hamper by the solids. As this machine is used only for sludge not for dehydration of sediments, the challenge is to demonstrate its ability for sediments: VOLUTE® process and first test results are presented.
Note: DMS = dry matter of sediment