DYNAMIC THICKNER WITH ROTATING DRUM
Dynamic thickner type CAD is a rotating drum machine, which is able to thicken the sludges not thickened, till arriving to a concentration of 10-12%. The flocculated sludge is conveyed inside the thickening drum. Flocculated sludge is drained by the belt in polyester, which wraps completely the drum. Water present in the sludge passes through the belt and is collected by the bottom tank, then it is discharged. Sludge remained on the belt is conveyed towards the external side of drum by the internal screw. Screw does also function of mechanic retention, in the sense that it increases times of staying of sludge on belt. Drained and thickned sludge is unloaded outside by the exit opening and is discharged in a collection tank, or in one of our belt filter presses, to be pressed more and dehydrated.
To increase efficiency of drainage, belt is continuously washed with water at 3 bar by a rack of spraying nozzles positioned all along drum.
Water used for washing can be clean or dirt. In this case, it is possible to use the filtrate water, recycling it using a pump, and putting a filter to capture the rough impurities. Capacity is adjustable by a motovariator directly coupled to the drum, supported by a set of wheels. The special type of belt permits to obtain a solids retention till 98% of sludges in inlet with variable dry concentrations from 0,8 to 3% of suspended solids.
The self-bearing structure is made by bent pressed plates in AISI 304 electro-welded, so to obtain a strong structure which is resistant to the mechanic stresses. Structure is complete of supporting feet for anchoring to floor. It is also equipped of lateral protections to avoid contact with the drum in rotation and, at the same time, to reduce dispersion of aerosol due to the internal washing system. Drum is realized with profiles in bent plate, circular stiffenings and internal screw completely electro-welded to the structure of drum. Drum is supported by a bearing in a side, and by a set of wheels in the opposite side. A particular system permits inclination of drum, to increase efficiency. Drainage belt is fixed to drum by a special “comb system” with external fixing bolts, and by two rings in stainless steel with tie-rod, which block the two ends of belt. In this way, when necessary, it is very easy the replacement of belt.