Our client wanted to remove and dewater the pulp stock created in the bottle wash process (bottle labels and glue), returning the caustic soda back into the bottle wash stream. The pulp stock containing label pulp, broken glass and bottle caps are dewatered enough to go to landfill.
Solution from Atara Equipment Ltd.:
The Atara Equipment dewatering and compacting unit receives the caustic soda pulp, broken glass and bottle caps mix stream from a hinge conveyor and/or Disco strainer, the stream enters at the lower end of the press conveyor.
The free standing liquid is evacuated through a fine wedge wire screen mounted over the drain. The pulp stock sits on top of the wedge wire where the spiral sweeps the pulp forward transporting it towards the press end.
The press end consists of a dewatering basket, a spray wash system to keep the basket free from debris ensuring the dewatering galleries are kept open to allow that material can be dewatered at maximum efficiency.
The wash water system is controlled by timers opening and closing solenoids, it is important that the minimum amount of water is used at all times, first to ensure that no new water re-moistens the dewatered material, secondly to limit the dilution of the caustic soda returning to the stream.
Using a shaftless screw in this application has the benefit of a full screw feeding the dewatering zone, maximizing the dewatering efficiency of the press.
The standard press end had to be modified to make sure that the center core of the pulp dewaters at the same rate as where the spiral flight presses the material against the pneumatically operated door. This modification forces the wet material running through the center core to the outside, so the spiral will pick it up and dewater at the same place and rate as the rest of the material.
Due to the fact that the shaftless spiral runs at slower speeds while processing the same volume of material as a shafted unit, the abrasiveness of the combined materials factors less in the overall performance of the equipment.