From Biogas Technology
Take over procedure is the same as described before. In addition, there is the possibil-ity to take over liquid wastes like fats, restaurant garbage and residues from indus-trial processes and slaughter houses which are stored in separate tanks.
Pre-crushing is necessary only to open plastic bags and other packing. It is done by a slow running screw mill producing a particle size of approx. 40 mm. The final milling and homogen-isation takes place in the next step. Since pre-separated garbage is delivered, the separation is done automatically. The screw mill is placed on top of the suspending unit and is fed with the bio waste by a crane.
- Homogenisation, Suspension, and Separation
This is done in one single stage by means of a special suspending unit consisting of a steel tank with a built in mixer. The pre-crushed material is fed from the top and di-luted with the process water up to a dry matter content of about 10 %. During the di-luting process the pre-crushed material is intensively mixed and suspended. In order to achieve better solu-bility of fats and proteins and for hygienisation purposes, the suspension is heated up to about 70 °C. Due to the intensive movement of the liquid, small plastic particles, wood, and paper are separated from adhesive fats etc. and float. The floating fraction is removed from the surface by an especially designed screen and conveyed to a container. Glass and metals are separated from the liquid by sedimentation. They are removed from the bottom of the tank and gahered in a separated container.
- As a result, a homogeneous suspension of water and organic material is created which is free of foreign matters. This suspension with a dry-matter-content of about 10% is pumped to a buffer tank to allow a constant feeding of the rector over 24 h/d. From the buffer tank the suspension can be either pumped directly into the methane reactor or mixed with other liquid wastes prior to fermentation.