Digester for fermenting organic waste to produce methane etc. - screw circulates waste contg. 18 to 35 per cent dry matter

摘要

Waste material is pressure-injected into the base of a digester vessel. Crust formation and other head on top of the fermenting material is conveyed by a conically convergent, radial feed screw into the top of a discharge downpipe. The downpipe houses a conveyor screw which positively discharges fully fermented material to the exterior of the vessel. Pref. the downpipe is vertical and coaxial with the vessel; the radial feed screw is then geared to rotate around the axis of the vessel to break up surface crust. Pref. an air-lock chamber at the top of the vessel facilitates maintenance of the driving gear to the radial and discharge screws without interruption of the fermentation process. The process and installation are for the fermentation of organic waste to produce methane and convert the waste into an inoffensive fertiliser. The vessel is equipped for positive circulation of the raw material by the three feed screws. This enables the digester to handle waste contg. 18 % - 35 % dry matter. Previous digesters have had difficulty in handling waste with more than 10 % dry matter.