Patent FR-2987370-A1 (FR)
Title: Device, useful for producing biogas from organic material waste, comprises mixing unit immersed in waste in course of digestion in internal part of methanisation tank in four successive treatment areas along displacement direction of waste
Inventor: BEAULIEU BERNARD
IPC: C12M1/107
Filed: 2012-02-23
Abstract: The device comprises an input opening provided for inputting organic waste to be treated and located at one of ends of a methanisation tank (1), an output opening provided for outputting the treated residue or digestate by a waterbed effect located at an opposite end of the tank, an evacuation opening provided for releasing biogas towards an upper part of the tank, and a mixing unit immersed in the waste in the course of digestion in an internal part of the tank in four successive treatment areas (Z1-Z4) along a displacement direction of the waste. The device comprises an input opening provided for inputting organic waste to be treated and located at one of ends of a methanisation tank (1), an output opening provided for outputting the treated residue or digestate by a waterbed effect located at an opposite end of the tank, an evacuation opening provided for releasing biogas towards an upper part of the tank, and a unit for mixing the waste in the course of digestion in an internal part of the tank during a longitudinal displacement of the waste between the input opening and the output opening. The mixing unit is immersed in the waste in the course of digestion in the internal part of the tank in four successive treatment areas (Z1-Z4) along a displacement direction of the waste, where the first treatment area is equipped with pushing units for homogenization and fractionation of waste, the second treatment area is equipped with a unit of slow mixing and packaging of waste without homogeneous mixing of the waste, the third treatment area or zone of rest for allowing decantation of solid fragments of the waste that remains in suspension in a liquid fraction or gathers at a bottom of the tank when a density goes up on a surface, and a fourth treatment area is equipped with units for aspiration of the liquid fraction of the waste and lengthening of residence time of the solid fragments in the tank. The pushing units include a double reversed coil helix (7) movable in rotation around a first shaft (4) parallel with an axis of the tank and actuated at slow speed by a motor reducer (5), where a profile of the double helix has a sharp rectangular section with sharp angle. The double helix is equipped with side squares positioned perpendicularly on the section, where branches of the double helix are asymmetrical. The unit for slow mixing and packaging of waste include a paddle wheel movable in rotation around the first shaft and equipped with a series of longitudinal blades with a flat profile directed according to an axial angle of 25-30[deg] . The units for aspiration of the liquid fraction and lengthening of the residence time of the solid fragments in the tank include: two radial blade propellers that includes a concave profile in the displacement direction in the course of digestion in the two radial blade propellers, and are mounted in rotation around a second shaft parallel with the axis of the tank and pulled by the motor reducer at variable speed, where the second radial blade propeller has greater dimension than the first radial blade propeller; and a truncated cone that is coaxially mounted at the second shaft in order to surround the two radial blade propellers and widens in a direction of the output opening of the tank to surround the output opening, while releasing a free space at a right of the cone. The input opening is equipped with a feed hopper of waste to be treated emerging tangentially in the tank. The output opening is positioned opposite to the input opening and equipped with a outlet piping in a swan neck. The tank is equipped with a draining opening at a lower part of the tank.