Patents
 Accordingly, the present invention provides a reactor for anaerobic digestion of slurry comprising a tank defining a bottom zone, a separation zone and a top zone. A slurry inlet mechanism is located at about the bottom zone for feeding the slurry and a gas inlet mechanism is located at about the bottom zone for feeding gas so as to mix the slurry at the bottom zone. The reactor comprises a transporting mechanism for assisting in an upward movement of the slurry from the bottom zone to the top zone based on a differential pressure between the zones. The reactor is further provided with a downer operatively connecting the top zone and the bottom zone for assisting in a downward movement of the slurry in the absence of the 1 j differential pressure. The reactor is further provided with a gas withdrawal mechanism for i withdrawing a bio-gas produced within the tank. The gas withdrawal mechanism is operably i I connected to the gas inlet mechanism for recirculating at least a part of the bio-gas withdrawn. The reactor is further provided with an automatic pressure sensitive valve mechanism operably connected to the gas withdrawal mechanism andlor the gas inlet mechanism so as to maintain a predetermined pressure inside the tank.Â