Patent ID: 8105823

Claim:
Method for shutting down a fermenter in a biogas installation, the biogas installation comprising the fermenter which operates on the principle of dry fermentation for production of biogas in the batch mode with a biogas outlet and a purging gas inlet; a biogas line connected to the biogas outlet, an off-gas line by means of which off-gas containing carbon dioxide is supplied to the purging gas inlet, an off-gas chimney connected to the biogas outlet via a first biogas/off-gas line, an off-gas flare connected via a second biogas/off-gas line to the biogas outlet, a fresh air line connected to the purging gas inlet, a control device for connection of the biogas outlet to the biogas line or to an off-gas chimney via the first biogas/off-gas line or to the off-gas flare via the second biogas/off-gas line and for connection of the purging gas inlet to the off-gas line or to the fresh air line, a measurement device which is connected to the control device and has a first measurement sensor for detection of the methane concentration and a second measurement sensor for detection of the carbon dioxide concentration in a gas mixture emerging from the at least one fermenter, and a loading and unloading opening, said method comprising the method steps of: a) maintaining the connection between the biogas outlet and the biogas line; b) connecting the off-gas line to the purging gas inlet of the fermenter to be shut down; c) purging of the fermenter to be shut down with off-gas from the off-gas line until the methane concentration detected by the first measurement sensor has fallen to an upper limit value; d) disconnecting the biogas line from the biogas outlet of the fermenter to be shut down; e) connecting the biogas outlet of the fermenter to be shut down to the first biogas/off-gas line, and supply of the off-gas/biogas mixture to the off-gas chimney until the methane concentration detected by the first measurement sensor has fallen to a lower limit value, the lower limit value lower than the upper limit value; f) disconnecting the off-gas line from the purging gas inlet of the fermenter to be shut down; g) connecting the fresh air line to the purging gas inlet of the fermenter to be shut down, and supply of fresh air into the fermenter to be shut down, until the carbon-dioxide concentration detected by the second measurement sensor has fallen to a first limit value; h) opening of the loading and unloading opening of the fermenter that has been shut down; and i) unloading the used biomass from the fermenter.