Look behind the scenes
This example follows Agrivalor Énergie in Alsace, which feeds its cogeneration plant with biogas from leftover food production and food that has passed its sell-by-date. Mixtures from maize silage, liquid manure, and grape marc, but also food waste from restaurants, schools and supermarkets are conveyed into a mixing tank from where they travel on to the fermenter, where the biogas is formed.
However, the varying mixtures of materials put a major strain on the plant’s conveying systems. Some of the materials, such as the liquid manure, are corrosive and some are fibrous and likely to cause obstructions, such as grain waste. Materials of animal origin also have to be exposed to intense heat to prevent disease, so some media are still at 70 or 80°C when they are conveyed.
Agrivalor Énergie ordered ten NETZSCH-made NEMO® progressing cavity pumps to achieve maximum possible reliability without significant maintenance or downtimes, despite the tough conditions. Two of the larger pumps with capacities of around 40 m³/h are used to transport the mixture from the collecting tank (with around six to seven percent dry matter content) into the fermenter. Other NEMO® pumps with a capacity of 20 m³/h are used to convey the recirculated substance and introduce the sanitised hot liquid manure into the mixer. All the units are extremely compact and have a block design with flange-mounted motor, saving a lot of space on the premises of the privately owned biogas plant. The efficient pump design only requires minimal power, which – along with the long service life and long maintenance intervals – leads to low overall operating costs.