Biogas from biowaste: Robust pumps enable a range of substrates to be conveyed, from liquid manure to food waste
Aug 23 2017 Read 1419 Times
Biogas is in high demand as a source of energy for power and heat generation. Systems that not only process crops specifically grown for power and heat generation, but also use otherwise unusable biowaste, are excellent for the environment and are highly economical. A community of farmers in Alsace founded Agrivalor Énergie to exploit that potential – the company primarily feeds its cogeneration plant with biogas from leftover food production and food that has passed its sell by date. As a significant range of different substrates has to be conveyed, depending the source material, the company uses the robust progressing cavity pumps from NETZSCH Pumpen & Systeme GmbH. Maintenance has so far been unnecessary in the two years of operation since, and any obstructions are also simple to clear thanks to the flexibility of the pump technology.
The aims of farmer Philippe Meinrad and his two colleagues when they founded Agrivalor Énergie included finding a solution to disposal of general biowaste, producing natural fertiliser and generating power and heat. The company has been operating a biogas plant with attached cogeneration plant in Ribeauvillé, Alsace, since 2012, mainly recycling typical basic substances such as maize silage, liquid manure, and grape marc, but also food waste from restaurants, schools and supermarkets, such as fats and dairy products. Instead of laborious and expensive waste disposal, the waste is used for a meaningful purpose.
The waste is sorted and shredded in a hammer mill, before being pressed, sanitised and conveyed into a mixing tank with liquid manure and marc. From there, the mixture travels on to the fermenter, where the biogas is formed.
Reliable conveying thanks to resilient design
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 from the manufacturer of their biogas plant 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.
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