How Efficient are Agitators in Biogas Digesters? Determination of the Efficiency of Submersible Motor Mixers and Incline Agitators by Measuring Nutrient Distribution in Full-Scale Agricultural Biogas Digesters

Andreas Lemmer, Hans-Joachim Naegele and Jana Sondermann
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Andreas Lemmer: State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, Garbenstraße 9, Stuttgart 70599, Germany
Hans-Joachim Naegele: State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, Garbenstraße 9, Stuttgart 70599, Germany
Jana Sondermann: State Institute of Agricultural Engineering and Bioenergy, University of Hohenheim, Garbenstraße 9, Stuttgart 70599, Germany

Energies, 2013, vol. 6, issue 12, 1-19

Abstract: The goal of this work was to evaluate the efficiency of two different agitation systems by measuring the nutrient distribution in a digester fed with renewable energy crops and animal manure. The study was carried out at the practical research biogas plant of Hohenheim University. A unique probe sampling system has been developed that allows probe sampling from the top of the concrete roof into different parts and heights of the digester. The samples were then analyzed in the laboratory for natural fatty acids concentrations. Three different agitation setups were chosen for evaluation at continuous stirring and feeding procedures. The results showed that the analysis approach for agitator optimization through direct measurement of the nutrients distribution in the digester is promising. The type of the agitators and the agitation regime showed significant differences on local concentrations of organic acids, which are not correlated to the dry matter content. Simultaneous measurements on electric energy consumption of the different agitator types verify that by using the slow-moving incline agitator with large propeller diameters in favor of the fast-moving submersible mixer with smaller propeller diameters, the savings potential rises up to 70% by maintaining the mixing quality.

Keywords: biogas; mixing; stirring; agitators; mixers; energy efficiency; nutrient distribution; incline agitator; submersible mixer; renewable energy crops; volatile fatty acids (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2013
References: View complete reference list from CitEc
Citations: View citations in EconPapers (8)

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