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

Abstract

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.

Effect of substrate pretreatment on particle size distribution in a full-scale research biogas plant

“…In the case of perfect mixing and distribution, uniformity in volume distribution must be achieved. These findings are in accordance with results from Lemmer et al (2013), who found that VFAs in the digester substrate are also not distributed evenly. Although Kusch et al (2008) report floating layers in BGP fed with large amounts of fibrous material, our results show that only 6.7-13.1% of the total particle volume are of a particle size >4 mm.…”

“…1c) for invasive sampling from the top of the digester is unique in a full-scale BGP. It is designed to take samples from different positions and heights in the digesters through the gas-phase from the fermenting substrate with consideration of all safety and environmental precautions as described by Lemmer et al (2013). The samples (n = 24) were taken at both digesters and deep frozen (À18°C) until further analysis.…”

Expanding the Potential of G‐Quadruplex Structures: Formation of a Heterochiral TBA Analogue

“…The solid substrate was supplied by a vertical mixer system into a cross‐flow grinder disintegration unit (Bio‐QZ, MeWa, Gechingen, Germany) and subsequently fed into the digester. Digester 1 is equipped with a submersible motor mixer (4670, ITT Flygt AB, Sweden) and a propeller incline shaft agitator (Biogator HPR 1, REMA, Germany) to ensure a uniform distribution of the feed and heat and to enable gas lift from the fermenting substrate 32.…”

Real‐Time Gas Quality Data for On‐Demand Production of Biogas

“…The research biogas plant, its technical setup, and operation modes have been already fully described . The biogas is produced from a mixture of renewable energy crops (∼ 70 % maximum) as well as liquid and solid manure from animal husbandry (minimum ∼ 30 %) under thermophilic (40.5 ± 1) °C conditions in two digesters of identical construction with a volume of 923 m 3 , respectively.…”