Mixing non-Newtonian flows in anaerobic digesters by impellers and pumped recirculation

Meister, Michael; Rezavand, Massoud; Ebner, Christian; Pümpel, Thomas; Rauch, Wolfgang

doi:10.1016/j.advengsoft.2017.09.015

Cited by 60 publications

(50 citation statements)

References 28 publications

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“…These include operating parameters (such as temperature, pH and alkalinity, carbon to nitrogen ratio, particle size, retention time and loading rate) and their influence in AD processes; feedstock moisture content; feed rate, and process conditions including co-digestion of different feedstocks [62,86]. Others are fluid flow patterns (such as unstirred and stratified fluid flows) [87][88][89][90]; retention time; carbon to nitrogen ratio and organic loading rates as well as types of digesters and their influence in digestion processes [61,62,[79][80][81][82][83][84][85][86][87][88][89][90][91][92][93]. Although a host of other issues have been addressed by previous investigations, which could not all be captured in this review.…”

Section: Brief Synopsis Of Issues Hitherto Addressed In Ad Researchmentioning

confidence: 99%

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

et al. 2019

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The anaerobic digestion technology has been in existence for centuries and its underlying theory established for decades. It is considered a useful technology for the generation of renewable energy, and provides means to alleviate problems associated with low access to energy. However, a great deal of current research is targeted towards the optimization of this technology under diverse digestion process conditions. This review presents an in-depth analysis of the chemistry of anaerobic digestion and discusses how process chemistry can be used to optimize system performance through identification of methods that can accelerate syntrophic interactions of different microorganisms for improved methanogenic reactions. Recent advances in addition to old research are discussed in order to offer a general but comprehensive synopsis of accumulated knowledge in the theory of anaerobic digestion, as well as an overview of previous research and future directions and opportunities of the AD technology. Achieving a sustainable energy system requires comprehensive reforms in not just economic, social and policy aspects, but also in all technical aspects, which represents one of the most crucial future investments for anaerobic digestion systems.

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Section: Brief Synopsis Of Issues Hitherto Addressed In Ad Researchmentioning

confidence: 99%

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

et al. 2019

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“…Figure 5 presents the fitting curves of the biogas production rate obtained using Equations (4) and (6). As shown in Table 4, the DD group had a shorter lag time, a higher biogas production rate, and a greater cumulative biogas production than those of the SD group.…”

Section: Effect Of Dynamic Digestionmentioning

confidence: 98%

“…Conversely, mixing by dynamic digestion can effectively improve the digestion efficiency and biogas production rate. At present, there are three general mixing methods, namely, mechanical (impeller) mixing [6], slurry recirculation [7], and gas recirculation [8]. The advantages of mechanical mixing are high heat and mass transfer rates, in addition to the effective reduction of the hydraulic dead space, maintenance of reproduction, and metabolism of anaerobic bacteria.…”

Section: Introductionmentioning

confidence: 99%

Biogas Production and Heat Transfer Performance of a Multiphase Flow Digester

Guo

Zhou

et al. 2019

Energies

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Traditional static anaerobic digestion technology presents the disadvantages of a low gas production rate and long digestion cycle, which is not conducive to the treatment of livestock manure. A 12 m3 multiphase flow anaerobic digester (MFD) was developed in this study to improve the biogas production rate and maintain constant temperature digestion during winters. Full-scale field experiments were conducted on the biogas production rate at different temperatures, the dynamic digestion effects, and the dynamic heating digestion effects of the system at Sichuan, China. A comparison of the dynamic and static digestion results of 50 days indicated that the biogas production for the dynamic digestion (DD) group was 115.22 m3 or 127.1% higher than that of the static digestion (SD) group with the same digestion temperature. The results of the heat transfer performance experiment revealed that the heat transfer rate of the system increased significantly, and the temperature of the biogas slurry increased rapidly. The optimization analysis of the system was based on the experimental results of the relationship between the slurry temperature and biogas production rate, and the economical digestion temperature of the system was proposed and calculated. Different insulation materials or insulation thicknesses have an influence on the economical digestion temperature. Additionally, the economical digestion temperature of the system in which the polystyrene insulation layer with a thickness of 90 mm was used, was found to be 27.2 °C. When digestion temperature was 22.3 °C, the energy efficiency ratio (EER) of dynamic anaerobic digestion system is 1. The advantages of MFD are low biogas production unit cost and high heat and mass transfer rate. However, the disadvantage of high operation energy consumption needs further improvement. And additional energy was required when system digestion temperature below 22.3 °C. The proposed MFD and dynamic anaerobic digestion system can play a significant role in using biomass resources and promoting the development of biogas projects.

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“…Instead of monitoring biogas production, fluid flow patterns are investigated and velocity distributions are analyzed [8][9][10]. Additionally, computational fluid dynamics (CFD) is a powerful tool, which can be used to numerically simulate flow patterns [11][12][13]. A review on CFD simulation methods for biogas fermentation fluid materials was recently published by Wang et al [14].…”

Section: Introductionmentioning

confidence: 99%

Numeric Simulation‐Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants

2020

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Stirring systems with two rotational three-bladed propellers were analyzed using computational fluid dynamics. The propellers are located at three heights and seven angles in a tank with 9 m radius. The fluid was characterized by non-Newtonian rheology and simulated by applying the k-e turbulence model and the standard k-w model. Reynolds numbers were estimated. High fluid speeds were obtained with the propellers located at a height of 2 m and oriented at 90°with respect to the tank radius. In the top regions of the tank, the fluid velocity was generally less intense and less affected by the angle setting. The configurations identified as good mixing systems showed power consumptions broadly distributed around 30 kW.

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Mixing non-Newtonian flows in anaerobic digesters by impellers and pumped recirculation

Cited by 60 publications

References 28 publications

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

Biogas Production and Heat Transfer Performance of a Multiphase Flow Digester

Numeric Simulation‐Based Analysis of the Mixing Process in Anaerobic Digesters of Biogas Plants

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