Evaluation of liquid and solid phase mixing in Chinese dome digesters using residence time distribution (RTD) technique

A.O. Jegede*, G. Zeeman, H. Bruning

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

The Residence Time Distribution (RTD) technique was applied to evaluate mixing of liquid and solid phases in laboratory scale Chinese dome digesters mixed via hydraulic variation. To achieve this purpose, six laboratory scales digesters with different mixing modes and two total solids (TS) concentrations using appropriate tracers were studied over a theoretical hydraulic retention time (HRT) of 30 days. The three different mixing modes were impeller, unmixed and hydraulic mixing, each at influent concentration of ca. 7.5 and 15% TS concentrations. The mode of mixing strongly affected the effective or actual residence time (ta) and directly influenced the percentage of dead zones. The Chinese dome digesters had more dead volumes than the impeller mixed reactors and less than the unmixed reactors. This implied that mixing was more efficient in the impeller mixed reactors followed by the hydraulic mixed reactors and then the unmixed reactors, irrespective of the TS concentration. There was a clear relation between the RTD results and anaerobic digestion performance viz. methane production. There is need to optimize the hydraulic variation in the Chinese dome digester to reduce dead zones while also optimizing the effective residence time (ta).

Original languageEnglish
Pages (from-to)501-511
JournalRenewable Energy
Volume143
Early online date8 May 2019
DOIs
Publication statusPublished - Dec 2019

Keywords

  • Chinese dome digester (CDD)
  • Liquid phase
  • Mixing
  • Residence time distribution (RTD)
  • Solid phase

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