Yohannis Mitiku Tobo

Name:

Nationality:

Ethiopia

Project ID:

ESR06

Model-based knowledge buildup of mixing behavior in anaerobic digesters with view of maximizing performance

Short CV / biography:

At Jimma University, Ehtiopia, I graduated in mechanical engineering (bachelor degree – 2010) and in sustainable energy engineering (master degree - 2014). I worked as assistant lecturer (2010-2014) and lecturer (2014-2016) positions at Jimma university. Since October 2016,I am a PhD student and scholarship recipient of the super-W European joint doctoral training program, combining positions both at Ghent University and Technical University of Delft for the next three years.

Short description of my topic:

My PhD topic is titled: model-based knowledge buildup of mixing behavior in anaerobic digesters in view of maximizing performance. Anaerobic digesters (AD) at full scale often do not reach their full potential of biogas production. It is postulated that this is caused in large extent due to incomplete mixing, resulting in heterogeneities and stratification, thus inducing reduced performance. Dedicated rheological and density experiments with AD influent, sludge and mixtures will be performed as well as at different locations in AD. This will lead to new process insight and is to be used as input in computational fluid dynamics (CFD). The modelling work will be initiated by studying the behavior of Anaerobic Digestion Model 1 (ADM1) in conjunction with a continuous stirred tanks (CSTR) and Tanks-in-series (TIS) approach. Next, a CFD model will be developed to model hydrodynamics full scale AD reactors of different design to optimize the mixer impeller (blade number, speed, position, and etc.). Computed CFD is used to derive a more accurate compartmental model (CM) based on velocity patterns. This work lead to process insight and potential actions for process optimization. The optimal CM needs to be translated into an AD and a mixer design. The ADM1 model will be linked to frozen CFD solutions to get an idea about the impact of incomplete mixing on the distribution of different process rates in the reactor and the possible occurrence of stratification or even short-circuiting.

My progress / state of the art :

The literature review is ongoing. An activated sludge rheological measurement plan will take place from March 14-17, 2017 at TU Delft, The Netherlands. Preliminary results, obtained by ADM1 modelling using CSTR and TIS are promising and allow us to move forward for more detailed study work.