Abstract
A thermal model was used to compare an actual and a computational heat losses in an existing the semi-buried anaerobic digester (AD) during the winter season in Northeast Poland. This work is an attempt to answer the question whether the cause of the temperature decrease of the manure AD is underestimated the heat exchanger or its low efficiency. The answer to this question is important for manager to take appropriate action. Understanding the heat loss of biogas digester is important to use these technologies to produce the biogas on assumed level in cold environment - like winter in Northeast Poland. From anaerobic digester point of view, the maintaining of optimal fermentation temperature is crucial. In the current study 2-D axisymmetric steady heat transfer model was carried out to calculate heat loss of AD for a real biogas plant located in north-eastern Poland and compared with actual state.
Highlights
Temperature is one of the most important parameter to control the microbiological activity in the anaerobic digester
It can be concluded that neglecting convective heat transfer through the cover can lead to an oversizing the heat flux
Based on the numerical model, it can be concluded that the power of the heat exchangers should cover heat losses for the average monthly temperatures assumed (the calculated temperature in the area of analyzed biogas plant is (-22)oC) for AD number 2 and the manure temperature in that anaerobic digester should be near constant
Summary
Temperature is one of the most important parameter to control the microbiological activity in the anaerobic digester. Many models were validated in warm climate with good agreement between the predicted and field data [2]. The numerical model the biogas system integrated with solar collectors is presented in [6]. For cold climate the temperature of the slurry, the biogas, membrane, wall and cover in function of solar radiation, wind velocity, ambient temperature and digester geometry are important. Wu and Bibeau [9] presented a three-dimensional steadystate model for simulating heat transfer for anaerobic digesters for cold weather conditions. There are very developed mathematical models for the prediction of the temperature distribution within the reactor under steady state conditions [10]. Simulated heat transfer results were compared to a one-dimensional model and validated against experimental data using an operating anaerobic digester
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