Simple and rapid method to estimate biokinetics design constants, biochemical methane (BMP) and hydrogen (BHP) potential of leather fleshing co-digested with MSW
Shanmugam, P. and Horan N.J., The University of Leeds, UK
(free)
Biogas production from municipal and industrial solid and liquid waste has gained considerable interest from engineers and managers both in the UK and globally due the substantial benefits of achieving environmental protection, energy generation and GHG emission reductions. However, there are number of problems involved in scaling up promising results in experimental anaerobic digester (AD) plants to field scale production plants. One such problem associated with AD is mixing, which is a vital component that segregates synthesized gas and biomass from digester liquid. This enhances homogeneity ensuring adequate contact between bacteria and substrate in the AD. Problematic fluid flow situations such as these are well suited to analysis by Computation Fluid Dynamic (CFD), where models can be calibrated and validated using the pilot plant measurements and then used to accurately simulate the performance of the large-scale reactors. In this present study an investigation of gas mixing efficiency in a lab scale AD using CFD analysis has been undertaken. One of the more recently established techniques for mixing the contents of a reactor is to use bubble mixing – where the produced gas is recirculated through the vessel contents to induce mixing. In this work the aim has been to further understand and enhance the use of bubble mixing approaches to improve the performance of future bioreactors. A computational model has been developed to simulate the complex flows occurring in an experimental two litre capacity suspended growth AD. Results are presented for various CFD simulations of this lab scale AD for a range of bubble sizes. These results are discussed in relation to their suitability for evaluating mixing characteristics and understanding requirements for developing accurate simulations of mixing conditions in the large scale reactors. Improved mixing efficiency of AD pilot plant will contribute to the future design of large scale AD at different hydraulic retention times and organic loading rate for managing different types of solid and liquid waste in the near future.
Key words: green house gas (GHG), anaerobic digestion (AD), bubble mixing
