Design of Cow-Dung and Grass- Clippings Isothermal Continuous Stirred Co-digester for biogas production

Abstract

The continuous search in renewable energy sources for industrial and domestic utilization is very imperative and motivated this
study. The study of Cow- dung and grass clippings Co-digestion are important due to the fact that the successful outcome of the
studies will provide a basis for waste minimization and enhance renewable energy production for global consumption. This work,
therefore, is focused by exploiting the modified Gompertz kinetic equation in developing design models for the simulation of continuously stirred co-digester (CSC) at the isothermal condition. Co-digester functional dimensions such as volume, length,
space-time, space velocity and heat generation per unit volume were developed for Continuous Stirred Co-digester type..The
developed models were simulated using Matlab codes programming technique using the design basis of 50,000 metric tons of
biogas per annum at 370 C isothermal condition. The developed performance models were solved numerically using MATLAB
version 7.1 within the operational limit of conversion degree, XA = 0.1 to 0.9. The results obtained showed that the increase in
fractional dimensions of Co-digester volume VR, length LR, and Spacetime SV- increases with an increase in fractional conversion at a constant radius. Results of space velocity (SV-) and heat generation/per unit volume (q) showed inverse characteristic behavior as an increase in fractional conversion decreases space velocity and heat generation per unit volumes.. Further careful examination of the results, demonstrated that at an optimal yield of 0.9 degrees of conversion, Co-digester volume value of 10.0m3 at constant radius was feasible. The results as obtained in this work proved a dependable relationship with the fractional conversion.