Design modification, CFD simulation, fabrication and experimental validation of continuous feeding biochar producing cook stove

Abstract

Household energy use and biochar in developing countries like Ethiopia have gained a tremendous interest in the past decade. The adoption of a simple household pyrolytic stove has the potential to provide multiple benefits from reducing the rate of deforestation, improved soil fertility, enhanced household air quality to mitigating climate change. The Green Solution Concept focuses on using biomass waste resources. The main objective of this study is Design optimization, CFD simulation, fabrication and experimental validation of continues feeding biochar producing cook stove. Overall, approximately 45 cases were studied during the development of this model. The majority of these cases were run to gain an understanding of how various parameters affected the solution. This paper summarized the CFD applications in biomass combustion and system design. There is evident that CFD can be used as a powerful tool to predict biomass combustion and heat transfer processes as well as to design combustion chamber or reactor. CFD has played an active part in system design including analysis the flow, and temperature. During the course of this research project, realistic geometry, flow conditions, and fuel properties were incorporated into a 3D numerical model using Fluent CFD software (ANSYS 14.5). By performing simulations with different direction of air inlet and mesh size, it was shown that the 3D model performed fairly well, and exhibited the expected trends for temperature, and flow gases. Similar with CFD simulation, experimental results shows the temperature variation within biomass bed is high in both NA and CFAT stoves while it is small temperature variation in CFBP stove. Thermal efficiency was performed on the three selected stoves using eucalyptus tree as a fuel. It was observed that the CFBP cook stove, CFAT stove and NA stove shows a thermal efficiency of 25%, 18%, and 17% in the case of high power test (cold start). and also the thermal efficiency of CFBP stove, CFAT stove and NA stove shows 15%, 13%, and 13% in the case of low power test (simmering) Thus, it was found that the thermal efficiency of CFBP cook stove is found to be higher when compared with the other two pyrolytic stoves in both cases. The biochar produced is highly alkaline, with all pH values recorded above pH 9.33 to a maximum pH of 9.63. The variability within the sample chosen from each burn is low, which means that coffee husk biochar produced experimentally is consistent in terms of pH with in a given burn.