Effect of briquette geometry on their thermal performance and combustion properties

Abstract

The quality of briquettes varies greatly among small scale producers in Uganda due to the different methods of production, absence of standardization, lack of technical knowledge and quality control protocols. The study was undertaken to investigate the effect of briquette geometry on thermal performance and combustion properties of briquettes developed from 1kg of coffee and /or rice husk bio-char bounded with cassava starch as a binder in the percentage mixtures of 3.5%, 4.5%, 5.5% and 6.5%. The research focused on cylindrical and rectangular briquettes. The physical properties (moisture content, volatile matter, fixed carbon and ash content) of the developed briquettes were determined using Thermogravimetric analysis. All processing variables (physical properties) in this study were the same for cylindrical and rectangular briquettes at the same binder levels. Drop test method (at a height of 1.5m) was used to determine the mechanical and storage integrity of the developed briquettes. The results show that the level of binder had an effect on strength. Generally rectangular briquettes had more drop strength than cylindrical briquettes. The cylindrical and rectangular briquettes were evaluated in a 3191g cook stove (Burn-Jiko-koa) using water boiling tests of ignition time, burning rate, specific fuel consumption and water boiling time. The results show that their performance varied with binder levels but generally cylindrical briquettes had a less ignition time, higher burning rate and took less time to boil a half liter of water compared to rectangular briquettes. The results also show that cylindrical briquettes had lower specific fuel consumption than rectangular briquettes. Thus cylindrical briquettes should be more encouraged than rectangular briquettes since they are more economical in terms of domestic energy use.