Effect of Densification Pressure on Physical and Combustion Properties of Binderless Briquettes Made from Rice-Husk and Coffee-Pulp

Abstract

Agricultural residues such as rice husk and coffee pulp are abundantly available highlighting its potential as source of renewable energy. Utilizing this kind of biomass as a raw material for bio-briquettes can be considered as an effective way to minimize their wastage. This study aims to examine the characteristics of bio-briquettes produced from rice husk and coffee pulp through a cold-forming process at a pressure of 100, 150 and 200 kg/cm2 without binder. Prior to briquetting process, coffee pulp was sun-dried, ground and sieved to mesh 20 while rice husk was dried and carbonized before grinding and sieving. Mixtures of 50% rice husk char-50% coffee pulp and 100% coffee pulp were made by adding water followed by molding and drying processes. Characterization of the briquette employs a number of techniques including DSC, TGA, bomb calorimeter and proximate analyses as well as mechanical testing. The results show that the calorific value of 100% coffee-skin briquette is 4764 cal/g containing 16.5 wt% of moisture, 12 wt% ash. The rate of combustion is 0.019 g/s with ignition time of 196 s. Varying briquetting pressure results in a change in ignition time of bio-briquettes as the density is increased. However, no significant change was observed on the rate of combustion upon increasing the briquetting pressure. This investigation concludes the potential use of agriculture residues as raw material for solid biomass fuel production.