Development of a Model for Selecting the Required Compaction Pressure of Heterogeneous Briquettes from Agricultural Wastes

Abstract

In low-pressure compaction, the application of excessive pressure during compaction often results in poor quality briquettes. This is owing to the fact that the binding materials are often squeezed out of the briquettes. An empirical model for selecting the required compaction pressure of heterogeneous briquettes of agricultural waste was developed in this research. Heterogeneous briquettes of Sawdust/Palm kernel shell were produced by mixing Sawdust and Palm kernel shell at certain varying ratios, with Cassava starch as the binder. The optimum compaction pressures of the homogeneous briquettes were 686.5 N/cm2 and 981 N/cm2, for sawdust and palm kernel shell, respectively. The predicted required compaction pressures of the heterogeneous briquettes, as predicted from the model, ranged from 715 N/cm2 to 950 N/cm2 for the briquettes. It was revealed that the respective compaction pressures at which the agricultural wastes offered good quality heterogeneous briquettes depend on the type of material and the mixing ratios of the constituent materials; this finding was the basis on which the empirical model was developed. A comparison between the calorific values and densities of heterogeneous briquettes compacted at a fix compaction pressure of 1177 N/cm2 and those compacted at their respective predicted compaction pressures showed that good quality briquettes were obtained when compacted at the predicted compaction pressures, than at the fixed compaction pressure. The developed model will offered ease of compaction and effective utilization of materials and will be of great use in the design of variable pressure briquetting machines.