Effect of Pretreatment on the Physical Properties and Heating Values of Briquettes

Briquettes from agro-residues have been promoted as a better replacement to firewood and charcoals for heating and cooking in the rural communities. In view of this, a study was carried out to investigate the effect of pretreatment methods on physical properties and heating values of briquettes produced from corncob. To accomplish this work, the experiment was designed as a 2×3×3×3 completely randomized with three replicates. The parameters are pretreatment methods (carbonized and uncarbonized), binder types (cassava, corn and gelatine), binder concentrations (10, 20, 30%) and compacting pressure (50, 100 and 150 kPa). A charcoal kiln was fabricated to obtain the pretreatment through pyrolysis and a punch and die was also fabricated to enable the briquette densification. The physical properties tested were limited to moisture content (MC), density and compressive strength and were determined using a conventional method. The heating value of the briquettes produced was determined using bomb calorimeter. The results showed that average moisture content ranged between 5.29-6.58% and 12.75-13.72%, mean relaxed density varied from 813-925 kgm-3 and 963-1166 kgm-3, compressive strength ranged between 2.27-5.07 MPa and 5.97-10.12 MPa and heating value ranged between 28.85-32.36 MJkg-1 and 27.58-28.80 MJkg-1 for carbonized and uncarbonized briquettes, respectively. Briquettes produced from carbonized corncob had a better moisture content and heating value, while briquettes produced from uncarbonized corncob had higher density and compressive strength. The study shows that pretreatment methods under different binder types and concentrations and the compacting pressure significantly affected briquette’s physical properties and heating values.