Effect of Pressuring Time and Number of Holes on the Combustion Characteristics of Coconut Shell Char Briquettes

Abstract

Briquettes have long been known as solid fuels that have particular specifications and uses. The briquettes utilization is very limited, mainly due to various obstacles, one of which is related to briquettes combustion. This study aims to determine the physical and combustion characteristics of briquette by comparing the effect of the pressuring time and the hole numbers of the briquette made of coconut shell biomass waste. Pre-dried coconut shell's raw material was carbonized in a closed vessel in less oxygen condition at a temperature of 450-500oC. Coconut shells char was then crushed and sieved to 60 mesh. The char powder was mixed with an amount of binder made of starch and stirred well to form a paste. Furthermore, the paste was put into a metal mold of 33 mm diameter, pressurized using a 160 kg.cm-2 hydraulic press for 30, 45, 60, and 75 seconds of holding time. The briquette products were then sun-dried and holed to 3 mm for 1, 2, and 3 holes for each briquette vertically. The product then analyzed for the density, compressive strength, ignition time, combustion duration, combustion rate, and thermal decomposition. The results showed that the density and compressive strength of briquettes were significantly influent by the hole numbers, which ranged from 0.834 -1.057 g.cm-3 of the density, and 47,7 - 50 kg.cm-2 of the compressive strength.  The relaxations of the briquettes were in the range of 0,51 – 10,98%. The ignition time of the three holes briquette was 5.33 minutes, while the no-hole briquette was 7.47 minutes. The combustion duration of three holes briquette was 160 minutes, while 185 minutes for no hole briquette with the combustion rate of 0.116 g.min-1 and 0.120 g.min-1 respectively. Thermal decomposition analysis showed that the decomposition of biomass started at a temperature of 337oC and the weight lost up to 0.635 mg or 12.70%.