A study to investigate the briquette forming ability of rice straw, rice husk, and sawdust to produce a fuelwood substitute was conducted by Hasina Yeasmin, a master degree student of the Energy Technology Division, Asian Institute of Technology, under the supervision of Dr. S.C. Bhattacharya.
In the densification process, the fuel properties of the densified fuel varies widely with the applied pressure and its duration, temperature, particle size, moisture content, etc. In this study the effect of temperature and pressure on the properties of the briquettes produced were investigated.
A compaction apparatus was designed and detailed components are shown in Fig. 1. Briquettes of rice straw, rice husk, and sawdust were produced, and the properties of the briquettes, such as density, compressive strength, percentage of weight retained on a drop shatter test, and elongation on immersion in water were studies to find the capability of the of the briquettes to withstand various conditions- transportation, storage, feeding and other handling processes.
It was found that a briquette with a higher density is generally obtained at a higher pressure and temperature. The rice straw shows a decrease of density at pressures above an optimum. In general there is an optimum temperature of about 210°C at which the compressive strength is at a maximum. The percentage of initial weight retained after a drop shatter test ( R) is generally higher at higher densification pressures and temperatures. However for rice straw there is an optimum at which R is maximum; this temperature is around 250°C. The ultimate elongation of the briquettes on immersion in water is lower at higher temperatures and pressures.
More details are available in Fuel from Agricultural Residues by Hasina easmin, Master Degree Thesis, Asian Institute of Technology, Energy Technology Division, 1984, vil + 57p.