Thermal characteristics of rice hulls

Abstract

Evaluation of the thermal characteristics of rice hulls is described. Decomposition was negligible below 20O0C, but on heating above 200"C, the amount of volatile matter evolved increased steadily with increasing temperature up to 450°C, where > 90% of the total volatile matter was separated. Decompositionis rapid and is temperature dependent. The effect of temperature on the composition of the residues is also described. The carbon content of the residues increased while the oxygen and hydrogen content decreased sharply when the temperature of pyrolysis was increased.

Chemically Treated Rice Husk Blends as Green Desiccant Materials for Industrial Application

“…The third stage of decomposition (III) took place in the range of about 180-420°C, indicated by a sharp drop and a harsh peak in the TG and DTG curves, respectively. The mass loss of 47.4-60.7 % associated with this stage may be due to the removal of volatile matter [15]. Major decomposition occurred in the third (III) and fourth (IV) stages.…”

“…The specimens were cured at room temperature for 24 h after being removed from the mold. Since RHs are a very stable agricultural waste and the thermal decomposition of oven-dried husks was reported to be negligible below 200°C [15], they were dried in an oven at 105°C for 2 h and cooled in a desiccator. Use of PVA as a binder (adhesive) provides appropriate physical shape for characterization and application.…”

Rice Hulls

“…Loss of weight continued slowly up to 500°C, which indicated that fine carbon was burned inside the silica pores. At 450°C, more than 90% of the total volatile matter was removed in the absence of air (Hamad 1981). Loss of weight was higher in the presence of air because of oxidation reactions.…”

“…The carbon content of the residue increased with pyrolysis temperatures between 200 and 500°C, whereas oxygen and hydrogen content decreased sharply. Pyrolysis of hull at 800-850°C for 7 min resulted in 37-40% residue containing 50% organic matter and 50% ash, but the char of combustion at 800°C in the presence of oxygen was 32%, consisting of 38% organic matter and 62% ash (Hamad 1981). Increasing air rates during combustion of rice hull in a fixed-bed furnace favored crystallization of silica, probably because of the higher combustion temperature (Hamad and Khattab 1981).…”

“…The char obtained from traditional rice-hull furnaces contains 36-40% organic matter, mainly carbon, reflecting incomplete combustion of hull as a result of its high ash content (Hamad 1981). The temperature of combustion and sufficient oxygen supply are the major factors influencing the degree of combustion of rice hull.…”