Thermogravimetric Analysis on The Pyrolysis
Two varieties of Philippine rice hulls, R-302 and R-19 were pyrolyzed at three heating rates of 10, 20 and 50 K/min using a dynamic thermogravimetric analyzer (TGA) in a nitrogen environment. Results show that the decomposition of hemicellulose starts at lower temperature than cellulose. Lignin decomposes at higher temperature than hemicellulose and cellulose. An abrupt weight loss can be noticed at second peak of active pyrolysis. As the heating rate is increased, there is a shift to higher temperature and total percentage weight loss showed a very slight change. Likewise, the rates of degradation of the two varieties are practically similar. Kinetic parameters were obtained using Arrhenius law and global mass loss kinetic models. Results show that the major components of the rice hulls have the following order of activation energy: cellulose>hemicellulose> lignin.Key words: rice hulls, thermogravimetric analysis, pyrolysis Rice hull or husk is the thin but tough outer sac of the rice grain. It accounts for about 20% by weight of the whole rice (Grist, 1975; Beagle, 1978). It is considered a major agricultural waste in rice producing countries like the Philippines. An estimated 150 thousand metr
Figure 6 shows the Arrhenius plot of the 3-stage decomposition of rice hull variety R-302 at a heating rate of 20 K/min. The results from the TGA are analyzed to determine the kinetics of pyrolysis of rice hulls. However, the actual composition is variable and changes with variety, climate, and geographic location of growth (Liou & Chang, 1997) The chemical complexity of the decomposition of rice hull as well as other biomass materials has made researchers very busy. Rice variety R-302 was obtained from the northern province of the Philippines, specifically, San Juan, La Union. Results show that the first stage which corresponds to hemicellulose and cellulose pyrolysis have an overall value of E equal to 90. This trend was also observed when thermogravimetric experiments using fine particles of wood showed that moisture in the wood is evaporated first followed by a sequential decomposition of hemicellulose, cellulose and lignin (Salazar,1993; Reina,1988; Williams, et al. These kinetic parameters can be used to predict the decomposition of hemicellulose, cellulose and lignin of the rice hull. From the Arrhenius Law kinetic model,the activation energy (E) and frequency factor (A) for R-302 is equal to 80. Thus, the order of E for R-19 is in the order of: hemicellulose and cellulose> lignin. 28 million metric tons of rice produced in the Philippines for this year up to year 2000 (Manila Star, July, 1999). Moisture content of the sample was not determined.
Common topics in this essay:
R-302 R-19,
K/min Over-all,
Peak TempK,
Williams Besrel,
K/min Figure,
Variety Lump,
Williams Besler,
Arrhenius Law,
Shimadzu TGA-50,
Liou Chang,
rice hulls,
rice hull,
weight loss,
et al,
50 k/min,
hemicellulose cellulose,
kinetic parameters,
heating rate,
20 k/min,
r-302 r-19,
50 k/min over-all,
global mass loss,
teng et al,
et al 1998,
kinetic parameters rice,
|
Acceptance Essays
