การเปรียบเทียบการสลายตัวด้วยความร้อนของน้ำยางดำที่ใช้วัตถุดิบจากไม้ไผ่และยูคาลิปตัสโดยเทคนิคเทอร์โมกราวิเมทริค / วัทน์สิริ จินาทองไทย = Comparison on thermal decomposition of bamboo and eucalyptus based black liquor by thermogravimetric technique / Watsiri Jinatongthai
The objective of this research was to study the decomposition of black liquor from 2 pulp mills in Thailand that has different raw materials. Only pyrolysis step and parameter that effect the decomposition were determined to calculate the instantaneous kinetic constant and model of decomposition. The experiment was carried out by thermogravimetric analysis under nitrogen atmosphere. Two sets of experiment were performed: Isothermal and dynamic. In isothermal experiments, the sample was heated using constant heating rate of 100 °C/min up to the final pyrolysis temperature from 200 to 900 °C, which was maintained for 15 h to assure complete decomposition but from experiments the sample was not completely disintegrated. In dynamic experiments, the sample was heated at different heating rates ranging from 5 to 100 °C/min, up to a temperature of 1000 °C and hold for 20 min. It can be observed that the solid conversion increase with final pyrolysis temperature and heating rate. Assuming a first order for thermal decomposition rate to calculate kinetic constant, it was found that the kinetic value for isothermal experiment is initially high and then drop near zero and that the kinetic constant is not depend on final pyrolysis temperature. For prediction of the kinetic equation for isothermal, it can be determined that the calculated values of kinetic constant and the experimental data is quite good at final pyrolysis temperature 200 °C and 250 °C for first black liquor sample and at under 500 °C for second black liquor sample. For calculated equation to predict the value of solid conversion in dynamic experiment due to the predicted equation must use parameter from isothermal experiment, so the results are not agree well with values for calculated of solid conversion and experimental values in dynamic experiment. Calculation of the activation energy cannot be performed because the DTA thermogram was not indicated distinct peak to divide the graph for calculated activation energy.