ANALYTICAL PYROLYSIS FOR STRUCTURAL MODIFICATION AND THERMOCHEMICAL TRANSFORMATION OF LIGNOCELLULOSIC BIOMASS

Abstract

This thesis explores the applications of analytical pyrolysis to understand the structural modification and thermochemical transformation of lignocellulosic biomass. So, to understand the applications of analytical pyrolysis in the thermochemical transformation of lignocellulosic biomass, microscale research work was performed with the objective of the role of pyrolysis in the combustion of biomass by using analytical instruments such as thermogravimetric analyzer (TGA) and FTIR. The investigation required a holistic approach to study the fundamentals of lignocellulosic biomass combustion which involves analysis of ignition properties, energy, mass transport limitations, and the quantity of energy released/demanded at various stages of the combustion process. Combustion in a solid involves three primary stages such as pyrolysis, gasification, and oxidation. Pyrolysis, which is also the combustion process's first step, is endothermic and requires energy from external sources to progress. On the other hand, gasification and oxidation are exothermic processes. The study hypothesizes that pyrolysis as an energy-demanding process dramatically influences the overall combustion process. This study conducts pyrolysis and combustion experiments using a thermogravimetric analyzer (TGA) at various heating rates (5, 10, 15, 20, 25 ◦C/min) in nitrogen and air atmospheres, respectively. Mass loss (TG), differential thermogram (DTG), differential thermal analysis (DTA), and heat flow (DSC) data were recorded concerning temperature and time for both processes. The Isoconversional methods such as Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) are employed to estimate the activation energy of the process concerning the conversion. The differential calorimetry analysis reveals that the combustion process has two exothermic zones: one related to the combustion of volatiles released during the pyrolysis step and another associated with char combustion. In terms of magnitude, the second exothermic step is predominated by the first one. The FTIR analysis of the raw biomass and char produced from the isothermal reveals the structural transformation of the biomass concerning temperature and conversion.