Modellering av pyrolys i roterande trumma

Sammanfattning: This project focuses on the numerical modeling of a rotary kiln pyrolyzer such as found in the e.g. WoodRoll multistage gasification process. The model consists of two parts: a granular flow model, and a pyrolyzer model. In the first part, Saeman's equation was employed to develop a model which can describe the behavior of solid granular flow in a rotary kiln without reaction. Residence-time distribution (RTD) is the main aim to study in this part, which was simulated by axial dispersion model (ADM). The model requires only one fitting parameter that is dispersion coefficient (Dax), which was studied in parallel by two cases: constant value of Dax, and Dax as a function of kiln's length. The result of both models show good predictable in comparison to experimental data from literature, and represent narrow distribution of residence times that behave similar to plug flow reactor. Unfortunately, the result still cannot claim which model of Dax is the best model to describe RTD in rotary drum. The second part of the thesis purpose to design the model of rotary kiln pyrolyzer, which contains specific behavior of granular flow, heat transport in a kiln, and primary pyrolysis of wood. The model of steady-state condition with constant wall temperature was simulated to generate temperature profile and conversion along a kiln. This model included all heat transport features such as conduction, convection, and radiation. According to the result, supplied energy from outer surface of the kiln essentially transfer through the kiln via heat conduction, which occur between solid bed and rotating surface of the kiln. Temperature profile that generated by this model looks reasonable to the process of rotary kiln pyrolyzer, which affected by heating system and heat of reaction along the kiln. The result also demonstrated that conversion of wood is strongly dependent of wall temperature or heating rate of the system. Nonetheless, kinetics data for wood pyrolysis still a debatable issue in many research, and this model required validation by experiment of rotary kiln pyrolyzer.