DETERMINATION OF DEVOLATILIZATION KINETICS IN INERT AND CO2-ENRICHED ATMOSPHERES IN A PLUG FLOW REACTOR

摘要

The current paper presents pyrolysis experiments carried out using an isothermal laminar drop tube reactor. The reactor is operated with argon to gain an inert atmosphere. Additional CO_2 was admixed. A maximum process temperature of 1300 ℃ and high heating rates of 104 - 105 K/s ensure conditions comparable to pulverized coal-fired boilers. Pulverized coal is continuously fed into the pyrolysis reactor and further downstream collected with a cooled sampling probe. Different residence times are provided by different sampling probe positions leading to time resolved measurements. Samples of char are collected and analyzed concerning elemental composition (C, H, N, S). The mass loss of the coal is determined with the ash tracer method.rnTwo different ways of rate parameter determination are compared in the current work. The simplest approach to convert measured coal mass loss into a kinetic expression is the assumption of linear particle movement with constant velocity, hence residence time can be computed by mean reactor gas velocity and sampling probe position. This method is usually applied to drop tube experiments without any particle velocity measurement. However, the gas velocity profile is not homogeneous and the particle temperature, the second key parameter for kinetics determination, is not constant. Therefore, a method based on CFD-calculations of the reactor is presented to calculate residence time and particle temperature. The kinetic parameters are then derived from simulations of the reactor combined with the mass loss results from solid samples in an iterative procedure.