Experimental and Kinetic Study of NOx Reduction by Reburning Using Syngas from Updraft Biomass Gasification with Phenol As a Model Compound for Tar

An experimental and kinetic study of NOx reduction by reburning using syngas from updraft biomass gasification has been carried out in this paper. A 10 kW updraft gasifier close-coupled to a 20 kW entrained flow combustion reactor was the experimental system. Experiments were carried out in a temperature range of 1000-1200 degrees C, and the stoichiometric ratio in the reburn zone (SR2) was in the range of 0.6-1.0. Phenol (C6H5OH) was selected as a model compound for tar according to GC-MS analysis of gasification tar components. Experimental results of NO reduction by syngas with tar revealed that NO reduction efficiency of approximately 85% could be achieved at SR2 = 0.7 and reactor wall temperature = 1200 degrees C. In order to model the syngas reburning process with tar, a kinetic mechanism which consisted of 22 global reactions concerning tar conversion and NO reduction was set up and implemented in a two-dimensional computational fluid dynamics (CFD) program to simulate the NO reduction effect. The modeling results are discussed and compared with experimental data. It is shown that the combustion and reburning process can be reasonably modeled with the kinetic mechanism under the experimental conditions, and the effect of tar on NO reduction should not be neglected in the syngas reburning process, especially when the tar content is high.