Thermochemical and analytical approach to describe secondary slag phase formation and local process conditions in a full-scale BGL gasifier

Abstract

This study aims to directly analyze untreated process samples from a full-scale BGL gasifier. It assesses as well as categorizes the findings to identify the most important effects governing the behavior of slags under gasifier conditions. A process slag sample from the Schwarze Pumpe BGL-type waste gasifier is thoroughly analyzed via X-ray diffraction (XRD), X-ray fluorescence (XRF), and using a scanning electron microscope with energy dispersive X-ray spectroscopy (SEM-EDX). The results are interpreted with the aid of thermodynamic equilibrium calculations using the FactSage™ software package to yield the main influence factors on slag viscosity and -structure. Since these are derived from full scale process samples, the severity of the impact to these processes can be assessed. Especially the effect of secondary phases apart from the main slag phase is evaluated. The differences between laboratory measurements and full-scale processes are identified. The composition of the gas atmosphere above the slag bath cannot easily be determined. This study uses a method to determine and include this gas atmosphere into the process slag analysis through thermodynamic equilibrium calculations. The temperature of the slag bath and the gas atmosphere around the slag is backtracked via analytically validated thermodynamic equilibrium calculations.