VALIDATION OF PROPOSED MECHANISM TOWARDS IN-SITU CO_2 CAPTURE DURING GASIFICATION BY SIMULATING A HIGH Si/AI and LOW Ca CONTENT COAL SOURCE

摘要

The mechanistic behaviour of Ca-containing mineral species towards the in-situ capture of CO_2 during gasification, as well as understanding the chemistry and the interpretation of the mechanism involved, as measured by means of high temperature X-ray diffraction (HT-XRD), in combination with FACTSAGE? modelling, is known. The CaO content of a South African and another coal source investigated previously ranged from 6 mass % to 30 mass % respectively. The basic components present in the coal, or specifically CaO, only act as a fluxing component (lowering of the melting temperature) up to a specific percentage, where after the AFT of the coal starts to increase again. At this turning point the (Si+AI):Ca ratio is 2.75, which is the stoichiometric chemical ratio for anorthite, which implies that after the turning point, the formation of anorthite is maximized and can thereafter only remain at the same level, or decrease with increasing temperature as the anorthite starts to become a slag-liquid.