Crystallization of Synthetic Coal−Petcoke Slag Mixtures Simulating Those Encountered in Entrained Bed Slagging Gasifiers†

Abstract

Commercial entrained bed slagging gasifiers use a carbon feedstock of coal, petcoke, or combinations of them to produce CO and H2. These carbon sources contain mineral impurities that liquefy during gasification and flow down the gasification sidewall, interacting with the refractory linear and solidifying in the cooler zones of the gasifier. Proper slag flow is critical to good gasifier operation. A hot-stage confocal scanning laser microscope (CSLM) was used to analyze the kinetic behavior of slag crystallization for a range of synthetic coal−petcoke mixtures. On the basis of the observed precipitation during cool down studies in the 1200−1700 °C temperature range, a time−temperature-transformation (TTT) diagram was created. The crystallization studies were conducted with a CO/CO2 (=1.8) corresponding to a gasification PO2 of approximately 10−8 atm at 1500 °C. Ash chemistries were chosen such that they correspond to coal−petcoke feedstock mixtures with coal ash amounts of 0, 10, 30, 50, 70, and 100% (by...