CCS and Power Systems
Advanced Energy Systems - Gasification Systems
A Technology To Mitigate Syngas Cooler Fouling - Phase II
Performer: Reaction Engineering International
Project No: SC0004499
REI has completed analysis of gasifier feed and samples of fouling deposits taken from the syngas cooler of an IGCC plant. REI researchers, with support from the University of Utah and collaborators from the gasification industry, have conducted laboratory tests on the samples to characterize gasifier feed composition and deposit composition and morphology. The deposits are quite different from deposits that occur in coalfired boilers. The syngas cooler deposits are enriched in specific metals from the ash contained in the gasifier fuel. The deposits contain a substantial amount of fine (sub-micron) particulate, with the average particle size being about one micron and nearly all particulate is less than five microns. Layering and large char particles (~10 microns) are rarely observed in the deposits. Data collected supports the hypothesis that the deposits are not the result of surface condensation but rather are formed by aerosols generated when vaporized materials pass through cooler regions upstream of the syngas cooler.
REI has created a computational fluid dynamics (CFD) model for a "generic" syngas cooler. The model simulates a transition duct, tube sheet face, and tube bank. Deposition in the CSC was predicted using an advanced version of the REI deposition model, a mechanistic model that includes the impacts of (1) ash properties (individual particle composition, particle size, temperature, density and viscosity), (2) local conditions (gas composition, temperature, heat flux to surfaces), and (3) properties of deposits (composition, temperature, density, viscosity). The model provides predictions for the properties of particles exiting the furnace in suspension, deposition rate (growth rate) and the impacts of fouling on overall heat transfer. Model results indicate that most of the deposition occurs on uncooled surfaces upstream of the syngas cooler and on the tube sheet face of the syngas cooler. Little if any deposition occurs on the tubes themselves after the tube entrance region; this is in agreement with behavior reported by plant operators.