Tar Fouling of Heated Metal Transfer Line in Biomass Gasification

Tar and ash fouling are majorly disruptive in the operation of biomass-driven thermal plants. This research is focused on the fundamental reactions of tar fouling on commercial boiler metal surfaces. A DuPont Instruments 951 Thermogravimetric Analyzer (TGA) was modified to simulate on a bench scale system the tar deposition that occurs on a metal transfer line. The transfer line material being tested was Stainless Steel 316 (SS 316) in the form of coupons that are approximately 0.5 square inch in area and spheres whose total surface area was approximately 6.66 square inches. The downstream section was joined to a Wilmad LabGlass impinger, which collects solid and liquid materials that exit the line. Fouling rates were be calculated by measuring mass change from the start to the finish of each experiment. Tar was successfully formed on the Stainless Steel 316 surfaces. Temperatures near 750°C appeared to promote bimolecular recombinations which formed higher order polynuclear aromatic hydrocarbons. Coking did not appear to be significantly different between 589.6 and 678.4 degrees Celsius.