Effect of HCl on the corrosion and wear of in-bed tubes in a laboratory simulated bubbling fluidized bed

Heat-exchanger tubes in fluidized bed combustors (FBCs) often suffer materi al loss due to combined corrosion and erosion. The effect of chlorine on in -bed tube wastage and its possible mechanism are being studied using the EP RI/LBNL FBC wastage simulator. This test rig was designed to simulate dense particle impacts on tube bottoms with well-controlled parameters, and has been proven to closely reflect situations found in operating bubbling FBCs, In this study, HCl gas was chosen to be the Cl source and was introduced i nto the fluidizing air with a 50-ppm concentration. Tests were performed at temperatures ranging from ambient to 400 degrees C using 1018 low carbon s teel rods in a bed of commercial SiO2 sand that had an average size of 800 mu m. The wear profile after each test was measured using a profilometer. R esults showed an increase in material wastage rates in the presence of HCl, and that the rate was significantly higher with higher test temperatures. Microstructural and chemical analysis of the wear surface and corrosion pro ducts are reported. It is concluded that the dominating effect of HCl on th e wastage rates is due to an enhanced oxidation and a reduced scale adheren ce. (C) 1999 Elsevier Science S.A. AU rights reserved.