Corrosivity of lead chloride containing salt mixtures – characterization of corrosion products

B3 Non-refereed conference proceedings


Internal Authors/Editors


Publication Details

List of Authors: Hanna Kinnunen, Dorota Bankiewicz, Kristina Hellström, Mikko Uusitalo, Sonja Enestam
Publication year: 2015
Publisher: International Flame Research Foundation
Book title: N/A


Abstract

Waste-based fuels are turning into one of the conventional fuel types in power boilers. Not only a cheap price but also good availability and renewable energy benefits increase the use of waste-based fuels. These types of fuels typically contain elevated concentrations of harmful elements such as lead (Pb), zinc (Zn), chlorine (Cl), alkali metals (Na, K) and sulphur (S).

Lead chloride has been previously identified with fine particle and gas measurements in a waste fuel firing circulating fluidized bed boiler. Based on the measurements, lead chloride was present at all studied locations throughout the boiler. It is known that lead chloride increases the corrosion risk in furnace walls and lower temperature superheater areas when condensing on metal surfaces.

In this work, the corrosivity of the lead chloride with respect to material surface temperature was studied with several laboratory scale measurement techniques. The effect of the lead chloride amount on corrosion was also examined. Salt mixtures containing different amount of lead chloride mixed with potassium sulphate were used as synthetic deposits. Low alloy commercial boiler steel, EN10216-2 10CrMo9-10, was used. After the experiments, the characterization of the corrosion products was carried out by scanning electron microscope and x-ray diffraction analysis methods.

At a temperature of 325 °C, the thickness of the oxide layer increased with increasing PbCl2 amount in the salt mixture. An exception was pure lead chloride salt which was less corrosive than for example 50% PbCl2-50% K2SO4 salt mixture. However, no significant corrosion was detected at this temperature. At 350 °C, no clear correlation between the amount of lead chloride and corrosion could be observed.

Iron / spinel oxides were identified from each sample. SEM- and XRD-analyses revealed also the presence of lead oxide and lead oxide chloride in all of the samples. Lead rich areas were formed around the potassium sulphate particles, if potassium sulphate was present.


Last updated on 2019-18-11 at 04:16