EVALUATION OF CORROSIVE EFFECTS IN CO-FIRING PROCESS OF BIOMASS AND COAL

Abstract

Listen

Translate article

Abstract The paper examines the effects of high temperature corrosion of the surfaces of heat exchange due to corrosive components formed in the co-combustion of biomass and coal. High temperature corrosion of the surfaces of heat exchange becomes a priority in the combustion of biomass with high chlorine and alkali metals, as alkali chlorides formed deposited on the surfaces of heat transfer, leading to serious consequences for them. Forms of manifestation of corrosion are numerous, the most important being: pitting corrosion (point), inter-granular corrosion, crevice corrosion, selective and uneven. One of the most important limitations to the use of biomass for energy purposes is the increased corrosion of the surfaces of heat exchange. Key words: biomass, combustion installations, corrosion ∗ Author to whom all correspondence should be addressed: e-ma il: glazaroiu@yahoo.com; Phone: +40-21-4029868; Fax: +40-21-4029868 1. Introduction At some stage in human history, biomass in all its forms has been the most important source of various basic needs: food, feed, fuel, feedstock, fibers, fertilizers (Ciubota-Rosie et al., 2008; Gavrilescu, 2008; Lako, 2008). Nowadays, biomass continues to be a subject of growing significance worldwide, in particular due to its suitability as source of bioenergy, as a result of global increase in the demand for energy, the constant rise in the price of fossil fuels and the need to reduce greenhouse gas emissions One of the most important limitations to the use of biomass for energy purposes is the increased corrosion of the surfaces of heat exchange which leads to serious damage to them. Usually, higher losses of metal due to the effects of corrosion in high temperature values of up to 2.5 mm/year/ unit. High temperature corrosion of the surfaces of heat exchange becomes a priority in the combustion of biomass with high chlorine and alkali metals, as alkali chlorides formed deposited on the surfaces of heat transfer, leading to serious consequences for them. Forms of manifestation of corrosion are numerous, the most important being: pitting corrosion (point), inter-granular corrosion, crevice corrosion, selective and uneven. Knowing the reaction mechanism and the influence of various parameters on the rate of speed corrosion is a prerequisite for scientific substantiation of corrosion processes control. Chloride-induced corrosion at high temperatures appears regardless of the type of outbreak (the firing) and the combustion conditions, both in the outbreak area (the sprayer) and the convective super-heaters zone, where temperatures produce overheating of steam over 350oC (Meyer, 1995).