Chloride corrosion in biomass-fired boilers – Fe-O-Cl system thermodynamic analysis

Abstract

Abstract. The most common and easiest alternative technologies for conventional fossil fuel combustion are biomass combustion and co-combustion. However, high-chlorine fuels (Cl ar >0,2%) like: biomass, waste and high chlorine coals generate the risk of intensified corrosion process and a limited steel mechanical strength is observed.The paper presents a thermodynamic analysis of chloride-induced corrosion in the Fe-O-Cl system. The ranges of the metallic, oxide and chloride phase stability are determined within the temperature range T = 750-1000 K. Based on the parametric equations the equilibrium concentration of gaseous phase determined by Deacon reaction are presented. The effect of H 2 O concentration in the gaseous phase on high-temperature corrosion process and gaseous NaCl influence on NaFeO 2 formation in the passive oxide scale layer (FeO/Fe 3 O 4 /Fe 2 O 3 ) are discussed as well. The results are correlated with available in the literature laboratory experimental data and industrial corrosion process observations. Presented thermodynamic analysis is compared with assumptions of "active oxidation" model. The results may be used for experimental research prediction and a corrosion prevention in the industry.

Fireside corrosion on T24 steel pipes and HVOF NiCr coatings exposed to different salt mixtures

“…Once a sufficient oxygen partial pressure (PO2) is reached, the chlorides destabilize and form Fe2O3, while Cl2(g) regenerates following Equation ( 4). These reaction steps are endlessly repeated causing severe damage [30], let alone that corrosion is fostered through the alloy grain boundaries (Fig. 6d) as also demonstrated upon chromizing an austenitic AISI 304 stainless steel due to the volatilization of FeCl2 [35].…”

“…In our case, NaFeO2 could form from reaction between NaCl and Fe2O3 under oxidizing conditions according to Equation (1). Sodium ferrite is also accompanied by the formation of Cl2(g) [17,30]. Therefore, the dominant corrosion mechanism involves (i) the initial production of chlorides, (ii) their subsequent diffusion through metal oxide layer and their reaction with the metal according to Equation ( 2) and…”

Residual Agroforestry Biomass–Thermochemical Properties

“…(352.7 mg kg −1 ) as well as Ulex europaeus (277.3 mg kg −1 ). These values should be taken into account since the main effect of Cl is the corrosive effect of chloride salts and HCl on metal parts in furnace and boiler [30,46,50,[52][53][54][55][56][57][58].…”

Fuel modification based on some metals compounds and their environmental impact

“…However, NaCl and the other metallic chlorides are quite corrosive to the ferrous alloys commonly used in flue ducts of typical air-tight stoves. The inorganic chlorides and sulphates are well-known as progressive corrosion compounds on iron based metal, especially in higher temperatures [13]. Even stainless steel pipe is pitted and severely corroded by use of metallic chlorides and sulphates black carbon and creosote removers.…”