WP3 Results

D3.2.3 - Results of corrosive depositions on super-heater pipes
This deliverable presents results from corrosion measurements performed at USTUTT’s 200 kW CFBC facility in air and oxy-fuel combustion conditions. The samples collected in the facility in both settings evidence a clear attack by corrosion phenomena. During oxy-fuel operation, the short exposure time in combination with the relatively high chlorine content of the fuel led to an insufficient buildup of an oxidic protective layer (i.e., oxide scale). Consequently, chlorine diffused through the porous oxide scale and attacked the material surface directly. Besides, increased HCl values were measured during oxy-fuel operation, postulating HCl as the driver of the corrosion mechanism. In contrast, the HCl content in the flue gas during air-firing was relatively low. Hence, the strong corrosion attacks here were more likely to be originated from alkali salt deposits. On the other hand, chlorine and sulfur (partially) infiltrated the protective metal oxide layer in both combustion settings, breaking it off by side reactions between sulfates, chlorides, iron, and alkalis.
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This deliverable presents an experimental investigation on the air and oxy-fuel combustion of solid recoveredfuel at a 200 kWth circulating fluidized bed facility. In the course of three experimental campaigns, the effects of combustion atmosphere and temperature on pollutant formation (i.e., NOx, SO2, and HCl) and reactor hydrodynamics were systematically studied. In contrast to air-firing conditions, the experimental results showed that oxy-fuel combustion enhanced the volume concentration of NOx by about 50% while simultaneously decreasing the fuel-specific NOx emissions (by about 33%). The volume concentrations of SO2 and HCl were significantly influenced by the absorption capacity of calcium-containing ash particles, yielding corresponding values close to 10 and 200 ppmv at 871−880 °C under oxy-fuel combustion conditions. In addition, the analysis of hydrodynamic data revealed that smooth temperature profiles are indispensable to mitigate bed sintering and agglomeration risks during oxy-fuel operation.
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In this document results from lab-scale BFB combustion experiments under air and oxy-fuel firing conditions are presented. Cold dosing experiments of four SRF candidates have been investigated in a first phase of the tests. A pelletised SRF from Spain (i.e. ECO-P) has been then used for the air and oxy-fuel combustion experiments. In the air combustion experiments, the influence of the reactor temperature over the ash behavior and flue gas species has been investigated. For the oxy-fuel tests, the same process evaluation has been performed, though at a reference temperature (i.e. 850 °C) and at different inlet oxygen concentrations (i.e. 21 vol%db, 30 vol%db and 40 vol%db).
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