Calcium-based sorbents behaviour during sulphation at oxy-fuel fluidised bed combustion conditions

Optimum temperature for sulphur retention in fluidised beds working under oxy-fuel combustion conditions

“…These results are in good agreement with the results obtained in previous works of our research group where the sulphur retention capacity of the limestone "Granicarb" was analysed in a TGA and in a batch FB reactor under different operating conditions [15][16]. In these works, it was found that the effect of the temperature was different for the direct and indirect sulphation reactions.…”

“…Table 1). Previous studies carried out under oxy-fuel combustion conditions in a TGA [15] and in a batch FB reactor [16] demonstrated that the sulphation conversion of the sorbent increased as the SO 2 concentration increased.…”

“…Some previous works on sorbent sulphation with long reaction times [15,25] have demonstrated that the residual activity of the sorbents after pore plugging can be very important. However, as it was previously commented in the experimental section, an important feature of the tests carried out in this work was the certainty that the results were obtained under steady state conditions.…”

“…However, it must be remarked that in these tests the steady-state was not achieved and no quantitative data can be obtained, although the trend is clear. Figure 9 shows the sorbent sulphation conversion obtained in a TGA in a previous work as a function of the reaction time working with the Granicarb limestone (dp=0.3-0.5 mm, 3000 vppm SO 2 , 900 ºC, and 60 vol.% CO 2 ) [15]. Considering this plot as representative of the sorbent sulphation pattern exhibited by the limestone in the BFB combustor, an important increase in sorbent sulphation (ΔX) can be achieved by increasing the residence time as it would be usual in industrial FB combustors.…”

“…Our research group have recently carried out several tests in a thermogravimetric analyser (TGA) and in a batch fluidised bed reactor to analyse the behaviour of limestones for SO 2 retention under oxy-fuel operating conditions [15][16]. We found that the major effect of increasing the CO 2 concentration in the reacting gas was to shift the CaCO 3 decomposition to CaO until a higher temperature.…”