IMPACT FRAGMENTATION OF SORBENT PARTICLES FOR CALCIUM LOOPING APPLICATIONS

a relevant role is played by the possible presence, in the flue gas to be treated in the carbonator, of SO2 and/or H2O. Moreover, as CaL is commonly proposed in Dual interconnected Fluidised Bed (DIFB) configuration, Ca-based sorbent particles can undergo various attrition phenomena, of which impact fragmentation has been relatively less investigated, in particular with reference to operating conditions entailing the presence of SO2 and/or H2O. In this research work, we have submitted a reference high-calcium commercial limestone to CaL tests in a lab-scale DIFB apparatus in presence of sulphur dioxide and/or steam: in particular, calcination was carried out at 940°C in an atmosphere containing 70% CO2; carbonation was carried out at 650°C, in an atmosphere containing 15% CO2. To evaluate the effect of SO2 and/or H2O, six carbonation atmospheres were simulated (steam, when present, was fed at 10% inlet concentration; sulphur dioxide, when present, was fed at either 75 ppm or 1500 ppm inlet concentration). After ten cycles, the particles were sent to an ex-situ impact test apparatus, based on the concept of entraining particles in a gas stream at a controlled velocity and impacting them against a target. The apparatus was operated at room temperature at various impact velocities (six values from 10 to 45 m/s), and the impacted fragments were sieve-analysed (obtaining probability density functions of particle size, and fractions of generated fragments) to discuss their fragmentation modes by also referring to outcomes arising from the exercise of the CaL fluidised bed system under various operating conditions.