The carbonate looping (CaL) process is a promising efficient CO2 capture technology aiming at the decarbonisation of the cement and lime industries. The CaL is based on the reversible carbonation reaction of limestone, which comprises synergies with lime and cement plants since both process make use of limestone. A novel development of this process is the indirectly heated carbonate looping process (IHCaL), having the advantage over the standard CaL that no air separation unit (ASU) is necessary to generate the heat for calcination. Recently, 400 h of testing at a 300 kWth pilot plant were performed under conditions that are close to industrial applications for the cement and lime industry. The test rig consists of three coupled fluidized bed reactors: two bubbling fluidized bed reactors (BFB), calciner and combustor, and one circulating fluidized bed reactor (CFB), carbonator, while the system of calciner and carbonator are coupled through circulation of the solid sorbent. In this study, different operational conditions – such as variations in particle size distribution of the limestone, fluidization velocity, and solid inventory – are assessed and compared with regard to the hydrodynamic and thermodynamic behaviour of the fluidized bed system as well as the process performance.