A dual circulating fluidized bed (DCFB) reactor system for chemical looping combustion is proposed. The reactor is designed to operate with a Ni-based oxygen carrier and is fueled with either natural gas or designed mixtures of CH4, CO, H-2, and higher hydrocarbons at 120-kW fuel power. The main design parameters are determined and the DCFB system, which promises large scale applicability, is introduced. The DCFB reactor system features effective control of the solid circulation rate via the primary fast fluidized bed (air reactor) without changing the fluidization regime in the secondary reactor (fuel reactor). Therefore, the secondary reactor can be optimized on fuel conversion without affecting the global solid circulation rates. The air reactor design can focus on the transportation of the solids to the fuel reactor. Besides a short introduction of the auxiliary units of the reactor system, a pressure profile of the pilot rig in hot operation is presented.