Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite
Kiattikhoon Phuakpunka,b, Benjapon Chalermsinsuwanc,d,e,*, Sompong Putivisutisake,f, Suttichai Assabumrungrata,e
In this work, the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production, and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome. However, the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2. The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production, with both reforming and sorbent regeneration occurring simultaneously. The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system. The reforming riser and bubbling bed regenerator are studied separately but related to each other. Two-dimensional transient models using the Euler‒Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite, to investigate a conceptual regenerator system and determine its key conditions. A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200 kg/(m2 s) and a catalyst to sorbent ratio of 2.54 kg/kg. A double-stage bubbling bed regenerator system was designed with 1.2 m width, 0.8 m bed height, a gas inlet velocity of 0.2 m/s and solid preheating at 950 °C. The used dolomite was regenerated with an assumed CaO conversion of 3%; the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.
CaO sorbent; Regenerator; Computational fluid dynamics; Circulating fluidized bed; Multiphase flow model