Partic. vol. 50 pp. 156-172 (June 2020)
doi: 10.1016/j.partic.2019.08.005

Simulations of sorbent regeneration in a circulating fluidized bed system for sorption enhanced steam reforming with dolomite

Kiattikhoon Phuakpunk^a,b, Benjapon Chalermsinsuwan^c,d,e,*, Sompong Putivisutisak^e,f, Suttichai Assabumrungrat^a,e

Benjapon.C@chula.ac.th

Abstract

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.

Graphical abstract

Keywords

CaO sorbent; Regenerator; Computational fluid dynamics; Circulating fluidized bed; Multiphase flow model