From sour to sweet: multi-stage fluidized beds for sour gas removal using adsorption

This thesis investigates the removal of sour gas (hydrogen sulfide and carbon dioxide) using multi-stage fluidized beds (MSFBs) from natural gas using adsorption because of potential energy consumption reduction and increased productivities. Chapter 2 introduces the concept of a MSFB and demonstrates that deep removal of sour gas (from 1% to <3.5 ppm CO2) is possible at atmospheric pressures using a commercial amine sorbent. Chapter 3 assesses intraparticle mass transfer limitations using a Thiele modulus-effectiveness factor approach, which provides a priori insights. In addition, two approximations were considered and compared to a full particle model. Chapter 4 characterizes mass transfer in shallow fluidized beds as used I MSFBs using (a) independent experiments for mixing, hold-ups, intraparticle mass transfer and adsorption kinetics and (b) a phenomenological fluidized bed model. It is concluded that shallow fluidized beds provide good mass transfer characteristics. Chapter 5 presents the design of an experimental pressurized MSFB setup where the adsorption is performed at elevated pressures up to 10 bara and the desorption at atmospheric pressure. The CO2 concentration in the adsorber decreased several orders of magnitude in just three stages, showing that the adsorption in a pressurized MSFB benefits from elevated pressures. Chapter 6 compares the proposed sorbent-based sour gas to the benchmark solvent process using equilibrium modelling. Various configurations for the sorbent process were investigated. When a combination of a tertiary and a primary/secondary amine sorbent is used, it is foreseen that the sorbent process can produce a H2S-rich and CO2-rich stream. Chapter 8 shares some reflections and perspectives on the work presented in this thesis.
Original promotion date was April 24, 2020 (COVID-19)