A three-bed six-step TSA cycle with heat carrier gas recycling and its model-based performance assessment for gas drying

To avoid the waste heat exhaust of a gas dryer based on the conventional two-bed five-step temperature swing adsorption (TSA) cycle, we designed and developed a three-bed six-step TSA cycle with heat carrier gas (HCG) recycling. To clarify the impact of the retrofit from the two-bed system to the three-bed system on the gas dryer performance, numerical studies on the three- and two-bed systems were carried out in this work. Firstly, a nonisothermal, nonadiabatic, nonequilibrium mathematical model of the TSA process was established. Secondly, an industrial-scale dryer with electrical HCG heaters was provided for case study, and two concrete cases were studied to examine the effect of regeneration pressure on the energy-saving potential of the three-bed system. Thirdly, the bed profiles and historical curves of the online adsorption and offline regeneration of the two systems were obtained by simulations, thereby the two systems were comparatively analyzed in terms of energy efficiency, drying performance and head loss. Moreover, the economic analysis on the retrofit from the two-bed system to the three-bed system were carried out. In conclusion, the case studies show that, with a comparable drying performance, the three-bed system saved around 40% energy compared with the conventional two-bed system. The economic analysis shows that the additional investment for the retrofit from the two-bed system to the three-bed system is convenient since the payback periods are around one year.