Cycle Development and Process Optimization of High-Purity Oxygen Production Using Silver-Exchanged Titanosilicates

Producing oxygen with purity higher
than 95.0% from atmospheric
air (78.0% N2, 21.0% O2, and 1.0% Ar) is challenging
because of the similar physical properties of oxygen and argon. Silver-exchanged
titanosilicates have shown the potential to separate these gases based
on their thermodynamic affinities. In this study, various vacuum swing
adsorption (VSA) cycle configurations including the simple Skarstrom
cycle and more complicated 6-step VSA cycles were simulated using
mathematical models to maximize O2 purity and recovery.
The simulations were verified by conducting simple 3-step and Skarstrom
VSA cycle experiments. A mixture of 95.0%/5.0% O2/Ar feed
was considered in the simulations, and a rigorous multiobjective optimization
was conducted to maximize O2 purity and recovery. The simulations
predicted 27.3% recovery for a product with 99.5% purity for a 6-step
cycle with pressure equalization and light product pressurization
steps. The recovery for the same level of purity was improved significantly
to 91.7% by implementing a heavy product pressurization step. The
effect of bed length on O2 purity and recovery and the
comparison of VSA with pressure swing adsorption and pressure–​vacuum
swing adsorption for high-purity O2 production were also
investigated. Rigorous multiobjective optimizations were conducted
to maximize oxygen productivity and minimize energy consumption of
the VSA cycles, while meeting different purity constraints, and significant
improvement in the performance indicators was obtained through process
optimization.