The multiport rotary valves are capable of efficient switching of gases between adsorbent beds to match the fast cycling capability of the structured adsorbent. The rotary valves also allow for the design of highly efficient complex PSA cycles; and fast cycle PSA systems with 6 to 36 individual adsorbent beds have been demonstrated to date. Multibed fast-cycle PSA systems can be efficiently packaged in an integrated, modular rotating bed design. The fast cycle speed and multibed design produces a uniform flow of product and exhaust gas, removing the necessity for large surge tanks on the product and exhaust streams.
The net result of fast-cycle PSA technology: Large field-erected PSA systems made up of multiple vessels of beaded adsorbent, complex process piping and multiple switching valves can be replaced with integrated fast-cycle PSA modules that are one-fiftieth the size of an equivalent PSA production unit (Fig. 3).
In addition, no exotic materials are used in the adsorbent structure or rotary valve designs, which means that materials costs are minimized. Additional benefits include:
Scalability: Fast-cycle PSA technology can be scaled from very small, portable-style devices to large industrial-scale applications.
Modularity: The integrated mechanical design of rotary fast-cycle PSA systems is inherently modular and can easily be skid-mounted. This gives plant operators a high degree of flexibility to reduce equipment installation time and cost, and expand processing capacity to match incremental increases in demand.
QuestAir Technologies is currently developing a small-scale fast-cycle PSA system together with HydrogenSource, a 50:50 joint venture between Shell and United Technologies based in South Windsor, Conn.
This compact hydrogen PSA module, will be integrated into small-scale natural gas reforming systems based on HydrogenSource's proprietary catalytic partial oxidation (CPOx) reformer technology. The integrated hydrogen production and purification product will be marketed for the supply of hydrogen to stationary fuel cell power plants for distributed power generation.
The unit will also be modified for use in skid-mounted systems for on-site production of high-purity (99.999%) hydrogen for industrial uses for volumes in the 20-1,000 Nmch capacity range (700-35,000 scfh). Other potential applications include:
Hydrogen recovery: Several refinery and chemical processes generate large quantities of hydrogen-containing offgas, which is typically flared or burned for low-grade heat recovery. Large-scale fast-cycle PSA presents an economic alternative for the recovery of hydrogen from up to 10 MM scfd of these off-gas streams, for either on-site of over-the-fence use.
Syngas modification: Fast-cycle PSA can be used to tailor the H2/CO ratio of crude syngas for applications including ammonia production.
Methane separations: High natural gas prices have renewed interest in technologies for recovering methane from CO2 contaminated sources such as low-grade natural gas, coal bed methane and various sources of biogas.