Applications: Proper management of hydrogen molecules within the refineries and chemical plants is becoming increasingly important due to the introduction of stringent product sulfur specifications. Hydrogen recovery/purification from fuel gas and hydrogen containing offgas streams in refining and chemical processes offers many potential benefits, including product uplift, reduced H2 costs, avoided H2 plant expansion and emission reductions.
Rapid-cycle pressure swing adsorption (RCPSA) technology offers a more-compact, less-expensive and more-energy-efficient solution for H2 recovery compared to conventional PSA (cPSA) technology. This technology has been jointly developed by ExxonMobil Research and Engineering Co. (EMRE) and QuestAir Technologies. The RCPSA unit for hydrogen recovery/purification is marketed as the QuestAir H-6200.
Some of the potential applications of RCPSA are:
H2 recovery/purification from:
• Fuel gas
• Recycle gas loop in hydrotreater
• Naphtha reformer hydrogen offgas
• Hydrocracker offgas and purges
• Steam cracker offgas.
Description: RCPSA technology overcomes the inherent disadvantages of cPSA, namely, slow cycle speeds, relatively large adsorbent beads and complex networks of individual switching valves. RCPSA uses two novel proprietary technologies: structured adsorbents—replacing conventional beaded cPSA adsorbents—and integrated rotary valves—replacing solenoid-actuated valves used in cPSA. Structured adsorbents provide mass transfer coefficients that are up to 100 times higher than beaded adsorbents used in cPSA; thus, significantly increasing the productivity of a unit volume of adsorbent bed. The multi-port rotary valves are used for rapid and efficient switching of gases between adsorbent beds, effectively capturing the increased capacity of the structured adsorbent.
Multi-bed RCPSA systems can be efficiently packaged in an integrated, modular rotating bed design. The net result is that large PSA systems made up of multiple vessels of beaded adsorbent, complex process piping and multiple switching valves can be replaced with integrated modular skid-mounted QuestAir H-6200 plants that are a fraction of the required footprint of a cPSA of equivalent capacity. In addition, the RCPSA’s modular skid mounted design reduces installation time and cost. In the high feed pressure (p > 500 psig) applications, RCPSA can be stably operated without a tail-gas compressor resulting in further reduction of total installed cost in comparison to cPSA. Flexible product purity, enhanced recovery and better control of RCPSA can result in capital and operating cost savings. The modular skid mounted design of the RCPSA makes it possible for refiners to manage H2 molecules closer to the processing units as needed, a new paradigm for distributed H2 recovery technology for refineries and chemical plants Yields: Available upon request.
Utilities: Compact RCPSA technology results in significantly less inert gas consumption in operation or in purging. Furthermore, since the switching valve function is controlled through an electric motor, instrument air is only required for the operation of each module’s product control valve and automated isolation valves.
Nitrogen consumption: Estimated inert purge gas requirement: 40.4 nm3
Typical N2 consumption in normal start-up operation: 0.12 nm3/h per H-6200 module
Instrument air consumption: 1.5 Nm3h estimated for operation per H-6200 module
Power: 480 – 600V 3ph, 50 or 60 Hz to suit local requirements, consumption: 37 kw/module
Licensor: ExxonMobil Research and Engineering Co., and QuestAir Technologies Inc.