Madhu Anand

Hydrogen production by hybrid SMR–PSA–SSF membrane system

Abstract Pressure swing adsorption (PSA) processes are commonly used to produce pure hydrogen from the steam–methane reformer (SMR) off-gas. The typical hydrogen recoveries for PSA processes producing 99.999+% hydrogen are in the range 70–85%. The nanoporous selective surface flow (SSF) carbon membrane can be used to extract hydrogen from the low pressure waste gases of the PSA processes and the enriched hydrogen stream can be recycled as feed gas to the PSA process after recompression. The net result of this integration between the PSA process and the SSF membrane is increased hydrogen recovery from the SMR off-gas. The separation performance of the SSF membrane in producing a hydrogen-enriched gas from the PSA waste gas was experimentally evaluated and two different schemes to integrate the membrane with a specific PSA process for hydrogen purification were studied. The performance of the PSA process was simulated using a software package called SIMPAC. It is demonstrated that the integrated process can increase the net hydrogen recovery to 84–85% from a hydrogen recovery value of 77–78% by the base PSA process.

Multicomponent gas separation by selective surface flow (SSF) and poly-trimethylsilylpropyne (PTMSP) membranes

Abstract A selective surface flow (SSF) membrane consisting of a thin layer of a nanoporous carbon was produced in a tubular form using a macroporous alumina support. The membrane was tested for hydrogen enrichment applications. Simulated waste gases from a petrochemical refinery and a hydrogen pressure swing adsorption unit were used as the feed gas to the membrane. Very high rejections of C 1 C 3 hydrocarbons (saturated and unsaturated) and carbon dioxide over hydrogen were exhibited by the membrane at low feed gas pressures. The hydrogen enriched stream was produced at the feed gas pressure. The separation characteristics of a polymeric poly-trimethylsilylpropyne (PTMSP) membrane in a tubular form was also tested for the same applications using identical conditions of operation. This membrane also selectively rejected heavier components of the feed gas mixture over hydrogen and produced the hydrogen enriched stream at the feed gas pressure. The SSF membrane exhibited much higher hydrogen recovery and hydrocarbon rejections than the PTMSP membrane for these applications under identical conditions of operations using identical support materials.

Scale-Up of Selective Surface Flow Membrane for Gas Separation

Abstract The Selective Surface Flow (SSF) membrane, consisting of a nanoporous carbon layer supported on a macroporous alumina tube, can be used to enrich hydrogen from a feed gas containing hydrogen and hydrocarbon mixtures. The membrane produces a hydrogen-enriched product stream at feed gas pressure by selectively rejecting the hydrocarbons to the low pressure side of the membrane. Bench-scale testing of the membrane showed that very high rejections of C+ 2 hydrocarbons can be achieved from a feed gas containing low concentrations of hydrogen at moderate pressure. The membrane has been scaled-up in length and field-tested in modular form using a real refinery waste gas under actual operating conditions. It successfully tracked the performance of the bench-scale unit under field conditions. Both bench-scale and field-scale performance data are described. Six months of continuous operation in the field did not exhibit any degradation of membrane performance.

Surface Fluorination of Polymers

This chapter describes the existing commercial applications of direct fluorination of polymer surfaces and briefly discusses some emerging applications that have not yet been commercialized. To those familiar with the highly oxidizing and toxic nature of gaseous elemental fluorine, its acceptance by industries that have traditionally avoided the use of potentially hazardous substances may be surprising. This acceptance in industries such as blow-molding is a tribute to the engineers, materials scientists, and chemists who have worked to develop safe and reliable methods for the production, storage, transport, and application of this powerful fluorinating agent.