Two-zone convective reformer for the decentralized production of H2/syngas from biomethane

Abstract

This study presents design results of two novel intensified convective reactors aimed at hydrogen/syngas productionfrom biomethane. The first design (Design I) features a reactor housing two tube banks, operating atdifferent temperature levels. The second design (Design II) advancing towards process intensification, incorporatespalladium-based membranes in the low-temperature zone (LTZ). Superalloy tubes, capable to withstandhigh-temperature operating conditions, are disposed in the high-temperature zone (HTZ), whileconventional stainless steel is profited for the tubes in the LTZ. These bayonet-type tube designs offer notableadvantages in terms of energy integration, mechanical integrity, and reduced manufacturing costs. In both designs,the bayonet configuration in the HTZ enables a heat recovery of approximately 13.5 % from the returningsyngas. The results demonstrate high methane conversions of about 76.41 % and 82.12 % for Design I and DesignII, respectively. Hydrogen production yields ca. 524 Nm3/h for Design I and 567 Nm3/h for Design II, with H2/CH4 yields of 2.62 and 2.83 kmol H2 per kmol CH4 feed, respectively. The incorporation of a Pd-based membranein Design II allows the selective extraction of pure H2, resulting in an 8.28 % increase in H2 production by shiftingthe thermodinamic equilibrium. The implementation of a membrane-based purification unit downstream thereactor aiming achieving pure H2 would require an approximate membrane area of 14 m2 for both designs.Design II, when coupled with this downstream membrane module, would exhibit an increase of 10.64 % in purehydrogen yield compared to Design I.