(540b) Non-Conventional Analysis of Hydrogen Upgrading in Membrane Reactor By Process Intensification Metrics

Non-conventional analysis of hydrogen upgrading in membrane reactor by process intensification metrics

Giuseppe Barbieri^1,*,  Enrico Drioli^1,2,  Adele Brunetti¹

¹ National Research Council - Institute for Membrane Technology (ITM–CNR)
c/o The University of Calabria, cubo 17C, Via Pietro BUCCI, 87036 Rende CS, Italy
www.itm.cnr.it; Tel. +39 0984 492029; Fax. +39 0984 402103; g.barbieri@itm.cnr.it

² The University of Calabria - Department of Chemical Engineering and Materials, cubo 44A Via Pietro BUCCI, 87036 Rende CS, Italy

The always increasing necessity arose in the last decennia in redesign the industrial processes with new unit operations more compact, efficient and, thus, able to address various environmental concerns, has led to the definition of new process indexes, so-called, metrics, that supply additional and important information to the conventional technical analysis for the selection of the type of technology and the identification of the operating condition windows for making a process more profitable [1].

In this work, some sustainability indexes, mass and energy intensities [2], volume and conversion indexes [3-4] were used in a no‑conventional evaluation of the up-grading stage in hydrogen production, i.e. the water gas shift reactor, by means of membrane reactors.

Defined as the ratio between the total inlet mass and total energy involved in the reactor, with respect to the hydrogen fed and produced by the reactor, mass and energy intensity provide useful information about the material exploitation and the energy efficiency of this new technology. On the other side, Volume and conversion index provide an indication on the gain offered by membrane reactor in terms of catalyst volume required and reactants conversion achieved, at the same operating conditions of a traditional unit. The comparative study of membrane reactor performance with respect to the conventional reactor was analysed as function of the main process variables, such as temperature, pressure, feed molar ratio and space velocity.

In the comparison between the two unit operations, the membrane reactor resulted always more material and energy intensive than a traditional reactor, particularly at the high feed pressure indicating that membrane reactor requires less material as feed and makes available more energy in producing the same amount of H₂. The advantage offered by a membrane reactor was also quantified in terms of ratios referred to the equilibrium condition of the traditional reactor. The membrane reactor resulted always more intensified than a traditional reactor operated in similar conditions and exceeded also the ideal performance achievable by a traditional reactor, at a temperature higher than 350°C. At the highest temperature (450°C) and gas hourly space velocity (40000 h^-1) the indexes for the membrane reactor were quite the same of the ideal values (the ones at equilibrium) of the traditional reactor; the membrane reactor can, thus, be operated with different combinations of operating conditions, achieving the same performance in terms of material exploitation and energy efficiency. An outlook of all the results in a phase diagram highlights a region where only MR has access. This is the most intensified in terms of both mass and energy intensity. Mass and energy intensities demonstrated, in line with the process intensification strategy, the assets of the membrane reactor technology also in terms of better exploitation of raw materials (reduction up to 40%) and higher energy efficiency (up to 35%). In addition, the catalyst volume required by membrane reactor was more than three times lower than the one of traditional unit, for achieving the same conversion.

[1] Drioli E.; Brunetti A.; Di Profio G.; Barbieri G.; “Process intensification strategies and membrane engineering”, Green Chem. 2012, 14, 1561-1572

[2] Brunetti A.; Drioli E.; Barbieri G. “Energy and mass intensities in hydrogen upgrading by a membrane reactor”, Fuel Processing Technology, 2014, 118, 278-286

[3] Brunetti A.; Caravella A.; Drioli E.; Barbieri G.; “Process intensification by membrane reactors: high temperature water gas shift reaction as single stage for syngas upgrading”, Chemical Engineering and Technology, 2012, 35, 1238-1248

[4] Barbieri G.; Brunetti A.; Caravella A.; Drioli E.; “Pd-based Membrane Reactors for one-stage Process of Water Gas Shift”, RSC Adv., 2011, 1 (4), 651-661