Steam methane reforming membrane reactors

Steam methane reforming with membrane WGS reactor for hydrogen production. 

One of the possible problems in a steam reforming membrane reactor is the formation of carbon, either by cracking of methane (Reaction 4) or the Bou-douard reaction (Reaction 5). 

Adhs. A.M., 1994, A Fluidized Bed Membrane Reactor for Steam Methane Reforming Experimental Verification and Model Validation, Ph.D. dissertation, Univ. of British Columbia, Vancouver, Canada. 

Kikuchi, E., Menoto, Y., Kajiwara, M., Uemiya, S., Kojima, T. (2000). Steam reforming of methane in membrane reactors comparison of electroless-plating and CVD membranes and catalyst packing methods. Catalysis Today 56, 75-81. 

In recent years, new concepts to produce hydrogen by methane SR have been proposed to improve the performance in terms of capital costs reducing with respect to the conventional process. In particular, different forms of in situ hydrogen separation, coupled to reaction system, have been studied to improve reactant conversion and/or product selectivity by shifting of thermodynamic positions of reversible reactions towards a more favourable equilibrium of the overall reaction under conventional conditions, even at lower temperatures. Several membrane reactors have been investigated for methane SR in particular based on thin palladium membranes [14]. More recently, the sorption-enhanced steam methane reforming (Se-SMR) has been proposed as innovative method able to separate CO2 in situ by addition of selective sorbents and simultaneously enhance the reforming reaction [15]. 

A. M. Adris, C. J. Urn, J. R. Grace, The fluidized bed membrane reactor for steam methane reforming Model verification and parametric study, Chem. Eng. Sci. 1997, 52, 1609-1622. 

Jorgensen S, Nielsen PEH, Lehrmann P (1995) Steam reforming of methane in membrane reactor. Catal Today 25 303-307... 

On the other hand, the main eritieism in steam reforming membrane reactors is the necessity to impose the same operating conditions for membrane and catalyst, whereas the catalyst should be at high temperature due to reactions endothermicity while membrane temperature must not exceed a threshold for assuring its stability. Considering that for the present technology the thermal limit for Pd-based selective dense membrane has to be imposed at values lower than 800 K, the MR performance is limited as well. Calculations reported in this chapter show that, at industrial operating conditions, methane conversion in MRs is limited at 35% about. 

I. A. Abba, J. R. Grace and H. T. Bi, Application of the generic fluidized-bed reactor model to the fluidized-bed membrane reactor process for steam methane reforming with oxygen input, Ind. Eng. Chem. Res., 2003, 42, 2736-2745. 

Grace, J.R., Li, X. and Lim, C.J. (2001) Equilibrium modelling of catalytic steam reforming of methane in membrane reactors with oxygen addition. Catalysis Today, 64, 141-149. 

Li A, Lim C J and Grace J R (2008), Staged-separation membrane reactor for steam methane reforming , Chem EngJ, 138,452-459. 

Andres, M. B., Chen, Z., Grace, J. R., Elnashaie, S. S. E. H., Jim Lim, C., Rakib, M., et al. (2009). Comparison of fluidized bed flow regimes for steam methane reforming in membrane reactors a simulation study. Chemical Engineering Science, 64, 3598—3613. Ayturk, M. E., Kazantzis, N. K., Ma, Y. H. (2009). Modeling and performance assessment of Pd- and Pd/Au-based catalytic membrane reactors for hydrogen production. Energy Environmental Science, 2, 430—438. 

Roses, L., Gallucci, F., Manzolini, G., van Sint Annaland, M. (2013). Experimental study of steam methane reforming in a Pd-based fluidized bed membrane reactor. Chemical Engineering Journal, 222, 307—320. Scopus Exact. 

Ye, G., Xie, D., Qiao, W., Grace, J. R., Lim, C. J. (2009). Modeling of fluidized bed membrane reactors for hydrogen production from steam methane reforming with Aspen Plus. International Journal of Hydrogen Energy, 34, 4755—4762. 

Fig. 24. Operating principle of a membrane reactor for steam methane reforming.

Another measure to increase the hydrogen partial pressure difference between permeate and retenate is to use sweep gas on the retenate side. Because the hydrogen requires humidification for low temperature PEM fuel cells to prevent membrane dry-out, steam is the preferred sweep gas [405]. OHany et al. highlighted the effect of steam as the sweep gas for the permeate in a methane steam reforming membrane reactor [406]. Higher methane conversion was observed, which originated from back-diffusion of steam from the permeate to the reaction side of the membrane, which increased the S/C ratio and consequently the conversion. 

Barbieri et al. also performed experimental work on a methane steam reforming membrane reactor, which will be discussed in Section 7.1.4. 

Marigliano et al. compared the performance of two different types of tubular methane steam reforming membrane reactors by numerical simulations [413]. In the first, the catalyst was packed into the palladium/silver membrane tube, and in the second it was positioned in the annular region surrounding the membrane tube. Both configurations were heated from the outside. Owing to the indirect heat transfer to the catalyst bed inside the membrane tube, methane conversion was lower in this instance, and under certain conditions it was even inferior to a conventional fixed bed... 

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