Membrane Reactor Architectures

On previous published data, laquaniello [42] was calculating for a open membrane reactor architecture a surface of 1,000 m for an installed capacity of 10,000 Nm /h of Hydrogen. The envisaged installed capacity in the hydrogen market is today around 1 MM Nm /h of capacity per year, which translated into a production of 100,000 m of membrane year, once the new technology will supersede the conventional one. 

With reference to the book content, the authors divided it into 11 chapters. The book starts with an overview on membrane selective membranes integrated in the chemical reaction environment. The thermodynamics and kinetics of membrane reactors are also formulated and assessed for different membrane reactor architectures. 

In configuration 1, the reformer and membrane module (RMM) where hydrogen selective membrane is assembled in separation modules applied downstream to reaction units so that the process scheme is composed by a series of reaction-separation units (staged membrane reactor architecture)... 

High-temperature applications of perovskite-type membrane reactors require improved material performances and operational stability. The reactor microstruc-ture and architecture controls were found to be crucial for thermo-mechanical integrity and oxygen permeation kinetics. A multilayer reactor was developed, using second-phase particles to control its microstructure and a co-sintering process to control its architecture. 

An actual breakthrough is to design both the microstructure (grain size, porosity,...) of the different system materials (support-membrane-catalyst) and the reactor architecture in order to obtain improved permeation properties and stability during the time on stream [19]. Considering all the parameters, a special consideration was given in this paper to the stack of the different materials at different length scale, from the microscopic-scale (microstructure) to the assembly of materials on the whole reactor thickness (architecture). An example of the architecture/microstructure concept was used in the Multi Electrode Assembly (MEA) approach. 

Membrane integration with the IGCC could practically be realized in two possible reactor architectures determined by a relative placement of the membranes and catalysts. In the simplest arrangement, two membrane passive separators could be located in front of each of the conventional HTS and LTS... 

In this chapter, the most popular approaches for hydrogen production from H2S are reviewed before a novel open reactor architecture (OA) is presented, where the coupling of reaction and hydrogen separation is achieved in the series of consecutive conventional catalytic reactors (CR), each followed by a membrane separator (MS). Experimental study on the development of a suitable H2S decomposition catalyst is also presented, and the theoretical calculations for one... 

Recently, the first membrane reactor pilot plant has been realized. A staged membrane reactor for natural gas steam reforming, also called reformer and membrane modules (RMM) test plant, having the capacity of 20 Nm /h of hydrogen, has been designed and constructed to investigate at an industrial scale level the performance of such innovative architecture. 

The coupling of membrane separation modules and the conventional WGSR reactors through this kind of architecture results in a better overall efficiencies (97.5% as compared to 91% for the reference case). By this configuration, the fuel stream is enriched in H2 by the membrane reactor and requires only polishing by PSA. 

The typical and most straightforward configuration for a membrane reactor is composed of two concentric tubes, where the catalyst is packed in the annular zone while the inner tube is the membrane itself (closed architecture) as shown in Fig. 11.2. 

Effect of catalyst effectiveness factor on WGS membrane reactor performance in closed architecture (a) CO conversion and (b) temperature. 

Finally, when a membrane reactor was employed in open architecture configuration along with a catalyst effectiveness factor of 0.6, the hydrogen recovery factor was evaluated as a function of the membrane permeation surface. The results are shown in Fig. 11.6. 

This chapter discusses the development, breakthrough performance and reliability of nanocomposite membranes, and explores how nanoengineered composition and architecture can influence the separation ability of membrane reactors at the macroscale. 

Nanomaterials and molecular architectures (e.g., zeolite reactors, nanocomposite ceramic process technique, resists, NLO elements, catalysts with increased surface, systems of compact nanomaterials, i.e., membranes, polymers, light-absorbing material, aerogels, light emitters). 

Gas-diffusion to surfaces is mainly dependent on reactor configuration (geometry) and is to be taken under considerations when the membrane architecture includes a porous layer (grain size, porosity, interconnection shapes and dimensions,...). 

The term architecture refers to the specific spatial arrangement of different materials constimting the reactor. As the membrane placed in a catalytic reactor has to satisfy various functions such as oxygen separation from air, high oxygen permeation kinetics and catalytic reactions with methane, a reactor can be defined as a Functionally... 

On the other hand, the membrane can be integrated externally, by an architecture which allows the reaction and separation steps to occur in series. In this way, the catalyst and membrane operating conditions are independent and their optimal operating conditions can be defined separately, but the membrane integration benefits are reduced. It is worth noting that the development of such innovative reactors requires the ad hoc definition of design criteria. 

In an alternative configuration, the selective membrane is placed outside the reactor in units located downstream (open architecture. Fig. 11.3). In this case, after the membrane separation module another reaction unit is required, in which the enhancement in hydrocarbon conversion may be observed. 

The results of mathematical modeling developed for closed architecture with a catalyst effectiveness factor of 0.6 clearly show the effect of the presence of the membrane on CO conversion profile along the catalyst bed. The most important effect is that the reactor, in this case, can overcome the thermodynamic limitations and the maximum CO conversion is higher than that obtained without the membrane. In addition, it is worth noting that the equilibrium CO conversion can be obtained by using a lower catalyst volume, or in other words at a shorter reactor length. 

The effect of the catalyst effectiveness factor on the membrane assisted WGSR in closed architecture is shown in Fig. 11.4, in terms of CO conversion (Fig. 11.4a) and reactor temperature profile (Fig. 11.4b). 

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