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The suitability of polymer electrolyte membrane fuel cells (PEMFC) for stationary and vehicular applications because of its low operating temperatures, compactness, higher power density, cleaner exhausts and higher efficiencies compared to conventional internal
combustion engines and gas turbines adds to the already soaring demand for hydrogen prod...
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A cell producing electricity (without combustion) from a chemical reaction by converting hydrogen and oxygen into water is a fuel cell. It is a cleaner and greener alternative source of energy and thus is an important area of research. This paper presents an overview of the two major types of fuel cells and their relation to sustainable management...
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... The results exhibited that up to 9.5% and 11.2% more H 2 were produced by increasing the fraction of air in the burner fuel and the thickness of the insulation shield, respectively, by 50% [260]. Similarly, various researchers worked on the lumped parameters for simulation-based SMR [261][262][263]. A two-phase reactor model was developed for a fluidized-bed Pd-based membrane reactor. ...
Fossil fuel depletion, global warming, climate change, and steep hikes in the price of fuel are driving scientists to investigate commercial and environmentally friendly energy carriers like hydrogen. Steam methane reforming (SMR), a current commercial route for H2 production, has been considered the best remedy to fulfill the requirements. Despite the remarkable quantity of H2 produced by the SMR, this technology still faces major challenges such as catalyst deactivation due to the sintering of metal nanoparticles, coking, and generation of a large quantity of CO2. Firstly, the effects of catalyst types, kinetic models, and operating conditions on high-yield H2 production, the evolution path from gray to blue, via the conventional SMR are comprehensively reviewed. Secondly, exploiting intensified techniques such as membrane technology, sorption, fluidization, and chemical looping for SMR to blue H2 are discussed in detail. Further, a novel and sustainable path for the SMR process, hybridizing the use of novel materials and emerging technologies to produce turquoise H2, is proposed. Finally, the critical points for steam reforming process technology that can help leverage environmental, social, and governance (ESG) profiling have been discussed.
... Still, direct use of these materials as a membrane is hindered due to the formation of oxide layers and the occurrence of surface reactions, which promote the reduction of the H 2 permeability through the membrane. Thus, the main criteria for membrane selection are high permeability, high selectivity, resistance to reactive gases-particularly CO, CO 2 , CH 4 and H 2 O-and resistance to coking [334]. ...
Olive oil mill wastewater (OMW) is a polluting stream derived from the production of olive oil and is a source of environmental pollution; this is relevant in many countries around the world, but particularly in all the Mediterranean region where major producers are located. In this effluent, several pollutants are present—namely, sugars, fatty acids, and polyphenols, among others. Nowadays, to reduce the pollutant load, several treatment techniques are applied, but these technologies have numerous cost and efficiency problems. For this reason, the steam reforming of the OMW (OMWSR) presents as a good alternative, because this process decreases the pollutant load of the OMW and simultaneously valorizes the waste with the production of green H2, which is consistent with the perspective of the circular economy. Currently, the OMWSR is an innovative treatment alternative in the scientific field and with high potential. In the last few years, some groups have studied the OMWSR and used innovative reactor configurations, aiming to improve the process’ effectiveness. In this review, the OMW treatment/valorization processes, the last developments on catalysis for OMWSR (or steam reforming of similar species present in the effluent), as well as the last advances on OMWSR performed in multi-functional reactors are addressed.
... Summary of the hydrodynamic parameters used in the 1D phenomenological model[59] Bed voidage at minimum fluidization velocity ...
Palladium-based membrane-assisted fluidized bed reactors have been proposed for the production of ultra-pure hydrogen at small scales. Due to the improved heat and mass transfer characteristics inside such reactors, it is commonly believed that they can outperform packed bed membrane reactor configurations. It has been widely shown that the performance of packed bed membrane reactors can suffer from serious mass transfer limitations from the bulk of the catalyst bed to the surface of the membranes (concentration polarization) when using modern highly permeable membranes. The extent of concentration polarization in fluidized bed membrane reactors has not yet been researched in detail. In this work, we have quantified the concentration polarization effect inside fluidized bed membrane reactors with immersed vertical membranes with high hydrogen fluxes. A Two-Fluid Model (TFM) was used to quantify the extent of concentration polarization and to visualize the concentration profiles near the membrane. The concentration profiles were simplified to a mass transfer boundary layer (typically 1cm in thickness), which was implemented in a 1D fluidized bed membrane reactor model to account for the concentration polarization effects. Predictions by the TFM and the extended 1D model showed very good agreement with experimental hydrogen flux data. The experiments and models show that concentration polarization can reduce the hydrogen flux by a factor of 3 even at low H2 concentrations in the feed (10%), which confirms that concentration polarization can also significantly affect the performance of fluidized bed membrane reactors when integrating highly permeable membranes, but to a somewhat lesser extent than packed bed membrane reactors. The extraction of hydrogen also affects the gas velocity and solids hold-up profiles in the fluidized bed.
... The kinetic analysis has to be carried out at particular experimental conditions, to be sure that the mass transfer can be neglected. The effect of intra-particle mass transfer limitations is strongly related to the catalyst particle size and is evaluated by calculating the overall effectiveness factor h for the reactions, which is defined as the ratio of the integrated reaction rates over the radius of the particle and the reaction rate at bulk phase conditions [19]. During the kinetic tests, it has been found that the effect of internal diffusion is negligible for a particle size smaller than 125–250 m as will be demonstrated in the next sections of the paper. ...
... Dynamic models can also be found, but for reactors operating in the permanent unsteady state e.g. for the reverse-flow MR syngas production [12][13][14]. Majority of papers describe tube and shell reactor configuration with reaction zone either in the tube or in the shell, but a case of fluidized MR for ultrapure hydrogen production is also analysed in [15,16]. Some models assume isothermal MR operation [2,4,5,8] while the other include heat or enthalpy balances, allowing to simulate non-isothermal or adiabatic operation, what is much more suitable for exothermal WGS reaction. ...
Gas from coal gasification contains less hydrogen than from other syngas production methods. An attractive option is its further hydrogen enrichment for pure hydrogen production in a membrane reactor (MR) by Water Gas Shift (WGS). The goal of present study was to analyse MR fed with coal derived gas. Simulations for feasible membrane permeation parameters revealed that to get high conversion above 90% a relatively high S/C should be applied. Moreover, hydrogen recovery is in this case low (below 30%) so for hydrogen production an additional H2 separation after the MR should have been applied. The paper also shows that a clear advantage of counter- over co- current flow configuration in MR appears only for low pressure in the reaction zone. The realistic feasible Pd-Cu-Ni membrane parameters result in a rather large membrane area, thus possible heat exchange between the reaction and permeation zone can have important influence on temperature profiles in the MR. This cooling effect could lessen excessive temperature increase in the reaction zone. Results for other than single step MR configurations are also presented in the paper. It is stated in conclusion that future successful application of MRs for coal-derived gas depends on development of not only new catalysts with adequately wide operational temperature range, but also membranes with a high enough permeability.
... An interesting very flexible software tool (a model library) for MR dynamic simulations is presented in [14]. Majority of papers cited here describe tube and shell reactor configuration with reaction zone either in tube or in the shell, but a case of fluidized MR for ultrapure hydrogen production is also analysed in [15,16]. Some models assume isothermal MR operation [1,3,4,7] while the other include heat or enthalpy balances, allowing to simulate non-isothermal or adiabatic operation, what is much more suitable for exothermal WGS reaction. ...
Mathematical model of a membrane reactor for the water-gas-shift (WGS) reaction and results of simulation studies are presented. The physicochemical phenomena and brief description of the model are given. Due to the fact that membranes for CO2 separation exhibit poor selectivity at the elevated temperature range (indispensable for the desired activity of WGS catalysts), the simulations were carried out only for H2 selective membranes, containing Pd or its alloys. Comparison of the conventional two-stage WGS reactor with the membrane reactor revealed that operating temperature range of the catalyst used in the membrane reactor unit has to be much wider than that in conventional industrial reactors with separate high- and low temperature catalyst stages and with cooling in between. Thus, the research of new catalysts should accompany development of the membrane reactor technology. Simulations discussed in the present paper were focused on processing the gas derived from the coal gasification plant. Some results of mathematical simulations are presented. They reveal that under some conditions the membrane reactor technology can be promising for the hydrogen production from the coal-derived gas.
... Given these advantages of membrane assisted fluidized bed reactor, a number of theoretical and experimental studies have been performed in recent years (Adris, 1994;Deshmukh, 2004;Patil, 2005). ...
In this work, a dynamic model for a cascade fluidized-bed hydrogen permselective membrane methanol reactor (CFBMMR) has been developed in the presence of long-term catalyst deactivation. In the first catalyst bed, the synthesis gas is partly converted to methanol in a water-cooled reactor, which is a fluidized-bed. In the second bed, which is a membrane assisted fluidized-bed reactor, the reaction heat is used to preheat the feed gas to the first bed. This reactor configuration solves some observed drawbacks of new conventional dual type methanol reactor (CDMR) and even fluidized-bed membrane dual type methanol reactor (FBMDMR) such as pressure drop, internal mass transfer limitations, radial gradient of concentration and temperature in both reactors. A dynamic two-phase theory in bubbling regime of fluidization is used to model and simulate the proposed reactor. The proposed model has been used to compare the performance of a cascade fluidized-bed membrane methanol reactor with fluidized-bed membrane dual-type methanol reactor and conventional dual-type methanol reactor. The simulation results show a considerable enhancement in the methanol production due to the favorable profile of temperature and activity along the CFBMMR relative to FBMDMR and CDMR systems.
... Het idee van zo'n authothermal reformer is dat de reactor geen externe warmte nodig heeft om te draaien. Patil [19] heeft het volgende concept bedacht dat in Figuur 18 staat weergegeven. Laten we dan nu ook zorgen dat we zelfstandige studenten opleiden die tijd hebben om zichzelf tijdens hun studie te ontdekken. ...
The combination of membrane separation and catalytic reactors in the so-called membrane reactor concept provides a high degree of process integration that results in substantial process intensification. In particular, combining perovskite-based membranes in membrane reactors can provide great benefits for many reaction systems including hydrogen production or ethylene production. In this chapter, the membrane reactor concept will be first highlighted and a few examples of perovskite-based membrane reactors will be discussed.
This work investigates the production of pure hydrogen by steam methane reforming in a fluidized bed membrane reactor. Hydrogen is separated though palladium based dense membranes from the products of steam methane reforming reaction in a fluidized bed containing a catalytic partial oxidation (CPO) catalyst. First, a 2 weeks run test was performed assessing the reactor stability during the whole test and the membrane perm-selectivity (H2/other gases) remained 100% even operating at elevated temperatures (903 K) and under bubbling fluidization regime. As the reactor demonstrated to be reliable and the membrane stable for a long period, a parametric study has been carried out highlighting the reactor performances in terms of methane conversion and hydrogen permeation. Moreover, the deviation from ideal reactor operation is outlined by studying the approach to equilibrium conversion and its connections with operating conditions. The operating conditions tested varied in the 773–903 K temperature range and 2.0–5.3 bar reacting pressure. The effect of weight hourly space velocity, steam to carbon ratio and dilution of the reacting mixture with an inert gas on the reactor performance were also investigated. Experimental results show that higher temperatures and pressures have positive effect both on approach to equilibrium conversion and on hydrogen yield, while opposite effects arise from increasing steam to carbon ratio and weight hourly space velocity.
