1,721,313 research outputs found
Techno-economic analysis for the design of membrane reactors in a small-scale biogas-to-hydrogen plant
Full text linkPd-based membranes are a key-component to obtain high-purity hydrogen from gaseous mixtures. They can be integrated in reactors called Membrane Reactors (MR), where the selective removal of reaction products allows to circumvent equilibrium limitations of traditional reactors. MRs for hydrogen production from methane reforming have been already investigated in literature, where they showed potentialities in small-scale biogas plants. However, analyses have typically been performed fixing many operating conditions and geometrical parameters, while only investigating few of them. It is therefore difficult to generalize the conclusions and to have a clear overview of the process behaviour. This article proves that MR performance can be summarized in generalized performance charts, where it is possible to characterize the reactor and the overall MR-based system only based on the membrane area it contains, for each set of temperatures, pressures, feed composition, catalyst amount and steam-carbon-ratio. From techno-economic analysis, it turned out that LCOH is 6.81 €/kg for a system with 100 kg/day of hydrogen production at 20 bar, reaching 7.49 €/kg if compressed up to 700 bar. System performance have been compared with a traditional reactor followed by a PSA (LCOH = 7.31 €/kg), showing that MR-based solution outperforms benchmark for its higher capacity to separate hydrogen. A sensitivity analysis assessed the influence of major uncertain costs.</p
Definition of validated membrane reactor model for 5 kW power output CHP system for different natural gas compositions
Full text linkOver the last years, many studies focused on the development of membrane reactors for micro-cogeneration systems based on PEM fuel cells, thanks to its unique feature of separating pure hydrogen. This work deals with (i) the design of a fluidized bed membrane reactor flexible towards different natural gas (NG) qualities and (ii) its integration in PEM based systems of 5 kW power output. Four typical NG compositions from reference European countries have been identified in this study featuring an average condition and three extreme cases. Two different membrane reactor models were developed: a 1D phenomenological model and a quasi-lumped model inside the overall system implemented in Aspen Plus. Results show the importance of taking into account the natural gas composition in the design phase: only assuming the NG with the highest inert content as base case, the target electric efficiency of 39% can be reached for any other case
Membrane reactors for green hydrogen production from biogas and biomethane: A techno-economic assessment
Full text linkThis work investigates the performance of a fluidized-bed membrane reactor for pure hydrogen production. A techno-economic assessment of a plant with the production capacity of 100 kgH2/day was carried out, evaluating the optimum design of the system in terms of reactor size (diameter and number of membranes) and operating pressures. Starting from a biomass source, hydrogen production through autothermal reforming of two different feedstock, biogas and biomethane, is compared. Results in terms of efficiency indicates that biomethane outperforms biogas as feedstock for the system, both from the reactor (97.4% vs 97.0%) and the overall system efficiency (63.7% vs 62.7%) point of views. Nevertheless, looking at the final LCOH, the additional cost of biomethane leads to a higher cost of the hydrogen produced (4.62 €/kgH2@20 bar vs 4.39 €/kgH2@20 bar), indicating that at the current price biogas is the more convenient choice.</p
Definition of validated membrane reactor model for 5 kW power output CHP system under different natural gas composition
No full textButadiene production in membrane reactors: A techno-economic analysis
Full text linkThe direct dehydrogenation of butane (BDH) is emerging as an attractive on-purpose technology for the direct production of 1,3-butadine. However, its product yield is hindered by the high rate of carbon deposition associated to the high temperature required for the highly endothermic reaction. In this work, we evaluated the use of H2-selective membrane reactor, to increase the yield of the dehydrogenation process at milder operating conditions. The novel proposed membrane reactor (MR)-assisted BDH technology is compared from a techno-economic point of view with the benchmark technology. The results of this analysis reveal that the MR technology enables to work at milder operating temperatures (−85 °C), reducing carbon formation (−98.5%) and reactor duty (−10%). Due to the higher reaction yields, the MR-assisted BDH technology can lower the required shale gas-based feedstock, maintaining same production capacity as in the benchmark; this will result in an overall plant efficiency of 50.92% in the MR-assisted plant, compared to 37.7% of the benchmark case. This work demonstrates that MR-assisted technology is a valuable alternative to the conventional BDH technology, reducing of almost 20% the final cost of production of 1,3-butadiene, due to the lower installation costs and the higher energy efficiency
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Techno-economic analysis of the Ca-Cu process integrated in hydrogen plants with CO2 capture
Full text linkIn this work, a techno-economic analysis of a hydrogen production plant based on the Ca-Cu process has been carried out. The simulation of the whole hydrogen production plant has been performed, including the calculation of the Ca-Cu fixed bed reactors system using a sharp front modelling approach. From the analyses carried out, it has been demonstrated that the optimal operation point from the energy performance point of view is reached when fuel needed for sorbent regeneration is entirely supplied by the off-gas from the PSA hydrogen purification unit, which corresponds to operating the plant with the minimum steam-to-carbon ratio in the reforming step. Moreover, lowering the operating pressure of the Ca-Cu system results beneficial from the hydrogen production efficiency, but the CO2 emissions and the economics worsen. The Ca-Cu based hydrogen production plant operating at a high pressure has been demonstrated to be cost efficient with respect to a benchmark hydrogen production plant based on conventional fired tubular reformer and CO2 capture by MDEA absorption. A hydrogen production cost of 0.178 €/Nm3 and a CO2 avoided cost of 30.96 €/ton have been calculated for this Ca-Cu hydrogen production plant, which are respectively 8% and 52% lower than the corresponding costs of the benchmark
Optimization of Small-Scale Hydrogen Production with Membrane Reactors
Full text linkIn the pathway towards decarbonization, hydrogen can provide valid support in different sectors, such as transportation, iron and steel industries, and domestic heating, concurrently reducing air pollution. Thanks to its versatility, hydrogen can be produced in different ways, among which steam reforming of natural gas is still the most commonly used method. Today, less than 0.7% of global hydrogen production can be considered low-carbon-emission. Among the various solutions under investigation for low-carbon hydrogen production, membrane reactor technology has the potential, especially at a small scale, to efficiently convert biogas into green hydrogen, leading to a substantial process intensification. Fluidized bed membrane reactors for autothermal reforming of biogas have reached industrial maturity. Reliable modelling support is thus necessary to develop their full potential. In this work, a mathematical model of the reactor is used to provide guidelines for their design and operations in off-design conditions. The analysis shows the influence of temperature, pressures, catalyst and steam amounts, and inlet temperature. Moreover, the influence of different membrane lengths, numbers, and pitches is investigated. From the results, guidelines are provided to properly design the geometry to obtain a set recovery factor value and hydrogen production. For a given reactor geometry and fluidization velocity, operating the reactor at 12 bar and the permeate-side pressure of 0.1 bar while increasing reactor temperature from 450 to 500 °C leads to an increase of 33% in hydrogen production and about 40% in HRF. At a reactor temperature of 500 °C, going from 8 to 20 bar inside the reactor doubled hydrogen production with a loss in recovery factor of about 16%. With the reactor at 12 bar, a vacuum pressure of 0.5 bar reduces hydrogen production by 43% and HRF by 45%. With the given catalyst, it is sufficient to have only 20% of solids filled into the reactor being catalytic particles. With the fixed operating conditions, it is worth mentioning that by adding membranes and maintaining the same spacing, it is possible to increase hydrogen production proportionally to the membrane area, maintaining the same HRF
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