1,123 research outputs found
Bioenergy–Intensified Biomass Utilization
No full textA major objective of European energy policy is to move towards more sustainable development based on diverse mix of resources, in particular, renewable resources including biomass. This chapter addresses broad field of power and combined heat and power (CHP) generation from biomass: more specifically, advances in biomass gasification technology aimed at increasing the overall conversion and efficiency and hence in a decreased cost of electricity. Poly-generation strategies are also considered, with particular reference to recent technological innovations in hot gas cleaning and conditioning; these have been developed to achieve the required improvements in syngas quality and have been validated under industrially relevant conditions. Biomass gasification is a thermo-chemical conversion process for the production of a fuel gas. Various combinations of air, oxygen and steam may be used as the gasification agent. This chapter focuses on steam gasification processes carried out in fluidized bed reactors for the production of H2-rich syngas. © 2015 John Wile
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
Butadiene 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
Uma cena de Fausto
No full textO assunto fáustico atravessa a obra de Púchkin. Ainda que o autor não tenha tido contato com a segunda parte da tragédia de Goethe, é possível enxergar inúmeros paralelismos do “fomentador” Fausto, nas palavras de Marshall Berman, em O Cavaleiro de Bronze. Em “Uma cena de Fausto”, Púchkin recorre a alguns motivos da história do homem que vendeu a alma ao diabo, os principais são: o esquecimento e o tédio do homem sem limites. Este que é ampliado na composição de Púchkin, para representar, como é típico do autor, temas estrangeiros tendo em vista necessidades históricas do seu país. Na presente tradução, optou-se por uma versão prosaica da “Cena de Fausto”.The faustian subject runs through Pushkin\u27s work. Even though the author has not had contact with the second part of Goethe\u27s tragedy, it is possible to see countless parallels of “The Developer” Faust, in the words of Marshall Berman, in The Bronze Horseman. In “A scene from Faust”, Pushkin resorts to some motifs from the story of the man who sold his soul to the devil, the main ones being: forgetfulness and the boredom of the man without limits. This one is expanded in Pushkin\u27s composition, to represent, as is typical of the author, foreign themes in view of the historical needs of his country. In the present translation, a prosaic version of the “Scene from Faust” was chosen
Enhancing Pt-Ni/CeO2 performances for ethanol reforming by catalyst supporting on high surface silica
No full textIn this paper, bimetallic Pt-Ni/CeO2 catalysts supported over mesoporous silica were employed for ethanol reforming in the low-temperature range. In particular, catalyst behaviour was investigated under a H2O/C2H5OH/N2 as well as H2O/C2H5OH/AIR mixture between 300 and 600°C at different space velocities (10000-30000h-1). Ethanol conversion, for both steam (ESR) and oxidative steam reforming (OSR) reactions, was not affected by contact time decrease at T>480°C while at lower temperatures, the space velocity growth led to reduced C2H5OH conversion, more pronounced when tests were performed without O2 co-feeding. Moreover, the catalysts showed high resistance to deactivation during reforming tests at 500°C and 20000h-1: the improvement of active species dispersion, as a consequence of catalyst formulation enrichment by SiO2 addition, resulted in lower carbon selectivity with respect to the SiO2-free sample. However, the higher extent of coke gasification reaction for OSR further increased catalyst stability and total ethanol conversion was recorded for almost 3500min, 1000min more than ESR case
Definition of validated membrane reactor model for 5 kW power output CHP system under different natural gas composition
No full textOptimization 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
Reacting porous solids with phase segregation
Full text linkIn this work, a detailed single particle model was developed to describe the reaction of porous solids consisting of different solid species, with an initial composition that can be non-uniformly distributed along its radius, and multiple reactions. The continuous particle model is used to describe the rate of reduction of iron-titanium oxide particles for Chemical Looping Combustion processes, considering a two-step reaction mechanism involving two solid reagents: hematite and pseudobrookite. The experimentally observed non-uniform initial distribution of solid species, as a consequence of the solids activation procedure, was accounted for by assuming an initial core-shell structure with a diffused interface with different compositions of the two areas of the pellets. A detailed sensitivity analysis was carried out assuming different kinetics and initial concentration profiles of the different solid species involved. The results confirm that the initial distribution of hematite and pseudobrookite has a major influence on the predicted particle conversion rate. A comparison was carried out with experimental data obtained by thermogravimetric analysis for the reduction of small spherical ilmenite particles (200μm) with CO and H2 at 600-800°C and at atmospheric pressure. The study proves that the model can explain features of the experimental results that do not fit any shrinking core model
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