Home About us Contact
|
Home About us Contact | ||
|
|
||
Gas Shift (gas + shift)
Terms modified by Gas Shift Selected AbstractsBehaviour modelling of a PEMFC operating on diluted hydrogen feedINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2008M. Minutillo Abstract The polymer electrolyte membrane fuel cell (PEMFC) using reformate gas as fuel is regarded as an attractive solution for the near-term introduction of fuel cells in stationary or mobile power generation market. With respect to hydrogen feeding, the reformate gas fuelling involves additional polarization losses because of the hydrogen dilution and the impurities contained in the gas. In this paper a one-dimensional model has been developed to investigate the behaviour of a PEMFC operating with reformate gas mixture. The model, based on a semi-empirical approach, considers the kinetic reactions in the anode side taking into account the effect of reverse water,gas shift (RWGS) due to the presence of CO2 in the fuel. As it is well known, the exhaust stream from fuel reformers can contain a high carbon dioxide concentration (>20%) that can have a detrimental effect on the fuel cell performance because of the combination of the dilution and the formation of CO by the RWGS reaction. The numerical simulation results have been compared with the experimental data, obtained in the test room of Industrial Engineering Department of Cassino University, and a good match has been observed. The model has been developed by using a simplified approach that, nevertheless, can allow to obtain a good numerical prediction of the fuel cell performance reducing the simulation time and computational efforts. Copyright © 2008 John Wiley & Sons, Ltd. [source] Kinetic model for noncatalytic supercritical water gasification of cellulose and ligninAICHE JOURNAL, Issue 9 2010Fernando L. P. Resende Abstract This article reports the first kinetics model for Supercritical Water Gasification (SCWG) that describes the formation and interconversion of individual gaseous species. The model comprises 11 reactions, and it uses a lumping scheme to handle the large number of intermediate compounds. We determined numerical values for the rate constants in the model by fitting it to experimental data previously reported for SCWG of cellulose and lignin. We validated the model by showing that it accurately predicts gas yields at biomass loadings and water densities not used in the parameter estimation. Sensitivity analysis and reaction rate analysis indicate that steam-reforming and water,gas shift are the main sources of H2 in SCWG, and intermediate species are the main sources of CO, CO2, and CH4. © 2010 American Institute of Chemical Engineers AIChE J, 2010 [source] Enhancing high water content biomass gasification with impregnated Ca in fuel dryingAICHE JOURNAL, Issue 10 2006Guangwen Xu Abstract In view of energy conversion efficiency, the gas production from high water content (>60 wt.%) biomass via gasification is necessarily conducted with fuel drying in advance. In regard to this kind of processes, the present study was devised to impregnate Ca onto fuel during fuel drying and thereby to increase fuel's gasification reactivity to raise the gas production efficiency with minimal additional cost. By employing wet coffee grounds as a model biomass fuel and slurry dewatering in kerosene as the adopted drying technology, the Ca impregnation was implemented through dosing Ca(OH)2 into a fuel-kerosene slurry and in turn treating the slurry in the same way as for the case without Ca addition. The resulting Ca (4.0 wt.% load in CaO base) exhibited high dispersion through the fuel matrix in both SEM-EDX image and XRD spectrum. Gasification of the fuel in a pilot dual fluidized gasification setup further demonstrated that the fuel possessed distinctively high reaction reactivity. This led it to show C and H conversions of 91% and 138%, respectively, at a reaction temperature of about 1083 K, whereas these conversions were only 70% and 92% for the fuel with a similar amount of physically mixed CaO. The catalytic effect of the impregnated Ca manifested also on hydrocarbon reforming and water gas shift, making the resulting product gas evidently rich in H2 and lean in CO and hydrocarbons. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Catalysts for water,gas shift processing of coal-derived syngases,ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2010San Shwe Hla Abstract Although the gasification of coal is an efficient means of producing syngas, the carbon content of coal is such that gasification produces significantly higher ratios of carbon oxides to hydrogen than those obtained by the steam reforming of natural gas. The CO:H2 ratio can be adjusted, and more hydrogen produced, by the subsequent application of the water,gas shift (WGS) reaction. This article presents a review of technologies associated with the catalytic WGS reaction in a fixed-bed reactor that might be incorporated into a coal gasification-based system for H2 production with CO2 capture. The main output from this review is the identification of key project areas requiring further research. The performance of existing, commercially available catalysts,designed for use in natural gas reforming processes,with coal-derived syngases is an important aspect of developing technologies for coal-based H2 production. This article presents an experimental assessment of the performance of selected commercially available WGS catalysts, two high-temperature catalysts (HT01 and HT02) and a sour shift catalyst (SS01), with such syngases. For the three commercial catalysts investigated in this study, CO reaction order is found to be in a range of 0.75,1. The effect of changes in H2O concentration over HT01 is insignificant, whereas H2O reaction orders determined using HT02 and SS01 are found to be significantly positive even at high H2O:C ratios. The CO conversion rate is significantly reduced by increasing CO2 concentration, whereas increasing H2 concentration also causes a slight reduction in CO conversion rate for the three commercial catalysts investigated. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd. [source] A model for the dynamic behavior of a commercial scale slurry bubble column reactor applied for the Fischer,Tropch synthesisASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010Samira Ghasemi Abstract Fischer-Tropsch synthesis (FTS) is an important chemical process for the production of liquid fuels. In the present study, a dynamic model for a commercial size slurry bubble column reactor (SBCR) operating under heterogeneous flow regime and dealing with the FTS has been developed. In such a model a detailed kinetics expressions for the FTS and water gas shift (WGS) reactions have been considered. A selectivity model combined with SBCR hydrodynamics and the multicomponent VLE scheme have been applied to estimate the distribution of olefins and paraffins in the products. In addition, the effects of catalyst deactivation on reactor performance and product distribution under transient conditions may be predicted from this model. The data calculated from the model have been correlated with the experimental results available in the literature. It seems that the present model could be applied to estimate the main characteristics of the reactor's dynamic behavior. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Pd,Ag membranes for auto-thermal ethanol reformingASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010Silvano Tosti Abstract The auto-thermal ethanol reforming was carried out at 200 kPa by a two-step process consisting of a traditional reformer operating at high temperature (700,740 °C) and a Pd,Ag multitube membrane module where the separation of hydrogen took place at 350,380 °C. The membrane module was a bundle of 11 thin-wall Pd,Ag tubes of wall thickness 50,60 µm, diameter 10 mm, and length 270 mm: permeation tests were performed at 300,395 °C with lumen pressure of 150,200 kPa, and nitrogen sweep flow rates in the shell side ranged from 10 to 30 l min,1 at atmospheric pressure. A hydrogen permeance Pe = 1.317 × 10,2 exp (,3.622 × 103/T(K)) mol m,2 s,1 Pa,0.5 was measured and complete hydrogen selectivity was verified. A water/ethanol mixture of molar ratio 2.50/1.00 was used as feed stream for carrying out ethanol reforming in the traditional fixed-bed reactor filled with a Ni on alumina catalyst. As a second step, the water gas shift (WGS) membrane reaction was carried out in the multitube membrane reactor: the Pd,Ag alloy of the membrane tubes worked for both catalyzing the reaction and for separating all the hydrogen produced in the reformer and in the membrane reactor itself. The hydrogen separated through the membrane was collected in the shell side of the membrane module: by operating with a water/ethanol feed flow rate of 200 g h,1, up to 1.2 l min,1 of pure hydrogen was produced. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Mapping the Transformation [{RuII(CO)3Cl2}2],[RuI2(CO)4]2+: Implications in Binuclear Water,Gas Shift ChemistryCHEMISTRY - A EUROPEAN JOURNAL, Issue 8 2010Moumita Majumdar Abstract The complete sequence of reactions in the base-promoted reduction of [{RuII(CO)3Cl2}2] to [RuI2(CO)4]2+ has been unraveled. Several ,-OH, ,:,2 -CO2H-bridged diruthenium(II) complexes have been synthesized; they are the direct results of the nucleophilic activation of metal-coordinated carbonyls by hydroxides. The isolated compounds are [Ru2(CO)4(,:,2 - C,O -CO2H)2(,-OH)(NPF -Am)2][PF6] (1; NPF -Am=2-amino-5,7-trifluoromethyl-1,8-naphthyridine) and [Ru2(CO)4(,:,2 - C,O -CO2H)(,-OH)(NP-Me2)2][BF4]2 (2), secured by the applications of naphthyridine derivatives. In the absence of any capping ligand, a tetranuclear complex [Ru4(CO)8(H2O)2(,3 -OH)2(,:,2 - C,O -CO2H)4][CF3SO3]2 (3) is isolated. The bridging hydroxido ligand in 1 is readily replaced by a ,-donor chlorido ligand, which results in [Ru2(CO)4(,:,2 - C,O -CO2H)2(,-Cl)(NP-PhOMe)2][BF4] (4). The production of [Ru2(CO)4]2+ has been attributed to the thermally induced decarboxylation of a bis(hydroxycarbonyl),diruthenium(II) complex to a dihydrido,diruthenium(II) species, followed by dinuclear reductive elimination of molecular hydrogen with the concomitant formation of the RuIRuI single bond. This work was originally instituted to find a reliable synthetic protocol for the [Ru2(CO)4(CH3CN)6]2+ precursor. It is herein prescribed that at least four equivalents of base, complete removal of chlorido ligands by TlI salts, and heating at reflux in acetonitrile for a period of four hours are the conditions for the optimal conversion. Premature quenching of the reaction resulted in the isolation of a trinuclear RuI2RuII complex [{Ru(NP-Am)2(CO)}{Ru2(NP-Am)2(CO)2(,-CO)2}(,3:,3 - C,O,O, -CO2)][BF4]2 (6). These unprecedented diruthenium compounds are the dinuclear congeners of the water,gas shift (WGS) intermediates. The possibility of a dinuclear pathway eliminates the inherent contradiction of pH demands in the WGS catalytic cycle in an alkaline medium. A cooperative binuclear elimination could be a viable route for hydrogen production in WGS chemistry. [source] | ||||||||||