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Hydrogen Recovery (hydrogen + recovery)

Distribution by Scientific Domains
Chemistry75%

Selected Abstracts

Computational study of staged membrane reactor configurations for methane steam reforming.

AICHE JOURNAL, Issue 1 2010

Abstract This article and Part II report a computational study carried out to analyze the performance achievable using a staged membrane reactor in the methane steam reforming process to produce high purity hydrogen. A reaction/separation unit in which reactive stages are laid out in series to permeative stages already proposed in literature (Caravella et al., J Memb Sci. 2008;321:209,221) is modified here to increase its flexibility. The improvement includes the consideration of the Pd-based membrane along the entire length. Two- and ten-staged reactors are examined in terms of methane conversion, hydrogen recovery factor and hydrogen recovery yield, considering co- and counter-current flow configurations. Individual stage lengths are obtained by maximizing either methane conversion or hydrogen recovery yield, comparing the results to the ones of an equivalent traditional reactor and a conventional membrane reactor. The analysis allows demonstrating that the counter-current configuration leads to significant improvements in the hydrogen recovery, but proves almost irrelevant with respect to methane conversion. The influence of the number of stages and the amount of catalyst is quantified in the accompanying part II article. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]

Four beds pressure swing adsorption for hydrogen purification: Case of humid feed and activated carbon beds

AICHE JOURNAL, Issue 9 2009
Ana M. Ribeiro
Abstract The novelty of this manuscript is the study of purification of hydrogen from a mixture of H2/CO2/CH4/CO/N2 saturated in water vapor. Simulations results of fixed bed behavior and of an eight steps PSA process are presented using an activated carbon as adsorbent. Several operating conditions were considered, namely different feed flow rates, humid/dry feed and adiabatic/nonadiabatic operation. Simulation with single column PSA showed that a 99.9979% purity hydrogen stream could be obtained with a recovery of 71.3% and a productivity of 63.9 mol/kgads/day. The simulation of a four columns PSA predicted a decrease in H2 purity to 99.8193% for the same operating conditions, due to the impurities present in the recycled stream of the continuous multicolumn process. To increase the hydrogen purity above 99.99%, the feed time was decreased 25%. Thus, the multicolumn simulation predicted a hydrogen recovery, purity, and productivity, respectively, of 62.7%, 99.9992%, and 55.2 mol/kgads/day. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Effects of high- and low-fiber diets on fecal fermentation and fecal microbial populations of captive chimpanzees

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 7 2009
Svetlana Ki, idayová
Abstract We examined fiber fermentation capacity of captive chimpanzee fecal microflora from animals (n=2) eating low-fiber diets (LFDs; 14% neutral detergent fiber (NDF) and 5% of cellulose) and high-fiber diets (HFDs; 26% NDF and 15% of cellulose), using barley grain, meadow hay, wheat straw, and amorphous cellulose as substrates for in vitro gas production of feces. We also examined the effects of LFD or HFD on populations of eubacteria and archaea in chimpanzee feces. Fecal inoculum fermentation from the LFD animals resulted in a higher in vitro dry matter digestibility (IVDMD) and gas production than from the HFD animals. However, there was an interaction between different inocula and substrates on IVDMD, gas and methane production, and hydrogen recovery (P<0.001). On the other hand, HFD inoculum increased the production of total short-chain fatty acids (SCFAs), acetate, and propionate with all tested substrates. The effect of the interaction between the inoculum and substrate on total SCFAs was not observed. Changes in fermentation activities were associated with changes in bacterial populations. DGGE of bacterial DNA revealed shift in population of both archaeal and eubacterial communities. However, a much more complex eubacterial population structure represented by many bands was observed compared with the less variable archaeal population in both diets. Some archaeal bands were related to the uncultured archaea from gastrointestinal tracts of homeothermic animals. Genomic DNA in the dominant eubacterial band in the HFD inoculum was confirmed to be closely related to DNA from Eubacterium biforme. Interestingly, the predominant band in the LFD inoculum represented DNA of probably new or yet-to-be-sequenced species belonging to mycoplasms. Collectively, our results indicated that fecal microbial populations of the captive chimpanzees are not capable of extensive fiber fermentation; however, there was a positive effect of fiber content on SCFA production. Am. J. Primatol. 71:548,557, 2009. © 2009 Wiley-Liss, Inc. [source]

Production of hydrogen via glycerol steam reforming in a Pd-Ag membrane reactor over Co-Al2O3 catalyst

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2010
A. Iulianelli
Abstract Generally, biodiesel fuel, when converted from vegetables oils, produces around 10 wt% of glycerol as a byproduct, which could be used for producing hydrogen by a steam-reforming reaction. Different scientific works have been realized in conventional reactors on the steam reforming of glycerol (GSR) in the aqueous or the gas phase. High reaction pressure and a relatively small catalyst deactivation are noticed when GSR is carried out in an aqueous phase, whereas the catalyst deactivation is the main disadvantage in the gas phase. In this work, GSR reaction was performed in a perm-selective Pd-Ag membrane reactor (MR) packed with a Co-Al2O3 commercial catalyst in order to extract a CO-free hydrogen stream and also enhance the performances in terms of glycerol conversion and hydrogen yield with respect to a traditional reactor (TR), both working at weight hourly space velocity (WHSV) = 1.01 h,1, 400 °C and H2O/C3H8O3 = 6/1. In MR, a maximum glycerol conversion of around 45.0% was achieved at 1.0 bar as reaction pressure, whereas it was around 94% at 4.0 bar. Moreover, as best value, more than 60.0% of CO-free hydrogen recovery was achieved in the MR at 4.0 bar and 22.8 of sweep factor (sweep gas to glycerol ratio). Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]