Reactivity of Iron/Zirconia Powder in Fluidized Bed Thermochemical Hydrogen Production Reactors

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
F. Al-Raqom ◽  
J. F. Klausner
Keyword(s):  
Particle Size ◽  
Hydrogen Production ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Iron Powder ◽  
Volume Ratio ◽  
Apparent Volume ◽  
Zirconia Powder ◽  
Equivalent Mass

A fluidized bed reactor has been developed which uses a two-step thermochemical water splitting process with a peak hydrogen production rate of 47 Ncm3/min.gFe at an oxidation temperature of 850 °C. Of particular interest, is that a mixture of iron and zirconia powder is fluidized during the oxidation reaction using a steam mass flux of 58 g/min-cm2. The zirconia powder serves to virtually eliminate iron powder sintering while maintaining a high reaction rate. The iron/zirconia powder is mixed in a ratio of 1:2 by apparent volume and has a mass ratio of 1:1. Both iron and zirconia particles are sieved to sizes ranging from 125 μm to 355 μm. The efficacy of zirconia as a sintering inhibitor was found to be dependent on the iron and zirconia mean particle size, particle size distribution and iron/zirconia apparent volume ratio. At 650 °C, the oxidation of iron powder with a mean particle size of 100 μm and a wide particle size distribution (40–250 μm) mixed with 44 μm zirconia powder with an iron/zirconia apparent volume ratio of 1:1 results in 75–90% sintering. In all cases, when iron is mixed with zirconia, the hydrogen production rate is not affected when compared with the pure iron case assuming an equivalent mass of iron is in the mixture. When iron powder is mixed with zirconia, both with a narrow particle size distribution (125–355 μm), the first oxidation step results in 3–7% sintering when the reactions are carried out at temperatures ranging between 840 and 895 °C. The hydrogen fractional yield is high (94–97%). For subsequent redox reactions, the macroscopic sintering is totally eliminated at 867 and 895 °C, although the hydrogen fractional yield decreases to 27 and 33%, respectively. It is demonstrated that mixing iron with zirconia in an equivalent mass ratio and similar particle size range can eliminate macroscopic sintering in a fluidized bed reactor at elevated temperatures up to 895 °C.

Reactivity of Iron/Zirconia Powder in Fluidized Bed Thermochemical Hydrogen Production Reactors

2012 ◽  
Author(s):  
F. Al-Raqom ◽  
J. F. Klausner
Keyword(s):  
Particle Size ◽  
Hydrogen Production ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Iron Powder ◽  
Volume Ratio ◽  
Apparent Volume ◽  
Fluidized Bed Reactors ◽  
Zirconia Powder

A fluidized bed reactor has been developed which uses a two-step thermochemical water splitting process with a peak hydrogen production rate of 47 Ncm3/min.gFe at an oxidation temperature of 850°C. Of particular interest, is that a mixture of iron and zirconia powder is fluidized during the oxidation reaction using a steam mass flux of 0.58 g/min-cm2, and the zirconia powder serves to virtually eliminate iron powder sintering while maintaining a high reaction rate. The iron/zirconia powder is mixed with a ratio of 1:2 by apparent volume, equivalent mass ratio, and both iron and zirconia particles are sieved to sizes ranging from 125–355 μm. Fluidized bed reactors are advantageous because they have high reactivity, strong thermal and chemical transport, and tend to be compact. There has been significant interest in developing fluidized bed reactors for solar thermochemical reactors, but sintering of the reactive powder has inhibited their development. The current powder mixture and reactor configuration shows great potential for achieving high hydrogen production rates for operation at high temperature. The experimental investigations for utilizing zirconia as a sintering inhibitor was found to be dependent on the iron and zirconia particle size, particle size distribution and iron/zirconia apparent volume ratio. For example at 650 °C the oxidation of iron powder with a mean particle size of 100 μm and a wide particle size distribution (40–250 μm) mixed with 44 μm zirconia powder with an iron/zirconia apparent volume ratio of 1:1 results in 75–90 % sintering. In all cases when iron is mixed with zirconia, the hydrogen production rate is not affected when compared with the pure iron case. When iron powder is mixed with zirconia, both with a narrow particle size distribution (125–355 μm) the first oxidation step results in 3–7% sintering when the reactions are carried out at temperatures ranging between 840–895 °C. The hydrogen fractional yield is high (94–97%). For subsequent redox reactions, the sintering is totally eliminated at 867 and 895 °C although the hydrogen fractional yield decreases to 27 and 33%, respectively. This study demonstrates that mixing iron with zirconia in an equivalent mass ratio and similar particle size can eliminate sintering in a fluidized bed reactor at elevated temperatures up to 895°C.

Soil Cohesion Development under Different Pore and Size Characteristics

2020 ◽  
Author(s):  
Cagla Temiz ◽  
Fikret Ari ◽  
Selen Deviren Saygin ◽  
Sefika Arslan ◽  
Mehmet Altay Unal ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Soil Properties ◽  
Size Distribution ◽  
Fluidized Bed ◽  
Soil Mass ◽  
General Terms ◽  
Soil Cohesion ◽  
Wide Range ◽  
Fluid Bed

<p>Soil cohesion (Co) is one of the most important physical soil characteristics and it is closely related to the basic soil properties and physical distribution forces (e.g. particle size distribution, pore sizes, shear strength) and so it is mostly determined by experimentally approaches with the help of other soil properties in general terms. Instead of using these assumptions, the fluidized bed approach provides an opportunity for direct measurement of intrinsic soil cohesion. In this study, soil cohesion development for different soil types was investigated with the fluid-bed method by which pressure drop in soil mass measures under increasing water pressures until the cohesion between particles disappears. For this purpose, 20 different soils varying with a wide range of relevant soil physical properties were sampled; such that clay, silt and sand contents varied between 2% and 56%, 1% and 50%, and 1% and 97%, respectively while porosity values were between 0.38 and 0.92. By those textural diversities of the soils, obtained cohesion values changed between 5203 N m<sup>-3</sup> and 212276 N m<sup>-3</sup>. Given results from regression analysis, a significant relationship was found between cohesion values of the soils and their porosity and silt fractions (R<sup>2</sup>: 86.6).These findings confirm that the method has a high potential to reflect differential conditions and show that soil cohesion could be modeled by such basic and easily obtainable parameters as particle size distribution and porosity, as well.<strong> </strong></p><p><strong>Key words</strong>; <strong>Mechanical soil cohesion, particle size distribution, fluidized bed approach, porosity</strong></p>

Steady-State and Oscillating Behaviour of the Particle Size Distribution in Fluidized Bed Granulation

2001 ◽  
Vol 73 (6) ◽  
pp. 702-702
Author(s):  
Stefan Heinrich ◽  
Mirko Peglow ◽  
Matthias Ihlow ◽  
Markus Henneberg ◽  
Lothar Mörl
Keyword(s):  
Particle Size ◽  
Steady State ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Fluidized Bed
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