8 research outputs found
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Nanofibrous Materials for Improved Sorbent Performance in the Sorption-Enhanced Steam Methane Reforming System
This work focuses on improving material deficiencies in calcium oxide CO2 sorbents for applications in sorption-enhanced steam methane reforming (SE-SMR). Challenges such as low sorption conversion and low stability of calcium oxide sorbents were addressed with studies on material synthesis and material chemistry. Calcium oxide decomposed from electrospun PVP-Ca(NO3)2 nanofibers lead to higher conversions and higher carbonation kinetics compared to calcium oxide from marble and synthesized via decomposition and hydrothermal treatment. Favorable material properties such as large macropores, high surface area and porosity, and small agglomerate size were enabled by electrospinning and led to the improved material performance. Electrospinning led to calcium oxide reaching stoichiometric capacity, 0.79 gCO2 gCaO-1, at 600 and 650�C in 100% CO2. In order to address the low stability of calcium oxide sorbents, metal additives were incorporated in the electrospinning solution so that upon nanofiber decomposition there was a mixture of additive metal oxide and calcium oxide. A systematic study was carried out on additive oxides using Al, Co, Cr, Er, Ga, In, La, Li, Mg, Nd, Y, and Zn additives to probe which properties impact the sorption capacity and stability of modified calcium oxide. Material properties such as molecular weight of the additive oxide or the formation of a mixed oxide (MxCayOz) and the M:Ca ratio directly impact the sorption capacity of the modified sorbents due to the effect of dilution and consumption of CaO in the mixed oxide. The Tammann temperature of the additive oxide was found to have a strong effect on the conversion of the modified sorbent. If the Tammann temperature was higher than the maximum treatment temperature the sorbent approached 100% conversion, however if the Tammann temperature was lower than the maximum treatment, conversion decreased with decreasing Tammann temperature. Further, Tammann temperature was found to be the primary material property influencing the stability of the modified sorbent and the formation of mixed oxides did not impact material stability. The stability of the modified sorbents increased with increasing Tammann temperature of the additive oxide. By optimizing the metal loading the alumina modified CaO-nanofibers, 1Al-20Ca-O, reached 0.75 gCO2 gCaO-1, while being an order of magnitude more stable during carbonation-regeneration cycling compared to unmodified CaO-nanofibers. Calcium oxide was also tested in a packed bed reactor in CO2 breakthrough experiments and in bench-scale SE-SMR experiments. The CO2 breakthrough experiments show that calcium oxide sorbents are even less stable when they carbonate in the presence of steam. SE-SMR experiments showed that the sorption capacity determined in the TGA related directly to the CO2 breakthrough time during the reforming reaction, with CaO-nanofibers having the highest breakthrough time and CaO-marble having the lowest breakthrough time. Further, the modified 1Al-20Ca-O sorbent lost only 5% of its CO2 breakthrough time over 10 cycles, indicating that modified sorbents retain their stability benefits under realistic SE-SMR operating conditions
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Nanofibrous Materials for Improved Sorbent Performance in the Sorption-Enhanced Steam Methane Reforming System
This work focuses on improving material deficiencies in calcium oxide CO2 sorbents for applications in sorption-enhanced steam methane reforming (SE-SMR). Challenges such as low sorption conversion and low stability of calcium oxide sorbents were addressed with studies on material synthesis and material chemistry. Calcium oxide decomposed from electrospun PVP-Ca(NO3)2 nanofibers lead to higher conversions and higher carbonation kinetics compared to calcium oxide from marble and synthesized via decomposition and hydrothermal treatment. Favorable material properties such as large macropores, high surface area and porosity, and small agglomerate size were enabled by electrospinning and led to the improved material performance. Electrospinning led to calcium oxide reaching stoichiometric capacity, 0.79 gCO2 gCaO-1, at 600 and 650�C in 100% CO2. In order to address the low stability of calcium oxide sorbents, metal additives were incorporated in the electrospinning solution so that upon nanofiber decomposition there was a mixture of additive metal oxide and calcium oxide. A systematic study was carried out on additive oxides using Al, Co, Cr, Er, Ga, In, La, Li, Mg, Nd, Y, and Zn additives to probe which properties impact the sorption capacity and stability of modified calcium oxide. Material properties such as molecular weight of the additive oxide or the formation of a mixed oxide (MxCayOz) and the M:Ca ratio directly impact the sorption capacity of the modified sorbents due to the effect of dilution and consumption of CaO in the mixed oxide. The Tammann temperature of the additive oxide was found to have a strong effect on the conversion of the modified sorbent. If the Tammann temperature was higher than the maximum treatment temperature the sorbent approached 100% conversion, however if the Tammann temperature was lower than the maximum treatment, conversion decreased with decreasing Tammann temperature. Further, Tammann temperature was found to be the primary material property influencing the stability of the modified sorbent and the formation of mixed oxides did not impact material stability. The stability of the modified sorbents increased with increasing Tammann temperature of the additive oxide. By optimizing the metal loading the alumina modified CaO-nanofibers, 1Al-20Ca-O, reached 0.75 gCO2 gCaO-1, while being an order of magnitude more stable during carbonation-regeneration cycling compared to unmodified CaO-nanofibers. Calcium oxide was also tested in a packed bed reactor in CO2 breakthrough experiments and in bench-scale SE-SMR experiments. The CO2 breakthrough experiments show that calcium oxide sorbents are even less stable when they carbonate in the presence of steam. SE-SMR experiments showed that the sorption capacity determined in the TGA related directly to the CO2 breakthrough time during the reforming reaction, with CaO-nanofibers having the highest breakthrough time and CaO-marble having the lowest breakthrough time. Further, the modified 1Al-20Ca-O sorbent lost only 5% of its CO2 breakthrough time over 10 cycles, indicating that modified sorbents retain their stability benefits under realistic SE-SMR operating conditions
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Improved Sorption-Enhanced Steam Methane Reforming via Calcium Oxide-Based Sorbents with Targeted Morphology
Genome-wide association and genomic prediction of growth traits in the European flat oyster (Ostrea edulis)
The European flat oyster (Ostrea edulis) is a bivalve mollusc that was once widely distributed across Europe and represented an important food resource for humans for centuries. Populations of O. edulis experienced a severe decline across their biogeographic range mainly due to overexploitation and disease outbreaks. To restore the economic and ecological benefits of European flat oyster populations, extensive protection and restoration efforts are in place within Europe. In line with the increasing interest in supporting restoration and oyster farming through the breeding of stocks with enhanced performance, the present study aimed to evaluate the potential of genomic selection for improving growth traits in a European flat oyster population obtained from successive mass-spawning events. Four growth-related traits were evaluated: total weight (TW), shell height (SH), shell width (SW) and shell length (SL). The heritability of the growth traits was in the low-moderate range, with estimates of 0.45, 0.37, 0.22, and 0.32 for TW, SH, SW and SL, respectively. A genome-wide association analysis revealed a largely polygenic architecture for the four growth traits, with two distinct QTLs detected on chromosome 4. To investigate whether genomic selection can be implemented in flat oyster breeding at a reduced cost, the utility of low-density SNP panels was assessed. Genomic prediction accuracies using the full density panel were high (> 0.83 for all traits). The evaluation of the effect of reducing the number of markers used to predict genomic breeding values revealed that similar selection accuracies could be achieved for all traits with 2K SNPs as for a full panel containing 4,577 SNPs. Only slight reductions in accuracies were observed at the lowest SNP density tested (i.e., 100 SNPs), likely due to a high relatedness between individuals being included in the training and validation sets during cross-validation. Overall, our results suggest that the genetic improvement of growth traits in oysters is feasible. Nevertheless, and although low-density SNP panels appear as a promising strategy for applying GS at a reduced cost, additional populations with different degrees of genetic relatedness should be assessed to derive estimates of prediction accuracies to be expected in practical breeding programmes