This thesis focuses on the analysis of kinetics of i) low-temperature pyrolysis of gaseous hydrocarbons, ii) high-temperature steam gasification of char of wood pellets (&gt;700oC), iii) high temperature pyrolysis of straw pellets in an atmosphere of argon and steam, and iv) high temperature pyrolysis of slices of transversally cut wooden sticks. The results of the kinetic measurements in the high-temperature cases are approximated using a least-square based optimization software, which was specially developed to analyse kinetics prone for deviation from the Arrhenius law.In the thesis a general analysis of the researched materials and kinetics of their pyrolysis and gasification is presented from the self-organization perspective. The energy transfer phenomena in both the pyrolysis and gasification processes of biomass are discussed with an emphasis on an analysis of basic phenomena involving the self-organized dynamics on fractal structures in the chosen biomass samples. / <p>QC 20150324</p>

Graduate

Most of the wastes in Sweden end up in incinerator plants. These trashes are full of metals, especially aluminium, which will not oxidize, they can’t always be recycled and they will instead oxidize in water and leak hydrogen gas to its surrounding. Estimations calculate it could be an average potential of around 40-50 kWh/ton of burnt trash. Ignoring the imported trash, the national recovery potential of Sweden’s 4,3 million tonnes of trash would then be equal to 170-220 GWh/year due to non-recyclable metals, which are currently going to temporary landfills. The requirements to harness this potential are technically simple, and can be achieved by a quick separation of the recyclables and the non-recyclables. This report will review the factors which increase the rate of reaction and study different ways of extracting the energy, by electrolysis, thermal treatment and mechanical mixing. This was done by taking small samples from the MSWI, owned by Umeå Energi AB, and putting them in small containers. While using the different methods, electrolysis, thermal treatment and mechanichal mixing, the amount of developed H2 gas over time was measured. The result shows that the best methods are mechanical mixing together with thermal treatment, where mechanical mixing seems to give the biggest effect of them two. The electrolysis did not work as intended, where there could be issues with the conductivity of the ash-mixture.

Desulfurization of liquid and gas phase sulfur compounds has been receiving dramatic attention since sulfur compounds cause environmental damages (especially acid rain) and pose industrial challenges (i.e. corrosion of equipment and deactivation of catalysts). This thesis has focused on the removal of liquid phase aromatic sulfur compounds (i.e. thiophene or dibenzothiophene (DBT)), as well as on the removal of gas phase hydrogen sulfide (H2S) through adsorption method by metal oxide/graphene composites. More specifically, the effects of graphene (or reduced graphite oxide) as a substrate were thoroughly investigated. For liquid phase sulfur removal, graphene which possesses π orbitals can adsorb aromatic sulfur compounds through π-π interactions. In addition, depending on the synthesis methods, higher quality graphene (i.e. thinner or larger graphene) could be obtained; and it improved the amount of DBT adsorption. For gas phase desulfurization (i.e. H2S adsorption), zinc oxide (ZnO) and reduced graphite oxide (rGO) composites have been studied. This study highlights the critical role of rGO as a substrate to enhance the H2S adsorption capacity. The presence of rGO with ZnO increases the surface area compared with pure ZnO since the oxygen functional groups on rGO prevent the aggregation of nano-sized ZnO particles for mid temperature sulfidation processes. The average particle size for pure ZnO was increased from 110 nm to 201 nm during the adsorption process while that for ZnO/rGO was maintained as 95 nm even after adsorption at 300°C. This contributes to explain that the presence of rGO with ZnO can enhance the H2S adsorption capacity from 31.7 mg S/g ads (for pure ZnO) to 172.6 mg S/g ads (for ZnO/rGO), that is more than a 5-fold increase. Morever, the presence of rGO with ZnO considerably improves the stability of the adsorbent; for multiple regeneration cycles at 600°C (in N2 environment), the adsorption capacity for ZnO/rGO stabilized at 93.1 mg S/g ads after the 8th cycle, while that for pure ZnO was nil after 5 cycles. The effects of copper (5, 10, 15, 20 and 25 mol%) with zinc oxide (ZnO) and reduced graphite oxide (rGO) composite on the hydrogen sulfide (H2S) adsorption capacity have also been studied. It was found that depending on the copper loading, the H2S adsorption capacity has been increased by up to 18 times compared to pure ZnO. In order to investigate the oxidation changes on copper and zinc oxides, crystallite analysis by XRD and chemical state analysis by XPS were performed. It was confirmed that the 2D rGO substrate, containing abundant oxygen functional groups, promoted the metal oxide dispersion and increased the H2S adsorption efficiency by providing loosely bonded oxygen ions to the sulfur molecules. In addition, it was determined that the optimum content of copper was 15 mol% relative to ZnO for maximizing the H2S adsorption. The 15% copper with ZnO/rGO led to the highest portion of zinc ions located in the Zn-O lattice; and led to the co-existence of Cu1+ and Cu2+ ions with ZnO. The H2S exposure at 300°C produces metal sulfides (i.e. zinc sulfide and copper sulfide) and sulfate ions.

No description available.

The endothelial layer of blood vessels is able to produce a number of vasoactive substances, and these substances can work to either relax or contract the underlying vascular smooth muscle. A hallmark of hypertension is the development of endothelial dysfunction, a shift in the balance of these substances to a state of increased contraction. Hydrogen sulfide (H2S) has recently garnered much interest as a gaseous signaling molecule with the discoveries that is can relax isolated blood vessels and lower blood pressure in young spontaneously hypertensive rats (SHR). Here we investigate whether chronic H2S treatment (56 μmol/kg of the H2S donor sodium hydrosulfide (NaHS), once daily for 5 weeks) can lower the blood pressure of adult aged SHR when compared to normotensive control Wistar Kyoto rats (WKY), and whether there are changes in the endothelium-dependent relaxation and contraction pathways. Invasive hemodynamic measurements including systolic, diastolic, and mean blood pressure, as well as heart rate were measured. Isolated vessel myography was performed on the common carotid artery to determine whether there were changes in the endothelium-dependent and independent relaxation and contraction pathways. This was achieved using a number of dose response curves. Changes in endothelium dependent dilation to ACh, VSM sensitivity to NO and H2S, and NO bioavailability were tested with dose response curves using ACh, SNP (an NO donor), H2S and indomethacin, respectively. TP receptor sensitivity, as well as COX-mediated constriction in quiescent vessels was also examined by using the TP receptor agonist U46619 and L-NAME (eNOS inhibitor), respectively. Biochemical analyses included Western blotting to assess protein levels of CSE (H2S generating enzyme) and eNOS (NO generating enzyme) as well as determining prostacyclin production. Determination of H2S concentration in the blood via a sulfide electrode was also performed to confirm that the H2S treatment was effective. There were no main effects of H2S treatment in any of the hemodynamic measurements taken. ACh dose response revealed a blunting in the recontraction at 10-5 and 10-4.5 log M concentrations (p<0.05) in SHR treated with H2S. No effects were observed, however, in any other myography protocol. Western blot analysis revealed no difference in the protein expression of CSE or eNOS with H2S treatment, and there were no differences in prostacyclin production with H2S treatment. In conclusion, these data suggest that H2S may not be an effective treatment for hypertension in adult SHR, in contrast to previous work finding a similar dosing regimen to be effective at lowering blood pressure in young SHR. Further work must be completed to ascertain the mechanism for the alteration in the ACh dose response curve and to determine at what time point the H2S treatment becomes ineffective.

I have developed an analytical method for the determination of molecular hydrogen in seawater. It is based on the change of hydrogen concentration in a 30 cc. volume of air as it is equilibrated with a one-liter sample of seawater. The change in hydrogen concentration in the air is measured using a gas chromatograph with a helium ionization detector. The system has been utilized aboard ship on several occasions and has been proven to be both dependable and readily transportable. The accuracy of a single measurement is limited to about plus or minus fifteen per cent by the analytical precision of the method. The precision is limited by the random errors in the GC analysis. Shipboard and laboratory experiments have shown that contamination of near-surface and near-bottom samples can be a major problem unless special precautions are taken. / Graduation date: 1978

Hydrogen is an environmentally friendly and highly efficient energy source. Fermentative hydrogen production is an exciting R&D area that offers a means to produce hydrogen from a variety of renewable resources or even wastewaters. However, the development of fermentative hydrogen production processes has been hampered due to their low yield and relatively high costs. The aim of this thesis was to improve fundamental knowledge of hydrogen-producing bacteria, provide genetic information associated with the hydrogen evolution, and to optimise operating conditions to enhance hydrogen yield. Isolation and identification of hydrogen producing bacteria from activated sludge were conducted using 16S rRNA gene-directed PCR-denaturing gradient gel electrophoresis (DGGE), clone library and heterotrophic plate isolation. The results showed that Clostridium sp. were dominant and active hydrogen producers. For the first time, three hydrogen producers, which harboured the [FeFe] hydrogenase gene, were characterised by 16S rDNA sequencing, and further physiologically identified as Clostridium sp. (W1), Clostridium butyricum (W4) and Clostridium butyricum (W5). The structure of the putative [FeFe] hydrogenase gene cluster of C. butyricum W5 was also described. The changes in [FeFe] hydrogenase mRNA expression of C. butyricum W5 during fermentation were monitored. Statistical analysis showed that both the [FeFe] hydrogenase mRNA expression level and cell growth have positive relationships with hydrogen production. The newly isolated C. butyricum W5 demonstrated highly promising hydrogen fermentation performance and was therefore used as the working strain. Optimization of operating conditions in terms of carbon and nitrogen sources, pH, temperature and inoculum size was carried out in a laboratory scale batch system. Use of molasses and NH₄NO₃ resulted in a high hydrogen production yield. Under the optimized fermentation conditions, 100g/L molasses, 1.2g/L NH₄NO₃, and 9×10⁴ cell/ml initial cell number at 39°C and pH 6.5, a maximum hydrogen yield of 1.85 mol H₂/ mol hexose was achieved. This corresponded to a hydrogen production rate of 17.38 mmol/h/L. Acetic, lactic and butyric acids were found to be the main by-products of the fermentation. The interrelations between the hydrogen yield and other yields of metabolites were statistically analysed corresponding to the variation in operating conditions. The dry cell weight was found to have a power relationship with hydrogen production. The results from this study have provided a better understanding of metabolic processes and gene expression involved in fermentative hydrogen production, and an improved bioengineering process for hydrogen production. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339837 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Hydrogen is an environmentally friendly and highly efficient energy source. Fermentative hydrogen production is an exciting R&D area that offers a means to produce hydrogen from a variety of renewable resources or even wastewaters. However, the development of fermentative hydrogen production processes has been hampered due to their low yield and relatively high costs. The aim of this thesis was to improve fundamental knowledge of hydrogen-producing bacteria, provide genetic information associated with the hydrogen evolution, and to optimise operating conditions to enhance hydrogen yield. Isolation and identification of hydrogen producing bacteria from activated sludge were conducted using 16S rRNA gene-directed PCR-denaturing gradient gel electrophoresis (DGGE), clone library and heterotrophic plate isolation. The results showed that Clostridium sp. were dominant and active hydrogen producers. For the first time, three hydrogen producers, which harboured the [FeFe] hydrogenase gene, were characterised by 16S rDNA sequencing, and further physiologically identified as Clostridium sp. (W1), Clostridium butyricum (W4) and Clostridium butyricum (W5). The structure of the putative [FeFe] hydrogenase gene cluster of C. butyricum W5 was also described. The changes in [FeFe] hydrogenase mRNA expression of C. butyricum W5 during fermentation were monitored. Statistical analysis showed that both the [FeFe] hydrogenase mRNA expression level and cell growth have positive relationships with hydrogen production. The newly isolated C. butyricum W5 demonstrated highly promising hydrogen fermentation performance and was therefore used as the working strain. Optimization of operating conditions in terms of carbon and nitrogen sources, pH, temperature and inoculum size was carried out in a laboratory scale batch system. Use of molasses and NH₄NO₃ resulted in a high hydrogen production yield. Under the optimized fermentation conditions, 100g/L molasses, 1.2g/L NH₄NO₃, and 9×10⁴ cell/ml initial cell number at 39°C and pH 6.5, a maximum hydrogen yield of 1.85 mol H₂/ mol hexose was achieved. This corresponded to a hydrogen production rate of 17.38 mmol/h/L. Acetic, lactic and butyric acids were found to be the main by-products of the fermentation. The interrelations between the hydrogen yield and other yields of metabolites were statistically analysed corresponding to the variation in operating conditions. The dry cell weight was found to have a power relationship with hydrogen production. The results from this study have provided a better understanding of metabolic processes and gene expression involved in fermentative hydrogen production, and an improved bioengineering process for hydrogen production. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1339837 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona. / Includes bibliographical references.