One of the great opportunities for waste utilization and reduction of global warming (carbon footprint) is the utilization of the methane in the gas to produce electric power with a fuel cell. These waste gases are primarily methane which must be reformed to hydrogen before use in a fuel cell. There are three basic types of methane reforming—steam, autothermal and partial oxidation. Temperature, pressure, and steam-to-carbon ratio play an important role in the performance of steam reforming. These variables also influence the reversible work and reaction enthalpy of the reforming products. A fuel cell stack or cell integrated steam reformer allows a recirculation of reversible heat as long as the operational temperature of the fuel cell is appropriate to the temperature of the reformer. The maximum total reversible work (highest exergetic efficiency) of the hydrogen and the carbon monoxide Wrev,H2,CO,ox is achieved at 762 kJ per 1 mol methane which is converted in the fuel processor. This corresponds to a maximum intrinsic thermal efficiency ηTh,Max, of 95% at an optimum temperature of 1023 K. This optimum temperature is in the operating temperature range of the high-temperature fuel cells like the molten carbonate and solid oxide fuel cells. Higher efficiencies can be expected with these fuel cells with steam reforming when utilizing natural gas, anaerobic digestor gas, or landfill gas.
The 10~25 mol% Yb-doped BaZrO3 ceramics having relative densities higher than 98% were obtained by the stoichiometric addition of 4 mol% ZnO as a sintering aid and then sintering at 1300°C for 10 hours. The crystal structure of the 10 mol% Yb-doped BaZrO3 ceramics was monoclinic (space group: Pm), while the crystal structures of the 15~25 mol% Yb-doped BaZrO3 ceramics were cubic (space group: Pm3m). When the crystal structures were cubic, the activation energy of the proton conductivities increased as the Yb-concentration increased. Due to the high activation energy, the proton conductivities of the 25 mol% Yb-doped BaZrO3 ceramics were significantly lower than those of the 10~20 mol% Yb-doped BaZrO3 ceramics, especially as the temperature decreased.
Soil contaminated with PCBs and dioxins was remediated using an intermediate air intake rotary kiln with a low oxygen process combining high-temperature (1100°C or higher) oxidation. The concentration of dioxins in the treated soil and burned ash was 0.0038–6.1 pg-TEQ/g and the concentration of PCBs was 0.91–3.3 ng/g. The dioxin concentration in the treated exhaust gas was 0.016/0.011 pg-TEQ/m3N and the PCB concentration was 14/4.7 ng/m3N. These results were all cleared for Japanese Environmental regulations. It also revealed that PCB particles could be easily collected using a bag filter because the majority of PCBs in the flue gas emitted from the kiln were in particle form. In addition, these particle-bound PCBs were not regenerated in the kiln or secondary combustion chamber. It is resulted that this combined process is suitable for the remediation of contaminated soil containing waste.
In order to recover trace of platinum (Pt) from hydrochloric acid (HCl) leaching solution of Cobalt-Rich Crust (CRC), the absorption properties of four kinds of seaweeds (Undaria pinnatifida, Laminaria angustata, Enteromorpha linza and Gloiopeltis tenax) and activated carbon were studied. At first, their adsorption abilities for Pt ion as well as selective adsorption properties for other coexisting metal ions contained in CRC (including iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni) and copper (Cu)) were investigated by using artificial solutions. Finally, the application to CRC HCl leaching solution was also carried out. The results showed that all seaweeds achieved their best Pt adsorption capacity only at pH 2, whereas activated carbon possessed a high Pt adsorption ability over a wide pH range from pH 0 to 6 as well as in HCl solution up to 3 mol/L. Regarding the CRC leaching solution obtained by 0.5 mol/L HCl and 1 vol.% hydrogen peroxide (H2O2), 46.9% and 100% Pt was recovered by Enteromorpha linza and activated carbon, respectively. It was found that seaweed and activated carbon are both effective adsorbents for recovering Pt from HCl leaching solution of CRC.
The effect of Fe(III) and Ca as coexistent elements on the extraction of Pb from contaminated soils with the biodegradable chelating agent [S,S]-ethylenediaminedisuccinic acid (EDDS) and the low biodegradable chelating agent ethylenediaminetetraacetic acid (EDTA) was investigated as a series of studies for their applicability for the removal of Pb from contaminated soils by soil washing and electrokinetic processing. The results obtained in this study are summarized as follows: The extraction of Pb with EDTA is suppressed by Ca as coexistent elements at the pH above 7 and by Fe(III) as coexistent elements at acidic region. Meanwhile, the extraction of Pb with EDDS has no effect of Ca at the wide pH range. However, the extraction of Pb with EDDS is significantly suppressed by Fe(III) at the wide pH.