Applying an external electric field enables electrostatically charged particles to move without any external mechanical forces. As a result, electrostatic-based techniques have attracted considerable attention in the field of particle handling. In this experiment, a plate electrode and a mesh electrode were used for lower and upper electrodes, respectively. Dielectric particles (glass beads with particle diameters of 100 µm) were piled on the lower electrode. A voltage of +5 kV was applied to the lower electrode, and the upper electrode was grounded, producing an electric field directed upwards. Owing to induction charging, the electric charge polarity of the particle layer is identical to that of the lower electrode, leading to particles in the upper layer being levitated by the Coulomb forces. The observation of both the particle behavior and the levitation process using a high-speed microscope camera showed that agglomerates as well as individual particles were levitated. The dielectric particles were polarized in the electric field, the electrostatic interaction between which leads to the formation of chain agglomerates. When the specific charge of the particles was small, the resulting Coulomb force was small, and the agglomerate did not levitate. However, when the magnitude of the total Coulomb force of the primary particles consisting the agglomerate exceeded the interparticle and gravitational forces, the agglomerate levitated. Estimating particle charge based on both electric field analysis and particle trajectory analysis showed that the specific charge of the agglomerate decreases and the interparticle force increases with an increase in the number of primary particles in the agglomerate.
The influence on batch gravity sedimentation behavior of the cation valence and concentration of inorganic salts added to activated sludge pretreated by ultrasonication was examined to clarify the synergistic flocculation effect of ultrasonication and salt addition. Among the salts tested, the addition of those with divalent cations such as Ca2+ and Mg2+ were found to be most effective in improving the sedimentation properties of ultrasonicated sludge. For instance, the addition of a tiny amount of Ca2+ formed enormously large flocs with high apparent densities, thereby upgrading the sedimentation performance. The addition of 10 mM Ca2+ increased the constant rate sedimentation velocity during the initial stage of sedimentation by 40.4 times and decreased the sediment volume index after 300 min by 23 points compared to the values for untreated sludge. Mg2+ addition showed a similar trend, suggesting the non-specific binding of divalent cations to intracellular metabolic polymer substances released from cells disrupted by ultrasonication, rather than the interaction and gel formation specific to Ca2+ known as the egg-box structure of alginate that is seen in the presence of Ca2+. The constant rate sedimentation velocity for ultrasonicated sludge increased with increasing concentration of monovalent cations such as Na+ and K+. However, the addition of trivalent cations such as Fe3+ and Al3+ to ultrasonicated sludge was ineffective in improving sedimentation performance, even though their addition to untreated sludge is most effective among the monovalent, divalent, and trivalent cations tested in this research. This ineffectiveness is probably due to steric hindrance between polymeric substances induced by trivalent cations. The results obtained from the cation addition to untreated sludge were qualitatively in line with the Schulze–Hardy rule, supported by the DLVO theory elucidating the compression of the electrical double layer occurring in association with cation addition.
A membrane reformer (MRF) in which the production and separation of hydrogen proceed simultaneously in a single reactor allows the production to proceed without the constraint of chemical equilibrium. An MRF can thus be made more compact and provide higher efficiency than a conventional reformer. In this study, a Pd-based membrane of less than 10 µm in thickness was fabricated on a porous catalytic substrate, and a hydrogen production module was developed with the thin Pd-based membrane-on-catalyst (MOC) module. The steam reforming performance of the MOC module was evaluated under different conditions of city gas feed rate and temperature. At process side pressure/permeation side pressure of 0.90 MPa/0.04 MPa, the hydrogen production rate of the MOC module was 11.4 N cm3/(min·cm2) at a city gas feed rate of 3.0 N cm3/(min·cm2) and 547°C, which is almost equal to the performance of the conventional membrane reformer system for hydrogen production.
Methanol is an important industrial material for producing medicine, fuel and resin. It is generally synthesized through the reaction of CO and H2 in steam reforming of methane. This process is, however, energy consuming; development of a direct method of methanol synthesis that is less energy consuming is required. This paper introduces an experimental study on flow-type hydrothermal oxidation of methane by H2O2. Experiments were conducted under different H2O2 preheating conditions (no-preheating, 120°C, over 270°C) at reaction temperatures from 100 to 350°C. Methane conversion was significantly higher without preheating than when H2O2 was preheated to over 270°C. As a result, methanol yield also increased and showed higher values than previously reported. The increased methane conversion in the absence of preheating was considered to result from elimination of the thermal decomposition of H2O2 that would occur during preheating and the formation of strongly oxidizing OH radicals at the reaction site due to the rapid rise in temperature. This experimental results also suggested that all H2O2 was decomposed to O2 before it reached the reaction tube when it was preheated at over 270°C.
Industrial symbiosis is an option to reduce waste and to improve resource productivity by exchanging usable wastes or byproducts between neighboring industries. While case examples of industrial symbiosis have mainly been conducted in industrial areas, the application of industrial symbiosis to rural areas should be carefully examined as a means to revitalize local agriculture, forestry, and related industries. A method for planning a system with industrial symbiosis is strongly needed in order to extract the essence of systems integration among different industrial process systems. In this study, a systematic procedure for planning industrial symbiosis in rural areas is proposed. Firstly, the planning problems to be solved for application of industrial symbiosis were characterized by comparing the conditions in industrial and rural areas based on activity modeling applied in systematic chemical process design. The procedure for planning industrial symbiosis to solve specified problems was visualized as an activity model. Focusing on the simulation of changes in material and energy flows within characterized planning problems, the data structure activating the specified activities was constructed by data modeling. The developed activity and data models were validated through the demonstration of actual case examples of industrial symbiosis in rural areas. The clarification of similarities and differences among various areas and industries based on such modeling facilitates the planning of industrial symbiosis.
Humic substances are organic compounds that form complexes with heavy metals. Humic substances are classified into three types, humin, fulvic acids, and humic acids, of which the latter most easily forms complexes and humic acid is most easily extracted. Humic substances are easily degraded by microorganisms. Humic acids were extracted from humus collected at regular intervals from a site with fallen leaves and their properties were investigated, including exchangeable proton capacity and the adsorbed amounts of Cu2+, Cu2+ in the presence of Ca2+, and 2,4-dichlorophenoxyacetic acid dimethylamine, a typical pesticide applied to agricultural land. The exchangeable proton capacity of humic acidssw was found to increase with humification time, but no relationship was found between the adsorbed amount of Cu2+ and humification time. The presence of Ca2+ significantly changed the amount of Cu2+ adsorbed by some humic acids. The adsorption isotherms of 2,4-dichlorophenoxyacetic acid dimethylamine could be fitted to the Freundlich model, and the adsorption coefficient was found to decrease as humification time increased.
A stochastic event with an expectation value of waiting time of roughly 1200 years occurred during August to October 2012 in Lake Shinjiko, a brackish lake. Abnormally strong salt stratification gave rise to oxygen deficiency at the lake bottom and the movement of a large amount of soluble phosphorus to the surface to flow out of the lake eventually. As a result, the former generation of blue–green algae has not been observed in fact since 2013. The reduction in phosphorus at the lake bottom is thought to have caused a regime shift from blue–green algae to diatoms. A series of phenomena is also important in considering the water pollution mechanism of Lake Shinjiko. For example, the effect of extension of the public sewerage system by Shimane prefecture may be hidden by the stochastic occurrence of soluble phosphorus and the reproductive cycle of the withered blue-green algae. If this assumption holds true, it means that the desirable regime shift is sustainable. It is necessary, however, to make clear the contribution of rivers smaller than the River Hiikawa in the phosphorus balance, and to promote immediately executable countermeasures to reduce phosphorus in order to make the current diatom regime more reliable.
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