In a cream storage tank fitted with a special anchor impeller, the upper and lower blades move the fluid away from the tank wall and upwards with normal rotation, and onto the wall and downwards with reverse rotation; and changes in the rotational direction and the phase difference between the upper and lower blades are known to influence the cooling speed and degree of damage to the product. In this study, cooling was simulated using computational fluid dynamics for this phenomenon, and the computational results agreed well with previously reported experimental values, confirming the validity of this method of analysis. The results further showed that, during reverse rotation, the flow onto the tank wall from the upper blades increases heat flux, and that the down-flow from the lower end of the upper blades and the up-flow from the end of the lower blades improve uniformity inside the tank. It was also found that introducing a phase difference between the upper and lower blades tended to decrease the power consumption and shear stress.
The dynamic behavior of a bubbling fluidized bed that requires only vibration and not the use of an external air supply system as a driving source was analyzed in detail. Alumina particles of 8 µm in diameter were placed into a cylindrical glass tube with a bottom plate, and a small horizontal vibration of 300 Hz was applied using a piezoelectric vibrator. The bubbles generated in the powder bed and the particle behavior were then observed using a high-speed camera. In addition, the pressure distributions in the powder bed and pressure–time variations were measured. The time series of images showed that bubbles were continuously generated at the bottom sidewall of the glass tube and rose vertically in series in the powder bed; and the powder layers between bubbles often collapsed, with repeated coalescence of bubbles. The bubble movement generated not only upward flow but also downward flow, resulting in formation of circulation flows in the powder bed. Pressure measurements showed that the bubbles flowing upward had a positive pressure, and those flowing downward had a negative pressure; and the pressure in the bubbles oscillated with the same frequency as the external vibration. Further, through experiments where the bottom plate was separated from the bottom edge of the glass tube with a small gap and both the plate and tube were vibrated, it was shown that bubbles were generated by the effect of compression in the powder bed. Air would then enter through the small gap owing to the negative pressure arising from the convection flow, forming a vigorous bubbling fluidized bed.
Titania nanoparticles were dispersed with a dual axis beads mill that enables nanoparticles to be dispersed with much lower energy than usual, and their dispersion characteristics were examined. In a recent study, titania nanoparticles were found to disperse to a primary nanoparticle size by evaluating the size and crystallinity of dispersed particles. In this study, the dispersed titania nanoparticles were further characterized by examining TEM, small angle X-ray scattering, ξ-potential, specific surface area and optical properties. TEM revealed that the dispersion of titania nanoparticles at low energy gave the primary particle size without crushing the crystals, while dispersion at higher energy gave rise to coagulation of crushed titania nanoparticles of around 10 nm in size. The large agglomerated nanoparticles were re-dispersed to around 10 nm by adding dispersant under the appropriate conditions to give a transparent titania slurry.
In hemodiafiltration, ultrafiltration by use of a hemodiafiltration membrane in addition to dialysis is essential in order to remove medium and high molecular weight solutes. Depending on the ultrafiltration rate and the membrane parameters of solute permeability and sieving coefficient, which in turn depend on both solute and membrane properties, it was assumed that concentration polarization might arise in a hemodiafiltration system in the same way as in reverse osmosis and nanofiltration. In this study, by applying reported analysis equations to the author's former simulation model, it was confirmed that concentration polarization does occur at the blood-side boundary layer of the hemodiafiltration membrane under specific conditions of high molecular weight solute, with a conventional hemodialysis membrane operated at above a certain ultrafiltration flow rate. This result demonstrated that the simulation model based on the analysis equations used can be applied widely to separation, ranging from hemodialysis to hemodiafiltration.
In Japan, steel works discharge carbon dioxide about 15% of total discharging amount. For reducing CO2 emission, development of separation and recovery technology of carbon dioxide from blast furnace gas by utilizing PSA technology is in progress. At first, 14 kinds of adsorbents from the market are evaluated by adsorption isotherms. It was found that zeolite called “Zeolum F-9” was suitable for carbon dioxide separation with its higher carbon dioxide adsorption capacity and selectivity. Then, Zeolum F-9 was evaluated with laboratory PSA testing apparatus. PSA was operated with 3 steps, that is, “adsorption,” “purge” and ”desorption” step to separate carbon dioxide from mixed gas, which composition was similar to blast furnace gas. The influence of the three PSA operation factors on CO2 purity and yield were evaluated. 1) The ratio of Feed gas flow and adsorbent weight ratio effects on CO2 recovery. The CO2 recovery was proportional to the raito until to some extent. Over that, the CO2 recovery became constant. 2) The concentration of CO2 in the feed gas was evaluated. The time of purging decreased (purge gas decreased), so that CO2 concentration in the feed gas was increased. 3) The effect of moisture in the feed gas was evaluated. At first, CO2 yield decreased, but after that, CO2 yield became constant. It was explained that supplied water adsorbed and desorbed on the adsorbent such like other gas species and no effect on the CO2 separation. COURSE 50 project including this study is conducted under the financial support of NEDO (New Energy and Industrial Technology Development Organization in Japan).
Intercalation behavior of anionic surfactants such as dodecyl sulfate ion (DS-), dodecylbenzene sulfonate ion (DBS-) and octyl sulfonate ion (OS-) was researched using Mg/Al type layered double hydroxide (LDH) with anion exchange ability. The effect of ion size and amount of surfactant adsorbed on the interlayer distance of LDH was investigated. In order to apply the LDH modified with the surfactants to the adsorption of organic compounds in aqueous solution, adsorption tests were carried out for six kinds of organic compounds. Adsorption isotherms of DS-, DBS- and OS- with the LDH were of the Langmuir type. Saturated adsorption amounts calculated by the Langmuir analysis were in the order, DBS-> DS-> OS-. In the case of DBS-, the saturated adsorption amount was almost equal to the theoretical exchange capacity of LDH (341 meq/100 g), whereas the adsorption equilibrium constant was in the order, DS-> DBS-> OS-. The surfactants in the LDH interlayer were horizontally orientated in the direction of the LDH basal seat in the region of lower adsorption, becoming vertically orientated with an increase in amount of surfactant adsorbed. The amount of surfactant adsorbed in the transition region was found to vary with the kind of surfactant. The order of toluene removal with the surfactant-modified LDH was as follows; DBS-> DS-> OS-. In the case of DS--modified LDH, the adsorption isotherms for various organic compounds were classified as Henry type, and their slopes corresponded to the octanol-water distribution coefficient, which indicates the degree of hydrophobicity of organic compounds.
A system was devised to recycle fluorine from exhaust gas in the semiconductor industry. The system is composed of a perfluoro-compound (PFC) decomposition section using electric heating and a fluorine fixation section. The decomposition properties required to design industrial scale equipment were examined in laboratory-scale tests for NF3 and SiH4 as exhaust gas components. Apparent reaction rates were calculated from the observed decomposition ratios and used to estimate the necessary volume of a full-scale decomposition furnace. In bench-scale equipment based on the obtained volume, decomposition of more than 99.997% was confirmed for NF3 at 650°C and SiH4 at 600°C.
Liquefied natural gas (LNG) is mixed with liquefied petroleum gas (LPG) at LNG terminals to adjust its calorific value in line with the stringent gas quality criteria. One method used for adding LPG to LNG is liquid/liquid calorific value adjustment, in which both LPG and LNG are maintained in the liquid phase. In this method, impurities present in LPG, such as water and methanol, may precipitate in an LNG/LPG mixture. In the present study, liquid-phase adsorption using a Na-X type zeolite was investigated for removal of methanol from low-temperature LPG. Pilot scale experiments were conducted to evaluate the effects of variation of process conditions. As the result, it was showed that variations of LPG flow rate and methanol concentration had little effect on adsorption capacity and the width of the adsorption band, known as the mass transfer zone. The results obtained demonstrated adequate performance for the purpose of a designing a practical system.
Lithium ion batteries (LIBs) are used for products that require high capacity and voltage, such as hybrid vehicles and electric vehicles. With increasing worldwide demand and the localized distribution of sources for the Li and Co that are critical for manufacture of LIBs, it is important to separate and recover these materials from used batteries.In this study, the recovery process of Li and Co was investigated by using the undersize products after a series of roasting, crushing and classification of LIBs. Li was selectively leached from the undersize products with water and recovered as Li2CO3 by applying solvent extraction and crystallization-stripping operations. Co was selectively leached with dilute nitric acid from the leaching residue of the previous step and was recovered asoxalates. The proposed process is very simple, consisting of selective leaching and crystallization-stripping for Li and oxalate precipita tion for Co.
Fluorescent powder contains rare earth elements in the form of phosphates of La3+, Ce3+ and Tb3+ and oxides of Y3+ and Eu3+. The phosphates are sparsely soluble, and are generally dissolved by treatment with concentrated sulfuric acid or sodium hydroxide at high temperature. In this study, a more environmentally friendly process was developed for leaching and effective separation of rare earth elements from waste fluorescent powder. Leaching of fluorescent powder with sulfuric acid at 50°C dissolved more than 90% of Y3+ and Eu3+. Mechanochemical treatment with NaOH of the leaching residue of the previous step removed more than 90% of the phosphates of La3+, Ce3+ and Tb3+. Each rare earth element was then extracted from the leaching solutions by solvent extraction and precipitation. Y3+ and Tb3+ were extracted in the organic phase comprising PC-88A and recovered as Y2(C2O4)3 and Tb2(C2O4)3 by crystallization–stripping using oxalic acid. Oxalic acid precipitation was used to recover Eu3+ in the raffinate, while hydroxide and oxalic acid precipitation respectively were applied for Ce3+ and La3+. Ce3+ was oxidized to Ce4+ by adding H2O2, and Ce4+ was precipitated as Ce(OH)4. La3+ was recovered as La2(C2O4)3.