In applying a backmixing model of liquid mixing characteristics in vertical vessels with three multiple impellers, the effects of the opening ratio of a perforated partition plate and the stirring speed on the backflow rate and the exchange rate of liquid were experimentally investigated. The vessel diameter DT was 0.10 m and the impeller diameter Di was one-half of the vessel diameter DT. In the vertical stirred vessels with three multiple impellers, the relationship of the backflow rate f to the feed flow rate q and the exchange rate Q was established as f=Q−q/2. The exchange rate Q increased in proportion to the stirring speed of impellers n and the opening ratio of a perforated partition plate Ar. The value of the modified dimensionless exchange rate in the vertical vessels with three impellers Q/(nDi3Ar) was proportional to the agitated Reynolds number NRe to the power of 0.20 when the range of the agitated Reynolds number NRe was 1×103 to 6×103, and it was almost constant at 0.17 when the agitated Reynolds number NRe was greater than 6×103.
A new home base (HB) impeller with 3S performance (simple, speedy and stable) was developed based on the streak line visualization method (Kato et al., 2015a, 2015b). The new HB impeller was a typical glass-lined impeller of the dual type, separated into upper and lower parts. Compared with the normal HB impeller, the new type of HP impeller was found to have the same mixing performance.
Co-flow glass capillary microfluidic devices with injection and collection capillaries of different inner diameters were prepared. Nitrogen gas and ultrapure water were injected into the devices to prepare monodisperse microbubbles. By changing the inner diameters of the injection and collection capillaries, gas pressure, and liquid flow rate, monodisperse microbubbles with a coefficient of variation (CV) of less than 2% were generated in a diameter range of 4 to 70 µm at a generation rate of 1.7×105 to 1.5×102 bubbles/s.
Plant biomass is attracting attention as an abundant replacement for fossil resources. However, because the use of plant material as biomass at a time of continuing population growth may give rise to new food problems, the use of a non-food biomass such as coffee residue avoids such competition. Based on previous findings that coffee residue is a source of extractable fatty acids, the present study investigated conditions for extraction of useful components from coffee residue with supercritical carbon dioxide and producing fatty acids esters in high yield using an enzyme. For supercritical carbon dioxide extraction and enzymatic reaction, it was found that the optimum ethanol flow rate and extraction yield was improved by adding 10% of water (based on raw material) as an entrainer.
Mixtures of bio-dried sludge and coal in different ratios were subjected to co-pyrolysis in a 50 kg/h scale rotary kiln carbonizer, and the effects of mixing ratio on the pyrolysis behavior and char characteristics were evaluated by measuring the char yield, composition, and heating value, and by surface observation. Thermo-gravimetric analysis with a TG analyzer was also conducted in order to understand the co-pyrolysis behavior in the kiln. The chars obtained in the kiln had closely similar characteristics to the char obtained in a lab-scale experiment. As the proportion of coal in the mixtures undergoing co-pyrolysis in the rotary kiln increased, the resulting char had higher heating value and lower ash content. Feedstock mixing in the rotary kiln co-pyrolysis influenced the char characteristics, and volatile matter from coal could be deposited on the sludge char surface, as seen in a lab-scale experiment.
Supercritical carbon dioxide (ScCO2) is a promising solvent for regeneration because of its high diffusivity into the microstructure of activated carbon and its ability to operate at a moderate temperature. In this study, we investigated a ScCO2 cleaning method of the activated carbon used in the exhaust processor of a semiconductor manufacturing process. The ScCO2 cleaning was carried out at temperature of 80°C, pressure of 20 MPa and regeneration time of 6.0 h. The experimental results showed the activated carbon used in the exhaust processor for a long duration could not be regenerated. Thermogravimetric analysis (TGA) showed that ScCO2 could remove low boiling point adsorbates (100–400°C) but not high boiling point adsorbates (400–900°C). Analysis of the results of ScCO2 cleaning in terms of a high boiling point ratio, defined as the proportion of high boiling point adsorbates, showed that regeneration rates of 90% and 80% respectively were achieved at high boiling ratios of 2.0% and 4.0%, suggesting that the high boiling point ratio could serve as an indicator of potential regeneration rate.
The amount of carbon fiber-reinforced plastic (CFRP) used in automobiles and other products because of its lightness and strength is expected to increase year on year. Thus, low-cost, low-energy recycling technology will be required to recover carbon fiber from waste CFRP. Because fiber length is reported to decrease with each recycling, resulting in lowered performance, the present study investigated the effect of repeated recycling on the properties of carbon fiber recovered in a two-step thermal process of carbonization and calcination. It was found that fiber length decreased after the first recycling but scarcely changed after the second and third times, and that tensile strength decreased exponentially with repeated recycling.