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JACA (Japan Air Cleaning Association)

The Abstracts of the paper carried by the Journal of JACA

vol.56-6(2019/3/31)

Synthesis of porous polymer fiber via electrospinning method

A combination of thermally induced phase separation and the breath figure mechanism has been employed to synthesize porous cellulose triacetate (CTA) fibers using an electrospinning method.  The ambient humidity, the concentration of the polyvinylpyrrolidone (PVP) co-polymer and the ethanol co-solvent have been all adjusted to modify the Taylor cone formation, jet stability and fiber porosity.  After CTA-PVP composite fiber formation, the PVP has been removed to obtain porous structures in the CTA fiber.  Porous and non-porous fibers having similar sizes have been compared to elucidate the effect of pores on aerosol filtration performance.  Trials with a variety of dust particle sizes demonstrated that the particle collection efficiency of the porous fibers within the most penetrating particle size region has been also significantly improved (to 95%), providing evidence that the presence of dynamic pores can greatly improve particle capture.

Control of air quality and thermal environment using buoyancy in high-rise building

In this paper, researches on the application of natural convection which controls air quality and thermal environment have been reviewed.  For the examples of air quality control, applications on the natural ventilation in the single room and multi zones are shown.  For the examples of thermal control, night purge of slabs and cooling of external elements using the natural convection driven by the stack effect in the double skin façade structure which are currently studied by the authors are also shown.  These ideas have been inspired by the concept of Solar Up-draft tower which is recently studied to apply to power generation and air pollution control.

A study on separation technique of water from solvent (NMP) by vacuum evaporation with air flow

Solvents produced by pharmaceutical companies have a severe restriction on purity.  However, if solvents such as NMP (N-Methyl-2-Pyrrolidone) are open in the air, the purity of them will decrease by dissolving water vapor in the air.  Therefore, a technique to remove water from solvent is necessary.  In this study, we have investigated recycling of NMP that is used in manufacturing the cathode of lithium ion battery by using “vacuum evaporation with air flow”.  The temperature exhaust gas of NMP at 98.3℃ decreased to 9.4℃ by removal equipment with cooling fins to condense NMP gas, so that 2055ppm of NMP gas concentration in the exhaust gas decreased to 133ppm.  We have investigated to remove the water from NMP by using “vacuum evaporation with air flow”.  The evaporation temperature has been calculated from the water vapor pressure at each temperature.  It has been theoretically confirmed that most of water in NMP has been removed by the optimum experimental parameters.  As a result, it has been possible to remove more than 90% of water in NMP.

Highly effective decomposition of organic contaminants in water using ultrasonic transition to gas phase and UV irradiation

430 kHz of ultrasonication which can cause simultaneously pyrolysis by chemical effect and atomization by physical effect was selected and applied to highly effective decomposition of organic pollutants in water.  In order to investigate the influence of physical properties on the degradation rate, three different aldehydes, formaldehyde, acetaldehyde and benzaldehyde, were chosen as model substances.  As a result, removal ratio of formaldehyde, acetaldehyde and benzaldehyde reached 21.1%, 53.0% and 100% after 120 min by only US irradiation, respectively.  On the other hand, in the case of combining the UV irradiation and the ultrasonic atomization, formaldehyde and acetaldehyde with hydrophilic property were effectively decomposed on the mist surface in gas phase.  By this combined use of US and UV irradiation, it was confirmed that US irradiation acts on effective degradation of hydrophobic substances and UV irradiation promoted the decomposition and the mineralization of hydrophilic substances including degradation products formed from hydrophobic substances.  These results mean that the effective decomposition of organic pollutants can be performed regardless of those properties in interaction with water.

Study on the possibility of a unified criterion for a leakage test of an installed filter system

Currently, ISO14644 Part 3 : 2005 and JIS B 9917-3 : 2009 have been used as standard leakage test method of high-performance air filter installed in a clean room.  For in-situ leak test, two methods with different criteria for leakage detection using Aerosol photometer and discrete particle counter (DPC) are presented.  The possibility of a unified criterion for a leakage test of an installed filter system between a photometer method and DPC method is studied by comparing the difference between evaluation by mass concentration (photometer) and number concentration (DPC) measurement.  It was found that for the filter having H14 or higher performance in European standard EN 1822-1 (2009), the same leakage evaluation standard 0.01% as the photometer method can be applied in the DPC method.  On the other hand, it was not possible to apply the uniform criterion for filters with H13 or lower performance, and it was necessary to establish certain criteria for each filter grade.

Measurement and evaluation of the airtightness on clean room

The architectonic airtightness at the clean room and biosafety facilities is very important function from contamination control and the energy saving.
This report explains about architectonic airtightness, method for measurement, investigation method of leaking spots, measuring evaluation cases at cleanrooms and the original evaluation standard.