An electrospraying (E/S) and a corona discharging experiment are carried out to investigate the charging characteristics of sub-micron particles. The measurement of particle charging and collection efficiency was conducted with electrometer, condensation nuclei counter (CNC) and scanning mobility particle sizer (SMPS) . E/S is a process that relies on electrostatic force to break the liquid into fine charged droplets. During this process many highly charged small droplets or ions are attached to the foreign particles and eventually charge the particles. This processing is unique and distinct from corona discharging. The difference in charging rate between corona discharge and E/S results in the difference in collection efficiency for sub-micron particles. The control of particles by charging and collection with E/S and corona discharge has been investigated experimentally. The result shows that the collection efficiency of E/S-ESP system is higher than 99.9 % for particles with a geometric mean diameter (GMD) of 50 ∼ 100 nm at the mean face velocity of 0.5 m/s and 1.0 m/s.
An air washer system with functions of both chemical contaminant removal and heat recovery is developed in this study. The system consists of a heat recovery equipment to recollect heat from scrubber and an air washer to remove undesirable gases such as NH3, SOx, et al. in makeup air unit. The fundamental research and experimental results are reported in this paper, and the principal results are as follows: 1) An optimum L/G (ratio of water to air weight) is obtained, considering the energy saving and gas removal efficiency. 2) The removal efficiency is 90 percent or more for NH3, and 85 percent or more for SOx. 3) The efficiency of heat recovery is about 50 and 30 percent in summer and winter respectively.
We developed a new AMC (Airborne Molecular Contaminant) removal system of wetted-wall with the counterflow. The wetted-wall unit is composed of hydrophilic membrane matrix to which DI water is supplied. The DI water necessary for this system is small in amount (the water/gas ratio, Ls/G, is less than 0.01) . In the present work, we first conducted lab-scale experiment and then field experiments in order to evaluate the performance of the system. As a result, 1) the lab-scale experiment showed that the newly developed removal system has high removal efficiency, 2) the field experiment showed that the AMC removal system can maintain the high removal efficiency for one year, and AMC is removed mainly by trapping into the condensed water on cooling coil fins especially in summer, 3) even when the water/gas ratio is as small as Ls/G = 0.005, the wetted-wall with the counterflow system can maintain high removal efficiency.
Particle contamination control during plasma processing for manufacturing semiconductors has increasingly become important because of increased integration of LSI. The behavior of particles in a plasma-processing chamber was investigated using a laser light scattering (LLS) technique and the particle growth mechanisms in plasma were clarified. Since LLS technique can measure only high concentration of particles, it is difficult to follow the behavior of particles that flow from the plasma region. Consequently, the measurement of particles in the plasma-processing chamber was conducted by a particle counter using a sampling probe inserted in the chamber. Through the comparison of the measurement results by the LLS and those with the sampling method, the feasibility of the sampling method for the measurement of particles in the plasma process was clarified.
In order to study aerosol behavior in a cover gas region of LMFRs (Liquid Metal Fast Reactors) , a numerical method was developed by considering the aerosol radius as one of the space coordinates. In our previous model, heterogeneous nucleation was assumed for the aerosol generation. However, homogeneous nucleation might be included since sodium cluster are considered to be produced in the cover gas region, which subsequently form aerosol particles. Therefore we developed a new calculation model by taking into account the homogeneous nucleation. The same governing equations for mixed gas and the calculation schemes as the previous study were employed in the model. As a result, although the new model gave the same distributions of temperature and mass fraction of the sodium vapor as those by the previous model and the experimental data, the previous model without homogeneous nucleation was found to give better prediction for the aerosol mass concentration in the cover gas region. From these results, it can be said that there would be almost no possibility of aerosol production via the sodium cluster and therefore heterogeneous nucleation model is sufficient for the prediction of aerosol behavior.