Browsing by Author "Chein, HM"

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Axial flow cyclone for segregation and collection of ultrafine particles: Theoretical and experimental study
(2005-03-01)
Hsu, YD
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Chein, HM
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Chen, TM
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Tsai, CJ
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環境工程研究所
In this study, an axial flow cyclone was designed, fabricated, and evaluated at different conditions of air flow rates (Q(0)) and low-pressure environments (P), especially for the segregation and collection of ultrafine particles. An evaporation/condensation type of aerosol generation system consisting of tube furnace and mixing chamber was employed to produce test aerosols. The test aerosol was then classified by a differential mobility analyzer (DMA) and number concentration was measured by a condensation nuclei counter (CNC) and an electrometer upstream and downstream of the cyclone, respectively. The s-shaped curve of the collection efficiency in submicron particle size range was obtained to be similar to the traditional cyclone found in the literatures when the particles were largerthan 40 nm at Q(0) = 1.07, 0.455 L(STP)/min, and P= 4.8-500 Torr. The curve was found to be fitted very well by a serniempirical equation described in this paper. Forparticles smaller than 40 nm, however, the collection efficiency was unusually increased as the particle diameter was decreased due to the fact that the diffusion deposition becomes the dominant collection mechanism in the low pressure conditions. A model composed of centrifugal force and diffusion deposition is presented and used to fit the experimental data. The cyclone was demonstrated to separate and collect ultrafine particles effectively in the tested vacuum conditions.
Differences in PM10 concentrations measured by beta-gauge monitor and hi-vol sampler
(2001-11-01)
Chang, CT
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Tsai, CJ
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Lee, CT
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Chang, SY
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Cheng, MT
In this paper. differences between the 24-h average PM10 concentrations of Wedding beta -gauge monitor and Andersen or Wedding hi-vol sampler were studied. When the deliquescent point is not exceeded, PM10 concentrations of the beta -gauge are close to those of the manual samplers. The ratio of beta -gauge PM10 to Andersen PM10 and Wedding PM10 is 1.08 +/-0.06 and 1.09 +/-0.12, respectively. However, when the deliquescent point is exceeded, water absorption by the inorganics of aerosols leads to higher PM10 concentrations of the beta -gauge compared to those of the manual sampler. The ratio of beta -gauge PM10 to Andersen PM10 and Wedding PM10 is 1.21 +/-0.22 and 1.27 +/-0.15, respectively. However., due to evaporation of water from the aerosols collected on the filter tape of the beta -gauge, differences in PM10 concentrations are much less than theoretically calculated. (C) 2001 Elsevier Science Ltd. All rights reserved.
Emission characteristics and control efficiency of acidic and basic gases and aerosols from packed towers
(2004-02-01)
Tsai, CJ
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Chang, CT
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Liu, TW
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Huang, CC
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Chien, CL
Large amount of acidic liquids, such as H2SO4, HF, HCl and HNO3, and basic NH3 liquid are used in high-tech industries in cleaning and etching processes in the Hsinchu Science-Based Industrial Park in Taiwan. The industries use packed towers (or scrubbers) to control emission of these inorganic pollutants, in which acidic gases but not particles are regulated by the Taiwan EPA's strict emission standard for semiconductor industry. To understand whether the emission standard is met and to investigate the emission rates, emission profiles, emission factors, and control efficiencies of various gaseous/aerosol species, measurement of pollutants before and after the packed towers was conducted using a sensitive porous metal sampler during January 2001 to February 2003. Results show that the pollutants are mainly in the gaseous phase, and the control efficiency of pollutants is low and variable when the inlet concentration is low. In addition to the control efficiency data, emission factors before the control device for various gas and particle species have also been developed for estimating the emission rates. (C) 2003 Elsevier Ltd. All rights reserved.
Inorganic acid emission factors of semiconductor manufacturing processes
(2004-02-01)
Chein, HM
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Chen, TM
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Aggarwal, SG
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Tsai, CJ
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Huang, CC
A huge amount of inorganic acids can be produced and emitted with waste gases from integrated circuit manufacturing processes such as cleaning and etching. Emission of inorganic acids from selected semiconductor factories was measured in this study. The sampling of the inorganic acids was based on the porous metal denuders, and samples were then analyzed by ion chromatography. The amount of chemical usage was adopted from the data that were reported to the Environmental Protection Bureau in Hsin-chu County according to the Taiwan Environmental Protection Agency regulation. The emission factor is defined as the emission rate (kg/month) divided by the amount of chemical usage (L/month). Emission factors of three inorganic acids (i.e., hydrofluoric acid [HF], hydrochloric acid [HCl], and sulfuric acid [H2SO4]) were estimated by the same method. The emission factors of HF and HCl were determined to be 0.0075 kg/L (coefficient of variation [CV] = 60.7%, n = 80) and 0.0096 kg/L (CV = 68.2%, n = 91), respectively. Linear regression equations are proposed to fit the data with correlation coefficient square (R-2) = 0.82 and 0.9, respectively. The emission factor of H2SO4, which is in the droplet form, was determined to be 0.0016 kg/L (CV = 99.2%, n = 107), and its R-2 was 0.84. The emission profiles of gaseous inorganic acids show that HF is the dominant chemical in most of the fabricators.
Particle transmission efficiency through the nozzle of the API Aerosizer (TM)
(1999-09-01)
Tsai, CJ
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Yang, WS
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Szymanski, WW
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Chein, HM
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環境工程研究所
This study has investigated the particle transmission efficiency through the nozzle of the API Aerosizer(TM) numerically. Two-dimensional flow field in the nozzle was first simulated. Particle trajectories for both liquid and solid particles were then calculated to obtain the particle transmission efficiency under various conditions. This study shows that particle aerodynamic diameter, particle materials, particle density and laser beam diameter influence the transmission efficiency. The transmission efficiency is found to increase with increasing particle diameter when the particle aerodynamic diameter is less than several micrometers. The efficiency for liquid particles drops significantly when particle aerodynamic diameter increases from several micrometers because of particle impaction loss in the nozzle. For solid particles, the relationship of the efficiency with particle diameter is found to be more complicated. For particles less than several micrometers in aerodynamic diameter, solid particles behave similarly to the liquid particles. However, as particles are greater than several micrometers, the effect of solid particle bounce is to increase the transmission efficiency with increasing aerodynamic diameter until particles become large enough so that plastic deformation occurs in the particles. Then the transmission efficiency will decrease with increasing particle aerodynamic diameter. (C) 1999 Elsevier Science Ltd. All rights reserved.
Performance evaluation of an API Aerosizer (TM)
(1998-08-01)
Tsai, CJ
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Chein, HM
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Chang, ST
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Kuo, JY
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環境工程研究所
A numerical method was developed to simulate the compressible flow field and particle trajectory in an API Aerosizer(TM). Experimental particle time-of-flights (tau(TOF)) data using mono-disperse solid and liquid particles were also obtained. Theoretical particle tau(TOF) results were compared with the present experimental data and those of Cheng er al. (1993, J. Aerosol Sci. 26, 501-514). Good agreement was found for solid particles. The original tau(TOF) calibration for the API Aerosizer(TM) was found to underestimate measured tau(TOF) mainly because of the assumption of one-dimensional flow in the nozzle, and incorrect use of the particle drag coefficient in the supersonic flow field. Effects of decreasing ambient pressure and increasing particle density on increasing tau(TOF) were found to be important. (C) 1998 Elsevier Science Ltd. All rights reserved.
The effect of environmental conditions and electrical charge on the weighing accuracy of different filter materials
(2002-07-03)
Tsai, CJ
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Chang, CT
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Shih, BH
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Aggarwal, SG
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Li, SN
Different filter materials and electrical charge elimination methods were used to investigate the weighing accuracy of filter papers under different environmental conditions. The results show that the standard deviations (S.D.) of weight data for glass fiber and MCE filters were substantial without environmental control, whether or not the electrical charge eliminators were used. Values of 0.157 and 0.349 mg were determined for glass and NICE filters, respectively. The accuracy of weighing was substantially improved and the S.D. was reduced to 0.01 and 0.09 mg for glass fiber and MCE filters, respectively, after applying the environmental control conditions. For PVC and Teflon filters, the accuracy of weighing was good, even in the uncontrolled environmental conditions, whether or not the electrical charge eliminators were used. The S.D. values of weighing data of PVC and Teflon filters were 0.007 and 0.011 mg, respectively. (C) 2002 Elsevier Science B.V. All rights reserved.
Theoretical and experimental study of an axial flow cyclone for fine particle removal in vacuum conditions
(2004-09-01)
Tsai, CJ
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Chen, DR
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Chein, HM
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Chen, SC
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Roth, JL
An axial flow cyclone to remove fine particles at low pressure conditions (6-23 torr) was designed and tested. The inner diameter of the cyclone is 3.0 cm and tested flow rates are 0.455 and 1.0 slpm. A theoretical evaluation was first carried out to calculate the particle collection efficiency and cutoff diameter for the axial flow cyclone. Experiments were then conducted to test the theory at different flow rates, pressures and cyclone designs. It was demonstrated that at sufficiently low pressure of 6 torr (flow rate = 0.455 slpm), the axial flow cyclone is able to remove particles below 100 nm efficiently, and the flow Reynolds number was found to have a great effect on the particle collection efficiency. (C) 2004 Elsevier Ltd. All rights reserved.