| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 91 === The packed tower inside a thermal-type local scrubber can''t remove particles generated in the reaction chamber with high efficiency. It will cause the emission of fine particles. The study combines a local scrubber and a high efficiency venturi scrubber to design a combined gas-particle treatment system (System 1). It used process SiH4 gas to produce a large number of SiO2 particles, which were used to test the relationship between the removal efficiency, and pressure drop, waste gas flow rate, and scrubbing water flow rate in the System 1. Particle removal efficiency was measured by a SMPS (Scanning Mobility Particle Size) and MOUDI (Micro-Orifice Uniform Deposit Impactor) while gas abatement efficiency is also measured by means of FTIR （Fourier Transform Infrared spectroemeter）. The results are compared with those derived from Calvert’s (1972), Yung’s (1978) and Slinn’s (1983) theories. According to the results of System 1, a commercial unit (ECS2000PB, System) was designed and tested.
1 % and 100 % SiH4 were used to test System 1. When temperature inside the reaction chamber is 850℃, gas abatement efficiency was found to be higher than 99%. If temperature was decreased to 650℃，1 % SiH4 abatement efficiency was decreased to 91 % but 100 % SiH4 abatement efficiency remained over 99%. The results show that the local scrubber can remove silane gas efficiently. As to particle removal efficiency, 1 % SiH4 of 0.5, 1.0, 1.6 lpm flow rate and 1.0 lpm of 100 % SiH4 were used. Total flow rate passing through the venturi tube was 180 lpm and liquid to gas ratio were 1.17, 1.50, 1.80 l/m3, respectively. Experimental results show that the System 1 can have high particle removal efficiency and whether particles grow by heterogeneous nucleation is a key factor. Particle removal efficiency was found to be below 40 % without nucleation and was increased to over 90 % with nucleation. Higher SiH4 flow rate or concentration generated higher particle concentration, which indicates higher removal. Taking the liquid to gas ratio of 1.17 l/m3 for example, maximum particle removal efficiency with nucleation was found to be 84 %, 96 %, 98 % and 99 %, respectively for 1 % SiH4 flow rate of 0.5, 1.0, 1.6 lpm and 1.0 lpm of 100 % SiH4. If without nucleation, maximum removal efficiency is only 22 %, 23 %, 20 % and 20 %, respectively. It indicates nucleation influences particle removal efficiency of the scrubber greatly.
Compared with three theoretical values, Slinn’s value is higher than those derived from Calvert’s and Yung’s equations. Experimental data with nucleation matched the theoretical values except under high particle concentration. If the particle concentration is lower, Calvert’s and Yung’s values matched experimental data better while Slinn’s value underestimated experimental data. As to non-nucleation, efficiency is only compared with Calvert’s theoretical value. The difference between them is not great and there is only greater error in the region of smaller diameter. It is also due to neglect of diffusion of smaller particles in Calvert’s equation.
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