| 英文摘要 |
Determination of particulate matter emissions from stationary sources is the most complicate and challenging task among all environmental sampling and analytical procedures. It is speculated that the dust concentration measurement is affected by the interactions among exhaust velocity, temperature, humidity, aerosol concentration, aerosol size distribution, type of sampling equipment and level of experience of the sampling team. The results of this work can be used to identify the factor(s) contributing to the variability of measurements. The primary goal is to enhance the proficiency of stack particulate measurement.
Built in 1997, this testing system simulating a stack is composed of an inlet filtration unit, a 15-Hp blower, a 13.4-m height, 60-cm diameter stainless steel duct, and an outlet filtration unit. The blower is capable of propelling the face velocity up to 15 m/sec. A Palas Powder Disperser is used to generate aerosol particles. A heater of 750 kW with a PID feedback system is used to control the temperature of the exhaust gas. A 120 kW steam generator is used to change the humidity of the exhaust gas, i.e., water content ranging from 2 % to 10 %. The major operation parameters include dust concentration, temperature, relative humidity, and fan rotation speed.
According to the analysis of variance, the duct velocity is the most influential operation factor, followed by dust feed rate, and the interaction of duct velocity and water content in determining the aerosol concentration in the stack. However, neither temperature nor water content of the exhaust gas shows significant effect. A statistical model for predicting mass concentration of particles in the stack is established. This proficiency testing program has now been executed for 10 years. The cost-effectiveness is clear. The participated stack sampling teams showed clearly better performance.
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