| Summary: | 碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 100 === In this thesis, by using the improved high-temperature oxidation process, the cadmium and lead can be reduced in the raw material during the production process of zinc oxide powder. Also, we reduce the agglomeration effect and the mixed air impurities, resulting in the particle size reduction and the purity increase on the high-quality zinc oxide powder.
In our experiments, we use different boiling points and atomic weight to reduce the lead and cadmium inside the waste zinc dross. Since the waste zinc dross is an alloy material, the interior contains iron, aluminum, lead, cadmium, and etc. and the melting point temperature is not a constant value. Thus, we need to apply both the thermocouple and infrared thermometer to monitor the actual temperature of the waste zinc dross, and control of purification process temperature between 450℃±10℃ so as to make the purity is above 99.7%, the raw material cadmium is below 20ppm (0.002 wt%), and the lead is less than 100ppm (0.01 wt%).
Since the high-temperature oxidation process is a kind of atmospheric processes, it is easy to cause process contamination with atmospheric impurity, resulting in decreased powder purity. Thus, we build a closed and isolated space in the half area of the oxidation furnace so as to reduce the impurities mixed into the zinc vapor and air, and enhance the oxidation of zinc powder purity.
On the other hand, since the zinc oxide powder has the agglomeration effect in the formative stage, we use the thermal convection at the joint of the exports and vacuum pumping tube in the oxidation furnace, and apply different types of openings to achieve an optimal design, so that the oxidation furnace outlet temperature can be quickly decreased and the agglomeration effect can also be reduced. In order to reduce production and maintenance cost of the cooling system, we use the thermal convection to perform effective cooling of the vacuum pipe. This way made a uniform particle size of newly formed zinc oxide powder, which can be reduced to 250nm with a specific surface area above 4cm2/g.
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