| Summary: | 碩士 === 國立高雄第一科技大學 === 環境與安全衛生工程系碩士班 === 106 === The flammable powder can float in the air and form a dust cloud. When the concentration reaches the explosion limit, there can be a risk of ignition and dust explosionwith the presence of the minimum ignition energy.On the other hand, in the processes of transportation, screening, grinding, mixing, etc., the powder is liable to generate static electricity for friction or other reasons. If the electrostatic charge accumulates to a specific potential, it can induce a discharge phenomenon and form an ignitionsource, thereby igniting the flammable dust cloud and causing a fire or explosion accident.
Therefore, in order to control the risk of dust explosion, we must grasp the potential factors that may affect the characteristics of electrification during the dust cloud formation to reduce the probability of such accidents.
In this study, the powder is dispersed into a dust cloud in two ways: "Ejection" and "Stir-up", where the flow volume, flow rate, pipe material and measurement position through Powder Ejection, and the volume of powder stirred up, the air flow, and the distance of the powder from the air supply port during Powder Stir-up are used to investigate the characteristics of electrification in the powder under the two ways.
Either "Powder Ejection" or "Powder Stir-up" can charge the powder and form a charged dust cloud. When the amount of powder ejected or stirred up increases to form a dust cloud, the electric potential of the powder will increase as well. Therefore, when we use the powder, we should prevent the powder from forming a dust cloud and being scattered in the space.
The larger the flow rate, the larger the upward trend of the electric potential of the powder. Therefore, the overly high flow rate at the time of powder ejection should be avoided. When the flow rate remains constant, the flow rate can be reduced by increasing the pipe diameter. At the same time, it is also possible to reduce the chance of collision between the powder and the tube wall, so that the electric potential of the powder can be lowered. In addition, the process piping can be made of a material with a lower resistivity, thereby reducing the electric quantityon the pipe.
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