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煤矿中经常碰到的浮游粉尘是由不同大小的粒子、比重、形状和集合状态组成的复杂的混合体。这些粒子在气流中的速度是不相同的,而且由于它们的化学组成不同、对人体的危害也不相同。在煤矿中粉尘的浓度,在不同的地方是不相同的,在同一个地方也随时间而变化。采掘工作的断续和位置的变化,在采掘过程中产生的大小不同的粉尘粒子散播到气流中,较大的粒子,较快的落下,沉降在尘源附近,小的粒子缓慢地落下,大部分被风流带到较远的位置。由于气流的扰动,使某些粒子保持到它们期望保持时间还要长的气载性质,因而,粉尘浓度随时间的减少不是直线关系,而属于对数曲线关系。保持在空气中并且难于用粉尘控制方法排出的粉尘粒子是呼吸性粉尘粒子,它们有渗入肺部的能力。
Frequently encountered in coal mine fly ash is a complex mixture of particles of different sizes, specific gravity, shape and aggregate state. The velocity of these particles in the gas stream is not the same, and because of their different chemical composition, the harm to the human body is also different. The concentration of dust in coal mines varies from place to place and in the same place over time. Discontinuity of excavation and change of position, dust particles of different sizes generated in the excavation process are dispersed into the air flow. Larger particles fall faster and settle near the dust source. Small particles slowly fall down. Large Some are brought to the faraway location. Due to the disturbances of the air flow, some particles are kept in the air-borne nature that they expect to remain for longer periods of time. Therefore, the decrease of dust concentration with time is not a straight line but a logarithmic curve. Dust particles that remain in the air and are difficult to discharge with dust control are respiratory dust particles that have the ability to penetrate the lungs.