用示踪气体法评价和优选吸气罩

目的 在粉尘发生源处设置适用的局部吸气罩,可以有效地控制粉尘向周围扩散,是预防尘肺病发生的有效措施。为了提供适宜吸气罩的设计,使用了示踪气体法评价吸气罩的效率,对吸气罩的设计进行优选,以提高捕集效率和降低能耗。方法 建立示踪气体评价吸气罩效率的实验风道和方法,采用人工煤气作为示踪气体。结果 实验了长方形和无延伸挡板及有特殊延伸挡板的条缝形吸气罩在不同罩口风速下对示踪气体的捕集效率。导出了捕集效率和距离的关系方程式。实验结果表明:(1)吸气罩与污染源的距离和罩口风速对捕集效率有明显的影响。当罩口风速一定时。吸气罩越靠近污染源,捕集效率越高;而在同一距离上,罩口风速越大,捕集效率就越高。(2)有延伸挡板的条缝形吸气罩的捕集效率高于无延伸挡板条缝形吸气罩,前者采用较低的罩口风速(抽风量)可以得到相应的高捕集效率。结论 使用示踪气体对吸气罩进行优选的结果表明,通过改进吸气罩的形式可以降低所需风量并达到要求的效率,从而为减少通风设施的费用提供了一种重要途径。

Evaluating and selecting superior exhaust hood by using tracer gas methods

Objective Installing appropriate local exhaust hood at or near the dust source could effectively control the spread of dust into the environment, it is an important measure for preventing workers from catching silicosis. In order to provide the appropriate exhaust hood design, tracer gas method was used to evaluate the effectiveness of exhaust hoods.On this basis we can find the superior design of exhaust hood with higher efficiency and lower energy consumption.Methods A experimental tunnel was installed for evaluating the collecting efficiency of exhaust hood for a tracer gas, coke gas was used as tracer gas. Results Under different hood face velocities, the collecting efficiencies for tracer gas of different exhaust hoods (including rectangular, special designed slot type and flanged slot type) were tested. Relations between efficiencies and distances were put forward. Experimental results showed: (1) The collecting efficiencies for tracer gas of exhaust hoods had close relations with the distances between the source and hood face, and also the hood face air velocity. With a certain hood face air velocity, the collecting efficiency was higher as the distance became shorter; At a certain distance, the collecting efficiency was higher as the hood face air velocity became greater. (2) The collecting efficiency of the improved slot hood (with flanges on its two sides) was higher than the slot hood without flanges. Conclusion Test results of evaluating the collecting efficiency of exhaust hood and selecting the superior by tracer gas show that improving the design of exhaust hood could lower the exhaust volume with the required efficiency, which provided an important way of lowering the expense of the exhaust ventilation facilities.