طراحي، اجراء و بررسي عملكرد مولد ميست كروم شش ظرفيتي

Design, construction and performance of chromium mist generator

Background and aim: The chromium mist generator is an essential tool for research and for making evidence-based recommendations in evaluating air pollution and its control systems. The purpose of this study was to design and construct a homogeneous chromium mist generator and to look at the effects of factors such as sampling height and distance between samplers in side-by-side sampling on the chromium mist sampling method. Material and Methods: First we developed a mist generator, using a chromium electroplating bath in pilot scale. Concentrations of Cr03 and sulfuric acid in plating solution were 125 g Lʹ1 and 1.25 g L*1, respectively. To set up permanent air sampling locations, a Plexiglas cylindrical chamber (75 cm height, 55 cm i.d) was installed as the bath overhead. Sixty holes were made on the chamber in 3 rows (20 in each row). The distance between rows and holes was 15 and 7.5 cm, respectively. Homogeneity and the related factors were studied using a side-by-side air sampling method. Forty- eight clusters of samples were collected on polyvinyl chloride (PVC) filters contained in sampling closed-face cassettes. Cassettes were located 35, 50, and 65 cm above the solution surface with < 7.5 and/or 7.5-15 cm distance between heads. All samples were analyzed by the NIOSH method 7600. Results: ANOVA tests showed no significant differences between locations in side-by-side sampling (P=0.82) or between different sampling heights or sampler distances (P=0.86 and 0.86, respectively). However, there were notable differences between means of coefficients of variation (CV) in various heights and distances. Conclusion: We conclude that the most chromium mist homogeneity could be obtained at a height of 50 cm from the bath solution surface and with a distance of <7 5 cm between samplers.