Abstract:

Objective To address the problems of uneven airflow velocity distribution along the length of edge exhaust hoods on long pickling tanks and the consequent limited capture efficiency of acid mist, this study aimed to optimize the structure of the local exhaust ventilation system and improve airflow uniformity in order to provide a technical reference for controlling acid mist hazards in pickling tanks.

Methods In July 2025, a hydrochloric acid pickling tank in a pickling workshop, with dimensions of 9.0 m in length, 0.6 m in width, and 1.0 m in height, was selected as the research subject. A segmented single-sided slot-type edge exhaust hood configuration was designed using theoretical calculations, and a numerical model was subsequently established based on computational fluid dynamics (CFD). The standard k-ε turbulence model and the SIMPLE algorithm were applied to simulate airflow distribution within the exhaust system under different rectangular tee configurations. The airflow uniformity for each scheme was evaluated using the ratio of the maximum velocity to the minimum velocity (V_max /V_min).

Results The long pickling tank was divided into six exhaust units along its length, with each unit designed for an exhaust flow rate of 1 620 m³/h, yielding a total exhaust flow rate of 9 720 m³/h. By optimizing the dimensions of the rectangular tees, the horizontal dimensions of the rectangular tees in Scheme 7 were 120, 140, 160, 200, 300, and 500 mm, respectively, which achieved exhaust velocities of 5.83, 5.88, 5.94, 5.94, 6.17, and 6.00 m/ s, corresponding to a maximum-to-minimum velocity ratio of 1.06. This represented the best airflow uniformity among all schemes and satisfied the control velocity requirement for acid mist capture. Furthermore, a generalized segmented exhaust hood configuration was proposed for pickling tanks with widths up to 600 mm and lengths up to 9.0 m.

Conclusions The combination of a segmented single-sided slot-type edge exhaust hood and optimized rectangular tee dimensions can effectively improve airflow uniformity in local exhaust ventilation systems for long pickling tanks, ensuring compliance with the control velocity requirements for acid mist capture. This approach provides a technical reference for the optimization design of exhaust ventilation systems in pickling tanks.