Key Takeaways & Executive Findings
- •• • Numerical simulation of toluene dispersion matched experimental data within a maximum average error of -3.9%, validating the CFD model for predicting VOCs behavior in industrial settings. • • Existing hood inlet velocities ranged from 0.04 to 0.2 m/s, indicating severe maldistribution; this leads to fugitive emissions and necessitates redesign for uniform capture. • • At a design air volume of 2700 m³/h per vulcanizer, the enclosed hood achieved a toluene concentration of 80 mg/m³ versus 63 mg/m³ for the semi-enclosed hood, demonstrating superior capture efficiency for hot fumes. • • After optimizing the semi-enclosed hood with soft curtains and a height of 1200 mm, and adding 900 mm gradual reducers, branch air volume deviations were reduced to -0.44% and 0.38%, with individual hood deviations below 10%, achieving negative pressure balance and effective collection.
Abstract
To address the issues of high air volume and unorganized emissions of waste gas in semi-steel vulcanization production lines, a combined approach of experimental testing and numerical simulation was employed to study the diffusion characteristics of VOCs-containing waste gas and the air volume of the collection system. The structure of the semi-enclosed hood was optimized, and pipe diameters were adjusted to achieve negative pressure balance, enabling efficient waste gas collection. Results showed that toluene concentration distributions from numerical simulation were largely consistent with experimental measurements, with a maximum average error of -3.9%. Existing hood inlet wind speeds ranged from 0.04 to 0.2 m/s, indicating uneven distribution. Under calm wind conditions, toluene diffusion in enclosed and semi-enclosed hoods was similar, with concentrations of 248 mg/m³ and 115 mg/m³, respectively, and deposition observed in trenches. For a single vulcanizer, at a design air volume of 2700 m³/h, the enclosed hood achieved a toluene concentration of 80 mg/m³ versus 63 mg/m³ for the semi-enclosed hood, demonstrating superior capture of hot fumes. Optimizing the semi-enclosed hood with soft curtains and a height of 1200 mm, at a total design air volume of 1.0×10⁵ m³/h, yielded an average hood inlet velocity of 0.35 m/s but still uneven distribution. Adding 900 mm gradual reducers and adjusting branch pipe diameters resulted in total air volume deviations of -0.44% and 0.38% for branches I and II, respectively, with individual hood deviations below 10%. This achieved negative pressure balance, effective collection, and improved workshop hygiene.
1. Introduction
The rubber manufacturing industry is a cornerstone of industrial production, yet the vulcanization process generates substantial volatile organic compounds (VOCs) with complex composition, low concentrations, and high emission rates. In semi-steel tire production lines, these unorganized emissions pose significant environmental and occupational health risks. Existing collection systems often suffer from uneven airflow distribution, leading to inefficient capture and poor workshop air quality. The challenge lies in designing a system that balances high air volume requirements with effective containment, particularly under calm wind conditions where pollutant dispersion is limited.
This study addresses this bottleneck by integrating experimental measurements with numerical simulation to analyze toluene dispersion patterns and optimize the semi-enclosed hood structure. By adjusting pipe diameters and incorporating gradual reducers, the system achieves negative pressure balance, ensuring uniform capture across all hoods. The findings provide industrial parameter references for designing efficient gas collection systems in vulcanization lines, directly tackling the issue of uneven airflow and fugitive emissions.
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YAN Zimeng, DANG Xiaoqing, ZHENG Huachun, JI Shuo, QU Jiaxin, HAN Wei, WANG Leifeng, ZHANG Chunhui (2026). Analysis of Exhaust Gas Dispersion Patterns and Design of High-Efficiency Gas Collection Systems in Semi-Steel Tire Vulcanization Production Lines. Journal of Environmental Engineering Technology. https://doi.org/10.13205/j.hjgc.202604018
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Frequently Asked Questions
What is the maximum average error between numerical simulation and experimental results for toluene concentration, and how does this validate the CFD model?
The maximum average error is -3.9%, indicating that the CFD model accurately predicts toluene dispersion. This level of accuracy is acceptable for engineering design, allowing reliable optimization of hood structures and airflow distribution.
How does the enclosed hood compare to the semi-enclosed hood in terms of toluene capture efficiency at a design air volume of 2700 m³/h?
At 2700 m³/h, the enclosed hood achieves a toluene concentration of 80 mg/m³, while the semi-enclosed hood reaches 63 mg/m³. The lower concentration in the enclosed hood indicates superior capture of hot fumes, but the semi-enclosed hood still provides adequate control with lower material costs.
What specific modifications were made to achieve negative pressure balance in the collection system, and what were the resulting air volume deviations?
Modifications included adding 900 mm gradual reducers and adjusting branch pipe diameters. After optimization, branch I had a total air volume deviation of -0.44%, and branch II had +0.38%. Individual hood deviations were all below 10%, ensuring uniform capture and preventing fugitive emissions.
How does the optimized semi-enclosed hood design affect the average hood inlet velocity and overall system performance?
With soft curtains and a hood height of 1200 mm, the average hood inlet velocity increased to 0.35 m/s at a total design air volume of 1.0×10⁵ m³/h. This velocity is sufficient to capture VOCs, but the initial distribution was uneven, necessitating further pipe adjustments to achieve balance.
What are the implications of toluene deposition in trenches under calm wind conditions, and how does the design address this?
Toluene deposition in trenches indicates that heavy VOCs can accumulate in low-lying areas, posing an explosion risk and prolonged exposure. The optimized hood design, with soft curtains and proper airflow, helps to draw these vapors upward and into the collection system, reducing accumulation.
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