BIM provided an accurate and cost-eﬀective method for the firm to predict performance of the casthouse emission control system under real-world conditions
“Autodesk CFD Simulation proved to be an indispensable analytical method for optimizing design of the emission control system for the Severstal casthouse.” — Brian Bakowski, Design Engineer, SNC-Lavalin
When steel company Severstal North America recently rebuilt one of its blast furnaces, it faced a challenge: the emission control system had to be designed for a casthouse that didn’t yet exist. The project would have been diﬃcult—maybe nearly impossible—without the help of Canadian engineering ﬁrm, SNC-Lavalin, and Autodesk CFD.
The redesigned casthouse included a new set of hoods, ductwork, fabric ﬁltration equipment, and fans. Under U.S. Environmental Protection Agency (EPA) regulations, casthouse particulate emissions must be controlled with Maximum Achievable Control Technology (MACT). MACT compliance is measured by stack emission concentrations and the opacity of emissions that escape from the casthouse building. The Michigan Department of Environmental Quality (MDEQ) also has established an opacity limit. The new Severstal casthouse needed to meet both EPA and MDEQ environmental regulations by capturing 98% of emissions.
MACT compliance usually is based on actual observations of casthouse operations to determine emission intensities, crosswind speeds, and vertical rise rates. However, Severstal could not do that because the rebuilt casthouse was very diﬀerent in conﬁguration and operation from previous ones. The solution was to use Autodesk CFD to conduct a comprehensive design study that simulated the new equipment under every conceivable operating condition.
After establishing the fundamental geometry and base set of conditions, ﬁnding the optimal design was an iterative four-step process. First, SNC-Lavalin needed to determine capture eﬃciencies for tapholes, iron tilters, and slag pot areas using initial hood designs and ventilation rates. Then, if the initial hood and ventilation combinations did not achieve the 98% emission control rate, SNC-Lavalin revised the geometry of the hood and/or the ventilation rate. The third step was to re-run the model with the revised hood and ventilation design. Then, the second and third steps were repeated until acceptable emission control was achieved; the acceptable model parameters to the emission control system design were then applied.
Capture eﬃciency for the casthouse model was computed as the probability that a fume particle generated at each source (taphole, tilter, or slag shanty) would be captured by each hood and subsequently drawn through the ductwork to the bag house. The next—and most important—step in the calculation was to determine fume capture percentages for each individual operation.
The entire study involved dozens of computational ﬂuid dynamics (CFD) simulations to arrive at an optimal mix of hood conﬁgurations and ventilation volumes. In addition to numerical results, Autodesk CFD provided the SNC-Lavalin team with static and dynamic images that created a better understanding of what was occurring during the simulations.
“Autodesk CFD proved to be an indispensable analytical method for optimizing design of the emission control system for the Severstal casthouse,”says Brian Bakowski, design engineer at Montreal-based SNC-Lavalin. “It enabled us to successfully establish ventilation volumes, hood conﬁgurations, and volume distribution proﬁles for 50 separate operating scenarios for the new blast furnace. It was all done in three months, without costly physical testing.”
The new furnace is now fully operational and in compliance with MACT regulations. Autodesk CFD proved to be an accurate and cost-eﬀective method for SNC-Lavalin to predict actual performance of the casthouse emission control system under real-world conditions.