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CFD Analysis of Low-Cost Solutions to Minimize Gas and Dust Emissions during the Emergency Opening of Blast Furnace Bleeders

The article presents the solution adopted in an existing blast furnace with only two safety valves to minimize the dust and gas emissions to the atmosphere, in case of emergency relief due to abnormal overpressure during operating issues in the blast furnace process. Before the implementation of the system, several openings of the emergency bleeder valves were observed: These led to sensitive pollutant emissions, also in terms of acoustic and visive events, with high impact on the surrounding environment. The new relief system, in addition to the existing bleeder valves, has been engineered with a Computational Fluid Dynamic (CFD) analysis using Ansys Fluent to find out the most effective solution and to minimize modifications on the plant. Few plant modifications, while guaranteeing the achievement of the target of reducing the bleeder openings, allow to reduce the plant shutdown costs for the modifications themselves and the maintenance costs during plant operation and to simplify the operating logic of the blast furnace overpressure control systems. The new installation increased the safety operation of the blast furnace, and it drastically reduced the bleeder valves openings—4% of the pre-intervention total opening time per year—and the associated emissions in spite of the rise of the pig iron production, as recorded by the monitoring and supervision system.