A 130-ton-hot-metal desulfurisation station (DeS) and a new dedusting system supplied by Austrian plant builder Primetals Technologies has commenced operation at ArcelorMittal Monlevade in Brazil, an integrated steel works in João Monlevade, 120 km from Belo Horizonte, the state capital of Minas Gerais.

The new equipment is part of an expansion and quality improvement program at ArcelorMittal Monlevade.

The desulfurisation station, claims Primetals, represents the first installation of the company's combined volumetric dosing device for Magnesium (Mg) and a pressure dispenser for Calcium Oxide (CaO). Low sulfur levels of lesser than 0.005% (50ppm) can be achieved. The company says that processing times and the consumption of desulfurisation agents have been significantly reduced.

The associated level 2 system supplied by Primetals Technologies predicts the end sulfur content with high accuracy, deviations of real from predicted value is below 5ppm on average. The dedusting system installed in the melt shop processes approximately 900,000 m3/hr. A handling system for 130-tonne hot-metal ladles was also part of the project.

Primetals was responsible for the engineering, supply and advisory services for reaction and start-up of the desulfurisation station. Equipment encompassed a volumetric dosing device for dosing of Mg, a pressure dispenser for dosing CaO, lance and injection systems, the materials handling system – including an unloading station, silos for storage, and material transport. An important part of the project is the complete level 1 and level 2 automation system with process models, enabling precise process control and dosing as well as reliable prediction of end sulfur content. This allows for flexible and optimum injection ratios of CaO/Mg from 2:1 to 10:1. The co-injection takes places with fully decoupled control of the conveying of Mg and CaO. The DeS station is designed to operate with fluidised CaO or CaC2 (Calcium Carbide) as well. Pure Mono-injection of CaO or CaC2 is also possible.

The system's volumetric dosing device has two collateral pistons for continuous and precise injection of Mg. The Mg flow rate is determined by the piston speed only and does not depend on the pressure in the system – there is no interaction with the pressure dispenser. With this mechanical system, the conveying rate of Mg can vary in a wide range of 3 to 15 kg/min. Powder materials, such as lime and calcium carbide, are injected via the high performance pressure dispenser. All installed valves and control devices are designed to the highest safety standards, the company claims.

The new desulfurisation station, says Primetals, has replaced an existing system preformed in torpedo cars, reducing both the consumption of desulfurisation agents and processing times. In addition, the effort for cleaning of torpedo cars is also lowered, deslagging simplified and metal losses during deslagging reduced.

The new dedusting system covers two BOF converters, the DeS and slag skimming stand as well as the HM mixer. Primetals engineered, supplied and installed charging coolers for BOF charging evacuation, pulse jet filters with eight chambers and a filter area of 11,270 m2, and two induced draft (ID) fans with a power rating of 1,500 kW each. The filtered dust is discharged to containers. A handling system for the 130-tonne hot metal ladles completed the scope of supply, including ladles, a transfer car with integrated ladle tilting device and a deslagging machine.