Siemens offers new system for hot metal desulfurization

Siemens VAI Metals Technologies has developed a new system for hot metal desulfurization. HM De-S combines the pressure-vessel based injection technology for powder agents – such as burnt lime and calcium carbide – with the addition of magnesium granules by means of the patented Simetal Feldhaus process. This combination facilitates precise, cost-saving dosing of the individual desulfurizing agents, and consequently a highly flexible process operation to achieve the desired residual sulfur content. The system can be operated according to requirements in mono-, co- or multi-injection mode. Further advantages are short process times, less slag generation and low maintenance costs.

The use of sulfur containing fuels in the blast-furnace process results in a certain sulfur concentration in the tapped hot metal that has to be reduced, depending on the product steel grade, to low or even lowest levels. This is usually achieved by injection of desulfurizing agents – such as powdered burnt lime (CaO) or calcium carbide (CaC₂) together with magnesium (Mg) granules – into the charging ladle by an immersion lance. The type, quantity and time-related distribution of the desulfurizing agents required, is strongly dependent on the produced steel grades as well as the initial sulfur content. To optimize the agent costs, it is essential to dose these agents very precisely – this is especially valid for the expensive Mg granules.

With its new HM De-S system, Siemens is offering steelworks operators a flexible solution for need-oriented, cost-effective desulfurization. This combines gravimetric dosing of the powdered CaO and CaC₂ with volumetric dosing of the Mg granulate by the Simetal Feldhaus. Simetal Feldhaus dosing system has been specially developed for pneumatically conveying dense flows of granular materials, which have different requirements to those of powder materials. The Siemens HM De-S is characterized by highly precise dosing and low maintenance requirements.

The pre-dosed desulfurizing agents are then fed through a common injection pipe and the immersion lance into the hot metal. The system can be operated according to requirements in mono-, co- or multi-injection mode. As the pre-dosing is material-specific, the individual flow rates of the CaO, CaC₂ and Mg can be optimally and reproducibly adjusted to meet the requirements for the grades of steel being produced. This saves desulfurizing agents – especially in co and multi-injection mode – and thus also reduces the amount of slag formed.

For an average desulfurization station with an annual capacity of around 1.75 million tonnes of hot metal and ladle tapping weights between 165 and 180 tonnes, the injection rate of CaO or CaC₂ can be varied between 20 and 60 kilograms per minute, and that for Mg between 6 and 14 kilograms per minute. This enables the sulfur content to be reduced from typically 200 to 400 ppm to 20 ppm and subjacent. A typical process time for reducing the sulfur by around 250 ppm is 13 minutes. This requires less than 0.6 kilograms of Mg and about 2.8 kilograms of CaO per ton of hot metal. The process creates approx. 9 kilograms of slag per tonne hot metal.

The desulfurization system is offered as a complete solution. This includes the unloading station for the desulfurizing agents, silo and storage facilities, the gas supply and distribution, the dosing systems, the desulfurization station, and lances, lance magazines and ladle cars. The enclosure can have either a fixed or movable cover. As well as the mechanical and processing equipment, HM De-S also includes the electrical equipment, instrumentation, the complete basic and process automation, process models, analysis and optimization software, and the operator control and visualization system.

A hot metal desulfurization system based on the HM-De-S design is currently being constructed for ArcelorMittal Monlevade S.A., a Brazilian steelmaker in João Monlevade, in the state of Minas Gerais, Brazil. The system is part of an expansion of the steel works, for which Siemens is also supplying ladles, deslagging stations, ladle and slag pot transfer cars, and the associated electrical and automation equipment. Siemens is also enlarging the material feed system and installing two secondary dust cleaning systems.

Further information about solutions for steel works, rolling mills and processing lines is available at http://www.siemens.com/metals

A photo supplements this press release. Please see: http://www.siemens.com/mt-picture/IMT201205162

(The new HM De-S system concept from Siemens for hot metal desulfurization)

The Siemens Industry Sector (Erlangen, Germany) is the world’s leading supplier of innovative and environmentally friendly products and solutions for industrial customers. With end-to-end automation technology and industrial software, solid vertical-market expertise, and technology-based services, the Sector enhances its customers’ productivity, efficiency, and flexibility. With a global workforce of more than 100,000 employees, the Industry Sector comprises the Divisions Industry Automation, Drive Technologies and Customer Services as well as the Business Unit Metals Technologies. For more information, visit www.siemens.com/industry

The Metals Technologies Business Unit (Linz, Austria), part of the Siemens Industry Sector, is one of the world’s leading life cycle partners for the metallurgical industry. The Business Unit offers a comprehensive technology, modernization, product and service portfolio as well as integrated automation and environmental solutions covering the entire lifecycle of plants. For more information, visit www.siemens.com/metals

Based on Siemens (Industry Sector, Metals Technologies) information