Midrex is a gas-based shaft furnace process that converts iron oxides – in the form of pellets or lump ore – into direct reduced iron (DRI). The Midrex technology is highly adaptive to our customers’ needs, which is reflected in a broad variety of configurations. The performance of Midrex plants typically exceeds nominal capacity ratings. This trend will continue with the implementation of new technologies such as oxide coating, oxygen injection, OXY+, centrifugal process gas compressors and our process optimization system. As a licensee of Midrex technology, Primetals Technologies has been successfully building Midrex direct reduction plants and is able to supply all sizes of packages right up to turnkey solutions. About one third of all Midrex plants worldwide have been built with significant involvement (e.g., consortium leadership) of Primetals Technologies.
The Midrex Process is unsurpassed in the Direct Reduction industry in terms of production and process flexibility to meet the constantly evolving nature of steelmakers and ore-based metallic providers. Adjustable product quality and the flexibility to produce various forms of iron together with some of the best production records industry-wide make Midrex Plants the most profitable DRI plants in the world to own and operate.
Plant special features
Whether the requirement is for 500,000 tons per year or 2.5 million tons per year and higher, owners know they will receive high performance and reliability from the Midrex Process. The shaft furnace-based Midrex Process provides outstanding investment value through an efficient way to reduce iron oxide with the greatest operational flexibility.
Derive reducing gas from the energy source most readily available and competitively priced.
Efficiently reduce local iron oxide pellets and ores of varying quality either separately or in differing combinations.
Discharge DRI either cold or hot and in any combination simultaneously to produce cold DRI (CDRI), hot briquetted iron (HBI) and hot DRI (HDRI).
The DR Plant Process Optimization System is designed to assist operators and process engineers in reaching specific targets in Midrex DR plant operation. Process models as well as a rule-based expert system support plant operators in optimizing process parameters at an early stage. The package can be easily integrated in both existing and new Midrex DR plants.
Due to the process model results and the expert system control, major benefits are achieved:
- Stabilized product quality
- Smooth plant operation due to small and frequent control actions
- Standardized control philosophy and shift independent plant operation
- Early detection of undesired process conditions
- Reduced energy demand due to stabilized process conditions
- Longer lifetime of reformer catalyst
Fig.1- DR System Control
Based on a regular evaluation of the actual process conditions, the DR Plant Expert System generates diagnoses and corrective actions to avoid or settle undesired process conditions. Set-points are calculated to keep the process stable and run the plant in best practice conditions. Particular corrective actions can be switched to closed-loop mode to send set-points directly to the process control system.
The system comprises three prediction models, the Product Metallization Prediction Model, the Discharge Temperature and the Product Carbon Prediction Model, all of them reaching an excellent accuracy of the prediction results. The metallization as well as the carbon content of the product are essentially completed when the material leaves the reduction zone. However, it takes several hours more before operation finally receives this information from the laboratory. The models bridge this delay by cyclically calculating the predicted product metallization and carbon content based on process data and raw-material quality parameters. – Thus plant operators can immediately adjust process parameters based on the metallization and carbon forecast to achieve a stabilized product quality.
Technological model calculations provide further process information. The Midrex Superdata Model is fully integrated into the DR Plant Process Optimization System. The model runs automatically on a regular base and performs technical calculations using online measurements, feed materials and product analyses.
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Fig.1- MERIM plant for Midrex
Fig.2- MERIM plant layout