Begehrter Siemens Preis für Innovation
25. November 2013
The media reported the set-up of a globally unique Midrex Plant with Hot Fines Recycling by voestalpine-Stahl in Corpus Christi/Texas/USA. The plant designed to produce two million tons of hot-briquetted iron (HBI or DRI) is equipped with four newly developed high performance bucket elevators made by MFL Special Machinery.
Developing a completely new plant fulfilling almost impossible customer requirements under enormous time pressure – that was the challenge the special machinery team of Mr Josef Ziegler had to meet for the MFL client Primetals Technologies Austria. The time frame was one year which could only be observed due to the engineering support given by Rabofsky + Partner and the committed manufacturing carried out by MFL Mechanical Engineering.
Extremely High Demands
The bucket elevators had to be heat-resistant (750° C hot DRI), gas-proof, explosion pressure-proof and capable of resisting strong winds (directly at the Gulf of Mexico) and earthquakes.
If there is an explosion in the bucket elevator the sheathing must not burst, and pressure relief to the immediate environment was not admissible due to danger to life and limb. Pressure propagation to peripheral equipment (material feed and material discharge) was no alternative either as the upstream or downstream equipment is only designed for operating at ambient (environmental) pressure.
The only possibility to solve this task was to develop especially pressure-proof feeders and dischargers. Due to the given temperature and atmosphere inside the bucket elevator, a highly-sophisticated bucket elevator chain with a new type of lubrication was developed. Even the lubricant had to be especially tuned during extensive tests to meet these particular requirements.
In addition to the technological challenge the engineering team had to perform a balancing act between European and American standards as a multitude of American regulations had to be observed.
The bucket elevators are used to recover DRI (direct-reduced iron = Hot Fines), a very valuable waste material that could not be recycled during briquetting until then. Thanks to this additional equipment these Hot Fines can be preserved for the Midrex process and can be utilised by 100%.
From now on this Midrex DRI Plant will (among others) provide the Austrian voestalpine locations Linz and Donawitz with briquetted sponge iron to produce steel.