Direct Reduction of Iron Ore
The Midrex Direct Reduction process is based upon a low pressure, moving bed shaft furnace where the reducing gas or syngas moves counter-current to the lump iron oxide ore or iron oxide pellet solids in the bed. The reducing gas is produced from the reforming of natural gas using two nickel based catalyst types and one inert ceramic support. Taking into account the very severe operational conditions in Midrex reformers due to high gas temperatures, low pressures, low steam to carbon ratio and high CO2 content in the reformer feedstock, two variants of catalyst along with an inert layer should be loaded to avoid catalyst deterioration, one with higher nickel oxide content and activity based on alumina and the other with lower nickel oxide and activity on rugged magnesium oxide carrier. Unlike conventional steam reformers, in Midrex process, feedstock moves upward inside the tubes and accordingly the catalysts loading pattern should be adjusted so that the feed gas stream is firstly pre-heated over a sufficient volume of ceramic support layer, then partially reformed and heated over a semi-active magnesium oxide based catalyst to facilitate the process conditions of the application of an alumina based high active catalyst. Hence, the ultimate reforming will be done over a high active catalyst.
Several significant features of the robust DRI reforming catalysts are as follows:
- High catalytic activity for converting feedstock
- High resistance against coke formation
- High heat transfer coefficient
- Low pressure drop and high geometric surface area
- Excellent stability of catalyst performance.
ReforMex 15 RWH : A highly active DRI reforming catalyst based on alumina carrier. This 6-hole ribbed ring shaped catalyst containing high nickel oxide content is loaded inside the Midrex reformer tubes as the major layer. It is considered for the complementary reforming of natural gas purposes along with a semi-active catalyst.
ReforMex 7 RWH : A highly active DRI reforming catalyst based on alumina carrier. This 6-hole ribbed ring shaped catalyst containing high nickel oxide content is loaded inside Midrex reformer tubes along with the inert layer.
ReforMex 14 RR : A superior semi-active DRI reforming catalyst with lower nickel oxide content based on a magnesium oxide (MgO) carrier.
ReforMex 13 : An Alumina based high strength inert ceramic support used for loading the bottom section of Midrex reformer tubes.