DRI Process
Natural gas reforming is a key process in the formation of syngas for Sponge Iron Production and Petrochemical plants. Syngas is the mixture of hydrogen (H2) and carbon monoxide (CO) and reforming of natural gas is one of the most common process of producing such mixture because of cheapness, easy availability and abundance of natural gas in the country. Reforming process can be characterized through the following major reactions:
CH4 + H2O ⇌ CO + 3 H2
CH4 + CO2 ⇌ 2 CO + 2 H2
CnHm + n H2O à (n + m/2) H2 + n CO
The first reaction is the one generating syngas with a stoichiometric ratio of H2/CO=3 while the second one yields that ratio equals to one. However, other side reactions (like water gas shift reaction) may cause this ratio to be varied which its extent’s based on the operating conditions. The third reaction is due to the presence of heavy components in the natural gas feedstock.
Some other unfavorable reactions result in formation of coke over the surface of the catalyst (such as Boudouard reaction or hydrocarbons thermal cracking) and gradually reduce the catalyst activity and reformer tubes life and increase reformer pressure drop.
CH4 ⇌ C + 2 H2
CnHm à n C + m/2 H2
2 CO ⇌ C + CO2
The total of mentioned reactions is strongly endothermic, hence high amount of energy requires to supply the heat of reactions and this indicates that natural gas reforming is a very costly process and engineers must do their utmost in order to increase economic profits.
Many operating factors affect the reformer product composition including pressure, temperature, individual or sum of steam and carbon dioxide to carbon ratio and space velocity. The continuing progress in the field of reformer design modifications leads to applying higher pressures and temperatures for reforming process operation and these modifications paved the way for improving and optimizing these operating conditions. Besides the above-mentioned factors, the most critical aspect of this process is the performance of catalyst during the operation. In every chemical and petrochemical reactor, catalysts play the most important role to yield the desired products.
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 reforming of natural gas using two nickel-based catalyst types and one inert ceramic support. Regarding to the very sever operational conditions in MIDREX reformers due to reformer high temperatures, low pressures, low steam to carbon ratio and high CO2 content in the reformer feedstock, two varieties of catalysts along with an inert bed layer should be loaded to avoid catalyst deterioration, one with higher nickel oxide content and activity based on α-alumina and the other with lower nickel oxide and activity on rugged magnesium oxide carrier. Unlike steam reformers, in MIDREX reformers, feedstock moves upward inside the tubes and accordingly the catalysts loading pattern should be adjusted so that the feed gas stream firstly pre-heated over sufficient volume of ceramic support layer, then partially reformed and heated over semi-active magnesium oxide based catalyst to facilitate the process conditions of application of an alumina based high active catalyst. Hence, the ultimate reforming will be done over high active catalyst. The ratio of H2 to CO produced is controlled at about 1.5 to 1.9, and reducing quality at 11 to 12 for best operation.
Several significant features of the robust DRI reforming catalysts are as follows:
Khwarizmi Catalyst Features
The industrial scale process performance of KhTD DRI reforming catalysts demonstrates their superior catalytic activity and life-time stability during a long period of time. The reported results of industrial plants reformers prove that KhTD DRI reforming catalysts represent a definitely comparable or in some cases even slightly better performance than foreign commercial catalyst manufacturer.
DRI-6HGRR-HA-01: is a high active DRI reforming catalyst based on α-alumina carrier. This 6-hole ribbed ring-shaped catalyst containing high nickel oxide content loaded inside MIDREX reformer tubes as the major layer, is considered for the complementary reforming of natural gas purposes along with semi-active catalyst.
DRI-1HRR-SA-01: A superior semi-active DRI reforming catalyst with lower nickel oxide content is based on basic magnesium oxide (MgO) carrier. Considering MgO carriers as a basic catalyst support, the coke formation during the reforming of natural gas feedstock will be significantly retarded compared to α-alumina carriers, especially when the amounts of steam to carbon ratio is substantially low contrary to high carbon dioxide (CO2) content which is significantly high, as can be seen in MIDREX reformers. Therefore, this rugged catalyst type can considerably tolerate the most severe conditions present in MIDREX reformers. The catalyst pellets with uniform and high crush strength is allowed to be charged in the middle layer of MIDREX reformer tubes to partially reform the natural gas feed.
DRI-1HR-I-01: is a high strength inert ceramic support used for loading in the bottom section of MIDREX reformer tubes.
