Steam Reforming of Methane on Sponge Iron: Influence of Gas Composition on Reaction Rate

Abstract

Direct Reduction processes use gases (CO and H 2 ) for iron reduction and production of sponge iron or direct reduced iron (DRI). The generation of this gas occurs through methane reforming, which can be done in a reformer or inside the reduction shaft with the sponge iron as a catalyst. The latter occurs in the auto-reforming processes. The kinetics of steam reforming of methane catalyzed by sponge iron was studied at temperatures between 875°C and 1 050°C. Results showed that sponge iron acts as a catalyst and methane conversion is increased in higher temperatures and with higher H 2 /H 2 O ratio in the inlet gas. The inlet gas composition like one of the industrial auto-reforming processes led to intense carburization and hindered the catalytic reforming reaction.

Kinetics Analysis of Steam Reforming of Methane on Sponge Iron

“…H O(g) O(ads) H g In a paper published previously, 11) the present authors showed results of the catalytic activity of sponge iron in steam reforming of methane. Gas composition with a higher H 2 /H 2 O ratio resulted in higher conversions of methane, which agrees with the mechanism proposed by Münster and Grabke.…”

“…The chemical composition of such pellets is shown in Table 1. The pellet size distribution of Pellet Vale can be found in the previous paper 11) with an average diameter of 12.6 mm. Pellet A was supplied in two size ranges that were combined in the same proportion, 8 mm to 12 mm and 12 mm to 16 mm, resulting in an average diameter of 12 mm.…”

“…The detailed description of experimental apparatus and procedure can be found in the same previous paper. 11) In summary, the experimental apparatus consisted of a gas injection system that controlled inlet flows of Ar, CH 4 , H 2 , and steam. The gases were directed to a double-walled metallic reactor that contained the bed of solids, either pellets or sponge iron.…”

“…Methane conversion was calculated through a carbon balance, considering that no carbon deposited unto sponge iron, and that reacted methane would form either CO or CO 2 that were continuously analyzed in the off gas. 11) Interrupted tests were performed to measure the carbon content in the DRI after reforming experiments. The carbon content was determined in a LECO CS-300 equipment.…”

“…One way to control the amount of carbon deposited is to add steam to the gas, and therefore both carburization and steam reforming of methane can happen. 11) Much work has been done in the fundamentals of iron ore reduction [2][3][4][5][6][7][12][13][14][15][16] and carburization [17][18][19][20][21][22][23][24][25][26] in gas-based direct reduction processes. The catalytic behavior of sponge iron has been studied [27][28][29] regarding dry reforming of methane 27) or in conditions similar to blast furnace operations.…”