(271i) Mill Scale-Steam Reforming: a Novel and Inexpensive Route of Hydrogen Generation

Hydrogen has
been touted to be the ideal fuel for PEMFCs. Unfortunately, it is not as
abundant a commodity in nature as oxygen and nitrogen. Therefore, the question
of its storage and supply arises only after it is produced in large enough
quantity so as to cater to the need of its use. In the light of the serious
economic constraints and safety concerns associated with production, storage
and supply of gaseous hydrogen, one needs to find ways and means of generating,
storing, transporting and supplying hydrogen to the end use port - in more
reversible, much simpler and far safer ways.

An economically
viable and environment friendly method of generating hydrogen is by the
reaction of certain metals with steam, also appropriately called ?steam-metal
reforming'. The reaction, 3 Fe + 4 H₂O → Fe₃O₄
+ 4 H₂ which occurs at ~ 600ºC, has been known for a long time
and has recently been described as one of the ways of generating hydrogen [1].
The reverse reaction could be viewed as a hydrogen storage scheme. However, the
kinetic of metal oxidation (forward) and oxide reduction (reverse) in a cyclic
fashion has to be significantly improved to mitigate sintering and coarsening
of iron and iron oxide particles during repeated redox cycles [2-3].

We report an
effective technique of producing hydrogen (in a way consistent with the
criteria listed above: environment, availability and price) by using the
so-called ?mill-scale' waste from steel industry. The mill-scale is a hard
brittle coating of several distinct layers of iron oxides formed during the processing
of steel. It is magnetic in nature (Fe₃O₄ predominantly)
with iron content ranging between 66 to 88%.

In order to
establish the feasibility of hydrogen production and recycling of the iron
oxide waste on a laboratory scale, the mill-scale was successfully and
quantitatively (~100%) reduced to elemental iron both via H₂ and
carbothermic reduction. In an attempt to eliminate the use of high temperature
and H₂ gas and, the CO/CO₂ emission a solution-based
technique has been devised resulting in the formation of nanoscale elemental
iron particles from mill-scale powder near room temperature, which could be
used directly in metal-steam reforming process to produce H₂. Some
preliminary results of this investigation will be presented.

Fig. 1. TEM image of iron particles obtained from steel industry
waste by room temperature processing.

Scale bar: 100 nm

References:

1. K. Otsuka , T. Kaburagi, C. Yamada and S. Takenaka, in
R.D. Venter, T.K Bose, N. Veziroglu (Eds.), Proceedings of the 14^th World
Hydrogen Conference, Montreal, Canada, (Session A1.9 - Storage and Material
systems I) 2002.

2. K. Otsuka, T. Kaburagi, C. Yamada and S. Takenaka, J. Power
Sources, 122 (2003) 111.

3. S. Takenaka, T. Kaburagi, C. Yamada, K. Nomura and K.
Otsuka, J. Catal. 228 (2004) 66.