Hydrogen Production from the Steam−Iron Process with Direct Reduction of Iron Oxide by Chemical Looping Combustion of Coal Char

Experimental results performed with a fluidized-bed reactor supported the feasibility of the three processes including direct reduction of iron oxide by char, H 2 production by the steam−iron process, and the oxidation of Fe 3 O 4 resulting from the steam−iron process to the original Fe 2 O 3 by air. Chars resulting from a Chinese lignite loaded with K 2 CO 3 were used successfully as a reducing material, leading to the reduction of Fe 2 O 3 to FeO and Fe for the steam−iron process, which was confirmed by both the off-gases concentrations and X-ray diffractometer analysis. The reduction of Fe 2 O 3 by K-10-char at 1073 K is desirable from the perspective of the carbon conversion rate and high concentration of CO 2 . The carbon in char was completely converted to CO 2 when the mass ratio of Fe 2 O 3 /K-10-char was increased to 10/0.3. The oxidation rate of K-10-char by Fe 2 O 3 without a gasifying agent was comparable to the K-10-char steam gasification rate. The fractions of FeO and Fe in the reduced residue were 43 and 57%, respectively, in the case of 3 g of Fe 2 O 3 and 0.5 g of K-10-char, which was verified by the total H 2 yield equaling 1000 mL/g K-10-char from the steam−iron process. The time that it took to achieve complete oxidation of Fe 3 O 4 to Fe 2 O 3 by air with an 8.7% O 2 concentration at 1073 K was about 15 min.