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

• Published in: Energy & fuels Vol. 22; no. 4; pp. 2570 - 2579
• Main Authors: Yang, Jing-biao, Cai, Ning-sheng, Li, Zhen-shan
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-07-2008
• Subjects: 01 COAL, LIGNITE, AND PEAT; 08 HYDROGEN; Alternative fuels. Production and utilization; Applied sciences; CHARS; COAL; COMBUSTION; Energy; Exact sciences and technology; FLUIDIZED BED REACTORS; Fuels; Hydrogen; HYDROGEN PRODUCTION; IRON OXIDES; LIGNITE; REDOX REACTIONS; REDUCING AGENTS; REDUCTION; STEAM-IRON PROCESS; Asia; China; Fluidized bed reactor; Iron oxide; Conversion rate; Combustion; Iron; X ray analysis; Water vapor; Lignite; Char; Coal; Feasibility; Oxidation; X ray diffractometry; Hydrogen production
• ISSN: 0887-0624; 1520-5029
• DOI: 10.1021/ef800014r

Experimental results performed with a fluidized-bed reactor supported the feasibility of the three processes including direct reduction of iron oxide by char, H2 production by the steam−iron process, and the oxidation of Fe3O4 resulting from the steam−iron process to the original Fe2O3 by air. Chars resulting from a Chinese lignite loaded with K2CO3 were used successfully as a reducing material, leading to the reduction of Fe2O3 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 Fe2O3 by K-10-char at 1073 K is desirable from the perspective of the carbon conversion rate and high concentration of CO2. The carbon in char was completely converted to CO2 when the mass ratio of Fe2O3/K-10-char was increased to 10/0.3. The oxidation rate of K-10-char by Fe2O3 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 Fe2O3 and 0.5 g of K-10-char, which was verified by the total H2 yield equaling 1000 mL/g K-10-char from the steam−iron process. The time that it took to achieve complete oxidation of Fe3O4 to Fe2O3 by air with an 8.7% O2 concentration at 1073 K was about 15 min.