Oxygen-carrier selection and thermal analysis of the chemical-looping process for hydrogen production

Kyoung Soo Kang, Chang Hee Kim, Ki Kwang Bae, Won Chul Cho, Sung Hyun Kim, Chu Sik Park

Research output: Contribution to journalArticlepeer-review

166 Citations (Scopus)

Abstract

The three-reactor chemical-looping process (TRCL) for the production of hydrogen from natural gas is quite attractive for both CO2 capture and hydrogen production. The TRCL process consists of a fuel reactor, a steam reactor and an air reactor. In the fuel reactor, natural gas is oxidized to CO2 and H2O by the lattice oxygen of the oxygen carrier. In the steam reactor, the steam is reduced to hydrogen through oxidation of the reduced oxygen carrier. In the air reactor, the oxygen carrier is fully oxidized by air. In this process, the oxygen carrier is recirculated among the three reactors, which avoids direct contact between fuel, steam and air. In this study, various candidate materials were proposed for the oxygen carrier and support, and a thermal analysis of the process was performed. The oxygen carrier for the process must have the ability to split water into hydrogen in its reduced state, which is a different chemical property from that of the chemical-looping combustion medium. The selection of the oxygen carrier and support require careful consideration of their physical and chemical properties. Fe2O3, WO3 and CeO2 were selected as oxygen carriers. Thermal analysis indicated an expected hydrogen production of 2.64 mol H2 per mol CH4 under thermoneutral process conditions. The results indicated that hydrogen production was affected mainly by the steam-conversion rate. The solid-circulation rate and temperature drop in the fuel reactor were calculated for the selected oxygen carriers with different metal oxide contents and solid-conversion rates.

Original languageEnglish
Pages (from-to)12246-12254
Number of pages9
JournalInternational Journal of Hydrogen Energy
Volume35
Issue number22
DOIs
Publication statusPublished - 2010 Nov

Bibliographical note

Funding Information:
This work was supported by the New & Renewable Energy R&D program ( 2009T100100424 ) of the Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy . d stoichiometric factor in the fuel combustion reaction with oxygen, mol-O 2 mol-CH 4 −1 G S specific solids-circulation rate, kg m −2  s −1 H inlet, i enthalpy of component i in inlet gas H outlet, j enthalpy of component j in outlet gas m ˙ C characteristic circulation rate, kg-oxygen carrier, sec −1  MW f −1 m ˙ OC circulation rate of fully oxidized oxygen carrier, kg-oxygen carrier, sec −1  MW f −1 m ox mass of the fully oxidized form of metal oxides, kg kg-mol −1 m red mass of the fully reduced form of metal oxides, kg kg-mol −1 M O atomic weight of oxygen, 16 g mol −1 N CO 2 number of moles of CO 2 N CO number of moles of CO N H 2 O number of moles of H 2 O N H 2 number of moles of H 2 N inlet, i the moles of component i in inlet gas N outlet, j the moles of component j in outlet gas R O oxygen-transport capacity of the pure metal oxide, kg-oxygen kg-metal oxide −1 R OC oxygen-transport capacity of the oxygen carrier, kg-oxygen kg-oxygen carrier −1 S CO 2 CO 2 selectivity S H 2 O H 2 O selectivity S cross-sectional area of the riser per MW f , m 2  MW f −1 x MeO metal oxide content ΔX S variation of the solid conversion in the fuel reactor Δ H C o standard heat of combustion of methane, 802.3 kJ mol −1

Keywords

  • CO capture
  • Chemical looping
  • Hydrogen
  • Methane
  • Oxygen carrier

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Fuel Technology
  • Condensed Matter Physics
  • Energy Engineering and Power Technology

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