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- Keller, Martin, 1985, et al.
(author)
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Chemical Looping Tar reforming with Fe,Sr-doped La2Zr2O7 pyrochlore supported on ZrO2
- 2018
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In: Applied Catalysis A: General. - : Elsevier BV. - 1873-3875 .- 0926-860X. ; 550, s. 105-112
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Journal article (peer-reviewed)abstract
- Chemical Looping Reforming (CLR) has been proposed as a new technology for tar removal from hot raw gas derived from biomass gasification. In this two-reactor fluidized bed process at atmospheric pressure, the bed material is circulating between a reformer, in which the bed material is in contact with the raw synthesis gas, and a regenerator, in which the bed material is regenerated by oxidizing coke deposits and sulfides with air. In this study Fe,Sr-doped La 2 Zr 2 O 7 pyrochlores supported on ZrO 2 with different Fe and Sr loadings were investigated for their use as a catalyst in CLR. By decreasing the Fe loading to Fe/La = 0.25 the benzene-to-syngas conversion could be improved by about 50% at T = 800 °C in comparison with the reference material with Fe/La = 1.25. With this material, benzene and ethylene conversion could be further improved by co-feeding O 2 with the gasification gas, achieving a benzene conversion of up to 80% and an ethylene conversion of about 95% at a temperature of 850 °C and a Gas Hourly Space Velocity of 6800 h −1 . The performance of the bed material was found stable over at least 3 redox cycles. Considering the expected lower costs and non-toxicity of this material compared to precious metal- and Nickel-containing catalysts, normally used in fixed-bed systems, it is a promising material for a fluidized CLR system for tar removal.
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| 2. |
- Mattisson, Tobias, 1970, et al.
(author)
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Chemical-looping technologies using circulating fluidized bed systems: Status of development
- 2018
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In: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 172, s. 1-12
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Research review (peer-reviewed)abstract
- In chemical-looping combustion (CLC), an oxygen carrier provides lattice oxygen for complete combustion of a fuel for heat and power production. The reduced metal oxide is then oxidized in a separate reactor. The combustion products CO 2 and H 2 O are obtained in pure form, without any nitrogen in the gas. As no gas separation work is needed, this could be a breakthrough technology for carbon capture (CCS). Normally, the fuel- and air-reactor are designed utilizing inter-connected fluidized beds. The same underlying reversible redox reactions of CLC can be used for other fuel conversion technologies. These include fluidized bed processes for gas, solid and liquid fuels for heat, power, syngas or hydrogen production. Some of these concepts were suggested as far back as the 1950's, while others have just recently been proposed. This paper will provide a review of some recent developments with respect to CLC with gaseous, liquid and solid fuels, with focus on operational experience. Today, more than 35 continuous units have been used worldwide, with over 9000 h of operational time. Although most experience has been reported for methane and natural gas, significant testing has now also been performed with various solid fuels. Some recent developments include i) shift from Ni-based materials to more benign metal oxide oxygen carriers, ii) use of different types of biomass and iii) operation at semi-commercial scale. Furthermore, this paper will also provide an overview some related technologies which also utilize oxygen carriers in interconnected fluidized beds: i) Chemical-looping gasification (CLG), ii) Chemical-looping reforming (CLR) and iii) Chemical-looping tar reforming (CLTR). In these processes, a pure syngas/hydrogen can be produced effectively, which could be utilized for chemical or fuel production.
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