Chemical-looping with oxygen uncoupling for combustion of solid fuels

Abstract Chemical-looping with oxygen uncoupling (CLOU) is a novel method to burn solid fuels in gas-phase oxygen without the need for an energy intensive air separation unit. The carbon dioxide from the combustion is inherently separated from the rest of the flue gases. CLOU is based on chemical-looping combustion (CLC) and involves three steps in two reactors, one air reactor where a metal oxide captures oxygen from the combustion air (step 1), and a fuel reactor where the metal oxide releases oxygen in the gas-phase (step 2) and where this gas-phase oxygen reacts with a fuel (step 3). In other proposed schemes for using chemical-looping combustion of solid fuels there is a need for an intermediate gasification step of the char with steam or carbon dioxide to form reactive gaseous compounds which then react with the oxygen carrier particles. The gasification of char with H 2 O and CO 2 is inherently slow, resulting in slow overall rates of reaction. This slow gasification is avoided in the proposed process, since there is no intermediate gasification step needed and the char reacts directly with gas-phase oxygen. The process demands an oxygen carrier which has the ability to react with the oxygen in the combustion air in the air reactor but which decomposes to a reduced metal oxide and gas-phase oxygen in the fuel reactor. Three metal oxide systems with suitable thermodynamic properties have been identified, and a thermal analysis has shown that Mn 2 O 3 /Mn 3 O 4 and CuO/Cu 2 O have suitable thermodynamic properties, although Co 3 O 4 /CoO may also be a possibility. However, the latter system has the disadvantage of an overall endothermic reaction in the fuel reactor. Results from batch laboratory fluidized bed tests with CuO and a gaseous and solid fuel are presented. The reaction rate of petroleum coke is approximately a factor 50 higher using CLOU in comparison to the reaction rate of the same fuel with an iron-based oxygen carrier in normal CLC.

[1]  Hongguang Jin,et al.  A Novel Combustor Based on Chemical-Looping Reactions and Its Reaction Kinetics , 1994 .

[2]  Stuart A. Scott,et al.  In situ gasification of coal using steam with chemical looping: a technique for isolating CO2 from burning a solid fuel , 2006 .

[3]  Anders Lyngfelt,et al.  CO2 Capture from Coal Combustion Using Chemical-Looping Combustion - Reactivity Investigation of Fe, Ni and Mn Based Oxygen Carriers Using Syngas , 2006 .

[4]  Anders Lyngfelt,et al.  Comparison of Oxygen Carriers for Chemical-Looping Combustion Using Methane-Rich Fuels , 2005 .

[5]  A. Abad,et al.  Chemical Looping Combustion in a 10 kWth Prototype Using a CuO/Al2O3 Oxygen Carrier: Effect of Operating Conditions on Methane Combustion , 2006 .

[6]  Anders Lyngfelt,et al.  Chemical-looping combustion in a 300 W continuously operating reactor system using a manganese-based oxygen carrier , 2006 .

[7]  Marcus Johansson.  Screening of oxygen-carrier particles based on iron-, manganese-, copper- and nickel oxides for use in chemical-looping technologies , 2007 .

[8]  Jerald A. Cole,et al.  Unmixed combustion: an alternative to fire , 2000 .

[9]  A. Lyngfelt,et al.  Comparison of iron-, nickel-, copper- and manganese-based oxygen carriers for chemical-looping combustion , 2004 .

[10]  Jens Wolf,et al.  Comparison of nickel- and iron-based oxygen carriers in chemical looping combustion for CO2 capture in power generation , 2005 .

[11]  Anders Lyngfelt,et al.  Design and Operation of a 10 kWth Chemical-Looping Combustor for Solid Fuels - Testing with South African Coal , 2008 .

[12]  Juan Adánez,et al.  Reduction Kinetics of Cu-, Ni-, and Fe-Based Oxygen Carriers Using Syngas (CO + H2) for Chemical-Looping Combustion , 2007 .

[13]  M. Johansson,et al.  Chemical-looping combustion as a new CO2 management technology , 2006 .

[14]  Stuart A. Scott,et al.  In situ gasification of a solid fuel and CO2 separation using chemical looping , 2006 .

[15]  A. Lyngfelt,et al.  A fluidized-bed combustion process with inherent CO2 separation; Application of chemical-looping combustion , 2001 .

[16]  A. Lyngfelt,et al.  Construction and 100 h of operational experience of a 10-kW chemical looping combustor , 2005 .

[17]  Anders Lyngfelt,et al.  The use of petroleum coke as fuel in a 10 kWth chemical-looping combustor , 2008 .

[18]  A. Lyngfelt,et al.  A 300 W laboratory reactor system for chemical-looping combustion with particle circulation , 2006 .

[19]  A. Abad,et al.  Selection of Oxygen Carriers for Chemical-Looping Combustion , 2004 .

[20]  Anders Lyngfelt,et al.  160 hours of chemical-looping combustion in a 10 kW reactor system with a NiO-based oxygen carrier , 2008 .

[21]  A. Lyngfelt,et al.  Combustion of Syngas and Natural Gas in a 300 W Chemical-Looping Combustor , 2006 .

[22]  Anders Lyngfelt,et al.  The use of petroleum coke as fuel in chemical-looping combustion , 2007 .

[23]  M. Anheden,et al.  Chemical-looping combustion -- Efficient conversion of chemical energy in fuels into work , 1995 .

[24]  Anders Lyngfelt,et al.  Solid fuels in chemical-looping combustion , 2008 .

[25]  M. Johansson,et al.  The use of iron oxide as oxygen carrier in a chemical-looping reactor , 2007 .

[26]  K. Heek,et al.  Chemical Kinetics of Carbon and Char Gasification , 1991 .