Kinetics of solid reactions with gas intermediates in chemical looping combustion

Abstract

• Reaction route of the CLC reactions with gas intermediates were identified. • The effect of solid particle size ranges was analyzed. • The sensitivity of reaction temperature was determined. • The kinetics models could be used in the solid reactions with gas intermediates. Chemical looping combustion (CLC) is an advanced technology for converting solid fuel with in-situ CO 2 capture in a low-cost and sustainable way. However, unlike gaseous fuel, the CLC process of solid fuel is lack of the reaction understanding between fuel particles and OC particles (solid-to-solid), and this result directly influences the design of the reactor. In this context, the study focused on the solid reactions with gas intermediates taking place in the CLC reactor. Well-mixed solid particles of the coal char and the hematite were investigated on the thermogravimetric and mass spectrometry (TG-MS) system. The effects of different particle size ranges and different reaction temperatures were determined. The kinetics on this kind of solid reactions was calculated and discussed. The result showed that the carbon gasification was identified as the control step in reactions. The diffusional resistance of 45–75 µm char particles could be ignored. Two models of kinetic reactions were developed based on the contracting sphere rate law and the first order rate law. The Activation Energy E a of the surface reaction model and the first order reaction model was 208.75 kJ/mol and 224.75 kJ/mol, respectively. Overall, the experiments and the kinetic models carried out in the present work improved the reaction understanding on the field of the solid reactions with gas intermediates in CLC.