Extremely Stable and Durable Mixed Fe–Mn Oxides Supported on ZrO2 for Practical Utilization in CLOU and CLC Processes

Ewelina Ksepko,Rafal Lysowski

doi:10.3390/catal11111285

Abstract

This paper contains the results of research on a promising combustion technology known as chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU). The remarkable advantages of CLC are, among others, that concentrated CO2 stream can be obtained after water condensation without any energy penalty for its separation or significant decrease of NOx emissions. The objective of this work was to prepare a novel bi-metallic Fe–Mn supported on ZrO2 oxygen carriers. Performance of these carriers for the CLOU and CLC process with nitrogen/air and hard coal/air was evaluated. One-cycle CLC tests were conducted with supported Fe–Mn oxygen carriers in thermogravimetric analyzer utilizing hard coal as a fuel. The effects of the oxygen carrier chemical composition and process temperature on the reaction rates were determined. Our study proved that for CLOU, properties formation of bixbyite and spinel forms are responsible. Among iron ferrites, we concluded that iron-rich compounds such as Fe2MnO4 over FeMn2O4 spinel type oxides are more effective for CLOU applications.

Highlights

Due to increased demand on electrical energy combined with the necessity of the reduction of greenhouse gases emissions, new energy production methods need to be developed
Oxidation of fuel may take place due to: (1) the releasing of gaseous oxygen from oxygen carrier (OC), in so-called CLOU—chemical looping with oxygen uncoupling; (2) due to direct reaction between OC and fuel, in so called CLC—chemical looping combustion; or (3) as a result of reaction of gaseous products coming from preliminary gasification of solid fuel particles and OC [4]
Since fuel in the CLC process is separated from atmospheric air, this is the reason for restricting the production of nitrogen oxides which are usually formed during the conventional combustion process

Summary

Introduction

Due to increased demand on electrical energy combined with the necessity of the reduction of greenhouse gases emissions, new energy production methods need to be developed. CLC (chemical looping combustion) is a new, promising technology for fuel combustion that allows to burn a wide range of fuels such as: gaseous (e.g., hydrogen, methane, syngas), liquid (hydrocarbons including heavy oils), and solid (coal, biomass) with significantly reduced emissions of pollutants as carbon dioxide or nitrogen oxides [1,2,3]. In the CLC process, a system of two reactors is used. Since fuel in the CLC process is separated from atmospheric air, this is the reason for restricting the production of nitrogen oxides which are usually formed during the conventional combustion process. Assuming that the combustion process occurs only in the presence of oxygen, similar to combusting fuels in pure oxygen (Oxy-combustion), the final products from the fuel reactor will be both carbon dioxide and steam.

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Conclusion