Utilization of ventilation air methane as an oxidizing agent in chemical looping combustion Yongxing Zhang a , Elham Doroodchi b , Behdad Moghtaderi a,⇑ a Priority Research Centre for Energy, Faculty of Engineering & Built Environment, The University of Newcastle, Australia b Priority Research Centre for Advanced Particle Processing & Transport, Chemical Engineering, School of Engineering, Faculty of Engineering & Built Environment, The University of Newcastle, Australia article info Article history: Available online xxxx Keywords: Ventilation air methane Chemical looping combustion Fe 2 O 3 /Al 2 O 3 Fixed bed reactor abstract Release of fugitive methane (CH 4 ) emissions from ventilation air in coal mines is a major source of greenhouse gas (GHG) emissions. Approximately 64% of methane emissions in coal mine operations are the result of VAM (i.e. ventilation air methane) which is difficult for use as a source of energy. A novel ancillary utilization of VAM was thereby proposed. In this proposal, the VAM was utilized instead of air as a feedstock to a chemical looping combustion (CLC) process of coal. In this case, Fe 2 O 3 /Fe 3 O 4 particles were shuttled between two interconnected reactors for combustion of syngas produced by an imbedded coal gasifier. The effect of VAM flow rate and methane concentration on the performance of CLC was analyzed ther- modynamically using Aspen Plus software. Results indicated that the variations of air reactor tempera- ture with VAM flow rate and methane concentration can be minimized as expected. The effect of temperature and inlet methane concentration on the conversion of CH 4 was examined experimentally in a fixed bed reactor with the presence of particles of Fe 2 O 3 /Al 2 O 3 . Not surprisingly, the reaction temper- ature put a significant influence on the conversion of CH 4 . The conversion started at the temperature about 300 °C and the temperature to achieve full conversion was around 500 °C while the temperature in empty reactor between 665 °C and 840 °C. This is due to the catalytic effect of oxygen carriers (i.e. Fe 2 O 3 /Al 2 O 3 ) on the conversion of methane. Moreover, it was observed that the methane conversion rate decreased with the increase in inlet methane concentration while increasing with Fe 2 O 3 loading content. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction CH 4 is the third most important greenhouse gas after H 2 O vapor and carbon dioxide (CO 2 ) and has a Global Warming Potential (GWP) 25 times that of CO 2 on a 100-year timescale. The release of fugitive methane (CH 4 ) from coal mines is the major source of GHG emissions, accounting for 8% of the total anthropogenic meth- ane emissions. Typically it is emitted from a coal mine in the form of ventilation air methane (VAM) (0.1–1 vol% CH 4 ) or coal seam gas (30–95 vol% CH 4 ) [1]. Approximately 64% of methane emissions in coal mines are the result of VAM which is found to be difficult to mitigate primarily because (1) the methane concentration in the mixture is dilute and (2) the concentration and flow rate of meth- ane is variable. Several methods have been developed to mitigate the emissions of VAM, which can be categorized into principle use and ancillary use. The principle utilization technology is referred to the use of methane in VAM as the energy source and no need for additional fuel in assistance to the ignition of methane. In terms of the reac- tion kinetic mechanism, the existing principle utilization technolo- gies for mitigation of VAM in mining operations can be classified into thermal oxidation and catalytic combustion [1]. The only dif- ference between these two processes is with respect to the use of catalyst. Based on the thermal oxidation principle, a thermal flow- reversal reactor (TFRR) was offered by MEGTEC. But it suffers from an extremely high auto-ignition temperature (above 1000 °C) which causes plenty of energy loss to start the operation [2]. It is also a great challenge to maintain such a high temperature level for a long term run as far as the huge flow rate is concerned. To lower the start temperature, a catalytic flow-reversal reactor (CFRR) was developed by CANMET. As a result of this new technol- ogy, the auto-ignition temperature is decreased by several hundred degrees Celsius [2]. Although the CFRR delivers some advantages over the TFRR, it comes up with some challenges on the design and operation. For instance, it needs to consume some expensive metals or metal oxides as catalyst like Pd, Pt, Rh or PdO [3–6]. Also its reactor design is more complicated in order to get enough con- tact surfaces. The performance of CFRR can be improved using the design of catalytic monolith reactor (CMR) developed by CSIRO, 0196-8904/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.enconman.2014.01.005 ⇑ Corresponding author. Tel.: +61 2 49854411; fax: +61 2 49216893. E-mail address: Behdad.Moghtaderi@newcastle.edu.au (B. Moghtaderi). Energy Conversion and Management xxx (2014) xxx–xxx Contents lists available at ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman Please cite this article in press as: Zhang Y et al. Utilization of ventilation air methane as an oxidizing agent in chemical looping combustion. Energy Con- vers Manage (2014), http://dx.doi.org/10.1016/j.enconman.2014.01.005