(140b) Characterization of Ilmenite As Oxygen Carrier during Chemical Looping Combustion and Reforming
- Conference: AIChE Annual Meeting
- Year: 2016
- Proceeding: 2016 AIChE Annual Meeting
- Group: Innovations of Green Process Engineering for Sustainable Energy and Environment
- Time: Monday, November 14, 2016 - 12:51pm-1:13pm
<span" roman"="Roman"" new="New">CH4Â + 4MexOyÂ â?? CO2 + 2H2O + 4MexOy-1(1)
<span" roman"="Roman"" new="New">CH4Â + MexOyÂ â?? CO + 2H2 + MexOy-1(2)
<span" roman"="Roman"" new="New">MexOy-1 + 1/2O2Â â?? MexOy(3)
<span" roman"="Roman"" new="New"> CanmetENERGY has two on-going research programs on CLP, one is pressurized chemical looping combustion (PCLC) for the production of power and steam, the other one is pressurized chemical looping reforming (PCLR) for hydrogen production. High reactivity and proper flow behaviour of the oxygen carrier are crucial in developing both PCLC and PCLR technologies. Among all the low-cost materials including ores and industrial residues, ilmenite, a nature-occurring mineral material, has been paid much more attentions for their potential in CLP due to its desired thermodynamical properties resulting in 100 % theoretical combustion efficiency. Crushed ilmenite ore, henceforth referred to as ilmenite, is considered a leading candidate for oxygen carrying in CanmetENERGYâ??s pressurized chemical looping (PCL) processes since it is relatively inexpensive and possesses good physical attributes. However, as an iron-based oxygen carrier, the reactivity of ilmenite is lower than Mn-, Co-, Ni- and Cu-based ones. Lower reactivity will result in large bed inventory (8-10 times that required for the synthetic Fe-based oxygen carriers) and high pressure drop when used in CFB, and unconverted gas fuels in the outflow of fuel reactor. In addition, there is evidence of attrition, sintering and agglomeration of ilmenite in certain CLP conditions, which negatively impact its reactivity and operating behaviour. This study focuses on introducing nonporous (or mesoporous) dopants of CeO2, ZrO2, NiO or Al2O3into the ilmenite (mainly immobilized on their surface) to improve the reactivity of the ilmenite-based OCs towards methane combustion and reforming. On the other hand, when mesoporous dopants are employed, the agglomeration of ilmenite particles could be eased.
<span" roman"="Roman"" new="New"> A pressurized thermogravimetric analyzer (PTGA) and a pressurized fixed-bed reactor (PFBR) are used for testing the doped ilmenite particles at various temperatures (850-1050°C), gas compositions, pressures, and cycle stages. These particles are then analyzed by X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX). The results from the measurements and discussion on the OC performance are outlined in this paper.