Manganese/Iron, Manganese/Nickel, and Manganese/Silicon Oxides Used in Chemical-Looping With Oxygen Uncoupling (CLOU) for Combustion of Methane

Abstract

Chemical-looping with oxygen uncoupling (CLOU) is a developing technology, which allows for inherent separation of carbon dioxide during combustion of gaseous and solid fuels. In contrast to the related chemical-looping combustion technology (CLC), where gaseous or gasified fuels react directly with oxygen carrier materials, CLOU utilizes oxygen carriers capable of releasing gaseous oxygen, provided appropriate thermal conditions exist in the fuel reactor, whereupon fuel reacts with the released oxygen. The oxygen carriers are thereafter regenerated by oxidation in the air reactor. In this work, a set of oxygen carrier materials synthesized from manganese oxides mixed with iron, nickel, and silicon oxides are evaluated in terms of their ability to release oxygen and to be regenerated with oxygen and in terms of demonstrated methane conversion in a quartz fluidized bed batch reactor at 810, 850, and 900 °C. The results demonstrate that two Mn/Fe oxygen carriers and one Mn/Ni oxygen carrier have both oxygen release characteristics and high reactivities with methane. The Mn/Fe oxygen carrier synthesized at 1100 °C was additionally shown to have an increasing methane conversion on a long-term basis, which opens for a possibility to use Mn/Fe oxygen carriers in time-extended large-scale chemical-looping operations.

Combined oxides as oxygen-carrier material for chemical-looping with oxygen uncoupling

“…It can be seen that [13], and Ksepko et al [14]. Studies [8][9][10][11][12] are all in good agreement with the reasoning presented above. In particular the study by Azimi et al [8] which was conducted according to the principles proposed in this paper using (Mn 0.8 Fe 0.2 )O x as oxygen carrier, showed very fast O 2 uncoupling and rapid oxidation of both methane and wood char already at 850°C.…”

“…In fact, such oxides have already been proven to be capable of releasing considerable amounts of gas phase O 2 , see Azimi et al [8,9,10], Rydén et al [11] and Shulman et al [12]. This family of materials is believed to be resistant towards fuel impurities such as sulfur and could also be manufactured from cheap and relatively harmless raw materials.…”

Identification of operational regions in the Chemical-Looping with Oxygen Uncoupling (CLOU) process with a Cu-based oxygen carrier

“…There are only a small number of materials proposed in the literature dealing with the use of Cu- [16][17][18]20,21], and Mn-based [22][23][24][25][26] based materials for CLOU process. An overview of the characteristics of these materials can be found in [9,20,21].…”

“…In the research group at Chalmers University of Technology, 20 different CLOU materials were tested in batch fluidized bed for combustion of gaseous (CH 4 ) or solid fuels [13,15,17,[22][23]25]. Good results were obtained using an oxygen carrier based on CuO and ZrO 2 as support [13,17].…”

“…Cyclic testing with solid fuels in the temperature range of 880-985 ºC verified a very rapid release of oxygen and combustion of fuel started with a high conversion rate. Regarding the use of manganese oxides for CLOU process, Shulman et al [22] analyzed the CLOU properties of different Mnbased materials combined with Fe 2 O 3 , NiO or SiO 2 prepared by freeze granulation. They found that some Mn/Fe oxygen carriers showed very high reactivity towards methane.…”