Manganese ores as oxygen carriers for chemical-looping combustion
Doktorsavhandling, 2017

Chemical looping combustion (CLC) is a fluidized bed system that circulates metal oxide particles in order to transport oxygen from an air reactor to a fuel reactor. In the fuel reactor a fuel reduces the oxygen carrier while producing CO2 and H2O. The oxygen carrier is then transported back to the air reactor and reoxidized. Chemical looping with oxygen uncoupling (CLOU) is similar to CLC, however the oxygen carrier differ as it has the ability to release gaseous oxygen in the fuel reactor. The advantage is that the oxygen released can react with the fuel directly, without the need for an intermediate gasification step. Mainly oxide from Mn, Fe, Ni and Cu has been investigated as oxygen carrier. Of these, manganese oxides could be of interest for CLOU due to the ability to release O2, especially when combined with other metals or metal oxides. Most of the investigated oxygen carriers are produced using various production methods, which could be costly. Another option is to use natural Mn-based minerals, such as manganese ores, which often contains the same elements as used to promote the CLOU effect, e.g. Fe, Si, Ca and Mg. This thesis is a comprehensive study of manganese ore as oxygen carrier for CLC and CLOU. Here, twenty manganese ores have been investigated as potential oxygen carriers. They are evaluated with respect to reactivity with gaseous fuels CO/H2 and CH4 as well as their ability to release gaseous oxygen via oxygen uncoupling. Experiments were conducted with both batch and continuous CLC reactors. From the experiments in this thesis it was found that all manganese ore release oxygen to varying degree, which suggests the presence of combined manganese oxides in the ores, something which was confirmed through particle and phase analysis. By utilizing solid char the extent and rates of oxygen release were determined for several ores at varying temperatures. It was found that most oxygen was released by Ca-rich ores, where up to 1 wt% oxygen could actually be released at higher temperatures. The reactivity with fuel components and the mechanical stability varied depending on the ore utilized. Elemental mapping of individual particles indicate a significant inter-particle heterogeneity, while the intra-particle distribution was more even. Combination of XRD and SEM-EDX confirms a complex mineralogy with the presence of multiple phases which could be involved in CLC and CLOU, including (Mn,Fe)2O3, Mn7SiO12 and CaMnO3. The presence of these phases explains the CLOU effect that has been observed.

Chemical-looping with oxygen uncoupling

gaseous fuel

methane

syngas

Chemical-looping combustion

manganese ores

combined oxides

wood char and solid fuels

HA3
Opponent: Zhenshan Li, Tshinghua University, China

Författare

Sebastian Sundqvist

Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi

Screening of different manganese ores for chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU)

International Journal of Greenhouse Gas Control,; Vol. 43(2015)p. 179-188

Artikel i vetenskaplig tidskrift

Manganese ores as oxygen carriers for chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU)

Journal of Environmental Chemical Engineering,; Vol. 5(2017)p. 2552-2563

Artikel i övriga tidskrifter

Sundqvist, S. Mattisson, T. Leion, H. Lyngfelt, A. The use of manganese ores for chemical-looping with oxygen uncoupling.

Moldenhauer, P. Sundqvist, S. Mattisson, T. Linderholm, C. Chemical-Looping Combustion of Synthetic Biomass-Volatiles with Manganese-Ore Oxygen Carriers.

Sundqvist, S. Moldenhauer, P. Leion, H. Lyngfelt, A. Mattisson, T. Influence of heat treatment on manganese ores as oxygen carriers.

Today, there is a need for rapid and substantial decrease in emissions of carbon dioxide to the atmosphere, especially from the combustion of fossil fuels. This is needed in order to combat climate change and stabilize the surface temperature increase to below 2°C. This is a challenge, as there is a rapid economic development in many populated areas, combined with a dominating use of fossil fuels for energy conversion. Thus, our dependence on fossil fuels cannot continue if we are to avoid serious climate change. There are several options available, such as increasing the efficiency of power production, energy utilization, and switching to renewable source, such as wind and solar, conversional alternatives with no or small emissions. However, while these are important parts of the solution, these methods alone will most likely not be enough to achieve emission reductions needed for the 2°C target. . Another option, which is the basis of this thesis, is carbon capture and storage (CCS).

In carbon capture and storage (CCS), the carbon dioxide (CO2) is captured from big point emission sources, such as power plants, and then stored in the ground for significant periods of time. This would prevent the emission of greenhouse gases to the atmosphere and still make it possible to use fossil fuel while at the same time switching to a more sustainable way of converting energy.

One method of capturing the CO2 is chemical looping combustion (CLC) which is a combustion process which splits the reaction in two parts, each one taking place in a different chamber. The combustion of fuel takes place in the fuel chamber where an oxygen carrier supplies the oxygen to the fuel, in the absence of air. The oxygen carrier is normally a metal oxide, which takes up oxygen from the air in the other chamber, the so called air reactor. The metal oxide is then transported back to the fuel chamber where the oxygen can take part in the combustion reaction again. The overall heat release over the system is the same as for normal combustion, but the advantage is that CO2 and H2O is obtained in pure form, without the need for any gas separation step. This is one benefit with CLC compared with other methods of CCS, which all requires some sort of gas separation, and such separation always has an energy penalty associated with it. The penalty can be as high as 30% of the power produced, which would drastically increase the cost of electricity or heat

One big difference between other CCS technologies and CLC is of course the use of a metal oxide as an oxygen carrier. This is one of the key aspect of the process, and it is important to find cheap and functional oxygen carrier materials. This thesis will presents a comprehensive work on natural manganese ore as oxygen carriers in CLC. Such natural minerals have the benefit of being readily available at low to moderate cost. Manganese ores are especially interesting, as they often contain active phases which have been found to be very reactive for fuel combustion, and this is the topic of this thesis.

Ämneskategorier

Oorganisk kemi

Kemiska processer

ISBN

978-91-7597-633-4

Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4314

Utgivare

Chalmers tekniska högskola

HA3

Opponent: Zhenshan Li, Tshinghua University, China

Mer information

Skapat

2017-09-04