Chemical Looping Combustion Technology Research Articles

Studies on the redox reaction kinetics of selected, naturally occurring oxygen carrier

This paper presents the results of a chemical-looping combustion (CLC) study. The CLC technology is believed to be one of the most promising combustion technologies. The production of a concentrated CO2 stream that is obtained after the water condensation without any loss of energy in its separation is one of the most crucial advantages of this technology. The objective of this work was to study the kinetics of both the reduction and oxidation reactions for naturally occurring oxygen carriers that show promising reactivity in CLC reactions, and might therefore be utilized as oxygen carrier materials. Kryvbas, a Fe-based ore, was selected for this analysis because it possessed sufficient concentrations of the active metal oxides (Fe oxide above 80 % and traces of Mn oxide) and a high melting temperature that was above 1500 °C. Experiments were conducted under isothermal conditions within the temperature range of 750–950 °C with multiple redox cycles using a thermogravimetric analyzer (TG). For the reduction and oxidation reactions, CH4 (at different concentrations) and air were used, respectively. The sample showed promising results where a sufficient reactivity was observed with the fuel, and these results were reproducible. Both fresh material and samples that were used in multiple redox cycles were characterized by X–ray Diffraction (XRD) and Scanning Electron Microscopy combined with X–ray Microanalysis (SEM–EDS) in order to detect any structural or morphological changes as well as to determine the stability of the ore in repetitive CLC cycles. Kinetic parameters, such as the activation energy, the preexponential factor, and the reaction model, were determined for the redox reactions. Models of the redox reactions were selected by using a model fitting method. The F1 model (volumetric) was a suitable model for the modeling of the Kryvbas ore reduction reaction kinetics. The calculated E a was equal to 42.00 kJ mol−1, while the reaction order was determined to be equal to 1.98. The best fit for the oxidation reaction was obtained for the R3 model (shrinking core model). The oxidation (regeneration) reaction activation energy was equal to 16.70 kJ mol−1, and the reaction order was determined to be equal to approximately 0.49.

A comparative simulation study of power generation plants involving chemical looping combustion systems

This work presents a simulation study on both energy and economics of power generation plants with inherent CO2 capture based on chemical looping combustion technologies. Combustion systems considered include a conventional chemical looping system and two extended three-reactor alternatives (exCLC and CLC3) for simultaneous hydrogen production. The power generation cycles include a combined cycle with steam injected gas turbines, a humid air turbine cycle and a simple steam cycle. Two oxygen carriers are considered in our study, iron and nickel. We further analyze the effect of the pressure reaction and the turbine inlet temperature on the plant efficiency. Results show that plant efficiencies as high as 54% are achieved by the chemical looping based systems with competitive costs. That value is well above the efficiency of 46% obtained by a conventional natural gas combined cycle system under the same conditions and simulation assumptions.

Integrated petroleum coke and natural gas polygeneration process with zero carbon emissions

In the present work, a new polygeneration system is developed that uses petcoke and natural gas as feedstocks and coproduces different products such as chemicals, olefins, electricity and transportation fuels. Furthermore, by incorporation of chemical looping combustion and chemical looping gasification technologies, 100% of CO2 emissions are captured effectively. The particle swarm optimization technique is implemented with Aspen Plus models to determine the optimum product portfolio at different market conditions. Techno-economic optimization results show that this plant can be profitable for a broad range of petcoke consumption (up to 74%) and various feeds and products price changes.

Comparison of carbon capture IGCC with chemical-looping combustion and with calcium-looping process driven by coal for power generation

Three types of coal based integrated gasification combined cycle (IGCC) systems with CO2 capture using physical absorption, chemical looping combustion (CLC), and calcium looping process (CLP) for power generation are modeled using Aspen Plus. The effects of key variables on the thermodynamic performance, such as the energy efficiency and the exergy efficiency, are investigated separately. The process variables examined are mainly in the gasification unit, they are steam to coal mass ratio (S/C) in the range of 0–20% and oxygen to coal mass ratio (O/C) in the range of 70–105%. The performances of the above three capture technologies are compared with respect to their energy and exergy efficiencies. An IGCC plant without carbon capture is also considered as a benchmark to quantify the efficiencies. The results show that the CLC technology has an energy efficiency of 39.78%, which is 2.06% and 3.57% higher than the CLP and physical absorption-based technologies, respectively. Additionally, the CLC technology has an exergy efficiency of 35.67%, in contrast to 33.86% for CLP and 32.74% for physical absorption technology. Furthermore, the economic evaluations are performed for estimation of capital cost, net present value (NPV), internal rate of return (IRR) and other economic values.

Energy and exergy analysis of chemical looping combustion technology and comparison with pre-combustion and oxy-fuel combustion technologies for CO2 capture

Carbon dioxide (CO2) emitted from conventional coal-based power plants is a growing concern for the environment. Chemical looping combustion (CLC), pre-combustion and oxy-fuel combustion are promising CO2 capture technologies which allow clean electricity generation from coal in an integrated gasification combined cycle (IGCC) power plant. This work compares the characteristics of the above three capture technologies to those of a conventional IGCC plant without CO2 capture. CLC technology is also investigated for two different process configurations—(i) an integrated gasification combined cycle coupled with chemical looping combustion (IGCC–CLC), and (ii) coal direct chemical looping combustion (CDCLC)—using exergy analysis to exploit the complete potential of CLC. Power output, net electrical efficiency and CO2 capture efficiency are the key parameters investigated for the assessment. Flowsheet models of five different types of IGCC power plants, (four with and one without CO2 capture), were developed in the Aspen plus simulation package. The results indicate that with respect to conventional IGCC power plant, IGCC–CLC exhibited an energy penalty of 4.5%, compared with 7.1% and 9.1% for pre-combustion and oxy-fuel combustion technologies, respectively. IGCC–CLC and oxy-fuel combustion technologies achieved an overall CO2 capture rate of ∼100% whereas pre-combustion technology could capture ∼94.8%. Modification of IGCC–CLC into CDCLC tends to increase the net electrical efficiency by 4.7% while maintaining 100% CO2 capture rate. A detailed exergy analysis performed on the two CLC process configurations (IGCC–CLC and CDCLC) and conventional IGCC process demonstrates that CLC technology can be thermodynamically as efficient as a conventional IGCC process.

Evaluation of a Mixed Fe–Mn Oxide System for Chemical Looping Combustion

In coal-based chemical looping combustion (CLC) technology, relatively cheap metal oxides, referred to as oxygen carrier materials (OCMs), are required because some of the OCMs will be removed together with the residual ashes after combustion. CLC technology will have an estimated loss in efficiency of around 2% compared to standard combustion technology without capture if a proper OCM is found that can give full combustion, removing the need of an air separation unit (ASU). Materials with a chemical looping oxygen uncoupling (CLOU) effect will even give further benefits in faster gasification and combustion of the fuel. One can already find produced materials that can give such a desirable effect, but fabrication and material cost are still an issue in these cases. If such a material can be delivered by the mining industry, cost savings and plant efficiency will be high. Before selection of the natural minerals with strong inert inherent support that contain Fe and Mn, the need for a better understanding...

A systematic investigation of the performance of copper-, cobalt-, iron-, manganese- and nickel-based oxygen carriers for chemical looping combustion technology through simulation models

The Integrated Gasification Combined Cycle coupled with chemical looping combustion (IGCC-CLC) is one of the most promising technologies that allow generation of cleaner energy from coal by capturing carbon dioxide (CO2). It is essential to compare and evaluate the performances of various oxygen carriers (OC), used in the CLC system; these are crucial for the success of IGCC-CLC technology. Research on OCs has hitherto been restricted to small laboratory and pilot scale experiments. It is therefore necessary to examine the performance of OCs in large-scale systems with more extensive analysis. This study compares the performance of five different OCs – copper, cobalt, iron, manganese and nickel oxides – for large-scale (350–400MW) IGCC-CLC processes through simulation studies. Further, the effect of three different process configurations: (i) water-cooling, (ii) air-cooling and (iii) air-cooling along with air separation unit (ASU) integration of the CLC air reactor, on the power output of IGCC-CLC processes – are also investigated. The simulation results suggest that iron-based OCs, with 34.3% net electrical efficiency and ~100% CO2 capture rate lead to the most efficient process among all the five studied OCs. A net electrical efficiency penalty of 7.1–8.1% points leads to the IGCC-CLC process being more efficient than amine based post-combustion capture technology and equally efficient to the solvent based pre-combustion capture technology. The net electrical efficiency of the IGCC-CLC process increased by 0.6–2.1% with the use of air-cooling and ASU integration, compared with the water- and air-cooling cases. This work successfully demonstrates a correlation between the reaction enthalpies of different OCs and power output, which suggests that the OCs with higher values of reaction enthalpy for oxidation (ΔHr, oxidation) with air-cooling are more valuable for the IGCC-CLC.

Capture of CO2 from coal using chemical-looping combustion: Process simulation

Coal direct chemical-looping combustion (CLC) and coal gasification CLC processes are the two basic approaches for the application of the CLC technology with coal. Two different combined cycles with the overall thermal input of 1,000MW (LHV) were proposed and simulated, respectively, with NiO/NiAl2O4 as an oxygen carrier using the ASPEN software. The oxygen carrier circulation ratio in two CLC processes was calculated, and the influence of the CLC process parameters on the system performance such as air reactor temperature and the turbine inlet supplementary firing temperature was investigated. Results found were that the circulation ratio of the oxygen carrier in the coal gasification CLC process is smaller than that in the coal direct CLC process. In the coal direct CLC combined system, the system efficiency is 49.59% with the CO2 capture efficiency of almost 100%, assuming the air reactor temperature at 1,200 °C and the fuel reactor temperature at 900 °C. As a comparison, the system efficiency of coal gasification CLC combined system is 40.53% with the CO2 capture efficiency of 85.2% when the turbine inlet temperature is at 1,350 °C. Increasing the supplementary firing rate or decreasing the air reactor temperature can increase the system efficiency, but these will reduce the CO2 capture efficiency.

Enhancing the Activity of Iron Based Oxygen Carrier via Surface Controlled Preparation for Lignite Chemical Looping Combustion

We selected Fe2O3 as the model oxygen carrier for chemical looping combustion(CLC) to theoretically detect the electronic properties of the high index surface(104) and the referenced low index surface(001). Fe2O3(104) exhibits better electronic structure for the interaction to lignite. Then,based on the theoretical calculations,Fe2O3(104) supported on Al2O3 was obtained via surface-controlled preparation. The reaction between lignite and the prepared Fe2O3(104) /Al2O3 is more efficient than the reaction between lignite and the reference Fe2O3/ Al2O3 prepared via traditional impregnation method,which corresponds to the theoretical calculations. Ultimate analysis shows less carbon deposit on the reduced Fe2O3(104) /Al2O3 than on the reduced Fe2O3/ Al2O3. Further,the fresh and the regenerated oxygen carrier were characterized,which verified the regeneration ability of Fe2O3(104) after severe structural relaxation during the reaction processes.These findings indicate that morphological control of oxygen carrier is very rewarding and will throw light to the next generation of highly efficient oxygen carriers for CLC technology.

On a Highly Reactive Fe2O3/Al2O3 Oxygen Carrier for in Situ Gasification Chemical Looping Combustion

Interest in the direct use of solid fuel in chemical looping combustion (CLC) technology makes the in situ gasification chemical looping combustion (iG-CLC) an attractive approach for the low-cost capture of CO2. Highly reactive material is required in iG-CLC in order to achieve a fast reaction between the fuel and oxygen carrier. In this work, a material, Fe2O3/Al2O3 synthesized by sol–gel, was evaluated in a fluidized-bed reactor by reaction with lignite. This is the first time sol–gel-derived Fe2O3/Al2O3 material has been used in an iG-CLC process. Operation conditions, including steam content in the fluidization gas, temperature, and potential oxygen ratio, were investigated to explore their influence on combustion and char conversion. The results show that a higher steam concentration can greatly enhance the rate of char gasification and hence the reaction between the lignite and the oxygen carrier, whereas a negligible effect of the steam content was noticed on volatile combustion. In addition, the use of the highly reactive Fe-based material prepared by the sol–gel method significantly increased the char gasification rate as compared to other previously evaluated materials. Moreover, the combustion efficiencies of volatiles and char from the lignite, respectively, were studied. Using the Fe2O3/Al2O3 material enabled a low oxygen carrier inventory of 600 kg/MWth to be reached in order to achieve 99% char combustion, which is much lower than that reported in other works. These findings suggest that Fe2O3/Al2O3 prepared by sol–gel is a highly reactive oxygen carrier for iG-CLC.

Energy exploitation of acid gas with high H2S content by means of a chemical looping combustion system

In gas and petroleum industry, the waste gas stream from the sweetening process of a sour natural gas stream is commonly referred as acid gas. Chemical Looping Combustion (CLC) technology has the potential to exploit the combustible fraction of acid gas, H2S, to produce energy obtaining a flue gas highly concentrated on CO2 and SO2, which can be cost-effectively separated for subsequent applications, such as sulfuric acid production. At the same time, a concentrated CO2 stream ready for storage is obtained. The resistance of oxygen carriers to sulfur becomes crucial when an acid gas is subjected to a CLC process since the H2S content can be very high. In this work, a total of 41h of continuous operation with acid gas and H2S concentrations up to 20vol.% has been carried out in a 500 Wth CLC unit with two oxygen carriers based on Cu (Cu14γAl) and Fe (Fe20γAl). The formation of copper sulfides and the SO2 emissions in the air reactor made the Cu14γAl material not adequate for the process. In contrast, excellent results were obtained during acid gas combustion with the Fe20γAl oxygen carrier. H2S was fully burnt to SO2 in the fuel reactor at all operating conditions, SO2 was never detected in the gas outlet stream of the air reactor, and iron sulfides were never formed even at H2S concentrations as high as 20vol.%. Furthermore, it was found that a H2S content of 20vol.% in the acid gas was high enough to turn the CLC process into an auto-thermal process. Based on these results, it can be concluded that the Fe-based materials prepared by impregnation are very adequate to exploit the energy potential of acid gas mixtures with CO2 capture.

Thermodynamic analysis of H2production from CaO sorption-enhanced methane steam reforming thermally coupled with chemical looping combustion as a novel technology

In this novel paper, a technique for hydrogen production route of CaO sorption-enhanced methane steam reforming (SEMSR) thermally coupled with chemical looping combustion (CLC) was presented (CLC-SEMSR), which perceived as an improvement of previous methane steam reforming (MSR) thermally coupled with CLC technology (CLC-MSR). The application of CLC instead of furnace achieves the inherent separation of CO2 from flue gas without extra energy required. The required heat for the reformer is provided by thermally coupling CLC. The addition of CaO sorbents can capture CO2 as it is formed from the reformer gas to the solid phase, displacing the normal MSR equilibrium restrictions and obtaining higher purity of H2. The Aspen Plus was used to simulate this novel process on the basis of thermodynamics. The performances of this system examined included the composition of reformer gas, yield of reformer gas (YRg), methane conversion (αM), the overall energy efficiency (η), and exergy efficiency (φ) of this process. The effects of the molar ratio of CaO to methane for reforming (Ca/M) in the range of 0–1.2, the molar ratio of methane for combustion to methane for reforming (M(fuel)/M) in the range of 0.1–0.3, and the molar ratio of NiO to methane for reforming (Ni/M) in the range of 0.4–1.2 were investigated. It has been found to be favored by operating under the conditions of Ca/M = 1, M(fuel)/M = 0.2, and Ni/M = 0.8. The most excellent advantage of CLC-SEMSR was that it could obtain higher purity of H2 (95%) at lower operating temperature (655 °C), as against H2 purity of 77.1% at higher temperature (900 °C) in previous CLC-MSR. In addition, the energy efficiency of this process could reach 83.3% at the optimal conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Performance of Cu- and Fe-based oxygen carriers in a 500 Wth CLC unit for sour gas combustion with high H2S content

Sour gas represents about 43% of the world's natural gas reserves. The sustainable use of this fossil fuel energy entails the application of CO2 Capture and Storage (CCS) technologies. The Chemical Looping Combustion (CLC) technology can join the exploitation of the energy potential of the sour gas and the CO2 capture process in a single step without the need of a sweetening pre-treatment unit. In this work, a total of 60h of continuous operation with sour gas and H2S concentrations up to 15 vol% has been carried out in a 500 Wth CLC unit, from which 40 corresponded to a Cu-based oxygen carrier (Cu14γAl) and 20 to a Fe-based material (Fe20γAl). This is the first time that so high H2S concentrations are present in a fuel to be burnt in a CLC process. The Cu14γAl oxygen carrier seems to be not recommendable for the combustion of sour gas because, although all the H2S is burnt to SO2, copper sulfides were formed at all combustion conditions. In contrast, the Fe20γAl oxygen carrier presented an excellent behavior with no agglomeration problems and maintaining the reactivity of the fresh material. The sour gas (CH4, H2 and H2S) was completely burnt, and neither SO2 was released in the AR nor iron sulfides were formed at usual CLC operating conditions. These tests demonstrated the possibility to use sour gas in a CLC process with 100% CO2 capture without any SO2 emissions to the atmosphere.

Ca0.9Mn0.5Ti0.5O3−δ: A Suitable Oxygen Carrier Material for Fixed-Bed Chemical Looping Combustion under Syngas Conditions

Power generation using chemical looping combustion (CLC) technology has emerged as a promising CO2-capture-based alternative to conventional technology. In this study, the performance of a Ca0.9Mn0.5Ti0.5O3−δ perovskite-type oxygen carrier material for use in fixed-bed CLC reactors is investigated. The main focus of the study is on the material’s oxygen-carrying capacity and reactivity with and conversion of syngas in the fixed-bed reactor. Pressurized thermogravimetric analysis in model gases indicates neither Boudouard coking nor reactivity of the oxygen-carrier material toward CO2. A fuel gas conversion of 95% was achieved in the fixed-bed reactor using this oxygen-carrier material.

Comparative Assessment of Gasification Based Coal Power Plants with Various CO2 Capture Technologies Producing Electricity and Hydrogen

Seven different types of gasification-based coal conversion processes for producing mainly electricity and in some cases hydrogen (H2), with and without carbon dioxide (CO2) capture, were compared on a consistent basis through simulation studies. The flowsheet for each process was developed in a chemical process simulation tool “Aspen Plus”. The pressure swing adsorption (PSA), physical absorption (Selexol), and chemical looping combustion (CLC) technologies were separately analyzed for processes with CO2 capture. The performances of the above three capture technologies were compared with respect to energetic and exergetic efficiencies, and the level of CO2 emission. The effect of air separation unit (ASU) and gas turbine (GT) integration on the power output of all the CO2 capture cases is assessed. Sensitivity analysis was carried out for the CLC process (electricity-only case) to examine the effect of temperature and water-cooling of the air reactor on the overall efficiency of the process. The results show that, when only electricity production in considered, the case using CLC technology has an electrical efficiency 1.3% and 2.3% higher than the PSA and Selexol based cases, respectively. The CLC based process achieves an overall CO2 capture efficiency of 99.9% in contrast to 89.9% for PSA and 93.5% for Selexol based processes. The overall efficiency of the CLC case for combined electricity and H2 production is marginally higher (by 0.3%) than Selexol and lower (by 0.6%) than PSA cases. The integration between the ASU and GT units benefits all three technologies in terms of electrical efficiency. Furthermore, our results suggest that it is favorable to operate the air reactor of the CLC process at higher temperatures with excess air supply in order to achieve higher power efficiency.

Release of pollutant components in CLC of lignite

The recently developed Chemical Looping Combustion technology (CLC) is nowadays considered an interesting option to capture CO2 at low cost in fossil fuelled power plants. In the past years, significant advances have been achieved in the combustion of both gaseous and solid fuels. Nevertheless, pollutant gas emissions from CLC systems have received little attention. This paper focuses on sulphur, nitrogen and mercury emissions during lignite combustion in a 500Wth CLC unit. Ilmenite was used as oxygen carrier, as it is one of the most common materials used for CLC of solid fuels. The main sulphur species detected in the fuel reactor were H2S and SO2. The amount and proportion depended on the temperature of the fuel reactor. The higher the temperature, the more H2S converted to SO2. In the air reactor, the sulphur in the unconverted char was released as SO2. Regarding the emission of nitrogen in coal, most of the nitrogen was found as N2 at the outlet of the fuel reactor. No NH3 or HCN were registered and only small amounts of NO were detected. The nitrogen contained in the char reaching the air reactor was released as NO. Mercury speciation was also analyzed and the ratio Hg2+/Hg0 determined. In the fuel reactor, the major mercury species was Hg0 and in the air reactor Hg2+. The incorporation of a carbon separation unit between fuel and air reactors would help to reduce the sulphur emissions in the air reactor and comply with the current legislation for power generation systems.

Sewage sludge ash as an alternative low-cost oxygen carrier for chemical looping combustion

In this paper, novel low-cost oxygen carriers containing Fe2O3 are evaluated for use in chemical looping combustion. Sewage sludge ashes and reference samples were prepared and used in cyclic reduction and oxidation experiments in a thermogravimetric analyzer (TG). A gaseous (3 % H2) fuel and a solid fuel (hard coal) were tested. Three-cycle CLC tests were carried out in the 600–800 °C temperature range and long-term testing was performed at 950 °C. A reactivity study showed that the natural sewage sludge ash sample was stable during the cycling TG tests when hydrogen was used as a fuel at all of the temperatures investigated. Strong temperature effects on the oxygen transport capacity were observed. An one-cycle test at 900 °C showed also that the sewage sludge ash successfully reacted with coal. The oxygen released was fully used for coal combustion, with appreciable reaction rate at temperature of ~750–800 °C, that is significantly lower than that obtained for pure Fe2O3-based oxygen carrier. The oxidation reaction was much faster than the reduction reaction. Moreover, the sewage sludge ash showed a low tendency toward agglomeration in the cyclic test, which was superior to the behavior of synthetic materials. The sewage sludge ash exhibited also high mechanical strength, an attrition index of 1 % and a high-temperature resistance of 1,170 °C in a reducing atmosphere. We conclude that sewage sludge ash can be effectively used as a low-cost, valuable oxygen carrier in practical application in chemical looping combustion technology for power generation.

Interaction between iron-based oxygen carrier and four coal ashes during chemical looping combustion

Chemical looping combustion (CLC) is a novel technology with inherent CO2 capture, especially for solid fuels. The existence of ash in solid fuels is one major challenge for CLC technology development. In this work, interaction between an iron-based oxygen carrier and four different types of coal ash was studied in a laboratory-scale fluidized reactor. Different factors – the ash component, the redox cycle number, and the ash size – were taken into account. Chemical composition of the ash had effect on the reduction time from Fe2O3 to Fe3O4 in the fluidized bed. The presence of reactive components (such as Fe2O3 and CaSO4) in the ash, functioning as oxygen carriers, extended the reduction time. However, the chemical combination between the ash contents and the carrier can shorten the reduction time. The effect of ash on the carrier’s reactivity depended on the ash type. Most ashes decreased the reactivity of the carrier, except the ash mainly composed of CaSO4 which showed an increased reactivity due to the deposited reactive CaSO4. The effect of ash on decreasing the carrier’s reactivity increased with the cycles. Meanwhile, the larger ash (900–1000μm) corresponded to a higher CO conversion, and thus had less effect on the reactivity than the smaller ash (300–400μm). This occurrence can be attributed to the non-uniform solid–solid contact between the larger ash and the carrier. Sintering and agglomeration of the carrier particles occurred in the existence of most ashes, except the lignite ash enriched in CaO. Ash deposition and the formation of new compounds were detected. One common compound formed in the presence of SiO2-rich ash was Fe2SiO4, which has a low melt point (1170°C) and a low thermal conductivity with a greater adhesion. The physical ash deposition and the formation of Fe2SiO4 through chemical reactions were proposed to be the main reasons for the effect of ash on the carrier’s reactivity and the occurrence of sintering and agglomeration. The existence of ash not only has impact on the carrier’s reactivity, but also causes solid fluidization disturbances. More effort is deserved to put into the ash-related issue in solid fuel CLC.

ChemInform Abstract: Some Remarks on Direct Solid Fuel Combustion Using Chemical Looping Processes

AbstractReview: 48 refs.

The fate of sulphur in the Cu-based Chemical Looping with Oxygen Uncoupling (CLOU) Process

The Chemical Looping with Oxygen Uncoupling (CLOU) process is a type of Chemical Looping Combustion (CLC) technology that allows the combustion of solid fuels with air, as with conventional combustion, through the use of oxygen carriers that release gaseous oxygen inside the fuel reactor. The aim of this work was to study the behaviour of the sulphur present in fuel during CLOU combustion. Experiments using lignite as fuel were carried out in a continuously operated 1.5kWth CLOU unit during more than 15h. Particles containing 60wt.% CuO on MgAl2O4, prepared by spray drying, were used as the oxygen carrier in the CLOU process. The temperature in the fuel reactor varied between 900 and 935°C. CO2 capture, combustion efficiency and the sulphur split between fuel and air reactor streams in the process were analysed. Complete combustion of the fuel to CO2 and H2O was found in all experiments. Most of the sulphur introduced with the fuel exited as SO2 at the fuel reactor outlet, although a small amount of SO2 was measured at the air reactor outlet. The SO2 concentration in the air reactor exit flow decreased as the temperature in the fuel reactor increased. A carbon capture efficiency of 97.6% was achieved at 935°C, with 87.9wt.% of the total sulphur exiting as SO2 in the fuel reactor. Both the reactivity and oxygen transport capacity of the oxygen carrier were unaffected during operation with a high sulphur content fuel, and agglomeration problems did not occur. Predictions were calculated regarding the use of a carbon separation system in the CLOU process in order to reduce sulphur emissions. Coals with high sulphur content, such as lignite and anthracite, would require a carbon separation system in order to comply with legislation governing sulphur-limits. In conclusion, coals with a high sulphur content can be burnt in a CLOU process using Cu-based material to obtain high carbon capture efficiencies.