A promising copper based oxygen carrier produced using industriallyrelevant manufacturing equipment has been aged in IFPEN's 10 kW th Chemical Looping Combustion pilot plant. Methane combustion was performed at 900°C for 160h with an OC/fuel ratio of 1.2. While full methane conversion to CO 2 and water was achieved in the early stage of the experiment, fast deactivation was observed. The oxygen carrying particles were thoroughly characterized at various stages of the ageing experiment, from which a pathway leading to deactivation is proposed.

Chemical Looping Combustion (CLC) is a promising technique to achieve fuel combustion in a nitrogen free atmosphere, therefore giving the possibility to separate and store or use CO 2. Several potential applications are considered in the field of power generation with gas, liquid and mostly solid fuels. In the Carbon Capture, Storage and Utilization (CCSU) context, energy penalty is reduced with CLC compared to other routes. In addition, other applications of Chemical Looping Technology are considered in the field of H 2 production or gasification for instance. In the past years, a huge effort has been conducted worldwide to investigate CLC materials and process issues. In 2008, IFPEN and Total have started an ambitious collaboration to develop CLC applications. Nowadays, the CLC concept is well demonstrated on the pilot scale. The next step is to demonstrate the technology over time on a larger scale. For further developments, some challenges should be addressed, both on market and technical aspects: • Short term market is limited. Uncertainties around CO 2 emission market (i.e. carbon credits) and storage issues are hindering policy and public acceptance and still must evolve in the right direction, • Financing of demonstration units for carbon capture in this context is challenging and other applications of CLC may require to be investigated such as utilization of captured CO2 for EOR purpose. • The industrial use of synthetic metal oxides or natural ores at large scale generates a lot of issues related to availability, price, waste disposal, health and safety, additionally to chemical and mechanical aging, reactivity, and oxygen transfer capacity, • Chemical looping reactor and process technology concepts have to be explored, developed, modeled and scaled-up in order to ensure adequate power production together with good gas solid contact and reaction requirement, controlled circulation of mixtures of particle (oxygen carrier, ash, solid fuel for instance). All these points should be considered on very large scales for carbon capture and storage (CCS) applications in order to minimize energy penalty and cost in severe operating conditions (temperatures above 800°C and intense so lid circulation). Technical challenges remain to be solved and proven with large demonstration over long periods of time. In this context, research in the field of fluidization technology is essential and we will address some key points investigated at IFPEN as related to control of solid circulation, oxygen carrier attrition, conceptual design of CLC reactors and process performance.

No abstract

A circulating turbulent fluidized bed (CTFB) connected with a riser and an annular carbon stripper (CS) is proposed to be used as a fuel reactor (FR) in chemical looping combustion. The bottom section of the FR is operated under turbulent fluidization regime which can achieve enough solid residence time and enhance the mixing of oxygen carrier with solid fuel. A 1.5 MWth cold model of the FR was designed, constructed and tested in order to investigate the hydrodynamics of solid particles with different size. Three kinds of quartz sands with different particle sizes (d50=122 μm, 249 μm, and 392 μm) were used as bed materials to simulate the oxygen carrier.Continuous operation with reasonable pressure balance was achieved in the cold model. The effects of important variables including gas velocity, static bed height and 2 particle size on the gas-solid hydrodynamics of the FR were measured and discussed.It was found that the transition velocities from bubbling to turbulent fluidization for different particles of d50=122 μm, 249 μm, and 392 μm were measured to be 0.78 m/s, 0.95 m/s and 1.06 m/s respectively, indicating the transition velocity increased with increasing particle size. The solid fraction profile along reactor height and solid circulation rate were affected by gas velocity and static bed height. A modified correlation was proposed to predict the solid fraction of the annular CS dilute phase, and the predicted results agree well with the experimental data under wide range of operational conditions.

Predicting bubble properties in fluidized beds is of high interest for reactor design and modeling. While bubble sizes and velocities for low velocity bubbling fluidized beds have been examined in several studies, there have been only few studies about bubble behavior at superficial gas velocities up into the turbulent regime. For this reason, we performed a thorough investigation of the size, shape and velocity of bubbles at superficial gas velocities ranging from 0.18 m/s up to 1.6 m/s. Capacitance probes were used for the determination of the bubble properties in three different fluidized bed facilities sized of 0.1 m, 0.4 m and 1 m in diameter. Particles belonging to Geldart’s group B (Sauter mean diameter: 188 µm, solid density: ρs = 2600 kg/m3) were used. Correlations for the determination of bubble phase holdup, vertical bubble length and bubble velocity are introduced in this work. The shape of bubbles was found to depend on superficial gas velocity. This implies that at large superficial gas velocities the horizontal size of a bubble must be much smaller in comparison to its vertical size. This leads to a decrease of pressure fluctuations, which is observed in the literature as a characteristic of transitioning into a turbulent regime.