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International audience; Chemical looping combustion (CLC) technology has emerged as one of the most important clean fossil fuel combustion technologies, because it allows for sequestration of CO2 with a minimal increase in energy requirements and fuel demand in comparison to traditional plants. In the framework of the Chinese–European Emission-Reducing Solutions project, the core technology of the CLC process is being developed in a 3 MWth system prototype for demonstration in an operational environment using petcoke as fuel. One of the main objectives is the selection of the oxygen carrier because it will impact the design and sizing of the demonstration unit as well as the nominal power of the unit. Two minerals, ilmenite T1 and LY Mn ore, with high potential for a well-performing oxygen carrier were tested in a 10 kWth continuous pilot unit. The collected fines were analyzed by scanning electron microscopy and X-ray fluorescence analysis to characterize the compositional and morphological evolution of the particles during operation. The performance of both oxygen carriers was compared with respect to solid fuel conversion, capacity for oxygen transfer, and particle lifetime in continuous circulation. A higher methane conversion can be obtained using ilmenite, while LY Mn is better at converting petcoke. Where the reduction potential of oxygen carriers is concerned, it was observed that LY Mn ore has a high initial R0ΔX value (R0ΔX = 0.8), which leads to a shorter activation period in comparison to ilmenite T1, which requires a longer activation period to reach its full potential. LY Mn ore is however more sensitive to attrition than ilmenite, under similar operating conditions, which is a critical characteristic for large-scale deployment. Finally, key operating parameters were identified for large-scale unit operation, including fuel reactor temperature, oxygen carrier flow rate, and fuel flow rate.

Cyclones are commonly used in the process industry to separate entrained particles from gas streams. Particles entering a cyclone are subjected to a centrifugal force field, driving them to the cyclone walls, where they experience collisional and rapid shearing stresses. Consequently, particle attrition and erosion of the cyclone walls occur, depending on the mechanical properties of the particles and cyclone walls. In this work, the attrition of manganese oxide particles, intended for use in the Chemical Looping Combustion (CLC) process, flowing through a standard design cyclone (Stairmand design) is analysed as an example by considering surface damage processes of chipping and wear. A new methodology is developed, whereby Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations are used to analyse the particle motion and interactions with the cyclone walls. The approach is then coupled with breakage models of chipping and wear to predict the extent of attrition. The impact breakage due to chipping is evaluated experimentally first as a function of particle size and impact angle and velocity. The data are fitted to the chipping model of Ghadiri and Zhang. The model is then coupled with the frequency of collisions and impact velocity, obtained from the CFD-DEM simulation, to work out the particle attrition by chipping. For surface wear the model of Archard is used to account for particle wear by shearing against the walls. The outcome of the work provides a methodology for describing the extent of attrition in different regions of the cyclone.

International audience; Solid circulation in chemical looping combustion (CLC) is very important and affects the mass and heat balance and autothermal operation of a CLC system. A key task in developing CLC technology is to control the solid circulation. In this work, the solid circulation characteristic of a 1.5 MWth CLC cold flow model is reported. The solid circulation between the fuel reactor and the simplified air reactor riser is controlled by the overflow method. Three kinds of quartz sands are selected as fluidized particles, and their median particle diameters are 392, 249, and 122 μm, respectively. A reasonable pressure profile is obtained in the 1.5 MWth CLC cold flow model. The effects of operational parameters, including the fuel reactor gas velocity, loop seal gas velocity, simplified riser gas velocity, particle size, and static bed height, on the solid circulation and hydrodynamic characteristics are measured and analyzed. The maximum solid circulation rate can approach 130 kg/(m2·s), and this value satisfies the requirements of mass and heat balance in the CLC system. The static bed height in the fuel reactor should be higher than the overflow port to prevent it from becoming a constraint factor on the solid circulation rate. An overflow model is developed to predict the solid circulation rate, and the relative errors between the predicted result and the experimental data are within 25%.

International audience; One of the best low-cost approaches for capturing carbon dioxide from the combustion of solid fuels is chemical looping combustion (CLC) technology, where the processes of fuel oxidation and extraction of oxygen from the air are split in two separate reactors. In order to model the petroleum coke (petcoke) conversion in a CLC method, detailed knowledge about the reactions of pet-coke with O2, CO2, and H2O at temperatures between 750 and 1100 °C is required. Due to the lack of sufficient literature data, in this paper, the reactivity of these reactions is investigated in a custom-built test rig that enabled measurements of the mass loss of the fuel sample and the composition of the released gases. The Avrami, Random Pore, Shrinking Core, and Hybrid models were applied to the experimental results to determine the kinetic parameters of petcoke gasification. At temperatures up to 1000 °C, the reaction with CO2 was found to be negligibly slow. An activation energy of 103.91 kJ/mol was obtained for petcoke gasification in 10–40 vol% of H2O, while a value of 15.87 kJ/mol was found for oxidation in 2–4 vol% O2, as described by best-fitting models, i.e. Hybrid and Random Pore models, respectively.

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 CO2. 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 H2 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 CO2 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 industrial Carbon Capture and Storage units 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 solid 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.

Chemical Looping Combustion (CLC) is a promising combustion technology with inherent CO2 capture. This process consists in use of metal oxides, called oxygen carriers, to transfer oxygen from Air Reactor into the Fuel Reactor for combustion of Fuels. Accordingly, Air and Fuel are not mixed and the produced flue gas is concentrated in CO2 and not diluted with nitrogen. This inherent CO2 capture results in higher energy and carbon capture efficiencies compared to conventional capture technologies. This paper presents recent achievements of TOTAL in collaboration with IFPEN on CLC development for the refining and chemical industry with petcoke feedstock. A novel concept has been developed with a two-stage combustion reactor, an integrated solid-solid separator (Carbon Stripper), and non-mechanical solid flow control devices. These technologies have been demonstrated at different scales up to a 1 MWth equivalent cold flow prototype and in a 10 kWth continuous pilot plant. These experimental works permitted to carry out a full-scale process simulation with steam and electricity cogeneration. Different sections of CLC are represented in this simulation including reactor system, flue gas treatment, CO2 compression, and steam cycle. In addition, the cost of avoided CO2 has been evaluated for power generation with Chemical Looping technology. Finally, CHEERS project is introduced in which CLC process will be demonstrate in 3 MWth scale via an international collaboration including nine partners from Europe and China.

International audience; A promising copper based oxygen carrier produced using industrially-relevant 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.

International audience; This work aims to study the evolution of NiO/NiAl2O4 redox performance with CO as fuel for Chemical Looping Combustion (CLC) applications. The oxygen carrier (OC) was investigated under alternating oxidizing and reducing conditions in a fixed bed reactor simulating the cyclic conditions of CLC. The study of the operating temperature influence reveals that total reduction capacity increases with temperature, due to the reaction of the binder NiAl2O4. Regeneration step performed under low oxygen concentration (5 vol.%) shows that the decrease in total reduction capacity during multiple cycles is minimized and the purity of produced CO2 is higher. Therefore, carrying out the regeneration step at lower oxygen concentrations can increase oxygen carrier lifetime. Characterization studies revealed the formation of a nickel rich layer at the surface (up to 20 μm thick at 900 °C) and a partial sintering of particles regenerated under 20 vol.% of oxygen. However, these phenomena are not observed on the particles regenerated under low oxygen concentration. The formation of this layer can be explained by the fact that nickel oxidation is carried out by migration of Ni2+ cations through the layer of NiO initially oxidized at the surface of the particle, the layer becomes thicker during cycles, because NiO does not return to its initial position. At higher temperature, the diffusion velocity increases and therefore the layer formed is thicker.Specific surface area of the oxygen carrier decreases as cycles number increases from 9.4 m2/g for the fresh material to 4.4 and 2.3 m2/g after thirty cycles at 750 °C and 900 °C respectively. The same trend is observed for porous volume. However, the decrease is lower when particles are regenerated under low oxygen concentration (6 m2/g).

Particles attrition is an important phenomenon to account for when developing and scaling up new fluidized bed processes. Most of the time, little amount of particles is available at the early development stage and only lab scale experiments can be carried out. Most of the available tools and methodologies to investigate attrition at small scale were developed for the FCC process on group A particles. However, attrition also needs to be evaluated for new applications such as Chemical Looping Combustion (CLC) with different particle properties. In this work, we propose a method using a jet cup apparatus that aims to compare attrition rate of solids having different properties. Materials studied in this paper are a Group A FCC catalyst (Dp50 of 70 μm, grain density of 1450 kg/m3) and a Group B CLC oxygen carrier (Dp50 of 180 μm, grain density of 3600 kg/m3). Based on experimental data and CFD modeling, comparative testing conditions could be defined in order to apply the same mechanical stress for all solids tested. Classical attrition indexes usually quantify the generation of fine particles below 40 μm which does not describe fully attrition of Group B powders. Therefore, a new attrition index was defined to calculate the total amount of particles generated by attrition over the entire size range of all solids tested. Finally, the attrition rates of both materials were compared applying the methodology developed. It was found that attrition rate is less important for the oxygen carrier. It is important to notice that attrition due to thermal or chemical stresses is not investigated in this study and needs separate evaluation.

International audience; In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected tomechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradualdegradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition.One significant contribution of attrition comes from the air jets of the fluidised bed distributor. Particles areentrained into the air jet, where they get accelerated and impacted onto the fluidised bed particles. The jetinduced attrition only affects the part of the bed which is limited by the jet length, where the mode of attritionis largely collisional. The overall jet attrition rate is therefore the result of the combination of the single particledamage and the flux of particles entering into that region. The attrition behaviour of particles in the jet regionis analysed by evaluating their propensity of breakage experimentally and by simulating an air-jet in a bed ofparticles by CFD-DEM. The frequency of collisions and impact velocities are estimated from which theattrition due to a single air-jet is predicted.

International audience; The aim of this work is to investigate the contribution of the binder (NiAl2O4) on the performances of the oxygen carrier NiO/NiAl2O4. To this purpose, oxidation/reduction cycles have been performed in a fixed bed reactor using CO as a fuel. The results reveal that the binder can react with the fuel to form CO2, and that its total reduction capacity increases with temperature. XRD characterizations performed on the binder (on the fresh and after several cycles) show a shift of the diffraction peaks of NiAl2O4 toward the ones of γ-alumina, which can be attributed to a progressive decomposition of NiAl2O4 to alumina and NiO.

International audience; This work was devoted to study experimentally and numerically the oxygen carrier (NiO/NiAl2O4) performances for Chemical-Looping Combustion applications. Various kinetic models including Shrinking Core, Nucleation Growth and Modified Volumetric models were investigated in a one-dimensional approach to simulate the reactive mass transfer in a fixed bed reactor. The preliminary numerical results indicated that these models are unable to fit well the fuel breakthrough curves. Therefore, the oxygen carrier was characterized after several operations using Scanning Electronic Microscopy (SEM) coupled with equipped with an energy dispersive X-ray spectrometer (EDX). These analyses showed a layer rich in nickel on particle surface. Below this layer, to a depth of about 10 µm, the material was low in nickel, being the consequence of nickel migration. From these observations, two reactive sites were proposed relative to the layer rich in nickel (particle surface) and the bulk material, respectively. Then, a numerical model, taking into account of both reactive sites, was able to fit well fuel breakthrough curves for all the studied operating conditions. The extracted kinetic parameters showed that the fuel oxidation was fully controlled by the reaction and the effect of temperature was not significant in the tested operating conditions range

International audience; A circulating turbulent fluidized bed 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 a turbulent fluidization regime, which can achieve enough solid residence time and enhance the mixing of the oxygen carrier with solid fuel. A 1.5 MWth cold model of the FR was designed, constructed, and tested to investigate the hydrodynamics of solid particles with different sizes. Three kinds of quartz sands with different particle sizes (d50 = 122, 249, and 392 μm) were used as bed materials to simulate the oxygen carrier. Continuous operation with a reasonable pressure balance was achieved in the cold model. The effects of important variables, including gas velocity, static bed height, and 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, 249, and 392 μm were measured to be 0.78, 0.95, and 1.06 m/s, respectively, indicating that the transition velocity increased with increasing the particle size. The solid fraction profile along the 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 a wide range of operational conditions.