As a typical fluidization technology, Fluid Catalytic Cracking (FCC) is faced with the problem of catalyst particle abrasion and crushing. However, due to the small particle size of catalyst particles and the complex flow in the reactor, it is difficult to study the flow, collision, and crushing characteristics of catalyst particles by experimental methods. In order to reveal the flow, collision, and crushing characteristics of catalyst particles in FCC reactor, the crushing models of single particle Abt(10) and all particles were established. By tracking the particle breakage process, the particle size distribution after particle breakage was obtained, the abrasion type of particles was determined, and the energy conversion path of particles was clarified. It was found that a few sub-particles inherit most of their mechanical energy after single particle crushing, and it was speculated that most of the dissipated mechanical energy comes from the transformation of particle rotation energy to internal energy. In the simulation of all particle crushing processes, the overall particle crushing probability is 3.90%, and the particle size distribution curve after crushing shows a bimodal distribution. Considering the abrasion mechanism, it is mainly dominated by the surface peeling mechanism.

The exponential development of new electric vehicles has led to the inevitable retirement of lithium-ion batteries as a power source. Recovery of spent lithium-ion batteries (LIBs) with remarkable resource and pollution characteristics is an essential solution to alleviate the shortage of lithium resources and drive the sustainable industrial development. Herein, a novel strategy was proposed as chemical looping complementary reduction (CLCR) for recycling valuable metals from spent LiCoO2 battery as chemical-looping cyclic carriers. The influ-encing factors of reduction temperature, time and H-2 flows on reduction characteristics of LiCoO2 carriers were investigated on a laboratory-scale fixed bed. The results indicated that both high temperature and elevated H-2 flows were conduce to enhancing LiCoO2 conversion with fairly high crystallinity and purity of reduction products (mainly Li2O and Co monomers) and 98.36 % conversion of LiCoO2 was attained at 1000 degrees C for 120 min with the H-2 flow of 60 mL/min. Thermodynamic analysis proved that complementary matching properties existed between reduction temperature and H-2 concentration affecting the phase equilibrium of products, while 650 degrees C similar to 900 degrees C was favorable to obviate the formation of liquid LiOH and the loss of target products. Finally, the mechanism of CLCR along with its environmental and economic impacts were insightfully elaborated to provide a technical and cost-efficient scheme for spent LIBs recycling.

During the chemical looping process, oxygen carriers are subjected to extremely challenging conditions, such as high temperatures, fluidization, and redox reactions, which significantly increase their susceptibility to attrition. Overall, particle attrition is caused by mechanical, thermal, and chemical stresses, but their exact contribution and mechanism are unclear. In this work, five distinct experimental conditions and cold jet attrition tests were established to discern the contributions of different stresses to attrition and their impact on performance. Particle size versus strength was obtained for up to 1320 particles, and hotspot plots were used to reveal the relationship between the two. It was found that thermal stress was the dominant factor only during the pre-attrition phase, contributing 45 % to attrition. And then swiftly superseded by mechanical stress. Chemical stress emerged as the primary cause of attrition during the middle and late stages of the experiments, contributing up to 90 % of attrition. OC's strength typically ranged between 6 and 8 N without chemical stress and, conversely, dropped to below 1 N. Furthermore, chemical stress was found to induce an increase in particle volume and oxygen transport capacity, primarily achieved by reducing apparent density. The volume of particles can be enlarged by a factor of 1.56, and the oxygen release rate was increased from 4 % to 5.6 % under chemical stress. And a correlation was observed between apparent density and both attrition rate and strength.

Human activities and industrial processes result in substantial methane emissions, predominantly at low concentration. This is particularly evident in coal mining where the gas concentration is notably low, posing challenges for effective utilization. Chemical looping catalytic oxidation (CLCO) is believed to be a potential approach for the disposal of ultra-low concentration methane (UCM) and the capture of CO2. Unlike pure air, which is generally used to oxidize OC in air reactor, UCM typically contains 0.1 similar to 1 %CH4 and less than 60 ppm H2S, therefore, the introduction of UCM into the air reactor would potentially threaten oxygen carrier (OC). In this study, the evolution of OC in CLCO process was investigated in terms of reaction performance and physicochemical parameters compared to traditional chemical looping process. XRD showed that the phase compositions of OC remained stable over 300 cycles and no sulfur-containing compounds were detected. The comparison showed that CLCO process negatively affected the performance of OC, especially for attrition. The attrition behavior of OC can be summarized in three stages: fines blowing out, steady-state attrition and intenseattrition stage. The main reason for increased attrition was attributed to methane oxidation, which released a large amount of heat and would impose a heat shock on OC. Contrary to the commonly reported "L"-shape, our data showed a "U"-shaped attrition rate trend in long-term cycles. The difference was that the attrition rate would suddenly increase after a certain number of cycles, indicating that the actual service life of OC may be significantly lower than predicted.

Fluid Catalytic Cracking (FCC), a typical fluidization technology, faces serious issues of catalyst particle attrition and loss. Attrition is an important cause of catalyst loss. Due to the small particle size and complex flow process inside the reactor,it is difficult to conduct experimental research on it. The flow, collision and attrition characteristics of catalyst in the reactor are still unclear. This study established a geometric model of a catalytic cracking unit and used CFD-DEM bidirectional coupling numerical simulation method to study the flow and collision characteristics of catalyst particles in the catalytic cracking unit. The result indicate that particles collide with the wall most frequently, with an average collision frequency of 141,501.89 Hz. The particle wall collision frequencies above the nozzle, at the top of the riser, and in the cyclone separator are the highest, with an average collision frequency of 244.90 Hz, 1441.2 Hz, and 3571.15 Hz, respectively. Strong single collisions and slight continuous collisions of large size particles often occurred in the device. For small particles, the difference in strength between each collision within the device is not significant.

Chemical looping combustion (CLC) relies on cyclic circulation of oxygen carriers (OCs) between fuel reactor and air reactor to transfer lattice oxygen and heat. OCs’ attrition is an important issue hindering large scale application of CLC technology. Attrition is caused by cracks and abrasion, and method to stop crack propagation is an effective way to mitigate attrition. Biomass ash contains inert and alkali metal components, and it may have the potential to increase the reactivity and reinforce the skeleton structure of OCs. The effects of rape straw ash, corn straw ash and bagasse ash on the reactivity, cumulative attrition rate of red mud OCs were evaluated, and their effects on skeleton structure were analyzed, and finally, the strengthening mechanism of OCs skeleton structure was proposed. The results showed that the rape straw ash rich in K and Ca components promoted the reactivity of OCs. Although the Si-rich bagasse ash decreased the reactivity of OCs, it improved the attrition resistance of OCs. Corn straw ash rich in K and Si components was an effective skeleton strengthening material, which improved both the reactivity and the attrition resistance. The cumulative attrition rate of red mud was 2.74%, and the cumulative attrition rate of CSA sample was 0.35%, which was 87.32% lower than that of OC sample, indicating fine attrition resistance. The fiber structure could strengthen the skeleton of OC, therefore, decreasing attrition rate.

Oxygen carrier (OC) is of great importance in chemical looping combustion (CLC) technology. The migration rate of bulk lattice oxygen during reduction process is detrimental in reaction rate. However, the migration path of lattice oxygen is still not clear. In this study, a thermogravimetric analyzer (TGA) was used to investigate the reaction characteristics and kinetic parameters of the OC. The oxygen migration paths of CuO and CuFe2O4 bulk lattices were studied by density functional theory (DFT) in a five-layer (2 x 1) CuO (1 1 1) and nine-layer (1 x 1) CuFe2O4 (1 0 0) plane model. The kinetic parameters, activation energy changes and relative kinetic model of the OC reduction were explored. According to the DFT results, the deeper bulk phase oxygen requires greater more energy toovercome energy barrier for migration. CuO has a lower oxygen release capacity than CuFe2O4 in the early stages, but higher in the later stage. The reaction kinetics study revealed that the reaction mechanism of the reduction of the copper-iron composite OC is a tertiary chemical reaction control mechanism. During the reaction, the activation energy of the OC changes continuously. The macroscopic reaction kinetics agree with the microscopic simulation, proving the simulation model's validity.

Chemical looping technology is an innovative method for CO2 capture. Oxygen carrier (OC) is the key to the chemical looping process. The mechanical properties of OC are a major uncertainty limiting the economics of the technology. The chemical looping process usually operates as a fluidized bed, during which OC is constantly subjected to mechanical, thermal and chemical stresses, leading to severe attrition. In addition, the long operating time also greatly accelerates the attrition process. This study provides a comprehensive review of OC attrition, including the parameter changes in long-term operation, mechanisms and measurement methods of attrition, models for simulation, methods to reduce attrition, and sensitivity analysis of attrition. Numerous studies have found severe OC attrition in operations. However, there is no systematic understanding of OC attrition in the chemical looping field. Therefore, in future studies, it is recommended to provide systematic and complete particle parameters to construct a more complete database. On this basis, further insight into the attrition mechanism of OC is expected to be obtained.

Sewage sludge and red mud are industrial wastes that are potentially harmful to the environment. Their envi-ronmentally friendly treatment has been a global challenge due to their huge production and limited disposal capacity. Red mud, which contains Fe2O3 and Al2O3, can be used as an oxygen carrier. The organic matter contained in the sludge can be used as fuel. Based on the above characteristics, we propose a comprehensive waste reuse method: red mud was used as an oxygen carrier, sewage sludge was used as fuel and ultra-low concentration methane was used as an oxidizing gas. The method employs waste's heat and mass transfer properties to achieve comprehensive treatment and reuse of gas-solid phase waste. The factors influencing waste treatment efficiency as well as the mechanism of the reaction process have been thoroughly investigated. By adjusting the O/C ratio and water vapor percentage at 950celcius, the carbon conversion and CO2 selectivity could reach 94.34 %, 76.50 %, respectively. The methane conversion was close to 99.80 %, and the H2 and CO yields were up to 37.98 x 10-4 mol and 21.67 x 10-4 mol, respectively. The microscopic morphology and properties of used OC particles remained stable. The migration characteristics of heavy metal elements indicated that bed material composed of sludge and red mud has the potential to be used as a raw material for construction after sieving. This study proposes a new comprehensive method for reusing sewage sludge, red mud, and low -concentration methane that would be efficiently recycled in one process.

Chemical looping combustion relies on high performance oxygen carriers (OCs). Iron-based OCs have excellent overall properties, but the disadvantage of low reduction reactivity limits their application prospects. Clarification of oxygen transfer pathways and bulk phase properties is essential to improve oxygen transfer rates and increase the reactivity of OCs. High-resolution transmission electron microscopy, electron energy loss spectroscopy and X-ray photoelectron spectroscopy had been used to study the lattice oxygen transport properties, the Fe and O elemental contents and Fe elemental valence changes at different positions on the radial surface of Fe2O3 OC, as well as the related elemental compositions, atomic valence and surface energy distribution on the surface of the OC during the reduction process of OC. The results show that during the reduction process, the active components at different locations of the OC are simultaneously reduced and lattice oxygen is released. Both internal and external lattice oxygen are involved in the reaction. Besides, reaction interface is believed to be fixed at a OC surface. This study reveals the migration direction of the reduction interface and the mechanism of oxygen release in the bulk phase, and would provide a theoretical basis for the structural design of Fe-based OCs.

Fluidized beds are widely used in chemical reactors. Particles in fluidized bed usually circulate between reactors, and therefore, particle attrition cannot be avoided. Catalyst particle attrition in the fluidized bed significantly shortens their lifespan and raises operating costs. This study established an irregular polyhedron model of the particles to acquire their motion and force characteristics by the Euler-Lagrangian method and then employed the Ab-T10 breakage model to predict the particle's breakage process. The collision frequency and stress characteristics of the three-dimensional surface of a single particle were explored, as well as the time-dependent variations in the collision frequency and impact power between particles. The breakage and elutriation processes of a single particle were observed. The investigation found that the velocity differential between particles was the main factor that caused impact power. The particles were typically crushed one to six times before becoming completely fine powder, and their size evolution can be summarized in three stages. The complete process of particle breakage was revealed by tracing the size evolution of a single particle. This work would contribute to a deeper understanding of particle collision behavior and breakage mechanisms in fluidized beds.

化学链燃烧技术是目前最有前景的CO2捕集技术之一,载氧体是该技术的关键组成部分.铁基载氧体因其来源广泛、价格便宜和环境友好等优点,被认为最具备有工业化应用的潜力,但其存在寿命短、释氧能力弱的问题,磨损是造成该问题的主要原因之一.采用机械混合法制备了煅烧温度为1300、1400和1500℃的Fe-Al复合载氧体,分别开展了冷态、热态以及反应态多组流化床磨损试验,分析了煅烧温度对载氧体的磨损和释氧能力的影响,分别研究了氧化反应和还原反应对其磨损的影响,明确了机械碰撞、温度以及化学反应对载氧体磨损的影响程度.研究结果表明:煅烧温度为1400℃的载氧体展现了抗磨损性和循环稳定性能两者之间最佳平衡,基于反应前后载氧体表面的元素分布、晶相分离和微观形貌演变的分析,发现了化学反应中由还原反应引发的载氧体孔容的增加对其磨损和破碎起重要作用,本工作对开发、设计长寿命的复合载氧体有一定的指导作用.