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This review discusses the influence of three key factors on agglomeration of chemical looping technology from the aspects of reaction conditions, the oxygen carrier and biomass composition. In addition, the existing agglomeration mechanisms are extended, and the technologies of detection and prevention of the agglomeration is reviewed. In the process of chemical looping reaction, high reaction temperature, the oxygen carrier materials with poor anti-sintering ability and the reaction system containing more alkali metals and silicon-based materials will easily cause agglomeration. Previous literatures have summarized the agglomeration produced by two mechanisms, and both of them pointed out that the alkali metal in the biomass ash is the main component to induce the agglomeration. For the SiO2-based oxygen carrier material, it is speculated that the alkali metal will react with the support to inactivate the active metal component through the inclusion of the molten material. However, the oxygen carrier without SiO2-based material is mainly produced through the mechanism of melt-induced, but not the coating-induced agglomeration. The predication of agglomeration focuses on the biomass ash test before the reaction and the monitoring of some variables during the reaction process, such as temperature and pressure analysis. Moreover, the agglomeration can be prevented or controlled by condition adjustment, reactor design, oxygen carrier design and biomass pretreatment. In addition, the use of additives is also a reliable method to reduce the agglomeration.

For a domestic 350 MW coal-fired power plant, the effect of heterogeneous agglomeration technology on the migration and emission of three trace elements of arsenic, selenium and lead in tail flue gas was studied. The results show that heterogeneous agglomeration technology can promote the attachment of gaseous harmful trace elements to particulate matter effectively. The reduction rates of gaseous As, Se and Pb concentrations at the ESP outlet were 24.10%, 61.08%, and 70.38%, respectively. Under the synergistic effect of ESP, more As, Se, and Pb are enriched in fly ash, and the concentration of As, Se, and Pb in fine particles below 10 μm at the ESP outlet is reduced by 54.48%, 56.47%, and 75.17%, respectively. In addition, after spraying the agglomerating agent, the final As, Se, and Pb concentrations in the atmosphere were 1.29 μg/m3, 2.01 μg/m3, and 1.12 μg/m3, which were far lower than those of the relevant EPA emission limits.

Pongamia seedpods are recognized as a potential feedstock for sustainable aviation fuel production due to the relatively high oil content of the seeds. Pongamia pods are byproduct residues available after seed separation. Pods have high chlorine and potassium content that may be problematic in thermochemical energy conversion systems. Leaching experiments were performed to remove inorganic constituents of pods and thereby reduce the potential for fouling, slagging, and agglomeration. A 23 factorial design determined the impacts of process operating parameters (i.e. rinse water temperature (25 °C vs. 75 °C), rinse duration (10 min vs. 2 h), and particle size (

Gas hydrate formation during subsea oil and gas production can result in flowline blockages, which present enormous economic and safety risks. Certain crude oils have natural anti-agglomerant (AA) properties, which facilitate their non-plugging behavior over a defined operating window. Thus, it is crucial to be able to easily screen a crude oil system for its tendency to form hydrate plugs. In this paper, we present a Hydrate Plugging Assessment (HPA) technique that can be used as a rapid screening method to evaluate the plugging tendency using a high pressure differential scanning calorimeter (HP-DSC). The technique requires a small crude oil sample (~15 mg), and the experimental time is relatively short. In this work, HP-DSC tests were conducted on 13 crude oils (22 to 45 ˚API). Tests were conducted at various water contents, salinity, chemical dosage (without/with AAs), and different hydrate structures. The results show that an increase in water content destabilizes the emulsion, and increases the hydrate plugging risks. An increase in salinity decreases hydrate plugging tendency. Different hydrate crystal structures showed that for a similar water content, salinity, and driving force, structure II (sII) hydrates have a slightly greater agglomeration tendency compared to structure I (sI) hydrates. Finally, the effect of combining a low stability oil with a high stability oil showed that the resulting emulsion retained the high stability property, paving the possibility for natural oil treatment. In summary, these studies show that the HPA technique is a cost-effective and attractive method to evaluate hydrate plugging tendency.

Supercritical water gasification (SCWG) technology is one of the most promising ways to realize efficient and clean utilization of coal because of the special physical and chemical properties of supercritical water. K2CO3 is the most preferable catalyst to improve gasification efficiency. However, K2CO3 leads to ash agglomeration and massive volatility of alkali metals. The accumulation of agglomerated ash prevents the continuous operation of the system, and the volatility of alkali metals weakens the coupling of high-grade H2/CO2/H2O mixture with downstream process. In this study, K2CO3-catalytic SCWG of coal with NaAlO2 loading was firstly investigated in a laboratory-scale continuous reaction system to check whether NaAlO2 can inhibit ash agglomeration and lower the volatility of alkali metals without decreasing the gasification efficiency. The concentration of coal slurry was 20 wt%-35 wt% and the loading content of NaAlO2 was 0 wt%-7.5 wt% of dry coal. By doing GC, PSD, XRD, SEM and ICP-OES analysis for three-phase products collecting from the experiment, it was found that, when NaAlO2 loading increased from 0 wt% to 7.5 wt%, the carbon gasification efficiency of 20 wt%, 30 wt% and 35 wt% coal slurry improved from 90.7% to 93.9%, from 83.8% to 88.6% and from 72.6% to 80.5%, the percentage of H2 increased and the percentage of CO2, CH4 and CO decreased. The addition of NaAlO2 transformed K and Si of coal into K(Na,K)3Al4Si4O16 instead of K2Si2O5, which contributes to the distribution of ash particles into smaller size. 5 wt% NaAlO2 loading decreased the total volatility of alkali metals, and 7.5 wt% NaAlO2 loading will increase the total volatility of alkali metals.

Particle agglomeration plays a major role in the mechanism of gas hydrate accumulation and pipeline plugging. Gas hydrates are solid inclusion compounds composed of natural gas trapped in a three-dimensional water lattice that can form in petroleum flow lines and impede fluid transfer. Agglomeration mechanics are complex yet essential to creating reliable and accurate rheological models for optimizing fluid flow operations, of which the state-of-the-art includes the contact-induced and shear-induced agglomeration models. Particle size distribution measurements of water droplets in an oil-continuous phase reacting to form gas hydrate agglomerates over time can be performed using in situ focused beam reflectance measurement (FBRM) and particle video microscope (PVM) probes, or other similar tools. Particle sizing and interfacial interaction measurements form the basis of gas hydrate hydrodynamic multiphase flow models, which incorporate particle agglomeration/viscosity models and the capillary bridge theory-based cohesion model. In situ particle sizing probes can also serve as a supplementary process indicator of gas hydrate formation onset. It is essential to perform in situ particle-scale experiments to develop and validate an accurate gas hydrate agglomeration model, which is integral to state-of-the-art hydrate flow assurance modeling and risk assessment.