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For the production of high-strength lump coke from non-baking coals the processing, agglomeration and gentle coking of the agglomerates are essential steps. In previous studies the influence of the processing regime and the briquetting and coking parameters were systematically analysed. The current investigations combined the intensive processing of German and Indonesian brown coals in a twin-screw extruder and a swing mill with the addition of 5 wt% draff as a coking additive. Briquetting the mixture of coal and draff leads to an increasing briquette compressive strength. This binding capability of the draff is probably caused by the denaturation of protein during the processing in the twin-screw extruder and the swing mill. The produced coke as well offers a high mechanical strength. During the coking process the protein and cellulose material could be partially converted to solid bridges between the particles causing a higher coke compressive strength.

Two kinds of polymer solutions with different chemical properties were adopt to conduct the chemical agglomeration experiment via the simulated coal-fired facility, and the atomization performances of sesbania gum (SBG) and styrene butadiene emulsion (SBE) solutions were also investigated using a Phase-Doppler anemometry (PDA) system. The results revealed that the abatement of fly ash fine particles was obviously influenced by the atomization performance of chemical agglomeration solution, which were mainly depended on the mass concentration of agglomerant and the air pressure of nozzle. Owing to the viscosity of SBG solution was higher than that of SBE solution at the same mass concentration, the atomization performances of SBG was deteriorated faster leading to the removal performance of SBE on fine particles was better than that of SBG. When the mass concentration was 0.5%, the median diameter (D50) of SBG solution was 24.032 μm, and removal efficiency on fine particles was 28.44%. Whereas for SBE, the removal efficiency was up to 33.19% with a D50 of droplets was 16.918 μm. Besides, the increasing of nozzle air pressure was beneficial to improve the atomization of chemical agglomeration solution, resulting in the reduction of fine particles number concentration after chemical agglomeration. According to the analysis of SEM, EDS and XPS spectrum, the results indicated that the fine particles could be adhered together to form newly larger aggregate by chemical force.

When using biomass as fuel for power and heat production, compounds in the biomass ash may cause problems for fluidized bed boilers, such as corrosion and agglomeration. Especially high alkali biomass has been shown to cause agglomeration that may lead to defluidization. Many laboratory scale studies have been done to clarify which compounds cause agglomeration and to identify actions to minimize the agglomeration tendency. However, most studies have used fuels or ashes; only a few studies using pure alkali salts can be found. To be able to study the agglomeration mechanisms in more detail, pure alkali salts were fed into a quartz bed as a function of time at different bed temperatures. Each test was terminated either at the point of defluidization or after a certain amount of salt had been fed. Samples of agglomerates and bed material were analyzed by SEM/EDX after the tests. The results showed that Na2CO3 reacted with the bed material to form sodium silicate, while NaCl, as well as Na2SO4, melted and glued the bed particles together. However, when water was added to the fluidization air, NaCl also reacted with the bed material, forming sodium silicate at temperatures above the melting point of NaCl. The amount of melt causing defluidization was calculated (based on analysis) to be around 0.10–0.13 wt% for the melting compounds. Furthermore, the amount of sodium silicate melt that was formed in the tests with Na2CO3 was calculated (based on fed Na2CO3) to be much higher (0.59–0.96 wt%) at defluidization.

The characteristics and mechanisms of inorganics and mineral transformation, particle agglomeration and ash deposition during Zhundong lignite combustion in a 0.2 t/d lab-scale circulating fluidized bed (CFB) furnace were experimentally investigated. A sample of Zhundong lignite with particle size

Hydrate formation and slurry flow experiments were conducted in w/o emulsion systems using a high-pressure flow loop to investigate the effect of hydrate agglomeration and deposition on hydrate slurry viscosity. Hydrate agglomeration process was recorded by a particle video measurement probe and the wetted agglomeration between hydrate particles and water drops was observed. Results showed that due to the effect of the water drops, it formed complicated hydrate agglomerates that could encapsulate water phase inside. Therefore, the unconverted water phase must be considered and a modified fractal dimension is required when estimating the hydrate effective volume fraction. The required fractal dimension for the agglomeration stage was larger than that for the stabilization stage by about 0.25. Hydrate deposition could affect the slurry viscosity by lowering the hydrate effective concentration and decreasing the flow diameter, while it had little effect on the required fractal dimension. Effect of water cut and shear rate were analysed. The slurry viscosity increased with the increase of the water cut and decreased with the increase of the shear rate, demonstrating the hydrate slurry was shear thinning. The best-fit fractal dimension was larger in higher water cut conditions and increased with the increasing shear rate. According to the experiment results, evolution of the head loss and slurry viscosity in a real long-distance transportation pipeline was divided into 5 stages.

To investigate the microprocess of hydrate particle agglomeration, a high-pressure visual cell was used for repeated experiments of hydrate particle formation and flow from methane + water systems at an experimental temperature of 275.15 K, an initial pressure of 6 MPa and a rotation rate of 200 rpm. During the experiments, a high-speed camera was used to capture the micromorphologies and micro flow behavior of hydrate particles. Based on the experimental data obtained by the high-speed camera, three types of micromorphologies were identified for hydrate particles. Then, the variation in the average diameter of hydrate particles and the characteristics of hydrate particle size distribution were investigated by calculating the equivalent projection area diameter of hydrate particles. During the experiments, particle collision, particle agglomeration and particle breakage were the three main micro flow behaviors of hydrate particles captured by the high-speed camera. The whole process of hydrate agglomeration under flow conditions was also captured by the high-speed camera. Finally, according to the variation in the average diameter of hydrate particles and the micro flow behavior of hydrate particles, a physical model for the whole process of hydrate particle “agglomeration” was established.

Additive water is usually needed to preserve 9–11% moisture content of blended coal in the stamp-charging coking process, which in fact is unfavorable for coking property. An insight into the improvement of coking property of coal blends with much low-rank coal (long flame coal SFC, lignite HLH) by regulating additive water was proposed in terms of its effects on the metaplast fluidity and the particle agglomeration behavior. The results indicate that the cohesiveness of gas coals (GC) can be properly enhanced by adding water. The restrictions on the condensation of aromatic structures and the break-up of –CH2– structure and the development of the polyhydroxy groups in aromatic structures are favorable to increase the fluidity of metaplast after adding water, as demonstrated by the optical texture and FTIR analysis of the semicoke (450 °C). The great difference in the hydrophilic properties for various rank coals leads to the particle agglomeration of gas coal and fat coal (GC and FC), which makes them difficult to mix uniformly with SFC after adding water, thus reduces the coking property. A reasonable approach of adding water suggests that H2O and SFC should be well mixed prior to blending with caking coals, which can lead to a uniform particle distribution and a better coking property. This approach promotes the direct and efficient utilization of low-rank coal (especially lignite) by the blending coking with no or less drying and dewatering processes.

Turbulent agglomeration is a simple and economical method to improve the agglomeration of fine particles from coal combustion, which is beneficial to the particle removal efficiency of conventional equipment. However, the agglomeration efficiency for fine particles is low by single turbulent agglomeration because of the weak adhesion forces between particles, which leads to plenty of ineffective collisions. In this study, a novel technique was presented to improve the effect of fine particles agglomeration in turbulent agglomeration by adding chemical spray. The influence of single turbulent agglomeration and chemical-turbulent agglomeration on fine particle concentrations, particle size distributions, ESP performance, particle removal efficiencies in different stages and total dust concentrations after ESP were investigated respectively. The results showed the chemical-turbulent agglomeration had better effects on the agglomeration and removal of fine particles than single turbulent agglomeration. After chemical-turbulent agglomeration, the PM10 number concentration decreased about 34.1% than single turbulent agglomeration, and particle number concentration dropped at each stage under 10 µm, especially at 0.1 µm. Meanwhile, the application of chemical-turbulent agglomeration led to the number removal efficiency of PM10 increasing from 82.6% to 89.9%, the mass removal efficiency increasing from 84.5% to 91.8%, and the total dust concentrations after ESP reducing about 638 mg·m−3 than single turbulent agglomeration, respectively. Furthermore, the enhancement mechanism of chemical-turbulent agglomeration was explored by analyzing adhesion forces between particles and calculating the turbulent agglomeration kernel. In this study, the capillary and solid-bridge forces between particles and the increasing value of KTS after chemical spray were considered as the main reasons for better effects of chemical-turbulent agglomeration.

A comprehensive analysis of coal quality factors affecting coal agglomeration characteristics was carried out. The influence weight of seven main coal quality indices on agglomeration was calculated by the entropy method. Furthermore, a reliable and comprehensive coal quality index was obtained to evaluate the characteristics of coal agglomeration by the agglomeration experiment results. The proximate analysis, ultimate analysis, and petrographic analysis results were applied for the analysis of organic constituents. The XRF and ash fusion temperatures were applied for the analysis of inorganic constituents. Results show that there is an absolute positive correlation between the C/H, FC/V and the characteristics of coal agglomeration. Both of the vitrinite content and the average reflectivity of the vitrinite have a positive effect on the coking ability of coal. Alkali oxides not only have a low melting point but also can react with Si and Al to form low melting point eutectics. Both of these characteristics result in coal ash slagging. The entropy method was adopted to analyze the effect weight of C/H, FC/V, vitrinite content Vi, vitrinite average reflectivity Rave, ash deformation temperature (DT), Base/Acid ratio (B/A) and Silicon ratio (G) on the agglomeration characteristics of coal. The weights are 11%, 10%, 26%, 12%, 9%, 14% and 18%, respectively. Among them, vitrinite content had the largest effect, and DT had the least effect. In addition, an empirical index of coal agglomeration characteristics is proposed, and the discriminant limits are provided. The results are helpful to the evaluation of coal agglomeration, and useful to the safe and efficient operation of boilers.

Fuel diversity is critical in the utilization of fluidized bed combustors. To support the use of diverse fuels including low rank coals and biomass, interactions of chemical components that lead to operational issues such as agglomeration need to be studied. Low rank coals and biomass are generally rich in alkali and alkaline earth metals and their role in the initiation of agglomeration is investigated in this work. A novel modeling methodology to quantify the contribution of these components to the initiation of agglomeration via the condensation of gaseous species was developed. This condensation modeling methodology complements thermodynamic simulations such as those using FactSage and agglomeration models used for high rank coals. The study shows that at temperatures below 800 °C condensed phases play a critical role in the initiation of agglomerate growth. The condensation temperature is computed to be about 30–50 °C lower than the predicted molten slag-liquid formation temperature (740 °C for the lignite and 810 °C for the subbituminous coals studied). The extent of condensation correlates to the amount of alkali metals in the ash. Sodium sulfate forms a major component of condensates for low rank coals with condensation occurring over a larger temperature range for lignite than the sub-bituminous coals studied.

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.

The co-combustion of sewage sludge and woody biomass is a key issue in coal power plants. Different combustion and ash behaviors of sewage sludge and woody biomass cause unpredictable operating concerns. In this study, the combustion and ash agglomeration behavior of blended fuel of sewage sludge and woody biomass (BSW) were investigated while coal co-combusted with it. Thermogravimetric analysis (TGA) revealed that adding a high amount of BSW into the coal lowered volatilization, ignition, and burn-out temperature. The char combustion reactivity of coal differed from that of BSW. The shrinking core model (SCM) and volumetric reaction model (VRM) were used to fit the char combustion reactivity of coal and BSW. In the case of ash agglomeration behavior, BSW addition led to increasing particle agglomeration at fouling temperatures. In particular, phosphorus composition influenced particle growth, which was verified using scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM–EDX) analysis. Furthermore, the ash mixture ratio of BSW and coal changed the intensity of the phosphorus-bearing mineral phase from X-ray diffraction (XRD) analysis, and finally influenced the melting temperature of the ash.

To study the velocity sensitivity of a lignite reservoir under different stresses and formation water conditions, orthogonal experiments are performed with pH, salinity, and effective stress as the main factors, and evaluation indexes are extracted at different stages. The effects of the main factors on each index are analyzed by means of range analysis, variance analysis, and effect diagram to study the mechanism of velocity sensitivity in a lignite reservoir. Under a given effective stress condition, the change in lignite permeability with the variation of fluid pressure undergoes three evolutionary stages (stable-rise, decline, and fluctuation) and two effects (sensitization and velocity sensitivity effects) exist. On the basis of the seven evaluation indexes, an evaluation index ( D m ) suitable for describing velocity sensitivity damage in the presence of sensitization stage is proposed. Extreme and variance analyses show that salinity is the main factor that controls the lignite sensitization (rise) stage. In the velocity sensitivity (decline) stage, the permeability attenuation rate is controlled by pH and salinity, and the sustained range of velocity sensitivity is affected by pH and effective stress. The fluctuation stage is mainly affected by effective stress. It is analyzed that pH mainly controls the migration and agglomeration of pulverized coal particles through hydrophilicity, and salinity controls the dispersion and agglomeration of pulverized coal particles through the zeta potential generated by an electric double layer. Effective stress influences the sensitivity of lignite reservoir by effecting pore structure.

Oil agglomeration can be a promising technique to recover fines and ultra-fines coal particles from the discarded tailing generated from coal preparation plants. In the present study, an artificial neural network (ANN) and response surface methodology (RSM) was used to predict the behavior of coal oil agglomeration in terms of % ash rejection (% AR) and % combustible matter recovery (% CMR). A three layered Feed Forward Neural Network was developed by varying process variables such as solid concentration (SC), oil dosage (OD) and agglomeration time (AT). Waste soybean oil was used as bridging liquid. An approach of Multilayer Forward Back Propagation Neural Network has been used in conjugation with the hyperbolic tangent sigmoid (tansig) as transfer function. The network is well trained (learning) with Levenberg-Marquardt (LM) algorithm. For further improvement in the generalization of the developed ANN model Bayesian regularization technique has been adopted. Sensitivity analysis was performed using Garson’s algorithm, Pearson correlation coefficient and Connection weight approach. The % CMR values predicted from ANN have been in good agreement with the obtained experimental values (R2 0.9965) and shows better correlation between predicted and observed values than RSM (R2 0.9892). Also, for % AR the correlation (R2 0.9965) obtained using ANN found to be higher than RSM (R2 0.9956).

An effective bed material is crucial to remit slagging/agglomeration for high-sodium lignite during circulating fluidized bed (CFB) gasification. In this study, the exploration of effective bed material for use as slagging/agglomeration preventatives of high-sodium lignite mined from Zhundong district was conducted in a 0.4 T/D CFB test system. Three mineral materials, SiO2-based quartz sand, Al2O3-based corundum and CaO/Fe2O3-rich boiler ash collected from bottom ash of a CFB industrial boiler, were selected as the potential bed material. Their impacts on the de-fluidization tendency, transformation and migration of alkali metals, priority of reactions involving sodium-based species, formation of liquid slags and ash fusibility were investigated through the characterization of ash samples and thermodynamic equilibrium calculation by Factsage 6.1. The particle-size analysis results presented the improvement of three bed materials in the growth of ash particles followed the order of quartz sand > corundum > boiler ash. This order was ascribed to their reaction priority with sodium-based compounds in coal and the chemical property (mainly referring to ash fusibility) of corresponding products. Generally, reactions between sodium-based species and minerals (Al2O3 and SiO2) were the main way of sodium retention within the ash in gasifier. As boiler ash was used, however, Al2O3 and SiO2 preferentially reacted with the CaO enriched in boiler ash rather than sodium-based species in coal, resulting in very low sodium retention. Under such circumstances, computing results suggested the ash in gasifier could withstand higher gasification temperature, consistent with the measured results of ash fusibility. Additionally, the gasification temperature operating range could be largely widened by simply increasing CaO/Fe2O3 content in gasified ash. Therefore, boiler ash is an effective and low-cost bed material for use as the slagging/agglomeration preventative of high-sodium lignite during CFB gasification.

Fly ash fine particles emitted from flue gas during coal combustion are the primary atmospheric pollutants in China. The purpose of this study was to investigate the characteristics of the zeta potential of fine particle suspensions. The relationship between the zeta potential and the fine particle removal efficiency was also discussed. Batch experiments were conducted to evaluate the zeta potential of fine particle aqueous solutions under various pH, ion concentration, surfactant, polymer, and chemical agglomeration solution conditions. A chemical agglomeration system was designed to simulate the removal process of the fine particles. The test results indicated that the zeta potential absolute value of the solution decreased initially and then increased as the pH increased. As the pH increased from 4 to 12, the zeta potential decreased from Zp = 9.4 mV to Zp = −45.4 mV. The isoelectric point (IEP) was 4.3. Also at the IEP, the highest fine particle removal efficiency of 25.9% was achieved. The zeta potential increased as the metal cation concentration of the solutions increased. The trivalent cation Al3+ exhibited the best performance, which increased Zp from −32.1 mV to −11.2 mV and produced the highest fine particle removal efficiency of 9.2%. Polymers significantly impacted the zeta potential. As the concentration of kappa-carrageenan (CAR) increased from 0.01% to 5%, the zeta potential increased from −30.1 mV to 12.6 mV. The highest fine particle removal efficiency of 41.8% was acquired at a concentration of 0.5%, which had the lowest zeta potential absolute value of 3.5 mV. It can be inferred that the increase in the zeta potential induced the growth of the energy barrier, which prevented particle agglomeration. The suspension with a lower zeta potential exhibited a better fine particle removal efficiency.

Fine particles are significantly harmful to the human body and the atmospheric environment. However, the electrostatic precipitator (ESP) removal efficiency for PM 2.5 is low, therefore chemical agglomeration technology, which uses various chemical agents to induce particle agglomeration, improving the efficiency of ESP seems to be a promising pretreatment technology. In the present contribution a combination of experimental and DFT calculations has been used to study this technique. We used water, pectin and sodium alginate solutions as agglomeration agents. Experimental results showed that sodium alginate solutions is most effective, the particle diameter increased from 0.1 μm to 1 μm and the ESP removal efficiency of number concentration increased above 20% with chemical agglomeration technology. In theoretical studies we simulated various molecular clusters consisting of water, pectin and sodium alginate in combination with simple model silica particles (TOS) by using DFT calculations to explore the internal interactions in ESP system at molecular level. In our results, water, pectin and sodium alginate interacted with TOS by hydrogen bond, with interaction energy of 4.0 kcal/mol, 6.7 kcal/mol and 7.4 kcal/mol, respectively. Finally, according to the experimental and theoretical results, the chemical agglomeration models were put forward.

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.

Coal catalytic hydrogasification is an efficient approach to produce CH4. This study investigated hydrogasification characteristic of coal with diverse properties (caking propensity, high rank and sulfur content) in a pressurized fluidized bed. The approaches to realize high CH4 yield and stable fluidization were explored. Experimental results showed that carbon structure and sulfur content in coal were the key factors influencing hydrogasification reactivity. The mechanically mixed CaO/CaCO3 migrated into the interior of coal particle to enhance the activity of Co towards graphite carbon, and capture sulfur adsorbing on Co surface. The caking propensity of coal brought little resistance to the activity of catalyst, whereas, caused serious agglomerating phenomenon. The blending of caking coal with non-caking, low rank coals induced the active hydrogen spill-over and the volatiles-catalyst-coal interactions, which not only in-situ minimized the agglomeration propensity, but also enhanced the overall hydrogasification reactivity. Furthermore, the mechanism of hydrogasification was proposed by taking account of coal property, to broadening the application range of hydrogasification and producing CH4 efficiently (~80.0 wt% in 1.0 h).

The rapid formation of gas hydrates is one of the major concerns in offshore oil and gas transportation due to the possible plugging of unmanaged hydrate agglomerates. Within the oil and gas industry, hydrate management guidelines have shifted over the last decade from hydrate avoidance to hydrate management. Allowing hydrate formation in pipelines without blockages requires understanding of the hydrate formation and plugging mechanisms under different operational conditions. Furthermore, a predictive tool which can be coupled with the multiphase flow conditions encountered in the field is highly desired in order to ensure successful transportation of hydrate slurries. In the realm of modeling, one such hydrate plugging mechanism that remains unaddressed is the bedding of hydrate particles, which may occur when hydrate particles aggregate within the pipeline. In this work, a bedding model based on force balances has been developed and coupled with a transient multiphase flow simulator. It is proposed that agglomeration controls bedding and bedding is a function of the agglomerate size, which is assumed to follow a log-normal distribution based on an autoclave experimental study. The bedding model has been tested and validated against large-scale flowloop experiments at different water cuts and liquid velocities. Pressure drop comparison between the simulations and experiments shows an improvement after implementing the bedding model for simulations with low liquid velocity. This work may contribute to the understanding of the hydrate plugging mechanisms and be applied to optimize hydrate management guidelines in offshore oil and gas production.

Supercritical water gasification (SCWG) technology shows huge advantages to achieve efficient and clean utilization of coal. Ash agglomeration caused by K2CO3 addition makes ash discharging process more difficult and inhibits gasification reaction of carbon in agglomerated ash, which prevents the constant operation of the system and decreases gasification efficiency. This study investigated the formation mechanism of ash agglomeration in potassium carbonate-catalyzed SCWG of coal and find a solution to inhibit this problem. Experiments were conducted in an autoclave to figure out the effect of K2CO3 (0 wt%-10 wt%) and Al2O3 (0 wt%-20 wt%) on ash agglomeration level at 750 °C. After every single experiment, solid residue was dried and classified into different sizes (0–100 μm, 100–1000 μm, >1000 μm). The ash agglomeration characteristics was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDS). Results indicated that K2CO3 reacted with clay and quartz in raw coal, then formed K2Si2O5, KAlSiO4, KAlSi2O6 and KAlSi3O8. K2Si2O5 plays a cohesive role between different ash particles. Adding Al2O3 can effectively solve this problem by forming KAlSiO4 instead of K2Si2O5. Besides, Al2O3 enhances carbon gasification efficiency by increasing heating rate of feedstock temperature. Simulation work was also done to investigate the boundary condition for ash agglomeration.

Fly ash fine particles emitted from coal-fired power plants are the primary atmospheric pollutant in China. The pressure, temperature, and velocity distribution of the flow field in a chamber was simulated to evaluate chemical agglomeration. The effect on the removal efficiency of composition, concentration, pH, K + content, and zeta potential of the chemical agglomeration solutions as well as surfactant and flue gas temperature were evaluated. The results suggested that suitable solutions could significantly improve the removal efficiency of fine particles. Among these, kappa-carrageenan performed best and achieved a removal efficiency of 47.1%. Synergism was detected as two different chemical agglomeration solutions were mixed together: a mixture of kappa-carrageenan and konjac glucomannan attained a removal efficiency of 59.3%, higher than their individual values. The efficiency improved initially and then decreased as the solution K + concentration increased. Also surfactants affected agglomeration: cationic and non-ionic surfactants enlarged the removal efficiency by 9.0% and 3.7%, respectively, whereas anionic surfactants lessened average removal efficiency by 5.6%. Zeta potential influenced the removal efficiency as well: it peaked as the zeta potential was around 0 mV.

Electric agglomeration is a useful method to improve fly-ash particle collection efficiency in traditional electrostatic precipitators (ESPs) by increasing particle diameter and achieving particle pre-charging. In this study, a laboratory agglomerator, which consisted of a pre-charging region and a static mixer, was designed and tested for fine particle agglomeration. The pre-charging provided both positive and negative discharges in parallel channels. Fine water droplets were used to enhance particle agglomeration and collection efficiency in a downstream small ESP. The operating effects were evaluated under various applied voltages and droplet concentrations. Experimental results showed that the presence of water droplets effectively improved coal-fired particle agglomeration, pre-charging, and collection in the ESP. The total number collection efficiency improved from 53.91% to 86.02% compared with the condition without the agglomerator. In addition, a novel sampling method was used to observe agglomerated particles using scanning electron microscopy, and theoretical adhesive force analysis supported the proposal of a series of power-plant particle electric agglomeration modes.

Multi-field synergistic agglomeration is a promising pretreatment technology for improving the control and removal of fine particles. In this work, a novel agglomerator coupling with plasma charged ultrasonic spray and turbulent vortex generator was put forward, which has three agglomeration modes, namely turbulent agglomeration, atomized turbulent agglomeration and charged atomized turbulent agglomeration. As a pretreatment device, the agglomerator was combined with a fabric filter for the experimental investigation. The result indicated that the agglomeration efficiencies of the PM1 for the three agglomeration modes were 21.8%, 53.2% and 68.9%, respectively; and the removal efficiencies of the PM1 for the only fabric filter and the fabric filter combined with the three agglomeration modes were 66.5%, 83.9%, 86.8% and 89.7%, respectively. The characteristic experiment of the designed electrode showed that the stable voltage was about 19–38 kV and the charge-to-mass ratio was in the range of 1–5 mC kg−1. The optimization study of the two important parameters showed that the atomization quantity was recommended in the range of 1.6–2.7 kg∙h−1 and the inlet flue gas velocity should be as small as possible and close to 4.8 m/s to ensure the agglomeration effect.

Separating unburned carbon (UC) from coal fly ash (CFA) via froth flotation may be quantitatively characterized by the bubble–particle attachment angle (BPAA), susceptible to operational factors. This study established a novel experimental system to directly observe attachment behaviors between irregularly shaped UCs and a stationary air bubble. The independent and coupling effects of the main operational factors on the BPAA, including solution temperature, pH value, and collector dosage, were investigated via high-speed photography. The BPAA increased rapidly at the beginning of magnetic stirring for each factor, and then grew steadily when agitation time exceeded 180 s, gradually leveling off at its maximum value. The maximum BPAAs were 195°, 176°, and 169° at solution temperatures of 35, 30, and 25 °C, respectively. They were 169°, 144°, and 166° for pH values of 7, 9, and 11, respectively, and 169°, 189°, and 184° at collector dosages of 0, 1, and 2 mL/L, respectively. An overhigh dosage of collector kerosene resulted in oil agglomeration that hindered collision and adhesion. Response surface methodology (RSM) was adopted to analyze and optimize interactions between various factors, indicating that the predicted model that correlated the BPAA and the independent variables were in good agreement with the experimental data. The results show that the importance degree in BPAA decreases in a certain order. Moreover, several optimum solutions were obtained to achieve a maximum BPAA (~196°) under suitable conditions. The outcomes of this study strengthen bubble–particle attachment during the recovery of UCs from CFA by froth flotation, contributing to the comprehensive utilization of CFA.

Bitumen froth treatment is an important process step of the bitumen recovery from oil sands by surface mining. In bitumen froth treatment, water and mineral solids are separated from the target organic bitumen product by using hydrocarbon solvents. Residual water and mineral solids in the bitumen product are detrimental to pipeline transport and downstream processes. Depending on the solvent composition, the commercial naphthenic and paraffinic bitumen froth treatment processes proceed via the oil-water separation mechanisms of coalescence and agglomeration, respectively. This study presents an experimental proof-of-concept for the existence of a transition region at ambient conditions and solvent-to-bitumen ratio of 1.6, where the advantages of the two commercial froth treatment processes may be combined and the drawbacks essentially eliminated. The bitumen product obtained in the transition region is virtually free from residual water and solids (

As emission regulations for vehicles have become stricter, the survival of direct injection technologies has been threatened due to increased particle emissions. By many researchers, there has been the effort to reduce the particle emissions. Nonetheless, the sources of particle emissions from turbocharged gasoline direct injection engines (T-GDI) were still not investigated enough. In this research, the particle emission from a modern turbocharged gasoline direct injection engine was investigated through combustion analysis accompanying simultaneous flame visualization. The experiments were conducted under three load conditions from naturally-aspirated to highly boosted conditions. The start of injection was swept to identify the effect of fuel mixing processes and differed combustion phenomena by the fuel injections and the boosting on engines. As results, the boosting changed the influence of heterogeneity and flow interaction by sprays, resulting differences in heat release from combustion and particle generation. The boosting on engines suppressed the agglomeration of particles into large aggregate in half, but promoted the nucleation of particles become double compared to natural aspiration. With optimized injection systems, the most impacting factors are the control of spray interaction with in-cylinder flow and oxidation processes of particles. In the boosted conditions, the uncertain particle sources could occur, such as spontaneous ignitions by mixture stratification and biased flame propagation by flow interaction. Through optimization of injection strategies, the combustion phenomena can be controlled to reduce the particle emissions in the moderate boosted conditions. The results of combustion analysis affecting the particle generation can provide the clues to reduce particle emission from T-GDI engines.

This paper reports the diagnosis of bed agglomeration during biomass fast pyrolysis in a fluidized-bed reactor at a wide range of temperatures (200–700 °C). The results show that under all conditions, bed agglomeration can be modelled using sand loading ( S L ), which is the mass of sand that directly interacts with the incoming biomass feed normalised to the total mass of biomass fed into the reactor. The values of sand loading S L during pyrolysis is greatly influenced by the ethanol-soluble extractive contained within the raw biomass. For the pyrolysis of the raw biomass, at temperatures S L follows an endothermic reaction pathway ( E a = 28 kJ/mole) during which its values increases with increasing temperature. However, at higher temperatures >350 °C, S L follows an exothermic reaction pathway ( E a = –45 kJ/mole) during which its values decrease with increasing temperature.

This paper reports the experimental investigation of fine particle agglomeration through an in-situ trial on aerodynamic agglomerators installed in front of the electrostatic precipitator (ESP) of a 330 MW PC-fired (i.e. pulverized-coal-fired) boiler. It is demonstrated that the agglomerators greatly reduce the fine particles entering the ESP. In particular, for the present case, the fine particles of the aerodynamic diameter ⩽2.5 μm (PM 2.5 ) and those ⩽10 μm (PM 10 ) are found to decrease 56.2% and 50.6%, hence reducing the overall particle concentration by 26.3 mg/Nm 3 at the outlet of the ESP. Also, the mercury concentration of 891.08 ng/g obtained in the ash from hoppers of the ESP with the agglomerators is 26.4% higher than that of the ESP without agglomerator. Therefore, the application of aerodynamic agglomerators is believed to reduce both emissions of fine particles and mercury from the flue gas of PC-fired boilers. In addition, the reason for the above observations is also explored in the paper.

The combustion of ethanol and dimethyl ether (DME) was performed over Pt/ZSM-5 catalyst in a packed-bed reactor to investigate the combustion characteristics and catalyst deactivation. Results showed that the CO2 yield and wall temperature for the combustion of DME were higher than those for the combustion of ethanol. The maximum CO2 yield for both fuels surpassed 72%. After 48 h of continuous combustion, CO2 yields of DME and ethanol decreased by 13.8% and 38.9%, respectively, attributed to the agglomeration of Pt and the formation of carbonaceous deposits on the catalyst. Transmission electron microscopy images showed considerable Pt agglomeration after ethanol combustion. Temperature-programmed oxidation results revealed two types of carbonaceous deposits with oxidation temperatures of 225 and 345 °C after DME combustion, but only the former type was detected after ethanol combustion. X-ray photoelectron spectra revealed that the mainly increased surface carbonaceous species were C C/C H and O C O after the combustion of ethanol and DME, respectively.

The characteristics of the interaction between fine particles and droplets in acoustic field were investigated experimentally in an acoustic agglomeration chamber. A novel technique to promote fine particles removal in the coupling effect of acoustic field and seed droplet with wetting agent was presented. The results showed that fine particle removal efficiency in the acoustic field correlates well with the wettability of wetting agent. As the relative contact angle decreases from 83° to 0°, fine particle removal efficiency increased by 18% at the sound pressure level (SPL) of 150 dB. The stage removal efficiencies with primary alcohol ethoxylate (JFC) and fluorinated surfactant (FS-310) solution droplets addition were close to those with water droplets addition in the acoustic field, but the stage removal efficiencies with sodium dodecyl sulfonic salt (SDS) and modified polysilanol surfactant (Silanol w22) solution droplets addition were much higher than those with water droplets addition. Particles can be separated effectively in acoustic field with wetting agent droplets addition, especially in a low intensity acoustic field. The removal efficiency was increased by 25% with SDS solution droplets addition than without droplets addition in acoustic field at the SPL of 130 dB. The wettability of fine particle surface was changed by wetting agent, making the coagulation processes irreversible in acoustic field. Therefore, fine particle removal efficiency was highly improved in the combined effect of acoustic wave and wetting agent solution droplets.

Energy crops and biogeneous residues offer the highest potential for future growth in biomass utilization. Traditional forest grown wood types, along with their consistent combustion characteristics, will thus be replaced by fuels with highly heterogeneous composition. Reliable prediction of their combustion characteristics and in particular of their ash behavior is essential for plant designers and operators trying to harvest this potential for energy conversion. In fluidized bed combustion, the fuel–ash induced agglomeration of the bed materials is one such behavior that needs to be described. In this paper a black-box model for agglomeration prediction was created through multivariate regression modeling using R-statistics v3.0.2. It based on the input variables bed ash concentration, particle size, fluidization velocity and fuel ash composition and predicts the maximum operable agglomeration-free temperature. Three linear and nine non-linear modeling algorithms have been applied to the data, optimized and validated in independent subsets. This validation was performed on results of controlled agglomeration tests, partly performed on our own test reactors and partly derived from literature. The final data set comprises 350 test results, covering 83 different fuels tested in seven different reactors. The validation revealed good predictive performance of the regression models, in particular of non-linear ensamble algorithms such as random forests, or cubist. These exhibit average deviations of around 60 K between model predictions and experimental results, which is very promising given the complexity of the system. After transformation of these prediction errors into agglomeration probabilities, a set of operational parameters unlikely to cause agglomeration can reliably be identified. A final evaluation of selected cases in controlled long-term tests could confirm the validity of these predictions.

In this study, vinasse, a by-product of sugar industry, was analysed for its behaviour during combustion in a fluidised bed combustor. Due to potential agglomeration problems owing to its high potassium content, the vinasse was first pre-assessed using agglomeration indices and muffle furnace tests. Subsequently it was co-fired with Thoresby singles coal in a bubbling fluidised bed of 25 kW thermal capacity. It is found that the agglomeration indices are good indicators of agglomeration tendency of biomass fuels and should be used to pre-analyse the material before firing in a fluidised bed. It was observed during cofiring in fluidised bed that agglomeration occurred very quickly due to high alkali content of vinasse. It is found that not only the alkali content of the material but its feed rate and combustion temperature are also controlling parameters for agglomeration. Vinasse can be used as potential fuel source by carefully controlling operational parameters or by adding alkali getters such as kaoline.

Ash residues produced from biomass gasification could agglomerate and cause severe ash-related problems. The objectives of this study were to determine the impacts of different operating parameters (including equivalent ratio (ER), residence time (RT), and gasification temperature (GT)) on ash deposits during corncob gasification and to further elucidate ash agglomeration mechanisms. The results indicated that the major difference between the ashes in gasifier and the cyclone fly ash (CFA) in mineralogy was that the CFA had a higher content of potassium-bearing compounds, particularly sylvite and potassium silicates, the contents of which could be as high as 47.33 wt% and 12.61 wt%, respectively. Compared with the gasifier fine ash (GFA), the microstructure of gasifier slagging block (GSB) seemed to be much denser and could be divided into three types, skeleton structure, porous texture, and dense structure. However, the melting of CFA was more severe than that of the gasifier ashes. During gasification, a higher ER and a higher GT favored the capture of more volatile species such as K, Ca, S and Cl in the cyclone while a lower GT and an increased RT favored the retention of Si, Al and Fe in the bottom residues. Moreover, when the ER was increased, less silicate minerals could be concentrated on the CFA. With regards to the operations performed at different times, no obvious variation in the ash mineralogy was observed. The ER had little influence on fly ash morphology while the slagging degree of fly ash could be enhanced with the increasing of RT.

Hydrate decomposition is inevitable in the process of hydrate formation, and has an important research significance. In order to study the crystal decomposition process, the formation and flow of hydrate particles in natural gas + pure water system were experimentally studied in a high-pressure visual autoclave. During the experiments, the high-speed digital camera was used to capture the micro-morphology and decomposition process of gas hydrate particles, and the high definition camera was used to capture the agglomeration state of nature gas hydrate at the visual window to connect macro-and micro-phenomena organically. By analyzing the data obtained from experiments, we find that the micro-morphology of hydrate particles can be roughly divided into two categories: planar flake particles and polyhedral solid particles. The planar flake particles are further refined into non-trunk snowflake particles and dendritic particles with trunk growth. When snowflake particles begin to decompose, they tend to decrease in area and have rounded edges. The decomposition time of dendritic particles is longer, and there is always trunk in the system. During the decomposition process, the number of particles gradually decreases to zero, but there will be a slightly increase. Meanwhile, it is found that the higher heating temperature and initial pressure will aggravate the fluctuation of particle number. Finally, according to the microscopic changes of hydrate particles in the decomposition process obtained by high-speed digital camera and other equipment, and based on the independent physical models of two types of hydrate particles, the physical model of hydrate particles decomposition is established.

Gas hydrate interparticle cohesive forces are essential to evaluate hydrate interfacial properties and determine the hydrate particle agglomeration behavior. In this study, a technique was developed in a modified high-pressure micromechanical force (HP-MMF) apparatus that enables hydrate anti-agglomerants (AAs) to be evaluated at an interfacial level under deepwater petroleum flowline conditions of high pressure and low temperature in a liquid hydrocarbon-dominated system. The hydrate cohesive force was found to decrease from the baseline (23.5 ± 2.5 mN m−1) to a non-measurable force value (

Fe2O3-based chemical looping combustion can be combined with steam-iron reaction and dry reform of methane for high-value-added products if Fe2O3 is deeply reduced. However, the deactivation caused by sintering and agglomeration worsens, which is an essential issue to be solved. In this study, the stability of Fe2O3-MgAl2O4 oxygen carriers was investigated not only in a packed bed reactor but also a fluidized bed reactor using CO as fuel and air as oxidant at 850 °C. Four oxygen carriers, with Fe2O3 loadings of 20 wt%, 30 wt%, 40 wt% and 50 wt%, were prepared through coprecipitation method. The results of 30 cycles in the packed bed reactor showed that the rate of CO2 production for each oxygen carrier deteriorated with cycling, indicating each oxygen carrier suffered deactivation. The CO2 yield of the oxygen carrier with 20 wt% Fe2O3 during the reduction stage dropped from 4.23 mol/kg Fe2O3 to 2.46 mol/kg Fe2O3, while that of the oxygen carrier with 50 wt% Fe2O3 changed from 7.26 mol/kg Fe2O3 to 2.56 mol/kg Fe2O3. Also, the SEM images after cyclic experiments demonstrated the size of crystallite for oxygen carrier with 20 wt% Fe2O3 was the smallest. In addition, the cycles in the fluidized bed reactor exhibited that defluidization occurred to all oxygen carriers except the one with Fe2O3 content of 20 wt%. These results proved the positive effects of decreasing Fe2O3 proportion on sintering and agglomeration.

Hydrates and waxes are two of the biggest flow assurance challenges during subsea oil production. They are both depositing species which can cause stenosis of the pipeline, reducing the available area for flow and increasing the pressure load for production. In extreme scenarios, the pipe can become completely blocked by either of these species. However, little is known about the interaction between waxes and hydrates and less still is known about how treatments for hydrates may affect waxes or vice versa. Hydrate deposition in a waxy pipeline may follow significantly different mechanisms from a bare steel pipeline due to a shift from a typically hydrophilic steel surface to a hydrophobic wax-coated surface. This study utilized a micromechanical force measurement apparatus in order to explore some of the interactions between waxes, both surface-deposited and dissolved in the bulk phase, and hydrates which have been treated with anti-agglomerant chemicals. It was found that waxes can significantly alter both the cohesive and adhesive forces caused by hydrate particles, but that the effect when anti-agglomerants are present may vary based on the composition of the anti-agglomerant. This incompatibility is important for operators to understand better, because the ineffectiveness of an anti-agglomerant when waxes are present could result in hydrate agglomeration and potential plug formation.

Asphalenes are regarded as the most polar and heaviest components in crude oil system. Their precipitation and agglomeration cause problems in oil recovery, production, and transportation. Asphaltenes are directly responsible for determining the viscosity of crude oil. In this work, the effects of asphaltene concentration and asphaltene agglomeration on viscosity were investigated. Toluene and heptane were used as asphaltene solvent and precipitant. The viscosities of asphaltenes-toluene solutions with various asphaltene concentrations were measured to investigate the impact of asphaltene concentration on viscosity. The results indicate that the viscosity of asphaltene-toluene solution exponentially increases with the asphaltene concentration. Elevated temperature causes viscosity reduction. The effect of temperature on viscosity reduction is more significant at higher asphaltene concentration. The dependence of viscosity on temperature can be well described by the Arrhenius equation, by considering the significance of activation energy. On the other hand, the asphaltene agglomerates form and grow with the increase of heptane concentration in crude oil-heptane-toluene mixture. A sharp viscosity rise of crude oil-heptane-toluene mixture was observed beyond heptane threshold concentration of 60 vol%. This is mainly resulted from the significant formation and growth of asphaltene agglomerates in asphaltene suspensions. The interactions between micro-sized asphaltene agglomerate particles could significantly affect the viscosity of liquid–solid system. The particle properties of asphaltene agglomerates including size, size distribution, number and shape factor were analyzed by microscopic images of the synthetic diluted oil. These contribute to the understanding of the effect of particle properties of asphaltene agglomerates on the viscosity of oil suspension.

Removing fine solids suspended in aqueous or oil media is crucial in many chemical, petroleum and environmental engineering processes with ever-increasing demands on improving product quality and meeting waste management standard. In oil industry, the removal of fine mineral solids is required to achieve high-quality oil products but remains a great challenge. This difficulty is due to hydrophobic and oleophilic nature of the mineral matters and small dimension of fine particulates. Here we introduce a two-step agglomeration method to destabilize bitumen-coated silica particles in cyclohexane by simply modifying their surface wettability using the amphiphilic polymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG), and then adding a small amount of water to trigger the formation of large particle aggregates. By sedimentation tests, we demonstrate that the two-step method can significantly enhance settling rate of the particles and reduce content of residual solids in the supernatant simultaneously. The underlying physical interaction mechanisms have been investigated using atomic force microscope (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D). The results suggest that PEG-PPG-PEG can readily adsorb to the bitumen-coated silica surface, thereby altering the surface from hydrophobic to hydrophilic and tuning its interaction with added water drops from repulsion to attraction in cyclohexane. This work provides useful insights into the development of effective strategies of removing suspended fine solids from oil media in petroleum production processes.

Oil agglomeration is an alternative technique for the cleaning and upgrading of low-rank coal or high-ash content coal slimes. Therefore, this approach was used to beneficiate coal slime with high-ash content of 31.34% in this work. The single-factor tests of oil agglomeration were performed to determine the appropriate ranges for various operational factors, including pulp concentration, reagent concentration, and agitation speed. The separation results suggested that considering the yield and ash content of clean coal, and combustible material recovery, the optimal pulp concentration and reagent concentration should be adjusted as 12%–16%, and 20%–24%, respectively, and the optimal agitation speed should be controlled as 800–1200 r/min. The Response surface methodology (RSM) based on Box–Behnken design (BBD) was adopted to investigate the significance of various operational factors, and the interactions between various operational factors on the response of combustible material recovery. A mathematical model was established to predict the response, and the results indicated that the established model was proved to be highly accurate in the prediction of response. The optimization of the solutions suggested that the maximal combustible material recovery of 97.49% was obtained with the pulp concentration of 12%, reagent concentration of 20%, and agitation speed of 1200 r/min. This work provides an experimental foundation for the operation design and process optimization in the oil agglomeration of coal slimes.

Agglomeration in fluidized beds begins locally by the sticking of slag–liquid-covered particles. Analysis of the composite fuel is not adequate in predicting agglomeration problems. Separation of the high rank Pittsburgh seam coal into particle classes based on specific gravity (SG1: 3 ; SG2: 1.3–1.6 g/cm 3 ; SG3: 1.6–2.6 g/cm 3 and SG4: >2.6 g/cm 3 ) and particle size (PS1 through PS7) helped to identify important particle-level slag–liquid formation tendencies. Slag–liquid formation tendencies under fluidized bed operating temperatures were determined both computationally and experimentally. Particles rich in certain iron and calcium phases melt at very low temperatures that are well within fluidized bed operating conditions. The iron rich particle classes (SG3 and SG4) showed the presence of several phases containing iron in different oxidation states. The presence of these iron phases was not detected in the composite bulk fuel. The possibilities of equilibrium liquid phase formation in the presence of different ratios of these iron and calcium oxides to alumino-silicates were determined. Presence of hematite was found to delay slag–liquid formation. Each of the particle classes showed distinct slag–liquid formation tendencies that indicate initiation of agglomeration around SG3 and SG4 particles. The study revealed the importance of particle class-level differences in mineral matter composition for the prediction of agglomeration during fluidized bed gasification. A novel integrated ash agglomeration model that accounts for particle hydrodynamics as well as particle class level ash chemistry has been outlined to predict agglomeration kinetics.

During initial drawdown in coal bed methane (CBM) production, the coal permeability declines due to partial fracture closure. The recently proposed technique for stimulation of natural coal fractures and cleats by the graded proppant injection targets a uniform cleat filling by the proppant. It provides maximum opening and conductivity during pressure depletion. The technique for graded particle injection below the fracturing pressure has been experimentally evaluated using injection of micro-sized ultra-light high-strength particles into coal cores. The laboratory tests on one-dimensional injection of different size particles into coal cores have been conducted under different effective stress conditions. Calculation of electrostatic interactions results in determining physico-chemical conditions that are favourable for particle–particle and particle–coal repulsion. The repulsion condition prevents particle attachment to the coal surface, particle agglomeration and also formation damage due to external and internal cake formation on the fractures’ surface. Particle placement in repulsion condition with low-salinity water results in almost three-time increase in coal permeability. Implementation of an empirical permeability shape factor allows matching the laboratory data by the mathematical model. The laboratory-based mathematical modelling as performed for the field conditions shows that the proposed method can yield up to six-time increase in productivity index.

Coal–oil agglomeration has been a prominent fine coal processing technique, which involves agitation of coal–water slurries in presence of immiscible oil forming coal–oil agglomerates. The present study investigates this technique using Taguchi (L16) design of experiments (DoE) methodology. Further, the process parameters like oil dosage, agitation speed, agglomeration time, pH and temperature were optimized using Analysis of Mean (ANOM) statistical approach and the percentage contribution of each of these parameters towards organic matter recovery (OMR) was determined by Analysis of Variance (ANOVA) statistical approach. The optimum conditions for maximum OMR (91.38%) were identified as oil dosage of 30%, agitation speed of 2500 rpm, agglomeration time of 2 min, pH of 12 and temperature of 30 °C. The contribution of each of the above process parameters towards the OMR was found to be in the following order: pH (30.38%) > agitation speed (23.06%) > oil dosage (20.63%) > agglomeration time (13.72%) > temperature (10.61%). Multiple linear regression analysis carried out using SPSS 19.0 ascertained a similar order of influence on the OMR. The highest contribution of suspension pH further establishes the fact that oil agglomeration process is a surface property based technique, as pH affects the surface charge on coal/mineral matter/oil droplets. A mathematical model was also developed using SPSS 19.0 to predict the OMR by oil agglomeration under the given set of experimental conditions. The developed model could predict the OMR to a significant extent, which can be further improved by a DoE technique of higher order.

Gasification of wood pellets in downdraft gasifier is confronted with the problem of granulated fuel agglomeration. It occurs when the wood pellets are moving from the pyrolysis zone to the oxidation zone and pellets stick together in lumps, which disrupts the movement of fuel and stops further process. In order to investigate the cause and regularities of fuel agglomeration, experimental studies of wood pellets thermal deformations during pyrolysis were carried out. Experimental studies were performed in an electrically heated horizontal tubular furnace from 300 °C to 1000 °C temperature in an inert atmosphere capturing wood pellet thermal deformations by a digital camera. During investigation the center temperature of the pellet was also measured. Analyzed results showed that wood pellet final diameter decreased when the heating temperature increased. It was also established that the pellet expanded from 400 °C to 900 °C heating temperature at the beginning of pyrolysis process. The maximum swelling effect was reached at 550 °C temperature and after it swelling intensity was decreasing till 900 °C temperature. Over 900 °C heating temperature, the expansion phenomenon was no longer visible. The tendency of wood pellet size alteration (swelling and shrinking) depends on heating temperature. The obtained results explain the reason for adhesion of wood pellets in the gasifier and reveal regularity of wood pellet size changes with increasing heating temperature.

Jetting pre-oxidation was proposed to destroy the caking property of bituminous coal in a fluidized bed (FB) gasifier. By defining an index omega to characterize the degree or realized effect of caking destruction, experiments were conducted in an electrically heated laboratory FB reactor under different conditions to investigate the feasibility and required conditions for effectively destroying the caking propensity of a kind of bituminous coal. The tested major parameters were the equivalence air ratio (ER) of jetting gas and the temperature in the jetting zone. At relatively lower temperatures it was hard to completely destroy the caking propensity of the tested coal particles. Without oxygen inside the jetting gas, it was also impossible to fully destroy the caking propensity of the coal even at sufficiently high temperatures. Thus, oxidation of coal particles at suitably high temperatures was essential to the expected good destruction of their caking propensity. For the tested bituminous coal this was achieved at temperatures above 1000 degrees C in the jetting zone and an equivalent oxygen ratio above 0.1 for the jetting gas (up to 0.3 considering gasification applications). For coal pre-oxidation in a FB, the agglomeration state of char particles due to caking adherence in the reactor could be anticipated via the unsteady variations in the bed temperature and H-2/CO concentrations in the effluent gas with reaction time. (C) 2014 Elsevier Ltd. All rights reserved.