•High content of AAEM species Zhundong lignite was combusted.•The formation of eutectic mixtures contributes to the severe slagging near burner.•Zhundong lignite presents higher deposition propensity ...than other contrast fuels.•Zhundong lignite produces more fine particles than other contrast fuels.•Sticky surfaces enhance deposition tendency of Zhundong lignite.
The high-reserve Zhundong lignite, rich in Alkali and Alkaline Earth Metal (AAEM) elements, causes severe fouling and slagging problems in stationary combustion systems. In this paper, the ash deposition propensity as well as its relation to AAEM-rich fine particulates was investigated in a 25kW down-fired furnace possessing similar conditions to practical combustors. The high content AAEM (mainly calcium) species in Zhundong lignite results in the molten slag at the vicinity of the burner inlet, differing from other case burning high-ash-fusion (HAF) bituminous coal. The ash deposits were collected at a position with gas temperature of 800°C, whereas the fine particulates were sampled at the same position by a two-stage nitrogen-dilution isokinetic probe. The deposition tendency of ash particles from Zhundong lignite is apparently higher than those from contrast fuels and even herbaceous biomass. It is then related to the sticky surfaces of both bare deposition tube and bulk fly ash particles, forming from large amounts of AAEM species, which enhances the deposition propensity.
Manufacturing of nanostructured materials and functional devices offers many exciting opportunities for substantial contribution in renewable energy utilization, environmental compliance, and product ...development. In the past two decades, gas-phase flame synthesis has not only proved to be one of the most scalable and economical technologies for producing well-controlled nanostructured materials, including single metal-oxide, mixed-oxide nanocomposite, and carbon nanostructures, but also has been recognized as robust fabrication method of nano-devices. In this paper, we focus our review mainly on the recent trends in specific applications of flame aerosol synthesis in the last decade, e.g., (a) usage of a substrate in stagnation geometry with controlled particle temperature–time history, (b) application of external fields to control particle characteristics, (c) development of advanced spray technique for doping synthesis of nanocomposites of multicomponent metal oxides or carbon–metal oxides, and (d) fabrication of nanomaterial-based functional devices. For the possibility to improve the design and operation of flame aerosol reactors, we summarize recent advances in: (i) in situ optical diagnostics for either gas phase or particle phase in flame field; (ii) multi-scale modeling and simulation employing gas-phase chemistry, population balance method, molecular dynamics and nanoscale particle dynamics.
In this paper, recent advances in the discrete-element method (DEM) for describing motion, deposition, agglomeration or aggregation of a large number of adhesive spherical particles immersed in fluid ...flows, termed as adhesive particulate flow, are reviewed. The constitutive equations together with the length and time scales of DEM are compared with those of other similar Lagrangian particle methods, e.g., molecular dynamics (MD), Brownian dynamics (BD), dissipative particle dynamics (DPD). The adhesive contact force and torque models in the presence of different adhesive effects are examined, including van der Waals force, ligand-receptor binding, liquid bridging force, interface adhesion, and sintering forces, all of which play an important role in DEM formulations for different types of adhesive particulate flow problems of interest in energy, combustion and environmental fluid mechanics problems. A summary of various kinds of particle-field interactions is presented, including fluid forces, electric field forces, acoustic force, and thermophoretic force. The computational method is illustrated by application to a series of examples involving capture of spherical particles by a fiber in a uniform upstream flow, examining the deposition/aggregation patterns of both mono-size and binary-size particles on the cylinder with and without the presence of electric field effects, which may be due either to charging of the cylinder or polarization of the particles. Particle capture problems of this sort are commonly encountered in filtration problems and ash-removal problems experienced in environmental and combustion applications, respectively. The article concludes with a discussion of remaining modeling challenges in development of discrete-element methods for adhesive particulate flow fields.
In this paper, we examine the dynamic behavior of sodium (Na) release during the pulverized coal combustion of Zhundong lignite using a laminar, Hencken flat-flame burner technique. By utilizing the ...gap between the excitation energies of the gas and particle phases, a new low-intensity laser-induced breakdown spectroscopy (LIBS) is developed to distinguish the existence of sodium in the particle or gas phase along the combustion process. Within the coal flame domain, Na atomic spectra in the particle phase are clearly detected that consistently agree with the NIST database. For the first time, the in situ verification of the gas phase Na release accompanying coal devolatilization is fulfilled when the ambient temperature is high enough. The residence time, indicating Na release from particle to gas phases, is determined from the signal. By using a theoretical analysis, the Na release time approximately coincides with the characteristic pyrolysis time of lignite, further confirming the observation above. The effects of ambient temperature, coal rank and oxygen concentration are further discussed. This work may provide a basis for exploring the formation mechanism of submicron fine particulates during coal combustion.
Moutan Cortex charcoal has been used to ameliorate blood heat symptoms and treat pathologic hemorrhage down the ages. Although well known as an agent with the effect of astringency and hemostasis, ...its active ingredients and action mechanism remain unclear. In the present study, molecular docking technology was employed to screen the potential hemostatic compounds in Moutan Cortex charcoal and their target proteins. Protein–protein-interaction (PPI) analysis was performed to explain the functions and enrichment pathways of the target proteins. The results showed that a total of 25 compounds were estimated as active constituents targeting multiple proteins related to hemostatic diseases, including 5 proteins (SERPINC1, FVIII, FX, FII and FXII) that were considered as the key targets. Then the drug-target (D-T) network was constructed to analyze the underlying hemostatic mechanism of Moutan Cortex charcoal, followed by a hierarchical cluster analysis (HCA) for compounds clustering, and a coagulation screening test for compound verification on their coagulation activities, with the results indicating that M15 (5-Tetradecenoic acid) and M31 (1-Monolinolein) might be the key compounds contributing to the hemostasis effect of Moutan Cortex charcoal by involving in the pathways related to complement, coagulation cascades and the platelet activation, particularly by activating FVIII, FX, FII and FXII and inhibiting SERPINC1. This study has demonstrated that Moutan Cortex charcoal may work as a hemostatic through the interaction between multiple-compounds and multiple-proteins, which provides the basis for further researches on the hemostasis mechanism of Moutan Cortex charcoal.
This work is assessing a study of the collective ignition behaviors of dispersed coal particle streams, with ambience temperature from 1200K to 1800K and oxygen mole fractions in the range of 10–30%. ...The dispersed coal particles of 65–74μm are injected into an optical Hencken flat-flame burner by a novel de-agglomeration feeder. Three kinds of pulverized coals from different ranks, Hulunbel lignite, high-ash-fusion bituminous and low-ash-fusion bituminous, are considered. The normalized visible light signal intensity, deleting the background noise, is established to characterize the ignition delay of coal particle streams. Firstly, the prevalent transition from heterogeneous ignition to hetero–homogeneous ignition due to ambience temperature is observed. The pure homogeneous ignition rarely occurs, with an exception under high temperature and low oxygen for high-volatile coal. By comparing time scales between pyrolysis and heating processes, the competition of the volatile evolution and heterogeneous surface reaction are discussed. Then, the effects of ambience temperature, oxygen mole fraction and coal rank on the characteristic ignition delay are examined. Finally, the transient mode is developed, which not only well interprets the observed ignition transition phenomena, but also approximately predicts a variation of heterogeneous ignition time as a function of oxygen fraction.
The clogging mechanism has attracted increasing attention due to widespread applications of fibrous filtration in the industry. We carry out computational fluid dynamics with a discrete element ...method to investigate the clogging in a two-fiber system. The role of interparticle adhesion among microparticles in the unclogging-clogging transition is examined. A clogging phase diagram in the form of the Stokes number and the adhesion parameter (Ad) is built. We show that the formation of clogs contains two sequential processes, the growth of particle chain and the formation of bridges connecting two fibers. A stronger adhesion results in a longer growing time but a shorter bridging time of particle chains. These competing trends yield an “optimal” Ad range with the fewest penetrating particles. The structural analysis of the clogs shows that as Ad increases, the average local volume fraction and coordination number decrease. The reconstruction of particles mainly happens in the initial cake filtration stage.
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•A clogging phase diagram in the form of St and an adhesion parameter Ad is built.•For St=1.55, we find that there is an “optimal” clogging domain with Ad=18–36.•For the cake, the average coordination number drops significantly as Ad increases.•The reconstruction of particles happens in the initial the cake filtration stage.
The collision-sticking phenomenon among micron-sized particles is ubiquitous in nature and plays an important role in formation of particle agglomerates or deposits. In this paper, a validated 3D ...JKR-based discrete-element method (DEM) is employed to investigate oblique collisions of micron-sized particles. Special attention is paid to the effects of impact parameter and particle size on the sticking/rebound criterion and energy dissipation pathways. Various energy dissipation mechanisms, including viscoelastic effect, sliding resistance and rolling resistance, are incorporated in our DEM model. Based on our simulation results, the temporal evolution for the collision process is revealed in detail to establish a deeper understanding of collision dynamics. Moreover, two regimes are clarified according to the effect of impact angles on the sticking criterion. In the low impact angle regime, the normal critical velocity VCN keeps as a constant. While in the regime of high impact angle, VCN rapidly drops. Furthermore, the strong effect of particle size ratio on the critical velocity is also analyzed. This effect can be well described by the dimensionless adhesion parameter, Ad. Finally, a generalized formula is drawn as the sticking/rebound criterion for collisions of fine particles, which can be readily implemented in computational fluid dynamics (CFD) codes.
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•Microscopic information of oblique collisions between micro-particles is revealed.•Energy dissipation pathways during collisions are investigated.•An explicit formula is drawn as a sticking/rebound criterion for binary collisions.•The criterion incorporates both effects of particle size and impact parameters.
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•AO improves joint swelling, joint score, bone and cartilage destruction in AA rats•AO inhibits inflammatory infiltration and MMPs in AA model rats•AO principally improves RA by its ...differential effect on 11 important metabolites
Atractylodes Rhizoma is one of two principal components in Ermiaosan, a well-known traditional Chinese medicine for the treatment of rheumatoid arthritis (RA). Atractylodes oil (AO) represents a potential alternative treatment for RA. The purpose of this study was to investigate the effect of AO in rats with Adjuvant Arthritis (AA) by exploration of changes in serum metabolites using gas chromatography-mass spectrometry (GC-MS). Foot thickness and arthritis score, ankle joint pathological structure, the concentrations of TNF-α, IL-1β, IL-6, IL-17 and the expression of MMPs in ankle joint tissue were measured as indicators of efficacy of treatment using AO. In addition, multivariate statistical analysis was used to identify differential production of metabolites and biomarkers, and to analyze metabolic pathways. The results demonstrate that administration of AO resulted in a good therapeutic effect in the AA rat model, with significantly improved joint swelling, reduced joint score, and inhibition of inflammation, synovial pannus hyperplasia, and bone and cartilage destruction. Furthermore, AO was found to exert its effect against rheumatoid arthritis principally by differentially affecting 11 metabolites and six metabolic pathways, predominantly related to abnormal amino acid metabolism, in addition to energy-related metabolic pathways. This study evaluated the capability of AO to effectively treat AA rats, providing a novel strategy for the treatment of RA.
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