Effects of surfactant on the evaporation, shell formation and disruptive behavior of slurry droplets

Wong, Shwin-Chung; Lin, Ar-Cheng; Chi, Haoyuan

doi:10.1016/s0082-0784(06)80405-4

Cited by 39 publications

(15 citation statements)

References 10 publications

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“…(3) Finally, as the viscous shell inhibits vaporization, the flame moves closer to the surface (contraction), heating up the shell quickly beyond the heterogeneous nucleation temperature of xylene and 2-EH acid, initiating disruptions. Moreover, disruptions are only observed if Sn(II)2-EH is present, coinciding with the observations of Wong et al 73,74 and Byun et al 75 In addition, the disruption may also be initiated by soot or nanoparticles, which are formed in the flame and transported back to the droplet by thermophoresis as proposed by Shaw et al 31 Very small particles (d p 200 nm ) from the gas phase can get close to the droplet surface, as was shown by Ben-Dor et al 76 The probability of such an effect may increase as the flame contracts due to a decreasing vaporization rate ( Figure S1 of Supporting Information), thus reducing the force (i.e., drag force due to the Stefan flow) counteracting thermophoresis. Entrapped ambient gas ( Figure 9) may also draw particles into the liquid, where they can act as nuclei.…”

Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehsupporting

confidence: 91%

“…Furthermore, they found that the decomposition characteristics of the surfactant influence the time delay until disruption. Similar observations were also made by Wong et al, 72,73 who showed that slurry droplets, which evaporate at temperatures higher than the decomposition temperature of the surfactant, exhibit strong disruption, whereas evaporation below that temperature decreases the droplet size monotonically. With increasing ambient temperature, increased intensity of droplet disruption has also been observed.…”

Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehsupporting

confidence: 85%

“…With increasing ambient temperature, increased intensity of droplet disruption has also been observed. Moreover, Wong et al 73,74 showed that only the addition of low-volatile surfactants in slurry droplets suppressed evaporation, superheating, and heterogeneous nucleation of the carrier fuel. Likewise, Byun et al, 75 observed a decrease in the vaporization rate and droplet disruption only when surfactant was present in the slurry droplet.…”

Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehmentioning

confidence: 99%

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Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

et al. 2013

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Flame spray pyrolysis is an established technique for synthesizing nanoparticles in the gas phase through aerosol combustion of precursor/solvent droplets. The combustion characteristics of isolated micron-sized precursor/solvent droplets are investigated experimentally. Pure solvent droplets burn uniformly and classically quasisteady, whereas precursor/ solvent droplets manifest disruptive combustion behavior. The fast onset of droplet disruption, which occurs only for solutions with dissolved metal precursors, is not due to solid-particle precipitation within the droplet. Instead, the mechanism of disruptive droplet burning is similar to that of slurry droplets, consisting of three main steps: (1) diffusioncontrolled burning of the high-volatile solvent, (2) viscous-shell formation due to decomposition of the low-volatile metal precursor, and (3) subsequent disruption due to heterogeneous nucleation. The time sequence of the three steps depends on the concentration and decomposition characteristics of the metal precursor, shortening with increased concentration and higher incremental decomposition temperature.

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Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehsupporting

confidence: 91%

Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehsupporting

confidence: 85%

Section: Decomposition During Combustion Of Binary Xylene/ Metal-2-ehmentioning

confidence: 99%

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Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

et al. 2013

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“…2. In this study, the temperature of 492 K corresponding to a 2% weight loss of surfactant is selected as the reference temperature for surfactant pyrolysis following the de®nition by Wong et al [6].…”

Section: Slurry Samplesmentioning

confidence: 99%

“…Also, for a slurry droplet, the solid particles accumulated lead to the porous shell formation as evaporation process advances. Due to its limited diusion through the monolayer and the shell formation, the evaporation rate is reduced as observed by Wong et al [6]. To account for an extent of evaporation suppression due to the surfactant addition, which is dicult to be modeled theoretically, the suppression factor, A is introduced in the modi®ed Clausius± Clapeyron Eq.…”

Section: Initial and Boundary Conditionsmentioning

confidence: 99%

Microexplosion of aluminum slurry droplets

Byun

Baek

Cho

1999

International Journal of Heat and Mass Transfer

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The microexplosion of a slurry droplet is experimentally and theoretically investigated. The microexplosion was considered to be caused by the shell formation and the following pressure build-up in the shell which would be promoted by the suppression of evaporation, subsequent superheating and heterogeneous nucleation of a liquid carrier. Experimentally, the microexplosion phenomena was examined for various surfactant concentrations and particle loading under dierent ambient temperature ranges (500±900 K). To closely investigate the pressure buildup and the heterogeneous nucleation, a numerical model was introduced by considering the three stages such as the shell formation, suppression of evaporation and pressure build-up inside. The microexplosion time was estimated by postulating the limit of superheat for heterogeneous nucleation. The simulation yielded a reasonably good agreement with experimental results for Al/n-heptane slurry droplets under various solid loadings (10±40 wt.%). #

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Measurement of slurry droplets in coal-fired flue gas after WFGD

Zhao

Zhang

et al. 2014

Environ Geochem Health

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China owns the world's largest capacity of coal-fired power units. By the end of 2012, the capacity of installed national thermal power has been 819.68 million kilowatts. The latest standard requires that newly built power plants emit SO2 in no more than 100 mg/m(3) and the emission of old ones be lower than 200 mg/m(3) while in some key areas the emission should be controlled under 50 mg/m(3). So by the end of 2012, 90% of the active coal-fired units have been equipped with flue gas desulfurization devices. Among the desulfurization methods adopted, limestone-gypsum wet flue gas desulphurization accounts for 92%, causing the problem of fine droplets in the exhaust gas after defogger, which may even form "gypsum rain." At present, sampling methods are widely used at home and abroad, such as magnesium ion tracer method, modified magnesium ion tracer method and chemical analysis. In addition, some scholars use aerodynamic methods, such as ELPI, to measure the diameter distribution and concentration. The methods mentioned above all have their own demerits, such as the inability to on-line, continuous measurements and the need of prolonged measuring time. Thus, in this paper some potential optical on-line methods are presented, such as Fraunhofer diffraction pattern analysis and wavelength-multiplexed laser extinction. Also brought up are their measuring scope and merits. These methods have already been utilized to measure small liquid droplets and their demonstrations and evaluations are as well stated. Finally, a 3D imaging method based on digital holographic microscope is proposed for in-line measurement of size and concentration of slurry droplets. The feasibility of this method is demonstrated by preliminary experimental investigation.

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Effects of surfactant on the evaporation, shell formation and disruptive behavior of slurry droplets

Cited by 39 publications

References 10 publications

Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

Microexplosion of aluminum slurry droplets

Measurement of slurry droplets in coal-fired flue gas after WFGD

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