Mechanism and Microkinetics of Soot Formation upon Thermal Decomposition of Carbon and Fiberglass Plastics under One-Sided Radiant-Convective Heating

The paper reports experimental methods for studying soot formation upon thermal decomposition of carbon and fiberglass plastics in flows of high-temperature gas and flame. The mechanism of the process is analyzed and its microkinetic parameters are determined. The problem of unsteady heating of a semi-infinite body of semitransparent fiberglass plastic is formulated and solved numerically taking into account the process of soot formation under conditions of radiant-convective heat transfer. A comparison of calculation results with experimental data is given in dimensionless variables.     

Thermal Diffusion Factor for Carbon Tetrachloride-Cyclohexane and Benzene-n-Heptane Mixtures from Thermogravitational Column Separation

Abstract

Measurements of the separation of liquid mixtures of n-heptane/benzene and carbon tetrachloride/cyclohexane in a thermogravitational column are reported. The results show that thermal diffusion columns of little mechanical precision can furnish suitable thermal diffusion factors when the diffusion coefficient, viscosity, density, and compressibility factor for the mixture are known.     

An Inter-Comparison of Instruments Measuring Black Carbon Content of Soot Particles

Inter-comparison studies of well-characterized fractal soot particles were conducted using the following four instruments: Aerosol Mass Spectrometer-Scanning Mobility Particle Sizer (AMS-SMPS), Single Particle Soot Photometer (SP2), Multi-Angle Absorption Photometer (MAAP), and Photoacoustic Spectrometer (PAS). These instruments provided measurements of the refractory mass (AMS-SMPS), incandescent mass (SP2) and optically absorbing mass (MAAP and PAS). The particles studied were in the mobility diameter range from 150 nm to 460 nm and were generated by controlled flames with fuel equivalence ratios ranging between 2.3 and 3.5. The effect of organic coatings (oleic acid and anthracene) on the instrument measurements was determined. For uncoated soot particles, the mass measurements by the AMS-SMPS, SP2, and PAS instruments were in agreement to within 15%, while the MAAP measurement of optically-absorbing mass was higher by ～ 50%. Thin organic coatings (～ 10 nm) did not affect the instrument readings. A thicker (～ 50 nm) oleic acid coating likewise did not affect the instrument readings. The thicker (～60 nm) anthracene coating did not affect the readings provided by the AMS-SMPS or SP2 instruments but increased the reading of the MAAP instrument by ～ 20% and the reading of the PAS by ～ 65%. The response of each instrument to the different particle types is discussed in terms of particle morphology and coating material.     

Mass Separation Due to the Rapid Expansion of Supercritical Carbon Dioxide Fluid across a Radial Thermal Gradient

Abstract

Enhanced mass transport and compound selectivity are possible for low molecular weight components solubilized in a carrier media of supercritical carbon dioxide fluid and subjected to radial thermal field-flow fractionation. In preliminary studies we observed separation of methanol and benzophenone through rapid expansion of carrier fluid at 135 bar from a 100-μm diameter capillary tube into a larger-bore tube that extended across a 20°C radial thermal gradient. We can only assume that the localized drop in pressure imposed by the rapid expansion of fluid coupled with its behavior when subjected to the thermal gradient have enormous effects on fluid density which appear to be more effective in mass transport than conventional liquid solvents for extending field-flow fractionation to a range of low molecular weight compounds that classically could only be separated by chromatography.     

Supercritical Fluid Extraction of Fullerenes C60 and C70 from Carbon Soot

Abstract

A new branch of organic chemistry has begun to emerge following the development of a carbon-arc electric discharge process by Krätschmer et al. which produced a carbon soot containing a series of caged buckminsterfullerene C₆₀, C₇₀, and higher homologues. While these compounds are normally recovered either by sublimation in an inert atmosphere or by extraction with benzene, toluene, or a higher boiling aromatic, enhanced selectivity can be achieved by operating at supercritical conditions. The ability of supercritical fluid solvents to fractionate the extractable material of the carbon soot by pressure and/or temperature tuning of the solvent power appears to be possible due to the significant molecular weight and size difference between C₆₀ and C₇₀ which yield different threshold solubility densities. While CO₂ is unable to extract any fullerenes, selective extraction of C₆₀ is obtained when using a nonaromatic modifier such as cyclopentane. Quantitative recoveries are achieved by employing moderate concentrations of an aromatic solvent modifier such as toluene at pressures imparting solvent densities greater than 0.8 g/cm³.     

Carbon Isotope Separation by Absorptive Distillation

Abstract

The feasibility of separating carbon isotopes by absorptive distillation has been studied for CO absorption by cryogenic solvents. Phase equilibrium, isotopic separation, and mass transfer data were taken between 77.4 and 114.3 K for the following solvents: propane, propylene, 1:1 propane-propylene, 1-butene, isobutane and nitrogen.

Carbon monoxide solubility followed Henry's Law, with a maximum experimental solubility of 6.5 mole per cent. Isotopic separation between CO in the gas and liquid phases using hydrocarbon solvents was several times that for pure CO vapor-liquid equilibrium. The maximum observed isotopic separation factor was 1.029 at 77.4 K with the propane-propylene solvent mixture. Mass transfer measurements yielded calculated HTU's of 2 to 5 cm for a possible separation system.

An attempt has been made to correlate isotopic separation data using Hildebrand's theory of solutions. The differential absorption of isotopic CO species is expressed as a difference in solubility of the isotopic CO molecules. Data for propane, propylene, and 1-butene show approximately the same behavior at varying temperatures.     

Examining the Relationship Between Black Carbon and Soot in Flames and Engine Exhaust

This article investigates the black carbon (BC) content of soot formed in premixed and diffusion flames and emitted by light duty gasoline and diesel vehicles. BC is measured photoacoustically and compared with particulate mass collected by filter and calculated from particle size distributions. The BC fraction of soot from rich premixed ethylene flames increases with height above the burner, but can remain well below unity in modestly sooting flames. The BC fraction produced by a propane diffusion flame soot generator (combustion aerosol standard, CAST) falls as the fuel is diluted with nitrogen, the principal means used to adjust the desired particle size. Thermally treating the soot to remove possible condensed semivolatile species does little to change these trends. Transmission electron microscopy (TEM) images show that despite low BC content, these particles display the characteristic fractal-like agglomerate morphology of soot. Particle mass spectra reveal polycyclic aromatic hydrocarbon (PAH) and fullerene fragments associated with low BC soot, which disappear as the BC fraction approaches unity. The results suggest that low BC content reflects immature solid soot that has not carbonized. Particulate matter (PM) measurements from current technology diesel and gasoline vehicles exhibit a high, >80% BC fraction. This is attributed to effective soot carbonization during the expansion and exhaust strokes of the engine, and to the substantial reductions of condensable hydrocarbons by catalytic aftertreatment. These results are discussed with respect to using light absorption-based instruments to monitor engine exhaust PM and using flame-generated soot for PM instrument calibration.     

Separation of Biological Solutes by Liquid Thermal Diffusion

Abstract

A number of phenolic components of urine reactive to phosphomolybic acid were separated by the use of liquid thermal diffusion.     

Separation by Thermal Diffusion in a Rotary Column

Abstract

A rotary thermal diffusion column with the inner cylinder rotating and the outer cylinder static was used to separate n-heptane-benzene mixtures at different speeds of rotation. The results show that the column efficiency depends on the speed of rotation. For the optimum speed the increase in efficiency relative to the static column was of the order of 8%. The role of the geometric irregularities in the annulus width on performance of the rotary column is also discussed.     

富含二氧化碳的天然气分离及其利用

论述了国内外对富含二氧化碳的天然气分离技术的研究进展,包括：膜分离法、变压吸附（PSA）法、物理吸收法和化学吸收法等,并分析了天然气资源的深加工利用及其产品开发前景。     

活性炭吸附法分离纯化ADN

采用静态吸附试验,研究了3种活性炭(AC、BC、CC)的静态吸附与解吸,筛选出一种较好的活性炭AC;通过动态吸附和解吸实验,对二硝酰胺铵(ADN)的吸附、解吸工艺条件进行了优化。结果表明,AC的吸附能力与解吸能力均优于活性炭BC与CC,是分离纯化ADN的理想吸附剂;当上样溶液质量浓度为30 155.32mg/L、流速为5mL/min时,活性炭AC对ADN的吸附量较大。以80℃热水为洗脱溶剂,洗脱至第10个柱体积时,总洗脱率达95.64%。     

Separation of m-Xylene and Ethylbenzene in Gaseous Carbon Dioxide

Abstract

The separation of an equal amount of ethylbenzene (EB) and m-xylene on silicalite using carbon dioxide as the carrier was studied. The experimental results indicated that operations in gaseous carbon dioxide provide a better separation efficiency than those at supercritical conditions. The effects of temperature, pressure, and flow rate on separation were also examined. It was found that the most appropriate conditions for obtaining purities of EB and m-xylene over 98% were a temperature around 353 K, a pressure of 40.8 atm, and a flow rate about 15 cm³/min. Comparison of the response curves for single- and two-component injection systems indicated that the model proposed by Gu et al. might be employed to interpret the data.     

活性炭吸附法分离铼钼的研究

活性炭吸附法分离铼钼的研究表明,调整吸附液的pH值,使铼钼能有效分离,且当pH>8.2时,分离系数SRe/Mo>3042,铼的吸附符合Freundlich等温式,即lga=0.69+0.81lgc。     

膜法分离二氧化碳研究现状及发展趋势

从膜法气体分离的优点出发,阐述了膜法分离CO2的原理、工艺流程,并将其应用于分离烟道气中的CO2.介绍了几种常见的分离CO2的膜材料,针对现有膜材料的缺点,提出了改进方法,展望了膜法分离CO2的发展方向.     

Separation of Alkanes and Aromatics with Supercritical Carbon Dioxide

Abstract

The separation of alkanes and aromatics with supercritical carbon dioxide has been studied by measuring vapour-liquid equilibria and selectivities in the model systems 2-methylnaphthalene/hexadecane/ carbon dioxide and 2-methylnaphthalene/dodecane/carbon dioxide. The results have been modelled with the Peng-Robinson equation of state. In both model systems supercritical carbon dioxide appeared selective for the component with the highest vapour pressure, 2-methylnaphthalene respectively dodecane. Consequently alkanes and aromatics will be separated by supercritical carbon dioxide on basis of their difference in vapour pressure instead of their difference in chemical structure.     

聚丙烯／碳纳米管复合材料的热稳定性研究

通过机械共混法和原位聚合法制备了聚丙烯做纳米管复合材料，采用热失重仪测定了复合材料在氮气和空气气氛中的热失重行为。结果表明：碳纳米管可以显著提高复合材料在氮气气氛中的热稳定性；原位聚合所得复合材料的起始分解温度比机械共混法有较大幅度提升。采用机械共混法，添加2％和5％碳纳米管的复合材料起始分解温度比纯聚丙烯分别提高了36℃和41℃；采用原位聚合法，添加5％碳纳米管的复合材料起始分解温度比纯聚丙烯提高80℃。此外，碳纳米管也使复合材料在空气中的热稳定性稍有提高，添加2％、5％和10％碳纳米管的复合材料起始分解温度均比纯聚丙烯提高了大约10℃，同时碳纳米管降低了复合材料在空气中的热分解速率。     

碳纤维／超高相对分子质量聚乙烯复合材料的热性能研究

研究了碳纤维/超高相对分子质量聚乙烯复合材料的热性能变化。结果表明：加入少量的乙烯-丙烯酸共聚物（EAA）及炭黑后,可使复合材料的热变形温度明显提高;此外,不同的加工工艺对复合材料的热性能也有一定的影响。     

液膜分离二氧化碳气体的研究进展

简要回顾了分离二氧化碳气体的研究现状,分析了液膜种类、结构和传质过程,介绍了近年来改进液膜稳定性方面的发展,并展望了液膜分离二氧化碳气体的前景。     

Powdered Activated Carbon Separation from Water by Foam Flotation

Abstract

Powdered activated carbon was separated from dilute aqueous suspensions (200–1000 mg/L) by foam flotation using surfactants (anionic or cationic). The effects of surfactant type, pH value of the suspension, initial carbon and surfactant concentrations, flotation time, and air flow rate on the dispersed-air flotation of powdered activation carbon were investigated. In optimum conditions the powdered activated carbon separation was almost complete. The ζ-potential of powdered activated carbon was also measured in the presence and absence of surfactants. Finally, carbon flotation was examined after the carbon had adsorbed chromate ions from an acidic solution (pH 2). Almost complete separation of Cr(VI)-loaded carbon was obtained by using an anionic surfactant.