Modeling batch melting: Roles of heat transfer and reaction kinetics

Development of mathematical models of heat and mass transfer in glass-melting furnaces began in the 1970s and progressed rapidly with advances in sophisticated experimental/numerical techniques and increasing computational power. Today, practically all newly built or rebuilt furnaces are optimized with these models to meet stringent quality requirements, reduce the unit costs of manufacturing, or control emissions. One remaining hurdle is to model the batch-to-glass conversion accurately enough to reliably assess the glass production rate. This article summarizes two key aspects of the batch-conversion modeling—the heat transfer and the kinetics of conversion—and reviews the current state-of-the-art approaches to simulating them. We critically examine the advantages of the commonly used heat transfer approach, but also explain that its predictive capabilities are significantly restricted by the dependence of batch thermal properties on the time-temperature history. We argue that kinetic approaches to the batch-conversion modeling would offer a significant improvement when coupled with the heat transfer approach. Finally, we summarize key areas requiring further research on the way toward a realistic model of the batch blanket.     

Effect of Si Addition on Martensitic Transformation and Microstructure of NiTiSi Shape Memory Alloys

Metallurgical and Materials Transactions A - The effect of Si addition on microstructure and martensitic transformation of the Ni-Ti-Si SMA was investigated in this work. The...     

PARTITION BETWEEN α-METHYL AND α-METHYLENE PROTONS IN 1H NMR SPECTRA OF COAL TARS

Cut-off points between protons in a-methyl and or-methylene groups were proposed for the evaluation of 'H NMR spectra of coal tars. The position of the cut-off points depended on the proton aromaticity and related structural features of the samples. Equations for the calculation of the cut-off points as a function of proton and carbon aromaticity, and atomic H/C ratio were proposed for the range of proton aromaticity between 0.2 and 0.6.     

ALIPHATIC C-H BOND RESPONSES IN THE 900-700 cm-1 REGION OF THE FTIR SPECTRA OF COAL TARS

Four bituminous coals were comprehensively separated by column chromatography into a number of fractions. Four aromatic hydrocarbon fractions of each tar were analyzed by FTIR spectroscopy, and the 900-700 cm^-1 spectral region was evaluated. This spectral region was found to be composed of at least 14 separate bands, which were resolved by using self-deconvolution and curve-fitting procedures. The bands near 821 cm^-1, 791 cm^-1, and 784 cm^-1 were proposed to originate from rocking vibrations of aliphatic C-H bonds. For the tar samples with a proton aromaticity between 0.21 and 0.37, these bands account for on average 12% of the total integral intensity of the 900-700 cm^-1 region. This percentage cannot likely be neglected in a correct quantitative evaluation of the region and calculation of the aromatic hydrogen concentration. However, a correct resolution of the bands can be very difficult in the FTIR spectra of a complex material, such as coal.     

Fractionation of a statistical copolymer in a demixing-solvent system: Theory and experiment

It has been shown that, under specific conditions, a demixing-solvent fractionation according to chemical composition can be applied to statistical copolymers. Formally, identical expressions have been derived for the distribution of a copolymer between coexisting phases in precipitation (sol-gel) and demixing-solvent fractionations. Theory predicts that the effects of molar mass and chemical composition cannot be separated in either of the phaseequilibrium fractionations. With demixing solvents, the partition coefficient depends steeply on copolymer composition, which enables one, e.g., to separate homopolymers from a blend. Multistep demixing-solvent fractionation of a copolymer may proceed only in specific cases, e.g., immediately below the maximum of the coexistence curve. A feasibility study was performed with a chemically heterogeneous statistical copolymer of styrene and 2-methoxyethyl methacrylate; the experimental results have confirmed the theoretical predictions. © 1993 John Wiley & Sons, Inc.     

Heat transfer evaluation of impingement cooling in hot rolling of shaped steels

The accuracy of mathematical modelling is strongly influenced by the boundary conditions assumed. A shape rolling mill was instrumented to provide on-line temperature measurements during hot rolling of steels. An inverse heat conduction technique was used to convert the measurement data to surface heat fluxes and heat transfer coefficients. The heat transfer coefficient or heat flux could then be used as the necessary boundary condition for the computation of temperature field in the entire roll and workpiece by means of conventional heat transfer analysis. The heat transfer phenomena involved and the influence of the major operating parameters on the heat transfer results have also been discussed. Finally, the paper has shown that the numerical evaluation procedure adopted has at least the same influence on the results as the accuracy of temperature sensors and the properness of experiment design.     

Polymerization of acrylamide in inverse microemulsion in the presence of mixtures of oleophilic and hydrophilic surfactants

The preparation of single-phase toluene/sodium bis(2-ethylhexyl)sulfosuccinate(AOT)/water/acrylamide/sodium dodecyl sulfate(SDS) inverse microemulsions is described and their properties prior to polymerization (macroviscosity as a function of volume fraction Φ_aw of the dispersed aqueous (water + acrylamide(AAm) + SDS) phase, and of SDS/AAm mass ratio) are studied. At 20°C three viscosity maxima are observed. At 50°C all three peaks remain, the viscosity of the first and third peak, respectively, is lowered to 5–8 mPa· s while the second, most prominent peak still marks the level of ca. 250 mPa· s. The polymerization of acrylamide in dispersion systems is initiated by water-soluble ammonium peroxodisulfate (APS) and oilsoluble dibenzoyl peroxide (DBP) at 60°C. The polymerization rate of acrylamide for a given [toluene]/[AOT] molar ratio and AAm/water mass ratio monotonically decreases for Φ_aw values greater than 20%. The polyacrylamide viscosity molecular mass increases up to a Φ_aw value of ca. 30%, irrespective of the nature of initiator. For Φ_aw values over 30% the viscosity molecular mass of polyacrylamide seems to level off with some sings of shallow minimum close to Φ_aw of 50%.     

Indentation and piercing of steel in a mushy state

Semisolid or mushy-state processing permits a material to partially solidify before shape-making operations. The understanding of material behavior in the mushy state is critical for better control of various semisolid processes. The aim of the current study is to experimentally quantify the indentation and piercing behavior of steel in mushy states. Semisolid specimens under indentation and piercing were evaluated at various forming speeds and mushy states. The correlation between the temperature and the percentage of the solid phase is used to control the characteristics of the mushy state. It was found that the forming resistance of steel in a mushy state is dependent on the deformation rate and the solid phase percentage.     

Polychlorierte Biphenyle (PCB) im menschlichen Fettgewebe

Zusammenfassung Die vorliegende Arbeit beschreibt die Kontamination menschlichen Fettgewebes mit den sechs als Indikator-Kongeneren bekannten Polychlorbiphenylen, mit PCB Nr. 49 und den Mischinducern PCB Nr. 156, 170 und 189. Die niedrig chlorierten Biphenyle Nr. 28, 49 und 52 konnten nicht nachgewiesen werden, die Konzentration von PCB Nr. 101 betrug im Mittel 9 g/kg. Die Gehalte von PCB Nr. 138, 153 und 180 lagen geringfügig unter den von der DFG angegebenen Werten. Der Anteil der Mischinducer Nr. 138, 156, 170 und 189 machte nahezu 40% der Gesamtbelastung aus. Die Höhe der PCB-Kontamnation des Fettgewebes war altersabhängig, wobei für die Gruppe der 61-bis 70jährigen mit Ausnahme von PCB Nr. 101 ein sprunghafter Anstieg der Konzentrationen beobachtet wurde.

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Polychlorinated biphenyls in human adipose tissue

Summary This study describes the contamination of human adipose tissue with six selected polychlorinated biphenyls (PCB) known as indicator congeners, with PCB no. 49 and the mixed inducer PCB nos. 156, 170, and 189. The low chlorinated biphenyls nos. 28, 49, and 52 could not be found in the tissue samples, while the average concentration of PCB no. 101 was 9.0 g/kg. The content of PCB nos. 138, 153, and 180 was slightly below the values published by the Deutsche Forschungsgemeinschaft (DFG). The mixed inducer nos. 138, 156, 170, and 180 amounted to approximately 40% of all the PCBs measured. The PCB contamination was positively correlated with age: for the age group 61–70 years, with the exception of PCB no. 101, a distinct increase in the concentrations could be observed.

     

Calculation of countercurrent separation processes—III. Computation of two interlinked columns.

The relaxation procedure is used for solution of two interlinked distillation columns. Both approaches-sequential iterative method and the block relaxation technique are compared. A new algorithm making use of simultaneous solution of all equations is proposed.