BRIEFS KINETICS OF THERMAL CRACKING OF PARAFFINIC AND NAPHTHENIC FUELS AT ELEVATED PRESSURES
Six highly refined hydrocarbon jet fuels were thermally cracked in a flow reactor at a wall temperature of 1200" F. (reaction temperature of 1070' to llOOo F.) and pressures from 200 to 1000 p.s.i.g. The calculated first-order rate constants for highly paraffinic and highly naphthenic fuels containing negligible unsaturates were affected only slightly by pressure and were about twice as large as the value for pure n-hexadecane under the same conditions. At 500 p.s.i.g., a paraffinic fuel containing 16 weight % olefins had a first-order rate constant approximately 2.5 times greater than those for fuels containing negligible olefins ; however, this decreased rapidly with increased pressure. Product composition was determined as a function of the degree of reaction and the results were fitted to a kinetic model.
B. M . Fabuss, J . 0. Smith, R. I. Lait, and M . A . Fabuss, Monsanto Research Gorp., Everett, Mass., and C. N SatterJeld, Department of Chemical Engineering, Massachusrtts Instatute of Technology, Cambridge, Mass. IND. ENG.CHEM.,PROCESS DESIGN DEVELOP. 3,33-37 (1964) MECHANISM OF HYDROCRACKING. AND OLEFINS
REACTIONS OF PARAFFINS
Reactions of paraffins and olefins during hydrocracking have been studied. The types of reactions are shown to depend to a major extent on the activity of the hydrogenation component in dualfunction catalysts. The almost exclusive reaction noted previously with hydrocracking catalysts under representative hydrocracking conditions was extensive splitting, primarily to low molecular weight paraffins (C8-G). In direct contrast, a catalyst with very high hydrogenation activity gave products not noted previously: isomerized uncracked paraffins, higher molecular weight cracked paraffins characteristic of primary rather than secondary cracking, and cyclics. A mechanism is presented to predict and explain contrasting reactions and products from different types of catalysts.
Harry L. Coonradt and William E. Garwood, Socony Mobil Research Department, Paulsboro Laboratory, Paulsboro, N .J . IND.END.CHEM.,PROCESS DESIGN DEVELOP. 3,38-45 (1964) DESIGN CRITERIA FOR SEDIMENTATION BASINS
This study was undertaken to resolve some relatively minor discrepancies between additional experimental data and the correlations presented in a previous paper by the authors, and also to provide simple graphical representations of calculated data. Two simultaneous equations were found to provide a more accurate description of data for the case (mvPL/M) > 525; (dvps/p) < 3.00 than the previously given single equation. The effects of basin depth have been mathematically expressed to yield optimum values. A method has been described for graphical representation of calculated performance data. The accuracy and usefulness of the previous correlations of sedimentation data have been improved.
Henry C. Bramer and Richaid D . Hoak, Mellon Institute, Pittsburgh 73,Pa. IND.ENG.CHEM.,PROCESS DESIGN DEVELOP. 3,46-48 (1964) CONDENSING HEAT TRANSFER IN STEAM-AIR MIXTURES IN TURBULENT FLOW
Graphical correlations and empirical equations show the effects of mixture composition over the complete range, of gas phase turbulence, and ofliquid layer thickness on the over-all heat transfer coefficient. The latter two variables are correlated in terms of Reynolds numbers. The condensing surface used was a vertical tube with gas flow vertically down.
Paul B. Stewart, James L. Clayton, Benign0 Loya, and Stanley E. Hurd, Department of Mechanical Engineering, and Sea Water Conversion Laboratory, University of California, Berkeley 4, Gal$. IND. ENG.CHEM.,PROCESS DESIGN DEVELOP. 3,48-54 (1964)
PRODUCTIONOF FRESH WATER FROM SEA WATER WITHOUT METALLIC TRANSFER SURFACES. THERMODYNAMIC ANALYSIS OF A FLASH DISTILLATION METHOD
A flash distillation method of converting sea water has been analyzed thermodynamically. This method is of interest since it might reduce construction and replacement costs by eliminating metallic condensing and heat transfer surfaces. Furthermore, operation at small temperature differences could reduce maintenance costs by reducing scale and corrosion problems and reduce energy costs by using to a greater advantage the temperature difference found in the seas or available in certain industrial processes. It has been found that the ratio of fresh water produced to sea waters handled is a maximum, for given inlet stream temperatures, if the heat exchanger is large and efficient and if the flow rates of the entering warm and cool sea water streams are equal. High plant efficiency is realized if the temperature difference within each distillation cell approaches the boiling point elevation caused by minerals. Eldon L. Knuth, Department of Engineering, University of California at Los Angeles, Los Angeles 24, Calif. IND.END.CHEM.,PROCESS DESIGN DEVELOP. 3,55-60 (1964) DRYING AIR WITH ACTIVATED ALUMINA UNDER ADIABATIC CONDITIONS
Sorption of water vapor from air at 1 atm. under dynamic adiabatic conditions was studied to improve understanding of industrial gas dryer operation. A new type of behavior was caused by a temperature wave which preceded the sorption wave under certain conA multiple correlation yielded a high correlation coditions. efficient and a regression equation which expressed operating time below 0" F. effluent dew point as a function of four independent variables: temperature, moisture content and flow rate of inlet air, and desiccant bed depth. The adiabatic operating capacity of a desiccant bed is much less than that calculated from isothermal equilibrium data. The regression equation for adiabatic capacity here presented can be used for design of large industrial gas dryers which operate without internal cooling.
Robert J . Getty and W. P. Armstrong, Chemical Engineering Depai tment, Washington University, St. Louis 30, Mo. IND.ENG.CHEM.,PROCESS DESIGN DEVELOP. 3,60-65 (1964) AVIATION GASOLINE CORROSIVENESSCAUSED BY SULFATE-REDUCING BACTERIA. PREVENTION BY GROWTH INHIBITORS
A sulfate-reducing bacteria, Desulfovibrio desulfuricans, has been found to be responsible for the corrosiveness occasionally omurring in aviation gasoline stored in tanks with small water bottoms, under the climatic conditions prevailing in Israel. In laboratory experiments, gasoline stored on culture media inoculated with D . desulfuricans became corrosive after 1 week of incubation. The diffusion of H2S in gasoline stored on aqueous H2S solutions and its consequent oxidation to free sulfur were determined experimentally. Of the numerous bacterial inhibitors tested initially on Desulfovibrio cultures, methyl violet, a mixture of chloramphenicol and streptomycin, and sodium azide were selected for experimental investigation of their capability of preventing corrosiveness in gasoline stored over inoculated culture media. Under the test conditions, the best results were obtained with methyl violet.
Albmto M . Wachs, Shimshon Bentur, Yehnuda Kott, Menahem Babitz, and Alfred B. Stern, Technion, Israel Institute of Technology, Haifa, Israel. IND.ENG.CHEM.,PROCESS DESIGN DEVELOP. 3,65-69 (1964) DIFFUSION FLAME BURNER FOR CONTINUOUS COMBUSTION OF HYDROGEN
A diffusion flame burner has been developed for use in an electrolytic heavy water reconcentration plant. For the range of flows investigated (2 to 10 normal cubic meters of hydrogen per hour), the flame height is almost linearly proportional to the (Continued on page 7 7 ) VOL. 5 6
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