BRIEFS Summary of papers published in this month’s research quarterly, IBEC Process Design and Develofiment
PARTICLE SEPARATION BY CONTROLLED CYCLING
PERIODIC PROCESSES:
Controlled cycling was applied to the separation of near-mesh particles in the 40- to 140-mesh region. An apparatus was designed and built, and many of the variables which control the rate of separation were identified and studied. The experimental results indicate that the Cycle-Screener can efficiently separate near-mesh particles of various bulk densities. I t can reduce or eliminate many of the problems present in commercial screeners by its flexibility of operation. The results also suggest the areas in which further study would be most fruitful.
The class of periodic processes contains as subclasses the batch and the steady-state processes. Simulation and optimization of periodic processes are discussed. In particular, the conditions are explored under which an optimum steady state process can be improved by periodic control. Some of the general results are demonstrated by means of the example of a chemical reaction process.
A VARIATIONAL APPROACH
D . C. Robertson and A . J . Engel, Pennsylvania State University, University Park, Pa.
IND.END.CHEM.PROCESS DESIGNDEVELOP. 6, 21-30 (1967)
F. J . M . Horn and R. C. Lin, Rice University, Houston, Tex.
IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,2-6 (1967) VAPOR PULSING IN A SIEVE PLATE LABORATORY DISTILLATION COLUMN
Substantial increases in the efficiency of a sieve plate distillation column can be obtained by variation in pulse amplitude and pulse frequency at different internal flow rates are shown. A qualitative mechanism for explaining this increase in efficiency is given. The effect of frequency-amplitude product on efficiency varies with flow rate, but maximizes a t each flow rate. Under certain conditions of loading, pulsing decreases column efficiency.
G. V. McGurl, Jr., and R. N . Maddox, Oklahoma State University, Stillwater, Okla.
PERIODIC COUNTERCURRENT PROCESSES
The over-all stage efficiency of a periodically operated distillation column depends in a complicated way on the number of stages in the column as well as on equilibrium and transport parameters. Simple and accurate asymptotic formulas for the stage efficiency have been derived which show that the performance of a distillation column can be improved considerably by periodic operation.
F. J . M . Horn, Rice University, Houston, Tex.
IND.ENO.CHEM.PROCESS DESIGN DEVELOP. 6, 30-35 (1967)
IND. ENG.CHEM.PROCESS DESIGNDEVELOP. 6, 6-9 (1967) PERFORMANCE OF CHROMATOGRAPHIC REACTORS IN CYCLIC OPERATION
+
A reaction of the type A e B C has been studied under chromatographic reaction conditions for cyclic feed compositions. T o compare performance, a model of isothermal reaction kinetics and simultaneous chromatographic separation has been programmed for digital simulation. Time average conversion at steady state was calculated as a function of the dimensionless parameters describing the system. Feed concentration of reactant A in an inert diluent followed wave f o r m of different shapes. The effects of wave form and frequency, the thermodynamic equilibrium constant, and reaction rate are shown.
F. E. Gore, Monsanto Co., St. Louis, M o . IND.END.CHEM.PROCESS DESIGN DEVELOP. 6,lO-16 (1967) A CRYSTAL PURIFICATION COLUMN WITH CYCLIC SOLIDS MOVEMENT
Fractional crystallization is used for separating and purifying many chemicals and hydrocarbons and for concentrating aqueous systems that cannot be separated economically by other separation techniques. Phillips Petroleum Co. has developed a n efficient crystallization process which utilizes cyclic movement of crystals. Efficiency of separation or concentration depends on phase equilibrium and process variables affecting the process. The flow, pressure, and composition patterns in the system are presented. The influence of crystal size, bed porosity, mother liquor viscosity, and resolidification of reflux liquid in the purification zone of the column is explained. Examples of separation of pure chemicals and freeze concentration of heat-sensitive products are included. Information developed in commercial as well as pilot plant and bench scale equipment is presented.
Dwight L. McKay and Howard W . Goard, Phillips Petroleum Co., Bartlesuille, Okla. IND. ENG.CHEM.PROCESS DESIGN DEVELOP. 6,16-21 (1967)
CONTROLLED-CYCLE OPERATION APPLIED TO EXTRACTION PROCESSES
The technique of controlled-cycle operation as applied to liquidliquid extraction is discussed, with particular emphasis on comparing results reported in the literature with those of a n experimental program using a low interfacial tension, low density difference solvent system. The literature claims of relatively high throughputs and stage efficiencies were verified. Indications were that, at constant stage height, the stage efficiency was independent of a n increase in column diameter (from 2 to 6 inches) and in the number of stages. Mathematical analysis of a controlled-cycle unit, using a n idealized model, shows that for certain conditions the unit could give 2 N theoretical stages for N actual stages. The implications of this finding as related to the performance obtained are discussed.
P. A . Belter and S. M . Speaker, The Upjohn Co., Kalamazoo, Mich.
IND.ENG.CHEM.PROCESS DESIGNDEVELOP. 6, 36-42 (1967)
PERIODIC REACTOR OPERATION
An analtyical procedure for determining the frequency response of a simple nonlinear reactor is described in detail. The time average value of the reactor effluent is different from the steadystate value, and therefore the optimum steady-state reactor design does not always give the most profitable system. Sometimes it is better to design control systems which amplify the effects of disturbances than to force the system to operate close to the optimum steady-state conditions.
J . M . Douglas, Uniuersity of Rochester Rochester, N. Y.
IND.ENS. CHEM.PROCESS DESIGNDEVELOP.6, 43-48 (1967) (Continued on page 708) VOL. 5 9
NO. 1 J A N U A R Y 1 9 6 7 107
BRIEFS CLOGGING OF FILTER MEDIA
A simple relationship was derived for the effective resistance of a partly clogged filter medium and the resistance of the filter medium at the beginning of a filtration cycle. This relationship holds for both complete blocking and standard blocking mechanisms and was verified by experimental work. Five woven wool filter cloths were tested at constant low pressures, 11.2 to 61.2 cm. of water, and feed concentrations of 2 to 10 grams per liter of ground polystyrene in water. The effective resistance of open filter cloths increased to a relatively low constant value. The effective resistance of tight filter cloths was independent of pressure and feed concentration, for the range of variables in this work, and increased from cycle to cycle. A simple correction to the classical filtration theory, that includes the effect of clogging of filter media, is suggested.
Ephraim Kehat, Arieh Lin, and Abraham Kaplan, Technion-Israel Institute of Technology, Haifa, Israel
IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6 , 48-55 (1967) ION EXCLUSION EQUILIBRIA IN THE SYSTEM SUCROSE-POTASSIUM CHLORIDE-WATER-DOWEX 50W X4
The effect of temperature and sugar and salt concentration on equilibria in the system sucrose-KCI-water-Dowex 50W X 4 at sucrose concentrations from 0 to 60 weight yo and KC1 concentrations of 0, 1, 3, and 6 weight yG has been measured. For KC1, increasing temperature 60 weight yo sucrose, 0 weight 70 increased the amount of sucrose sorbed. From 60’ to 90” C. the increase was 4.3 mg. of sucrose per dry gram of K+’ resin per degree C. Equilibrium measurements at 90’ C. showed that the amount of sucrose sorbed decreased with increasing KC1 concentration ; at fixed solution KC1 concentration increasing solution sucrose concentration increased the amount of salt sorbed by the resin. The average distribution ratio of sugar to salt in the resin and solution was 2.32 for solutions containing 1 weight yosalt; it decreased to 1.65 for concentrations of 3 and 6 weight 7 ‘. These results show sucrose can be separated from the salt by successive batch or continuous countercurrent columnar treatment. Sucrose sorption data were correlated by the n form of the BET multimolecular adsorption equation. This equation was applied to the correlation of other ion exclusion data and found to be generally applicable to systems where the sorbed solute shows a limited solubility in the solvent phase.
Walter Meyer, R. S. Olsen, and S.L. Kalwani, Oregon State University, Coroallis, Ore. IND.ENG. CHEM.PROCESS DESIGNDEVELOP.6, 55-62 (1967)
EFFICIENCY MEASUREMENTS ON AN ALL-GLASS WIPED-FILM STILL
The performance of an all-glass laboratory-scale wiped-film evaporator has been evaluated with a dodecaneoctadecene mixture at varying feed rates, temperatures, pressures, and rotating speeds of the glass wiper. Separation sharpness, split ratios, coefficients of heat transfer, and residence times were determined. Analyses of both the overhead and bottom product indicate that the observed separations correspond closely to theoretically computed values obtained from the smoothed out data of Jordan and Van Winkle using the equations for a simple batch distillation. Based on analogous findings of Kirschbaum and Dieter on a commercial-size wiped-film evaporator, the data obtained on these laboratory-scale stills can, therefore, be used to demonstrate the feasibility of extrapolating to commercial-size film evaporators.
T. H. Gouw and R. E. Jentoft, Chevron Research Go., Richmond, Calq. IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6, 62-67 (1967)
cc. volume at pressures u p to 200,000 p.s.i. and temperatures up to 800” F. and to demonstrate its utility by studying the partial oxidation of methane at high pressures. The effect of pressure on the product distribution of the partial oxidation of methane has been studied up to 200,000 p.s.i. In general, an increase in pressure increases the yield of methanol and other oxygenated organic liquid products. J . L. Lott and C. M . Sliepcevich, University of Oklahoma, Norman, Okla. IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6 , 67-74 (1967) PYROLYSIS OF COAL PARTICLES IN PULVERIZED FUEL FLAMES
Information on the pyrolysis of coal particles in pulverized fuel flames was obtained by using water-cooled instruments to probe a one-dimensional flame stabilized in a parallel-sided duct with a new type of “burner.” The composition of the solid material and the flame temperature were measured along the axis of propagation. While providing a basic description of the kinetics of devolatization, the study also produced several results contrary t o initial expectations. Particles attain a temperature or about l l O O o C. before ignition or a significant amount of devolatilization occurs, and the rate of devolatilization does not become rapid until a short time after ignition. We conclude that ignition occurs on the surfaces of solid particles since the amount of volatiles liberated before ignition is too small to form a flammable gaseous mixture. Devolatilization of particles in the size range 0 to 200 microns seems to be a volumetric reaction, independent of particle size, The value obtained for the activation energy of devolatilization was 6 kcal. per mole in the preignition zone and 28 kcal. per mole in the postignition zone of the flame.
Jack R. Howard, Massachusetts Institute of Technology, Cambridge, Mass., and Robert H. Essenhigh, The Pennsylvania State University, University Park, Pa. IND. ENG.CHEM.PROCESS DESIGNDEVELOP. 6, 74-84 (1967) SMALL CONTINUOUS UNIT FOR FLUIDIZED COAL CARBONIZATION
A small-scale continuous unit for the fluidized carbonization of coal has been developed to match commercial gas-coal ratios and thus give representative tar yields. Good heat transfer and mixing are maintained at these subfluidization gas rates by use of a stirrer, which also allows carbonization of highly caking coals without preoxidation. Incentive is shown to develop a commercial process without preoxidation by mechanical forcing of operability of the carbonizer. Data show the effects of preoxidation and sweep gas rate on tar yield from a coking coal. At high sweep rates (50 cu. feet per pound of coal) the tar yields are 1.7 times the Fischer assay value for untreated coal. Injection of air during carbonization causes a loss in tar yield of 0 to 1.2 pounds per pound of oxygen, depending upon whether the air enters at a point in the bed considerably below the coal feed point or with the coal.
Robert T. Struck, Philip J . Dudt, and Everett Gorin,Consolidation Coal Go., Library, Pa. IND.ENC. CHEK PROCESS DESIGN DEVELOP. 6, 85-88 (1967) KINETICS OF WAX CRACKING FOR ALPHA-OLEFIN PRODUCTION
Thermal cracking of paraffin wax was studied in isothermal bench scale and pilot unit reactors. The range of operating conditions was 1000° to 1160’ F., 0.25 to 4.0-atm. hydrocarbon partial pressure, and 1.5 to 12-second reaction time. The data were correlated by an over-all reaction order of 1.3 and a n activation energy of 49,600 cal. per mole, rather than the first-order kinetics traditionally assumed. The results were supported by calculations based on various assumed chain-terminating reactions. -4dditional data were obtained in a cracking coil of commercial size. Since the temperature and pressure varied with distance along the coil, an analog computer simulation was used to predict conversion and fit the data. Results were in good agreement with 1.3-order kinetics.
PARTIAL OXIDATION OF METHANE AT HIGH PRESSURES
G. R. Worrell, R. F. Chapman, and S. G. Woinsky, Atlantic Richjeld Co.,
The objectives of this research were to develop experimental equipment for studying chemical reactions in fluid systems of at least 500-
IND.ENG.CHEY.PROCESS DESIGN DEVELOP. 6, 89-95 (1967)
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INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
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BRIEFS
ENTRAINMENT AND PRESSURE DROP WITH JET TRAYS IN AN AIR-WATER SYSTEM
Entrainment and pressure drop have been studied using an airwater system for jet trays with the following range of variables investigated. Gas rate, 700 to 1750 lb./hr./sq. ft.; liquid rate, 2900 to 30,000 lb./hr./ft. of weir length; hole size, l / 4 and */a inch; tab angle 45' and 60'; weir height, 0 to 3 inches; tray spacing, 12 to 24 inches; A correlation was developed which empirically relates liquid rate, gas rate, hole size, and tab angle, along with tray spacing. No significant effect of weir height on entrainment was evident for the weir height study.
solvent extraction procedures used in the Hanford Purex Plant can be prepared from either strip solution. Trilaurylamine solutions have limited chemical and radiolytic stability when in contact with the waste solution.
W.W. Schulz, Pacific Northwest Laboratory, Division of Battelle Memorial Institute, Richland, Wash. IND.END.CHEM.PROCESS DESIGN DEVELOP. 6,115-121 (1967)
W. G. Todd and Matthew Van Winkle, University of Texas, Austin, Tex.
IND.ENG. CHEM.PROCESS DESIGNDEVELOP.6, 95-101 (1967) SAMPLED-DATA PROPORTIONAL-INTEGRAL CONTROL OF A CLASS OF STABLE PROCESSES
The analysis of sampled-data, feedback, proportional-integral control of processes adequately molded as first-order with delay is presented. Controller settings are recommended as functions of the model parameters and sampling period. Control of an experimental higher-order system is used to verify the suggested design.
H. A. Mosler, L. B. Koppel, and D . R. Coughanowr, Purdue University, Lafayette, Ind. IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,101-105 (1967)
TURBULENT REGION PERFORMANCE OF REVERSE OSMOSIS DESALINATION TUBES. EXPERIENCE AT COALINGA PILOT PLANT
Equations describing the turbulent region performance of reverse osmosis desalination tubes are developed. The characteristic performance quantities, desalinized water flux and desalination ratio, are expressed as functions of experimentally determinable membrane coefficientsand of operating conditions. Experimental data from a tubular pilot plant, now in operation at Coalinga, Calif,, were utilized to examine the validity of the equation relating desalination ratio to membrane properties and operating conditions. The experimental results appeared to support this equation which is based on the concentration polarization studies of Sherwood and Brian and on the salt diffusion work of Merten.
Judy Rosenfeld and Sidney Loeb, University of California, Los Angeles, Calq.
IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,122-127 (1967) PLUTONIUM AND URANIUM HEXAFLUORIDE HYDROLYSIS KINETICS
The hydrolysis rates of gaseous plutonium hexafluoride and uranium hexafluoride were measured in a packed bed at room temperature. The reaction product is solid plutonyl fluoride (PuOzFz) or uranyl fluoride ( U02F2), respectively. At low concentrations of the hexafluorides in the gas phase, the reaction rate is directly proportional to both the partial pressure of the hexafluoride and moisture and the area of the solid surfaces available for reaction. Adsorbed hexafluoride and HF on the reaction surface reduce the reaction rate a t partial pressures greater than 0.001 mm. of Hg. Reaction in the gas phase was detected at moisture partial pressures greater than 1.0 mm. of Hg and results in part of the solid reaction product being produced as fine particles, less than 0.1 micron in diameter, in the gas phase.
HEAT TRANSFER TO AGITATED, TWO-PHASE LIQUIDS IN JACKETED VESSELS
IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,105-111 (1967)
Unsteady-state heat transfer experiments were carried out in a jacketed, agitated, glass-lined vessel using as heat transfer media both single-phase and two-phase fluids: water, toluene, lubricating oil, water-toluene mixtures, and water-lubricating oil mixtures. Data were first obtained for the single-phase fluids and were found to agree with those of previous investigators. The rate of heat transfer to two-phase, agitated fluids was then measured and compared with the results for single-phase heat transfer. Several correlation techniques for the two-phase heat transfer results were attempted; these differed in the methods used to compute the physical properties of the two-phase mixtures. The use of bulk, volume-average properties yield the most consistent correlation of the data. Gravitational effects at low agitator speed are discussed in some detail.
DIALYSIS FOR SEPARATING SOLUTES OF DIFFEREHT MOLECULAR WEIGHTS PROCESS OPTIMIZATION
S. W. Bodman and D . H. Cortex, School of Chemical Engineering Practice, Massachusetts Institute of Technology, American Cyanamid Co., Bound Brook, N . J .
Robert W. Kessie, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Ill. 60439
Dialysis is a useful tool for separating low molecular weight impurities in the manufacture of larger molecules such as pesticides, pharmaceuticals, and related organics. The effects of dialysis process variables are analyzed. Correlations are presented to aid in selecting conditions such that product loss, investment, operating cost, and other economic factors can be optimized.
C.C. Oldenburg, Stauffer Chemical Co., Richmond, Calif. IND. END.CHEM.PROCESS DESIGN DEVELOP. 6,111-114 (1967) TRILAURYLAMINE EXTRACTION OF NEPTUNIUM AND PLUTONIUM FROM PUREX PROCESS WASTE
A batch solvent extraction process, used to recover Npza7 from a radioactive waste solution generated during processing of irradiated uranium in the Hanford Purex Plant, also recovers the small amount of plutonium lost to the waste stream in Purex process operation. Trilaurylamine diluted with kerosine is the extractant. Hydrazine added to the acidic waste establishes both neptunium and plutonium in the +4 valence state for maximum extraction. More than 95% of both elements is extracted in a single batch contact of equal volumes of solvent and waste. Both elements are stripped from the solvent effectively by contact with dilute hydroxylamine sulfate or sodium sulfate-ferrous sulfamate solution. A satisfactory feed solution for final separation and purification of the recovered neptunium and plutonium by the tributyl phosphate
IND.ENG.CHEM.PROCESS DESIGN DEVELOP.5 , 127-133 (1967) KINETIC STUDY OF THE PYROLYSIS OF A HIGH-VOLATILE BITUMINOUS COAL
Constant temperature data are presented for the pyrolysis of a Utah high-volatile bituminous coal at temperatures ranging from 409' to 497' C . The reactions are approximately secondorder for the first 60 minutes, with an activation energy of 36.6 kcal. per mole. This region is followed by a period of approximately 100 minutes, during which the reaction is first-order, with an activation energy of 5.36 kcal. per mole. A zero-order reaction takes place at times above approximately 300 minutes, extending throughout the balance of the observations, in some cases up to 1500 minutes. Apparent entropies of activation, including the unknown factor of reacting surface sites, were calculated to be -63 entropy units for first-order region and -12 entropy units for the second-order region. A model which relates the change in reacting sites to entropy change and a model for the pyrolysis of high-volatile bituminous coal are presented.
Wendell H . Wiser, George Richard Hill, and Norbert J . Kertanus, University of Utah, Salt Lake City, Utah IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,133-138 (1967) (Continued on page 7 70) VOL. 5 9
NO. 1
JANUARY 1 9 6 7
109
BRIEFS
OXIDATION OF ACETALDEHYDE TO ACETIC ACID IN A SPARGER REACTOR
The kinetics of oxidation of acetaldehyde to acetic acid was studied in a sparger reactor using manganese acetate as the catalyst. Data obtained in a stirred tank reactor are used for analyzing the sparger reactor data. The rate of chemical reaction is extremely fast and can be neglected for the rate equation of the sparger reactor. A kinetic model applicable at any temperature and concentration within the range of the variables studied is developed which predicts the performance of the sparger reactor satisfactorily.
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B. Venugojal, R. Kumar, and N. R. Kuloor, Indian Institute of Science, Bangalore, India IND.ENG.CHEM.PROCESS DESIGN DEVELOP. 6,139-146 (1967)
FORMATION OF SPHERES FROM FINELY DIVIDED SOLIDS I N LIQUID SUSPENSION
Finely divided solids suspended in a liquid are caused to agglomerate by agitating the suspension with a small amount of a second (bridging) liquid which preferentially wets the solid. Spherical agglomerates can be produced in a specially designed vessel shaken in a reciprocating fashion. The agglomeration of sands of various size distributions suspended in organic liquids and collected with aqueous solutions has been investigated as a model system. Spherical agglomerates were generally formed when the bridging liquid filled between 44 and 81% of the voids between the highly compacted sand particles. The ways in which the sphere size attained in the process may be controlled have also been investigated. The results are consistent with the postulate that the sphere size represents a balance between the destructive and COhesive forces acting on the agglomerates. C. E. Capes and J. P. Sutherland, National Research Council, Ottawa, Canada
IXD.ENG.CHEM.PROCESS DESIGN DEVELOP. 6, 146-154 (1967)
REVERSE OSMOSIS SEPARATION AND CONCENTRATION OF SUCROSE I N AQUEOUS SOLUTIONS USING POROUS CELLULOSE ACETATE MEMBRANES
BOWEN ENGINEERING, Inc.
The effects of operating pressure and feed concentration on solute separation and product rate for the system sucrose-water were studied, and the data correlated by empirical equations. Some parameters of process design are illustrated from the point of view of developing this separation process as a practical batchwise concentration technique. The variation of product rate as a function of feed concentration was studied a t the operating pressure of 1500 p.s.i.g. using three typical films capable of giving more than 997, solute separation in the entire feed concentration range 0.1 to 1.4M. Performance of films was also studied in a month-long continuous test run. On the basis of experimental results, it is estimated that the porous cellulose acetate membranes of the type employed may be expected to have actual processing capacities of 20 to 30 gallons of feed solution per day per square foot of film area at a n operating pressure of 1500 p.s.i.g. for concentrating aqueous sucrose solutions from 3.3 to 32.4 weight yo. A few experiments were conducted with natural maple sap containing 3.76% equivalent sucrose; increases in solute concentration up to 34.6Y0 with reasonable processing capacities for the membrane, and essentially 100% solute recovery, were obtained.
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IND.END.CHEM.PROCESS DESIGN DEVELOP. 6 , 1 5 4 1 6 0 (1967)
