Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The carbon gasification has a great effect on reduction behavior of iron ore pellets containing carbon, especially in neutral atmosphere. General speaking, adding any additives, which can promote carbon gasification reaction, can enhance the reduction rate of iron ore pellets containing carbon in neutral atmosphere. Investigations［1-4］ showed that alkali-metal compounds have obviously catalysis effect on the carbon gasification reaction, but the mechanism is understood insufficiently. As the vaporization temperatures of these alkali-metals are lower than 1 373 K, such as the vaporization temperature of sodium and potassium is 1 153 K and 953 K［5］ respectively, at this temperature iron ore pellets may be reduced at a higher reduction rate, and alkali-metals may be vaporized in the catalytic process of composite pellets by different mechanisms. Those vaporized alkali metals may react with iron ore pellets containing carbon in pre-reduction furnace, such as shaft furnace to generate cyanides, fluorides, silicates, carbonates and oxides. As those generated matters can deposit on the surface gaps both on pellets and furnace refractory lining, and then affect adversely the strength pellets and destroy furnace refractory lining. From the viewpoint of metallurgical industry, adding some alkali-metal compounds to enhance reduction rate of composite pellets［6-9］ is challenging. The effect of some metallurgical fluxes, such as CaO, CaCO3, on reduction rate of composite pellets has not been reported extensively［10-12］. This paper is to present the effect of CaO and CaCO3 on reduction rate of iron ore pellets in nitrogen atmosphere.

NUMERICAL SOLUTION OF VISCOUS FLOW PAST A SOLID SPHERE WITH THE CONTROL VOLUME FORMULATION

The control volume formulation with the QUICK finite difference scheme is used to solveincompressible liquid flow past a solid sphere in terms of stream function and vorticity.Several tech-nical points are addressed on improving the accuracy and efficiency of numerical simulation of similarproblems of fluid flow.In particular,the importance of suitable specification of the distortion func-tion to enforcing the far field boundarv conditions is emphasized.

Separation and Purification of Thrombin-like Enzymes by Affinity Adsorbents

An affinity adsorbent, benzamidine Sepharose 4B, was used to separate and purify thrombin like enzymes. The p aminobenzamidine as a specific ligand was coupled to the matrix-Sepharose 4B. The recombinant thrombin like enzyme-defibrase was used as a model in order to evaluate the efficiency of this biospecific affinity adsorbent. The homogeneity of the enzyme preparation was comfirmed as one band on sodium dodecyl sulfate polyacrylamide gel electrophoresis.

Quantifying the impact of mineralogical heterogeneity on reactive transport modeling of CO_(2)+O_(2) in-situ leaching of uranium

CO_(2)+O_(2) in-situ leaching(ISL)of sandstonetype uranium ore represents the third generation of solution mining in China.In this study,reactive transport modeling of the interaction between hydrodynamic and geochemical reactions is performed to enable better prediction and regulation of the CO_(2)+O_(2) in-situ leaching process of uranium.Geochemical reactions between mining solutions and rock,and the kinetic uranium dissolution controlled by O_(2)(aq)and bicarbonate(HCO_(3)-)are considered in the CO_(2)+O_(2) ISL reactive transport model of a typical sandstone-hosted uranium ore deposit in northern China.The reactive leaching of uranium is most sensitive to the spatial distribution of the mineralogical properties of the uranium deposit.Stochastic geostatistical models are used to represent the uncertainty on the spatial distribution of mineral grades.A Monte Carlo analysis was also performed to simulate the uranium production variability over an entire set of geostatistical realizations.The ISL stochastic simulation performed with the selected geostatistical realizations approximates the uranium production variability well.The simulation results of the ISL reactive transport model show that the extent of the uranium plume is highly dependent on mineralogical heterogeneity.The uncertainty analysis suggests the effect of uranium grade heterogeneity was found to be important to improve the accurate capture of the uncertainty.This study provides guidance for the accurate simulation and dynamic regulation of the CO_(2)+O_(2) leaching process of uranium at the scale of large mining areas.

CORRELATION BETWEEN HYSTERESIS OF GAS-LIQUID MASS TRANSFER AND LIQUID DISTRIBUTION IN A TRICKLE BED

The hysteresis of gas-liquid mass transfer rate and the corresponding radial liquiddistribution in a trickle bed reactor are measured to provide evidence for the correlation between thesetwo behaviors.Experimental results indicate that the hysteresis of gas-liquid mass transfer originatesfrom the nonuniformity of the hydrodynamic state of gas-liquid flow and the radial maldistributionof local kgia corresponds very well to the radial maldistribution of liquid flow in the bed.The localliquid flow rate is also found to be nonuniform in the azimuthal direction.In view of maldistributedliquid flow even in the pulsing flow regime,the conventional plug flow model seems oversimplifiedfor describing the behavior of a trickle bed.

STUDY AND IMPROVEMENT OF RIHANI-DORAISWAMY ESTIMATION METHOD FOR Cp° WITH COMPUTER PROGRAM

Based on the group contribution method of Rihani and Doraiswamy, a program system has been set up for automatically analyzing structures and computing ideal gas heat capacities. The method was verifled by using evaluated literature data of 479 organic compounds. The assessment of its computing precision and applicability has been made and some new group parameters recommended.

BREAKAGE AND COALESCENCE RATES OF DROPLETS IN KARR COLUMNS

Breakage and coalescence rates of droplets in reciprocating plate extraction columns were investigated bystep change in mixing intensity.Mean drop size was measured by laser light transmission technique combinedwith measurement of local holdup.Batch and countercurrent flow experiments with and without mass transferoccurring show that the dispersion mechanisms are different.The Monte Carlo simulation by digital computerwas used to treat the experimental data and models of breakage and coalescence rates were obtained.

KINETICS OF PHASE TRANSFER CATALYZED DISPROPORTIONATION OF ELEMENTAL SULFUR

The kinetics of phase transfer catalyzed （PTC） disproportionation of elemental sulfur was studied in the range of OH- concentrationlin the aqueous phase from 0.02 to 0.14 mol/dm3 and temperature from 45 to 70℃. A kinetic expression, Rsa=k*[Q+]aq[OH-]aq[S]org1/2, derived from the theory of mass transfer with rapid chemical reaction in liquid liquid system can be adopted to correlate the experimental data, and the apparent activation energy of the reaction was found to be 79kJ/mol. Kinetic evidence for PTC reaction of the system was given and a mechanism of PTC disproportionation of elemental sulfur was proposed.

MONTE CARLO MODEL OF BACKMIXING AND REACTION OF PARTICLES IN CONTINUOUS FLOW SYSTEM

A stochastic approach,namely,Monte Carlo method with"tree structure pattern"has been adopted tosimulate the random backrnixing,residence time,reaction and dynamics of solid particles with size distribu-tion and with complex reaction in a complex flow system.Turbulence of particles in reactor system is simu-lated by stochastic tree pattern which is shown by pseudo-random number series picked from a uniformlydistributed set of numbers between zero and one.A Monte Carlo procedure is employed to model the par-ticles’ stochastic residence time,random flow and reaction with fluid.A large number of discrete bundlesof particles have been simulated and followed.Statistic results of all particles in the last information representthe solution to the problem under steady state of flow.The approach has a simple physical concept and simulation procedure.All calculation has been carriedout easily with a computer.For simple reaction system,results are in good agreement with those obtainedfrom the known approach and experiments.The method could provide a new kind of technique for simu-lating the behavior of particles in a continuous flow reactor.

Kinetics of Reduction of Iron Oxide in CaO-SiO_2-Al_2O_3-Fe_tO Slags with Graphite Powder

The reduction rate of Fe_tO in CaO-SiO_2-Al_2O_3-Fe_tO slags with graphite powder has been determined in an alumina crucible at 1 673-1 823 K.The effects of temperature,slag basicity and Fe_tO content on the reduction rate have also been discussed.Test results show that the reduction rate increases with the increase of temperature or Fe_tO concentration in slags,and the reduction rate has a parabolic relation with slag simple basicity or optical basicity.The maximum reduction rate is observed around CaO/SiO_2 = l.5 of molten slags.The reaction order is 1.26 or 1.31,and the reduction activation energy is 126.8 or 129.7 kJ/mol respectively in regard to Fe_tO content or Fe_tO activity calculated by using regular solution model.The reduction rate of Fe_tO in CaO-SiO_2-Al_2O_3-Fe_tO slags with graphite powder is in the range of 0.15×10^(-4)- 0.86×10^(-4) mol-O/cm^2 · s.

ON THE RESPONSE FUNCTION AND RESIDENCE TIME DISTRIBUTION OF THE AXIAL DISPERSION MODEL FOR TUBULAR REACTORS

In view of confusion on the residence time distribution and transfer fucntions for dispersion models, the solution of the model subject to possible combinations of closed and open type boundaries at the ends of a chemical reactor is investigated systematically. In particular, some new results are obtained for the closed-open and open-closed types of reactors. It is found that the interchange of boundary conditions for these reactors is not immaterial. In several cases, caution is necessary to distinguish whether the transfer function is applied to the concentration or the flux. When the dispersive flux is notable, measurement techniques must be carefully selected to match the kind of transfer functions derived.

NONUNIFORMITY OF TWO PHASE FLOW IN CAPILLARY SYSTEMS

Gas-liquid flow in simple systems consisting of capillaries is analyzed by theory of irreversible thermodynamics so as to shed light on induction of nonuniformity of multiphase flow. By the Prigogine’s theorem of minimum entropy production, stability of uniform two-phase flow and possible transition to nonuniform distribution are discussed. The analysis of model systems suggests potential application of irreversible thermodynamics to research of multiphase hydrodynamics in chemical reactors.

Ion Flotation of Scandium

Scandium was recovered from dilute chloride solutions with potassium salt of saturated C8～C12fattyacids as surfactant by Ion flotation.The optimum comprehensive results of physical properties,stability andscandium concentration of the foam formed with potassium caprate CH3（CH2）8 COOK can be obtained.Re-covery of scandium in the foam was 98% at pH 3.8～5.0 and 25～55℃.The experimental results of 0.3 L/minairflow rate was satisfactory for flotation column.It is of a great potential for using ion flotation technique toconcentrate scandium from dilute solutions.

A NEW PROCESS FOR THE EXTRACTION OF PENICILLIN G FROM THE FILTRATE OF FERMENTATION BROTH WITH TBP IN BUTYL ACETATE

The mixture of neutral phosphorus esters and butyl acetate (BA) can be used, as the extractant for the extraction of penicillin G. The extraction equilibrium pH can be increased to pH3—4 due to the stronger extraction capability of the solvent mixture, instead of pH1.8—2.2 with butyl acetate as solvent. The experimental results indicate that the total recovery of penicillin G can reach 96.6% with the new extraction process, which is 5—6% higher than that obtained with the traditional process using BA as solvent at pH1.8—2.2.

Kinetics of α-FeO(OH)Formation in Weak Acidic Medium

The kinetics of α-FeO（OH） formation in weakacidic medium was studied.The effects of the initialconcentration,temperature,pH value,partial pres-sure of oxygen,air flow rate and agitating intensityon the oxidation rate of Fe（OH）2 suspensions havebeen investigated.It is confirmed that the reactionorder for Fe（Ⅱ） is zero at the stage of α-FeO（OH）seeds formation,and about 0.5 at the stage of theseeds growth,and in the whole process partial pres-sure of oxygen appears in first order.The activationenergy is determined.The dissolution-oxidationequilibrium which exists in the process of seedsformation has been suggested,by which the zeroorder reaction for Fe（Ⅱ） and the plateau in thepH-t curve were explained.Physical process is therate-determining step of the heterogeneousreaction.The study on the kinetics of α-FeO（OH）formation may provide some fundamental informa-tion for the reactor design,the engineering amplifi-cation and the optimization control in the industrialprocess.

CORRELATION OF CRITICAL LOCI FOR FLUID MIXTURES

The hard-sphere three-parameter equation of state proposed in our previous investigation was applied to correlate binary critical loci of alkane-alkane, aromatic-aromatic, hydrocarbon-inorganic gas and systems containing oxygenated hydrocarbons including those exhibiting type Ⅲ behaviors as classified by van Konynenberg and Scott. A new procedure was also presented which simplified mathematical manipulations and permitted the reduction of the computation time.Results were compared with those obtained by Patel-Teja equation with temperature-dependent binary interaction parameters. Significant improvements were achieved by the proposed equation with temperature-dependent parameters.In addition parameters obtained from the critical locus calculations were used to predict vapor-liquid equilibria of hydrogen-carbon monoxide and hydrogen-carbon dioxide systems. Prediction accuracies were found to be very satisfactory.

ADSORPTION MECHANISM OF SOME BIVALENT HEAVY METAL CATIONS IN SOLUTIONS USING MONTMORILLONITE

The frontier orbital energies of montmorillonite molecule and[Me(H_(2)O)_(6)]^(2+)(Me=Cu^(2+),Zn^(2+),Co^(2+)and Ni^(2+))were calculated by INDO method.Results showed that the chemical interaction between montmorillonite molecule and[Cu(H_(2)O)_(6)]^(2+)or[Zn(H_(2)O)_(6)]^(2+)was possible.The experimental results of powder X-ray diffraction and isothermal adsorption supported the above-mentioned calculation results.

FT-RAMAN SPECTROSCOPY FOR MONITORING THE POLYMERIZATION OF ACRYLIC ACID IN AQUEOUS SOLUTION

FT-Raman spectroscopy was used to monitor the polymerization of acrylic acid in aqueoussolution. A simple method to avoid the noise in the background during the signal processing via Fouriertransformation was used in this work. The effects of the amount of initiator used on the polymerization arestudied. When the amount of the initiator in the polymerization was increased, both the rate and extent ofpolymerization of acrylic acid will be increased.

Foaming Behavior in Molten Slag Caused by Decomposition of Carbonate Minerals

The average foam life is proposed as an index to the foaming behavior in molten slag. The molten slag system of Na2B4O7-CaO-MgO is foamed by the gas from the thermal decomposition of carbonate minerals as the foamer. The experimental results show that foamer type and particle size have influence upon the average foam life of slag. The concentration of CaO and MgO in molten slag not only varies the physical properties of melt but also influences directly the decomposition rate of carbonate and the bubble size of gas, thus playing an important role in foaming and to foam stability of slag.

V-L EQUILIBRIUM OF WEAK ELECTROLYTE SOLUTION OF THE NH_3-CO2-H_2O,NH_3-H_2S-H_2O AND NH_3-SO_2-H_2O SYSTEM

In this paper we have systematically studied V-L equilibrium in ternary aqueous solutions containingvolatile electrolytes by introducing a ternary interaction term into Edwards generalized molecular thermody-namic model and optimizing several adjustable parameters.The program PARA9 with flexible functions ofdoing a series of calculations has been developed and carried out on a TQ-16 computer.It can be usedeither for directly calculating the V-L equilibrium or for optimizing the adjustable parameters.For the sys-toms（NH3-CO3-H2O3,NH3-H2S-H2O and NH3-SO2-H2O）satisfactory results have been obtained withrelative mean deviation of 5-10%.Besides,several sets of adjustable parameters and valuable information ofactivity coefficients,equilibrium concentrations of ions and molecules in solutions are obtained.