A maximum bubble pressure apparatus, described in a previous publication, has been used at pressures to 13.9 MPa (2000 psig) and temperature to 623 K (350degreesC) to measure the static surface tension of several alkanes and paraffinic petroleum fractions, and two types of Alberta bitumens in contact with hydrogen, helium and hydrogen/methane mixtures. With hydrogen, the surface tensions of alkanes or mixtures of alkanes were nearly independent of pressure, whereas with helium surface tension increased significantly. With hydrogen/ methane mixtures, the surface tension decreased in value as pressure increased, with the effect increasing at the higher methane concentrations. For the two bitumens used, the surface tension with hydrogen showed a 10-15% increase as pressure increased at constant temperature. Some discussion is also given concerning methods of predicting the effects of pressure and temperature in hydrogen/hydrocarbon systems.

An apparatus for the measurement of surface tensions of organic liquids in contact with a gas has been developed which is capable of operation to 400degreesC and to 14 MPa. It is based on the maximum bubble pressure technique, modified for hydrocarbon oils at high pressures and temperatures. Accuracy of measurement is of the order of +/-3% for non-aqueous systems for values down to 5 mN/m. Only a 20 to 30 mL liquid sample is required, and small gas volumes. In practice, it was found that measurements with most organic liquids could only be made to a maximum of about 350degreesC because of the thermal instability of most of these compounds, in particular, for hydrocarbon liquids. Any thermal decomposition or coke deposition leads to inaccurate results. Results obtained for known liquids are compared with values given in the literature.

An ore sample from a pegmatite deposit at Wekusko Lake in northern Manitoba contained 1.70% lithium oxide, Li2O. Scanning electron microscope analysis showed that lithium is present as spodumene at a concentration of approximately 7.4% Li2O. The SEM micro-analysis identified that the Fe2O3 concentration ranges between 0.94 and 1.64%. It was further found that potassium and sodium oxide concentrations in the spodumene are relatively low, 0.01% K2O and 0.21% Na2O. Major minerals associated with the spodumene are Na-feldspar, K-feldspar, and quartzite. Muscovite, apatite, and garnet are present at low concentrations. Despite its relatively high iron content, it is expected that this spodumene is suitable for the glass and chemical industry. The extraction process of lithium as Li2CO3 from the ore consists of oleic acid froth flotation resulting in a concentrate containing around 6.6% Li2O. A heat treatment at 1100 degrees C of the concentrate is subsequently applied in order to produce a chemically activated spodumene. Subsequently, the spodumene is subjected to sulphuric acid roasting, leaching, solution purification and precipitation of Li2CO3, containing above 98% Li2CO3.

Concentrate fines (<0.43 mm) produced from North American chromite deposits, were used in smelting reduction tests conducted in a DC electric-arc furnace. The furnace feed plus nitrogen as a carrier gas were fed to the furnace through a 30 mm diameter hole bored along the axis of a 102 mm diameter graphite electrode. Tests were conducted at various burden feed rates and power levels. Optimal operating conditions for these tests were a feed rate of 58 kg/h at an average power input of 98 kW while operating at a temperature of approximately 1600 degrees C. The chemical composition of the furnace dust was different than that of fine constituents in the feed indicating that the very fine particles in the feed did not by-pass smelting. Experiences with burden feed entering into the limited are attachment zone to the liquid bath are discussed and energy flux data (W/m(2)) are presented.

After conducting preliminary chromite reduction tests in a18 kW combined plasma induction furnace, a100 kW DC plasma-arc furnace facility was utilized to conduct additional reduction tests on North American chromite concentrate fines. The fines were successfully fed through a hollow graphite electrode with low chromium losses in the offgas. Reduction tests conducted with a plasma-arc produced a slag with a low chromium oxide content. After tapping, the slag was found to contain on average 3.6 percent Cr 2 O 3 . This resulted in chromium recoveries above 93.5 percent When the liquid metal and slag were retained in the furnace after burden feeding ceased, the concentration of chromium oxide in the slag was observed to decrease with time reaching levels below 0.5 percent. In several tests, high quantities of sulfur, in the form of nickel sulfides, were added to the charge. It was found that in most cases more than 60 percent of the sulfur charged to the furnace could not be accounted for based upon assay results of the metal and slag produced. It is believed that the sulfur that cannot be accounted for has been transferred to the gas phase and leaves the furnace as yet to be identified gaseous components of the offgas. The sulfur concentrations in the alloy were below 0.030 percent Similar analytical test results were also found in the small scale 18 kW plasma-arc/induction unit.

A process has been developed at the laboratory scale for the recovery of titanium, vanadium and iron from the vanadium bearing titanomagnetite deposit at Pipestone Lake, Manitoba, by combined pyro- and hydrometallurgical processing route. The ore which contains 57.5% Fe, 0.66% V and 16.6% TiO2 was subjected to selective reduction smelting so that most of the iron reported to the metal phase and the vanadium and titanium to the slag phase. The iron had a purity of 99%. The slag contained between 9–35% FeO, 31–46% TiO2, and 1.2–1.6% V. Over 98% of the titanium and vanadium reported to the slag phase. The slag was roasted with soda ash at 950°C and then leached with hot water at 80°C to recover vanadium. The leach residue was further treated with hydrochloric acid at 105°C in order to upgrade TiO2 content by removing mainly iron, magnesium and aluminum. The final product contained 82.9% TiO2, 1.5% FeO, 15.6% SiO2, 1% MgO, 2% Al2O3, and 0.3% CaO with an overall titanium recovery above 90%. This product can be utilized as feedstock to the pigment industry.

Experiments conducted in 0.15 m diameter bubble columns using water and non-aqueous liquids have shown that the gas velocity at which transition from the bubbly flow to the churn-turbulent flow regime occurs is a function of gas density. The transition velocity increased with increasing gas density. The direct effect of gas density on gas holdup in the bubbly flow regime is small with only a slight increase in holdup being observed at higher densities (epsilon(G) alpha rho(g) 0.04). In the churn-turbulent region a much greater effect of gas density on gas holdup was observed. These differences were found to be a direct function of the differences in holdup values at the transition points. Gas holdup was found to be a function of the gas phase momentum. In the bubbly flow regime holdup was directly proportional to momentum while in the chum-turbulent regime holdup was proportional to momentum to the one third power.Reasons for this behaviour are discussed, as well as the implied effects on liquid mixing in bubble column slurry reactors. The effects of gas density may offer an explanation for some apparently anomalous published results.

The axial dispersion-sedimentation model is commonly used to describe the axial concentrations of solids in three phase bubble columns at low liquid velocities. When the two parameters of this model, the particle settling velocity and the solids axial dispersion coefficient, are uncoupled by the use of various assumptions, physically unrealistic values of these parameters often result.Direct experimental measurements of solids settling rates in bubbly gas-liquid mixtures were carried out. The measured mean settling velocities decreased slightly with gas flow rate and were equal to or slightly less than the single particle free settling velocity in the liquid alone. Solids axial dispersion coefficients were also obtained from the solids settling rate distribution data, and gave values considerably less than the experimental liquid axial dispersion coefficient.

The so-called axial dispersion-sedimentation model has been widely used to describe the axial solids concentration profile in bubble columns. This model contains two basic parameters - a solid particle settling velocity and a solids axial dispersion coefficient. Various workers have determined these parameters in different ways. Two methods are most common. The first assumes that the solid and liquid axial dispersion coefficients are equal and then correlates empirically the calculated settling velocities. The second uses the liquid flow rate as an uncoupling variable and solves the model equations simultaneously for the values of the two parameters. In both cases, values calculated for settling velocities for the solids are often much higher than the single particle free settling velocity in pure liquid. When superficial liquid flow velocities are not high, the actual settling velocities of particles (or the slip velocities) probably bear little relationship to liquid velocity in the column. Further, no plausible explanation has yet been offered for the apparent increase in settling velocities of particles. Our experimental studies have led to a simplified model for the axial solids profile in three-phase bubble columns which requires only one experimental parameter. A correlation for this parameter is given, which appears to apply for a wide variety of solids and liquids. Justification for the use of this simple model is also presented through measurements of the settling velocities of particles in bubbly gas-liquid mixtures. Although the one dimensional axial dispersion-sedimentation model for three-phase bubble columns gives a good description of experimental results, it is not appropriate on phenomenological grounds. The parameters of this model, therefore, should not be given quantitative physical meaning.

The exit discontinuity in slurry bubble columns, i.e., the difference in the apparent solids concentration at the very top of the column (Ct) and the concentration in the effluent (C e ), was studied in a 0.3 m ID bubble column, using air as the gas phase, water, a light hydrocarbon oil (Varsol) and trichloroethylene as liquids and glass beads of different sizes and density as solids. The results showed that the drop in solids concentration occurs in a very small layer at the gas/liquid interface. By changing the column exit configuration and removing the gas/liquid interface the exit discontinuity disappeared. The extent of the exit discontinuity depended on the liquid properties and appeared to be related to the foaming tendency of the liquid. In addition, in those systems where the exit discontinuity was significant, it depended on the solids properties and the gas and liquid superficial velocities. The magnitude of the exit discontinuity, expressed as Ct/C e , decreased with increasing superficial gas velocity in the water and Varsol systems. In trichloroethylene no exit discontinuity was observed. The correlation Ct/Ce = 1 + 0.5(U g /Vt)4. 4 derived by others from measurements in an air/water system,accurately predicted the exit discontinuity in water. Predictions for the other systems were not in agreement with our measurements. The exit discontinuity in Varsol was very much larger, particularly when foaming was not suppressed.

AbstractA review of existing literature for the purpose of comparing correlations which allow the explicit predictiosn of gas holdup in two‐ or three‐phase bubble columns shows wide disagreement concerning the effect of various variables. Further, various correlations, apparently of equal validity, show equally wide disagreement in the predicted absolute values of gas holdup among three test systems; water‐air, hydrocarbon solvent—air, and trichloroethytene air. Some possible reasons for these disagreements are discussed.Extensive gas holdup data obtained in a 0.30 m diameter column for the three test systems were correlated statistically for the transition and the turbulent region. The resulting correlation gives agreement with experiment to within ±20%, with most data showing ± 10% agreement. The proposed correlation was also tested against thirteen data sets (from eight researchers) which corresponded to its region of validity and gave good agreement. Three additional relevant data sets were not satisfactorily predicted.

AbstractExperimental leaching runs were carried out in a continuous concurrent laboratory size bubble column 5.2 cm in internal diameter and 2.90 m tall. The system studied was the dissolution of a synthetic covellite (CuS) in ammoniacal solution in the presence of pure oxygen. Behaviour of the column with respect to gas holdup and solids concentration profiles was measured without reaction by using nitrogen in place of oxygen. Gas holdup values were in agreement with literature results. However, solids concentration profiles for the mixed particle size solid used were of a more complex nature than those obtained for uniformly sized solids.Conversions obtained at various temperatures and gas and liquid velocities were analyzed in terms of the estimated rates of the individual rate processes occurring. From these results, gas absorption rate was clearly the controlling mechanism at high temperatures, and surface chemical reaction rate was controlling at low temperatures. Hence, the rate controlling steps can be identified in bubble column reactors from currently available literature correlations, together with independent kinetic measurements.

Results of a preliminary study of the ammoniacal leaching of synthetic covellite (CuS) in an aqueous oxidizing system in the presence of a nonmiscible organic sulfur solvent are described. Up to 60 pct of the sulfur can be recovered from the solvent as elemental sulfur while achieving high degrees of solubilization of the mineral. The effects of temperature, particle size, oxygen pressure, ammonia concentration and ammonium ion concentration on the degree of sulfur recovery were investigated. Maximum recoveries were achieved at moderate temperatures and in well-buffered systems, with a large excess of ammonia. Oxygen pressure and particle size were found to have little effect on fractional recovery of sulfur.

AbstractThe rate of dissolution of a chalcopyrite concentrate was measured in ammoniacal solutions under oxygen pressure for conditions when chemical reaction rate controlled. Temperatures from 50°‐95°C, oxygen pressures to 689 kPa and ammonia concentrations from 2.5 to 7.0 mol/l were investigated. An electrochemical surface reaction model in which the cathodic reduction of oxygen on the solid surface is rate determining satisfactorily predicts experimental behaviour in the range of experimental data. The activation energy for the reaction was found to be 74.1 kJ/mol.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Leaching of Cupric Sulfide in AmmoniaIrvine G. Reilly and Donald S. ScottCite this: Ind. Eng. Chem. Process Des. Dev. 1976, 15, 1, 60–67Publication Date (Print):January 1, 1976Publication History Published online1 May 2002Published inissue 1 January 1976https://pubs.acs.org/doi/10.1021/i260057a012https://doi.org/10.1021/i260057a012research-articleACS PublicationsRequest reuse permissionsArticle Views157Altmetric-Citations8LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts

AbstractExperimental work was carried out for the study of natural convection heat transfer from heated vertical plate to a non‐Newtonian fluid. Successive correlations were obtained and the results agree substantially with the theoretical prediction.