It is a well-known fact that the selection of the raw material and how it is further treated within the stock preparation system has a major affect on the quality of paper obtained. While the pulp selection is important for a good product, the refining treatment received by that pulp is the determining factor for the properties of the product. It is for these reasons that it is interesting and beneficial to study the pulp quality and refining results. The focus of this research work was to study the behaviour of selected clones of Eucalyptus materials from different site indices under different refining conditions. Poor and good sites were investigated. The strength properties of the resulting refined pulp were investigated. The project was conducted in three phases with the focus of the project being phase 3. The work began with refining of commercial Eucalyptus pulp obtained from Mondi Richards Bay (phase 1). The objective here was to get an understanding of the influence of the various parameters affecting refining. This knowledge could then be used on a more focused research program on the well defined pulps with limited refining variables being considered. The results indicated that of the three variables investigated (i.e. stock flow rate, stock consistency and refiner speed of rotation) the parameter speed of rotation gave the most repeatable results when varied and also resulted in the largest range of refining intensity (SEL) achievable compared to the variation of the other two parameters. It was decided that the work on the different pulps investigated in phase 3 would be carried out using the parameter speed of rotation to vary the SEL and multiple passes through the refiner to vary the specific refining energy (SRE). A comparison between the refining characteristic of bleached and unbleached pulp was carried out (phase 2). It was seen that there were differences in the refining characteristics between bleached and unbleached pulp. These differences however, occurred in a predictable manner. This indicated that with further investigations on the differences in refining characteristics, it would be possible to extend the results obtained from refining studies using unbleached pulp to what can be expected from the refining of bleached pulp. Phase 3 of the project considered the refining of different pulps. Two different clones of Eucalyptus (GU A380 and GC G438) each from two site indices (good and poor), were selected to provide raw materials having different wood anatomy. These were pulped under similar cooking conditions using the kraft pulping process. The kappa numbers were in the range of 18 to 21. The refining trials were then conducted to determine how the different pulps affected the refining process and also how the refining process affected the pulp properties. Refining was carried out at three different refiner speeds. It was seen that for the overall results SRE was a good predictor of all the pulp properties measured except for the tear. The pulp fibre length was able to predict the tear best. It was seen that refining higher intensities reduced the SRE required to obtain a pulp freeness of 400 ml. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005

A novel static total pressure apparatus was designed, built and commissioned for the measurement of VLE data at low to moderate pressures and temperatures. The apparatus of Fischer and Gmehling [1994] was used as a basis for the current design. The continuous-dilution technique (Gibbs and Van Ness [1972]) for sample introduction has been incorporated in our apparatus, so that the full composition range of a mixture can be covered in two runs. This procedure has the considerable advantage of speed. If the liquid is properly degassed, the main limitation of the method is the accuracy with which one can establish overall compositions from metered volumes. Accurate injection of the two components is accomplished with a patented dual-action piston-injector (Raal [1999]). In the micromode the pump can accurately dispense submicrolitre volumes and the apparatus is thus particularly suited for VLE measurement in the very dilute region, and thus for determining limiting activity coefficients. r~ calculated using the method proposed by Maher and Smith [1979] ranged from about 3.8 to 59. The estimated accuracy of the injected volumes is ± 0.002 cm3 ; this was obtained from calibration with distilled water. The estimated accuracies of the equilibrium temperature and pressure are ± 0.2 °C and ± 0.01 kPa respectively. The pure liquids were degassed for at least 8 hours according to the procedure proposed by Van Ness and Abbott [1978]. The static assembly and experimental procedure have been tested via pure component vapour pressure and binary vapour-liquid equilibrium measurements for a range of test systems (Water (1) + I-Propanol (2) at 313.17 K, Water (1) + 2-Butanol (2) at 323.18 K, n-Hexane (1) + 2-Butanol at 329.22 K). The test systems data compared well with literature data and a high degree of confidence was then placed on the equipment set-up and experimental procedure. New vapour-liquid equilibrium (VLE) data were measured for the following binary systems: • I-Propanol (1) + n-Dodecane at 342.83K and 352.68 K • 2-Butanol (1) + n-Dodecane at 342.83 K and 352.68 K • Water (1) + o-Cresol at 342.83 K The VLE measurements of the new systems were very challenging because of the large boiling point differences between the systems' constituents. An accurate new method for determining the net interior volume of the cell V cell was tested and P. -p J gave excellent linear plots of cumulative volume of injected liquid, vt against 1 Po 0 , with the sIot pe representing. Vcell The VLE data for all the systems measured were modeled using the combined (r - ¢ ) method. The Barker's method of data reduction was implemented to convert the number of moles of each component injected into the cell to mole fraction of the vapour and liquid phase (Uusi-Kyyny et al. [2002]). Different Gibbs excess models namely NRTL, T-K Wilson and Van Laar together with the virial equation of state for vapour phase non-idealities were used. The T -K Wilson and NRTL gave the best fit. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.

Pulp and paper mills are facing the possibility of stricter effluent discharge limits. End-of-pipe treatment for discharge no longer guarantees compliance, nor is it the most cost-effective way of solving mills' effluent problems. In this dissertation, water pinch analysis is used as a tool to determine the optimum effluent treatment conditions to ensure compliance at the least cost to the mill. It is also shown that the environment and the mill can benefit simultaneously if the correct effluent discharge philosophy is implemented. Mill simulation results were used to set up a water pinch analysis model. Maximum permissible inlet concentrations were specified for all process units. Mass transfer equations were used to describe the relationships between inlet and outlet concentrations of the process units. A number of generic effluent treatment units with preset performance specifications were added to the pinch model. These treatment units can be sized and used in an optimal way by the pinch model to obtain an optimum effluent treatment and recycling scheme. Capital and operating costs for different treatment units were included in the analysis. The capital cost for treatment units decrease as the volume treated by the unit decreases. The operating cost is generally expressed in terms of volume; however, certain treatment units have treatment cost expressed on load treated rather than volume. The validity of the results obtained from WaterPinch™, the pinch analysis software used for building the pinch model, was checked by using a process simulation package, WinGEMS™, to simulate the proposed effluent treatment scenarios. This step ensured that the mass transfer relationships used in the water pinch model were valid. This was an important part of the work, as the results generated by the optimisation model have to be reliable in order to make the results obtained applicable to the mill. The verified water pinch model was used to find optimum treatment plant layouts for different effluent discharge volume and concentration specifications. This resulted in an optimum-cost profile for a range of effluent discharge volumes and concentrations. Optimum-cost profiles could be a decision making tool in the negotiation between the mill and the regulatory authority to set effluent discharge regulations in such a way that the environment benefits without unnecessarily restricting economical and social development of the region. Using optimum-cost profiles, the differences between a load-based and a concentration-based discharge permit was illustrated. Comparing the pinch analysis results for these scenarios showed that the mill has no financial incentive to reduce effluent volume if a concentration-based permit is in place. However, a load-based permit could make it financially viable for a mill to reduce effluent volume and load rather than to simply treat and discharge. It is also shown that both the mill and the environment (river) benefit from a load based permit. The impact of possible future waste discharge charges on the economical feasibility of various effluent treatment options is also investigated. The results indicate that the implementation of waste discharge charges will only benefit the environment if it is linked with a load-based effluent discharge permit. This illustrates the usefulness of pinch analysis as a basic risk analysis and risk management tool. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.

Elutriators or commonly known as Teetered Bed Separators (TBS) consist of a column with water being introduced at the base (known as teeter water), which rises up the elutriator at a constant velocity. Mineral particles are separated according to their density and size. Particles with a settling velocity less than the velocity of the teeter water will report to the overflow stream, while those with a higher velocity will sink to the underflow. Finer and lower density particles report to the overflow whereas coarser, denser particles report to the underflow. In commercial mineral processing by gravity concentration, the intermediate size range (-2mm+ 75 ,LIm) has not been effecti vel y processed due to industries lack in knowledge of equipment that are capable of effectively beneficiating this size material. This project involved testing the effectiveness of the elutriator with regards to fines beneficiation as well as the development of a prototype unit. Regarding coal (-2.0+ 1.0mm), the Eriez Crossflow unit produced the best results with an E.p. of 0.095, Dso of 1.52 and a product ash content of 8.3%. For the -1.0+ 0.5mm fraction the Eriez Crossflow elutriator was also utilized yielding best results at an E.p. of 0.06, Dso of 1.6 and ash content of 9.1 % (feed ash content of 22.7%). Regarding ferrochrome ore (-2.0+ 1.0mm), no noticeable separation occurred using the Eriez Crossflow unit. For the -1.0+ 0.5mm fraction the Linatex elutriator performed the best yielding an E.p. of 0.085, Dso of 3.18 and a FeCr grade of 85.1 % (feed grade of 28.1 %). For this size fraction the Eriez unit only upgraded the FeCr to 39.6% Regarding hematite ore (-2.0+ 1.0mm), the Linatex unit produced the best results at an E.p. of 0.15, D50 of 3.4 and a Fe grade of 46.7% (feed grade of 32.4%). For the -1.0+ 0.5mm fraction the Linatex elutriator was also utilized yielding best results at an E.p. of 0.45, D50 of 3.75 and a Fe grade of 57.9% (feed grade of 32.4%). The efficiency of separation with regards to different ore types was noticed to be partially dependent upon the feed point to the column. Lighter material was observed to separate more effectively with a tangential feed entry and denser material being separated more effectively with an entry point above the bed. Test work on a prototype unit constructed was conducted using the -1.0+ 0.5mm ferrochrome material. This unit performed well compared with both the Eriez unit and the Linatex unit obtaining an E.p. of 0.075 as opposed to E.p. values of 0.085. The FeCr material was upgraded from 28.1 % to 76.4% with the prototype unit. A continuous two day run undertaken revealed that the elutriator is capable of operating at steady state for a period of time without loss of efficiency. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008

In this work, a novel experimental apparatus has been designed, constructed and commissioned for the measurement of VLE at pressures up to 750 kPa and temperatures up to 600 K. The project undertaken represents a complete re-working of the design of Harris (2004), which was plagued by irregularities in the equipment operation and in the acquisition of experimental data. As in the work of Harris (2004), the design of the apparatus presented here is based upon the highly successful glass VLE still design of Raal (Raal and Muhlbauer, 1998). The novel apparatus is principally constructed from machined 316 stainless steel and features sight glasses in strategic positions to allow for an observation of the fluid flow characteristics in specific sections of the apparatus. The key criteria that encompassed the design of the equipment were expediency, operational efficiency and versatility in the acquisition of reliable VLE data. An initial test of the performance of the equipment was achieved through the measurement of pure-component vapour pressures of selected hydrocarbons (n-alkanes and a cycloalkane) and alkanols. The test system for vapour-liquid equilibrium (P-T-x-y) measurements with the novel apparatus was that of cyclohexane + ethanol at a pressure of 40 kPa. Good agreement between the literature and the experimental data was observed. Isobars for the cyclohexane + ethanol system at 69.8 kPa, 97.7 kPa and ISO kPa were also measured. The latter constitutes new data that have been measured for this system. Novel vapour-liquid equilibrium data were also obtained for the systems of I-propanol + 2-butanol, I-propanol + n-dodecane and 2-butanol + ndodecane at temperatures of 373.15 K, 393.15 K and 423.15 K. For the very high relative volatility alkanol + n-dodecane systems, uncertainties in the measurement of the vapour phase (y) resulted in only P-T-x experimental data being presented here, where the vapour phase composition was computed with the Wilson equation. The theoretical treatment of the experimental VLE data was achieved through a combination of the gamma-phi and the phi-phi approaches in the fitting of the VLE data to various thermodynamic models. In the gamma-phi method, a variety of activity coefficient models (Wilson, T-K Wilson, NRTL, UNIQUAC and modified UNIQUAC) together with the truncated virial equation of state were employed to find the best fit for the data. In the phi-phi method, the isothermal data sets were treated with the Peng-Robinson-Stryjek-Vera equation of state with the original Huron-Vidal (HV) and the modified Huron-Vidal mixing rules (MHVI and MHV2) in the correlative procedure. Thermodynamic consistency testing was also performed with the Direct Test of Van Ness (1995) to assess the quality of the experimental P-T-x-y VLE data sets measured in this study. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2006.

A stirred gas-solid reactor has been used to study the Fischer-Tropsch synthesis over a supported ruthenium catalyst. Detailed catalyst characterisations were conducted on both fresh and used catalyst samples and included such techniques as physisorption and chemisorption, electron microprobe examination, carbon determination and mercury porosimetry. The product obtained from the synthesis consisted largely of n-alkanes and the product selectivity of individual carbon number fractions is demonstrated to have certain advantages over the corresponding selectivities (adapted from the literature) obtained over iron, cobalt and molybdenum catalyst. The rate data obtained is fitted to two empirical models: a simple power law model and a previously-described mechanistic model. Energies of activation for methanation and carbon monoxide removal (at approximately 34,3 and 19 kcal/mol respectively) are compared with regressed values obtained by other workers. Rate data for the synthesis of higher hydrocarbons are fitted to a simple power law model and energies of activation for individual carbon number fractions up to C8 are presented. / Thesis (Ph.D.)-University of Natal, Durban, 1979.

No abstract available. / Thesis (Ph.D.)-University of Natal, 1975.

While the significant effect that the froth phase has on the performance of a flotation operation has recently been widely recognised, little work has been published which promotes an understanding of the physical processes occurring in the froth phase. A more intimate understanding of these processes and their relative importance and interactions would lead to a more rational design of froth chambers and froth removal methods, with resultant improvements in flotation plant performance. In pursuit of this understanding the following investigations were performed: (1) In a specially designed cell the variation of mineral grade with height above the froth-slurry interface - as affected by gas rate, frother concentration, the presence of froth baffles (to minimise mixing) and final product removal rate - was measured. A mathematical model was formulated to assist in the interpretation of this data. (2) The residence time distribution of a 2-phase froth (air and water without solid particles) was measured as a function of froth height, gas rate and frother concentration. Small polystyrene balls were used as a tracer. The results were interpreted using two theoretical models: (a) a streamline model which involved the solution of the 2 - dimensional Laplace equation for frictionless flow of froth in the froth chamber; (b) a semi-phenomenological model which relates the froth residence time distribution to cell dimensions, gas rate and froth stability. On the basis of insights gained in these investigations, a number of objectives which should be met by froth removal methods were formulated: (1) froth removal efficiency should be maximised, i.e. there should be no stagnant zones in the froth; (2) froth stability should be optimised; (3) the minimum residence time of froth elements in the froth phase should be maximised. One novel method of froth removal was designed, and this and a number of other methods of froth removal were compared experimentally. It was found that substantial improvement in flotation performance could be obtained by (1) sprinkling the froth with water, which removed entrained particles and improved froth stability; (2) inserting a baffle in the froth phase near the concentrate weir which increased the minimum residence time of a froth element in the froth phase, thereby improving the drainage of entrained particles from the froth; and (3) placing a froth scraper near the back of the cell, thus ensuring that no stagnant froth zones developed. / Thesis (Ph.D.)-University of Natal, Durban, 1979.

The problem of predicting the general ion exchange equilibria pertaining to systems of industrial significance is generated by the multicomponent nature of such systems and the nonidealities which may be present in both the solution and exchanger phases. A general framework applicable to multicomponent systems incorporating nonideal effects in both phases is presented. For the solution phase a well established procedure for calculating activity coefficients is adopted. Deviations from ideal behaviour in the exchanger phase are modelled by the Wilson equation, which expresses the excess Gibbs free energy of mixing of the resinates as a function of composition. A Significant advantage is afforded by this equation in that theoretically a multicomponent system may be predicted from the binary interaction coefficients of this equation which are determined experimentally, thereby reducing the otherwise extensive experimental program. These ideas are applied to systems of increasing complexity from simple binary characterisation experiments to the prediction of a six component system related to that encountered in the recovery of uranium from sulphuric acid leach liquors. Experimentation for the systems involving the ions S04 2-, Cl- and NO-3 and a strong base anion exchanger have provided a severe test for the procedure proposed. The agreement between the predicted and experimental resin phase composition data for this ternary system is within ± 5%. The addition of complexing agents complicates the procedure in that it becomes physically impossible to decompose the system into the desirable experimental binary systems. In this case higher order systems are characterised. Introducing a mineral acid to the ternary system discussed previously generates the HSO-4 ion which necessitates the characterisation of other ternary systems before the quaternary system may be predicted. The agreement between the predicted and experimental resin phase composition for the quaternary system is shown to be within ± 10%. The work is easily extended to include the more complex systems generated by the complexation of metal ions with the various ligands present. .Provided the stoichiometry of the complex species in the exchanger phase is well defined the complexes present no difficulties in the characterisation procedures. Experimental studies on the acidic uranyl sulphate quaternary system provide the desired ion exchange equilibrium constants and the interaction coefficients. In order that the interaction coefficients for the ion pairs such as UO2 (SO4)2-2, Cl- and U02 (SO4)2-2, NO-3 may be estimated it is necessary to characterise two quinary systems. Nevertheless the characteristics of lower order systems are employed to reduce the number of unknown parameters. Finally it is possible to predict the resin phase composition of the six component system which results from chloride and nitrate species being included in the acidic uranyl sulphate system. The quantitative effects of all the components in the solution phase on the extent of uranium loading are predicted. Although the ferric ion is an important component in the industrial situation this ion has been excluded from this work because at this stage it is not possible to identify or measure the quantity of the various ferric complexes present in the resin phase for a particular solution condition. / Thesis (Ph.D.)-University of Natal, Durban, 1976.

No abstract available. / Thesis (Ph.D.)-University of Natal, Durban, 1977.