Copy of author's previously published article inserted. Bibliography: leaves 180-195. Investigation of the contribution of polyphenol oxidase (PPO) and peroxidase (POD) to enzymic browning in sugarcane juice.

The soil being delivered with sugar cane consignments. from the cane fields to the factories, has been a recent cause for concern in the South African sugar industry. The soil impurities increase the wear of processing machinery reduce extraction efficiency and represents an unnecessary transport of material. The cost due to soil was estimated at R63 million (about US $8 million) over the 1996/97-season. The need to reduce costs, due to the unwanted soil component, has been given a high priority. Ashing is currently used by the sugar industry to estimate the amount of soil in cane. Although simple to implement, the method is destructive, requires long processing times and limited to small sample sizes. In fecent times, non-destructive techniques have become more prominent in industry. Hence, the decision to apply such techniques to the soil in cane-problem. This dissertation describes an experimental investigation into Dual-Energy Transmission (DuET) and X-ray lmaging for quantifying the amount of soil in cane. DuET can determine the relative concentrations of the components of a binary mixture by measuring the transmission of low- and high-energy gamma photons through the mixture. The principle of DuET was successfully demonstrated with aqueous solutions of ferric chloride. Experimentally-determined mass attenuation coefficients of water and ferric chloride were compared to theoretical values. DuET was then applied to dried, shredded sugar cane spiked with various amounts of soil. Results showed large variations in the predicted soil concentrations. These variations were attributed to radiation scatter and incomplete volume sampling by the radioactive source. However, new experimental arrangements are expected to improve the technique: initial test results are given of a sample holder that continuously rotates a sample up and down through the source-detector axis. An alternative approach to processmg DuET-spectra, using the discrete wavelet transform coupled with an artificial neural network, is also introduced. X-ray Imaging was the second technique investigated. A literature survey revealed that this technique had not previously been applied to the soil in cane-problem. The present work constituted an initial investigation to determine the feasibility of applying X-ray imaging to measure the amount of soil in cane. The soil/cane-samples, that were used for DuET, were imaged us ing a commercial mammography unit, and the resulting radiographs were analysed using image processing techniques. Although the results are promising, a more comprehensive investigation is foreseen. / Thesis (M.Sc.)-University of Natal, Durban, 2001.

The objective of this work was to determine the operating conditions which would maximise the crystallisation performance of continuous vacuum pans used in the sugar industry. The specific application investigated in detail is crystallisation of high grade product sugar (A-sugar) in a South African raw cane sugar factory. The optimisation studies are based on a detailed dynamic mathematical model of a continuous pan. Whilst this model is based on the published work of others, the selection of variables and the formulation of the equations have been structured to produce a modular model of an individual compartment with the minimum number of independent variables. The independent variables have also been selected to meet the requirements of both a state-space control formulation and those necessary for the dynamic programming technique of optimisation. The modular compartment models are linked together to model a multi-compartment pan and the steady state model is derived as a special case of the dynamic model. For the model to simulate the conditions in South African sugar factories adequately requires appropriate descriptions of sucrose solubility and growth kinetics. Given the limited applicability of published data, experiments were undertaken to determine these parameters. Sucrose solubility in impure solutions was determined in laboratory tests designed to approach equilibrium by dissolution at conditions approximating those during pan boiling. The dependence of crystal growth rate on the concentration of impurity present in the mother liquor was investigated in both laboratory scale and pilot scale batch pan boiling experiments. The primary dependence of crystal growth rate on the super-saturation driving force was determined by fitting the steady state model to results of tests on an industrial scale continuous pan. The dynamic programming technique was used in conjunction with the mathematical model to determine the operating conditions which maximise steady state crystallisation performance. Using the crystallisation parameters determined for South African conditions, this approach has shown that the conventional wisdom of running with high crystal contents in all compartments of continuous pans boiling A-massecuite is not optimum. Pans should operate at lower crystal contents in earlier compartments, only increasing to higher crystal contents towards the final compartment. The specific values depend on seed conditions, pan design and the solubility and growth kinetics. To reap the benefits of being able to determine the optimum steady state operating condition for a continuous pan, it is necessary to be able to achieve effective steady state operation under industrial conditions. This requires both a steady loading on the pan and effective control of the crystallisation conditions within the pan. To stabilise loading, a strategy has been developed which uses buffer tanks in an optimal way to damp out flow fluctuations. This strategy accommodates multiple buffer tanks in series without the amplification of disturbances that occurs with some of the simpler published techniques. The dynamic behaviour of absolute pressure control and compartment feed control were investigated in an industrial scale pan. This work has demonstrated the importance of high quality absolute pressure control and developed techniques for effective automatic tuning of pan feed controls. As part of this research, computer control systems were developed as tools to provide the appropriate monitoring and control of the experiments undertaken. / Thesis (Ph.D.)-University of Natal, 2002.

The main objective of this work is to propose a mechanism for the transfer of impurities into the sucrose crystal. To this end the transfer of impurities into the sucrose crystal was investigated, under crystallisation conditions similar to those found industrially. Most of the impurities, namely, colour bodies, potassium, calcium and starch, were selected on the basis of their industrial importance, but some exotic species, namely lithium and nickel, were chosen to represent other mono- and di-valent ions respectively, and dyes, such as methylene blue, which have been used in work with single crystal sucrose crystallisation, were included to make the results more general. A parameter to measure the rate at which impurities are transferred into the sucrose crystal was proposed. Experiments, carried out in a pilot plant evaporative crystalliser, were performed to establish the effect of selected factors on both the concentrations of impurities found in the sucrose crystal, and on the rate at which these impurities are incorporated into the crystal. All the factors selected, namely the rate of crystallisation, the temperature, the concentration and type of impurity, the diffusivity of the impurity in concentrated sucrose solutions, and the crystal dimensions, are shown to influence the rate of impurity transfer. Only the concentration in the feed and type of impurity, however, affect the final concentration of the impurity in the crystal. Concepts involving partition coefficients and adsorption isotherms were also investigated. The experimental data did not fit the adsorption isotherm models well, but the values obtained for the partition coefficients were similar to those quoted in the literature when exchange types of reactions are operative. Activation energies have been measured, both for the rate of crystallisation of sucrose, and for the rates of impurity transfer. The values obtained, particularly for the rate of impurity transfer, indicate that a transport mechanism is effective. The experimental results have been used to investigate the relevance of two models, one involving a two-step approach and the other an interfacial process, for the incorporation of the impurity into the sucrose crystal. The results obtained indicate that the interfacial breakdown model describes the transfer of all the impurities studied here, except for starch. / Thesis (Ph.D.)-University of Natal, Durban, 1998.

South Africa has an annual sugarcane milling capacity of about 22 million tonnes on average producing about 3.3 million tonnes of dry bagasse, of which one third is surplus to factory requirements. Currently surplus bagasse is used for furfural, pulp and paper and cogeneration but significant amounts still remain . This prompted the need to find viable alternative and appropriate technology to utilize the surplus. A laboratory pilot plant was used to investigate the production of activated carbon from bagasse. Experiments were carried out to investigate conditions for making the best activated carbon in a rotary batch kiln, and also to examine potential ene rgy recovery from process gases using Gas Chromatography. Derived results from the laboratory experiments were used to develop a conceptual design for a demonstration plant sited within a sugar mill. The conceptual design was evaluated for economic and environmental impacts using a robust Excel spreadsheet and GABI-3 modelling software respectively. Excellent activated carbon was produced from sugarcane bagasse by a two-stage physical process involving pyrolysis and gasification with steam. The best operating conditions were pyrolysis at 700°C for 1 hr and activation at 850°C for 1hr, a heating rate of 10°C/min and a steam flow of 15g/g of char per hour. The active carbon yield was 7% on dry bagasse basis with a Methylene Blue Number of 257mglg of carbon. The active carbon had a sugar decolourisation capacity of 20% at a carbon dosage rate of 0.7 wt% on Brix using clear juice (l2°Brix) and 70% at 0.5 wt% on Brix using brown liquor (65°Brix) . The Freundlich isotherm showed that the bagasse-based activated carbon was a suitable adsorbent for sugar colour bodies. Gas analysis results revealed that the off gases from the pyrolysis and activation stages had calorific values of about 63MJ and 31MJ per kg of activated carbon respectively . The total combustion energy of 94 MJ/kg of active carbon was enough to satisfy the process energy requirements for drying, pyrolysis and activation. By burning combustibles like tar, methane, carbon monoxide, ethylene and hydrogen for process thermal energy needs, the environmental impact of the manufacturing process was reduced to a Global Warming Potential of llkg CO2 Equiv per kg of carbon produced. The demonstration plant requires a capital investment of US$lOA million to give a competitive bagasse-based activated carbon (BPAC) selling price of US$1.80 per kg and IRR, ROI and Investment payback time of 17.93%, 23.93% and 3.80 years respectively. A sensitivity analysis was also carried out to investigate the effect of possible variation in the main project forecasts which are BPAe selling price , bagasse buying price, capital investment and production costs on IRR, ROI and payback time . The benefits of process integration within a sugar mill would be expected to improve the business feasibility ; If bagasse was free the IRR would increase to 28.59% and even better to 32.12% if extra boiler and electricity capacity was also available at the mill. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2005.

Copy of author's previously published article inserted. / Bibliography: leaves 180-195. / xii, 195 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Investigation of the contribution of polyphenol oxidase (PPO) and peroxidase (POD) to enzymic browning in sugarcane juice. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1995

Dissertation submitted in the compliance with the requirements for the Masters Degree in Technology: Electronic Engineering, Light Current at Technikon Natal, 2000. / The CANEGRO model is a mechanistic model that describes environmental, physiological and managerial features of the agricultural sugarcane production system. The model originated from many sources of crop, climatic and soil research work. This caused a fragmentation in the model's components. The objectives of this study was to give a detailed model overview after an investigation into the model's code, published and unpublished documentation and to propose a mechanistic approach in the modelling of tiller populations. / M

Submitted in partial fulfilment of the academic requirements for the Degree of Master's Degree in Technology: Chemical Engineering, ML Sultan Technikon, 2001. / There are two process operations in the sugar factory that directly affect the recovery of sugar from evaporated syrup, namely crystallisation (boiling) and centrifugal operation. Successful automation of the vacuum pans (boiling) has been implemented using brix (total dissolved solids) control, but to date on-line measurement of continuous centrifugal performance has not been successfully accomplished in South Africa. The purpose of this investigation was to continue the preliminary work performed by Tongaat Hulett Sugar in developing a purity meter for the measurement of sugar purity (sucrose content) in a continuous centrifugal. This instrument would provide the centrifugal operator with a reliable tool to perform on-line measurement of sugar purity and would also facilitate the automation of the centrifugal / M

The drying of sugar is the last step in the recovery of solid sugar from sugar-cane. To ensure that the sugar can be transported and stored, the final moisture content leaving the sugar mill must be carefully controlled. Data spanning periods of normal plant operation were collected at the Tongaat-Hulett Ltd Darnall sugar mill. These measurements were reconciled to achieve instantaneous mass and energy balances across the sugar dryer. Using these measurements, a general model has been developed to simulate the sugar drying. It includes ten compartments through which the sugar and drying air flow, with a mass and energy balance in each compartment. It was assumed that a "film" around the sugar crystal is supersaturated, and that crystallisation is still occurring. A sorption isotherm determining the equilibrium moisture content of the sugar, at which point mass transfer ceases, was included. The model has been matched to process measurements by adjusting the heat and mass transfer coefficients. A Dynamic Matrix Controller was developed and tested off-line on the model, using the reconciled measurement sequences. The controller manipulated the inlet air temperature in order to control the exit sugar moisture content. The model predictive control format successfully dealt with the large process dead-time (5 minutes). / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2001.

Surplus sugarcane bagasse, estimated at a maximum of 0,9x106 tons/year, represents an annual renewable resource which is readily available at the mill site and is a suitable potential source of alternative fuels and chemical feedstocks. This work contains an extensive literature survey which covers the production of C5- and C6- sugars from lignocelluloses by chemical hydrolysis and the pretreatment of cellulosic materials for enzymatic hydrolysis of the cellulose fraction. This survey was then used to determine the final direction of this research into the utilisation of bagasse for the production of fermentable sugars. It was decided that research should be directed at the dilute acid hydrolysis of the bagasse hemicellulose fraction to determine whether this fraction could be selectively hydrolysed from the complex lignocellulose structure and to obtain xylose yields under different hydrolysis conditions. Acids, especially acetic acid, are liberated from bagasse by steaming at elevated temperatures. In this acid medium the hemicelluloses are hydrolysed and become soluble. Autohydrolysis tests on whole bagasse indicate that hemicellulose hydrolysis becomes significant at temperatures above 140°C. However, the autohydrolysis liquor would still require dilute mineral acid hydrolysis to convert the pentose oligomers to their monomeric forms. Dilute sulphuric and batch hydrolysis of whole bagasse hemicellulose has thus been investigated at a solid to liquid ratio of 1:15 over the following temperature and acid concentrations ranges : 80° to 150°C and 3 to 40 g/l acid. Xylose, glucose, furfural and acetic acid formation and sulphuric acid consumption were monitored during these hydrolyses. Hemicellulose hydrolysis to produce mainly xylose is readily achieved over the entire range of acid hydrolysis conditions tested with little removal of the other bagasse components (lignin and cellulose). At the upper end of the temperature range acid concentrations below 20 g/l are sufficient for hemicellulose hydrolysis due to the effect of temperature on reaction rate. The bagasse hemicellulose consists of two fractions, an easily hydrolysable portion containing 165 mg of potential xylose/g bagasse and a resistant fraction containing 105 mg of potential xylose/g bagasse. A first order reaction model has been developed using the batch acid hydrolysis results. It is based on two hemicellulose fractions reacting simultaneously to give a common product (xylose) and predicts total xylose yield as a function of hydrolysis time for a given set of hydrolysis conditions. The encouraging xylose yields obtained during the batch hydrolyses led to the design of a continuous hydrolysis reactor to process bagasse at low liquid to solid ratios to determine whether xylose yields similar to the batch hydrolysis yields could be obtained at the same hydrolysis conditions. The continuous hydrolyses showed that for the conditions tested the xylose yields are unaffected by the decrease in liquid to solid ratio (down to 3,6:1) and it would appear that reactor performance is still controlled by reaction kinetics. A number of reactor configurations for the industrial production of pentoses from bagasse hemicelluloses are also proposed. / Thesis (M.Sc.)-University of Natal. Durban, 1982.