Progress 01/01/01 to 12/31/06
Outputs
1. Laboratory batch pan investigations. The two pilot plant vacuum pan crystallizers have been re-commissioned in the new pilot plant lab, and the automatic controls re-established. Some modifications to piping and instrumentation were necessary. The pans have been well utilized in establishing the effect of process conditions on crystal growth and the work extended to include the effect of impurities on the kinetics and the effect on the inclusion of impurities and color in sugar crystals. Samples have also been collected at some mills for a parallel investigation on the inclusion of impurities in sugar crystals. 2. Optimizations of measurement and control. A new K-Patents refractometer was installed in one of the pans, and compared with other transducers used for the measurement and control of batch crystallization. This has proved to be very useful in crystallization rate measurements. 3. Extension to continuous crystallization. Work on CFD modeling of the flow
dynamics inside both batch and continuous crystallizers is almost complete. It has lead to a new understanding of the fundamental issues surrounding the circulation and boiling of massecuite in vacuum crystallizers. Investigation into the effect of these conditions on drag coefficients has enabled the predicted flow patterns to be confirmed by actual measurements in a full-size continuous pan at Enterprise mill. Subsequently the CFD model has enabled a study of the factors affecting performance, enabling optimizations of the equipment design to be carried out. Samples of sugar boiled in batch and continuous pans have been collected, to see how the mode of operation affects the inclusion of impurities, particularly dextran.
Impacts
Factors affecting sugar quality have been identified on the pilot plant and will be confirmed by measurements made on mill samples. A new insight into crystallization has been achieved. Work on modeling circulation in continuous crystallizers has led to some recommended improvements in equipment design, which will lead to improved productivity of crystallizers.
Publications
- Rein P.W.; Bento L.S.M.; Cortes R. (2006): The direct production of white sugar in a cane sugar mill. Proc Sugar Proc. Res. Conf. In press.
- Rein P.W. (2006): Some fundamental considerations of crystallization and their implications for the control of sugar boiling. Sugar Ind. Technol. 65, 77-89.
- Martins P. M.; Rocha F. A.; Rein P (2006): Effect of cane sugar impurities on sucrose growth kinetics. Sugar Ind. Technol. 65, 212. (Poster)
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Progress 01/01/05 to 12/31/05
Outputs
Crystallization rates were measured on the pilot plant vacuum pan and have now been fully assessed. The work was successful in developing a model to characterize solubility and kinetic relationships. The result of the model compared well with microscopic crystal image analyses in terms of crystal growth rate. The inclusion of nonsucrose in the sugar crystals was studied, and a competitive absorption model developed to describe the inclusion of impurities. Work is continuing in investigating dextran and color inclusion in sugar crystals. Work using CFD to study conditions in full scale vacuum pans has made good progress. The CFD predictions have been checked against PIV measurements in the lab and measurements have been made using a hot film anamometer in a full scale continuous vacuum pan. A discrepancy between drag coefficients measured and those predicted by previous workers is being investigated further.
Impacts
New insights into factors affecting the crystallization of sugar have been obtained. This will help in optimizing crystallization at the mills and in improving sugar quality.
Publications
- Echeverri L.F.; Rein P.W.; Acharya S. (2005): Numerical and experimental study of the flow in evaporating crystallizers. Zuckerindustrie 130, 538-544.
- Echeverri L.F.; Acharya S.; Rein P.W. (2005): Computational and experimental study of the flow in evaporative crystallizers. Proc. NHTC Amer. Soc. Mech. Eng. Heat Transfer Conf. July 17-22.
- Martins, P. M.; Rocha, F. A.; Rein, P., Modeling Sucrose Evaporative Crystallization. Part 1. Vacuum Pan Monitoring by Mass Balance and Image Analysis Methods. Ind. Eng. Chem. Res. 2005, 44, (23), 8858-8864.
- Martins, P. M.; Rocha, F. A.; Rein, P., Modeling Sucrose Evaporative Crystallization. Part 2. Investigation into Crystal Growth Kinetics and Solubility. Ind. Eng. Chem. Res. 2005, 44, (23), 8865-8872.
- Martins, P. M.; Rocha, F.; Rein, P., New methods for characterization and control of industrial crystallization. VDI Berichte 2005, (1901 II), 1051.(on behalf of the ISIC 16 - 16th International Symposium on Industrial Crystallization, Dresden, Alemanha, 2005)
- Martins P.M.; Rocha F.A.; Rein P.W. (2005): Vacuum pan monitoring by mass balance and image analysis methods. Sugar Ind. Technol. 64, 241-249.
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Progress 01/01/04 to 12/31/04
Outputs
Because of the move of the Audubon Sugar Institute from the Baton Rouge campus to St Gabriel, the pilot plant vacuum pan crystallizers were disconnected for most of the year. This has put work on crystallization on hold for most of the year. The larger of the two pans was connected up and the automatic control systems re-installed. The opportunity was taken to improve the installation with some new control elements. A course on pan boiling was run at Audubon using this pilot plant pan. Little progress was made in identifying what action to take in the event of pan death syndrome, where the pan stops boiling due to particular molasses characteristics. This phenomenon did not recur in the 2003 or 2004 season.
Impacts
Experience gained on the pilot plant system was used in the design of some automatic control schemes in some of the Louisiana mills. Work done in the previous year in the pilot plant on crystallization rate measurements was analyzed. Useful results have been obtained which are being prepared for publication.
Publications
- Saska M. (2005): Boiling rate, heat transfer and viscosity of technical sugarcane liquors. Proc. Int. Soc. Sugar Cane Technol. 25, 51-62
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Progress 01/01/03 to 12/31/03
Outputs
The performance of various sensors for controlling crystallization was evaluated. A new automation system was designed, implemented and commissioned on a lab pilot plant pan to enable further controlled experiments to be undertaken. Heat transfer measurements on different samples of molasses were undertaken to establish the factors affecting heat transfer and try to establish what factors lead to hard-to-boil characteristics. Crystallization rates were measured for different grades and purities to asses the effect on crystallization rates. The inclusion of color into the crystal was studied.
Impacts
Experience gained on the pilot plant system was used to design a system for St James Mill, which was implemented and run in the 2003 season with success. Some progress was made in identifying what action to take in the event of "pan death syndrome", where the pan stops boiling due to particular molasses characteristics. This phenomenon did not occur in the 2003 season. Significant progress was made in the pilot plant on crystallization rate measurements. The data are still being evaluated but are expected to add to our understanding of this complex process.
Publications
- Rein P.W. (2003): The importance of achieving a high crystal content in high grade molasses. Sugar Bulletin. 81, 8, 12-17.
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Progress 01/01/02 to 12/31/02
Outputs
A new automatic control system has been installed on a laboratory pilot plant vacuum pan, to enable reproducible batch crystallizations to be undertaken. Methods of measurement of quantities of interest, all indirect methods, which can be used for control purposes, have been compared, and recommendations made to mills in the industry. As a result, successful automation of a batch pan has been achieved at St. James sugar mill, based on information from the pilot plant work. Short courses have been run to train industry personnel in the techniques of pan boiling and automatic control. A second laboratory pilot pan is being automated, using a PLC system, which can be compared with a conventional control system on the first pan. The lab pans have been used extensively to investigate problems with low heat transfer rates in massecuites in certain Louisiana Sugar mills in the past season. It is expected that some fundamental information on heat transfer in vacuum pans will
be obtained.
Impacts
A pilot plant crystallization facility has been developed at Audubon Sugar Institute which is showing its value in assisting the Louisiana industry to advance using automatic control techniques, and train operating personnel. The facility has shown its worth in investigating heat transfer problems in poor quality massecuite.
Publications
- Saska, M. and Rein, P.W. (2001). Supersaturation and Crystal Content Control in Vacuum Pans. Proceedings of the Sugar Industry Technologists, Inc. 60: 809
- Rein, P.W. (2002). Education and Training in Sugar Process Engineering. Sugar Bulletin. 80, 7: 11-15.
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