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Benefits/ Evaluation of Pan Circulator By Javed Hasan (Senior Manager Process) Shakarganj Mills Limited, Jhang

Benefits/ Evaluation of Pan Circulator By Javed Hasan (Senior Manager Process) Shakarganj Mills Limited, Jhang. Introduction. Circulation of Massecuite in the pan while boiling play a prime role in proper growth of crystals and exhaustion of molasses.

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Benefits/ Evaluation of Pan Circulator By Javed Hasan (Senior Manager Process) Shakarganj Mills Limited, Jhang

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  1. Benefits/ Evaluation of Pan Circulator By Javed Hasan (Senior Manager Process) Shakarganj Mills Limited, Jhang

  2. Introduction • Circulation of Massecuite in the pan while boiling play a prime role in proper growth of crystals and exhaustion of molasses. • The benefits associated with good circulation are: • Quality: Improved crystal size distribution and low sugar colour due to uniformity of fluid conditions within the vacuum pan • Recovery: A high massecuite dry substance concentration is possible, leading to a higher crystal yield and a lower purity of molasses. • Capacity: Improved heat transfer leads to a higher crystallization rate and increased throughput. • Energy Efficiency: Use of vapor from later evaporator effects becomes possible

  3. Mechanical Circulation • Pan Stirrers if properly designed can significantly: • Improve the performance of a batch pan. • The assisted circulation improves heat transfer and shortens the duration of Batch boiling, thus improving capacity. • Stirrers improves the quality of the high grade sugar produced. • Pan stirrers provide the option of achieving an acceptable heat transfer with temperature difference as low as 20oC, compare to at least 45-50oC in the absence of stirrer. • The use of low pressure vapor become possible, allowing reductions in the factory steam requirements.

  4. Mechanical Circulator Assembly Mechanical circulator assembly consists of the following elements • a circulator carrying vanes or other propelling means • A vertical shaft • A driving system connected with the shaft The driving system usually consists of the shaft, coupling, bearings, gearing, pulleys and belts. The power is supplied by an electric motor.

  5. Top Mounted Mechanical Circulator

  6. Advantages of Mechanical Circulation • Quality improvement of product • Reduction in water consumption • Height of massecuite • Capacity improvement • Better heat economics • Less deposition on calandria tubes

  7. VACUUM PAN MECHANICAL CIRCULATOR

  8. Design Specification • The stirrer itself is located in the down take if it is an axial flow impeller, or just below the down take in the case of a radial flow impeller. • Installed power should be in the range of 1-1.7 kW/m3 • Tip speed has to be kept below 7 m/s • The impeller blade tip clearance shall be no less than 5% of the impeller diameter. • The stirrers shall be supplied with either • A two speed motor • Direct torque conrtol variable speed drive

  9. Benefits • Saving in strike time of up to 30% • Good circulation maintained through the strike • Provide more uniform grain • Increased pan capacity by 20-30% • Increase in crystal yield up to 5% • The color removal has improved from 88% without circulator to 92% with circulator • Sugar conglomerates counts have been reduced by about 80% • Strike level in pans can be raised by 30-40 cm with the use of stirrer • Increase in heat transfer coefficients from 0.78 kW/m2/oC to 0.87 kW/m2/oC with stirrer

  10. Effects of stirrer on • Refine sugar colour • Conglomerate count • Sugar Quality • Boiling Times • Evaporation Rates and Heat Transfer Co-efficient • Sugar production (T/Hr) • Boiling time (Hr)

  11. Comparison of Results

  12. Refined Sugar colour

  13. Effect of the Stirrers on Boiling Times

  14. Quality of crystals

  15. Mechanical Circulator

  16. Comparison • In top mounted mechanical circulators, the circulator shaft extends through the height of the pan. (between 5-8 meters) • Bottom mounted mechanical circulators offer a distinct advantage that in comparison to top mounted mechanical circulators, the shaft length is reduced to 1.7-2.5 meters as compared to 5-8 meters

  17. Novel Mechanical circulator Assembly

  18. Bottom Mounted Mechanical Circulator

  19. Feature of Mechanical circulator Assembly

  20. Feature of Mechanical circulator Assembly

  21. Mechanical Circulator

  22. Speed and Power Requirements

  23. Comparison of Pan Capacity Vs Installed Power • Operating at 33/48/63 RPM with VFD depending upon pan duty,design and operation on various viscosities

  24. Conclusions The installation of mechanical stirrers to pan has to a no. of improvements in the performance of pan both in respect of sugar quality, exhaustion efficiency, reduction in strike times and increase in sugar production rate The most consistent improvement in terms of sugar quality has been in lower colors, reduced color formation in the pan, and more homogeneous crystallization conditions have lowered the color in the crystal The color removal has improved from 88% without circulator to 92% with circulator Pan yields and heat transfer co-efficients have been improved and taken together are worth approximately 10% additional pan capacity Less deposit on the tubes due to friction of the faster circulating massecuite Sugar conglomerates counts have been reduced by about 80%

  25. Thanks

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