Evaluating the suitability of measuring massecuite dry substance for control on Australian pan stages

Summary

Australian sugar factories currently use massecuite conductivity to control the feed rate of syrup and molasses to pans. Conductivity control is inexpensive and works well, although it does require close attention from pan operators since the conductivity value is affected by variations in the impurity composition in the cane supply.

Microwave transducers to measure massecuite dry substance (DS) are now being used in several overseas refineries and factories for control of the massecuite condition in pans. The sensitivity of this parameter to control the supersaturation conditions was investigated in three papers presented by QUT at the 2023 Australian Society of Sugar Cane Technologists (ASSCT) Conference. The advantage of DS over conductivity is that it is an absolute and meaningful value in terms of massecuite concentration. Therefore, it should be feasible to set a DS profile for pan run-up and heavy up right through to pan drop that can be repeated every pan cycle.

Therefore, the overall aim of this project is to evaluate the measurement of massecuite dry substance as a superior process variable for controlling pan boiling operations in Australian factories. Improved control will result in cost reduction due to less manual interaction than currently required with conductivity control. Steam savings resulting from tight control are also expected.

Objectives

  • Install and calibrate the Berthold DS transducer in Pan 9 at Farleigh Mill (190 t). This stirred pan has a new honeycomb calandria and boils A massecuite and high-grade seed.
  • Link the data output to the factory’s DCS (distributed control system) to allow comparison with conductivity measurement and other process variables on the host pan.
  • Determine the accuracy of the calibrated DS transducer against massecuite samples collected from a sampler installed adjacent to the DS transducer.
  • Compare the responses of conductivity and DS for many cycles under different cane supply conditions and for different pan operations e.g. run-up, fine grain wash, heavy up, different boiling temperatures.
  • Evaluate the pan’s performance when using the DS transducer signal to control the pan to a pre-set DS profile and compare with the use of conductivity, including an assessment of the need for manual intervention by operators.
  • Prepare report and incorporate recommendations for future work in sugar pan control.

Expected Outputs

The main outputs from the project are:

  • Knowledge of the accuracy of a microwave transducer to measure the massecuite dry substance in high grade seed and A massecuite boiling duties and determine the reliability for extended operation.
  • Knowledge of the pan’s performance when using the transducer signal to control it to a pre-determined massecuite dry substance profile as a comparison with the use of conductivity, including an assessment of the need for manual intervention by operators.
  • Knowledge of the impact of impurity composition (through its influence on sucrose solubility) on the need to change the massecuite dry substance profile at times of differing cane supplies.
  • Knowledge of the requirements for microwave transducer to accommodate adequately the effects of operation at different head space pressures (different massecuite boiling temperatures).

Expected Outcomes

The main potential benefits, if massecuite DS measurement provides to be reliable and accurate, are tighter control of individual pans, less likelihood of forming fine grain, and reduced manual input from pan stage operators.

The massecuite DS measurement should prove to be a process variable that is less impacted by changes in cane supply as is currently the case with conductivity. Greater consistency in pan control will have benefits for milling operations in terms of:

  • Minimise the ‘manual checking’of pans by operators, thus providing opportunities for increased automation of the process.
  • Reduce the incidence of fine grain formation, thus providing benefits of:
    • Increasing the capacity of the pan stage as the non-productive fine grain washing step is avoided
    • Steam savings are expected of up to $82,500 per crushing season for a single high-grade pan, by eliminating the fine grain washing step.
  • The technology would be applicable for use in all Australian mills for pan control and to enhance the competitiveness of Australian factories in the international market.
SRA PROJECT CONTACT: Dr Tinashe Chiurugwi
RESEARCH AGENCY: Mackay Sugar Limited

CHIEF INVESTIGATOR: Bryan Lavarack

PROJECT NUMBER: 2023/202

END DATE: 01/07/2024