A new design of jigger system to improve vacuum pan performance

A new jigger system has been designed by SRI to boost circulation and heat transfer rates in vacuum pans. The jigger system injects and distributes numerous small bubbles of steam/incondensible gases at controllable rates into the base of the pan. Circulation is improved through a combination of the rising bubbles and the increased heat transfer that results from the increased velocity of massecuite through the tubes. The jigger system offers benefits to the pan's performance throughout the entire pan cycle. Trials were undertaken during the 2004 and 2005 seasons on batch and continuous pans in Australia to determine the performance during operation with and without the jigger system. The performance was assessed by taking circulation measurements using anemometer probes, measuring heat transfer from the calandria section of the pan, monitoring the calandria pressure and steam flow rate during operation and monitoring the production rate of massecuite. The installation of the jigger system shows substantial performance improvements including reduced calandria pressure, improved heat transfer coefficients, increased circulation velocities, shorter batch pan cycle times and production of massecuites at higher brix. Additional advantages of the jigger system include relatively cheap and low maintenance, reduced need for balance water and the use of surfactants, and the pipework system does not block with massecuite so non-return valves are not required. The jigger system can be retrofitted to existing batch and continuous pans of any design.