Further progress on crystal growth on-line monitoring

A good characterization of the main variables affecting a strike can lead to an improved operation of any type of pan. Crystal growth on-line monitoring performed by new generation of microscopes provides a better knowledge of those variables, essential to achieve highest yield and cost-effective production of homogeneous crystals. The microscope operation is described at different stages of the process and comparisons are made between different applications: ? Before seeding, the microscope can detect contaminant particles from 4 ?m or so-called grand-pas present inside the pan or highlight bad syrup issues that will limit the production of high-quality crystals. ? At the seeding stage, crystals are counted and measured to make sure that the good volume and initial grain size have entered the pan at the right time. The study compares different selected strategies that are applied according to the type of pan and the type of strike used (high-grade or low-grade pans or mother and daughter strikes). ? During graining phase, real-time crystal size measurements and statistical information (CV, MA) are monitored to check normal crystal crop. Non conformities can be detected (air bubbles, false crystals apparition, bad circulation, etc) and registered for future analysis and complete traceability. Particular attention must be paid to the location of the microscope onto the pan: it has to be mounted in front of a representative area to provide good monitoring of the crystallization and valuable statistical information, especially in the first stages of the process. This new tool will quickly become indispensable to create standard strikes: the ultimate goal being to achieve full automation of the pan operation.