CANE DIFFUSER TRACER TEST: DEVELOPMENT OF EQUIPMENT TO TUNE PERFORMANCE

Tracer testing is a commonly used technique to determine the flow and percolation parameters required to configure juice distribution trays in a diffuser for efficient operation. Sodium chloride has become the preferred tracer medium for diffusers since the cost is low and, unlike other tracers such as lithium or fluorescent dye, it can be quantified in real time using conductivity change measurements. Early workers used commercial conductivity probes but these were expensive and a challenge to integrate into a convenient data acquisition system. In the previous two decades, the Sugar Milling Research Institute NPC (SMRI) developed a custom-made system which used probes suspended in containers of overflowing juice and linked to a central data collector using long cables. Variations in resistance as well as cable breakage meant that data were not always reliable. This paper describes the basic principles of operation and capabilities of a new conductivity tracer test system that has been developed by the SMRI. Flow-through conductivity cells with a temperature measurement are used. Each conductivity cell is connected to an outstation which in turn has a wireless link to a central base station. The base station is connected to a notebook computer through a USB port. Custom software was used to control the measurement and data acquisition process. The temperature compensated conductivities can be displayed in real time. The results of the tracer test (percolation velocities and angles) can be calculated immediately after completion of the test, allowing rapid feedback on the diffuser performance.