This is a classic problem in which an over temperature causes process problems and avoiding the over temperature results in longer cycle times. In my view, the simplest approach to this is to control the oil temperature to a maximum of 90°C and circulate it through the jacket at a very high rate so that the discharge temperature of the oil is still close to 90°C. This may make for a very long melt time but it is the most conservative way of avoiding overshoot. A somewhat more complicated method would be to measure both the oil and the fat and institute a control scheme which reduces the oil temperature to 90°C as soon as the fat temperature exceeds 70°C. Utilizing the existing scheme of controlling the oil temperature can be improved by changing the oil temperature set point upward until the desired cycle time is achieved or the overshoot becomes unacceptable. This approach requires a series of controlled experiments. However, it will define the best operating range within the capabilities of the existing equipment.
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