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Tempering Process

The project consisted in implementing an ADEX control system for the tempering process at the fabrication plant of Chocolates Valor in Villajoyosa, Alicante (Spain).

Tempering is one of the most important processes in the production of chocolate and includes a series of cooling stages of the chocolate which is part of the crystallisation process. The production is carried out in batches, alternating different types of product and adapting each of the operating conditions accordingly.

Chocolates Valor has 4 tempering lines. The optimised ADEX control system was applied to the highest volume production line with a capacity of 4 T/h. The equipment comprised circular heat exchanger plates where the chocolate circulates inside the internal part in the form of a fine layer in order to maximise the heat transfer while water circulates in the external part thereby functioning either as a heater or cooler depending on the mode of operation.

There are 7 zones in the temperator. Each of them incorporates a temperature control loop with an independent water circuit. The chocolate, which enters continuously at the lower part with an operating temperature of 45ºC is cooled towards its set point in each zone, following a characteristing cooling curve defined by the product recipe. The flow rate is determined by valves in the water circuit.

The precision of the chocolate tempering process has a large effect on the energy consumption of the tempering line as well as on the percent of production rejections. It is for this reason that the control system plays a crucial role in the quality of chocolate and in the performance of the plant. A few tenths of a degree deviation in the characteristic cooling curve can seriously affect these factors. ADEX control technology has enabled a 75% reduction in the level of temperature oscillation compared to the existing conventional control system, resulting in a 5% reduction in the number of production rejects with an estimated energy saving of 20%. 

Comparison between the conventional control system (Local Mode) and the ADEX System (ADEX Mode) (1/2)

This comparison shows one and a half hours of production in each operating mode under the same operating conditions.

In Local Mode, the maximum deviation with respect to the average is 1.04ºC (zone 3), with an average across all the zones of 0.72ºC. The standard deviation, which is a more representative parameter of quality control, lies between 0.55 for zone 3, and 0.27 for zone 6, with an average of 0.40. In ADEX Mode, the maximum deviation with respect to the average is 0.25ºC (zone 5), with an average across all the zones of 0.23ºC. The standard devation lies between 0.15 for zone 3, and 0.06 for zone 1, with an average of 0.10.

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