INCORPORATING COLD CHAIN
PROJECT
Some of the hot and cold pipework at the site for the de-greening rooms .
The chiller installation .
The chilled water pumps and pipework showing the fibre glass and resin insulation .
affected by de-greening and therefore when de-greening fruit , it is critical to apply the process in mature fruit based on particular colour . The correct degreening process also assists in the shelf life of the product .
Degreening is necessary for several reasons , including that consumers
The facility at the start of the construction process .
One of the installed coils .
associate green citrus fruit with immaturity and thus poor quality while the fruit colour is due to the interaction of chlorophyll ( green ) and carotenoid ( red – yellow ) pigments . Colour change in the field is especially stimulated when night-time temperatures drop below a specific value .
ROOM DESIGN Each room has a chilled water ( 110kW ) and hot water ( 80kW ) coil with two evaporator fans .
Temperature control is achieved with two-way modulating valves to control the room temperature between 19 ° C and 22 ° C depending on the citrus cultivar being de-greened .
Each room has a water spray nozzle to maintain the humidity in the rooms at 98 % relative humidity ( RH ). Control in this element is with dry bulb and wet bulb sensors for accurate measurement and spark-proof solenoids . Ethylene classification will be changed to flammable gas and thus the spark-proof solenoids were selected as a precaution .
Each room is fitted with a CO₂ extract fan to control the CO₂ levels below 5 000PPM . The rooms also each have an ethylene supply which again is controlled with a spark-proof solenoid . Ethylene is introduced into the room only when the room temperature and RH are at the set values and kick-starts the de-greening process . Each room , with a 480-bin capacity of citrus , will be de-greened over a 72-hour cycle . This is an industry norm but can be achieved in a shorter time if required .
Each room is controlled via a PLC , connected to the Eliwell Telivis monitoring system and an HMI installed in front of each room . Each room can be controlled and monitored from the Telivis or the HMI . A history on the performance of each room can also be downloaded from the Telivis BMS system .
Chilled water is maintained at 6 ° C . Hot water is maintained at 45 ° C .
EQUIPMENT USED IN THE PROJECT
Two Daikin water cooled chillers , with a cooling capacity of 519kW each , were installed for the cooling requirements .
Two IWC cooling towers were installed for each of the chillers with a THR of 675kW each .
Two 10 000 litre insulated plastic buffer tanks were installed as hot and cold well storage tanks for the chilled water .
Two secondary chilled water pumps were installed for the water distribution to the chilled water coils . The pumps are controlled with variable speed drives ( VSD ) to maintain constant water flow .
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