PROJECT
INCORPORATING COLD CHAIN
system that sends out an email should
there be any alarm condition. •
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IMPROVING THE DE-GREENING
PROCESS •
De-greening is achieved by keeping
citrus at a constant pre-set temperature
at maximum set humidity, regulating CO 2
level, and introducing ethylene (ripe gas).
Van Zyl explains how their solution differs
from more traditional methods.
Traditional de-greening methods
operate using direct expansion
refrigeration design to provide cooling.
Electrical elements in each room provide
heating. The refrigeration evaporator
coil is fitted in a false ceiling area above
the room. Humidity is introduced into
the room via water/air nozzles or steam
humidifiers creating a mist. In most cases,
this function is switched on when the
room starts. CO 2 is extracted via extract
fans operating on an on/off pulse timer.
Ethylene is also introduced via an on/off
pulse timer.
Drawbacks
• Large quantities of synthetic refrigerant.
• Servicing/repair work on the
evaporator is time-consuming.
• No accurate CO 2 level control.
• No accurate ethylene gas control.
• No accurate temperature control.
• Electrical heating creates expensive
energy bills.
•
No water recycling.
No automatic programming of
different de-greening cycles.
Loading/unloading of product takes
longer as door opening is small.
No gas-tight sectional doors.
Redesigning the traditional de-greening
facility allowed the design team to
make use of the latest technologies
available, optimising efficiency using
minimal refrigerant with lower global
warming potential (GWP) and reducing
electrical load.
The equipment layout has been
changed by moving the evaporator coil to
ground level, behind the room. This allows
for easy maintenance and repair work to
be carried out, and less steel construction
as the overhead weight is reduced.
The door size has been increased to
allow fork trucks to load rooms right up to
the door, as well as making use of a gas-
tight door, reducing ethylene gas leakage
and temperature loss.
The new system is capable of reading
real-time CO 2 , ethylene and humidity
levels and controls these levels according
to set-points. The room is operated by a
sophisticated PLC, allowing full control of
the room operation, real-time data, as well
as remote access for off-site management.
Pre-set programs can be created for
different scenarios and all alarms are
monitored and reported via email.
Chilled water evaporator with control valves.
Humidity nozzles fitted in false ceiling void.
Rear view of de-greening rooms showing heat pump chillers, chilled water
evaporators, and buffer tank layout.
16
Humidity water harvesting allows for a
percentage of the new water to be
collected, stored in a tank, filtered, and
re-used in the humidity system. The ethylene
system is fitted with alarm-monitored
pressure gauges and will alert when bottles
are close to empty. This reduces the risk of
operating without ethylene. Where multiple
de-greening rooms are installed, each
room can operate totally independently,
allowing one room to be on heating,
one on cooling, and one on holding. No
unnecessary equipment will be operating if
not required.
Benefits
• Operational control via touch screens
at each room.
• Customisable access level control.
• Custom programming of room cycle
operation.
• Gas-tight sectional door.
• Wider custom room entrance
allowing crates to be stacked right
up to the door.
• Minimal refrigerant with reduced
GWP.
• Automatic CO 2 -level control.
• Automatic humidity level control.
• Automatic ethylene level control.
• Humidity water harvesting allows water
saving.
• No electrical heaters installed (energy-
saving benefits).
• Reduction in steel support for roof
structure as evaporator is placed at
floor level.
www.coldlinkafrica.co.za
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Polyurethane-coated evaporator coil
fins, reducing corrosion.
Optimised heat pump with reduced
electrical demand.
Heating/cooling can be obtained at
the same time in multiple rooms.
The ‘plus’ feature allows de-greening
rooms to operate as cold rooms when
de-greening is not required. This is
Room 1 ready for de-greening while room 2 is
already de-greening.
COLD LINK AFRICA • March/April 2019