A Flow Ice generator, designed and built by Pam Refrigeration in Cape Town, is now in use for the rapid cooling of freshly caught salmon in road tankers for a Tasmanian salmon farm.
The output of three tones per hour of slurry (30% ice concentration) is stored in a bulk storage tank with agitator, and from the tank the slurry is pumped into a semi-trailer road tanker. The mass of slurry pumped into the tanker is automatically controlled at the level set on the control panel of the filling system by the driver. In summer months the fill is set at seven tonnes and varies according to the season.
Once charged with slurry, the road tanker is driven onto a barge which travels to the 50 salmon breeding pens 32km from the truck landing. The salmon is automatically harvested from the circular breeding pens and sucked by vaccum pump to the onboard culling machine. The live salmon is first stunned and then culled by a pneumatic hammer which strikes the head. The dead salmon, with any blood, then passes into the road tanker. All blood from the fish travels with the fish into the tanker as none can be discharged into the sea.
An automatic counter in the line limits the amount of fish into a tanker at 2,500 and once filled the barge returns to the coast. After being driven off the barge, the remaining space in the tanker is filled completely with slurry to stabilise the vehicle for the 350km journey to the processing plant.
Before installing the Flow Ice machines, a mixture of flake water was pumped into the tanker at the processing plant. Being only partially filled and with a slopping solution, the trailer was not very stable on the road and caused the driver unease, especially when having to stop suddenly and the load moved forward. With the Flow Ice system, the back haul from the processing plant is with an empty tanker and when travelling to the plant is completely filled, which adds to vehicle stability on the road.
The Flow Ice machine has six ice generators, a Grasso 4.10 reciprocating compressor driven by a 55kw motor. At -90C suction the package has a refrigerating capacity of 165kw. A titanium shell and tube heat exchanger cools the incoming sea water from 14 to 00C before entering the ice generator. The change from flake ice to Flow Ice has lowered the fish storage temperature from 4-50C to 00C and the cooling rate is much quicker after culling because of the fish being fully immersed in the slurry.
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