World’s first Grenco CO2/NH3 cascade system
Freezing capacity > 230,000 kg fish/day with reduced freezing time
Hold capacity: 91,000 cartons
Grasso screw compressors

Operator	Parlevliet & Van der Plas The Netherlands
Plant contractor	Grenco b.v.
Supplier of GEA components	Grasso screw compressors, type D Grenco CO2 cascade system
Capacity	1200 kW at -50 0 C
Refrigerant	CO2 & NH3

The trawler “Dirk Dirk” is owned by Parlevliet & Van der Plas, The Netherlands. An international company with 800 employees, which owns besides a large shipping fleet with some of the biggest freezer trawlers, cold stores, trading offices and a fleet of trucks. Their high quality seafood is exported worldwide.
“Dirk Dirk” is used for fishing herring, mackerel, blue whiting and many others.
The trawler has a length of 95,18 metres and a width of 14,50 meters. The engine output is 4400 MAK and the service speed: 14,00 knots.

GEA Refrigeration Division ...
Trawler „Dirk Dirk“,
equipped with CO2/NH3 refrigeration system

In many countries the use of R22 in new refrigeration systems is prohibited. Alternative refrigerants like R507 and R404a are subject to very strict legislation and are likely to be prohibited in the near future. Several Dutch fishing fleet owners have, therefore, chosen refrigeration systems with complete environmentally friendly, refrigerants like ammonia (NH3) and carbon dioxide (CO2).

The Dutch fishing company Parlevliet & Van der Plas granted Grenco b.v. the order for replacing the existing R22/CaCl2 brine deep freeze plant by a CO2 /NH3 cascade system for their trawler “Dirk Dirk”.

The benefits of freezing with CO2 are: lower freezing temperatures, less freezing equipment, safe and natural refrigerant, world wide availability and a cheap refrigerant.

CO2 has a high pressure (6,8 bar at -50 °C and 39,7 bar at 5 °C) and it is therefore
required to install a primary cooling system with another refrigerant (e.g. NH3) in order to keep the CO2 pressures in the secondary system within limits. NH3 is the preferred choice by most owners as the efficiency with regard to power consumption, is approximately 25% better than R507 or R404a.
As the CO2 temperature is accurately controlled at a temperature of -50 °C, the freezing time of the fish is reduced by 25% compared to freezing at -38 °C.

In practice it is possible to freeze a
100 mm block of herring from +2 °C to
-20 °C within 150 minutes. With the reduction of the freezing time the amount of plate freezers can also be reduced by
25 % while keeping the same production.

To freeze the fish, Grenco b.v. has installed 23 vertical plate freezers. The CO2 is pumped through the plate freezers at a temperature of -50 °C. Also connected to the system is the hold cooling. The refrigerating system consists of a primary or high stage (NH3) system and a secondary or low stage system (CO2). The primary ammonia system is installed to cool down the discharge gases of the secondary CO2 system. In the so-called cascade condenser the evaporating ammonia (at -15 °C) will condense the CO2 gases (at -10 °C).

The primary system consists of two compact duo pack compressor units, each equipped with two single stage screw compressors and two cascade condensers. The secondary CO2 system consists of two compact duo pack compressor units, each equipped with two single stage screw compressors suitable for CO2.

Parlevliet & Van der Plas is very satisfied with the result. The engineers stated “that the system is working even better than expected and without any flaws”.