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Fine-tuned refrigeration - fine tunaRefrigeration technology at its best - corrosion protection andhygienic requirements dictate style of air-cooler

Line of Busi-ness:

Industrial Refrigeration

Application: Fish Product Cooling

Country / City: Germany / Sassnitz (Ruegen Is-land)

Fluid: NH3, CO2, Glycol

Product: Wall/ceiling unit cooler GHN,Ceiling air cooler DGN, Wall/ceiling air cooler GGN, Drycool-er GFH, Fin and Tube heat ex-changer (finoox) GCO, Con-denser GVH

In mid-2003, Europe’s most modern andGermany’s largest fish-processing centre wentinto operation in Sassnitz on the island of Rü-gen. It not only secures a great proportion ofGermany’s herring-catch quota, but also cre-ates 150 mostly skilled jobs. The novelty is thatalmost all routine work is automated, with workprocesses like those in a high-tech company.The trade media are already talking about the“factory of the future”. The refrigeration tech-nology is equally visionary. The actual refriger-ation takes place in a separate engine house,

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using the natural refrigerant NH3, and the cool-ing is distributed to the deep-freeze store andthe many storage and processing rooms bymeans of the secondary refrigerant CO2 or thecoolant propylene glycol.

Güntner not only delivered 136 air coolers forvarious application areas and power classes,but were also able to contribute to the extreme-ly short construction time of only nine monthsneeded for the refrigeration system through avery high degree of flexibility in manufacturing,just-in-time delivery, and assistance in the caseof last-minute change requests.

Sassnitz fish-processing centre: Europe’s most mod-ern fish factory, with a processing area of 14,000 sq.

metres and a deep-freeze building of 7,000 sq. metres.

In the mid 90s, the Netherlands' deep-sea fish-ing company Parlevliet & Van der Plas B.V.recognised the synergic effects of fishing, fishprocessing and closeness to market, and sawSassnitz as the ideal location for a fish-pro-cessing centre in this context. And more: Sass-nitz also offered all the infrastructural oppor-tunities for extending the market to Poland,the Baltic states, Scandinavia and, via Rus-sia, to the Asian fish consumers. Add to thatthe prospect of subsidies from the structur-al funds of the State of Mecklenburg-Vorpom-mern, the Federal Republic and the EuropeanUnion, which would secure the Sassnitz loca-tion in the long term. This even preserved aportion of the German herring quota, whichwould otherwise have been distributed amongother Baltic states.

High-tech and fish fillets

The Sassnitz fish-processing centre wasplanned on the principle of as much automa-tion and technology as possible, and only asmuch manual work as necessary. This seemsto have been achieved in every respect, be-cause the trade press hailed the “Sassnitz fishshop” as the “factory of the future”, with pro-cessing technologies “like from another plan-et”. Fish are “pumped” from the trawlers in-to the factory, sorted by species and size byvideo image recognition, and automatically fil-leted and packed. Waste and remnants areprocessed to fish meal and fish oil on site –with no smell detectable in the surroundings,because the entire waste air from the fish fac-tory, which is air-conditioned at low pressure,does not escape until it has passed throughseveral stages of filtering.

Fully automatic:Sorting system: Landed fish are sorted byspeciesand size for further processing.Hanging from the

ceiling are 6 Güntner glycol unitcoolers,Type S-GGN 071A.

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The customers thought carefully about the pro-cedures in fish processing in the early stages ofplanning, as demonstrated by the smooth lo-gistic processes, with automated shelf vehiclesand forklifts apparently steered by magic in theproduction area and the deep-freeze store.

Environmentally compatible refrigerationtechnology with natural refrigerantsThe fish-processing centre being a subsidisedinvestment, it was necessary to invite tendersfor the project as a whole and for all partialwork at a European level as defined in VOB(contracting rules for award of public workscontracts). The functional invitation for tenderusual in such construction projects had the ad-vantage that the bidders were able to introducenew ideas and technologies, especially with re-gard to energy efficiency and environmentalprotection. In the area of refrigeration, the con-cept presented by Axima refrigeration, Lindau,was the most convincing, both technically andeconomically.

This concept is structured as follows (see box“Refrigeration equipment in figures”):

• Cooling with the natural refrigerantammonia (NH3) in a separate ma-

chine house, atmospherically separat-ed from the processing area

• Transmission of the cooling via anNH3/CO2 cascade on the principle of a

pump system to the refrigeration andfreezing equipment, with a -42 °C axisfor the frosters and deep-freeze store,and a -8 °C axis for the +2 °C refriger-ation rooms

• A cold glycol line with -1 °C flow/+5°C return to supply the +16 °C and+18 °C refrigeration rooms

• Warm glycol at 30 °C flow tempera-ture and 20 °C return temperaturegenerated by an NH3 heater for de-

frosting the air coolers in the +2 °Crefrigeration rooms, and as a protec-tion against sub-freezing in the deep-freeze store

• Hot-gas defrosting on the basis of CO2

for defrosting the frosters.

Factory of the future: The floor vehiclesare guided inductively, as if by magic.

In this NH3/CO2 propylene-glycol refrigerationplant, Axima Refrigeration combine the high-energy efficiency of NH3 cooling with safe andeasy-to-handle CO2. Wherever a CO2 applica-tion would have been too elaborate becauseof the pressure, the refrigeration experts choseglycol as the coolant. An elaborate safety con-cept protects the CO2 circuits from rising pres-sure should the cooler fail. At - 42 °C, for in-stance, the pressure of the CO2 is around 9 bar;at - 8 °C – typical of the supply to the aircool-ers in the +2 °C refrigeration rooms – the de-signed pressure is around 28 bar. If the +16 °Cand +18 °C rooms were also supplied via theCO2 axis, the tube system would have to be di-mensioned for 42 bar. In this case, it thereforemakes more sense economically to use glycolas the coolant. For the hot gas defrosting of thefrosters (used for the first time world-wide asa replacement for the otherwise usual electricdefrosting) the tube system had to be dimen-sioned for a working pressure of 50 bar. TheCO2 hot gas defrosting is therefore used onlyfor the frosters, and not for the aircoolers.

Air-cooling excellence

Fish processing is the area of food process-ing that makes the highest demands on hy-giene, corrosion resistance, ease of mainte-nance and longevity. One could, of course, exe-cute this kind of project in nothing but stainlesssteel, but neither is this material cheap, nor arebuildings like the fish factory dimensioned forthe tremendous weight of stainless steel pipingand stainless steel aircoolers. For Güntner, asthe supplier of all the air coolers for the Sass-nitz fish factory and the associated cold stor-age, the customer’s high requirements on hy-

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giene and corrosion resistance, coupled withthe calls of economy on the side of the systemconstructor, meant a stiff challenge. However,on the basis of years of cooperation with AximaRefrigeration it was met successfully.

Stainless: Cold storage: Aircooler in V4A stain-less steel (SS316) with epoxy-resin-coated fin coil

Together, it was decided to select the aircoolerson the principle of as many standard productsas possible, and only as many special versionsas necessary. Where standard products fromthe Güntner range could not be used directly,individual parts and components were upgrad-ed to meet the requirements of the fish factory.

This affected in particular:

• Fans with stainless steel grilles• Accessories, such as air-throw nozzles,

in stainless steel• Surface treatment of housings, fins

and drip trays with powder coating

Unpacking and defrosting:Unpacking room: Reversible fansin the air coolers contribute to quality preservation during

defrosting of frozen fish at precisely +2°C. Two S-DGN 046Cin the hygienic version (epoxy-resin-coated fins) are in use.

Because the whole fish factory is process ori-ented, almost every aircooler had to be individ-ually dimensioned. This led to very few of the136 units being really identical. Basically, eachindividual aircooler had to be closely inspectedwith regard to its location and purpose, includ-ing the possibility of draughts occurring in ar-eas with a lot of staff, or particularly corrosivezones, such as the areas in which marinadesare made or the maturing zones for the vari-ous fish specialties. The standard versions ofthe aircoolers were upgraded with the follow-ing accessories or variants:

• Evaporators designed for CO2 pump

operation• Evaporators designed for brine opera-

tion• Housing powder coated both sides• Built-in climatisation coil for drying

the room during cooling operation andafter cleaning

• Brine defroster• Folding drip tray• Folding ventilator flap• Fins with epoxy-resin coating• Housing in V4A stainless steel

(SS316)• Single or double drip tray in V4A

(SS316), folding• Air throw unit in V4A (SS316)• Fan nozzle in V4A (SS316)• Protective cage, fan shaft and connec-

tor in VA or V4A (SS316)• Ventilator with blades 650/36°• Repair switch

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• Reversible fan direction (for defrostingoperation)

Almost all the rooms in the fish-processingcentre are cleaned at night with a disinfectantsolution, and then thoroughly rinsed. Thiscleaning includes all machines, even the aircoolers. The basic ventilation of the rooms isnot sufficient for the following drying, so so--called climatisation coils have been built intothe air coolers. The moist air from the room iscooled down in the air coolers, being dried inthe process, and then heated again with warmbrine. With this drying function integrated inthe air coolers, each room can be cleaned anddried individually.

Bottle-washing system:Here, empty bottles are cleanedfor reuse. Theroom has two Güntner S-GGN 046A.

Flexibility above all

Axima Refrigeration had only nine months forthe work from the placing of the order, so prac-tically every minute had to be used to assem-ble the elaborate refrigeration systems. Any de-lay on site meant changes in the constructionlogistics, with corresponding knock-on effectson the manufacturing at Güntner. Deliveries ofcertain air coolers, precisely allocated to cer-tain rooms and already with a fixed shippingdate, sometimes had to be put on hold at shortnotice because a consignment of air coolers -planned for a later date was needed urgently.Armin Metzger, in Project Management for re-frigerator construction at Axima Refrigerationrecalls, “Güntner proved to us, week after week,that they take their much-vaunted flexibilityvery seriously. The Güntner employees madethe impossible possible. Cooperation betweena plant constructor and a supplier just couldn’tbe better.”

Highest quality requirements: Maturing room: Marinades con-taining vinegar and salt demand the use of unit coolers withV-4A (SS316) housings and tubes, and epoxy-resin-coatedfins, Type S-GHN 071C. The fan plates can be folded down.

The uncomplicated, even collegial cooperationdid not just happen. After all, this was not thefirst large contract with a tight schedule, a com-plex requirement profile and construction lo-gistics that call for just-in-time deliveries. “Weknow each other from many projects, we workon call, everything is very non-bureaucratic yetprofessional. With plants like Sassnitz it’s par-ticularly important to be able to rely on yoursupplier,” says Armin Metzger. In spite of alter-ations in the ancillary equipment or the spec-ified delivery dates, all the aircoolers arrivedat the construction site at the right time, inthe right sequence, and in the right version.To eradicate any source of error right from thestart, the respective room was specified on thetype plates. Some 12 low-loader articulatedlorries were used to transport the 136 aircool-ers.

”CO2 will make its mark in the deep-freezingsector”

For the refrigeration specialists at Axima Re-frigeration, the FPC Sassnitz is the confirma-tion of their strategy of using only natural re-frigerants. “Today, we are a step farther on withour CO2 cooling concept. CO2 has great advan-tages, especially in the area of deep-freezing,and is comparable to an NH3 plant from bothenergy and economic points of view", ArminMetzger sums up. One main advantage of two-stage NH3 coolers is the pressure of 8.3 barat a vaporising temperature of - 45 °C, as op-posed to NH3, which has a vacuum of 0.4 bar at- 45 °C, making additional safety precautionsnecessary. Compressors and pipelines can al-so be smaller proportioned in the case of CO2

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systems. There is meanwhile a wider range ofCO2 compressors at a favourable price, so thatthe hitherto higher investment costs for CO2 re-frigeration plants are at least comparable withthose for NH3 systems, according to Metzger.In the case of skating rinks, the migration fromNH3 to CO2 has already taken place. Metzgersays, “The safety aspect of CO2 is of greater im-portance than the energy efficiency in the caseof skating rinks.”

The fish-processing centre in figures

Total area of site: 12 hectaresProcessing area: 14.000 m2

Processing capacity: 800 tonnes of herrings /day

Sorting capacity: 35 tonnes per hourRefrigeration capacity: 600 tonnes capacity:

per 24 hoursFroster capacity: 240 tonnes per 24

hoursDeep-freeze storageArea:

7,000 sq. metres

Storage capacity: 22,000 tonnes herringStorage temperature: -28 °CFresh fish refrigeratedstorage Storage capaci-ty:

3,000 tonnes of fish

Storage temperature: 0 °C

Refrigeration equipment in figures

Process Power CoolantDeep-freeze store, roomtemperature -28°C

300 kW CO2 at t0 =-42 °C

Plate froster by DSI Sami-fi with CO2 hot-gas defrost-ing

1.200 kW CO2 at t0 =-42 °C

Frosting capacity 240 t per day, final stage 480 t perdayCO2 hot-gas generator fordefrosting plate froster

250 kW CO2 at t0 =10 °C

Room cooling for roomtemperatures of 0°C to 6°C

1.300 kW CO2 at t0 =-8 °C

Propylene glycol for roomtemperatures of 12 to 18°C

2.000 kWNH3 at t0

NH3 at t0 =-4 °C

Flow -1°C/Return 5°C 350 kW NH3 at t0 =-4 °C

Iced water generationWarm glycol for defrostingand desiccation with wastewarmth from the oil coolerof the screw compressorsand NH3 hot-gas cooler

2.000 kW Glykol at t0 =30 °C

Advantageous Güntner services

Güntner supplied 136 aircoolers for variousapplication areas and power ranges. Their flex-ibility, just-in-time delivery and competent as-sistance with short-notice alterations, helped tocomplete the construction of the refrigerationsystems in an extremely short time.

Axima Refrigeration GmbH

Axima Refrigeration GmbH is a group that isactive in all areas of cooling and refrigerationtechnology, with a close-knit sales and ser-vice network all over Germany. The companyplans, manufactures, operates and advises onall kinds of refrigeration systems, refrigerationunits and cooling towers.

Installed Components

3 NH3 screw-compressor units at t0 -45 °C andtc -11 °C 3 NH3 screw-compressor units at t0 -11 °C andtc 35 °C 1 NH3 screw-compressor unit at t0 -4 °C andtc 35 °C 1 tube bundle cascade unit with leak monitor-ing of spaces, CO2 at t0 -42 °C/NH3 at t0 -45°C 1 tube bundle cascade unit with leak monitor-ing of spaces, CO2 at t0 -8 °C/NH3 at t0 -11 °C 3 evaporative coolers with a power of 2,200 kWeach1 NH3 separator at t0 -4 °C/ t0 -11 °C/t0 -45°C 1 CO2 separators at t0 -8 °C/ t0 -42 °C 5 CO2 pumps, -8 °C4 CO2 pumps, -42 °C 3 Cold glycol pumps -1 °C3 Warm glykol pumps 30 °C 136 Güntner aircoolers for various areas of useand power ranges 2 EWK 900/09 cooling towers with cooling-wa-ter basin for fish meal plant 1 Fish-water cooler, marine version, for sortingsystem, with CO2 at t0 -3 °C/150 kW für 67 cu.metres salt water per hour 2 Split air-conditioning units for air-condition-ing of PC server room, each 12.7 kW