Overview Line

FREEZING SYSTEMS FOR THE FOOD INDUSTRY 1137 ________MF 1 FRIGO SCÀNDIA

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Annual production (tons)

Figure 28. Freezing cost as function of utilization per year for mechanical freezing and cryogenic freezing. Constant evaporating temperature.

Annual production (tons)

Figure 28. Freezing cost as function of utilization per year for mechanical freezing and cryogenic freezing. Constant evaporating temperature.

as on the final product quality and cost is similarly high. For the investor, it is essential to ensure that the design of the freezing system allows it to be properly integrated into the process and consistently operated at an optimal level.

Reliability

The value of the food products that pass through a freezer in a few weeks' time is often much higher than the invest ment cost of the freezer itself. This makes reliability a crucial consideration for the food processor.

Not only is the time the freezer is in operation important, but also the amount of time it is working to full capacity. A breakdown of any part of the line stops the whole line, and product that moves through a line without freezing properly may loose much or most of its market value.

With some systems, product blows out of the freezing zone, lodging in and freezing to other parts of the equipment. This can jam up the line and eventually cause damage.

Dehydration

Dehydration losses will always be present in any freezing system. The evaporation of water vapor from unpacked products during freezing becomes evident as frost builds up on evaporation surfaces. This frost is also caused by excessive infiltration of warm, moist air into the freezer. Still air inside the diffusion-tight carton often creates larger dehydration losses than does the unpackaged products frozen in an IQF freezer. Heat transfer is poor because no air circulation occurs within the package. The result is an evaporation of moisture that can be significant; however, the frost may stay inside the carton.

A poorly designed freezing tunnel may operate with dehydration losses of 3-4%, while a well-designed tunnel can be built to operate with losses of 0.5-1.5%. Liquid nitrogen tunnels normally operate with a dehydration loss of about 0.2-1.25%. This loss occurs when the nitrogen gas is circulated over the product at the infeed end of the freezer.

Freezing Cost Comparison

The cost of a freezing system comes both from the purchase price and the true cost of operation over the lifetime of the system. High operating costs can offset the advantages of a low initial purchase price. Consequently, it is essential to consider all the factors before making an investment, ie, to consider a freezer's "all-in economy."

In making preinvestment analyses, a comparison should be made of all pertinent factors involved, eg, capital, power, operation, cleaning, and maintenance, dehydration, and downtime costs. Figure 29 shows the relative costs when the real-life data from a GYRoCOMPACT were compared with the data from a conventional spiral freezer.

The graphs in this cost study (based on freezing of 1500 kg/h of hamburgers) clearly illustrates that the real cost of a freezer is not merely a question of the initial capital outlay. All the other factors involved in the economics of freezing contribute to the all-in cost picture. Figure 30 shows the effect of an efficient operation over a 5-yr period.

With all the crucial factors taken into account, the somewhat higher purchase price of one freezer was more than offset by the unique module design concept of the same freezer, including a particular belt design indicating major overall cost savings. The extra investment has a

Savings

Capital 32.5%

Power 4. Operator/cleaning 4.1%

Maintenance 2.8%

Dehydration 21.5%

Power 4. Operator/cleaning 4.1%

Maintenance 2.8%

Dehydration 21.5%

Downtime

Downtime

Conventional spiral freezer

Power 3.8% / Operator/cleaning 1.1% Maintenance 1.4%

Dehydration 14.8%

Savings 21.9%

Downtime 17.4%

GYRoCOMPACT Figure 29. Relative freezing cost

Savings 21.9%

Difference in initial capital outlay \L

Difference in initial capital outlay \L

Years

Figure 30. Accumulated annual savings.

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