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Cryogenics VS Mechanical Freezing Systems
Most all of us are fully aware that the U.S. does not have an energy policy. Our political system and/or politicians cannot seem to arrive at a solution to the energy crisis. This obviously provides the management of a food processing plant with a rather obvious dilemma - "How does he plan for the future"? For decades he has been expending energyin lieu of capitalHe could buy the freezing system with the lowest capital cost and even though this system usually required an excessive amount of energy it was a good "buy" because he could "expense" the energy costs. Our existing taxation system still promotes this type investment -- at the expense of our energy resources. Somehow our country must find a way to regulate the use of energy by legislation or taxation in some equitable manner that will require the "User" to minimize the use of expendable energy -- i.e., fossil fuels.
However, despite the absence of an energy policy the rapid escalation of electrical energy costs has provided management with a real incentive to reduce energy usage.
In order to put these escalating energy costs Into perspective let's take a look at 1970 costs vs. 1980 costs, of both capital and energy for a specific food freezing system. Let's assume that in 1970 a customer bought any l.Q.F. Fluldized Freezing System for 6000 pounds per hour of fried onion rings. This system cost about $235,000 and requires 600 BHP for operation including all compression and ancillary equipment. The cost of electricity was about 1$/KW or lower in most areas at that time. At 1cent/KW if this system operated 4000 hours the total yearly cost of energy was about $19,460 a year. Now, 1980, just 10 years later, prices have escalated and the same system would now cost $510,000. Electricity has risen from 5 to 8 times. Assuming that electricity cost 5 cents/KW the operating cost for 4000 hours per year is $97,304. (See Exhibit "A")
EXHIBIT A
MECHANICAL FREEZING SYSTEM 6000 POUNDS/HOUR
1970 1980 1980 (1)
MECHANICAL SYSTEM INSTALLED $235,000 $510,000 $560,000
ELECTRICAL ENERGY COSTS 1cent/KW/HR 5cent/KW/HR 5cent/KW/HR
COST FOR 4,000 HOURS OPERATION $19,460 $97,304 $82,700
OPERATING COST AS % OF INVESTMENT 8.3% 19% 14.8%
(1) WITH ADDITIONAL INVESTMENT FOR ENERGY SAVINGS
Now the investor mustanalyze his total owning and operating costs and install an energy efficient system in order to reduce the electrical energy requirements. In most cases an additional investment of 5 to 10% will reduce operating costs up to 15%. With electrical costs in many areas of the U.S. at 8 ecents and 10$ cents/Kw It will behove investors to fully analyze their energy usage in any food freezing or other type of industrial refrigeration system.

So you save only 20 h.p. in your quest to reduce energy consumption. What is that worth? Lots. If you are now paying 5$cents/KMWfor electricityand operate the equipment for 4000 hours per year you would save $3243 this year. However, it the cost of energy continues to escalateat 10%per year in 20 yearsyou will have saved $186,058 or an average of $93O2/year. This type of projection is well within the escalation predicted for energy sources by many experts.

While comparing cryogenics with mechanical freezing systems we will compare liquid carbon dioxide and liquid nitrogen with a typical mechanical system that was designed for the same type duty.

Freon freezants have been considered as "cryogenics" in some circles. However, due to the fluorocarbaron/ozone controversy and the probability of restriction being placed on the use of certain ha locarbons freon freezants (F-12) comparisons have not been made. Over the last 10 years freon freezing has found very limited applications - mainly being used in the freezing of peeled and deveined shrimp, cob corn, and certain specialty items.
Precooling is refuted
In addition to fully freezing food products, the cryogenic freezing proponents are now proposing "precooling' or "preconditioning" of products before they enter an existing mechanical freezer. This may be applicable to some older and inadequate freezers, but it is not the panacea It is advertised to be. Most proposals indicate a savings in shrink of 5% for wet vegetables. This has been refuted by many authors including "Rassmussen". Any wet product such as peas or carrots or diced onions carries considerable surface moisture and even if "dehydration" occurs the net effect on salable product is Insignificant. When a wet product at 60F. enters a -25F. to -30F. high velocity air blast (IQF Fluidized Bed Freezer) the external moisture is quickly frozen, thus, minimizing the possibility of "shrink loss". The potential "shrink" in the CO2 "pretreating" tunnel could be more than the mechanical system as the temperature of the carbon dioxide could be as low as -80F. and the vapor pressure diffential would be much more than the mechanical system. Where wet vegetables or fruits are concerned a refrigerated hydrocooler is the best approach to cooling prior to freezing.

Mechanical systems for freezing various products such as fried onion rings or meat patties (the two items that we will analyze in detail) come in various configurations also. Single double and triple belt in-line freezers and spiral freezers are used. Each has its specific applications.
EXHIBIT M
Single Belt
EXHIBIT N
Dual Belt IQF
EXHIBIT 0
Multibelt IQF
EXHIBIT P
Spiral
Quality fried onion rings freezing can be accomplished by either mechanical or cryogenic freezing. In each case the quality is commercially the same. The shrink loss will be minimal provided the onion rings, either natural or fabricated, are introduced into the freezer immediately upon exit from the "fryer".
costs in perspective
In order to keep energy costs in perspective, here is a basic cost analysis between liquid nitrogen, liquid carbon dioxide, and mechanical refrigeration. (See Exhibit "B"). Mechanical refrigeration is by far the "miser" in energy usage. Liquid carbon dioxide energy costs are 4.5 times mechanical and liquid nitrogen energy costs are 17.5 times mechanical. Because of liquid nitrogens high energy usage most cryogenic freezant suppliers started to switch their liquid nitrogen customers to liquid carbon dioxide as early as 1975.
EXHIBIT B
COMPARISON OF ENERGY USAGE FOR FOOD FREEZING SYSTEMS
KW/100 BTU
LIQUID N2

.383 KW

LIQUID CO2

.100 KW
The energy required to produce liquid nitrogen and liquid carbon dioxide are not the only energy costs effecting the total price of the delivered product. Liquid carbon dioxide is normally delivered by trailer to the "Userin an insulated tank designed to operate at 250 psig (-10F). Liquid nitrogen is delivered in a similar way at atmospheric pressure (-320F.). Liquid nitrogen trailers and customer stations usually cost twice that of comparable liquid carbon dioxide equipment. The cost of transportation exceeded the cost of liquid carbon dioxide production some 7 to 10 years ago - before the price of fuel started to rise.

Liquid carbon dioxide is selling at prices ranging from 2.5cents to 4.0cents/pound delivered depending upon the plant location, and amount of freezant being used. Liquid nitrogen prices vary in a similar manner from 3.0cents/pound to 7.0cents/ pound. This varies quite drastically where the "Usersplant is adjacent to the liquid nitrogen manufacturing facility.

Thus, with the cost of electrical energy, gasoline and diesel fuel rising at a rapid rate both liquid nitrogen and liquid carbon dioxide will Increase in price at a much more rapid rate than mechanical systems.

The physical characteristics of carbon dioxide that are relevant are: (Exhibit "C")
I) Normal transportation and storage 250 psig (-10F.)
2) Triple point 60 psig (-70F.). The element is a solid, liquid and/or gas at this condition.
3) At atmospheric pressure carbon dioxide exists as a vapor or solid only at -109F. When used In a freezing system there are about 140 BTU/pound available for freezing a product if the carbon dioxide is exhausted at about +0F.
EXHIBIT C
TRANSPORT PROPERTIES OF NITROGEN AND CARBON DIOXIDE CARBON DIOXIDE (CO2)

CARBON DIOXIDE (CO2)

250 PSIG (Liquid) -10°F
Triple Point 60 PSIG -70°F (Solid) (Liquid) (Gas)
Useful BTU/# 140

NITROGEN (N2)

O PSIG -320°F (Liquid)
Useful BTU/# 160

Nitrogen at atmospheric pressure exists as a liquid at -320F. When used in a freezing system there Is approximately 160 BTU/pound available for useful work if the vapors formed are exhausted at +0F.
The selection of a freezing system for many products is relatively simple
Vegetable products such as peas, corn, lima beans, carrots, and other "staples" are normally frozen in an "lQF" Mechanical System. These systems usually consist of one or two mesh belts which convey the product through an enclosure while being gently agitated by high velocity cold air (-20 to -25F.) directed from beneath the belt.

Cryogenics are seldom used for such products as their usage is in general limited to the following: (Exhibit "E")
I) High cost items
2) Freezers for small quantities
3) Freezers for test markets
4) Quality considerations
5) Advertizing and/or sales advanced
EXHIBIT E
APPLICATIONS OF CRYOGENIC FREEZERS

(1) HIGH COST ITEMS
(2) SMALL QUANTITIES
(3) TEST MARKETS
(4) QUALITY CONSIDERATIONS
(5) ADVERTISING AND/OR SALES ADVANTAGES

Some facts were absolutely false
For many years buyers of food freezing systems have been making decisions based on "facts", some real, some imagined, and some that were absolutely false.

Cryogenic freezing proponents have been selling their system on the following criteria:
EXHIBIT F

1) A savings in "shrink" (dehydration)
2) A savings in capital investment
3) A "quality" motive
Except for a very few frozen products, mechanical systems can be designed to provide results comparable to cryogenic systems.

Most of the data never analyzed!
Dehydration or shrinkage is a very elusive criteria. It is most difficult to define and even more difficult to identify. Most of the data that had been published over the years has never analyzed cryogenic and mechanical systems of comparable design or quality.

"Shrink" or" dehydration" is difficult to measure. Shrink increases or decreases in accordance with the following:
EXHIBIT G

1) I) Vapor pressure between freezant and frozen item
2) Time required to freeze the product
3) Quality of food Introduced Into the freezer system

Cryogenic "advertising claims" are usually "vague" and even data published by reputable Universities are usually based on "the best cryogenic systems VS. the mechanical freezing systems of the 194O and 1950's". I quote from a study that indicated that cryogenic freezing of ground beef was the optimum process; (this is the last paragraph In a 30 page report): "It should be noted in this study that the conditions chosen are not representative of freezing rates of which mechanical systems are capable. Rather the experimental conditions were chosen to represent those often used and as a result are representative of slow freezing. Any mechanical system that will decrease freezing time will probably decrease the quality differences noted in the study".

Considerable work has been done over the years in analyzing dehydration in freezing systems. It has been proven that dehydration Is minimal in air blast systems that are of proper design. Well designed mechanical systems approach cryogenic freezing systems in both the areas of dehydration and freezing times as the vapor pressure differences are lower than cryogenic by about 60%, and the time to freeze-approaches that of cryogenic freezing.

The author has been involved in inumerable tests that indicate that the "shrink" for most products in a high quality mechanical freezer is generally difficult to measure as the "time" element is reduced to a minimum.
The deduction has been verified by Rassmussen in
"Freezing Methods Related to Cost and Quality", i.e. "The almost universal concern about evaporation losses during "Freezing" is groundless". It is the evaporation during "cooling" that is critical. A product that enters the freezer at 32F. would have little dehydration in any type freezer.

"Dehydration" or "shrink" is used as the "sales approach" for cryogenic freezers - It is not the major factor that it is reported to be. "Quality" as described by the cryogenic proponents is provided by quick freezing and low shrinkage. This may have some merit, however, it will only apply to a few products. A ground meat patty frozen in 5 to 8 minutes in a cryogenic freezer can be frozen in 6 to 8 minutes In a good mechanical system. The "commercial" quality and "shrink difference" would probably be difficult to determine. However, there are certain chemical reactions between red meat and carbon dioxide that provide advantages in "shelf life", and so called bloom or color.

Unfortunately, the Mechanical Systems companies have not seen fit to sponsor "tests" by a qualified university research staff to "prove" that there is little, If any, difference in the cryogenic and mechanical system approach to freezing, either in "shrink" or quality.

Cryogenic Freezing Systems vary with products to be frozen.
EXHIBIT H
Nitrogen Freezer In-line Single Belt
EXHIBIT I
In-line CO2 Freezer with storage tank
EXHIBIT J
CO2 Freezer
EXHIBIT K
Spiral
EXHIBIT L
Tumble Type Freezers
Each type has a particular application.

Each costs about 20% to 40% of its mechanical counterpart.
EXHIBIT Q
A cost comparison (Exhibit "Q") indicates that the "cost to freeze fried onion rings in a mechanical system is much less than in a liquid carbon dioxide or liquid nitrogen freezer.
EXHIBIT Q - COMPARISON OF FREEZING COSTS
MECHANICAL SYSTEM VS. LIQUID NITROGEN VS. LIQUID CARBON DIOXIDE for FRIED ONION RINGS
ITEM MECHANICAL SYSTEM LIQUID NITROGEN LIQUID CARBON
DIOXIDE SYSTEM
Freezer Capacity & Production
Rate Lbs. /Hr
6,000 6,000 6,000 6,000 6,000 6,000
No. of Shifts/Day 1 2 1 2 1 2
Operating Time - Hrs./Yr. 2,100 4,200 2,200 4,400 2,200 4,400
Annual Production-M Lbs./Yrs. 12 24 12 24 12 24
Freezant Usage:
--LN2 Lbs./Lb. @ $.O5/Lb -- -- 1.5 1.5 -- --
--CO 2 Lbs./Lb. @ $.035/Lb -- -- -- -- 1.8 1.8
Total Investment (Installed)
Freezer & Refrigeration
510,000 510,000 140,000 140,000 150,000 150,000
Operating Cost - $/YR
1. Investment Related - Fixed
--Depreciation at 10% Year 51,000 51,000 14,000 14,000 15,000 15,000
--Interest @ 12% Simple
(10 year amortization)
27,030 27,030 8,400 8,400 9,000 9,000
--Maintenance @ 4% 20,400 20,400 -- -- -- --
--Maintenance LN2 and LC02 @ 10% -- -- 14,000 14,000 15,000 15,000
2. Variable Costs -- --
--Power @ $.05/kwh 51,000 102,169 -- -- -- --
--Operator Labor @ $8.00/Hr. 16,800 33,600 16,800 33,600 16,800 33,600
--Cleanup Labor @ $4/Hr.-15 Hrs/Wk 3,200 3,200 3,200 3,200 3,200 3,200
Freezant Cost - $/Yr 900,000 1,800,000 756,000 1,512,000
Total Annual Operating Cost $165,530 $232,499 $956,400 $1,873,200 $815,000 $1,587,800
Unit Operating Cost - /Lb. 1.12 0.97 7.97 7.80 6.79 6.61
*Electricity 5/KW/HR.
The capital cost and organizing information was obtained from an onion ring freezing plant. The data was taken from their last years operating cost analysis.

Another cost comparison (Exhibit "R") Indicates the "cost to hamburger patties in a mechanical system is much less than that experienced in a liquid carbon dioxide or liquid nitrogen freezer.
EXHIBIT R - COMPARISON OF FREEZING COSTS
MECHANICAL SYSTEM VS. LIQUID NITROGEN VS. LIQUID CARBON DIOXIDE
DIOXIDE SYSTEM
Freezer Capacity & Production
Rate Lbs./Hr.
6,000 6,000 6,000 6,000 6,000 6,000
No. of Shifts/Day 1 2 1 2 1 2
Operating Time - Hrs./Yr. 2,100 4,200 2,200 4,400 2,200 4,400
Annual Production - M Lbs./Yr. 12 24 12 24 12 24
Freezant Usage:
LN2 Lbs./Lb. @ $.05/Lb. -- -- .7 .7 -- --
CO2 Lbs./Lb. @ $.035/Lb. -- -- -- -- .8 .8
Total Investment (Installed)
Freezer & Refrigeration
600,000 600,000 240,000 240,000 250,000 250,000
Operating Cost - $/Yr.
1. Investment Related
-- Fixed Depreciation @ 10% 60,000 60,000 24,000 24,000 25,000 25,000
--Interest @ 12% Simple 36,000 36,000 14,400 14,400 15,000 15,000
--Maintenance @ 4% 24,000 24,000 -- -- -- --
--Maintenance LN2 & LCO2@ 10% -- -- 24,000 24,000 25,000 25,000
2. Variable Costs
--Power @ $.05/kwh 29,800 59,600 -- -- -- --
--Operator Labor @ $8/Hr. 16,800 33,600 16,800 33,600 16,800 33,600
--Cleanup Labor @ $4/Hr.
15 Hrs./Wk
3,200 3,200 3,200 3,200 3,200 3,200
Freezant Cost - $/Yr. -- -- 420,000 840,000 336,000 672,000
Total Annual Operating Cost 169,800 216,400 502,40 938,800 420,000 772,800
Unit Operating Cost - it/Lb. 1.42 0.90 4.19 3.91 3.50 3.22

CONCLUSION
In analyzing various studies regarding hamburger patties using liquid nitrogen or liquid carbon dioxide the referenced tests indicate theminimal losses occur when the hamburger patty is frozen in less than 8 ninut3s from 40F. to 0F. in a -80F. carbon dioxide atmosphere. There have been quite a few test that
Indicate hamburger patties can be frozen in lQF Fluidized Freezers within 6 to 8 minutes with air at -35F. to -40F. with a minimum of so-called freezer burn or greying of the edges of the patty. The comparison offered have disregarded the "shrink" factor as mechanical systems can be designed to provide equal if not better performance than cryogenic system with regards to shrink and quality.

Over the last 8 to 10 years several proponents of cryogenic freezing using liquid carbon dioxide have proposed a combination mechanical-cryogenic system whereby 70% to 90% of the carbon dioxide would be "recovered", compressed to 250 psig, condensed by a two stage ammonia refrigeration system at -10F. and reused in the freezing process. To date this system has not been successfully applied to a food freezing system as far as can be determined. It certainty has merit. Such a system would probably provide a "freezing cost" near mechanical freezing, with capital cost no more than mechanical and provide all of the quality features of both. You may expect to see future developments in this area.

CONCLUSION
Most every frozen food product is better today than It was yesterday but nowhere near as good as it Will be tomorrow, and if we all do our job properly the freezing will be accomplished employing ammonia refrigeration systems using a minimum of energy.

REFERENCES
(I) Nitrogen Liquefaction in LNG Regasification Gazzi & Mattioti, IIR, Washington, D.C.
(2) Liquid Carbon Dioxide vs. Liquid Nitrogen in Food FreezingAirco Industrial Gases, Murray
Hill, New Jersey, 07974, November, 1975.
(3) Freezing Methods As Related To Cost and Quality. C. L. Rassmussen & R. L.
Olson, Western Region Laboratories, U.S.D.A., Berkley, California, 94710.
(4) Cryogenic Freezing of Ground Beef. Cooperative Extension Service, Iowa
State University, Ames, Iowa, 50011. EC 1249.