US3768272A - Direct contact food freezer - Google Patents

Abstract

This invention provides a direct contact freezing device using a low boiling point, inert refrigerant in a stream having portions at different velocities for the direct contact freezing of comestibles without clumping of the particles or icing of the freezer.

Description

United States Patent [191 Barrett 7 1 Oct. 30, 1973 DIRECT CONTACT FOOD FREEZER Inventor: Lee A. Barrett, 2928 Lothair Way,

Michigan City, lnd. 46360 Filed: June 17, 1970 Appl. No.: 48,912

Related U.S. Application Data Continuation of Ser; No. 734,676, June 5, 1968.

U.S.Cl 62/60, 62/64, 62/85, 62/266, 62/374 Int. Cl. F25d 3/10, F25b 43/00 Field ofSearch 62/64, 63, 266, 60, 62/374 References Cited UNITED STATES PATENTSBottoms 62/64 X 3,298,188 1/1967 Webster et al 62/63 3,498,070 3/1970 Allen et a1. 62/64 3,039,276 6/1962 Morrison 62/64 3,228,838 1/1966 Rinfret et a1. 62/74 UX 3,258,935 7/1966 Ross 62/380 X 3,368,363 2/1968 Alaburda et al. 62/64 3,485,055 12/1969 Webster et al..... 62/63 3,498,069 3/1970 Waldin 62/63 Primary ExaminerWilliam E. Wayner Attorney-E. Wallace Breisch 57 ABSTRACT This invention provides a direct contact freezing device using a low boiling point, inert refrigerant in a stream having portions at different velocities for the direct contact freezing of comestibles without clumping of the particles or icing of the freezer.

12 Claims, 9 Drawing Figures PATENIEDnm 30 Ian SHEET 1 [1F 5 IIVVENTOR ARTHUR L. BARRETT PATENIED um 30 ms SHEET 3 OF 5 l/VVE/VTOR ARTHUR L. BARRETT SHEETBF 5 PATENIEU our 3 0 ms IN VE/V r01? ARTHUR L. BARRETT 1 DIRECT CONTACT FOOD FREEZER This application is a continuation of Ser. No. 48,912, now abandoned.

This direct contact freezing device provides for the introduction of surface wetted comestibles from a dewatering conveyor which controls the amount of water introduced into the system, and which is sealed with respect to the surrounding atmosphere, into a relatively high velocity stream of liquid refrigerant traveling at a rate which will provide for separation between the particles while an initial shell of ice is formed around each particle. There may also be overhead sprays in this initial zone which will enhance the quick surface freezing of the particles. Following this zone the comestibles enter a more slowly flowing body of fluid through which they travel at a greatly, reduced speed, and at a considerably increased depth for a time duration sufficient to provide complete freezing of the particles. In this zone also liquid refrigerant may be sprayed over the unconsolidated bed of comestibles to enhance the freezing rate. Motion in this low velocity zone is created by the low velocity flow of the refrigerant stream supporting the bed, but may be enhanced by mechanical devices arranged to provide direction movement of the comestible particles through the freezing zone. At the exit of the main freezing portion of the freezer, the stream depth is reduced; its velocity is increased, and the comestibles are carried to a refrigerant draining conveyor; thence through an exit leading to a sealed packaging zone. The liquid refrigerant from the drain conveyor is returned through a screen, or filter, and a valve to a storage container sufficient to contain all of the refrigerant in the system. Liquid refrigerant is removed from the storage container through another valve; thence to a circulating pump and a flow control valve to the zone of the freezer at which the comestibles are initially introduced. Valves associated with the storage container provide for removal and storage of all refrigerant so that the system may be repaired or cleansed. The storage container is formed of pressure containing material, such that the refrigerant is contained at ambient temperature without leakage. There is thus provided a circulatory direct contact refrigeration system adequate to freeze comestible particles without clumping as well as transportation of the comestibles through the freezer at a controlled rate. Condensation and purification of the refrigerant liquid and gas for this system will be provided as hereinafter described.

FIG. 1 is a schematic representation of the freezing system of this invention; FIG. 2 is a schematic representation of a liquid purifier and air separator constructed according to theprinciples of this invention;

FIG. 3 is a phase equilibrium chart for CClgFg and air;

FIG. 4 is an overall schematic layout of a second embodiment of this invention;

FIG. 5 is a schematic representation of plastic lined structural container constructed according to the principles of this invention;

FIG. 6 is a schematic layout of a refrigerant recovery system embodying the container of FIG. 5;

FIG. 7 is schematic representation of a refrigerant circulation, purification and recondensation system for a direct contact food freezer constructed as a fourth embodiment of the principles of this invention;

FIG. 8 is a fragmentary three dimensional view of a channeling food delivery means constructed according to the principles of this invention; and

FIG. 9 is a schematic representation of a food glazing means constructed according to the principles of this invention.

In FIG. 1 there is shown a draining transportingconveyor 1 preferably of the shaking type into which the comestibles such as particles or portions 17 have been deposited by a sealed conveyor system (not shown). Excess water is drained from the comestibles being shaken and transported in this conveyor into awater catch portion 2 through openings in the bottom of the shaking conveyor zone in a well known manner. Water is returned by sealed conventional means fromcatch portion 2 to the primary conveyor system. The comestibles travel along the shakingconveyor 1 to a discharge point 3 through a relatively sealedopening 4 in an insulatedshell 35 surrounding amain freezer body 5. This sealingportion 4 is provided to minimize the entry of water vapor from the conveyor area into the main body of thefreezer 5. It is desirable to minimize the entry of water vapor into the freezing compartment since any that enters will later have to be removed in the purifying system. For the same reason, thefall distance 6 from the conveyor to the refrigerant liquid stream 15 is made a practical minimum.

Refrigerant liquid from a storage tank 7 located below the level of themain body 5 flows out through apipe 8, apump 10, acontrol valve 11, aninlet pipe 12 andsealing valve 9 to a flow equalizing chamber 13. At the bottom of the equalizing chamber 13, there is an adjustable horizontal orifice 14 which allows a relatively shallow stream of rapidly flowing refrigerant 15 as shown byarrows 38 to enter the: mainfreezing compartment 5. The equalizing chamber 13 provides an increasing outflow stream velocity through orifice 14 as the level of the fluid in the equalizing chamber increases; thus with an increased fluid flow through the system the level in the chamber increases and a higher velocity stream exists. The outlet orifice 14 may be adjusted in the case of greater changes in flow volume to provide the proper velocity of exiting stream 15. This stream 15 flows down asloping bottom portion 16 and its velocity can be maintained by inclination of theslope portion 16 with respect to the horizontal high velocity stream 15 across the width of the mainfreezing body 5 and provides an area into which the comestible particles or portions 17 may fall without touching the sides of the mainfreezing body 5 or the bottom of thestream channel 16 or each other. In this area 15 liquid refrigerant is sprayed on the particles from a spray manifold 19 to insure complete contact of refrigerant with all of the surface of each particle. This method of treatment and introduction of the comestible particles insures that each particle will be glazed or encased in a protective layer of ice created by the high heat transfer rate between the boiling liquid refrigerant and the wetted particles before they touch anything except the boiling liquid refrigerant. Thus the formation of ice on any portion of the freezer by direct contact is eliminated as is clumping of particles caused by freezing together of a number of particles. After the particles have traveled the length of the sloping high velocity stream 15, they enter thelow velocity portion 18 of themain freezer body 5. In this portion the comestibles will travel at a much slower rate and will accumulate to a height of several inches as they travel acrosslow velocity zone 18 as shown by thearrows 40 in this zone.

Liquid refrigerant spray is introduced through several spray manifolds 19 to provide adequate boiling refrigerant to all of the particles through all portions of themain freezer body 5. Since the particles 17 were encased by a shell of very cold ice almost from the moment of their introduction there is no clumping of the particles as they proceed through thelow velocity zone 18.

The jets emitted from manifolds 19 may also be located and set directionally to stir the particles or food portions and to provide conveying action as the particles proceed with the flowing refrigerant through any or all portions of the freezer.

To enhance the motion of awkwardly shaped comestible particles such as broccoli, cauliflower or spinach a mechanical conveyor preferably of adjustable speed and any conventional type may be provided. Shown in FIG. 1 is a useful form of such a conveyor. Rake-like elements 20 are attached to aframe 21 which is driven in a circular path by suitably powered, synchronized rotatingelements 22 having apin portion 23 attached to rotatingelements 22 associated withbearing portion 24 connected toframe 21, all portions of the frame and rake assembly travel in an orbital path similar to that traveled bypin 23. This is illustrated by a bottom point 25 on one of therakes 20. The orbit as shown by the arrow 42 for this point has a horizontal component of motion in its bottom portion of travel in the direction in which the comestibles travel throughzone 18. While in the upper portion of its orbit where it is not engaged with the comestibles its horizontal component of motion is in the opposite direction to the flow of comestibles inflow zone 18. All points on all rakes have a similar orbit. Thus the comestibles can be gently urged throughflow zone 18 by a conveyor as well as by the flow of the liquid refrigerant. It is obvious that other conveyor forms can be used.

At the exit from the main lowvelocity freezing zone 18 the bottom of the freezer is sloped upwardly as shown at 26 to increase the velocity of the outflowing refrigerant stream 27 in order that a thin high velocity flow of comestibles may exit from themain freezer portion 18 to therefrigerant drainage conveyor 28. This is to provide certainty of comestible outflow.Drainage conveyor 28 has an upward sloped perforated bottom portion so that exit refrigerant will flow out at 29 and the drained comestibles will flow out into a sealed discharge chute 33. The liquid refrigerant flows through a screen orfilter portion 30 into a pipe 31, through a storagetank sealing valve 32 into the storage tank 7. Level of the refrigerant liquid as shown at 34 of the storage tank is variable depending on the amount of refrigerant contained in the system and supplies a reservoir from which losses in the system may be made up. At all times however a storage capacity above the level 34 is maintained such that all of the refrigerant in the system may be returned and sealed in the storage container 7 byvalves 9, 36 and 32; thus the system may beemptied for cleaning or maintenance without loss of refrigerant. The gaseous refrigerant formed by a boil off during the freezing process is compressed, condensed, separated from entrained air and other impurities and returned to the circulating system by means hereinafter described and illustrated. It will also be necessary to purify the circulated liquid refrigerant to remove oils and other impurities gathered.

The main body of thefreezer 5 is encased in a continuous sealedhousing 35 preferably made of metal so that air or water vapor may not enter into themain freezer body 5.

It is to be understood that while this is a preferred embodiment of this invention and principles proposed by this invention may be equally well practiced in other forms and with other elements.

In the operation of this direct contact food freezer the freezing compartment as a whole is enclosed inhousing 35 which is sealed from the outside environment to prevent the loss of refrigerant and the entrance of water or air. The system is preferably operated at one atmosphere of pressure to minimize sealing problems but could be operated at any desired pressure with proper seals. Not shown in FIG. 1 are the seals associated with the inlet of the comestibles fed to shakingconveyor 1 or the outlet sealing arrangements associated with outlet food chute 33. A refrigerant preferably CCL F (R-l2) is circulated from storage tank 7 throughpipe 8, pump 10 andpipe 12 to equalizer chamber 13, out of equalizer chamber 13 through orifice 14 along sloped highvelocity flow path 16 intolow velocity chamber 18 past upward sloping bottom 26 to high velocity exit stream 27 through the perforated bottom ofexit conveyor 28 throughfilter 30 and pipe 31 back to storage chamber 7. This refrigerant in flowing through the various velocity portions of the freezer provides the function of a boiling heat transfer source to extract heat from the freezer comestibles, provides a high velocity particle isolating conveying medium for the entering comestible particles at 15, provides a low velocity transport means in the main freezingarea 18 and a high velocity transport means at 27 for the comestibles as they exit the freezer.

The comestibles are dropped a short distance fromconveyor 4 into high velocity liquid zone 15.Conveyor 4 is arranged near the lateral center of the flow path formed by high velocity flow portion 15 so that the comestible particles drop from the conveyor into the liquid without touching the sides of thefreezer body 35 or the bottom of theflow path 16. They are subjected to a continuous spray of refrigerant liquid from manifold 19 in this flow phase so that each particle becomes completely encrusted with a shell of very cold ice near 2l F. in the case of R-l2 which boils at 21 F. at 1 atmosphere. While the thickness of the shell is small, nevertheless, it provides a non-sticking surface for each of the particles so that when they leave the high velocity liquid zone 15 and enter the main freezing section,low velocity zone 18, the particles may be accumulated to a thickness of several inches, in fact, to any practical thickness desired without a tendency for them to clump together as freezing continues.

Since comestible particles are, without exception, lighter than R-l2, the particles will float on the surface of the bath inzone 18 with approximately one-third of the bed submerged in refrigerant and two-thirds of the bed supported above the liquid level. Refrigerant is supplied for the elevated portion of the bed by sprays from the manifolds 19; thus each particle is continuouslycovered by a layer of boiling refrigerant and the freezing of the particles progresses at a rapid rate.

Directional sprays from manifolds 19 are useful in providing agitation in the high velocity portion of thechannel 5 and aimed sprays in thelow velocity zone 18 are useful through the kenetic energy of the sprayed liquid to provide conveying action to the floating particles in the direction of flow inzone 18.

The flow rate in thiszone 18 is controlled by adjustment of a regulatingvalve 11 in the circulating system so that the comestibles will be completely frozen at the time they have reached sloping portion 26 where the stream velocity increases to carry particles out of the freezer to exitconveyor 28.Exit conveyor 28 has a perforated bottom portion which slopes upward toward its discharge end and drains refrigerant from the comestibles for return to the storage chamber 7.

The flow rate throughfreezer portion 18 has been adjusted in the case of R-l2 refrigerant at 1 atmosphere to discharge the comestibles at a temperature below the freezing point of the comestibles but above the boiling point of the refrigerant and there is available heat in the comestible particles with respect to the refrigerant as they reachconveyor 28. This retained heat is sufficient to boil off any refrigerant remaining on the comestibles as surface wetness after draining inconveyor 28; thus the comestible particles when flow rates and temperatures have been adjusted as described exit into discharge chute 33 completely free ofliquid refrigerant and at a temperature above that of the boiling refrigerant.

When it is desired to clean or repair the freezingchamber 35 pump is stopped, adrain valve 36, communicating betweenzone 18 and the storage tank 7, is opened and the fluid refrigerant will drain into tank 7,pipe 12,pump body 10 andpipe 8. At thistime valves 9, 36, and 32 are closed, Preferably pump 10 is a hermetically sealed unit as normally used in refrigeration systems with the motor inside the enclosure. Under these circumstances withvalves 9, 32 and 36 closed a gas and liquid tight storage system is provided for the refrigerant which may be constructed of materials adequately strong to resist the pressure generated by the refrigerant at ambient temperatures. Thus no auxiliary refrigeration is required to assure long time storage of the refrigerant. With the refrigerant drained fromchamber 35 the chamber may be warmed up as desired and opened for maintenance or cleaning without the loss of significant quantities of refrigerant.

Conveyor 21 can be provided if desired'to move irregular shaped comestible particles such as broccoli through thezone 18 if because of their interlocking nature they do not move freely as the result of liquid refrigerant flow.

A second embodiment of this invention provides a direct contact food freezer using a low boiling point inert refrigerant condensed by heat transfer to another refrigerant (see FIGS. 2, 3 and 4).

This direct contact freezing device provides for the introduction of surface wetted comestibles from a dewatering conveyor which controls the amount of water thereon and which is sealed with respect to the surrounding atmosphere, into a body of a first refrigerant in which the comestibles are frozen, removal of the comestibles from the body of the first refrigerant by means of a conveyor device which provides drainage of the excess first refrigerant from the comestibles, delivery of the comestibles to a sealable outlet device from which they travel to a sealed container. in the process of freezing the comestibles the first refrigerant is boiled off and is recondensed in a heat exchanger communieating with the condensable first refrigerant gas in the freezing compartment. The first liquid refrigerant con densed .by the heat exchanger is returned to the main body of first liquid refrigerant associated with the freezer. A second refrigerant used in the inside of the condenser is preferably a boiling refrigerant and the system is operated as a flooded system with an excess amount of refrigeration available in the heat exchanger from the second refrigerant so that the pressure in the direct contact freezer body may be retained at approximately 1 atmosphere through any variation of comestible throughput that may occur.

The comestibles entering the feeder conveyor are carried in suspension in water through a barometric seal and this water on leaving after the comestibles have been removed also exits through a barometric seal. Comestibles leaving the main body of the freezer are discharged to a chute which leads to a storage container made of an impervious material preferably a plastic bag contained in a transportation compartment such as a wooden box. In order to provide effective sealing the mouth of the plastic bag is attached in gas tight relationship to the discharge chute. The discharge chute is fashioned with a valve near its outlet end which when closed seals the chute and provides a short time storage pocket for comestibles above it so that when the valve is closed, the system remains sealed for the time period during which a filled plastic bag is detached from the discharge chute and an empty one is installed in its place.

The freezing system includes a filter which separates solid materials from the returning circulating refrigerant, a pump to induce circulation of the refrigerant through the freezer, a purifier to remove from the liquid refrigerant dissolved oils and other materials, a gas purifying system to remove from the boiled off refriger ant gas entrained air and other gaseous components.

FIG. 4 shows the inlet flow pipe 101 containing comestible particles or portions in suspension in a stream of water. This suspension passes through a barometric seal shown at 102 disposed vertically a distance adequate to provide a water pressure barrier to either outflow or inflow of gases from themain body 103 of the refrigerator. The flow of water and suspended comestibles is carried through pipe 101 and is discharged onconveyor 104, in aclosed compartment 107 the bottom of which has an upward slope to themain body 103 of the refrigerator. Theconveyor 104 is preferably of the shaking type; it effectively separates the comestible portions from the carrying water, and conveys the comestibles into the main body of thefreezer 103. The water separated from the comestibles byconveyor 104 is discharged throughpipe 105 and a barometric seal 106. Barometric seal 106 is effective to prohibit passage of gas into or out offreezer body 103 through the water return system.Compartment 107 is constructed to completely encloseconveyor 104 and seal the area except for the entering stream of water and comestibles, the discharge stream of water and the channel connecting theconveyor 104 with thefreezer body 103. The main body of thefreezer 103 contains abath 113 of boiling liquid refrigerant preferably CCLgFg (refrigerant R-12, the assigned name of the refrigeration industry). While this freezer is shown using a pump circulated conveying fluid, the freezer might also be constructed with a moving link belt and sprays for delivering refrigerant liquid to the comestibles.

A discharge conveyor 157 delivers the frozen comestibles to anoutlet chute 108. Theoutlet chute 108 is constructed with a sealing valve 109 so placed that there is a pocket formed in the chute at 110 when the valve is closed. The valve is closed, when it is desired to remove a filled plastic container 111 and replace it with an empty comestible container. The top of the plastic container is clamped or tied around the chute at 112 to effect a gas seal between the plastic container and the discharge chute; thus no gaseous R-l2 may escape during the process of filling the plastic container orbag 11 1 with the frozen comestibles, nor can outside air or other contaminates leak into thechute 108 to reach the main body of thefreezer 103. During the changing period, the comestibles accumulate in pocket 110, after the bags are changed, valve 109 is opened allowing the stored comestibles in pocket 110 as well as those being steadily delivered from conveyor 157 tochute 108, to flow into bag 111, the system remaining at all times in a sealed condition.

As the comestibles are frozen inliquid bath 1 13 or by the sprayed refrigerant emitting from manifolds 114, heat is given up to the direct contact refrigeration fluid which boils vigorously. This refrigerant gas is recondensed on the outside of heat exchanger or coolingcoils 115 which are preferably cooled by the circulation of a second lower boiling point refrigerant such as ammonia in the interior of the coil or heat exchanger. This heat exchanger is operated as a flooded system preferably with a circulatingpump 116, pumping excess quantities of liquid ammonia through pipe 117,heat exchanger 115 andpipe 1 18 back tolevel control chamber 119 in which the ammonia level may be controlled by a level control device. Liquid ammonia is supplied to the level control chamber bypipe 120 and evaporated ammonia gas is discharged throughpipe 121.Heat exchanger 115 has a heat transfer capacity greater than that required to refrigerate the maximum amount of comestibles to be delivered in any time period. This available heat transfer capacity together with a continuous supply of liquid ammonia refrigerant pumped fromlevel control chamber 119 insures that the boiled off R-l2 frombath 113 and/or sprays 114 can always be condensed and that no excess pressure will build up in the main body of thefreezer 103 which might cause leakage through the containing walls 122, through thebarometric seals 102 and 106, through the plasticcontainer clamping seal 112, or through the plastic container 111 by reason of rupture.

Pressure control infreezer body 103 may be accomplished by a number of means all correlated to sensed pressure infreezer body 103.

fromchamber 119.Flow control valve 71 is responsive to pressure sensing means sensing the pressure infreezer body 103. With a pressure decrease infreezer body 103,sensor 70 effects a closure ofvalve 71 at a rate responsive to the rate of and/or the pressure decrease infreezer body 103. Closure ofvalve 71 results in an increase in pressure in the ammonia inexchanger 115 at which it boils, quickly increasing the temperature of the boiling liquid NI-I and reducing the condensation of R-l2 thus holding the pressure infreezer body 103 at or near ambient pressure.

In a direct contact freezer for comestibles there will be contamination of the liquid refrigerant. Certain comestibles such as French fried potatoes will carry oil which is miscible with R-l2, vegetables such as lima beans will have surface waxes which will be soluable in R-l2, other products will contribute other contaminants to the refrigerant R-l2 to a degree that the refrigerant must be purified in order to maintain high flavor standards and minimum sedimentation or deposition in the freezer. To effect purification, refrigerant is removed from the body of therefrigerator 103 throughexit pipe 123 to filter 124 where solid entrained particles are removed. The refrigerant continues throughpipe 56 to pump 125 andpipe 127 back to the body of therefrigerator 103 and also to spray manifolds 114. A controlled side stream to be further purified is removed frompipe 127 throughpipe 126, through throttlingvalve 128 andpipe 129 toliquid purifier body 130, see FIG. 2. Inpurifier body 130 this stream of fluid is in heat exchange with a condensing flow of gas insideheat exchanger 147. The flow of liquid through the throttlingvalve 128 is adjusted so that all of thefluid entering purifier 130 can be vaporized. The boiled off gas passes out ofpurifier 130 throughpipe 131,valve 132 andpipe 133 to the main body of therefrigerator 103. Condensibles remain in the body ofpurifier 130 and from time to time as requiredvalve 128 is closed and contained R-l2 fluid in the main body ofpurifier 130 is boiled off,valve 132 is then closed and the remaining Condensibles inpurifier body 130 are drained out throughpipe 57, valve 58 to waste. Cleaning solutions may be introduced through pipe normally closedvalve 61 andpipe 62 to flush out remaining contaminants and sediments from the body ofpurifier 130.

There will be some contamination by air and water vapor of the gas at the top of the body of thefreezer 103, FIG. 4. These gases will be principally concen- 1. By controlling the flow of R-l2 fromchamber 103 to heat exchanger by an adjustable opening or resistance in the flow passage between them.

2. By controlling the mass inflow rate of the entering comestibles.

3. By controlling the rate of flow of NH toheat exchanger 115.

4. By adjusting the pressure of the NI-I in theheat exchanger 115 and thus the boiling temperature of the NH;, in the heat exchanger.

A preferred means of controlling pressure infreezer body 103 is to provide acheck valve 69 in the inflow ammonia line to prevent outflow of gas or liquid from ammonialevel control chamber 119. Aflow control valve 71 is installed in ammoniagas outflow line 59 trated in the areas above the R-12 liquifying coils 115 and are best withdrawn at a point located as at 134 above or remote from thefreezer 103 with respect toheat exhanger 115. These gases are conducted throughpipe 135 to filter 136 of FIG. 2 where solid foreign materials as well as water crystals are removed. The gas then proceeds through apipe 137 to thefirst stage 138 of oilfree compressor 151,pipe 142 to theinterstage cooler 139 ofcompressor 151 where it is cooled in heat exchange with a stream of water entering at 140 and exiting at 141. The gas leaves the intercooler throughpipe 143 entering the oilfree compressor stages 144 exiting through pipe 145 toaftercooler 146. Inaftercooler 146 the mixture of R-l2 and contaminants, principally air, having been compressed to approximately 400 PSlA by the last stage ofcompressor 144 is cooled in heat exchange with a stream of water entering throughpipe 63 and exiting throughpipe 64 andflow control valve 65.Flow control valve 65 is governed bylevel sensor 66 associated with the level 148 of the boiling liquid inpurifier 130. The partially cooled gas fromaftercooler 146 exits throughpipe 67 and enters the inside ofheat exchanger portion 147 located in the body ofpurifier 130. In this heat exchanger the condensible gas is liquified and flows out throughpipe 68 to separatingchamber 149 along with gas that has not been condensed. Liquid direct contact refrigerant is removed fromseparation chamber 149 in a controlled manner bylevel control valve 50 and enterspipe 52 for return to the main body of refrigerant inpipe 127 or inrefrigerator body 103. Non-condensible gas is vented from the separating chamber throughpipe 53constant pressure regulator 54 andpipe 55 to atmosphere. The non-condensible gases will consist primarily of air and water. As is seen in FIG. 3 when a mixture of R-l 2 (CCL F and air at 400 PSIA is cooled to approximately --30 F. as would be the case with the mixture of R-l2 and air existing in this system and boiling at 1 atmosphere inpurifier body 130 as proposed in this freezer the gas remaining at this temperature and pressure would have a content of 13 percent R-l2 by weight and 87 percent air by weight. If constantinlet pressure valve 54 is set at 400 PSIA gas can only reach this pressure and exit throughvalve 54 given adequate heat exchange inheat exchanger 147 at 30 f. when the mixture of air and R-l 2 is at a concentration of 87 percent air by weight or greater, see 400 PSIA phase equilibrium curve FIG. 3. The air will carry a small amount of water vapor with it as the air is exited through regulatingvalve 54 to waste.

In this manner the boiling refrigerant contained in the freezer is purified byfilter 124, by condensing the condensibles inpurifier 130 and separating the R-l2 from air in theheat exchanger 147 ofpurifier 130. Heat transfer inpurifier 130 is balanced by control of the fluid level 148 inpurifier 130 through appropriate linkage of .level control 66 andvalve 65 controlling the cooling water flow throughaftercooler 146 and control of refrigeration liquid inlet flow byadjustable throttle valve 128.

In the operation of the direct contact freezer shown in FIGS. 2 and 4 the direct contact refrigerant R-12 (CCL F is condensed either in the same chamber as the comestibles of the R-12 or in a chamber directly associated with the freezing chamber. There are a number of simultaneous requirements in direct contact freezing necessary to successful operation of the freezer. As a primary objective therefrigerant bath 113 infreezer body 103 in FIG. 4 must be sealed from the surrounding atmosphere otherwise a substantial loss of refrigerant will be sustained. The refrigerant must be maintained in a pure state in both the gaseous and liquid phases thus the refrigerant must be refined to maintain it in a pure state. The proper temperature must be maintained in the recondensing coils 115 otherwise pressures either above or below ambient pressure will exist in the body of thefreezer 103. In the operation of this invention comestibles are delivered in pipe 101 throughbarometric seal 102, which effectively seals the inflow circuit, toconveyor 104 where the major portion of water is removed through the perforated bottom and returned throughpipe 105 and barometric seal 106 to the primary comestible conveyor system. Barometric seal 106 operates as an effective seal between chamber and outside ambient conditions. The comestibles are delivered relatively dewatered fromconveyor 104 andcompartment 107 through relatively restricted opening 73 into the main body of thefreezer 103 where they are sprayed with refrigerant from manifolds 114 and/or put in contact with a main body ofliquid refrigerant 1 13 for freezing. After removal from the main body ofrefrigerant 113 the comestibles are delivered by dewatering conveyor 157 here shown as an uphill vibrating or other mechanical conveyor tochute 108 for exit from the system. Conveyor 157 might also be a stationary gravity conveyor made of longitudinal wires or slates to provide a porous bottom and effect the removal of refrigerant as the comestibles travel on their way tochute 108.Chute 108 is effectively sealed to a delivery container 111 preferably an impervious plastic bag tieing the plastic bag .aroundchute 108 or clamping it aroundchute 108. As a part of chute 108 a sealed valve 109 is provided which may be closed at the time afull container 1 11 would be removed and replaced by an empty container 111. When valve 109 is closed a pocket 110 is formed inchute 108 such that the outflowing comestibles from conveyor 109 may be contained at this point for the container changing period. When thenew container 1 11 has been placed and sealed tochute 108, valve 109 is opened and the comestibles in pocket 110 as well as those in regular process throughfreezer body 103 are delivered to container 111.Chute 108, valve 109,seal 112 and container 111 thus effectively seal the outlet of themain freezer body 103 with respect to the surrounding air. All systems associated with circulation ofliquid refrigerant 113, purification, recondensation and removal of the air from the vaporizedliquid 1 13 are closed systems within themselves and thus act as effective seals between the main body of thefreezer 103 and the outside ambient air. v

Overflow refrigerant removed by conveyor 157 is returned throughpipe 123 to filter 124 where particles of ice, comestibles of foreign material is removed before the liquid progresses throughpipe 56 to sealedpump 125 which delivers the main portion of circulating refrigerant throughpipe 127 to the main body ofrefrigerant 113 in thefreezer 103. A side stream is removed frompipe 127 throughpipe 126 of FIG. 2 passing through throttlingvalve 128, which controls the amount of refrigerant flowing in the side stream, into the boiler portion of theboiler condenser 130. Here the side stream is vaporized by warm condensing gas flowing inheat exchanger 147 in such quantity that when the gas is fully condensed all of the refrigerant liquid entering inpipe 129 will have been fully evaporated, contaminants remaining. The boiled off gases pass out throughvalve 132 andpipe 133 to the main body of thefreezer 103 in FIG 4. A stream of gas is removed from themain body 103 throughintake 134 located remotely from themain body 103 with respect toheat exchanger 1 15 which continuously reliquifies boiled off refrigerant fromliquid body 113 for return to liquid 145 to anaftercooler 146 where the compressed gas is put in heat exchange with water or other cooling medium entering throughpipe 63 and exiting throughpipe 64 andcontrol valve 65.Control valve 65 operates in cooperation with liquidlevel sensing device 66 to con trol the flow of coolant toaftercooler 146 so that gas passing from theaftercooler 146 throughpipe 67 toheat exchanger 147 will be liquified inheat exchanger 147 ofboiler condenser 130 to refrigerant air equilibrium at a temperature approximately that of the boiling liquid refrigerant being maintained at liquid level 148 by this control action. Thus, a mixture, principally remaining air and refrigerant, will be delivered throughpipe 68 to separatingcompartment 149 where purified liquid refrigerant is withdrawn throughpipe 52 bycontrol device 50 to provide constant liquid level 51 in thecontrol compartment 149. The remaining gas principally air is discharged through inletpressure control valve 54 to atmosphere. Regulatingvalve 54 is set at a pressure level such that the discharged air will contain a minimal amount of refrigerant.

The relationship between the quantities of air and refrigerant in an air refrigerant mixture is shown in the curve of FIG. 3.Curve 75 on this graph shows the relationship of a mixture of air and R-l2 gas at a pressure of 400 PSIA (pounds per square inch absolute) and stabilized conditions above a corresponding mixture of air and R-l2 liquid.Curve 75 shows the gas side of what is usually shown as a pair of curves. The area abovecurve 75 consists completelyof a gaseous mixture. If a temperature line of 100 F is followed horizontally across the sheet to the intersection withcurve 75 it is seen that the per cent by weight of R-l2 (CCL F in the gas mixture about 60 percent the remaining 40 percent being air. This means that if a mixture of air and gas is present at 100 F and 400 PSIA the mixture at the dew point will be about 60 percent R-l2, and 40 percent air. Conversely any vapor boiled off from a liquid mixture of air and R-l 2 which boils at 100 F and 400 PSIA will be about 60% R-12 and 40% air. For illustra-- tion presume that the pressure maintained inheat exchanger 147 by regulatingvalve 54 working in conjunction with compressor low andhigh states 138 and 144 respectively is 400 pounds per square inch absolute. The equilibrium point on the 400 PSIA curve at 21 F ispoint 74 corresponding to mixture of 15 percent R-l2 and 85 percent air. If the high stage of thecompressor 144 delivers at least 400 PSIA of a mixture ofR-l 2 and air containing more than 14 %percent R-l2, ifvalve 65 actuated bycontrol device 66 provides proper temperature control of gas enteringheat exchanger 147 through pipe 145, ifexchanger 147 has enough heat transfer surface, and if the temperature in the liquid insideboiler condenser 130 is 2l F the condition of the gas exiting throughpressure regulating valve 54 will be shown atpoint 74 FIG. 3. Another combination of pressure and temperature would provide equilibrium at another point on a similar curve showing the relationship at the dew point between a refrigerant and air mixture.Curves 76, 78 and 79 respectively show this relationship at 14.7 PSIA, 140 PSIA and 200 PSIA.

A similar control system could be achieved by generally controlling the gas exiting from 146 in FIG. 2 through 67 toheat exchanger 147 in pressure and temperature. Under these conditions given adequate surface area inheat exchanger 147 an interrelation of controls between themeter valve 128 andlevel control valve 66 would insure that gas exiting through constantpressure regulating valve 54 would fall on or above a chosen point on a curve such as shown in FIG. 3.

In conjunction with the above described process, refrigeration forheat exchanger 147 is furnished by the bath of refrigerant retained inboiler condenser 140 entering throughcontrol valve 128. Liquid enteringboiler condenser 130 throughpipe 129 is continuously vaporized or distilled inboiler condenser 130 and exited throughvalve 132 topipe 133 to the main body of thefreezer 103, FIG. 4. This process of distillation purifies the refrigerant entering at 129 and results in high boiling point constituents being retained inboiler condenser 130.

From time to time it is necessary to remove the contaminants accumulating inboiler condenser 130. Preferably this is done byclosing throttling valves 128 and 65 (FIG. 3). At this time though not essential theexit pipe 55 frompressure regulator valve 54 would best be connected to the body ofmain freezer 103, FIG. 4, since no separation of air from refrigerant is occurring in 147. With warm gas flowing into 147 throughpipe 67 the residual refrigerant inboiler condenser 130 is evaporated, the refrigerant passing as usual throughvalve 132 topipe 133 and to the main body of the freezer 103 (FIG. 1). When a desired concentration of impurities has been reached in the body of boiler condenser 130 (FIG. 2), they may be withdrawn to waste throughpipe 57 and valve 58. Flushing may be provided if desired throughinlet pipe 60,valve 61 andpipe 62. After purgingboiler condenser 130,valves 58 and 61 are closed,valves 128 and 65 are reopened and whenboiler condenser 130 has again been filled to the level 148 the process will continue as previously described.

The flow of comestibles to the freezer through pipe 101 (FIG. 4) andconveyor 104 under normal conditions is unlikely to be constant and it is desirable to deliver the frozen comestibles into container 111 at a constant temperature. In order to meet this requirement it is necessary to control the refrigeration being A delivered byheat exchanger 115. This is particularly desirable since without close control of the refrigeration delivered byheat exchanger 115 there will be a variation in the pressure existing in the main body offreezer 103. A liquid boiling at a given temperature has a fixed vapor pressure over the liquid and an increase in heat introduced toliquid bath 113, by an increased comestible flow, results without a corresponding increase in refrigeration furnished byheat exchanger 1 15 in increased pressure in the main body offreezer 103. In the case of a decreased flow of comestibles there would be a corresponding requirement for decreased refrigeration inheat exchanger 115 if an under pressure is to be avoided in the main body offreezer 103. Either condition is undesirable as at some point a barometric or other sealing means could be overcome with a resulting flow of air into the main body of thefreezer 103 or a flow of refrigerant from the main body of the freezer to outside air. Either case results in loss of refrigerant either directly or through the refrigerant recovery system.

To avoid this undesirable condition a preferred control means is shown in FIG. 4 the refrigerant is supplied in this instance by ammonia entering throughcheck valve 69 and pipe to aconstant level reservoir 1 19.

The refrigerant being circulated from this reservoir throughpump 116, pipe 117,heat exchanger 115 andpipe 118 back to the reservoir. Evaporated ammonia refrigerant would exit throughpipe 118 along with the liquid toreservoir 119 returning to the primary refrigeration system throughpipe 59, throttlingvalve 71 andpipe 121. Apressure sensing valve 70 extends through the walls of the main freezer body 122 and communicates to throttlingvalve 71 and change in the pressure insidefreezer body 103. The control mechanism between 70 and 71 may be any of a number of wel1- known sensor valve control valve mechanisms. By means of thiscontrol system valve 71 is moved toward a closed position when a decrease of pressure is sensed at 70. As the boiling ammonia gas inheat exchanger 115 has no other means of escape the pressure and the temperature of the boiling liquid in the circulating ammonia system rises and the refrigeration supplied to the main body offreezer 103 byheat exchanger 115 is reduced. Other means of reducing the heat transfer ofheat exchanger 115 might be reduction of refrigerant flow through the heat exchanger or restriction of the flow from the main body of thefreezer 103 toheat exchanger 115.

This process has been described in respect to direct contact refrigerant R-l2 and primary refrigerant ammonia. It is to be understood that the process will work equally well with other refrigerants. Particular arrangement of details and devices have been described but it is understood thatother similar arrangements of equipment are also contemplated.

A third embodiment of this invention provides a means to remove refrigerant from the interstices of comestibles frozen in a direct contact food freezer and stored in a receiving container (see FIGS. 5 and 6).

This refrigerant removal device, as shown in FIGS. 5 and 6, provides for the removal of trapped refrigerant in the interstices of comestibles or the like which have been frozen in a direct contact food freezer and deposited in a sealed container for transportation or storage. It is generally true that the volume accounted for by the interstices between comestibles in a container is greater than the volume of comestibles in the container. When comestibles are frozen in a sealed direct contact freezer system, the interstices are completely filed with refrigerant normally in a gaseous form. A typical refrigerant such as CCL F (R-12) at a temperature of 0 F has a weight of 0.375 pounds per cubic foot. It is thus advantageous for economic reasons to recover a high proportion of the refrigerant. In this invention a preferred arrangement includes a plastic impervious storage liner inside a structurally competent storage container, the storage liner being adapted for sealing to a discharge chute for a direct contact food freezer. Prior to filling, a tubular member is inserted to the bottom of the plastic storage container and sealed near its exit end and supported above the eventual level of the comestibles in the storage container. Subsequent to the filling of the storage container with comestibles the tube is attached to an evacuating means which removes the dense refrigerant gas from the bottom of the storage container through the tube. Air or other gas less dense than the refrigerant is admitted to the top of the container to replace the refrigerant being removed from the interstices between the comestibles. The refrigerant withdrawn by the evacuating device is delivered for purification and/or recondensation.

Referring to FIG. 5, 201 is structurally adequate transportation or a storage container having supportingelements 202 adapted to receive the fork means of a motorized lift truck (not shown).Storage container 201 is preferably lined with aplastic bag 203 which is sealed in generally gas tight relationship to adischarge duct 204 forming a gas tight flow path through whichcomestibles 205 are delivered into the main body ofcontainer 206. Sealing ofplastic container 203 toduct 204 is effected by clamping device 207 which might be a rubber band or spring. Prior to attachingplastic bag 205 to discharge 204 flexible tubular means 208 is inserted to the bottom ofplastic bag 203 contained incontainer 201. The exit portion oftubular member 208 is sealed or clamped byelement 209.Tubular element 208 may be recessed into acavity 210 ofdischarge duct 204 such that theend 211 oftubular member 208 projects outside of the plastic container. It would also be practical to supporttubular member 208 by an attachment insideduct 204 so that it would be held above thefinal filling level 212 of the comestibles in the main body ofcontainer 203.

Referring now to FIG. 6 theplastic container 203 has been removed fromdischarge duct 204, theend 211 oftubular member 208 has been attached to an evacuatingdevice 213 which could appropriately be a fan. Evacuatingdevice 213 is connected toduct 214 which can deliver gas evacuated bydevice 213 either directly to the main body of a direct contact freezer 113 (see FIG. 4) or to apurifying device 215 in which the refrigerant may be separated from the gases delivered by evacuatingdevice 213 throughduct 214. As shown in FIG. 6 whenplastic bag 203 is connected to theevacuation device 213, a relativelysmall opening 216 is left between the neck of the plastic bag and thetubular member 208 so that when the evacuatingdevice 213 is operated a flow of gas (arrow 217) may enter the main body of thecontainer 206.

Purifying device 215 is preferably an activated charcoalpurifier having chambers 218 and 219 adapted to alternately receive unpurified refrigerant throughduct 214.Valves 220, 221, 222, 223,. 224 and 225 are adapted to control the flow of refrigerant through thechambers 218 and 219 ofpurifier 215 alternately in a manner to provide continuous purification of refrigerant flowing in throughduct 214 to one chamber of the purifier while the refrigerant is being recovered from the other chamber for return to the direct contact freezer. As an example, refrigerant entering throughduct 214 may pass throughopen valve 221 tochamber 218 for refrigerant collection. Valves 220 and 224 being closed. The contaminating gases of the refrigerant flowing induct 214 being discharged through valve 223 to exit 226. Upon reversal of the cycle gases fromduct 214enter chamber 219 through valve 220,valves 221 and 225 being closed with gases. separated from the refrigerant stream being exited throughvalve 222 to exit 227. At alternate periods refrigerant retained inchamber 218 after application of appropriate recovery means are discharged through valve 224 to exit 228 for return to the direct contact freezer system.Valves 221, 223 and 225 being closed. Alternately refrigerant recovered inchamber 219 is returned throughvalve 225 andexit 228 to the direct contact freezer system;valves 220, 222 and 224 being closed.

In the operation of this inventionplastic container 203 in FIG. 5 is inserted in a collapsed minimal internal volume condition intostructural container 201 and attached toduct 204 by clamping device 207.Tubular member 208 having been previously inserted intoplastic container 203 withdischarge end 211 emerging from theopening 229 inplastic container 203. The collapsed state ofplastic bag 203 provides a minimal amount of air in themain body 206 ofplastic bag 203 which air passes throughopening 230 indischarge duct 204 to the main body of the freezer to whichduct 204 is attached in sealing relationship. If an opennoncollapsed container 203 is attached to duct 204 a considerable quantity of air will be contained incontainer 203 which on filling ofcontainer 203 will be displaced intoduct 204 and thence to the body of the direct contact freezer. The presence of this pollutant air in the direct contact freezer results in either excess purification equipment, loss of refrigerant, or both. Tubular member 208'is retained by clamping insideduct 204 or by passing betweenduct 204 andplastic bag 203 which is attached in sealing relationship toduct 204 by clamping device 207. It is necessary thattubular member 208 be thus retained in an accessible position with respect to theopening 229 inplastic bag 203 so that opening 211 oftubular member 203 may be attached to evacuatingdevice 213 as shown in FIG. 6 when it is desired to recover the refrigerant from the interstices between the comestibles.Tubular member 208 is sealed by an appropriate clamping or sealingdevice 209 so that refrigerant gas entering with the comestibles throughduct 230 cannot escape throughtubular member 208.Tubular member 208 when located betweenplastic bag 203 anddischarge duct 204 is preferably recessed into acavity 210 induct 204 in order to provide adequate sealing ofplastic bag 203 toduct 204 by sealing member 207. I

Whenplastic bag 203 supported incontainer 201 is filled to anappropriate level 212, sealing element 207 is loosened or removed and plastic bag'203 is detached fromdischarge chute 204. Theend 211 oftubular member 208 is retained on the outside ofneck 229 ofplastic bag 203. As shown in FIG. 6 the neck or opening 229 ofplastic bag 203 is held in position in proximity totubular element 208 by an appropriate means.Tube 208 is connected at itsend 211 to anevacuation device 213. Sealing orclamping device 209 is removed fromtubular member 208 and whenevacuation device 213 is activated a flow of dense refrigerant preferably R-l2 is withdrawn from themain body 206 ofcontainer 203. Air or other less dense gas enters opening 229 of theplastic bag 203 in stream indicated by arrow 217 in relatively restrictedflow channel 216. The relatively restrictedflow channel 216 and the relatively great difference in density prevents ready defusion of refrigerant to the air being admitted into the main body of thecontainer 206 or between the air and the heavy body of refrigerant gas filling the interstices of the comestibles in the bottom portion of the container and being withdrawn byevacuation device 213. In normal practice evacuation is continued until the greater portion of refrigerant inmain body 206 is withdrawn byevacuation device 213. The period of operation ofevacuation device 213 may be controlled by timing means or by means of an instrument sensing the percentage of refrigerant present and being withdrawn throughtubular member 208, stopping the process of evacuation at a predetermined preferable low percentage of refrigerant versus air or other gas introduced in stream 217.

The refrigrant collected from themain body 206 ofcontainer 203 is discharged throughduct 214 either directly to the direct contact freezer refrigerant system or to apurifying device 215.Purifying device 215 would preferably be a dual chamber activated carbon type. Gas fromduct 214 on one half of the cycle entering through valve 220 to activatedcarbon chamber 219 in which chamber the refrigerant is retained by the activated carbon while the air or other gas present in the mixture entering throughduct 214 would be discharged throughvalve 222 to exit 227.Valves 221 and 225 being closed at this time. At an appropriate time when the activated carbon incontainer 219 has approached its capacity with respect to the collection of refrigerant from the stream entering throughduct 214;valves 220 and 222 are closed andvalves 221 and 223 are opened so that the stream of entering refrigerant and other gas fromduct 214 passes throughvalve 221 intopurifying chamber 218 the refrigerant as before being retained by the activated carbon and the air or gas passing out through valve 223 to discharge 226. During the period when gases induct 214 are purified inchamber 218, the activated carbon inchamber 219 is being reactivated preferably by introducing stream intochamber 218 thereby raising the temperature of the activated carbon inchamber 219, recondensing the steam to water incondenser 231 while passing the separated refrigerant out throughvalve 225 andexit 228 to the direct contact freezer refrigeration system;valves 220 and 222 being closed during this process. For increased performance eachpurifier chamber 218 or 219 may be preconditioned for improved purification action, after it has been purged of refrigerant, by cooling the active contents of the chamber below ambient temperature, preferably to approximately the temperature of the boiling refrigerant in the main body of the direct contact food freezer, with a refrigerating medium such 'as circulating refrigerated air. When the cycle is again reversed the purging process described forpurifier chamber 219 is repeated inpurifier chamber 218;valves 221, 223 and 225 being closed and valve 224 open. Steam condensation occurring incondenser 232. It is to be understood that other forms of purifiers may be used in place of the activated carbon purifier described.

The refrigerant air mixture induct 214 will be essentially pure refrigerant at the beginning of the operation ofevacuation device 213 and after some period of operation ofevacuation device 213, a decrease in refrigeration purity will be experienced due to mixing of air entering throughflow channel 216 with the remaining refrigerant inmain body 206 ofcontainer 203. If it is desired,duct 228 may be connected directly with the refrigeration system of the direct contact food freezer during the first portion of this evacuation cycle or during the total portion of the evacuation cycle in which case purification of the evacuated refrigerant air mixture will be performed by the purification apparatus associated with the direct contact freezer.

In this preferred embodiment one form of container, evacuator system, and purifier have been described, it is understood that the intent of this invention may be practiced with variations in the form of container, evacuator, or purification system.

A fourth embodiment of this invention provides a food freezing device (see FIG. 7) using a low boiling point, inert refrigerant for the direct contact freezing of comestibles.

This direct contact food freezing device provides for the introduction of comestibles through an entrance which is sealed with respect to the surrounding atmosphere into a body of refrigerant in which the comestibles are frozen, removal of the comestibles from the body of the refrigerant and delivering them through a gas tight flow channel to a storage container. Refrigeration for freezing the comestibles is provided by a direct contact refrigerant such as CCL F (11-12). This refrigerant is purified as a liquid to remove soluble oils and other impurities from the refrigerant and it is purified as a gas to remove gaseous contaminants principally air from the refrigerant. As the refrigerant is evaporated in the sealed direct contact freezer compartment, it is evacuated by a compressor through an intake filter and compressed. The compressed refrigerant gas is circulated to a water cooled condenser where a major portion of the refrigerant is condensed. This condensed portion of refrigerant may be further cooled as a liquid to cause solidification of crystals of dissolved liquid components principally water. The liquid is then returned through a reducing valve to the liquid circulating system of the food freezer. A noncondensed stream of gas from the first cooler or condenser is passed through a further cooler in heat exchange with refrigerant R-l2 boiling near atmospheric pressure or below where an additional quantity of refrigerant is condensed, filtered and returned through a reducing valve to the circulating system of the direct contact freezer. A stream of noncondensed gas from the refrigerant cooled condenser is further compressed and subsequently cooled in a heat exchanger cooled by R-l2 at near'or below atmospheric pressures to provide a final condensation of refrigerant. Unwanted gaseous contaminants principally air are discharged into a throttling valve and the refrigerant is returned through a filter and reducing valve to the refrigerant circulating system of the directcontact food freezer. The refrigerant used to freeze the food in the direct contact freezer is thus purged of its impurities and reliquified for continued use as a food freezant.

In FIG. 7reference numeral 301 indicates the body of the freezer in which comestibles are frozen by direct contact with the refrigerant preferably CCL F (R-l2). Liquid is circulated through this freezer being withdrawn throughpipe 305 to filter 302, throughpipe 306, to astorage compartment 303 throughpipe 307 to pump 304 which returns the refrigerant throughpipe 308 to the main body of thefood freezer 301. The evaporated gaseous refrigerant being produced as a result of freezing comestibles infreezer 301 exits throughpipe 309, throughfilter 310 andpipe 311 to oilfree compressor 312. After compression inocmpressor 312 to a desired level, the refrigerant progresses throughpipe 313 to water or air cooledheat exchanger 314. Water entering said heat exchanger throughpipe 315 and exiting throughpipe 316. A major portion of the refrigerant is condensed in this heat exchanger and returns throughpipes 317 toheat exchanger 318 where it may be supercooled in heat exchange with a refrigerant such as R-l2 boiling near or below atmospheric pressure whereby the condensed liquid is cooled to a temperature approximately equal to or less than the temperature of the liquid refrigerant infood freezer 301. Liquid refrigerant entersheat exchanger 318 throughpipe 319 and exits throughpipe 329. The supercooled liquid then flows throughpipe 321 to filter 322 where crystalized foreign materials principally water are removed before the refrigerant flows intopipe 323 topressure reducing valve orvalves 324. In usual refrigeration systems a pressure reducing valve such as 324 reduces the temperature and pressure directly from that at the discharge ofheat exchanger 314 to that in the body of thefood freezer 301. This reduction in temperature may result in crystalization of water in the reducing valve causing erratic operation. The above described supercooling arrangements for the refrigerant liquid before pressure reduction eliminates this possibility. After pressure reduction in throttlingvalve 324, liquid refrigerant flows throughpipes 325 and 308 to main body offreezer 301.

A stream of noncondensed gases is passed fromheat exchanger 314 through pipe 324' toheat exchanger 325. Inheat exchanger 325 the noncondensed gas is placed in heat exchange with R-l2 entering throughpipe 326 and exiting through 327 at a pressure near or below atmosphere such that the noncondensed gases entering at 324 are stripped of condensibles to a temperature equal to or below that of the liquid refrigerant in the main body of thefood freezer 301. The condensed liquids primarily R-l 2 pass through pipe 328 to filter 329 where crystalized or solidified materials such as water are removed thence throughpipe 330 toexpansion valve 331 where the pressure of the liquid is reduced, the liquid being returned throughpipe 332 andpipe 308 to the main body of thefreezer 301.

An uncondensed flow of gas including refrigerant and contaminants principally air exits fromheat exchanger 325 through pipe 333 to oil free compressor 334 where the gas is compressed to a considerably higher pressure. After compression the gas passes through pipe 335 toheat exchanger 336 where the contaminated high pressure gas is placed in heat exchange with R-l2 entering throughpipe 337 and exiting throughpipe 338 at approximately atmospheric pressure or below which cools the uncondensed gases to a temperature approximately equal that of the liquid refrigerant in the main body offreezer 301 or below. R-l2 is liquified inheat exchanger 336, exits throughpipe 339 to filter 340 throughpipe 341, throughpressure reducing valve 342, topipe 343 andpipe 308 to the main body of thefreezer 301. A stream of noncondensed gas principally air is exited from the top ofheat exchanger 336 throughpipe 344 to inletpressure control valve 345 to exit pipe 346 either to atmosphere or to an additional purification device for removal of the small amount of R-12 still contained in this exit gas.

A stream of liquid refrigerant is removed fromstorage reservoir 303 throughpipe 347 toboiler condenser 348 where it is placed in heat exchange with a stream of gaseous refrigerant flowing throughpipe 313 and pipe 349. In theboiler condenser 348 the liquid is evaporated for purification and returned to the main refrigeration system throughpipe 350, the impurities being retained in the boiler and eventually being discharged throughpipe 352,valve 353 to exit 354. The gaseous refrigerant entering through pipe 349 is condensed inboiler condenser 348; noncondensibles exiting throughpipe 350 andcontrol valve 351. Condensed gaseous refrigerant enteringboiler condenser 348 through 349 is returned throughpipe 357, throttlingvalve 358 andpipe 359 torefrigerant storage container 303.

A preferred embodiment of this invention has been described, but it is understood that other similar arrangements can be used for purifying and recondensing the refrigerant. One alternate system includes the elimination ofheat exchanger 318 and providing an additionalrefrigerant throttling valve 356 inline 325. This provides two levels of temperature and pressure in the refrigerant since it is not supercooled byheat exchanger 318, a quantity of liquid refrigerant will flash in each of the throttling valves to provide the refrigeration necessary to cool the discharged liquid to a temperature corresponding to the pressure existing at the discharge of the throttling valve. The flash gas present between theexpansion valves 324 and 356 might be returned interstage tocompressor 312 thereby reducing somewhat the work required for compression.

In the operation of this invention unfrozen comestibles are introduced through a sealing means to the main body of the sealedfreezer 301 in which it is frozen and exited to storage. Freezing is effected in the main body of the freezer by direct contact with a stream and- /or sprays of liquid refrigerant. The comestibles are frozen and an amount of heat is transferred from the comestibles to the refrigerant causing evaporation of the refrigerant. In addition certain substances such as surface oils or cooking oils are dissolved by the liquid refrigerant and circulated with it. The gaseous refrigerant in the freezer becomes contaminated primarily by air which leaks past the seals, is carried by the incoming product or leaks in through inadvertent openings in the casing of thefood freezer 301. To provide a satisfactory continuous operation of such a freezer, these contaminants must be removed and the gasified refrigerant must be reliquified for return to the circulating main body of refrigerant infreezer 301. The evaporated gas removed from the main body of thefreezer 301 exits throughpipe 309 and carries with it a small amount of food material as well as some ice crystals formed as a result of the entrance of water vapor into thebody 301 of the freezer, associated with the entering comestibles or the air inadvertently leaking into the freezer. These food particles and ice crystals are removed infilter 310. The gas remaining passes throughpipe 311 to oilfree compressor 312 where it is compressed, passing throughpipe 312 toheat exchanger 314 which is cooled by water on the opposite side of the heat exchanger surface with respect to the gas stream. A major portion of the refrigerant is condensed in this heat exchanger and returns throughpipe 317 toheat exchanger 318 where it is cooled to a temperature approximately that of or below the temperature of the liquid refrigerant in thefood freezer 301. When the condensed liquid refrigerant is supercooled with respect to its existing pressure and temperature, dissolved water insoluble at that temperature is converted to particles of ice which pass throughpipe 321 to filter 322 where they are removed along with any other solid particles which might be contained in the liquid at that point. The filter liquid refrigerant passes throughpipe 323,pressure reducing valve 324 where it is reduced in pressure, but not in temperature, to at least the pressure and temperature of liquid infreezer 301. By this process there is no formation of ice cyrst als in the throttlingvalve 324 thus it is not plugged or affected by a deposit of ice which would occur if the pressure reduced liquid were not supercooled prior to the valve. A noncondensed stream of gas containing refrigerant and air exits fromheat exchanger 314 throughpipe 324 to anadditional heat exchanger 325 where it is cooled in a heat exchange with R-l2 refrigerant at approximately or below atmospheric pressure. This reduces the temperature of the gas entering throughpipe 324 and an additional quantity of refrigerant is condensed exiting through pipe 328 in a supercooled condition with respect to its pressure. It is filtered infilter 329 to remove crystalized particles of water or other solids, exited throughpipe 330 topressure reducing valve 331 for return to thefreezer 301 throughpipes 332 and 308. As before the supercooling of the liquid refrigerant inheat exchanger 325 and the filtering of the liquid refrigerant infilter 325 prevents the formation of solids incontrol valve 331 thus insuring reliable operation. A stream of gas containing considerable R-12 is uncondensible at the pressure and temperature ofheat exchanger 325 and passes out through pipe 333 to oilfree compressor 354 where it is additionally compressed. Exiting through pipe 335 it is cooled inheat exchanger 336 approximately to or below the temperature of the liquid refrigerant in the body offreezer 301. The liquid refrigerant exiting throughpipe 339 is supercooled with respect to its pressure and may contain particles or other solid material which is filtered out byfilter 340. The fluid being passed throughpipe 341 to pressurecontrol valve 342 is exited throughpipe 343 tofreezer body 301. A stream of gas noncondensible at the pressure and temperature inheat exchanger 336 is removed from the top portion of theheat exchanger 336 throughpipe 344 and discharged through inletpressure controlling valve 345 and exit 346 either to atmosphere or to a purification device where additional R -l 2 may be removed for return tofreezer 301.

In order to purify the liquid refrigerant in freezer which may have picked up oils or the like a stream removed throughpipe 305 filtered throughfilter 302 passes throughpipe 306 tostorage container 303 and is removed throughpipe 347 to aboiler condenser 348 where it is evaporated in heat exchange with a stream of warm gas entering through pipe 349 which is condensed while evaporating the liquid entering throughpipe 347. The non-evaporated liquid impurities entering throughpipe 347 are withdrawn from time to time throughpipe 352 andvalve 353 to exit 354 while any non-condensed gases enteringboiler condenser 348 through pipe 349 are exited throughpipe 355 andpressure control valve 351. Liquids condensed inboiler condenser 348 from entering gas stream 349 are returned throughpipe 357, throttlingvalve 358 andpipe 359 to therefrigerant storage tank 303.

An alternate arrangement is to pass the gases exiting from compressor 334 through dot and dashline circuit 360 to pipe 349 instead of having gases from pipe 349 picked up frompipe 313. In this case theboiler condenser combination 348 would provide the function ofheat exchanger 336, throttlingvalve 342 andpressure control valve 345.

In FIG. 8 is shown a conveyor 461 adapted to carry liquids or a flowable mixture of liquids and solids. The conveyor formed bybottom portion 467 andside portions 470 has formed in the bottom channelizing paths 463 beginning in the relativelysmooth portion 467 atpoints 465. The conveyor may be operated as a stationary device, or to enhance the formation of discrete food portions the conveyor may be pulsated or vibrated as byarms 468 attached to the conveyor 461 bypins 469.Arms 468 may be driven in a pulsating manner by conventional mechanical, hydraulic or magnetic vibratmg means.

Referring to FIG. 8 conveyor 46] is adapted to carry solid foods associated with liquid such as fruits in syrup,

solid foods in their own juices or liquid foods such as soups or juices such foods herein described as flowable foods. All of these foods may be frozen in individual separate pieces by discharging them in relatively small streams into contact with flow R-l2 or by spraying them with R-12 refrigerant as they fall from a channelizing element such as shown in FIG. 8. Various other configurations or channelizing such as dividing a single pipe into mulitple pipes may also be used; the essential point being that the flowable foods must be delivered in relatively small streams such that surface tension will break up the streams into discrete portions. The flowable foods introduced into the bottom of conveyor 461 are broken up in this manner by channels 463 beginning at thepoints 465 in thebottom 467 of the food conveying duct 461. The duct or conveyor may be open or closed at the top and may have an inclination suitable for forming the flowable food materials into discrete streams; a steep slope may be required for more viscous fluid conglomerates.

In order to promote the formation of discrete liquid portions of flowable foods it is desirable to create a pulsing flow. In FIG. 8conveyor 460 may be pulsed through arms througharms 468 acting throughpins 469. Other methods of pulsating may also be used including flow interrupting means inconveyor 460 and flow variation means in the channel feeding liquid to theconveyor 460.

FIG. 9 is a schematic drawing ofa direct contact food glazing system.Conveyor 446 is formed bybottom portions 458 andside Portions 460 and 462. Frozen food pieces from the earlier described direct contact freezer are fed through chute 33 of FIG. 1 intoconveyor 446, FIG. 9, where they are transported to dischargeedge 456 by oscillations supplied throughsupport oscillating arms 464 connected to the conveyor through pins 466.Longitudinal slots 450 are formed in theconveyor bottom 458 of a width to retain passing food pieces but to pass glazing water sprayed frommanifold 452 to contact food carried byconveyor 446.Heating element 447 and 448 are energized by electrical means (not shown) or by flowing warm fluids and are adpated tomaintainer conveyor 446 at just over 32 F so that no ice will be formed on theconveyor 446. Water sprayed frommanifold 452 also is maintained at a temperature just over 32 F. In order that no excess heat may be transferred to the food pieces normally arriving at the conveyor at a temperature of F, and forms an ice layer on the food pieces as a result of the heat extracted from the 32 F water by the lower temperature 0 F food pieces.

In operation of the apparatus of FIG. 9 frozen food pieces are retained inside theconveyor 446 bybottom portions 458,side portions 460 andback portions 462. Frozen food pieces delivered to this conveyor, resting above theslots 450, are sprayed bywater 454 being projected fromspray manifold 452. The water sprayed over the food frommanifold 452 is maintained at a temperature very close to but just above 32F so that it will transfer a minimum amount of heat to the frozen 22 food pieces being carried byconveyor 446. The food pieces delivered to 446 would normally be at a temperature of approximately 0 F; consequently, when they contact water at about 32 F, a film of ice is formed on the exterior of the food pieces. This is highly desirable in cases where a water seal preventing dehydrationand deterioration of food pieces is desired or in cases where the liquid surrounding a food piece contains a solution of liquids and solvents such as a sugar syrup or in fruit juice containing sugars and other material in solution with water. In such cases differential freezing occurs, the first frozen crystals being essentially pure water and the final ice formed carrying a higher content of sugar or other materials in solution in the water. The resulting outside ice formed freezes at a much lower temperature than water and in some instances may retain a sticky characteristic which would cause the food pieces to agglomerate when stored. By encasing the final frozen pieces in a shell of ice, as hereinabove set forth a non-sticking surface can be created which will provide for good storage characteristics with no adhesion or freezing between food pieces during storage at the normal storage temperatures of around 0 F. In order to prevent ice buildup on theconveyor 446,side heating elements 448 and bottom heating elements 447 make contact with the conveyor. These heating elements may be electric resistance devices or they may be circulated fluid devices connected to a source of heated liquid of appropriate flexible tubing (not shown).Conveyor 446 is carried and oscillated byarms 464 attached toconveyor 446 bypins 466. These arms are activated by conventional pneumatic, hydraulic electrical or mechanical vibrating devices to provide a constant vigorous motion ofconveyor 446. This motion providing a vigorous agitiation of food pieces being carriedbyconveyor 446 such that the food pieces are only momen tarily in contact with each other, thus preventing the food pieces from freezing together. Excess water flows out ofconveyor 446 throughlongitudinal slots 450 in theconveyor bottom 458. These :slots are sufficiently narrow to retain the food, but allow the excess water delivered fromspray manifold 452 to be drained away from the conveyor for recirculation.

What is claimed is:

1. A method of freezing food portions in a direct contact food freezer comprising the steps of introducing said food portions into a freezing compartment, contacting said food portions with a boiling liquid refrigerant, having a boiling point at 1 atmosphere higher than -50 F. to freeze said food portions, discharging said food portions from said freezer, receiving said food portions in a substantially impervious container and recovering the gaseous refrigerant from said container to said food freezer, said container being in releasable sealed relationship with said food freezer.

2. The method of direct contact food freezing as specified inclaim 1 in which the said receiving container is a substantially impervious pliable container.

3. The method of direct contact food freezing as specified inclaim 1 in which the said container has a smaller internal volume when containing no food portions than when at least partially filled with food portions.

4. The method as specified inclaim 1 including the additional step of returning said recovered gaseous refrigerant to said freezer.

5. The method as sepcified inclaim 1 including the additional step of purifying said recovered gaseous refrigerant subsequent to said recovering.

6. The method as specified inclaim 1 wherein said recovering of said gaseous refrigerant is by withdrawing the gaseous refrigerant from said container at a location below the horizontal centerline of said container.

7. The method as specified inclaim 6 including the additional step of admitting to said container at a location above said horizontal centerline a gas having a lesser density than said gaseous refrigeration, while simultaneously withdrawing said gaseous refrigerant.

8. The method as specified inclaim 11 wherein said discharging is into a substantially impervious sealed food storage zone and including the additional step of recovering excess gaseous refrigerant from said storage zone.

9. The method as specified inclaim 8 wherein said recovering of said excess gaseous refrigerant is by withdrawing said excess gaseous refrigerant from said storage zone al a location below the horizontal centerline of said container while simultaneously admitting to said storage zone at a location above said horizontal centerline a gas having a lesser density than said excess gaseous refrigerant.

10'. The method as specified inclaim 8 including the additional step of purifying the excess gaseous refrigerant subsequent to said recovering.

11. A method of freezing food in a direct contact food freezer comprising the steps off: introducing said food into a freezing compartment by hydraulic sealing means including a liquid barometric seal; subsequent to said introducing contacting said food with a liquid refrigerant having a boiling point at one atmosphere higher than 50 F to freeze said food; simultaneously with said introducing and said contacting maintaining a separation between said liquid refrigerant and said hydraulic sealing means; and discharging said food from said freezing compartment through an exit adapted to seal at least a major portion of the gasified refrigerant within said food freezer.

12. A method of freezing food in a direct contact food freezer specified inclaim 11 in which the said food includes food portions in liquid; the said hydraulic sealing means includes a conveying liquid in an enclosed flow path and including the additional step of removing said conveying liquid from said direct contact food freezer through a second barometric seal.

Claims (12)

1. A method of freezing food portions in a direct contact food freezer comprising the steps of introducing said food portions into a freezing compartment, contacting said food portions with a boiling liquid refrigerant, having a boiling point at 1 atmosphere higher than -50* F. to freeze said food portions, discharging said food portions from said freezer, receiving said food portions in a substantially impervious container and recovering the gaseous refrigerant from said container to said food freezer, said container being in releasable sealed relationship with said food freezer.

2. The method of direct contact food freezing as specified in claim 1 in which the said receiving container is a substantially impervious pliable container.

3. The method of direct contact food freezing as specified in claim 1 in which the said container has a smaller internal volume when containing no food portions than when at least partially filled with food portions.

4. The method as specified in claim 1 including the additional step of returning said recovered gaseous refrigerant to said freezer.

5. The method as specified in claim 1 including the additional step of purifying said recovered gaseous refrigerant subsequent to said recovering.

6. The method as specified in claim 1 wherein said recovering of said gaseous refrigerant is by withdrawing the gaseous refrigerant from said container at a location below the horizontal centerline of said container.

7. The method as specified in claim 6 including the additional step of admitting to said container at a location above said horizontal centerline a gas having a lesSer density than said gaseous refrigeration, while simultaneously withdrawing said gaseous refrigerant.

8. The method as specified in claim 11 wherein said discharging is into a substantially impervious sealed food storage zone and including the additional step of recovering excess gaseous refrigerant from said storage zone.

9. The method as specified in claim 8 wherein said recovering of said excess gaseous refrigerant is by withdrawing said excess gaseous refrigerant from said storage zone at a location below the horizontal centerline of said container while simultaneously admitting to said storage zone at a location above said horizontal centerline a gas having a lesser density than said excess gaseous refrigerant.

10. The method as specified in claim 8 including the additional step of purifying the excess gaseous refrigerant subsequent to said recovering.

11. A method of freezing food in a direct contact food freezer comprising the steps of: introducing said food into a freezing compartment by hydraulic sealing means including a liquid barometric seal; subsequent to said introducing contacting said food with a liquid refrigerant having a boiling point at one atmosphere higher than -50* F to freeze said food; simultaneously with said introducing and said contacting maintaining a separation between said liquid refrigerant and said hydraulic sealing means; and discharging said food from said freezing compartment through an exit adapted to seal at least a major portion of the gasified refrigerant within said food freezer.

12. A method of freezing food in a direct contact food freezer specified in claim 11 in which the said food includes food portions in liquid; the said hydraulic sealing means includes a conveying liquid in an enclosed flow path and including the additional step of removing said conveying liquid from said direct contact food freezer through a second barometric seal.

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