US 3768272 A
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.
Claims available in
Description (OCR text may contain errors)
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 of Search 62/64, 63, 266, 60, 62/374 References Cited UNITED STATES PATENTS Bottoms 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 SHEET BF 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 transporting conveyor 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 a water 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 from catch portion 2 to the primary conveyor system. The comestibles travel along the shaking conveyor 1 to a discharge point 3 through a relatively sealed opening 4 in an insulated shell 35 surrounding a main freezer body 5. This sealing portion 4 is provided to minimize the entry of water vapor from the conveyor area into the main body of the freezer 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, the fall 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 the main body 5 flows out through a pipe 8, a pump 10, a control valve 11, an inlet pipe 12 and sealing 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 by arrows 38 to enter the: main freezing 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 a sloping bottom portion 16 and its velocity can be maintained by inclination of the slope portion 16 with respect to the horizontal high velocity stream 15 across the width of the main freezing body 5 and provides an area into which the comestible particles or portions 17 may fall without touching the sides of the main freezing body 5 or the bottom of the stream 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 the low velocity portion 18 of the main 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 across low velocity zone 18 as shown by the arrows 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 the main 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 the low 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 a frame 21 which is driven in a circular path by suitably powered, synchronized rotating elements 22 having a pin portion 23 attached to rotating elements 22 associated with bearing portion 24 connected to frame 21, all portions of the frame and rake assembly travel in an orbital path similar to that traveled by pin 23. This is illustrated by a bottom point 25 on one of the rakes 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 through zone 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 in flow zone 18. All points on all rakes have a similar orbit. Thus the comestibles can be gently urged through flow 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 low velocity 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 the main freezer portion 18 to the refrigerant 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 or filter portion 30 into a pipe 31, through a storage tank 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 by valves 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 the freezer 5 is encased in a continuous sealed housing 35 preferably made of metal so that air or water vapor may not enter into the main 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 in housing 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 shaking conveyor 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 through pipe 8, pump 10 and pipe 12 to equalizer chamber 13, out of equalizer chamber 13 through orifice 14 along sloped high velocity flow path 16 into low velocity chamber 18 past upward sloping bottom 26 to high velocity exit stream 27 through the perforated bottom of exit conveyor 28 through filter 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 freezing area 18 and a high velocity transport means at 27 for the comestibles as they exit the freezer.
The comestibles are dropped a short distance from conveyor 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 the freezer body 35 or the bottom of the flow 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 in zone 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 the channel 5 and aimed sprays in the low 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 in zone 18.
The flow rate in this zone 18 is controlled by adjustment of a regulating valve 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 exit conveyor 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 through freezer 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 reach conveyor 28. This retained heat is sufficient to boil off any refrigerant remaining on the comestibles as surface wetness after draining in conveyor 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 freezing chamber 35 pump is stopped, a drain valve 36, communicating between zone 18 and the storage tank 7, is opened and the fluid refrigerant will drain into tank 7, pipe 12, pump body 10 and pipe 8. At this time 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 with valves 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 from chamber 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 the zone 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 the main body 103 of the refrigerator. The flow of water and suspended comestibles is carried through pipe 101 and is discharged on conveyor 104, in a closed compartment 107 the bottom of which has an upward slope to the main body 103 of the refrigerator. The conveyor 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 the freezer 103. The water separated from the comestibles by conveyor 104 is discharged through pipe 105 and a barometric seal 106. Barometric seal 106 is effective to prohibit passage of gas into or out of freezer body 103 through the water return system. Compartment 107 is constructed to completely enclose conveyor 104 and seal the area except for the entering stream of water and comestibles, the discharge stream of water and the channel connecting the conveyor 104 with the freezer body 103. The main body of the freezer 103 contains a bath 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 an outlet chute 108. The outlet 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 or bag 11 1 with the frozen comestibles, nor can outside air or other contaminates leak into the chute 108 to reach the main body of the freezer 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 to chute 108, to flow into bag 111, the system remaining at all times in a sealed condition.
As the comestibles are frozen in liquid 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 cooling coils 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 circulating pump 116, pumping excess quantities of liquid ammonia through pipe 117, heat exchanger 115 and pipe 1 18 back to level 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 by pipe 120 and evaporated ammonia gas is discharged through pipe 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 from level control chamber 119 insures that the boiled off R-l2 from bath 113 and/or sprays 114 can always be condensed and that no excess pressure will build up in the main body of the freezer 103 which might cause leakage through the containing walls 122, through the barometric seals 102 and 106, through the plastic container clamping seal 112, or through the plastic container 111 by reason of rupture.
Pressure control in freezer body 103 may be accomplished by a number of means all correlated to sensed pressure in freezer body 103.
from chamber 119. Flow control valve 71 is responsive to pressure sensing means sensing the pressure in freezer body 103. With a pressure decrease in freezer body 103, sensor 70 effects a closure of valve 71 at a rate responsive to the rate of and/or the pressure decrease in freezer body 103. Closure of valve 71 results in an increase in pressure in the ammonia in exchanger 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 in freezer 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 the refrigerator 103 through exit pipe 123 to filter 124 where solid entrained particles are removed. The refrigerant continues through pipe 56 to pump 125 and pipe 127 back to the body of the refrigerator 103 and also to spray manifolds 114. A controlled side stream to be further purified is removed from pipe 127 through pipe 126, through throttling valve 128 and pipe 129 to liquid purifier body 130, see FIG. 2. In purifier body 130 this stream of fluid is in heat exchange with a condensing flow of gas inside heat exchanger 147. The flow of liquid through the throttling valve 128 is adjusted so that all of the fluid entering purifier 130 can be vaporized. The boiled off gas passes out of purifier 130 through pipe 131, valve 132 and pipe 133 to the main body of the refrigerator 103. Condensibles remain in the body of purifier 130 and from time to time as required valve 128 is closed and contained R-l2 fluid in the main body of purifier 130 is boiled off, valve 132 is then closed and the remaining Condensibles in purifier body 130 are drained out through pipe 57, valve 58 to waste. Cleaning solutions may be introduced through pipe normally closed valve 61 and pipe 62 to flush out remaining contaminants and sediments from the body of purifier 130.
There will be some contamination by air and water vapor of the gas at the top of the body of the freezer 103, FIG. 4. These gases will be principally concen- 1. By controlling the flow of R-l2 from chamber 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 to heat exchanger 115.
4. By adjusting the pressure of the NI-I in the heat exchanger 115 and thus the boiling temperature of the NH;, in the heat exchanger.
A preferred means of controlling pressure in freezer body 103 is to provide a check valve 69 in the inflow ammonia line to prevent outflow of gas or liquid from ammonia level control chamber 119. A flow control valve 71 is installed in ammonia gas 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 the freezer 103 with respect to heat exhanger 115. These gases are conducted through pipe 135 to filter 136 of FIG. 2 where solid foreign materials as well as water crystals are removed. The gas then proceeds through a pipe 137 to the first stage 138 of oil free compressor 151, pipe 142 to the interstage cooler 139 of compressor 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 through pipe 143 entering the oil free compressor stages 144 exiting through pipe 145 to aftercooler 146. In aftercooler 146 the mixture of R-l2 and contaminants, principally air, having been compressed to approximately 400 PSlA by the last stage of compressor 144 is cooled in heat exchange with a stream of water entering through pipe 63 and exiting through pipe 64 and flow control valve 65. Flow control valve 65 is governed by level sensor 66 associated with the level 148 of the boiling liquid in purifier 130. The partially cooled gas from aftercooler 146 exits through pipe 67 and enters the inside of heat exchanger portion 147 located in the body of purifier 130. In this heat exchanger the condensible gas is liquified and flows out through pipe 68 to separating chamber 149 along with gas that has not been condensed. Liquid direct contact refrigerant is removed from separation chamber 149 in a controlled manner by level control valve 50 and enters pipe 52 for return to the main body of refrigerant in pipe 127 or in refrigerator body 103. Non-condensible gas is vented from the separating chamber through pipe 53 constant pressure regulator 54 and pipe 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 in purifier 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 constant inlet pressure valve 54 is set at 400 PSIA gas can only reach this pressure and exit through valve 54 given adequate heat exchange in heat 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 regulating valve 54 to waste.
In this manner the boiling refrigerant contained in the freezer is purified by filter 124, by condensing the condensibles in purifier 130 and separating the R-l2 from air in the heat exchanger 147 of purifier 130. Heat transfer in purifier 130 is balanced by control of the fluid level 148 in purifier 130 through appropriate linkage of .level control 66 and valve 65 controlling the cooling water flow through aftercooler 146 and control of refrigeration liquid inlet flow by adjustable 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 the refrigerant bath 113 in freezer 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 the freezer 103. In the operation of this invention comestibles are delivered in pipe 101 through barometric seal 102, which effectively seals the inflow circuit, to conveyor 104 where the major portion of water is removed through the perforated bottom and returned through pipe 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 from conveyor 104 and compartment 107 through relatively restricted opening 73 into the main body of the freezer 103 where they are sprayed with refrigerant from manifolds 114 and/or put in contact with a main body of liquid refrigerant 1 13 for freezing. After removal from the main body of refrigerant 113 the comestibles are delivered by dewatering conveyor 157 here shown as an uphill vibrating or other mechanical conveyor to chute 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 to chute 108. Chute 108 is effectively sealed to a delivery container 111 preferably an impervious plastic bag tieing the plastic bag .around chute 108 or clamping it around chute 108. As a part of chute 108 a sealed valve 109 is provided which may be closed at the time a full container 1 11 would be removed and replaced by an empty container 111. When valve 109 is closed a pocket 110 is formed in chute 108 such that the outflowing comestibles from conveyor 109 may be contained at this point for the container changing period. When the new container 1 11 has been placed and sealed to chute 108, valve 109 is opened and the comestibles in pocket 110 as well as those in regular process through freezer body 103 are delivered to container 111. Chute 108, valve 109, seal 112 and container 111 thus effectively seal the outlet of the main freezer body 103 with respect to the surrounding air. All systems associated with circulation of liquid refrigerant 113, purification, recondensation and removal of the air from the vaporized liquid 1 13 are closed systems within themselves and thus act as effective seals between the main body of the freezer 103 and the outside ambient air. v
Overflow refrigerant removed by conveyor 157 is returned through pipe 123 to filter 124 where particles of ice, comestibles of foreign material is removed before the liquid progresses through pipe 56 to sealed pump 125 which delivers the main portion of circulating refrigerant through pipe 127 to the main body of refrigerant 113 in the freezer 103. A side stream is removed from pipe 127 through pipe 126 of FIG. 2 passing through throttling valve 128, which controls the amount of refrigerant flowing in the side stream, into the boiler portion of the boiler condenser 130. Here the side stream is vaporized by warm condensing gas flowing in heat exchanger 147 in such quantity that when the gas is fully condensed all of the refrigerant liquid entering in pipe 129 will have been fully evaporated, contaminants remaining. The boiled off gases pass out through valve 132 and pipe 133 to the main body of the freezer 103 in FIG 4. A stream of gas is removed from the main body 103 through intake 134 located remotely from the main body 103 with respect to heat exchanger 1 15 which continuously reliquifies boiled off refrigerant from liquid body 113 for return to liquid 145 to an aftercooler 146 where the compressed gas is put in heat exchange with water or other cooling medium entering through pipe 63 and exiting through pipe 64 and control valve 65. Control valve 65 operates in cooperation with liquid level sensing device 66 to con trol the flow of coolant to aftercooler 146 so that gas passing from the aftercooler 146 through pipe 67 to heat exchanger 147 will be liquified in heat exchanger 147 of boiler 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 through pipe 68 to separating compartment 149 where purified liquid refrigerant is withdrawn through pipe 52 by control device 50 to provide constant liquid level 51 in the control compartment 149. The remaining gas principally air is discharged through inlet pressure control valve 54 to atmosphere. Regulating valve 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 above curve 75 consists completelyof a gaseous mixture. If a temperature line of 100 F is followed horizontally across the sheet to the intersection with curve 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 in heat exchanger 147 by regulating valve 54 working in conjunction with compressor low and high states 138 and 144 respectively is 400 pounds per square inch absolute. The equilibrium point on the 400 PSIA curve at 21 F is point 74 corresponding to mixture of 15 percent R-l2 and 85 percent air. If the high stage of the compressor 144 delivers at least 400 PSIA of a mixture of R-l 2 and air containing more than 14 %percent R-l2, if valve 65 actuated by control device 66 provides proper temperature control of gas entering heat exchanger 147 through pipe 145, if exchanger 147 has enough heat transfer surface, and if the temperature in the liquid inside boiler condenser 130 is 2l F the condition of the gas exiting through pressure regulating valve 54 will be shown at point 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 to heat exchanger 147 in pressure and temperature. Under these conditions given adequate surface area in heat exchanger 147 an interrelation of controls between the meter valve 128 and level control valve 66 would insure that gas exiting through constant pressure 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 for heat exchanger 147 is furnished by the bath of refrigerant retained in boiler condenser 140 entering through control valve 128. Liquid entering boiler condenser 130 through pipe 129 is continuously vaporized or distilled in boiler condenser 130 and exited through valve 132 to pipe 133 to the main body of the freezer 103, FIG. 4. This process of distillation purifies the refrigerant entering at 129 and results in high boiling point constituents being retained in boiler condenser 130.
From time to time it is necessary to remove the contaminants accumulating in boiler condenser 130. Preferably this is done by closing throttling valves 128 and 65 (FIG. 3). At this time though not essential the exit pipe 55 from pressure regulator valve 54 would best be connected to the body of main freezer 103, FIG. 4, since no separation of air from refrigerant is occurring in 147. With warm gas flowing into 147 through pipe 67 the residual refrigerant in boiler condenser 130 is evaporated, the refrigerant passing as usual through valve 132 to pipe 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 through pipe 57 and valve 58. Flushing may be provided if desired through inlet pipe 60, valve 61 and pipe 62. After purging boiler condenser 130, valves 58 and 61 are closed, valves 128 and 65 are reopened and when boiler 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) and conveyor 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 by heat exchanger 115. This is particularly desirable since without close control of the refrigeration delivered by heat exchanger 115 there will be a variation in the pressure existing in the main body of freezer 103. A liquid boiling at a given temperature has a fixed vapor pressure over the liquid and an increase in heat introduced to liquid bath 113, by an increased comestible flow, results without a corresponding increase in refrigeration furnished by heat exchanger 1 15 in increased pressure in the main body of freezer 103. In the case of a decreased flow of comestibles there would be a corresponding requirement for decreased refrigeration in heat exchanger 115 if an under pressure is to be avoided in the main body of freezer 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 the freezer 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 through check valve 69 and pipe to a constant level reservoir 1 19.
The refrigerant being circulated from this reservoir through pump 116, pipe 117, heat exchanger 115 and pipe 118 back to the reservoir. Evaporated ammonia refrigerant would exit through pipe 118 along with the liquid to reservoir 119 returning to the primary refrigeration system through pipe 59, throttling valve 71 and pipe 121. A pressure sensing valve 70 extends through the walls of the main freezer body 122 and communicates to throttling valve 71 and change in the pressure inside freezer 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 this control system valve 71 is moved toward a closed position when a decrease of pressure is sensed at 70. As the boiling ammonia gas in heat 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 of freezer 103 by heat exchanger 115 is reduced. Other means of reducing the heat transfer of heat exchanger 115 might be reduction of refrigerant flow through the heat exchanger or restriction of the flow from the main body of the freezer 103 to heat 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 supporting elements 202 adapted to receive the fork means of a motorized lift truck (not shown). Storage container 201 is preferably lined with a plastic bag 203 which is sealed in generally gas tight relationship to a discharge duct 204 forming a gas tight flow path through which comestibles 205 are delivered into the main body of container 206. Sealing of plastic container 203 to duct 204 is effected by clamping device 207 which might be a rubber band or spring. Prior to attaching plastic bag 205 to discharge 204 flexible tubular means 208 is inserted to the bottom of plastic bag 203 contained in container 201. The exit portion of tubular member 208 is sealed or clamped by element 209. Tubular element 208 may be recessed into a cavity 210 of discharge duct 204 such that the end 211 of tubular member 208 projects outside of the plastic container. It would also be practical to support tubular member 208 by an attachment inside duct 204 so that it would be held above the final filling level 212 of the comestibles in the main body of container 203.
Referring now to FIG. 6 the plastic container 203 has been removed from discharge duct 204, the end 211 of tubular member 208 has been attached to an evacuating device 213 which could appropriately be a fan. Evacuating device 213 is connected to duct 214 which can deliver gas evacuated by device 213 either directly to the main body of a direct contact freezer 113 (see FIG. 4) or to a purifying device 215 in which the refrigerant may be separated from the gases delivered by evacuating device 213 through duct 214. As shown in FIG. 6 when plastic bag 203 is connected to the evacuation device 213, a relatively small opening 216 is left between the neck of the plastic bag and the tubular member 208 so that when the evacuating device 213 is operated a flow of gas (arrow 217) may enter the main body of the container 206.
Purifying device 215 is preferably an activated charcoal purifier having chambers 218 and 219 adapted to alternately receive unpurified refrigerant through duct 214. Valves 220, 221, 222, 223,. 224 and 225 are adapted to control the flow of refrigerant through the chambers 218 and 219 of purifier 215 alternately in a manner to provide continuous purification of refrigerant flowing in through duct 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 through duct 214 may pass through open valve 221 to chamber 218 for refrigerant collection. Valves 220 and 224 being closed. The contaminating gases of the refrigerant flowing in duct 214 being discharged through valve 223 to exit 226. Upon reversal of the cycle gases from duct 214 enter chamber 219 through valve 220, valves 221 and 225 being closed with gases. separated from the refrigerant stream being exited through valve 222 to exit 227. At alternate periods refrigerant retained in chamber 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 in chamber 219 is returned through valve 225 and exit 228 to the direct contact freezer system; valves 220, 222 and 224 being closed.
In the operation of this invention plastic container 203 in FIG. 5 is inserted in a collapsed minimal internal volume condition into structural container 201 and attached to duct 204 by clamping device 207. Tubular member 208 having been previously inserted into plastic container 203 with discharge end 211 emerging from the opening 229 in plastic container 203. The collapsed state of plastic bag 203 provides a minimal amount of air in the main body 206 of plastic bag 203 which air passes through opening 230 in discharge duct 204 to the main body of the freezer to which duct 204 is attached in sealing relationship. If an open noncollapsed container 203 is attached to duct 204 a considerable quantity of air will be contained in container 203 which on filling of container 203 will be displaced into duct 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 inside duct 204 or by passing between duct 204 and plastic bag 203 which is attached in sealing relationship to duct 204 by clamping device 207. It is necessary that tubular member 208 be thus retained in an accessible position with respect to the opening 229 in plastic bag 203 so that opening 211 of tubular member 203 may be attached to evacuating device 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 sealing device 209 so that refrigerant gas entering with the comestibles through duct 230 cannot escape through tubular member 208. Tubular member 208 when located between plastic bag 203 and discharge duct 204 is preferably recessed into a cavity 210 in duct 204 in order to provide adequate sealing of plastic bag 203 to duct 204 by sealing member 207. I
When plastic bag 203 supported in container 201 is filled to an appropriate level 212, sealing element 207 is loosened or removed and plastic bag'203 is detached from discharge chute 204. The end 211 of tubular member 208 is retained on the outside of neck 229 of plastic bag 203. As shown in FIG. 6 the neck or opening 229 of plastic bag 203 is held in position in proximity to tubular element 208 by an appropriate means. Tube 208 is connected at its end 211 to an evacuation device 213. Sealing or clamping device 209 is removed from tubular member 208 and when evacuation device 213 is activated a flow of dense refrigerant preferably R-l2 is withdrawn from the main body 206 of container 203. Air or other less dense gas enters opening 229 of the plastic bag 203 in stream indicated by arrow 217 in relatively restricted flow channel 216. The relatively restricted flow channel 216 and the relatively great difference in density prevents ready defusion of refrigerant to the air being admitted into the main body of the container 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 by evacuation device 213. In normal practice evacuation is continued until the greater portion of refrigerant in main body 206 is withdrawn by evacuation device 213. The period of operation of evacuation device 213 may be controlled by timing means or by means of an instrument sensing the percentage of refrigerant present and being withdrawn through tubular 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 the main body 206 of container 203 is discharged through duct 214 either directly to the direct contact freezer refrigerant system or to a purifying device 215. Purifying device 215 would preferably be a dual chamber activated carbon type. Gas from duct 214 on one half of the cycle entering through valve 220 to activated carbon chamber 219 in which chamber the refrigerant is retained by the activated carbon while the air or other gas present in the mixture entering through duct 214 would be discharged through valve 222 to exit 227. Valves 221 and 225 being closed at this time. At an appropriate time when the activated carbon in container 219 has approached its capacity with respect to the collection of refrigerant from the stream entering through duct 214; valves 220 and 222 are closed and valves 221 and 223 are opened so that the stream of entering refrigerant and other gas from duct 214 passes through valve 221 into purifying 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 in duct 214 are purified in chamber 218, the activated carbon in chamber 219 is being reactivated preferably by introducing stream into chamber 218 thereby raising the temperature of the activated carbon in chamber 219, recondensing the steam to water in condenser 231 while passing the separated refrigerant out through valve 225 and exit 228 to the direct contact freezer refrigeration system; valves 220 and 222 being closed during this process. For increased performance each purifier 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 for purifier chamber 219 is repeated in purifier chamber 218; valves 221, 223 and 225 being closed and valve 224 open. Steam condensation occurring in condenser 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 in duct 214 will be essentially pure refrigerant at the beginning of the operation of evacuation device 213 and after some period of operation of evacuation device 213, a decrease in refrigeration purity will be experienced due to mixing of air entering through flow channel 216 with the remaining refrigerant in main body 206 of container 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. 7 reference 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 through pipe 305 to filter 302, through pipe 306, to a storage compartment 303 through pipe 307 to pump 304 which returns the refrigerant through pipe 308 to the main body of the food freezer 301. The evaporated gaseous refrigerant being produced as a result of freezing comestibles in freezer 301 exits through pipe 309, through filter 310 and pipe 311 to oil free compressor 312. After compression in ocmpressor 312 to a desired level, the refrigerant progresses through pipe 313 to water or air cooled heat exchanger 314. Water entering said heat exchanger through pipe 315 and exiting through pipe 316. A major portion of the refrigerant is condensed in this heat exchanger and returns through pipes 317 to heat 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 in food freezer 301. Liquid refrigerant enters heat exchanger 318 through pipe 319 and exits through pipe 329. The supercooled liquid then flows through pipe 321 to filter 322 where crystalized foreign materials principally water are removed before the refrigerant flows into pipe 323 topressure reducing valve or valves 324. In usual refrigeration systems a pressure reducing valve such as 324 reduces the temperature and pressure directly from that at the discharge of heat exchanger 314 to that in the body of the food 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 throttling valve 324, liquid refrigerant flows through pipes 325 and 308 to main body of freezer 301.
A stream of noncondensed gases is passed from heat exchanger 314 through pipe 324' to heat exchanger 325. In heat exchanger 325 the noncondensed gas is placed in heat exchange with R-l2 entering through pipe 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 the food 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 through pipe 330 to expansion valve 331 where the pressure of the liquid is reduced, the liquid being returned through pipe 332 and pipe 308 to the main body of the freezer 301.
An uncondensed flow of gas including refrigerant and contaminants principally air exits from heat 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 to heat exchanger 336 where the contaminated high pressure gas is placed in heat exchange with R-l2 entering through pipe 337 and exiting through pipe 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 of freezer 301 or below. R-l2 is liquified in heat exchanger 336, exits through pipe 339 to filter 340 through pipe 341, through pressure reducing valve 342, to pipe 343 and pipe 308 to the main body of the freezer 301. A stream of noncondensed gas principally air is exited from the top of heat exchanger 336 through pipe 344 to inlet pressure 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 from storage reservoir 303 through pipe 347 to boiler condenser 348 where it is placed in heat exchange with a stream of gaseous refrigerant flowing through pipe 313 and pipe 349. In the boiler condenser 348 the liquid is evaporated for purification and returned to the main refrigeration system through pipe 350, the impurities being retained in the boiler and eventually being discharged through pipe 352, valve 353 to exit 354. The gaseous refrigerant entering through pipe 349 is condensed in boiler condenser 348; noncondensibles exiting through pipe 350 and control valve 351. Condensed gaseous refrigerant entering boiler condenser 348 through 349 is returned through pipe 357, throttling valve 358 and pipe 359 to refrigerant 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 of heat exchanger 318 and providing an additional refrigerant throttling valve 356 in line 325. This provides two levels of temperature and pressure in the refrigerant since it is not supercooled by heat 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 the expansion valves 324 and 356 might be returned interstage to compressor 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 sealed freezer 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 the food 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 in freezer 301. The evaporated gas removed from the main body of the freezer 301 exits through pipe 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 the body 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 in filter 310. The gas remaining passes through pipe 311 to oil free compressor 312 where it is compressed, passing through pipe 312 to heat 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 through pipe 317 to heat exchanger 318 where it is cooled to a temperature approximately that of or below the temperature of the liquid refrigerant in the food 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 through pipe 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 through pipe 323, pressure reducing valve 324 where it is reduced in pressure, but not in temperature, to at least the pressure and temperature of liquid in freezer 301. By this process there is no formation of ice cyrst als in the throttling valve 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 from heat exchanger 314 through pipe 324 to an additional 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 through pipe 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 in filter 329 to remove crystalized particles of water or other solids, exited through pipe 330 to pressure reducing valve 331 for return to the freezer 301 through pipes 332 and 308. As before the supercooling of the liquid refrigerant in heat exchanger 325 and the filtering of the liquid refrigerant in filter 325 prevents the formation of solids in control valve 331 thus insuring reliable operation. A stream of gas containing considerable R-12 is uncondensible at the pressure and temperature of heat exchanger 325 and passes out through pipe 333 to oil free compressor 354 where it is additionally compressed. Exiting through pipe 335 it is cooled in heat exchanger 336 approximately to or below the temperature of the liquid refrigerant in the body of freezer 301. The liquid refrigerant exiting through pipe 339 is supercooled with respect to its pressure and may contain particles or other solid material which is filtered out by filter 340. The fluid being passed through pipe 341 to pressure control valve 342 is exited through pipe 343 to freezer body 301. A stream of gas noncondensible at the pressure and temperature in heat exchanger 336 is removed from the top portion of the heat exchanger 336 through pipe 344 and discharged through inlet pressure controlling valve 345 and exit 346 either to atmosphere or to a purification device where additional R -l 2 may be removed for return to freezer 301.
In order to purify the liquid refrigerant in freezer which may have picked up oils or the like a stream removed through pipe 305 filtered through filter 302 passes through pipe 306 to storage container 303 and is removed through pipe 347 to a boiler 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 through pipe 347. The non-evaporated liquid impurities entering through pipe 347 are withdrawn from time to time through pipe 352 and valve 353 to exit 354 while any non-condensed gases entering boiler condenser 348 through pipe 349 are exited through pipe 355 and pressure control valve 351. Liquids condensed in boiler condenser 348 from entering gas stream 349 are returned through pipe 357, throttling valve 358 and pipe 359 to the refrigerant storage tank 303.
An alternate arrangement is to pass the gases exiting from compressor 334 through dot and dash line circuit 360 to pipe 349 instead of having gases from pipe 349 picked up from pipe 313. In this case the boiler condenser combination 348 would provide the function of heat exchanger 336, throttling valve 342 and pressure 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 by bottom portion 467 and side portions 470 has formed in the bottom channelizing paths 463 beginning in the relatively smooth portion 467 at points 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 by arms 468 attached to the conveyor 461 by pins 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 the points 465 in the bottom 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. 8 conveyor 460 may be pulsed through arms through arms 468 acting through pins 469. Other methods of pulsating may also be used including flow interrupting means in conveyor 460 and flow variation means in the channel feeding liquid to the conveyor 460.
FIG. 9 is a schematic drawing ofa direct contact food glazing system. Conveyor 446 is formed by bottom portions 458 and side Portions 460 and 462. Frozen food pieces from the earlier described direct contact freezer are fed through chute 33 of FIG. 1 into conveyor 446, FIG. 9, where they are transported to discharge edge 456 by oscillations supplied through support oscillating arms 464 connected to the conveyor through pins 466. Longitudinal slots 450 are formed in the conveyor bottom 458 of a width to retain passing food pieces but to pass glazing water sprayed from manifold 452 to contact food carried by conveyor 446. Heating element 447 and 448 are energized by electrical means (not shown) or by flowing warm fluids and are adpated to maintainer conveyor 446 at just over 32 F so that no ice will be formed on the conveyor 446. Water sprayed from manifold 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 the conveyor 446 by bottom portions 458, side portions 460 and back portions 462. Frozen food pieces delivered to this conveyor, resting above the slots 450, are sprayed by water 454 being projected from spray manifold 452. The water sprayed over the food from manifold 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 by conveyor 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 the conveyor 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 by arms 464 attached to conveyor 446 by pins 466. These arms are activated by conventional pneumatic, hydraulic electrical or mechanical vibrating devices to provide a constant vigorous motion of conveyor 446. This motion providing a vigorous agitiation of food pieces being carried byconveyor 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 of conveyor 446 through longitudinal slots 450 in the conveyor bottom 458. These :slots are sufficiently narrow to retain the food, but allow the excess water delivered from spray 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 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 sepcified 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 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 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 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 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.