Patent Grant
12135149
Existing multi-stage refrigeration systems utilize multiple compressors and evaporators, with each stage employing a refrigerant having a lower boiling point, in a stage-cooling process for condensing and cooling the initial refrigerant. As an example, a refrigeration system using propane as a refrigerant could be used to cool an ammonia refrigerant, which can then be used to cool natural gas. These refrigeration systems are often placed out-of-doors, because of the volume of refrigerant employed. When used indoors, fire regulations limit the quantity of flammable refrigerant to less than 500 lbs., which must be accompanied by fire suppression, gas detection, and gas exhaust systems, as basic equipment. Further, all electrical devices must be switched on and off using remote shunt switches to avoid sparks.
Use of carbon dioxide requires large quantities of the liquid, and use in enclosed areas requires CO2 gas detection devices and alarms. The vapor pressure of liquid CO2 requires high-pressure capable piping since the vapor pressure of CO2 at room temperature (20° C.) is 826 psi. Liquid nitrogen can also be used for cooling, but cost and handling procedures make it prohibitive on a large scale.
In accordance with the purposes of embodiments of the present invention, as embodied and broadly described herein, the device heating and cooling system, hereof, includes: a compressor for generating superheated vapor from a refrigerant; a condenser for receiving superheated vapor, for removing heat from the superheated vapor, and for generating a liquid refrigerant therefrom; and at least one sub-cooler, including: a first chamber having a first outer surface, a top and a bottom, enclosing a core volume; a second chamber surrounding the first outer surface of the first chamber having a second outer surface, a top and a bottom, forming a second volume; a first valve for filling the second volume with refrigerant from the core volume; and a first manifold for directing cooled refrigerant in the core volume to devices to be cooled.
In another aspect of embodiments of the present invention, and in accordance with their purposes, an embodiment of the method for heating and cooling devices, hereof, includes: generating superheated vapor by compressing a refrigerant; removing heat from the superheated vapor, whereby a liquid refrigerant is generated therefrom; and filling the core volume of a chamber with liquid refrigerant; filling a second volume of the chamber surrounding the core volume and in thermal communication therewith with liquid refrigerant; vaporizing the liquid refrigerant in the second volume of the chamber into the inlet of a compressor, whereby the refrigerant in the core volume is cooled; and directing cooled refrigerant in the core volume to devices to be cooled.
Benefits and advantages of the present invention include, but are not limited to, providing an apparatus and method for heating and cooling devices where it has been confirmed that the system uses less power the lower the pressure becomes and the colder the system gets. Further, by reintroducing refrigerant at or near the temperature of evaporation, the operating pressure does not increase upon injection of liquid into the second evaporator, and therefore does not increase the amount of work performed by the compressor.
The accompanying drawings, which are incorporated in and form a part of the specification, illustrate the embodiments of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings:
Briefly, embodiments of the present invention include apparatus and methods for heating and cooling a refrigerant that may also be used for chemical extractions requiring heating and/or cooling. As examples, suitable refrigerant/solvents are hydrocarbon solvents such as propane, butane, and isobutane, and mixtures thereof, and the chemical extractions may include extraction of cannabinoids. In operation, the refrigerant contained in the core of a jacketed container is cooled by depressurization and evaporation of a portion of the refrigerant contained in the jacket of the container. For improved heat transfer, the jacket may include tubing surrounding the core containing the refrigerant. The vapor resulting from the evaporation is directed to the inlet of a compressor for pressurizing the vapor, which is then passed through a condenser where heat is removed causing the high-pressure refrigerant vapor to transition to hot vapor, warm liquid, and cold vapor. An accumulation of low-pressure vapors, from other vessels being cooled, may also be directed to the compressor, often by first passing through a liquid-vapor separator.
Heat is generated by compression of the hydrocarbon refrigerant vapor to a state of super-heated vapor that can then be directed to the jacket of a vessel requiring heating. Other refrigerants, such as ammonia and freon, can be utilized for this process, but are not as useful as hydrocarbon solvents for chemical extractions. It should be noted that the solvent used for chemical processing, although potentially having the same identity as that utilized in the cooling and heating processes, is not used for both functions in the same apparatus, except in the situation where both functions are not separated. That is, the refrigerant used for heating and cooling can be used to heat and cool the solvent used for chemical processing. As examples, an extraction column, recovery basin, a wiped film evaporator and/or a rising/falling film evaporator may be heated to remove liquid solvent from crude extract material for solvent recovery by vaporization, as well as to raise the solvent temperature during the extraction process for increasing the solubility of the solvent. The refrigerant used for heating and cooling is recirculated, as may the solvent for the chemical processing, but in separate systems.
As stated, traditional multi-stage refrigeration systems utilize multiple compressors and evaporators to stage-cool the initial refrigerant. Embodiments of the present apparatus and method utilize the same hydrocarbon refrigerant for all stages, and one having the same identity as that employed for a chemical extraction process. A second refrigeration system, such as a glycol chiller or ethanol chiller, is therefore not required to cool the solvent by heat exchange prior to use; however, a condenser utilizing a glycol-water heat exchanger has been used to remove the majority of heat from the vapor directly exiting a compressor for condensing the solvent vapor prior to storage, or in preparation for further cooling, if it has not otherwise been consumed in the process.
After exiting the condenser, the liquified solvent still contains significant latent heat, which is removed by further cooling before injecting the liquid into a cooled vessel since the injected liquid would otherwise warm the vessel, thereby creating higher pressure and rendering the system less efficient. Therefore, the injected refrigerant is close to being as cold as the solvent in the vessel being chilled.
Thermal mass is related to the quantity of liquid refrigerant at a given pressure, as opposed to the quantity of vapor moving through the compressor, which tends to be small when the remaining volume of liquid is cold. As the liquid is removed from the jacket of a vessel being chilled in the form of a vapor, fresh liquid must be introduced in order to maintain chilling. Already chilled, fresh refrigerant is injected into the jacket so that the temperature of the refrigerant entering the jacket is close to the current temperature of the jacket. When refrigerant is injected into a low-pressure region already at low temperature, the pressure can be further decreased to achieve further chilling, and the same amount of solvent is used to operate the system, but less energy is required for chilling.
In accordance with embodiments of the present invention, a multi-stage system using the same refrigerant for all stages is employed. Because the solvents used for cannabinoid extraction, typically n-butane, iso-butane, or propane are also refrigerants (R290, R600, R600a), both functions are available, and the refrigerant may also be used as the solvent for the extraction process. Propane, when used at saturation (liquid and vapor in dynamic equilibrium), can attain temperatures as low as a few degrees above it's freezing point at −188° C. (−138° C. for butane). As a result, propane at saturation can be used to cool a warmer refrigerant to a point at which it is being injected at the temperature of operation, whereby the injected liquid maintains the liquid level within the system being cooled. The volume of refrigerant that needs to be at a specified pressure to maintain the desired temperature must be determined, along with the ability of the system to compress the vapor into a high-pressure, super-heated state, which can then lose heat to required heating functions, and ultimately condense into a liquid once past the saturated vapor point, thereby providing on-demand heat as needed.
After the initial condensation stage, a second condenser, defined as the sub-cooling condenser, is used to cool the refrigerant below that temperature obtained in the initial stage, in effect sub-cooling the refrigerant. The refrigerant is caused to flow from either end of a condensed refrigerant storage vessel (the condenser), if employed, into the either end of the sub-cooling condenser, and into the core thereof. The refrigerant exits through an outlet at the bottom of the condenser, where the remaining sub-cooled refrigerant may be directed to vessels that require cooling, such as the extraction columns, a portion of the refrigerant being directed into the volume inside the jacket of the condenser from the tubes forming the core through a valve, thereby permitting the refrigerant to surround the tubes of the sub-cooling condenser. A liquid-vapor separator, or oil separator, may be used to prevent liquid from entering the compressor. The output from the compressor is in fluid communication with a high-pressure vapor supply tube that directs the compressed refrigerant through a pressure differential valve before entering the first condenser, thereby forming a fluid loop, not required for refrigeration, but for heating only.
Refrigerant, after having been introduced into the extraction columns or other vessels being chilled, exits these vessels as a vapor and joins the vapor exiting the cooling jacket of the second and/or any subsequent sub-cooling condensers, before entering the compressor. In the situation where a liquid-vapor separator, or oil separator, is employed, the vapor passes through this apparatus as well. The internal pressure of the vapor within the sub-cooling condenser jacket and the columns being cooled, determine the vapor temperature. Since the vapor is being depressurized as it flows toward the compressor, a saturated liquid-vapor mixture is formed, which lowers the temperature of the remaining liquid and can absorb heat. By using a sub-cooled refrigerant, heat is not added to the work evaporator or sub-cooling columns, and the liquid level therein can be maintained without increasing the pressure in the system. A dedicated back-pressure valve is used to maintain pressure between the compressor outlet held between about 150 psi and about 300 psi, more typically about 250 psi, and the condenser inlet, typically held between about 50 psi and about 200 psi, most typically about 150 psi, when using propane as the refrigerant. This back-pressure zone provides on-demand heat to the columns when the liquid injection and vapor removal valves are closed, and the heat injection valve at the column to be heated or cooled is opened. This generates additional volume to be pressurized over that of the compressor outlet, which heat of compression can then be utilized at individual locations prior to condensing the refrigerant at the condenser once beyond the back-pressure valve, which when condensed and sub-cooled is used for maintaining the column liquid level. The back-pressure valve differential: (a) provides additional heat not otherwise present at the condenser; and (b) the heat from compression of the vapor is provided directly to each system to be heated. When the fluid pathway from the compressor outlet to the condenser inlet flows through each heated station in a series path, the hot vapor from the compressor performs the heating in a loop, since the tubing following the compressor outlet and pre-condenser inlet forms a vessel which is pressurized above that of the condenser, before any heat is removed, which then allows the column pressure to equalize with the compressor outlet pressure, thereby reducing the imbalance of heat provided to each system location. Pressurizable zones are thus formed in the tubing between the compressor outlet and the condenser inlet back-pressure valve by using individual valves, thereby avoiding dead-short conditions. The condenser back-pressure valve provides the pressure differential between the condenser and the compressor outlet, which then provides the on-demand heating capacity while simultaneously providing the on-demand cooling capacity. In accordance with the teachings of embodiments of the present invention, extraction columns can be both heated or cooled such that some may be hot and others cold at the same time.
Heat may also be generated in the columns requiring heat by closing the liquid injection valve and the vapor outlet valve to a column, while opening the hot vapor inlet valve thereto. This allows pressure to build within the head-space contained within the jacket volume, the pressure being related to the temperature within the pressurized volume of liquid within the column; that is, all of the liquid will have the same temperature. The vapor head-space will be slightly super-heated, typically around 1.5° C. to 2.5° C., beyond the saturated vapor point found at the liquid-vapor interface. The head-space receives the super-heat provided by the compressor at the outlet stage along the series path to the back-pressure valve since, without the flow of heated molecules across the volume they are entering, would be principally saturated vapor instead of super-heated vapor, which may become a problem when heating multiple columns within the system, since they are arranged in series with the compressor outlet to the condenser inlet provided that sufficient back-pressure has been achieved.
Embodiments of the present refrigeration system may be operated using a single compressor, which also operates the extraction system, or it can have a dedicated compressor for achieving lower operational temperatures and maximize solvent transfer with the primary transfer compressor. When utilizing a single compressor, the refrigeration process is performed independently of the extraction process, as the required inlet pressure will prevent high volume flow through the compressor. A first column jacket is chilled by the compressor by first filling the column, and subsequently using the compressor to decrease the pressure so that the temperature of the solvent/refrigerant in the jacket auto-refrigerates until the desired temperature is reached. The jacket inlet and outlet valves are then closed and the thermal capacity is provided by the cooled solvent/refrigerant and the cooled container holding the solvent, typically stainless steel, or other metal, or glass. This thermal energy absorbs heat from the system during the extraction process. As the thermal energy is absorbed by incoming solvent, the jacket temperature will increase as internal pressure builds within the jacket. To maintain a single compressor extraction, the extraction process will have to be stopped in order to re-chill the jacket system. Once the desired temperature is restored, extraction may continue, and lost time will be that required for cooling the jacket. It is possible to overcome this if the compressor is over-sized.
In other embodiments, the system may be operated using two compressors; one dedicated to the extraction process, whereby solvent transfer through the system is maximized, thereby speeding extraction; while the other compressor is dedicated to the thermal control system for providing the ability to both warm or cool a column on-demand. Typically, an extraction compressor is operated between about 10 psi and about 100 psi at the inlet, most typically, between about 50 psi and about 100 psi when utilizing propane as the solvent. This will maximize the solvent transferred through the extraction compressor while the thermal control compressor operates independently of the extraction system.
The vapor from either compressor outlet of a two-compressor embodiment (extraction compressor and refrigeration compressor) may be directed into a vessel or device for vaporizing solvent contained therein, such as a collection basin, a wiped/rolled film evaporator, a rising/falling film evaporator, or a centrifugal evaporator, as examples. This allows the heat of compression to be utilized for heating without a secondary heating system. The heat of compression can be utilized for evaporation of the process solvent by utilizing a back-pressure device that allows the compressor outlet to be at a higher pressure than that of the condenser inlet. Vapor which condenses within the system prior to the condenser, thereby reduces the work-load of the condenser upon depressurization into the condenser. The liquid self-cools by means of auto-refrigeration due to the pressure drop between zones. A portion of this liquid is thereby vaporized and becomes the work-load that the compressor must handle.
Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. In the Figures, similar structure will be identified using identical reference characters. It will be understood that the FIGURES are presented for the purpose of describing particular embodiments of the invention and are not intended to limit the invention thereto. Turning now to
After additional heat is removed, the refrigerant remaining in the core of sub-cooler 20, is directed to evaporator 24, where work can be performed upon refrigerant expansion using second expansion valve, 26. Second evaporator 24 is the primary heat exchanger for external work, whereas sub-cooler 20 removes heat from the remaining liquid refrigerant in condenser 16 before expansion through second expansion valve 26. That is, sub-cooler 20 removes additional enthalpy after refrigerant condensation (16) and prior to entering evaporator 24. This allows the liquid refrigerant to enter the second evaporator at or near the temperature of evaporation. Thus, the liquid level in the second evaporator can be maintained without: (a) introducing heat; or (b) decompressing introduced refrigerant, rendering refrigeration systems capable of operation at approximately 100% efficiency. After performing work, vapor, 32, exiting evaporator 24 may be combined with vapor 22 from sub-cooler 20 to enter the low-pressure inlet 13 of compressor 12.
In operation, the condenser has an open fluid pathway to the core of the sub-cooler, and all liquid exiting the condenser must first pass through the core of the sub cooler before being utilized elsewhere. Once the condensed liquid passes through the core of the sub-cooler, then it can be delivered to the work evaporator or sub-cooler second volume, the jacket or shell. In this manner, the liquid in the jacket is the initial source of cold, which then cools what is in its core. As vapor is removed from the jacket, the liquid level decreases and will eventually need to be replenished. Now that the liquid is cold and the subsequent liquid held in the core is also cold, core liquid is injected into the jacket so as to maintain liquid level. Upon this injection, because the liquid in the core is very close to or at the temperature of the jacket (from previous cooling cycle), very little or no pressure is introduced and its temperature can continue to decrease along with the temperature of the work vessel. At this point, the sub-cooler can maintain its own temperature and also supply liquid of the same temperature to the work evaporator. The second volume maintains a liquid level no different than the work evaporator and should be at least 20% full but preferably closer to 80% full in the outer jacket with liquid sourced from its core. A full sub-cooler can transfer a larger amount of subcooled liquid into the work evaporator or more rapidly to its own jacket, and will be closer to the temperature of evaporation at the work evaporator. In this manner, whenever liquid is refilled to an evaporator, minimal heat is introduced upon injection.
A portion of cooled liquid propane exiting from the bottom of sub-cooler 20 through fitting 46 is directed into outer shell, 50, of at least one evaporator/condenser 24 through fitting, 52. Multiple columns (N) may be employed, for example, for extractions of plant oils, in both heated and cooled modes by utilizing manifolds, 53a, and 53b, respectively, for this purpose, as illustrated in
In use, the temperature of the refrigerant entering sub-cooler 20 should be as close to or at the temperature of condensation at the experienced pressure, since the colder the solvent entering the sub-cooler, the less energy that will be required to maintain an exit temperature close to the temperature of evaporator 24.
Refrigeration/heating system 10 is described above, and utilizes compressor 12. Process system, 60, utilizes process compressor, 62, to heat at least one (N) extraction systems, 64, by directing hot vapor through fitting 54 into outer shell 50, and maintaining the pressure therein using valve, 67, or utility compressor 12 can cool at least one evaporator system 64, depending on the requirements of the extraction process. The extracted product would be separated from the solvent which would be returned to refrigeration system 10.
As stated above, refrigerant flows into the top of the sub-cooling condenser and into the core thereof. The liquid then exits from the bottom of sub-cooler whereby outlet 46 delivers a portion of the core liquid, which may be a sub-cooled liquid, to thermally controlled areas, such as the extraction columns or vessels being chilled, and valve, 78, entering jacket 66 of the sub-cooling condenser permits the liquid from the inside the core tubes to enter jacket 66 surrounding the core tubes. A simple fitting at the outlet is in fluid contact with inlet 13 of compressor 12, typically first entering a liquid-vapor separator or oil separator to prevent liquid from entering compressor 12, not shown in
Under vacuum, the temperature of a liquid refrigerant decreases rapidly with a small decrease in pressure. Further, the amount of heat absorbed when compared to the amount of vapor generated are greatly different when operating under vacuum vs positive pressure. The lower the evaporation pressure, the less power is required to recompress the refrigerant. Assuming R290 (propane) as a refrigerant, at an inlet pressure of −10 psi gauge pressure (−65° C.), the compressor employed uses 3.2 hp or 10 A @ 220 V, and can move 0.45 lb. of vapor per minute. By contrast, at an inlet pressure of +10 psi gauge pressure (−30° C.), the compressor employed uses 6.2 hp or 20 A @220 V, and can move 3 lb. of vapor per minute. Working under vacuum is not required for operation embodiments of the present apparatus, but a significant increase of efficiency of the over the previously described apparatus has been observed.
Thus, once the system is below zero psi it can remove more than twice the amount of heat per psi that it could otherwise remove under positive pressure. The total amount of heat that can be absorbed beyond the baseline sub-cooled liquid, is related to the level of vacuum of the system. It is anticipated by the inventor, that a true cryogenic system (−150° C.) can be generated using a single-stage refrigeration system. Traditionally, a cascade refrigeration system is required to cool below −60° C., where a cascade system is comprises multiple compressors using different refrigerants, where each system works on the next system in order to reduce the end point temperature. With cascade systems, there is a large power consumption requirement, and such systems are limited by the amount of vapor that passes through the compressor.
As stated, embodiments of the present apparatus use about 10 amps at −50° C., and less power as the temperature drops, and is not regulated by the amount of vapor which passes through the compressor. Embodiments of the present method of refrigeration expands on the first law of thermodynamics, where the system should require more power the colder it gets; however, this assumes no additional enthalpy is removed post condensation. With both calculations and direct observation, it has been confirmed that the system uses less power the lower the pressure becomes/the colder the system gets.
Finally, embodiments of the present invention do not rely on the volume of vapor that moves through the compressor as with the traditional methods. A small amount of vapor moves through the compressor while a very large volume of liquid provides cooling ability within the system. Reliance is instead on the volume of liquid refrigerant that is at or below zero psi gauge. By reintroducing refrigerant at or near the temperature of evaporation, the operating pressure does not increase upon injection of liquid into the second evaporator, and thereby does not increase the amount of work by the compressor.
Liquid refrigerant with heat removed will remain cold for a very long time. Only vapor above the liquid needs to be removed to force all of the remaining liquid to become the temperature set by the pressure of its vapor.
The foregoing description of the invention has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
The present application claims the benefit of U.S. Provisional Patent Application No. 63/104,650 for “Thermal Control System For Extraction Processes” which was filed on 23 Oct. 2020, the entire content of which Patent Application is hereby specifically incorporated by reference herein for all that it discloses and teaches.
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