PRIORITY

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 62/858,455, filed June 07, 2019, and European Patent Application No. 19208679.1 which was filed November 12, 2019, the disclosures of which are incorporated herein by reference in their entireties.

FIELD

[0002] Embodiments disclosed herein generally relate to refrigeration. More particularly, such embodiments relate to processes for reducing fouling in refrigeration systems and refrigeration systems having reduced fouling.

BACKGROUND

[0003] Refrigeration systems are typically employed to help separate process steams through fractionation in hydrocarbon processes such as steam cracking. Conventional refrigeration systems typically include a compressor, a condenser, an expansion apparatus, and an evaporator through which a refrigerant circulates and is repeatedly condensed and evaporated to provide a refrigeration effect. The compressor can be sealed with an oil (seal oil) and also contains moving parts that are lubricated with an oil (lubrication oil). The refrigerant, e.g., ethylene and/or propylene, can sometimes become contaminated with the seal oil and/or the lubrication oil, collectively (hydrocarbon oil).

[0004] The relatively low temperature that refrigeration systems operate at, e.g., typically less than -20°C, the hydrocarbon oil can become viscous, which can lead to the hydrocarbon oil fouling equipment, e.g., heat exchangers. Fouling within heat exchangers leads to a loss of heat transfer and renders the refrigeration system less effective in cooling the desired process stream. As the amount of fouling in the refrigeration system increases the loss of valuable products, e.g., ethylene, into lower valuable products, e.g., fuel gas, increases and loss of process efficiency. The fouling can also increase to a point that requires the refrigeration system to be shut down.

[0005] There is a need, therefore, for improved processes that can reduce fouling within refrigeration systems and refrigeration systems having reduced fouling caused by a hydrocarbon oil contaminating the refrigerant during operation thereof.

SUMMARY

[0006] Processes for reducing fouling within a refrigeration system and refrigeration systems having reduced fouling are provided. In some examples, the process can include compressing a refrigerant to produce a compressed refrigerant. The refrigerant can include ethane, ethylene, propane, propylene, or a mixture thereof. At least a portion of the compressed refrigerant can be condensed to produce a first liquid phase refrigerant at a first pressure. A pressure of the first liquid phase refrigerant can be reduced to produce a second liquid phase refrigerant at a second pressure. At least a portion of any vapor phase refrigerant can be separated from the second liquid phase refrigerant to produce a first exchanger duty liquid phase refrigerant. A liquid solvent can be combined with the first exchanger duty liquid phase refrigerant to produce a solvent modified liquid phase refrigerant. The solvent can be selected from the group consisting of: a first mixture that can include methanol and ethanol; a second mixture that can include methanol and n-propanol; a third mixture that can include ethanol and n-propanol; a C ₅ -C ₇ paraffinic hydrocarbon; and a fourth mixture that can include at least two C ₅ -C ₇ paraffinic hydrocarbons. Heat can be indirectly exchanged from a process fluid to the solvent modified liquid phase refrigerant and at least a portion of a contaminant can be dissolved in the solvent to produce a cooled process fluid and a heated contaminant-rich solvent modified refrigerant. The contaminant can include a hydrocarbon oil.

[0007] In other examples, the process can include contacting an exchanger duty liquid phase refrigerant with a solvent to produce a solvent modified liquid phase refrigerant that can include about 1 vol. % to about 25 vol. % of the solvent, based on a volume of the solvent modified liquid phase refrigerant. The refrigerant can be ethane, ethylene, propane, propylene, or a mixture thereof. The solvent can be selected from the group consisting of: a first mixture that can include methanol and ethanol; a second mixture that can include methanol and n-propanol; a third mixture that can include ethanol and n-propanol; a C ₅ -C ₇ paraffinic hydrocarbon; and a fourth mixture that can include two or more C ₅ -C ₇ paraffinic hydrocarbons. The solvent modified liquid phase refrigerant can flow through an apparatus that can include a contaminant disposed on an inner surface thereof. The solvent can dissolve at least a portion of the contaminant as the solvent modified liquid phase refrigerant flows through the apparatus to produce a contaminant-rich solvent modified refrigerant. The contaminant can include a hydrocarbon oil. At least a portion of the solvent comprising the dissolved contaminant from the contaminant-rich solvent modified refrigerant can be removed to produce a contaminant- lean refrigerant.

[0008] In some examples the refrigeration system can include a compression unit configured to compress a refrigerant to produce a compressed refrigerant. The refrigerant can include ethane, ethylene, propane, propylene, or a mixture thereof. The system can also include a first heat exchanger configured to condense at least a portion of the compressed refrigerant to produce a first liquid phase refrigerant at a first pressure. The system can also include an apparatus configured to reduce a pressure of the first liquid phase refrigerant to produce a second liquid phase refrigerant at a second pressure. The system can also include a separator configured to remove at least a portion of any vapor phase refrigerant from the second liquid phase refrigerant to produce an exchanger duty liquid phase refrigerant. The system can also include first conduit configured to introduce a solvent to the exchanger duty liquid phase refrigerant to produce a solvent modified liquid phase refrigerant. The solvent can be selected from the group consisting of: a first mixture that can include methanol and ethanol; a second mixture that can include methanol and n-propanol; a third mixture that can include ethanol and n-propanol; a C5-C7 paraffinic hydrocarbon; and a fourth mixture that can include C5-C7 paraffinic hydrocarbons. The system can also include second heat exchanger configured to indirectly exchange heat from a process fluid to the solvent modified liquid phase refrigerant to produce a cooled process fluid and a heated solvent modified refrigerant.

[0009] In some examples, the process can include compressing a refrigerant to produce a compressed refrigerant. The refrigerant can include ethane, ethylene, propane, propylene, or a mixture thereof. At least a portion of the compressed refrigerant can be condensed to produce a first liquid phase refrigerant at a first pressure. A pressure of the first liquid phase refrigerant can be reduced to produce a second liquid phase refrigerant at a second pressure. At least a portion of any vapor phase refrigerant can be separated from the second liquid phase refrigerant to produce a first exchanger duty liquid phase refrigerant. A liquid solvent can be combined with the first exchanger duty liquid phase refrigerant to produce a solvent modified liquid phase refrigerant. The can be an iso-hexane, hexane, or a mixture thereof. Heat can be indirectly exchanged from a process fluid to the solvent modified liquid phase refrigerant and at least a portion of a contaminant can be dissolved in the solvent to produce a first process fluid and a heated contaminant-rich solvent modified refrigerant. The contaminant can include a hydrocarbon oil having an ISO viscosity classification of ISO VG 7 to ISO VG 150 as defined by ISO 3448: 1992. A vaporized refrigerant and a contaminant-rich solvent can be separated from the heated contaminant-rich solvent modified refrigerant. At least a portion of the contaminant-rich solvent comprising the dissolved contaminant can be removed from the process. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.

[0011] FIG. 1 depicts an illustrative closed loop refrigeration system, according to one or more embodiments described.

[0012] FIG. 2 depicts an illustrative open loop refrigeration system, according to one or more embodiments described.

DETAILED DESCRIPTION

[0013] It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, and/or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the Figures. Moreover, the exemplary embodiments presented below can be combined in any combination of ways, i.e., any element from one exemplary embodiment can be used in any other exemplary embodiment, without departing from the scope of the disclosure.

[0014] It has been discovered that certain solvents can be used to reduce or eliminate fouling within a refrigeration system caused by a contaminant, e.g. , a hydrocarbon oil, in the refrigerant used in the refrigeration system. The viscosity of the contaminant can increase at the refrigeration temperature to a point that the contaminant does not sufficiently flow through an apparatus, e.g., a heat exchanger, and/or the contaminant deposits onto surfaces within an apparatus, e.g., an inner surface within a heat exchanger, which can lead to a significant reduction in heat exchange efficiency.

[0015] The solvent can be mixed, blended, contacted, or otherwise combined with the refrigerant to produce a solvent modified refrigerant that can flow through the apparatus. For example, the solvent can be combined with the refrigerant when the refrigerant is in the liquid phase to produce the solvent modified refrigerant. In some examples, the refrigerant in the liquid phase that can be combined with the solvent can be referred to as an exchanger duty liquid phase refrigerant or a first exchanger duty liquid phase refrigerant. In some examples, the solvent modified refrigerant can be referred to as a solvent modified liquid phase refrigerant. The solvent in the solvent modified liquid phase refrigerant can dissolve at least a portion of the contaminant that has become mixed with the refrigerant and/or has deposited onto an inner surface of an apparatus, e.g., a heat exchanger, to produce a contaminant-rich solvent modified refrigerant. The contaminant-rich solvent modified refrigerant can be removed from the system, e.g., via one or more blow down lines configured to remove at least a portion of the solvent and the hydrocarbon oil dissolved therein. Certain solvents comprising C5-C7 paraffinic hydrocarbon will now be described in more detail. The invention is not limited to these solvents, and this description should not be interpreted as excluding other solvents within the broader scope of the invention.

[0016] The solvent can be or include one or more of a first mixture that can include methanol and ethanol; a second mixture that can include methanol and n-propanol; a third mixture that can include ethanol and n-propanol, a C5-C7 paraffinic hydrocarbon; and a fourth mixture that can include two or more C5-C7 paraffinic hydrocarbons. The C5-C7 paraffinic hydrocarbon of the third mixture can be the same as the C5-C7 paraffinic hydrocarbon of the fourth mixture, but this is not required. Likewise, C5-C7 paraffinic hydrocarbon can be present in the same relative amounts in the third and fourth mixtures, but this is not required. Illustrative C5-C7 paraffinic hydrocarbons can be or include, but are not limited to, pentane, isopentane, neopentane, hexane, 2-methylpentane (iso-hexane), 3-methylpentane, 2,2-dimethylbutane, 2,3- dimethylbutane, heptane, 2-methylhexane, 3-methylhexane, 2,2-dimethylepentane, 2,3- dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpenane, 3-ethylpentane, 2,2,3- trimethylbutane, isomers thereof, enantiomers thereof, or any mixture thereof. In some examples, the refrigerant can be or include 2-methylpentane (iso-hexane). In other examples, the refrigerant can be or include hexane.

[0017] In some examples, the C5-C7 paraffinic hydrocarbon can have an atmospheric boiling point of about 55°C to about 95°C. For example, the C5-C7 paraffinic hydrocarbon can have an atmospheric boiling point of about 55°C, about 60°C, about 65°C, or about 70°C to about 80°C, about 85°C, about 90°C, or about 95°C. In another example, the C5-C7 paraffinic hydrocarbon can have an atmospheric boiling point of about 57.9°C to about 94°C, about 60°C to about 95°C, or about 65.5°C to about 93.3°C. In some examples, the C5-C7 paraffinic hydrocarbon can have an atmospheric boiling point of > 55°C, > 60°C, > 63°C, > 65°C or > 70°C and < 95°C, < 90°C, or < 85°C. In some examples, the fourth mixture can have an atmospheric boiling point of about 55°C, about 60°C, about 65°C, or about 70°C to about 80°C, about 85°C, about 90°C, or about 95°C.

[0018] In some examples, if the solvent includes the first mixture, the second mixture, the third mixture, or the fourth mixture, an amount of each component in the mixture can provide the solvent with a freezing point that is within 50°C, 40°C, 30°C, 25°C, 20°C, 15°C, 10°C, 7°C, 5°C, 4°C, 3°C, 2°C, or 1°C of a eutectic freeze point of the particular mixture. The particular ratio or amount of each component in the mixture that can provide the solvent within a desired range of the eutectic freeze point can readily be determined by well-known processes. In one example, the solvent can be the first mixture and can include about 25 vol. % or about 30 vol. % to about 35 vol. % or about 40 vol. % of methanol and about 60 vol. % or about 65 vol. % to about 70 vol. % or about 75 vol. % of ethanol, e.g., about 30 vol. % of methanol and about 70 vol. % of ethanol, at atmospheric pressure and at a temperature of about 25°C. In another example, the solvent can be the second mixture and can include about 50 vol. % or about 55 vol. % to about 65 vol. % or 70 vol. % of methanol and about 30 vol. % or about 35 vol. % to about 45 vol. % or about 50 vol. % of n-propanol, e.g., about 60 vol. % of methanol and about 40 vol. % of n-propanol, at atmospheric pressure and at a temperature of about 25°C. In another example, the solvent can be the third mixture and can include about 50 vol. % or about 55 vol. % to about 65 vol. % or about 70 vol. % of ethanol and about 30 vol. % or about 35 vol. % to about 45 vol. % or about 50 vol. % of n-propanol, e.g., about 60 vol. % of ethanol and about 40 vol. % of n-propanol, at atmospheric pressure and at a temperature of about 25°C.

[0019] The refrigerant that can be used in the refrigeration system can be or include, but is not limited to, methane, ethylene, ethane, propylene, propane, butane, or any mixture thereof. In some examples, the refrigerant can include a majority of ethane, i.e., > 50 vol. % of ethane, based on a total volume of the refrigerant when in the liquid phase. In some example, the refrigerant can include a majority of ethylene, i.e., > 50 vol. % of ethylene, based on a total volume of the refrigerant when in the liquid phase. In other examples, the refrigerant can include a majority of propane, i.e., > 50 vol. % of propane, based on a total volume of the refrigerant when in the liquid phase. In other examples, the refrigerant can include a majority of propylene, i.e., > 50 vol. % of propylene, based on a total volume of the refrigerant when in the liquid phase. In still other examples, the refrigerant can include a majority of ethane, ethylene, or a mixture thereof, i.e., > 50 vol. % of ethane and/or ethylene, based on a total volume of the refrigerant when in the liquid phase. In other examples, the refrigerant can include a majority of propane, propylene, or a mixture thereof, i.e., > 50 vol. % of propane and/or propylene, based on a total volume of the refrigerant when in the liquid phase.

[0020] The solvent-modified liquid phase refrigerant can include about 1 vol. %, about 2 vol. %, about 3 vol. %, about 4 vo. %, or about 5 vol. % to about 8 vol. %, about 10 vol. %, about 15 vol. %, about 20 vol. %, about 25 vol. %, or about 30 vol. %, based on a volume of the solvent modified liquid phase refrigerant. In some example, the solvent modified liquid phase refrigerant can include about 2 vol. % to about 20 vol. %, about 3 vol. % to about 15 vol. %, about 3 vol. % to about 10 vol. %, about 4 vol. % to about 6 vol. %, or about 3 vol. % to about 12 vol. % of the solvent, based on the volume of the solvent modified liquid phase refrigerant.

[0021] In some examples, the solvent can have a viscosity that the same or substantially similar to the viscosity of the liquefied refrigerant. In other examples, the solvent can have a viscosity that is less than the viscosity of the liquefied refrigerant. In still other examples, the solvent can have a viscosity that is greater than the viscosity of the liquefied refrigerant.

[0022] In some examples, the solvent can be used for a short period of time, e.g. , a few hours (such as from 1 to 5 hours), or for long periods of time, e.g., a day, two days, weeks, or even months (such as from one day to 180 days, or from 10 days to 90 days), before the solvent or the solvent containing a contaminate dissolved therein is separated from the refrigerant. In other examples, the refrigerant can continuously be in contact with the solvent such that the refrigerant includes the solvent for an extended period of time. If a contaminant enters the refrigeration system, the solvent that includes the contaminant dissolved therein can be removed from the refrigeration system and a fresh or make-up solvent can be combined with the refrigerant to maintain the solvent in the refrigeration system. As such, the refrigeration system can use the solvent modified refrigerant periodically or essentially continuously with the solvent being exchanged or replaced with fresh or new solvent as needed to remove at least a portion of any contaminant dissolved therein.

[0023] The contaminant can be or include one or more hydrocarbon oils. Illustrative hydrocarbon oils can be or include, but are not limited to, one or more seal oils, one or more lubrication oils, or a mixture thereof. In some examples, the hydrocarbon oil can have an ISO viscosity classification of ISO VG 7 to ISO VG 150 as defined by ISO 3448: 1992. In other examples, the hydrocarbon oil can have an ISO viscosity classification of ISO VG 7, ISO VG 10, ISO VG 15, ISO VG 20, ISO VG 25, or ISO VG 30 to ISO VG 35, ISO VG 45, ISO VG 55, ISO VG 65, ISO VG 75, ISO VG 85, ISO VG 100, ISO VG 125, or ISO VG 150 as defined by ISO 3448: 1992. Mixtures of such hydrocarbon oils are within the scope of the invention.

[0024] FIG. 1 depicts an illustrative closed loop refrigeration system 100, according to one or more embodiments. The refrigeration system 100 can include one or more compression units 110, one or more heat exchange stages (three are shown) 120, 160, and 170, one or more pressure reduction apparatus 130, and one or more separation stages 140. In some examples, a refrigerant in line 105 can be introduced into the compressor unit 110 to produce a compressed refrigerant via line 115. The compression unit 110 can be or include any suitable compressor(s) that can include any number of compression stages. In some examples, the compression unit 110 can be or include a multi-stage compressor. Illustrative compressors can include, but are not limited to, axial compressors, centrifugal compressors, rotary positive displacement compressors, diagonal or mixed-flow compressors, reciprocating compressors, dry screw compressors, oil flooded screw compressors, scroll compressors, or any combination thereof.

[0025] The compression unit 110 can compress the refrigerant introduced via line 105 at a desired pressure ratio to produce the compressed refrigerant in line 115. For example, the compression unit 110 can include one or more compression stages that can each compress the refrigerant at a pressure ratio of about 1: 1.5 to about 1:3. The desired refrigeration levels can be obtained via any number of compression stages, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more compression stages. The particular pressure ratio can be based, at least in part, on the desired pressure of the compressed refrigerant in line 115, the composition of the refrigerant in line 105, the type and/or number of compressor(s), a desired maximum temperature of the compressed refrigerant, the cooling provided by 120, or any combination thereof.

[0026] The compressed refrigerant via line 115 and a cooling medium via line 117 can be introduced into the first heat exchange stage 120 to produce a first liquid phase refrigerant at a first pressure via line 125 and a heated coolant via line 127. The first heat exchange stage 120 can be or include any apparatus or combination of apparatus suitable for indirectly transferring heat from one fluid to another fluid. Illustrative heat exchange apparatus can be or include, but are not limited to, a shell-and-tube heat exchanger, a plate and frame heat exchanger, brazed aluminum heat exchangers, a plate and fin heat exchanger, a spiral wound heat exchanger, a coil wound heat exchanger, a U-tube heat exchanger, a bayonet style heat exchanger, any other apparatus, or any combination thereof. In some examples, the heat exchange stage 120 can also include surface enhanced tubes, e.g., fins, static mixers, rifling, heat conductive packing, turbulence causing projections, or any combination thereof.

[0027] The first liquid phase refrigerant via line 125 can be introduced into the pressure reduction apparatus 130 to produce a second liquid phase refrigerant at a second pressure via line 135, where the second pressure is less than the first pressure. In some examples, the pressure reduction apparatus 130 can be or include any apparatus or combination of apparatus suitable for adiabatically or substantially adiabatically reducing the pressure of compressed fluid, e.g., the liquid phase refrigerant. Illustrative pressure reducing apparatus 130 can be or include, but are not limited to, one or more valves, one or more nozzles, one or more orifices, one or more expansion devices, one or more porous plugs, or any combination thereof.

[0028] The second liquid phase refrigerant via line 135 can be introduced into the separation stage 140. The separation stage 140 can remove at least a portion of any vapor phase refrigerant via line 141 that can be recycled back to the compressor via line 105. The separation stage 140 can be or include any apparatus or combination of apparatus suitable for separating gas from liquid. For example, the separation stage 140 can be or include one or more flash tanks, one or more flash drums, or any combination thereof. The separation stage 140 can contain one or more internal structures including, but not limited to, trays, random packing elements such as rings or saddles, structured packing, or any combination thereof. In some examples, the separation stage 140 can be or include an open column without internals. In other examples, the separation stage 140 can be a partially empty column containing one or more internal structures.

[0029] The second liquid phase refrigerant or“first exchanger duty liquid phase refrigerant” via line 143 can be introduced via lines 145 and 155 into the second and third heat exchange stages 160 and 170, respectively. A process fluid via lines 148 and 158 can be introduced into the second and third heat exchange stages 160 and 170, respectively. The process fluid in lines 148 and 158 can have the same composition or different compositions with respect to one another. Heat can be transferred from the process fluids to the first heat exchanger duty liquid phase refrigerant to produce cooled process fluids via lines 164 and 174 and heated first exchanger duty refrigerants via lines 162 and 172, respectively. In some examples, the second and third heat exchange stages 160 and 170 can be or include one or more thermosyphon type heat exchangers.

[0030] The refrigerant in the heated first exchanger duty refrigerants in lines 162 and 172 can be in the gas phase, the liquid phase, or a combination of gas phase and liquid phase. In some examples, the refrigerant in the heated first exchanger duty refrigerant can be in the gas phase. In some examples, the heated first exchanger duty refrigerant in lines 162 and 172 can be combined and introduced via line 165 into the separation stage 140. The refrigerant in the gas phase can be removed via line 141 and re-introduced via line 105 into the compression unit 110. In some examples, the heated first exchanger duty refrigerant in line 165 can be at substantially the same or a lower pressure than the second liquid phase refrigerant in line 135.

[0031] In some examples, if the refrigerant, at any point or location within the refrigeration system 100 becomes contaminated with the contaminant the solvent via lines 144 and 154 can be mixed, blended, contacted, or otherwise combined with the first exchanger duty liquid phase refrigerant in lines 145 and 155 to produce a solvent modified liquid phase refrigerant in lines 146 and 156, respectively. In other examples, the refrigerant can be contaminated with the contaminant, but the solvent via lines 144 and 154 may be added after or when the second heat exchange stage 160 and/or the third heat exchange stage 170 begin to experience a drop in heat exchange efficiency due to fouling from the contaminant in the refrigerant. In some examples, the solvent could be mixed, blended, contacted, or otherwise combined with the second liquid phase refrigerant in line 135.

[0032] The solvent modified liquid phase refrigerant via lines 146 and 156 can be introduced into the second and third heat exchange stages 160, 170, respectively, and flow therethrough. As the solvent modified liquid phase refrigerant flows through the second and third heat exchange stages 160, 170 the solvent can dissolve at least a portion of the contaminant contained in the refrigerant and/or at least a portion of the contaminant disposed on an inner surface of the second and/or third heat exchange stages 160, 170. As such, when the refrigerant includes the contaminant and/or when the contaminant is disposed within the second and/or third heat exchange stages 160 and 170, a heated contaminant-rich solvent modified refrigerant via lines 162 and 172, respectively, can be recovered therefrom. It should be understood that the solvent can be introduced via line 144, line 154, and/or lines 144 and 154. As such, the solvent can selectively be introduced into one or both of the second and third heat exchange stages 160, 170.

[0033] In some examples, as the solvent modified liquid phase refrigerant flows through the second and third heat exchange stages 160 and 170, the refrigerant can be at least partially vaporized as heat transfers from the process fluid to the solvent modified refrigerant. The solvent and the contaminant dissolved therein in the heated contaminant-rich solvent modified refrigerant can remain in the liquid phase. As such, the heated contaminant-rich solvent modified refrigerant in lines 162 and 172 can include gaseous and/or liquid phase refrigerant, liquid phase solvent, and liquid phase contaminant dissolved in the solvent.

[0034] As shown, the solvent modified liquid phase refrigerant via lines 146 and 156 and the process fluid introduced via lines 148 and 158 into the second and third heat exchange stages 160 and 170, respectively, can flow counter currently therethrough. It should be understood that the flow paths of the solvent modified liquid phase refrigerant and the process fluid within the second and third heat exchange stages 160 and 170 can have any desired relationship relative to one another and can vary depending on the particular configuration of each heat exchange stage 160 and 170.

[0035] The second heat exchange stage 160 and the third heat exchange stage 170 can be or include any apparatus or combination of apparatus suitable for indirectly transferring heat from one fluid to another fluid. Conventional heat exchangers (and combinations thereof) are suitable, but the invention is not limited thereto. Illustrative heat exchange apparatus can be or include, but are not limited to, a shell- and-tube heat exchanger, a plate and frame heat exchanger, brazed aluminum heat exchanger, a plate and fin heat exchanger, a spiral wound heat exchanger, a coil wound heat exchanger, a U-tube heat exchanger, a bayonet style heat exchanger, any other apparatus, or any combination thereof. In some examples, the second and/or third heat exchange stages 160, 170 can also include surface enhanced tubes, e.g., fins, static mixers, rifling, heat conductive packing, turbulence causing projections, or any combination thereof.

[0036] In some examples, the heated contaminant-rich solvent modified refrigerant in lines 162 and 172 can be combined and introduced via line 165 into the separation stage 140. The refrigerant in the gas phase, i.e., vaporized refrigerant, can be removed via line 141 and re introduced via line 105 into the compression unit 110 to produce additional compressed refrigerant via line 115. At least a portion of the additional compressed refrigerant can be condensed in the first heat exchange stage 120 to produce additional first liquid phase refrigerant via line 125. The additional first liquid phase refrigerant via line 125 can be introduced into the pressure reduction apparatus 130 to produce additional second liquid phase refrigerant at a second pressure via line 135, where the second pressure is less than the first pressure. In some examples, a majority, i.e., > 50 wt. %, of the solvent and the contaminant dissolved therein can remain in the liquid phase in the separation stage 140 and can be mixed, blended, contacted, or otherwise combined with the additional second liquid phase refrigerant introduced via line 135 to the separation stage 140 to produce a second exchanger duty liquid phase refrigerant via line 143.

[0037] In some examples, the second exchanger duty liquid phase refrigerant via lines 145 and 155 that includes the solvent and the contaminant dissolved therein can be introduced into the second and third heat exchange stages 160 and 170, respectively. In other examples, at least a portion of the solvent that includes the contaminant dissolved therein in lines 145 and 155 can be removed via blow down lines 147 and 157, respectively, to produce a contaminant- lean second exchanger duty liquid phase refrigerant. In some examples, when a concentration of the contaminant dissolved in the solvent reaches a predetermined amount or when the solvent has been used for a predetermined period of time to remove contaminant from the refrigeration system 100, at least a portion of the solvent and the contaminant dissolved therein can be removed via blow down lines 147 and 157 from the refrigeration system 100 to produce the contaminant-lean second exchanger duty liquid phase refrigerant.

[0038] In some examples, the contaminant- lean second exchanger duty liquid phase refrigerant can be introduced into the second and third heat exchange stages 160 and 170. Heat can be transferred from additional process fluid introduced via lines 148 and 158 to the contaminant-lean second exchanger duty liquid phase refrigerant to produce additional cooled process fluids via lines 164 and 174 and a heated contaminant-lean refrigerant via lines 162 and 172. In other examples, additional, fresh, or make-up solvent via lines 144 and/or 154 can be mixed, blended, contacted, or otherwise combined with the contaminant-lean second exchanger duty liquid phase refrigerant to produce additional solvent modified refrigerant that can be introduced into the second and third heat exchange stages 160 and/or 170 via lines 146 and 156, respectively. Heat can be transferred from additional process fluid introduced via lines 148 and 158 to the additional solvent modified refrigerant to produce additional cooled process fluids via lines 164 and 174 and a heated additional solvent modified refrigerant via lines 162 and 172.

[0039] FIG. 2 depicts an illustrative open loop refrigeration system 200, according to one or more embodiments. The refrigeration system 200 can include the one or more compression units 110, the one or more heat exchange stages (three are shown) 120, 160, and 170, the one or more pressure reduction apparatus 130, and the one or more separation stages 140, which can be the same or substantially the same as those describe with reference to FIG. 1. A refrigerant via line 205 can be introduced to the compression unit 110 to produce a first compressed refrigerant via line 115. The first compressed refrigerant can flow through the first heat exchange stage 120, the pressure reduction apparatus 130 and into the separation stage 140. From the separation stage 140, a first exchanger duty refrigerant via line 143 can be removed and introduced via lines 145 and 155 into the second and third heat exchange stages 160 and 170, respectively. The heated first exchanger duty refrigerants via lines 162 and 172 can be recovered from the first and second heat exchange stages 160 and 170, respectively, combined in line 165 and introduced into the separation stage 140. Gaseous or vaporized refrigerant via line 241 can be removed from the separation stage 140. Rather than recycling or reintroducing the vaporized refrigerant into the compression unit 110, the vaporized refrigerant can be removed from the refrigeration system 200. The addition of the solvent to the exchanger duty liquid phase refrigerant, the removal of the contaminant, e.g., hydrocarbon oil deposited on an inner surface of the second and/or third heat exchange stages 160 and 170, and the removal of the solvent containing the contaminant dissolved therein can be as discussed and describe above with reference to FIG. 1.

[0040] Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and/or the combination of any two upper values are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are "about" or "approximately" the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

[0041] Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

[0042] While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.