Method for removing moisture from LNG refrigerant

Abstract

A method and system for removing moisture from a refrigerant utilizing a desiccant-based moisture removal unit can be used in the production of liquid natural gas (LNG). For example, the method can include compressing a refrigerant; conveying at least a portion of the refrigerant to a moisture removal unit including a desiccant to form a dehydrated refrigerant; cooling and condensing the dehydrated refrigerant to provide a cooled, dehydrated liquid refrigerant; conveying the cooled, dehydrated refrigerant to a heat exchanger; and passing a methane-rich LNG stream through the heat exchanger to cool at least a portion of the LNG stream by indirect heat exchange with the cooled, dehydrated refrigerant.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No. 62 / 798,722, filed January 30, 2019, entitled "Method for Removing Moisture from LNG Refrigerant." [Background technology]

[0002] background The present disclosure relates to preventing water accumulation in a cryogenic refrigeration circuit. The processing of cryogenic hydrocarbon liquids, such as liquefied natural gas (LNG), conventionally utilizes refrigeration to cool the inlet gas to the required liquefaction temperature (e.g., methane is cooled to LNG). The refrigerant gas used in the refrigeration circuit may be a single component (e.g., methane, nitrogen, propane, ethylene, etc.) or a mixed refrigerant. A mixed refrigerant is a mixture that may include, but is not limited to, methane, nitrogen, ethane, ethylene, propane, and other commercially available refrigerant compounds. The refrigeration circuit is initially charged with refrigerant, but due to some losses during the operation of the process, additional refrigerant material may be added periodically to replenish the required amount. Since neither the initial refrigerant nor the make-up refrigerant are generally completely devoid of water, small amounts of water often find their way into the refrigeration circuit. In places where the system is below the freezing point of water (e.g., in the tubes of a heat exchanger), this water may form an ice film. When a heat exchanger is taken out of service and warmed up (e.g., planned maintenance, unplanned downtime, etc.), this distributed solid film melts and forms a pool of liquid water within the heat exchanger. When the heat exchanger is recooled and returned to service, the water can freeze, potentially damaging the heat exchanger and reducing the efficiency of LNG production. Therefore, it is common practice to remove liquid water from the refrigeration circuit before recooling. Summary of the Invention [Problem to be solved by the invention]

[0003] Currently, as a standard industry practice, water is typically removed from the refrigeration circuit by "defrosting." In defrosting, the refrigerant is completely de-inventoried from the refrigeration circuit and disposed of (e.g., written off). Dry gas is then passed through all refrigeration circuit conduits, valves, and heat exchangers to warm the refrigeration circuit components and vaporize any accumulated water. This water is blown away by the dry gas stream and burned in a facility flare. This procedure is very time consuming, requires a significant amount of offline time, is expensive, and is wasteful. Thus, a more efficient method for removing moisture from the refrigeration circuit is needed. [Means for solving the problem]

[0004] Summary of the Invention The present disclosure relates to preventing water accumulation in the refrigeration circuits of liquefied natural gas (LNG) plants by passing the refrigerant through a moisture removal unit. In one aspect, the present invention provides a system for removing moisture from a refrigerant in an LNG refrigeration circuit, the system may include a refrigerant compressor, a refrigerant condenser, a moisture removal unit including a desiccant, and a heat exchanger, fluidly connected in a loop with the refrigerant compressor upstream of the moisture removal unit, the moisture removal unit upstream of the refrigerant condenser, the refrigerant condenser upstream of the heat exchanger, and the heat exchanger upstream of the refrigerant compressor. The system may contain one or more valves capable of distributing the refrigerant flow, for example, directing a first refrigerant flow to a moisture removal unit and a second refrigerant flow to a conduit that bypasses the moisture removal unit.

[0005] In another aspect, the invention provides a method for removing moisture from a refrigerant in an LNG refrigeration circuit, comprising conveying the refrigerant stream through a moisture removal unit containing a desiccant, the moisture removal unit being available both when the system is offline and warming up (e.g., to ambient temperature) and when the refrigeration circuit is online processing LNG. In another aspect, the present invention provides a method for cryogenically processing LNG, comprising the steps of: a) providing a liquid natural gas stream; b) Supplying a refrigerant: c) Compressing the refrigerant: d) conveying at least a portion of the refrigerant to a moisture removal unit containing a desiccant to form a dehydrated refrigerant; e) cooling and condensing the dehydrated refrigerant to provide a cooled dehydrated liquid refrigerant; f) conveying the cooled, dehydrated refrigerant to a heat exchanger; and g) passing the methane-rich gas stream through a heat exchanger to cool at least a portion of the gas stream by indirect heat exchange with a cooled, dehydrated refrigerant. The present invention provides a method comprising:

[0006] The method may be useful for processing natural gas liquids having a composition between about 87 mole percent and about 97 mole percent methane. In either embodiment, the refrigeration circuit may contain one or more valves capable of distributing the refrigerant flow, for example, directing a first refrigerant flow to a moisture removal unit and a second refrigerant flow to a conduit that bypasses the moisture removal unit. In either embodiment, the moisture removal unit may be a permanent fixture in the refrigeration circuit or may be removably attached to the system. In either embodiment, the desiccant may be, for example, silica, activated carbon, calcium sulfate (gypsum), calcium chloride, molecular sieves, or any combination thereof. In either embodiment, the moisture removal unit may include a desiccant bed, which may be loose or packed, through which the refrigerant flows, over, or both. In either embodiment, and in some cases, the refrigeration circuit may be fluidly connected to a source of refrigerant so that refrigerant can be added to the circuit. In either embodiment, the refrigeration circuit may include a moisture analysis unit capable of monitoring moisture in the refrigerant, which may be downstream of the moisture removal unit and may, for example, measure the dew point of the refrigerant. The following drawings are included to illustrate certain aspects of the embodiments and should not be considered as exclusive embodiments. The disclosed subject matter is capable of considerable modification, alteration, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure. [Brief description of the drawings]

[0007] [Figure 1] 1 shows a non-limiting example of a refrigeration circuit incorporating a moisture removal unit downstream of the compressor and upstream of the condenser. [Diagram 2] 1 depicts a non-limiting example of a contemplated moisture removal unit in which the refrigerant stream is conveyed through a bed of desiccant. [Diagram 3] 1 depicts a non-limiting example of a contemplated moisture removal unit in which the refrigerant stream is conveyed over a bed of desiccant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Detailed Description The present invention will now be described more fully hereinafter, with reference to exemplary embodiments thereof. However, the present invention may be embodied in many different forms and should not be construed as limiting the invention to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In one aspect, the present invention provides a method for removing moisture or water from a refrigerant in a refrigeration circuit without draining the refrigerant or using large amounts of dry gas. As used herein, de-inventorying and its grammatical variants refer to the process of removing refrigerant from a refrigeration circuit and disposing of or storing it elsewhere. Conversely, inventorying and its grammatical variants refer to the process of adding sufficient refrigerant to a refrigeration circuit, where the refrigeration circuit is initially substantially devoid of refrigerant, to enable operation of the refrigeration circuit. This may be upon first use of the refrigeration circuit or after draining the refrigeration circuit, for example, for repair. Draining does not include redirecting the refrigerant through the additional piping and valving required to carry the refrigerant through a moisture removal unit.

[0009] The methods disclosed herein provide methods for removing water from refrigeration circuits not currently or previously utilized in the LNG industry. These methods extend the use of existing equipment and utilize additional equipment and procedures, such as new piping connections. Advantageously, the methods disclosed herein do not require draining refrigerant from the refrigeration circuit and may not require warming of the refrigeration circuit, thereby reducing time spent offline and realizing cost savings by extending refrigerant life (and avoiding the purchase of new refrigerant). As used herein, a "refrigeration circuit" includes a system in which a refrigerant circulates to enable the refrigerant to absorb energy from a gas stream (e.g., a natural gas stream). The refrigeration circuit may be part of an industrial system, for example, in gas-to-liquid cryogenic processing (e.g., in a liquefied natural gas train). The refrigeration circuit may have multiple components, including, but not limited to, a refrigerant compressor, a refrigerant condenser, a heat exchanger, an evaporator, or any combination thereof.

[0010] Generally, a refrigeration circuit has a directional flow during use. For example, in the refrigeration circuit disclosed herein, the refrigerant is compressed to a high pressure gas by a compressor and then conveyed to a condenser to liquefy and cool the refrigerant. The cooled liquid refrigerant can then be conveyed to a heat exchanger where it absorbs energy from a gas stream (e.g., natural gas) to cool and liquefy the gas stream, thus achieving the purpose of the refrigeration circuit. The present disclosure considers these components and steps in this order and uses the terms "downstream" and "upstream" to indicate the direction of fluid flow as the system is in functional use (e.g., cooling). As used herein, the term "downstream" is used to indicate that it is in the direction of refrigerant flow. "Upstream" is used to indicate that it is in the opposite direction to the refrigerant flow. As used herein, the term "cryogenic" is intended to mean a liquid, gas, or mixed-phase fluid having a temperature below -70 degrees Celsius. Examples of cryogens include liquid nitrogen (LIN), liquefied natural gas (LNG), liquid helium, liquid carbon dioxide, and pressurized mixed-phase cryogens (e.g., a mixture of LIN and gaseous nitrogen). As used herein, "cryogenic temperature" is intended to mean a temperature below -70 degrees Celsius.

[0011] As used herein, the term "compressor" broadly refers to any device or series of devices capable of compressing a refrigerant into a high pressure gas. Although the singular compressor is used herein, it is considered within the scope of the present invention for "compressor" to include any system, including those that may have multiple components, that compress a refrigerant into a high pressure gas. Those skilled in the art will be familiar with a variety of suitable compressor systems, including, but not limited to, mechanical, low speed, high speed, and centrifugal. As used herein, the term "condenser" broadly refers to any device or series of devices capable of condensing high pressure refrigerant to a liquid state. Although reference is made herein using the singular condenser, it is considered within the scope of the present invention for "condenser" to include any system, including those that may have multiple components, that condenses high pressure refrigerant into a cooled liquid. Those skilled in the art will be familiar with a variety of suitable condenser systems. As used herein, the term "heat exchanger" broadly refers to any device or devices capable of transferring heat from one medium to another, and specifically includes any structure, e.g., device commonly referred to as a heat exchanger. Although reference is made herein using the singular heat exchanger, it is considered within the scope of the present invention that "heat exchanger" includes any system, including those that may have multiple components that allow for the transfer of energy from one source (e.g., a natural gas stream) to a refrigerant. Those skilled in the art will be familiar with suitable heat exchangers. For example, coil-wound and aluminum brazed heat exchangers are commonly utilized in LNG applications.

[0012] The present disclosure further incorporates a moisture removal unit in a refrigeration circuit or an access to a moisture removal unit. As used herein, a "moisture removal unit" refers to a component or series of components capable of removing moisture from a refrigerant and having an inlet conduit connecting the moisture removal unit to the refrigeration circuit and an outlet conduit feeding back to the refrigeration circuit. Although the singular moisture removal unit is used herein, it is considered within the scope of the present invention for a "moisture removal unit" to include any system, including those that may have multiple components that remove moisture from a refrigerant. Optimally, the refrigeration circuit may include a moisture analysis unit capable of monitoring the moisture content of the refrigerant. For example, the moisture analysis unit may be incorporated in a conduit downstream of the moisture removal unit and upstream of the condenser. The moisture analysis unit and required conduits may be incorporated in series (where the entire refrigerant flow is conveyed to the moisture analysis unit) or in parallel (e.g., where only a portion of the refrigerant flow is conveyed to the moisture analysis unit).

[0013] Those skilled in the art will be familiar with common methods for measuring the water content of a refrigerant. For example, a moisture analysis unit may measure the water dew point of a refrigerant. As used herein, water dew point is the temperature at which condensation begins to form (at a particular pressure). Water dew point can be measured manually or automatically. Those skilled in the art will be aware of suitable methods for measuring the water dew point of a refrigerant. For example, in an automated system, a refrigerant sample can be conveyed over a chilled mirror and the formation of condensation can be detected by changes in the light reflected off the mirror. The moisture removal unit may be a desiccant-based system. For example, the moisture removal unit may include a chamber with a desiccant bed and an area in which vaporized or gaseous refrigerant can be conveyed to contact the desiccant in the bed. The desiccant may be any known hygroscopic material. Many suitable desiccants are used and are known in the art, such as, for example, silica, activated carbon, calcium sulfate (gypsum), calcium chloride, molecular sieves, and combinations thereof. The desiccant may be regenerated for continued use or reuse, or it may be used, discarded, and replaced with fresh desiccant. Regeneration of the desiccant can be accomplished by methods well known in the art, for example, by drying the desiccant in an oven.

[0014] Conduits connecting the moisture removal unit to other components in the refrigeration circuit may include valves / valves. The moisture removal methods and apparatus disclosed herein may be used in any type of refrigeration circuit, including, but not limited to, cascade cycles, mixed refrigerant cycles, gas expander cycles, or any combination thereof known in the art. A refrigeration circuit may also contain pipes, tubing, valves, valve elements, etc. for connecting and directing flow from one component to another. As used herein, these components are collectively referred to as "conduits." As used herein, a "conduit" may be or include one or more passages that form a closed passage through which refrigerant flows or can flow and that pass through one or more other components, such as one or more sections of tubing or pipe, e.g., fittings, valve elements, accumulators, or combinations thereof. Additionally, a conduit described herein as "connecting" two components forms a closed passage between the two components through which refrigerant flows or can flow in at least one or more operating modes. Additionally, the refrigerant conduits described herein may differ in shape or length from those shown in the drawings, which are not to scale.

[0015] The term "refrigerant" as used herein refers to a refrigerant in liquid, vapor, or gaseous form, or any combination thereof. The components of the closed circuit cause the refrigerant to experience temperature / pressure changes. Depending on its location in the refrigeration circuit, the refrigerant may be a liquid, vapor, or gas. The temperature / pressure changes of the refrigerant result in energy transfer. The refrigerant may be a single gas component or a mixture of gas components ("mixed refrigerant" or MR). Examples of suitable refrigerants include those known in the art, such as methane, ethane, propane, ethylene, nitrogen, and any combination or mixture thereof. The refrigerant may also contain impurities, moisture, or both. As used herein, the terms "moisture" and "water" are synonymous and are used interchangeably. Moisture may be present in the refrigeration circuit in liquid water, vapor, gas, ice, or any combination thereof. Sources of water include, but are not limited to, the initial refrigerant charge, make-up refrigerant, and combinations thereof. The present disclosure provides methods for removing any water introduced into the circuit by any means.

[0016] As used herein, "dehydrated" refers to a refrigerant that has had at least a portion of the water removed compared to its condition in the refrigerant source. The amount of water in the refrigerant can be indicated by the water dew point of the refrigerant. The relationship between the water dew point and the saturation or percentage of water in the refrigerant depends on the pressure of the refrigerant, but one of ordinary skill in the art can easily convert the dew point to a measured percentage based on a well-known and easily determined relationship. Thus, the refrigerant exiting the moisture removal system may have about 98 to about 100% of the water removed, such as 98% to 99%, 98.5% to 99%, 99% to 99.5%, 99% to 100%, and 99.5% to 100%. As used herein, 100% removal of water means that the refrigerant may have no detectable levels of water. In any embodiment, the methods herein can remove moisture from the circulating refrigerant sufficiently such that there are no detectable levels of water in the refrigerant.

[0017] FIG. 1 shows a schematic diagram of a refrigeration circuit 1 utilizing a moisture removal unit 11. FIG. 1 is a general illustration and other components may be included in the refrigeration circuit 1 to ensure correct and safe operation of the refrigeration circuit 1. The refrigeration circuit 1 includes a compressor 3, a condenser 5, a heat exchanger 7, and a moisture removal unit 11. Optionally, a moisture analysis unit 29 may be included and some or all of the refrigerant may be conveyed to the moisture analysis unit 29 via conduit 20 and then returned to the refrigeration circuit via conduit 22. In configurations where the moisture analysis unit 29 is not present or where only a portion of the refrigerant is conveyed to the moisture analysis unit 29 via conduit 20, all or the remainder (respectively) of the refrigerant may be conveyed through the moisture removal unit 11 and returned to the refrigeration circuit 1 via conduit 18. Although FIG. 1 depicts the refrigerant being conveyed through the moisture analysis unit 2 downstream of the moisture removal unit 11 before rejoining the refrigeration circuit 1, the moisture analysis unit 29 may be incorporated anywhere in the refrigeration circuit 1 where the refrigerant is a gas. For example, moisture analysis unit 29 may be located downstream of moisture removal unit 11 after the refrigerant passing through moisture removal unit 11 rejoins refrigeration circuit 1. The moisture analysis unit and any necessary conduits may be incorporated into conduit 24 or in parallel with conduit 24.

[0018] Additional components of the refrigeration circuit 1 may include, but are not limited to, distributors, filters, valves, pressure gauges, sensors, etc., and combinations thereof. As used herein, when a diagram depicts a solid line (including one with an arrow) connecting two components, the line is used as a general representation to encompass the line(s) that fluidly connect the two components as well as other hardware such as pumps, connectors, pipes / tubing, and valves that may be located along the line. As used herein, the arrows represent the direction of refrigerant flow when the refrigeration circuit 1 is in use for cryogenic processing (e.g., cooling). The refrigeration circuit 1 of FIG. 1 conveys refrigerant from the compressor 3 to the condenser 5, and from the condenser 5 to the heat exchanger 7. In FIG. 1, the moisture removal unit 11 is downstream of the compressor 3 and upstream of the condenser 5, and thus the refrigerant is conveyed from the compressor 3 through the moisture removal unit 11 via conduit 17 to the condenser 5 via conduit 24.

[0019] The refrigeration circuit 1 may have one or more valves 16, 19 to control flow direction or distribute the refrigerant flow, or both. Optional valve 19 may direct the refrigerant leaving the compressor 3 to bypass optional moisture removal unit 11 by traveling through conduit 15 or through moisture removal unit 11 by traveling through conduit 17. Alternatively, valve 19 may distribute the refrigerant flow into two streams, one bypassing moisture removal unit 11 through conduit 15 and the other through moisture removal unit 11 through conduit 17. Optional valve 16 directs the refrigerant leaving moisture removal unit 11 to moisture analysis unit 29 through conduit 20 or bypassing moisture removal unit 29 through conduit 18. The configuration of refrigeration circuit 1 shown in FIG. 1 may be useful in both methods where the refrigerant is circulated through the moisture removal unit after the system is taken offline and warmed, and where no warming is required. As used herein, "warming" and grammatical variants thereof refer to a refrigeration circuit in which the refrigerant temperature downstream of the condenser and upstream of the heat exchanger is higher than the refrigerant temperature at that location during LNG production operations.

[0020] 1 may include optional valves 16, 19 for distributing the refrigerant flow. For example, these valves may distribute the flow so that the flow delivered to the moisture removal unit is between about 5% and about 15% of the total refrigerant volume. This range includes 5%-10% and 10%-15%. Optionally, a refrigerant source may be connected to the refrigeration circuit shown in Figure 1 to add refrigerant to the refrigeration circuit. The refrigerant source may be connected by any conduit or any part of the refrigeration circuit. In a particularly useful configuration, the refrigerant source is connected such that refrigerant is added to the refrigeration circuit downstream of heat exchanger 7 and upstream of compressor 3. One method for removing water from a refrigeration circuit includes warming a refrigeration circuit such as that shown in FIG. 1. When warmed, the refrigerant becomes a gas or vapor and may then be passed through a moisture removal unit at any location in the refrigeration circuit. For example, the refrigeration circuit may be warmed to a temperature at which the desiccant can sufficiently absorb water from the refrigerant. The operating temperature of the desiccant varies from desiccant to desiccant, and one of ordinary skill in the art will be familiar with useful operating temperatures for suitable desiccant. In either embodiment, the refrigeration circuit may be warmed, for example, to ambient temperature. As used herein, "ambient" temperature refers to the temperature of the air surrounding the refrigerant circuit and the temperature at which the circuit would be in equilibrium when taken offline.

[0021] For example, using a system such as that shown in FIG. 1, after conveying the refrigerant through the compressor 3, all or a portion of the refrigerant flow can be conveyed through the moisture removal unit 11, depending on the operation of the optional valve 19. The valve 19 can direct the refrigerant to proceed through the conduit 15 or the conduit 17. Alternatively, the valve 19 can divide the gas flow into a first and a second flow, directing the first flow through the conduit 15 bypassing the moisture removal unit 11 and the second flow through the conduit 17 to the moisture removal unit 11. The refrigerant bypassing the moisture removal unit 11 proceeds via conduit 24 to the condenser 5 and combines with the refrigerant leaving the moisture removal unit 11 through the conduit 18. The refrigerant completes the refrigeration circuit 1 being conveyed through the condenser 5 to the heat exchanger 7 and then back towards the compressor 3. Optionally, the refrigerant leaving the moisture removal unit 11 can be conveyed through the conduit 20 through the moisture analysis unit 29. Some or all of the refrigerant may be routed through optional valve 16 to conduit 20 .

[0022] Alternatively, the refrigerant may be conveyed through the moisture removal unit during normal operation of the refrigeration circuit without the need to warm and take it offline. Since the refrigerant should be in gas or vapor phase when passing through the moisture removal unit, the moisture removal unit may be incorporated into the refrigeration circuit after the compressor and before the condenser, as shown in FIG. 1. Depending on the operation of an optional valve 19, all or a part of the refrigerant flow may be conveyed to the moisture removal system 11 for removing moisture from the refrigerant. The valve 19 may distribute the refrigerant to proceed through the conduit 15 or the conduit 17. The valve 19 may also divide the gas flow into a first gas flow and a second gas flow, directing the first gas flow to the conduit 15 bypassing the moisture removal unit 11 and directing the second gas flow to the conduit 17 to the moisture removal unit. The refrigerant bypassing the moisture removal unit 11 will go to the condenser 5 to join the refrigerant leaving the moisture removal unit 11. The refrigerant may be conveyed to a condenser 5 to cool and liquefy the refrigerant. The liquefied refrigerant is then conveyed to a heat exchanger 7 to liquefy a natural gas stream (not shown) whilst completing the refrigeration circuit 1 and being conveyed back to the compressor 3.

[0023] The moisture removal unit may be a desiccant-based system. For example, the moisture removal unit may include a chamber with a desiccant bed and an area in which vaporized or gaseous refrigerant can be conveyed to contact the desiccant in the bed. Referring now to FIG. 2, refrigerant (represented by an open-head arrow) can enter moisture removal unit 11a through conduit 15a, pass through voids 23 between solid desiccant particles 25 in desiccant bed 21, and then exit moisture removal unit 11a through conduit 13a. The moisture removal unit may cycle the refrigerant over or through the desiccant bed multiple times. After a desired number of cycles of the refrigerant and a desired level of dehydration, the refrigerant may re-enter the refrigeration circuit.

[0024] In either embodiment, the moisture removal unit may be a permanent fixture in the refrigeration circuit where refrigerant flows continuously through the moisture removal unit during operation. Alternatively, the moisture removal unit may remain off-line until desired when appropriate valves are operated to direct refrigerant to the moisture removal unit. Alternatively, the moisture removal unit may be removable such that the moisture removal unit may be attached to the refrigeration circuit when desired and appropriate valves are operated to direct refrigerant to the moisture removal unit. For example, the moisture removal unit may be mounted on a mobile platform, such as a trailer towable by a vehicle. After a desired number of cycles, the moisture removal unit may be removed for use in a different refrigeration circuit or LNG train. Alternatively, the moisture removal unit may be a facility moisture removal unit and may direct refrigerant through a pipe to the facility moisture removal unit when desired. Although FIG. 1 depicts a refrigeration circuit having a single moisture removal unit 11, it is contemplated that the refrigeration circuit may incorporate multiple moisture removal units. For example, the refrigeration circuit may incorporate moisture removal units both downstream of the heat exchanger and downstream of the compressor.

[0025] In another method, the present disclosure provides a method for liquefying a gas stream using a system incorporating a moisture removal unit, for example as shown in Figure 3. The method includes the steps of: a) providing a gas flow; b) supplying a refrigerant; c) compressing the refrigerant to provide a compressed refrigerant; d) conveying at least a portion of the compressed refrigerant through a moisture removal unit; e) cooling and condensing the compressed refrigerant to provide a cooled refrigerant; f) conveying the cooled refrigerant to a heat exchanger; and g) passing the gas stream through a heat exchanger to cool at least a portion of the gas stream by indirect heat exchange with a cooled refrigerant. may include:

[0026] In FIG. 3, all numbered elements are the same as identified in FIG. 1. Additionally, the flow of a gas stream entering and exiting heat exchanger 7 is depicted. The gas stream, for example, natural gas, enters heat exchanger 7 via conduit 2, and the cooled condensed refrigerant absorbs energy from the natural gas and liquefies the gas. The liquefied gas then exits heat exchanger 7 via conduit 4. The gas stream may be methane rich, for example, natural gas. Natural gas contains methane as its major component (e.g., greater than 87 mole percent), but may have other components, for example, ethane, propane, isobutene, n-butane, isopentane, n-pentane, hexane, nitrogen, carbon dioxide, hydrogen, oxygen, sulfur, water, or any combination thereof. As discussed above, the refrigerant may be any type of refrigerant or refrigerant mixture, for example, methane, nitrogen, ethane, ethylene, propane, other commercially available refrigerant compounds, or combinations thereof. The refrigerant may be compressed. After all or a portion of the refrigerant has been compressed, it may be conveyed through a moisture removal unit that contains a desiccant bed to absorb any moisture in the refrigerant. It may then be conveyed to a condenser that liquefies and cools the refrigerant. The cooled refrigerant may then be conveyed to a heat exchanger such that energy from gas streams that are simultaneously conveyed through different portions of the heat exchanger are transferred to the cooled refrigerant, resulting in liquefaction of the gas stream.

[0027] In any of the embodiments described herein, the refrigerant downstream of the moisture removal unit 11 will have a lower moisture content than the refrigerant upstream of the moisture removal unit. The refrigerant downstream of the moisture removal system may be fully or partially dehydrated compared to the refrigerant entering the moisture removal unit. The efficiency of dehydration may depend on a variety of factors including the initial moisture content, the amount of desiccant, the type of desiccant, the physical properties of the desiccant (e.g., surface area, size, shape), and the amount of time the refrigerant spends in the moisture removal unit. The refrigerant may be cycled through the moisture removal unit multiple times. In any of the embodiments disclosed herein, the refrigerant can be circulated through the refrigeration circuit, including the moisture removal unit, for a desired time, which may depend on the time it takes for the refrigerant to complete a full cycle through the refrigeration circuit and the desired number of cycles through the refrigeration circuit. Those skilled in the art will be able to modify the equipment to achieve the desired dehydration results. The fully or partially dehydrated gas can cause sublimation of ice precipitates or vaporization of water precipitates upon contact with the fully or partially dehydrated gas elsewhere in the refrigeration circuit. The water vapor can then join the gas flow and be exposed to a downstream moisture removal unit.

[0028] By using the methods disclosed herein to remove moisture from the refrigerant, water can accumulate less frequently in the components of the refrigeration circuit (e.g., heat exchangers) than would occur without the use of a moisture removal unit. By implementing one of the many embodiments of a moisture removal unit in a refrigeration circuit as disclosed and described herein, it is believed that the traditional "defrost" process may not be necessary or may be performed less frequently. By using the methods and systems disclosed herein, the time required between defrosts can be increased compared to methods that do not use a moisture removal unit. It is believed that in some cases, defrosting may not be necessary at all to maintain normal and continuous operation of the refrigeration circuit for cryogenic processing. EXAMPLES

[0029] Example embodiment One non-limiting example embodiment is a system for removing moisture from a refrigerant in an LNG refrigeration circuit, the system including: a refrigerant compressor; a refrigerant condenser; a moisture removal unit including a desiccant; and a heat exchanger, fluidly connected in a loop where the refrigerant compressor is upstream of the moisture removal unit, the moisture removal unit is upstream of the refrigerant condenser, the refrigerant condenser is upstream of the heat exchanger, and the heat exchanger is upstream of the refrigerant compressor. Optionally, this embodiment may further include the following elements: element 1: the system further includes a valve capable of distributing the refrigerant flow into a first flow and a second flow; element 2: a moisture removal unit is removably attached to the system; element 3: the refrigerant flows through a desiccant packed bed in the moisture removal unit; element 4: the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof; element 5: the system further includes a conduit for fluidly connecting a refrigerant source to the refrigeration circuit; element 6: the system further includes a moisture analysis unit downstream of the moisture removal unit; element 7: element 6 and the moisture analysis unit measure the dew point of the refrigerant. Exemplary combinations include, but are not limited to, combinations of element 1 and one or more of elements 2-7; combinations of element 2 and one or more of elements 3-7; combinations of element 3 and one or more of elements 4-7; combinations of element 4 and one or more of elements 5-7; combinations of element 5 and one or more of elements 6-7; combinations of elements 6 and 7.

[0030] Another non-limiting example embodiment is a method for removing moisture from a refrigerant in an LNG refrigeration circuit, the method comprising: conveying the refrigerant stream from a compressor to a moisture removal unit; conveying the refrigerant stream through a moisture removal unit containing a desiccant; and conveying the refrigerant stream from the moisture removal unit to a condenser. Optionally, this embodiment can further include one or more of the following elements: element 2; element 4; element 8: the refrigeration circuit is at ambient temperature; and element 9: the method further comprises splitting the refrigerant stream into a first stream and a second stream and conveying the second stream to the moisture removal unit. Exemplary combinations include, but are not limited to, a combination of elements 2 and 4, optionally further in combination with element 8 and / or element 9; a combination of elements 8 and 9, optionally further in combination with element 2 and / or element 4; a combination of elements 2 and 8, optionally further in combination with element 4 and / or element 9; a combination of elements 4 and 9, optionally further in combination with element 2 and / or element 8; a combination of elements 2 and 9, optionally further in combination with element 4 and / or element 8; and a combination of elements 4 and 8, optionally further in combination with element 2 and / or element 9.

[0031] Yet another non-limiting example embodiment is a method for cryogenic processing of LNG, the process comprising the steps of: compressing a refrigerant; conveying at least a portion of the refrigerant to a moisture removal unit containing a desiccant to form a dehydrated refrigerant; cooling and condensing the dehydrated refrigerant to provide a cooled, dehydrated liquid refrigerant; conveying the cooled, dehydrated refrigerant to a heat exchanger; and passing a methane-rich LNG stream through the heat exchanger to cool at least a portion of the LNG stream by indirect heat exchange with the cooled, dehydrated refrigerant. Optionally, this embodiment can further include one or more of the following elements: element 2; element 4; element 9; element 10: the LNG stream comprises between 87 mole percent and 97 mole percent methane; and element 11: the method further includes conveying some or all of at least a portion of the refrigerant to a moisture analysis unit downstream of the moisture removal unit. Example combinations include, but are not limited to, combinations of embodiments 2 and 4, optionally further combined with one or more of elements 9-11; combinations of two or more of elements 9-11, optionally further combined with element 2 and / or element 4; and combinations of one or more of elements 9-11 with element 2 and / or element 4.

[0032] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties, e.g., molecular weight, reaction conditions, and the like, used in the specification and related claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties sought to be obtained by embodiments of the present invention. In any event, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. One or more exemplary embodiments incorporating embodiments of the invention disclosed herein are presented. For the sake of clarity, not all physical implementation features are described or shown in this application. In developing a physical embodiment incorporating an embodiment of the invention, many implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary from implementation to implementation and from time to time. Although the developer's efforts may require significant time, the efforts are nevertheless routine to undertake for those skilled in the art and having the benefit of this disclosure.

[0033] Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. Thus, the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. The specific embodiments described above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, there is no intention to be limited to the details of construction or design shown herein, other than as set forth in the claims that follow. It is therefore evident that the specific exemplary embodiments described above may be altered, combined or modified, and all such variations are considered to be within the scope and spirit of the invention. The inventions illustratively disclosed herein may suitably be practiced in the absence of any element not specifically disclosed herein and / or any element disclosed herein. Although compositions and methods are described in terms "comprising," "containing," or "including" various components or steps, the compositions and methods may "consist essentially of" or "consist of" the various components and steps. All of the above numbers and ranges may vary slightly in amount. Whenever a numerical range with a lower and upper limit is disclosed, any numerical value falling within the range and any encompassing range is specifically disclosed. In particular, any range of values ​​disclosed herein (in the form "about a to about b," or in other words, "about a to b," or in other words, "about a b") should be understood to represent any numerical value and range encompassed within the broader range of values. Moreover, the terms in the claims have their plain and ordinary meanings unless expressly indicated otherwise and unless expressly defined by the patentee. Moreover, the indefinite article "a" or "an," as used in the claims, is defined in this application to mean one or more of the element it introduces. It can be said that the present invention includes the following features. (Appendix 1) the below described: Refrigerant compressor; Refrigerant condenser; a moisture removal unit containing a desiccant; and A heat exchanger is included. These are fluidly connected in a loop, with the refrigerant compressor upstream of the moisture removal unit, the moisture removal unit upstream of the refrigerant condenser, the refrigerant condenser upstream of the heat exchanger, and the heat exchanger upstream of the refrigerant compressor. (Appendix 2) 2. The system of claim 1, further comprising a valve capable of distributing the refrigerant flow into a first flow and a second flow. (Appendix 3) 3. The system according to any one of claims 1 to 2, wherein the moisture removal unit is removably attached to the system. (Appendix 4) 4. The system of any one of claims 1 to 3, wherein the refrigerant flows through a packed bed of desiccant in the moisture removal unit. (Appendix 5) 5. The system of any one of claims 1 to 4, wherein the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof. (Appendix 6) 6. The system of any one of claims 1 to 5, further comprising a conduit fluidly connecting a refrigerant source to the refrigeration circuit. (Appendix 7) The system of any one of claims 1 to 6, further comprising a moisture analysis unit downstream of the moisture removal unit. (Appendix 8) The system of any one of claims 1 to 7, wherein the moisture analysis unit measures a dew point of the refrigerant. (Appendix 9) the below described: conveying the refrigerant stream from the compressor to a moisture removal unit; conveying the refrigerant stream through the moisture removal unit, which includes a desiccant; and conveying said refrigerant stream from said moisture removal unit to a condenser; The method includes: (Appendix 10) 10. The method of claim 9, further comprising splitting the refrigerant stream into a first stream and a second stream, and conveying the second stream to the moisture removal unit. (Appendix 11) 11. The method according to any one of appendix 9 to 10, wherein the refrigeration circuit is at ambient temperature. (Appendix 12) 12. The method of any one of claims 9 to 11, further comprising splitting the refrigerant stream into a first stream and a second stream, and conveying the second stream to the moisture removal unit. (Appendix 13) 13. The method of any one of claims 9 to 12, wherein the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof. (Appendix 14) the below described: Compressing the refrigerant; conveying at least a portion of the refrigerant to a moisture removal unit including a desiccant to form a dehydrated refrigerant; cooling and condensing the dehydrated refrigerant to provide a cooled dehydrated liquid refrigerant; conveying the cooled dehydrated refrigerant to a heat exchanger; and passing a methane-rich liquid natural gas (LNG) stream through a heat exchanger to cool at least a portion of the LNG stream by indirect heat exchange with the cooled, dehydrated refrigerant; The method includes: (Appendix 15) 15. The method of claim 14, wherein the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof. (Appendix 16) 16. The method of any one of claims 14-15, wherein the LNG stream comprises between 87 mole percent and 97 mole percent methane. (Appendix 17) 17. The method of any one of claims 14 to 16, wherein the moisture removal unit is removably attached to the system. (Appendix 18) 18. The method of any one of claims 14 to 17, further comprising splitting the refrigerant stream into a first stream and a second stream, and conveying the second stream to the moisture removal unit. (Appendix 19) 19. The method of any one of claims 14 to 18, further comprising conveying some or all of the at least a portion of the refrigerant downstream of the moisture removal unit to a moisture analysis unit.

Claims

1. Refrigerant compressor; Refrigerant condenser; A moisture removal unit including a desiccant; and A heat exchanger is included. a system in which the refrigerant compressor is upstream of the moisture removal unit, the moisture removal unit is upstream of the refrigerant condenser, the refrigerant condenser is upstream of the heat exchanger, and the heat exchanger is fluidly connected in a refrigeration circuit upstream of the refrigerant compressor, a cooling circuit dividing a first flow through the moisture removal unit and a second flow through a conduit that bypasses the moisture removal unit, and wherein the refrigerant in the cooling circuit passes directly from the refrigerant condenser to the heat exchanger as liquid refrigerant.

2. The system of claim 1 , further comprising a valve capable of directing a second flow through the conduit.

3. 3. The system of claim 1 or 2, wherein the refrigerant flows through a packed bed of desiccant in the moisture removal unit.

4. The system of any one of claims 1 to 3, wherein the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof.

5. The system of any one of claims 1 to 4, further comprising a conduit fluidly connecting a refrigerant source to the cooling circuit.

6. The system of any one of claims 1 to 5, further comprising a moisture analysis unit downstream of the moisture removal unit.

7. conveying a refrigerant stream through a cooling circuit including a refrigerant compressor, a refrigerant condenser, a moisture removal unit including a desiccant, and a heat exchanger, which are fluidly connected such that the refrigerant compressor is upstream of the moisture removal unit, the moisture removal unit is upstream of the refrigerant condenser, the refrigerant condenser is upstream of the heat exchanger, and the heat exchanger is upstream of the refrigerant compressor, the refrigerant stream passing from the refrigerant compressor such that the refrigerant in the cooling circuit passes directly from the refrigerant condenser to the heat exchanger as liquid refrigerant, a first portion of the refrigerant stream being conveyed to the moisture removal unit, and a second portion of the refrigerant stream being conveyed through a conduit that bypasses the moisture removal unit; conveying a first portion of said refrigerant stream through said moisture removal unit; recombining the first portion of the refrigerant stream with the second portion of the refrigerant stream to form a recombined refrigerant stream; and conveying said recombined refrigerant stream to said refrigerant condenser. The method includes:

8. 8. The method of claim 7, wherein the cooling circuit is at ambient temperature when the cooling circuit is taken offline and the moisture removal unit is operated.

9. 9. The method of claim 7 or 8, wherein the desiccant is selected from the group consisting of silica, activated carbon, calcium sulfate, calcium chloride, molecular sieves, and combinations thereof.

10. The system of any one of claims 1 to 6, wherein the moisture removal unit is removably attached to the cooling circuit.

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