Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J5/00—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants
  • F25J5/002—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger
  • F25J5/005—Arrangements of cold exchangers or cold accumulators in separation or liquefaction plants for continuously recuperating cold, i.e. in a so-called recuperative heat exchanger in a reboiler-condenser, e.g. within a column
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D9/0006—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the plate-like or laminated conduits being enclosed within a pressure vessel
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/026—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits
  • F28F9/027—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits in the form of distribution pipes
  • F28F9/0273—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits in the form of distribution pipes with multiple holes
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/026—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits
  • F28F9/0278—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits in the form of stacked distribution plates or perforated plates arranged over end plates
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/02—Header boxes; End plates
  • F28F9/026—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits
  • F28F9/028—Header boxes; End plates with static flow control means, e.g. with means for uniformly distributing heat exchange media into conduits by using inserts for modifying the pattern of flow inside the header box, e.g. by using flow restrictors or permeable bodies or blocks with channels
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2250/00—Details related to the use of reboiler-condensers
  • F25J2250/02—Bath type boiler-condenser using thermo-siphon effect, e.g. with natural or forced circulation or pool boiling, i.e. core-in-kettle heat exchanger
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2290/00—Other details not covered by groups F25J2200/00 - F25J2280/00
  • F25J2290/32—Details on header or distribution passages of heat exchangers, e.g. of reboiler-condenser or plate heat exchangers

Definitions

• the present invention relates generally to equipment utilized during liquefaction of natural gas. More particularly, but not by way of limitation, embodiments of the present invention include a refrigerant inlet flow distributor used to introduce two-phase refrigerant into a shell of a heat-exchanging apparatus.
• Natural gas is an important resource widely used as energy source or as industrial feedstock used in, for example, manufacture of plastics. Comprising primarily of methane, natural gas is a mixture of naturally occurring hydrocarbon gases and is typically found in deep underground natural rock formations or other hydrocarbon reservoirs. Other components of natural gas include, but are not limited to, ethane, propane, carbon dioxide, nitrogen, and hydrogen sulfide.
• natural gas is transported from source to consumers through pipelines that physically connect a reservoir to a market. Because natural gas is sometimes found in remote areas devoid of necessary infrastructure (i.e., pipelines), alternative methods for transporting natural gas must be used. This situation commonly arises when the source of natural gas and the market are separated by great distances, for example a large body of water. Bringing this natural gas from remote areas to market can have significant commercial value if the cost of transporting natural gas is minimized.
• One alternative method of transporting natural gas involves converting natural gas into a liquefied form through a liquefaction process. Because natural gas exists in vapor phase under standard atmospheric conditions, it must be subjected to certain thermodynamic processes in order to be liquefied to produce liquefied natural gas (LNG). In its liquefied form, natural gas has a specific volume that is significantly lower than its specific volume in its vapor form. Thus, the liquefaction process greatly increases the ease of transporting and storing natural gas, particularly in cases where pipelines are not available. For example, ocean liners carrying LNG tanks can effectively link a natural gas source with a distant market when the source and market are separated by large bodies of water.
• LNG liquefied natural gas
• Converting natural gas to its liquefied form can have other economic benefits. For example, storing LNG can help balance out periodic fluctuations in natural gas supply and demand. In particular, LNG can be more easily "stockpiled" for later use when natural gas demand is low and/or supply is high. As a result, future demand peaks can be met with LNG from storage, which can be vaporized as demand requires.
• the natural gas In order to store and transport natural gas in the liquid state, the natural gas is typically cooled to -160°C at near-atmospheric vapor pressure. Liquefaction of natural gas can be achieved by sequentially passing the gas at an elevated pressure through a plurality of cooling stages whereupon the gas is cooled to successively lower temperatures until the liquefaction temperature is reached. Cooling is generally accomplished by indirect heat exchange with one or more refrigerants such as propane, propylene, ethane, ethylene, methane, nitrogen, carbon dioxide, or combinations of the preceding refrigerants (e.g., mixed refrigerant systems).
• refrigerants such as propane, propylene, ethane, ethylene, methane, nitrogen, carbon dioxide, or combinations of the preceding refrigerants (e.g., mixed refrigerant systems).
• Cryogenic exchangers e.g., shell-and-tube exchanger, brazed aluminum heat exchanger, core-in-shell exchanger, etc.
• Cryogenic exchangers may be used, for example, to transfer heat from a natural gas stream to a refrigerant stream.
• Some conventional core-in-shell heat exchangers feature a brazed aluminum heat exchanger (BAHX) core inserted in a horizontally-oriented, cylindrical pressure vessel shell. These shells tend to be long in length to ensure that the BAHX core is submerged in a pool of evenly distributed refrigerant.
• BAHX brazed aluminum heat exchanger
• a BAHX exchanger is typically compact, rigid, and constructed of several different aluminum alloys.
• Aluminum has no endurance limit, or stress value below which the material will withstand infinite load cycles.
• BAHX's are susceptible to fatigue failure when subjected to repeated thermal cycles, high internal temperature gradients, or excessive thermal transients. Erosion damage to the core can result when liquid refrigerant repeatedly impinges on the BAHX core directly inside the shell. Consequently, flow control that results in good distribution of fluid may be particularly important when introducing a two-phase refrigerant into a core-in-shell exchanger as two-phase fluids can rapidly change BAHX metal temperature.
• a conventional LNG facility typically features a two-phase expander that can at least partially expand a refrigerant into the vapor phase to produce a two-phase refrigerant.
• Piping arrangements used to transfer fluids in LNG facilities are typically elaborate and asymmetrically configured which can lead to momentum-induced flow maldistribution of a two-phase refrigerant as it enters core -in- shell exchangers.
• the present invention relates generally to equipment utilized during liquefaction of natural gas. More particularly, but not by way of limitation, embodiments of the present invention include a refrigerant inlet flow distributor used to introduce two-phase refrigerant into a shell of a heat-exchanging apparatus.
• One example of a heat-exchanging apparatus comprises: an exchanger shell; a heat-exchanging core disposed inside the exchanger shell; and an inlet flow distributor for directing incoming fluid comprising: a baffle plate with an array of orifice holes, wherein the orifice holes are off-set from the heat-exchanging core.
• FIG. 1 is a schematic illustrating a core-in-shell exchanger equipped with a refrigerant inlet flow distributor according to one or more embodiments.
• FIG. 2 is a cross-sectional view of the core-in-shell exchanger from FIG. 1.
• the present invention disclosed herein is directed to an inlet flow distributor designed to improve flow of a fluid entering a relatively large cross-sectional area (e.g., shell of a core-in-shell exchanger) from a relatively small cross-sectional area (e.g., conduit).
• the inlet flow distributor is designed to impart a predetermined and/or desired pressure drop on the entering fluid (e.g., refrigerant in an LNG liquefaction process) for the purpose of improving flow distribution.
• this device can also counteract momentum-induced refrigerant flow maldistribution problems resulting from non-symmetrical external piping arrangement in a core-in-shell exchanger.
• the inlet flow distributor can prevent or impede erosion damage to certain components (e.g., BAHX cores) by reducing or preventing liquid refrigerants from impinging directly onto the certain components installed inside the exchanger shell.
• Some conventional core-in-shell exchangers address flow distribution and erosion protection issues by, for example, utilizing an internal flow distributor having large slots in the bottom or employing an internal flow distributor open at both ends.
• These conventional core-in-shell exchangers may be hampered by certain design issues.
• the large slots in the former design typically do not impart sufficient pressure drop to provide good refrigerant flow distribution inside the shell.
• core-in- shell exchangers employing these internal flow distributors can allow refrigerants to impinge directly on the BAHX core.
• the inlet flow distributor may be integrated or otherwise utilized in a compatible system to control fluid flow.
• references herein are made to a core-in-shell exchanger as an example compatible system, this is not intended to be limiting.
• Other compatible systems e.g., shell and tube exchanger comprising tube bundle as the heat-exchanging core
• core-in-shell exchanger configurations not disclosed herein may be used in conjunction with the inlet flow distributor of the present invention.
• While at least one embodiment described herein relates to a core-in-shell exchanger featuring an inlet flow distributor of the present invention installed in a liquefied natural gas facility for use during an LNG process, this is not intended to be limiting.
• Other compatible facilities/processes may include, but are not limited to, gas plants, NGL processing plants, ammonia processing plants, ammonia refrigeration systems, ethylene plants and the like.
• FIGS. 1-2 are schematics only and, therefore, many items of equipment that would be needed in a commercial core-in-shell exchanger for successful operation have been omitted for sake of clarity. Such items may include, for example, nozzles, inlets, outlets, header tanks, spacer bars, and the like.
• Core-in-shell exchangers (sometimes referred to as "core-in-drum” or a commercially available version called Core-in-Kettle® from Chart E & C located in La Crosse, WI) are well-known heat exchangers often used in lieu of shell-and-tube cryogenic exchangers during liquefaction of natural gas ("LNG process").
• Some core-in- shell exchangers can contain up to 10 times more heat transfer surface per unit volume than a shell-and-tube unit despite being as little as about half in size and about a fifth in weight.
• the core-in-shell heat exchanger 5 includes a BAHX core 20 housed in a hollow exchanger shell 10. As shown, the exchanger shell 10 is cylindrical and horizontally-oriented such that its dimension along the horizontal axis is substantially longer than its dimension along the vertical axis.
• the illustrated BAHX (sometimes referred to as "plate-fin exchanger") core 20 can be constructed from alternating layers of corrugated fins and flat separator sheets. The stacked arrangement is then vacuum brazed to yield the BAHX core 20.
• FIG. 2 is a cross-sectional view of the core- in-shell exchanger illustrated in FIG. 1. For clarity, same reference numbers are used in FIGS. 1 and 2.
• the inlet flow distributor 30 is installed near or at the top portion of the core-in-shell exchanger 5 such that fluid injected horizontally into the exchanger through inlet nozzles 50 is discharged vertically down through the orifice holes 40.
• the arrows in FIG. 2 indicate the direction of fluid flow.
• the inlet flow distributor 5 comprises of a two perpendicular plates joined along an edge to form an "L" shaped structure as illustrated in FIG. 2.
• the vertical plate 35 is solid while round orifice holes 40 have been drilled on the horizontal baffle plate 60
• Plate dimensions and orifice hole diameters will vary depending on a number of factors including, but not limited to, physical size of the shell, amount of refrigerant flow entering the shell, and physical properties of the refrigerant.
• the orifice holes 40 are strategically-sized, -shaped and located to provide a preselected and/or desired distribution of refrigerant flow.
• the inlet flow distributor 30 includes an array of orifice holes comprising two rows of orifice holes 40, each row extending out to the lateral ends of the inlet flow distributor 30. The rows are defined by the orifice holes that have been drilled and/or fashioned onto the horizontal baffle plate 60. As illustrated in FIG.
• the top row comprises a non- interrupted row of orifice holes while the bottom row is interrupted by a non-drilled area such that the array of orifice holes are off-set or misaligned vertically to the BAHX core to ensure that the two-phase refrigerant mixture does not jet out of the orifice holes and impinge directly on the BAHX core (see FIG. 2).
• the horizontal baffle plate 60 may contain any arrangement of orifice holes, including any number of rows, columns, non-drilled area, etc.
• the specific dimensions and arrangement of the orifice holes depend a number of factors including, but not limited to, BAHX core dimensions, shell length and width, refrigerant inlet weight fraction vapor, refrigerant inlet liquid density, refrigerant inlet vapor density, number of orifice holes, orifice hole diameter, and orifice hole discharge coefficient.
• the total area of the orifice holes can be about 5% to about 25% of total area of the baffle plate.
• the orifice holes may have non-round shapes. Suitable examples of non-round shapes may include, but are not limited to, squares, rectangles, hexagons, stars, crosses, and the like.
• the inlet flow distributor 30 may include one or more lateral solid plates that flank the lateral sides of the inlet flow distributor 30.
• the inlet flow distributor may be made from a material selected from the group consisting of: stainless steels, austenitic stainless steels, carbon steel alloys, aluminum, aluminum alloys, and combinations thereof.
• the core-in-shell exchanger 5 can be integrated in a refrigeration system such that a two-phase refrigerant stream enters through inlet nozzles 50.
• the inlet flow distributor 30 is used to control the flow of the two-phase refrigerant to the exchanger shell 10.
• the two-phase refrigerant is injected into the inlet flow distributor 30 where it flows laterally, away from the inlet nozzles 50 before exiting through the array of orifice holes 40 such that the refrigerant does not directly impinge the BAHX core 20 and collecting evenly at the bottom of the exchanger shell 10. Over time, the BAHX core 20 becomes submerged in a pool of liquid refrigerant.
• the cold refrigerant boils and partially vaporizes as a warm process stream flowing through the BAHX core 20 is simultaneously cooled as described above.
• the inlet flow distributor 30 resists flow maldistribution that can result from non- symmetric refrigerant piping external to the core-in-shell exchanger.
• the round orifice holes are located such that a refrigerant entering the exchanger shell 10 does not impinge directly on the BAHX core and thus prevents erosion damage to the brazed aluminum core.
• This example calculates a sample pressure drop (i.e., decrease in pressure from one point in a tube to another point downstream) that can occur on a two-phase refrigerant as it is introduced through a refrigerant inlet flow distributor according to one or more embodiments.
• Equations (1) and (2) show different forms of a separated flow two-phase pressure loss model where AP is a single phase pressure drop through a tube, / is friction factor,
• L is orifice hole length
• D is orifice hole diameter
• v velocity
• g c gravitational constant (1.00)
• /? density
• Equation (3) describes the relationship between total mass velocity ( G t ), total mass flow rate and total area ( A mal ) of orifice holes, where D orifice is orifice hole diameter.
• Velocity (v ) is equal to the total mass flow rate divided by density and total area as shown in equation (4). Rearranging and substituting for G t yields equation (5). m total G,
• Equation (6) which describes the single-phase pressure drop in general form.
• Single-phase liquid pressure drop ⁇ AP l can be calculated by multiplying the general form pressure drop with (1-y) as shown in equation (7) below.
• Equation (9) expands the pressure loss model to two-phase pressure drop ⁇ AP f ):
• AP f 22.715— y ⁇ -— 1-19.58- (22.715- ⁇ X498.56- ⁇ ) + 498.56- ⁇ - m ⁇ s V m- s m - s m- s
• Table 2 summarizes geometry of the inlet flow distributor of Example 1.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Separation By Low-Temperature Treatments (AREA)
• Details Of Heat-Exchange And Heat-Transfer (AREA)

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• 2014
  • 2014-03-07 US US14/200,431 patent/US20140284032A1/en not_active Abandoned
  • 2014-03-07 JP JP2016504302A patent/JP2016516972A/ja active Pending
  • 2014-03-07 WO PCT/US2014/021935 patent/WO2014150033A1/en active Application Filing
  • 2014-03-07 EP EP14768055.7A patent/EP2976587A4/en not_active Withdrawn

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