Fluid heating system and method

Abstract

A method and apparatus is provided for warming a liquid or gas. The apparatus may be suitable for the vaporization of liquefied natural gas. In order to warm the liquid or gas for vaporization for other purposes, a heating tower is used. The heating tower can include a system for drawing air through, and spraying water over, a tube bundle type heat exchanger. The heat exchanger may include the material to be heated itself, or may be part of an intermediate loop containing an intermediate heat exchange fluid. In the case of the intermediate loop, a second heat exchanger is provided which on one side receives fluid from the intermediate loop which is warmed by the heating tower, and on the other side provides heat to the material which is desired to be heated.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 10/965,176, filed on Oct. 15, 2004, entitled “Power Generating System and Method,” the disclosure of which is hereby incorporated by reference in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 11/068,388, filed on Mar. 1, 2005, entitled “Water Cooler Apparatus And Method,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is a continuation-in-part of U.S. patent application Ser. No. 11/068,389, filed Mar. 1, 2005, entitled “Dual Drive Apparatus And Method,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 11/068,387, filed Mar. 1, 2005, entitled “Fluid Cooling With Drift Eliminator,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 10/942,940, filed Sep. 17, 2004, entitled “Heating Tower With Isolation,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 11/181,863, filed Jul. 15, 2005, entitled “Dry Heating Tower Apparatus and Method with Isolation of Outlet and Inlet Air,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 10/942,939, filed Sep. 17, 2004, entitled “Heating Tower Apparatus And Method With Wind Direction Adaptation,” the disclosure of which is also incorporated by reference herein in its entirety, and this application is also a continuation-in-part of U.S. patent application Ser. No. 11/181,864, filed on Jul. 15, 2005, entitled “Dry Heating Tower Apparatus and Method with Air Adaptation,” the disclosure of which is also incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates generally to a system and method for imparting heat to a circulating fluid. More particularly, the present invention relates, for example, to an apparatus and method that can impart heat to a fluid such as liquefied natural gas (LNG) or the like, in some applications, as part of a process of vaporizing the liquid natural gas.

BACKGROUND OF THE INVENTION

The cryogenic liquefaction of natural gas is routinely practiced as a means for converting natural gas into a more convenient form for transportation. Such liquefaction typically reduces the volume by about 600 fold and results in an end product that can be stored and transported more easily. Also, it is desirable to store excess natural gas so that it may be easily and efficiently supplied when the demand for natural gas increases. One practical means for transporting natural gas and also for storing excess natural gas is to convert the natural gas to a liquefied state for storage and/or transportation and then vaporize the liquid as demand requires.

Natural gas often is available in areas remote from where it will ultimately be used, therefore the liquefaction of natural gas is even of greater importance. Typically, natural gas is transported via pipeline from the supply source directly to the user market. However, it has become more common that the natural gas be transported from a supply source which is separated by great distances from the user market, where a pipeline is either not available or is impractical. This is particularly true of marine transportation where transport must be made by ocean-going vessels. Ship transportation of natural gas in the gaseous state is generally not practical because of the great volume of the gas in the gaseous state, and because appreciable pressurization is required to significantly reduces the volume of the gas. Therefore, in order to store and transport natural gas, the volume of the gas is typically reduced by cooling the gas to approximately −240° F. to approximately −260° F. At this temperature, the natural gas is converted into liquefied natural gas (LNG), which possesses near atmospheric vapor pressure. Upon completion of transportation and/or storage of the LNG, the LNG must be returned to the gaseous state prior to providing the natural gas to the end user for consumption.

Typically, the re-gasification or vaporization of LNG is achieved through the employment of various heat transfer fluids, systems, and processes. For example, some processes used in the art utilize evaporators that employ hot water or steam to heat the LNG to vaporize it. These heating processes have drawbacks however, because the hot water or steam often times freezes due to the extreme cold temperatures of the LNG, which, in turn, causes the evaporators to clog. In order to overcome this drawback, alternative evaporators are presently used in the art, such as open rack evaporators, intermediate fluid evaporators, and submerged combustion evaporators.

Open rack evaporators typically use seawater or like as a heat source for countercurrent heat exchange with LNG. Similar to the evaporators mentioned above, open rack evaporators tend to “ice up” on the evaporator surface, causing increased resistance to heat transfer. Therefore, open rack evaporators must be designed having evaporators with increased heat transfer area, which entails a higher equipment cost and increased footprint of the evaporator.

Instead of vaporizing LNG by direct heating by water or steam, as described above, evaporators of the intermediate type employ an intermediate fluid or refrigerant such as propane, fluorinated hydrocarbons or the like, having a low freezing point. The refrigerant can be heated with hot water or steam, and then the heated refrigerant or refrigerant mixture is passed through the evaporator and used to vaporize the LNG. Evaporators of this type overcome the icing and freezing episodes that are common in the previously described evaporators, however these intermediate fluid evaporators require a means for heating the refrigerant, such as a boiler or heater. These types of evaporators also have drawbacks because they are very costly to operate due to the fuel consumption of the heating means used to heat the refrigerant.

One practice currently employed in the art to overcome the high cost of operating boilers or heaters is the use of water towers, by themselves or in combination with the heaters or boilers, to heat the refrigerant that acts to vaporize the LNG. In these systems, water is passed into a water tower wherein the temperature of the water is elevated. The elevated temperature water is then used to heat the refrigerant such as glycol via a first evaporator, which in turn is used to vaporize the LNG via a second evaporator.

These systems, while often generating desirable performance, do not always provide a desired level of heating of the fluid in certain applications and/or atmospheric conditions or site locations.

Accordingly, there is a need in the art to provide a system and method for warming a circulating fluid to a desired extent.

SUMMARY OF INVENTION

The foregoing needs are met, to a great extent, by the present invention, wherein in one aspect an apparatus is provided that in some embodiments provides a system and method for warming a circulating fluid.

In accordance with one embodiment of the present invention, an apparatus for warming a second liquid comprises a tower which comprises a first heat exchanger; a spray head above the tube bundle for spraying a first liquid over the first heat exchanger; a first fluid collection basin disposed below the first heat exchanger; and a pump for recirculating the first liquid from the collection basin to the spray head; and a supply of second liquid to the first heat exchanger which is colder than ambient conditions, whereby the second liquid exiting the first heat exchanger is heated to a warmer temperature than the second liquid entering the first heat exchanger.

In accordance with another embodiment of the present invention, an apparatus for warming a second liquid comprises a tower comprising a first heat exchanging means; a spraying means above the tube bundle for spraying a first liquid over the first heat exchanging means; a first fluid collecting means disposed below the first heat exchanger; and a means for recirculating the first liquid from the collecting means to the spraying means; and a supply of second liquid to the first heat exchanging means which is colder than ambient conditions, whereby the second liquid exiting the first heat exchanging means is heated to a warmer temperature than the second liquid entering the first heat exchanging means.

In accordance with yet another embodiment of the present invention, a method for warming a second liquid using a tower comprising a first heat exchanger, a spray head above the tube bundle for spraying a first liquid over the first heat exchanger a first fluid collection basin disposed below the first heat exchanger; and a pump for recirculating the first liquid from the collection basin to the spray head the method comprising:

supplying the second liquid to the first heat exchanger at colder than ambient conditions, in order to heat the second liquid exiting the first heat exchanger to a warmer temperature than the second liquid entering the first heat exchanger.

There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto.

In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic view of a circuit for vaporizing liquefied natural gas in accordance with an embodiment in the invention.

FIG. 2 is a perspective view of a fluid heating tower in accordance with a preferred embodiment of the invention.

FIG. 3 is a perspective view of the tower of FIG. 2, with a fan shroud cut away.

FIG. 4 is a perspective view of a tower of FIG. 2, showing a plurality of tube bundles resting on a support lattice.

FIG. 5 is a perspective view of a spray module used in the heating tower of FIG. 2.

DETAILED DESCRIPTION

Some preferred embodiments of the present invention provide systems and methods for heating a circulating fluid. In one example, the circulating fluid is an intermediate fluid such as a refrigerant, that in turn is used to warm an intermediate heat exchanger, to impart heat via the intermediate heat exchanger, to liquefied natural gas, which is to be vaporized by the addition of the heat. It should be understood, however, that the present invention is not limited in its application to liquefied natural gas, but can also be used to heat any suitable circulating fluid, whether via an intermediate heat exchanger or via direct circulation through the tower without an intermediate heat exchanger.

Referring now to FIG. 1, a liquefied natural gas vaporization circuit generally designated 12 is illustrated. As illustrated in FIG. 1, the liquefied natural gas vaporization circuit 12 includes a liquefied natural gas storage tank or vessel 16 that stores the liquefied natural gas to be vaporized.

The liquefied natural gas storage vessel 16 is in fluid communication with, or connected to, via a conduit 20, a heat exchanger assembly 18, the function of which will be described in more detail below. The liquefied natural gas passes through a side 18A of the heat exchanger 18 and absorbs heat that is imparted to it from a side 18B of the heat exchanger 18. The heated natural gas is output from an output 19 in a vaporized state for subsequent use. The heat exchanger 18 has a side 18B that interacts with a closed loop circuit that passes an intermediate fluid through a heating tower 22. The closed loop circuit is filled with a suitable intermediate heat transfer liquid, such as, for example, a refrigerant. Although a refrigerant is given as an example, it will be appreciated that the heating tower may be used to heat any suitable liquid.

The details of a preferred heating tower 22 are illustrated in FIGS. 2-5 and discussed in further detail later below. The heating tower 22 receives the intermediate liquid from the heat exchanger 18 via an input conduit 24. The heating tower 22 heats the received intermediate fluid, and outputs the relatively warmed intermediate fluid to an output conduit 26. The output conduit 26 feeds relatively warm intermediate fluid to the side 18B of the heat exchanger 18, which is used to heat and vaporize the liquefied natural gas that arrives in conduit 20, and is output from conduit 19.

Some examples of types of heating towers 22 that can be used include both so-called “dry” cooling towers, and so-called “wet” cooling towers. In the circuit in FIG. 1, the LNG remains in conduits 19 and 20 and one side of the heat exchanger 18, and a separate intermediate fluid is used in a closed loop circuit including, conduits 24 and 26. However, it will be appreciated that in some embodiments, the intermediate heat exchanger 18 can be dispensed with, and the LNG or other liquid to be heated or vaporized could be directly fed through conduits 24 and 26. However, the intermediate circuit arrangement illustrated in FIG. 1 may be preferable in many instances, because this avoids the LNG needing to travel all the way to the location of the heating tower 22, and also avoids the heating tower 22 needing to be designed to handle LNG directly.

FIGS. 2-5 illustrate a preferred wet cooling tower that can be used in the circuit illustrated in FIG. 1. Turning to FIGS. 2-5, an exemplary closed loop heating tower 22 for heating the intermediate fluid is illustrated. This tower 22 includes a basin 110 that collects a circulating open loop heat exchange liquid, such as, for example, as water with suitable additives. The open loop liquid that is collected in the basin 110 is fed to an inlet (not visible in FIG. 2) that leads into an upper distribution assembly 112 illustrated in FIG. 5. The upper distribution assembly is not visible in FIG. 2, but is disposed beneath a shroud/cover assembly 113 that provides the fan shroud and also covers the top of the tower 22.

Returning to FIG. 2, a shrouded top fan 114 is driven by a fan motor 115 and draws air upwards through the tower 22. Turning to FIG. 3, it will be appreciated that a water distribution system 116 is provided near the top of the tower 22 and has spray heads 118 which spray the heat exchange liquid down over intermediate coils (described below) which then falls into the basin 110. Turning to FIG. 5, an example of an upper spray module system 116 is illustrated having a plurality of individual spray heads 118 arranged in an array.

Now, with reference to FIG. 4, it can be seen that the inside of the cooling tower includes, above the basin 110, a lattice type framework 120. The lattice type framework supports a plurality of tube bundles 122. Each of the tube bundles has an inlet 124 and an outlet 126. The inlet and outlet may be reversed depending on application. For example, with direct vaporization of LNG, the liquid would be inserted at the bottom and the vaporized gas exited at the top. The placement of inlet(s) and outlet(s) is by way of example only. The intermediate fluid arriving via conduit 24 in FIG. 1 is fed into the inlets 124. At this stage, the incoming intermediate fluid is relatively cool due to its having interacted with the heat exchanger 18 in order to vaporize the liquefied natural gas. The cool intermediate fluid that enters ports 124 will generally be much colder than ambient atmospheric conditions. The fluid entering at port 124 flows through a serpentine path in the tube bundles 122 and exits in a warmer temperature at outlet 126.

The tube bundles 122 warm the intermediate fluid in several ways. First, the tube bundles 122 are typically made of a heat conductive material, so that mere contact with the surrounding air tends to warm the intermediate fluid. Further, the illustrated example involves a heating tower 22 having spray modules 116 which are circulating open loop heat exchange fluid from the basin 110 so it is sprayed over the tube bundles 122. As the open loop heat exchange fluid is sprayed over the tube bundles 122, it imparts some heat which it has picked up from the basin 110 and the ambient air. Thus, the open loop heat exchange fluid that is sprayed is warmer than the intermediate fluid in the tube bundles 122, and heats the tube bundles 122 further. As the water drops off of the tube bundles 122 into the basin 110, it is relatively cool but it picks up heat by being in the basin 110 and also from contact with air around the basin 110.

Further, the fan 114 draws ambient air upwards, which enters the tower 22 under the tube bundles (the region supported by lattice framework 120) and above the basin 110. The air drawn in this space flows upward through the tube bundles 122, thereby further adding heat to the tube bundles 122. This air becomes relatively cool and is exhausted out of the plenum by the fan 114.

From the foregoing, it can be seen that a heating tower 22 having an open loop heat exchange liquid sprayed onto a tube bundle 122 can be advantageously used to warm the fluid in the tube bundle 122. The fluid in the tube bundle 122 can be an intermediate liquid that is used then to provide warmth to a heat exchanger 18 that warms liquefied natural gas for vaporization.

Returning to FIG. 1, the illustrated embodiment has two fluid loops, a first fluid loop on the LNG side, which passes the LNG through a side of the heat exchanger 18A, and a second fluid loop using a warming fluid such as example a refrigerant or other fluid that passes through the heat exchanger side 18B. Heat is transferred from the relatively warmer side 18B to the LNG side 18A in order to vaporize the LNG. The refrigerant in the second loop passes through the tube bundles 122 in the heating tower 22. The heating tower 22 itself has its own spray fluid, which may be water with chemical additives, which is being sprayed in an open loop fashion, so that it falls into a basin 110 and is recirculated. During this process, in many instances, some of the spray liquid may evaporate into the atmosphere, and thus a supply of make-up spray fluid is often required.

It will be appreciated however, that in the case of materials other than LNG, or even in some cases with LNG, the invention may be utilized without the intermediate heat exchanger 18. Instead, any liquid or gas that is to be heated could be passed directly into the tube bundles 122 in the tower 22, and a spray fluid can be applied over the tube bundles 122 in order to warm the liquid or gas that is in the tower 22.

While the invention has been described in the context of LNG processing, and is particularly beneficial for LNG processing, some embodiments of the invention are not limited to vaporization of LNG, but could also be used for the warming of any liquid or gas material in any suitable industrial or other process.

As noted above, relatively cool air is exhausted out of the fan at the top of the heating tower 22. In order to reduce plume, condensation, and/or also to reduce recirculation of the cold exhaust air back into the lower part of the cooling tower, it may be desirable to use some from of air direction control on the cold air outlet and/or the warm air inlet.

The described system including a spray type-warming tower utilized with closed circuit tube bundles 122 can be implemented in other applications, such as for example in the system described in U.S. patent application Ser. No. 10/965,176, entitled “Power Generating System and Method.”

In some embodiments, for example, in the case of vaporizing LNG in the heating towers described above, the extremely cold temperature of the LNG can cause freezing of the open loop fluid as the outside of the tubes forming the bundles. To avoid this, or if otherwise desired, in some embodiments some or all of the tubes can be insulated. One example of such is to form the tubes to be a tube-within-a-tube with the liquid to be warmed traveling, therefore the central tube and the area between the tubes filled with a material such as for example a gas. An example of a gas for some applications is nitrogen, other methods to avoid freezing can include centralizing the amount of open loop water flow to be sufficient to replace or present icing, if the temperature gradient amount permits this.

The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims

1. An apparatus for warming a second liquid, the apparatus comprising:

a tower comprising: a first heat exchanger; a spray head above the tube bundle for spraying a first liquid over the first heat exchanger; a first fluid collection basin disposed below the first heat exchanger; and a pump for recirculating the first liquid from the collection basin to the spray head; and

a supply of second liquid to the first heat exchanger which is colder than ambient conditions, whereby the second liquid exiting the first heat exchanger is heated to a warmer temperature than the second liquid entering the first heat exchanger.

2. The apparatus of claim 1, wherein the first heat exchanger comprises a tube bundle.

3. The apparatus of claim 2, further comprising a second heat exchanger, wherein the second liquid is an intermediate heat exchange fluid, which passes through the tube bundle, and also passes through the second heat exchanger via a closed circuit loop, and wherein the second heat exchanger warms a third material also passing through the second heat exchanger.

4. The apparatus of claim 3, wherein the third material is liquefied natural gas, and wherein the second heat exchanger evaporates the liquid natural gas.

5. The apparatus of claim 4, wherein the second liquid is a refrigerant type liquid material.

6. The apparatus of claim 2, further comprising a framework that supports the tube bundle at a space above the liquid collection basin.

7. The apparatus of claim 1, wherein the spray head comprises a manifold providing the first liquid to a plurality of individual spray heads arranged in an array.

8. The apparatus of claim 3, wherein the second heat exchanger is a two sided heat exchanger, with the second liquid passing through one side and the third liquid passing through another side, wherein the second liquid and the third liquid do not come into direct contact, and heat transfer between the second liquid and the third liquid is facilitated.

9. The apparatus of claim 1, further comprising a fan for drawing air over the first heat exchanger in a predetermined direction.

10. The apparatus of claim 2, further comprising a fan located above the tube bundle, to draw air from under the tube bundle upward through the tube bundle.

11. An apparatus for warming a second liquid, the apparatus comprising:

a tower comprising: a first heat exchanging means; a spraying means above the tube bundle for spraying a first liquid over the first heat exchanging means; a first fluid collecting means disposed below the first heat exchanger; and a means for recirculating the first liquid from the collecting means to the spraying means; and

a supply of second liquid to the first heat exchanging means which is colder than ambient conditions, whereby the second liquid exiting the first heat exchanging means is heated to a warmer temperature than the second liquid entering the first heat exchanging means.

12. The apparatus of claim 11, wherein the first heat exchanging means comprises a tube bundle.

13. The apparatus of claim 12, further comprising a second heat exchanging means, wherein the second liquid is an intermediate heat exchange fluid, which passes through the tube bundle, and also passes through the second heat exchanging means via a closed circuit loop, and wherein the second heat exchanging means warms a third material also passing through the second heat exchanging means.

14. The apparatus of claim 13, wherein the third material is liquefied natural gas, and wherein the second heat exchanging means evaporates the liquid natural gas.

15. The apparatus of claim 14, wherein the second liquid is a refrigerant type liquid material.

16. The apparatus of claim 12, further comprising a framework that supports the tube bundle at a space above the liquid collecting means.

17. The apparatus of claim 11, wherein the spraying means comprises a manifold providing the first liquid to a plurality of individual spraying means arranged in an array.

18. The apparatus of claim 13, wherein the second heat exchanging means is a two sided heat exchanging means, with the second liquid passing through one side and the third liquid passing through another side, wherein the second liquid and the third liquid do not come into direct contact, and heat transfer between the second liquid and the third liquid is facilitated.

19. The apparatus of claim 11, further comprising a fan for drawing air over the first heat exchanging means in a predetermined direction.

20. The apparatus of claim 12, further comprising a fan located above the tube bundle, to draw air from under the tube bundle upward through the tube bundle.

21. A method for warming a second liquid using a tower comprising a first heat exchanger, a spray head above the tube bundle for spraying a first liquid over the first heat exchanger a first fluid collection basin disposed below the first heat exchanger; and a pump for recirculating the first liquid from the collection basin to the spray head the method comprising:

supplying the second liquid to the first heat exchanger at colder than ambient conditions, in order to heat the second liquid exiting the first heat exchanger to a warmer temperature than the second liquid entering the first heat exchanger.

22. The method of claim 21, wherein the first heat exchanger comprises a tube bundle.

23. The method of claim 22, wherein the tower further comprises a second heat exchanger, wherein the second liquid is an intermediate heat exchange fluid, which passes through the tube bundle, and also passes through the second heat exchanger via a closed circuit loop, and wherein the second heat exchanger warms a third material also passing through the second heat exchanger.

24. The method of claim 23, wherein the third material is liquefied natural gas, and wherein the second heat exchanger evaporates the liquid natural gas.

25. The method of claim 24, wherein the second liquid is a refrigerant type liquid material.

26. The method of claim 22, wherein the tower further comprises a framework that supports the tube bundle at a space above the liquid collection basin.

27. The method of claim 21, wherein the spray head comprises a manifold providing the first liquid to a plurality of individual spray heads arranged in an array.

28. The method of claim 23, wherein the second heat exchanger is a two sided heat exchanger, with the second liquid passing through one side and the third liquid passing through another side, wherein the second liquid and the third liquid do not come into direct contact, and heat transfer between the second liquid and the third liquid is facilitated.

29. The method of claim 21, wherein the tower further comprises a fan for drawing air over the first heat exchanger in a predetermined direction.

30. The method of claim 22, wherein the tower further comprises a fan located above the tube bundle, to draw air from under the tube bundle upward through the tube bundle.