Patent Application
20090065181
The invention pertains generally to the field of hydraulics and fluid handling. More particularly, the invention relates to a hydraulic system and method for handling fluids that are used in heat exchangers. More particularly, the invention pertains to a system for circulating heat exchange fluid between two heat exchange devices, where one device is an atmospheric heating or cooling tower.
Heat exchangers are in wide use in industry. Many of these heat exchangers involve some form of circulating fluid. The fluid may be water, water treated with chemicals, or some other liquid. The words “water” and “fluid” are used interchangeably in this specification.
One type of heat exchanger is an atmospheric cooling tower. Such cooling towers are traditionally used in industrial applications to cool fluid that is supplied to the tower at a relatively warm temperature, i.e., above an ambient temperature, down to a relatively cooler temperature closer to the ambient temperature. Cooling towers in some cases involve the spraying of the warm fluid from the top of the tower, sometimes over a fill medium, and also in some instances using a fan to force air through the tower so that the water falls through the tower, contacting the fill medium and the air and falls into a collection basin at the bottom of the tower. As the warm fluid falls through the tower, it will generally be cooled to a cooler temperature. These are called open loop cooling towers because the fluid being cooled contacts the air. There are also closed loop towers where the fluid being cooled circulates through a closed coil in the tower, but another fluid is sprayed over the coil as discussed above. Also, dry cooling towers use only the coils and do not have the falling spray water. The details of these and other types of cooling towers are well known to those skilled in the art.
It is also possible to operate a cooling tower type structure to be a heating tower. In such circumstances where the fluid is supplied to the tower starting at a temperature cooler than the ambient air temperature, the supply of the cool fluid into the top of the tower will result in a warming of the fluid so that the fluid collected at the basin at the bottom of the tower is warmer than when it entered the tower.
It has generally been most common in industrial applications to utilize heat exchange towers as cooling towers. However, there are arising certain situations where a heating tower can be beneficial. One such situation is in the case of liquid natural gas (LNG) evaporators. In these evaporators, liquid natural gas is vaporized by the addition of heat. This can result in a supply of cold fluid which is desired to be warm.
Turning to a different aspect of LNG vaporization, there are some known heat exchangers for use in LNG vaporization. One example is a so-called open rack vaporizer. An open rack vaporizer is essentially a large water tank having a closed coil submerged in the tank. The LNG is passed through the closed coils. Water is drawn from a relatively warm external source, such as sea water, and is circulated into and through the tank. The LNG is warmed by the vaporization coil being in contact with the warm sea water. The water becomes cooled by contact with the vaporization coils and then is discharged, usually back into the sea. In some instances there are environmental limits on the use of these evaporators.
Another type of LNG evaporator is a shell and tube arrangement with the LNG in tubes that have a shell surrounding the tubes having warmer water passed through it.
Yet another type of LNG evaporator is a so-called submerged combustion vaporizer (SCV). An SCV is similar to an open rack vaporizer in that it is essentially a tank of water having the vaporization coils submerged therein. However, rather than circulating any water into and out of the tank in an SCV, heat is continually added by means of a gas fired burner submerged in the tank. The details of SCVs can vary, but in general the gas fired burner is operated so as to add heat into the water tank at substantially the same rate at which heat is being drawn out from the water by the vaporization coil. The amount of heat added by the submerged burner can be relatively steady, controlled by modulating the gas burn rate and using the water as a temperature change buffer. Although the water in the SCV is generally self-contained, there is some water produced in the combustion process and condensed out of the hot gas stream. It is removed to prevent flooding the burner, usually by an overflow outlet port.
Each of the methods described above is useful in industry and has various advantages. However, it would be desirable to have a heat exchange fluid handling system and method that provides in some instances a more controllable, energy efficient, or otherwise beneficial-to-operate arrangement.
The invention in one aspect pertains to a fluid handling system, comprising a first heat exchange device having a first fluid inlet and a first fluid outlet; a second heat exchange device having a second fluid inlet and a second fluid outlet; a first conduit connected to the first fluid outlet to the second fluid inlet; a first reservoir that receives fluid from the first fluid outlet; a second reservoir that receives fluid from the second fluid outlet; a second conduit connected to the second reservoir to the first fluid inlet; and a third, fluid equalization, conduit connected to the first reservoir to the second reservoir and equalizes the fluid levels in the first and second reservoirs with each other, further comprising a weir in fluid communication with the second fluid outlet, wherein the weir is disposed between the second fluid outlet and the second reservoir so the second reservoir receives fluid from the weir. The second heat exchange device comprises a liquefied natural gas (LNG) vaporizer.
Another aspect of the invention pertains to a fluid handling system, comprising an atmospheric heating tower having a first fluid inlet and a first fluid outlet; a submerged combustion vaporizer (SCV) having a second fluid inlet and a second fluid outlet; first means for connecting the first fluid outlet to the second fluid inlet; and second means for the second fluid outlet to the first fluid inlet.
Yet another aspect of the invention pertains to a fluid handling method, providing a first heat exchange device having a first fluid inlet and a first fluid outlet, a second heat exchange device having a second fluid inlet and a second fluid outlet, a first conduit connected to the first fluid outlet to the second fluid inlet, a first reservoir that receives fluid from the first fluid outlet, a second reservoir that receives fluid from the second fluid outlet, a second conduit that connects the second reservoir to the first fluid inlet, and equalizes the fluid levels in the first and second reservoirs with each other.
In another aspect of the invention, a fluid handling method comprises providing an atmospheric heating tower having a first fluid inlet and a first fluid outlet; a submerged combustion vaporizer (SCV) having a second fluid inlet and a second fluid outlet, circulating fluid from the first fluid outlet to the second fluid inlet, and circulating fluid from the second fluid outlet to the first fluid inlet.
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.
Turning to
In some conditions, the use of the combustion device 22 by itself may not be the most efficient way to add heat to the system. Therefore, in the embodiment of
After the fluid falls beneath the fill material 40, it is collected in a lower basin 42. The fluid in the lower basin 42, which is warmer than the fluid that was drawn from SCV 10, can now be supplied back to the SCV 10 using a conduit 43 and a pump 44, labeled P2. The pump 44 supplies the warmer fluid through a conduit 45 which may simply terminate into the SCV, or may distribute the warm water through a variety of outputs 46.
It will be appreciated depending upon atmospheric conditions and other conditions within the equipment, as well as factors such as gas cost, it may be desirable sometimes to operate only with the heating tower, for example, if the ambient air is extremely warm and the heating tower is scaled so that it can add enough heat for vaporization. However, due to climactic changes, or other design factors, it may be desirable to operate the SCV part of the time. It is possible to control and modulate the SCV, as well as the heating tower, to operate both of them to supply heat at the same time and at different rates, or to operate only one or the other of the heating tower and the SCV. In this way, use of fuel can be reduced, and other operating efficiencies can be obtained.
In the example shown in
The system described in
Another possible undesirable condition is if pump 36 fails. In such a case, it is possible that the pump 44 will feed excess water into the SCV 10 which is not removed, which could in some instances “swamp” the SCV burner.
Depending on the relative installation height of the SCV 10 and the heating tower 30, it may be possible to operate a system using only one pump (pump 36), if the heating tower were installed high enough that its head distance could provide the function presently shown by the pump 44. However, in most practical installations it is expected that a two pump system would be more desirable.
It can some times be desirable to have a system that would maintain the operating fluid levels at desired levels where a first heat exchanger (such as an SCV, for example) is connected to a second heat exchanger (such as a heating tower, for example). It can also some times be desirable to accommodate the failure of the pumps that are running in either direction from one device to another. It is noticed that while the examples of an SCV and an atmospheric heating tower are given, the systems described herein could be applied to any types of heat exchangers that involve the addition and removal of fluid from the heat exchangers to provide fluid communication between the heat exchangers, with at least one of the heat exchangers having a fluid level that is vented to the atmospheric pressure.
Turning now to
Somewhat similar to the embodiment of
The weir chamber 62 has a sidewall 66, and as the level in the weir chamber 62 exceeds the height of the sidewall 66, the fluid will further be transferred into a buffer tank 68. A conduit 35 for drawing water out of the holding reservoir 68 leads to the pump 36 which pumps the fluid through conduit 37 and up to the nozzles 38 in the heating tower.
The fluid is passed over the fill medium 40 and falls into the basin 42. Fluid is drawn from the basin 42 out by the pump 44 via conduit 43 and is supplied back to the SCV through the supply openings 46. Should the rate of supply of water into the basin 42 exceed the rate of the withdrawal of fluid from the basin 42, the level L2 of the basin fluid will increase. Should the level L2 of the basin fluid exceed a predetermined level, basin fluid will flow into a holding reservoir 70 as shown.
The holding reservoir 70 is in fluid communication with the holding reservoir 68 via a flow equalization pipe 72. Thus, the level L3 of the holding reservoir 70 will generally stay substantially equal to the level L4 of the holding reservoir 68. In this way, if either the heat exchanger basin 42 or the SCV fluid 20 is receiving an oversupply of fluid, the oversupply of fluid is deposited into the holding reservoirs 68 and 70, where they will equalize. Since the pump 36 draws from conduit 35 which is in fluid communication with both holding reservoirs 68 and 70, some fluid will always be available to be pumped into the heating tower.
As has been noted above, in some instances the heating tower will add water to the system via condensation. Thus, the additional water will overflow into the holding reservoirs 68 and 70, causing L3 and L4 to increase. A single overflow bleed device 80 can be provided at either the holding reservoirs 68 or 70. In the example shown, the overflow bleed device 80 is provided on the reservoir 68 such that when L4 reaches a suitably high level, the excess fluid will be removed. The height of the bleed device 80 will generally be less than a wall 82 that defines a side of the reservoir 70 and a wall 84 that defines a height of the weir chamber 62. Thus, the two separate overflow discharges such as 50 and 52 in
A benefit of the arrangement illustrated in
In the case of a failure of pump 44, pump 36 will withdraw fluid from the reservoir 68 and pump it through the cooling tower 30. Since pump 44 is inoperative, the fluid in the basin will rise such that it exits the weir 41 and enters the reservoir 70, traveling through the flow equalization pipe 72 back to the reservoir 68. In this case, another short circuit is provided where the heating tower will operate but will not be interacting in any way with the SCV. Thus, the SCV can continue to operate on its own.
Valves 90 and 92 can be provided as shown so that the SCV 10 can be isolated from the heating tower when desired. The valve at the outlet port 60 may also be closed in connection with this.
In the illustrated embodiment of
Similarly, in the illustration of
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.
