TECHNICAL FIELD
This invention pertains to the field of heat exchange and specifically to a more efficient design of heat exchangers for plume and emissions control from a wet gas scrubber or similar device.
BACKGROUND OF THE INVENTION
Plate fin and tube heat exchangers or externally finned tube exchangers have long been employed to recover process heat. These exchangers are most often employed to heat or cool a low density gas stream located on the finned side against a denser fluid with higher heat transfer coefficient within the tubes. The extended surface on the finned exterior pass allows greater heat transfer surface than a bare tube and provides greater heat transfer at a low-pressure drop.
The art has not heretofore recognized the unexpected advantage of using multiple cooling streams on the tube side of one or more heat exchanger and interlacing the heat transfer zones to allow more effective heat transfer and reduce the water dewpoint of the stream to reduce or eliminate visible vapor plume while also reducing SO3 emissions was not recognized in the art reported therein.
SUMMARY OF THE INVENTION
The invention may be described in several ways as alternate embodiments of the same novel discovery.
A finned tube exchanger that can be used in heat transfer system that comprises:
- a. Providing a first working fluid which has a water dewpoint above ambient air temperature on the finned exterior side of the heat transfer device,
- b. Providing 2 or more working fluids flowing in separate circuits within the tube circuits of the heat transfer device,
- c. feeding the first working fluid to the exterior finned side of a heat transfer zone or zones to transfer heat to or from the first working fluid thereby heating or cooling the first working fluid to a higher or lower temperature,
- d. feeding the second working fluid into a tube or group of tubes to be heated or cooled by the first working fluid,
- e. feeding the third or more working fluid(s) into a tube or group of tubes to be heated or cooled by the first working fluid,
In a preferred embodiment the invention provides:
- f. in a heat exchange device having one or more finned exterior side working fluid streams against multiple tube side circuits,
- g. the multiple tube circuits being interlaced to more effectively approach the cooling curve of the finned exterior side working fluid,
- h. cooling the high dewpoint working fluid on the exterior finned surface of the exchanger to reduce the water content of the exhaust stream
In a more preferred embodiment the invention further provides the steps of:
- i. A method of circuitry of a plate fin and tube or finned tube exchanger that allows for more effective heat transfer by recovering heat from the effluent stream with a first cooling stream,
- j. Using a second working fluid as a cooling stream to further remove heat from the effluent stream,
- k. Then circuiting and pumping the first cooling stream which has been heated in i above to circuitry in the finned tube exchanger to heat the effluent stream above its dew point.
- l. A method of construction and design allowing complex circuitry of a plate finned and tube or finned tube exchanger utilizing multiple tube side circuits that accomplish more effective heat transfer while reducing the heat rejection load on cooling towers or other heat removal devices while simultaneously reducing the energy input required to heat the exhaust stream above it's dew point for plume suppression.
- m.
In summary, the invention provides a system for more efficient heat transfer in a plate fin and tube or finned tube exchanger to reduce the plume of a stream that is being rejected to atmosphere that has a water dew point above that of the ambient air.
The invention is illustrated by the specific example set out below.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sketch of a typical finned tube coil having two working fluids
FIG. 2 is a sketch of an integrated coil having an exhaust stream on the finned side and cooling and heating circuitry on the tube side.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides a method of integrating circuitry with various working fluids in a common or multiple plate fin and tube or finned tube exchanger(s) to accomplish more efficient heat transfer and reduce the plume of a stream that is being rejected to atmosphere that has a water dew point above that of the ambient air. This example is provided to illustrate the invention and not to limit the concepts embodied therein. The invention is defined and limited by the claims set out below. The examples below were modeled using a commercial process simulator.
EXAMPLE 1
Turning to FIG. 2, a first working fluid enters the heat exchanger at 150F, 14.8 psia, 11,430 moles/hr and leaves the exchanger at 140 F, 14.7 psia. It exchanges heat with a 2nd working fluid which is water entering at 130 F, 80 psia, 9,800 moles/hr and leaving at 145 F, 70 psia. The first working fluid also exchanges heat with a 3rd working fluid which is water entering at 85 F, 39.7 psia, 81,750 moles/hr and leaving at 115 F, 24.7 psia. The first working fluid also exchanges heat with the 2nd working fluid which is water and was heated in the first exchanger pass entering at 145 F, 70 psia, 176,500 moles/hr and leaving at 130 F, 60 psia. 40,680 lb/hr of the water contained in the first working fluid is condensed in the first and second exchanger and removed, lowering the dewpoint; then the first working fluid is heated in the third exchanger and is discharged to atmosphere, resulting in less visible plumb.
Patent Application
20050263262
