Large scale field erected air-cooled industrial steam condensers and device and method for reducing accumulation of non-condensable cold spots

Abstract

An apparatus and method for reducing cold spots in large scale field erected air cooled industrial steam condensers having a plurality of heat exchanger panels including steam delivery manifolds, primary and secondary condenser sections, condensate collection manifolds, non-condensable collection manifolds, condensate return tubing and non-condensable (primarily air) take-off piping connection to a vacuum source, wherein the non-condensable take-off piping includes a flow restriction to resist backflow due to pressure differentials between different heat exchanger panels.

Description

Large Scale Field Erected Air-Cooled Industrial Steam Condensers and Device and Method for Reducing Accumulation of Non-Condensable Cold SpotsFIELD OF THE INVENTION

[0001] This invention relates to large scale field-erected air-cooled industrial steam condensers.BACKGROUND OF THE INVENTION

[0002] Since the inception of vacuum air-cooled condensers, cold spots in the condenser heat exchangers caused by the collection of non-condensable gases (air typically) have caused problems. These cold spots cause thermal inefficiency and introduce a higher likelihood of freezing inside the tubes in cold weather applications.

[0003] Typical large-scale field erected air-cooled industrial steam condensers (ACC) are constructed of heat exchanger bundles arranged in an A-frame configuration above a large fan (forced draft) or as a series of smaller heat exchangers arranged in multiple A-frames located below a large fan or multiple small fans (induced draft). In either case, the ACC will include both first stage or "primary" condenser tubes and second stage or "secondary" condenser tubes. Primary tubes are not equipped with a means of removing non-condensable gases. To sweep the non-condensable gases through the first stage tubes, a percentage of the heat exchanger is configured with secondary tubes which draw vapor from the outlet of the primary section(s). As the mixture of gases travels through the secondary tubes, the remainder of the steam condenses, concentrating the non-condensable gases at the secondary outlet while the condensate drains away. The secondary condenser tubes allow non-condensable gases to be separated and vented to atmosphere through the air-removal system (vacuum pumps or ejectors) which is connected via piping to each secondary outlet.

[0004] The variance in pressure drop through the steam side of the ACC ducting, piping, and tubes results in non-uniform pressures across the outlets of the various secondary condensers. The air-removal system will preferentially remove vapor from the higher-pressure outlets at greater rates than the lower pressure outlets until the increased pressure drop caused by largervapor flow balances the pressure at each outlet. Even with a properly sized air removal system (per HEI standards), when the secondary outlet pressure differences are large enough, backflow of steam and non-condensable gases from the higher pressure secondary outlets into the lower pressure secondary outlets results in the accumulation of the non-condensable gases and the familiar cold spots.SUMMARY OF THE INVENTION

[0005] The present invention solves the problem of cold spots in large scale field-erected aircooled industrial condensers. As mentioned, the secondary condenser section outlets are connected to the air removal system via piping. According to the present invention, a flowrestriction is provided in a portion of the outlet piping of each secondary condenser section that draws non-condensables into a vacuum line. The flow restriction may be made according to any known method, including, by way of non-limiting examples, placing a narrowed section of tubing or orifice plate in a section of tubing, or, using tubing that has an integrally formed internal narrowed area, or by placing an insert into the inside of a tube to create a localized narrowing. No matter the way that the restriction in the take-off piping is made, the restriction significantly reduces the accumulation of non-condensable gases in the secondary sections and associated cold spots.BRIEF DESCRIPTION OF DRAWINGS

[0006] Figure 1 is a schematic of an ACC cell according to an embodiment of the invention.

[0007] Figure 2 is a schematic of a heat exchanger panel according to an embodiment of the invention.

[0008] Figure 3 is a cross-sectional view of the heat exchanger panel of Figure 2.

[0009] Figure 4 is a underside view of an ACC according to an embodiment of the invention.

[0010] Figure 5 is an inside view of a steam delivery manifold of an ACC, including the secondary condensate removal and air / non-condensable removal piping according to another embodiment of the invention.

[0011] Figure 6 is a schematic of an orifice plate installed in take-off piping of an ACC according to an embodiment of the invention.

[0012] Figure 7 is a side view of an orifice plate according to an embodiment of the invention.

[0013] Features in the attached drawings are numbered with the following reference numerals.Table 1:2 heat exchanger panel 27 ACC condenser module (cell)4 primary condenser section 28 steam distribution manifold6 secondary condenser section 37 heat exchange section7 tubes 42 condensate piping8 condenser bundles 43 condensate return tube10 top tube sheet 44 T-junction12 top header 45 branch connection to vacuum line14 bottom tube sheet 46 vacuum line16 bottom header 47 flow control orifice18 stem inlet / condensate outlet 48 orifice plate24 secondary bottom header 62 understructure26 nozzle (for secondary bottom header) 64 plenum / fan support sectionDETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention may be used to improve the performance of any large scale field- erected air-cooled condenser having multiple heat exchange panels with first and second condenser sections, the panels typically arranged in an A-frame or V-frame configuration, with non-condensable take-off piping connected to a common manifold, under suction, to a plurality of adjacent heat exchange panels.

[0015] Example 1. One non-limiting example of a large-scale field-erected air cooled condenser that may benefit from the present invention is described in U.S. Patent No. 10,982,904, the entirety of which is incorporated herein by reference.

[0016] Condenser module may include heat exchange section 37 having a plurality of heat exchange panels 2, plenum section or fan support section 64, understructure 62, and steam distribution manifold 28 (Fig. 1). Each heat exchanger panel 2 (Fig. 2) includes primary condenser sections 4 and secondary condenser section 6. At their top, all of the tubes 7 of both the primary and secondary sections 4 and 6 are joined to a top tube sheet 10, on which sits a hollow top header 12 which runs the length of the top of the heat exchanger panel 2. The bottom of all of the tubes 7 of the primary and secondary sections 4 and 6 are connected to a bottom tube sheet 14, which forms the top of a bottom header 16. The bottom header 16likewise runs the length of the heat exchanger panel 2. The bottom header 16 is in direct fluid communication with the tubes 7 of the primary section 4 but not with the tubes of the secondary section 6. The bottom header 16 is fitted at the center point of its length with a single steam inlet / condensate outlet 18 which receives all the steam for the heat exchanger panel 2 and which serves as the outlet for condensate collected from the primary sections 4. A secondary bottom header 24 is in direct fluid connection with only the tubes 7 of the secondary section 6 and extends the length of the secondary section 6. The secondary bottom header 24 may optionally be placed inside the primary bottom header 16.This secondary bottom bonnet 24 is fitted with a nozzle 26 (Fig. 3) to withdraw non-condensables and condensate.

[0017] The steam inlet / primary condensate outlet 18 for the heat exchanger panel 2 and the steam inlet / primary condensate outlets 18 for all of the heat exchanger panels in the same ACC cell / module 27 are connected to steam distribution manifold 28 which runs the length of, and feeds the heat exchange panels of, a plurality of heat exchange modules along a street / row of condenser cells. The steam distribution manifold runs perpendicular to the longitudinal axis of the heat exchange panels and is connected to the heat exchange panels at their center points through a plurality of Y-shaped connections to the pair of header inlets / outlets 18 of each adjacent pair of heat exchanger panels.

[0018] The uncondensed steam and non-condensables are collected in the top header 12 and are drawn to the center of the heat exchanger panel 2 where they travel down the tubes 7 of the secondary section 6 co-current with the condensate formed therein. Non-condensables are drawn into the secondary bottom header 24 and out through an outlet nozzle 26. Additional condensed water formed in the secondary section 6 collects in the secondary bottom header 24 and travels through the outlet nozzle 26. Take-off piping 42 (Figure 4) delivers condensate to a condensate return tube 43 and, via a T-junction 44, also branches into an L-shaped connection 45 to a vacuum line 46 for drawing off non-condensables such as air. The flow control orifice 47 of the invention is placed in the connection to the vacuum line, preferably in a vertical portion thereof, inhibiting backflow of air through the take-off piping due to high pressures in adjacent heat exchange panels / secondary condensing sections / take-off piping. In some ACCs, the takeoff piping 42 is routed inside the steam distribution manifold 28 (Fig. 5). According to various embodiments, the flow control orifice may take the form of a orifice plate 48 (Figs. 6 and 7) that is welded into place in the connection to the vacuum line. While Figure 6 shows the placementof the flow restriction in a horizontal portion of the connection to the vacuum line, it is more preferred to place the flow restriction in a vertical portion of the connection to the vacuum line as indicated in Fig. 4.

[0019] Example 2. Another non-limiting example of a large-scale field-erected air cooled condenser that may benefit from the present invention is the typical / traditional A-Frame configuration in which primary condenser stage tubes receive steam from a steam delivery manifold located at the top of the A-frame, condensate collects in condensate collection headers at the bottom of each side of the A-frame, uncondensed steam and non-condensables are drawn upward from the condensate collection headers into tubes of secondary stage tubes where additional condensate is formed and falls down into the condensate collection header. The tops of the secondary bundles are connected to a vacuum manifold which removes the noncondensable gases from the system under suction from a vacuum source. According to this configuration, one or more fans are typically located below each A-frame. The present invention may be used to reduce the cold spots that occur in this design by placing a flow restriction in the tubing that connects the vacuum manifold to the vacuum source.

[0020] Example 3. Another non-limiting example of a large-scale field-erected air cooled condenser that may benefit from the present invention are variations to the traditional ACC arrangement disclosed, for example in US Patent No. 9,551,532, the disclosure of which is incorporated herein in its entirety. While the design disclosed in the '532 patent uses shorter tubes and assembles multiple A-frames over a single fan, the operation of these configurations is similar to the traditional configurations described in Example 2. While the design of the '532 patent purports to address issues relating to pressure at the exit of the secondary bundles being lower than the vacuum, this system does not remove the problem of cold spots. Accordingly, the present invention may be used to reduce the cold spots that occur in this design by placing a flow restriction in the tubing that connects the secondary bundle outlet to the vacuum source.

[0021] Example 4. Another non-limiting example of a large-scale field-erected air cooled condenser that may benefit from the present invention is a variation to the ACC arrangement of Example 1 in which a third condensation stage is provided. See, e.g., U.S. Patent No. 11,378,339, the entirety of which is incorporated herein by reference. According to this arrangement, non-condensables are drawn into the bottom of a set of third stage condensation tubes and condensate that forms in the third stage condenser tubes falls down into a transferheader at the bottom of both the secondary and third stage tubes._The tops of the third stage condenser tubes are connected to a vacuum manifold from which the non-condensable gases are removed from the system under suction from a vacuum source. As with the configurations of Examples 1-3, the present invention may be used to reduce the cold spots that occur in a three-condenser-stage design by placing a flow restriction in the tubing that connects the vacuum manifold to the vacuum source.

[0022] Notwithstanding the specific embodiments, features, elements, combinations and subcombinations disclosed herein, it is expressly considered and here disclosed that every single element, every single feature, and every combination and sub-combination thereof disclosed herein may be combined with every other element, feature, combination and sub-combination disclosed herein.

[0023] It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as outlined in the present disclosure and defined according to the broadest reasonable reading of the claims that follow, read in light of the present specification.

Claims

Claims1. A large scale field erected air cooled industrial steam condenser connected to an industrial steam producing facility, comprising: a plurality of heat exchanger panels, each heat exchanger panel comprising: a plurality of primary condenser tubes, a combined steam delivery and condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube, a plurality of secondary condenser tubes, a transfer manifold connected to and in fluid communication with a top end of each said primary condenser tube and each said secondary condenser tube, a condensate and non-condensable collection manifold connected to and in fluid communication with a bottom end of each secondary condenser tube; and take-off piping connected to said condensate and non-condensable collection manifold, wherein said take-off piping branches into condensate collection piping and air-take-off piping, said condensate collection piping connected to a condensate return tube, said air take-off piping connected to a suction tube, said air take-off piping comprising a flow restriction having a narrower cross-sectional area than cross- sectional areas of immediately upstream and downstream piping.

2. A large scale field erected air cooled industrial steam condenser connected to an industrial steam producing facility, comprising: a plurality of heat exchanger panels: each said heat exchanger panel comprising: a plurality of primary condenser tubes, a steam delivery manifold connected to and in fluid communication with a top end of each said primary condenser tube, a plurality of secondary condenser tubes,a condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube and each said secondary condenser tube, a non-condensable collection manifold connected to and in fluid communication with a top end of each secondary condenser tube; and take-off piping connected to said non-condensable collection manifold, wherein said take-off is connected to a suction tube, said air take-off piping comprising a flow restriction having a narrower cross-sectional area than cross-sectional areas of immediately upstream and downstream piping.

3. A method for inhibiting the accumulation of cold spots in a large scale field erected air cooled industrial steam condenser, the large scale field erected air-cooled industrial steam condenser comprising a plurality of heat exchanger panels, each heat exchanger panel comprising: a plurality of primary condenser tubes, a combined steam delivery and condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube, a plurality of secondary condenser tubes, a transfer manifold connected to and in fluid communication with a top end of each said primary condenser tube and each said secondary condenser tube, a condensate and non-condensable collection manifold connected to and in fluid communication with a bottom end of each secondary condenser tube; and take-off piping connected to said condensate and non-condensable collection manifold, wherein said take-off piping branches into condensate collection piping and air-take-off piping, said condensate collection piping connected to a condensate return tube, said air take-off piping connected to a suction tube, the method comprising placing a flow restriction in said air take-off piping to create a cross-sectional area that is narrower than cross-sectional areas of immediately upstream and downstream piping.

4. A method for inhibiting the accumulation of cold spots in a large scale field erected air cooled industrial steam condenser,the large scale field erected air cooled industrial steam condenser comprising a plurality of heat exchange panels, each said heat exchange panel comprising: a plurality of primary condenser tubes, a steam delivery manifold connected to and in fluid communication with a top end of each said primary condenser tube, a plurality of secondary condenser tubes, a condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube and each said secondary condenser tube, a non-condensable collection manifold connected to and in fluid communication with a top end of each secondary condenser tube; and take-off piping connected to said non-condensable collection manifold, wherein said take-off piping is connected to a condensate return tube, said air take-off piping connected to a suction tube, the method comprising placing a flow restriction in said air take-off piping to create a cross-sectional area that is narrower than cross-sectional areas of immediately upstream and downstream piping.

5. A large scale field erected air cooled industrial steam condenser connected to an industrial steam producing facility, comprising: a plurality of heat exchanger panels, each heat exchanger panel comprising: a plurality of primary condenser tubes, a combined steam delivery and condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube, a plurality of secondary condenser tubes, a plurality of third condenser tubes, a transfer manifold connected to and in fluid communication with a top end of each said primary condenser tube and each said secondary condenser tube, a condensate collection and non-condensable transfer manifold connected to and in fluid communication with a bottom end of each secondary condenser tube; and a bottom end of each third condenser tube, anda vacuum manifold connected to a top of each third condenser tube, and take-off piping connected at one end to said vacuum manifold and connected at another end to a suction source, wherein said take-off piping comprises an air-flow restriction having a narrower cross- sectional area than cross-sectional areas of immediately upstream and downstream piping.

6. A method for inhibiting the accumulation of cold spots in a large scale field erected air cooled industrial steam condenser, the large scale field erected air cooled industrial steam condenser comprising a plurality of heat exchange panels, each said heat exchange panel comprising: a plurality of primary condenser tubes, a combined steam delivery and condensate collection manifold connected to and in fluid communication with a bottom end of each said primary condenser tube, a plurality of secondary condenser tubes, a plurality of third condenser tubes, a transfer manifold connected to and in fluid communication with a top end of each said primary condenser tube and each said secondary condenser tube, a condensate collection and non-condensable transfer manifold connected to and in fluid communication with a bottom end of each secondary condenser tube; and a bottom end of each third condenser tube, and a vacuum manifold connected to a top of each third condenser tube, and take-off piping connected at one end to said vacuum manifold and connected at another end to a suction source, the method comprising placing a flow restriction in said air take-off piping to create a cross-sectional area that is narrower than cross-sectional areas of immediately upstream and downstream piping.

7. An air cooled industrial steam condenser connected to an industrial steam producing facility, comprising: a plurality of heat exchanger panels, each heat exchanger panel comprising: a plurality of condenser tubesa steam delivery manifold configured to deliver steam to said plurality of condenser tubes, a non-condensable collection manifold configured to collected non-condensables from said plurality of condenser tubes, take-off piping connected at a first end to said non-condensable collection manifold and connected at a second end to a suction source, said air take-off piping comprising a flow restriction having a narrower cross-sectional area than cross-sectional areas of immediately upstream and downstream piping.

8. The air cooled industrial steam condenser of claim 7, wherein said steam delivery manifold is also configured and located to collected condensate.

9. The air cooled industrial steam condenser of claim 7, wherein said non-condensable manifold is also configured and located to collected condensate.

10. The air cooled industrial steam condenser of claim 7, further comprising a first transfer manifold configured to transfer non-condensables from a first set of said plurality of condenser tubes to a second set of said plurality of condenser tubes.

11. The air cooled industrial steam condenser of claim 10, further comprising a second transfer manifold configured to transfer non-condensables from said second set of said plurality of condenser tubes to a third set of said plurality of condenser tubes.

12. A method for inhibiting the accumulation of cold spots in a large scale field erected air cooled industrial steam condenser, the large scale field erected air cooled industrial steam condenser comprising a plurality of heat exchange panels, each said heat exchange panel comprising: a plurality of condenser tubes a steam delivery manifold configured to deliver steam to said plurality of condenser tubes, a non-condensable collection manifold configured to collected non-condensables from said plurality of condenser tubes, take-off piping connected at a first end to said non-condensable collection manifold and connected at a second end to a suction source,the method comprising placing a flow restriction in said air take-off piping to create a cross-sectional area that is narrower than cross-sectional areas of immediately upstream and downstream piping.

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