US 7,065,970 B2 · Condensers and their monitoring

Abstract

Disclosed is a method for operating a condenser of the type having a housing inside of which is disposed a bundle of water tubes, a steam inlet for steam to flow inside the housing for contacting the tube bundle for cooling, and having a stagnant air zone during operation wherein any air in-leakage preferentially collects and condensate in the air zone becomes subcooled. A trough or drain is placed beneath the stagnant air zone for collecting subcooled condensate from the stagnant air zone. Collected subcooled condensate is transported from the trough or drain in a pipe to said steam inlet. The transported condensate is injected with an injector for contacting with steam entering the condenser, whereby the injected condensate is heated by the steam for expelling dissolved oxygen in the injected condensate. Advantageously, the condenser is fitted with an array of temperature sensors at the stagnant air zone for determination of its presence and/or size. Additionally, disclosed is a method for preventing air bound zones in the tube bundle sections of the condenser.

Claims72

Dependent claims

A method for operating a condenser of the type having a housing inside of which is disposed a bundle of water tubes comprising one or more spaced-apart water tube bundle sections, a steam inlet for steam to flow inside said housing and outside of said tube bundle for contacting said tube bundle for heat removal, an exhaust system with an air removal section (ARS) disposed within said tube bundle to promote in equilibrium removal of any gas entering therein, and a hotwell disposed beneath said tube bundle for collecting condensate, the improvement for one or more of reducing one or more of the dissolved oxygen (DO) or other gases content in a said condensate, reducing excess pressure in the condenser, or improving condenser measured heat transfer coefficient, which comprises the steps of:

(a) identifying one or more of:
(i) a stagnant zone of high gas concentration during operation wherein at high air in-leakage one or more of air or other noncondensable gases preferentially collect in equilibrium with air remove rate by said ARS and condensate in said stagnant zone and said ARS becomes subcooled, allowing said gases to become partially absorbed by said subcooled condensate;
or
(ii) an air bound zone;
and
(b) responsive to identification of one or more of said zones, modifying one or more of said condenser or operation of said condenser to retard the adverse affect said zones exert on condenser performance.

3 more elements

In a condenser of the type having a housing inside of which is disposed a bundle of water tubes, a steam inlet for steam to flow inside said housing and outside of said tube bundle for contacting said tube bundle for heat removal, an exhaust system with an air removal section (ARS) disposed within said tube bundle to promote in equilibrium removal of any gas entering therein, and a hotwell disposed beneath said tube bundle for collecting condensate, the improvement which comprises:

(a) a collector for collecting subcooled condensate from an identified stagnant zone and said ARS of high gas concentration during operation wherein at high air in-leakage, air and other noncondensable gases preferentially collect and condensate in said stagnant zone and said ARS become subcooled, allowing said gases to become partially absorbed by said subcooled condensate;
(b) a deaeration system having capacity for treating said collected subcooled condensate;
and
(c) a transporter for transporting collected subcooled condensate in said collector to said deaeration system for removing at least dissolved oxygen from said transported condensate therein.

1 more element

A method for operating a condenser of the type having a housing inside of which is disposed a bundle of water tubes, a steam inlet for steam to flow inside said housing for contacting said tube bundle for heat removal, and potentially having a stagnant zone of higher air and other non-condensable gases concentration during operation wherein at high air in-leakage, air and other noncondensable gases preferentially collect and condensate in or passing through said stagnant zone becomes subcooled allowing said gas to become partially absorbed, an air removal section (ARS) comprising a vent line to an outside pumping device for equilibrium removal of gases along with water vapor, and a hotwell disposed beneath said tube bundle for collecting said condensate, the improvement for reducing the dissolved oxygen (DO) and other gases content in said subcooled condensate which comprises the steps of:

(a) collecting subcooled condensate from one or more of said stagnant zone or said ARS;
(b) providing one or more of a deaerator or deaeration section;
(c) transporting collected subcooled condensate to said one or more of a deaerator or said deaeration section for expelling dissolved gases therefrom.

In a method for operating a combined cycle power plant where one or more turbines feed steam to a condenser of the type having a housing inside of which is disposed a bundle of water tubes, a steam inlet for steam to flow inside said housing for contacting said tube bundle for heat removal, wherein for off-line operation the turbines are powered down and a vacuum maintained in at least one of said turbines and said condenser, the improvement for off-line operation which comprises:

(a) passing a flow of steam into one of said turbines, which flow of steam enters said condenser via said steam inlet;
(b) establishing a flow of cooling water through a limited number of select water tubes;
and
(c) disposing a shroud one or more of at or near said select water tubes and connecting said shroud to a vent line that terminates outside of said condenser with an air removal device,
whereby, said flow of steam flushes any air leaking into one or more of said turbines or said condenser to said select water tubes for one or more of forming a condensate enriched in dissolved oxygen (DO) for its collection or removal of air by via said vent line and said air removal device.

2 more elements

A method of describing the steam air mixture dynamics throughout a tube bundle of a condenser of the type having a housing enclosing said bundle of water tubes, consisting of singular or multiple bundle sections separated by gaps, a steam inlet for steam to flow inside said housing and outside of said tube bundle or bundle sections for contacting said tube bundle for heat removal, an exhaust system with an air removal section (ARS) disposed within said tube bundle to promote in equilibrium removal of any gas entering therein, and a hotwell disposed beneath said tube bundle for collecting condensate, the improvement for understanding performance indicators of condensers and optimizing design of condensers to achieve operating performance objectives to include one or more of:

design pressure, heat transfer coefficient, or low dissolved oxygen over wide steam load conditions, which comprises the steps of:
(a) recognizing that all tubes in the condenser can effectively condense the same amount of steam;
(b) understand that steam is a vapor in equilibrium with a liquid phase dominated by the hotwell surface temperature;
(c) knowing that as steam enters the tube bundle and is condensed on the tubes, the steam vapor density to air density ratio is reduced and becomes lower with further penetration;
(d) recognize that air typically interferes significantly with heat transfer and the condensation process deep within the bundle and becomes significant near and within the air removal section;
(e) understand that a stagnant zone near the center of the tube bundle will develop at high air in-leakage but have a size dependence on exhauster pump capacity;
(f) appreciating that air bound zones will develop within the tube bundle sections when steam is permitted to surround said bundle section having no air removal section, but stagnant zones are not fully developed because falling condensate provides a scavenging effect on air contained in the air bound zone;
(g) knowing that stagnant and air bound zones have a temperature below that of the steam providing a lower water vapor pressure, therein, permits the presence of air in the said zone having a finite partial pressure;
(h) understanding that the cool zones have a total pressure essentially equal to the steam pressure at the outside boundary of the tube bundle;
(i) while operating mathematically using good engineering practices on the tube bundle geometry, predicting the flow of steam and air to determine if air binding is expected that affects performance;
(j) recommend fixing leaks in stagnant zones are indicated;
(k) design a tube bundle layout using good engineering practices to promote high condensation rate to a location near the air removal section without developing a center of air concentration and the establishment of air binding;
and
(l) provide means for deaeration of condensate produce near or within the air removal section if low dissolved gases are needed.

11 more elements

Dependencies are inferred from the claim text.

Condensers and their monitoring

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Condensers and their monitoring

Life of this patent

Abstract

Claims72