one source one purpose many solutions utility users group meeting orange beach, al august 4, 2015...

ONE SOURCE ONE PURPOSE MANY SOLUTIONS

Utility Users Group MeetingOrange Beach, AL

August 4, 2015

Steam Surface Condensers: GUIDELINES & TECHNIQUES FOR THE EFFECTIVE CONTROL OF CONDENSATE DISSOLVED OXYGEN

(DO2) IN STEAM SURFACE CONDENSERSPrepared and Presented by

Darren M. NightingaleDirector of Engineering, TEi Condenser Division

© 2015 Information contained herein is proprietary and confidential to Babcock Power Inc. All Rights Reserved

http://www.google.com/url?sa=i&rct=j&q=&esrc=s&frm=1&source=images&cd=&cad=rja&uact=8&ved=0CAcQjRxqFQoTCI3GxKqa_MYCFQWUiAod8AAD2A&url=http://www.newworldencyclopedia.org/entry/Oxygen&ei=9pu2VY3zKoWoogTwgYzADQ&psig=AFQjCNF7iEcvcb2nIP7ry1zOdi1WGovcUg&ust=1438117212643481

Darren M. Nightingale Director of Engineering,

Condenser Division

Telephone: 323.838.1173 (Office)

Telephone: 323.627.5527 (Cell)

E-Mail: [email protected]

THERMAL ENGINEERING INTERNATIONAL, INC.

10375 SLUSHER DRIVE

Santa Fe Springs,

CA 90670-3748

Introduction


GUIDELINES & TECHNIQUES FOR THE EFFECTIVE CONTROL OF CONDENSATE DISSOLVED OXYGEN IN

STEAM SURFACE CONDENSERS:

Low levels of dissolved oxygen in the condensate produced within steam surface condensers, is highly desirable and an increasingly important aspect related to the efficient operation of today’s power plants. The presence of high levels of dissolved oxygen within condensate can quickly contribute to accelerated corrosion & additional treatment requirements as well as increased maintenance and operational challenges. Under certain operating conditions, steam surface condensers can be expected to produce condensate with pre-defined, or guaranteed, levels of dissolved oxygen. However, these levels can only be achieved by a combination of following design guidelines and not exceeding operational limitations - this is not always the case. This 20min presentation includes the latest design guidelines, operational limitations and general considerations, as well as practical techniques, for minimizing dissolved oxygen levels for condensate produced within the condenser.

Abstract - Overview


• WHAT? – Is Dissolved Oxygen?• WHY? – Is DO2 a Problem?

• WHERE? – Does DO2 Come From?• HOW? – Should My Condenser Perform?• WHEN? – Does ‘High’ DO2 Occur?

• HELP!? – Can I Reduce my DO2?!

Presentation Agenda


WHAT? – Is Dissolved Oxygen?

• Oxygen: Colorless, Odorless & Tasteless Gas.• Occurs in its Free State as a Gas, O2

• Liquid only at -297.4°F. • Oxygen in Air is 20.9% by Volume.• Oxygen in Air is 23.1% by Mass.• DO2 in Air Saturated Make-up: 8,000 – 14,000 ppb O2

…the amount of free (NOT chemically combined)

oxygen dissolved in the condensate, usually

expressed in milligrams per liter, parts per million/billion,

or percent of saturation. Often called DO or DO2.


WHAT? – Is Dissolved Oxygen?


Power Plant System Diagram - FOSSIL

Cooling TowerDeaerator

LPHeaters

Air Preheater

Condenser

Stack

Flue gasdesulfurization

Electrostaticprecipitator or Baghouse

Steam Turbine

Utility Boiler

Air

Superheater

Reheater

Economizer

FuelFiring

System

Generator

Low NOx Burners

SCR (DeNOx)

Pulverizer

Boiler Tubes

HPHeaters

WHY? – Is DO2 a Problem?


LOWPRESSURETURBINE

HIGHPRESSURETURBINE

CONDENSER

BOILER

LOWPRESSUREHEATER 4

LOWPRESSUREHEATER 3

HIGHPRESSUREHEATER 2

HIGHPRESSUREHEATER 1

DA

Nuclear / Coal Fired

Typical Steam Power Plant Cycle




• HENRY’S LAWBased on Henry's Law formulated by the English chemist William Henry states that at a given temperature, the solubility of a gas is directly proportional to the pressure of the gas directly above the liquid.

• LE CHATELIER’S PRINCIPLELe Chatelier's principle states that a change in any of the factors determining equilibrium will cause the system to adjust to the changes in order to restore equilibrium.

Le Chatelier's principle predicts that the solubility of a gas willincrease as a system loses heat, and will decrease as a system gains heat.

• Steam Surface CondenserNeeds to operate with maximum efficiency to remove as much Dissolved Oxygen as possible, however, this IS limited by Operational Parametrics!



• CORROSION!!• pH Levels,• Seal Faces,• Cavitation Pumps, etc.

• 5ppb+ can induce pitting corrosion!!


• LP Exhaust – Steam.• LP Exhaust – Shaft Seals.• Gland Seal Steam.• Steam Bypass (CCGT).

> Desuperheater• Entrained in Condensate.• ‘Cold Water’ Make-Up.

Especially if TMU < TSat

• Air In-Leakage.• Shell Cracks.• Gasket Leaks.• Etc., etc.

WHERE? – Does DO2 Come From? Problem?


WHERE? – Does DO2 Come From? Problem?


• 7 ppb … 0.005 cc/l• 14 ppb … 0.010 cc/l• 21 ppb … 0.015 cc/l• 42 ppb … 0.030 cc/l

• Most Condensers should not exceed 42ppb under practical operating conditions. [BWR-Nuke, 10-50ppb]

• Condensers can achieve as low as 7ppb and 14ppb given stable operation at the Design conditions (100% Duty!).

• Condensers do NOT perform well when they…• …Operate at LOW LOAD Conditions!• …Cycle or have Transient Operation!• …Have to deal with High Quantities of Make-Up < TSat!!

HOW? – Should My Condenser Perform?


KNOW THE ‘3/7 - 5/14’ RULE!• To Maintain ≤ 7ppb

• ‘Cold’ Make-Up < TSat.

• < 3% Steam Flow.• To Maintain ≤ 14 ppb

• ‘Cold’ Make-Up < TSat.

• < 5% Steam Flow.• HEI > DO2 Curves > Guarantees!

• Figures 3 & 5.• 7ppb and 14ppb Curves.• C.W. Inlet Temp., Duty & Back-Pressure.



HEI: Standards for Steam Surface CondensersHEI (Heat Exchange Institute)Standards for Steam Surface Condensers

– 11th Edition [Oct. 2012]– Addendum 1 [Aug. 2014]– Design Guidelines for DO2

– Section 4.3 – O2 Condensate– Sample Calculations– Venting Capacity– Performance Curves

HEI = Guaranteed Performance!!!



HEI Figure 3Absolute Pressure Limit Curves for Oxygen Content

Saturation Pressure versus C.W. Inlet Temperature

Predicts Condensate Dissolved Oxygen Content at

Curve A ≤ 7ppb

Curve B ≤ 14ppb

Superimpose Figure 3 on Condenser Performance Curves (versus Load)…



HEI Figure 5Absolute Pressure Limit Curves for Guarantees.

Saturation Pressure versus C.W. Inlet Temperature.

Predicts Cut-Off Point and Zero Load Performance.

Curve A ≤ Cut-Off

Curve B ≤ Zero LoadSuperimpose Figure 3 and Figure 5 onto Condenser Performance Curves – C.W. Inlet, Duty & Back-Pressure vs DO2 Levels



HEI Figure 5

Cut-Off to Zero Load must be reflected on Performance Curves to predict DO2 Performance!

NOTE: 5°F TTD is a Guarantee Limit!!



PERFORMANCE CURVES Back-Pressure (0.5-6.0 inHgA)

Heat Duty (0-120%)

Circ. Water Temps. (70-110°F)

Cleanliness Factor (85%)

Curve A ≤ 7ppb

Curve B ≤ 14ppb

Performance Curves should be provided by all Condenser

OEM’s for predicting your DO2 performance!!



• Do Not Address Leaks! i.e Fix Leaking Gaskets, etc.• Make-Up <Tsat

• 3%+ of WS >> 7ppb+• 5%+ of WS >> 14ppb+

• Make-Up is in Poor Location• Below Bundle!• NO Reheat!!

• Baffle/Elbow vs Spray Pipe• Operational Parametrics

• LOW LOADS!• Cycling / Transient• Low C.W. Inlet (Winter)

WHEN? – Does ‘High’ DO2 Occur?


• 1. Connection (Re)Design Convert Baffles to Spray Pipes! Revised Location to ABOVE Bundle, not side, or below Install a properly designed Spray Pipe (Reheat)

• 2. Install a Hotwell Sparger High Make-Up (5%+ Q) &/or Low Make-Up Temp (<TSat) Operational Conditions (Low Load, Cycle, Low C.W. Temps)

• 3. Install a Vacuum Deaerator High Make-Up (5%+ Q) &/or Low Make-Up Temp (<TSat) Achieve <5ppb

HELP?! – Can I Reduce My DO2?!


1. CONNECTION (RE)DESIGN• Effective for

• Improve Reheat Levels.• Improve Deaeration.• Avoid Baffles/Elbows.• Use Spray Pipes (proven).• Re-Engineer Existing Baffles.• Re-Route Internally (if Head!).• Follow HEI & EPRI Guidelines.• Locate above Bundle.• not below, or at side• Improve Distribution• Improve Reheat!• Use St/St Piping (longevity).

• $ Lowest Cost Option (Outage).



1. CONNECTION (RE)DESIGN &/OR (RE)LOCATION



1. CONNECTION (RE)DESIGN &/OR (RE)LOCATION


Spray Pipe above vs Baffle on side of Bundle!! Increased Distribution Area & Volume. Improved the Contact/Residence Time. Reheating was vastly improved. Dissolved Oxygen liberated IN Bundle. Dissolved Oxygen removed from Bundle via

Air Draw Off, Vent Duct & Vacuum Equipment Eliminated “Spikes” in DO2 during Make-Up. Reduced DO2 by up to 21 ppb.


2. INSTALL HOTWELL SPARGER• VERY Effective for

• Raising Condensate Temperature.• START-UP!

• Use for Cold Start-Up.• Use of Hot Start-Up.

• Design for 30-60 mins. to TSat.

• LOW (Transient) LOADS (Reheat).• LOW C.W. Temperatures (Winter).• Simple Control (On/Off).• Popular in Combined Cycle Plants.• And.…Base Loaded Fossil Units that now Cycle!• Auxiliary Steam (typ. 50psiG @ 350°F & 1,200+ Btu/lb)• When to Operate a Hotwell Sparger? V. IMPORTANT!

• $$ Medium Cost Option (Outage).



Typical Hotwell with Steam Sparger Piping to control dissolved

Oxygen in condensate during Start-Up, Low

Loads & Low C.W. Temperatures.

2. INSTALL HOTWELL SPARGER




WHEN TO OPERATE A HOTWELL SPARGER?

• LOW LOADS!• LOW DUTY!• LOW C.W. INLET!• HIGH MAKE-UP!• CYCLING!• ONE BUNDLE

OPERATION!


3. INSTALL A VACUUM DEAERATOR

• Highly Effective for

• Large Volume Make-Up.• 5%+ of Steam flow

• Low Temp Make-Up.• Make Up <TSat

• Spray & Tray (proven).• Robust (Range of Conditions).• Uses Steam from Condenser.• OR, Auxiliary Steam.• Excellent for Cycling/Transient.• Condenser Mounted !• Operates Continuously.

• $$$ Highest Cost Option (PROJECT)



3. INSTALL A VACUUM DEAERATOR



SUMMARY• Know Your Condenser!• OEM Performance Curves;• w/ HEI 7 & 14 ppb Curves.• Address Air In Leakage.• For ‘Cold Water’ Make-Up.

Especially if TMU < TSat

• Make-Up Design (Spray Pipe)• …and Location (above Tubes)• Use of Hotwell Sparger.• Vacuum Deaerator?• Always Monitor DO2.• Address ‘High’ DO2!!!

SUMMARY – Dealing with Condensate DO2


THANK YOU FOR YOUR TIME!!

THANK YOU!


QUESTIONS?& ANSWERS!

QUESTIONS? & ANSWERS!


one source one purpose many solutions utility users group meeting orange beach, al august 4, 2015...

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