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Steam Generator Upgrades & Maintenance

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Presentation on theme: "Steam Generator Upgrades & Maintenance"— Presentation transcript:

1 Steam Generator Upgrades & Maintenance
Presented by: David King, Manager Steam Generation Equipment Engineering APP Site Visit October 30 – November 4, 2006

2 Topics of Discussion Steam Generator Upgrades & Maintenance
Steam flow balancing Air heater baskets & seals Component replacement upgrades (material & design) Online detonation cleaning Water Cannons/HydroJets Acoustic leak detection Weld overlay & coatings Balanced draft conversion on FGD units Nose installation on 800 MW units Boiler tube failure program 4th generation low NOx burners

3 Topics of Discussion Fuel Considerations
Matching steam generator design with fuel characteristics Benefits of washing coal Coal additive injection

4 Steam Flow Balancing Aptech TubMod Analysis at Glen Lyn Unit 6
The unit experienced high temperature variations across the boiler, caused by tube circuit design and gas temperature/flow imbalances. TubMod analysis was performed to improve the temperature profile and extend the life of the superheater tubing. Through the TubMod process, temperature imbalances can be corrected by redistributing the steam flow. The result is an evening out of the tube metal temperature across the superheater elements, and a reduction in the temperature on the elements operating excessively hot.

5 Steam Flow Balancing

6 Air Heater Baskets Modifications are necessary to accommodate high sulfur fuel switch programs and SCR retrofits. Considerations to address high sulfur applications: Increased attention to exit gas temperatures being maintained above the acid dew point. Modifications to address SCR retrofits: Redesign of the heat transfer surface arrangement. 3 layers reduced to 2 to envelope the ABS formation temperature within an area that can be cleaned with conventional sootblowing. The use of closed channel elements to better contain and focus the cleaning media to the areas of likely deposition. The utilization of multimedia blowers to facilitate both conventional on-line cleaning, and off-line washing.

7 Cleaning Media Discharge
Air Heater Baskets ALSTOM Power Inc. Air Preheater Company Open Channel Surface Closed Channel Surface Cleaning Media Discharge Cleaning Media Inlet Cleaning energy dissipates rapidly Cleaning media diverted around deposits Requires higher pressure for effective cleaning Higher risk of element damage from cleaning Each channel acts like a closed pipe Cleaning energy cannot divert around deposits Deposits are readily removed, at lower pressures Lower risk of element damage from cleaning

8 Air Heater Seals Paragon air heater seal installation at Welsh Unit 3
Air heater leakage across air heater radial seals can average as much as 15 to 20%. The air heater leakage results in excess FD and ID fan motor amps, with the recognizance that the fan motors are one of the largest auxiliary power consumers in the plant. Reducing air heater leakage will show immediate heat rate benefits. Welsh Unit 3 saw a 30% reduction in ID fan amps after the installation of the Paragon Airheater Technologies radial and circumferential/bypass seals.

9 Air Heater Seals The Paragon DuraMax radial seals incorporate unique, self-adjusting bellows that ensure positive contact with the sealing surfaces. The Paragon DuraFlex high-performance circumferential and bypass seals use a patented revolutionary interlocking design which reduces the air gaps.

10 Component Upgrades Total Platen Replacement Projects
Upgrade tube material to all stainless steel vs. in-kind material selection with croloy and stainless steel material transitions. Improves the boiler’s slag shedding capability. Expands the types of coal a particular unit can burn. Stainless Steel Weld Overlay for Shielding Use SS weld overlay on new boiler tube components in lieu of tube shields at sootblower locations. Spiral weld overlay has higher upfront cost, but minimal future O&M costs to maintain. AEP has some spiral weld overlay tubing in sootblower lanes with 10 years of service and no reported issues.

11 Component Upgrades New Alignment and Attachment Designs

12 Online Detonation Cleaning
Pratt & Whitney SHOCKSystem Economizer Cleaning at Rockport Unit 2 Provides non-line-of-sight cleaning of tube bundles to remove bridging and platenization. Middle Economizer Bundle Problem: Excessive Ash Piles and Bridging Cause Delta P and Heat Transfer Impact Spatial Constraints Prevent Installation of Conventional Sootblowers North Wall Lower Economizer Bundle Ash Piles Extend Beyond Hangers

13 Online Detonation Cleaning
BEFORE AFTER SHOCK Blasts SHOCK Blasts Before SHOCKSystem™ After SHOCKSystem™ Ash Pile Accumulation Over Nine Months of Continuous Boiler Operation First Two Ash Piles Removed After Two Days of SHOCKSystem™ Operation

14 Online Detonation Cleaning
Five Combustor Economizer Cleaner at Rockport Unit 2

15 Online Detonation Cleaning
Rockport Unit 2 Economizer Cleaning Installation Five Days of Intensive SHOCKSystem™ Operation Delta T Across Economizer Increased By 15°F Effective Heat Transfer Increased By 10% Temperature of Gas to Airheater Decreased By 30°F Temperature of Gas from Airheater Decreased By 15°F Weight of Ash Removed 240,000 Lbs

16 Water Cannons/HydroJets
Provides “intelligent” real-time cleaning of furnaces using water cleaning hardware and a closed-loop control system that utilizes sensors and software. Displaces conventional wall blowers or water lances as the best available technology for furnace cleaning. Uses cross-furnace cleaning where a controlled water jet is transmitted across the firebox to the opposite or adjacent walls.                                                                                                                                        Water Cannon HydroJet

17 Water Cannons/HydroJets
Gavin Unit 2 Water Cannon Performance Testing Furnace Exit Gas Temperature Decreased by 112°F NOx Emissions Reduction of 0.04 lb/MMBTU Heat Rate Decreased by 25 BTU/kwh S02 to S03 Conversion Reduction of 8-10%

18 Acoustic Leak Detection
Acoustic leak detection system at Gavin Unit 1 & 2 Consists of 30 remote acoustic sensors attached to membrane of exterior furnace walls and penthouse roof. Ethernet daisy-chain provides communication to control room were central computer is located. Information is processed, filters applied (sootblowers, furnace penetration seal air, etc.) and information is displayed on operator PC screen. Alarms are established for each sensor and refined as leaks are detected. Acceptance and reliance on acoustic leak detection has reduced forced outage durations from weeks to days. Provides better indication of tube leak than any other method, including older style acoustic leak systems and water loss tests.

19 Acoustic Leak Detection
Gavin sensor layout along with HP heater screen which also have 1 acoustic leak detector per heater. Leak detection screen and alarm indication threshold at 92 dB.

20 Weld Overlay & Coatings
Efforts to minimize NOx production have led to increases in furnace waterwall wastage, which has necessitated furnace corrosion protection. To combat high levels of corrosion, AEP currently reviewing various furnace protections including: Weld overlay Metal spray coatings Ceramic coatings The industry is working to optimize the choice of overlay and metal spray materials. Computer Modeling and/or thickness surveys are utilized to identify the areas needing protection. The overlay and metal spray processes have been automated by the vendors.

21 Balanced Draft Conversion
Converting positive pressure units to balanced draft operation while retrofitting FGD’s. Improves the work environment of the boiler house, thus increasing productivity and equipment longevity. Reduces the likelihood of fugitive emissions occurrences due to casing leaks. Utilizes multi-speed motors on existing FD fans and the application of variable pitch axial ID fans. Provides the additional head to overcome the added resistance of the FGD. Optimizes unit efficiency over the load range and provides improved unit control. FD fan controls volume flow while ID fan maintains furnace pressure. Requires upgrading steam generators to accommodate the extremes of balanced draft operation.

22 Furnace Nose Installation
Furnace nose installation on AEP’s 800 MW units completed in conjunction with FGD retrofit. Reduces the peak temperatures leaving the furnace, thereby reducing the slagging potential with higher sulfur coals. Serves to improve mixing and heat absorption in the furnace. Spreads the flue gas flow out over the leading edge surface of the pendants. Installed a 10 foot long nose in a 39’ x 80’ furnace.

23 Furnace Nose Installation
Mitchell Unit 1&2 CFD Modeling Expected Performance Furnace Exit Gas Temperature Decreased by 17°F Superheater Heat Absorption Increased by 15% Boiler Efficiency Improved by 0.07% Coal Consumption Reduced by 0.12% Loss on Ignition Reduced by 0.05% Aperture Floor Velocity Reduced from 200 fps to 56 fps

24 Boiler Tube Failure Program
Provides centralized boiler tube failure data and metallurgical analysis results. Makes for easy access to information/data for capital replacement justification purposes or O&M repairs. Centralized boiler tube failure tracking helps to alert other like series units of potential related tube failure mechanisms or issues. All tube failures are routed through corporate engineering. Based on visual review, the failure samples may be forwarded to AEP’s internal lab for further metallurgical and root cause analysis.

25 4th Gen Low NOx Burners Existing Low NOx Burners New Low NOx Burners
25 hot tips/burner fires per year NOx emissions 0.75 lb/MMBTU Projected 135 hot tips/year with future coal (high sulfur and slagging) New Low NOx Burners 0 hot tips to date NOx emissions 0.48 lb/MMBTU Potential urea cost reduction of $350/dry ton urea (365 day ozone control)


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