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Operational Improvements at the Grant Town Power Plant. Presented By: Steve Friend Sr. Plant Engineer Edison Mission O&M 2005 ARIPPA Technical Symposium. Improvements at the Grant Town Power Plant. Fuel Handling and Processing Ro-Pro Facility Silt System Ash Handling
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Operational Improvementsat theGrant Town Power Plant Presented By: Steve Friend Sr. Plant Engineer Edison Mission O&M 2005 ARIPPA Technical Symposium
Improvements at the Grant Town Power Plant • Fuel Handling and Processing Ro-Pro Facility Silt System • Ash Handling Bottom Ash Screw Coolers Bottom Ash Piping • Limestone Processing DFM • Boilers Grid Nozzles Tube Erosion Cyclones NOx Control • DCS Foxboro Migration
Fuel Processing and Handling • Addition of the Ro-Pro facility has added flexibility to the fuel production process and additional means for final product cost • Removal of the wet circuit equipment from the original preparation plant eliminated excessive reject and reduced costs of product – dewatering chemicals and equipment no longer used • Silt system installation and modifications have allowed facility to maximize amount of lowest cost fuel to be added into final fuel blend – higher silt percentage = minimum fuel costs
Bottom Ash Handling Improvements • Screw Cooler capacity was approximately 20% lower than design with a 6” Pitch Auger – required running the screw cooler at higher RPM for adequate bed level control • 7” Pitch Auger allowed screws to be slowed down – reduced erosion rates on the cooler components • Addition of rifle bars has helped to control trough erosion but has increased wear rate on the auger • Application of weld overlays, wear strips, and thicker materials has helped control auger wear
Bottom Ash Piping Modifications • Initial design was sweep elbows on both the primary and redundant pressurized bottom ash conveying systems • Sweep elbows had very low mean time between failures due to erosion – on the order of a few weeks • Reconfiguration of the system using blinded tees for the direction transitions has reduced maintenance costs. • Effective pipe rotation program has helped to further reduce ash conveying system maintenance costs
Limestone Handling System • Williams Direct Fired Mill for processing limestone for injection into the CFBs • Velocity Cone did not have any impact on final product size • Optimization of air flow though the mill has helped to produce more ideally sized product • Installation of VFD on the product cyclone rotary valve has helped to minimize transport line pluggage and system processing delays
Boiler Modifications • Erosion Control • Sootblower lane shielding • Economizer hanger tube tube monitoring/shielding/replacement • Flame Spray • Pad Welding • Refractory Extensions • Stainless Steel Overlay
Boiler Modifications • Arrowhead Nozzles • Provide nominal improvement in limestone utilization • Backsifting is a BIG problem • Internal stand pipe erosion now becoming a major concern • Increased maintenance costs offsetting any benefit realized in reduced limestone consumption • Considering repair/replacement options
Boiler Modifications • Cyclones • Segmented Vortex Finders • Narrowing of cyclone inlet opening • Design of vertical bullnose on the cyclone inlet to narrow the opening about 10% • Narrowing of the opening has increased inlet velocity to >75 ft/sec • Both changes had major impacts on limestone consumption – improvement of about 20% in total when paired with the DFM optimizations.
DCS Modifications • Foxboro Migration Package • Poor availability of Bailey replacement parts and support • Electrolytic capacitor failures • No changes to I/O wiring • Low cost alternative to wholesale DCS replacement
