Scr Scrub ubber bers: s: Land Land-based based V Ver ersus - PowerPoint PPT Presentation

Scr Scrub ubber bers: s: Land Land-based based V Ver ersus sus Marine Marine Philip Song, PhD Bud Ross, PE Nickel Institute

Summary • 40 Years Experience in North America and Europe • Land-Based FGD (Flue Gas Desulfurization) Corrosion - Failures/Solutions • NACE Response to Marine Scrubber Industry

Background Land-based Power Plants FGD • Pollution Control Began In The United States With The Passage Of The Clean Air Act In 1970 • Over 350 Scrubber Units In 2010 In USA • Today, 700 FGD Systems Globally • Over 40 Years Experience With Scrubber Corrosion

Background Shipboard Marine Scrubbers • IMO Sets Emissions Limits On Marine Diesel Exhaust • Preferred Compliance-method Is With Wet Scrubbers • Over 2,100 Ships Fitted With Wet Scrubbers In 2019 • Thousands Of Scrubbers Projected Globally By 2025

Background • Shipping Industry Appears To Be Following The Materials Selection History Of The Land-based Electric Power Plant’s Experience • Open Literature Has No Information On Corrosion Performance Of Any Marine Scrubber System • Industry Needs NACE Task Group 575

Land-Based Scrubber Corrosion Important Lessons Learned Important: Poor Quality Imp y Co Control of Fabrication And Welding Ca An Causes ses Co Corrosi sion Most st Severe Corrosi Co sion: Ac Acidic Inlet Du In Duct, De Deposi sits Severe Corrosion: Crevice Corrosion Under Deposits Major Failure Cause

Wet Inlet Duct Condensing Acids and Deposits

Absorber Sump Perforations Crevice Corrosion Under Deposits

Absorber Crevice Corrosion Under Deposits

Quality of Fabrication and Welding Reduces Corrosion Resistance • Weld Spatter Crevices • Microcrevices (Grinding Marks, Scratches) • Embedded Iron • Under Paint Markings • Weld Metal (High Heat Input, Roughness) • Weld HAZ (Heat Affected Zone) • Weld Heat Tint

Weld Spatter/Embedded Iron

Microcrevices Grinding Marks, Scratches

Under Paint Markings

Some Alloys Show Weld HAZ (Heat Affected Zone) Corrosion

Weld HAZ (Heat Affected Zone) HAZ Weld HAZ

Designers Were on a Learning Curve: 1960s - 1980s • Carbon Steel • Coated Carbon Steel • Rubber Linings • FRP • Borosilicate Glass Block Lining • Acid Brick Lining • Stainless Steels, Alloys 904L, 825 • Alloy 625 • C-Family of Alloys, Titanium

Designers Were on a Learning Curve: 1960s - 1980s • Availability Of Suitable Candidate Alloys Is Often Overlooked • Large Quantities May Require Typically Four Or More Months Of Lead Time • Specific Product Forms May Not Be Available

Designers Need to Define the Environment (Crevice Corrosion) • Full-immersion Environment In The Scrubber Sump • Falling, Thin-film Environment In The Absorber • Hot-gas Entry In The Quench Section • Acidic Condensate In The Outlet Ducting • pH – Chloride Content – Temperature Variations

Effect of pH and Chlorides on Crevice Corrosion in FGD Temperature 60⁰C 2205 Estimated Chlorides, ppm C-276 pH

Success Analysis FGD >30 Years Absorber Towers Alloy 904L pH = 6.2 – 6.5 Chloride = 1,400 ppm Alloy 625 pH = 4.2 – 4.5 Chloride = 28,000 ppm

Success Analysis FGD >30 Years Alloys 904L and 625 Absorber Towers

Success Analysis FGD >35 Years Alloy 625 183 m Stack Liners

Success Analysis FGD > 25 Years Alloy C-276 Clad Steel Plate 148 m Stack Liner

Success Analysis FGD >30 Years Alloy C-276 Wallpaper Outlet Duct

Design for Success Marine Scrubbers Operating Slurry: 1. Hotter And More Acidic 2. Both Will Accelerate Corrosion, Especially Crevice Corrosion 3. Alkaline Slurry Is Much Less Corrosive, But Must Monitor Chloride Contamination

Design for Success Marine Scrubbers I. May not have bypass ducting, so need to design for dry exhaust gas at hotter temperatures (300-450 ° C) for prolonged periods. II. The potential for higher operating temperatures prohibits the use of all plastic and elastomeric materials, except in cooler piping sections where FRP can be used.

NACE Response to Marine Scrubber Industry • STG 45 (T-5F) Technical Committee - Active Since 1977 • Standards SP0292 Wallpaper and SP0199 Clad Plate • Annual Conference Papers – 40 Years • AirPol Seminars 1981 - 2007

Marine Scrubber Summary • No Service History in Open Literature • No Corrosion Data in Open Literature • pH, Chlorides, Temperature Major Variables • Fabrication/Welding Precautions Must be Identified as Major Design Parameter

Marine Scrubber Summary Land-based Experience shows selecting a marginal, low initial-cost material can result in premature failures. This leads to scrubber system leaks, downtime, and additional repair costs that can be many times more than the original material cost. NACE TG 575 objective is to gain and share knowledge to prevent corrosion of shipboard scrubber systems in the Marine Industry.

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