4-17-08

Corrosion is a continuing Challenge for the FGD industry - Hot Topic Yesterday

There are still lots of challenges in corrosion protection of FGD systems. A group of experts provided valuable insights in the 90 minute Corrosion Materials Hot Topic Hour yesterday.

Ron Richard, a consultant with decades of experience with FGD materials said that even C-276 is subject to corrosion and lasted only two years in a scrubber bypass application. He had a number of suggestions on how to avoid problems at various points in the system. Some were as simple as laying plywood down on the duct floor before doing maintenance and making sure there is adequate drainage around expansion joints.

Mike Walsh of Marsulex contrasted the materials used in U.S systems with those used in China. China is using carbon steel with flake glass lining in the inlet and outlet ducts and carbon steel with an abrasion resistant vinyl ester lining in the absorbers. Most units have gas-to-gas heat exchangers with flake glass linings. In China some of the earlier alloy applications have been replaced with FRP, including the oxidation air lance. There have been lots of problems, much of it due to the gas-to-gas heat exchangers. As a result there is going to be lots of work done to retrofit these systems. Recently the trend has been to wet stacks.

Mike also cited the materials used in the ammonia scrubber system. The scrubber vessel is 317 L or 2205 with flake glass or rubber lining below the liquid level and 316 L with linings above the liquid level.

Dave Brysacz of International Protective Coatings (Ceilcote) explained that they divide the scrubber into six zones and have different linings to address the situation in each zone. Corrosion, abrasion, and temperature parameters are taken into account. The company has decades of experience and can point to linings in U.S. FGD systems which have lasted for decades.

David McKissock of Hadek introduced us to a new slim concrete chimney design with borosilicate glass block lining which is specifically designed for plants with FGD systems. The savings in capital cost can be 10 percent or more over older designs. The Patnow Power station is an example.

Clair Guess of Augusta Fiberglass displayed a picture of a 119 ft. x 57 ft. JBR scrubber of fiberglass which was built on site by Augusta. FRP stack liners have been proven over nearly 40 years. Recently FRP slurry tanks have proven to be a good alternative to lined carbon tanks.

A resent study by an OEM showed that the cost of FRP is less than linings and is half that of C-276 clad.

Biographies and pictures of the presenters are displayed at

Presenter Bios and Photos Hot Topic Hour April 17, 2008

The presentations in the FGD Decision Tree can be viewed directly through the following links.

David McKissock – Hadek Protective Systems

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Scrub

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Component Specification