Steels_ Metallurgy and Applications, Third Edition

368 Steels: Metallurgy and Applications

Table 4.17 Materials used in absorber towers of FGD plant

Alloy Chloride ion pH Plant

designation content (ppm)

316L 1000 7.5

316LM 1700 6

317L Not specified
317LM 7000 6.5

94L Few thousand 6
Hastelloy G 1600 -
Inconel 625 10 000 2

Cane Run 5, La Cygne 1, Cane Run 4,

Colstrip 1 and 2, Duck Creek 1, Coal

Creek 1 and 2, Jeffrey 1 and 2,

Lawrence 4 and 5 (new) and Green

River

Dallman 3, Jim Bridger 2 and Laramie

River 1 and 2

Museatine 9

Schahfer 17 and 18, Colstrip 3 and 4,

Four Comers 4 and 5 and Jim Bridget 4

Big Bend 4

Cholla 1

San Juan 1, 2, 3 and 4 and Somerset 1

After Lane and Needham. 12

In the heat exchanger, the conditions become more aggressive as the tempera-
ture falls below the dewpoint of the flue gas and grades such as 316L and 317LM
are used in this region.
As indicated in Table 4.16, the conditions can vary significantly in the
prescrubber and absorber and the choice of grade will depend very much on the
particular combination of chloride ion concentration and acidity (pH). A summary
of the stainless grades used in the absorber section is shown in Table 4.17. The
compositions of these grades are included in Table 4.8.

Nuclear fuel reprocessing plant

The nuclear fuel reprocessing industry is a major user of stainless steels in the
form of plates, tubes and forgings and the selection of steels in this sector has
been reviewed very thoroughly by Shaw and Elliott. 36 Whereas the choice of
materials for chemical plant is generally governed solely by the nature of the
process stream, due regard must also be paid in the nuclear industry to the hazards
of radiation which have a major influence on the opportunity for equipment
repair and maintenance. Thus materials operating in areas of high radioactivity
in nuclear reprocessing plant, where access is difficult or even impossible, are
designated primary plant materials, whereas those operating in more accessible
areas with low levels of radiation are defined as secondary plant materials.
Reprocessing is based upon the dissolution of irradiated nuclear fuels in hot
nitric acid, followed by solvent extraction and evaporation stages. The first
reprocessing plant at Sellafield in Cumbria was commissioned in 1952 and was
constructed in two main types of stabilized stainless steel, namely 18% Cr 13%
Ni-Nb (similar to Type 347) for primary plant and 18% Cr 9% Ni-Ti (Type 321)