Page 244 - Gas Purification 5E

230 Gas PuriJcation

(1979A, B), and are also available from amine vendors. Use of antifoam should not be
regarded as a permanent solution to plant foaming problems. Once foaming is under control,
the source of trouble should be investigated and the basic problem corrected.

Amine Solution Monitoring Program

Foaming of amine solutions and corrosion of amine units are best controlled by a compre
hensive amine solution monitoring program. Pauley (1991) suggests that the following
amine solution tests be performed by an outside laboratory:

Organic acids (liquid chromatography)
Heat-stable salts (ion exchange)
Amine concentration (gas chromatography and alkalinity)
Soluble metal content (atomic absorption)
Iron sulfide content
Liquid hydrocarbon content
Water content

Bacon (1987) recommends the following tests:

Lean and rich amine solution loadings
Total heat-stable salts-free vs. total amine
Anion assay-type and amount of anions
Cation assay-type and amount of cations
Soluble iron content of solution
Gas chromatography-compare amine concentration against alkalinity. Identify and quanti-
fy degradation products
Foaming tendency-extent and duration

While the exact needs will vary from system to system, most plants should run these tests
about every two to three weeks at a minimum. In addition, tests for determining the lean and
rich amine loading should be performed on at least a biweekly basis, and the performance of
the activated carbon filter should be checked periodically (foaming test, turbidity, pressure
drop, color change across filter). Detailed test procedures are available from amine vendors.
In addition to these tests, there are a number of observations that can indicate the quality
of the amine solution. Lieberman (1980) suggests filling a clean glass quart bottle with unfil-
tered amine solution and observing the solution color and turbidity. According to Lieberman,
solution quality can be rated as follows:

1. Amine solution is bright and clear. Amine is in excellent condition. A blue or green tinge
is of no consequence; however, if the amine looks brownish, air is getting into the system
and oxidizing the amine. Oxidized amine is corrosive.
2. Amine solution is a pale, dull gray and objects can be seen through bottle without difficul-
ty. The amine solution is still in good condition; however, the solution quality should be
monitored carefully to ensure that the quality does not deteriorate.
3. Amine solution is translucent black, objects can be barely seen through the bottle, and a
small amount of sediment can be seen after the solution has been left standing for 10 min-
utes. Under these circumstances, corrosion is occurring faster than the corrosion products
can be removed. The source of contamination (feed gas contaminants, high heat-stable