(34e) Fate of Ammonia in Refinery Amine Systems

Fate of Ammonia in
Refinery Amine Systems

Ralph
H. Weiland, Nathan A. Hatcher & R. Scott Alvis

Optimized
Gas Treating, Inc.

Sugar
Land, TX

ABSTRACT

Ammonia
ingress and accumulation in refinery and bio-gas amine systems is not a new
problem. However, increasing utilization of advantaged crudes with higher
nitrogen content may present challenges in today's capital-constrained
operating environment. Many refiners have instituted guidelines for purging
amine regenerator reflux water for corrosion control. Historically, this has
been done empirically based upon periodic lab analysis and adjustment of the
purge water rate.

The
true amount of ammonia ingress, and its material balance across refinery amine
unit is not a topic that has been discussed in great detail, because until now,
rate-based mass transfer models have not been available. Using the well-known
ProTreat? rate-based mass transfer process simulator, this paper addresses the following
questions. Where available, comparisons to plant data measurements are
provided.

1.     
How
much ammonia can accumulate based upon choice of regenerator operating
conditions?

2.     
How
much ammonia rejection into the amine acid gas does this correspond to, and is
this a significant concern to downstream (i.e., sulfur plant) operations?

3.     
Can
ammonia build to levels that will cause additional H₂S to be trapped
leading to higher lean loadings, reduced treating performance, or even regenerator
flooding?

4.     
How
does the choice of HDS cold separator operating conditions impact the ingress
of ammonia to the amine system; just how effective is water washing?

5.     
How
much ammonia skates through refinery amine treaters?

Ultimately,
we attempt to answer whether the ammonia balance on a refinery amine system can
be fully characterized based upon the knowledge of a few simple parameters.