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.