Ammonia Analysis – SRU Protection

SRE is the only firm in the Oil & Gas industry that can provide timely, on-site results with respect to ‘bulk’ and ‘trace’ ammonia testing. In addition to our standard ‘bulk’ ammonia analysis of refinery-based sour water stripper (SWS) acid gas feed streams, we are capable of measuring the ammonia content (i.e. ppm level) in amine acid gas and the stream exiting your reaction furnace (RF). These specialized services are another example of SRE’s commitment to the efficient and long-term operation of our clients’ SRUs by way of research and development.

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Based on 20+ years of field-testing experience, SRE strongly recommends ammonia breakthrough from the RF is kept below 150 ppm. The prevention of ammonia salt formation in downstream condensers will ensure optimal sulfur recoveries are realized without capacity reduction, all while preventing costly shutdowns to unplug or replace condenser tubes.  While on-site, SRE Engineers will work with operations to maximize ammonia destruction by way of optimizing your front-side split parameters and, if applicable, adjusting the fuel gas co-firing strategy.

The combination of an SRU performance test and ammonia destruction study will minimize the potential risk of downstream ammonia salt formation in your SRU. SRE’s specialized services are designed to protect your facilities, personnel, and bottom line.

Trace Oxygen in Raw Gas To Determine Corrosion Source

Q4 2017 saw SRE complete a number of interesting projects.  For one gas plant in Canada, SRE was involved with determining the source of corrosion with our client’s gas sweetening unit.  In an amine system, corrosion problems can easily be identified by the color of the amine: pale green indicating light corrosion; brown indicating corrosion greater than the filtration capabilities; and black indicating dangerous levels.  Although there are many sources for corrosion, our client had already identified that their corrosion was most likely cause by an increased amount of Bicine.

There are several mechanisms for producing bicine in amine gas treating facilities which include (1) reaction of diethanolamine (DEA) with glyoxal – a common hydrogen sulfide (H2S) scavenger – and (2) exposure of the heated gas treating solution to an oxidizer. Bicine impacts gas treating amine solutions in two ways. First, it forms heat stable amine salts (HSAS) and second, it increases the corrosivity of the amine solution.  Here, it was thought that the oxidizer was Oxygen (O2) ingress from the field raw gas.

As such, SRE’s scope of work was to complete trace O2 analyses at various points through the gas plant, including the raw gas from each field and throughout the inlet lines to the Amine contactors.  In one day, SRE conducted 22 trace O2 measurements from 10 different locations.  Sampling was extensive as a 3-minutes sample time and portable equipment allowed the site Engineer to be able to request extra measurements for due diligence.  These capabilities are in stark contrast to a trailer full of equipment and a 2-hour run time – 1 hour to mobilize, 30 minutes to warm up line and 30 minutes to conduct analysis – used by other testing companies, where 22 samples could take a few days & cost 3 times more.

Results ranged from 20 ppm to 250 ppm with all raw gas inlets having a measurable amount of O2.  The site Engineer planned to use the data to conduct their own material balance and to continue to mitigate the amine system corrosion.

KPIs for the SRU

Sulfur Recovery Engineering (SRE) clients often ask about Key Performance Indicators for their Sulfur Recovery Units.

It is difficult to identify KPIs for the SRU without compositional analysis and feed stream data.  If you think about it, the data that you see from the DCS – flows, temperatures and air demand analyzer (ADA) info – are all directly related to what is actually coming into the SRU.

Things to look at are inlet flows to the SRU, temperature differentials across the catalytic converters, and the concentrations reported by your tail gas analyzer.  It is important to note that these data points are dependent on the compositional analysis of feed streams. SRE can provide our clients with this analysis, and recommends that a Performance Evaluation and Optimization be conducted periodically as part of any SRU routine maintenance program.

If your crude or gas wells change frequently, it is recommended that feed streams are tested more regularly as operating parameters may need to be adapted in order to compensate for varying acid gas quality or contaminants. For example, if the H2S content in the amine acid gas drops significantly (i.e. a drop in sulfur loading) then the combustion air requirements, the converter bed temperature profile, and the measured ADA concentrations will all change as well.

In a refinery, it is important to do regular sampling of both the amine acid gas and the sour water stripper acid gas to determine their respective compositional analysis, especially if the source of crude supplying the refinery is constantly changing.  Some SRE clients have us come to site and conduct this analysis on a quarterly basis.

Here is the short list of SRU KPIs to monitor for performance and optimization that we consider important:

1. Flow rates of the amine acid gas, sour water stripper acid gas and air (main, trim and total) to the SRU;

2. Amine Acid Gas H2S, CO2, & hydrocarbons content;

3. Sour Water Stripper Acid Gas, Ammonia (NH3), H2S, H2O content;

4. Differential temperature across the first and second converter (i.e. the maximum bottom bed temperature of the converter minus the outlet temperature from the reheater);

5. H2S and SO2 concentrations from the ADA;

6. Stack Emissions.

Regular reviews of your SOPs, PMO plan and other operating manuals will ensure that you are up to date with the most efficient operating procedures.