Spotlight on the Gulf Coast Conference - Analytical Instrumentation
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In the RFG PTP program, D7039 outperforms D2622 100% of the time, and outperforms D5453 91% of the time when evaluating samples with a mean sample concentration of 5 – 15 ppm.
PRECISION & ILS RESULTS
Hundreds of participants are involved in the monthly ULSD PTP program, which exclusively looks at sulfur. The monthly RFG PTP boasts over a hundred participants running a variety of test methods for differing RFG parameters. The data shown represents sulfur data collected throughout the study from January 2015 to December 2017.
Understanding the Data (Mean Concentration and Reproducibility)
Both graphs and tables shown below track average sample concentration and reproducibility (R). Reproducibility is the difference between two single and independent results obtained by different operators applying the same test method in different laboratories using different apparatus on identical test material. A lower reproducibility value correlates to a better level of precision which can minimize risks from inaccurate reporting such as regulatory fines and contract disputes.
The data presented is filtered to show all samples whose average concentration ranged between 5 and 15 ppm. These values were chosen based on the most common regulatory requirements for sulfur content in automotive fuel in Europe, United States, China, and others around the world. It is critical for an analyzer to have low reproducibility values (better precision) when measuring these types of samples. When interpreting the data, keep in mind:
In the ULSD PTP Program, D7039 outperforms D2622 89% of the time, and is equal to or better than D5453 67% of the time when evaluating samples with a mean sample concentration of 5 - 15 ppm.
Graphs 1 & 2 • Both graphs are sorted by decreasing sample mean.
• Each column cluster in the graphs represents reproducibility for one sample measured by multiple laboratories each using D7039, D2622, or D5453.
• Within each column cluster, each color-coded bar corresponds to reproducibility for one test method. D7039 is in orange, D2622 is in gray, and D5453 is in blue.
• The numerical value of each method/bar is graphed on the left axis. (remember - lower R values are indicative of better precision).
• For many test methods, precision is often dependent on concentration. For context, the monthly average sulfur concentration is graphed as a red dot and its value is shown on the right axis of the graphs.
Tables 1 & 2 • Both tables are sorted by decreasing sample mean.
• Both tables are color-coded to indicate relative monthly performance; green represents the best method reproducibility, yellow represents the second best reproducibility, and red represents the poorest reproducibility.
The average R value across the 3 years of study data is the key performance indicator shown in both graphs and tables. A summary of the reproducibility of the RFG and ULSD PTP samples for 2015 - 2017 showed that ASTM D7039, using MWDXRF, had:
• The best precision for RFG 100% of the time compared to D2622 • The best precision for RFG 91% of the time compared to D5453 • The best precision for ULSD 89% of the time compared to D2622 • The best precision for ULSD 67% of the time compared to D5453
It is important to note that while the D7039 method had the best reproducibility in the PTP data, it is possible to utilize an instrument that complies with D2622 methods while obtaining the level of performance of D7039 technology. Those looking to meet D2622 compliance with D7039 precision can use XOS’ Sindie 2622 analyzer which uses the same monochromatic excitation of D7039 analyzers while still meeting the D2622 methodology.
In both Tables 1 and 2, test method D7039 contains most of the lower R values (marked as green) which indicates better PTP precision.
When measuring for critical elements such as sulfur, a highly precise testing method is vital. Low precision methods can lead to products being off spec which can costs refineries millions of dollars in fines, or product downgrading. Reducing variability in sulfur analysis is critical to reducing sulfur giveaway, and from the data shown, MWDXRF methods offer the highest level of precision and reliability.
CONCLUSION
For any refinery, a simple, streamlined elemental analysis process with high precision and reliability is critical to maximizing efficiency in every step of the refinement process. Whether monitoring ULSD or considering the refinery process strategy, refiners should take care when selecting the methodology for elemental analysis. With better precision as identified in the ASTM PTP data above, MWDXRF analyzers utilizing ASTM D7039 methodology offer users the most reliability when evaluating sulfur in automotive fuel.
Table 1: RFG PTP Sulfur Reproducibility
(5 – 15 ppm samples sorted by decreasing sample mean) ASTM RFG Proficiency Test
Program Sulfur Reproducibility Reproducibility (ppm)
Date
Sample Mean
Apr-15 15.49 Jun-15 14.29 Sep-16 13.51 Oct-15 Feb-16
11.83 11.82
Jan-17 11.13 Dec-16 11.00 Sep-15
8.42
Sep-17 6.95 Oct-16
6.90 May-17 5.92
ASTM D5453
4.20 4.17 3.60 2.71 2.63 3.09 2.99 2.02 1.90 1.86 1.79
ASTM D2622
4.40 3.49 3.49 2.94 3.07 2.36 3.07 2.41 2.30 2.94 2.04
Table 2: ULSD PTP Sulfur Reproducibility (5 – 15 ppm samples sorted by decreasing sample mean)
ASTM ULSD Proficiency Test
Program Sulfur Reproducibility Reproducibility (ppm)
Date Jun-17
Sample Mean
9.16
Nov-17 9.15 Feb-17 Oct-17 Oct-16 Mar-17 Apr-16 Dec-16 Apr-15 Aug-15 Aug-16 Dec-15 Feb-15 Jul-16 Jun-15 Dec-15 Jun-16 Feb-16
9.14 8.33 8.31 8.31 8.29 8.28 8.23 8.17 8.15 8.05 6.49 6.42 6.41 6.40 6.39 6.36
ASTM D5453
1.47 2.00 1.83 1.39 1.69 1.58 1.25 1.33 1.36 1.50 1.28 1.53 1.28 1.03 1.33 1.28 1.19 1.17
ASTM D2622
1.62 1.84 1.81 1.62 1.56 1.81 1.59 1.73 1.92 2.03 1.62 1.98 1.78 1.62 1.76 1.53 1.42 1.34
ASTM D7039
1.64 1.31 1.34 1.23 1.48 1.11 1.50 1.39 1.25 1.23 1.56 1.53 1.25 1.03 1.23 1.23 1.23 1.42
ASTM method D7039 outperforms D2622 89% of the time, and is equal to or better than D5453 67% of the time. KEY
Green = Best Reproducibility Yellow = Second Best Reproducibility Red = Poorest Reproducibility
AUGUST / SEPTEMBER •
WWW.PETRO-ONLINE.COM
ASTM D7039
2.38 3.13 2.55 1.58 2.22 1.89 1.88 2.13 1.61 1.58 1.71
ASTM method D7039 outperforms method D5453 91% of the time, and outperforms method D2622 100% of the time.
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