Crude oil contains water. Before transport, water is removed to reduce costs. Furthermore, the presence of water in crude can cause corrosion. Therefore, it is essential to determine the water content in crude oil.
Previously, ASTM D4928 described a direct coulometric Karl Fischer titration to determine water in crude oil. This quickly contaminated the titration cell, requiring regular cleaning and frequent reagent exchange. ASTM D4928 was then revised to include coulometric Karl Fischer titration in combination with the oven method. In this method, the sample is heated in an oven. The water evaporates and is carried into the titration cell by an inert carrier gas. The water content is determined in the titration cell.
The oven method avoids titration cell contamination and significantly reduces reagent consumption. It can be fully automated, minimizing handling errors and workloads, with outstanding reproducibility.
The method is demonstrated for three different crude oil types. The samples are homogenized before being filled into sample vials.
This analysis is carried out on an automated system consisting of an 874 Oven Sample Processor and an 851 Titrando equipped with a coulometric titration cell (Figure 1).
The analysis demonstrates acceptable results and well-defined titration curves. The results for the three different crude oil samples are shown in Table 1. An example titration curve is displayed in Figure 2.
Table 1. Results for the water content determination in crude oil according to ASTM D4928.
| Water content (n = 4) |
Mean in μg H2O/g sample | SD(rel) in % |
|---|---|---|
| Sample 1 | 853 | 2.09 |
| Sample 2 | 4865 | 0.44 |
| Sample 3 | 41111 | 0.43 |
The oven method is the perfect option to determine water content in crude oils precisely and reliably.
Using the 874 Oven Sample Processor allows fully automated determination, freeing up valuable time and thus increasing laboratory productivity. Furthermore, by fully automating the analysis, the reproducibility can be increased and sample analysis failures due to improper handling can be reduced.
Share via email
Download PDF