Given the large volumes of LNG under transport, ROI on real-time measurement systems such as the ClearView db can be measured in days. LNG is natural gas cooled to a liquid state. Natural Gas is composed primarily of methane, but may also contain propane, ethane, and other heavier hydrocarbons as well as small residual quantities of N2, O2, CO2, H2O, and some sulfur-containing compounds. Prior to liquefaction, these residual materials are removed with only clean hydrocarbons remaining. The composition of natural gas can vary slightly from different producing locations. Typically LNG is a colorless material, but during distillation, the carryover of larger hydrocarbons (C6+) can affect the color of the LNG (typical specification for C6+ in LNG is 0 to 0.05%).

Measuring the Saybolt or ASTM color online is a key parameter in many light hydrocarbon mixes for quality control to detect this carryover. Monitoring the color allows the refiner to verify that the product is within specification. Any “out of spec” product can be reprocessed before being sold. The flowchart in Figure 1 shows a typical natural gas to LNG pocess with target measuring points for online analysis.