Petrochemical Industry | Transport of liquefied petroleum gas | Identification of different liquefied gases on delivery

Liquefied petroleum gas (LPG) refers to liquified gas, consisting primarily of the hydrocarbons propane and butane. Similar to methane-based liquefied natural gas (LNG), LPG is being accorded an increasingly important role in energy supply in Germany and worldwide as a bridging technology.

LPG is obtained during the extraction of natural gas and crude oil, but also while processing crude oil in refineries. It becomes liquid through compression and thereby reduces its volume to a fraction of its original gas volume. The term LPG refers to both a mixture of different hydrocarbons but also the single gases. The specific application described here involves the analysis of the pure hydrocarbons propane and butane.

Versatile areas of application and good environmental performance

Because of their low-pollutant and CO2-reduced combustion, which produces hardly any soot or particulate matter, liquefied gases are often regarded as promising energy sources for the future. The gases are used in households for heating, cooking, and as fuel, but also in the petrochemical industry and in agriculture.

To rule out the possibility of mix-ups when loading the two gases butane and propane from the gas tankers into the liquefied gas tank farms at the port terminals, it is necessary to re-identify the gases in the pipelines.

Liquified gas is under high pressure when transported and pumped into the pipelines. The gas is highly flammable. The measurement technology employed must therefore comply with the regulations relating to use in a potentially explosive environment.

A precise qualitative analysis of the liquid gas in the lines is possible using spectroscopic inline measurement technology. Butane and propane are spectroscopically detectable. Measurement in the IR range or with Raman technology would show particularly well differentiable signals due to the high sensitivity and excellent selectivity. However, these methods have disadvantages in the process environment, especially regarding the potentially explosive environment. Currently available IR or Raman spectrometers can fail to meet the ATEX requirements needed for measurements under these conditions.

The two gases butane and propane can also be spectroscopically differentiated in the NIR range. Measurements in this wavelength range have the advantage that robust measurement technology with fiber optics can be used. The electronics can thus be housed at a safe distance from the potentially explosive area.

For precise spectroscopic transmission measurements of gases and liquids under demanding process conditions, Hellma has two products in its portfolio that, owing to their robust design, can be used at high pressures and temperatures.

Due to the use of robust sapphire windows and welded metal seals, they provide an extremely robust and durable seal. They thus provide a high level of fail-safety, reliable measurement results and are also maintenance-free.

With the robust stainless steel Excalibur HD FCP measurement cell, the process flow can be measured via a bypass.

This optical flange measurement cell Excalibur HD Flange from Hellma consists of two optics which, combined with a central part, result in a flow cell. This compact measurement cell can be safely integrated into an existing system with little effort. For larger media flows larger diameter flanges are possible.

Using spectroscopic inline measurement technology, the composition as well as quality of liquids and gases can be determined directly in the process stream.

The robust measurement cells offer a reliable, fail-safe way to obtain precise measurement results in real time and thus contribute to optimizing and improving the safety of the process.