Sampling of liquid hydrocarbons, chemicals and
and CO2 in refineries, chemicals and petrochemicals

Chemicals and petrochemicals

SOCLEMA offers specific solutions forsampling liquid hydrocarbons, chemicals and CO2, with filtration and separation systems, traced tubing and sampling probes. 

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Liquid hydrocarbons, adapted sampling solutions by SOCLEMA

Liquid hydrocarbons are :

Crude oil including so-called "unconventional" oil such as shale oil, oil extracted from tar sands and "extra-heavy" oils,

Condensates or "natural gas well liquids", i.e. light fractions such as pentane and octane. These hydrocarbons are present in a gaseous state in deposits and condense at atmospheric pressure.
Natural gas liquidsThese are ethane, propane and butane. The last two, produced in natural gas plants and oil refineries, are known as liquefied petroleum gas (LPG).
Synthetic liquids produced from natural gas and coal
Biofuels (bioethanol and biodiesel), produced from non-fossil organic materials.
Liquefied natural gas (LNG) is not counted among liquid hydrocarbons, as this state is limited to the transport phase.

Hydrocarbons are organic compounds made up exclusively of carbon (C) and hydrogen (H) atoms. They are all different in origin and chemical composition.

They are of great commercial importance, as they are used as fuels, combustibles, lubricating oils and base products in petrochemical synthesis. It is therefore important to analyze them.
Sampling is necessary to determine their physical and chemical properties, such as water and sediment content, viscosity, density and vapor pressure. A distinction must be made between manual and automatic sampling.

Manual sampling of liquid hydrocarbons

Manual sampling is used when the mass to be sampled is homogeneous. ISO 3170: 2004 and ASTM D4057 provide guidelines for manual sampling of liquid and semi-liquid petroleum products, crude oil, intermediates, water and heavy components associated with petroleum products.

These texts standardize the conditions for taking samples of liquid or semi-liquid hydrocarbons from tanks, drums or pipelines, by manual means. The standards specify operating procedures designed to reduce or even eliminate losses of light fractions that may occur during sample handling. The purpose of these procedures is toobtain samples that can be used to determine hydrocarbon quality, water content and the presence of other impurities not normally present in the transferred liquid.

The standards provide a guide to the equipment to be used, container preparation and manual sampling procedures to ensure the safety of the personnel involved. There are many possible types of sampler, including cylinders, bottles and containers, which can be made of glass, plastic or metal.

Preferably, equipment should be selected which does not require the sample to be transferred from the initial container to an intermediate container. The equipment used should be designed and manufactured to ensure that it is fit for purpose. It must be sufficiently resistant and hermetically sealed to preserve the sample's initial characteristics. Materials of construction must be compatible with the product being sampled, and there must be no interaction between the two, otherwise the integrity of the sample could be affected.

Automatic sampling of liquid hydrocarbons

Manual sampling is appropriate when the liquids to be sampled are homogeneous, and their composition and quality do not vary significantly over time. Where this is not the case, automatic sampling is the recommended procedure: the continuous or repeated taking of small samples ensures that all changes are reflected in the collected sample. ISO 3171:1999 and ASTM D4177 provide guidelines for automatic sampling of liquid petroleum products.

Representative samples are essential for determining the physico-chemical properties used to establish volumes and prices in accordance with commercial and regulatory specifications. To ensure that the sample is as representative as possible, it is vital to ensure that the recommendations relating to sample homogeneity at the sampling point and sampling frequency are respected. Non-homogeneous hydrocarbons must be mixed at the sampling point; the volume must be consistent and taken from the stream in such a way that it is representative of the total volume. The sample must be kept in the collector without being altered. Samples must be mixed to ensure that the final sample supplied to the analyzer is representative.

Automatic sampling systems consist of a system to condition the flow upstream of the sampling point, a system to physically take the sample, a system to measure the flow rate, a system to control the volume taken, and a tank to collect and store the samples. Depending on the application, it may be necessary to isolate individual components or the entire system. The sampling system can be installed on the main line or on a fast loop. Both systems provide a representative sample.