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Understanding Cricondentherm & Hydrocarbon Dew Point & Their Significance in Hydrocarbon Prossesing

Updated: Mar 4


 

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In today’s world, where precision and innovation drive the modern energy landscape, an interesting concept exists that has a significant impact on the way we extract value from resources such as natural gas processing: Cricondentherm – a seemingly complex term that can be used to significantly optimize hydrocarbon processing.

In this article, we will discuss the significance of this concept in hydrocarbon processing and its relationship to hydrocarbon dew point.

What is Cricondentherm?

The cricondentherm of a natural gas mixture is simply its highest possible dew point at any pressure. Cricondentherm is expressed in units of temperature. An associated term is “Cricondentherm Pressure”. This is the pressure at which Cricondentherm occurs. This typically occurs between 25-35 bar (~360-520 psi) of pressure for pipeline-quality natural gas. The significance of cricondentherm lies in the fact that if the temperature of the gas is kept above this value, there is no possibility of condensing the hydrocarbon gas into liquids, even if the pressure of the gas changes.

A diagram showing hydrocarbon cricondentherm point.
Gas Mixture Cricondentherm

Role in Hydrocarbon Transportation

Avoiding the creation of hydrocarbon liquids is a key concern in operation of natural gas pipelines. It is critical to understand that if a gas is kept at a temperature above its cricondentherm, then it will not condense into any liquids, at any pressure. However, one cannot control the temperatures of pipelines or pipeline components. Therefore, an estimation must be made of the lowest temperature to which the pipeline may be exposed to.

For example, let's assume that a particular pipeline will be exposed to temperatures as low as -16 °C (~0 °F). Then it is essential to make sure that the gas has a cricondentherm below -16 °C. Therefore, the gas has to be refined to an extent where the cricondentherm is reduced to -16 °C or below. Then regardless of changes in pressure during pressure increases (compression cycles) or pressure reduction (during transport), the gas will stay purely in vapor form, avoiding any condensation.


The Relationship between Hydrocarbon Dew Point and Cricondentherm

Cricondentherm is simply the highest possible dew point of a natural gas mixture at any pressure. In natural gas, if the pressure is reduced from the cricondentherm pressure, the hydrocarbon dew point is reduced. If the pressure increases (the retrograde region) then the hydrocarbon dew point is reduced as well.

How Do You Measure the Cricondentherm

Measuring hydrocarbon dew point in gas transportation through pipelines and production facilities is essential to ensure safe and efficient operations. To measure the cricondentherm, the hydrocarbon dew point should be measured at the cricondentherm pressure. For pipeline-quality natural gas, this pressure is about 25-25 bars (~350-520 psi). Since the phase diagram is almost vertical close to the cricondentherm, small deviations in pressure will not have a significant effect on the hydrocarbon dew point.

Therefore, to measure the Cricondentherm in pipeline-quality natural gas, one simply has to measure the hydrocarbon dew point at a pressure between 25-35 bar. There are agreements in some countries to simply measure at 27 bars.

How to Measure the Hydrocarbon Dew Point

Measurement of hydrocarbon dew point is discussed in detail in other blog entries. Remember, using a GC and some equation-of-state software is not a measurement, but a guesstimation. It is typically very inaccurate and can have errors in excess of 50 °C.

The only way to measure hydrocarbon dew point is through the use of a chilled-mirror based analyzer, using extractive sampling. Advances in chilled-mirror technology, such as CEIRS™ (Chilled-mirror Evanescent IR Spectroscopy) offer a simple, accurate, and unambiguous measurement of this important property.

Engineer using dew point analyzer.
Engineers use dew point analyzers in gas transportation facilities to measure dew point.

FAQ

What is the Cricondentherm?

Cricondentherm is the highest possible hydrocarbon dew point at any pressure.

What are the practical applications of Cricondentherm in the hydrocarbon industry?

Gas transportation companies can use the cricondentherm value to avoid condensation in networks that have different operational pressures along their pipeline network.




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