The dehydrocarbonation and dehydration process of natural gas is a core technology for removing liquid hydrocarbons and moisture from natural gas to meet pipeline transportation, processing or sales indicators. It mainly consists of two categories: dehydration process and dehydrocarbonation process, and is often used in combination.

I. Dehydration Process (Core: Reducing water dew point to prevent freezing/formation of hydrates)

The objective is to reduce the water content of natural gas to the specified value (typically ≤100 mg/m³) to prevent pipeline blockage or equipment corrosion.

1. Adsorption dehydration method

Principle: Utilize the porous structure of solid adsorbents (such as molecular sieves, silica gel, and alumina) to adsorb moisture.

Features: High dehydration depth (water dew point can be reduced to below -60℃), suitable for high-pressure and cryogenic working conditions, and is one of the mainstream processes at present.

Application: Dehydration of long-distance pipeline natural gas and LNG feedstock gas.

2. Absorption dehydration

Principle: Liquid absorbents (such as glyols, commonly triethylene glycol TEG) are used to come into countercurrent contact with natural gas, dissolving the moisture within.

Features: Simple equipment, low operating cost, medium dehydration depth (water dew point usually drops to -20 to -40℃), suitable for medium and low pressure natural gas processing.

Application: Associated gas in oil and gas fields, natural gas dehydration in gathering and transportation stations.

3. Low-temperature dehydration method

Principle: Natural gas is cooled to below the dew point of water through refrigeration (such as throttling expansion, refrigerant refrigeration), causing water to condense and precipitate.

Features: It is often combined with dehydrocarbon processes (such as low-temperature separation), does not require regeneration of adsorbents/absorbents, and is suitable for high-moisture natural gas.

Ii. Dehydrocarbon Process (Core: Reducing hydrocarbon dew Point and removing C3+ Heavy hydrocarbons)

The objective is to remove heavy hydrocarbons of C3 and above (such as propane and butane) from natural gas to prevent the formation of liquid hydrocarbons at low temperatures that could clog pipelines, while also recovering liquefied petroleum gas (LPG) or light oil.

Low-temperature separation method

Principle: Cool the natural gas to below the dew point of hydrocarbons (typically -10 to -40℃), causing heavy hydrocarbons to condense into liquid, and then separate them through a separator.

Features: It can simultaneously achieve dehydration and dehydrocarbonation, with a compact process. It is currently the most widely used process (such as expansion mechanism refrigeration and refrigerant refrigeration).

2. Dehydrocarbon by absorption method

Principle: Absorption oil (such as light diesel oil or naphtha) is brought into contact with natural gas to dissolve the heavy hydrocarbons in it. Then, the absorption oil and heavy hydrocarbons are recovered through distillation.

Features: It is suitable for natural gas with a high content of heavy hydrocarbons (such as associated gas from oil and gas fields), but the energy consumption for absorbing oil regeneration is relatively high.

3. Dehydrocarbon removal by adsorption method

Principle: Heavy hydrocarbons are selectively adsorbed by adsorbents such as activated carbon and molecular sieves. After adsorption saturation, regeneration is carried out through heating/depressurization.

Features: High dehydrocarbon removal accuracy (hydrocarbon dew point can be reduced to below -50℃), but with a relatively small processing capacity, suitable for small-scale or high-precision demand scenarios.

Iii. Typical Combined Processes (Mainstream in Practical Applications)

In industry, dehydration and dehydrocarbonation are often combined to ensure that natural gas simultaneously meets the requirements of water dew point and hydrocarbon dew point. A typical process is:

Raw natural gas → pretreatment (filtering impurities) → absorption dehydration (TEG)/adsorption dehydration (molecular sieve) → low-temperature separation dehydrocarbon (expander) → Qualified natural gas for external transportation

This process can efficiently remove moisture and heavy hydrocarbons, while recovering by-products such as LPG. It is highly economical and practical.