Heavy hydrocarbons, emitted during preparation and/or processing of gas are not the final product.

Depending on using technology, they are like unstable condensate or wide spread of light hydrocarbons (WSLH) and are mixture of ethane, propane, butanes and heavier components. Fractional separation of these components and getting a final product of gas processing realized by rectification units. There is a sequence of rectification towers.

The sequence of rectification towers, quantity and parameters depends on quantity of final products. In simply case, rectification unit is made as one column – de-ethaniser, and derived product is mixture of propane and heavier components (WSLH).  The most high-demanded product of gas processing is propane-butane, that’s why the most popular configuration is chain deethanizer (WSLH product) - debutanizer (propane-butane and gas gasoline products). In case of processing significant volume of hydrocarbons in chain can appears depropanizer (propane product), deisobutanizer (n-butane and i-butane products), rectification towers of gas gasoline to obtain pentane, hexane and other fractions. 

Condensate stabilizer is special case of fractionation units. Scheme below is typical for facilities receiving three liquid products: propane, butanes and gas gasoline.

Pic. 1 LPG fractions extracrion 3-D model

Рiс. 2 LPG fractions extracrion DWG


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There is a demand for effective ways to treat both associated petroleum gas, common at oil production sites as well as gas condensate produced alongside natural gas at gas condensate fields. This demand is boosted by several reasons: growth in oil and gas production, tightening of the ecological norms and emission standards, gradual decline in dry Cenoman gas deposits and a consequent shift to development of new gas condensate fields.


Let’s analyze potential gas-processing options for a small oil company. It is extracting up to 120 mln scm of associated petroleum gas per year. Currently the gas is flared.

A gas pipeline of intermediate pressure (3.5 Mpa) passes 10 km away from the oil treatment unit, where oil and gas are separated. Technical specs for adding the gas to the pipeline are as follows: -10°С dew point for water, -5°С dew point for hydrocarbons. Company’s oilfield can be reached by wheeled transport by road.

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