Coolers and dewpointing in gas processing

A typical production stream from the wellhead contains oil, condensate, gas and water. Initial separation produces a hot gas stream that is likely to be saturated with both hydrocarbon liquid and water. It is necessary to drop both the hydrocarbon and water dewpoints below the lowest possible export pipeline temperature otherwise two-phase flow may occur and hydrates may form.

Gas Dewpoint Control

Warm wet feed gas enters the gas -gas exchanger where it is cooled using cold dry gas from the low temperature separator. The warm feed gas stream's pressure is then reduced across a JT Valve or turbo expander before entering the LTS.

The cold dry gas leaves the LTS, flows back to the gas gas exchanger and on to the sales gas system. PCHEs allow for further cold recovery from the cold liquids stream in a multi stream exchanger.

PCHEs also allow for direct injection of glycol solutions into each passage for hydrate inhibition of wet gas. Where a refrigerant system is used in place of pressure drop as a source of cold this can often be incorporated in the multi stream PCHE. As PCHEs can achieve closer approach temperatures than Shell & Tube type exchangers more cold can be recovered from the cold gas (& liquid streams). This enhanced cold recovery means that less pressure drop is required (or refrigerant duty) offering further operational savings.

Heatric's Advantage

Many other types of dewpoint control process exist, but in all cases the diffusion-bonded heat exchanger has advantages.

High efficiency counter flow contact means that Heatric exchangers can perform the gas/gas duty in a single compact unit, reducing or eliminating the need for refrigeration and making considerable space and weight savings.

The multi-fluid capability of diffusion-bonded heat exchangers allows incorporation of the recovered liquids, refrigeration and glycol injection into the exchanger core, saving further space and weight.

High efficiency heat exchange reduces the amount of pressure let down required across the J-T valve. There is also no special limit in pressure drop across the Heatric exchanger, retaining more available pressure for downstream utilisation. As they can be specified for services over 600 bar (9000 psi), they will be capable of the full pressure range normally handled by shell and tube heat exchangers.