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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.
In one process, the warm wet pressurised gas from the inlet separator is pre-cooled in the gas/gas exchanger and then throttled in a Joule-Thomson (JT) valve to some lower pressure. The drop in pressure produces a cooling effect and both hydrocarbon liquids and water condense out of the gas. The two phase stream passes to a separator where the liquids are removed. The cold dry gas from the separator is returned to the exchanger to chill the incoming warm, wet gas.
Refrigeration is sometimes introduced to reduce the pressure drop used by the JT in chilling the gas and thereby retains more available pressure for downstream utilisation. Hydrate formation may also be suppressed by glycol injection upstream of the heat exchanger.
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.
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