Method for recovering ethane in high-pressure natural gases

Abstract

The invention discloses a method for recovering ethane in high-pressure natural gases, relating to the technical field of natural gas processing technology. The method is characterized by combining high-pressure and low-temperature absorption, partial low-temperature gas supercooling, an externally transported gas reflux process and refrigeration with an expansion machine and dividing both the supercooled gas in a low-temperature separator and externally transported gas reflux into two parts, wherein one part of the supercooled gas and the externally transported gas reflux enter a high-pressure absorption tower and the other part of the supercooled gas and the externally transported gas reflux enter a demethanizer to improve the ethane recovery rate which can be adjusted according to the target value of the recovery rate. The method has the beneficial effects that the operating pressures of the high-pressure absorption tower and the demethanizer can be independently arranged, thus reducing the compression power of an externally transported gas booster set and the heat load of a reboiler of the demethanizer; the method is suitable for devices with feed gas pressures more than 7.0MPa for recovering ethane in the natural gases and has the characteristics of high recovery rate, low system energy consumption, and the like.

Description

technical field [0001] The invention relates to the technical field of natural gas processing technology, in particular to an ethane recovery method for high-pressure natural gas. Background technique [0002] In recent years, with the development of the natural gas industry, the technology of using expander refrigeration to recover natural gas condensate has developed rapidly. The expander refrigeration process uses the difference in raw material pressure to obtain cooling capacity. The larger the expansion ratio, the lower the outlet pressure of the expander. The more cooling capacity, the higher the condensate recovery rate. The existing typical ethane recovery flow chart is as follows: figure 2 As shown, the characteristic of the process is that the dehydrated natural gas passes through the cold box E21 for heat exchange and cooling, and then enters the low-temperature separator V21 for separation. The gas phase of the low-temperature separator is divided into two strea...

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Problems solved by technology

[0005] In order to overcome the above typical ethane recovery process ( figure 2 ) to reduce the system energy consumption of the high-pressure natural gas ethane recovery device, the present invention develops a method for recovering ethane of high-pressure natural gas for raw material gas whose intake pressure is higher than 7.0MPa, and recovers ethane and ethane in natural gas condensate above alkanes

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