Natural gas ethane recycling method with high carbon dioxide adaptability

Abstract

The invention discloses a natural gas ethane recycling method with high carbon dioxide adaptability and relates to the technical field of natural gas treatment processes. The method comprises the following steps: firstly, dividing a raw material gas into two parts, respectively cooling the two parts, feeding a part of the raw material gas into a low-temperature separator, performing separation, depressurizing and cooling the separated gas phase by an expansion end of an expansion unit, feeding the gas phase to the upper part of a demethylation tower, mixing a part of the gas phase with remained raw material gas, performing heat exchange cooling, further performing pressure adjustment overcooling, feeding the gas phase to the upper part of the demethylation tower, performing pressure adjustment on the remained part of a liquid phase, and feeding the liquid phase to the middle and lower part of the demethylation tower; and performing heat exchange heating on a gas phase discharged from the top of the demethylation tower, and outadding the gas phase. By adopting the method, a low-temperature gasification absorption refrigeration principle and a phase equilibrium principle are utilized, and the raw material gas and a part of the liquid phase of the low-temperature separator are mixed and refluxed at the top of the demethylation tower, so that the concentration of the gas phase carbon dioxide at the top of the demethylation tower can be improved, separation of carbon dioxide solid can be effectively controlled, and the adaptability to the content of the carbon dioxide in the rawmaterial gas can be improved to the maximum extent while the recycling rate of ethane is ensured.

Description

technical field [0001] The invention relates to the technical field of natural gas processing technology, in particular to a method for recovering natural gas ethane with high carbon dioxide adaptability. 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 process is that the natural gas enters the low-temperature separator V21 for separation after heat exchange and cooling in the cold box E21. The gas phase of the low-temperature separator is divided into two streams, and one gas stream is ex...

AI Technical Summary

Problems solved by technology

However, when the feed gas contains a small amount of carbon dioxide, along with the improvement of the ethane recovery rate (higher than 95%), the reflux ratio of the externally transported gas is constantly increasing. On the one hand, it may cause solids on several trays at the top of the demethanizer. The precipitation of carbon dioxide will cause the occurrence of carbon dioxide freezing blockage; on the other hand, it will also lead to a significant increase in the shaft power of the external gas recompression unit, and...

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