Method and system for recycling ethylene in tail gas through barren liquor effect in demethanization process

Abstract

The invention relates to a method and system for recycling ethylene in tail gas through barren liquor effect in the demethanization process. The method comprises the following steps of: separating nine tenths of hydrogen and a part of methane from feedstock by matching an absorption tower with all levels of separating equipment of chilling series at the front end, and then leading another part of methane and nine tenths of C<2+> to enter a fractionation tower for fractionation. In the processes, ethylene possibly lost in the tail gas can be more thoroughly recovered by using the characteristic that the C<2+> is superiorly dissolved by an absorbent of the absorption tower. The absorbent of the absorption tower is barren liquor coming from the interior of the system, namely a part of reflux of the fractionation tower, thus showing the barren liquor effect. compared with the prior art that levels of the chilling series at the front end are changed into the fractionation subsystems with multiple theoretical plates, the method and the system are more excellent in effect on controlling the loss of ethylene in the tail gas, lower in energy consumption, and lower in investment.

Description

technical field [0001] The invention relates to a light hydrocarbon separation method and a separation system, in particular to a method and a system for recovering ethylene in tail gas in a demethanization process by utilizing the lean liquid effect. Background technique [0002] Separation of light hydrocarbons refers to hydrogen and C1 to C5 hydrocarbon mixtures (abbreviation: H 2 -C 1 -C 5 ) for separation. [0003] The mixture of hydrogen and methane is abbreviated as C 1 - , carbon one and heavier fractions are abbreviated as C 1 + , the carbon distillate is abbreviated as C 2 , the separation of hydrogen and methane is abbreviated as H 2 / CH 4 Separation, C 1 - with C 2 + The isolated abbreviation for C 1 - / C 2 + Separation, C 1 - with C 2 The isolated abbreviation for C 1 - / C 2 separate. [0004] C in light hydrocarbon separation process 1 - / C 2 + Separation or C 1 - / C 2 Separation is also known as "demethanization". Demethanizatio...

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Problems solved by technology

[0009] The first way is limited to the engineering market because of the high investment; the second way is the same as the first way, and it also saves energy because of the increase of the number of theoretical plates of the whole front cooling. Although the investment is higher than the first way Low but still high, but the energy saving effect is not significant

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