Method and device for recovering light hydrocarbon through refrigeration using compound refrigerant and secondary dealkylation

Abstract

The invention discloses a method and a device for recovering light hydrocarbons through refrigeration using a compound refrigerant and secondary dealkylation, wherein the advantages of the traditional natural gas-dealkylation direct heat exchange process are combined with the method of the invention; the precooling of the raw material natural gas, the condensation of a deethanizer top gas, and the cold quantity recovery of the product natural gas and the liquid-phase material of a low-temperature separator are all realized in a main heat exchanger; the cold quantity source of the dealkylation process is provided by a compound refrigerant refrigerating system. The composition, the component contents, the flow rate and the evaporation pressure of the compound refrigerant are adjusted and matched cold quantity and different refrigeration temperatures are provided for the light hydrocarbon condensation process, so that the flexibility of the method in operation and good adaptability of the method to the amount, the pressure and the composition change of the raw material gas; and the method has the characteristics of low energy consumption, high C3 yield and good adaptability to the change of working conditions.

Description

technical field [0001] The invention relates to a condensation and separation process of hydrocarbon mixtures, in particular to a method and device for deep recovery of light hydrocarbons in natural gas by compound refrigerant refrigeration. Background technique [0002] Light hydrocarbon recovery refers to the process of recovering ethane, propane, butane, pentane and other hydrocarbon compounds from natural gas, also known as natural gas condensate recovery. According to whether ethane is recovered or not, natural gas light hydrocarbon recovery devices can be divided into two categories: one is to recover C 2 The component is the purpose; the other is to recover the C 3 and C 3 + component for purpose. Since ethane has a low boiling point and is difficult to transport in liquid form, recovery of ethane is usually only considered if there is an ethylene production facility nearby. [0003] At present, most of the light hydrocarbon recovery devices in domestic oil and ga...

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Problems solved by technology

[0011] 1) When the raw material gas pressure decreases or the raw material gas volume changes greatly, the expander deviates from the design working conditions, resulting in reduced expansion efficiency and unstable operation, and the expander cannot provide sufficient cooling capacity for the device, C 3 Yield drops, liquid hydrocarbon production decreases

[0012] 2) The document "Efficiency of Turboexpander Refrigeration Device and Application of Composite Refrigerant" (Sang Tian, ​​"Petroleum and Natural Gas Chemical Industry", Volume 13, Issue 5) shows that to recover C 3 + In the light hydrocarbon recovery unit for the purpose, the cooling efficiency of turboexpander refrigeration is lower than that of composite refrigerant refrigeration

[0014] 4) In the case that there is no surplus pressure energy available for the raw natural gas, after the raw gas is expanded and decompressed by the expander, it is necessary to increase the booster compressor, which increases the equipment investment

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