Ethylene cryogenic separation method for large-sized ethylene device

Abstract

The invention relates to an ethylene cryogenic separation method for a large-sized ethylene device. The method includes the steps that mixed gas is precooled, cooled by a series of coolers and separated by a component separation container so that a gas phase and multi-strand liquid phases can be obtained; the gas phase is separated by a series of plate-fin heat exchangers and a component separation container so that a gas phase and multi-strand liquid phases can be obtained, after the pressure of liquid phase methane is reduced, cooling capacity is recycled through the heat exchangers, the liquid phase methane is conveyed to a downstream system, one of the multi-strand liquid phases and the liquid phase methane after pressure reduction are mixed, the rest of the liquid phases enter a demethanizer, and coarse hydrogen products enter the downstream system; the two firstly-coagulated liquid phases in the multi-strand liquid phases respectively enter a pre-demethanizer, and the rest of the liquid phases respectively enter the demethanizer; the pre-demethanizer separates the liquid phases into gas and liquid, the gas is delivered to the demethanizer, and the liquid is delivered to the downstream system; the demethanizer separates the gas phase into methane and C2 which are delivered to the downstream system, and the methane is delivered to the downstream system. By means of the ethylene cryogenic separation method for the large-sized ethylene device, 30% of the size of a cold box is decreased, equipment and cost are reduced, energy saving and cost reduction are achieved, and operating stability is guaranteed.

Description

technical field [0001] The invention relates to a cryogenic separation method for ethylene, in particular to a cryogenic separation method for mixed gas containing light hydrocarbon components such as C2, C3, methane and hydrogen in large-scale ethylene plants. Background technique [0002] The raw material is a mixed gas containing ethylene and propylene components obtained through tube cracking furnace cracking, heavy oil catalytic cracking or coal-to-olefins process. After cooling and separating the liquid phase, the gas phase enters the compressor to boost the pressure, and then undergoes multiple separations to finally obtain ethylene. , propylene, hydrogen, methane and other products. The function of cryogenic separation in ethylene process is to separate methane and hydrogen from the feed mixture (mainly hydrogen, methane and carbon dioxide, etc.) Since the separation principles are all based on low temperature and flash separation, and the operating temperature can ...

AI Technical Summary

Problems solved by technology

[0004] In the 1980s and 1990s, most of the ethylene technologies introduced in my country used figure 1 As shown in the complex cold box process, the cold box designed according to this has many channels, many nozzles, complex stress at the nozzles, and large dimensions, making it difficult to manufacture

In recent years, with the gradual increase in the production scale of ethylene plants, especially the construction of million-ton ethylene plants, according to figure 1 The cold box process shown will inevitably lead to a large size of the cold box, which will bring great difficulties to manufacturing, transportation, installation, etc.

The higher the complexity of the syst

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