Copious cooling recycling system and recycling method of ethylene in tail gas

Abstract

The invention relates to a copious cooling recycling system of ethylene in tail gas. The copious cooling recycling system comprises a methane fractionating tower, a backflow separation device of the methane fractionating tower, at least two heat exchanging devices and an absorption tower; a top portion material outlet of the methane fractionating tower is communicated with the material inlet of the backflow separation device of the methane fractionating tower, a first liquid phase branch of the bottom portion liquid phase outlet of the backflow separation device of the methane fractionating tower is successively connected with a first heat exchanging device and a second heat exchanging device in a serial mode, the bottom end inlet of the absorption tower is communicated with the first heat exchanging device, the top end gas phase outlet of the absorption tower is communicated with the gas phase inlet of the second heat exchanging device, the top end liquid inlet of the absorption tower is communicated with the liquid phase outlet of the second heat exchanging device, the bottom end liquid phase outlet of the absorption tower is communicated with the bottom end inlet of the first heat exchanging device, and the bottom end liquid phase outlet of the first heat exchanging device is communicated with a first liquid inlet of the methane fractionating tower. The invention further relates to a copious cooling recycling method of ethylene in tail gas. The copious cooling recycling system and the recycling method of ethylene in tail gas improve recovery rate of ethylene, are more simple and reasonable in device-arranging, and can not increase energy consumption of the system.

Description

technical field [0001] The invention relates to the technical field of ethylene recovery, in particular to a cryogenic recovery system and recovery method of ethylene in tail gas. Background technique [0002] One of the main purposes of the cryogenic separation part of the ethylene production process is to feed the gas phase (mainly hydrogen, methane, ethylene) in a plate-fin heat exchanger under a certain low temperature range (generally the lowest can reach -170 ° C). After cooling and condensation, the liquid phase with heavier components (mainly methane and ethylene) is separated in the gas-liquid separation container, and then the gas phase is separated by condensation. After multiple condensation and separation, hydrogen, methane and ethylene are finally separated to obtain a hydrogen product. and methane hydrogen by-product (the main component is methane, but also contains a small amount of hydrogen), the methane hydrogen by-product basically provides fuel for the cr...

AI Technical Summary

Problems solved by technology

Since the top condenser is part of the plate-fin heat exchanger used for separation, the condenser is placed at the top of the tower or higher than the top of the tower. It is impossible to make it too large, and the plate-fin heat exchanger has a great influence on the strength design of the tower; the latter scheme needs to design a frame higher than the tower, which is not economical in comprehensive consideration

Since the design and manufacture of plate-fin heat exchangers are currently dominated by suppliers, there are more restrictions on projects with tight schedules

In addition, the cooling capacity required for the condensation of the gas phase at the top of the tower is taken from the cryogenic separation part, so the cooling capacity of the cold separation part is insufficient. pre-cooled system, which increases overall system energy consumption and size of associated equipment

Since the cooling capacity mainly comes from the cryogenic separation part, the result is that it is impossible to condense the gas phase at the top of the absorption tower at a lower temperature, otherwise the cooling capacity required for the subsequent separation cannot be compensated, or the circulation of the system needs to be increased To make up for the cooling capacity required by the system, resulting in greater waste of energy, which largely offsets the benefits obtained from recycling ethylene. Due to the increase in circulation volume, equipment investment will also increase

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