Method for recovering polyolefin tail gas hydrocarbons through full-temperature-range absorption extraction

Abstract

The invention discloses a method for recovering polyolefin tail gas hydrocarbons through full-temperature-range absorption extraction. The method comprises a hydrocarbon adsorption and concentration process, a hydrocarbon extraction and desorption process, a hydrocarbon separation and recovery process and a PSA nitrogen separation and purification process. Polyolefin tail gas is subjected to the hydrocarbon adsorption and concentration process first, most of C<2+> hydrocarbon components are adsorbed in an adsorption tower, nitrogen-enriched gas flows out of the tower top and enters the PSA N2separation and purification process so as to obtain N2 by-products with the purity of 99%, and desorbed gas is pressurized to return to the hydrocarbon adsorption and concentration process to furtherrecover the N2 and C<2+> hydrocarbon components. After the adsorption step is completed, the hydrocarbon extraction and desorption process is performed, the active ingredients, namely C<2+> hydrocarbon components, are dissolved out, the extracted and desorbed gas enters the hydrocarbon separation and recovery process to be subjected to pressure reduction or condensation cooling, non-condensable gas N2 escapes out to be mixed with the nitrogen-enriched gas and then enters the PSA N2 separation and purification process. Then, the extraction agent escapes and is recycled for cyclic utilization. According to the method disclosed by the invention, energy consumption investment is reduced, the process is short, the efficiency is high, and the service life of the adsorbent is long.

Description

technical field [0001] The invention belongs to the technical field of separating and recovering valuable substances in petrochemical tail gas, and more specifically relates to a method for recovering hydrocarbons in polyolefin tail gas by adsorption and extraction throughout the temperature range. Background technique [0002] During the production process of polyethylene and polypropylene units, a certain amount of hydrocarbon-containing tail gas will be produced, the hydrocarbon content is about 20-40%, and the rest is inert gas nitrogen (N2) and a small amount of hydrogen (H2) as protective gas. Exhaust gas directly discharged into the atmosphere will have a negative impact on the environment, and most petrochemical companies discharge the tail gas to the flare for burning. These tail gases contain ethylene, propylene, ethane and other high-value resources that can be reused. With the advancement of technology and the renewal of concepts, the tail gas of resource utiliza...

AI Technical Summary

Problems solved by technology

The obvious disadvantage of this method is that the purity and yield of the recovered olefin components are not high

This is because olefin components are easily adsorbed, but desorption is very difficult, and the contradiction between adsorption and desorption is very prominent, which has become a technical bottleneck of the PSA method.

[0007] Sichuan Tiancai Technology Co., Ltd., the inventor, recently invented a method for the separation and extraction of olefins in polyolefin tail gas by full temperature range pressure swing adsorption (FTrPSA), which is aimed at the single compression condensation method, cold oil absorption method, The traditional pressure swing adsorption (PSA) method and membrane separation method cannot solve the purpose of fractional recovery of hydrocarbons with carbon two and above (C2+), whether it is using condensation method or cold oil absorption method, or membrane separation method Either the PSA method or the PSA method, the front-end must be pressurized and condensed to recover the carbon four and above heavy components (C4+) in the polyolefin tail gas. The integration and coupling of various methods can successfully recover ethylene propylene

Although, to a certain extent, the FTrPSA method solves the technical bottleneck or low efficiency of polyolefin tail gas, which is easy to adsorb and difficult to desorb in the PSA cycle operation of ethylene and propylene components at a certain temperature, and the problem of heavy components such as C4 / C5 in a large amount It is very easy to achieve equilibrium and difficult to completely separate when directly pressurized, cooled and condensed in N2. However, the FTrPSA method still needs to be coupled with other separation methods such as cold oil absorption to solve the contradiction between adsorption and desorption regeneration. If it is too long, the equipment will increase and the investment will be large

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