System and method for preparing polymer-grade propylene through absorption and separation of catalytic cracking product gas

Abstract

The invention provides a system and a method for preparing polymer-grade propylene through absorption and separation of catalytic cracking product gas. A debutanizing tower, an absorption tower, and a desorption tower are sequentially arranged between a pre depropanizing tower and a post depropanizing tower. A propylene tower is arranged behind the post depropanizing tower. A gas enrichment balancing tank is arranged between the absorption tower and the desorption tower. Through the pre depropanizing tower, catalytic cracking product gas is separated into C3 and lighter components and C4 and heavier components. The C4 and heavier components are processed by using the debutanizing tower, such that C4 component or C5 and heavier components are obtained. The obtained component is adopted as an absorption agent, and is used for absorbing the C3 and lighter components of the pre depropanizing tower top gas in the absorption tower. With the desorption tower, C3 component and C2 and lighter components are separated through desorption. The tower kettle liquid of the desorption tower is delivered to the post depropanizing tower. Post depropanizing tower top gas is subjected to propane-propylene separation in the propylene tower, such that the polymer-grade propylene product is obtained at the top of the propylene tower. With the system and method provided by the invention, an oil absorption method is adopted; the application of low-temperature cold energy is avoided; energy consumption is reduced; and equipment investment is saved.

Description

Technical field [0001] The invention relates to a method for oil absorption and separation of catalytic cracking reaction product gas. More specifically, it relates to a system and method for preparing polymerization-grade propylene from catalytic cracking product gas by using an oil absorption method to replace the traditional cryogenic distillation separation method. Background technique [0002] The catalytic cracking reaction product gas, which mainly contains methane, carbon two, carbon three, carbon four, carbon five and heavier components, is generally separated by a traditional cryogenic distillation separation method that is pressurized and condensed by a low-temperature refrigerant. Usually the process flow of this method can be seen figure 1 , Firstly, the catalytic cracking product gas is compressed to 1.0MPa-1.6MPa by the first compressor P1, and then the gas phase and the condensate between the compressor sections are sent to the depropanizer P2 to separate the carb...

AI Technical Summary

Problems solved by technology

This conventional separation method has high energy consumption and high equipment investment. The reason is that the carbon three and lighter components need to be compressed to enter the ethylene tower for separation, which has high energy consumption and requires an additional compressor or A special compression section is added to the product gas compressor, which increases equipment investment; at the same time, the top of the ethylene tower needs to be condensed with -15°C refrigerant, which consumes high energy. If a refrigeration unit is installed separately, the device investment will increase

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