Polypropylene tail gas recovery device and recovery method

Abstract

The invention discloses a polypropylene tail gas recovery device. The polypropylene tail gas recovery device comprises a compression unit, a drying unit, a membrane separation unit and a cryogenic separation unit, wherein the compression unit, the drying unit, the membrane separation unit and the cryogenic separation unit are connected in sequence. The compression unit comprises at least one compressor, a heat exchanger and a gas and liquid separator, wherein the compressors, the heat exchanger and the gas and liquid separator are connected in sequence. The drying unit comprises at least two adsorption towers which are connected in sequence, and drying agents are placed in the adsorption towers. The membrane separation unit comprises a membrane separator. The cryogenic separation unit comprises at least one high-efficiency multi-channel heat exchanger, at least one low-temperature gas and liquid separator, at least one gas expansion device and at least one liquid expansion device. According to a polypropylene tail gas recovery method adopting expansion refrigeration, propylene in polypropylene tail gas is liquefied to be recovered, and meanwhile nitrogen is purified to meet the requirement for nitrogen recycling; in combination with a membrane separation technology, hydrogen in the polypropylene tail gas is removed; the recovery rate of the propylene in the polypropylene tail gas reaches above 98%.

Description

technical field [0001] The invention relates to the field of polyolefins, in particular to a recovery device and recovery method for propylene and nitrogen in tail gas discharged during the production process of polypropylene. Background technique [0002] In the production process of polypropylene, during the refining of propylene monomer, polymerization reaction and degassing process of polypropylene resin, tail gas containing a large amount of propylene monomer will be discharged. For example, the small stream of light components coming out of the top of the degassing tower during the propylene refining process, and the reaction purge gas used to control the content of inert gases during the polymerization reaction, the mixed gas of nitrogen + steam is sent from the bottom of the degassing chamber to Removal of hydrocarbons and deactivation of residual catalysts resulting in debinning tail gas, etc. These gases are collectively referred to as polypropylene tail gas, and ...

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Problems solved by technology

However, this method needs to use a vacuum pump to analyze the adsorption tower, and at least two compressors are required to pressurize the recovered hydrocarbon gas and nitrogen respectively. There are many moving equipment and complicated operation. The vacuum analysis process will easily cause air to infiltrate into the recovery system, which is safe. Hidden danger, when the exhaust gas contains a certain concentration of hydrogen, the adsorption process cannot achieve the separation of nitrogen and hydrogen, resulting in nitrogen that cannot be recycled and can only be discharged to the torch, resulting in waste of resources and environmental pollution. At the same time, the equipment occupies a large area

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