Technology and device for purifying and recycling polypropylene tail gas through pressure swing adsorption

Abstract

The invention relates to the technical field of tail gas treatment, in particular to a technology and a device for purifying and recycling polypropylene tail gas through pressure swing adsorption. Thetechnology comprises the following steps: recycling a material in a polypropylene polymerization kettle under an isobaric medium pressure, then enabling the material to enter a flash evaporation kettle, recycling a part of gas in the flash evaporation kettle under an isobaric low pressure, enabling the gas to enter a gas cabinet, pressurizing the gas in the gas cabinet by using a propylene condensing compressor, then exchanging heat by using a heat exchanger, enabling the gas to enter a liquefaction tank, separating non-condensable gas in the liquefaction tank by using a gas-liquid separator,decompressing and then enabling the non-condensable gas to enter a buffer tank; performing pressure swing adsorption treatment to the gas in the buffer tank, enabling recycled propylene to enter thegas cabinet, cooling impurity gas by using an expander, enabling the impurity gas as a cold source medium to enter the heat exchanger for heat exchange, and then recycling or emptying. By the technology, the yield of propylene is higher than or equal to 99% and the purity of the recycled propylene gas is higher than or equal to 95%.

Description

technical field [0001] The invention relates to the technical field of tail gas treatment, in particular to a process and a device for purifying and recovering polypropylene tail gas by pressure swing adsorption. Background technique [0002] In batch liquid phase bulk polypropylene production, there are two propylene-containing exhaust gases. One is that the unreacted propylene is recovered at medium pressure after the reaction of the polymerization tank is completed, and the recovered gas of the low pressure part is put into the gas cabinet; the other is the replacement gas of the flash tank. [0003] In batch liquid-phase bulk polypropylene production, the polypropylene powder obtained after polymerization contains unreacted propylene. In order to ensure granulation, discharge safety and product quality, degassing operation is required. The usual way is to carry out medium-pressure and isobaric recovery, then pass the synthesis kettle material into the flash tank, first ...

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Problems solved by technology

Patent CN201620322214.5 discloses a device for recovering propylene by pressure swing adsorption method. Multiple adsorption towers are connected in parallel on the feed pipeline, the feed pipeline is connected to the raw material buffer tank, and the top nozzles of the adsorption towers are respectively connected in parallel On the non-condensable gas pipeline, the non-condensable gas pipeline transports the separated non-condensable gas to the flare pipe network for combustion or discharge directly, and the top nozzles of multiple adsorption towers are also connected in parallel to the pressure equalization pipeline, and the pressure equalization pipeline will be more Each adsorption tower carries out pressure equalization; the tower bottom nozzles of multiple adsorption towers are also connected in parallel on the reverse discharge pipeline respectively, and the end of the reverse discharge pipeline is connected with an input port of the propylene buffer tank. propylene recovery, the recovered propylene is put into the polypropylene device as the production raw material; but the device still needs to pass through after the reverse discharge process is completed. In the process of vacuuming, the power consumption is large, and not only the adsorbent but also the catalyst need to be filled in the adsorption tower, the cost is high

[0006] Patent CN200810166621.1 discloses a pressure swing adsorption process for treating non-condensable gas in a bulk polypropylene device, using a secondary adsorption pressure swing adsorption separation process to obtain purified nitrogen with low propylene concentration and desorbed gas with high propylene concentration ; but it adopts vacuum desorption during gas desorption, and the power consumption is relatively large, and the non-condensable gas to be processed is in the bulk method polypropylene device, which is discharged into the gas holder by self-pressure from the flash tank, and pumped by the flash tank The mixed gas discharged into the gas cabinet during the vacuum and nitrogen replacement process is mixed in the gas cabinet, and the gas-liquid mixture obtained after compression and condensation, and the non-condensable gas obtained after the separation of liquid propylene, the nitrogen content in the gas compressed by the condensing compressor is high, Compressor idle work increases

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