Propylene gas recovery process for batch bulk process polypropylene plant

Abstract

The invention discloses a pressure swing adsorption process comprising a concentration step and a concentrated waste gas pre-adsorption step at least in a process flow. The method comprises the following steps: concentrating an adsorption bed after the adsorption step and pressure equalizing drop step, exhausting non-adsorbent components in the adsorption bed, discharging concentrated waste gasescontaining a certain amount of adsorbent components discharged in the concentration process into the adsorption bed in the pre-adsorption step after the recovery step, and recovering the adsorbent components in the concentrated waste gases inside the pressure swing adsorption unit. Therefore, the aims of clearly separating the adsorbent components and the non-adsorbent components and obtaining high-purity adsorbent components and non-adsorbent components at a high recovery rate can be achieved.

Description

technical field [0001] The invention relates to a propylene gas recovery process for recovering propylene monomer carried in polypropylene powder in a batch bulk polypropylene device. Background technique [0002] The batch bulk polypropylene process is a polypropylene production process independently developed and widely used in China. In the production process of batch bulk polypropylene plant, under the action of catalyst and activator, liquid propylene undergoes polymerization reaction in the polymerization tank under the reaction pressure of 3.6MPa (absolute) and reaction temperature of 75°C to produce solid polypropylene Powder. After the polymerization reaction, the remaining propylene in the polymerization tank needs to be recovered to obtain solid polypropylene powder without propylene. Under normal circumstances, the high-pressure recovery of propylene is carried out first, which is to rely on the pressure of the polymerizer itself to condense and recover the pro...

AI Technical Summary

Problems solved by technology

One is the waste of propylene resources. In the process of venting and replacing, 0.5~1% of the propylene in the exhaust gas of the flash tank is discharged into the atmosphere along with the low-concentration propylene gas in the whole polypropylene process, and the membrane separation is discharged into the flare system. The tail gas also contains about 0.5% propylene, and the two items together account for about 2% of the propylene loss in the entire polypropylene process; the second is the waste of nitrogen. Every time the nitrogen is pressurized and discharged from the flash tank, the consumption value is roughly The amount of nitrogen equivalent to the product of the volume of the flash tank and the pressure difference before and after discharge, and part of the nitrogen enters the membrane separation tail gas and is discharged into the flare system, and the other part is discharged into the atmosphere with low-concentration propylene gas. The main factor for the relatively high nitrogen consumption in the process; the third is that a large amount of nitrogen enters the gas cabinet from the flash tank and returns to the gas cabinet with the permeate gas circulation of the membrane separation device, which increases the load of the entire propylene gas recovery system. If you want to further recover the flash tank The discharged propylene and the propylene discharged from membrane separation are often limited by the capacity of gas cabinets and compressors; fourth, the low-concentration propylene gas discharged from the flash tank greatly exceeds the relevant national environmental protection standards, which are not tolerated by environmental protection standards and are harmful to the atmosphere. Causes pollution and threatens safe production; in addition, the tail gas discharged from the membrane separation device contains a large amount of nitrogen, which will significantly reduce the calorific value of the fuel gas after being further recovered in the flare system, thereby affecting the efficiency of the process furnace of the factory

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