Process for cooling and separating gas phase mixture on top of polyester process column

Abstract

The invention provides a novel process for cooling and separating a gas phase mixture on the top of a polyester process column. The gas phase mixture firstly enters a condenser for condensation, condensed liquid taking wastewater as a main component fully enters a stripping tower, air is blown to the bottom of the stripping tower to cool the high-temperature wastewater refluxed on the top, and volatile organic matters in the wastewater are separated into gas phase and discharged from the top; and simultaneously, a compressed air ejector pump or hydro-stream ejector pump is adopted, low-pressure tail gas of a polyester device is extracted into a gas phase pipeline on the top of the stripping tower, tail gas rich in air is discharged, acetaldehyde concentration in the prior tail gas is diluted into a safe concentration range and then sent to a gas-liquid separator for gas-liquid separation, liquid is refluxed to the stripping tower, and the tail gas is sent to a heating furnace of the polyester device for combustion. The process has the technical advantages of separating organic waste gases contained in the wastewater such as acetaldehyde and the like on line, improving the separating efficiency of the process column for water and glycol, reducing the COD content in the finally discharged wastewater, and the like.

Description

technical field [0001] The invention relates to a PTA polyester production process, in particular to the cooling and separation of a gas-phase mixture in a process tower used in the esterification stage, and belongs to the technical field of chemical production. Background technique [0002] The production of polyethylene terephthalate (abbreviation: polyester, PET) by PTA method is through continuous esterification and polycondensation reaction of purified terephthalic acid (PTA) and ethylene glycol (EG) with high purity. Obtain polyester products (including: melt or chips). These reactions are carried out in multiple reactors connected in series. First, the esterification reaction is carried out under positive pressure, and the obtained esterified product is further subjected to polycondensation reaction under negative pressure. When the degree of polymerization reaches a certain level and the product meets the specified intrinsic viscosity, the reaction It's done. [00...

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Problems solved by technology

[0006] The disadvantage of the above technology is that the waste water from the esterification process tower of the polyester plant needs to be transported to the vicinity of the heat medium heating furnace far away from the polyester plant to use steam for heating, and the water content in the exhaust gas during the "stripping" process Larger, relatively high energy consumption, and this "stripping" process does not contribute to the efficiency of the process tower for separating water and glycol

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