A method for removing excess glycol in alcoholysis solution

Abstract

The invention provides a method for removing excessive dihydric alcohol in an alcoholysis solution, which comprises the following steps: A) heating a waste polyester material, an initiator and a dihydric alcohol, carrying out alcoholysis, cooling, and filtering to obtain a dihydric alcohol alcoholysis solution; b) enabling the dihydric alcohol alcoholysis solution to enter an evaporation chamber,heating the dihydric alcohol alcoholysis solution by adopting an external heat source, and enabling steam generated by the dihydric alcohol alcoholysis solution to heat the dihydric alcohol alcoholysis solution again to obtain secondary steam; c) compressing the secondary steam through a compressor to obtain steam and a dihydric alcohol cooling liquid; and D) adopting the steam obtained in the step C) to replace the external heat source as a heat source to enter the evaporation chamber again to heat the dihydric alcohol alcoholysis solution, and the step B) and the step C) are carried out circularly. According to the method for removing the excessive dihydric alcohol in the alcoholysis solution, the dihydric alcohol can be removed, meanwhile, steam can be continuously generated, the steamis taken as a circulating heat source to achieve removal of the dihydric alcohol in the alcoholysis solution, and therefore the heating heat source and circulating cooling water are saved.

Description

technical field [0001] The invention relates to the technical field of recycling waste polyester, in particular to a method for removing excess dihydric alcohol in alcoholysis liquid. Background technique [0002] Using waste textiles (polyester-based clothing, leftover materials, etc.), low-value and low-quality old polyester bottle materials to synthesize polyester melt spinning regenerated polyester fibers through alcoholysis and repolymerization technology is a kind of recycling of waste. A new approach to high-value recycling of polyester materials. This method is different from the pure physical method of selecting and sorting recycled polyester, crushing, cleaning, dehydrating and drying. The method is to put the waste polyester raw material into the alcoholysis kettle, add excess dihydric alcohol and a small amount of initiator 2 to 8 times the mass of the raw material, alcoholyze at 170~245°C for 1~5h, cool and filter out the insoluble matter, remove The excess et...

AI Technical Summary

Problems solved by technology

[0004] The applicant found that the amount of ethylene glycol used in the depolymerization of PET is not particularly limited during the spinning process of recycled polyester fibers, and the amount of ethylene glycol can be used from 10% to 800% to achieve depolymerization of waste PET and repolymerization into valuable polyester , but will affect the quality, yield and cost of polyester

The advantages of 10% ethylene glycol depolymerization of waste PET: the production and operation costs are very low, because the ethylene glycol that needs to be evaporated and refined is very small and low energy consumption; the disadvantage: the alcoholysis temperature is above 240°C, and alcoholysis will produce diethylene glycol, The alcoholyzate has high viscosity, difficult to filter, and large waste. The main waste is that 95% of the alcoholyzate will solidify and adhere to the filter screen when unloading the slag. It will be scrapped and indirectly increase the cost, and calcination will also increase the pressure on environmental protection, and because the viscosity of the alcoholyzate is high, the pressure during filtration will be high, so the fine particles will penetrate the filter screen, and the presence of diethylene glycol will make the repolymerized product Can only be applied to the lowest end products, thereby reducing the added value of the depolymerized final product

According to the above description, it can be seen that the depolymerization temperature can be lowered when the excess diol is depolymerized, the side reactions are less and controllable during the depolymerization process at low temperature, the depolymerization is more thorough, the monomer yield is higher, and the viscosity of the depolymerization liquid is low. The fine filtration operation is carried out smoothly at a lower temperature, the pressure during filtration is very low, the filtration accuracy is very high, the product of alcoholysis and repolymerization has less impurities and is stable, and the added value of high-end products is increased; the disadvantage is excessive glycol In the evaporation cycle, a large amount of heat source is consumed, so the energy consumption is high, and the investment in production equipment is high, which makes the production cost high

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