Method and system for distillation recycling of dimethyl formamide rectified residual liquid

Abstract

The invention discloses a method for distillation recycling of a dimethyl formamide residual liquid. The method includes the steps: allowing the dimethyl formamide rectified residual liquid to enter a dryer, controlling the pressure intensity in the dryer to be 40-60 kPa and the temperature to be 180-200 DEG C, allowing a part of the residual liquid after distillation to return back into the dryer, mixing with a dimethyl formamide rectified residual liquid newly entering the dryer, and controlling the solid content of the mixed residual liquid to be 25-35 wt%; and successively carrying out condensation and gas-liquid separation on a gas-phase substance discharged from an exhaust port of the dryer, and thus obtaining a dimethyl formamide product. The invention also discloses a system for distillation recycling of the dimethyl formamide residual liquid. The method can effectively recycle dimethyl formamide in the dimethyl formamide rectified residual liquid, and besides, realizes harmless treatment of hazardous waste; and dimethyl formamide in the production process is not cracked, an equipment coking phenomenon is less, system running is safe and stable, and the production efficiency is high.

Description

technical field [0001] The invention relates to a method and a system for recovering dimethylformamide rectification raffinate by distillation. Background technique [0002] When wet manufacturing polyurethane (polyurethane, referred to as PU) synthetic leather, it is necessary to use dimethylformamide (abbreviated as DMF) as a solvent to dissolve the polyurethane resin to form a slurry, and the obtained slurry is impregnated and coated on the surface of the base fabric, and then water Washing removes dimethylformamide, resulting in dimethylformamide-containing wastewater. In order to avoid environmental pollution caused by wastewater containing dimethylformamide, it is necessary to recycle the dimethylformamide in the wastewater. [0003] The above-mentioned waste water containing dimethylformamide recovers dimethylformamide through a distillation recovery system. First, it passes through a dehydration tower to remove part of the water, and then enters a rectification towe...

AI Technical Summary

Problems solved by technology

However, in actual operation, the raffinate is seriously coked during the distillation process, which leads to the frequent shutdown of the system to clean up the coke or overhaul the equipment; if the coking is severe, the surface of the heating body may even crack due to dry burning, resulting in high equipment maintenance costs and low production efficiency; In addition, in the distillation process, dimethylformamide is often cracked due to improper distillation conditions.

Therefore, when the dimethylformamide in the rectification raffinate of dimethylformamide is recovered by conventional distillation methods, the overall economic benefits are poor, and generally no enterprises actually put it into operation

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