Double effect process rectification diaminotoluene separation method

Abstract

A method for separating diaminotoluene through double-effect flow rectification belongs to the rectification process optimization field with better energy conservation and consumption reduction effect. The method comprises the following steps that a coarse TDA material containing water, solvent and tar is dewatered at first; then, the solvent is removed and then the TDA containing tar undergoes isomer separation so as to remove ortho position TDA and meta position TDA; and finally, pure TDA is obtained.

Description

technical field [0001] The invention relates to a separation method for rectifying diaminotoluene (TDA) in a double-effect flow process, and belongs to the field of rectification process optimization with great energy-saving and consumption-reducing effects Background technique [0002] The product quality of diaminotoluene (TDA) directly affects the production and separation process of toluene diisocyanate (TDI) and the quality of the final product. In the production process of TDA, the crude TDA obtained by hydrogenation of dinitrotoluene (DNT) contains water, solvent, meta-TDA, ortho-TDA, residue and traces of para-TDA, wherein water, solvent and residue must be removed . Ortho TDA reacts with phosgene not to generate isocyanate, but to generate cyclic urea and its polymers, which are easy to cause precipitation and blockage, and must be removed. In the traditional refining process of TDA, the process that consumes the most energy is the process of crude TDA dehydration...

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Problems solved by technology

[0003] The traditional multi-tower continuous distillation process is commonly used in the separation of TDA. Through analysis, it is found that although the temperature at the bottom of the dehydration tower reaches 210°C, the water content in the bottom stream is relatively high, which not only reduces the concentration of ortho isomers at the top of the tower. content, and increase the separation difficulty of the isomer separation tower, so that the isomer separation tower needs a large amount of reflux, and the heat load of the tower increases

This process consumes a lot of energy, and the bottom load of the dehydration tower is very high, which requires more high-pressure steam consumption

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