Cleaning and dehydrating method of toluenediamine

Abstract

The invention belongs to the technical field of chemical rectifying, separating and dehydrating, and relates to a cleaning and dehydrating method of toluenediamine. The cleaning and dehydrating method comprises the following steps: dehydrating in a double-tower dehydrating device, so that crude TDA (Toluenediamine) enters the lower part of a dehydrating tower, tower-top gaseous phase of the dehydrating tower enters a tower-top condenser for condensing; continuously collecting liquid-phase process water at the middle lateral line part of the dehydrating tower, wherein the liquid-phase process water enters a wastewater storage tank after being cooled by a wastewater cooler to carry out wastewater biochemical treatment; entering the tower-bottom materials of the dehydrating tower into a tower-bottom re-boiler through a tower-bottom circulating pump; entering the tower-bottom materials of the dehydrating tower into the tower top of a stripping tower; and entering tower-bottom liquid phase of the stripping tower into a follow-up vacuum distillation system. The cleaning and dehydrating method is reliable in process principle, simple in device structure, convenient for assembling operation, good in dehydrating effect, high in dehydrating rate and good in environment-friendliness, and resources and raw materials are saved.

Description

Technical field: [0001] The invention belongs to the technical field of chemical distillation, separation and dehydration, and relates to a new process for distilling and removing water from a reaction mixture of toluenediamine, in particular to a method for cleaning and dehydrating toluenediamine. Background technique: [0002] Toluene diamine (TDA) is the main raw material for the production of toluene diisocyanate (TDI), which is widely used in the synthesis of polyurethane flexible foams, elastomers and coatings due to its excellent performance; currently, TDA is usually hydrogenated with dinitrotoluene The reaction is obtained, except that the target product TDA is contained in the reaction mixture, and by-products such as water and ortho-toluenediamine generated by the reaction, as well as high-boiling impurity tar and low-boiling impurity toluidine and cyclohexyl compounds are contained in the reaction mixture; the reaction mixture is usually passed through A series o...

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Problems solved by technology

The literature with Chinese patent number 200810018118.1 uses negative pressure to remove a small amount of water. Chinese patent ZL200580002158.1 directly performs vacuum distillation on crude TDA containing trace water. The former adds a new vacuum device to remove trace water. The latter rectifies TDA under vacuum conditions, and the existence of trace water will inevitably increase the load of vacuum equipment, and will also cause the water content in the product TDA to exceed the standard; Chinese patent CN101848885A adopts a two-stage vacuum double-tower dehydration process, which is suitable for TDA products Separation from water, but does not consider the removal method of low boiling point components in the mixture. Although the water content of TDA can be reduced to less than 200ppm or even lower, the COD content in the discharged wastewater is usually 3000mg / L or higher , which will inevitably increase the difficulty and cost of subsequent wastewater treatment

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