Closed-cycle drying process for 3,3'-dimethyl-4,4'-diaminodiphenylmethane

Abstract

The invention discloses a closed-cycle drying process for 3,3'-dimethyl-4,4'-diaminodiphenylmethane. The closed-cycle drying process is adopted, so that a solvent in wet materials is evaporated underaction of hot air; o-toluidine and MDT products are taken out by tail gas; dust content in the tail gas is enabled to meet requirements of a gas cycle and a compressor through cyclone separation, cloth-bag dust removal and medium-effect filter dust removal; the tail gas enters a condenser, the o-toluidine and water are condensed and recycled, so that content of o-toluidine in circulating air is reduced, and therefore, concentration of the o-toluidine in the tail gas is always kept to be lower than the lower explosive limit; the tail gas is pressurized by a circulating fan to re-enter a dryingprocess system to circulate, so that the drying effect is improved; MDT particles of waste gas in a drying process are removed by a cloth-bag dust remover and a medium-effect filter, so that dust content in the gas meets requirements of the gas cycle and the compressor, and therefore, a gas closed cycle is realized; and residual o-toluidine in the waste gas is condensed and recycled, so that emission of poisonous gas is avoided, and therefore, the closed-cycle drying process has very good economical and environmental effects.

Description

technical field [0001] The invention belongs to the technical field of chemical product drying, and relates to a 3,3'-dimethyl-4,4'-diaminodiphenylmethane closed-circuit circulation drying process, in particular to the closed-circuit circulation drying of dust particles containing MDT, especially to adjacent MDT closed loop drying process for methylaniline solvent recovery. Background technique [0002] At present, the industrial production of 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MDT) mainly uses o-methylaniline as a raw material, and the product is obtained through a catalytic reaction. The wet product during workup contains unreacted o-toluidine. After the MDT wet material is dried by hot air, the exhaust gas is directly discharged after the product is recovered by the cyclone separator and the bag filter. The exhaust gas contains a certain amount of o-methylaniline solvent, which is a known carcinogen. O-methylaniline is mostly a light yellow oily liquid at room t...

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Problems solved by technology

Due to the high cost of aniline incineration, and the smoke and gas after incineration contain a large amount of nitrogen oxides, the cost of incineration tail gas treatment is relatively high

[0004] On the other hand, hot air is used as the drying medium for MDT products, and a spin flash dryer is used in series with a cyclone dryer for drying. After the product is recovered by a cyclone separator and a bag filter, the drying waste gas is directly discharged. Not only o-methylaniline The emission content cannot meet the standard, and there is also a small amount of dust (MDT particles) in the exhaust gas, which is not good for the environment

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