Covestro Deutschland Ag

Covestro LLC

Covestro Intellectual Property Gmbh & Co. Kg

Zhangyong Ming

Wolfgang Taube

Yuguo Gai

Bernd Pennemann

Volker Michele

Joachim Zechlin

Qiang Wei

Thomas Bludowsky

Juergen Bausa

Shuang Liang

Yiming Mao

The present invention provides a method for operating a rectification column () for separating a mixture (S) containing a component A and a component B having a boiling point higher than that of the component A at an operating pressure of the rectification column () which is lower than ambient pressure, wherein the method comprises a step for controlling the mass fraction of the component B in the product stream of the component A (P) to a value within a first target range from 0.1% to 5.0% and the mass fraction of the component A in the product stream of the component B (P) to a value within a second target range from 0.1% to 5.0%, wherein the control is carried out as a function of a controlling temperature (TC) for which a setpoint TCis calculated according to the equation TC=T2+F&#xb7;(T1&#x2212;T2), where F is a factor which is in the range from 0.1 to 0.9 and T1 and T2 are reference temperatures, wherein in the case of a deviation in the measured control temperature (TC) from its setpoint TCbeing found the control temperature (TC) is readjusted to the setpoint TCby varying one or more of the following actuating variables: (i) heating of the column bottom () by the evaporator (), (ii) the mass flow {dot over (m)}of the reflux (A) fed back into the rectification column, (iii) the mass flow {dot over (m)}of the product stream Pand (iv) the mass flow {dot over (m)}of the product stream P

Method for operating a rectification column

The invention relates to a method for cleaning a phosgene-conducting apparatus by pressurization with ammonia gas to constant pressure. In this way, phosgene residues in the apparatus to be cleaned are decomposed effectively.

Method for cleaning phosgene-conducting apparatuses

A process for quenching, in a quenching zone, a gaseous reaction mixture that includes a diisocyanate, phosgene and hydrogen chloride that is obtained in a reaction zone upstream of the quenching zone by phosgenation of a diamine in the gas phase. The process includes injecting a deposit preventing liquid in a deposit preventing zone located between the reaction zone and the quenching zone by passing the deposit preventing liquid through spray nozzles for the deposit preventing liquid at the entrance to the deposit preventing zone. Each spray nozzle for the deposit preventing liquid sprays the deposit preventing liquid (i) onto a wall segment of the deposit preventing zone that is adjacent to said spray nozzle for the deposit preventing liquid to produce a film of the deposit preventing liquid flowing along the wall, and/or (ii) to areas in a cross-sectional plane of the deposit preventing zone before the entrance to the quenching zone.

Process for quenching a gaseous reaction mixture obtained in the gas phase phosgenation of diamines

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Shanghai, China

Zhangyong Ming