Abstract: The invention provides a process for the continuous manufacture of trioxan, optionally together with cyclic formals, from aqueous formaldehyde solutions in a circulation reactor with evaporator, the vapor/liquid mixture leaving the evaporator is fed in below the liquid level of the reaction mixture. The process of the invention allows to attain especially high space/time yields.

Abstract: The inventive combination provides for a profitable and efficient utilization of low-pressure waste heat in conjunction with medium-pressure steam. The combination of mechanical and thermodynamic compression for the generation of superheated low-pressure steam is a method that has better results regarding energy and cost than any other known configuration.

Abstract: The invention relates to a process for the continuous manufacture of trioxan, if appropriate together with cyclic formals, from aqueous formaldehyde solutions in a circulation reactor with an evaporator, wherein the vapor/liquid mixture, before it enters the reactor, is separated into the vapor phase and the liquid phase, and subsequently the two phases are fed separately to the reactor. In particular, high space-time yields can be achieved by the process according to the invention. Moreover, equipment for carrying out this process is a subject of the invention.