Reactor for the high-pressure non-catalytic synthesis of melamine from urea, comprising coaxial inner reaction zone (6) and outer reaction zone (7) wherein a crude melamine is formed in the inner reaction zone and contacted with gaseous ammonia for stripping in the outer reaction zone, wherein a gaseous phase liberated in the outer zone is collected in a gas collection chamber (12) above the reaction zones, wherein the crude melamine melt is transferred from the inner zone into the outer zone via a submerged liquid passage below the liquid level to provide a liquid seal between the chambers.

Disclosed is a process for the integrated production of urea and melamine. A urea production zone produces a urea synthesis stream comprising urea, water and ammonium carbamate. This stream is subjected to processing, preferably involving stripping, so as to separate an aqueous urea stream from residual dissociated carbamate vapor comprising ammonia, carbon dioxide, and water. The urea is fed to a melamine synthesis zone and subjected to melamine forming conditions so as to form melamine and off-gas comprising carbon dioxide and ammonia. The dissociated carbamate vapor and the melamine off-gas are subjected to combined condensation so as to form a dilute melamine off-gas condensate.

Disclosed is a process for the integrated production of urea and melamine. A urea production zone produces a urea synthesis stream comprising urea, water and ammonium carbamate. This stream is subjected to processing, preferably involving stripping, so as to separate an aqueous urea stream from residual dissociated carbamate vapor comprising ammonia, carbon dioxide, and water. The urea is fed to a melamine synthesis zone and subjected to melamine forming conditions so as to form melamine and off-gas comprising carbon dioxide and ammonia. The dissociated carbamate vapor and the melamine off-gas are subjected to combined condensation so as to form a dilute melamine off-gas condensate.

In an integrated process for urea and melamine production, urea is produced in a urea plant (10) comprising a high pressure urea synthesis section (11) from which an aqueous solution comprising urea, ammonium carbamate and ammonia is obtained and a urea recovery section (21) operating at low pressure, and melamine is produced in a melamine plant (40) wherein off-gases resulting as by-products of the melamine synthesis are discharged from said plant at a medium pressure and recycled to the high-pressure urea synthesis section (11).

In an integrated process for urea and melamine production, urea is produced in a urea plant (10) comprising a high pressure urea synthesis section (11) from which an aqueous solution comprising urea, ammonium carbamate and ammonia is obtained and a urea recovery section (21) operating at low pressure, and melamine is produced in a melamine plant (40) wherein off-gases resulting as by-products of the melamine synthesis are discharged from said plant at a medium pressure and recycled to the high-pressure urea synthesis section (11).

A process for converting an anhydrous off-gas stream from melamine synthesis plants to urea and the relative plant for the direct conversion of an anhydrous off-gas stream from melamine synthesis plants into urea, are described.

A process for converting an anhydrous off-gas stream from melamine synthesis plants to urea and the relative plant for the direct conversion of an anhydrous off-gas stream from melamine synthesis plants into urea, are described.

Combustion gas of an internal combustion engine passes through an exhaust system to an outlet opening. A detection device generates a state signal that describes an engine noise of the internal combustion engine. A control apparatus actuates at least one loudspeaker to produce a sound at the outlet opening based on the state signal to compensate for the engine noise or produce another engine noise, independently of the state signal based on predetermined audio data and thereby to use the at least one loudspeaker to audibly output an advisory signal described by the audio data.

Process and respective reactor for urea or melamine synthesis, comprising sonication treatment of at least part of a reaction liquid mass or two-phase mixture contained inside said reactor.

Process and respective reactor for urea or melamine synthesis, comprising sonication treatment of at least part of a reaction liquid mass or two-phase mixture contained inside said reactor.