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.

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.

A process for the synthesis of melamine from urea, preferably of the high-pressure type, wherein offgas quenching is performed in a quenching vessel wherein in the upper part of the vessel, a rising flow of offgas is contacted in counter-current with liquid ammonia to obtain precipitation of melamine contained in the offgas and melamine-free anhydrous washed offgas; in the lower part of the vessel, the solid melamine is contacted with a liquid solvent to form a solution of melamine or a melamine slurry.

A process for the synthesis of melamine from urea, preferably of the high-pressure type, wherein offgas quenching is performed in a quenching vessel wherein in the upper part of the vessel, a rising flow of offgas is contacted in counter-current with liquid ammonia to obtain precipitation of melamine contained in the offgas and melamine-free anhydrous washed offgas; in the lower part of the vessel, the solid melamine is contacted with a liquid solvent to form a solution of melamine or a melamine slurry.

A process for synthesis of urea from ammonia and carbon dioxide comprising the synthesis of urea in parallel in a first urea reactor (1) at a first urea synthesis pressure and in a second urea reactor (2) at a second and lower urea synthesis pressure; a stripping step of the reaction effluent of the first reactor, which is performed in a stripper (4) operating at a stripping pressure lower than the first urea synthesis pressure; the reaction effluent (21) of the second reactor (2) and the stripper liquid effluent (11) are sent to a recovery section (13) where a carbamate-containing recycle solution (17) is produced, and said recycle solution (17) is sent partly to said first reactor and partly to said second reactor.

A process for synthesis of urea from ammonia and carbon dioxide comprising the synthesis of urea in parallel in a first urea reactor (1) at a first urea synthesis pressure and in a second urea reactor (2) at a second and lower urea synthesis pressure; a stripping step of the reaction effluent of the first reactor, which is performed in a stripper (4) operating at a stripping pressure lower than the first urea synthesis pressure; the reaction effluent (21) of the second reactor (2) and the stripper liquid effluent (11) are sent to a recovery section (13) where a carbamate-containing recycle solution (17) is produced, and said recycle solution (17) is sent partly to said first reactor and partly to said second reactor.

Plant for the synthesis of melamine starting from urea, wherein the stream of offgas containing NH3 and CO2 produced by the synthesis of melamine is converted into urea in a dedicated urea plant.

Plant for the synthesis of melamine starting from urea, wherein the stream of offgas containing NH3 and CO2 produced by the synthesis of melamine is converted into urea in a dedicated urea plant.

A pulse jet system and method is disclosed. In an example, the pulse jet system includes a combustion chamber, intake ports to deliver combustion agents to the combustion chamber, an expansion chamber to cool a combustion product following combustion of the combustion agents in the combustion chamber, and an exhaust to exit the cooled gas from the expansion chamber. In another example, the pulse jet system includes a combustion chamber with intake ports to deliver combustion agents to the combustion chamber, wherein the combustion chamber is part of a four cycle engine. The pulse jet system also includes an expansion chamber to cool a combustion product following combustion of the combustion agents in the combustion chamber.

A pulse jet system and method is disclosed. In an example, the pulse jet system includes a combustion chamber, intake ports to deliver combustion agents to the combustion chamber, an expansion chamber to cool a combustion product following combustion of the combustion agents in the combustion chamber, and an exhaust to exit the cooled gas from the expansion chamber. In another example, the pulse jet system includes a combustion chamber with intake ports to deliver combustion agents to the combustion chamber, wherein the combustion chamber is part of a four cycle engine. The pulse jet system also includes an expansion chamber to cool a combustion product following combustion of the combustion agents in the combustion chamber.