An improvement in the cyclic process for producing urea wherein CO.sub.2 and NH.sub.3 are reacted in the presence of an aqueous ammoniacal solution in a urea synthesis reactor at an elevated temperature and at an elevated pressure in excess of 1800 PSIG to form a urea synthesis reactor effluent fluid at high pressure. The said effluent fluid is split into a minor stream and a major stream. The major stream is let down in pressure and then passed into a gas liquid separator wherein the gas stream...

Internal water balance within a liquid carbamate recycle urea process is controlled. Pressure in decomposer and/or condenser system can be varied to effect control. Also, refractive index of carbamate recycle solution can be determined and related to water balance.

Ammonia, CO.sub.2 and ammonium carbamate are reacted in a reactor at elevated temperature and pressure to form urea. From 10 to 100 percent of the CO.sub.2 fresh reactor feed stream, which is substantially equivalent to the stoichiometric net amount of urea formed in the reactor, is reacted with NH.sub.3 at 10 - 670 psia to form an aqueous ammonium carbamate solution, and this solution is charged to the reactor to form urea.

Ammonium carbamate in an aqueous urea solution containing the carbamate, urea, water and ammonia, obtained as a urea synthesis reactor effluent is decomposed, with the formation of a liquid phase containing urea, water, residual ammonium carbamate and residual ammonia, and a gaseous phase containing ammonia, carbon dioxide and water vapor. The liquid and gaseous phases are discharged into an upper portion of a decomposer and are separated effectively.

Mechanical failures of pumps adapted to transfer ammoniacal aqueous solutions of ammonium carbamate are avoided or minimized by including a pulsation dampener in the suction line to such pumps. A system for transferring such solutions from lower to higher pressures, and a method for operating the system, are provided.

Urea is prilled by spraying urea droplets downwardly into a solidification zone where it is contacted with a substantially inert gas. Prills are directed into a collector by diverting their flow by directing a gas through a perforated, inverted cone or pyramid located at the bottom of and in communication with said zone.

Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems. Ammonia, carbon dioxide and ammonium carbamate feed streams are charged to the lower portion of a reactor, which has indirect heat exchange means positioned therein extending from the lower portion to the upper portion and which includes a heat exchange medium. Said means has a first header positioned in said upper portion, a second header positioned in the lower portion, and con...

Urea synthesis process with liquid carbamate recycle, in which the reactor effluent is divided into major and minor streams. The major stream is reduced in pressure and subjected to heating and substantial carbamate decomposition to ammonia and carbon dioxide decomposer off gas, either directly or after preliminary ammonia separation. The minor stream is reduced in pressure and is contacted with decomposer off gas and fresh make up carbon dioxide, either directly or after preliminary ammonia sep...

Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems. Ammonia, carbon dioxide and ammonium carbamate feed streams are charged to the lower portion of a reactor, which has an indirect heating coil positioned therein extending from the lower portion to the upper portion. This coil has a heat exchange medium therein and has its inlet and its outlet located at the upper portion of the reactor. Heat of reaction of the feed streams is imp...

Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems. Ammonia and carbon dioxide reactor feed streams are charged to a first heat exchanger external to a urea synthesis reactor and are contacted at a NH.sub.3 /CO.sub.2 molar ratio of 2.5/1 to 3.5/1 in the exchanger to form ammonium carbamate. Heat of reaction is removed simultaneously. The resulting reaction mixture is charged to the lower portion of said reactor having an indirect ...