Abstract: 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 rises through a packed midsection into the upper portion of the separator and is then taken off.

Abstract: 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 heating coil positioned therein extending from the lower portion to the upper portion thereof. The coil contains a heat exchange medium and has an inlet and an outlet located at the upper portion of the reactor. Heated heat exchange medium passes from the coil inlet to the coil outlet, with heat being transferred to the resulting reaction mixture as said mixture passes upwardly in the reactor. Heat exchange medium removed through the outlet is substantially cooler than that at the inlet. Additional NH.sub.

Abstract: 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 separation, and in indirect heat exchange with a relatively colder fluid, whereupon ammonium carbamate is formed from the mixture of the minor stream, fresh make up CO.sub.2 and decomposer off gas in an aqueous solution of urea and the resulting solution is recycled to the urea synthesis reactor.

Abstract: 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 imparted to the medium at said lower portion. The resulting reaction mixture and the heat exchange medium are passed to said upper portion, with heat being transferred from the medium to the reaction mixture. Heated heat exchange medium is charged through said inlet to said lower portion, with heat being transferred to the ascending reaction mixture. Heat exchange medium is removed from said outlet and is substantially cooler than when charged to the inlet.

Abstract: 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 conduit means interconnecting the headers for passing the medium therebetween. Heat of reaction of the feed streams is imparted to the medium in the second header. The resulting reaction mixture is passed to the upper reactor portion, as is the heated medium to the first header, with heat of the medium being transferred to the reaction mixture as it is so passed.

Abstract: Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems.

Abstract: 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.

Abstract: Heat recovery and conversion of reactants to urea are improved in adiabatic and in isothermal urea synthesis systems.

Abstract: 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.

Abstract: 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.