Abstract: A cell receiver includes, in addition to a cell decomposing unit, an interleaving memory, an error correcting unit, a FIFO memory, and a delay fluctuation absorption control unit, a delay fluctuation absorption buffer for absorbing delay fluctuation of a received cell, and a buffer control unit for controlling a read operation of a cell from the delay fluctuation absorption buffer. Since the delay fluctuation of a received cell is absorbed by the delay fluctuation absorption buffer, the number of memories necessary for interleaving can by reduced to two memories.

Abstract: Disclosed herein is a process of synthesizing urea including reacting ammonia and carbon dioxide at a urea synthesis pressure and temperature in a urea synthesis zone, separating excess ammonia and unreacted ammonium carbamate from the thus-obtained urea synthesis melt as a gaseous mixture containing ammonia and carbon dioxide, recirculating the gaseous mixture to the urea synthesis zone, and, on the other hand, obtaining urea from an aqueous urea solution which has been obtained by separating the excess ammonia and unreacted ammonium carbamate. The above process features ingeniously combined conditions of various process steps. It produces urea using less high-pressure steam and recovers less low-pressure steam. A stripping operation making use of carbon dioxide can be effectively incorporated in the above process. The above process permits to cut the construction cost of a urea synthesis plant.

Abstract: In the process for urea synthesis, an effluent from a reactor 2 containing urea, ammonium carbamate, excess ammonia and water is introduced in a first heater 3 to separate excess ammonia and to decompose ammonium carbamate, thereby separating them from the liquid phase; then the liquid effluent from the first heater 3 is introduced in a second heater 6 to separate the remaining excess ammonia and to decompose ammonium carbamate in the presence of starting carbon dioxide used as stripping gas, thereby separating them from the liquid phase; the liquid effluent from the second heater 6 is introduced into a urea solution purification step in which pressure is lower than in the above step; and the separated gaseous effluents from the first and the second heaters are returned into the reactor.

Abstract: In a process in which a urea synthesis effluent obtained by reacting ammonia with carbon dioxide is subjected to a stripping step of bringing the urea synthesis effluent into countercurrent contact with carbon dioxide under heating to obtain an aqueous urea solution containing a small amount of ammonia and ammonium carbamate, the improvement comprises first bringing the urea synthesis effluent is into contact with a separated gas evolved in the stripping step under adiabatic conditions or with a little cooling. The use of the above process enables a reduction in size of the stripper and a recovery of the high pressure steam without keeping the ammonia to carbon dioxide molar ratio lower than that of the conventional method.

Abstract: An inert gas containing carbon dioxide and ammonia and separated from a urea synthesis effluent under urea synthesis pressures is brought into contact with an absorbent along with unreacted carbon dioxide and ammonia separated in high pressure distillation at a pressure of from 10 to 25 kg/cm.sup.2 G to absorb substantially all of the carbon dioxide and the major portion of the ammonia, and is cooled to be separated from the resulting liquid ammonia and then is discharged. The inert gas can be treated with little or no danger of explosion by the above method.

Abstract: In a urea synthesis process, the reaction product from the reaction vessel is flowed in series through high pressure, medium pressure and low pressure decomposing and stripping devices to decompose ammonium carbamate to NH.sub.3 gas, CO.sub.2 gas and water vapor, and to remove those gases and unreacted starting materials from the aqueous urea solution. CO.sub.2 gas is used as the stripping gas in the decomposing and stripping devices.

Abstract: An aqueous urea solution is concentrated to a substantially water-free molten urea by conducting successively a first step of concentrating said aqueous urea solution under the conditions forming a urea slurry and a second step of concentrating said urea slurry under conditions forming a substantially water-free molten urea free from crystalline urea.