carbamate is recirculated through line 9 to the high pressure synthesis section 1 by means of pump 10 with which the recirculated solution is brought to the high synthesis pressure again in the final processing section 8 the urea is separated from water by evaporation of the solution supplied through line 7 usually granulated and carried off at 11 as finished product the water separated from the urea is largely condenced to process condensate part of this process condensate is carried off from the process threough line 12 another part is recirculated through line 3 to low pressure section 6 and used to lower the concentration of the ammonium carbamate solution recirculated through line 9 to synthesis section 1 without this measure the said solution would often be so concentrated that crystallization might occur for instance in line 9 or pump 10 which is undesirable in view of the danger of clogging however the amount of process condensate recirculated through line 13 must not exceed what is required for the certain prevention of this crystallization because the addition of water will reduce the urea synthesis efficiency in section 1 and all the water added must moreover be evaporated again furthermore extra nh 3 is preferably supplied to low pressure section 6 through line 14 in order to bring the nh 3 co 2 ratio of the solution recirculated through line 9 to the desired value for regulating the quantity of process condensate recirculated through line.