Abstract: A method for repairing and restoring the functionality of equipment subjected to internal corrosion during its operation at high or medium pressure in a plant for the synthesis of urea. The method includes the cleaning of the corroded area, the formation of suitable supporting and/or holding surfaces for the placement of a new metallic lining, the formation of a new anticorrosive sealed off lining, obtained by positioning and welding flat elements and metallic plates which are suitably shaped and placed next to each other to become adapted to the internal profile of the equipment. The spaces and interstices below this new lining all communicate with at least one weep-hole present in the pressure resistant body. The entire repair is carried out through the manhole of the equipment and enables the restoring of its functionality for times similar to the normal duration of corresponding newly constructed equipment.

Abstract: A urea production process with high energy efficiency, in which the urea solution obtained from the synthesis stage is subjected to a first stage of high pressure thermal decomposition of the ammonium carbamate which has not undergone conversion to urea together with simultaneous self-stripping by excess ammonia, the gaseous products from said decomposition being condensed in two stages at different temperatures, in the first of which the heat is directly transferred to a second ammonium carbamate decomposition stage which is divided into two parts, namely a first thermal decomposition part and a second part consisting of adiabatic stripping with part of the carbon dioxide feed to the process.

Abstract: Process for vacuum-concentrating urea solutions in which the final step of evaporation of the urea solution under vacuum is carried out within the injection of overheated water vapor in the overhead portion of the concentrator, in order to counteract the formation and deposition of high-melting, fouling compounds derived from urea.

Abstract: A process for neutralizing the ammonia present in the molten urea originating from the concentration section of a plant for its production, comprising adding to the molten urea a small quantity of an acid.

Abstract: A urea production process in which the urea solution produced in the reaction zone is treated in sequence with a first thermal decomposer at the same pressure as the reaction, to decompose part of the residual ammonium carbamate into its components, then with an adiabatic stripper in which the free ammonia is stripped with CO.sub.2 operating at a pressure which is 1-7 MPa less than the synthesis pressure, then with two further carbamate thermal decomposition stages at decreasing pressures. The gaseous products obtained from those stages at pressures less than the synthesis pressure are mixed with the recycle solutions from the downstream stages, condensed by heat transfer against said downstream stages, and then recycled to the reaction as liquid.

Abstract: Process for vacuum-concentrating urea solutions in which the final step of evaporation of the urea solution under vacuum is carried out within the injection of overheated water vapor in the overhead portion of the concentrator, in order to counteract the formation and deposition of high-melting, fouling compounds derived from urea.

Abstract: A process for purifying the effluent originating from urea production plants, consisting of three successive treatment stages, namely stripping of the volatile components, thermal hydrolyis of the urea and biuret in a plurality of zones traversed with piston flow, and final stripping of the volatile components produced by the hydrolysis.

Abstract: Process and apparatus for the production of urea, wherein the carbamate decomposers and/or condensers are equipped with stainless steel tubes internally lined with zirconium.