Saipem S.p.a.

Snamprogetti S.p.a.

Salpem, S.p.a.

Alessandro Gianazza

Lino Carlessi

Paolo Casara

Domenico Sanfilippo

Ivano Miracca

Lorenzo Bruno

Giuseppe Merelli

Luca Mairano

Gustavo Capannelli

Aldo Bottino

The present invention relates to a method for contemporaneously recovering ammonia and carbon dioxide from an aqueous solution thereof, possibly comprising their condensates, in a synthesis process of urea, characterized in that it comprises a hydrophobic microporous membrane distillation phase of an aqueous solution comprising ammonia, carbon dioxide and their saline compounds or condensates, said distillation being carried out at a temperature ranging from 50 to 250&#xb0; C. and a pressure ranging from 50 KPa to 20 MPa absolute, with the formation of a residual aqueous solution, possibly comprising urea, and a gaseous permeate stream, comprising ammonia, carbon dioxide and water. The present invention also relates to an apparatus for effecting the above method and a production process of urea which comprises the above method.

Method for the separation of ammonia and carbon dioxide from aqueous solutions

A bimetallic tube consisting of at least one tubular element in a first metal resistant to the corrosive and/or erosive action of a process fluid with which it is put in contact, having at least one end, or an area close to an end, externally coated with a layer of a second metal, different from the first and more suitable, with respect to this, for being seal-welded to a support. Tube bundle equipment to be used for thermal exchange operations at high temperatures and pressures, under conditions of high aggressiveness of the process fluids, wherein the tube bundle comprises at least one tube having the above characteristics. Said equipment is particularly used as a heat exchanger and decomposer, for example as a stripper, in the cycle of urea synthesis processes where there are conditions of high pressure, high temperatures, high aggressiveness of the process fluids, and in which the tube bundle consists of at least one tube having the above characteristics.

Corrosion-resistant bimetallic tube and its use in tube bundle equipment

A process for the direct synthesis of urea from ammonia and carbon dioxide with increased corrosion resistance, comprising, in the high-pressure synthesis section, a reaction step in a vertical reactor fed with at least one stream of fresh carbon dioxide containing a passivating agent and a decomposition-stripping step of the non-converted reagents, wherein the gas-liquid mixture collected at the head of the reactor is separated into a gaseous stream and a liquid stream fed to the tail and head of the stripper, respectively.

Process for the synthesis of urea comprising a passivation stream at the stripper bottom

Tube-bundle equipment of the falling liquid film type, comprising a vertical cylindrical body closed at the ends and divided into at least an upper section, an intermediate section and a lower section by means of two perforated tube sheets arranged transversally to support the tubes forming the bundle, wherein each of said tubes is surmounted, on the upper end, by a ferrule, for the inlet and distribution of the liquid in the form of a film, which comprises in the upper part, one or more openings for the outlet of vapors, at an intermediate height one or more openings, preferably tangential, for the inlet of the liquid and below, a circular base for resting on said tube from which an internal cylindrical section, inserted in the tube for a length varying from 10 to 200 mm, protrudes downwards together with an outer metallic strip for a length of at least 2 mm, so that, in the circular area defined between said outer metallic strip and said protruding cylindrical section, there is a gasket, inserted between said circular base of the ferrule and said upper edge of the tube.

Tube bundle equipment with liquid flow regulator elements

A process for the direct synthesis of urea from ammonia and carbon dioxide at high pressures and temperatures, with the formation of ammonium carbamate as intermediate, comprising a decomposition step of the ammonium carbamate and stripping of the gases formed, operating substantially at the same pressure as the synthesis step, wherein the recycled liquid streams are fed, at least partially, to the same decomposition and stripping step after being preheated by heat exchange with a stream included in the high-pressure synthesis cycle.

High-yield process for the synthesis of urea

A process for the recovery of ammonia contained in a gaseous stream is described, said process comprising the following phases: (a) subjecting the gaseous stream containing ammonia to a washing (S) with an aqueous washing solution () having a pH lower than 7.0, with the formation of a purified gaseous stream () and an aqueous solution () containing an ammonium salt; (b) subjecting the aqueous solution containing the ammonium salt coming from phase (a) to a distillation process (MD) with a hydrophobic microporous membrane at a temperature ranging from 50 to 250&#xb0; C. and a pressure ranging from 50 KPa to 4 MPa absolute with the formation of a regenerated washing solution () and a gaseous stream () comprising NHand HO; (c) recycling said generated washing solution to phase (a). The equipment for carrying out the above process is also described.

Process for the recovery of ammonia from a gaseous stream

Tube-bundle equipment for heat exchange operations at high pressures and temperatures, under conditions of high aggressiveness of the process fluids, comprising a titanium lining () and a series of tubes () consisting of at least one layer of zirconium (), positioned in contact with said fluids, wherein the tube plate on which said tubes are inserted comprises an outer layer (S) of zirconium or an alloy thereof and an underlying layer () of titanium welded to the lining of the equipment. Said equipment is particularly used as a heat exchanger, for example as a stripper, in the high-pressure cycle of urea syntheses processes.

Tube-bundle equipment for processing corrosive fluids

A process for the recovery of ammonia contained in a gaseous purging stream produced in a synthesis process of urea.

Method for the recovery of ammonia from a gaseous stream in a synthesis process of urea

An enhanced process is described for the synthesis of urea from ammonia and carbon dioxide, at a high pressure and temperature, with the formation of ammonium carbamate as intermediate, which includes a high pressure synthesis section, comprising at least one separation step by decomposition-stripping with ammonia of the non-converted ammonium carbamate, carried out in a vertical apparatus, commonly called stripper, characterized in that said step also comprises a feeding, in the lower part of said stripper, of a stream of CO, heated to a temperature ranging from 130 to 230&#xb0; C., in a quantity of 1 to 15% by weight with respect to the total weight of the fresh COfed to the process, containing a passivating agent in such a quantity that its equivalent content of Oin moles varies from 0.05% to 0.80% with respect to the moles of COof said stream.

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Legnano, Italy

Alessandro Gianazza