Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1992-12-08
2001-08-14
Kumar, Shailendra (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C203S031000, C422S186220, C422S186220, C422S198000, C422S198000, C423S359000, C564S068000, C564S069000
Reexamination Certificate
active
06274767
ABSTRACT:
DESCRIPTION
This invention concerns a process for the industrial synthesis of urea, by reacting ammonia (NH3) and carbon dioxide (CO2), in at least one reaction space at very high pressures and temperatures, and by recycling at least partially the non-reacted products obtained in a recovery section, in which the following actions take place: a) a synthesis reaction between highly pure reagents and b) a synthesis reaction between less pure reagents substantially recycled from said recovery section.
A highly innovative and novel process of this kind is described in European Patent Application No, 91116297.2/0479103 by the Applicant.
A very advantageous invention, the process according to above mentioned European Patent Application, is based on an original combination of two synthesis reactors placed in parallel, one operating according to the so-called “once through” technology (i.e. fed by pure reagents without recycle water) with high yield, and a second reactor according to the total recycle technology (i.e. fed not only by pure reagents, but also with a aqueous recycle solution) with high yield.
In this manner it is possible to obtain very high global conversion yields of CO2 into urea, much higher than those obtainable with conventional processes. In said European Patent Application No 91116297.2 an example is shown of the revamping of a urea plant based on the urea production process with NH3 stripping (selfstripping).
Continuing their research and experiments, the Applicants were able to develop a new revamping process appliable to existing Ammonia Stripping Urea Plants consisting of a stripping stage with NH3, with the aim of notably increasing the capacity and reducing the energy consumption.
This new process is to be considered an original variation of the invention cited in the said European Patent Application.
In particular, in FIG. 3 of the published Patent No. 0479103, a stripping plant with NH3 was shown revamped with the addition of a high yield reactor R in parallel to the “once through” reactor (in particular of the Vulcan type), the urea solution of which was sent directly downstream to the existing HP stripper. It should be noted that said reactor was of adiabatic type, in the sense that all the reaction heat developed from the formation of ammonium carbamate and subsequently dehydrated to urea, was needed to make the reactants reach the necessary operating temperature of the reactor.
The aim of this invention is now to provide an improved process that consents the obtainment of average high conversion yields, reduction of investment and operation costs, better plant exploitation and more ample overload margins of the existing equipment, and considerable plant debottlenecking.
This and other aims are reached with a kind of process, according to the said European Patent Application No. 91116297.2/0479103, characterized now by the fact that from the parallel reactor (“once through”) at least a part of the reaction heat is removed, and the relevant urea solution is sent upstream the existing stripper. Very advanteously, the production capacity of the existing reactor is reduced with respect to the projected one, and the capacity of the “once through” reactor is increased correspondingly.
REFERENCES:
patent: 3091637 (1963-05-01), Cook et al.
patent: 3470247 (1969-09-01), Guadaluki
patent: 4210600 (1980-07-01), Zardi
patent: 4670588 (1987-06-01), Zardi
patent: 4801746 (1989-01-01), Baenens
patent: 0155735 (1985-03-01), None
patent: 479103A1 (1992-04-01), None
patent: 0497215 (1992-05-01), None
patent: 6808167 (1968-06-01), None
R. Powell,Urea Process Technology, pp. 88-146 (1968).
Abstract of GB 1,147,734.
File history from Opposition to EP-B 479 102, i.e., Patentee's letter of Jul. 11, 1997.
Schematic results of calculation performed by Dr. Granelli of Snamprogetti.
Pagani Giorgio
Zardi Umberto
Kumar Shailendra
Ostrolenk Faber Gerb & Soffen, LLP
Urea Casale S.A.
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