Process for the displacement to the gaseous phase of the excess of NH.sub.3
US4613697A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 26, 1984 |
| Grant date | Sep 23, 1986 |
| Priority date | — |
| Expiry date | Dec 26, 2004 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P20/141
- WIPO fieldOrganic fine chemistry
- WIPO sectorChemistry
Abstract
A process for the displacement to the gaseous phase, at 80-250 Kg/cm.sup.2, of the excess NH.sub.3 contained in an aqueous urea solution, coming, at 150.degree.-230.degree. C., from a former stripping, isobaric with the urea synthesis, and containing also CO.sub.2 as ammonium carbamate. The CO.sub.2 is, at most, 25% b.w. of the urea, and the displacement is performed by means of a CO.sub.2 stripping within a falling-film exchanger, hereinafter called the CO.sub.2 stripper, isobaric too with said synthesis. The amount of carbamate leaving the bottom of said CO.sub.2 stripper is substantially equal to the amount of carbamate entering the same stripper. The global NH.sub.3 :CO.sub.2 ratio, in the solution entering the CO.sub.2 stripper, is from 2 to 8 b.w. and heat is supplied only to the uppermost portion of the pipes of the CO.sub.2 stripper, wherein the surface ratio between the lowermost portion and said uppermost portion is at least 1:1 and wherein the residence time ratio between said lowermost portion and said uppermost portion is at least 1/1, the residence time in said uppermost portion being from 1 to 3 s.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.