Urea, AVANCORE process Process by Stamicarbon B.V.

To produce urea from ammonia (NH3) and carbon dioxide (CO2) using the Stamicarbon CO2 stripping urea technology. Urea finds its application for 90% as fertilizer; further urea is used as base material for the production of resins, melamine as cattle feed, and as a NOx reducing agent “Ad Blue.”

Ammonia and carbon dioxide are introduced to the highpressure (HP) synthesis using a HP ammonia pump and carbon dioxide compressor (Fig. 1). The NH3, together with the carbamate solution from the downstream recirculation section, enters the pool condenser. The major part of the CO2 enters the synthesis through the HP stripper counter-current to the urea/carbamate solution leaving the reactor. On the shell side, the HP stripper is heated with steam. The offgas of the HP stripper, containing the CO2, together with NH3 and CO2 resulting from dissociated carbamate, is fed into the pool condenser. The minor part of the CO2, entering the synthesis as a feed, enters the urea reactor at the bottom in order to produce sufficient heat for the endothermic urea reaction.

In the pool condenser, NH3 and CO2 are condensed to form carbamate, and a substantial part of the conversion to urea is already established here. The heat released by condensation and subsequent formation of carbamate is used to produce re-usable low-pressure (LP) steam. Downstream from the pool condenser, the urea-carbamate liquid enters the vertical reactor, if required, located at ground level. Here, the final part of the urea conversion takes place. The urea solution then leaves the top of the reactor, all by gravity flow via an overflow funnel, before being introduced into the HP stripper. Gases leaving the urea reactor are directed to the pool condenser.

Gases leaving the pool condenser are fed into the scrubber operating at a reduced pressure. Here, the gases are washed with the carbamate solution from the LP recirculation stage. The enriched carbamate solution is then fed into the pool condenser. This enriched carbamate flow contains no more water than in earlier generations of Stamicarbon CO2-stripping plants, meaning that the conversions in the synthesis section are as high as ever. Inert gases leaving the scrubber at reduced pressure containing some NH3 and CO2 are then released into the atmosphere after treatment in an LP absorber.

Licensor: Stamicarbon B.V.

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