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 CO2 react at synthesis pressure of 140 bar to urea and carbamate (Fig. 1). The conversion of ammonia as well as CO2 in the synthesis section is 80%, resulting in an extreme low recycle flow of carbamate. Because of the high ammonia efficiency, no pure ammonia is recycled in this process. The synthesis temperature of 185°C is low and, consequently, corrosion in the plant is negligible.
Because of the elevation difference within the synthesis section, the internal recycle is based on gravity flow. This results in very low electrical energy requirement. Synthesis gas condensation in the pool condenser or pool reactor generates steam, which is used in downstream sections within the plant. Process steam consumption is low. Processing inerts are vented to the atmosphere after washing; thus, ammonia emissions from the plant are virtually zero.
Because of the high conversions in the synthesis, the recycle section of the plant is very small. An evaporation stage with a vacuum condensation system produces urea melt with the required concentration either for the Stamicarbon fluidized-bed granulation or prilling. Process water produced in the plant is treated in a desorption/hydrolyzer section. This section produces an effluent, which is suitable for use as boiler feedwater.
With Stamicarbon’s pool condenser technology, condensation can be done very efficiently by reversing the former high-pressure carbamate condenser’s process and steam side. The entire heat exchanging part is submerged in condensed carbamate. This pool-type condensation enables higher heat transfer, while staging two-thirds of the entire synthesis section’s urea conversion in its liquid holdup. Thus, the urea reactor can be much smaller, and the plant will be smaller. Stamicarbon’s Urea 2000plus technology can be offered for capacities up to 5,000 metric tpd–6,000 metric tpd.
Taking this a stage further, Stamicarbon invented the pool reactor (Fig. 2), which effectively combines the pool condenser and the downstream urea reactor into a single piece of high-pressure equipment. Pool reactor type of urea plants are currently offered for capacities up to 2,300 metric tpd.
Licensor: Stamicarbon B.V.