Urea reactor CO₂ conversion
CO₂ conversion and the NH₃/CO₂ and H₂O/CO₂ feed ratios of a urea reactor, from a lab analysis of the reactor outlet.
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How this calculator works
Urea forms from ammonia and CO₂ through carbamate: 2 NH₃ + CO₂ → urea + H₂O. The lab reports urea, total NH₃ and total CO₂ (free plus carbamate) and water in the reactor outlet. An element balance turns this back into the reactor feed: each mole of urea used one CO₂ and two NH₃ and made one water; each mole of biuret holds two ureas. Then CO₂ conversion = CO₂ turned into urea ÷ all CO₂ fed, and the feed NH₃/CO₂ and H₂O/CO₂ molar ratios follow.
The example — 34 % urea, 29 % NH₃, 16 % CO₂, 21 % water — gives 60.9 % CO₂ conversion, NH₃/CO₂ = 3.05 and H₂O/CO₂ = 0.64, typical of a modern CO₂-stripping synthesis loop.
Limits: the sample must be the reactor outlet only, and taken and analysed so that no ammonia or CO₂ escapes. Inerts and any extra streams into the reactor are not counted. Equilibrium conversion depends on temperature, pressure and the ratios — use it to compare with this measured value. References: Ullmann's Encyclopedia of Industrial Chemistry, "Urea"; Kirk-Othmer Encyclopedia of Chemical Technology, "Urea".