Shigeru Inoue

Equilibrium of Urea Synthesis. II.

A test of the equilibrium conversion of CO2 to urea was carried out using a batch autoclave. Some results different from those reported by Frejacques were obtained, as was expected from the latest data on commercial urea plants. The equilibrium conversion reached its maximum value at about 195°C by 5–15% higher than that reported by Frejacques. On the contrary, at temperatures above 200°C the value was lower, and falled rapidly with the raise of temperature. This phenomenon may be due to the mechanism of the equilibrium of urea synthesis, and not to the experimental method, as our sampling was made directly from the liquid phase. The equilibrium conversion, x, may be expressed with respect to NH3/CO2, a, H2O/CO2, b, and temperature, t, as (Remark: Graphics omitted.) Therefore, a limited conversion exists in the conventional urea process.

The Optimum Operating Conditions of Urea Autoclave

The operating conditions of urea autoclave in the partial recycle process were determined by the optimum condition of the process, but by the problem of mategials for high pressure equipment, by-produced ammonium salts and biuret. We have analyzed the above conditions from the following points of view.First, the optimum molar ratio of NH3CO2 in the total feed to autoclave was discussed from the point of equilibrium of urea synthesis and thermochemistry, and second, the optimum residence time of the feed into the autoclave was discussed from the points of reaction kinetics and economics of the whole process.The results obtained in the above analyses are that the optimum NH3CO2 is about 4-5 and the optimum residence time is about half an hour. These two conditions are in very good agreement with those adopted in the actual plant. The reason to come to this conclusion consists in the existence of the maximum conversion with change of temperature and higher cost of utilities than that of investment.

A Design Method for the Urea Reactor

管内での流動が気相も伴ったビストンプローに近いものであれば, 複雑な気液平衡式を用いる代祭にLなる吸収係数を導入することによって, 合成管容積の計算が容易になることを示した。実際の試験結果てもバフル・プンートつきであれば, ピストン・フローに近い乙とが判萌して, このデータよりLを求めると簡単な傾向を示した。このLを用いて液相分の容積を先ず求め, さらに気相分を補正して得た合成管の容積は試験値とよく一致した。

Urea Hydrolysis and Distillation of Its Solution

化学工平, 37, 732～738 尿素合成液の蒸留て問題となる 素ヒ水の2次反応として速度定数, の結果を考慮て蒸留試験を行ない, ことにより同伴水分の少ないNH3, CO2の分離が行 間ての温度, 組成か一定てある特異性はCO2の吸収により CO2が下ることにある, このため蒸留に多い段数は必要ない。こからの成果は新しい完全循環法の開発に貢献した。