| 摘要 |
<p>PURPOSE:To produce urea safely at a low cost, by recycling and reusing a part of the gaseous mixture discharged from the urea preparation apparatus to the high-pressure system of the apparatus as a passivator for the corrosion-protection of the apparatus, thereby shifting the composition of the discharged gas out of the explosion range. CONSTITUTION:Carbon dioxide (containing impurities such as hydrogen, nitrogen, methane, etc.) is supplied through the line 11 and ammonia is supplied through the line 23 to the synthetic tower 15, and made to react with eact other under high temperature and pressure to obtain urea. Oxygen or air is supplied to the system through the line 12 as a passivator for the corrosion-protection of the urea preparation apparatus. In the above process, a part of the gaseous mixture discharged from the preparation apparatus is recycled and reused as a passivator through the line 13 to the high-pressure system of the synthesis tower 15. By this method, the amount of air supplied through the line 12 can be reduced and the composition of the discharged gas is shifted out of the explosion range, and accordingly, the explosiveness of the gaseous mixture can be eliminated to enable the safe production of urea.</p> |
