| 摘要 |
An I.D.R. process for the manufacture of urea, comprising two subsequent loops, wherein: A) In the first (high pressure) loop the solution coming from the synthesis zone contains, after the first isobaric strip per (E1), a strong NH3 excess and a low CO2 percentage and contains, before the second isobaric stripper (E2), an amount of carbamate lower than the amount of carbamate contained in the solution leaving the same (E2) stripper, wherein the consequent overproduction of carbamate (in E2) releases an amount of heat sufficient to displace a major proportion of the residual NH3 contained therein; B) In the second (low pressure) loop, the solution leaving (E2) is flashed at 20-30 ata and enters a first (medium pressure) still (E3), heated by a low pressure recovery steam, coming from the isobaric condensation (in E8) of the vapors leaving the top of (E2) said recovery steam having such a thermal level to decompose at least said overproduction of carbamate; C) the solution leaving (E3) is flashed substantially at 5 ata and enters a second (low pressure) still (E4) and then a vacuum concentrator (E5) wherein the heat of the vapors leaving the head of (E3) is exploited for the working run of (E4) and (E5). |
