| 摘要 |
<p>In the synthesis of urea from ammonia and carbon dioxide, off-gases are recovered from the urea product stream by reducing the pressure and with heating, gaseous carbon dioxide is added to the recovered off-gases and the combined gases are adiabatically compressed to urea synthesis pressure after which ammonia is added and the gases passed to urea synthesis. If the off-gas is generated in a plurality of stages at successively reduced pressure levels, the gaseous carbon dioxide is suitably added, prior to compression, to the fff-gas stream recovered from the last stage of the multi-stage recovery, which is at the lowest pressure, and each off-gas at each level is adiabatically compressed and added to the off-gas at the next higher pressure level.</p> |
