| 摘要 |
<p>1,184,004. Urea. SNAM PROGETTI S.p.A. 27 June, 1968 [29 Sept., 1967], No. 30814/68. Heading C2C. Urea production comprises feeding gaseous CO 2 and an excess of liquid or gaseous NH 3 to a synthesis zone in a reactor, reacting the CO 2 and NH 3 therein so as to produce, as the reaction product, a solution of urea contaminated with ammonium carbamate and containing the excess NH 3 , causing or allowing the said solution to flow as a thin film over a surface in a decomposition chamber in which the temperature and pressure are substantially the same, heated to an extent sufficient to cause at least part of the ammonium carbamate to decompose into gaseous CO 2 and NH 3 , recycling the decomposition products as well as the excess NH 3 to the synthesis zone, and recovering the urea solution having a reduced ammonium carbamate content. The thin liquid film may be obtained, e.g. by allowing the reaction product to drop along the inside wall of a heat exchanger or along the wall of part of the reactor other than the synthesis zone. Synthesis and decomposition may be effected at a temperature of 180- 350‹ C. and pressure of 100-300 atm. The presence of NH 3 excess and consequent dissolved NH 3 in the solution from the synthesis zone is essential and the usual NH 3 /CO 2 ratio is from 2À3:1 to 5À5:1.</p> |
