Processs and plant for production of urea with differentiated yield reaction spaces.

Processs and plant for production of urea with differentiated yield reaction spaces.

  • CN 1,034,014 C
  • Filed: 08/11/1992
  • Issued: 02/12/1997
  • Est. Priority Date: 11/14/1991
  • Status: Active Grant
First Claim
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1. A process for the preparation of urea in a plant comprising at least one reaction zone for reacting ammonia with carbon dioxide at high temperature and pressure and a recovery zone for recovering the unreacted reactants, the process comprising the steps of:

  • (a) reacting high purity ammonia with carbon dioxide in a first reaction zone (R-1) at a predetermined pressure and temperature sufficient to effect the reaction;

    (b) flash separating the product stream of the first reaction section (R-1) into a gaseous stream and a liquid stream;

    (c) in the second reaction zone (R-2), at a pressure of less than 200kg/cm2At a pressure and at a temperature sufficient to carry out the reaction, the gaseous stream obtained as above is reacted with the recycle carbamate solution coming from the recovery zone;

    (d) feeding the liquid streams from said first and second reaction sections (R-1, R-2) to a recovery section, decomposing the liquid streams in the recovery section and recovering the urea solution therein,characterized in that high-purity ammonia and carbon dioxide are reacted in the first reaction stage (R-1) under the following conditions;

    a1) under adiabatic conditions, the pressure is higher than 300kg/cm2At a temperature above 200 ℃ and

    an ammonia/carbon dioxide ratio above 4, ora2) Below 300kg/cm2Part of the heat of reaction is removed under pressure at a temperature not higher than about 200 ℃ and

    at an ammonia/carbon dioxide ratio lower than 4.

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