FIELD: medicine.
SUBSTANCE: invention relates to method of urea synthesis from ammonia and carbon dioxide with formation of ammonium carbamate as intermediate chemical compound. Method includes following stages: a) reaction of ammonia and carbon dioxide as it is or in form of ammonium carbamate in molar ratio of NH3/CO2 in range from 2.3 to 6, at temperature ranging from 140 to 215 °C and under pressure in range from 12 to 25 MPa to form first liquid mixture, containing urea, ammonium carbamate, ammonia and water; b) supply of above first liquid mixture to stage of decomposition-stripping for decomposition of, at least, multiple amount, in compliance with preferable example of present invention from 50 to 99 % of ammonium carbamate, ammonia and carbon dioxide, at operation under the same pressure, as at said reaction step (a) and at temperature within range of 160 to 240 °C, simultaneously exposing liquid mixture to stripping to form first gaseous mixture, containing ammonia and carbon dioxide, and second liquid mixture, containing urea, water, ammonia and ammonium carbamate; c) condensing at least 50 % of said first gaseous mixture at stage of condensation during operation at substantially same pressure as at said step (a) to make third liquid mixture, containing ammonium carbamate, ammonia and, possibly, urea, directly or indirectly supplied to reaction stage (a); d) extraction of urea, contained in said second liquid mixture at one or more successive stages of decomposition and separation (P) to form fourth liquid mixture, containing water, ammonia and ammonium carbamate, and, possibly, liquid phase, containing ammonia; e) supply of at least part of said fourth liquid mixture, obtained at step (d), in compliance with preferable example of present invention from 50 to 100 %, to said stage of decomposition-stripping (b), directing possibly remaining part to said reaction stage (a), or, in compliance with preferable example of present invention, to condensation stage (c). Wherein said fourth liquid mixture, fully or partially supplied to stage of decomposition-stripper (b), is preliminarily heated by heat exchange with any of said mixtures, formed at stages (a), (b) or (c). Invention also discloses method of increasing urea output and method of modifying installation for urea synthesis.
EFFECT: invention allows to increase conversion of CO2 in urea to level above 70 % without significant additional heat supply to stage of stripping process.
13 cl, 1 dwg, 1 ex
