Japanese Patent JPH0460106

B2

PURPOSE:To calculate urea concentration from the crystallization temperature and suppress the amount thereof to a given value or below, by introducing partially an absorbing solution obtained by absorbing a mixed gas separated from a urea synthesis solution one after another into a constricted path having a constricted part while cooling the solution at a regular interval. CONSTITUTION:The unreacted ammonium carbamate contained in a urea synthesis solution is decomposed and separated as a mixed gas containing NH3, CO, steam and a very small amount of urea, passed through a line 1, led to an absorption column 2 and absorbed in an absorption medium, and the resultant absorbing solution is circulated through a urea synthesis region 17. In the process, the absorbing solution is partially passed through a line 9 and a water bath 10 and cooled at a given temperature interval. The cooled absorbing solution is then led to a constricted path 4 having one - several constricted parts, and part or all of the urea in the above-mentioned solution is crystallized to measure the crystallization temperature from the change in temperature (T3) in the constricted path 14 or near there. Thus, the concentration of the above-mentioned solution is measured from the correction between the crystallization temperature and concentration, and the concentration in the absorbing solution is suppressed to a given value or below. The crystallized urea is then dissolved under heating and returned to the line 1.

KAWABE TOYOTARO
ITAYA MASATO
MASUYUKI YASURO
YOSHAMA TETSUO

JP11937884A

September 25, 1992

June 11, 1984

Click for automatic bibliography generation  

MITSUI TOATSU CHEMICALS

C07C273/04; C07C67/00; C07C239/00

Next Patent: JPH0460107