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    CONCENTRATION OF AQUEOUS UREA SOLUTION
    2.
    发明专利
    CONCENTRATION OF AQUEOUS UREA SOLUTION 失效

    公开(公告)号：JPS5643257A

    公开(公告)日：1981-04-21

    申请号：JP11737179

    申请日：1979-09-14

    Applicant: MITSUI TOATSU CHEMICALS ,  TOYO ENGINEERING CORP

    Inventor： SAIDA TOYOYASU ,  SHIMOKAWA TAKATATSU ,  YANAGISAWA YUZURU

    IPC: C07C273/16 ,  C07C67/00 ,  C07C239/00

    Abstract: PURPOSE:A concentrated aqueous solution of urea is made to flow down through a packed zone where specific packings are regularaly filled and brought into contact with hot air flows cocurrently or countercurrently, thus effecting concentration in a short time with reduced biuret formed. CONSTITUTION:A group of tubes are vertically cut at every appropriate length and they are piled up by sliding them at a certain pitch so that the axis of tubes becomes horizontal. A concentrated urea solution in water is made to flow down through the pipe-packed zone and brought into contact with a hot air flow cocurrently or countercurrently to increase the concentration over 99.5wt%. The cross section of each tube is preferably hexagonal or tetragonal. These packings are filled so as not to form short cuts, whereby the solution and hot air flow in zig-zag to cause strong agitation and rapid diffusion of the steam into the hot air with the urea solution concentrated in a short time.

    CONCENTRATION OF AQUEOUS UREA SOLUTION
    8.
    发明专利
    CONCENTRATION OF AQUEOUS UREA SOLUTION 失效

    公开(公告)号：JPS5643256A

    公开(公告)日：1981-04-21

    申请号：JP11737079

    申请日：1979-09-14

    Applicant: MITSUI TOATSU CHEMICALS ,  TOYO ENGINEERING CORP

    Inventor： SAIDA TOYOYASU ,  SHIMOKAWA TAKATATSU ,  YANAGISAWA YUZURU ,  NAGAHAMA TAKASHI ,  ISHIDA KOUSHI

    IPC: C07C273/00 ,  C07C67/00 ,  C07C239/00 ,  C07C273/16

    Abstract: PURPOSE:After it has been brought into contact with a hot air flow countercurrently in the first stage, the urea aqueous solution is brought into contact with another hot air flow cocurrently in the packed zone in the second stage to reduce the back mixing of the urea solution and the formation of biuret, thus effecting the concentration of the urea aqueous solution. CONSTITUTION:For example, in the first stage, an aqueous urea solution of 70- 90wt% concentration from the urea purification system is fed to the top of the evaporator 12. The thin films of the urea solution flowing down on the inner surface of conduits 2 are brought into contact with hot air flow from line 5 to line 6 countercurrently so that the concentration rises up to 95-99wt%. Subsequently, in the second stage, the aqueous urea solution from the first stage is brought into contact with another hot air flow from line 15 to line 8 cocurrently in the packed layer 7 so that the concentration comes up over 99.5wt% and the product is taken out of line 9. The packed layer is preferably a regularly packed one, because it increases the vaporizing speed.

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