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.
SHIMOKAWA TAKATATSU
YANAGISAWA YUZURU
TOYO ENGINEERING CORP
| JPS466769A |