公开(公告)号：US3105093A

公开(公告)日：1963-09-24

申请号：US81090559

申请日：1959-05-04

Applicant: STAMICARBON

Inventor： ROTHKRANS LEONARDUS J

IPC: C07C273/04 ,  G05D23/00

CPC classification number: C07C273/04 ,  G05D23/00

公开(公告)号：US2826612A

公开(公告)日：1958-03-11

申请号：US55682856

申请日：1956-01-03

Applicant: STAMICARBON

Inventor： KLAAS OVER ,  ROTHKRANS LEONARDUS J

IPC: B01D9/00 ,  B01J2/30 ,  C05C9/00 ,  C07C273/16

CPC classification number: C07C273/16 ,  B01D9/0018 ,  B01D9/005 ,  B01J2/30 ,  C05C9/00 ,  Y10S159/04 ,  Y10S159/20 ,  C05G3/0088

Abstract: In the preparation of urea crystals from aqueous solutions having a concentration of at least 80 weight per cent of urea by propelling the solution through a vessel (or series of vessels) wherein the water is evaporated, a surface-active agent is added to the solution in such quantity that the material passes through the evaporating vessel(s) in the form of a thick froth. With urea solutions having a concentration of 90 weight per cent or more, the evaporation of water can take place by means of the heat of crystallization, i.e. no external heat being applied. In an example, a 90 per cent solution of urea at 107 DEG C. was fed at 400 kg. per hour through a vessel (length 4 m.) provided with a bladed shaft, which was rotated at 77 r.p.m. There was also fed into the vessel 1.65 kg. per hour of a 16 per cent solution of the sodium-sulphate ester of lauryl alcohol. The vessel was filled with a thickly-frothing, slowlymoving mass; and dry crystals of urea were discharged. About 54 per cent of the crystals had a size greater than 1 m.m.; and 38 per cent had a size between 1.0 and 0.5 m.m. Other frothing agents referred to are the sodium salt of an alkyl - aryl - sulphonic acid, sodium stearate, lauryl pyridine chloride, and alkylphenyl polyglycol ether.