Patent ID: 7504534

Claim:
A process for removal of water from an aqueous starting solution comprising N-(phosphonomethyl)glycine product and crystallization N-(phosphonomethyl)glycine product therefrom, the process comprising: introducing an aqueous evaporation feed mixture into an evaporation zone of a crystallizer, said feed mixture comprising said aqueous starting solution; evaporating water from said feed mixture in said evaporation zone in the presence of solid particulate N-(phosphonomethyl)glycine product, thereby producing a vapor phase comprising water vapor, precipitating N-(phosphonomethyl)glycine product from the aqueous liquid phase, and producing an evaporation product comprising N-(phosphonomethyl)glycine product solids and a mother liquor that is substantially saturated or supersaturated in N-(phosphonomethyl)glycine product; removing N-(phosphonomethyl)glycine product solids and mother liquor obtained in the evaporation product from the crystallizer; and maintaining a ratio of particulate N-(phosphonomethyl)glycine product solids to mother liquor in said evaporation zone which exceeds the ratio of N-(phosphonomethyl)glycine product solids incrementally produced by the effects of evaporation to mother liquor incrementally produced thereby, wherein maintaining said ratio of particulate N-(phosphonomethyl)glycine product solids to mother liquor in said evaporation zone comprises controlling the relative rates mother liquor and N-(phosphonomethyl)glycine product solids obtained in the evaporation product are removed from the crystallizer.