Method for preparing a fertilizer

Abstract

An oligomethylene urea product usable as a fertilizer can be more efficiently prepared in several steps by: a) introducing at least urea and an aqueous solution of formaldehyde in the overall molar ratio of urea to formaldehyde of the step 1:1-2:1 into a reactor with a retention time of at least 0.5 h, a temperature maintained in the range of 40 to 95° C. and a pH maintained in the range of 6.5 to 11, in order to produce a methylol urea composition, b) conducting the methylol urea composition to a second reactor with a temperature maintained in the range of 5 to 35° C. and a pH maintained in the range of 1.8 to 3.5, in order to produce a first oligomethylene urea slurry, and optionally, c) conducting the methylol urea composition or the first oligomethylene urea slurry to a third reactor with a temperature maintained in the range of 5 to 35° C. and a pH maintained in the range of 1.8 to 3.5, to produce a second oligomethylene urea slurry, d) conducting the oligomethylene urea slurry, selected from the first and the second oligomethylene urea slurry, to a filter and filtering it to form an oligomethylene urea precipitate and a filtrate, e) recycling the filtrate to the reactor, selected from the second and the third reactor, and f) neutralizing and drying the oligomethylene precipitate and recovering it as said oligomethylene urea product.

Dependencies are inferred from the claim text.