| abstract |
Process for making a powder or granule containing at least one chelating agent selected from alkali metal salts of methyl glycine diacetic acid (MGDA) and glutamic acid diacetate (GLDA) and iminodisuccinic acid (IDS), said process comprising the steps of (a) introducing an aqueous solution or aqueous slurry of the respective chelating agent (A) into a spray-dryer or spray-granulator, and removing most of said water by spray-drying or spray granulation using a gas with an inlet temperature of 125 to 250°C, (b) withdrawing powder or granules, respectively, from the spray-dryer or spray-granulator, respectively, (c) separating off fines from said powder or granules, wherein said fines have a maximum particle diameter of 350 µm, (d) separating off lumps from said powder or granules, wherein said lumps have a particle diameter of 1,500 µm or more, (e) milling said lumps to a maximum particle diameter of 500 µm, (f) re-introducing said fines from step (c) and milled lumps from step (e) into the spray-dryer or spray-granulator, wherein the share of fines is in the range of from 0.5 to 20 % by weight of the total chelating agent (A) withdrawn in step (b) and the share of milled lumps is in the range of from 5 to 60% by weight of the total chelating agent (A) withdrawn in step (b). |