Method and device for forced sieving; preparation of an intimate blend of pulverulent products

A method of preparing an intimate blend of at least two pulverulent products (PA+PD+Pi), said intimate blend having an adjusted content of at least one of said pulverulent products (PA), termed an active principle;

• said method comprising:
• forming a primary blend (PA+Pi) concentrated in said active principle(s) (PA) from said active principle(s) (PA) and at least one other pulverulent product (Pi);
• the dry milling of said primary blend (PA+Pi);
• the forced sieving of said milled primary blend (PA+Pi);
• the formation of said intimate blend (PA+Pi+PD) by dilution of said milled and sieved primary blend (PA+Pi), in a suitable amount of a dilution powder (PD) which has a single-mode granulometric spectrum, with a narrow distribution centered on a value of a few tens of microns;
• and
• wherein, for the purpose of providing said milled primary blend (PA+Pi) with a granulometric spectrum having a main mode close to that of the granulometric spectrum of said dilution powder (PD) and a proportion of micron-sized particles, said forced sieving is carried out through a rigid assembly of at least two superposed screens, in contact with each other;
• said milled primary blend (PA+Pi) successively passing through screens with an increasing aperture size;
• the aperture size of each of said screens of said rigid assembly being greater than that of a single screen, of the same type, which, when used under the same conditions, would provide said milled primary blend (PA+Pi) with a granulometric spectrum of the same type.