received by the International Bureau on 25 April 2019 (25.04.19)

[Claim 1] [Amended] A particle precise separation method by density,

comprising:

a process comprising two steps, a first step includes classifying or sieving particles into similar or equal size, being the size fractional difference between big and small particles smaller than the fractional density difference between the particles to separate, and a second step includes terminal velocity separation process, or particle drag difference in a fluid, to separate particles by density;

allowing the similar or equal size particles to free fall in a container filled with a fluid;

draining the falling particles to separate the falling particles by its terminal velocity;

separating the falling particles of similar or equal size by applying a counter flow fluid to its fall at a velocity between the terminal ve locities of the particles to be separated; or

using cyclone or hydro cyclone to particles classified or separated into similar or equal size to improve the separation by density.

[Claim 2] [Remains] The particle separation method of claim 1, wherein a fluid flow is facilitated through a duct or a chamber with different sizes to provide different fluid velocities through it so that the different terminal velocity of the particles suspend them at different stages of the duct or the chamber.

[Claim 3] [Amended] The particle separation method of claim 1, wherein a valve, door or compartment is activated in a fluid duct to guide the falling particles suspended in the counter flow fluid or a static fluid with settling particles flowing through it.

[Claim 4] [Remains] The particle separation method of claim 1, further

comprising an alternate fluid flow for terminal velocity separation to capture the suspended particles.

[Claim 5] Remains] The particle separation method of claim 1, further comprising setting the fluid flow velocity by calculating the terminal velocity of the falling particles considering temperature effect on fluid dynamic viscosity.

[Claim 6] [Remains] The particle separation method of claim 5, wherein the fluid flow velocity is obtained by calculating the terminal velocity of the falling particles considering the temperature effect on a fluid density of the fluid.