Method for producing particles, particles, and adsorption apparatus

1 . A method for producing particles, comprising:

preparing a liquid containing primary particles composed of a calcium phosphate-based compound and a dispersion medium;

feeding the liquid into a heated atmosphere in the form of droplets to obtain aggregates of the primary particles by removing the dispersion medium from each of the droplets and then bring the aggregates into a molten state so that the respective aggregates are formed into a spherical shape; and

solidifying the aggregates in the molten state to obtain dense secondary particles.

2 . The method for producing particles as claimed in claim 1 , wherein the heated atmosphere contains plasma produced by ionization of an ambient gas.

3 . The method for producing particles as claimed in claim 2 , wherein the plasma forms a plasma flame in the heated atmosphere; and

wherein the droplets are fed into the circumferential portion of the plasma flame.

4 . The method for producing particles as claimed in claim 3 , wherein the temperature at the circumferential portion of the plasma flame is in the range of 1,000 to 3,000° C.

5 . The method for producing particles as claimed in claim 1 , wherein the aggregates in the molten state each having the spherical shape are solidified by forcibly cooling them.

6 . The method for producing particles as claimed in claim 1 , wherein each of the obtained secondary particles has a surface with irregularities, and the surface of each secondary particle is subjected to a smoothing process to decrease or remove the irregularities.

7 . The method for producing particles as claimed in claim 6 , wherein the smoothing process includes a thermal treatment.

8 . The method for producing particles as claimed in claim 7 , wherein the temperature of the thermal treatment is in the range of 400 to 900° C.

9 . The method for producing particles as claimed in claim 1 , wherein the porosity of the obtained secondary particles is 5% or less.

10 . The method for producing particles as claimed in claim 1 , wherein an average particle diameter of the obtained secondary particles is in the range of 0.5 to 20 μm.

11 . The method for producing particles as claimed in claim 1 , wherein an average roundness coefficient C of the obtained secondary particles represented by the following formula (I) is in the range of 0.8 to 0.99:

C= 4 πS/L 2   ( I )

wherein S (μm 2 ) represents an area of a projection image of a particle as a measuring object, and L (μm) represents a circumferential length of the projection image of the particle.

12 . The method for producing particles as claimed in claim 1 , wherein the calcium phosphate-based compound includes hydroxyapatite or tricalcium phosphate.

13 . Particles produced by the method for producing particles defined by claim 1 .

14 . An adsorption apparatus, comprising:

a column having a filling space, and

an adsorbent filled in the filling space, the adsorbent including the particles defined by claim 13.