JP3206995B2 - Dispersion method of alkaline slurry and ball mill for dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball mill for slurry dispersion and a slurry dispersion method using the ball mill. In particular, the present invention relates to a method for dispersing a highly alkaline aqueous slurry and a ball mill used for the dispersion.

[0002]

2. Description of the Related Art Conventionally, a ball mill has been employed as an apparatus for finely pulverizing a solid contained in a slurry in a suspended state and dispersing the solid in a liquid medium. This ball mill is composed of a cylindrical vessel having a slurry inlet at one end and a slurry outlet at the other end, and a rotor rotatably arranged in the vessel. Is formed with a stirring member such as a rotor pin projecting outward in the radial direction. The vessel is filled with balls such as glass beads and steel balls, and the slurry is pumped into the vessel from the inlet at one end of the vessel and sent out from the outlet at the other end of the vessel. During this time, the solid suspended in the slurry is subjected to a frictional action between the balls, broken into fine particles, and dispersed in the slurry medium.

[0003] When the substance used as a dispersing agent or a grinding aid is an aqueous alkaline solution, there is a problem that the components of the ball mill, for example, vessels and rotors, are corroded. In general, chromium-nickel stainless steel is considered to be superior in corrosion resistance to alkaline aqueous solutions, and in consideration of the conditions of use of a ball mill, 18Cr-8Ni stainless steel is conventionally used for the vessel and rotor of a ball mill. Had been used.

[0004]

In the structure of the conventional ball mill, particularly, the rotor portion is severely worn, so that a problem of metal contamination to the slurry has occurred.
The present invention solves such a problem in dispersing an aqueous alkaline slurry, a dispersion method having less contamination with respect to the aqueous alkaline slurry, and a dispersion method having higher corrosion resistance and abrasion resistance than the conventional method and the same. It is intended to provide a ball mill for dispersion.

[0005]

According to the present invention, in dispersing an aqueous alkaline slurry, a cylindrical vessel having a slurry inlet at one end and a slurry outlet at the other end is provided. And a rotor rotatably arranged in the vessel, a stator pin protruding radially inward on the inner surface of the vessel,
A stirring member is provided on the outer surface of the rotor, and at least the rotor of the vessel and the rotor of the ball mill filled with the balls for dispersion is filled with 15 to 30 chrome.
% Of cast iron is heat-treated so as to have a hardness of HRC 57 or more, and is made of a material in which chromium carbide is dispersed.

Further, the present invention provides a ball mill suitable for the above method. That is, the ball mill according to the present invention is for performing dispersion using an aqueous alkaline slurry as a slurry, a cylindrical inlet having a slurry inlet at one end and a slurry outlet at the other end, A rotor rotatably disposed in the vessel, a stator pin protruding radially inward on the inner surface of the vessel, and a stirring member provided on the outer surface of the rotor, and the inside was filled with dispersion balls. It is characterized in that at least the rotor of the vessel and the rotor is made of cast iron containing 15 to 30% of chromium, having a hardness of HRC 57 or more, and having chromium carbide dispersed therein.

[0007]

According to the present invention, a chromium-carbon cast iron, which has been considered to be less corrosion-resistant to alkali than chromium-nickel stainless steel in the prior art, is used for a ball mill. This cast iron has been heat-treated to have a hardness of HRC 57 or more. When having such a high hardness, the corrosion resistance and abrasion resistance to alkali are superior to those of ordinary chromium-nickel stainless steel. I have. Chromium in cast iron strengthens the iron matrix and forms chromium carbide to improve material hardness.

If the chromium content is less than 15%, the corrosion resistance is insufficient, the hardness is low, and sufficient wear resistance cannot be obtained. As the chromium content increases, the chromium carbide increases and the hardness and wear resistance improve, but the chromium carbide having a lower hardness (Cr ₂₃ C ₆ or Cr ₇ C
_Since the amount of ₃ ) is increased, the hardness is lowered and the effect is not accompanied by the increased amount of chromium.

[0009] Carbon is contained in an amount of about 1 to 3% depending on the chromium content. Further, in addition to the above composition, IVa, Va,
Similar effects can be obtained with cast iron containing several percent of elements selected from the group VIa. When the hardness in the vicinity of the surface of the heat-treated cast iron is HRC 57% or more, the wear resistance is good, and if the hardness is less than that, a satisfactory effect cannot be obtained.
Therefore, when the ball mill of the present invention is used, corrosion and wear of the vessel and the rotor are suppressed, and the problem of metal contamination can be greatly reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The ball mill shown in the drawing has a cylindrical vessel 1, and both ends of the vessel 1 are closed by end plates 2, 3, respectively. A rotor 4 is arranged in the vessel 1,
The shaft 5 of the rotor 4 extends through the end plate 3 to the outside. A water jacket 6 is formed on the wall of the vessel 1 and on the end plate 2 to circulate cooling water in the wall of the vessel 1. The end plate 2 has a cooling water inlet 6a and the vessel 1
The cooling water outlet 6b is formed in the upper end part of each. Although not shown, a cooling water circulation passage is also formed in the rotor 4, and cooling water is circulated through the shaft 5.

A plurality of disk portions 7 are provided on the rotor 4 at intervals in the axial direction, and rotor pins 7a are implanted so as to protrude from the edge of the disk portion 7. Vessel pins 1a are implanted on the inner wall of the vessel 1 so as to be staggered with respect to the rotor pins 7a at axial positions. The rotor pin 7a and the vessel pin 1a are made of cemented carbide in consideration of wear resistance. The rotor 4 is rotationally driven by a drive motor provided outside.

The vessel 1 is filled with beads such as glass beads and hard spheres. A slurry inlet 8 is formed below the vessel 1, and a slurry outlet 3 b having a bead separating mechanism 9 is provided between the end plate 3 at the upper end of the vessel 1 and the rotor 4. The end plate 3 has a slurry discharge passage 3a and a slurry discharge port 3b. In operation, an aqueous slurry containing solid particles to be dispersed is pumped from the inlet 8 while driving the rotor 4. The slurry flows between the beads stirred by the rotor pins 7a, and moves toward the discharge port 9 while undergoing a frictional action between the beads. During this time, the solid particles in the slurry are pulverized to a fine powder and dispersed in the slurry medium.

The slurry comprises an aqueous alkali solution as a dispersant and a dispersing aid, and solid particles. Further, since the ball mill is cooled by the cooling water circulating in the vessel 1 and the rotor 4 as described above, the slurry temperature inside is 8.
It can be kept below 0 ^° C. Under these conditions,
As a material for the vessel 1 and the rotor 4, the inventors have found that chromium-based cast iron heat-treated to a predetermined hardness has better corrosion resistance to alkali than chromium-nickel stainless steel. Therefore, in this embodiment of the present invention, the inner wall material of the vessel 1 and the material of the rotor 4 and the material of the disk 7 provided on the rotor contain 15 to 30% of chromium and have a hardness of HRC 57 or more. It is formed of a heat-treated cast iron material. With the configuration of the embodiment of the present invention, the vessel 1 and the rotor 4 are
Compared with a ball mill formed of 8-chromium nickel stainless steel, the wear at the tip of the rotor 4 can be greatly reduced, and the problem of metal contamination of the slurry can be reduced. Experimental Example As an example of the present invention, a rotor 4 including a disk portion 7 of a ball mill was manufactured from cast iron of 20% Cr-2% C. The hardness of the rotor 4 was set to HRC 60 by heat treatment. As a comparative example, the rotor 4 was made of 18Cr-8Ni stainless steel as usual. The diameter of the rotor is 160 mm. A cemented carbide was used for the rotor pin 7a and the vessel pin 1a. Hard balls were filled in a ball mill using the rotor 4, and the test was performed by feeding a test solution containing 20% of graphite as solid particles to an aqueous ammonia solution of PH10, and the rotor was operated to check the worn state of the rotor.

As a result of the test, after 100 hours of operation, the wear of the rotor of the comparative example was 1.5 mm, while the wear of the rotor of the example of the present invention was about 1/20, that is, 0.08 mm. .

[0015]

According to the present invention, the corrosion and wear of the rotor due to alkali can be significantly reduced as compared with the conventional ball mill. Further, the material is cheaper than conventionally used chromium-nickel stainless steel, and the manufacturing cost of the ball mill can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an example of a ball mill to which the present invention is applied.

[Explanation of symbols]

1 is a vessel, 1a is a vessel pin, 4 is a rotor, 7a
Is a rotor pin.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-225746 (JP, A) JP-A-4-185697 (JP, A) JP-A-3-123541 (JP, U) 56825 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01F ^7/ 00-7/32

Claims (2)

(57) [Claims] 1. A cylindrical vessel having a slurry inlet at one end and a slurry outlet at the other end, a rotor rotatably disposed in the vessel, and a radius inside the vessel. A stator pin is provided which protrudes inward in the direction, a stirring member is provided on the outer surface of the rotor, and a ball mill filled with balls for dispersion is used therein, and slurry is introduced from the slurry introduction port. In the slurry dispersing method of dispersing the slurry by pumping toward the discharge port while rotating, using an alkaline slurry as the slurry, at least the rotor of the vessel and the rotor, carbon, 15-30% chromium
A method for dispersing an alkaline slurry, comprising using a material formed by dispersing chromium carbide by heat-treating contained cast iron so as to have a hardness of at least HRC 57. 2. A cylindrical vessel having a slurry inlet at one end and a slurry outlet at the other end, and a rotor rotatably disposed in the vessel, wherein an inner surface of the vessel has a radius. In order to perform dispersion using an aqueous alkaline slurry as a slurry in a ball mill in which a stator pin is provided that protrudes inward in the direction, a stirring member is provided on the outer surface of the rotor, and balls for dispersion are filled inside. Wherein at least the rotor of the vessel and the rotor is formed of cast iron containing carbon and containing 15 to 30% of chromium, having a hardness of HRC 57 or more and chromium carbide dispersed therein. , Ball mill for dispersion.