Method for processing fine kaolin
A method for processing fine kaolin which is comprised of the steps of dispersing (Dp) kaolin by adding the chemical dispersion agent in the optimum amount required, so that the pulp reaches a minimum viscosity and a maximum dispersion of particles, and submitting same to a deaeration step (Ds), and the latter is followed by the stages of conditioning (Co), centrifugation (Ce1, Ce2), magnetic separation (Sp), chemical bleaching (Br), said method also being comprised of the steps of: (a) introducing chemical dispersion agents in said aqueous kaolin suspension after the deaeration step (Ds), so that the titanium impurities can aggregate into one another; (b) adjusting the pH of the aqueous kaolin solution by adding a suitable amount of basic reagents; (c) submitting the pulp to a vigorous agitation, so that the kaolin is fully dispersed and also the titanium particles collide against one another to form micro-aggregates.
1 . A method for processing fine kaolin, which method is comprised of the steps of dispersing (Dp) kaolin by adding the chemical dispersing agent in the optimum amount required, so that the pulp can reach a minimum viscosity and a maximum dispersion of particles, and submitting same to a deaeration step (Ds), the latter being followed by the conditioning (Co), centrifugation (Ce1, Ce2), magnetic separation (Sp), and chemical bleaching (Br) steps, said method being characterized by comprising the steps of:
(a) introducing chemical dispersing agents into said aqueous kaolin suspension after the deaeration step (Ds), so that an aggregation of the titanium impurities can take place;
(b) adjusting the pH of the aqueous kaolin solution by adding the suitable amount of basic reagents;
(c) submitting the pulp to a vigorous agitation in mixers so that the kaolin is fully dispersed and also the titanium particles collide against one another to form micro-aggregates.
2 . The method for processing fine kaolin according to claim 1 , characterized in that said pulp is subject to at least one centrifugation step (Ce1).
3 . The method for processing fine kaolin according to claim 1 , characterized in that said pulp is subject to two centrifugation steps (Ce1, Ce2).
4 . The method for processing fine kaolin according to claim 1 , characterized in that the magnetic separation step (Sp) is carried out after at least a first centrifugation (Ce1) of kaolin is carried out.
5 . The method for processing fine kaolin according to claim 1 , characterized in that the magnetic separation step (Sp) is carried out after the first and/or second centrifugation (Ce1, Ce2) of kaolin.
6 . The method for processing fine kaolin according to claim 1 , characterized in that the second centrifugation (Ce2) is carried out after the conditioning step (Co).
7 . The method for processing fine kaolin according to claim 1 , characterized in that the second centrifugation (Ce2) must be carried through at high speed.
8 . The method for processing fine kaolin according to claim 1 , characterized in that the speed of the centrifugal machines during the centrifugation steps (Ce1, Ce2) is not lower than 2,000 rpm.
9 . The method for processing fine kaolin according to claim 1 , characterized in that the high speed of the centrifugation during the centrifugation steps (Ce1, Ce2) is approximately 4,000 rpm.
10 . The method for processing fine kaolin according to claim 1 , characterized in that the solid contents of the pulp in the conditioning step (Co) is approximately 40%.
11 . The method for processing fine kaolin according to claim 1 , characterized in that the pulp in the conditioning step (Co) is subject to an agitation per approximately 30 minutes.
12 . The method for processing fine kaolin according to claim 1 , characterized in that the peripheral speed of the mixer in the conditioning step (Co) is approximately 10 m/s.
13 . The method for processing fine kaolin according to claim 1 , characterized in that the chemical dispersing agent is present in an amount at least 50% higher than the amount spent in the kaolin dispersion step (Dp).
14 . The method for processing fine kaolin according to claim 1 , characterized in that the dispersing agent is at least a low molecular weight compound, or mixtures thereof.
15 . The method for processing fine kaolin according to claim 1 , characterized in that the dispersing agent is sodium polyacrylate and sodium silicate, or a mixture thereof.
16 . The method for processing fine kaolin according to claim 1 , characterized in that the chemical dispersing agent is present in an amount at least 50% higher than the amount spent in the dispersion (1) of kaolin, of which 25% is sodium polyacrylate and 25% is sodium silicate.
17 . The method for processing fine kaolin according to claim 1 , characterized in that the pH is adjusted between 7.5 and 12, preferable between 8 and 10, by using a basic reagent.
18 . The method for processing fine kaolin according to claim 1 , characterized in that the pH is 10.
19 . The method for processing fine kaolin according to claim 1 , characterized in that sodium or potassium hydroxide is used to adjust the pH.
20 . The method for processing fine kaolin according to claim 1 , characterized in that the centrifugation steps (Ce1, Ce2) are carried out in separate centrifugal machines.
21 . The method for processing fine kaolin according to claim 1 , characterized in that the centrifugal machines are of the vertical type and/or decanter.
22 . The method for processing fine kaolin according to claim 1 , characterized in that the kaolin is treated in the chemical bleaching step (Br) by using sodium dithionite (hydrosulfite) following a 3 kg/ton ratio.
23 . The method for processing fine kaolin according to claim 1 , characterized in that the selective aggregation is carried out after the first centrifugation (Ce1).
24 . The method for processing fine kaolin according to claim 1 , characterized in that the selective aggregation is carried out after the magnetic separation (Sp) and before the second centrifugation (Ce2).