Process for recycling spent pot linings (SPL) from primary aluminium production

1. A process for recycling spent pot lining (SPL) from primary aluminium production cells, the SPL being obtained by the method comprising:

disassembling the linings from the used cell cathodes in cuts or fractions, said fractions comprising refractory materials, carbonaceous materials and other materials like insulators and iron bars;

grinding each of the separated fractions or cuts; and

separating the materials of said fractions by mechanical treatment including sizing means, sieves and magnetic systems for separating iron particles,

and wherein the process for recycling the SPL comprises:

i. mixing salts slags recycled from aluminium refining with separated SPL materials to form a reaction mixture in a reactor, or mixing SPL and salt slags prior to feeding the obtained mixture in a reactor, and maintaining the temperature of the reaction mixture in the reactor within the range from 90 to 95° C.;

ii. reacting the mixture of salt slags and SPL with water at a basic pH so as to obtain a solution liquor of dissolved salt slag/SPL material and an undissolved fraction;

iii. sedimenting said solution liquor;

iv. eliminating cyanides from the solution liquor by adding sodium hypochlorite;

v. filtering the solution liquor to obtain a soluble fraction and another insoluble fraction;

vi. washing the insoluble fraction separated in the filtering step;

vii. crystallizing salts of the soluble fraction in the solution liquor by means of water evaporation, and

viii. aging or conditioning the insoluble fraction;

wherein the salt slags are mixed with SPL at a 3:1 ratio.

2. The process for recycling SPL from primary aluminium production according to claim 1 , wherein nitrides, aluminium, carbides and sulfides are eliminated and gases are also given off.

3. The process for recycling SPL from primary aluminium production according to claim 1 , wherein the crystallization is carried out by means of evaporation by heating.

4. The process for recycling SPL from primary aluminium production according to claim 1 , wherein the aging is carried out by means of analyzing the components and dehydrating by decanting.

5. A process for recycling spent pot lining (SPL) from primary aluminium production cells, the SPL being obtained by the method comprising:

disassembling the linings from the used cell cathodes in cuts or fractions, said fractions comprising refractory materials, carbonaceous materials and other materials like insulators and iron bars;

grinding each of the separated fractions or cuts; and

separating the materials of said fractions by mechanical treatment including sizing means, sieves and magnetic systems for separating iron particles,

and wherein the process for recycling the SPL comprises:

i. mixing salts slags recycled from aluminium refining with separated SPL materials to form a reaction mixture in a reactor, or mixing SPL and salt slags prior to feeding the obtained mixture in a reactor, and maintaining the temperature of the reaction mixture in the reactor within the range from 90 to 95° C.;

ii. reacting the mixture of salt slags and SPL with water at a basic pH so as to obtain a solution liquor of dissolved salt slag/SPL material and an undissolved fraction;

iii. sedimenting said solution liquor;

iv. eliminating cyanides from the solution liquor by adding sodium hypochlorite;

v. filtering the solution liquor to obtain a soluble fraction and another insoluble fraction:

vi. washing the insoluble fraction separated in the filtering step;

vii. crystallizing salts of the soluble fraction in the solution liquor by means of water evaporation, and

viii. aging or conditioning the insoluble fraction;

wherein the reaction is carried out in closed reactors with an inert atmosphere with stirring.

6. A process for recycling spent pot lining (SPL) from primary aluminium production cells, the SPL being obtained by the method comprising:

disassembling the linings from the used cell cathodes in cuts or fractions, said fractions comprising refractory materials, carbonaceous materials and other materials like insulators and iron bars;

grinding each of the separated fractions or cuts; and

separating the materials of said fractions by mechanical treatment including sizing means, sieves and magnetic systems for separating iron particles,

and wherein the process for recycling the SPL comprises:

i. mixing salts slags recycled from aluminium refining with separated SPL materials to form a reaction mixture in a reactor, or mixing SPL and salt slags prior to feeding the obtained mixture in a reactor, and maintaining the temperature of the reaction mixture in the reactor within the range from 90 to 95° C.;

ii. reacting the mixture of salt slags and SPL with water at a basic pH so as to obtain a solution liquor of dissolved salt slag/SPL material and an undissolved fraction;

iii. sedimenting said solution liquor;

iv. eliminating cyanides from the solution liquor by adding sodium hypochlorite;

v. filtering the solution liquor to obtain a soluble fraction and another insoluble fraction;

vi. washing the insoluble fraction separated in the filtering step;

vii. crystallizing salts of the soluble fraction in the solution liquor by means of water evaporation, and

viii. aging or conditioning the insoluble fraction;

wherein the dissolution is carried out at a pH within the range from 11 to 12.