Harmless treatment process of electrolytic aluminium scum

Abstract

The invention discloses a harmless treatment process of electrolytic aluminium scum and belongs to the technical field of solid waste cyclic utilization in the aluminium electrolysis industry. The harmless treatment process comprises the following steps: aluminium scum after crushing and impurity removal, a catalyst (mixture of nitrate of potash and sodium chloride) and a reactant (mixture of positive cryolite and metallurgical-grade aluminium oxide) are uniformly mixed, and in a combustion furnace, nitrate of potash generates decomposition when burns at 600-760 DEG C to generate combustion-supporting gas namely oxygen so as to enable carbon in the aluminium scum to fully burn; sodium chloride has an accelerating and catalytic action on decomposition of ammonium nitrate category substances; and the metallurgical-grade aluminium oxide can effectively adsorb melted sub cryolite and fluoride salt. With adoption of the harmless treatment process, in burnt aluminium scum residual ash, the carbon content is 3%, and regeneration electrolyte is obtained through molecular ratio adjustment; in burnt exhaust gas, content of fluoride salt is less than 3mg / m3, content of dust particle is less than 20mg / m3, and the burnt aluminium scum residual ash can be directly discharged to the atmosphere after being connected into an aluminium electrolysis exhaust gas purifying system through purification, so that the harmless treatment purpose of electrolytic aluminium scum is realized.

Description

technical field

[0001] The invention belongs to the technical field of solid waste recycling in the aluminum electrolysis industry, in particular to a harmless treatment process for electrolytic aluminum dross. technical background

[0002] At present, the prebaked anode carbon blocks used in aluminum electrolytic cells are all made of carbon materials kneaded and roasted. During the aluminum electrolysis reaction, due to the inhomogeneity of the carbon material in the anode carbon block, the generation of carbon slag in the liquid aluminum electrolyte is inevitable. The carbon slag floating in the aluminum electrolyte, that is, aluminum dross, will lead to the anode effect of aluminum electrolysis, and at the same time will increase the voltage of the aluminum electrolyte, reduce the current efficiency of aluminum electrolysis, and increase the power consumption per ton of aluminum.

[0003] After analysis and research, the main components of aluminum dross are carbon powd...

Examples

Embodiment 1

[0025] (1) Use a ball mill to crush the electrolytic aluminum scum to a particle size of 0.1mm, and then use a 0.25m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum scum is 0.25%;

[0026] (2) Use a mixture of 73% potassium nitrate and 27% sodium chloride as a catalyst, a mixture of 70% ortho-cryolite and 30% metallurgical grade alumina as a reactant, and crush the catalyst and reactant to particle size through a ball mill 0.1mm;

[0027] (3) The aluminum dross after impurity removal in step (1), the catalyst and reactants in step (2) are transported to the mixer through the conveyor, and a uniform mixed material is prepared at a mass ratio of 6 : 0.7 : 3.3 ;

[0028] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 600°C for 8 minutes to obtain residual aluminum dross ashes and combustion flue gas; the carbon content in the residual aluminum dross ashes i...

Embodiment 2

[0031] (1) Use a ball mill to crush the electrolytic aluminum scum to a particle size of 0.25mm, and then use a 0.3m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum scum is 0.27%;

[0032] (2) A mixture of 82% potassium nitrate and 19% sodium chloride is used as a catalyst, a mixture of 80% ortho-cryolite and 20% metallurgical grade alumina is used as a reactant, and the catalyst and reactant are crushed to particle size by a ball mill 0.25mm;

[0033] (3) The aluminum dross after impurity removal in step (1), the catalyst and the reactant in step (2) are transported to the mixer through a conveyor, and a uniform mixed material is prepared at a ratio of 7:1:3;

[0034] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 760° C. for 13 minutes to obtain residual ash of aluminum scum and combustion flue gas; the carbon content in the residual ash of aluminum scu...

Embodiment 3

[0037] (1) Use a ball mill to crush the electrolytic aluminum dross to a particle size of 0.2mm, and then use a 0.3m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum dross is 0.29%;

[0038] (2) A mixture of 81% potassium nitrate and 19% sodium chloride is used as a catalyst, a mixture of 85% ortho-cryolite and 15% metallurgical grade alumina is used as a reactant, and the catalyst and reactant are crushed to particle size by a ball mill 0.2mm;

[0039] (3) The aluminum dross after impurity removal in step (1), the catalyst and the reactant in step (2) are transported to the mixer through a conveyor, and a uniform mixed material is prepared at 8:1.2:0.8;

[0040] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 700°C for 15 minutes to obtain residual aluminum dross ashes and combustion flue gas; the carbon content in the residual aluminum dross ashes is 2.5 ...

technical field

[0001] The invention belongs to the technical field of solid waste recycling in the aluminum electrolysis industry, in particular to a harmless treatment process for electrolytic aluminum dross. technical background

[0002] At present, the prebaked anode carbon blocks used in aluminum electrolytic cells are all made of carbon materials kneaded and roasted. During the aluminum electrolysis reaction, due to the inhomogeneity of the carbon material in the anode carbon block, the generation of carbon slag in the liquid aluminum electrolyte is inevitable. The carbon slag floating in the aluminum electrolyte, that is, aluminum dross, will lead to the anode effect of aluminum electrolysis, and at the same time will increase the voltage of the aluminum electrolyte, reduce the current efficiency of aluminum electrolysis, and increase the power consumption per ton of aluminum.

[0003] After analysis and research, the main components of aluminum dross are carbon powd...

Examples

Embodiment 1

[0025] (1) Use a ball mill to crush the electrolytic aluminum scum to a particle size of 0.1mm, and then use a 0.25m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum scum is 0.25%;

[0026] (2) Use a mixture of 73% potassium nitrate and 27% sodium chloride as a catalyst, a mixture of 70% ortho-cryolite and 30% metallurgical grade alumina as a reactant, and crush the catalyst and reactant to particle size through a ball mill 0.1mm;

[0027] (3) The aluminum dross after impurity removal in step (1), the catalyst and reactants in step (2) are transported to the mixer through the conveyor, and a uniform mixed material is prepared at a mass ratio of 6 : 0.7 : 3.3 ;

[0028] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 600°C for 8 minutes to obtain residual aluminum dross ashes and combustion flue gas; the carbon content in the residual aluminum dross ashes i...

Embodiment 2

[0031] (1) Use a ball mill to crush the electrolytic aluminum scum to a particle size of 0.25mm, and then use a 0.3m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum scum is 0.27%;

[0032] (2) A mixture of 82% potassium nitrate and 19% sodium chloride is used as a catalyst, a mixture of 80% ortho-cryolite and 20% metallurgical grade alumina is used as a reactant, and the catalyst and reactant are crushed to particle size by a ball mill 0.25mm;

[0033] (3) The aluminum dross after impurity removal in step (1), the catalyst and the reactant in step (2) are transported to the mixer through a conveyor, and a uniform mixed material is prepared at a ratio of 7:1:3;

[0034] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 760° C. for 13 minutes to obtain residual ash of aluminum scum and combustion flue gas; the carbon content in the residual ash of aluminum scu...

Embodiment 3

[0037] (1) Use a ball mill to crush the electrolytic aluminum dross to a particle size of 0.2mm, and then use a 0.3m filter screen to remove impurities. After the removal of impurities, the content of Fe in the electrolytic aluminum dross is 0.29%;

[0038] (2) A mixture of 81% potassium nitrate and 19% sodium chloride is used as a catalyst, a mixture of 85% ortho-cryolite and 15% metallurgical grade alumina is used as a reactant, and the catalyst and reactant are crushed to particle size by a ball mill 0.2mm;

[0039] (3) The aluminum dross after impurity removal in step (1), the catalyst and the reactant in step (2) are transported to the mixer through a conveyor, and a uniform mixed material is prepared at 8:1.2:0.8;

[0040] (4) Transport the mixed material in step (3) to the combustion furnace through a conveyor, and burn at 700°C for 15 minutes to obtain residual aluminum dross ashes and combustion flue gas; the carbon content in the residual aluminum dross ashes is 2.5 ...