The present invention discloses a method for detoxifying chromium slag by using high sulfur coal. The method includes: sieving chromium slag into coarse-grained chromium slag and fine-grained chromium slag, air-drying and crushing both the coarse-grained chromium slag and the fine-grained chromium slag; separately mixing the crushed coarse-grained chromium slag and fine-grained chromium slag with the crushed high sulfur coal uniformly; adjusting pH values of a coarse-grained slag mixture and a fine-grained slag mixture to 8.0-11.0 and moisture content thereof to 12%-18%; conducting reduction on the treated coarse-grained slag mixture and fine-grained slag mixture, where the reduction temperature of the fine-grained slag mixture is 500-700 C., the reduction time of the fine-grained slag mixture is 10-30 min, the reduction temperature of the coarse-grained slag mixture is 800-1000 C., the reduction time of the coarse-grained slag mixture is 10-30 min; after the reduction, conducting water quenching, and discharging the product.

A system and method for recovering a high yield of low carbon ferrochrome from chromite and low carbon ferrochrome produced therefrom. A stoichiometric mixture of feed materials including scrap aluminum granules, lime, silica sand, and chromite ore are provided into a plasma arc furnace. The scrap aluminum granules are produced from used aluminum beverage containers. The feed materials are heated, whereupon the aluminum in the aluminum granules produces an exothermic reaction reducing the chromium oxide and iron oxide in the chromite to produce molten low carbon ferrochrome with molten slag floating thereon. The molten low carbon ferrochrome is extracted, solidified and granulated into granules of low carbon ferrochrome. The molten slag is extracted, solidified and granulated into granules of slag.

A method and system for recovering a high yield of low carbon ferrochrome from chromite and low carbon ferrochrome produced by the method. A stoichiometric mixture of feed materials including scrap aluminum granules, lime, silica sand, and chromite ore are provided into a plasma arc furnace. The scrap aluminum granules are produced from used aluminum beverage containers. The feed materials are heated, whereupon the aluminum in the aluminum granules produces an exothermic reaction reducing the chromium oxide and iron oxide in the chromite to produce molten low carbon ferrochrome with molten slag floating thereon. The molten low carbon ferrochrome is extracted, solidified and granulated into granules of low carbon ferrochrome. The molten slag is extracted, solidified and granulated into granules of slag.

A method for extracting and recycling chromium from hexavalent chromium-containing residues includes the following steps: 1) adding water to the hexavalent chromium-containing residues and mixing uniformly; 2) adding sodium sulfate, sodium chlorate and sulfuric acid to a solution obtained in step 1) and stirring sufficiently to obtain a mixed liquid; 3) treating the mixed liquid by a hydrothermal method or direct heating; 4) after the heating treatment, naturally cooling a solid-liquid mixture to room temperature for holding; 5) separating solid residues and a chromium-containing supernatant, and washing filtered residues with water and then drying; 6) precipitating the supernatant and the water used for washing the filtered residues with a precipitant CaCl2, then centrifugally washing, dewatering and drying the precipitates; and 7) recycling a chromium-containing solution for returning to a work section, or for a treatment of recycling chromium.

A process for recovering chromium from hexavalent chromium-containing wastewater comprises the following steps: (1) extracting hexavalent chromium in wastewater to an organic phase by using an extracting agent, and separating hexavalent chromium from a water phase, so as to acquire a hexavalent chromium-loaded organic phase; (2) reducing the hexavalent chromium-loaded organic phase by using an aqueous solution of an organic reducing agent, reducing hexavalent chromium into trivalent chromium, reversely extracting trivalent chromium into the water phase, and separating the organic phase from the water phase to acquire a solution of the trivalent chromium and a renewable organic phase, wherein the organic reducing agent is one or a mixture of alcohols, aldehydes and carboxylic acids having the carbon atom number ranging 1 to 3; and (3) performing solvent evaporation on the solution of trivalent chromium, catalyzing, and recovering the trivalent chromium.

A process for recovering chromium from hexavalent chromium-containing wastewater comprises the following steps: (1) extracting hexavalent chromium in wastewater to an organic phase by using an extracting agent, and separating hexavalent chromium from a water phase, so as to acquire a hexavalent chromium-loaded organic phase; (2) reducing the hexavalent chromium-loaded organic phase by using an aqueous solution of an organic reducing agent, reducing hexavalent chromium into trivalent chromium, reversely extracting trivalent chromium into the water phase, and separating the organic phase from the water phase to acquire a solution of the trivalent chromium and a renewable organic phase, wherein the organic reducing agent is one or a mixture of alcohols, aldehydes and carboxylic acids having the carbon atom number ranging 1 to 3; and (3) performing solvent evaporation on the solution of trivalent chromium, catalyzing, and recovering the trivalent chromium.

A treatment method for resource recycling of hexavalent chromium-containing residues is provided. This method comprises steps as follows: 1) adding water to the hexavalent chromium-containing residues and mixing uniformly; 2) adding mineralizers to a solution obtained in step 1) and stirring sufficiently to obtain a mixed liquid; and the mineralizers are sodium chlorate, sodium perchlorate and hydrochloric acid; 3) treating the mixed liquid by a hydrothermal method or direct heating; 4) after the heating treatment, naturally cooling a solid-liquid mixture to room temperature for holding; 5) separating solid residues and a chromium-containing supernatant, and washing filtered residues with water and then drying; and 6) recycling a chromium-containing solution for returning to a work section, or for a treatment of recycling chromium.

A novel process for treating and recovering valuable metals and other components from pickling acid residue (PAR) has been developed. The metals and other components are recovered by neutralizing the pickling acid residue using a magnesium compound or a mixture of magnesium compounds, and separating components of the resulting mixture (metals and sulfates) into products that can be reused, such as magnesium sulfate, nickel sulfate, iron and chromium phosphate, or various metal hydroxides or oxides.

A method for producing ferronickel and removing chromium from nickel laterite ore, including the following steps: (1) subjecting the nickel laterite ore to ore washing and separating to obtain an ore slurry and a mineral aggregate, adding an alkali liquor and a bromate and introducing oxygen to the ore slurry to allow oxidation leaching, and then conducting solid-liquid separation to obtain a solid and a chromium-containing filtrate; (2) subjecting the solid obtained in step (1) to washing and solid-liquid separation to obtain a solid phase and washing water, and mixing the solid phase with quicklime and a reducing agent to obtain a mixture; and (3) subjecting the mixture obtained in step (2) to roasting and smelting successively to obtain a finished ferronickel product. The method achieves enrichment of chromium, and produces ferronickel through smelting of the nickel laterite ore while removing the impurity chromium, protecting the safety of a furnace.

A method for producing ferronickel and removing chromium from nickel laterite ore, including the following steps: (1) subjecting the nickel laterite ore to ore washing and separating to obtain an ore slurry and a mineral aggregate, adding an alkali liquor and a bromate and introducing oxygen to the ore slurry to allow oxidation leaching, and then conducting solid-liquid separation to obtain a solid and a chromium-containing filtrate; (2) subjecting the solid obtained in step (1) to washing and solid-liquid separation to obtain a solid phase and washing water, and mixing the solid phase with quicklime and a reducing agent to obtain a mixture; and (3) subjecting the mixture obtained in step (2) to roasting and smelting successively to obtain a finished ferronickel product. The method achieves enrichment of chromium, and produces ferronickel through smelting of the nickel laterite ore while removing the impurity chromium, protecting the safety of a furnace.