Electrical heating internal resistance electric melting method for decomposing mixed rare earth ore concentrate and electric heating decomposer thereof

Abstract

The invention provides a decomposition method for rare earth ore concentrate. The method comprises the following process steps: (1) mixing mixed rare earth ore concentrate with concentrated sulfuric acid according to mass ratio in an electric heating decomposer; (2) heating the material with resistance heat generated by current flowing through the material after energization of the electric heating decomposer; (3) leaching output roasted ore by water; and neutralizing the solution with magnesium oxide to obtain iron phosphate, thorium phosphate precipitate and phosphorus phosphate precipitate; (4) removing sulfuric acid mist and dust in roasting tail gas; then spraying with liquid caustic soda to absorb fluorine, so as to precipitate sodium acid fluoride; and emptying the gas with acid and fluoride removed; and (5) cleaning and discharging the leached slag. The method provided by the invention employs electric heating to substitute fuel burning heating to lower processing capacity of waste gas and wastewater to 5% of that of an original process, so as to save energy, investment and operation cost; waste gas and waste residue reach discharge standards, and waste water can be recycled; and recovery rate of rare earth, thorium and fluorine is improved, so as to solve the problem of reuse of thorium and fluoride.

Description

technical field [0001] The invention relates to a method for decomposing mixed rare earth concentrate, which belongs to the field of rare earth metallurgy. Background technique [0002] my country's Baotou mixed rare earth concentrate contains bastnaesite (REFCO 3 ), monazite (REPO 4 ) and fluorite (CaF 2 ), monazite contains more than 0.2% of the radioactive element thorium, which belongs to associated radioactive minerals. The existing mixed rare earth concentrate decomposition method is concentrated sulfuric acid roasting decomposition method, that is, the concentrated sulfuric acid and the mixed rare earth concentrate are mixed according to the mass ratio of 1: 1.1 to 1.7, and then heated in a rotary kiln at a high temperature (less than 900 ° C) or Roasting at low temperature (less than 300°C) converts rare earth minerals into water-soluble sulfates, and then produces various rare earth products through leaching, purification and impurity removal of roasted products....

AI Technical Summary

Problems solved by technology

This method has the following problems in terms of environmental protection and resource utilization: (1) The amount of exhaust gas is large and it is difficult to meet the emission standards

Roasting exhaust gas is treated by water spraying, waste heat is difficult to reuse, and the actual emission values ​​are far higher than the national emission standards (respectively: SO23 ;Sulfuric acid mist3 ; Fluoride 3 ), seriously polluting the environment

(2) The amount of waste water is large and the treatment cost is high

Due to its large discharge volume, complex composition, high impurities, and serious corrosion, it is very difficult to treat

Lime neutralization or alkali neutralization can not recover acid and increase operating costs; after adopting acid concentration recovery technology, 70% of sulfuric acid and 15% of hydrofluoric acid can be recovered, but the investment scale is large, the requirements for equipment and materials are special, and it is not easy to operate

(3) Generate radioactive waste

Chinese patent (Application No.: 98118153.8, publication date: March 8, 2000) "New Process for Decomposing Baotou Rare Earth Mine by Acid Method" proposes a mixture of mixed rare earth concentrate and concentrated sulfuric acid at 180-300°C for intermittent static roasting. 13 hours, reduce the decomposition of sulfuric acid, and at the same time solidify hydrogen fluoride gas with ammonia gas to ensure qualified exhaust gas, but it does not involve the radioactive pollution of thorium in the leaching residue

The problem with low-temperature roasting is that the roasting temperature is reduced to about 300°C by using a rotary kiln and burning chemical fuel, but the roasting time is extended from 1-2 hours in the high-temperature method to 7-16 hours, and the amount of waste gas and waste water produced exceeds High temperature method, high operating costs for the treatment of discharge standards

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