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Preparation of nickel-cobalt products from cobalt-containing magnetic steel slag
I. Overview
Metal material widely used in national defense and economic sectors, such as radar, meter, motors, and other automated instruments and medical equipment, in particular permanent magnet material comprising nickel, cobalt, 14% -34% alloy. Slag, waste and abrasive chips produced during smelting, pouring, and processing are good raw materials for cobalt and nickel. Compared with the treatment of raw ore, the treatment of these raw materials is simple, the processing cost is low, and the metal recovery rate is high.
The current process for processing cobalt and nickel magnetic steel scrap is as follows:
(1) Dissolving sulfuric acid and adding nitric acid to increase the dissolution rate. After dissolving the solution, the iron is removed by the method of pyrite, deepening the impurities such as aluminum , chlorine or sodium hypochlorite to form cobalt and nickel separation. Corresponding nickel, cobalt oxide, carbonate, or deep processing into the corresponding nickel cobalt salts can be produced. The flow chart of the magnetic steel slag treatment process is shown in Figure 1.
Figure 1 Magnetic steel slag treatment process
(2) The extraction method is used to replace the chlorine-cobalt-sinking process, such as P204-Na salt extraction to remove impurities, and P204-Na salt to extract and separate nickel and cobalt. It is also possible to extract and separate iron, aluminum and P204-Na salts by fatty acid extraction. Due to the high recovery rate of valuable metals in the extraction process, good working conditions, excellent product quality, easy to master operating technology conditions, etc., more and more attention is paid to manufacturers.
P204-Na salt extraction in addition to impurities, P204-Na extraction and separation of nickel, cobalt and the corresponding nickel-cobalt products process similar to Kovar treatment process, please refer to this website (from cobalt extractable alloy Nickel products).
The waste magnetic steel slag with low nickel-cobalt content can be smelted together with nickel- phosphorus iron by pyrometallurgy, and then refined into nickel anode plate by electrolysis. Please refer to this website (produce nickel electroplated nickel with nickel-phosphorus iron).
Second, raw materials
(1) The composition of No. 5 magnetic steel scrap and suede is as follows (%):
Co
Ni
Fe
Cu
other
~20
13
50
2
15
(2) The composition of magnetic steel wear debris is as follows (%)
Co
Ni
Fe
Cu
15~17
9 to 16
25~50
2 to 3
SiO 2
CaO
Al 2 O 3
H 2 O
4
0.5
7~8
twenty one
Third, technical operating conditions
(1) Acid dissolution
The magnetic steel slag grinding debris contains grinding wheel debris and a small amount of oil. Before processing, the oil must be removed first, and the non-magnetic component in the grinding debris is removed by a magnetic separator.
1, degreasing
The grinding chips are placed in a furnace and heated by direct heat until no fumes are emitted.
Temperature 300 °C ± time 1 ~ 2h
2, magnetic separation
The magnetic steel grinding chips are fine powders of permanent magnets such as cobalt, nickel and iron, and have magnetic properties, which are mixed with a small amount of grinding wheel grinding silicon carbide and other non-magnetic substances mechanically mixed. The magnetic field strength of the magnetic separator is 95493A/m, and it can be magnetically selected 1 or 2 times according to the situation. The composition of the magnetic substance after selection is as follows (%):
Co
Ni
Fe
Cu
Al 2 O 3
SiO 2
20
12
45
2
15
3
After magnetic separation, the content of cobalt and nickel in the magnetic part is related to the type of magnetic steel.
3. Acid leaching
The liquid-solid ratio generally controls the total concentration of metal ions in the solution to be 120 g/L, and the liquid-solid ratio (8 to 10):1.
With acid, sulfuric acid and hydrochloric acid are 1.2 times the theoretical amount.
At the temperature, the reaction is an exothermic reaction and the temperature is controlled at 90 to 95 °C.
Nitric acid is added to the amount of nitric acid, and the nitric acid is decomposed into Nox (ie, yellow smoke). The amount of nitric acid added and the rate of addition generally depend on the nature of the material and the amount of nitric acid recovered and returned to the solution. Usually, 95% concentrated nitric acid is added per ton of magnetic steel scrap. ~200kg.
The reaction time, the particle size of the magnetic steel scrap and the amount of nitric acid are 4-8 h.
The final pH value, 1.0 to 1.5.
The general method of nitrogen oxide absorption is as follows:
(1) Water absorption, air oxidation, Nox gas is absorbed through multiple stages, and it is handled properly. The soot exhaust does not see yellow. After absorption, the dilute nitric acid returns to dissolution. It eliminates environmental pollution and saves nitric acid.
(2) Absorption with dilute alkali solution to form sodium nitrite can reduce the harm of Nox, but the liquid can not be reused after absorption.
Generally, the recovery rate of nickel and cobalt in acid solution is 95% to 98%.
(2) Yellow sodium iron sputum method for removing iron
The amount of sodium chlorate is 0.35 to 0.4 times the amount of iron.
Oxidation temperature 85 ° C
The oxidation time was 1 h and maintained for 2 h.
Sinking control temperature ≥95°C
Sinking pH 1.5~2
Sinking time 3~4h
Neutralizer Na 2 CO 3 concentration 7% to 10%
Slag filtration rate 0.5m 3 /(m 2 ·h)
Hot water washing times 2 times
Hot water: slag 2L: 1kg
Cobalt nickel recovery rate 97% to 98%
(3) Comprehensive removal of impurities
Control the pH value 4~5.
Temperature 70～80°C
Na 2 CO 3 neutralizer concentration 80g/L
Filtration speed 0.3～0.5m 3 /(m 2 ·h)
(4) Production of nickel-cobalt products
1, precipitated cobalt hydroxide
The cobalt is precipitated by the sodium hypochlorite method, the nickel is separated, and the sodium hypochlorite is precipitated as follows:
Acidity Start pH=1.5～2.5
Process pH=2.0
End point pH=2~2.5
Temperature, 50 ~ 60 ° C, the end point increased to 60 ~ 70 ° C (chlorine drive)
Time 4~6h
The product Co(OH) 3 , after filtration and washing, Co/Ni ≥ 7:1, and the cobalt-containing solution contains Co, 0.4-0.5 g/L.
The composition of the cobalt slag after drying is as follows (%):
Co
Ni
Fe
Cu
Al
45
≤4.5
≤0.5
≤1
≤1
2. Precipitation of basic nickel carbonate
The precipitated cobalt post-solution directly precipitates basic nickel carbonate with Na 2 CO 3 .
Temperature, 85 ° C
End point pH, 8-9
Na 2 CO 3 concentration 150g/L
Time 4h
Hot filtered, hot water washed 2 times, wash water: basic nickel carbonate 2L: 1kg
An example of the basic nickel carbonate component after drying is as follows (%)
Ni
Co
Fe
Al
Cu
45
≤1
≤0.1
≤1
≤1
Fourth, the product
(a) Cobalt hydroxide
Example, Co 45% Ni ≤ 4.5%
(2) Crude nickel hydroxide
Example, Ni 45% Co≤1%
V. Technical and economic indicators
(1) Recovery rate, Ni 86.35% Co 85.17%
(2) Consumption of main materials (to treat each ton of magnetic steel slag)
H 2 SO 4 (93%) 1t
HCL (35%) 1.5t
HNO 3 (65%) 0.25t
Na 2 CO 3 0.32t
NaOH 0.5t
NaClO 3 0.1t
Liquid chlorine 0.1t
(3) Water, electricity and steam consumption
Water 200t
Electricity 2000kW·h
Vapor 70t