Reduction Behaviors of Copper， Cobalt and Iron in Smelting of Copper Oxide Concentrate

doi:10.12068/j.issn.1005-3026.2024.03.005

Abstract

Abstract:

For the cobalt‐bearing copper oxide concentrate from Congo， experiment of coke reduction smelting with fayalite slag was conducted. The effects of CaO‐to‐SiO₂ mass ratio， FeO‐to‐SiO₂ mass ratio and coke rate on the reduction rates of copper and cobalt were investigated. The reduction sequence and conditions of copper， cobalt， iron and silicon oxides were analyzed by thermodynamics. The reduction process of copper， cobalt and iron oxides was quantitatively analyzed by means of metal oxide reduction thermodynamics and coke gasification kinetics. The results show that the reduction of copper， cobalt and iron in the copper oxide concentrate can be divided into the competitive fast reduction period in the early stage and the slow reduction period of copper and cobalt in the later stage. The reduced metal iron in the slow reduction period will undergo reoxidation. The large amount of competitive iron reduction in the early stage and its reoxidation in the later stage will reduce the reduction rate of copper， cobalt and iron and the effective utilization rate of coke. The formation mechanism of ferroalloy layer on the surface of crude copper is revealed.

Key words: copper oxide concentrate, copper, cobalt, reduction of FeO, thermodynamics model, fayalite

CLC Number:

TF 811

Lei ZHANG, Kai-xi JIANG, Feng XIE, Dian-kun LU. Reduction Behaviors of Copper， Cobalt and Iron in Smelting of Copper Oxide Concentrate[J]. Journal of Northeastern University(Natural Science), 2024, 45(3): 337-345.

Figures/Tables 15

Fig.1 Relationships between pCO2/pCO ratios required for different oxide reduction reactions and temperatures

Fig.2 Relationships between pCO2/pCO ratios required for the reduction of FeO and SiO2 and temperatures under low iron and silicon activities

Table 2 Relationship between CO coefficient required by MO and temperatures under standard state

温度	Cu₂O+CO（g）=2Cu+CO₂（g）			CoO+CO（g）=Co+CO₂（g）			FeO+CO（g）=Fe+CO₂（g）
℃	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$
1 273	3.99×10⁶	1.00	1.00	13.27	0.93	1.08	0.428	0.30	3.34
1 373	1.41×10⁶	1.00	1.00	9.58	0.91	1.10	0.383	0.28	3.61
1 473	5.68×10⁵	1.00	1.00	7.29	0.88	1.14	0.348	0.26	3.87
1 573	2.15×10⁵	1.00	1.00	5.75	0.85	1.17	0.319	0.24	4.13
1 673	9.16×10⁴	1.00	1.00	4.66	0.82	1.21	0.288	0.22	4.47
1 773	4.28×10⁴	1.00	1.00	3.89	0.80	1.26	0.244	0.20	5.10

Table 2 Relationship between CO coefficient required by MO and temperatures under standard state

温度	Cu₂O+CO（g）=2Cu+CO₂（g）			CoO+CO（g）=Co+CO₂（g）			FeO+CO（g）=Fe+CO₂（g）
℃	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$	$K p (T)$	$ξ * / a = 1$	$a / ξ * = 1$
1 273	3.99×10⁶	1.00	1.00	13.27	0.93	1.08	0.428	0.30	3.34
1 373	1.41×10⁶	1.00	1.00	9.58	0.91	1.10	0.383	0.28	3.61
1 473	5.68×10⁵	1.00	1.00	7.29	0.88	1.14	0.348	0.26	3.87
1 573	2.15×10⁵	1.00	1.00	5.75	0.85	1.17	0.319	0.24	4.13
1 673	9.16×10⁴	1.00	1.00	4.66	0.82	1.21	0.288	0.22	4.47
1 773	4.28×10⁴	1.00	1.00	3.89	0.80	1.26	0.244	0.20	5.10

Fig.3 XRD pattern of copper oxide concentrate

Table 3 Main components of copper oxide concentrate

Cu	Co	S	FeO	CaO	MgO	Al₂O₃	SiO₂
20.92	0.23	0.82	1.94	2.91	5.99	4.65	39.08

Table 4 Effect of m（CaO）/m（SiO2） on the reduction smelting index with m（FeO）/m（SiO2）= 0.71

	m（CaO）/m（SiO₂）	还原率/%			$ε C$	$a F e O$ / $a F e$	产率/%
	g·g^-1	Cu	Co	Fe	$ε C$	$a F e O$ / $a F e$	金属	炉渣
0.2		99.39	98.38	54.54	1.28	1.39	32.60	74.47
0.3		99.59	98.30	60.27	1.41	1.60	32.33	78.07
0.4		99.00	98.31	55.46	1.30	1.42	37.13	77.60
0.5		99.38	98.11	43.73	1.02	1.03	31.53	86.87
0.6		99.56	97.99	39.04	0.91	0.89	29.13	92.40
0.7		99.07	96.62	41.47	0.97	0.96	28.80	97.07

Table 4 Effect of m（CaO）/m（SiO2） on the reduction smelting index with m（FeO）/m（SiO2）= 0.71

	m（CaO）/m（SiO₂）	还原率/%			$ε C$	$a F e O$ / $a F e$	产率/%
	g·g^-1	Cu	Co	Fe	$ε C$	$a F e O$ / $a F e$	金属	炉渣
0.2		99.39	98.38	54.54	1.28	1.39	32.60	74.47
0.3		99.59	98.30	60.27	1.41	1.60	32.33	78.07
0.4		99.00	98.31	55.46	1.30	1.42	37.13	77.60
0.5		99.38	98.11	43.73	1.02	1.03	31.53	86.87
0.6		99.56	97.99	39.04	0.91	0.89	29.13	92.40
0.7		99.07	96.62	41.47	0.97	0.96	28.80	97.07

Fig.4 Effect of m（FeO）/m（SiO2） on the reduction rate of metals with m（CaO）/m（SiO2）=0.4

Table 5 Effect of m（FeO）/m（SiO2） on the reduction smelting index with m（CaO）/m（SiO2）=0.4

m（FeO）	入炉FeO质量/g	$ξ$ /%	$ξ * / %$	$ε C$	$a F e O$	a
m（SiO₂）	入炉FeO质量/g	$ξ$ /%	$ξ * / %$	$ε C$	$a F e$	a
0.41	15.92	73.05	57.98	1.26	1.36	2.59
0.56	21.91	72.82	48.25	1.51	1.77	2.16
0.71	27.90	55.46	42.69	1.30	1.42	1.91
0.79	30.89	55.56	40.72	1.36	1.53	1.82
0.87	33.89	36.19	39.10	0.93	0.91	1.75
0.94	36.89	37.71	37.74	1.00	1.00	1.69
1.02	39.88	28.2	36.59	0.77	0.72	1.64
1.10	42.87	28.96	35.60	0.81	0.77	1.59
1.17	45.87	19.06	34.73	0.55	0.49	1.55
1.25	48.87	15.05	33.97	0.44	0.38	1.52

Table 5 Effect of m（FeO）/m（SiO2） on the reduction smelting index with m（CaO）/m（SiO2）=0.4

m（FeO）	入炉FeO质量/g	$ξ$ /%	$ξ * / %$	$ε C$	$a F e O$	a
m（SiO₂）	入炉FeO质量/g	$ξ$ /%	$ξ * / %$	$ε C$	$a F e$	a
0.41	15.92	73.05	57.98	1.26	1.36	2.59
0.56	21.91	72.82	48.25	1.51	1.77	2.16
0.71	27.90	55.46	42.69	1.30	1.42	1.91
0.79	30.89	55.56	40.72	1.36	1.53	1.82
0.87	33.89	36.19	39.10	0.93	0.91	1.75
0.94	36.89	37.71	37.74	1.00	1.00	1.69
1.02	39.88	28.2	36.59	0.77	0.72	1.64
1.10	42.87	28.96	35.60	0.81	0.77	1.59
1.17	45.87	19.06	34.73	0.55	0.49	1.55
1.25	48.87	15.05	33.97	0.44	0.38	1.52

Fig.5 Effect of coke coefficient on the reduction rate of metals with m（CaO）/m（SiO2）=0.4

Fig.6 Effect of coke rate on the reduction rate of metals with m（FeO）/m（SiO2）=0.71 and m（CaO）/m（SiO2）=0.4

Table 6 Slag composition with m（FeO）/m（SiO2）=0.71 and m（CaO）/m（SiO2）=0.4 under various coke rates

焦比/%	质量分数/%					$x S i O 2$ /%	n（O）/n（Si）
焦比/%	CaO	MgO	Al₂O₃	FeO	SiO₂	$x S i O 2$ /%	n（O）/n（Si）
2	14.47	5.59	10.20	24.38	37.88	0.410	3.76
4	17.71	6.85	9.18	25.19	43.34	0.436	3.55
5	20.43	8.26	9.15	11.33	48.64	0.497	3.23
6	18.09	6.92	11.30	21.87	45.72	0.455	3.49
8	19.84	7.94	9.86	16.21	52.2	0.498	3.23
10	20.90	8.34	9.20	11.94	51.55	0.506	3.19

Table 6 Slag composition with m（FeO）/m（SiO2）=0.71 and m（CaO）/m（SiO2）=0.4 under various coke rates

焦比/%	质量分数/%					$x S i O 2$ /%	n（O）/n（Si）
焦比/%	CaO	MgO	Al₂O₃	FeO	SiO₂	$x S i O 2$ /%	n（O）/n（Si）
2	14.47	5.59	10.20	24.38	37.88	0.410	3.76
4	17.71	6.85	9.18	25.19	43.34	0.436	3.55
5	20.43	8.26	9.15	11.33	48.64	0.497	3.23
6	18.09	6.92	11.30	21.87	45.72	0.455	3.49
8	19.84	7.94	9.86	16.21	52.2	0.498	3.23
10	20.90	8.34	9.20	11.94	51.55	0.506	3.19

Table 7 Effect of coke rate on iron reduction and coke utilization with m（FeO）/m（SiO2）=0.71 and m（CaO）/m（SiO2）=0.4

焦比/%		$ξ$ / %		$ξ *$ / %	$a$	$ε C$	$a F e O$ / $a F e$	焦炭利用率占比/%
焦比/%		$ξ$ / %		$ξ *$ / %	$a$	$ε C$	$a F e O$ / $a F e$	Cu	Fe
2	12.98		18.79		0.84	0.69	0.63	66.41	18.23
4	22.55		34.71		1.55	0.65	0.59	56.98	15.83
5	55.46		42.67		1.91	1.30	1.42	47.12	31.14
6	32.13		50.63		2.26	0.63	0.57	39.19	15.03
8	53.68		66.56		2.98	0.81	0.76	29.53	18.84
10	64.83		82.48		3.69	0.79	0.74	23.34	18.20

Table 7 Effect of coke rate on iron reduction and coke utilization with m（FeO）/m（SiO2）=0.71 and m（CaO）/m（SiO2）=0.4

焦比/%		$ξ$ / %		$ξ *$ / %	$a$	$ε C$	$a F e O$ / $a F e$	焦炭利用率占比/%
焦比/%		$ξ$ / %		$ξ *$ / %	$a$	$ε C$	$a F e O$ / $a F e$	Cu	Fe
2	12.98		18.79		0.84	0.69	0.63	66.41	18.23
4	22.55		34.71		1.55	0.65	0.59	56.98	15.83
5	55.46		42.67		1.91	1.30	1.42	47.12	31.14
6	32.13		50.63		2.26	0.63	0.57	39.19	15.03
8	53.68		66.56		2.98	0.81	0.76	29.53	18.84
10	64.83		82.48		3.69	0.79	0.74	23.34	18.20

Fig.7 Phase diagram of Cu?Fe alloy

Fig.8 SEM+EDS pattern of the slag with m（FeO）/m（SiO2）=0.71， m（CaO）/m（SiO2）=0.4 and coke rate 5%

Table 8 Element analysis of EDS spectrum points in Fig.8

元素	谱图1		谱图2		谱图3
元素	质量分数	原子分数	质量分数	原子分数	质量分数	原子分数
O	43.54	59.96	32.06	57.14	—	—
Mg	7.15	6.48	0.88	1.03	—	—
Al	6.27	5.12	—	—	—	—
Si	21.63	16.97	14.07	14.29	—	—
Ca	19.33	10.63	2.36	1.68	—	—
Fe	1.80	0.71	50.63	25.86	85.84	87.34
Ti	0.28	0.13	—	—	—	—
Cu	—	—	—	—	14.16	12.66

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