Characteristics of Residual Fine Particles in a Blast Furnace

Abstract

Fine particles can reduce the blast furnace’s gas and liquid permeability. The residual fine particle sampling and screening of the overhaul blast furnace were carried out to obtain particle size distribution. Chemical analysis, XRD, and SEM-EDS were used to analyze the chemical and phase composition, degree of graphitization, and microstructure to clarify the characteristics and evolution of fine particles. The results show a clear correlation between particle size and chemical composition. Although the phase components of different-size particles are similar in the same area, their chemical contents are quite different. The chemical and phase composition of particles with the same particle size significantly differ in the other regions. The fine particles in the S1 region mainly consist of coke powder, ZnO, and alkali metals. Significant amounts of slag iron minerals and C coexist in the fine particles of the S2 area. The slag iron minerals contents and the carbon graphitization degree of fine particles increase as the furnace burden descends.

1. Introduction

Coke and iron ore may degrade and pulverize during blast furnace (BF) operation due to mutual compression, friction, and high-temperature chemical reactions between the furnace ingredients.^1,2) Excessive fine particles can reduce the blast furnace’s gas and liquid permeability,^3,4,5) cause enhanced hot metal flow erosion around the deadman,^6,7,8) and increase slag retention and furnace wall temperature.^9,10) Excessive powder accumulation in the burden bed also causes a serious hanging phenomenon.¹¹⁾ Fine particles will also attach to the surface of iron minerals and coke, lowering the reducibility of iron ore and the carburization of molten iron, which is not conducive to replacing the deadman.^12,13,14)

The deadman’s primary sources of fine particles are ore and coke degradation, injection coal ash, and unburned injection coal in the raceway zone. The dynamic wettability of liquids on gasified metallurgical cokes significantly impacts the gas permeability and the gas flow stability in a BF.^15,16) The coke’s micro strength and pore structure determine coke deterioration and powder generation during the coke gasification process. Graphitization can promote the formation of coke powder during coke gasification.¹⁷⁾ A large number of fine particles lower the coke reactivity with CO₂.¹⁸⁾ Char and ash particles derived from pulverized coal affect permeability in the furnace.¹⁹⁾ Gornostayev S. et al.²⁰⁾ hypothesized that undeveloped hexagonal prism flake graphite crystals influenced the apparent reaction rate of coke. Gupta S. et al.²¹⁾ proposed that graphitization of coke in the deadman promoted coke powder formation. The surface graphitization of cokes had the contribution on the −0.45 mm size fraction of fines generation, particularly in the “raceway” and “bird nest” regions.²²⁾

Previous studies mainly concentrated on the impact of iron ore, coke, coal injection, and coke powder on the permeability of BF charging columns in the laboratory. There has been little research on the fine particles from a BF, and the characteristics and evolution of fine particles in a BF are unclear. A substantial residual powdered burden was discovered and collected from various areas during the BF overhaul. The chemical composition, phase composition, graphitization degree, and microscopic morphology of particles were analyzed to reveal residual fine particles’ characteristics and evolution process during the furnace burden descent.

2. Materials and Methods

2.1. The BF and the Sample Location

The residual fine particles were collected from Ansteel BF with 3200 m³. Table 1 lists the operation data and relevant parameters of the BF. The sampling operation was conducted during the BF overhaul after successfully dropping the stockline, water quenching, and opening the furnace wall. Figure 1 depicts the sampling scene and positions marked as S1 and S2. S1 is the core coke area at the tuyere level, and S2 is a mixing area of hot metal, slag, and core coke in the hearth, slightly above the tap hole level.

Table 1. The operation data and relevant parameters of the BF.

Volume (m3)	Working life (year)	Tuyere number	Utilization coefficient (t/m3·d)	Coke ratio (kg/ton iron)	Coal rate (kg/ton iron)	Hearth diameter (m)
3200	8	32	2.1	307	145	12.4

Fig. 1. The schematic of the sampling scene and positions. (Online version in color.)

2.2. The Sample Preparation and Analysis Methods

The S1 and S2 samples were filtered through test sieves with dimensions of 20 mm, 10 mm, 6 mm, 1 mm, and 0.073 mm to obtain different diameter particulates. Figure 2 depicts the S1 samples after sieving. Table 2 shows the mass fraction of various particle sizes after weighing and calculating. The mass fraction of fine particles less than 10 mm in the S2 region is substantially more significant than in the S1 region.

Fig. 2. Samples with different particle sizes in the S1 area. (Online version in color.)

Table 2. The mass fraction with varying sizes of fine particles in S1 and S2 areas (wt%).

Sampling Location	+20 mm	10–20 mm	6–10 mm	1–6 mm	0.073–1 mm	−0.073 mm
S1	73.7	10.7	5.8	4.6	3.6	1.6
S2	61.8	15.3	9.1	7.2	4.8	1.8

The micromorphology and composition of fine particles were analyzed and characterized using scanning electron microscopy energy dispersive spectroscopy (ZEISS, EvoMA25, Germany). Then, the particles were crushed and ground to less than 73 μm, respectively. Various-sized powders’ phase composition and graphite crystallite parameters were obtained using an X-ray diffractometer (XRD X’Pert PRO, Netherlands). Given the toughness of the metal iron in the particles, the hammer mill cannot smash it. The XRD test specimen is evaluated after removing more than 73 μm of metal iron.

3. Results and Discussion

3.1. Chemical Composition of Fine Particles in the BF

Table 3 shows the chemical composition of coke powder, BF slag, and different diameter residual particles in the S1 and S2 areas. Figure 3 shows the chemical composition changes of powdered furnace burden with varied particle sizes in the S1 and S2 regions. As illustrated in Fig. 3(a), the C content of the powder gradually increases as the particle size of the powder decreases. The carbon content of the powder less than 0.073 mm reaches 41.66%, indicating that many fine particles in the S1 zone originate from coke powder or unreacted PCI coal. The carbon content of powdered furnace burden in the S2 area decreases first and then increases with the particle size increasing. The melted particles in the hearth envelop unreacted coke powder, increasing the carbon content of the +10 mm particles. The adhesion and encapsulation between molten slag iron minerals and coke nut, as well as the wear resistance of coke, determine the composition of the +10 mm particles in the deadman. The C content of the powdered furnace burden in the S1 region is significantly higher than that in the S2 region, indicating that the carbon in the powdered furnace burden undergoes a reduction or carburization reaction during the descent of the furnace burden. Apart from the −0.073 mm particle, the degree of carbon content reduction in the particles gradually decreases as particle size increases. It implies that powdered carbon is more susceptible to reduction or carburization reactions. However, too many fine particles reduce permeability and specific surface area, reducing the degree of carbon reduction.

Table 3. Chemical analysis of coke powder, slag and residual fine particles.

	Chemical composition (%)											SiO2/ Al2O3	(CaO+MgO/ SiO2+Al2O3)
	C	S	K2O	Na2O	ZnO	SiO2	Al2O3	CaO	MgO	Fe	Fe3O4
Coke powder (−1 mm)	85.21	1.01	0.11	0.06	0.18	6.18	4.06	0.41	0.70	0.00	0.94	1.52	0.11
Slag	0.04	1.12	0.00	0.00	0.00	34.61	11.52	41.23	6.26	0.19	0.00	3.00	1.03
Fine particles in the S1 area
−0.073 mm	41.66	0.32	1.72	0.70	34.29	4.68	2.66	6.05	0.90	1.23	4.63	1.76	0.95
0.073–1 mm	41.34	0.30	2.16	0.81	20.20	10.72	5.96	9.55	1.74	3.25	2.37	1.80	0.68
1–6 mm	32.69	0.36	2.89	1.16	20.71	12.40	6.79	10.75	2.01	4.79	4.11	1.83	0.66
6–10 mm	23.38	0.38	2.59	1.23	12.08	15.91	9.43	14.28	2.56	13.35	3.11	1.69	0.66
10–20 mm	20.57	0.42	2.17	0.96	9.19	15.25	8.32	15.56	2.57	21.47	2.52	1.83	0.77
+20 mm	21.16	0.36	2.37	0.78	19.46	12.75	7.01	7.74	1.59	24.15	1.97	1.82	0.47
Fine particles in the S2 area
−0.073 mm	26.21	2.21	1.13	0.36	0.13	17.09	6.21	21.72	3.02	18.40	3.34	2.75	1.06
0.073–1 mm	14.15	1.54	0.56	0.26	0.05	20.84	8.95	25.07	4.09	22.45	1.94	2.33	0.98
1–6 mm	11.57	1.49	0.37	0.21	0.02	19.79	8.64	23.15	3.84	26.95	3.80	2.29	0.95
6–10 mm	11.44	1.40	0.34	0.22	0.01	19.87	7.99	25.70	3.88	27.41	1.60	2.49	1.06
10–20 mm	16.05	1.41	0.34	0.21	0.01	20.26	7.28	25.13	4.01	21.6	2.58	2.78	1.06
+20 mm	27.72	0.77	0.29	0.16	0.01	15.15	6.10	17.23	3.01	26.50	2.94	2.49	0.95

Fig. 3. Chemical composition analysis of fine particles in S1 and S2 areas.

According to Figs. 3(b) and 3(c), the alkali metals K₂O and Na₂O content exhibit a similar tendency when the particle size of the powder changes in the S1 and S2 regions. The alkali metal levels of K₂O and Na₂O in the S1 area can reach 2.89% and 1.23%, respectively, several tens of times higher than the BF feed material. Alkali metals are primarily absorbed on the coke pore walls as kalsilite or leucite.²³⁾ The alkali metals K₂O and Na₂O accelerate the deterioration of the surface layer, and the surface layer with alkali metals flakes off and turns into fine particles. The −1 mm fine powder cannot offer pore channels for alkali metal penetration, whereas +10 mm fine particles provide more channels for liquid slag iron to intrusion, resulting in a trend of first increasing and then decreasing as the particle size increases. The amount of K₂O and Na₂O decreases as the particle size increases in the S2 area. As the furnace burden gradually descends, more liquid slag iron erodes the residual coke nut, blocking the coke nut’s pore channels. For the same particle size, the K₂O and Na₂O content in the S1 region is 1.6–8.1 and 2.1–5.6 times higher than in the S2 region.

As demonstrated in Table 3 and Fig. 3(d), the highest ZnO content of the fine particles less than 0.073 mm is 34.29%, indicating significant Zn enrichment in the S1 area. As a detrimental element in the BF, the zinc vapor penetrates the coke through pores and adheres to the pore walls, producing and expanding micropores and increasing pore diameter.²⁴⁾ ZnO enrichment is not conducive to the reasonable gas flow distribution and the BF’s stability operation. The Zn enrichment phenomenon of the BF is evident later in the campaign.

The powdered residues also contain significant amounts of iron, slag, C, ZnO, and alkali metals. As shown in Fig. 3(e), the Fe content of particles more than 10 mm in the S2 region increases by 2–16 times compared to the S1 region; the C content of particles larger than 6 mm decreases considerably. Molten metallic iron enhances the gasification reaction of reducing agent.²⁵⁾ Considering the reducing atmosphere in the BF, some metal iron particles will move with the gas flow and become the powdered burden. The fine particles of the S1 and S2 areas consist of only a tiny quantity of Fe₃O₄ (seen in Fig. 3(f)). The Fe₃O₄ content of the small particles in the S1 region is higher than that in the S2 region, indicating the oxidation reaction of metal iron possibly occurs in the S1 area during the water cooling and excavation process.

Figures 3(g)–3(j) depicts the slag phase composition of different particle sizes in the S1 and S2 regions. Although the CaO and MgO contents of the particles in the S1 and S2 zones are remarkably diverse, the variation rules of CaO and MgO contents are highly comparable as the particle size changes, as shown in Figs. 3(g) and 3(h), suggesting that the elements of Ca and Mg exist in the similar minerals. The phase transition of minerals containing calcium and magnesium is not significant as the furnace burden descends from the S1 to the S2 area.

According to Figs. 3(i) and 3(j), the SiO₂ concentration increases first and then decreases with the particle size increasing. The SiO₂ concentration of fine particles in the S2 zone is higher than in the S1 region. As shown in Fig. 3(j), the variation trend of Al₂O₃ concentration is essentially the same as that of SiO₂ for particles less than 6 mm in the S1 and S2 regions. When the particle size is greater than 6 mm, the Al₂O₃ content of the particles decreases. Smaller particles are less prone to agglomerating, melting, and flowing in a liquid state. Larger particles with the Al₂O₃ easily transition into a liquid slag, dripping through the burden layer into the hearth. Al₂O₃ in smaller particles exhibits a declining tendency as the furnace burden moves down. According to Table 3 and Fig. 3(k), the SiO₂/Al₂O₃ ratio of coke powder is 1.52, the SiO₂/Al₂O₃ ratio of BF slag is 3, and the SiO₂/Al₂O₃ ratio of residual powder ranges from 1.52 to 3. Figure 3(l) depicts the alkalinity (CaO+MgO/SiO₂+Al₂O₃) of fine particles in the S1 area is mainly maintained between 0.47–0.95, which is less than the alkalinity of BF slag, indicating that SiO₂/Al₂O₃ ratio of the powdered burden is affected primarily by coke ash, coal ash or slag. The (SiO₂/Al₂O₃) and (CaO+MgO/SiO₂+Al₂O₃) ratios of fine particles have significantly increased in the S2 region compared to the S1 region, implying that the separation of slag and iron caused by carbon reduction substantially increases the more penetration of slag phase minerals into powdered furnace burden in the S2 region. The SiO₂/Al₂O₃ ratio of residual powder in the S2 zone has increased significantly due to Angang’s extensive use of self-produced high silicon iron ore, increasing the Si content of fine slag phase minerals.

3.2. Phase Composition of Particle Burden in the BF

Figure 4 demonstrates the phase composition of the powdered furnace burden in the S1 and S2 areas. Although the chemical composition of fine particles with varying particle sizes in the same area changes substantially, the phase composition is similar. The diffraction peaks of C, SiO₂, and ZnO are reasonably prominent in the S1 region, as shown in Fig. 4(a). The powdered furnace burden of the S1 region also contains a trace quantity of Fe, Fe₃O₄, and K(K, Na)₃Al₄Si₄O₆. Furthermore, most gehlenite crystals in Ca₂Al₂SiO₇ are concentrated in particles larger than 6 mm. The metallic iron removal during sample preparation obscures the Fe diffraction peak. Zn exists as ZnO in the powdered furnace burden of the S1 area, whereas K and Na coexist primarily as K(K, Na)₃Al₄Si₄O₆.

Fig. 4. Phase composition of particle burden with different sizes in S1 and S2 areas.

As depicted in Fig. 4(b), the diffraction peaks of C and Ca₂Al₂SiO₇ of the powdered furnace burden in the S2 area are relatively apparent. When the fine particles of the S1 area descend to the S2 area, the alkali metals (K, Na) and ZnO evaporate, and SiO₂ transforms into silicate minerals. According to Table 3 and Fig. 4(b), the major components of the powdered furnace burden in the S2 area are C, Ca₂Al₂SiO₇, and Fe, with a small amount of Ca₃(SiO₃)₃.

3.3. Micromorphology of Powdered Furnace Burden in the S1 Area

The accumulation of coke powder and slag-iron particles in the deadman affects the permeability of the BF. Figure 5 shows the micromorphology of fine particles in the S1 region. Table 4 displays the EDS analysis of residual fine particles of Fig. 5. As presented in Fig. 5(a) and Table 4, a typical hexagonal wurtzite structure mainly composed of ZnO is observed. In addition to ZnO, the particle with a high C, Zn, and O content is discovered in the SEM images of Fig. 5(b) according to the EDS analysis. The ZnO particles not only adsorb on the pore wall of coke but also accumulate in fine particles. Figure 5(c) demonstrates a multilayer graphitized structure with a shape similar to petals. The carbon content of the multilayer structure particle reaches 74.8%. The interaction of alkali vapors with coke micro graphite crystals results in the expansion of the coke carbon matrix and the formation of cracks,²⁶⁾ and the detached graphite crystals and alkali metals accumulate together in fine particles. Figure 5(d) shows the particle presents an adhesive cluster structure with the significant components of Zn, C, O, and a small amount of Na, Fe, Si, and Al. Relatively high levels of alkali metals compared to the coke powder are noticed in Figs. 5(a)–5(d). The lowest mass is 1.9%, and the highest is 5.1%. The severe degradation of coke quality caused by alkali metals is attributed to the lower wear resistance. Figure 5(e) shows the regular prismatic morphology particle’s surface is smooth. According to Table 4, the proportions of Ca, Si, Al, and Mg of the particle in Fig. 5(e) are close to the BF slag in Table 3, indicating that some inorganic minerals accumulate in fine particles. In Fig. 5(f), some carbon particles melt and coexist with inorganic minerals composed of C, O, Fe, Ca, and a small amount of Zn, Si, and Al. Under high-temperature conditions, molten slag iron minerals and carbon particles become mutual cementation, followed by the development of irregular particles.

Fig. 5. Microscopic morphology and EDS spectrum of particle burden of the S1 area.

Table 4. EDS analysis of residual fine particles of the S1 area.

	C	O	Zn	K	Na	Si	Al	Ca	Mg	Fe	S	Cl
a-1	13.5	19.3	59.3	–	5.1	0.2	–	–	–	2.1	–	–
b-2	55.3	12.2	29.3	0.2	1.7	0.2	–	–	–	1.1	–	–
c-3	74.8	13.3	2.1	4.4	–	0.4	0.2	–	–	3.1	–	1.8
d-4	–	18.2	49.1	–	3.2	0.3	0.3	–	–	2.6	–	–
e-5	13.7	28.8	–	–	0.8	12.2	4.2	–	2.8	2.9	–	–
f-6	41.0	29.0	3.6	1.0	0.8	2.9	1.0	8.0	0.4	11.8	0.4	0.3

3.4. Micromorphology of Powdered Furnace Burden in the S2 Area

The accumulation of coke powder and slag iron particles in the hearth affects the liquid fluidity of slag iron. Figure 6 depicts the micromorphology of the particle burden in the S2 region. Table 5 displays the EDS analysis of residual fine particles of Fig. 6. The particle size is significantly smaller than the S1 region. Most particles in Fig. 6(a) have inconspicuous edges and corners. Collision and friction between particles result in most particles being spherical or ellipsoidal. According to Table 5, the particles in Fig. 6(a) mainly comprise C, O, and inorganic elements Fe, Ca, and Si. A particle in Fig. 6(b) is composed of multiple adhesive tiny particles with the content of 41.9% C, 27.9% O and 25.2% Fe. Melted iron and iron oxide attached to carbon particles might induce low BF air permeability and uneven iron tapping. Figures 6(c) and 6(d) show the symbiotic particles that comprise the slag-iron and carbon. The carbon as the matrix adheres to slag-iron in the particle of Fig. 6(c).

Fig. 6. Microscopic morphology and EDS spectrum of particle burden of the S2 area.

Table 5. EDS analysis of residual fine particles of the S2 area.

	C	O	Zn	K	Na	Si	Al	Ca	Mg	Fe	S	Cl
a-1	30.7	22.2	–	0.4	–	5.2	0.4	4.0	0.3	35.9	0.5	–
b-2	41.9	27.9	–	1.3	–	0.2	–	1.4	–	25.2	1.5	0.4
c-3	27.7	33.4	–	0.6	–	1.7	0.6	15.5	–	19.5	0.6	0.2
d-4	8.6	30.1	–	–	0.5	4.0	1.5	7.6	0.6	46.9	–	–
e-5	8.5	26.2	–	–	–	0.5	–	–	–	64.8	–	–
f-6	27.6	34.0	–	–	–	8.2	3.7	19.2	2.1	4.8	0.4	–

On the contrary, the slag-iron as the matrix attaches to carbon in the particle in Fig. 6(d). Figure 6(e) illustrates the particle with the apparent edges and corners. According to Table 5, the higher O level of the particle in Fig. 6 (e) indicates that the iron particle undergoes oxidation during sampling. The component of the particles cling together is similar to BF slag but distinct from the particle in Fig. 5(e). The particle size of the granular material decreases dramatically in the S2 region, and most of the particle edges disappear, with more coexisting forms of C, Fe, Ca, Si, and Al multiphase.

3.5. The Graphitization of BF Residual Fine Particles

Graphitization promotes coke cracks and generates coke fines, which decreases the coke’s mechanical strength. The coke fines have a more excellent L_C than the coke lump, reaching a higher maximum temperature than the coke lump.²⁷⁾ The carbon peak intensity increases as the coke descends in BF, indicating a clear correlation between the carbon structure and the heated temperature.

According to the wavelength of X-ray radiation(λ), the entire width of 002 carbon peaks at half maximum intensity(β) and the diffraction angle of 002 bands(θ) of Fig. 4, the average stacking height (L_C), the interlayer spacing (d₀₀₂) and the average layer number (n) in the carbon crystallites of powdered particles were obtained by classical Scherrer’s equation and Bragg’s law, as shown Eqs. (1), (2), (3). Table 6 lists the structural parameters of powdered particles derived from XRD analysis.

  

$$Lc=\frac{0.91\lambda }{\beta cos\theta }$$(1)

  

$$d_{002}=\frac{\lambda }{2sin\theta }$$(2)

  

$$n=\frac{Lc}{d_{002}}$$(3)

Table 6. Structural parameters of powdered particles derived from XRD analysis.

Sampling Location	2θ (002) (°)	β (002)	Lc (nm)	d (002) (nm)	n
Coke powder (−1 mm)	25.45	3.969	2.08	0.35	5.94
Fine particles in the S1 area
−0.073 mm	26.65	1.16	7.12	0.33	21.29
0.073–1 mm	26.59	1.19	6.94	0.33	20.73
1–6 mm	26.40	1.26	6.54	0.34	19.39
6–10 mm	26.36	1.31	6.29	0.34	18.60
10–20 mm	26.53	2.17	3.80	0.34	11.31
+20 mm	26.03	2.33	3.53	0.34	10.32
Fine particles in the S2 area
−0.073 mm	26.65	0.14	56.99	1.17	48.59
0.073–1 mm	26.60	0.15	53.79	1.17	45.78
1–6 mm	26.56	0.15	53.74	1.18	45.67
6–10 mm	26.59	0.16	51.68	1.18	43.96
10–20 mm	26.62	0.16	51.97	1.17	44.26
+20 mm	26.57	0.17	48.46	1.18	41.19

The reaction temperature has the most significant effect on ordering the carbon structure of coke.²⁸⁾ The graphitization degree of the particles in the S1 and S2 regions significantly increases compared to raw coke powder. The average carbon layer number of carbon-containing particles is n_{coke powder}<n_S1<n_S2. As the particle size of the powder rises, the graphitization degree of carbon gradually reduces, as shown in Table 6, particularly in the S1 region. The graphitization degree of −0.073 mm particles is 2.05 times that of +20 mm particles. Coke’s surface layer is likely more prone to graphitization. The surface layer detaches from the coke, resulting in a more significant powdered furnace burden. In the S2 area, the graphitization degree of powdered furnace burden with different particle sizes does not vary substantially. Because most particles present a slagging state and have few pores, the carbon-containing powder at the bottom is obtained mainly from the unreacted powdered burden of the upper part of BF rather than the surface layer detaching from the coke core of the furnace bottom.

4. Conclusions

The residual fine particles in the overhaul BF were investigated to clarify the characteristics and evolution process. The results of these observations are:

(1) The C, ZnO, and alkali metals accumulate significantly in fine particles. In the S1 area, the coke powder and unburned PCI coal mainly concentrate on −1 mm particles. The C content of the powder gradually increases as the particle size decreases. The alkali metals accelerate the deterioration of the surface layer, and the surface layer containing alkali metals flakes off and turns into fine particles. Because −1 mm particles lack pore channels for penetration of alkali metal, most alkali metals only adsorb on the surface, whereas +10 mm particles are more prone to slag iron erosion, reducing alkali metal adsorption. The amount of alkali metals K and Na increases first and then decreases as the particle size increases. The detached graphite crystals and alkali metals accumulate together in fine particles.

(2) As the furnace burden descends from S1 to S2 area, the mass fraction of “small particles” rises. The ZnO and alkali metal in the form of K(K, Na)₃Al₄Si₄O₆ evaporate, SiO₂ transforms into Ca₂Al₂SiO₇, and more high silicon minerals penetrate and gather in fine particles, increasing the (SiO₂/Al₂O₃) ratio and alkalinity (CaO+MgO/SiO₂+Al₂O₃) of fine particles. Some metal iron particles can move with the gas flow and become the powdered burden, and the Fe content of fine particles increases significantly in the S2 region.

(3) As the burden descends, the graphitization degree of carbon-containing powdered burden is n_{coke powder} < n_S1< n_S2. In the S1 region, as the particle size decreases, the graphitization degree of carbon increases significantly. The graphitization degree of carbon in −0.073 mm particles is 2.05 times that of +20 mm particles. The detachment of the surface layer of coke is accelerated by graphitization, resulting in the generation of carbon-containing particles in the furnace charge. ZnO exists as a hexagonal wurtzite single crystal structure or as adsorption on the surface of carbon particles. Multilayer petal-shaped graphite charcoal and angular slag phase particles disappear, and most of the particles become mutual cementation with the coexistence of C, Fe, Ca, Si, and Al.

Acknowledgments

The authors gratefully acknowledge Angang Steel Co., Ltd., and the support provided by the National Key R&D Program of China [grant number 2018YFB0605102] and LiaoNing Revitalization Talents Program [grant number XLYC2007198].

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