镁铝对烧结矿中铁酸钙的矿物学特性影响

doi:10.13745/j.esf.sf.2020.5.44

摘要/Abstract

摘要：

铁酸钙是高碱度烧结矿中的主要黏结相矿物,它的含量、结晶形态、化学成分及晶体结构等矿物学特性对烧结矿质量起着关键性作用,而烧结原料中各组分的含量直接影响着铁酸钙的生成。以Fe₃O₄、SiO₂、CaO、MgO、Al₂O₃的化学纯试剂为原料,在实验室进行微型烧结实验,运用XRD、偏光显微镜、电子探针等手段,定量分析研究了原料组分中MgO、Al₂O₃对烧结矿中铁酸钙的生成及其矿物学特性的影响。原料中MgO含量的增加对铁酸钙的生成有一定抑制作用,尤其在MgO含量为2.0%~3.0%时,烧结矿中铁酸钙含量明显减少,其晶体形态也从以板柱状和针状为主逐渐过渡为它形不规则状;原料中Al₂O₃的增加,对烧结矿中铁酸钙的形成具有促进作用,即随着Al₂O₃的增加铁酸钙含量呈明显增加趋势,且铁酸钙的形态也由以柱状和针状为主向板柱状变化。电子探针成分分析及矿物化学式计算结果表明,铁酸钙是由Fe₂O₃、CaO、SiO₂、Al₂O₃及MgO组成的复杂结晶体,其化学通式为Ca_2.60Mg_0.44Si_1.07Al_0.96Fe_8.92O₂₀。原料中MgO、Al₂O₃含量的变化,对铁酸钙的化学成分中Fe₂O₃/CaO摩尔分数比影响不大,均接近3∶2。上述研究结果对于深刻理解烧结工艺条件下铁酸钙晶相的晶体化学特征及其对烧结矿质量的影响具有重要指导意义。

关键词: 铁酸钙, 矿物学特性, MgO, Al₂O₃, 烧结矿

Abstract:

Calcium ferrite is the main binder phase mineral in high basicity sintered ore. Its mineralogical characteristics such as content, crystal form, chemical composition and crystal structure play a key role in the quality of the sintered ore. The content directly affects the formation of calcium ferrite. In this paper, we used the chemically pure reagents of Fe₃O₄, SiO₂, CaO, MgO, and Al₂O₃ as raw materials and carried out micro-sintering experiments in the laboratory. Using XRD, polarizing microscope, electron microprobe and other means we performed quantitative analyses of MgO and Al₂O₃ in the raw material components to investigate the formation of calcium ferrite in sintered ores and its influence on mineralogical properties. The results showed that the increase of MgO content in the raw material had a certain inhibitory effect on the formation of calcium ferrite, especially when the MgO content was 2.0% to 3.0%. The calcium ferrite content in the sinter was significantly reduced, and its crystal morphology also changed from plate columnar and needle-like shape gradually transitioning to an irregular shape. The increase in Al₂O₃ in the raw material promoted the formation of calcium ferrite in the sinter as calcium ferrite content increased significantly with increasing Al₂O₃ and ferric acid contents. The morphology of calcium also changed from columnar and needle-shaped to columnar. Electronic probe composition analysis and mineral chemical formula calculation results show that calcium ferrite is a complex crystal composed of Fe₂O₃, CaO, SiO₂, Al₂O₃ and MgO, and its chemical formula is Ca_2.60Mg_0.44Si_1.07Al_0.96Fe_8.92O₂₀. The changes in MgO and Al₂O₃ contents in the raw materials had little effect on the mole fraction ratio of Fe₂O₃ to CaO in the chemical composition of calcium ferrite, both were close to 3∶2. The above research results are of great guiding significance for an in-depth understanding of the chemical characteristic of calcium ferrite crystal phase under sintering process conditions and its effect on the quality of sinter.

Key words: calcium ferrite, mineralogical property, MgO, Al₂O₃, iron ore sinter

中图分类号:

韩秀丽, 司天航, 李鸣铎, 周祥, 刘磊, 赵凯. 镁铝对烧结矿中铁酸钙的矿物学特性影响[J]. 地学前缘, 2020, 27(5): 280-290.

HAN Xiuli, SI Tianhang, LI Mingduo, ZHOU Xiang, LIU Lei, ZHAO Kai. Influences of MgO and Al₂O₃ on the mineralogical properties of calcium ferrite in iron ore sinter[J]. Earth Science Frontiers, 2020, 27(5): 280-290.

图/表 16

表1 烧结原料化学成分

Table 1 Chemical compositions of sintering raw materials

编号	w_B/%					碱度
编号	Fe₃O₄	SiO₂	CaO	MgO	Al₂O₃	碱度
M1.0	82.5	5.0	10.0	1.0	1.5	2.0
M1.5	82.0	5.0	10.0	1.5	1.5	2.0
M2.0	81.5	5.0	10.0	2.0	1.5	2.0
M2.5	81.0	5.0	10.0	2.5	1.5	2.0
M3.0	80.5	5.0	10.0	3.0	1.5	2.0
A1.0	82.5	5.0	10.0	1.5	1.0	2.0
A1.5	82.0	5.0	10.0	1.5	1.5	2.0
A2.0	81.5	5.0	10.0	1.5	2.0	2.0
A2.5	81.0	5.0	10.0	1.5	2.5	2.0
A3.0	80.5	5.0	10.0	1.5	3.0	2.0

表2 不同MgO、Al2O3含量烧结矿的矿物组成

Table 2 Mineral compositions of sintered ores with different MgO and Al2O3 contents

样号	黏结相含量/%			金属相含量/%		其他含量/%
样号	铁酸钙	玻璃质	硅酸二钙	磁铁矿	赤铁矿	氧化钙
M1.0	40~45	5~10	微量	25~30	20~25	微量
M1.5/ A1.5	35~40	5~10	微量	35~40	15~20	微量
M2.0	35~40	5~10	1~2	40~45	10~15	微量
M2.5	30~35	5~10	1~2	45~50	10~15	微量
M3.0	25~30	5~10	2~3	55~60	5~10	微量
A1.0	25~30	10~15	微量	35~40	15~20	3~5
A2.0	40~45	5~8	微量	35~40	10~15	微量
A2.5	45~50	5~8	微量	30~35	10~15	微量
A3.0	50~55	3~5	微量	25~30	10~15	3~5

图1 烧结矿的XRD分析图谱

Fig.1 X-ray diffraction pattern of the sinter

图2 偏光显微镜下不同MgO含量下烧结矿的显微结构 a—MgO 1.0% 斑状结构;b—MgO 1.5% 交织熔蚀结构;c—MgO 2.0% 熔蚀结构;d—MgO 3.0% 熔蚀结构;e—MgO 1.0% 骸晶赤铁矿;f—MgO 2.0% 短柱状铁酸钙;g—MgO 3.0% 板状铁酸钙;h—MgO 1.0% 集中出现的气孔;i—MgO 3.0% 连接成片的磁铁矿。1—磁铁矿;2—赤铁矿;3—柱状铁酸钙;4—针状铁酸钙;5—它形铁酸钙;6—玻璃质;7—气孔。

Fig.2 Polarizing microscope images showing the microstructures of sinters with different MgO contents

图3 偏光显微镜下不同Al2O3含量下烧结矿显微结构 a—Al2O3 1.0% 斑状结构;b—Al2O3 1.5% 熔蚀结构;c—Al2O3 2.0% 熔蚀结构;d—Al2O3 3.0% 熔蚀结构;e—Al2O3 3.0% 骸晶赤铁矿;f—Al2O3 2.0% 柱状铁酸钙;g—Al2O3 3.0% 板柱状铁酸钙;h—Al2O3 2.5% 成片磁铁矿;i—Al2O3 3.0% 连晶磁铁矿周围微裂隙。1—磁铁矿;2—赤铁矿;3—柱状铁酸钙;5—它形铁酸钙;6—玻璃质;7—气孔;8—裂隙。

Fig.3 Polarizing microscope images showing the microstructures of sinter with different Al2O3 contents

表3 不同形态铁酸钙的体积分数

Table 3 Volume fraction of different forms of calcium ferrite

样号	铁酸钙体积分数/%
样号	总量	针状	柱状	不规则状
M1.0	40~45	15~20	10~15	10~15
M1.5/A1.5	35~40	15~20	10~15	5~10
M2.0	35~40	10~15	15~20	5~10
M2.5	30~35	5~10	10~15	10~15
M3.0	25~30	5~10	10~15	5~10
A1.0	25~30	10~15	5~10	5~10
A2.0	40~45	15~20	15~20	5~10
A2.5	45~50	10~15	10~15	20~25
A3.0	50~55	5~10	15~20	25~30

图4 铁酸钙含量随烧结矿中MgO变化 a—铁酸钙总量随原料中MgO含量变化趋势;b—针状铁酸钙含量随原料中MgO含量变化趋势。

Fig.4 Changes of total(a) and needle-shaped(b) calcium ferrite contents with MgO in sinter

图5 偏光显微镜下铁酸钙微结构随MgO含量变化 a—MgO 1.5%;b—MgO 2.0%;c—MgO 2.5%;d—MgO 3.0%。1—磁铁矿;2—它形铁酸钙;3—针状铁酸钙;4—短柱状铁酸钙;5—玻璃质;6—裂隙。

Fig.5 Polarizing microscope images showing changes of calcium ferrite microstructures with MgO content

图6 铁酸钙含量随烧结矿中的Al2O3变化 a—铁酸钙总量随原料中Al2O3含量变化趋势;b—针状铁酸钙含量随原料中Al2O3含量变化趋势。

Fig.6 Changes of total(a) and needle-shaped(b) calcium ferrite contents with Al2O3 in sinter

图7 偏光显微镜下铁酸钙微结构随Al2O3含量变化 a—Al2O3 1.0%;b—Al2O3 2.0%;c—Al2O3 2.5%;d—Al2O3 3.0%。1—磁铁矿;2—赤铁矿;3—柱状铁酸钙;4—针状铁酸钙;5—它形铁酸钙;6—玻璃质;7—气孔。

Fig.7 Polarizing microscope images showing the changes of calcium ferrite microstructures with Al2O3 content

图8 不同MgO含量烧结矿中铁酸钙背散射电子图 a—MgO 1.0%;b—MgO 1.5%;c—MgO 2.5%;d—MgO 3.0%。a1—表4序号1;a2—表4序号2;a3—表4序号4;b1—表4序号5;b2—表4序号6;c1—表4序号11;c2—表4序号13;c3—表4序号14;d1—表4序号15;d2—表4序号17;d3—表4序号18。

Fig.8 EBSD images of calcium ferrite in sinters with different MgO contents

图9 不同Al2O3含量烧结矿中铁酸钙背散射电子图 a—Al2O3 1.0%;b—Al2O3 2.0%;c—Al2O3 2.5%;d—Al2O3 3.0%。a1—表5序号1;a2—表5序号2;b1—表5序号8;c1—表5序号14;c2—表5序号15;d1—表5序号16;d2—表5序号17。

Fig.9 EBSD images of calcium ferrite in sinter with different Al2O3 contents

表4 不同MgO含量烧结矿中铁酸钙电子探针数据

Table 4 Electron microprobe analyses of sinter with different MgO content

样号	序号	w_B/%						备注
样号	序号	Fe₂O₃	CaO	MgO	SiO₂	Al₂O₃	合计	备注
M1.0	1	82.69	9.77	3.05	1.80	3.99	101.30	柱状
	2	81.66	10.08	2.91	2.01	4.19	100.85	柱状
	3	77.33	12.91	1.95	3.63	4.57	100.39	针状
	4	79.72	10.37	2.77	2.44	4.79	100.09	它形
M1.5	5	67.16	16.94	2.43	8.08	4.10	98.71	柱状
M1.5	6	70.61	15.09	2.45	5.66	4.65	98.46	它形
M2.0	7	72.37	15.30	1.52	7.15	3.88	100.22	针状
	8	72.12	15.88	1.61	7.11	3.93	100.65	柱状
	9	72.64	15.57	1.63	7.09	4.30	101.23	它形
	10	69.22	18.13	1.47	8.58	3.95	101.35	它形
M2.5	11	78.21	11.66	1.82	3.90	3.80	99.39	针状
	12	77.31	12.38	1.29	3.82	3.67	98.47	柱状
	13	77.65	12.60	1.22	4.09	3.87	99.43	它形
	14	77.61	11.69	1.43	3.91	3.79	98.43	它形
M3.0	15	73.78	15.59	1.20	6.74	3.72	101.03	柱状
	16	74.07	15.56	1.27	6.97	3.81	101.68	针状
	17	73.82	15.46	1.19	6.91	3.19	100.57	它形
	18	73.24	15.79	1.30	6.99	3.43	100.75	它形
	19	72.51	16.19	1.04	6.85	3.82	100.41	它形
	20	72.53	16.17	1.02	6.81	4.07	100.60	它形

表5 不同Al2O3含量烧结矿中铁酸钙电子探针数据

Table 5 Electron microprobe analyses of sinter with different Al2O3 content

样号	序号	w_B/%						备注
样号	序号	Fe₂O₃	CaO	MgO	SiO₂	Al₂O₃	合计	备注
A1.0	1	70.42	15.92	1.70	6.86	3.11	98.01	柱状
	2	70.48	15.5	2.32	7.37	2.46	98.13	柱状
	3	70.26	15.49	2.16	7.99	2.70	98.60	针状
	4	69.57	15.77	0.96	7.63	3.01	96.94	它形
A1.5	5	67.16	16.94	2.43	8.08	4.10	98.71	柱状
A1.5	6	70.61	15.09	2.45	5.66	4.65	98.46	针状
A2.0	7	69.87	15.81	1.04	7.98	6.30	101.00	针状
	8	69.75	16.10	0.89	8.05	6.11	100.90	柱状
	9	69.10	15.26	1.67	8.94	4.45	99.42	它形
	10	69.08	15.86	1.29	8.74	6.76	101.73	它形
A2.5	11	68.99	15.40	2.17	7.74	6.25	100.55	柱状
	12	68.69	15.39	1.72	7.04	8.23	101.07	柱状
	13	69.44	14.46	2.27	6.65	7.19	100.01	针状
	14	70.32	14.29	2.09	6.52	7.22	100.44	它形
	15	68.13	14.78	1.89	6.84	7.82	99.46	它形
A3.0	16	61.56	15.36	1.40	9.38	10.99	98.69	柱状
A3.0	17	61.15	15.27	1.51	9.46	11.15	98.54	它形

图10 铁酸钙中MgO含量随原料中MgO变化趋势

Fig.10 Relationship of MgO content in calcium ferrite and in raw material

图11 铁酸钙中Al2O3含量随原料中Al2O3变化趋势

Fig.11 Relationship of Al2O3 content in calcium ferrite and in raw material

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