Состав некоторых железных руд и возможность их использования в производстве цемента (западный регион Монголии)

Iron ore is a mineral that contains high Fe 2 O 3 and a mixture of alumosilicates. In order to reduce module of Alumina in cement production, minerals that have high iron containment are used [1, 2]. Minerals such as magnetite (Fe 2 OyFeO), hematite (Fe 2 O₃), limonite (P-FeO(OH)), goethite (a-FeO(OH)), lepidocrocite (P-FeO(OH)), siderite (FeCO 3 ) and ilmenite (FeTiO 3 ) are contained in iron ore. As a result of the geological survey in Mongolia, approximately 200 iron ore mine were explored. The main objective of the study is to determine the chemical and mineral composition of the Western Mongolian iron ores and to investigate possibilities to use them in raw mix for obtaining cement.

Iron ores from “Kharganat” in Uvs aimag and “Suul Khar”, “Uvgundatsan” in Khovd aimag, and chemical pure calcium fluoride were used in this research. “Kharganat” iron ore deposit is located 45 km northwest from the center of Naranbulag soum and 3.2 km from lake Sharburd. The deposit length is 1200 m and width is 12-30 m. The geographic coordinates of Kharganat iron ores are 49^o37^/00^// (north latitude) and 92^o11^/00^// (east longitude). “Uvgundatsan” iron ore is located 105 km from Khovd city and 60 km northwest from Myangad soum. The geographic coordinates of Uvgundatsan iron ores are 48^o24^/24^// (north latitude) and 91^o51^/00^// (east longitude). “Suul Khar” iron ore is located 22 km from Khovd city and 45 km from Buyant soum. The geographic coordinates of Suul khar iron ores are 47^o51^/00^// (north latitude) and 91^o48^/00^// (east longitude). Chemical pure calcium fluoride (CaF 2 ) is used to study the effect of a mineralizing agent on the decomposition temperature of calcite in raw mix for obtaining cement clinker.

Experimental procedure

We used standard methods for taking and preparing samples. The mineral composition of raw materials was determined by X-Ray diffraction (XRD) and thermal analysis (TG/DTA); the chemical composition was determined by X-Ray fluorescence (XRF) analysis and calculation of cement raw mixture by Kinds method [1-3].

Results and discussion

Chemical composition of iron ores. The chemical composition of iron ores was determined by energy disperse X-ray fluorescence (ED-XRF) analysis. Table 1 shows that contents of iron oxide (Fe 2 O 3 ) in the Western Mongolian iron ores such as “Kharganat”, “Uvgundatsan”, “Suul Khar” are higher than in “Tumurt” (№4) iron ore, which is presently used in cement production.

Chemical composition of iron ores, %

Table 1

Iron ores	SiO 2	Al 2 O 3	Fe 2 O 3	CaO	Mn 2 O 3	MgO	SO 3	Na 2 O	K 2 O	Loi	Σ
№1	7.07	1.02	89.29	0.53	-	0.15	1.02	1.02	0.01	-	100.11
№2	9.684	1.164	87.227	1.408	0.129	-	-	-	-	1.18	99.995
№3	3.945	0.671	85.002	0.485	-	0.001	-	0.003	0.004	9.88	100.001
№4	8-20	0.5-4	58-74	1.8-6	-	3.5-7	2-7	8.5-20	0.5-3.6	2-7

№.1 “Kharganat” in Uvs aimag, №.2 “Uvgundatsan” in Khovd, №.3 “Suul Khar”in Khovd, №4 Tumurt

Mineral composition of iron ores. DTA/TG studies. The mineral composition of iron ores was investigated by TDA analysis. TG/TDA were undertaken. Derivatograph Q-1500, Hungary, thermo analyzer at a heating rate of 10^oC/min using a-Al₂O₃ was used as a reference material. The results are shown in the Fig. 1-3.

Fig. 1. DTA/TG curves of the “Kharganat” iron ore

From Fig. 1, we can see that:

• 1.    A small amount of heat was emitted due to the water evaporation in β-limonite [β-FeOOH) as in the case of β-Fe₂O₃∙H₂O] at 210^oC. At this point, sample weight was reduced by Δm = -4.5 mg ~ 0.3% and it can be calculated from weight loss curve. Iron oxide in β-limonite amount to 2.67% [4].

• 2.    Heat absorption was observed due to the γ-iron oxide (γ-Fe 2 O 3 ) in lepidocrocite composition (γ-FeOOH) as well as (γ-Fe₂O₃∙H₂O) was transformed into α -hematite ( α -Fe₂O₃) at 545^oC. At this point, sample weight was reduced by Δm = -3.0 mg ~ 0.2% and it can be calculated from weight loss curve. Iron oxide in lepidocrocite amount to 1.78%

• 3.    Heat absorption occurred due to transformation of α -hematite into β-hematite at 725^oC. In this transformation phase, sample weight increased by Δm =19 mg ~ 1.27%. The reason is that, during the process of α-Fe 2 O 3 to β-Fe 2 O 3 , density increases from 3.3 to 4.28 mg/cm³ [4].

Fig. 2. DTA/TG curves of the “Uvgundatsan” iron ore.

From Fig. 2, we can see that,

• 1.    A small amount of heat was emitted due to the water evaporation in β-limonite [β-FeO(OH), as β-Fe 2 O 3 ∙H 2 O] at the 220^oC. At this point, sample weight was reduced by Δm = -4 mg ~ 0.2% and it can be calculated from weight loss curve. Iron oxide in limonite amount to 1.87% [4].

• 2.    Heat absorption was observed due to the β-iron oxide (β-Fe 2 O 3 ) in lepidocrocite composition (γ-FeOOH) as well as γ-Fe 2 O 3 ∙H 2 O) transformed into α -hematite ( α -Fe 2 O 3 ) at 523^oC. At this point, sample weight was reduced by Δm = -3 mg ~ 0.15% and it can be calculated from weight loss curve. Iron oxide in lepidocrocite amount to 1.4% [4].

• 3.    Heat absorption occurred due to the transformation of α-hematite into β-hematite at 740^oC. In this transformation phase, sample weight increased by Δm =25 mg ~ 1.316%. The reason is that, during the process of α-Fe₂O₃ to β-Fe₂O₃, density increased from 3.3 to 4.28 mg/cm³.

From Fig. 3, we can see that,

• 1.    A deep endotherm peak was formed due to the hydro-hematite water evaporation at 310^oC. At this point, sample weight was reduced by Δm =110 mg ~ 7.38% and it can be calculated from weight loss curve. Iron oxide (Fe 2 O 3 ) in hydro-hematite amount to 65.601% [4]

• 2.    An exothermic effect occurred due to the process of γ-Fe 2 O 3 to α-Fe 2 O 3 in magnetite composition at 570^oC. In this transformation, sample weight reduced at m = -14 mg ~ 0.9395%. The reason is that, during the process sample density decreased from 4.28 to 3.3 mg/cm³.

Fig. 3. DTA/TG curves of the“Suul Khar” iron ore.

X-ray studies. X-ray diffraction (XRD) analysis was conducted by DRON-2 tool with iron cathodes and voltage of X-ray tube on 30 kV, ampera at 20 mA, width of slot at 1x10/0,25x6. Spacing between diffracting, which was minerals set, were calculated using ASTM card and directory and results are shown in the Fig. 4-6.

Fig. 4 showed that there are high intensity diffraction lines of magnetite at d=2.53 Å, medium intensity magnetite lines at d=2.95; 2.09 Ǻ, medium and low intensity diffraction lines of hematite at d= 4.88; 3.68; 2.69; 2.205 Ǻ and low intensity diffraction line of goethite at d=3.34 Ǻ; as in Fig. 5, which is for “Uvgundatsan” iron ore, there high and medium intensity diffraction lines of magnetite at d=4.85, 2.97, 2.72, 2.53, 2.41, 2.09, 1.71, 1.61 Ǻ, low intensity diffraction lines of hematite at d=3.69, 2.72, 2.69, 2.31, 2.20, 1.86, 1.69 Ǻ, quartz lines at d=4.27, 2.28, 2.00 Ǻ low intensity diffraction lines at d=3.34 Ǻ; as in figure 6, which is for “Suul Khar” iron ore, high and medium intensity diffraction lines of magnetite at d=2.97, 2.51, 2.45Ǻ, medium and low intensity diffraction lines of hematite at d=3.69, 2.2, 2.58, 2.30, 2.20, 2.18 Ǻ, quartz lines at d=2.34, 2.25 Ǻ and low intensity diffraction line of goethite at d=4.20, 3.34 Ǻ etc, respectively [5].

Fig. 4. X-ray Diffractogram of “Kharganat” iron ore

Fig. 5. X-ray Diffractogram of “Uvgundatsan” iron ore

Fig. 6. X-ray Diffractogram of “Suul Khar” iron ore

The results of mineral analysis showed that iron ores of “Kharganat” and “Uvgundatsan” mostly contain magnetite (Fe 3 O 4 ), whereas iron ore of “Suul Khar” – hematite (Fe 2 O 3 ).

The research result of the effect of calcium fluoride on decomposition temperature of calcite in raw mix for cement production. Raw mix used in cement clinker production that consists of “Shokhoit” limestone, “Shal” clay and “Kharganat” iron ore was calculated by Kinds method. Silica module was n=2.2 while Saturation coefficients (SC) were at 0.83, 0.88 and 0.93 in this calculation. The results are shown in Table 3 and chemical composition of the initial materials [6] which are used to make raw mixes is shown in Table 2.

According to the result of raw material evaluation, it can be observed that amounts of iron ore in 100 kg cement are approximate for every saturation coefficient level and modules (Table 3), in clinker composition they are within the limit of Portland cement standard [7]. In conclusion, it could be assumed that these iron ores can be used in cement production.

Research was conducted as follows: Calcium fluoride at 0%, 0.5%, 1.0% and 1.5% of raw material weight were added to limestone of “Shokhoit”, clay from “Shal” and iron ore of “Kharganat” at saturation coefficient of SC=0.93 and silica module at n=2.2 (Table 4). The effect of calcium fluoride on decomposition temperature of calcite in raw mix for obtaining cement we determined by DTA analysis. Result is shown in Fig. 7. From Fig. 7 shown, weak exothermic effect was observed due to the water evaporation of clay minerals in raw material composition at 325-185^oC, deep endotherm peak was observed due to the decomposition of calcite (CaCO₃), which is the main component of composition, at 865-870^oC. The sample weight loss was 32.52% when calcium fluoride was not available, the loss was 33.4% when calcium fluoride was added 0.5% while it was 1.0% the loss was 32.78%, and when it was 1.5% the loss was 32.96%. From Fig. 7 we can see that, the decomposition temperature of calcite (CaCO 3 ) was reduced by 5^oC, 10^oC, and 15^oC when calcium fluoride (CaF 2 ) in the raw mix for obtaining cement clinker that consists of “Shokhoit” limestone, “Shal” clay and “Kharganat” iron ore was added up to 0.5%, 1.0% and 1.5%.

Chemical composition of raw material, %

Composition and characteristics of mixes for obtaining cement clinkers

Composition of raw mixes with addition CaF 2

Table 2

Name of raw material	SiO 2	Al 2 O 3	Fe 2 O 3	CaO	MgO	SO 3	Na 2 O	K 2 O	Mn2O3	other	Loi	Σ
Limestone of Shokhoite	0.85	0.10	0.25	54.64	0.25	0.20	0.22	-	-	0.62	42.87	100
Clay of Shal	58.33	15.4	3.12	5.13	3.58	0.222	2.7	2.89	-	0.298	8.33	100
Iron ore of Kharganat	7.07	1.02	89.29	0.53	0.15	1.02	1.02	0.01	-		-	100.11
Iron ore of Uvguntsan	9.684	1.164	86.435	1.408	-	-	-	-	0.129		1.18	100
Iron ore of Suul khar	3.945	0.671	85.002	0.485	0.001		0.003	0.004	-		9.89	100.001

Table 3

Mix	Component content, (mass. %)			SC	Modules
	Lime stone	Clay	Iron ore		SM	AM
A-1	73.90	23.98	2.23	0.83	2.2	1.3
A-2	75.17	23.05	2.15	0.88	2.2	1.29
A-3	75.73	22.20	2.07	0.93	2.2	1.31
B-1	73.80	23.86	2.32	0.83	2.2	1.29
B-2	74.80	23.86	2.24	0.88	2.2	1.29
B-3	75.77	22.11	2.16	0.93	2.2	1.25
C-1	73.66	24.02	2.32	0.83	2.2	1.29
C-2	74.65	23.11	2.23	0.88	2.2	1.26
C-3	75.60	22.26	2.15	0.93	2.2	1.3

Mix A was calculated from Kharganat iron ore. Mix B was calculated from Uvgudatsan iron ore. Mix C was calculated from Suulkhar iron ore

Table 4

Mix	Amount of mix, (m. %)
	Amount of initial mix, (m. %)	Addition CaF 2 , (m. %)
A-3a	100	=
A-3b	99.5	0.5
A-3c	99	1.0
A-3d	98.5	1.5

Б. Цэрэнханд, Б. Баяраа, Г. Долмаа. Химический и минералогический состав некоторых глин Убснурского аймака (Монголия)

Conclusion

Based on the studies, the following conclusion can be drawn:

• •    The chemical investigation result showed that iron oxide (Fe₂O₃) in the Western Mongolian iron ores is contained in Uvgondatsan (in Khovd) – 87.23%, Suul khar (in Khovd) – 85.00% and Khargant (in Uvs) – 89.29%. Therefore, these iron ores can be used in cement production.

• •    X-ray diffraction and DTA analysis results show that iron ores of “Kharganat” and “Uvgundatsan” are mostly contained magnetite (Fe 3 O 4 ) while iron ore of “Suul Khar” is mostly contained hematite (Fe 2 O 3 ).

• •    A calculation of raw mix for obtaining cement clinker was done by using iron ores, clay of “Shal” and limestone of “Shokhoit”, and calculated modules that from clinker compositoin (n=2.2 p=1.25-1.30) are within the limit of Portland cement standard.

• •    The decomposition temperature of calcite (CaCO₃) was reduced by 5^oC, 10^oC, and 15^oC when calcium fluoride (CaF₂) in the raw mix for obtaining cement clinker that consists of “Shokhoit” limestone, “Shal” clay and “Kharganat” iron ore was added up 0.5%, 1.0% and 1.5%, respectively.