Additive for reducing the roasting temperature of fluxed magnetite pellets and a method of using it

Abstract

The present invention discloses additive for reducing the roasting temperature of fluxed magnetite pellets and a method of using it, consisting of components: B.sub.2O.sub.3, Mn.sub.2O.sub.3, the B.sub.2O.sub.3 and Mn.sub.2O.sub.3 are pure chemical reagents, the mass of the additive is 0.8%, 4% of the dry basis mass of the magnetite concentrate, respectively, the magnetite concentrate, bentonite clay, calcium flux and additives will be dosed with 12-14% water of the dry base mass ratio of the mixture, prepared into green pellets of 10-12.5 mm in diameter in a disc ball making machine. After the pellets are completely dried, preheat them for 15˜20 min at 600˜1000 ° C. to ensure that Mn.sub.2O.sub.3 is fully decomposed, then roasting is carried out for 15 min at 1200 ° C., and after roasting, the pellets are cooled to room temperature to obtain the finished pellets.

Claims

1. An additive that reduces the roasting temperature of fluxed magnetite pellets, wherein it is composed of components: B.sub.2O.sub.3, Mn.sub.2O.sub.3, the B.sub.2O.sub.3, Mn.sub.2O.sub.3 are pure chemical reagents, the additive is mixed with B.sub.2O.sub.3 and Mn.sub.2O.sub.3, wherein the mass percentage of B.sub.2O.sub.3 is 0.8% of the dry base mass of the magnetite concentrate, and the mass percentage of Mn.sub.2O.sub.3 is 4% of the dry base mass of the magnetite concentrate, appropriately extend the preheating time of 600˜1000 ° C. in the preheating temperature section, so that Mn.sub.2O.sub.3 slowly loses weight and decomposes at 600˜1000 ° C. and slowly releases O.sub.2, promotes the oxidative recrystallization of magnetite from the inside, and sets the roasting temperature below the melting point temperature of low melting point substances below 1200° C.

2. A method for using an additive that reduces the roasting temperature of flux magnetite pellets according to claim 1: the magnetite concentrate, bentonite clay, calcium flux and additives will be dosed with 12-14% water of the dry base mass ratio of the mixture, prepared into green pellets of 10-12.5 mm in diameter in a disc ball making machine, After the pellets are completely dried, preheat them for 15˜20 min at 600˜1000° C. to ensure that Mn.sub.2O.sub.3 is fully decomposed, then roasting is carried out for 15 min at 1200° C., and after roasting, the pellets are cooled to room temperature to obtain the finished pellets.

3. A method of using an additive for reducing the roasting temperature of fluxed magnetite pellets as claimed in claim 3: characterized in that said bentonite clay is 0.7% of the dry basis mass of the mixture.

Description

ILLUSTRATED CATALOGUE

[0012] FIG. 1: Flow chart of the pellet production process of the present invention.

[0013] FIG. 2: Experimental TG curve of thermal gravimetric analysis of the present invention.

SPECIFIC EMBODIMENT

[0014] Referring to the attached FIG. 1 pellet ore production process for implementation

EXAMPLE 1

[0015] Using local high-silica magnetite concentrate (TFe66.3%, SiO2 content 6.17%) was used as raw material, 0.7% bentonite and calcium flux CaO were added and mixed, no B.sub.2O.sub.3, Mn.sub.2O were added, after adding 12˜14% moisture, the raw balls of 10˜12.5 mm in diameter are prepared in the disc ball making machine, the falling strength of raw balls is 5 times/ball (0.5 m), the compressive strength of raw balls is 8.2N, after the raw balls are dehydration and dried, the preheating temperature is 900° C., the preheating time is 15 min, the roasting temperature is 1200° C., the roasting time is 15 min. the average strength of the roasted finished balls is 1980N/pc, and the strength of the pellet ore is lower at this time.

EXAMPLE 2

[0016] Using local high-silica magnetite concentrate (TFe66.3%, SiO2 content 6.17%) as raw material, adding 0.7% bentonite, calcium flux CaO, 4% Mn2O3 for mixing, without adding B.sub.2O.sub.3. after adding 12˜14% moisture, the raw balls of 10˜12.5 mm in diameter are prepared in the disc ball making machine, the falling strength of raw balls is 5 times/ball (0.5 m), the compressive strength of raw balls is 8.4N, after the raw balls are dehydration and dried, the preheating temperature is 600˜1000° C., the preheating time is 15 min, the roasting temperature is 1200° C., the roasting time is 15 min. the average strength of the roasted finished balls is 2274N/pc, and the strength of the pellet ore is slightly higher at this time.

EXAMPLE 3

[0017] Using local high-silica magnetite concentrate (TFe66.3%, SiO2 content 6.17%) as raw material, adding 0.7% bentonite, calcium flux CaO, 0.8% B.sub.2O.sub.3 and then mixing, without Mn.sub.2O.sub.3. after adding 12˜14% moisture, the raw balls of 10˜12.5 mm in diameter are prepared in the disc ball making machine, the falling strength of raw balls is 6 times/ball (0.5 m), the compressive strength of raw balls is 9.1N, after the raw balls are dehydration and dried, the preheating temperature is 900° C., the preheating time is 15 min, the roasting temperature is 1200° C., the roasting time is 15 min. the average strength of the roasted finished balls is 2631N/pc, and the strength of the pellet ore is higher at this time.

EXAMPLE 4

[0018] Using local high-silica magnetite concentrate (TFe66.3%, SiO2 content 6.17%) as raw material, add 0.7% bentonite, calcium melt CaO, 0.8% B.sub.2O.sub.3, 4% Mn2O3 and mix well, after adding 12˜14% moisture, the raw balls of 10˜12.5mm in diameter are prepared in the disc ball making machine, the falling strength of raw balls is 6 times/ball (0.5 m), the compressive strength of raw balls is 9.3N, after the raw balls are dehydration and dried, the preheating temperature is 600˜1000° C., the preheating time is 15 min, the roasting temperature is 1200° C., the roasting time is 15 min. the average strength of the roasted finished balls is 2962N/pc, and the strength of the pellet ore is very high at this time.

EXAMPLE 5

[0019] Using local high-silica magnetite concentrate (TFe66.3%, SiO2 content 6.17%) was used as raw material, 0.7% bentonite and calcium flux CaO were added and mixed, no B.sub.2O.sub.3, Mn.sub.2O were added, after adding 12˜14% moisture, the raw balls of 10˜12.5 mm in diameter are prepared in the disc ball making machine, the falling strength of raw balls is 6 times/ball (0.5 m), the compressive strength of raw balls is 9.5N, after the raw balls are dehydration and dried, the preheating temperature is 900° C., the preheating time is 15 min, the roasting temperature is 1280° C., the roasting time is 15 min. the average strength of the roasted finished balls is 3063N/pc, and the strength of the pellet ore strength at this time.

[0020] Macro strength indicates: B.sub.2O.sub.3 and Mn.sub.2O.sub.3 have a promoting effect on the oxidative recrystallization process of magnetite at low temperature, but the promotion methods are different. among them, Mn.sub.2O.sub.3 promotes the oxidation and recrystallization of magnetite from the gas phase, and B.sub.2O.sub.3 promotes the movement of Fe2+ from the liquid phase to accelerate the solid-phase consolidation. The combined promotion effect of the additive was greater than that of the single additive, and the macroscopic strength results showed that the compressive strength of pellet ore at 1200° C. after adding the additive was basically the same as the compressive strength of pellet ore in the roasted specimens at 1250-1280° C.

[0021] The traditional method to reduce the bonding rate of fusible pellets by high temperature roasting is to add MgO fusible to the pellets to produce a high melting point substance, which makes it unsuitable for bonding at high temperatures. Traditional oxidation roasting of magnetite pellets is carried out layer by layer from the outside to the inside. Calcium ferrate systems such as CaO.Math.Fe.sub.2O.sub.3, CaO.Math.2Fe.sub.2O.sub.3, CaO.Math.Fe.sub.2O.sub.3-CaO.Math.2FeO eutectic mixtures, which all have low melting points of 1216° C., 1226° C. and 1205° C. respectively, can play a role in promoting the bonding of iron ore particles and increasing the strength of pellets with the moderate amount of liquid phase during the high temperature oxidation roasting of pellets. However, in the pellet roasting process, the amount of liquid phase not only needs to be strictly controlled, but also the amount of calcium ferrate liquid phase is difficult to control, and too much liquid phase will lead to pellet bonding and porosity reduction, but worsen the pellet metallurgical properties.

[0022] The present invention starts from the root cause by adding other additives to increase the strength of the pellets as much as possible while appropriately lowering the pellet roasting temperature, fundamentally control the amount of liquid phase generation at high temperatures to avoid bonding problems, while reducing the roasting temperature of pellet ore is also conducive to energy saving and consumption reduction, prolonging the service life of equipment and ensuring the smooth roasting process, which is of great significance to the industrial production of pellet ore.