CN113166863A

CN113166863A - Charge for manufacturing ferrosilicon

Info

Publication number: CN113166863A
Application number: CN201980080310.XA
Authority: CN
Inventors: 德米特里杰·阿列克桑多维奇·卡萨特金; 鲍里斯·利本森; 安德烈·彼得罗维奇·洛坎金
Original assignee: Slavos Ltd
Current assignee: Slavos Ltd
Priority date: 2019-03-25
Filing date: 2019-11-25
Publication date: 2021-07-23
Also published as: EP3865599A4; RU2704872C1; WO2020197437A1; EP3865599A1

Abstract

The charge composition for manufacturing ferrosilicon comprises quartzite, carbonaceous reducing agent and iron-bearing material in the form of pyrite ember slag pellets in the following proportions: 34-50 wt% quartzite, 30-34 wt% carbonaceous reducing agent, and the balance pyrite cinder pellets. No carbon steel filings were used in the charging. The carbonaceous reducing agent comprises 40-67 wt% of nut coke and 33-60 wt% of wood waste, wherein the wood waste is in the form of particles or chips. The pyrite cinder pellets contained pyrite cinder and liquid glass as a binder in the following proportions: 85-93 wt% pyrite dross and 7-15 wt% liquid glass on a dry weight basis. The result is an expanded range of available charge compositions, the use of cheap and abundant raw materials, and improved operating characteristics of the furnace installation by using charge compositions with low electrical conductivity in ferrosilicon manufacturing processes, which results in increased silica recovery, increased filtration layer of the charge, and reduced formation of waste slag, and thus, it is possible to operate the furnace transformer at higher voltage levels, thereby increasing the electrical efficiency of the furnace installation.

Description

Charge for manufacturing ferrosilicon

Technical Field

The present invention relates to metallurgy, and is especially ferrosilicon.

Background

Ferrosilicon with 18-95% silicon content is smelted in ferroalloy furnace. The ore component of the charge is quartzite, which contains more than 95% SiO₂And a small amount of alumina (Al)₂O₃). The quartzite was crushed and the clay washed away. Metallurgical coke breeze is used as the reducing agent. The reducing agent basically requires that:

-low ash content;

-a high electrical resistance;

-low volatile content;

-tablet strength upon heating.

In order to produce the desired silicon concentration in the alloy, crushed chips of carbonaceous steel are introduced into the charge. In the presence of iron, the process is facilitated. Silicon is reduced by carbon according to the following reaction: SiO 2₂+2C＝Si+2CO。

When the reducing agent is in excess, silicon carbide is also formed: SiO 2₂+3C＝SiC+2CO。

The presence of silicon carbide is undesirable because, due to its refractory nature, the lower part of the furnace becomes cluttered and the efficiency is reduced. In the presence of iron, silicon carbide is freed from silicon dioxide (SiO) according to the following reaction₂) And (3) destruction:

2SiC+SiO₂＝3Si+2CO Si+Fe＝FeSi。

the more iron in the charge, the lower the temperature at which ferrosilicon is produced.

In a continuously operated smelting process, the electrode is immersed deep into the charge. When loading the charge material, one tries to create and hold the charge in the form of a cone around the electrode. The purpose of the charge cone is to make it difficult for the gases formed in the reaction zone to escape and to reduce heat losses. The wider the charging cone, the larger the active area of the furnace, the better the charging settlement and the more stable the operation of the furnace.

In the arc-shaped zone in the charge, a cavity is formed which is very hot. The walls of the cavity are continuously melted and the silicon is reduced and dissolved in the liquid iron to form the ferrosilicon alloy. The alloy descends into the reaction zone.

During normal furnace operation, once burned, the electrode slowly descends and the charge settles evenly around the electrode. The molten ferrosilicon is placed in a ladle 12 to 15 times a day and then poured.

From the application of invention RU 96113642 published on 10/20/1997, a charge for smelting ferrosilicon is known, comprising quartzite, bituminous coke, wood and metal scrap, characterized in that it also comprises metallurgical coke used in a mixture with bituminous coke, with the following composition ratios in% by weight: 4-50% of wood waste, 10-30% of mixture of asphalt coke and metallurgical coke, 5-20% of metal waste and the balance of quartzite, wherein the proportion of the metallurgical coke is 5-50% of the total mass of the coke mixture. Meanwhile, Banichi quartzite is used as the quartzite. Meanwhile, chips having a size of not more than 50mm are used as wood waste. Meanwhile, 14A grade scrap and transformer steel scrap having a size of not more than 42mm are used as metal scrap.

An invention is known from patent RU 2094518, published 10/27/1997, which relates to ferrous metallurgy, i.e. to charges for manufacturing ferrosilicon. The charge comprises quartzite, wood and metal scrap, and metallurgical coke in the form of a mixture with bituminous coke, having the following composition ratios in% by weight: 4-50% of wood waste, 10-30% of a mixture of asphalt coke and metallurgical coke, 5-20% of metal waste and the balance of quartzite, wherein the proportion of the metallurgical coke is 5-50% of the total mass of the coke mixture.

An invention is known from patent RU 2106423, published on 10.3.1998, which relates to ferrous metallurgy, i.e. to charges for manufacturing ferrosilicon. A charge for smelting ferrosilicon comprising pellets of quartzite, coke, metal scrap and chemically manufactured waste contact material having the following composition ratios in weight%: 10-40 parts of coke, 6-30 parts of metal waste, 0.3-20 parts of pellets and the balance of quartzite.

From the author certificate SU 618437 published on 8/5/1978, a charge for ferrosilicon smelting is known, which contains quartzite, a carbonaceous reducing agent and scrap iron, characterized in that, in order to reduce the aluminium in the alloy, it also contains pyrite, which has the following composition ratios in weight%: 40-70 parts of quartzite; 15-45 parts of carbonaceous reducing agent; 2-40 parts of pyrite; scrap iron-the balance.

From the author certificate SU 765389 published on 23.2.1983, a charge for manufacturing ferrosilicon low in silicon is known, which contains iron-containing material and coke, characterized in that, in order to increase the manganese in the alloy, reduce the release of graphite dust, no rare iron dust is used, the charge also contains limestone and lean ferromanganese ore, and as iron-containing material, iron-containing quartzite, which has the following composition ratios in weight%: iron-containing quartzite-44-58; 19-20 parts of lean iron manganese ore; limestone-6-9.

From the author certificate SU 998558 published on 23.2.1983, a charge for the preparation of ferrosilicon is known, which contains a carbonaceous reducing agent, a metal additive and quartzite, characterized in that, in order to increase the degree of reduction of silicon and to increase the furnace efficiency, it also contains silicate slag and quartzite barite, with the following composition ratios in weight-%: 20-35 parts of carbonaceous reducing agent; 1-40 parts of metal additive; 1-10 parts of silicate slag; 0.5 to 10 portions of quartzite barite; quartzite-balance.

From the author certificate SU 998567 published on 23.2.1983, a charge for smelting ferrosilicon low-silicon is known, comprising quartzite, scrap iron, coke, characterized in that, in order to reduce its electrical conductivity at the furnace top and to reduce the silicon loss, it also comprises manganite having the following composition ratios in weight%: quartzite-28-32; 40-47.5 of scrap iron; 7-12 parts of carbonate manganese ore; coke-16.5-18.

From the author certificate SU 1565913 published on 5/23/1990 charge for ferrosilicon is known, comprising quartzite, coke breeze and scrap iron, characterized in that, in order to improve the mechanical strength and the deoxidation capacity of the resulting alloy and to lower its melting point, it also comprises boron-containing agglomerates having the following composition ratios in% by weight: 20-58 parts of quartzite; coke breeze-10-34; 5-50 parts of scrap iron; boron-containing agglomerates-3-20, while the boron-containing agglomerates have the following composition in weight%: 63-70 parts of calcium borosilicate concentrate; fine coke screening-25-34; sulfite alcohol solution (sulfite-alcohol IQuor) -3-5.

An invention is known from patent RU 2109836, published on 27/4/1998, which relates to metallurgy, more specifically to the manufacture of ferroalloys, in particular to the preparation of ferrosilicon. The essence of this invention lies in the fact that the charge for the production of ferrosilicon also contains a mixture of fluxed iron ore pellets and iron filings in a ratio of 1 (1-3), having the following component ratios in weight%: 35-55 parts of quartzite; 20-30 parts of carbonaceous reducing agent; 10-30 parts of a mixture of fluxing iron ore pellets and scrap iron; steel scrap-balance. When a mixture of pellets and fines is used in a charge composition for smelting ferrosilicon, the escape of silicon with the off-gas is reduced. In addition, it is noted that the depth of immersion of the electrodes into the charge is increased, which allows melting to be carried out at a higher voltage on the low side of the transformer, and without the use of expensive semicoke.

Accordingly, various charge compositions for smelting ferrosilicon are known from the prior art. However, a disadvantage of the prior art is the use of rare steel scrap in the charge composition.

Due to the production cutbacks at machine manufacturing plants, there is currently a significant lack of raw materials for the sale of charges.

In addition, when steel scrap is used, the conductivity of the charge increases, which results in a decrease in the depth of immersion of the electrodes into the charge, or requires an increase in the amount of coke breeze in the charge composition. Due to this fact, the loss of SiO with the exhaust gas increases and the gas operating conditions of the closed furnace deteriorate. This situation affects especially the operation of furnaces with low arc arrangements, as the space under the arc becomes clogged.

The closest solution to the claimed invention is the charge composition disclosed in patent RU 2109836.

Thus, as a prototype, a charge composition disclosed in patent RU 2109836 was used, wherein the charge comprises quartzite, carbonaceous reducing agent (petite), steel scrap and additionally a mixture of fluxing pellets and iron scrap in a ratio of 1 (1-3), having the following component ratios in weight%: 35-55 parts of quartzite, 20-30 parts of carbonaceous reducing agent, 10-30 parts of mixture of fluxing iron ore pellets and scrap iron with the ratio of 1 (1-3), and the balance of steel scrap.

A significant drawback of the prototype is the presence of rare and expensive 14AGOST 2787-75 "ferro Secondary Metals" grade steel scrap in the charge composition, as well as scrap iron, which, due to the presence of moisture, easily agglomerates and freezes under winter conditions, making it difficult to transport and handle, including on the charge supply conveyor line of the furnace.

The above-mentioned drawbacks of the solutions represented in the prototype were remedied by further developing qualitative and quantitative charge compositions for manufacturing ferrosilicon.

Disclosure of Invention

According to the invention, the charge for manufacturing ferrosilicon does not contain rare metal shavings from carbonaceous steel as iron-containing component, but it contains pellets made of pyrite dross (technical waste) with the exemplary composition given in table 1 and liquid glass as binder.

TABLE 1

The essence of the invention is that the pellets made from the mixture of pyrite dross and liquid glass form a porous structure that accelerates the indirect reduction process (by means of CO) of the pellet iron by the components of the ferroalloy gas (these processes are carried out at the upper level of the furnace):

Fe₂O₃+3CO＝2Fe+3CO₂

Fe₂O₃+3H₂＝2Fe+3H₂O

Fe₂O₃+3SiO (gas) +2 Fe +3SiO₂(solid)

And prevents the formation of iron silicates which would interfere with the normal operation of the ferroalloy furnace (the process is carried out at the lower level of the furnace):

Fe₂O₃+SiO₂+С＝Fe₂SiO₄(slag) + CO,

that is, such adverse reactions are difficult to perform because there is no iron oxide at the lower level of the furnace.

This situation allows the use of a non-rare material, pyrite dross, which is a waste material of sulfuric acid manufacture, to completely replace steel scrap.

In view of the fact that these manufacturing wastes adversely affect the environment, the practice of the claimed invention will utilize alloys to address the disposal of hazardous manufacturing wastes.

The task of the present invention is therefore to remedy the drawbacks of the prior art, developing a charge composition for ferrosilicon production which is not of poor quality, but which allows the use of low-quality scrap from the production of sulphuric acid instead of rare steel filings without production losses, while solving the dual tasks of reducing raw material costs and disposing of technical products.

The technical result is that the range of charge compositions is extended, inexpensive and not rare raw materials are used, and the operational performance of the furnace installation is improved by using charge compositions with low electrical conductivity in the ferrosilicon manufacturing process, which results in increased silica recovery, while increasing the charge filtration layer, and reducing the formation of non-technical slag, and therefore, it is possible to perform furnace transformer operation at higher voltage levels, increasing the electrical efficiency of the furnace installation.

The technical result is achieved by means of a charge composition for manufacturing ferrosilicon, comprising quartzite, carbonaceous reducing agent and iron-containing material, whereas the iron-containing material is pyrite dross pellets having the following composition ratios in weight%: 34-50 parts of quartzite, 30-34 parts of carbonaceous reducing agent and the balance of pyrite cinder pellets.

The carbonaceous reducing agent comprises: nut coke-40-67 wt%, wood waste-33-60 wt%, and wood waste is particles or chips.

The pellets comprise pyrite dross and 7-15 wt% liquid glass as a binder on a dry weight basis.

The above and other objects, features, advantages and technical significance of the present invention will become more apparent from the following detailed description of the present invention with reference to the accompanying drawings.

Drawings

Figure 1 shows an electronic image of pyrite ash taken by a microscope at 320 x magnification.

Figure 2 shows an electron image of ferrosilicon taken by a microscope at 320 x magnification.

Fig. 3 shows a semi-industrial furnace, which is an ore-reducing electric furnace (RKO 0.2) with three graphitized electrodes and graphite lining.

Fig. 4 shows an X-ray image of ferrosilicon, where the experimental line is red, the calculated line is blue, and the difference between the experimental and calculated lines of the X-ray image is pink.

Figure 5 shows an X-ray image of ferrosilicon with the peak-to-phase distribution indicating the experimental line (red).

Figure 6 shows an electron image of the composition of phase ferrosilicon taken by a microscope.

Detailed Description

From laboratory studies conducted on smelting ferrosilicon in which the metal scrap was completely replaced with pyrite dross pellets, it was concluded that this alternative method was completely feasible. However, in order to prevent the specific energy consumption and increase of carbon for reducing iron oxide and heating the slag, both the electrical operating scheme of the furnace and the percentage content of the charge components have to be selected.

The charge compositions claimed according to the invention were studied using laboratory and semi-industrial furnaces.

Figure 1 shows an electronic image of pyrite dross taken by a microscope. The average composition is spectrum 1.

Table 2 below shows the compositional analysis of the pyrite ash for the spectrum shown in figure 1.

TABLE 2

Optical spectrum	O	Na	Mg	Al	Si	S	Ca	Fe	Zn	Ba
											Spectrum 1	35	1.0	1.0	2.7	10.2	1.9	0.9	44.7	0.6	1.4
Spectrum 2	45	2.1	7.1	16.6	18.8	0.0	0.1	8.3	0.3	1.8
											Spectrum 3	19	0.1	0.1	0.4	0.6	27.5	0.2	51.6	0.2	0.0

All results are in weight%.

Spectrum 1 is removed from the highlighted area, with the remainder being dotted.

Na₂O

MgO

Al₂O₃

SiO₂

CaO

FeO

Fe₂O3

BaO

1.4％

2％

5％

23％

1％

2.7％

62.9％

1.6％

In order to confirm the technical results claimed, microscopic and X-ray phase analyses were performed. Ferrosilicon micrographs obtained from charges using pyrite dross (see figure 6) show low slag content.

Figure 2 shows an electron image of ferrosilicon taken by a microscope. The average composition is spectrum 5.

The following is an analysis of the composition of the ferrosilicon shown in FIG. 2.

As can be seen from the spectral analysis shown in table 3, silicon was reduced with a small loss.

TABLE 3

Optical spectrum	Si	Fe	In total:
				spectrum 1	32.7	67.3	100.0
Spectrum 2	37.4	62.6	100.0
				Spectrum 3	18.1	81.9	100.0
Spectrum 4	18.6	81.4	100.0
				Spectrum 5	30	70	100.0 average value

Fig. 4 shows an X-ray image of ferrosilicon, where the experimental line is red, the calculated line is blue, and the difference between the experimental and calculated lines of the X-ray image is pink. Figure 5 shows an X-ray image of ferrosilicon with the peak-to-phase distribution indicating the experimental line (red). These X-ray images also confirm that ferrosilicon is obtained by complete replacement of the iron-containing material in the charge with pyrite dross pellets.

Thus, after studies using laboratory furnaces indicate the possibility of using pyrite dross in the charge composition, studies using semi-industrial furnaces RKO 0.2 were performed (see fig. 3).

A study using the charge of pyrite dross was conducted using an experimental ore reduction electric furnace with three graphitized electrodes and a graphite lining. The nominal power of the transformer of the furnace arrangement is 160KVA at an electrode voltage of 48V.

During the study, charges providing ferrosilicon of grade FS-45, FS-65 were used:

embodiment 1. a typical portion of a charge for smelting ferrosilicon ("charge batch") having the following composition:

components	Fraction(s) of	Content in kg	Content in weight%
				Quartz rock	20-40mm	15	34
Coke cubes	10-25mm	7	16
				Wood particles or chips	-	8	18
	5-30mm	14	32
				In total:		44	100

embodiment 2.

Components	Fraction(s) of	Content in kg	Content in weight%
				Quartz rock	20-40mm	15	50
Coke cubes	10-25mm	4	13
				Wood particles or chips	-	6	20
Pellets of pyrite dross	5-30mm	5	17
				In total:		30	100

embodiment 3.

Components	Fraction(s) of	Content in kg	Content in weight%
				Quartz rock	20-40mm	15	36
Coke cubes	10-25mm	8	20
				Wood particles or chips	-	4	10
Pellets of pyrite dross	5-30mm	14	34
				In total:		41	100

embodiments of charge compositions 1-3 demonstrated the achievement of the technical results with the specified ranges of component content, namely quartzite-34-50 wt%, carbonaceous reducing agents (coke and wood waste) -30-34 wt%, pyrite cinder pellets-balance.

Method for manufacturing a charge.

The charge mixture is prepared by layered loading into a "flexible disposable container" (FDC) with bottom unloading door, first laying the light components (coke, particles) and then the heavy components (pyrite-cinder pellets and quartzite) of the charge in layers in one "charge batch". A total of 4 charge batches were placed per FDC. The FDC is unloaded to the job site through the bottom unloading door for mixing of the charge components. The charge was then manually fed into the furnace with a spatula. In the furnace, a charge cone is held around the electrode to prevent radiation of the combustion arc. If necessary, pieces of the sintered charge are sewn with a wooden strip and then pushed into the hot zone of the furnace near the electrodes.

The tap hole of the furnace was pierced every 2-3 hours and the melt was released directly into the form of a flat casting and aligned with the refractory bricks covered with a non-stick sand mixture. The amount of slag coming out of the furnace is negligible and most of the surface of the ferrosilicon ingot is free of non-metallic inclusions.

The silicon content in the ferrosilicon obtained varies from 41% to 64%, depending on the composition chosen for the particular charge formulation.

An example of the phase composition of a ferrosilicon sample in weight percent:

formulation of	％
		Si	6
FeSi₂	94

According to FIG. 6, the chemical composition of ferrosilicon confirms its phase composition. From the electron image shown, a fairly uniform FeSi is obtained₂And (4) phase(s). The average impurity content in weight% is consistent with the X-ray images shown in fig. 4 and 5.

A typical composition of the ferrosilicon impurities is shown in table 4 below:

TABLE 4

Components	Content in weight%
		Al	0.25
C	0.017
		S	0.026
P	0.023
		Mn	0.11
Cr	0.069

Note that the sensitivity of the electrode position in the furnace to the charge loading level is weak: before the start of smelting, the electrode position is fixed according to the gear rack of the hoisting device drive. The lifting manoeuvre of the electrode does not exceed 100mm, whereas the loading of the charge has a thickness of 400 mm. At the same time, the transformer operating taps were the same (48V between the electrodes) and the current of the electrodes corresponded to the nominal value (1900 ± 50A). This means that the conductivity of the charge is negligible. The charge loading level was determined by predicting the integrity of the electrode body during the primary smelting.

Thus, an alloy corresponding to silicon iron was obtained.

In the prototype, the expensive and rare scrap cannot be completely replaced due to the fact that a large amount of iron silicate slag is formed and interferes with the operation of the furnace during smelting without using scrap. In the charge obtained according to the invention, it is possible to completely replace the expensive and rare scraps with sulfuric acid manufacturing waste (i.e. pyrite dross) that is almost free and available in large quantities, and to obtain a process with low slag yields, thus making it cost-effective and sustainable.

Meanwhile, in addition to the economic effect obtained from the use of charges using pyrite dross, since a charge composition having low electrical conductivity is used in the manufacturing process of ferrosilicon, improvement in the operational performance of the furnace apparatus is achieved, which results in increased silica recovery rate while increasing the charge filtering layer, and thus, it is possible to perform furnace transformer operation at a higher voltage level, increasing the electrical efficiency of the furnace apparatus.

Claims

1. Charge for manufacturing ferrosilicon comprising quartzite, carbonaceous reductant and iron-containing material, wherein the iron-containing material is pyrite dross pellets having the following composition proportions in weight%: 34-50 parts of quartzite, 30-34 parts of carbonaceous reducing agent and the balance of pyrite cinder pellets.

2. The charge of claim 1, wherein the carbonaceous reductant comprises, in weight%: pyrolidine-40-67 and wood waste-33-60, said wood waste being particles or chips.

3. The charge according to claims 1-2, wherein said pellets comprise pyrite dross and liquid glass as a binder in the following component proportions in weight%: pyrite dross-85-93, liquid glass-7-15 on a dry weight basis.