RU2570153C1 - Method of technical silicon melting - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes dosing, mixing, loading and continuous melting of charge containing quartzite, oil coke, charcoal and stone coal, wood chips. During dosing the charge is divided to two parts, one charge part is loaded in the centre of the furnace bath, and to another charge part silicone carbide is added, and it is loaded under electrodes, at that part of charge containing silicone carbide has the following composition, wt %: quartzite 45.3-50.1, charcoal 2.4-5.2, stone coal 9.8-21.2, oil coke 1.4-3.1, wood chips 4.4-9.8, silicone carbide 10.6-36.7. Deoxidant amounting to 2-5% of weight of loaded silicone carbide is periodically loaded to centre of the furnace bath.

EFFECT: invention reduced power consumption, and increases the furnace capacity.

2 cl, 2 tbl

Description

The invention relates to the field of metallurgy, in particular to the production of metals and alloys in ore-thermal electric furnaces, and can be used in the production of industrial silicon and silicon ferroalloys.

A known method of producing technical silicon, including dosing of quartz or quartzite, carbon reducing agents, loading them into an electric furnace, carbothermic reduction of silicon, its release from the furnace (Vengin S.I., Chistyakov A.S. Technical silicon. M., Metallurgy, 1972 , 206 p.). The disadvantage of this method is the low degree of extraction of silicon.

A known method of producing metallic silicon (patent RU No. 2160705, С01В 33/025, publ. 20.12.2000), comprising carbothermal reduction of silicon dioxide, in which liquid phenolic resin is used as a reducing agent, while the process of carbothermal reduction is carried out in three stages: from room temperature up to 160 ° С at 0.1-0.7 MPa, then up to 800 ° С with holding at this temperature for 1 h, up to 1700 ° С in an inert gas medium in two stages up to 1300-1400 ° С at 0 , 01 Pa and from 1300-1400 to 1700 ° C with increasing pressure from 0.01 Pa to 0.1 MPa. The disadvantage of this method is the difficulty of its implementation on a large industrial scale.

A known method of producing crystalline silicon by restoring quartz or pure quartz sand with silicon carbide by heating the briquetted mixture, the process is carried out in vacuum at a temperature of up to 1400 ° C (copyright certificate SU 119176, С01В 33/025, publ. 01.01.1959). The disadvantage of this method is the creation of briquette production and the need to create a vacuum in the duty cycle, which is problematic for an industrial furnace.

Closest to the technical solution is a method for producing crystalline silicon (patent RU No. 2121967, СВВ 33/025, publ. 20.11.1998). The inventive silicon is removed from the mixture by dividing the prepared mixture into two parts - first weighed and mixed quartzite, petroleum coke, coal and part of the chips, and the remaining part of the chips are mixed with charcoal in a volume ratio (2-3): 1, after which first loaded the second part of the mixture, and then the first part. Moreover, the second part of the charge is loaded only into the zones of its active descent. The disadvantage of this method is the low technical and economic indicators of furnaces for smelting silicon.

The basis of the invention is the task of reducing the consumption of technological electricity for the production of silicon.

Moreover, the technical result is to increase the productivity of the furnace.

The achievement of the above technical result is ensured by the fact that in the method of smelting technical silicon in electric furnaces, including dosing, mixing, loading and continuous melting of the mixture, consisting of quartzite, petroleum coke, charcoal and coal, wood chips, when dosing, the mixture is divided into two parts, one part of the charge is loaded into the center of the furnace bath, and silicon carbide is added to the other part of the charge and loaded under the electrodes, while the part of the charge containing silicon carbide has the following composition of components, m ac%:

quartzite 45.3-50.1 charcoal 2.4-5.2 coal 9.8-21.2 petroleum coke 1.4-3.1 wood chips 4.4-9.8 silicon carbide 10.6-36.7

In order to reduce silicon losses, in the center of the furnace bath and between the electrodes periodically, after 1.5-2 hours, the reducing agent is loaded in the amount of 2-5% of the weight of silicon carbide contained in the charge.

As a reducing agent, coal and / or charcoal is used.

The claimed technical solution is as follows.

A mixture consisting of quartzite, charcoal, coal, petroleum coke and wood chips was loaded into an industrial three-electrode ore-thermal furnace with a capacity of 16.5 MVA, silicon was reduced, and the melt was released from the furnace. The frequency of loading the charge on the top was 2-3 times per hour. The following ratio of charge components was supported, wt.%: Quartzite - 51.4; charcoal - 6.5; coal - 26.2; petroleum coke - 3.9; wood chips - 12.0. The furnace productivity was 751 kg of silicon per hour, the specific energy consumption was 16650 kWh per 1 ton of silicon.

Dividing the mixture into two parts during dosing, one part at the ratio of components indicated above was loaded into the center of the furnace bath (at the top), and silicon carbide was added to the other part of the charge and simultaneously loaded under the electrodes. Examples of various ratios of the components of the mixture with silicon carbide are presented below.

Example 1. The ratio of the components of the mixture was, wt.%: Quartzite - 50.8; charcoal - 6.1; coal - 24.6; petroleum coke - 3.6; wood chips - 11.3; silicon carbide - 3.6. This mixture was loaded under the electrodes. The furnace productivity was 784 kg / h, the specific energy consumption was 15940 kWh / t.

Example 2. Continued to increase the content of silicon carbide in the mixture at a ratio of the components of the mixture, wt.%: Quartzite - 48,40; charcoal - 4.50; coal - 18.10; petroleum coke - 2.70; wood chips - 8.30; silicon carbide - 18.0. The furnace productivity was 834 kg / h, the specific energy consumption was 14991 kWh / t.

Example 3. With a further change in the ratio of the components of the mixture, mass%: quartzite - 45.3; charcoal - 2.4; coal - 9.8; petroleum coke - 1.4; wood chips - 4.4; silicon carbide - 36.7. The furnace productivity was reached 1039 kg / h, the specific energy consumption was 12031 kWh / t silicon.

In examples 1-3, in a furnace bath, a mixture containing silicon carbide was loaded only under the electrodes, and a mixture not containing silicon carbide was loaded into the center of the furnace bath. The results of the furnace with this method of loading the mixture are summarized in table 1.

Table 1 Options The load center of the furnace,% The productivity of the furnace, kg / hour Specific energy consumption, kWh / t Charge with silicon carbide Charge without silicon carbide Example 1 one hundred 0 760 16443 80 twenty 762 16404 60 40 766 16318 40 60 770 16234 twenty 80 775 16129 10 90 780 16026 0 one hundred 784 15940 Example 2 one hundred 0 809 15462 80 twenty 813 15375 60 40 816 15319 40 60 821 15225 twenty 80 827 15118 0 one hundred 834 14991 Example 3 one hundred 0 1015 12321 80 twenty 1018 12279 60 40 1021 12243 40 60 1026 12183 twenty 80 1032 12112 0 one hundred 1039 12031

The productivity of the furnace increases with decreasing loading in the center of the furnace of a charge containing silicon carbide, and the highest performance is achieved in the absence of silicon carbide in the charge loaded in the center of the furnace.

In the interaction of quartzite silica and silicon carbide, the formation of gaseous silicon monoxide SiO is possible. To reduce the loss of silicon, in the center of the furnace bath and between the electrodes, when conducting reduction smelting with the charge specified in examples 2-3, periodically, after 1.5-2 hours, a reducing agent, coal or charcoal were loaded. The results of furnace performance indicators are summarized in table 2.

table 2 Options The load of the reducing agent,% by weight of silicon carbide Example 2 Example 3 The productivity of the furnace, kg / hour Specific energy consumption, kWh / t The productivity of the furnace, kg / hour Specific energy consumption, kWh / t one 0 834 14991 1039 12031 2 1,0 835 14970 1040 12019 3 2.0 8373 14934 1044 11973 four 3.0 839 14899 1049 11916 5 4.0 842 14845 1058 11815 6 5,0 846 14776 1066 11726 7 6.0 845 14795 1066 11726

The optimal amount of carbon loaded in the center of the furnace bath and between the electrodes is 2-5% of the weight of the loaded silicon carbide. With this ratio, the productivity of the furnace increases. A further increase in the amount of reducing agent loaded into the furnace does not lead to an increase in furnace productivity.

The maximum productivity of the furnace and the minimum energy consumption is achieved with the ratio of the components of the charge, wt.%:

quartzite 45.3-50.1 charcoal 2.4-5.2 coal 9.8-21.2 petroleum coke 1.4-3.1 wood chips 4.4-9.8 silicon carbide 10.6-36.7

loading the mixture without silicon carbide into the center of the furnace bath and periodically, after 1.5-2 hours, feeding to the center of the furnace and between the reducing agent electrodes, coal or charcoal, in an amount of 2-5% of the weight of silicon carbide contained in the loaded mixture.

Claims (2)

1. A method of smelting technical silicon in electric furnaces, including dosing, mixing, loading and continuous melting of a mixture consisting of quartzite, petroleum coke, charcoal and hardwood and wood chips, characterized in that when dosing the mixture is divided into two parts, one of which loaded into the center of the furnace bath, and silicon carbide is added to the other part of the charge and loaded under the electrodes, while the part of the charge containing silicon carbide has the following composition of components, wt.%:
quartzite 45.3-50.1 charcoal 2.4-5.2 coal 9.8-21.2 petroleum coke 1.4-3.1 wood chips 4.4-9.8 silicon carbide 10.6-36.7
moreover, periodically after 1.5-2 hours, a reducing agent is loaded in the center of the furnace bath and between the electrodes in an amount of 2-5% of the weight of silicon carbide contained in the charge. 2. The method according to p. 1, characterized in that as a reducing agent use coal and / or charcoal.