RU2248400C1 - Method for scouring of blast furnace - Google Patents

Abstract

FIELD: metallurgy, in particular cast iron manufacturing in blast furnace.

SUBSTANCE: clamed method includes charging of main batch components and interrupted charging of scouring material doses in form of metal flux containing CaO, MnO, FeO, and SiO₂ with basic capacity up to 4.0 in mixture with quartzite. Quartzite consumption is determined according the equation: K_B = (CaO_MF + MnO_MF/2 + FeO₂/2 - SiO_2MF)100SiO_2KB, wherein K_B is quartzite consumption, kg/kg; CaO_MF, MnO_MF, FeO₂, SiO_2MF are CaO, MnO, FeO, and SiO₂ content in metal flux; SiO_2KB is SiO₂ (mass %) content in quartzite, and scouring material dose is 0.01-0.1 parts of charged ore. Ratio of coke consumption and scouring material dose is 1:(1-5); scouring is carried out up to temperature differences in crucible and bottom cooler of 1.5⁰C and heat-flux density of 5 kW/m². Method of present invention makes it possible to increase capability by 5.4 %.

EFFECT: decreased relative cake consumption and improved capability.

2 cl, 1 ex, 3 tbl

Description

The invention relates to metallurgy and can be used in the production of pig iron in blast furnaces.

A known method of washing the hearth and walls of a blast furnace, including loading into the blast furnace the main components of the mixture: sinter, pellets, fluxes, coke and the addition of welding slag, in the form of production waste mixed with the main components of the mixture before loading them into the furnace, see a. from. USSR No. 1186635, M. cl. From 21 V 3/00, 85 g.

The disadvantage of this method is that the welding slag, which is used for production waste, cleans the hearth and walls only of small coke and sang, while highly basic refractory components in the form of rankinite (3СаО · 2SiO ₂ ) and larnite (2СаО · SiO ₂ ) remain in the oven. This limits the possibility of increasing the productivity of the blast furnace and increases the specific consumption of coke.

The closest analogue to the claimed method is a method of washing a blast furnace, which includes loading the main components of the charge, periodically loading doses of washing material and releasing melting products, in which metalloflux with a basicity of 0.6-1.0 in pieces of 10-60 mm is loaded mixed with pellets with a basicity of 0.05-0.5 in a ratio of 1: (0.5-2), see RU No. 2067998, M. cl. From 21 V 3/00, 94 g.

The metal flux used in this method is prepared from production wastes and has a basicity of 0.6-1.0, which does not ensure the removal (during washing) of highly basic refractory components in the form of rankinite (3СаО · 2SiO ₂ ) and larnite (2СаО · SiO ₂ ). In addition, in this flux there are insufficient components in the form of fayalite (2FeO · SiO ₂ ) and tephroite (2MnO · SiO ₂ ), which are necessary for the conversion (in a reducing high-temperature medium) of refractory high-base compounds to a low-base low-melting state. This leads to a decrease in temperature in the washing zone due to uncompensated heat consumption for heating and melting the washing material and, ultimately, to incomplete washing of the hearth, which reduces the productivity of the blast furnace and increases the specific consumption of coke.

The problem to which the claimed method is directed is to reduce production costs by disposing of production waste, as well as increase the productivity of the blast furnace and reduce the specific consumption of coke.

The solution to this problem is provided by the fact that in the method of washing a blast furnace, which includes loading the main components of the charge and periodically loading doses of washing material in the form of metal flux containing CaO, MnO, FeO and SiO ₂ , the release of smelting products, according to the invention, use metal flux with a basicity of up to 4 , 0 in a mixture with quartzite, the flow rate of which is determined from the following ratio:

Kv = (CaO _mph + MnO _mph / 2 + FeO _mph / 2-SiO _2mph ) 100 / SiO _2Kv ,

where Kv is the flow rate of quartzite, kg / kg of metal flux; CaO _mph , MnO _mph , FeO _mph and SiO _2mph — content in metal _flux CaO, MnO, FeO and SiO ₂ , in wt.%; SiO _2Kv - SiO ₂ content in wt.% In quartzite, moreover, the dose of washing material is 0.01-0.1 of the ore part of the feed, while, accordingly, the coke consumption is increased in proportion to the dose of 1: (1-5 ), and the washing is carried out until the water temperature difference in the hearth and bream refrigerators increases to 1.5 ° C and the heat flux density to 5 kW / m ² . In addition, the size of the pieces of flux and quartzite material is 10-30 mm.

The proposed method is as follows.

The expediency of washing a blast furnace by measuring the difference in water temperature and heat flux density in the hearth and bream refrigerators is assessed. The washing decision is made when the temperature of the water in the hearth and bream refrigerators is less than 1.5 ° C, and the heat flux density is less than 5 kW / m ² . The contents of FeO, MnO, CaO, SiO ₂ in the metal flux and SiO ₂ in quartzite are determined. According to practical data, the conversion coefficient of manganese to cast iron is taken. It is usually in the range of 0.5-0.7. The basicity of the metal flux is calculated: b = CaO / SiO ₂ , and when the value of b is less than 4.0, a decision is made on the suitability of the selected metal flux for washing. Next, calculate the consumption of quartzite in kg for every 1 kg of metal flux according to the proposed ratio. Set the dose of flushing material (D _ol , kg) in the range of 0.01-0.1 of the ore part of the feed (R _p , t): D _pr = 1000 (0.01-0.1) R _p . Then calculate the dose of metal flux (D _mf , kg) and quartzite (D _kv , kg) in the composition of the washing material, using the expressions: D _mf = D _pr · (1-Kv) and D _kv = D _pr -D _mf .

Determine the value of the coke portion of the feed (K _p , t). K _n = K + _n0 0,001D _ave + [1 / (1-5)], where K _n0 - the quantity of coke feeding portion before the application of the washing material, ie.

Ore and coke feed parts are loaded using flushing material, blast-furnace smelting is carried out, smelting products are released, monitoring the difference in water temperatures in the hearth and bream refrigerators and the heat flux density. The use of washing material is stopped after increasing the water temperature difference to 1.5 ° C and the heat flux density to 5 kW / m ² . It should be noted that the temperature difference in the hearth and bream refrigerators, as well as the heat flux density of up to 5 kW / m ^2, were obtained experimentally, as a result of tests. At lower values of these parameters, the gas pressure drop increases with the charge hanging and the need to reduce the purge intensity with a corresponding deterioration in the smelting performance. During the washing process, the metal flux and quartzite of the washing material, falling in the blast furnace in a mixed state, are heated and interact with each other. Single-calcium silicates are formed from SiO ₂ quartzite and CaO metalloflux (CaO · SiO ₂ - pseudowollastonite and wollastonite), from SiO ₂ quartzite and FeO metalloflux - fayalite (2FeO · SiO ₂ ), from SiO ₂ quartzite and MnO metalloflux - tefroit (2 ₂ ). The flushing material acquires a minimum melting point and low viscosity. Due to this, it easily penetrates into the space between the pieces of the charge components in the lower part of the shaft, in steam, shoulders and between the pieces of coke in the furnace of the blast furnace. At high temperatures, Fe is reduced from FeO fayalite and Mn from MnO tephroite with the consumption of coke fines and sang: 2FeO · SiO ₂ + 2C = 2Fe + SiO ₂ + 2CO; 2MnO · SiO ₂ + 2C = 2Mn + SiO ₂ + 2CO, with appropriate washing from coke breeze and sang. The released SiO ₂ interacts with rankinite (3СаО · 2SiO ₂ ) and larnite (2СаО · SiO ₂ ), turning them into pseudo-wollastonite and wollastonite with a corresponding decrease in melting point and viscosity and involvement in the slag phase: (3СаО · 2SiO ₂ ) + SiO ₂ = 3 (CaO · SiO ₂ ); (2CaO · SiO ₂ ) + SiO ₂ = 2 (CaO · SiO ₂ ), which leads to flushing from highly basic refractory components of the contents of the furnace.

Using the proposed ratio to determine the flow rate of quartzite in a mixture with metal flux provides a minimum melting point and low viscosity of the washing material. In accordance with the proposed ratio, quartzite (SiO ₂ ) is introduced in the stoichiometric amount necessary for the binding of CaO to single-calcium silicate (pseudowollastonite and wollastonite), FeO to fayalite, and MnO to tephroite. A higher consumption of quartzite compared with the calculated value leads to the flow of excess SiO ₂ , which does not bind to minerals, respectively, the melting temperature and viscosity of the washing material increases. A lower (calculated) consumption of quartzite causes a lack of SiO ₂ and an excess of CaO not bound to single-calcium silicate, with a corresponding increase in the melting temperature and viscosity of the washing material.

The use of metal flux with a maximum basicity of up to 4.0 allows you to involve previously unused waste with a basicity of 1-4, which, in particular, is converter slag. When the basicity of metalloflux is less than 4.0, it is possible to obtain (together with quartzite) washing material with a high concentration of fayalite and tephroite and a corresponding increased washing ability. With a metal flux basicity of more than 4.0, a significant amount of mono-calcium silicate (pseudo-wollastonite and wollastonite) is formed in the washing material, with a decrease in the concentration of fayalite and tephroite and a corresponding decrease in the washing ability.

The dose of washing material in the range of 0.01-0.1 of the size of the ore part of the feed provides the most favorable washing conditions. At a lower dose (below 0.01), complete washing is not achieved due to its lack of filling in the inter-voids with small details of coke, sang and highly basic refractory components. At a higher dose (above 0.1), a large part of the coke packing is removed, and the operation of the furnace after washing is disrupted.

The increase in coke consumption in relation to the dose of washing material 1: (1-5) allows you to compensate for the heat consumption for heating the washing material and carrying out reactions, as well as to prevent, due to this, lower temperatures in the region of the skull formation and excessive pressure increase.

The ratio of the mass parts of 1: 5, respectively, of coke and washing material ensures the preservation of the thermal regime of the hearth.

The ratio is 1: 1, i.e. the loading values of the washing material and coke in equal quantities by weight, provides an increase in the heating of the hearth, corresponding to an increase in the silicon content in pig iron by 0.1-0.2%. Within these limits of ratios, the creation of the most favorable temperature and thermal conditions for the washing process is ensured (accelerated washing with an increase in the furnace productivity after washing and a decrease in the specific coke consumption). At lower ratios, heating of the furnace is reduced due to a lack of coke to compensate for heat costs, which reduces the intensity of the processes and incomplete washing, uneven operation with downtimes and quiet strokes, reduces the productivity of the furnace and increases the specific consumption of coke. At large ratios, the coke consumption increases with the corresponding excessive heating of the furnace, while the gas dynamics of the lower part of the blast furnace with the release of silicon monoxide, the imposition of reduction processes on the melting and slag formation processes and the decrease in washing efficiency are worsened. The size range of the pieces of flux and quartzite material, amounting to 10-30 mm, provides a developed interfacial surface and allows to reduce the energy consumption for their melting.

Example. Smelting at blast furnace No. 6 of OJSC MMK with a volume of 1380 m ³ .

Agglomerate, pellets and coke were loaded as the main components of the charge. As metalloflux used production waste with a chemical composition shown in table 1.

Table 1
(Chemical composition of metal flux,%) Fe _ob Fe _meth FeO MnO SiO ₂ CaO MgO Al ₂ O ₃ R S 26.5 8.1 25.9 3,5 14.0 37.3 11,4 2.9 0,306 0.09

The basicity of the metal flux was b = CaO / SiO ₂ = 37.3 / 14.0 = 2.66, i.e. less than 4.0, which is suitable for inclusion in the composition of the washing material. For joint use with metal flux, quartzite with a SiO ₂ content of 98% wt. Was used.

Quartzite consumption in kg for every 1 kg of metal flux, taking into account the conversion coefficient of manganese to cast iron, amounting to 0.6, is the average value from ordinary values

((0.5 + 0.7) / 2 = 0.6) : Ap = (FeO _mf / 2 + η _Mn · MnO _mf / 2 + CaO -SiO _{2mf mf)} / SiO _Q2 = (25.9 / 2 + 0.6 · 3.5 / 2 + 37.3-14.0) / 98 = 0.38 kg / kg.

The dose of flushing material (D _ol , kg) will be 0.055 (average value is (0.01-0.1) / 2 = 0.055) of the ore supply part (R _p , t). The ore part of the feed R _p will be 26 tons

Accordingly: D _ol = 1000 × 0.055 × R _p = 1000 × 0.055 × 26 = 1430 kg.

The dose of metal flux (D _mf , kg) and quartzite (D _q , kg) in the composition of the washing material is: D _mf = D _pr · (1-Kv) = 1430 · (1-0.38) = 890 kg, D _q = D _ave = 1430-890 -D _mf = 540 kg.

The value of the coke portion of the feed (K _p , t) in relation to the dose of the washing material is set to 1: 3 (the average value from the established limits is 1: (1-5)). The quantity of coke feeding portion (C _n0) before the application of the wash material was 7.5 m Therefore:. K _n = K + _n0 0,001D _ave + [1 / (1-5)] = 7.5 + 0.001 · 1430 · 1 / 3 = 8 t.

The ore and coke feed parts were loaded using flushing material, blast-furnace smelting was carried out with the release of smelting products and control of the water temperature difference in the hearth and bream refrigerators, as well as the heat flux density. The use of washing material was stopped after increasing the water temperature difference to 1.5 ° and the heat flux density to 5 kW / m ² . The total consumption of washing material was about 0.55 of the furnace volume.

The performance indicators of the claimed method and prototype after washing in periods of 30 days are presented in table 2.

table 2
(The performance of blast furnace No. 6 of OJSC MMK in the conditions of the example) The name of indicators The value of indicators Prototype the claimed method The name of indicators The value of indicators Prototype the claimed method Productivity, t / day 2883 3038 Specific consumption of coke, kg / t of pig iron 476.8 450.3 Consumption of the main components of the charge, kg / t of pig iron: sinter 1034 1055 pellets 621 600 Dust removal (captured), kg / t of pig iron 25.7 26.5 Blast parameters: pressure, ati 2.82 2.78 temperature, ° С 1112 1101 humidity, g / m ³ 6.4 7.5 natural gas consumption, m ³ / t of pig iron 97.3 96.4 oxygen content,% 26,4 26.3 Parameters of blast furnace gas: pressure, ati 1.49 1.49 temperature, ° С 315 307 composition,%: CO ₂ 18,4 18.7 With 25.8 25.0 H ₂ 7.9 7.7 Cast iron composition,%: Si 0.78 0.76 Mn 0.25 0.26 S 0,020 0.019 R 0,063 0,062 FROM 4.66 4.65 Ti 0,089 0,095 The composition of the slag,%: SiO ₂ 36.1 35.9 Al ₂ O ₃ 12.6 12.8 CaO 39,4 39.2 MgO 7.7 7.8 MnO 0.24 0.23 FeO 0.25 0.22 S 0.96 0.99 TiO ₂ 0.93 0.93

Table 3.
(The results of blast furnace smelting, when deviating from the proposed method, are presented) Quartzite consumption Flushing dose Increase in consumption Basicity Specific consumption Performance for every 1 kg material of magnitude coke in relation to metalloflux coke after washing, after washing, t / day metal flux, kg ore feed dose rate kg / t of cast iron 0.25 0,055 1: 3 2.66 458.7 3009 0.45 0,055 1: 3 2.66 455.6 3025 0.38 0.008 1: 3 2.66 462.1 2975 0.38 0.12 1: 3 2.66 459.3 2989 0.38 0,055 1: 6 2.66 464.4 2952 0.38 0,055 1: 0.9 2.66 463.5 2965 0.38 0,055 1: 3 4,50 465.9 2958 declared way 0.38 0,055 1: 3 2.66 450.3 3038 Prototype 1: 2.0 0 0.8 476.8 2883

As follows from the table, the use of the proposed method provides (compared with the prototype) a decrease in the specific consumption of coke after washing, comprising 16.5 kg / t of pig iron, and an increase in productivity by 5.4%.

Claims (2)

1. The method of washing a blast furnace, including loading the ore and coke parts of the feed of the charge, periodically loading doses of washing material containing metalloflux, including CaO, MnO, FeO and SiO ₂ , the release of smelting products, characterized in that metalloflux is loaded as a washing material up to 4.0 mixed with quartzite, the flow rate of which is determined from the ratio: Kv = (CaO _mph + MnO _mph / 2 + FeO _mph / 2-SiO _2mph ) · 100 / SiO _2Kv , where Kv - quartzite consumption, kg / kg of metal flux; CaO _mF , MnO _mF , FeO _mF and SiO _2mf — content in metal flux of CaO, MnO, FeO and SiO ₂ , wt.%; SiO _2Kv - SiO ₂ content in quartzite, wt.%; set the dose of washing material in the range of 0.01-0.1 of the value of the ore part of the feed, set the value of the coke portion of the feed in relation to the dose of the washing material in the range of 1: (1-5), measure the difference in water temperatures and heat flux density in the hearth and bream refrigerators, and loading doses of flushing material are carried out until the water temperature difference in the hearth and bream refrigerators increases to 1.5 ° C and the heat flux density is up to 5 kW / m ² . 2. The method according to claim 1, characterized in that they load metalloflux and quartzite, the size of the pieces of which is 10-30 mm