RU2740547C2 - Method of steel and alloys melting in closed power metallurgical cycle - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention can be used for production of steel in closed power metallurgical cycle using metallized raw material. Reduction gases are generated from carbonaceous material by gasification in a gasifier to produce a low-calorie reducing gas, which is divided into low and high pressure gas streams, metallization of iron ore material in reducing unit using cooled and purified low pressure reducing gas, supply of metallized raw material and scrap to electric arc furnace for further melting, steel refining in ladle furnace, transfer of cooled and purified high-pressure reducing gas as energy gas to cogeneration steam-gas turbine plant for generation of electric power and steam using steam in gasifier, and electric energy—in electric arc furnace, ladle furnace and oxygen station, oxygen of which is used in electric arc furnace. Additionally, semi-coking carbon-containing material with carbon dioxide-oxygen blowing is used, in which high-calorie reducing gas is generated, which is cooled, purified and mixed in ratio of 1:(0.4–0.5) with low-calorie high-pressure reducing gas and is used in said steam-gas turbine plant, and obtained semi-coke is supplied to gasifier for production of low-calorie reducing gas.

EFFECT: invention allows improving steel quality with simultaneous reduction of power consumption, improve environmental situation without using natural gas and coking coal due to use of high-calorific gas of semi-coking.

3 cl, 1 dwg, 1 ex

Description

The invention relates to metallurgy, in particular to the processes of metallization and electric steel-making production and can be used in the production of high-alloy steels for mechanical engineering.

Known methods of smelting steel and alloys in electric arc furnaces (EAF) using metallized raw materials, in particular metallized pellets and scrap [1-5].

In the known methods for the production of metallized raw materials, expensive natural gas is used (processes Midrex, HIL-3 [5]). In this case, electric power for the operation of EAF is used from the centralized power supply network.

However, the disadvantage of these methods is the use of expensive high-calorific fuel - natural gas. In addition, in these methods, for the operation of EAFs, centralized (external) energy sources are used, which have low values of the efficiency for generating electricity (up to 25%) due to significant losses at power plants and during transportation.

In the known process Correx [5] for metallization of iron ore raw materials are used hot reducing gases obtained during the gasification of coal. However, in this process, cast iron is obtained and additional units are required for its desulfurization and dephosphorization and for the production of steel from cast iron.

There is also known a method of smelting steel in a closed energy-metallurgical cycle [6]. The method includes gasification of carbonaceous materials in a gasifier, metallization of iron ore raw materials in a reduced unit, supply of raw materials and scrap to an electric arc furnace for subsequent steel smelting in a furnace ladle.

However, the disadvantage of this method is the production in the gasifier of a low-calorific generator gas with a calorific value of not more than 10000-11000 kJ / m3, which requires the addition of natural gas to this generator gas for its use in a cogeneration steam-gas turbine plant. This speeds up the process and makes it impossible in the absence of a natural gas supply in the geographic location of the energy-metallurgical complex.

Thus, there is a known method for smelting steel in a closed power-metallurgical cycle, taken as a prototype. However, the disadvantage of this method is the production of a low-calorific generator gas in the gasifier, which requires the addition of high-calorific natural gas to this generator gas for its use in a cogeneration gas turbine plant [6].

The invention is aimed at solving the technical problem of improving the quality of steel while reducing energy consumption, improving the environmental situation [5] without the use of natural gas and coking coal.

At the same time, energy resources are saved, namely natural gas, due to the use of high-calorific semicoking gas.

A method for the production of steel in a closed power-metallurgical cycle, including the production of reducing gases from a carbon-containing material by gasification in a gasifier to obtain a low-calorie reducing gas, which is divided into low and high pressure gas streams, metallization of iron ore raw materials in a reducing unit using cooled and purified low reducing gas pressure, supply of metallized raw materials and scrap to an electric arc furnace for subsequent smelting, steel refining in a ladle furnace, transfer of cooled and purified high-pressure reducing gas as energy gas to a cogeneration combined-cycle gas turbine unit to generate electricity and steam using steam in a gasifier, and electricity - in an electric arc furnace, ladle furnace and oxygen station, the oxygen of which is used in an electric arc furnace. At the same time, an installation for semicoking carbon-containing material with carbon dioxide-oxygen blast is additionally used, in which a high-calorific reducing gas is generated, which is cooled, purified and mixed in a ratio of 1: (0.4-0.5) with a low-calorie high-pressure reducing gas and used in the mentioned a steam-gas turbine unit, and the resulting semi-coke is sent to a gasifier to generate a low-calorie reducing gas.

The proposed method differs in that the semi-coking resin obtained in the process is separated and used as a commercial product, and the gasoline obtained in the process of purifying high-calorific gas is used as a commercial product.

Thus, as in the patent [6], the metallurgical basis for the smelting of steel and alloys in the proposed method is a shaft furnace for metallization of fired pellets or a tubular rotary kiln for metallization of fired pellets or iron ore concentrates and an AC or DC electric arc furnace operating using metallized raw materials (pellets or iron ore concentrate) and scrap metal.

In this case, the work of the EAF is characterized as follows. The EAF is supplied with electrical power from a transformer, in addition, it provides for the supply of oxygen from an oxygen station and gaseous fuel; in EAF, both carbon and alloy steels and alloys are smelted; EAF works in conjunction with a ladle furnace to produce high quality steel and alloys.

The values of the released electrical power and the required consumption of high-calorific generator gas given in the description are justified in the example of the method implementation given below in accordance with the sources [1-11].

The energy basis of the proposed method is relatively cheap carbon-containing materials (coal, biomass, wood waste, etc.), which undergo semi-coking and subsequent gasification in a gasifier [1-8].

Carbonaceous materials fall into the semi-coking unit, as a result of which a high-calorific gas is obtained, which is cooled, purified, and its pressure is increased, which is used to generate electricity in a combined cycle plant and partially as additional fuel in an EAF. In this case, the resulting resin is used as a commercial product. The resulting semi-coke is used in a gasifier to obtain a low-calorie generator (reducing) gas. In this case, for example, carbon dioxide-oxygen blast is used. The generator gas is used as a reducing agent in a shaft or rotary tube metallization furnace. Metallized pellets are used as a feedstock in the EAF charge together with the loading of scrap metal (in a 1: 1 ratio).

The high-calorific value gas enters a gas turbine connected to an electric generator. The combined cycle gas turbine unit operates in a mixed cogeneration mode. Waste products of combustion of the gas turbine unit enter a waste heat boiler, in which steam is generated, which is fed to a steam turbine that rotates a corresponding electric generator. The electrical power generated in this way is used to power the EAF transformer, ladle furnace transformer, and oxygen station.

The ratio of the consumption of high-calorific gas in the semicoking unit and low-calorific generator gas is determined by the required process of generating electricity in a combined-cycle plant for feeding the EAF, ladle furnace, oxygen station, supplying high-calorific fuel to the EAF (for semi-coking gas) and the process of metallization of iron ore in a shaft or rotating tube furnace metallization. This ratio of low-calorific generator gas and high-calorific gas in relation to the calculations performed is 1: 0.4 ÷ 0.5.

1-2% of the generated high-calorific gas is used as an additional fuel for EAF, and during those periods of EAF melting, when gas-oxygen burners are not used, it is supplied as export gas.

4.5-5% of the steam produced in the waste heat boiler is taken for feeding into the gasifier during its operation in the air-steam gasification mode.

The proposed method is implemented using the installation shown in the drawing (see Fig. 1).

It includes a semicoking unit 1, a gas generator 2, a shaft furnace 3 for metallization or a tubular rotary furnace 4 for metallization (shown by a dotted line), a gas turbine unit 5, a waste heat boiler 6, a steam turbine 7, an electric generator 8 of a gas turbine 5, an electric generator 9 of a steam turbine 7 , supply transformer 10, EDP 11, oxygen station 12, ladle furnace 13, electric arc installation 14 of ladle furnace, generator gas collector 15, low pressure gas purifier 16, high pressure gas cooler 17, high pressure gas purifier 18, resin outlet 19 , a gas distribution point 20 of high-calorific gas directed to a steam-gas turbine unit, a gas distribution point 21 of generator gas directed to a shaft furnace (tubular rotary kiln), a gas distribution point 22 of the ratio of consumption of high-calorie gas directed to a steam-gas turbine installation of a generator gas directed to a shaft furnace ( ), feed to the semicoking unit: carbon-containing materials 23, combustion products 24 from the waste heat boiler, supplying oxygen 25, air 26, steam 27, char 28 from the semicoking unit to the gasifier, dispensing high-calorific energy high-pressure energy gas 29 from the semicoking unit, dispensing reducing gas 30 from the gas generator low pressure, ash 31, supply: cooled energy gas 32 to the purifier, purified high pressure energy gas 33 to the gas turbine, supply of surplus energy gas 34 to the export network, supply of gas turbine exhaust gases 35 to the waste heat boiler, supply of chemically treated water 36 to waste heat boiler, output from waste heat boiler 37 of waste gases and high pressure steam 38, mechanical connection 39 of gas turbine 5 with electric generator 8, mechanical connection 40 of steam turbine 7 with electric generator 9, output of electric power 41 of gas electric generator 8 and electric power 42 of steam electric generator to transformer EAF 10, supply of electricity 43 also to the oxygen station 12, supply of part of the steam 27 of the waste heat boiler 5 to the gasifier 1, output from transformer 9 of electric power 44 to EAF 10 and 45 to the electric arc installation of the ladle furnace, supply to the shaft furnace 3: reduction low pressure gas 46, roasted pellets 47, discharging from the shaft metallization furnace 3: metallized pellets 50, blast furnace gases 48, feeding into the tubular rotary metallization furnace 4 (as an option): reducing gas 46, coal 47, oxidized pellets or iron ore concentrate 49, delivery from the tubular rotary metallization furnace 4: metallized pellets or metallized iron ore concentrate 48, supply of electricity 43 to oxygen station 12, delivery of oxygen 51 from oxygen station 12, supply to EAF: metallized pellets or metallized iron ore concentrate 50, scrap 53, electricity 44 , oxygen 51, export gas 52, output from EAF: metal and into ladle-furnace 54 and slag 55, delivery of metal 56 from ladle-furnace.

The device works as follows.

Carbonaceous materials (coal, biomass, etc.) 23 are fed into the semicoking unit 1. Carbon dioxide blast 24 and the resulting resin 19 is discharged as a commercial product. The semi-coke obtained in the semicoking unit enters the gasifier 2. In the gasifier 2, air 26, oxygen 25 and steam 27 are supplied. Ash 31 is removed from the lower part of the gasifier.

The resulting cooled high-calorific gas purified in a semicoking unit is compressed by a gas turbine compressor (up to 4.0 MPa). This pressure is maintained by the compressor and the pressure and flow regulator 20. The generator gas has a low pressure (up to 0.2 MPa) and its pressure and flow are maintained by the pressure and flow regulator 21. The required ratio of these flows is maintained by the ratio regulator 22.

The energy gas 29 is cooled in the cooler 17, the cooled gas 32 enters the purifier 18 and through the compressor, the pressure and flow regulator 20, the high-calorific gas 33 is directed to the gas turbine 5, 1-2% of the energy gas is used as the export gas 34. The off-gases 35 are gas the turbines are fed into the waste heat boiler 6, which is filled with chemically treated water 36. The high pressure steam 38 obtained in the waste heat boiler 6 is sent to the steam turbine 6. In this case, 5% of the steam 27 of the waste heat boiler 6 is sent to the gasifier 1. Electric energy generated by the electric generators : gas 8 and steam 9 turbines, send 41 and 42: to the transformer EDP 10, 43 - to the oxygen station 12. From the transformer 10, electricity 44 is directed to the EDP 11 and 45 - to the electric arc installation 14 of the ladle furnace 13.

Hot - with a temperature of 800-850 ° C low pressure generator gas - reducing gas 30 is cooled and sent to the sulfur purifier 16 and through the pressure and flow regulator 21 further 46 to the shaft metallization furnace 3 or to the tubular rotary furnace 4.

Fired pellets 47 are fed into the shaft metallization furnace 3 and metallized pellets 50 are discharged from the furnace.

Alternatively, coal 47 and roasted pellets or iron ore concentrate 49 are fed into the rotary tube furnace 4, and metallized pellets or iron ore concentrate 50 are discharged from the furnace. Metallized pellets 50 of the shaft furnace 3, or metallized pellets, or metallized iron ore concentrate 50 are fed to the EAF 11. rotary furnace 4 (in relation to the metal part of the mine 30-40%), scrap 53, oxygen 51 oxygen station 12, export gas 52. From EAF 11 smelted steel 54 is fed into a ladle-furnace 13 connected to an electric arc installation 14 of a ladle-furnace 13. Finished steel is delivered from ladle furnace 13 for casting 56.

As an example, the quantitative ratios, the characteristics of the implementation of the proposed method of steelmaking in a closed power-metallurgical cycle are given. These characteristics are estimated as specific indicators - per 1 ton of EAF capacity (or, if the yield of suitable metal is 100%, per 1 ton of steel being melted). In this case, sources were used [4, 9-15]. Calculations were carried out for the maximum (peak) required power of the entire installation, taking into account the fact that the EAF consumes different electrical power in different periods of melting.

According to [13, 14], the relationship between the power of the transformer EAF N _TP and its capacity M _{ED is} determined by the ratio

those. specific power is 0.6 ÷ 0.8 MW per 1 ton of EAF capacity.

The consumption of metallized pellets (concentrate) G _OK will be [1, 2]

The specific consumption of reducing gas for metallization V _MG is V _MG = 1700-1800 m3 / t of metallized pellets [5],

Then, from relations (1), (2), the maximum specific consumption of reducing gas for metallization will be

The efficiency of steam and gas turbine plants is at the level of efficiency = 50% [11].

Let us determine the thermal power for high-calorific gas required for the operation of a steam-gas turbine unit, based on the ratio (1) and efficiency = 50% = 0.5:

МВт на 1 т емкости ЭДП.

MW per 1 ton of EAF capacity.

Thermal power when using fuel is

- низшая рабочая теплота сгорания высококалорийного газа.where V _V.G is the consumption of high-calorific gas,

- the lowest working heat of combustion of high-calorific gas.

The heat of combustion of a high-calorific gas depends on the fuel used [7, 8]. For example, when using brown coal, the heat of combustion will be

With a known heat of combustion of a high-calorific gas from formula (4), its consumption is determined by the ratio:

и N_B.Г = 1,6 МВт = 1600 кВтFor the considered example,

and N _B.G = 1.6 MW = 1600 kW

In this case, the specific consumption of high-calorific gas depends on the melting time in the EAF τ _pl

So, at τ _pl = 1 h = 3600 s,

Based on the specific consumption per hour of high-calorific energy gas for the generation of electrical energy to power the transformer EDP V _V.G and reducing gas for the metallization process υ _M.G, their ratio will be

For this example, the value of M _E.T. equals

When using the power of the steam-gas turbine unit to power the electric arc unit of the ladle-furnace, the value of _VVG increases by 10-15% [14], and in this case the required specific consumption of high-calorific gas will be

и среднем расходе кислорода 30 м3/т стали [14] получаем при КПД=0,5 парогазотурбинной установки дополнительный требуемый расход высококалорийного газаFor additional power supply of the oxygen station with the energy consumption of oxygen production E _k = 240.1 kg of fuel equivalent / 1000 m ³

and an average oxygen consumption of 30 m3 / t of steel [14], we obtain an additional required consumption of high-calorific gas at efficiency = 0.5 of a steam-gas turbine unit

which will amount to 20.6 of the value of B _V.G , i.e. in this case, the consumption of high-calorific gas

Thus, the total required consumption of high-calorific gas (for EAF, ladle-furnace electric arc unit and oxygen station) will be

In the considered example, based on the maximum values of costs, it was obtained

When using a part of the high-calorific gas as an additional fuel in the EAF at a flow rate of 5 m3 / t, its flow rate is additionally increased by 1% of the value of B _V.G. In certain periods of melting, this consumption can be increased up to 2%.

Thus, the maximum high-calorific gas consumption for a given installation will be

For the considered example

In this case, the ratio of the specific consumption of energy and reducing gases will be

For the example under consideration, this ratio will be

Thus, the ratio of the flows of gases of reduction and energy is taken under the condition of some scatter of the initial calculation data as 1: 0.4 ÷ 0.5.

энергетического газа [5] его максимальный удельный расход составитTaking into account the consumption of steam coal

energy gas [5] its maximum specific consumption will be

An uncooled generator gas with a temperature of 800-850 degrees Celsius and a pressure of 0.15 MPa is used to supply reducing gas to a shaft furnace or a rotary tube furnace [1-3]. To supply power gas to the gas turbine of the combined cycle gas turbine plant, generating gas is generated with a pressure of up to 4 MPa [6, 7].

и расходе пара d_пар=5 кг/с 1 МВт [11] составит на 1 т стали при N_г.г=1,6 МВт/тSpecific consumption of high-pressure steam for a steam turbine at the ratio of electric power of the steam and gas turbines

and steam consumption d _steam = 5 kg / s 1 MW [11] will be per 1 ton of steel at N _g = 1.6 MW / t

Then

With a melting time τ _PL = 1 hour = 3600 seconds, the steam consumption for the steam turbine will be

At the same time, steam is additionally taken to the gasifier from the waste heat boiler

Where ρ _steam is the density of steam (at T = 400 deg C and P = 4 MN / m2, ρ = 10 kg / m3) [15], ie magnitude

or 5% of the steam consumption for a steam turbine and 4.5% of the total steam consumption.

Thus, the total required steam consumption generated in the waste heat boiler will be

Based on these parameters, the heating surface of the waste heat boiler is calculated by a well-known method and its type is selected [15].

Since the above calculations were carried out for the specific consumption of gases, the corresponding costs for EAF are obtained by multiplying the corresponding specific indicators by the capacity of the EAF under consideration.

The effectiveness of this method, first of all, is determined by the difference in the efficiency of electricity production from a centralized source of efficiency ≈ 0.25 and in an autonomous cycle using a steam-gas turbine unit with an efficiency of 0.5.

In this method, both to generate electricity and to ensure the reduction process and use of additional fuel in EAF, as well as to generate steam for operation in the gasifier, cheap carbon-containing fuel is used. High waste-free production is also achieved using all primary and derived energy sources in a single autonomous cycle with significant savings in primary fuel for electricity generation. Accordingly, the emission of harmful and greenhouse gases is reduced.

экономия первичного топлива на производство электроэнергии в предлагаемом способе составитThen, with the calculated ratio of the energy and reducing gas

the savings in primary fuel for electricity generation in the proposed method will be

Accordingly, the consumption of greenhouse and harmful emissions will decrease.

INFORMATION SOURCES

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6. Patent for invention of the Russian Federation No. 2433188. Method of smelting steel and alloys in a closed energy-metallurgical cycle / Lisienko V.G. Appl. 2008135797/02, 03.09.2008 publ. 11/10/2011

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Claims (3)

1. A method of steel production in a closed energy-metallurgical cycle, including the production of reducing gases from a carbon-containing material by gasification in a gasifier to obtain a low-calorie reducing gas, which is divided into low and high pressure gas streams, metallization of iron ore raw materials in a reduction unit using cooled and purified reducing low pressure gas, supply of metallized raw materials and scrap to an electric arc furnace for subsequent smelting, steel refining in a ladle furnace, transfer of cooled and purified high pressure reducing gas as a power gas to a cogeneration steam and gas turbine unit to generate electricity and steam using steam in a gasifier, and electricity - in an electric arc furnace, ladle furnace and oxygen station, the oxygen of which is used in an electric arc furnace, characterized in that the installation is additionally used coking of carbonaceous material with carbon dioxide-oxygen blast, in which a high-calorific reducing gas is generated, which is cooled, purified and mixed in a ratio of 1: (0.4-0.5) with a low-calorie high-pressure reducing gas and used in the mentioned combined-cycle gas turbine unit, and the resulting semi-coke is sent to a gasifier to generate a low-calorific reducing gas. 2. A method according to claim 1, characterized in that the resin obtained during the charring process is separated and used as a commercial product. 3. The method according to claim 1, characterized in that the gasoline obtained in the process of purifying the high-calorific gas is used as a commercial product.

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