RU2843785C1 - Method of direct production of iron and shaft furnace for its implementation - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to the field of direct iron production (DIP) and a shaft furnace for its implementation. In compliance with proposed method, process gas flows are fed into shaft furnace and filtered via charge layer, charge is heated and subjected to thermochemical treatment in counter flow, used gas is discharged and metallized product is discharged from shaft furnace. Also, charge is loaded into a furnace with provision of its successive downward movement through a recovery zone, an intermediate zone, a repeated heating zone and a cooling zone. Reformed gas is introduced into the recovery zone with a specific consumption of 1.5-1.7 thousand nm³/t of spongy iron together with the reducing gas flow from the intermediate zone for the charge metallization process carrying out, after which the waste gas is removed from the charge layer into the blast-furnace gas pipeline with temperature of 300-500 °C. To improve gas distribution at the lower boundary of the recovery zone of the shaft furnace there is a two-tier tuyere belt for input of reformed gas. Distance between tiers makes 0.04-0.08 of recovery zone height.

EFFECT: improving quality of metallized product due to rational redistribution of material flows of shaft furnace.

7 cl, 1 dwg

Description

The invention relates to the field of direct iron production (DIP) in shaft furnaces, but can also be applied in other areas of technology (in the preparation of raw materials for metallurgical processing, in blast furnace production), where it is necessary to treat a layer of material with hot reducing gas uniformly across the cross-section of the unit.

Shaft furnaces for reducing the refining capacity using the Midrex, HiL or other methods are known, equipped with devices for supplying reducing gas to the working space from the periphery and peripheral gas vents for removing exhaust gas from the above-bed (blast-furnace) space of the furnace [1, 2].

The design of a shaft furnace is known as the closest analogue [3], where the total flow of reformed gas is divided into two tiers of input through inclined tuyeres with different projections into the layer of charge. Although the extension of tuyeres (in cases of increased adhesion of sponge iron - GI) can lead to the formation of crusts and stoppages of the charge.

Also known is a method and system for supplying hot direct reduced iron to multiple consumers [4] (adopted as a prototype), where the hot iron flow from the shaft furnace is fed to briquetting and/or transportation to the smelting furnace. However, there is no method for cooling the GR required for its transportation to consumers or storage in a warehouse.

The aim of the invention is to increase production and improve the quality of the metallized product through rational redistribution of material flows in a shaft furnace.

The stated objective is achieved by the fact that the method of direct iron production includes the supply to the shaft furnace and filtration of process gas flows through a bed of iron ore pellets (charge), heating and thermochemical treatment of the charge in countercurrent, as well as the removal of exhaust gases and unloading of the metallized product from the shaft furnace. Reformed gas is introduced into the reduction zone (specific consumption of 1.5-1.7 thousand ^nm3 /t of GF, together with the overflow of reducing gas from the intermediate zone) to carry out the process of charge metallization. After that, the exhaust gas leaves the charge layer into the blast furnace gas pipeline (temperature 300-500 °C, η = 1.5-2.5).

There is a method in which natural gas (NG) is introduced into the intermediate zone of the furnace for additional reduction and carburization of the charge (for pyrolysis and in-furnace conversion of hydrocarbons with their specific consumption of 0.1-0.2 thousand ^nm3 /t NG together with the flow of converted or cooling gases from the lower part of the furnace).

There is a method in which, to reheat metallized pellets, converted gas (products of oxygen conversion of natural gas) is supplied to the furnace, increasing the total consumption of reducing gas by 4-7% and increasing the productivity of the shaft furnace by 5-7%.

There is a method in which a cooling gas (with a specific flow rate of 0.5-0.7 thousand ^nm3 /t GC) is supplied to the lower part of the furnace to cool the metallized product, while the supply of converted gas for reheating the metallized product is completely disconnected.

To implement the above method, a variant of the shaft furnace design is proposed, comprising a shaft, devices for loading, unloading the charge, supplying process gases to the working zones of the shaft furnace, as well as removing exhaust gases and unloading the metallized product from the shaft furnace. To improve gas distribution in the reduction zone, a two-tier tuyere belt for introducing reformed gas is located at its lower boundary, while the distance between the tiers is 0.04-0.08 of the reduction zone height (H _ZV ).

There is a variant of the shaft furnace design, in which, in order to increase the working volume of the reduction zone by 10-12%, it is equipped with a blast furnace gas pipeline located coaxially on the shaft dome and connected to the above-layer (blast furnace) space of the shaft furnace. The batch loading pipes pass through the dome to the backfill level at a distance from the dome level of 0.3-0.5 of the shaft radius.

There is a variant of the shaft furnace design which is equipped with throttle control devices installed on the converted gas pipeline and in the cooling gas pipelines required for reheating or cooling the metallized product.

There is a design option for a shaft furnace that is equipped with a damper system for redistributing the flow of flammable liquid when unloading from the furnace: for hot briquetting, for steel smelting in electric furnaces, or it is transported cold to consumers or to a warehouse.

Fig. 1 shows the design of a shaft furnace, which includes a multi-zone shaft furnace 1, including a reduction zone 2, an intermediate zone 3, a reheating zone 5 and cooling zones 9 of the GM with the unloading of the metallized product along three main streams: for steel smelting 12, for hot briquetting 13 (HBI), for transportation to consumers and/or to a warehouse 14 (CDRI). Shaft furnace 1 contains charge loading devices with loading pipes 18, gas distribution devices (consisting of a collector and a two-tier tuyere belt 17) for feeding reformed gas into reduction zone 2, NG is fed through tuyeres 4 into intermediate zone 3, converted gas is fed (gas-oxygen conversion products) through tuyeres 6 into reheating zone 5 and cooling gas is fed through tuyeres 10 into cooling zone 9. Valves 15, 16 and gas outlet 8 of cooling gas must be closed in the hot briquetting mode of FL (valve 7 is open) or the same positions (15, 16 and 8) are open in the cooling mode of FL (valve 7 is closed).

The method of direct production of iron in a shaft furnace is carried out as follows.

Cold iron ore material (oxidized pellets) is lowered into shaft furnace 1 through loading pipes 18, forming a dense layer of charge, which moves downwards under the action of gravitational forces, successively passing all processing zones by technological gas flows with the formation of GR. In this case, reformed gas (with a temperature of 900-950 °C) is introduced into reduction zone 2 (where the temperature is 840-980 °C) by means of gas distribution devices (through a collector and a two-tier tuyere belt 17), is filtered through the charge layer, interacts with it (heating and reduction of the charge) and is removed from shaft furnace 1 through the dome through the central blast furnace gas outlet 19.

Then, in the intermediate zone 3 of the shaft furnace 1, the NG (the temperature of which is 5-400°C) is fed through the tuyeres 4 and is filtered through the hot charge layer by heating and pyrolysis of its hydrocarbons (with their specific consumption of 0.1-0.2 thousand ^nm3 /t of GF) with the formation of carbon and hydrogen according to equation (1). In this case, the NG and the pyrolysis products interact in the charge layer, taking into account the additional reduction of iron oxides according to equation (2), as well as the carburization of GF with the production of cementite according to equation (3) and a small release of soot according to equation (1) in the layer and pores of the charge:

CH ₄ → C + 2H ₂ (1)

FeO + _H2 = Fe + _H2O (2)

3Fe + CH ₄ = Fe ₃ C + 2H ₂ (3)

In addition, converted gas (in the form of products of oxygen conversion of natural gas with a temperature of 750-900°C) is fed into the reheating zone 5 (through valve 7) without cooling the liquefied gas (cooling gas valves 15, 16 are closed). There, the process of additional reduction of iron oxides takes place according to equation (2), and then in the intermediate zone 3, reactions occur according to equation (4, 5) of intra-furnace conversion:

CH ₄ + CO ₂ = 2CO + 2H ₂ (4)

CH ₄ + H ₂ O = CO + 3H ₂ (5)

As a result, the total consumption of reducing gas increases (by 4-7%) and the productivity of shaft furnace 1 increases (by 5-7%).

In the case of cooling the metallized semi-finished product, valves 15, 16 of the cooling zone 9 are opened and cooling gas is supplied (with a specific flow rate of 0.5-0.7 thousand ^nm3 /t of GC), while the supply of converted gas to the reheating zone 5 is turned off by closing valve 7.

After the cooling zone 9, the metallized semi-finished product (hot or cooled) moves down to the unloading table 11, and then it is sent to steel smelting 12, to hot briquetting 13 (HBI), or cold 14 it is transported to consumers or to a warehouse (CDRI).

The invention differs from known methods and devices for shaft furnaces by better conditions for reduction, as well as the creation of a more rational separation of sponge iron in specified directions for high-power installations, thereby ensuring large-scale production of metallized pellets and HBI for smelting high-quality steels.

LIST OF USED SOURCES

1. Yusfin Yu.S., Pashkov N.F. Iron metallurgy - M.: ICC "Akademkniga", 2007. - 464 p.

2. Pchelkin S.A., Yurtaev A.A. Gasman of a shaft metallization furnace. Moscow: Metallurgy, 1991, 127 p.

3. AS SU 1268919 A1, F26B 1/16, C21B 13/00, 1984. /Bokovikov B.A., Chervotkin V.V., Povolotsky V.Yu. etc. – Gas distribution device of a shaft furnace/.

4. Patent RU 2434948 C2, C21B 13/14, 2008. Matthews G.E., Montag S.K., Kakaley R. (US, Midrex) – Method and system for feeding hot direct reduced iron to multiple consumers.

Claims (7)

1. A method for directly producing iron, including feeding into a shaft furnace and filtering process gas flows through a charge bed, heating and thermochemically treating the charge in counter-current, as well as removing exhaust gas and unloading the metallized product from the shaft furnace, characterized in that the charge is loaded into the furnace with its sequential movement downwards through a reduction zone, an intermediate zone, a reheating zone and a cooling zone, while reformed gas is introduced into the reduction zone at a specific flow rate of 1.5-1.7 thousand ^nm3 /t of sponge iron together with an overflow of reducing gas from the intermediate zone to carry out the charge metallization process, after which the exhaust gas is removed from the charge bed into a blast furnace gas pipeline at a temperature of 300-500°C. 2. The method according to paragraph 1, characterized in that additional reduction and carburization of the charge is carried out in the intermediate zone of the furnace, for which purpose natural gas is introduced into it for pyrolysis and in-furnace conversion of hydrocarbons with their specific consumption of 0.1-0.2 thousand ^nm3 /t of sponge iron together with the flow of converted gas in the form of products of oxygen conversion of natural gas with a temperature of 750-900°C or cooling gas supplied from the lower part of the furnace for cooling the resulting sponge iron. 3. The method according to paragraph 2, characterized in that the charge is reheated, for which converted gas is supplied to the furnace with an increase in the total consumption of reducing gas by 4-7% and an increase in the productivity of the shaft furnace by 5-7%. 4. The method according to item 3, characterized in that, to cool the resulting sponge iron, a cooling gas with a specific flow rate of 0.5-0.7 thousand ^nm3 /t of sponge iron is supplied to the lower part of the furnace, while the supply of converted gas for reheating the metallized product is completely shut off. 5. A shaft furnace comprising a shaft, devices for loading and unloading the charge, supply of process gases to the working zones of the shaft furnace, as well as removal of exhaust gases and unloading of the metallized product from the shaft furnace, characterized in that it comprises a reduction zone, an intermediate zone, a reheating zone and a cooling zone, wherein, to improve gas distribution, a two-tier tuyere belt is located at the lower boundary of the reduction zone for introducing reformed gas, wherein the distance between the tiers is 0.04-0.08 of the height of the reduction zone. 6. The furnace according to item 5, characterized in that in order to increase the working volume of the reduction zone by 10-12%, it is equipped with a blast furnace gas pipeline located coaxially on the shaft dome and connected to the above-bed space of the shaft furnace, and the batch loading pipes pass through the dome to the level of the backfill at a distance from the dome level of 0.3-0.5 of the shaft radius. 7. A furnace according to item 5, characterized in that it is equipped with a damper system for redistributing the flows of sponge iron during unloading from a shaft furnace: for hot briquetting, for smelting steel in electric furnaces, for transporting cold sponge iron to consumers or to a warehouse.