RU2843646C1 - Method of direct production of iron and shaft furnace for implementation thereof - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: group of inventions relates to direct production of iron in shaft furnaces. When implementing the method for direct production of iron, the charge is loaded into the shaft furnace, reducing gases are supplied to the shaft furnace, process gas flows are filtered through the charge layer, the charge is heated and thermochemically treated in counter flow, Top gas is withdrawn from the shaft furnace and reduced iron is discharged from the shaft furnace. Reducing gases are supplied to the shaft furnace through two independent flows of reducing gases by means of a two-tier tuyere belt: flow 1 with temperature of 920–970 °C and stream 2 with temperature of 950–1050 °C, wherein the ratio of their consumption is 3.0–6.0. Said two-tier tuyere belt for two independent flows of reducing gases allows spacing there between equal to 0.1–0.2 of metal coating zone height.

EFFECT: optimal distribution of material flows at uniform heat treatment of charge layer along section of shaft furnace.

6 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 PPZh using the Midrex method (KhiL or others) 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-layer (blast-furnace) space of the furnace [1, 2]. The preferential distribution of gas along the periphery of the layer leads to non-uniformity in the quality of the metallized product and is a significant drawback of these designs, limiting the possibilities of increasing the transverse dimensions and unit capacity of the layer unit.

A shaft furnace design for PPZh is known, adopted as a prototype [3], where the total flow of reducing gas is divided into two sleeves, forming two ring pipelines with gas transfer through channels (two tiers of tuyeres) into the shaft furnace. However, there are no levers for redistributing gas flows, and the non-uniformity of the heat treatment of the charge (at the periphery and in the center of the layer) remains a problem. Therefore, it is necessary to expand the possibilities for controlling the metallization process in the shaft furnace for uniformity of the quality of the metallized product.

The first of the group of inventions is based on the task of improving the method of direct iron production by increasing the consumption of reducing gas for uniform heat treatment of the charge layer across the cross-section of the shaft furnace, which is achieved by feeding two autonomous flows of reducing gases into the shaft furnace, with the flow rate ratio of these flows being 3.0-6.0. Heated natural gas is introduced into the intermediate zone of the shaft furnace with a flow rate ratio to the total natural gas consumption in the shaft furnace of 0.12-0.17. Uniform gas distribution in the upper part of the charge layer is ensured by an additional gas outlet-bypass (one or more).

The second invention in the group is based on the task of improving the shaft furnace by placing a two-tier tuyere belt for two autonomous flows of reducing gases on the lower boundary of the metallization zone, with the distance between them being 0.1-0.2 of the height of the metallization zone. The lower part of the intermediate zone of the shaft furnace is equipped with natural gas pipelines (two or more) connected to a conical device for redistributing gas-material flows (from the center to the periphery). An additional gas outlet-bypass (one or more) is located in the upper part of the charge layer, connecting the above-layer working space of the shaft furnace with the blast-furnace gas pipeline.

The first set task is solved in that in the method of direct iron production, including loading the charge into a shaft furnace, supplying reducing gases to the shaft furnace, filtering the process gas flows through the charge layer, heating and thermochemically treating the charge in countercurrent, removing blast furnace gas from the shaft furnace, unloading reduced iron from the shaft furnace, according to the invention, the supply of reducing gases to the shaft furnace is carried out through two autonomous flows of reducing gases: flow 1 (temperature 920-970°C, η = 9.0-11.0) and flow 2 (temperature 950-1050°C, η = 7.0-9.0), while the ratio of their consumption is 3.0-6.0, natural gas heated to 400°C is introduced into the intermediate zone of the shaft furnace with a ratio of its consumption to the total consumption of natural gas in the shaft furnace of 0.12-0.17, the uniformity Gas distribution in the upper part of the charge layer is provided by an additional gas bypass (one or more).

The claimed method ensures an increase in the volume of reducing gases by 15-30% with its filtration to the center of the furnace, thereby increasing the uniformity of the heat treatment of the charge.

The second set task is solved in that in a shaft furnace containing a shaft, devices for loading, unloading the charge, supplying reducing gases to the working zones of the shaft furnace, as well as removing blast furnace gas from the charge layer, according to the invention, a two-tier tuyere belt for two autonomous flows of reducing gases is placed on the lower boundary of the metallization zone, wherein the distance between them is 0.1-0.2 of the height of the metallization zone, in addition, the shaft furnace in the lower part of the intermediate zone is equipped with natural gas pipelines (two or more), connected to a conical device for redistributing gas-material flows (from the center to the periphery), in the upper part of the charge layer an additional gas outlet-bypass (one or more) is placed, connecting the above-layer working space of the shaft furnace with the blast furnace gas pipeline.

The proposed design of the shaft furnace improves the uniformity of heat treatment of the charge from the periphery to the center of the furnace.

The essence of the invention is explained by the figure, where 1 is a shaft furnace shaft, 2 is a reduction zone, 3 is an intermediate zone, 4 is a cone-shaped device, 5 is an unloading of the metallized product (for briquetting and/or cooling), 6 is a pipeline with natural gas, 7 is the first tier of a two-tier tuyere belt, 8 is the second tier of a two-tier tuyere belt, 9 are batch loading pipes, 10 is an additional gas outlet-bypass, 11 is a blast furnace gas pipeline.

The claimed method is implemented as follows.

The iron ore charge (oxidized pellets) is lowered through charge loading pipes 9 into the furnace shaft 1, forming a dense charge layer, which moves downwards under the action of gravitational forces, successively passing all furnace zones for heat treatment with process gases. Initially, the charge layer is lowered into the reduction zone 2, interacting with the flow 1 of reducing gas with a temperature of 920-970 °C, η = 9.0-11.0, which is fed from the steam-carbon dioxide reformer of natural gas through the first tier 7 of the two-tier tuyere belt. After that, the charge layer is lowered lower and interacts with the flow 2 of reducing gas with a temperature of 950-1050 °C, η = 7.0-9.0, which is fed from the steam-oxygen reformer of natural gas. The charge is heated and reduced. In this case, the ratio of the consumption of reducing gases of stream 1 and stream 2 is 3.0-6.0. Then the charge is lowered into the intermediate zone 3, where natural gas heated to 400°C is fed through pipeline 6 (two or more), which exits from the cone-shaped device 4 to the periphery of the furnace. In this case, the ratio of the consumption of natural gas fed through pipeline 6 (two or more) to the total consumption of natural gas for the shaft furnace is 0.12-0.17. In the intermediate zone 3, carburization of the charge occurs. After carburization, the obtained metallized product (sponge iron) is fed for briquetting and/or cooling. Uniformity of gas distribution in the upper part of the charge layer is ensured by an additional gas outlet-bypass 10 (one or more) of the exhaust gas, which is connected to the blast furnace gas pipeline 11.

The claimed shaft furnace operates as follows.

The iron ore charge (oxidized pellets) is lowered into the furnace shaft 1 through charge loading pipes 9. Initially, the charge layer is lowered into the reduction zone 2, interacting with flow 1 and flow 2 of the reducing gas. The charge is heated and reduced. Then the charge is lowered into the intermediate zone 3, where heated natural gas is supplied through pipeline 6 (two or more), which exits from the cone-shaped device 4 to the periphery of the furnace. In the intermediate zone 3, the charge is carburized. After carburization, the resulting metallized product (sponge iron) is fed for briquetting and/or cooling. An additional gas outlet-bypass 10 (one or more) of the exhaust gas ensures uniform gas distribution in the upper part of the charge layer, which is connected to the blast-furnace gas pipeline 11.

The invention differs from known methods of controlling the metallization process by the possibility of organizing the optimal distribution of material flows for large shaft furnaces of increased capacity, thereby ensuring large-scale production of sponge iron.

LIST OF USED SOURCES

1. Yusfin Yu.S., Pashkov N.F. Iron metallurgy: textbook for universities – M.: ITC “Akademkniga”, 2007. – 464 p.

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

3. Patent DE 102006062689 B4, C21B 13/02, 2009. – Shaft furnace for direct reduction of iron oxides.

Claims (6)

1. A method for directly obtaining iron, which includes loading a charge into a shaft furnace, supplying reducing gases to the shaft furnace, filtering the process gas flows through the charge layer, heating and thermochemically treating the charge in counter-current, removing blast furnace gas from the shaft furnace, unloading reduced iron from the shaft furnace, characterized in that the supply of reducing gases to the shaft furnace is carried out through two autonomous flows of reducing gases by means of a two-tier tuyere belt: flow 1 with a temperature of 920-970°C and flow 2 with a temperature of 950-1050°C, while the ratio of their flow rates is 3.0-6.0. 2. A method for directly obtaining iron according to paragraph 1, characterized in that natural gas heated to 400°C is introduced into the intermediate zone of the shaft furnace, into which the charge is lowered after interaction with two streams of reducing gases, and the ratio of its consumption to the total consumption of natural gas for the shaft furnace is 0.12-0.17. 3. A method for directly obtaining iron according to paragraph 1, characterized in that uniform gas distribution in the upper part of the charge layer is ensured by an additional gas bypass, one or more. 4. A shaft furnace containing a shaft, devices for loading and unloading the charge, supplying reducing gases to the working zones of the shaft furnace, and also removing blast furnace gas from the charge layer, characterized in that a two-tier tuyere belt for two autonomous flows of reducing gases is placed at the lower boundary of the metallization zone, while the distance between them is 0.1-0.2 of the height of the metallization zone. 5. A shaft furnace according to item 4, characterized in that it is equipped with natural gas pipelines, two or more, in the lower part of the intermediate zone, connected to a conical device for redistributing gas-material flows from the center to the periphery. 6. A shaft furnace according to item 4, characterized in that in the upper part of the charge layer there is an additional gas bypass, one or more, connecting the above-layer working space of the shaft furnace with the blast furnace gas pipeline.