CN116694842A - A method for regulating the reduction gas flow in a hydrogen-based reduction shaft furnace - Google Patents

Abstract

The invention discloses a hydrogen-based reduction shaft furnace reduction gas flow adjustment method, in which a large-diameter pellet charge is arranged in the furnace to form a high-porosity charge area, and a small-diameter pellet charge is arranged in the furnace to form a low-porosity charge area, and The volume of the charge area with high porosity accounts for 12-30% of the volume of the whole charge, and the whole charge is equal to the sum of the large-diameter pellet charge and the small-diameter pellet charge. It can effectively increase the center temperature and reduction efficiency of the shaft furnace, and greatly increase the production efficiency of sponge iron; suppress the side airflow velocity, and can effectively prolong the residence time of the reducing gas in the shaft furnace, so that the hydrogen component has more time to interact with the furnace. The high consumption intensity of the reducing gas allows the proportion of hydrogen in the reaction gas ratio to be greatly increased. The effective use of clean energy in smelting can reduce carbon emissions and achieve the goal of carbon neutrality.

Description

A method for regulating the reduction gas flow of a hydrogen-based reduction shaft furnace

technical field

The invention relates to the field of shaft furnace smelting, in particular to a hydrogen-based reduction shaft furnace reduction gas flow regulator.

Background technique

The increasing environmental awareness urgently requires the development of innovative technologies. Hydrogen metallurgy uses clean and renewable energy in the ironmaking process, and is recognized as the cleanest and environmentally friendly metallurgical technology in the world.

In recent years, in order to reduce carbon emissions and achieve the goal of carbon neutrality, the hydrogen-rich injection technology at the blast furnace tuyere has been vigorously developed, and the proportion of hydrogen in the blast furnace gas is getting higher and higher. In the foreseeable future 20 years, the large-scale preparation of _H2 , a cheap and clean energy, will make the mixed gas of CO and _H2 (coal gas) produced by natural gas cracking or coal gas production as a reducing medium to produce direct reduced iron a high-quality blast furnace. The main production method of charge, and thus the vigorous development of the "hydrogen metallurgy" process represented by the short process of "hydrogen shaft furnace-electric furnace", has become the main direction of low-carbon transformation and high-quality development of the steel industry.

The direct reduction shaft furnace ironmaking process mainly relies on CO, H ₂ and coking coal as reducing agents, heats the pellets through chemical heat and gas physical sensible heat, and produces a short process of direct reduced iron under the premise of no material form transformation of the iron-containing charge craft. According to the types of reducing substances used in the pellet direct reduction process, the smelting process can be divided into gas-based shaft furnace and coal-based shaft furnace, and according to the type of reducing gas used in the gas-based direct reduction shaft furnace, it can be divided into the following A hydrogen-based shaft furnace with _H2 as the reducing gas and a carbon-based shaft furnace with CO as the main reducing gas. The statistical results of global direct reduction shaft furnace production in 2022 show that more than 80% of the sponge iron produced by direct reduction shaft furnaces is produced by gas-based shaft furnaces, and the proportion of gas-based shaft furnaces is increasing year by year.

There are three main processes for the production of sponge iron for steelmaking by direct reduction in gas-based shaft furnaces: MIDREX process, HYL-Ⅲ process, COREX process and PERED process. Among them, the COREX process is the most advanced, most complete, and easiest way to industrialize among the existing processes. Similar to the blast furnace block belt, the rationality of shaft furnace gas distribution directly affects the heat transfer and mass transfer efficiency between the gas and solid phases, thereby affecting the production efficiency of the entire direct reduction shaft furnace process. In order to achieve low power consumption, low energy consumption and high Productivity. In recent years, the newly built COREX process shaft furnace has been improved in the direction of large diameter and high furnace capacity. This has resulted in excess air flow at the edge of the shaft furnace, a serious shortage of gas supply in the center air flow, and air pressure in the upper and lower parts, center and edge of the shaft furnace. As the difference increases, the phenomenon of air flow reverse channeling is serious, which reduces the metallization rate of the pellets.

Contents of the invention

The purpose of the present invention is to solve the above technical problems, to provide a simple and reliable method, which can effectively improve the utilization rate of hydrogen in the reducing gas, strengthen the reaction conditions of the shaft furnace, and reduce the carbon emission of the shaft furnace. method.

In order to achieve the above purpose, the present invention provides a method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace, in which a large-diameter pellet charge is arranged in the furnace to form a high-porosity charge region, and a small-diameter pellet charge is arranged in the furnace to form a low-porosity region The high-porosity charge area, and the volume of the high-porosity charge area accounts for 12-30% of the overall charge volume, and the overall charge is equal to the sum of the large-diameter pellet charge and the small-diameter pellet charge.

Further, the arrangement of the high-porosity charge area and the low-porosity charge area is specifically: arranging the large-diameter pellet charge vertically in the center of the shaft furnace to form a central high-porosity charge area, and placing the small-diameter pellets The charging material is arranged around the central high-porosity charging material area to form a surrounding low-porosity charging material area.

Further, the arrangement of the high-porosity charge area and the low-porosity charge area specifically includes: alternately arranging high-porosity charge layers and low-porosity charge layers along the vertical direction in the shaft furnace.

Further, the equivalent diameter d ₁ of the large-diameter pellets is 0.005D-0.01D, the equivalent diameter d ₂ of the small-diameter pellets is 0.001D-0.005D, and D is the maximum inner diameter of the shaft furnace.

Further, the porosity _P1 of the high-porosity charge area is 26-33%, and the porosity _P2 of the low-porosity charge area is 15-26%.

Further, the intrinsic porosity of the large-diameter pellets and the small-diameter pellets is both 0.1575d ₁ -0.2175d ₁ , where d ₁ is the equivalent diameter of the large-diameter pellets.

Further, auxiliary powdery charge is added in the low-porosity charge region, so that the porosity of the low-porosity charge region to which the powdery charge is added is 15-26%.

Further, the equivalent diameter of the powder charge is 0.0001D-0.001D, and D is the maximum inner diameter of the shaft furnace.

Further, grooves are made on the surface of the large-diameter pellets and the small-diameter pellets so that the natural porosity of the large-diameter pellets and the small-diameter pellets are both 0.2175d ₁ to 0.3112d ₁ , d ₁ Equivalent straight for large diameter pellets

Compared with the prior art, the beneficial effects of the present invention are as follows: it can effectively improve the central temperature and reduction efficiency of the shaft furnace, and greatly increase the production efficiency of sponge iron; it can effectively prolong the reduction of the reducing gas in the shaft furnace by suppressing the side air velocity. The residence time within the range allows the hydrogen components to have more time to contact with the iron-containing charge. The high consumption intensity of the reducing gas allows the proportion of hydrogen in the reaction gas ratio to be greatly increased. The effective use of clean energy in smelting can Reduce carbon emissions and achieve the goal of carbon neutrality.

Description of drawings

Fig. 1 is the cloth diagram of first kind of improved mode of the present invention;

Fig. 2 is the cloth diagram of the second improved mode of the present invention;

Fig. 3 is the cloud map (central monitoring point) of hydrogen-based shaft furnace reducing gas velocity in the embodiment;

Fig. 4 is a cloud diagram of the reducing gas velocity of the hydrogen-based shaft furnace in the embodiment (edge monitoring point).

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

After the lower blowing parameters are established, they will not change frequently within a certain period of time. In order to form a suitable edge and center airflow distribution, we can only rely on the relatively convenient upper charging system to control the size of the batch of pellets in the shaft furnace. The gaps in the material layer can achieve the purpose of adjusting the distribution of reducing airflow in the furnace. Commonly used adjustment methods for the upper charging system include: adjusting the distribution angle of ore coke and the number of distribution loops to adjust the edge and center loads, adjusting the number of distribution loops to adjust the width of the distribution platform and the size of the funnel, and center coke, etc.

The hydrogen-based reduction shaft furnace reduction gas flow adjustment method of the present invention is as follows: arranging large-diameter pellet charge in the furnace to form a high-porosity charge area, arranging small-diameter pellet charge in the furnace to form a low-porosity charge area, and high porosity The volume of the high-rate charge area accounts for 12-30% of the overall charge volume (that is, the proportion of the high-porosity charge area Φ), and the overall charge is equal to the sum of the large-diameter pellet charge and the small-diameter pellet charge.

The first improvement method is: as shown in Figure 1, in order to increase the gap between the charges, increase the porosity of the charge, and provide more circulation channels for the air to pass through, the charge of large-diameter pellets is vertically arranged in the center of the shaft furnace to form a In the central high-porosity charge area, the small-diameter pellet charge is arranged around the central high-porosity charge area to form a surrounding low-porosity charge area. And the equivalent diameter d ₁ of large-diameter pellets is 0.005D-0.01D, the equivalent diameter d ₂ of small-diameter pellets is 0.001D-0.005D, and D is the maximum inner diameter of the shaft furnace; the porosity P ₁ of the high-porosity charge area The porosity P ₂ of the low-porosity charge area is 15-26%; the self-porosity of large-diameter pellets and small-diameter pellets are both 0.1575d ₁ ～0.2175d ₁ ; in order to A larger porosity deviation is formed between the high-porosity charging area in the center of the shaft furnace and the remaining space in the shaft furnace reaction area, and the metal yield is improved. In the low-porosity charging area, supplementary additions such as crushed iron ore, blast furnace slag, powder Coal ash and other powdery charge maintains the porosity of the low-porosity charge area added to the powder charge at 15 to 26%, and the equivalent diameter of the powder charge is 0.0001D to 0.001D; in order to increase the self-porosity of the charge Grooves can be made on the surface of the large-diameter pellets and the small-diameter pellets so that the self-porosity of the large-diameter pellets and the small-diameter pellets are both increased to 0.2175d ₁ -0.3112d ₁ . The porosity P ₁ of the high-porosity charging area in the control center is greater than the porosity P ₂ of the surrounding low-porosity charging area, so that the central airflow of the direct reduction shaft furnace is strengthened, the edge airflow intensity is suppressed, and a double airflow with high central strength and appropriate sidewall airflow is formed. The air flow ascending channel increases the utilization rate of reducing gas.

The second improvement method is: as shown in Figure 2, the charge is distributed on the upper part of the furnace roof without a bell. Through the rotation of the material chute of the distribution machine, a uniform material layer structure is formed in the shaft furnace, and the vertical direction is alternated in the shaft furnace. Arrange the high-porosity charge layer and the low-porosity charge layer to form a layer stacking method with high and low porosity charge alternately, and form a porosity gradient change between charge layers of different heights, so that when the edge airflow passes through the high-porosity charge layer, According to the fluid flow rules, it will move towards the direction with the smallest kinematic viscosity, which also effectively enhances the central airflow intensity. And the equivalent diameter d ₁ of the large-diameter pellets is 0.005D to 0.01D, the equivalent diameter d ₂ of the small-diameter pellets is 0.001D to 0.005D, and D is the maximum inner diameter of the shaft furnace; the porosity of the high-porosity furnace charge layer is P ₁ The porosity P ₂ of the low-porosity charge layer is 15-26%; the self-porosity of large-diameter pellets and small-diameter pellets are both 0.1575d ₁ ～0.2175d ₁ ; in order to A greater porosity deviation is formed between the high-porosity charge area in the center of the shaft furnace and the charge charge in the remaining space of the shaft furnace reaction zone, and the metal yield is improved. Additions such as crushed iron ore, blast furnace waste slag, and powder are added in the low-porosity charge layer The powdered charge such as coal ash maintains the porosity of the low-porosity charge layer added with the powdered charge at 15-26%. Under the smelting condition of 875K in the upper part, the powdery charge will quickly form a semi-molten state, adhere to the pellets to fill the intergranular pores of the pellets, and prevent the powdery charge from sinking and blocking while forming a low-porosity charge layer The intergranular pores of the high-porosity charge layer; in order to increase the natural porosity of the charge, grooves can be made on the surface of large-diameter pellets and small-diameter pellets to make the large-diameter pellets and small-diameter pellets have their own The porosity increases to 0.2175d ₁ ~0.3112d ₁ .

In the two improved methods, the proportion of the high-porosity charge area Φ is 12 to 30% of the volume of the overall charge. Excessively large high-porosity charge volume will seriously affect the metal yield of shaft furnace production and affect the production economy of sponge iron. benefit. Therefore, it is necessary to fully consider the factors that affect the smelting strength, such as the type of shaft furnace, the shape of the charge, and the inherent porosity of the pellets, and determine the optimal charge volume ratio through numerical simulation.

At the same time, the present invention uses the fluid simulation software ANSYS to simulate the velocity field and temperature field of the flow state of the gas flow in the porous charge during the smelting process of the hydrogen-based shaft furnace. According to the structural parameters of the hydrogen-based shaft furnace, a three-dimensional model is established and the structural grid is divided. The k-e turbulence model and the P1 radiation model are used for coupling setting, and the boundary conditions of the shaft furnace are treated as follows: the pellets in the shaft furnace are simplified as porous media, the size and position of the pores between the pellets are randomly distributed, and the diameter of the pellets is The change is simplified to the change of the porosity of the porous medium; the internal heat distribution of the pellets is ignored, the heat in the furnace is provided by the high-temperature reducing gas, and the thermal effect generated by the reduction reaction is all used to heat the reactants; the fluid flow mode between the gas-solid two-phase is plug flow; The gas is an ideal gas; the influence of the lining refractory material on the gas distribution and temperature distribution is not considered; only the influence of the transfer of reaction heat on the solid charge is considered, and the internal heat conduction between the iron-containing charges is ignored; it is assumed that the heat transfer coefficient does not change with the porosity as fixed constant. The charge in the hydrogen-based shaft furnace adopts unsteady fluidized heat transfer, and the udf (user-defined) file is used to define the high-porosity area of the shaft furnace. Use fluent to simulate and calculate hydrogen-based shaft furnaces in areas with different volume fractions and high porosity, and compare the velocity flow field and temperature flow field under the ratio of different high-porosity charge areas as shown in Figure 3. According to the temperature and temperature in the central area The velocity value determines the optimum Φ value.

By adopting the method for regulating the reducing gas flow of the hydrogen-based reduction shaft furnace of the present invention, the central temperature and reduction efficiency of the shaft furnace can be effectively improved, and the production efficiency of sponge iron can be greatly increased. According to the experimental data, in the reaction using hydrogen as the reducing gas, the decisive factor affecting the reaction rate is the propagation velocity of hydrogen in the gaps of the charge and the surface of the unreacted nuclear model, and suppressing the velocity of the side airflow can effectively prolong the reduction of the reducing gas. The residence time in the shaft furnace allows the hydrogen component to have more time to contact with the iron-containing charge. The high consumption intensity of the reducing gas allows the proportion of hydrogen in the reaction gas ratio to be greatly increased. The effective use of clean energy in smelting Using it can reduce carbon emissions and achieve the goal of carbon neutrality.

Example

Taking iron-containing charge pellets (average size 15mm) as an example, the self-porosity of iron-containing charge is 21.75% to 31.12%. To form a hydrogen-based shaft furnace charge stacking method with high porosity, one must adopt its own The pellet charge with higher porosity provides more air flow channels, on the other hand, it is necessary to use a charge with a large equivalent diameter to reduce the specific surface area of the charge. The iron-containing charge is randomly sampled, and the large-size iron-containing charge is screened, and the particle size of the screened charge is classified. The pellets with an equivalent diameter of 25 mm to 50 mm are defined as the first-grade charge, the pellets with an equivalent diameter of 5 mm to 25 mm are defined as the second-grade charge, and the pellets with an equivalent diameter of less than 5 mm are defined as the third-grade charge, namely Bulk charge.

According to the simulation results, the diameter of the high-porosity area of Φ=1m is the most suitable for this type of furnace. Furnace charge, the graded secondary charge and bulk charge are used to increase the iron content in the shaft furnace and increase the yield of sponge iron. An upflow barrier area is also formed above the tuyere area, which promotes the accumulation of unreacted reducing gas towards the center, which strengthens the reaction degree of the center and significantly increases the temperature.

When the diameter of the high-porosity area of Φ=1m is used in the center of the hydrogen-based shaft furnace, the center line is used as the monitoring point, as shown in Figure 3, the speed at the position 2m away from the top of the shaft furnace is significantly enhanced, and the speed is increased from 0.247m/s Increase to 0.356m/s, an increase of 30%. The closer to the center of the shaft furnace reaction zone, the greater the difference in gas reaction velocity. The position with the largest speed difference is 6.2m from the top of the shaft furnace. The gas flow rate increased from 0.437m/s to 0.626m/s, and the growth rate increased to 43.25m/s. %. Taking the edge line of the hydrogen-based shaft furnace as the monitoring point, as shown in Figure 4, it can be seen that the acceleration of the central airflow speed also makes the edge airflow have a certain acceleration effect, and the speed difference reaches the maximum at the position 5m away from the top of the shaft furnace. From 0.406m/s to 0.440m/s, the growth rate is only 8.4%, and the purpose of suppressing the edge airflow from developing the central airflow has been achieved.

Claims (9)

1. A reducing gas flow regulating method of a hydrogen-based reduction shaft furnace is characterized in that large-diameter pellet furnace burden is arranged in the furnace to form a high-porosity furnace burden region, small-diameter pellet furnace burden is arranged in the furnace to form a low-porosity furnace burden region, the volume of the high-porosity furnace burden region accounts for 12-30% of the volume of the whole furnace burden, and the whole furnace burden is equal to the sum of the large-diameter pellet furnace burden and the small-diameter pellet furnace burden.

2. The method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 1, characterized in that the arrangement of the high-porosity charge areas, the low-porosity charge areas is in particular: the large diameter pellet charge is vertically arranged in the center of the shaft furnace to form a central high porosity charge region, and the small diameter pellet charge is arranged around the central high porosity charge region to form a peripheral low porosity charge region.

3. The method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 1, characterized in that the arrangement of the high-porosity charge areas, the low-porosity charge areas is in particular: high porosity and low porosity furnace layers are alternately arranged in the vertical direction within the shaft furnace.

4. The method of adjusting the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 1, wherein the large-diameter pellet equivalent diameter d ₁ 0.005D to 0.01D, the small-diameter pellet equivalent diameter D ₂ 0.001D to 0.005D, D being the maximum internal diameter of the shaft furnace.

5. The method of claim 1, wherein the high porosity charge region has a porosity P ₁ 26-33% of the porosity P of the low porosity charge region ₂ 15-26%.

6. The method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 1, wherein the self-porosity of the large-diameter pellets and the small-diameter pellets is 0.1575d ₁ ～0.2175d ₁ ，d ₁ Is the equivalent diameter of the large-diameter pellets.

7. The method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 1, wherein the powdery burden is added in the low-porosity burden region in an auxiliary manner so that the porosity of the low-porosity burden region to which the powdery burden is added is 15-26%.

8. The method for regulating the reducing gas flow of a hydrogen-based reduction shaft furnace according to claim 7, wherein the equivalent diameter of the powdery charge is 0.0001D to 0.001D, and D is the maximum inner diameter of the shaft furnace.

9. The method for regulating the reducing gas flow in a hydrogen-based reduction shaft furnace according to claim 1, wherein grooves are formed in the surfaces of the large-diameter pellets and the small-diameter pellets so that the self-porosity of the large-diameter pellets and the small-diameter pellets is 0.2175d ₁ ～0.3112d ₁ ，d ₁ Is large-diameter pellets with straight equivalent.