Hydrogen-based shaft furnace process and primary design method of main body structure

Abstract

The invention discloses a hydrogen-based shaft furnace process and a primary design method of a main body structure, and belongs to the technical field of hydrogen metallurgy of a hydrogen-based shaft furnace for directly reducing iron oxide. The method comprises the following step: calculating the introduction amount of reducing gas consumed by the hydrogen-based shaft furnace for reducing iron oxide at different temperatures by adopting molar enthalpies of different substances in different states. And enthalpy tables of different substances under different temperature conditions are made, so that a designer can conveniently inquire and calculate. The height-diameter ratio of the height to the diameter of the reduction section of the hydrogen-based shaft furnace is introduced, the height and the diameter of the reduction section of the hydrogen-based shaft furnace are calculated, corresponding process parameters of the hydrogen-based shaft furnace are determined, and model selection of corresponding corollary equipment is facilitated. The invention provides a method for preliminarily and rapidly designing corresponding parameters of the hydrogen-based shaft furnace under different processes for designers.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen metallurgy of a hydrogen-based vertical furnace for direct reduction of iron oxide, and in particular relates to a calculation method for a hydrogen-based vertical furnace process and a preliminary design of a main structure. Background Art

[0003] my country's steel industry has long been dominated by the blast furnace-converter long process. Iron produced by blast furnace ironmaking still accounts for more than 95% of my country's total iron production. Blast furnace ironmaking is the process with the largest carbon dioxide emissions, accounting for about 70% to 90% of the total carbon dioxide emissions of the entire steel production process. Energy efficiency has become an important factor in measuring a country's competitiveness. Compared with the traditional "blast furnace + converter" smelting process, the direct reduction iron + electric furnace short process has obvious advantages in carbon emission reduction. The hydrogen metallurgical process uses hydrogen instead of coke as a reducing agent, which significantly reduces the production of carbon dioxide and helps to achieve low-carbon and green steel production.

[0004] Hydrogen metallurgy, which replaces carbon with hydrogen, is becoming a strategic technology option for the green and low-carbon development of the steel industry at home and abroad. Hydrogen-based vertical furnaces use hydrogen to reduce iron oxide, and its main products are metallic iron and water vapor, without other carbon-containing reducing gases such as CO, so low-carbon and green steel production can be achieved. With the accelerated popularization and utilization of green electricity such as photovoltaics and wind power and the rapid decline in the cost of water electrolysis hydrogen production technology, hydrogen metallurgy technology uses hydrogen as a reducing agent instead of carbon reduction, which is one of the important ways to reduce CO2 emissions from long-process steelmaking and ensure the green and sustainable development of the steel industry. Summary of the invention

[0005] The purpose of the present invention is to provide a preliminary calculation method suitable for hydrogen-based vertical furnace production process and vertical furnace structure design, which is convenient for designers to design hydrogen-based vertical furnace process and body structure parameters according to different working conditions.

[0006] To achieve the above purpose, the present invention provides the following design and calculation scheme:

[0007] 1. The amount of reducing gas consumed by the hydrogen-based vertical furnace to reduce iron oxide at different temperatures is calculated using the molar sensible heat enthalpy of different substances in different states and the reaction enthalpy of the reduction reaction.

[0008] 2. Introduce the height-to-diameter ratio of the reduction section of the hydrogen-based vertical furnace, calculate the height and diameter of the reduction section of the hydrogen-based vertical furnace, and finally determine the size of the hydrogen-based vertical furnace.

[0009] 3. Make a table of sensible heat enthalpy of different substances under different temperature conditions to facilitate designers to query and calculate.

[0010] 4. Determine the calculation formulas for various parameters of different processes of hydrogen-based vertical furnaces.

[0011] Compared with the prior art, the present invention has the following technical effects: by looking up the table to determine the values ​​of sensible heat enthalpy and reaction enthalpy of different substances in different states, the amount of each substance in different processes can be directly calculated, and at the same time, the height and diameter ratio of the reduction section of the vertical furnace to the reduction diameter is introduced, so that the height and diameter of the reduction section of the hydrogen-based vertical furnace can be directly calculated, which is convenient for personnel to design the structure of the hydrogen-based vertical furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Process flow chart for hydrogen-based vertical furnace reduction of iron oxide

[0013] Figure 2 Flow chart of the calculation method for the process parameters and structure of hydrogen-based shaft furnace reduction of iron oxide

[0014] Figure 3 is the sensible heat enthalpy of different substances at different temperatures

[0015] Figure 4 The internal structure of the hydrogen-based vertical furnace

[0016] In the figure: H1 is the height of the reduction section of the hydrogen-based vertical furnace, H2 is the height of the transition section of the hydrogen-based vertical furnace, and H3 is the height of the cooling section of the hydrogen-based vertical furnace. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0018] The purpose of the present invention is to calculate the process parameters of a hydrogen-based vertical furnace by querying the sensible heat enthalpy and reaction enthalpy of each substance at different temperatures, and to introduce a calculation method for the height-to-diameter ratio to facilitate designers to complete the vertical furnace structure design.

[0019] The process flow of hydrogen-based vertical furnace reduction of iron oxide is as follows Figure 1 As shown, it includes the feeding system (elevator, raw material bin, etc.), the vertical furnace body (reaction bin, dust removal and dehumidification system, compressor, heating system, etc.), and the unloading system (screw unloading, unloading bin, etc.). It can produce products such as HDRI and CDRI.

[0020] The design and calculation process of the hydrogen-based vertical furnace process and main structure is as follows Figure 2 As shown,

[0021] Hydrogen-based shaft furnace reduction process: 1 / 2Fe2O3+3 / 2H2=Fe+3 / 2H2O

[0022] The first step is to calculate the amount of hydrogen used in the vertical furnace:

[0023] Under certain temperature conditions, the main component of the oxidized pellets is Fe2O3. According to theoretical calculations, the consumption of hydrogen to reduce the pellets is about 600m 2 / t. However, the reduction reaction process is an endothermic reaction, and the furnace cannot maintain a too high reaction temperature. Excessive hot hydrogen needs to be continuously heated to maintain the internal temperature balance so that the reduction reaction can continue to proceed efficiently. The ventilation volume of hot hydrogen is much larger than the theoretical value, and the amount of reduction gas needs to be determined through heat balance calculation.

[0024] Heat balance calculation includes heat input and heat expenditure. Heat input is composed of gas phase sensible heat enthalpy H Tg,i and the sensible heat enthalpy of the solid raw material H Ts,i It consists of two parts; the heat expenditure mainly includes the heat enthalpy change of the reduction reaction ΔH Tr 、Sensible heat enthalpy H carried away by the furnace top gas Tg,o 、Sensible heat enthalpy H taken away by sponge iron pellets Ts,o , enthalpy of evaporation of water in the material H Tvapour And the heat loss Q loss .

[0025] H Tg,i +H Ts,i =ΔH Tr +H Tg,o +H Ts,o +H Tvapour +Q loss

[0026] By knowing the hydrogen inlet and heated temperature, pellet temperature, metal iron pellet finished product temperature, furnace reaction temperature, furnace top gas outlet temperature, Figure 3 By searching, we can obtain the different molar sensible heat enthalpy values ​​corresponding to each state, and by substituting them into the equilibrium formula, we can obtain the required amount of hydrogen.

[0027] The relevant parameters of the supporting facilities (heating furnace power, exhaust gas treatment volume, etc.) can be calculated accordingly based on the required amount of hydrogen.

[0028] The second step is to design and calculate the main structure of the vertical furnace. The vertical furnace reaction chamber includes the oxidation pellet reduction section, the hot and cold hydrogen transition section, and the metal iron pellet cooling section. Figure 4 shown.

[0029] The reduction section of the oxidized pellets is the most important position for the reduction reaction in the shaft furnace. In the normal feeding process, the feeding speed ν is certain. In order to ensure that the oxidized pellets undergo sufficient reduction reaction, the height of the reduction section should not be less than the distance that the material stays during the reduction cycle. Only then can the reduced product reach the predetermined metallization rate of the sponge iron pellets.

[0030] Height of the reduction section of the vertical furnace. To simulate the reduction process of the pelletized ore in the vertical furnace, the temperature reaches 850°C after about 1 hour, and then the reduction is carried out for about 3 hours under constant temperature conditions and a changing reducing atmosphere, and the degree of reduction reaches 97%, and the sponge iron with a predetermined metallization rate is obtained. Therefore, 3 hours can be used as the necessary reduction time under the reduction conditions. However, considering the difference between the ideal simulation and the complexity of reality, and considering the existence of the material-free zone above the vertical furnace, 6 hours is usually taken as the calculation time for the height of the reduction section of the vertical furnace, and the reduction time can also be appropriately shortened accordingly.

[0031] The furnace body angle of the reduction section of the hydrogen-based vertical furnace. The existence of the furnace body angle of the reduction section can reduce the extrusion between the furnace charge and the furnace charge and the furnace wall, improve the permeability of the furnace charge, reduce the friction between the furnace charge and the furnace wall, and facilitate the smooth flow of the furnace charge. Generally, the design of the modern furnace body angle is less than 10°. Under the same conditions, the reduction expansion caused by the reduction of iron oxides with H2 is less than the expansion caused by CO reduction. The furnace body angle of the hydrogen-based vertical furnace is generally less than 5°.

[0032] The height of the transition section of the hydrogen-based vertical furnace must be determined to ensure that the reduction hot gas and the cooling gas do not intersect. The pressures of the reduction section and the cooling section are adjusted through the transition section. The height of the transition section should not be too small to prevent excessive heat exchange between the cooling gas and the hot reduction gas, which would cause a large amount of heat waste.

[0033] The height of the cooling section of the hydrogen-based vertical furnace is determined according to the cooling process, and the cooling height and cooling gas consumption are calculated through heat balance. The cooling process is that the room temperature cooling gas enters the vertical furnace from the bottom of the cooling section, and forms a convection cooling process with the reduced sponge iron DRI at a temperature of 800°C, and gas-solid convection heat exchange occurs during the flow process. After cooling to less than 80°C, the cooling gas is discharged from the outlet of the cooling section and discharged from the top of the cooling section.

[0034] Generally, the charge stays in the vertical furnace for 10 hours, including 1 hour in the transition section and 3 hours in the cooling section. The heights of the transition section and cooling section of the vertical furnace are designed separately according to different residence times.

[0035] The height-to-diameter ratio b of the shaft furnace reduction section is introduced. Since the shaft angle of the hydrogen-based shaft furnace is small, the shaft furnace reduction section is regarded as a cylinder for calculation.

[0036] Given the daily output P1-t and pellet density ρ1-t / m 3 , reduction section volume utilization coefficient η-t / (m 3 ·d) Reduction period Th of reduction section, height of reduction section H1-m, ratio K of mass of iron ore required to produce 1 ton of sponge iron, and feeding speed ν-m / h.

[0037] Calculate the diameter of the reduction section of the shaft furnace. Considering the shaft angle and the space occupied by other devices, the diameter of the reduction section of the shaft furnace is:

[0038] The height H1=bD of the hydrogen-based vertical furnace reduction section is further calculated.

[0039] Further calculation of the material descent speed in the reduction section of the hydrogen-based shaft furnace

[0040] Further calculation of the effective volume of the hydrogen-based shaft furnace reduction section

[0041] Further calculation of the reduction section volume utilization coefficient

[0042] The present invention completes the preliminary design of the hydrogen-based vertical furnace through the above steps, and further designs the material operation system, hydrogen circulation system, electric control and monitoring system, etc. through the main parameters of the hydrogen-based vertical furnace.

Claims

1. A preliminary calculation method suitable for hydrogen-based shaft furnace production process and shaft furnace structure design, characterized in that: include: 1) The amount of reducing gas consumed by the hydrogen-based shaft furnace for reducing iron oxide at different temperatures is calculated by using the molar enthalpy of different substances under different states and the reaction enthalpy of the reduction reaction; 2) Introducing the height-to-diameter ratio of the reduction section of the hydrogen-based vertical furnace, calculating the height and diameter of the reduction section of the hydrogen-based vertical furnace, and ultimately determining the size of the hydrogen-based vertical furnace; 3) Make enthalpy tables of different substances under different temperature conditions to facilitate designers to query and calculate; 4) Determine the calculation formulas for various parameters of different processes of hydrogen-based vertical furnaces.

2. A preliminary calculation method for hydrogen-based vertical furnace production process and vertical furnace structure design according to claim 1, characterized in that: The method of using balance calculation to determine the amount of reducing gas introduced specifically includes: Heat balance calculation includes heat input and heat expenditure. Heat input is calculated by the gas phase enthalpy H Tg,i and the solid raw material enthalpy H Ts,i It consists of two parts; the heat expenditure mainly includes the heat enthalpy change of the reduction reaction ΔH Tr 、The heat enthalpy taken away by the furnace top gas H Tg,o 、The sponge iron pellets take away the heat enthalpy H Ts,o , enthalpy of evaporation of water in the material H Tvapour And the heat loss Q loss . H Tg,i +H Ts,i =ΔH Tr +H Tg,o +H Ts,o +H Tvapour +Q loss By knowing the hydrogen inlet and heated temperature, pellet temperature, finished metal iron pellet temperature, furnace reaction temperature, and furnace top gas outlet temperature, we can find the different enthalpy values ​​corresponding to each state through Figure 3, and put them into the balance formula to get the required hydrogen intake amount.

3. The preliminary calculation method for hydrogen-based shaft furnace production process and shaft furnace structure design according to claim 1, characterized in that: The height-to-diameter ratio b of the vertical furnace reduction section is introduced. Since the shaft angle of the hydrogen-based vertical furnace is small, the vertical furnace reduction section is regarded as a cylinder for calculation, which specifically includes: Calculate the diameter of the reduction section of the shaft furnace. Considering the shaft angle and the space occupied by other devices, the diameter of the reduction section of the shaft furnace is: The height H1=bD of the hydrogen-based vertical furnace reduction section is further calculated. Further calculation of the material descent speed in the reduction section of the hydrogen-based shaft furnace Further calculation of the effective volume of the hydrogen-based shaft furnace reduction section Further calculation of the reduction section volume utilization coefficient The present invention completes the preliminary design of the hydrogen-based vertical furnace through the above steps, and further designs the material operation system, hydrogen circulation system, electric control and monitoring system, etc. through the main parameters of the hydrogen-based vertical furnace.

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