A method for evaluating the effect of the degree of decarburization of the circulating coal gas on a hydrogen-rich carbon cycle oxygen blast furnace

Abstract

The present application belongs to the technical field of blast furnace ironmaking, and specifically discloses a method for evaluating the influence of the degree of decarburization of circulating gas on a hydrogen-rich carbon-circulating oxygen blast furnace, comprising the following steps: first, selecting a specific hydrogen-rich carbon-circulating oxygen blast furnace operation reference point, and setting the CO2 content in the circulating gas as a variable and setting a variation range; then, in the input parameters of the zoned heat and mass balance model, the CO2 content in the circulating gas is taken from the set range; then, by taking each CO2 content in the variation range, the zoned heat and mass balance model is run to obtain multiple sets of output index results; finally, according to the multiple sets of output index results, the influence law and critical point are analyzed, and targeted operation is given. The present application takes the CO2 content in the circulating gas as an input variable parameter, and reveals how this process parameter influences the terminal performance index of the blast furnace, so that the selection of the decarburization process has a basis.

Description

Technical Field

[0001] This invention relates to the field of blast furnace ironmaking technology, and specifically to a method for evaluating the impact of the degree of decarbonization of circulating gas on a hydrogen-rich carbon-circulating oxygen blast furnace. Background Technology

[0002] In the hydrogen-rich carbon-recirculating oxygen blast furnace process, the core technology involves removing carbon dioxide from the top gas before recirculation and injection. However, due to limitations in the efficiency and economy of decarbonization technology, the circulating gas often contains a certain proportion of residual CO2. This CO2, entering the tuyeres swirl zone with the high-temperature gas, participates in the carbon gasification reaction (C + CO2 → 2CO), a strongly endothermic reaction. The presence of residual CO2 is equivalent to introducing an "endothermic source" into the high-temperature zone, affecting not only the theoretical combustion temperature but also potentially altering the reducing atmosphere within the furnace, impacting fuel consumption and carbon emissions.

[0003] Currently, there is a lack of a method to quantitatively assess the impact of different residual CO2 contents on the technical indicators of the HyCROF system, making it difficult to make an optimal trade-off between investment in decarbonization equipment and the operating efficiency of the blast furnace. Summary of the Invention

[0004] The purpose of this invention is to provide a method for evaluating the impact of the degree of decarbonization of circulating gas on hydrogen-rich carbon-circulating oxygen blast furnaces, in order to solve the problem that there is currently no method to quantitatively assess the impact of different residual CO2 contents on the technical indicators of the HyCROF system, which makes it difficult to make an optimal trade-off between investment in decarbonization equipment and the operating efficiency of the blast furnace.

[0005] To achieve the above objectives, the basic solution provided by this invention is: a method for evaluating the impact of the degree of decarbonization of circulating gas on a hydrogen-rich carbon-circulating oxygen blast furnace, comprising the following steps: S1. Select a specific operating benchmark point for a hydrogen-rich carbon-circulating oxygen blast furnace, and at the same time, use the CO2 content in the circulating gas as a variable and set the range of variation. S2. In the input parameters of the zoned heat and mass balance model, the CO2 content of the circulating gas is taken from the range set in S1. S3. By taking each CO2 content within the range of variation, run the partitioned heat and mass balance model to obtain multiple sets of output index results; S4. Based on the results of multiple sets of output indicators, analyze the influencing patterns and critical points, and provide targeted actions.

[0006] The beneficial effects of this invention are as follows: By embedding the CO2 content in the circulating gas as an input variable parameter into the overall thermal-mass balance system model of the blast furnace, this invention reveals how this process parameter affects the final performance indicators of the blast furnace, providing a basis for the selection of decarbonization processes. It can predict changes in theoretical combustion temperature under different residual CO2 contents and identify the critical CO2 concentration values ​​that lead to insufficient hearth heat and increased operational risks. When the performance of the decarbonization equipment fluctuates or requires maintenance, this method can be used to assess the allowable range of CO2 content fluctuations in advance, guiding the blast furnace to make corresponding parameter compensation adjustments.

[0007] Option 2, which is a preferred option of the basic option, in S1, during the process of selecting the operating benchmark point for the hydrogen-rich carbon circulating oxygen blast furnace, the values ​​of the blast furnace's raw material conditions, smelting targets, pulverized coal injection ratio, hydrogen-rich gas injection volume, total circulating gas flow rate, and temperature remain constant. This ensures that the changes in the blast furnace operating indicators calculated subsequently are caused by fluctuations in CO2 content, eliminating interference from changes in other parameters and guaranteeing the accuracy of the evaluation results.

[0008] Option 3, which is the preferred option of the basic option, in S2, the partitioned heat and mass balance model follows the conservation of mass and energy and satisfies the basic constraints of blast furnace operation.

[0009] Option 4, which is the preferred option of Option 3, stipulates that the basic constraints for blast furnace operation are that the theoretical combustion temperature and the top gas temperature should not be lower than the safe value.

[0010] Option 5, which is a preferred option of the basic option, in S3, the output indicators include blast furnace carbon input, blast furnace energy input, tuyere theoretical combustion temperature, direct reduction degree, fuel ratio, and the quantity and composition of blast furnace belly gas and blast furnace top gas.

[0011] Option 6, which is the preferred option of the basic option, in S4, if the output indicators show that the reduction effect of carbon input is not obvious when the CO2 content is reduced from Y% to Z%, but the decarbonization energy consumption increases, then the result can be used as a reference for setting the decarbonization accuracy target. Detailed Implementation

[0012] The present invention will be further described in detail below through specific embodiments: A method for evaluating the impact of circulating gas decarbonization on a hydrogen-rich carbon-cycled oxygen blast furnace includes the following steps: S1. Select a specific operating benchmark point for the hydrogen-rich carbon-recirculating oxygen blast furnace, and at the same time, use the CO2 content in the circulating gas as a variable and set the range of variation; during the selection of the operating benchmark point, the raw material conditions, smelting objectives, pulverized coal injection ratio, hydrogen-rich gas injection volume, total circulating gas flow rate and temperature of the blast furnace are kept constant. S2. In the input parameters of the zoned heat and mass balance model, the CO2 content of the circulating gas is taken from the range set in S1. The zoned heat and mass balance model follows the conservation of mass and energy and meets the basic constraints of blast furnace operation. The basic constraints of blast furnace operation are that the theoretical combustion temperature and the top gas temperature are not lower than the safe value. The zonal heat and mass balance model is established as follows: Along the height of the blast furnace, the blast furnace is divided into a low-temperature zone and a high-temperature zone, with the 950°C heat reserve zone as the boundary. The input of the low-temperature zone is ambient temperature charge and rising 950°C gas, and the output is falling 950°C metal oxides, carbon, and rising top gas. The input of the high-temperature zone is hot blast injected into the tuyeres, pulverized coal, circulating gas, and charge from the low-temperature zone, and the output is molten iron, slag, and rising 950°C reducing gas. The mass conservation equations for each partition are as follows: Total mass conservation equation in the low-temperature region: In the formula, This refers to the total mass of the furnace charge fed into the furnace at room temperature. This refers to the total mass of the top gas entering the low-temperature zone. To reduce the total mass of the furnace charge entering the high-temperature zone at 950℃; The total mass of the top gas is expressed in kg / tHM. Total mass conservation equation in the high-temperature region: In the formula, The total mass of the material being sprayed from the air outlet; The total mass of the tuyere blower; 1000 is the standard mass of molten iron in tons; The output of slag per ton of iron ore furnace; The total mass of the top gas in the heat reserve area; all units are kg / tHM. The elemental balance equations for each partition are as follows: (1) Fe element equilibrium equation Overall Fe balance in the furnace: In the formula, This refers to the total mass of the iron-containing furnace charge entering the furnace. The total iron content of the ore fed into the furnace; The mass fraction of Fe in molten iron; The mass fraction of FeO in the slag; This represents the molar mass ratio of Fe in FeO; Fe equilibrium in the low-temperature region: In the formula, This refers to the mass fraction of Fe2O3 in the furnace charge. This represents the molar mass ratio of Fe in Fe₂O₃; (2) Balance equation for element C Overall furnace C balance: In the formula, , This refers to the consumption of coke and pulverized coal. , To fix the mass fraction of carbon in coke and pulverized coal; The mass fraction of carbon in the sprayed material; This represents the mass fraction of carbon in molten iron. This represents the mass fraction of CO2 in the top gas. The mass fraction of CO in the top gas; , These are the molar mass ratios of C in CO2 and CO, respectively. (3) Balance equation of H element In the formula, , This represents the mass fraction of hydrogen in coke and pulverized coal. The mass fraction of hydrogen in the sprayed material; The total moisture content carried in by the material entering the furnace; The molar mass ratio of hydrogen in H2O; This represents the mass fraction of H2 in the top gas. This represents the mass fraction of H2O in the top gas. (4) Balance equation of element O In the formula, The mass fraction of oxygen in the iron-containing furnace charge; The mass fraction of oxygen in the blower air; This represents the mass fraction of oxygen in pulverized coal. The mass fraction of oxygen in the slag; This represents the molar mass ratio of oxygen in H2O. This represents the mass fraction of CO2 in the top gas. The mass fraction of CO in the top gas; This represents the molar mass ratio of oxygen in CO. This represents the molar mass ratio of oxygen in CO2. The enthalpy balance equations for each region are as follows: Enthalpy balance equation in the low-temperature region In the formula, The total enthalpy of the furnace charge is input into the low-temperature zone; The total enthalpy of the gas input into the low-temperature zone; This represents the total enthalpy of the furnace charge output in the low-temperature zone. This represents the total enthalpy of the gas output from the low-temperature zone. This represents the total heat loss in the low-temperature region; Enthalpy balance equation in high temperature region In the formula, The total enthalpy of the furnace charge input to the high-temperature zone; The total enthalpy of the material being sprayed from the air outlet; The total enthalpy of the blower air / oxygen; The total physical heat of molten iron; The total physical heat of the slag; This represents the total enthalpy of the gas output from the high-temperature zone. This represents the total heat loss in the high-temperature zone; This refers to the total heat effect of chemical reactions in the high-temperature region. S3. By taking each CO2 content within the range of variation, run the partitioned heat and mass balance model to obtain multiple sets of output index results. The output indexes include blast furnace carbon input, blast furnace energy input, tuyere theoretical combustion temperature, direct reduction degree, fuel ratio, and the amount and composition of belly gas and top gas. S4. Based on the results of multiple sets of output indicators, analyze the influence patterns and critical points, and provide targeted operations; when the CO2 content is reduced from Y% to Z%, if the output indicators show that the reduction effect of carbon input is not obvious, but the decarbonization energy consumption increases, then the result can be used as a reference for setting decarbonization accuracy targets.

[0013] Assess the impact of CO2 content on hydrogen-rich carbon-cycle oxygen blast furnaces: Setting the baseline and variables: Select 2500m 3 Using a specific hydrogen-rich carbon cycle condition of the blast furnace as a benchmark, 30 Nm³ of natural gas is injected. 3 / tHM, total circulating gas volume is approximately 630 Nm 3 / tHM, temperature 1200℃, constant pulverized coal injection ratio. The CO2 content of the circulating gas is taken as 0%, 1%, 2%, 3%, and 4% within this range.

[0014] Theoretical combustion temperature: As the CO2 content increases from 0% to 4%, the theoretical combustion temperature drops significantly from 2073℃ to 1883℃. When the CO2 content reaches approximately 3%, the theoretical combustion temperature drops to 1933℃, close to the safe lower limit of 1900℃. To ensure that the theoretical combustion temperature remains above the safe line (1900℃) with sufficient margin, it is recommended to control the CO2 content in the circulating gas below 3%, ideally below 2%.

[0015] Carbon input: At 0% CO2 content, the carbon input is 334.8 kg / tHM. As the CO2 content increases to 4%, the carbon input rises slightly to 339 kg / tHM. This indicates that although more CO2 enters the furnace to participate in the endothermic gasification reaction, more CO is also generated, promoting indirect reduction and reducing the carbon consumption of direct reduction. The two partially offset each other, resulting in little change in net carbon input, or even a slight increase due to carbon consumption in the gasification reaction.

[0016] Energy Input: Calculates the total energy input including decarbonization energy consumption. Removing more CO2 will lead to an increase in decarbonization energy consumption.

[0017] Economic considerations: Reducing the CO2 content from 3% to 0% has a limited effect on reducing carbon input, decreasing it by only about 2 kg / tHM, but requires higher decarbonization energy consumption. Therefore, from a comprehensive cost perspective, setting the decarbonization target at a CO2 content of 1-2% is the more economical choice, ensuring a safe theoretical combustion temperature without excessively increasing the cost of front-end decarbonization.

[0018] The method of this invention provides an important analytical tool for the two key links of gas purification and blast furnace smelting in the HyCROF process.

[0019] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace, characterized in that, Includes the following steps: S1. Select a specific operating benchmark point for a hydrogen-rich carbon-circulating oxygen blast furnace, and at the same time, use the CO2 content in the circulating gas as a variable and set the range of variation. S2. In the input parameters of the zoned heat and mass balance model, the CO2 content of the circulating gas is taken from the range set in S1. S3. By taking each CO2 content within the range of variation, run the partitioned heat and mass balance model to obtain multiple sets of output index results; S4. Based on the results of multiple sets of output indicators, analyze the influencing patterns and critical points, and provide targeted actions.

2. The method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace according to claim 1, characterized in that, In S1, during the process of selecting the operating reference point for the hydrogen-rich carbon circulating oxygen blast furnace, the raw material conditions, smelting objectives, pulverized coal injection ratio, hydrogen-rich gas injection volume, total circulating gas flow rate, and temperature of the blast furnace remain constant.

3. The method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace according to claim 1, characterized in that, In S2, the partitioned heat and mass balance model follows the conservation of mass and energy and satisfies the basic constraints of blast furnace operation.

4. The method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace according to claim 3, characterized in that, The basic constraints for blast furnace operation are that the theoretical combustion temperature and the top gas temperature must not be lower than the safe value.

5. The method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace according to claim 1, characterized in that, In S3, the output indicators include blast furnace carbon input, blast furnace energy input, tuyere theoretical combustion temperature, direct reduction degree, fuel ratio, and the quantity and composition of blast furnace belly gas and blast furnace top gas.

6. The method for evaluating the impact of circulating gas decarbonization degree on a hydrogen-rich carbon-circulating oxygen blast furnace according to claim 1, characterized in that, In S4, if the output indicators show that the reduction in carbon input is not significant when the CO2 content is reduced from Y% to Z%, while the decarbonization energy consumption increases, then this result can be used as a reference for setting decarbonization accuracy targets.

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