Method and device for controlling nitrogen content of oxygen blast furnace

Abstract

The invention provides a method and a device for controlling the nitrogen content of an oxygen blast furnace. The method comprises the following steps: acquiring initial furnace top gas quantity and components as furnace entering parameters; and calculating the quantity and components of the furnace top gas by utilizing a pre-constructed furnace top gas circulation-oxygen blast furnace model and constraint conditions. If the result is not balanced, key parameters are calculated, and the model parameters are adjusted under the condition that the key parameters do not meet the reference working condition. And through iterative calculation, furnace entering parameters are updated until the gas amount and the components meet balance conditions or the nitrogen content reaches a threshold value. And determining an exhaust period according to the single-cycle smelting time and the cycle index, and executing external exhaust top gas operation according to the exhaust period. According to the scheme, the nitrogen aggregation rule in the oxygen blast furnace is obtained by utilizing the furnace top gas circulation-oxygen blast furnace model, and the time when the nitrogen is aggregated to the maximum value or the content threshold value is used as the exhaust period in combination with the nitrogen aggregation rule, the single-cycle smelting time and the cycle index, so that the purpose of controlling the nitrogen content in the oxygen blast furnace is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of blast furnace ironmaking, and in particular to a method and device for controlling nitrogen content in an oxygen blast furnace. Background Art

[0002] The top gas circulation-oxygen blast furnace process is an innovation of the traditional oxygen blast furnace process. The top gas is decarbonized and dusted before being pumped into the blast furnace hearth and body, solving the problem of "cold on top and hot on bottom" in oxygen blast furnaces. Among them, the top gas circulation process is the key to this process.

[0003] Although the largest nitrogen source of the top gas circulation-oxygen blast furnace system: blast, has been replaced by pure oxygen at room temperature, there is still a certain amount of nitrogen in the volatile matter of the raw fuel, the coal injection carrier gas, the hydrogen-rich gas, and the purge gas of the gas heating furnace pipeline. As the cycle proceeds, the nitrogen will accumulate in the furnace until the newly introduced nitrogen is equal to the amount of nitrogen leaving the system in the gas heating furnace combustion exhaust gas, and then the nitrogen in the furnace will stop accumulating. The accumulation of nitrogen will cause the calorific value of the circulating gas to decrease, the reduction ability to decrease, inhibit the indirect reduction of iron ore, increase fuel costs, and affect smelting efficiency. The high construction cost, operation cost and maintenance cost of the nitrogen adsorption device will undoubtedly increase the burden on the enterprise.

[0004] In summary, how to control the nitrogen content in the oxygen blast furnace is an issue that needs to be solved urgently. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides a method and device for controlling the nitrogen content in an oxygen blast furnace, so as to achieve the purpose of controlling the nitrogen content in the oxygen blast furnace.

[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] A first aspect of an embodiment of the present invention discloses a method for controlling nitrogen content in an oxygen blast furnace, the method comprising:

[0008] Obtaining an initial top gas volume and an initial top gas composition of a top gas circulation-oxygen blast furnace, and using the initial top gas volume and the initial top gas composition as furnace entry parameters;

[0009] Based on the furnace entry parameters, the pre-built top gas circulation-oxygen blast furnace model and the preset constraints, the top gas volume and the top gas composition are calculated;

[0010] If the amount of the furnace top gas and the composition of the furnace top gas do not satisfy the equilibrium condition, calculating key parameters based on the amount of the furnace top gas and the composition of the furnace top gas;

[0011] If the key parameters do not meet the preset benchmark operating conditions, adjusting the model parameters in the top gas circulation-oxygen blast furnace model;

[0012] Convert the furnace top gas volume and the furnace top gas composition to obtain new furnace entry parameters, return to execute the step of calculating the furnace top gas volume and the furnace top gas composition based on the furnace entry data, the pre-built furnace top gas cycle-oxygen blast furnace model and the preset constraint conditions, and record the number of cycles;

[0013] When the amount of top gas and the composition of top gas meet the balance condition, or the nitrogen content in the composition of top gas reaches the content threshold, an exhaust cycle is obtained based on the number of cycles and the single cycle smelting time of the top gas cycle-oxygen blast furnace;

[0014] Based on the exhaust cycle, the top gas circulation-oxygen blast furnace is operated to exhaust top gas externally.

[0015] Preferably, the construction process of the top gas circulation-oxygen blast furnace model includes:

[0016] Based on the material flow properties and energy flow properties inside the oxygen blast furnace in the top gas circulation-oxygen blast furnace, a multi-region energy and quality balance model of the oxygen blast furnace is constructed;

[0017] Based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace, a thermal efficiency model of the gas heating furnace is constructed;

[0018] The multi-region energy and quality balance model of the oxygen blast furnace is coupled with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model;

[0019] Obtain initial data for top gas circulation-oxygen blast furnace;

[0020] The top gas circulation-oxygen blast furnace model is set based on the initial data to obtain the constructed top gas circulation-oxygen blast furnace model.

[0021] Preferably, the key parameters calculated based on the furnace top gas volume and the furnace top gas composition include:

[0022] Calculating the hydrogen utilization rate based on the furnace top gas volume, the furnace top gas composition and the hydrogen utilization rate empirical formula;

[0023] Calculating a theoretical combustion temperature based on the furnace top gas volume, the furnace top gas composition and a theoretical combustion temperature formula;

[0024] Calculating fuel gas consumption for heating each cubic meter of top gas based on the amount of top gas and the composition of top gas;

[0025] The hydrogen utilization rate, the theoretical combustion temperature and the fuel gas consumption are taken as key parameters.

[0026] Preferably, the exhaust cycle is obtained based on the number of cycles and the top gas cycle-oxygen blast furnace single cycle smelting time, including:

[0027] The exhaust cycle is obtained by multiplying the number of cycles by the top gas cycle-single cycle smelting time of the oxygen blast furnace.

[0028] Preferably, after the calculation to obtain the amount of top gas and the composition of top gas, the method further comprises:

[0029] If the top gas amount is consistent with the top gas amount obtained in the previous cycle, and the nitrogen content in the top gas composition is consistent with the nitrogen content in the top gas composition obtained in the previous cycle, it is determined that the top gas amount and the top gas composition meet the equilibrium condition.

[0030] A second aspect of an embodiment of the present invention discloses a device for controlling nitrogen content in an oxygen blast furnace, the device comprising:

[0031] An acquisition unit, used for acquiring an initial top gas volume and an initial top gas composition of a top gas circulation-oxygen blast furnace, and using the initial top gas volume and the initial top gas composition as furnace entry parameters;

[0032] A first calculation unit is used to calculate the amount of top gas and the composition of top gas based on the furnace entry parameters, a pre-built top gas circulation-oxygen blast furnace model and preset constraints;

[0033] A second calculation unit is used for calculating key parameters based on the amount of top gas and the composition of top gas if the amount of top gas and the composition of top gas do not meet the balance condition;

[0034] An adjustment unit, configured to adjust the model parameters in the top gas circulation-oxygen blast furnace model if the key parameters do not meet the preset reference operating conditions;

[0035] a circulation unit, for converting the amount of top gas and the composition of top gas to obtain new furnace entry parameters, returning to execute the step of calculating the amount of top gas and the composition of top gas based on the furnace entry data, the pre-built top gas circulation-oxygen blast furnace model and the preset constraint conditions, and recording the number of cycles;

[0036] A third calculation unit is used for obtaining an exhaust cycle based on the number of cycles and the top gas cycle-oxygen blast furnace single cycle smelting time when the top gas amount and the top gas composition meet the balance condition or the nitrogen content in the top gas composition reaches a content threshold;

[0037] An exhaust unit is used for performing top gas exhaust operation on the top gas circulation-oxygen blast furnace based on the exhaust cycle.

[0038] Preferably, the device further comprises:

[0039] A construction unit is used to construct a multi-region energy and quality balance model of an oxygen blast furnace based on the material flow properties and energy flow properties inside the blast furnace in the top gas circulation-oxygen blast furnace; construct a thermal efficiency model of the gas heating furnace based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace; couple the multi-region energy and quality balance model of the oxygen blast furnace with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model; obtain initial data of the top gas circulation-oxygen blast furnace; set the top gas circulation-oxygen blast furnace model based on the initial data to obtain the constructed top gas circulation-oxygen blast furnace model.

[0040] Preferably, the second calculation unit for calculating the key parameters based on the furnace top gas amount and the furnace top gas composition is specifically used for:

[0041] Calculating the hydrogen utilization rate based on the furnace top gas volume, the furnace top gas composition and the hydrogen utilization rate empirical formula;

[0042] Calculating a theoretical combustion temperature based on the furnace top gas volume, the furnace top gas composition and a theoretical combustion temperature formula;

[0043] Calculating fuel gas consumption for heating each cubic meter of top gas based on the amount of top gas and the composition of top gas;

[0044] The hydrogen utilization rate, the theoretical combustion temperature and the fuel gas consumption are taken as key parameters.

[0045] Preferably, the third calculation unit for obtaining the exhaust cycle based on the number of cycles and the top gas cycle-single cycle smelting time of the oxygen blast furnace is specifically used for:

[0046] The exhaust cycle is obtained by multiplying the number of cycles by the top gas cycle-single cycle smelting time of the oxygen blast furnace.

[0047] Preferably, the device further comprises:

[0048] A judgment unit is used to determine that the top gas amount and the top gas composition meet a balance condition if the top gas amount is consistent with the top gas amount obtained in the previous cycle, and the nitrogen content in the top gas composition is consistent with the nitrogen content in the top gas composition obtained in the previous cycle.

[0049] Based on the above-mentioned embodiment of the present invention, a method and device for controlling nitrogen content in an oxygen blast furnace are provided, wherein the initial top gas volume and initial top gas composition of the top gas circulation-oxygen blast furnace are obtained, and the initial top gas volume and the initial top gas composition are used as furnace entry parameters; based on the furnace entry parameters, a pre-constructed top gas circulation-oxygen blast furnace model and preset constraints, the top gas volume and the top gas composition are calculated; if the top gas volume and the top gas composition do not meet the equilibrium condition, the key parameters are calculated based on the top gas volume and the top gas composition; if the key parameters do not meet the preset benchmark operating conditions, the top gas circulation-oxygen blast furnace is adjusted. The model parameters in the furnace model; the top gas volume and the top gas composition are converted to obtain new furnace entry parameters, and the step of calculating the top gas volume and the top gas composition based on the furnace entry data, the pre-built top gas circulation-oxygen blast furnace model and the preset constraints and recording the number of cycles is returned; when the top gas volume and the top gas composition meet the balance condition, or the nitrogen content in the top gas composition reaches the content threshold, the exhaust cycle is obtained based on the number of cycles and the single cycle smelting time of the top gas circulation-oxygen blast furnace; based on the exhaust cycle, the top gas circulation-oxygen blast furnace is operated to discharge the top gas. In this scheme, the top gas circulation-oxygen blast furnace model is used to obtain the nitrogen accumulation law in the oxygen blast furnace, and the nitrogen accumulation time, the single cycle smelting time and the number of cycles of the oxygen blast furnace are combined. The time when the nitrogen accumulates to the maximum value or the content threshold is used as the exhaust cycle, and the top gas is discharged based on the exhaust cycle to achieve the purpose of controlling the nitrogen content in the oxygen blast furnace. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0051] Figure 1 It is a schematic diagram of the operation of a top gas circulation-oxygen blast furnace disclosed in an embodiment of the present invention;

[0052] Figure 2A flow chart of a method for controlling nitrogen content in an oxygen blast furnace disclosed in an embodiment of the present invention;

[0053] Figure 3 A logic diagram of a theoretical calculation method for nitrogen content control disclosed in an embodiment of the present invention;

[0054] Figure 4 A schematic diagram of changes in the amount of furnace top gas and the nitrogen content of furnace top gas with the number of cycles disclosed in an embodiment of the present invention;

[0055] Figure 5 This is a structural diagram of a device for controlling nitrogen content in an oxygen blast furnace disclosed in an embodiment of the present invention. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] In this application, the terms "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0058] First, the technical terms appearing in this application are explained as follows:

[0059] Oxygen blast furnace: a smelting blast furnace that uses pure oxygen blast.

[0060] Regenerative gas heating furnace: a gas heating method that uses fuel combustion to heat a regenerative body. After the regenerative body stores a certain amount of heat, it is heated to a specified temperature, and the combustion state is changed to a blast state. The gas to be heated is introduced, and the heat stored in the regenerative body is used to heat the gas to the required temperature before being sent to the blast furnace. Generally, 3 or 4 regenerative heating furnaces are used in a cycle.

[0061] Top gas circulation: a method of utilizing the carbon monoxide in the top gas of a blast furnace. The top gas is purified, pressurized, and freed of carbon dioxide and water, and then heated and injected into the blast furnace again, thereby fully utilizing the carbon monoxide in the gas.

[0062] As can be seen from the background technology, although the largest nitrogen source of the top gas circulation-oxygen blast furnace system: blast, has been replaced by pure oxygen at room temperature, there is still a certain amount of nitrogen in the volatile matter of the raw fuel, the coal injection carrier gas, the hydrogen-rich gas, and the purge gas of the gas heating furnace pipeline. As the circulation proceeds, the nitrogen will accumulate in the furnace until the newly introduced nitrogen is equal to the amount of nitrogen leaving the system in the gas heating furnace combustion exhaust gas, and the nitrogen in the furnace will stop accumulating. The accumulation of nitrogen will cause the calorific value of the circulating gas to decrease, the reducing ability to decrease, inhibit the indirect reduction of iron ore, increase fuel costs, and affect smelting efficiency. The construction cost, operation cost and maintenance cost of the nitrogen adsorption device are high, which will undoubtedly increase the burden on the enterprise.

[0063] Therefore, an embodiment of the present invention discloses a method and device for controlling the nitrogen content in an oxygen blast furnace. In this scheme, a top gas circulation-oxygen blast furnace model is used to obtain the nitrogen accumulation law in the oxygen blast furnace. Combined with the nitrogen accumulation law, the single-cycle smelting time and the number of cycles of the oxygen blast furnace, the time when the nitrogen accumulates to the maximum value or the content threshold is used as the exhaust cycle, and the top gas exhaust operation is performed based on the exhaust cycle to achieve the purpose of controlling the nitrogen content in the oxygen blast furnace.

[0064] First, in order to illustrate the applicable scenarios of the embodiments of the present invention, Figure 1 As shown, it is a schematic diagram of the operation of a top gas circulation-oxygen blast furnace disclosed in an embodiment of the present invention.

[0065] The working principle of the top gas circulation-oxygen blast furnace circulation operation process is as follows:

[0066] 1. Use oxygen blast furnace technology to eliminate the circulation of N2 in the blast furnace;

[0067] 2. Combined with the coal gas CO2 removal process, the CO2 in the blast furnace top gas is separated. The generated high-reducing top gas is heated in the heating furnace and then sprayed back into the blast furnace to achieve full utilization of carbon chemical energy.

[0068] 3. While recycling coal gas, use hydrogen-rich coal gas (natural gas or H2 or coke oven gas, etc.) as a supplementary energy source to further reduce the consumption of solid carbon in the blast furnace process, thereby achieving carbon reduction.

[0069] The operation process of top gas circulation-oxygen blast furnace circulation is as follows:

[0070] Charging: Sintered ore and pelletized ore are used as raw materials and added into the blast furnace through the charging system.

[0071] Blast furnace ironmaking: Inside the blast furnace, the raw materials are mixed with oxygen-rich air (or total oxygen) blown in from the tuyere, and a reduction reaction occurs to produce molten iron and slag.

[0072] Oxygen production: High-purity oxygen is produced through an oxygen generator to improve the oxidizability of the tuyere and the reaction efficiency in the furnace.

[0073] Tuyere Injection: Pulverized coal is injected into the blast furnace through the tuyere as additional fuel and reducing agent to reduce the coke ratio and increase the furnace temperature.

[0074] Top gas treatment: The gas generated at the top of the blast furnace is subjected to gravity dust removal to remove large particles of dust.

[0075] Gas purification: The gas after preliminary dust removal enters the gas purification system to further remove fine particles to obtain clean blast furnace gas.

[0076] Gas washing and pressurization: The purified gas enters the gas washing tower to remove moisture and impurities in the gas, and then increases the pressure through the gas compressor and enters the decarbonization device.

[0077] Decarbonization: The coal gas passes through the decarbonization device to remove carbon dioxide and produce decarbonized coal gas.

[0078] Injection valve station: After the hydrogen-rich gas is mixed with the decarbonized gas, it is sprayed into a top-fired gas heating furnace for heating, and then sent into the blast furnace to improve the utilization rate of hydrogen in the furnace and reduce the nitrogen content.

[0079] Combustion-supporting air and chimney: Top-fired gas heating furnaces require combustion-supporting air. Part of the blast furnace gas can be used to support combustion in the heating furnace, and the chimney is used to discharge exhaust gas.

[0080] Taphole: The molten iron produced in the blast furnace is discharged regularly through the taphole.

[0081] Based on the process flow of a top gas circulation-oxygen blast furnace disclosed in the above embodiment of the present invention, Figure 2 FIG. 1 is a flow chart of a method for controlling nitrogen content in an oxygen blast furnace disclosed in an embodiment of the present invention, comprising the following steps:

[0082] Step S201: obtaining the initial top gas volume and initial top gas composition of the top gas circulation-oxygen blast furnace, and using the initial top gas volume and initial top gas composition as furnace entry parameters.

[0083] It should be noted that the changes in the top gas composition and the top gas volume are continuous. The instantaneous value at a certain moment is used as the furnace entry parameter to calculate the new top gas volume and top gas composition, and the calculation is iterated until the top gas volume and the top gas composition are stable within a certain range. It is considered that the top gas circulation-oxygen blast furnace has reached a balance, or the nitrogen content in the furnace does not meet the process requirements, and the top gas discharge operation is performed.

[0084] In one embodiment, in order to calculate the time from the beginning of accumulation of nitrogen content in the oxygen blast furnace to the saturation state, this time is used as the exhaust cycle, and no subsequent iteration is required, and only the top gas exhaust operation needs to be performed according to the exhaust cycle. In this case, the top gas composition and the top gas volume when the nitrogen content in the oxygen blast furnace has not yet begun to accumulate, or when the top gas exhaust operation has just been completed, are selected as the initial top gas volume and the initial top gas composition, so as to calculate the accurate exhaust cycle.

[0085] Step S202: Based on the furnace entry parameters, the pre-built top gas circulation-oxygen blast furnace model and the preset constraints, the top gas volume and top gas composition are calculated.

[0086] like Figure 3 As shown in the figure, it is a logic diagram of a theoretical calculation method for nitrogen content control disclosed in an embodiment of the present invention, from Figure 3 The construction process of the top gas circulation-oxygen blast furnace model can be seen in the figure.

[0087] Among them, the top gas circulation-oxygen blast furnace model is a mathematical model coupled by two mathematical models. The specific construction process is as follows:

[0088] Step S301: construct a multi-region energy and quality balance model of an oxygen blast furnace based on the material flow properties and energy flow properties inside the blast furnace in the top gas circulation-oxygen blast furnace.

[0089] It should be noted that the multi-zone energy and mass balance model of the oxygen blast furnace includes: material balance calculation block, whole furnace heat balance calculation block, tuyere vortex zone treatment theoretical combustion temperature calculation block, upper low temperature zone heat balance block and lower high temperature zone heat balance block. Among them, the whole furnace heat balance calculation block adopts the first total heat balance, and the tuyere vortex zone treatment theoretical combustion temperature calculation block adds the heat brought in by the circulating coal gas.

[0090] Step S302: construct a thermal efficiency model of the gas heating furnace based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace.

[0091] It should be noted that the thermal efficiency model of the gas heating furnace includes: the material balance section and the thermal efficiency section of the gas heating furnace. Figure 1 It can be seen that compared with the traditional hot blast stove, the heating medium is changed to oxygen blast furnace top gas with higher calorific value, and the heated medium is changed from air to decarbonized coal gas.

[0092] Step S303: coupling the multi-region energy and quality balance model of the oxygen blast furnace with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model.

[0093] Step S304: Acquire initial data of top gas circulation-oxygen blast furnace.

[0094] It should be noted that the initial data include: raw material data, blast parameters, preset molten iron composition, mixed ore ratio, oxygen enrichment rate, gas heating furnace air supply cycle, etc., all of which are provided by the ironmaking plant or design institute.

[0095] Exemplarily, some initial data are shown in Tables 1 to 5:

[0096] Table 1: Raw material composition / %

[0097]

[0098] Table 2: Fuel composition / %

[0099]

[0100] Table 3: Preset molten iron composition / %

[0101]

[0102] Table 4: Blast furnace injection parameters

[0103]

[0104] Table 5: Initial circulating gas composition / %

[0105]

[0106] Step S305: setting a top gas circulation-oxygen blast furnace model based on the initial data to obtain a constructed top gas circulation-oxygen blast furnace model.

[0107] In step S202, the amount of top gas and the composition of top gas, namely Figure 3 The corresponding flow rate and composition of the top gas are shown.

[0108] Among them, the constraints include: material balance relative error, heat loss, theoretical combustion temperature and other benchmark parameters. Constraints are artificially set by process designers based on comprehensive considerations based on experience and preset algorithms.

[0109] For example, in order to ensure the accuracy of the calculation results of the multi-region energy and mass balance model of the oxygen blast furnace, the relative error of the material balance must be less than 0.1%. To ensure sufficient heat in the furnace, the heat loss of the whole furnace must be higher than 4×105kJ / tHM, the regional heat loss must be greater than 0, and the thermal efficiency of the gas heating furnace is anchored at 80%, with an error of less than 0.1%. At this time, the relative error of the material balance is 0.074%, the heat loss of the whole furnace is 549511kJ / t (5.69%), the regional heat loss is greater than 0, and the thermal efficiency of the gas heating furnace is 79.95%.

[0110] It should be noted that by converting the furnace top gas volume and furnace top gas composition, we can get Figure 3 The gas volume and composition of the circulating gas are taken as new parameters for entering the furnace, and the process returns to step S202. For details, please refer to the following embodiments of the present invention.

[0111] Step S203: If the amount of top gas and the composition of top gas do not meet the balance condition, key parameters are calculated based on the amount of top gas and the composition of top gas.

[0112] It should be noted that when the furnace top gas volume and furnace top gas composition remain constant, or change slightly within a range, it is determined that the furnace top gas volume and furnace top gas composition meet the equilibrium condition, otherwise it is determined that they do not meet the equilibrium condition. Specifically, they can be compared with the furnace top gas volume and furnace top gas composition calculated in the previous cycle, as follows:

[0113] If the top gas amount is consistent with the top gas amount obtained in the previous cycle, and the nitrogen content in the top gas composition is consistent with the nitrogen content in the top gas composition obtained in the previous cycle, it is determined that the top gas amount and the top gas composition meet the equilibrium condition.

[0114] In step S203, based on the furnace top gas volume and furnace top gas composition, the process of calculating key parameters is as follows:

[0115] The hydrogen utilization rate is calculated based on the furnace top gas volume, furnace top gas composition and the empirical formula of hydrogen utilization rate.

[0116] The empirical formula for hydrogen utilization is:

[0117]

[0118] is the hydrogen utilization rate; is the carbon monoxide utilization rate.

[0119] It is understandable that the carbon monoxide utilization rate can be calculated using the furnace top gas volume and furnace top gas composition, and the hydrogen utilization rate can be calculated using an empirical formula.

[0120] The theoretical combustion temperature is calculated based on the furnace top gas volume, furnace top gas composition and theoretical combustion temperature formula.

[0121] Among them, the theoretical combustion temperature formula is:

[0122]

[0123] is the theoretical combustion temperature, in °C; is the heat release of coke combustion at the tuyere, in kJ / tHM; is the heat released by the combustion of the injected fuel, in kJ / tHM; is the sensible heat brought in by coke, in kJ / tHM; is the sensible heat brought into the hydrogen-rich gas, in kJ / tHM; The sensible heat brought into the circulating gas, unit is kJ / tHM; It is the heat consumed by the reaction between fuel and water in blast air, in kJ / tHM; The heat of decomposition and volatilization of pulverized coal, in kJ / tHM; is the heat consumption of methane decomposition in hydrogen-rich gas, in kJ / tHM; is the slag forming heat, in kJ / tHM; is the average heat capacity of gas in the tuyere vortex zone, in kJ / (℃·m 3 ); is the gas volume in the tuyere vortex zone, in m 3 / tHM; is the average heat capacity of the ash content of fuel i, where i is coke or coal powder, and the unit is kJ / (℃·kg); is the ash content of fuel i, in kg / tHM; is the average heat capacity of unburned coal powder, in kJ / (℃·kg); It is the amount of unburned coal powder, and its unit is kJ / tHM.

[0124] Based on the top gas volume and top gas composition, the fuel gas consumption for heating each cubic meter of top gas is calculated, and finally the hydrogen utilization rate, theoretical combustion temperature and fuel gas consumption are taken as key parameters.

[0125] Step S204: If the key parameters do not meet the preset reference operating conditions, the model parameters in the top gas circulation-oxygen blast furnace model are adjusted.

[0126] In step S204, the reference operating condition is composed of parameters such as hydrogen utilization rate, theoretical combustion temperature, gas heating furnace B value, etc. determined by adjustment and value optimization method.

[0127] The hydrogen utilization rate, theoretical combustion temperature and B value of the gas heating furnace can be determined by adjustment and optimization.

[0128] The process of determining the hydrogen utilization rate is as follows:

[0129] 1. Assume an initial hydrogen utilization rate: First, you need to set an initial hydrogen utilization rate value. This is an estimate, usually based on experience or previous data.

[0130] 2. Obtain the relative proportions of H2 and H2O in the furnace top gas: Through the initial hydrogen utilization rate value, the relative concentrations of hydrogen and water vapor in the gas can be obtained, and the furnace top gas composition can be further estimated based on the relative concentrations.

[0131] 3. Use the empirical formula to calculate the theoretical hydrogen utilization rate.

[0132] It should be noted that the empirical formula and calculation method of hydrogen utilization rate have been described in detail in the explanation corresponding to step S203, and can be referenced to each other.

[0133] 4. Iteratively adjust the initial hydrogen utilization rate: By continuously adjusting the assumed initial hydrogen utilization rate, recalculating the ratio of hydrogen and water vapor in the furnace top gas, and the theoretical hydrogen utilization rate, until the initial assumed hydrogen utilization rate and the theoretical hydrogen utilization rate are equal, the hydrogen utilization rate in the benchmark operating conditions is obtained.

[0134] The calculation of theoretical combustion temperature is similar to that of hydrogen utilization rate. It also requires a preset temperature, and then the preset temperature is used to calculate the theoretical combustion temperature. The preset temperature is continuously iterated to make the two temperatures equal. At this time, the preset temperature is the theoretical combustion temperature.

[0135] The B value of a gas-fired furnace is related to the fuel gas (i.e., the top gas used for heating part of the furnace) and the amount of top gas. It is defined as the amount of gas required to heat 1 m 3 The amount of fuel gas consumed by top gas.

[0136] Exemplarily, the hydrogen utilization rate is 0.4186, the theoretical combustion temperature is 2102°C, and the gas heating furnace B value is 0.2795.

[0137] In step S204, the model parameters, i.e., the maximum range control input boundary conditions, are mainly adjusted with the coke ratio, so that the key parameters obtained based on the furnace top gas volume and furnace top gas composition meet the benchmark operating conditions.

[0138] Step S205: convert the furnace top gas volume and furnace top gas composition to obtain new furnace entry parameters, return to execute step S202, and record the number of cycles.

[0139] In step S205, the purpose of the conversion is to obtain the value of the furnace top gas after passing through Figure 1 The top gas volume and top gas composition after the cycle process are shown.

[0140] It is understandable that in Figure 1 During the top gas circulation process shown, the amount of top gas re-input into the oxygen blast furnace and the top gas composition will inevitably change. The specific amount of change is related to the actual process flow, so the specific conversion process needs to be formulated based on the actual process flow.

[0141] The number of cycles refers to the number of times the execution of step S202 is returned, which also reflects the number of times the top gas is circulated in the top gas circulation-oxygen blast furnace.

[0142] Step S206: When the top gas volume and the top gas composition meet the balance condition, or the nitrogen content in the top gas composition reaches the content threshold, the exhaust cycle is obtained based on the number of cycles and the top gas cycle-oxygen blast furnace single cycle smelting time.

[0143] The purpose of setting the content threshold is to enable the critical value of nitrogen accumulation to be adjusted independently, so as to control the top gas circulation-oxygen blast furnace top gas discharge cycle.

[0144] In the specific implementation process of step S206, the number of cycles is multiplied by the top gas cycle-single cycle smelting time of the oxygen blast furnace to obtain the exhaust cycle.

[0145] It should be noted that the single-cycle smelting time includes the circulating coal gas in actual production, which is blown into the tuyere and discharged from the furnace top, and then dehydrated, decarbonized and heated until it is sprayed back into the tuyere. The main restrictive link in this process is the heating period of the gas heating furnace. Therefore, the length of the heating period can be used as the single-cycle smelting time.

[0146] like Figure 4 , which is a schematic diagram of the change of furnace top gas volume and furnace top gas nitrogen content with the number of cycles disclosed in an embodiment of the present invention.

[0147] Among them, circulating gas refers to the top gas, and the circulating gas injection volume refers to the top gas volume.

[0148] from Figure 4 It can be seen that as the number of cycles increases, the increase in the amount of circulating gas slows down, and the nitrogen in the circulating gas continues to be enriched. Until the end of the 29th cycle, the amount of circulating gas injection and the proportion of nitrogen in the circulating gas remain constant, indicating that the cycle has reached equilibrium at this time, the composition and volume of the circulating gas no longer change, and the nitrogen is enriched to 10.45% at most. If the nitrogen exhaust operation is not performed, the top gas circulation-oxygen blast furnace will continue to operate in this way.

[0149] The exhaust cycle is calculated based on the number of cycles being 29, and the heating period is calculated as 1.3 hours, which means that the top exhaust operation needs to be performed every 37.1 hours.

[0150] If the critical value (i.e., content threshold) of nitrogen in the circulating gas is set at 5%, it means that part of the top gas must be discharged after a maximum of 5 cycles. If the heating period is 1.3 hours, the nitrogen content in the circulating gas reaches the critical value after every 6.5 hours, and the top gas discharge operation must be performed.

[0151] Step S207: Based on the exhaust cycle, the top gas circulation-oxygen blast furnace is operated to exhaust the top gas.

[0152] In step S207, the external top gas operation refers to that an external gas pipeline that directly enters the factory network is provided on the blast furnace top gas pipeline, and a valve is provided on the pipeline. The valve is controlled by interlocking with the pressure P fluctuation value on the furnace top gas pipeline. At the same time, the pipeline flow is calculated and interlocked with the flow value and the external discharge cycle design.

[0153] Based on the above-mentioned method for controlling the nitrogen content in an oxygen blast furnace disclosed in an embodiment of the present invention, in this scheme, a top gas circulation-oxygen blast furnace model is used to obtain the nitrogen accumulation law in the oxygen blast furnace, and the nitrogen accumulation law, the single-cycle smelting time and the number of cycles of the oxygen blast furnace are combined, and the time when the nitrogen accumulates to the maximum value or the content threshold is used as the exhaust cycle, and the top gas discharge operation is performed based on the exhaust cycle to achieve the purpose of controlling the nitrogen content in the oxygen blast furnace, thereby alleviating the problem that N2 in the top gas is difficult to remove or the removal cost is too high, providing important technical support for the top gas circulation-oxygen blast furnace process, and avoiding the reduction of smelting efficiency due to the decrease of the reduction potential of the top gas.

[0154] Corresponding to the method for controlling nitrogen content in an oxygen blast furnace disclosed in the above embodiment of the present invention, as Figure 5 As shown, it is a structural diagram of a control device for nitrogen content in an oxygen blast furnace disclosed in an embodiment of the present invention, including: an acquisition unit 501, a first calculation unit 502, a second calculation unit 503, an adjustment unit 504, a circulation unit 505, a third calculation unit 506 and an exhaust unit 507.

[0155] The acquisition unit 501 is used to acquire the initial top gas volume and initial top gas composition of the top gas circulation-oxygen blast furnace, and use the initial top gas volume and initial top gas composition as furnace entry parameters.

[0156] The first calculation unit 502 is used to calculate the amount of top gas and the composition of top gas based on the furnace entry parameters, the pre-built top gas circulation-oxygen blast furnace model and the preset constraints.

[0157] In one embodiment, the device further comprises:

[0158] A construction unit is used to construct a multi-region energy and quality balance model of an oxygen blast furnace based on the material flow properties and energy flow properties inside the blast furnace in the top gas circulation-oxygen blast furnace; to construct a thermal efficiency model of the gas heating furnace based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace; to couple the multi-region energy and quality balance model of the oxygen blast furnace with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model; to obtain initial data of the top gas circulation-oxygen blast furnace; to set the top gas circulation-oxygen blast furnace model based on the initial data to obtain a constructed top gas circulation-oxygen blast furnace model.

[0159] In one embodiment, the device further comprises:

[0160] The judgment unit is used to determine that the furnace top gas amount and the furnace top gas composition meet the balance condition if the furnace top gas amount is consistent with the furnace top gas amount obtained in the previous cycle and the nitrogen content in the furnace top gas composition is consistent with the nitrogen content in the furnace top gas composition obtained in the previous cycle.

[0161] The second calculation unit 503 is used to calculate key parameters based on the top gas volume and the top gas composition if the top gas volume and the top gas composition do not meet the balance condition.

[0162] In one embodiment, the second calculation unit 503 for calculating the key parameters based on the furnace top gas volume and furnace top gas composition is specifically used for:

[0163] The hydrogen utilization rate is calculated based on the top gas volume, top gas composition and the empirical formula of hydrogen utilization rate; the theoretical combustion temperature is calculated based on the top gas volume, top gas composition and the theoretical combustion temperature formula; the fuel gas consumption for heating each cubic meter of top gas is calculated based on the top gas volume and top gas composition; the hydrogen utilization rate, theoretical combustion temperature and fuel gas consumption are taken as key parameters.

[0164] The adjustment unit 504 is used to adjust the model parameters in the top gas circulation-oxygen blast furnace model if the key parameters do not meet the preset reference conditions.

[0165] The circulation unit 505 is used to convert the furnace top gas volume and the furnace top gas composition to obtain new furnace entry parameters, return to execute the step of calculating the furnace top gas volume and the furnace top gas composition based on the furnace entry data, the pre-built furnace top gas circulation-oxygen blast furnace model and the preset constraints, and record the number of cycles.

[0166] The third calculation unit 506 is used to obtain the exhaust cycle based on the number of cycles and the top gas cycle-single cycle smelting time of the oxygen blast furnace when the top gas volume and the top gas composition meet the balance condition, or the nitrogen content in the top gas composition reaches the content threshold.

[0167] In one embodiment, the third calculation unit 506 for obtaining the exhaust cycle based on the number of cycles and the top gas cycle-single cycle smelting time of the oxygen blast furnace is specifically used to:

[0168] The exhaust cycle is obtained by multiplying the number of cycles by the top gas cycle - the single cycle smelting time of the oxygen blast furnace.

[0169] The exhaust unit 507 is used to perform top gas exhaust operation on the top gas circulation-oxygen blast furnace based on the exhaust cycle.

[0170] Based on the above-mentioned embodiment of the present invention, a control device for the nitrogen content in an oxygen blast furnace is disclosed. In this scheme, a top gas circulation-oxygen blast furnace model is used to obtain the nitrogen accumulation law in the oxygen blast furnace. Combined with the nitrogen accumulation law, the single-cycle smelting time and the number of cycles of the oxygen blast furnace, the time when the nitrogen accumulates to the maximum value or the content threshold is used as the exhaust cycle, and the top gas discharge operation is performed based on the exhaust cycle to achieve the purpose of controlling the nitrogen content in the oxygen blast furnace, thereby alleviating the problem that N2 in the top gas is difficult to remove or the removal cost is too high, providing important technical support for the top gas circulation-oxygen blast furnace process, and avoiding the reduction of smelting efficiency due to the decrease of the reduction potential of the top gas.

[0171] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can refer to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can refer to the partial description of the method embodiment. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0172] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0173] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for controlling nitrogen content in an oxygen blast furnace, characterized in that: The method comprises: Obtaining an initial top gas volume and an initial top gas composition of a top gas circulation-oxygen blast furnace, and using the initial top gas volume and the initial top gas composition as furnace entry parameters; Based on the furnace entry parameters, the pre-built top gas circulation-oxygen blast furnace model and the preset constraints, the top gas volume and the top gas composition are calculated; If the amount of the furnace top gas and the composition of the furnace top gas do not satisfy the equilibrium condition, calculating key parameters based on the amount of the furnace top gas and the composition of the furnace top gas; If the key parameters do not meet the preset benchmark operating conditions, adjusting the model parameters in the top gas circulation-oxygen blast furnace model; Convert the furnace top gas volume and the furnace top gas composition to obtain new furnace entry parameters, return to execute the step of calculating the furnace top gas volume and the furnace top gas composition based on the furnace entry data, the pre-built furnace top gas cycle-oxygen blast furnace model and the preset constraint conditions, and record the number of cycles; When the amount of top gas and the composition of top gas meet the balance condition, or the nitrogen content in the composition of top gas reaches the content threshold, an exhaust cycle is obtained based on the number of cycles and the single cycle smelting time of the top gas cycle-oxygen blast furnace; Based on the exhaust cycle, the top gas circulation-oxygen blast furnace is operated to exhaust top gas externally.

2. The method according to claim 1, characterized in that The construction process of the top gas circulation-oxygen blast furnace model includes: Based on the material flow properties and energy flow properties inside the oxygen blast furnace in the top gas circulation-oxygen blast furnace, a multi-region energy and quality balance model of the oxygen blast furnace is constructed; Based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace, a thermal efficiency model of the gas heating furnace is constructed; The multi-region energy and quality balance model of the oxygen blast furnace is coupled with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model; Obtain initial data for top gas circulation-oxygen blast furnace; The top gas circulation-oxygen blast furnace model is set based on the initial data to obtain the constructed top gas circulation-oxygen blast furnace model.

3. The method according to claim 1, characterized in that The key parameters calculated based on the furnace top gas volume and the furnace top gas composition include: Calculating the hydrogen utilization rate based on the furnace top gas volume, the furnace top gas composition and the hydrogen utilization rate empirical formula; Calculating a theoretical combustion temperature based on the furnace top gas volume, the furnace top gas composition and a theoretical combustion temperature formula; Calculating fuel gas consumption for heating each cubic meter of top gas based on the amount of top gas and the composition of top gas; The hydrogen utilization rate, the theoretical combustion temperature and the fuel gas consumption are taken as key parameters.

4. The method according to claim 1, characterized in that: The exhaust cycle is obtained based on the number of cycles and the top gas cycle-oxygen blast furnace single cycle smelting time, including: The exhaust cycle is obtained by multiplying the number of cycles by the top gas cycle-single cycle smelting time of the oxygen blast furnace.

5. The method according to any one of claims 1 to 4, characterized in that: After the calculation to obtain the amount of top gas and the composition of top gas, the method further comprises: If the top gas amount is consistent with the top gas amount obtained in the previous cycle, and the nitrogen content in the top gas composition is consistent with the nitrogen content in the top gas composition obtained in the previous cycle, it is determined that the top gas amount and the top gas composition meet the equilibrium condition.

6. A control device for nitrogen content in an oxygen blast furnace, characterized in that: The device comprises: An acquisition unit, used for acquiring an initial top gas volume and an initial top gas composition of a top gas circulation-oxygen blast furnace, and using the initial top gas volume and the initial top gas composition as furnace entry parameters; A first calculation unit is used to calculate the amount of top gas and the composition of top gas based on the furnace entry parameters, a pre-built top gas circulation-oxygen blast furnace model and preset constraints; A second calculation unit is used for calculating key parameters based on the amount of top gas and the composition of top gas if the amount of top gas and the composition of top gas do not meet the balance condition; An adjustment unit, configured to adjust the model parameters in the top gas circulation-oxygen blast furnace model if the key parameters do not meet the preset reference operating conditions; a circulation unit, for converting the amount of top gas and the composition of top gas to obtain new furnace entry parameters, returning to execute the step of calculating the amount of top gas and the composition of top gas based on the furnace entry data, the pre-built top gas circulation-oxygen blast furnace model and the preset constraint conditions, and recording the number of cycles; A third calculation unit is used for obtaining an exhaust cycle based on the number of cycles and the top gas cycle-oxygen blast furnace single cycle smelting time when the top gas amount and the top gas composition meet the balance condition or the nitrogen content in the top gas composition reaches a content threshold; An exhaust unit is used for performing top gas exhaust operation on the top gas circulation-oxygen blast furnace based on the exhaust cycle.

7. The device according to claim 6, characterized in that The device also includes: A construction unit is used to construct a multi-region energy and quality balance model of an oxygen blast furnace based on the material flow properties and energy flow properties inside the blast furnace in the top gas circulation-oxygen blast furnace; construct a thermal efficiency model of the gas heating furnace based on the material flow properties and energy flow properties inside the regenerative gas heating furnace in the top gas circulation-oxygen blast furnace; couple the multi-region energy and quality balance model of the oxygen blast furnace with the thermal efficiency model of the gas heating furnace to obtain a top gas circulation-oxygen blast furnace model; obtain initial data of the top gas circulation-oxygen blast furnace; set the top gas circulation-oxygen blast furnace model based on the initial data to obtain the constructed top gas circulation-oxygen blast furnace model.

8. The device according to claim 6, characterized in that The second calculation unit for calculating key parameters based on the furnace top gas volume and the furnace top gas composition is specifically used for: Calculating the hydrogen utilization rate based on the furnace top gas volume, the furnace top gas composition and the hydrogen utilization rate empirical formula; Calculating a theoretical combustion temperature based on the furnace top gas volume, the furnace top gas composition and a theoretical combustion temperature formula; Calculating fuel gas consumption for heating each cubic meter of top gas based on the amount of top gas and the composition of top gas; The hydrogen utilization rate, the theoretical combustion temperature and the fuel gas consumption are taken as key parameters.

9. The device according to claim 6, characterized in that The third calculation unit for obtaining the exhaust cycle based on the number of cycles and the top gas cycle-single cycle smelting time of the oxygen blast furnace is specifically used for: The exhaust cycle is obtained by multiplying the number of cycles by the top gas cycle-single cycle smelting time of the oxygen blast furnace.

10. The device according to any one of claims 6 to 9, characterized in that: The device also includes: A judgment unit is used to determine that the top gas amount and the top gas composition meet a balance condition if the top gas amount is consistent with the top gas amount obtained in the previous cycle, and the nitrogen content in the top gas composition is consistent with the nitrogen content in the top gas composition obtained in the previous cycle.

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