A rotary kiln partition apparent source term determination method

Abstract

The present application belongs to the technical field of numerical modeling of industrial rotary kiln thermal process and computational fluid dynamics, and discloses a rotary kiln partition apparent source term determination method. According to the spatial relationship of the coal gun, the secondary air inlet and the bed layer, the calculation domain is divided into a gas phase zone, an equivalent bed layer zone and a plurality of axial source term zones, and a partition gas phase apparent heat source, a bed layer equivalent heat source, a bed layer equivalent heat sink and O2, CO2 and CO target limiting type apparent component sources are set. The outlet dry basis gas composition of the first stable operation period is used to determine the component source parameters, the multi-axial gas phase temperature is used to determine the heat source and heat sink parameters, and the component-temperature cross-checking is carried out. The required frozen source term zone position, source term form, source term strength, target mass fraction and equivalent bed layer parameters are achieved; another stable operation period is adopted, only the actual changed operation input is updated, and the frozen model independent verification is carried out.

Description

Technical Field

[0001] This invention relates to the field of numerical modeling and computational fluid dynamics technology for thermal processes in industrial rotary kilns, specifically to a method for determining apparent source terms in rotary kiln partitions. Background Technology

[0002] Industrial rotary kilns are widely used in mineral roasting, reduction, calcination, and other high-temperature heat treatment processes. The interior of a rotary kiln simultaneously involves processes such as fuel jetting, zoned air supply, axial flue gas transport, solid bed movement, gas-solid heat exchange, and high-temperature radiative heat exchange. The gas phase temperature and major gas components exhibit significant spatial non-uniformity along the kiln's length.

[0003] Under industrial production conditions, long-term operational data typically includes material feed rate, fuel input rate, air volume or inlet velocity at each secondary air inlet, flue gas composition at the outlet, and temperature at a limited axial location. However, due to the high temperature, dust levels, and continuous production conditions, it is difficult to continuously measure the local gas composition, bed temperature, and local gas-solid heat transfer status within a rotary kiln. Furthermore, some kinetic and transfer parameters required for processes such as fuel conversion, fixed carbon oxidation, mineral reactions, bed movement, and local gas-solid heat transfer are difficult to obtain completely from the industrial site.

[0004] Existing computational fluid dynamics models for rotary kilns typically calculate the internal thermal state by explicitly setting combustion reactions, gas-solid heat transfer, and solid-phase reaction processes. When used for full-size industrial rotary kilns, these methods require numerous local reaction kinetic parameters, particulate property parameters, and heat transfer parameters. Furthermore, with incomplete on-site parameters, it is difficult to determine the internal heat release and component transformation processes based on long-term industrial operating conditions.

[0005] Furthermore, when using measured temperature or flue gas data to correct the parameters of the computational model, if the same operating data is used in the parameter determination stage and the model validation stage, or if the source terms and model parameters are adjusted based on measured output during the validation stage, it is difficult to evaluate the applicability of the determined parameters in another operating cycle.

[0006] Therefore, there is a need for a method to determine the net heat effect and net conversion effect of major gas components in different axial regions inside a rotary kiln using measurable industrial operating data, and to independently verify the apparent source terms by keeping the source term parameters unchanged after the parameters are determined and by using another stable operating cycle. Summary of the Invention

[0007] I. The technical problems to be solved; The purpose of this invention is to provide a method for determining apparent source terms in a rotary kiln. Under conditions where local reaction kinetic parameters, bed heat transfer parameters, and continuous field measurement data within the kiln are incomplete, this method determines apparent heat sources in the gas phase, equivalent heat sources in the bed, equivalent heat sinks in the bed, and apparent components of the main gases, all with axial spatial relationships, based on the rotary kiln equipment structure and stable industrial operation data. The method then uses the outlet flue gas composition and gas phase temperatures at multiple axial positions to determine the parameters and perform cross-verification for different types of apparent source terms. After the apparent source terms are determined, their spatial location, expression form, and parameters remain unchanged, and they are independently verified using another stable operating cycle with non-overlapping time periods.

[0008] II. Technical Solution; A method for determining apparent source terms in a rotary kiln zone includes: Step S1: Screening stable operating industrial data; Obtain stable operating cycle data of two non-overlapping times of the rotary kiln. The data of the first stable operating cycle is used as the apparent source term determination data, and the data of the second stable operating cycle is used as the independent verification data. The stable operating cycle data includes material feed rate, fuel input rate, operating parameters of multiple secondary air inlets, dry basis composition of outlet flue gas, and gas phase temperature at multiple axial positions. Step S2: Establish the computational domain and partition the axial source terms; establish the computational fluid dynamics computational domain according to the actual geometric dimensions of the rotary kiln, and divide the fluid dynamics computational domain into a gas phase region and an equivalent bed region; divide multiple source term regions along the axial direction of the rotary kiln according to the range of action of the coal gun, the axial position of multiple secondary air inlets, and the spatial relationship of the bed. Step S3: Construct zoned heat sources, zoned heat sinks, and target mass fraction-limited component sources; set up zoned apparent heat sources in each source term region of the gas phase region to characterize the unresolved heat release in the corresponding region; set up equivalent bed heat sources or equivalent bed heat sinks in each source term region of the equivalent bed region to characterize the heat absorption, heat release, and heat feedback of the bed to the gas phase; set up apparent component sources for O2, CO2, and CO to characterize the apparent net consumption or apparent net generation of components in the rotary kiln; the apparent component sources of O2, CO2, and CO adopt a target mass fraction-limited method to form mass fraction-limited component sources; the local source strength of the apparent component source is determined by the product of the corresponding baseline apparent source strength and the correction factor; the correction factor is determined based on the deviation between the local component mass fraction and the corresponding target mass fraction, and is limited to the range of 0 to 1; Step S4: Constrain apparent component sources on the dry basis at the outlet; determine the initial source strength magnitude of each apparent source term based on the material, fuel, and air inputs during the first stable operating cycle; determine the apparent component source parameters based on the dry basis O2, CO2, CO, and N2 at the outlet during the first stable operating cycle; and determine the zoned apparent heat source and bed equivalent heat source parameters or bed equivalent heat sink parameters for each source term region based on the mass flow weighted average gas phase temperature at multiple axial positions. Step S5 involves determining the heat source and heat sink for multi-axial temperature constraints in different zones, and performing cross-verification of the component-temperature dual indicators. This is followed by sequentially determining the apparent component source parameters, the apparent heat source parameters for the zoned gas phase, and the equivalent heat source parameters or equivalent heat sink parameters for the bed, as well as cross-verifying the outlet flue gas composition and axial gas phase temperature. Steady-state calculations and parameter adjustments are then repeated. If adjusting the apparent component source parameters reduces the deviation in outlet flue gas composition, but the axial gas phase temperature exceeds the allowable range, the adjustment of the apparent component source parameters for that round is cancelled or corrected. Similarly, if adjusting the zoned heat source parameters or zoned heat sink parameters reduces the deviation in axial gas phase temperature, but the outlet flue gas composition exceeds the allowable range, the adjustment of the zoned heat source parameters or zoned heat sink parameters for that round is cancelled or corrected until both the outlet flue gas composition and the axial gas phase temperature simultaneously meet the preset allowable range. Step S6: Fix the location, form, intensity, and target value of the apparent source term; fix the source term region location, apparent source term form, source term intensity, target mass fraction, and equivalent bed parameters that meet the preset allowable range to form a partitioned apparent source term set; Step S7: Form an independently verifiable set of partitioned apparent source terms; in the second stable operating cycle, only update the actually changed operating inputs and boundary conditions, and keep the set of partitioned apparent source terms unchanged; independently verify the calculation model using the set of partitioned apparent source terms based on the measured outlet flue gas composition and gas phase temperature at multiple axial positions in the second stable operating cycle; during the independent verification process, the measured outlet flue gas composition and axial gas phase temperature in the second stable operating cycle are not used to redetermine the apparent source term form, source term region location, source term intensity, target mass fraction, and equivalent bed parameters.

[0009] The stable operation cycle data is obtained by removing records of kiln shutdown, heating, cooling, maintenance, alarms, instrument malfunctions, and non-production stages. The stable operation mean and quantile interval are calculated for the retained data. The outlet flue gas analysis data are uniformly converted into dry basis composition, and the balance other than dry basis O2, CO2, and CO is used as the equivalent N2 content.

[0010] The equivalent bed zone uses porous media to represent the combined effects of the solid bed on gas phase flow resistance, gas-solid contact path and heat exchange under long-term average operating conditions, and adopts the Darcy-Forchheimer type porous media resistance model; the gas phase zone is used to characterize the coal gun jet, secondary air mixing, flue gas axial transport, and gas phase temperature and main gas component distribution.

[0011] The apparent heat source of the gas phase in each zone and the equivalent heat source or heat sink of the bed are all added to the energy conservation equation as volumetric energy source terms. The boundary of the source term zone is determined based on one or more of the following: the range of action of the coal gun, the axial position of the secondary air inlet, the main apparent heat release area, the spatial range of the bed, and the downstream cooling area. The apparent heat source or apparent heat sink in each source term zone is represented by a piecewise constant, piecewise linear, or parameterized function.

[0012] For O2, CO2, and CO, the target mass fraction-limited component sources satisfy: ; and: ; in, S i Components i Local source strength, S i,0 Components i The corresponding baseline apparent source strength, f i As a correction factor; The correction factor corresponding to O2 is: ; The correction factor for CO2 is: ; The correction factor for CO is: ; Here, clip indicates that the correction factor is limited to the range of 0 to 1. This represents the local mass fraction of component O2. This represents the target mass fraction corresponding to component O2. This represents the mass fraction of O2 in the air inlet. This represents the local mass fraction of component CO2. This represents the target mass fraction corresponding to component CO2. This represents the local mass fraction of component CO. This represents the target mass fraction corresponding to component CO. The baseline apparent source strength corresponding to O2 Negative values ​​represent the apparent net consumption of O2, and the baseline apparent source strength of CO2 and CO. and Take positive values ​​to represent the apparent net generation of CO2 and the apparent net generation of CO, respectively.

[0013] During the first stable operating cycle, the outlet dry basis O2, CO2, CO, and N2 are used to determine the baseline apparent source strength and target mass fraction of the apparent component source. The mass flow weighted average gas phase temperature at multiple axial positions is used to determine the zoned gas phase apparent heat source and bed equivalent heat source or bed equivalent heat sink for each source term region. After each round of parameter adjustment, steady-state calculation is performed again, and the outlet flue gas composition and axial gas phase temperature are checked simultaneously. When the parameter adjustment in this round improves the currently determined indicators while another type of check indicator exceeds the corresponding allowable range, the parameter adjustment in this round is canceled or corrected.

[0014] During the second stable operating cycle, the material feed rate, fuel input rate, and one or more of the secondary air inlet air volume or inlet velocity are updated according to the actual operating status, while keeping the computational domain geometry, grid, turbulence model, radiation model, equivalent bed parameters, apparent source term form, source term region location, source term intensity, and target mass fraction unchanged.

[0015] The independent verification simultaneously uses the outlet dry basis O2, CO2, CO, N2 and gas phase temperature at multiple axial positions during the second stable operating cycle as verification quantities, and uses one or more of the following to evaluate the independent verification results of the partitioned apparent source term set: relative error of major gas components, relative deviation of axial gas phase temperature and root mean square error of axial gas phase temperature.

[0016] After the apparent source term set of the partitioned area is independently verified, the spatial distribution of gas phase temperature and main gas components inside the rotary kiln is calculated using the apparent source term set of the partitioned area. The secondary air operating parameter variation conditions are set based on the independently verified calculation model. The secondary air operating parameter variation conditions include one or more of the following: increase or decrease of total secondary air volume, change of air volume of one or more secondary air inlets, and redistribution of air volume among different secondary air inlets under the condition that the total secondary air volume remains unchanged. Based on the response changes of outlet temperature, O2 and CO to the baseline conditions under different secondary air operating parameter variation conditions, the total amount of secondary air and the adjustment direction of air volume of each secondary air inlet are determined according to the joint changes of outlet temperature, O2 and CO.

[0017] III. Beneficial Effects; Compared with existing rotary kiln thermal modeling methods, the present invention has the following advantages: This invention divides the rotary kiln's computational domain into axial regions based on the coal gun's effective range, the location of the secondary air inlet, and the spatial relationship of the bed. In different regions, apparent heat sources of the gas phase, equivalent heat sources or equivalent heat sinks of the bed, and sources of apparent components of the main gases are set up respectively. This makes the apparent source terms correspond to the actual spatial structure of the rotary kiln, and can characterize the net heat effect and net conversion process of the main gas components in different axial regions of the kiln under the condition that the local reaction kinetic parameters and bed heat transfer parameters are difficult to obtain completely.

[0018] This invention uses the dry basis O2, CO2, CO and N2 at the outlet to determine the apparent component source parameters, and uses the mass flow weighted average gas phase temperature at multiple axial positions to determine the zoned gas phase apparent heat source and bed equivalent heat source or heat sink. After each round of parameter adjustment, the composition of the outlet flue gas and the axial gas phase temperature are checked simultaneously, thereby reducing the parameter uncertainty and internal thermal state distortion caused by using only a single outlet measurement to determine multiple source parameters.

[0019] This invention employs a target mass fraction-limited component source, adjusting the source strength based on the deviation between the local component mass fraction and the corresponding target mass fraction. When the local component mass fraction approaches the target mass fraction, the source strength automatically decreases, thereby limiting excessive apparent consumption of O2 and excessive apparent generation of CO2 and CO, and improving the stability of the calculation results for the main gas components.

[0020] After determining the apparent source term parameters of the partition in the first stable operating cycle, this invention keeps the source term region location, apparent source term form, source term intensity, target mass fraction, and equivalent bed parameters unchanged, and uses a second stable operating cycle with non-overlapping time for independent verification. This separates the parameter determination stage from the model verification stage in terms of data usage, avoiding the need to recalibrate the model using the measured output during the verification period.

[0021] The independently verified set of apparent source terms for each zone can be used to calculate the spatial distribution of gas phase temperature and major gas components inside the rotary kiln, and further analyze the impact of changes in total secondary air volume and spatial distribution of secondary air on outlet temperature, O2 and CO, providing a calculation basis for the thermal state analysis of the rotary kiln and the adjustment of secondary air operating parameters. Attached Figure Description

[0022] Figure 1 Flowchart of the method for determining apparent source terms in rotary kiln zones; Figure 2 A schematic diagram showing the structure of the rotary kiln, the gas phase zone, the equivalent bed zone, and the axial apparent source term partitioning; Figure 3 Schematic diagram of constructing a source for a target mass fraction-limited component; Figure 4 This is a schematic diagram of the secondary wind control logic. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. These embodiments are used to illustrate the establishment, parameter determination, parameter fixing, independent verification, and subsequent application processes of apparent source terms in rotary kiln zones, and are not intended to limit the scope of protection of the present invention. The rotary kiln geometry, number of source term zones, source term parameters, and verification error range in the embodiments can be determined according to the actual equipment structure and process conditions.

[0024] A method for determining apparent source terms in a rotary kiln zone includes: Step S1: Screening of stable operating industrial data; Obtain stable operating cycle data for two non-overlapping time periods of the rotary kiln. The data from the first stable operating cycle is used as the apparent source term determination data, and the data from the second stable operating cycle is used as independent verification data. The stable operating cycle data includes material feed rate, fuel input rate, operating parameters of multiple secondary air inlets, dry basis composition of outlet flue gas, and gas phase temperature at multiple axial positions. Two non-overlapping stable operating cycles are selected from the actual production data of the rotary kiln. The first stable operating cycle data is used to determine the source term parameters in the model; the second stable operating cycle data is not used for parameter adjustment, but only for checking whether the source term parameters determined in the first stable operating cycle are accurate. The stable operating cycle data includes at least: feed rate, fuel quantity, air volume or velocity at each secondary air inlet, outlet flue gas O2, CO2, CO, N2, and gas phase temperature at multiple axial positions inside the kiln.

[0025] Step S2: Establish the computational domain and partition the axial source terms. A computational fluid dynamics (CFD) computational domain is established according to the actual geometric dimensions of the rotary kiln. This domain is divided into a gas phase region and an equivalent bed region. Multiple source term regions are then partitioned along the rotary kiln axis based on the coal gun's operating range, the axial positions of multiple secondary air inlets, and the spatial relationship of the bed. The CFD computational model is established according to the actual dimensions of the rotary kiln. The CFD model is first divided into two parts: the upper part and the main flue gas flow area are designated as the gas phase region; the lower part, which is occupied by solid materials for extended periods, is designated as the equivalent bed region. Based on the coal gun's operating position, the positions of each secondary air inlet, and the bed position, the entire rotary kiln is divided into multiple sections along the axial direction. Each section corresponds to the location of different heat sources and component sources.

[0026] Step S3 involves constructing zoned heat sources, zoned heat sinks, and target mass fraction-limited component sources. Three types of "equivalent effects" are set in the CFD calculation model: where heat is generated, where heat is absorbed, and where O2, CO2, and CO are consumed or generated. Zoned apparent heat sources are set in each axial source region of the gas phase zone to characterize the unresolved gas phase heat release within the corresponding region. Combustion heat release varies at different locations in the rotary kiln; an equivalent heat release is given for each axial region to represent the overall gas phase heat release effect of that region. The initial source strength of the bed-equivalent heat source or bed-equivalent heat sink is estimated based on the ratio of the region's net heat to the equivalent bed volume of that region. The region's net heat is obtained by subtracting the heat absorbed by material heating, material reaction, and other equivalent heat losses from the effective fuel heat input allocated to that region. This calculation is only used to determine the initial source strength magnitude; the final source strength is adjusted zone by zone based on multiple axial temperatures during the first stable operating cycle and cross-checked using the outlet flue gas composition. Equivalent heat sources or sinks are set in each axial source term region of the equivalent bed layer to characterize the heat absorption, release, and thermal feedback of the bed to the gas phase. Since some areas of the material in the bed absorb heat while others may release heat to the gas phase, positive or negative energy source terms are set in different bed layer regions to represent the overall heat exchange between the bed and the gas phase. Apparent component sources are set for O2, CO2, and CO respectively to characterize the apparent net consumption or apparent net generation of components in the rotary kiln. The final effect is represented by the component sources: how much O2 is consumed in total, and how much CO2 and CO are generated in total. The apparent component sources of O2, CO2, and CO adopt a target mass fraction limitation method to form mass fraction-limited component sources. The local source strength of the apparent component source is determined by multiplying the corresponding baseline apparent source strength by a correction factor (the source term strengths of O2, CO2, and CO are not fixed). A baseline strength, i.e., the baseline apparent source strength, is first given, then multiplied by a coefficient between 0 and 1, i.e., the correction factor, to determine the actual source term used at the current location. (Baseline apparent source strength) S i,0 It is not a direct measurement. First, the initial magnitude is estimated based on the input of materials, fuel, and air, as well as the overall component balance. Then, it is adjusted and determined using industrial data of O2, CO2, CO, and N2 at the outlet during the first stable operating cycle. After each adjustment, the composition of the outlet flue gas and the axial temperature are checked simultaneously until both indicators meet the allowable error. The correction factor is determined based on the deviation between the local component mass fraction and the corresponding target mass fraction, and is limited to the range of 0 to 1. When the CFD calculation model calculates to each location, it compares the O2, CO2, or CO content at the current location with the predetermined target value. The farther away from the target value, the larger the correction factor and the stronger the source term effect; the closer to the target value, the smaller the correction factor and the gradually weakening source term effect. The minimum correction factor is 0 and the maximum is 1 to prevent the source term from being too large or having an abnormal direction.

[0027] Step S4: Constrain apparent component sources based on dry basis composition at the outlet. Use the actual output flue gas composition measured during production to determine the appropriate magnitudes for the apparent component sources O2, CO2, and CO. Determine the initial source strength magnitudes for each apparent source term based on the material, fuel, and air inputs during the first stable operating cycle. Since the CFD calculation model is initially unsure of the appropriate source term magnitudes, estimate the approximate order of magnitude for each source term based on the actual material, fuel, and air inputs during production. Determine the apparent component source parameters based on the dry basis O2, CO2, CO, and N2 at the outlet during the first stable operating cycle. Input the estimated O2, CO2, and CO component sources into the CFD calculation model and verify that the calculated outlet flue gas matches the actual output flue gas measured during the first stable operating cycle. The apparent heat source of the gas phase in each source term zone and the equivalent heat source or heat sink parameters of the bed are determined by the mass flow weighted average gas phase temperature at multiple axial positions. The actual temperature at different axial positions of the rotary kiln tells the CFD calculation model "which section has too much heat and which section has too little heat". Then, the gas phase heat source, bed heat source and bed heat sink in these regions are adjusted respectively until the overall axial temperature distribution is close to the actual production situation.

[0028] Step S5 involves multi-axial temperature-constrained zoned heat sources and heat sinks. The actual temperatures at multiple axial positions of the rotary kiln are used to determine the suitability of the heat source or heat sink settings for each zone. A cross-check of the component-temperature dual indicators is performed. The apparent component source parameters are determined sequentially, as are the zoned gas phase apparent heat source and bed equivalent heat source or heat sink parameters. The outlet flue gas composition and axial gas phase temperature are then cross-checked. Steady-state calculations and parameter adjustments are repeated. If adjusting the apparent component source parameters reduces the outlet flue gas composition deviation but the axial gas phase temperature exceeds the allowable range, the adjustment of the apparent component source parameters for that round is cancelled or corrected. Similarly, if adjusting the zoned heat source or heat sink parameters reduces the axial gas phase temperature deviation but the outlet flue gas composition exceeds the allowable range, the adjustment of the zoned heat source or heat sink parameters for that round is cancelled or corrected until both the outlet flue gas composition and the axial gas phase temperature simultaneously meet the preset allowable range. The first step is to adjust the component source parameters of O2, CO2, and CO. The second step is to adjust the gas phase heat source and bed heat source and heat sink in different regions. The third step is to recalculate the complete steady-state CFD calculation model. The fourth step is to compare the composition of the outlet flue gas and the temperature at each axial position. The fifth step is to continue adjusting and recalculating if there are still deviations.

[0029] Step S6: Fix the location, form, intensity, and target value of the apparent source term; fix the source term region location, apparent source term form, source term intensity, target mass fraction, and equivalent bed parameters that meet the preset allowable range to form a partitioned apparent source term set; Step S7: Form an independently verifiable set of apparent source terms for each zone; in the second stable operating cycle, only update the actually changed operating inputs and boundary conditions, keeping the set of apparent source terms for each zone unchanged; independently verify the calculation model using the set of apparent source terms for each zone based on the measured flue gas composition and gas phase temperature at multiple axial positions during the second stable operating cycle; during the independent verification process, the measured flue gas composition and axial gas phase temperature during the second stable operating cycle are not used to re-determine the apparent source term form, source term region location, source term intensity, target mass fraction, and equivalent bed parameters. After determining and fixing the model parameters in the first stage, verification is performed using stable production data from a completely different time period. In the second stage, only the actually changed production conditions such as feed, fuel, and secondary air are updated in the CFD calculation model; the previously determined heat sources, heat sinks, component sources, target values, and bed parameters are not modified. Then, the actual measured flue gas and axial temperature in the second stage are compared with the CFD calculation results. The data from the second stage is only used to determine the accuracy of the model and must never be used to readjust the model parameters.

[0030] The stable operating cycle data was obtained by removing records from kiln shutdowns, heating / cooling, maintenance, alarms, instrument malfunctions, and non-production phases. The mean and quantile range of the retained data were calculated. The outlet flue gas analysis data were uniformly converted to a dry basis composition. Under the condition of ignoring other dry basis trace components or incorporating them into the residual components, the residual amount other than O2, CO2, and CO on a dry basis was used as the equivalent N2 content. Furthermore, from the long-term production data, all data from kiln shutdowns, heating / cooling, maintenance, alarms, instrument malfunctions, and abnormal production phases were removed, retaining only the data from truly stable production. Then, the mean and fluctuation range of these stable data were calculated. The outlet flue gas data were uniformly converted to a dry basis composition; if other trace gases were not separately considered, the residual amount other than O2, CO2, and CO was used as the equivalent N2.

[0031] The equivalent bed region uses porous media to represent the combined effects of the solid bed on gas phase flow resistance, gas-solid contact path, and heat exchange under long-term average operating conditions, and employs a Darcy-Forchheimer porous media resistance model. The gas phase region is used to characterize the coal gun jet, secondary air mixing, flue gas axial transport, and the distribution of gas phase temperature and main gas components. Due to the complexity of the bed, it is not calculated particle by particle, but is equivalent to a porous region that "obstructs airflow and exchanges heat with the gas"; other spaces are calculated normally for gas flow, mixing, temperature, and composition.

[0032] The apparent heat sources in the gas phase of each zone, as well as the equivalent heat sources or heat sinks in the bed, are all added to the energy conservation equation as volumetric energy source terms. The boundaries of the source term zones are determined based on one or more of the following: the effective range of the coal gun, the axial position of the secondary air inlet, the main apparent heat release area, the spatial range of the bed, and the downstream cooling area. The apparent heat sources or heat sinks within each source term zone are represented by piecewise constants, piecewise linear functions, or parameterized functions. The rotary kiln is divided into several sections, each assigned a value indicating "how much heat is released or absorbed," and these values ​​are then added to the CFD energy equation.

[0033] For O2, CO2, and CO, the target mass fraction-limited component sources satisfy: and: in, S i Components i The local apparent source strength, S i,0 Components i The corresponding baseline apparent source strength, f i As a correction factor; The correction factor corresponding to O2 is expressed as follows: ; The correction factor for CO2 is: ; The correction factor for CO is: ; Here, clip indicates that the correction factor is limited to the range of 0 to 1. This represents the local mass fraction of component O2. This represents the target mass fraction corresponding to component O2. This represents the mass fraction of O2 in the air inlet. This represents the local mass fraction of component CO2. This represents the target mass fraction corresponding to component CO2. This represents the local mass fraction of component CO. This represents the target mass fraction corresponding to component CO. The baseline apparent source strength corresponding to O2 Negative values ​​represent the apparent net consumption of O2, and the baseline apparent source strength of CO2 and CO. and Take positive values ​​to represent the apparent net generation of CO2 and the apparent net generation of CO, respectively.

[0034] Give first Si,0 and Y i,target Initial values, during the CFD computation model, each grid position is determined based on the current... Y i work out f i Then obtain the actual source strength at that location. S i Then check if the outlet O2, CO2, CO, and N2 levels are close to the measured values ​​from the first stable operating cycle. If not, adjust accordingly. S i,0 Then recalculate the target quality score. After step S6: the formula continues to be used, but the parameters are no longer adjusted.

[0035] During the first stable operating cycle, the outlet dry basis O2, CO2, CO, and N2 are used to determine the baseline apparent source strength and target mass fraction of the apparent component sources. The mass flow weighted average gas phase temperature at multiple axial positions is used to determine the zoned gas phase apparent heat source and bed equivalent heat source or bed equivalent heat sink for each source term region. After each round of parameter adjustment, steady-state calculations are performed again, and the outlet flue gas composition and axial gas phase temperature are checked simultaneously. When the parameter adjustment in this round improves the currently determined indicators while another type of check indicator exceeds the corresponding allowable range, the parameter adjustment in this round is canceled or corrected. During the first stable operating cycle, the actual outlet O2, CO2, CO, and N2 are used to determine the baseline source strength and target mass fraction of O2, CO2, and CO; then, the gas phase temperature at multiple axial positions of the rotary kiln is used to determine the gas phase heat source and bed heat source or heat sink for different regions.

[0036] During the second stable operating cycle, the material feed rate, fuel input rate, and one or more of the secondary air inlet air volume or inlet velocity are updated according to the actual operating status, while keeping the computational domain geometry, mesh, turbulence model, radiation model, equivalent bed parameters, apparent source term form, source term region location, source term intensity, and target mass fraction unchanged. After the second stable operating cycle, if the actual feed rate, fuel quantity, secondary air volume, or secondary air inlet velocity changes during production, these input conditions are updated according to the actual operating conditions of the second cycle.

[0037] The independent verification simultaneously uses the outlet dry basis O2, CO2, CO, N2 and gas phase temperatures at multiple axial positions during the second stable operating cycle as verification quantities, and evaluates the independent verification results of the partitioned apparent source term set using one or more of the following: relative error of major gas components, relative deviation of axial gas phase temperature, and root mean square error of axial gas phase temperature. The outlet O2, CO2, CO, N2 and gas phase temperatures at multiple axial positions actually measured during the second stable operating cycle are compared with the CFD calculation results.

[0038] After the apparent source term set of the partitioned area is independently verified, the spatial distribution of gas phase temperature and main gas components inside the rotary kiln is calculated using the apparent source term set of the partitioned area. The secondary air operating parameter variation conditions are set based on the independently verified calculation model. The secondary air operating parameter variation conditions include one or more of the following: increase or decrease of total secondary air volume, change of air volume of one or more secondary air inlets, and redistribution of air volume among different secondary air inlets under the condition that the total secondary air volume remains unchanged. Based on the response changes of outlet temperature, O2 and CO to the baseline conditions under different secondary air operating parameter variation conditions, the total amount of secondary air and the adjustment direction of air volume of each secondary air inlet are determined according to the joint changes of outlet temperature, O2 and CO.

[0039] A specific embodiment is as follows, such as Figure 1 As shown: Stable operation of industrial data filtering; Data from two non-overlapping operating cycles are acquired from the DCS, flue gas analyzer, on-site temperature monitoring system, and production statistics system. This operating data includes at least material feed rate, fuel input rate, operating parameters of multiple secondary air inlets, outlet flue gas composition, and gas phase temperature at multiple axial positions. The outlet flue gas analysis data is uniformly converted to a dry basis composition. When the flue gas analyzer outputs a dry basis volume fraction, it is converted to a mass fraction based on the molar mass of each gas component for apparent component source calculation. During outlet flue gas composition verification and independent validation, industrial measurement results and CFD calculation results are uniformly converted to the same dry basis volume fraction caliber for comparison. Under the condition of ignoring other dry basis trace components or incorporating them into the balance components, the dry basis balance other than O2, CO2, and CO is used as the equivalent N2. Data from kiln shutdowns, heating / cooling, maintenance, alarms, instrument malfunctions, and non-production phases were excluded. Data from the first stable operating cycle was used to determine the apparent source parameters for each zone, while data from the second stable operating cycle was used for independent verification. The stable operating statistical mean and P10–P90 quantile intervals for each operating variable were calculated from the filtered stable operating data. The steady-state calculations used the statistical mean of the corresponding stable operating cycle as representative operating inputs and boundary conditions, and the P10–P90 quantile intervals were used to characterize the stable operating fluctuation range and to verify the calculation results.

[0040] Computational domain establishment and axial source term partitioning; A three-dimensional computational fluid dynamics domain was established based on the actual geometric dimensions of the rotary kiln, preserving the spatial relationships of the coal lance, multiple secondary air inlets, feed inlets, flue gas outlets, and bed layers. Figure 2As shown, the left end is the coal lance inlet, and the arrow below the left end indicates the material outlet; the upper right end is the feed inlet, and the right end outlet is the flue gas outlet; several inlets at the top of the whole structure are secondary air inlets, and the bottom of the whole structure is divided into multiple source term zones. The area mainly occupied by solid materials under long-term average operating conditions is set as the equivalent bed zone, and the remaining areas are set as the gas phase zone. Based on the effective range of the coal lance, the axial position of the secondary air inlet, the spatial relationship of the bed, and the thermal characteristics of different axial regions of the rotary kiln, multiple source term zones are divided along the kiln length.

[0041] Construct the partitioned appearance source item; In the gas phase region, apparent heat sources are set up in different axial source term regions to equivalently characterize the net heat release of the gas phase that is not explicitly resolved in the corresponding region; in the equivalent bed region, equivalent bed heat sources or equivalent bed heat sinks are set up in the corresponding axial source term regions to equivalently characterize the combined effect of bed heat absorption and release and heat exchange between the bed and the gas phase on the energy equation; apparent component sources are set up for O2, CO2 and CO respectively to equivalently characterize the net consumption or net generation of the corresponding gas components in the kiln.

[0042] The apparent component sources of O2, CO2 and CO are limited by a target mass fraction. The local source intensity of the apparent component source is determined by the product of the corresponding reference apparent source intensity and a correction factor. The correction factor is determined based on the deviation between the local component mass fraction and the corresponding target mass fraction and is limited to the range of 0 to 1. As the local component mass fraction approaches the corresponding target mass fraction, the correction factor decreases, causing the local source intensity of the corresponding apparent component source to decrease.

[0043] Determine the source parameters of the apparent components; The initial source strength of the apparent components is estimated based on the material, fuel, and air inputs during the first stable operating cycle. Based on the dry basis O2, CO2, CO, and N2 at the outlet during the first stable operating cycle, the baseline apparent source strength and target mass fraction of each component are adjusted so that the calculated main gas components at the outlet meet the preset allowable deviation from the industrial statistical results of the first stable operating cycle.

[0044] Determine the heat source parameters and heat sink parameters for each zone; While maintaining the apparent component source form and the determined component parameter relationship, the apparent heat source and equivalent heat source or equivalent heat sink of the gas phase in each source term region are adjusted according to the mass flow weighted average gas phase temperature at multiple axial positions, so that the calculated axial gas phase temperature distribution meets the preset allowable deviation from the industrial statistical results of the first stable operating cycle.

[0045] Cross-checking of outlet composition and axial temperature; After each round of adjustment of apparent component source parameters or zone heat source parameters and zone heat sink parameters, a steady-state calculation is performed again, and the composition of the outlet flue gas and the gas phase temperature at multiple axial positions are checked simultaneously. If the parameter adjustment in this round improves the index corresponding to the currently adjusted object, but causes another type of index to exceed the corresponding allowable deviation, then the parameter change in this round is canceled, reduced, or readjusted; the adjustment of apparent component source and zone heat source parameters and zone heat sink parameters is repeated until the composition of the outlet flue gas and the axial gas phase temperature simultaneously meet the preset allowable range.

[0046] Fixed partition appearance source item parameters; When the composition of the outlet flue gas and the gas phase temperature at multiple axial positions simultaneously meet the preset allowable range, the source term region location, apparent source term expression form, source term intensity of each source term region, target mass fraction of each component, and equivalent bed parameters are fixed to form a partitioned apparent source term set.

[0047] The term "fixed parameters" means that during subsequent independent verification processes, the above parameters are not readjusted based on the measured flue gas composition and axial temperature of the second stable operating cycle.

[0048] Independent verification across cycles; The second stable operating cycle, which does not overlap with the first stable operating cycle, was used for independent verification. Based on the actual operating status of the second stable operating cycle, only the material feed rate, fuel input rate, secondary air inlet operating parameters, and other boundary conditions that actually changed were updated, while the computational domain geometry, numerical model, equivalent bed parameters, and the determined set of apparent source terms for each zone remained unchanged.

[0049] The measured flue gas composition at the outlet and the gas phase temperature at multiple axial positions during the second stable operating cycle are only used for comparison with the calculation results and are not used to readjust the apparent source term form, source term region location, source term intensity, target mass fraction, and equivalent bed parameters.

[0050] Further applications of partitioned apparent source terms; After independent verification during the second stable operating cycle, the spatial distribution of gas phase temperature and main gas components inside the rotary kiln can be calculated using the determined set of apparent source terms for each zone, which can be used to characterize the internal thermal state of the rotary kiln.

[0051] Based on this, using the independently validated calculation model as a benchmark, we set up various operating conditions for secondary air parameters, including increases or decreases in total secondary air volume, changes in the air volume of one or more secondary air inlets, and spatial redistribution under the condition of constant total secondary air volume. We calculated the outlet temperature, O2, and CO for each operating condition and compared them with the benchmark operating condition. Based on the changes in outlet temperature maintenance, oxygen supply margin, and residual CO, we determined the direction of secondary air adjustment.

[0052] In one optional implementation, multiple secondary air operating conditions can be progressively screened based on preset outlet temperature, allowable ranges for O2 and CO. The screening only changes the secondary air operating parameters and does not change the already determined zonal apparent source term parameters.

[0053] Apparent heat source and axial thermal power; The apparent heat source in the gas phase and the equivalent heat source or equivalent heat sink in the bed are respectively added to the energy conservation equation of the corresponding computational domain in the form of volumetric energy source terms, with units of W·m. -3 A positive value for the apparent heat source indicates that energy is net added to the corresponding control volume, while a negative value indicates that energy is net removed from the corresponding control volume, i.e., it is used as an equivalent heat sink.

[0054] In axial position x At this point, the total apparent heat rate of the gas phase region and the equivalent bed region within a unit axial length can be expressed as: ; in, Axial position x Apparent heat rate per unit axial length, and These represent the cross-sectional areas of the gas phase region and the equivalent bed region at that axial position, respectively. As a gas-phase apparent heat source, It serves as the equivalent heat source or equivalent heat sink for the bed.

[0055] For the j The integral apparent thermal power of each axial source term region for: ; in, and The first j The volume of the gas phase region within the source term region and the first j The equivalent bed volume within each source term region.

[0056] When the j When the apparent heat source or heat sink within a single source term region adopts piecewise constant values, the above formula can be written as: ; For the first j Apparent heat sources in the gas phase within the source region; For the first j The equivalent heat source or equivalent heat sink of the bed layer within the source area; The initial source strength magnitude of the apparent heat source or heat sink in each source term region can be estimated by engineering based on the fuel heat input, material throughput, and the effective volume of the corresponding source term region. The engineering estimate is only used to provide the initial range for parameter adjustment. The final apparent heat source of the gas phase and the equivalent heat source or heat sink of the bed are determined based on the multiaxial gas phase temperature of the first stable operating cycle, and corrected by cross-checking the outlet flue gas composition and axial gas phase temperature. The total fuel heat input is not directly equated to the volumetric heat source of a single axial region.

[0057] Equivalent bed momentum resistance; To characterize the hindering effect of the solid bed on gas phase flow under long-term average operating conditions, the equivalent bed region is treated with a porous medium. The Darcy–Forchheimer type resistance model is preferably used, and in the first... k The momentum source term in each coordinate direction can be expressed as: ; in, S m,k For the first k Porous medium momentum source terms in each coordinate direction For gas dynamic viscosity, This is the equivalent bed permeability. C 2 represents the inertial drag coefficient. For gas density, The magnitude of the gas velocity vector. For the gas velocity at the th k Components in each coordinate direction.

[0058] The porous media resistance is used to equivalently characterize the combined effects of the bed on the gas phase flow path, flow resistance, and gas-solid contact process under long-term average conditions. Its parameters remain unchanged during the independent verification process of the second stable operating cycle after being determined in the first stable operating cycle.

[0059] Target mass fraction-limited component sources; Target mass fraction-limited component sources are set for O2, CO2 and CO respectively, which are used to equivalently characterize the apparent net consumption or apparent net generation of the corresponding gas components in the rotary kiln.

[0060] Components i The local apparent source strength is represented as: ; and: ; in, S i Components i The local apparent source strength at the current computation location, Components i The baseline apparent source strength,f i This is a correction factor determined based on the local component mass fraction and the corresponding target mass fraction.

[0061] The limiting function is defined as follows: ; In a preferred embodiment, the correction factor corresponding to O2 is expressed as: ; The correction factor for CO2 is: ; The correction factor for CO is: ; in, This means that the calculated correction factor is limited to the range of 0 to 1; Y i Components i Local mass fraction, The target mass fraction for the corresponding component. This represents the mass fraction of O2 in the air inlet.

[0062] The baseline apparent source strength corresponding to O2 Negative values ​​are used to characterize the apparent net consumption of O2; the baseline apparent source strengths of CO2 and CO are also considered. and A positive value is used to characterize the apparent net generation of CO2 and the apparent net generation of CO.

[0063] As the mass fraction of local components approaches the corresponding target mass fraction, the correction factor f i The correction factor gradually decreases, causing the local source strength of the corresponding apparent component to decay accordingly. When the local component reaches the corresponding target constraint, the corresponding correction factor decreases to zero, thereby causing the corresponding apparent component source to cease net consumption or net generation. The construction relationship of target mass fraction-constrained component sources is as follows: Figure 3 As shown.

[0064] To define the initial engineering magnitude of the baseline apparent source strength, it can also be estimated based on the overall gas component budget. For components... i ,have: ; in, This represents the gas outlet mass flow rate. Components in the outlet gas i The mass fraction, For the first r Mass flow rate of each gas inlet For the firstr Components in each gas inlet i The quality score. V To set the computational domain volume of the apparent component source ( S i Components i Local source strength; The above overall income and expenditure are only used to determine the initial engineering quantity of the baseline apparent source strength. The final baseline apparent source strength and target mass fraction are still determined based on the outlet dry basis gas composition of the first stable operating cycle, and are cross-checked in conjunction with the axial gas phase temperature.

[0065] Axial temperature check quantity; To ensure a consistent comparison between the calculated gas phase temperature and industrial temperature measurements at different axial positions, in the first... k The temperature parameters used to determine and verify the zoned heat source parameters or zoned heat sink parameters for each axial section are: ; in, For the first k Mass flow rate weighted average gas phase temperature of each axial section A k This represents the gas flow area corresponding to the axial cross-section. For gas density, Let be the component of the gas velocity in the normal direction of the cross section. T This refers to the local gas phase temperature.

[0066] Using mass flow rate weighted average gas phase temperature can comprehensively reflect the heat-carrying state of flue gas at the corresponding axial section, avoiding the use of a single calculation unit or local extreme value to represent the thermal state of the entire section. During the first stable operating cycle, the temperature values ​​of multiple axial sections are used to determine and verify the apparent heat source of the gas phase and the equivalent heat source or equivalent heat sink of the bed in each axial source term region.

[0067] Independently validate evaluation indicators; After the parameters of the apparent source terms of the partition are determined, independent verification is performed using a second stable operating cycle that does not overlap with the time of the first stable operating cycle.

[0068] The second stable operating cycle only updates the material feed rate, fuel input rate, secondary air inlet operating parameters and other boundary conditions that have changed according to the actual working conditions, while keeping the already determined source term region location, apparent source term form, baseline apparent source strength, target mass fraction and equivalent bed parameters unchanged.

[0069] For the main gas components of the dry basis at the outlet i Its relative error can be expressed as: ; in, The outlet dry basis component concentration is obtained from the CFD calculation model with fixed parameters. This refers to the industrial statistics corresponding to the second stable operating cycle.

[0070] No. k The relative deviation of the gas phase temperature at each axial position can be expressed as: ; The root mean square error of the axial vapor phase temperature can be expressed as: ; in, N The number of axial temperature locations that participated in the independent verification. For the model with fixed parameters in the first... k The calculated temperature was obtained at each axial position. This refers to the industrial statistical temperature at the location corresponding to the second stable operating cycle.

[0071] The measured flue gas composition and axial temperature of the second stable operating cycle are only used for evaluating the calculation results and are not used to redetermine the source term region location, apparent source term form, source term intensity, target mass fraction, or equivalent bed parameters.

[0072] Secondary wind response evaluation and adjustment direction; After the zonal apparent source item set has been independently verified through the second stable operating cycle, the CFD calculation model with fixed parameters is used as the benchmark model to set the operating conditions of secondary wind operating parameters.

[0073] The operating conditions for changes in secondary air parameters include increases or decreases in total secondary air volume, changes in the air volume of one or more secondary air inlets, and spatial redistribution among different secondary air inlets under the condition that the total secondary air volume remains unchanged.

[0074] Taking the baseline condition 0 as a reference, for the first... j Each secondary wind change condition and the response at any outlet R Its response change is expressed as: ; in, R 0 represents the output response corresponding to the baseline operating condition. R j For the first j The outlet response quantities corresponding to each secondary air change condition. The response changes include at least the outlet gas phase temperature, outlet O2, and outlet CO.

[0075] By comparing the response changes of outlet temperature, O2, and CO to the baseline under various secondary air variation conditions, the influence of total secondary air volume and spatial distribution on the oxygen supply status in the kiln, the outlet thermal status, and residual CO is evaluated, and the direction of secondary air adjustment is determined according to the requirements of outlet temperature maintenance, O2 oxygen supply margin, and CO suppression.

[0076] When the preset outlet temperature, O2 and CO target ranges are not met, the total amount or spatial allocation of secondary air can be further changed and recalculated at the calculation operating condition level; the adjustment of the secondary air operating condition only changes the operating input parameters and does not change the set of apparent source terms of the partition that has been independently verified. Figure 4 The loop shown represents the offline secondary wind condition screening based on a fixed parameter model, and does not represent the readjustment of CFD apparent source term parameters using the measured output of the second stable operating cycle.

[0077] This invention is a method for determining the apparent heat source of the gas phase, the equivalent heat source of the bed, the equivalent heat sink of the bed, and the target mass fraction-limited component source of a rotary kiln zone using stable industrial operation data, and for independently verifying the determined apparent source items of the zone through stable operation cycles with non-overlapping time periods.

[0078] Example 1: Industrial rotary kiln, computational domain, and source term partitioning; Taking a rotary kiln for reducing titanium-iron materials with a length of 48.0m and an inner diameter of 2.78m as an example, the coal lance is inserted axially along the kiln body from the kiln tail side, with an insertion length of approximately 2.0m. Five secondary air inlets are set along the kiln body, with axial positions of 11.0m, 18.8m, 21.6m, 25.3m, and 30.0m, respectively. The material is fed in from the kiln head side, the flue gas is discharged from the flue gas outlet on the kiln head side, and the solid material is discharged from the kiln tail side.

[0079] A three-dimensional computational fluid dynamics domain was established based on the actual geometric dimensions of the rotary kiln, and the domain was divided into a gas phase region and an equivalent bed region. Under long-term average operating conditions, the region mainly occupied by solid materials was set as the equivalent bed region, and the remaining regions were set as the gas phase region.

[0080] The computational domain was divided into zones based on the effective range of the coal gun, the axial position of the secondary air inlet, and the thermal characteristics of each axial region. Specifically, the 0m–2.0m zone represents the local section where the coal gun is inserted; the 2.0m–48.0m range is further divided into six main source term zones based on the positions of the five secondary air inlets. Figure 2 This is used to represent the spatial relationship between the gas phase region, the equivalent bed region, the secondary air inlet, and the axial source term region, and is not drawn according to the actual size scale of this embodiment.

[0081] The first stable operating cycle uses industrial operating data from 2024. For the selected minute-level operating records, the stable operating statistical mean and P10-P90 quantile intervals for material, fuel, secondary air, outlet flue gas composition, and axial temperature were calculated, and the statistical mean was used as the representative input for the steady-state CFD calculation of the corresponding stable operating cycle. After removing data from kiln shutdowns, heating up, cooling down, maintenance, alarms, instrument malfunctions, and non-production stages, 324 days and 466,560 minute-level operating records were retained. The second stable operating cycle uses industrial operating data from 2025, and after screening using the same principles, 328 days and 472,320 minute-level operating records were retained. The above calendar years are only used to illustrate this embodiment; the first and second stable operating cycles only need to be non-overlapping in time.

[0082] Example 2: Equivalent bed layer and numerical calculation model; The equivalent bed region is treated using a porous medium. In this embodiment, the porosity of the equivalent bed is 0.4, and the viscous resistance coefficient is 8.44 × 10⁻⁶. 6 m -2 The inertial drag coefficient is taken as 3.28 × 10⁻⁶. 3 m -1 .

[0083] The steady-state pressure-based solution method is used for gas phase flow, the SSTk-ω model can be used for turbulence model, the P1 model can be used for radiative heat transfer, and the WSGGM model can be used for gas participation in medium radiation.

[0084] The aforementioned model is used to calculate the coal gun jet, secondary air mixing, flue gas axial transport, and the distribution of gas phase temperature and main gas components. After the apparent source term parameters of the zones are determined in the first stable operating cycle, the computational domain geometry, grid, turbulence model, radiation model, equivalent bed parameters, and main numerical solution settings remain unchanged during the independent verification process in the second stable operating cycle.

[0085] Example 3: Zoned apparent heat source in the gas phase and equivalent heat source or equivalent heat sink in the bed; Based on the industrial operation data from the first stable operating cycle, parameters were determined for the apparent heat source in the gas phase and the equivalent heat source or heat sink in the bed for each axial source term region. A set of parameters obtained in this embodiment is shown in Table 1 below.

[0086] Table 1 Parameters for each section In this context, a positive volumetric energy source term represents the equivalent net energy added within the corresponding computational region, while a negative volumetric energy source term represents the equivalent net energy removed within the corresponding computational region. Figure 2The negative bed source term in the rightmost source term region is used to equivalently characterize the combined net heat effect formed by the bed sensible heat output, heat absorption on the gas phase, and other cooling effects in the downstream region of the rotary kiln.

[0087] The above parameters are all apparent quantities determined based on industrial operation data, used to characterize the combined net heat effect generated by the unexplained process in the corresponding region, and do not correspond to the heat of reaction or intrinsic reaction rate of a single chemical reaction.

[0088] Example 4: Target mass fraction-limited component source; In this embodiment, the O2 mass fraction of the inlet air is: ; The target mass fractions for O2, CO2, and CO are as follows: ; ; ; The baseline apparent source strengths determined after the first stable operating cycle are as follows: ; ; ; The baseline apparent source strength of O2 is negative, used to characterize the apparent net consumption of O2; the baseline apparent source strength of CO2 and CO is positive, used to characterize the apparent net generation of CO2 and CO.

[0089] The local apparent source intensity of each component is according to Figure 3 The target mass fraction constraint relationship shown is calculated by determining the correction factor based on the deviation between the local component mass fraction and the corresponding target mass fraction. As the local component mass fraction gradually approaches the corresponding target mass fraction, the correction factor decreases, causing the local source intensity of the corresponding apparent component source to decrease synchronously.

[0090] The aforementioned baseline apparent source strength and target mass fraction remain unchanged after the parameters are determined in the first stable operating cycle, and are directly used for independent verification in the second stable operating cycle.

[0091] Example 5: Determination and cross-verification of the order of apparent component sources and zoned heat sources; First, keeping the computational domain geometry, mesh, turbulence model, radiation model, and equivalent bed model unchanged, a baseline calculation condition is established based on the material feed rate, fuel input rate, and multiple secondary air inlet operating parameters of the first stable operating cycle.

[0092] Based on the statistical results of O2, CO2, CO, and N2 at the outlet dry basis during the first stable operating cycle, the baseline apparent source intensity of each component was adjusted. S i,0 and target quality score Y i,target This ensures that the calculated main gas components on the dry basis of the outlet meet the preset allowable deviation.

[0093] After each round of apparent component source parameter adjustment, steady-state calculations are re-executed, and the composition of the outlet flue gas and the gas phase temperature at multiple axial positions are checked simultaneously to avoid determining the apparent component source parameters based solely on a single gas component.

[0094] After the main gas components on the dry basis at the outlet meet the preset allowable deviation, while keeping the apparent component source form and the relationship between the main component parameters unchanged, the source term regions are adjusted according to the mass flow weighted average gas phase temperature of multiple axial sections. S h,gas and S h,bed .

[0095] After each round of adjustment of the heat source or heat sink parameters, the outlet flue gas composition and axial gas phase temperature are recalculated. When the adjustment of the heat source or heat sink parameters reduces the axial temperature deviation but causes the outlet flue gas composition to exceed the allowable range, the parameter adjustment for that round is reduced, canceled, or readjusted.

[0096] Repeat the above sequence to determine the apparent component source parameters, determine the zoned heat source / heat sink parameters, and cross-check the outlet component-axial temperature until both types of indicators simultaneously meet the preset allowable range.

[0097] Subsequently, the location of the source term region, the expression form of the apparent source term, and S h,gas , S h,bed , S i,0 , Y i,target With the equivalent bed parameters fixed, a set of partitioned apparent source terms is formed for subsequent independent verification.

[0098] Example 6: Independent verification across cycles; The partitioned apparent source item set determined in Example 5 was independently verified using the second stable operating cycle, as shown in Table 2.

[0099] Table 2 Independent Validation Table The second stable operating cycle updates only the changing operational inputs such as materials, fuel, and secondary air based on the actual production status. Source term location, apparent source term expression form, S h,gas, S h,bed , S i,0 , Y i,target And the equivalent bed parameters remain unchanged.

[0100] The measured outlet O2, CO2, CO, N2 and gas phase temperatures at multiple axial positions during the second stable operating cycle are only used for comparison with the calculated results and are not involved in the redetering of apparent source term parameters, rescaling of source strength, adjustment of target mass fraction, or real-time error compensation.

[0101] In this embodiment, the maximum relative error of the calculation model with fixed parameters for outlet O2, CO2, CO and N2 is 3.05%; the deviation of the calculated temperature at the 7 axial monitoring positions from the industrial statistical temperature of the second stable operating cycle is within ±5%, and the root mean square error of axial temperature (RMSE) is 34.58K.

[0102] The above results indicate that, without readjusting the apparent source term parameters based on the measured output of the second stable operating cycle, the partitioned apparent source term set determined in the first stable operating cycle can be used for thermal state calculations in another stable operating cycle with non-overlapping time periods.

[0103] Example 7: Thermal state calculation and secondary air operation parameter analysis; After the apparent source term set of the partition is independently verified through the second stable operation cycle, the spatial distribution of gas phase temperature and main gas components inside the rotary kiln is calculated using a calculation model with fixed parameters, and the operating conditions of secondary air operating parameters are further set.

[0104] This embodiment sets up a changing operating condition for secondary air parameters, taking the change in total secondary air volume as an example. This includes increasing or decreasing the total secondary air volume relative to the baseline condition. Each changing condition maintains the pre-determined set of apparent source terms for each zone and compares the changes in outlet temperature, O2, and CO with the baseline condition.

[0105] In this embodiment, when the total secondary air volume is reduced by 10% relative to the baseline operating condition, the outlet temperature increases by 17.6°C, the outlet O2 decreases by approximately 0.88 percentage points, and the outlet CO increases by approximately 0.26 percentage points; when the total secondary air volume is increased by 10% relative to the baseline operating condition, the outlet temperature decreases by approximately 18.3°C, the outlet O2 increases by approximately 0.91 percentage points, and the outlet CO decreases by approximately 0.20 percentage points.

[0106] Further, we will set up airflow redistribution scenarios under the conditions of partial secondary air inlet adjustment and constant total secondary air volume. When adjusting the partial secondary air inlet, only the airflow at the designated secondary air inlet is changed, while the airflow at the other secondary air inlets remains unchanged. In the redistribution scenario where the total secondary air volume remains constant, we will increase... Figure 2 The airflow distribution ratio of the rightmost secondary air inlet is calculated, and the airflow of the remaining secondary air inlets is reduced proportionally. The baseline outlet temperature is 470.9℃, and the dry basis volume fractions of O2, CO2, CO, and N2 at the outlet are 2.63%, 22.50%, 0.66%, and 74.21%, respectively. The calculation results for different secondary air disturbance conditions are shown in Table 3 below.

[0107] Table 3 Calculation Table for Different Secondary Wind Disturbance Conditions Compared to the baseline operating condition, Figure 2 When the air volume of the rightmost secondary air outlet increases by 10%, the outlet temperature decreases by 15.7℃, O2 increases by 0.55 percentage points, and CO decreases by 0.13 percentage points, indicating that the increase in secondary air near the outlet side has a significant impact on outlet cooling and oxygen supply. Figure 2 When the air volume of the rightmost secondary air outlet increases by 10%, the outlet temperature increases by 4.7℃, O2 increases by 0.25 percentage points, and CO decreases by 0.15 percentage points, indicating that the local secondary air at different axial positions has different response characteristics to the outlet thermal state and CO residue.

[0108] With the total secondary air volume remaining constant, increase Figure 2 Under the condition of the secondary air distribution at the rightmost vent, the outlet temperature decreased from 470.9℃ to 462.7℃, the outlet O2 increased from 2.63% to 2.98%, and the CO decreased from 0.66% to 0.58%. This result indicates that, with the total secondary air volume remaining constant, changing only the secondary air spatial distribution can still alter the outlet temperature, O2, and CO, demonstrating that the secondary air spatial distribution has an independent axial position effect.

[0109] Based on the calculation results of changes in total secondary air volume, local secondary air disturbances, and spatial redistribution under the condition of constant total secondary air volume, secondary air inlets at different axial positions exhibit different response characteristics to outlet temperature, O2, and CO. Increasing the total secondary air volume can increase outlet O2 and decrease CO, but may simultaneously decrease the outlet gas phase temperature. Local secondary air adjustment can utilize the differences in effects at different axial positions to control outlet temperature changes while altering oxygen supply and residual CO. Therefore, the direction of adjustment for total secondary air volume and spatial distribution can be determined based on the combined responses of outlet temperature, O2, and CO under different secondary air disturbance conditions relative to the baseline condition.

[0110] like Figure 4 As shown, when a certain secondary air operating parameter change condition cannot meet the preset outlet temperature, O2 and CO range, the total amount of secondary air or spatial allocation can be further changed and recalculated; in the above operating condition screening process, only the secondary air operating parameters are changed, and the zonal apparent source term parameters that have been independently verified are not readjusted.

[0111] The above-mentioned secondary air parameter adjustment process is used to evaluate the impact of different secondary air conditions on the thermal state of the rotary kiln and to provide the direction of operating parameter adjustment. It does not involve redetermining the apparent source term parameters using the measured output during the independent verification period.

[0112] Alternative implementation methods; 1. The length, diameter, number of coal guns, number of secondary air inlets, and axial position of the rotary kiln can be determined according to the actual equipment structure; the number of axial source areas is not limited to the 6 in this embodiment, and can be adjusted according to the working range of the coal guns, the position of the secondary air inlets, the spatial relationship of the bed, and the axial thermal characteristics.

[0113] 2. The equivalent bed can adopt an isotropic or anisotropic porous media resistance model, and its porosity, viscous resistance coefficient and inertial resistance coefficient can be determined according to the actual bed structure, material properties or industrial operating conditions.

[0114] 3. The apparent heat source and equivalent heat source or equivalent heat sink of the bed in the gas phase of the partition can be in the form of piecewise constant, piecewise linear or other parameterized functions; in addition to O2, CO2 and CO, the apparent component source can also be other gas components with stable industrial measurement data and that can reflect the net conversion state of the corresponding process.

[0115] 4. The first and second stable operating cycles are not limited to calendar years, as long as they do not overlap in time; during the independent verification process of the second stable operating cycle, the measured verification quantities are not used to redetermine the partition apparent source term parameters that have already been determined in the first stable operating cycle.

[0116] 5. The independently validated set of zonal apparent source terms can also be used to analyze spatial redistribution conditions under conditions of single or multiple secondary air inlet air volume changes and constant total secondary air volume; the zonal apparent source term parameters are kept constant in each condition, and the impact of secondary air spatial distribution is evaluated based on the response changes of outlet temperature, O2 and CO relative to the baseline condition.

Claims

1. A method for determining apparent source terms in a rotary kiln zone, characterized in that, include: Step S1: Stable operation of industrial data screening; Acquire stable operating cycle data for two non-overlapping time periods of the rotary kiln. The data from the first stable operating cycle is used as the apparent source term determination data, and the data from the second stable operating cycle is used as the independent verification data. The stable operating cycle data includes material feed rate, fuel input rate, operating parameters of multiple secondary air inlets, dry basis composition of outlet flue gas, and gas phase temperature at multiple axial positions. Step S2: Establish the computational domain and partition the axial source terms; establish the computational fluid dynamics computational domain according to the actual geometric dimensions of the rotary kiln, and divide the fluid dynamics computational domain into a gas phase region and an equivalent bed region; divide multiple source term regions along the axial direction of the rotary kiln according to the range of action of the coal gun, the axial position of multiple secondary air inlets, and the spatial relationship of the bed. Step S3: Construct zoned heat sources, zoned heat sinks, and target mass fraction-limited component sources; In the gas phase region, apparent heat sources are set up in each source term region to characterize the unresolved gas phase heat release within the corresponding region. In the equivalent bed region, equivalent bed heat sources or equivalent bed heat sinks are set up in each source term region to characterize the bed's heat absorption, heat release, and its heat feedback to the gas phase. Apparent component sources are set up for O2, CO2, and CO to characterize the apparent net consumption or apparent net generation of components in the rotary kiln. The apparent component sources of O2, CO2, and CO adopt a target mass fraction limitation method to form mass fraction-limited component sources. The local source strength of the apparent component source is determined by the product of the corresponding baseline apparent source strength and the correction factor. The correction factor is determined based on the deviation between the local component mass fraction and the corresponding target mass fraction, and is limited to the range of 0 to 1. Step S4, constrain apparent component sources for dry basis components at the outlet; The initial source strength magnitude of each apparent source term is determined based on the material, fuel and air inputs of the first stable operating cycle; the apparent component source parameters are determined based on the outlet dry basis O2, CO2, CO and N2 of the first stable operating cycle; and the zoned gas phase apparent heat source and bed equivalent heat source parameters or bed equivalent heat sink parameters of each source term zone are determined based on the mass flow weighted average gas phase temperature at multiple axial positions. Step S5 involves determining the heat source and heat sink for multi-axial temperature constraints in different zones, and performing cross-verification of the component-temperature dual indicators. This is followed by sequentially determining the apparent component source parameters, the apparent heat source parameters for the zoned gas phase, and the equivalent heat source parameters or equivalent heat sink parameters for the bed, as well as cross-verifying the outlet flue gas composition and axial gas phase temperature. Steady-state calculations and parameter adjustments are then repeated. If adjusting the apparent component source parameters reduces the deviation in outlet flue gas composition, but the axial gas phase temperature exceeds the allowable range, the adjustment of the apparent component source parameters for that round is cancelled or corrected. Similarly, if adjusting the zoned heat source parameters or zoned heat sink parameters reduces the deviation in axial gas phase temperature, but the outlet flue gas composition exceeds the allowable range, the adjustment of the zoned heat source parameters or zoned heat sink parameters for that round is cancelled or corrected until both the outlet flue gas composition and the axial gas phase temperature simultaneously meet the preset allowable range. Step S6: Fix the location, form, intensity, and target value of the apparent source term; fix the source term region location, apparent source term form, source term intensity, target mass fraction, and equivalent bed parameters that meet the preset allowable range to form a partitioned apparent source term set; Step S7: Form an independently verifiable set of partitioned apparent source items; in the second stable operating cycle, only update the actually changed operating inputs and boundary conditions, and keep the set of partitioned apparent source items unchanged; The calculation model using the partitioned apparent source term set was independently verified based on the measured flue gas composition at the outlet and the gas phase temperature at multiple axial positions during the second stable operating cycle. During the independent verification process, the measured outlet flue gas composition and axial gas phase temperature of the second stable operating cycle are not used to redetermine the apparent source term form, source term region location, source term intensity, target mass fraction, and equivalent bed parameters.

2. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, The stable operation cycle data is obtained by removing records of kiln shutdown, heating, cooling, maintenance, alarms, instrument malfunctions, and non-production stages. The stable operation mean and quantile interval are calculated for the retained data. The outlet flue gas analysis data are uniformly converted into dry basis composition, and the balance other than dry basis O2, CO2, and CO is used as the equivalent N2 content.

3. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, The equivalent bed zone uses porous media to represent the combined effects of the solid bed on gas phase flow resistance, gas-solid contact path and heat exchange under long-term average operating conditions, and adopts the Darcy-Forchheimer type porous media resistance model; the gas phase zone is used to characterize the coal gun jet, secondary air mixing, flue gas axial transport, and gas phase temperature and main gas component distribution.

4. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, The apparent heat source of the gas phase in each zone and the equivalent heat source or heat sink of the bed are all added to the energy conservation equation as volumetric energy source terms. The boundary of the source term zone is determined based on one or more of the following: the range of action of the coal gun, the axial position of the secondary air inlet, the main apparent heat release area, the spatial range of the bed, and the downstream cooling area. The apparent heat source or apparent heat sink in each source term zone is represented by a piecewise constant, piecewise linear, or parameterized function.

5. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, For O2, CO2, and CO, the target mass fraction-limited component sources satisfy: ； and: ； in, S i Components i Local source strength, S i,0 Components i The corresponding baseline apparent source strength, f i As a correction factor; The correction factor corresponding to O2 is: ； The correction factor for CO2 is: ； The correction factor for CO is: ； Here, clip indicates that the correction factor is limited to the range of 0 to 1. This represents the local mass fraction of component O2. This represents the target mass fraction corresponding to component O2. This represents the mass fraction of O2 in the air inlet. This represents the local mass fraction of component CO2. This represents the target mass fraction corresponding to component CO2. This represents the local mass fraction of component CO. This represents the target mass fraction corresponding to component CO. The baseline apparent source strength corresponding to O2 Negative values ​​represent the apparent net consumption of O2, and the baseline apparent source strength of CO2 and CO. and Take positive values, representing the apparent net generation of CO2 and the apparent net generation of CO, respectively.

6. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, During the first stable operating cycle, the outlet dry basis O2, CO2, CO, and N2 are used to determine the baseline apparent source strength and target mass fraction of the apparent component source. The mass flow weighted average gas phase temperature at multiple axial positions is used to determine the zoned gas phase apparent heat source and bed equivalent heat source or bed equivalent heat sink for each source term region. After each round of parameter adjustment, steady-state calculation is performed again, and the outlet flue gas composition and axial gas phase temperature are checked simultaneously. When the parameter adjustment in this round improves the currently determined indicators while another type of check indicator exceeds the corresponding allowable range, the parameter adjustment in this round is canceled or corrected.

7. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, During the second stable operating cycle, the material feed rate, fuel input rate, and one or more of the secondary air inlet air volume or inlet velocity are updated according to the actual operating status, while keeping the computational domain geometry, grid, turbulence model, radiation model, equivalent bed parameters, apparent source term form, source term region location, source term intensity, and target mass fraction unchanged.

8. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, The independent verification simultaneously uses the outlet dry basis O2, CO2, CO, N2 and gas phase temperature at multiple axial positions during the second stable operating cycle as verification quantities, and uses one or more of the following to evaluate the independent verification results of the partitioned apparent source term set: relative error of major gas components, relative deviation of axial gas phase temperature and root mean square error of axial gas phase temperature.

9. The method for determining apparent source terms of rotary kiln partitions according to claim 1, characterized in that, After the apparent source term set of the partitioned area is independently verified, the spatial distribution of gas phase temperature and main gas components inside the rotary kiln is calculated using the apparent source term set of the partitioned area. The secondary air operating parameter variation conditions are set based on the independently verified calculation model. The secondary air operating parameter variation conditions include one or more of the following: increase or decrease of total secondary air volume, change of air volume of one or more secondary air inlets, and redistribution of air volume among different secondary air inlets under the condition that the total secondary air volume remains unchanged. Based on the response changes of outlet temperature, O2 and CO to the baseline conditions under different secondary air operating parameter variation conditions, the total amount of secondary air and the adjustment direction of air volume of each secondary air inlet are determined according to the joint changes of outlet temperature, O2 and CO.

Images