Low-heat-value coal gas flue gas condensing waste heat recovery method and system

Abstract

The application discloses a low-calorific-value coal gas flue gas condensation waste heat recovery method and system, belongs to the field of metallurgical industrial waste heat recovery and flue gas condensation treatment, and aims at solving the problems of low-calorific-value coal gas flue gas dew point, recoverable heat, and continuous fluctuation of user load accompanied by acidic condensation corrosion. The application calculates water dew point and acid risk interval through a hierarchical heat exchange structure, identifies a water condensation front and an acid enrichment front, and realizes stable recovery of sensible heat and latent heat and collaborative control of corrosion, fouling and system resistance through real condensate feedback linkage control of heat exchange, shunting purification, load allocation and unit flushing.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery and flue gas condensation treatment in the metallurgical industry, and particularly to a method and system for waste heat recovery from the condensation of low-calorific-value coal gas flue gas. Background Technology

[0002] In iron and steel metallurgical production, blast furnace gas, converter gas, and other gases are commonly used in boilers, heating furnaces, or other thermal equipment. The composition, moisture content, lower heating value, and combustion load of these gases vary with production conditions, leading to continuous fluctuations in flue gas temperature, flow rate, moisture content, and water vapor dew point. Waste heat recovery from flue gas condensation requires that the heat exchange surfaces be within a temperature range suitable for water vapor condensation, in order to simultaneously recover both the sensible heat of the flue gas and the latent heat of the water vapor.

[0003] Existing flue gas waste heat recovery devices typically employ fixed return water flow rates, fixed inlet water temperatures, or integrated heat exchange structures. Insufficient cooling prevents complete condensation of water vapor, limiting latent heat recovery. Excessive cooling can cause the heat exchange surfaces to remain in the temperature range where acidic components accumulate for extended periods, leading to corrosion, ash buildup, and scaling from the acidic condensate. Relying solely on theoretical dew point control is insufficient to accurately reflect the actual condensation location; unrecognized differences in condensate quality can increase the load on total neutralization and subsequent purification processes.

[0004] Furthermore, the return water temperature and available heat for waste heat users can change. When there is a mismatch between the recovery and utilization sides, the unit needs to reallocate its operating boundaries among latent heat recovery, low-temperature corrosion, and system resistance. If the deep condensation unit becomes contaminated, a complete shutdown for cleaning will reduce continuous operation capability.

[0005] Therefore, there is a need for a method and system for recovering waste heat from the condensation of low-calorific-value coal gas flue gas that can overcome the shortcomings of the existing technologies. Summary of the Invention

[0006] One objective of this invention is to propose a method and system for recovering waste heat from the condensation of low-calorific-value coal gas flue gas. Addressing the problems of existing technologies being unable to adapt to fluctuations in coal gas composition, combustion load, flue gas moisture content, and waste heat user load, as well as discrepancies between theoretical dew point and actual condensation location, and the tendency of acidic condensate to cause corrosion and scaling, this invention proposes a technical solution that involves arranging a sensible heat exchange zone, a transition heat exchange zone, and multiple independently switchable deep condensation units in the flue gas exhaust channel. It calculates the water dew point range and the acid condensation risk range, identifies the water condensation front, acid enrichment front, and front confidence level based on wall temperature and segmented condensate conditions, and adjusts the circulating water flow rate, inlet water temperature, flue gas bypass ratio, and effective heat exchange area through feedforward boundary and dual front feedback linkage. This invention achieves the technical effects of recovering sensible and latent heat according to the actual phase change state, treating condensate separately, adapting to user load, and implementing unit isolation flushing.

[0007] This invention provides a method for recovering waste heat from the condensation of low-calorific-value coal gas, comprising:

[0008] S1. Collect data on the gas combustion process, flue gas status, and waste heat user return water status to determine the flue gas water dew point range and acid condensation risk range.

[0009] S2. Obtain the wall temperature and segmented condensate state of the sensible heat exchange zone, the transition heat exchange zone and multiple independently switchable deep condensation units arranged sequentially along the flue gas flow direction, and determine the water condensation front, acid enrichment front and front confidence level by combining the flue gas water dew point range and acid condensation risk range.

[0010] S3. Using the flue gas water dew point range and acid condensation risk range as feedforward boundaries, and the water condensation front, acid enrichment front and front confidence as feedback correction quantities, determine the control commands for circulating water flow rate, inlet water temperature, flue gas bypass ratio and effective heat exchange area of ​​each heat exchange zone under corrosion constraints and waste heat user return water constraints.

[0011] S4. Operate each heat exchange zone according to the control command, and guide the segmented condensate to the acid purification branch, the reusable fine treatment branch, or the flushing branch according to the collection section and real-time quality of the segmented condensate.

[0012] S5. Update the water condensation front, acid enrichment front, and front confidence based on the segmented condensate splitting results, and use the updated results for steps S2 and S3 in the next control cycle.

[0013] Optionally, S1 includes: performing a material balance of combustion products based on the composition of coal gas or flue gas, combustion load and excess air, and correcting the moisture content of flue gas using exhaust gas temperature, flue gas flow rate and moisture content characterization.

[0014] The water dew point range is determined based on the corrected flue gas moisture content and flue gas pressure.

[0015] The partial pressure of acidic components is determined based on the sulfur-containing and chlorine-containing components in the flue gas and their combustion conversion rates, and the acid condensation risk range is determined based on the partial pressure of acidic components and the wall temperature.

[0016] The moisture content characterization quantity is at least one of the following: humidity detection value, fuel water content, flue gas oxygen content and combustion load combination quantity.

[0017] Optionally, S2 includes: a liquid collection tank that does not cross-contaminate with each other is set below each depth condensation unit, and the condensate flow rate, pH, conductivity and wall temperature of the corresponding unit are detected respectively;

[0018] When the condensate flow rate and wall temperature of adjacent units along the flue gas flow direction show continuous abrupt changes within the preset observation window, the location of the abrupt change is determined as the water condensation front.

[0019] When the pH, conductivity, and wall temperature of adjacent units exhibit continuous abrupt changes within the preset observation window, the location of the abrupt change is determined as the acid enrichment front.

[0020] The continuous mutation is determined by the number of times the absolute value of the difference between the detection quantities of adjacent units within the observation window continuously reaches the corresponding detection quantity threshold. Each detection quantity threshold and the preset number are determined by the calibration data of the location of water dew point and the location of acidic condensate during the trial operation of the equipment.

[0021] Within a pre-set reliability evaluation window, the flow rate of condensate detected in each collection tank is integrated over time and summed to obtain the total amount of condensate in each segment;

[0022] Based on the corrected flue gas moisture content, a gas phase material balance is performed to obtain the theoretical condensate volume. The residual between the theoretical condensate volume and the total condensate volume in segments is compared with the allowable error band of the material balance. The frontier confidence level is determined based on the proportion of the number of samplings in which the residual is located within the allowable error band within the preset confidence evaluation window to the total number of samplings.

[0023] Optionally, S3 includes: maintaining the wall temperature of the sensible heat exchange zone above the upper boundary of the acid condensation risk zone, ensuring that the residence time of the flue gas in the transition heat exchange zone does not exceed the upper limit of the allowable residence time during the period when the corresponding wall temperature crosses the acid condensation risk zone, and ensuring that the wall temperature of the deep condensation unit enters below the water dew point range and maintains a continuous water film as a zone temperature constraint. The upper limit of the allowable residence time is determined by the flue gas residence time calibration data when the water quality of the segmented condensate reaches the acid purification criterion during the equipment trial operation.

[0024] The feedback correction weights for the water condensation front and the acid enrichment front are adjusted based on the front confidence level, and the feasible domain is composed of the zone temperature constraints, the upper limit of the pressure difference of each heat exchange zone, the temperature range of waste heat user return water, and the range of acceptable heat.

[0025] Within the feasible region, the circulating water flow rate, inlet water temperature, and flue gas bypass ratio are determined, and the effective heat exchange area is determined by determining the number of deep condensation units put into operation.

[0026] Optionally, S4 includes: providing independent cooling branches, independent liquid collectors, and three-way diversion valves for each heat exchange zone;

[0027] First, determine whether the pH or conductivity of the condensate in the collection section located at the acid enrichment front and its upstream adjacent collection section meets the acid purification criterion. If it does, direct the condensate in that section to the acid purification branch.

[0028] If the acid purification criterion is not met, then determine whether the pH and conductivity of the segmented condensate located downstream of the water condensation front meet the reuse criterion. If they do, the segmented condensate is directed to the reusable fine treatment branch, and the remaining segmented condensate is directed to the flushing branch.

[0029] The acid purification criteria and reuse criteria are determined based on the influent water quality limits of the corresponding treatment branches.

[0030] Optionally, S5 includes: summing up the condensate volume of the acid purification branch, the reusable fine treatment branch, and the flushing branch within the same preset reliability evaluation window according to the corresponding collection section to obtain the total condensate volume of the segments;

[0031] The residual between the total amount of segmented condensate and the theoretical condensate amount is used to correct the flue gas moisture content, the water condensation front, and the theoretical condensate amount obtained by gas phase material balance based on the corrected flue gas moisture content. The segmented water quality data is used to correct the acid enrichment front, and the pressure difference change of each depth condensation unit is used to update the scaling rate.

[0032] Based on the proportion of the number of samplings within the material balance error band within the evaluation window that are located within the residual between the theoretical condensate volume and the total condensate volume obtained again, the frontier confidence level is redefined, and the redefined frontier confidence level is used to adjust the feedback correction weight in the next control cycle.

[0033] When the diverted condensate volume is abnormal, maintain the flue gas moisture content and water condensation front correction amount of the previous control cycle. When the pH or conductivity is abnormal, maintain the acid enrichment front correction amount of the previous control cycle. When the differential pressure is abnormal, maintain the scaling rate of the previous control cycle. When any of the above abnormalities occur, multiply the front confidence by an abnormality coefficient less than 1 and issue a maintenance alarm. The abnormality coefficient is determined according to the proportion of the effective sampling number of the corresponding detection quantity to the preset sampling number.

[0034] Furthermore, when the load of waste heat users decreases, candidate heat allocation methods are determined under the corrosion constraints and waste heat user return water constraints described in step S3, based on the updated water condensation front, acid enrichment front, and front confidence.

[0035] When the stratified heat storage unit connected to the circulating water loop is in an available state and its remaining heat storage capacity is not less than the heat to be allocated in the current control cycle, stratified heat storage is listed as the first candidate mode, and the available candidate heat allocation modes are activated in the following order: stratified heat storage, reducing the number of deep condensing units put into operation, increasing the inlet water temperature, and increasing the flue gas bypass ratio, until the recovered heat enters the acceptable heat range determined according to the waste heat user return water status.

[0036] Before each activation of the next candidate heat allocation method, it is verified whether the wall temperature of the sensible heat exchange zone is maintained above the upper boundary of the acid condensation risk zone, whether the residence time of the flue gas in the transition heat exchange zone during the period when the corresponding wall temperature crosses the acid condensation risk zone does not exceed the upper limit of the allowable residence time calibrated by the equipment trial operation, and whether the wall temperature of the deep condensation unit enters below the water dew point range and maintains a continuous water film.

[0037] Furthermore, the condensate flow rate of any deep condensation unit is multiplied by the pollutant concentration obtained from the pH and conductivity of the condensate through the trial operation water quality calibration relationship to obtain the condensate pollution load of the deep condensation unit.

[0038] When the differential pressure growth rate of the deep condensation unit reaches the differential pressure growth rate threshold and its segmented condensate contamination load reaches the contamination load threshold, the remaining deep condensation units are kept running and the deep condensation unit is isolated. The low-salt condensate output from the reusable fine treatment branch is then transported to the isolated unit for pulse flushing.

[0039] The flushing process ends when the differential pressure recovery rate of the isolated unit reaches the differential pressure recovery rate threshold and the pH and conductivity of the flushing discharge meet the flushing end water quality criteria.

[0040] The pressure difference growth rate threshold, pollution load threshold, pressure difference recovery rate threshold, and flushing end water quality criterion are determined by the unit trial operation clean status, allowable operating resistance, and flushing branch drainage requirements, and the pressure difference and drainage water quality before and after flushing are used to update the scaling rate.

[0041] Furthermore, the lower limit of the confidence level is determined by the proportion of the number of samplings in which the residual between the theoretical condensate volume and the total condensate volume in the pre-set confidence evaluation window is located within the allowable error band of the material balance to the total number of samplings. The allowable error band of the material balance and the lower limit of confidence level are calibrated by the deviation distribution between the theoretical condensate volume and the measured total condensate volume in the segment during the trial operation of the equipment.

[0042] When the confidence level of the frontier does not reach the lower limit of the confidence level, the number of new deep condensation units is limited, and the wall temperature of the sensible heat exchange zone is kept above the upper boundary of the acid condensation risk zone.

[0043] Once the confidence level of the front recovers to above the lower confidence level, the restriction is lifted based on the consistency of the positions of the water condensation front and the acid enrichment front over two consecutive control cycles.

[0044] On the other hand, the present invention also provides a low-calorific-value coal gas flue gas condensation waste heat recovery system, comprising:

[0045] The exhaust duct, along the flue gas flow direction, is sequentially equipped with a sensible heat exchange zone, a transition heat exchange zone, and multiple independently switchable deep condensation units. Each heat exchange zone is connected to an independent cooling branch and an independent liquid collector. Below each deep condensation unit is a liquid collection tank that prevents cross-contamination. The independent liquid collectors and collection tanks are connected to an acid purification branch, a reusable fine treatment branch, and a flushing branch via three-way diversion valves, respectively. The reusable fine treatment branch is connected to the flushing inlet of each deep condensation unit. The exhaust duct has a flue gas bypass branch that bypasses at least part of the heat exchange zone, and this bypass branch is equipped with a bypass regulating valve. The detection components include wall temperature sensors and differential pressure sensors installed in each heat exchange zone, and condensate flow, pH, and conductivity detectors installed in each liquid collector and collection tank. The system includes a gas combustion process data interface, a flue gas status data interface, and a waste heat user return water status interface. A data acquisition and interval calculation module is connected to the detection components and the gas combustion process data interface, flue gas status data interface, and waste heat user return water status interface. The system comprises the following components: a port connection for determining the flue gas water dew point range and the acid condensation risk range; a dual-front identification module connected to the data acquisition and range calculation module for determining the water condensation front, acid enrichment front, and front confidence level based on the output of the detection components and the range; a staged heat exchange control module connected to the dual-front identification module, each independent cooling branch, each deep condensation unit, and the bypass regulating valve for generating and executing control commands for circulating water flow rate, inlet water temperature, flue gas bypass ratio, and effective heat exchange area; a condensate diversion module connected to the dual-front identification module and the three-way diversion valve for diverting condensate according to the collection stage and real-time quality, and outputting the diverted condensate volume, water quality data, and resistance status to the dual-front identification module; and a calibration and operation handling module connected to the dual-front identification module, the staged heat exchange control module, the flushing branch, and the stratified heat storage unit in the circulating water loop for updating the water condensation front, acid enrichment front, front confidence level, and scaling rate, and performing heat allocation or unit isolation flushing.

[0046] The beneficial effects of this invention are:

[0047] 1. By using feedforward calculations of the water dew point range and acid condensation risk range, and feedback correction of the water condensation front, acid enrichment front and their confidence levels, the staged heat exchange control can be adjusted according to the changes in the gas combustion process and flue gas state, taking into account both the recovery of latent heat of condensation and the constraint of low-temperature corrosion.

[0048] 2. Through the segmented collection structure that prevents cross-contamination of liquids and the three-way diversion based on the collection segment position, pH and conductivity, acidic condensate, reusable condensate and flushing condensate can be treated separately, and the front-line state can be further corrected by using the condensate volume and water quality.

[0049] 3. By using stratified heat storage when user load decreases, reducing the operation of cryogenic units, raising the temperature of cooling medium and regulating flue gas bypass, as well as independent isolation of contaminated units and low-salt condensate pulse flushing, the system can reduce downtime for cleaning and control the increase in system resistance. Attached Figure Description

[0050] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0051] Figure 1 This is a control flow diagram of the low-calorific-value coal gas flue gas condensation waste heat recovery method of the present invention.

[0052] Figure 2 This is a flowchart of the double frontal identification and confidence calculation in S2 of the present invention. Detailed Implementation

[0053] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0054] refer to Figures 1-2 A method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas, comprising:

[0055] S1. Collect data on the gas combustion process, flue gas status, and waste heat user return water status to determine the flue gas water dew point range and acid condensation risk range.

[0056] S2. Obtain the wall temperature and segmented condensate state of the sensible heat exchange zone, the transition heat exchange zone and multiple independently switchable deep condensation units arranged sequentially along the flue gas flow direction, and determine the water condensation front, acid enrichment front and front confidence level by combining the flue gas water dew point range and acid condensation risk range.

[0057] S3. Using the flue gas water dew point range and acid condensation risk range as feedforward boundaries, and the water condensation front, acid enrichment front and front confidence as feedback correction quantities, determine the control commands for circulating water flow rate, inlet water temperature, flue gas bypass ratio and effective heat exchange area of ​​each heat exchange zone under corrosion constraints and waste heat user return water constraints.

[0058] S4. Operate each heat exchange zone according to the control command, and guide the segmented condensate to the acid purification branch, the reusable fine treatment branch, or the flushing branch according to the collection section and real-time quality of the segmented condensate.

[0059] S5. Update the water condensation front, acid enrichment front, and front confidence based on the segmented condensate splitting results, and use the updated results for steps S2 and S3 in the next control cycle.

[0060] In this specific embodiment, S1 includes:

[0061] This specific implementation takes an industrial furnace exhaust system that uses a mixture of blast furnace gas and coke oven gas as its object. The exhaust channel is set with a sensible heat exchange zone, a transition heat exchange zone and six independently switchable deep condensation units along the flue gas flow direction. The data acquisition and interval calculation module establishes an operating condition record every 5 seconds. The record fields include timestamp, gas component volume fraction, standard volume flow rate of each gas, combustion load, excess air coefficient, fuel moisture content, exhaust temperature, absolute pressure of flue gas, standard volume flow rate of flue gas, humidity detection value, oxygen content of flue gas, waste heat user return water temperature, return water flow rate and upper limit of acceptable heat. All flow rates are uniformly converted to the same standard state and aligned within a 10-second tolerance according to the timestamp.

[0062] The acquisition module first performs range verification and conservation verification on the operating condition records. When the sum of the volume fractions of the gas components deviates from 1 by more than 0.02, the absolute pressure of the flue gas exceeds 80 kPa to 120 kPa, or the flow rate change of adjacent sampling points exceeds 20% of the equipment range without being accompanied by a change in combustion load, the corresponding field is marked as invalid. When a single field is invalid, the median of the three most recent valid sample values ​​is used. When six consecutive sampling points are invalid, the dew point range of the previous control cycle is frozen and a data quality alarm is written to the control module. The waste heat user return water status is calculated by combining the return water temperature, return water flow rate, and the allowable supply water temperature of the user-side heat exchanger to obtain the range of heat that can be received in this cycle.

[0063] The data acquisition and interval calculation module performs gas phase material balance based on the stoichiometric coefficients of the complete combustion of each combustible component, with the baseline water vapor molar flow rate calculated according to... calculate, This represents the baseline water vapor molar flow rate, in units of mol / s; This represents the set of hydrogen-containing combustible components that participate in the water generation calculation, because it is a discrete set of components. This set is generated by filtering the gas component records that have passed range verification and component conservation verification in this control cycle according to the component name. Represents a set The component index is used because it is a discrete index; Indicates the number of moles per mole The stoichiometric coefficients of the components that produce water upon complete combustion are dimensionless values. Indicates the first The molar flow rate of each component is calculated from the component volume fraction and the standard volume flow rate, and the unit is mol / s; The mass flow rate of water entering with the fuel is expressed in kg / s. It is obtained by multiplying the mass fraction of fuel water content after range verification and time alignment in this control cycle by the corresponding fuel mass flow rate. If any input is invalid, the median of the three most recent valid sample values ​​is used according to the data quality rules in step S1. If six consecutive points are invalid, the results of the previous cycle are frozen. This represents the molar mass of water, taken as 0.018 kg / mol.

[0064] The humidity detector first converts the humidity reading into the measured water vapor molar flow rate based on the instrument's temperature and pressure compensation curve, and then the module... Correcting the moisture content of flue gas, This represents the corrected water vapor molar flow rate, in mol / s. The formula for the baseline water vapor molar flow rate is taken from the aforementioned formula and its immediate interpretation in this step, and the unit is mol / s; This indicates the water vapor molar flow rate used for correction in this cycle, in mol / s. This represents the humidity correction factor, a dimensionless value ranging from 0 to 1, and is stored in the moisture content correction parameter table; when the humidity detection value is valid, Calculated from humidity readings, exhaust temperature, and flue gas flow rate. Take 0.70; when the humidity detection value is invalid but the fuel moisture content, flue gas oxygen content, and combustion load are all valid, The calculation is based on the fuel moisture content-oxygen content-load substitution estimation relationship for the corresponding load range in the moisture content correction parameter table, and... The value is 0.35. This substitution relationship is calibrated according to the three sets of stable load tests in step S1 and is only invoked within the valid range of the parameter table; the substitution relationship is also not available by time command. Take 0 and set Meanwhile, the data quality limitation flag from the previous period is maintained until it is removed after 12 consecutive effective humidity sampling points or 12 consecutive sets of effective alternative characterization values ​​are restored.

[0065] The module divides the corrected water vapor molar flow rate by the total wet flue gas molar flow rate to obtain the water vapor molar fraction, and then... Calculate the partial pressure of water vapor. This represents the partial pressure of water vapor, expressed in kPa. This represents the corrected water vapor mole fraction, a dimensionless value between 0 and 1. The absolute pressure of the flue gas, expressed in kPa, is obtained by the absolute pressure field of the flue gas written into the operating condition record by the pressure detector in the flue gas exhaust channel after range verification, time alignment and invalid value rollback in step S1. Then, linear interpolation is performed in the built-in saturated water vapor pressure table using water vapor partial pressure as the search key. The pressure table fields include partial pressure, saturation temperature, version number and effective time. In this specific embodiment, IAPWS calibration data with a resolution of 0.1 kPa is used, and the obtained saturation temperature is used as the center value of water dew point.

[0066] The lower and upper limits of the water dew point range are obtained by looking up the table at the minimum and maximum values ​​formed by the combined minimum and maximum values ​​of the corrected water vapor mole fraction, the instrument allowable error, the material balance deviation, and the flue gas pressure measurement error. The range results are recorded as the lower dew point limit, the center dew point value, the upper dew point value, the calculation time, and the validity flag. If the lookup key exceeds the calibration range of 0.5 kPa to 40 kPa, the adjacent boundary value is used and the validity flag is set to restricted. No new deep condensation units may be added to the control module under restricted conditions.

[0067] The combustion conversion of sulfur-containing and chlorine-containing components is calculated based on the gas composition, combustion load, excess air coefficient, and conversion rate parameters obtained from equipment trial operation. The molar flow rates of sulfur dioxide, sulfur trioxide, and hydrogen chloride are obtained respectively. These are then divided by the total molar flow rate of wet flue gas and multiplied by the absolute pressure of flue gas to obtain the corresponding partial pressure of acidic components. The acidic component conversion rate parameter table uses the gas source, combustion load range, and excess air coefficient range as the joint search key. The fields include the conversion rate of each acidic component, effective range, trial operation batch, and version number. If the search key is not matched, the conservative parameter record that causes the acid dew point to rise in the adjacent load range is selected.

[0068] The moisture content correction parameter table and the acid component conversion rate parameter table were constructed by three sets of stable load tests before the equipment was put into operation. Each set of tests was held for at least 30 minutes and the gas analysis, online humidity, flue gas oxygen content, flue gas flow rate and condensate mass were saved simultaneously. The parameter fitting adopted the bounded least squares rule with the minimum absolute value of the material balance residual. The parameters fitted by the first two sets of tests were taken and verified by the third set of tests. When the relative error of the water vapor molar flow rate exceeds 8% or the error of the first acid condensation temperature exceeds 3℃, the version is rejected. If the limit is exceeded for three consecutive evaluation windows during operation, it will fall back to the previous valid version and generate a recalibration task.

[0069] The interval calculation module also saves the dew point uncertainty source record, which is written into the repeatability of gas component analysis, flow meter allowable error, humidity detector allowable error, pressure transmitter allowable error and acid component conversion rate confidence range respectively. When calculating the upper and lower limits, the lower limit of the interval is taken for error combinations that may cause the dew point to decrease, and the upper limit of the interval is taken for error combinations that may cause the dew point to increase. Errors of different units are not directly added together. All instrument errors are first applied to their original measurements and then the material balance and pressure gauge interpolation are repeatedly performed.

[0070] The interval calculation module uses the partial pressure of acidic components, the current partial pressure of water vapor, and the zone wall temperature as search terms, and performs trilinear interpolation in the acid condensation calibration table established during equipment trial operation. The zone wall temperatures are taken from fixed-numbered wall temperature sensors in the sensible heat exchange zone, the transition heat exchange zone, and the six deep condensation units. Each sensor value is first corrected according to its calibration record's slope and intercept, then aligned by the control cycle number, and the arithmetic mean of the effective sampled values ​​within the same 60-second control cycle is taken. Each heat exchange zone or deep condensation unit forms a zone wall temperature. The calibration table is constructed from the records of segmented condensate under different combustion loads where the pH is not higher than 4.5 and the conductivity is not lower than 800 μS / cm for the first time. Fields include zone number, acidic component partial pressure combination, wall temperature, first acid condensation temperature, standard deviation of repeated measurements, and sample batch. The module performs trilinear interpolation on the sensible heat exchange zone, the transition heat exchange zone, and the six deep condensation units respectively. Interpolation yields eight local first acid condensation temperatures, and each temperature is adjusted by adding or subtracting twice the standard deviation to form eight local acid condensation risk intervals. The minimum value among the lower limits of the eight local intervals is fixed as the lower limit of the system-level acid condensation risk interval, and the maximum value among the upper limits of the eight local intervals is fixed as the system-level upper limit. If any partition has no effective wall temperature in the current cycle, the median of the three most recent effective sampled values ​​for that partition is used first. If six consecutive sampled points are invalid, the system-level acid condensation risk interval of the previous control cycle is maintained and a wall temperature data quality alarm is written. Other partitions are not used to replace the faulty partition. After 12 consecutive effective sampled points, the eight partitions are merged. Finally, the flue gas water dew point interval, the system-level acid condensation risk interval, the eight local intervals and their segment numbers, the corrected flue gas moisture content, and the range of heat that users can receive are written into the feedforward boundary record of the current cycle and sent to steps S2 and S3.

[0071] In this specific embodiment, S2 includes:

[0072] The dual-front-edge recognition module reads the feedforward boundary record formed in step S1 and simultaneously collects the wall temperature and pressure difference of the sensible heat transfer zone, the transition heat transfer zone, and the six deep condensation units. Each deep condensation unit is equipped with a liquid collection tank that does not cross-contaminate with each other. The liquid collection tank records are written according to the unit number, including condensate flow rate, pH, conductivity, liquid level, wall temperature, valve status, and sampling validity mark. The unit of condensate flow rate is uniformly kg / h, the conductivity is compensated at 25℃ temperature to μS / cm, the unit of wall temperature is ℃, and the sampling period is the same as in step S1, which is 5 seconds.

[0073] The module performs time alignment and three-point median filtering on the detection volume of each collection tank. When the pH exceeds 0 to 14, the conductivity is less than 0 or higher than 20000 μS / cm, the condensate flow rate is negative, or the wall temperature exceeds 0℃ to 250℃, the sampling point is marked as invalid. When the effective sampling ratio of a certain unit within the 10-minute preset observation window is less than 0.8, the unit does not participate in the front edge position update of this window and uses the position of the previous window. After the detection is restored, it will be re-added to the identification only after 12 consecutive effective sampling points are obtained.

[0074] For detection volume Modules are Calculate the difference between adjacent cells. Indicates the first The sampling time of the first sampling moment The unit and the downstream first Absolute difference in detection quantity between units, unit and detection quantity same; Indicates the first The sampling time of the first sampling moment The current detection count of each unit, Indicates the downstream of the same sampling time. The current detection volume of each unit, both the unit and the data source are different. The selection is determined by the condensate flow rate, pH, conductivity, or wall temperature. Indicates the selected current detection quantity. This represents the upstream element index of adjacent depth condensation element pairs arranged along the flue gas flow direction, and takes values ​​from 1 to 5. The index represents the sampling time within the observation window and ranges from 1 to 120. The threshold is retrieved from the double-front calibration parameter table by combustion load range and unit pair number.

[0075] The dual-front calibration parameter table is generated by manually confirming the location of water dew point and acidic condensate during equipment trial operation. The fields include unit pair number, load range, condensate flow difference threshold, pH difference threshold, conductivity difference threshold, wall temperature difference threshold, number of consecutive tests, and version number. In this specific embodiment, the number of consecutive tests is set to 8, that is, when at least 8 of the 10 most recent valid sampling points reach the threshold in chronological order and the last 3 sampling points also reach the threshold, it is considered as a continuous change. For a record with a load of 70% to 80%, the condensate flow difference threshold is set to 3 times the standard deviation of the stable value of the unit pair during trial operation, and the wall temperature difference threshold is set to 2.0℃.

[0076] When the condensate flow rate difference and wall temperature difference of the same unit pair both meet the continuous change condition, and the average wall temperature upstream of the unit pair is higher than the water dew point center value and the average wall temperature downstream is lower than the water dew point center value, the module determines the position between the unit pairs as the water condensation front. If multiple conditions are met at the same time, the position that first crosses the water dew point interval along the flue gas flow direction is selected. The position record is represented by the dimensionless segment number of the upstream unit plus 0.5, and the corresponding flow rate difference, wall temperature difference and window start and end time are saved at the same time.

[0077] When the pH difference, conductivity difference, and wall temperature difference of the same unit pair all meet the continuous abrupt change condition, and the pH of the downstream collection tank decreases, the conductivity increases, and falls into the wall temperature range of the corresponding local acid condensation risk interval determined in step S1, the module lists the position between the unit pairs as acid enrichment front candidates; if the pH does not decrease or the conductivity does not increase, no candidate unit pair is generated and the unit pair is marked as water quality direction conflict; when multiple candidates are established at the same time, they are first sorted by the average pH of the downstream collection tanks in this window from small to large. If the average pH is the same, they are sorted by the average conductivity compensated at 25℃ from large to small. If both are the same, they are sorted by the candidate segment along the flue gas flow direction from upstream to downstream, and the only segment with the first ranking is taken as the acid enrichment front; when all candidates are excluded due to direction conflict, the acid enrichment front of the previous window is maintained and this window is marked as water quality conflict.

[0078] During equipment trial operation, each liquid collection tank sensor is cross-calibrated using the same standard solution and the same constant temperature bath. The flow meter uses the weighing method to obtain the slope and zero point. The pH detector is calibrated using two-point buffer solution. The conductivity detector is calibrated using standard conductivity solution. The wall temperature sensor is calibrated using three points at 0℃, 50℃ and 100℃. The sensor calibration record saves the slope, intercept, allowable drift, calibration date and expiration date using the unit number and sensor serial number as the joint key. The operating value is first corrected by the corresponding slope and intercept before entering the adjacent difference calculation. Sensors that have exceeded their expiration date are only retained for monitoring purposes.

[0079] Candidate locations for water condensation fronts are generated when all three conditions are met: continuous abrupt changes in condensate flow rate, continuous abrupt changes in wall temperature, and crossing of the water dew point range. Candidate locations for acid enrichment fronts are generated when all four conditions are met: continuous abrupt changes in pH, continuous abrupt changes in conductivity, continuous abrupt changes in wall temperature, and consistency of the corresponding local acid risk range. Candidates for water condensation fronts are sorted from upstream to downstream along the flue gas flow direction, and the first crossing location is selected. Candidates for acid enrichment fronts are strictly sorted using the aforementioned three-level full sorting: ascending average pH, descending average conductivity, and ascending segment, and the first item is selected. Undefined acid evidence strength is no longer used. If the selection set is empty but a valid segment from the previous window exists, the segment from the previous window is used. When starting for the first time or when there is no valid segment from the previous window, the corresponding model prediction front segment is written as a restricted temporary segment and the feedback weight of the front is reset to 0. If water condensation is not predicted, the water condensation front is placed at the downstream boundary segment 6.5 of the sixth unit. If acid enrichment is not predicted, the acid enrichment front is placed at the downstream boundary segment 6.5 of the sixth unit. At the same time, the addition of new deep condensation units is prohibited and the relevant condensate is diverted according to the conservative branch without relaxing the water quality criteria. The temporary state is canceled and normal feedback correction is restored only after two consecutive windows have obtained valid candidates.

[0080] Within the same 10-minute preset reliability evaluation window, the module uses the actual non-bypass flue gas passing through the six deep condensation units and its six independent collection tanks to form the condensate material balance control body, and follows the... Calculate the total amount of condensate in each stage. This indicates the total amount of condensate in the segment of this control body within the evaluation window, in kg. Indicates the first The deep condensation unit in the first The condensate mass flow rate at each sampling time, in kg / h. This indicates the index of the deep condensation unit, and the index ranges from 1 to 6. This represents the index of the sampling time within the evaluation window, ranging from 1 to 120. This represents the time interval between adjacent sampling moments; in this specific implementation, it is set to 5 seconds. This represents the conversion factor between hours and seconds, with the conversion unit being s / h, derived from the fact that one hour equals 3600 seconds. Invalid sampling points are obtained by linear interpolation between two adjacent valid points, and the number of interpolation points must not exceed 20% of the total number of points in the window. When the proportion of invalid sampling in any deep condensation unit exceeds 20% or there are sampling points that cannot be linearly interpolated between two adjacent valid points in time, the module marks the entire material balance window as invalid and does not output any new data. , , and If the current window does not perform moisture content correction and front-edge position update, the flue gas moisture content and the two front-edge positions will retain the correction results of the previous valid window, and the front-edge confidence will be directly set to 0 and written to the material balance data quality alarm. Only if the effective sampling ratio of all six units is not less than 0.8 within a subsequent complete 10-minute window, all other invalid points can be interpolated according to the above rules, and all six flow detection chains have 12 consecutive valid sampling points, will the current window be restored. , , , The calculation of the frontier confidence level; the condensate in the sensible heat transfer zone and the transition heat transfer zone is separately diverted and metered, and is not included in this control volume;

[0081] The theoretical condensate volume is obtained by multiplying the water vapor molar flow rate corrected in step S1 by one and subtracting the flue gas bypass ratio at the same sampling time to get the actual water vapor molar flow rate entering the deep condensation unit. This is then combined with the saturated moisture content corresponding to the flue gas temperature at the deep condensation unit outlet and the window duration for gas-phase material balance calculation. The module calculates the window residual. , This represents the window residual between the theoretical condensate volume and the total condensate volume in segments, expressed in kg. This indicates the theoretical condensate volume of the six control units within the evaluation window, in kg. The total volume of condensate is taken from the aforementioned formula and its complete definition, in kg; to support step-by-step determination, the module performs the following at each sampling time. according to Calculate the cumulative residual. This indicates the cumulative total from the start of the window up to the [number]. The residuals at each sampling time point, in kg. This represents the theoretical condensate volume accumulated based on the hourly non-bypass flue gas flow rate, in kg. This indicates that the flow rate of the six deep condensation units is accumulated from the beginning of the window to the [number missing]. The measured condensate volume at each sampling time, in kg. This represents a discrete sampling index from 1 to 120; the module then... Calculate the cumulative relative residual. Indicates the first The cumulative relative residual at each sampling time point is a dimensionless value. The value is taken from the aforementioned cumulative residual formula and the unit is kg. The data is taken from the aforementioned hourly theoretical condensate volume and is in kg. The zero protection mass, which represents the cumulative residual normalization, is fixed at 10 kg in this specific embodiment. The source is the minimum theoretical condensate volume that can be stably identified during the equipment trial operation. This indicates that from two quantities both in kg, the value not less than the other is taken as the denominator; each Compared with the dimensionless allowable error band calibrated by the cumulative relative residual distribution of the trial run under the same cumulative duration, the unit of kg is no longer used. Directly compare with the dimensionless error band;

[0082] Frontier confidence level Sure, This represents the frontier confidence level, a dimensionless value ranging from 0 to 1. Indicates the cumulative relative residual within the evaluation window. Located in the same position as the The number of sampling times, corresponding to the cumulative duration of each sampling moment, within the allowable error band of the dimensionless material balance, and for which all detection quantities involved in frontier identification are valid. This indicates the preset total number of samples within the evaluation window; in this specific implementation, it is 120. Both are performed using the same window, the same interpolation rule, and the same... Statistics on zero protection value and version of the same error band; if a water quality conflict occurs, any front edge can only use the previous window position or is in a restricted temporary segment, then before the abnormal coefficient correction in step S5, the original confidence level of the window is limited to 0.7.

[0083] The dual-front identification unit writes the water condensation front segment, acid enrichment front segment, front confidence, evidence of each continuous mutation, total amount of segmented condensate, theoretical condensate volume, residual and data quality flag into the dual-front status record, sends it to step S3 with the control cycle number as the primary key, and retains the segmented detection data for use in steps S4 and S5.

[0084] In this specific embodiment, S3 includes:

[0085] The graded heat exchange control module reads the feedforward boundary record of step S1 and the double leading edge status record of step S2 in a control cycle of 60 seconds. At the same time, it reads the circulating water flow rate, inlet water temperature, valve position, pressure difference of each heat exchange zone, deep condensation unit switching status, waste heat user return water temperature and acceptable heat range of each independent cooling branch to form a control status record. The control command fields include the circulating water flow rate set value of sensible heat exchange zone, transition heat exchange zone and deep condensation zone, common inlet water temperature set value, flue gas bypass ratio, set of activated unit numbers and effective period.

[0086] The module uses the heat exchange response model formed during equipment trial operation to predict the wall temperature, outlet flue gas temperature, recovered heat and pressure difference under each candidate control combination. The response model takes combustion load, flue gas flow rate, inlet water temperature, circulating water flow rate in each zone, bypass ratio and set of input unit numbers as inputs, and uses the measured deviation of the most recent three control cycles for rolling correction. The model parameter table stores heat transfer coefficient, flow index, pressure difference coefficient, applicable range and version number according to the equipment cleanliness status and scaling rate range. When the search key is not matched, the conservative adjacent record with the heat transfer coefficient lowered and the pressure difference coefficient higher is used.

[0087] The heat exchange response model adopts a gray box structure that combines zoned energy conservation with trial operation parameter fitting. The sensible heat exchange zone and the transition heat exchange zone are established with calculation nodes based on the equal enthalpy difference between the flue gas side and the water side. The six deep condensation units are each added with latent heat nodes determined by the difference between the inlet moisture content and the outlet saturated moisture content. The model input records include the current operating condition field and the candidate control field. The output records include the wall temperature, flue gas residence time, outlet flue gas temperature, recovered heat, return water temperature and pressure difference of each zone. The trial operation samples are fitted with parameters in the first 70% in chronological order, the middle 15% are selected with regularization coefficients, and the last 15% are used to verify the prediction error.

[0088] The model acceptance requirements are to verify that the average absolute error of the wall temperature does not exceed 2℃, the relative error of the recovered heat does not exceed 6%, and the relative error of the pressure difference does not exceed 8%. After each control cycle, the measured output is subtracted from the model output of the same period to form a deviation vector. The weighted average of the deviations of the most recent three cycles is used as the output correction amount for the next cycle, and the correction amount shall not exceed 10% of the corresponding output range. If the error exceeds the acceptance error for three consecutive cycles, the parameter version is frozen, the addition of new deep condensation units is prohibited, and the clean status check and model recalibration process is called.

[0089] Front feedback correction weights Calculate and limit to 0.2 to 0.95. This represents the frontier feedback correction weight, which is a dimensionless value. This represents the frontier confidence level obtained in step S2, which is a dimensionless value between 0 and 1; This represents the lowest measured feedback weight that is retained; it is a dimensionless value. This represents the adjustable span from the lowest to the highest weight, and is a dimensionless value. Both are calibrated offline by the trial run's leading-edge positioning error and control stability: the parameter pair with the largest adjustable span is selected from combinations where the average absolute error of the leading-edge segment does not exceed 0.5 units and there is no overshoot exceeding the acid risk hard constraint for 20 consecutive control cycles, and saved according to the heat transfer response model version; the module then... Obtain the corrected leading edge segment. This indicates the correction front segment used for control constraints; it is a dimensionless element segment. This represents the leading edge segment predicted by the dew point range in step S1 and the heat transfer response model. This indicates the measured frontal segment in step S2. Both segments are expressed using the unit number plus 0.5. The water condensation front and the acid enrichment front are subject to the same correction rule. When the restricted temporary segment is written in step S2, this feedback formula is not substituted, but instead, it is directly set... Take 0 and set ;

[0090] The status fields in the control status record store combustion load, flue gas flow rate, dew point upper and lower limits, acid risk upper and lower limits, two correction front segments, front confidence, wall temperature of each zone, pressure difference of each zone, return water temperature, upper and lower limits of acceptable heat, and scaling rate in a fixed order. The candidate action fields store circulating water flow rate of three heat exchange zones, inlet water temperature, bypass ratio, and six-bit unit switching code in a fixed order. The candidate generator enumerates actions only within the range allowed by the equipment range, maintenance isolation flag, and the new input limit added in step S5, thereby enabling each candidate control combination to have traceable input status, action fields, and constraint judgment results.

[0091] The control module sets the first zone temperature constraint as the predicted wall temperature of the sensible heat exchange zone not being lower than the upper boundary of the acid condensation risk zone plus 3℃. The second zone temperature constraint is set as the predicted residence time of the flue gas in the transition heat exchange zone during the period when the wall temperature crosses the acid condensation risk zone not exceeding the upper limit of the allowable residence time. The third zone temperature constraint is set as the predicted wall temperature of the deep condensation unit not being higher than the lower limit of the water dew point zone minus 2℃ and the corresponding liquid level of the collection tank and the condensate flow rate meeting the continuous water film criterion. The continuous water film criterion is that the condensate flow rate is always higher than the minimum film-forming flow rate determined in the trial operation within the last 60 seconds and there are no two consecutive invalid sampling points.

[0092] The upper limit of the allowable residence time is determined by taking the 10th percentile of the flue gas residence time sample when the pH of the condensate reaches no higher than 4.5 or the conductivity is no lower than 800 μS / cm during the equipment trial operation. The sample is then written into the corrosion constraint table according to the combustion load range. The table fields include the load range, acid condensation risk range, upper limit of allowable residence time, minimum film formation flow rate, safe temperature difference in the sensible heat zone, safe temperature difference in the cryogenic zone, calibration batch and version number. When the operating data exceeds the load range in the table, the shorter allowable residence time and the larger safe temperature difference in the adjacent record are used.

[0093] Before generating candidate control combinations, the module first performs a load reduction judgment (described later) and obtains the initial heat to be allocated for the current cycle. Then, it generates candidate control combinations using a 5% step size for the circulating water flow rate in each heat exchange zone, a 1℃ step size for the inlet water temperature, a 0.02 step size for the flue gas bypass ratio, and an integer variation in the number of deep condensing units. Combinations that do not meet the three zone temperature constraints, the upper limit of the differential pressure in each zone, the pump and valve range, and the single-cycle change rate limit are first eliminated. For cycles where the initial heat to be allocated is greater than 0, if the stratified heat storage units are available, the remaining heat storage capacity is first divided by the duration of the current control cycle (60 seconds) to obtain the absorbable power corresponding to the capacity. This is then compared with the rated charging power, and the smaller value is taken. The absorbable power is then subtracted from the predicted recovered heat power of each candidate combination, and the resulting net waste heat delivered to users is used for the range of acceptable heat power. Enclosure verification; if the limit is still exceeded after deduction, or the stratified heat storage unit is unavailable, then combinations are generated step by step in the order of reducing the number of deep condensing units put into operation, increasing the inlet water temperature, and increasing the flue gas bypass ratio. After each additional action, the net waste heat user heat power is re-predicted and verified. For cycles where the initial heat to be allocated is equal to 0, the user-side verification is performed directly using the candidate combination to predict the recovered heat power. The module then removes combinations where the predicted return water temperature or net waste heat user heat power exceeds the range of the waste heat user return water temperature and the range of the acceptable heat power. The retained combinations are sorted in order of the smallest absolute deviation between the center value of the net waste heat user heat power and the center value of the acceptable heat power, the smallest pump power, the smallest flue gas bypass ratio, and the fewest changes in the switching state. If the sorting is completely the same, the set of units put into operation in the previous cycle is maintained.

[0094] After the control combination is determined, the module limits the circulating water flow rate of the sensible heat exchange zone and the transition heat exchange zone to no more than 10% of the current value per cycle, the circulating water flow rate of the deep condensation zone to no more than 15% of the current value per cycle, the inlet water temperature to no more than 2℃ of the current value per cycle, and the bypass ratio to no more than 0.05 of the current value per cycle. The control instructions are written in the following order: first adjust the circulating water flow rate, then adjust the inlet water temperature, then change the number of deep condensation units in operation, and finally change the flue gas bypass ratio, so as to avoid multiple actuators changing simultaneously in the same cycle.

[0095] Load reduction determination is performed before candidate generation and user-side acceptable range filtering: when the waste heat user load decreases and At that time, the module calculates the initial heat to be allocated. , This indicates the initial heat to be allocated in the current control cycle, in kJ. This represents the recovered heat power in kW before the candidate is determined. The initial state for this cycle is preferentially taken from the water-side heat metering value at the end of the previous control cycle, after range verification and time alignment. Only during the first startup or when the measured value from the same period is invalid, is the recovered heat power predicted by the heat exchange response model for the current actual valve and pump state used; values ​​already obtained in the current cycle are not taken. Output of candidate combinations filtered by the upper limit; This indicates the upper limit of the heat power that the waste heat user can receive, in kW. It is directly taken from the newly arrived upper limit of the waste heat user's receiveable heat in step S1 of this control cycle. This field is stored according to the upper and lower limits of power. When the waste heat user interface provides the upper limit of the heat that can be received in this control cycle in kJ, the module divides the upper limit of heat by the duration of the same control cycle. After converting kJ / s to kW, write Energy values ​​must not be directly correlated with Compare; This indicates the control cycle duration; in this specific implementation, it is taken as 60 seconds. The product of kW and seconds equals kJ. season Take 0 and do not trigger heat storage charging or sequential reduction actions; when When the value is greater than 0 and the stratified heat storage unit is available, the portion not exceeding its remaining capacity and rated charging power is written into the heat storage charging candidate. For the remaining heat that still needs to be allocated after stratified heat storage, candidate control combinations are generated step by step in the order of reducing the number of deep condensing units put into operation, increasing the inlet water temperature, and increasing the flue gas bypass ratio. At each level, the net waste heat user heat power is re-predicted and verified until it enters the range of heat power that users can receive. At the end of the control cycle, the verified synchronous measured recovered heat power is written into the initial state record of the next control cycle, and new data is received in the next cycle. The current judgment will be re-executed, and no action will be added directly at the end of the current cycle without bypassing candidate generation;

[0096] If the heat storage still exceeds the acceptable heat range or the stratified heat storage unit is unavailable, the module strictly follows the order of reducing the number of deep condensation units in operation, increasing the inlet water temperature, and increasing the flue gas bypass ratio to activate the candidate mode one by one. Before activating the next mode, the heat exchange response model is called again, and the wall temperature of the sensible heat exchange zone is checked to be higher than the upper boundary of the acid condensation risk zone, the residence time in the transition heat exchange zone does not exceed the allowable upper limit, and the deep condensation units still in operation maintain a continuous water film. If any check fails, the candidate mode is skipped without relaxing the corrosion constraint.

[0097] If the feasible region is empty, the control module first maintains the circulating water flow rate and inlet water temperature that met the constraints of the previous cycle, prohibits the addition of new deep condensation units, and increases the flue gas bypass ratio in increments of 0.02. After each increment, the sensible heat zone wall temperature, transition zone residence time, deep cryogenic continuous water film, and differential pressure hard constraints are checked. If the bypass is still not feasible after reaching the equipment's allowable upper limit, or if the previous cycle's instruction no longer meets any hard constraints under the current operating conditions, the module enters a controlled safety state: the flue gas bypass valve instruction is set to the allowable upper limit, new additions are stopped, and isolation is performed in the downstream-to-upstream sequence. The deep condensation unit maintains the cooling water flow rate in the sensible heat exchange zone at the minimum safe flow rate that keeps the wall temperature 3°C above the upper boundary of the acid risk. It outputs a load reduction request to the upstream combustion control and issues a constraint infeasibility latch alarm. The latch is released only after two consecutive control cycles have recalculated to find a feasible combination and all valves and pumps have responded. Finally, the circulating water flow rate, inlet water temperature, flue gas bypass ratio, and the set of activated unit numbers corresponding to the verified or safe state are converted into the effective heat exchange area, written into the control instruction record with a checksum, and sent to step S4 for execution.

[0098] In this specific embodiment, S4 includes:

[0099] After receiving the control command from step S3, the heat exchange operation and condensate diversion module first verifies the control cycle number, command checksum, valve and pump range, and deep condensation unit interlock status. If the verification passes, it adjusts the independent cooling branches, inlet water temperature regulating valves, bypass regulating valves, and deep condensation unit switching valves of each heat exchange zone according to the change rate specified in the command. If the verification fails, it freezes subsequent actions and immediately calls the wall temperature, residence time, pressure difference, and continuous water film hard constraint verification from step S3 according to the current flue gas condition, current valve and pump feedback, and current interlock status. The command from the previous cycle is maintained only if the valve and pump position in the previous cycle still meets all hard constraints; otherwise, the controlled safety state of step S3 is executed directly, and the command is latched to reject the alarm. The latch is released only after the command field is re-verified and the hard constraints of two consecutive control cycles are met.

[0100] The sensible heat exchange zone, transition heat exchange zone, and each deep condensation unit are equipped with independent liquid collectors or liquid collection tanks that do not cross-contaminate with each other. Each liquid collector and collection tank outlet is sequentially equipped with a spring-reset, power-off closed liquid collection outlet isolation valve, a three-way diversion valve, and a dedicated acidic condensate emergency tank passive discharge branch physically isolated from the recycled water. The spring-reset valve of the emergency tank branch is closed during normal power supply and open during complete power failure. The acid purification passage valve and the reusable passage valve are both closed during complete power failure. The diversion module records the diversion judgment every 5 seconds, combining the liquid collection section number, valve position, condensate flow rate, pH, conductivity, wall temperature, water condensation front section, acid enrichment front section, and front confidence level. A switching condition is used when three consecutive valid sampling points obtain the same judgment. Safety controllers, branch flow meters, emergency tank level gauges, outlet isolation valves, and necessary switching actuators are also included. The operating mechanism must be maintained by an independent safety power supply for no less than 30 minutes. This duration is determined by adding a 20% margin to the longest time during equipment trial operation from power failure detection to upstream controlled shutdown completion. If the pH or conductivity of any collection section exceeds the range, remains unchanged for six consecutive points, or the effective sampling ratio is lower than 0.8, that section is prohibited from entering or continuing to maintain the reusable fine treatment branch, and that section is sent to the acidic purification branch capacity determination section described later as an invalid water quality section. The acidic purification passage is only opened by the safety controller when both the capacity and branch tolerance determinations are passed. If any determination fails or the valve position is not confirmed within 10 seconds, the collection outlet isolation valve is closed first, then the emergency tank branch is opened, and a deterministic safety path of dedicated temporary storage, unit isolation, and load reduction is executed, while writing an invalid water quality data flag. Normal determination is only restored after 12 consecutive valid sampling points and normal feedback from the three-way valve.

[0101] The acid purification trigger boundary and the receiving boundary of the acid purification branch itself are stored in different fields of the treatment branch influent limit table. The fields include branch number, acid purification pH trigger upper limit, acid purification conductivity trigger lower limit, branch acceptable pH lower limit, branch acceptable pH upper limit, branch acceptable conductivity upper limit, allowable flow rate, effective time and version number. In this specific embodiment, the acid purification pH trigger upper limit of 4.5 and the acid purification conductivity trigger lower limit of 800 μS / cm are read field by field, and the acid purification trigger condition is a pH less than or equal to 4.5 or a 25℃ compensated conductivity greater than or equal to 800 μS / cm. The comparison signs are fixed as less than or equal to and greater than or equal to, respectively. The branch acceptable pH range and acceptable conductivity upper limit are calibrated by the tolerance samples and design influent conditions of the acid purification equipment trial operation and read according to the same version number. They are only used to determine whether the acid purification branch can accept the acid purification and do not replace the aforementioned trigger boundary. When the condensate exceeds the acceptance range, it must not be directly sent into the acid purification equipment. The table update only takes effect in the next control cycle.

[0102] The diversion module first maps the acid enrichment front segment from step S2 to a set of integer collection segments to be checked: when the effective segment is i+0.5 and i is 1 to 5, the downstream i+1 unit is fixed as the collection segment where the front is located, and the i unit is defined as its upstream adjacent collection segment. The collection segments to be checked are taken in ascending order of their numbers. When the model predicts a temporary segment position between 1.5 and 5.5, the same mapping is used. When it is below 1.5, the collection to be checked is truncated into segments 1 and 2. When it is above 5.5 but not in a restricted state, it is truncated into segments 5 and 6. When the segment position is 6.5, a restricted temporary segment, an invalid candidate set, or no effective segment, 6.5 is not mapped to the non-existent segment 7, but all segments from 1 to 6 are mapped. The segment is included in the inspection set, and acid purification capacity determination is prioritized for invalid water quality segments. Dual-segment mapping is only restored after two consecutive windows yield valid candidates and step S2 cancels the restricted temporary state. If the pH or conductivity of any segment in the inspection set reaches the acid purification trigger boundary, acid purification capacity determination is performed segment by segment in ascending order of collection segment number: the sum of the real-time flow rates of each segment with valve positions already fed back is used as the current cumulative flow rate. This current cumulative flow rate is added to the flow rate of the entire segment to be connected. Only when the total flow rate does not exceed the allowable flow rate of the corresponding version of the acid purification branch and the pH and conductivity of the segment to be connected are within the acceptable range of the branch, will the safety controller maintained by the independent safety power supply keep the collection outlet isolation valve open and connect the entire segment. Switch to the acid purification branch via the diversion valve, and update the cumulative flow after the valve position feedback is in place; when multiple collection sections make concurrent requests, maintain the above fixed sequence and do not split the instantaneous flow of the same collection section; if any of the capacity, tolerance, or valve position conditions are not met, the mechanical and electrical action priority is fixed as follows: first, de-energize and close the collection outlet isolation valve; then, de-energize and close the acid purification passage and the reuse passage; finally, de-energize and open the passive discharge branch of the emergency tank. The safety controller will only reopen the collection outlet isolation valve to allow condensate to enter the emergency tank after confirming that the emergency tank capacity is valid; when the independent safety power supply is completely exhausted, maintain the above passive final position and do not allow direct connection to the acid purification branch; the remaining capacity of the emergency tank must not be less than the following calculated based on the current flow of the section to be connected. The system controls the incoming liquid volume for one cycle. If the capacity is insufficient, the outlet remains closed, the flue gas inlet and cooling water inlet of the corresponding heat exchange unit are isolated, the upstream load is requested to be reduced, and the capacity alarm of the acid branch is locked. When the liquid collection tank reaches a high level, the emergency drainage path connected to the emergency tank is opened only after the capacity feedback of the emergency tank is valid and the above capacity conditions are met. Otherwise, the upstream emergency shutdown interlock is executed, and other units continue to operate as long as their respective hard constraints allow. The isolation and capacity alarm are released segment by segment in ascending order of the liquid collection segment number only when the current cumulative flow of the acid purification branch plus the flow of the section to be restored does not exceed 90% of the allowable flow, the water quality of the section to be restored is within the receiving range of the branch, the liquid level of the emergency tank drops below the normal upper limit, and the diversion valve feedback is confirmed to be normal at 12 consecutive sampling points.

[0103] For condensate segments that do not meet the acid purification criteria, the diversion module checks whether they are located downstream of the water condensation front and determines the reuse criteria based on the inlet water limit table for the reusable fine treatment branch. In this specific implementation, the reuse criteria are set as pH not lower than 5.5 and 25℃ compensated conductivity not higher than 300μS / cm. The collection segments that meet both criteria are sorted from upstream to downstream along the flue gas flow direction. The current flow rate of each segment is added to the cumulative reuse flow rate of this cycle. Only when the cumulative flow rate after adding a segment does not exceed the branch's allowable flow rate is the entire segment guided to the reusable fine treatment branch. Otherwise, the entire segment is guided to the flushing branch, and no instantaneous time allocation is performed for the same collection segment. If the sorting is the same, the collection segment number is used in ascending order. When the flow rate fluctuates during the anti-shake period, the previously fed-in segment allocation result is maintained.

[0104] For segmented condensate guide flushing branches that do not enter the acidic purification branch and do not simultaneously meet the reuse criteria, transitional condensate located between the two leading edges with a pH of 4.5 to 5.5 or a conductivity of 300 μS / cm to 800 μS / cm is also guided to the flushing branch. This maintains a fixed judgment order of prioritizing acidic purification, simultaneously meeting both reuse water quality indicators, and allowing other condensate to enter the flushing branch. If the confidence level of the leading edge is lower than the lower confidence limit calibrated in step S5, no water quality criterion is relaxed. The flushing branch receives material that enters a buffer tank that is physically isolated from the reusable low-salt condensate buffer tank. High liquid level, very high liquid level, effective capacity, and outlet valve feedback are set. When the liquid level is high, the reception of new entire condensate is stopped, and the aforementioned acidic purification branch receiving water quality and allowable flow rate are first applied to that entire segment. The process involves two checks: only when both checks pass can the entire section be transferred to the acidic purification branch; if both checks fail, the condensate is sequentially introduced into a dedicated acidic condensate emergency tank, the corresponding heat exchange unit is isolated, and a load reduction request is made. Each stage is only accepted after the capacity and valve position feedback passes. It is forbidden to directly force condensate exceeding the tolerance range or allowable flow rate into the acidic purification branch. When the buffer tank reaches a high level, the corresponding collection section is directly isolated and an alarm is locked. After neutralization, filtration, and conductivity verification, the condensate can only be transferred to the low-salt condensate buffer tank for pulse flushing in step S5 if it simultaneously reaches a pH of 5.5 to 8.5 and a conductivity not higher than 500 μS / cm. If it does not meet these requirements, it is sent to the subsequent wastewater treatment unit of the acidic purification system after capacity verification. It must never be mixed with untreated reusable low-salt condensate.

[0105] After each switching, the three-way diverter valve is set to have a 15-second anti-shake time. During the anti-shake period, only the detection quantity is recorded and the switching is not repeated. When the acid purification criterion changes from being met to not being met, it must be that six consecutive valid sampling points are not met before it is allowed to exit the acid purification branch. When the reuse criterion changes from being met to not being met, it will immediately exit the reusable fine treatment branch, thereby preventing acidic condensate from entering the reuse branch due to short-term measurement fluctuations.

[0106] The execution module uses the effective cycle in the control command as a unified time base. After adjusting the circulating water flow and inlet water temperature, it waits 20 seconds for confirmation feedback to enter the set value allowable band before executing the deep condensation unit switching. Finally, it adjusts the bypass ratio, with the allowable bands being ±3% of the flow set value, ±1℃ of the inlet water temperature, and ±0.01 of the bypass ratio. If a certain execution quantity does not enter the allowable band, subsequent actions are stopped, and the completed actions are first rolled back to the last group of valve and pump positions that have been fully verified in the previous cycle. After rolling back, the hard constraint verification in step S3 is called. If any feedback is not in place or the current wall temperature, residence time, pressure difference, and continuous water film are still not within the feasible region, the controlled safety state command in step S3 is executed immediately and the execution fault alarm is latched. The latch is only released after the actuator is confirmed to be under maintenance and feedback has entered the allowable band for two consecutive control cycles and the hard constraints are met.

[0107] The cumulative mass of each branch is based on the integral value of the flow rate of the collection section and is independently checked with the periodic increment of the weighing tank of the branch main pipe; the control body used for material balance in steps S2 and S5 only includes the collection tanks of the deep condensation unit numbered 1 to 6. When accumulating the mass of each branch, these six sections are selected according to the original collection section number. Although the condensate in the sensible heat exchange zone and the transition heat exchange zone are processed according to the same three-way rule, they are recorded by section number and excluded from the control body; the relative deviation between the sum of the cumulative mass of the six deep condensation collection sections in the three branches and the sum of the cumulative mass of the six collection sections in a single control cycle shall not exceed 5%. If it exceeds 5%, the data quality flag of the diversion result of this cycle is locked but the valve position that has been completed is not changed. The lock can only be released after the maintenance personnel confirm the cause of the flow meter or valve. During the lock period, step S5 maintains the correction amount of the previous cycle according to the abnormal branch;

[0108] The diversion module accumulates the condensate mass for the current control cycle by collecting the liquid in the collection section and branch, records the start and end valve positions, effective sampling count, average pH, average conductivity, average wall temperature, and diversion reason code, and writes the heat exchange execution status, diverted condensate volume, and segmented water quality records into the diversion result dataset. This dataset also records the window start and end times, sampled differential pressure values, differential pressure sampling timestamps, differential pressure validity flags, and differential pressure sensor calibration versions for each unit according to the control cycle number and deep condensation unit number. The differential pressure sampling uses the original differential pressure of the same cycle recorded in step S3 as the sole source, and aligns the sampling timestamp with the most recent time records of condensate, water quality, and valve positions in the corresponding collection section. If the time difference exceeds 5 seconds, the group of differential pressures is marked as invalid and cannot be used to update the growth rate, recovery rate, or scaling rate. The resulting diversion result dataset serves as the sole operational feedback for updating the double front, front confidence, differential pressure growth rate, flushing recovery rate, and scaling rate in step S5.

[0109] In this specific embodiment, S5 includes:

[0110] At the end of each 10-minute preset reliability evaluation window, the calibration and operation handling module reads the diversion result dataset from step S4. It accumulates the diversion condensate from the deep condensation units numbered 1 to 6 in the acid purification branch, the reusable fine treatment branch, and the flushing branch according to the original collection section number. The condensate during valve switching anti-shake is included in the branch that has been fed back before the switch. The total condensate volume of the segments is obtained by accumulating the six deep cryogenic collection sections, which has the same statistical caliber as step S2. The sensible heat exchange zone, the transition heat exchange zone, and the bypass flue gas do not contribute to the measured condensate of this control body. The theoretical condensate volume is calculated by multiplying the total flow rate of the sampled flue gas by one minus the non-bypass flow rate.

[0111] The module calculates the relative residual using the re-accumulated total condensate volume in segments and the theoretical condensate volume. , This represents the relative residual of the condensate material balance, and is a dimensionless value. This indicates the theoretical condensate volume within the current evaluation window, in kg. This indicates the total amount of condensate in the current evaluation window segment, in kg, and all of them are consistent with the six depth condensation unit control volumes in step S2; This represents the minimum theoretical condensate volume for zero protection, which is 10 kg in this specific embodiment; Indicates in and Take a value that is not less than the other number as the denominator. The unit of the denominator is kg and it is used for zero protection. If the relative residual is positive, it means that the theoretical condensate volume is higher than the actual measured total condensate volume of the segment.

[0112] Flue gas moisture content according to correction, This represents the corrected mole fraction of water vapor in the flue gas for use in the next control cycle; it is a dimensionless value. This represents the mole fraction of water vapor in the flue gas before the current cycle correction; it is a dimensionless value. The value is taken from the relative residual formula and its immediate interpretation mentioned in this step and is dimensionless. The dimensionless material balance residual correction gain is taken as 0.20 in this specific implementation. This value is selected from the candidate gains in the offline playback of the trial operation, where the correction amplitude of moisture content in a single cycle does not exceed 5% and the absolute value of the residual decreases for three consecutive windows, and is saved with the parameter version. and These represent the lower and upper limits of the allowable moisture content determined by the instrument error and material balance deviation in step S1, respectively, both of which are dimensionless values; Indicates in Time first and Find a value in the middle that is not less than another number, and then combine the resulting value with... Take a value that is no greater than another number, thereby truncating the result to a closed interval. Inside, Indicates the value to be truncated. Indicates the lower limit, The upper limit is indicated, and the units of the three are consistent with the input. The positive relative residual reduces the corrected water content, and the correction result is re-entered into the gas phase material balance in step S1 to obtain the theoretical condensate volume for the next cycle.

[0113] Both the water condensation front and the acid enrichment front are deterministically updated using the unit number from step S2 plus 0.5 segments. The water front candidate is generated when the incremental difference between the cumulative condensate volume of two adjacent cryogenic collection sections relative to the initial integral value of the window in step S2 reaches the mass threshold calculated from the condensate flow difference threshold in the dual front calibration parameter table for two consecutive windows, and the wall temperature crosses the water dew point range. In the case of multiple candidates, the segment first crossed along the flue gas flow direction is selected. The acid front candidate is generated when the average pH decrease and conductivity increase of adjacent collection sections both reach the threshold of the same unit in step S2, and the proportion of acidic purified condensate is continuously... When two windows are raised and the wall temperature is within the acid risk range, the window is generated. When there are multiple candidates, the one with the lowest average pH is selected first, followed by the one with the highest average conductivity. If they are still the same, the one upstream of the flue gas flow is selected. When the target candidate differs from the current segment by more than 1 unit, each evaluation window moves only 1 unit toward the target. When the pH and conductivity change directions conflict, the detection is abnormal, or there are no candidates, the current segment is maintained. The first update uses the segment initially identified in step S2 or the restricted temporary segment as the current segment. All position updates record the segment before and after the update, the candidate set, the threshold version, the conflict flag, the reason for the limit, and the effective period.

[0114] The module performs cumulative residual calculations according to step S2. The definition involves re-counting the effective sampling count within the same 10-minute window, using the same interpolation rule, and with the same allowable error band version, to obtain the original frontier confidence score. If any detection chain exhibits an anomaly, then... correction, This represents the leading-edge confidence level used in the next control cycle, and is a dimensionless value between 0 and 1. Represents the cumulative residual The proportion of the number of samples that are within the corresponding cumulative time allowable error band and that are effective in participating in the front edge identification detection is a dimensionless value of 0 to 1 out of the total number of preset samples. The total anomaly coefficient is a dimensionless value ranging from 0 to 1. The effective sampling ratios of the diverted condensate volume, water quality, and differential pressure detection chains are calculated separately. When multiple detection chains are simultaneously abnormal, the minimum effective sampling ratio among the abnormal detection chains is taken as the average. When a single line is abnormal, the proportion of that chain is taken; when there is no abnormality, the proportion of that chain is taken. Take 1; the module simultaneously records the anomaly types involved in the synthesis, the proportion of each chain, and the final result. This ensures that the synthesis result of concurrent exceptions is unique;

[0115] When the condensate flow rate is abnormal, the flue gas moisture content and water condensation front correction value of the previous control cycle are maintained. When the pH or conductivity is abnormal, the acid enrichment front correction value of the previous control cycle is maintained. When the pressure difference is abnormal, the scaling rate of the previous control cycle is maintained. The abnormality judgment is based on the conditions of effective sampling ratio being less than 0.8, exceeding the range, or remaining unchanged for six consecutive points. When any abnormality occurs, a maintenance alarm is written and the feedback weight of step S3 is limited by the corrected front confidence.

[0116] For the Each deep condensation unit retrieves pollutant concentrations from the trial operation water quality calibration relationship according to pH and conductivity ranges, and then... Calculate the staged condensate contamination load. Indicates the first The contamination load of each deep condensation unit, in mg / h. This represents the average segmented condensate mass flow rate within the evaluation window of this unit, in kg / h. This indicates the pollutant concentration determined by a combination of pH and conductivity, expressed in mg / kg. The index represents the deep condensation unit and ranges from 1 to 6. The water quality calibration table fields include pH range, conductivity range, pollutant concentration, sample batch, valid range, and version number. If no match is found, the adjacent record with the increased pollutant concentration is used.

[0117] Differential pressure growth rate calculate, Indicates the first The pressure differential growth rate of each deep condensation unit, expressed in units of 1 / h. This indicates the pressure difference of the unit at the end of the current evaluation window, in kPa. This represents the pressure difference of the unit at the end of the previous evaluation window, in kPa. This represents the time interval between the ends of two evaluation windows; in this specific implementation, it is taken as one-sixth of an hour. The index of the deep condensation unit is 1 to 6; when the differential pressure in the previous window is less than 0.1 kPa, 0.1 kPa is used as the denominator protection value of the same unit. 0.1 kPa is taken from twice the resolution of the differential pressure sensor and recorded with the sensor calibration version.

[0118] When the differential pressure growth rate of a certain unit reaches the threshold of the trial operation clean state and the allowable operating resistance calibration, and the pollution load of that unit reaches the pollution load threshold, the module first checks the availability markings, liquid level, water quality, supply pressure, available volume, and valve / pump feedback of the low-salt condensate buffer tank of the reusable fine treatment branch; the minimum available volume is determined by continuously supplying liquid for three 20-second pulses at the designed flushing flow rate plus a 20% margin, the supply pressure must not be lower than the design pressure of the flushing nozzle, the pH must be 5.5 to 8.5, and the compensated conductivity at 25℃ must not exceed 500 μS / cm; only after all interlocks are satisfied will the remaining depth be maintained. The condensation unit operates, the flue gas inlet and cooling water inlet of the unit to be flushed are closed, and the isolation valve is confirmed to be in place. Then, pulse flushing is performed with a cycle of 20 seconds of liquid supply and 10 seconds of pause. The flushing flow rate is 1.2 times the design flow rate of the unit in clean state and does not exceed the rated flow rate of the flushing pump. If any low-salt condensate interlock is not met, flushing is not started. The unit is kept safely isolated and enters the waiting queue. Qualified low-salt condensate continues to accumulate from the reusable fine treatment branch. An alarm for insufficient flushing material is issued. It is forbidden to replace it with condensate that does not meet the above water quality criteria. The queue is automatically re-queued after all interlocks have been valid for 12 consecutive sampling points.

[0119] Differential pressure recovery rate calculate, Indicates the first The differential pressure recovery rate of each deep condensation unit is a dimensionless value ranging from 0 to 1. This indicates the pressure difference before flushing, in kPa. This indicates the pressure difference after flushing, in kPa. Indicates the index of the deep condensation unit and takes values ​​from 1 to 6; only when Not less than and Calculate according to this formula. This represents the differential pressure zero protection threshold, in kPa, taken from twice the resolution of the differential pressure sensor during trial operation and recorded with the calibration version; when season Take 0 and mark flushing as invalid, when If differential pressure sampling is invalid, the recovery rate will not be calculated, the unit will remain isolated, and a differential pressure data alarm will be issued. The flushing will end when the effective differential pressure recovery rate reaches 0.30 and three consecutive drainage samples meet the flushing end water quality criteria of pH 5.5 to 8.5 and conductivity not higher than 500 μS / cm. If any condition is not met within 30 minutes, the unit will remain isolated and a manual inspection alarm will be issued.

[0120] The module divides the pressure difference before and after flushing by the cumulative operating hours before flushing to obtain the observed value of the scaling rate in this round, and updates it by weighted average of the historical scaling rate according to the time of the last five flushes. The updated value is written into the heat exchange response model parameter retrieval field in step S3. At the same time, the pressure difference before and after flushing, the pollution load, the number of pulses, the discharge pH, the conductivity, and the termination reason are retained for the trial operation verification of the pressure difference growth rate threshold and the pollution load threshold in the next run.

[0121] Within the normal evaluation window where flushing is not triggered, the pressure difference change of each deep condensation unit is also used to update the scaling rate. The module first deducts the pressure difference increment of the clean state caused by the change in flue gas flow rate, and then divides the remaining pressure difference increment by the duration of the evaluation window to obtain the unit scaling rate observation value. The six units respectively save the unit number, inlet flue gas flow rate, clean baseline pressure difference, measured pressure difference, pressure difference change, observed scaling rate and valid flag. Only when both the flow meter and the pressure difference sensor are valid are they included in the time-weighted average of the most recent five valid windows.

[0122] The differential pressure growth rate threshold, pollution load threshold, differential pressure recovery rate threshold, and flushing end water quality criteria are constructed from the same unit's trial operation record chain. The clean state test provides the benchmark differential pressure curve under different flue gas flow rates. The gradual ash accumulation test provides the combined distribution of differential pressure growth rate and pollution load before reaching the allowable operating resistance. The pulse flushing test provides the correspondence between differential pressure recovery rate and effluent water quality. The parameter table uses the unit number and flue gas flow range as the search key and saves the threshold, unit, sample quantity, version number, and effective time. Any change to the threshold version must be confirmed by a round of offline playback to ensure that it will not exceed the allowable operating resistance in advance.

[0123] The allowable error band and lower confidence level of the material balance are determined during the equipment trial operation according to the same formula and the same procedure in step S2. Zero protection quality and cumulative relative residuals calculated over the same cumulative duration The distribution is calibrated, and the error band field includes the cumulative duration index, the lower limit of relative residuals, the upper limit of relative residuals, zero protection quality, sample batch, version number, and effective time. The relative residual boundary and error band are dimensionless values. In this specific implementation, the 5th to 95th percentiles of each cumulative duration distribution are taken as the allowable error band corresponding to that duration, and the 10th percentile of the window proportion that meets the corresponding allowable error band and is not less than 0.75 is taken as the lower limit of confidence. Steps S2 and S5 both retrieve the same error band according to the cumulative duration index and version number. When the current confidence is lower than the lower limit, a restriction flag is written to step S3 to make the number of newly added deep condensation units in each control cycle zero and keep the sensible heat exchange zone wall temperature higher than the upper boundary of the system-level acid condensation risk zone.

[0124] Once the confidence level of the leading edge recovers to above the lower confidence level, the module compares the water condensation leading edge segment and the acid enrichment leading edge segment of two consecutive control cycles. The restriction on new input is lifted only when the position difference between the two leading edges does not exceed 0.5 unit segments and there are no detection anomalies. Finally, the corrected flue gas moisture content, water condensation leading edge, acid enrichment leading edge, leading edge confidence level, scaling rate, limit flag, and maintenance alarm status are written into the status record of the next control cycle and sent to step S2 for re-identification and step S3 for re-retrieving control commands, respectively.

[0125] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0126] This invention combines the predicted dew point and acid risk boundary with the actual wall temperature, condensate volume, and condensate water quality in the segmented heat exchange process, so that the position of the double front and its confidence level can be updated with changes in operating conditions. Based on this, a linkage control of circulating water, inlet water temperature, flue gas bypass, and effective heat exchange area is formed, thereby subjecting the recovery process of sensible heat of flue gas and latent heat of water vapor to determinable corrosion and user return water constraints.

[0127] This invention changes the operating structure of fixed return water and overall shutdown by segmented liquid collection residual correction, condensate quality priority diversion, orderly heat distribution when the load decreases, and independent pulse flushing of the contaminated unit. This allows the real phase change products to serve as feedback for heat exchange control, condensate purification, and scaling judgment.

Claims

1. A method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas, characterized in that, include: S1. Collect data on the gas combustion process, flue gas status, and waste heat user return water status to determine the flue gas water dew point range and acid condensation risk range. S2. Obtain the wall temperature and segmented condensate state of the sensible heat exchange zone, the transition heat exchange zone and multiple independently switchable deep condensation units arranged sequentially along the flue gas flow direction, and determine the water condensation front, acid enrichment front and front confidence level by combining the flue gas water dew point range and acid condensation risk range. S3. Using the flue gas water dew point range and acid condensation risk range as feedforward boundaries, and the water condensation front, acid enrichment front and front confidence as feedback correction quantities, the control commands for circulating water flow rate, inlet water temperature, flue gas bypass ratio and effective heat exchange area of ​​each heat exchange zone are determined under corrosion constraints and waste heat user return water constraints. S4. Operate each heat exchange zone according to the control instructions, and guide the segmented condensate to the acid purification branch, the reusable fine treatment branch, or the flushing branch according to the collection section and real-time quality of the segmented condensate. S5. Update the water condensation front, acid enrichment front, and front confidence based on the segmented condensate splitting results, and use the updated results for steps S2 and S3 in the next control cycle.

2. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 1, characterized in that, S1 includes: Combustion product material balance is performed based on gas composition or flue gas composition, combustion load and excess air quantity, and flue gas moisture content is corrected using exhaust gas temperature, flue gas flow rate and moisture content characterization. The water dew point range is determined based on the corrected flue gas moisture content and flue gas pressure. The partial pressure of acidic components is determined based on the sulfur-containing and chlorine-containing components in the flue gas and their combustion conversion rates, and the acid condensation risk range is determined based on the partial pressure of acidic components and the wall temperature. The moisture content characterization quantity is at least one of the following: humidity detection value, fuel water content, flue gas oxygen content and combustion load combination quantity.

3. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 2, characterized in that, S2 include: Each deep condensation unit is equipped with a liquid collection tank below it that prevents liquid from mixing with each other, and the condensate flow rate, pH, conductivity and wall temperature of the corresponding unit are measured respectively; When the condensate flow rate and wall temperature of adjacent units along the flue gas flow direction show continuous abrupt changes within the preset observation window, the location of the abrupt change is determined as the water condensation front. When the pH, conductivity, and wall temperature of adjacent units exhibit continuous abrupt changes within the preset observation window, the location of the abrupt change is determined as the acid enrichment front. The continuous mutation is determined by the number of times the absolute value of the difference between the detection quantities of adjacent units within the observation window continuously reaches the corresponding detection quantity threshold. Each detection quantity threshold and the preset number are determined by the calibration data of the location of water dew point and the location of acidic condensate during the trial operation of the equipment. Within a pre-set reliability evaluation window, the flow rate of condensate detected in each collection tank is integrated over time and summed to obtain the total amount of condensate in each segment; Based on the corrected flue gas moisture content, a gas phase material balance is performed to obtain the theoretical condensate volume. The residual between the theoretical condensate volume and the total condensate volume in segments is compared with the allowable error band of the material balance. The frontier confidence level is determined based on the proportion of the number of samplings in which the residual is located within the allowable error band within the preset confidence evaluation window to the total number of samplings.

4. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 1, characterized in that, S3 include: The temperature constraints for the partitioning are as follows: the wall temperature of the sensible heat exchange zone is kept above the upper boundary of the acid condensation risk zone; the residence time of the flue gas in the transition heat exchange zone during the period when the corresponding wall temperature crosses the acid condensation risk zone does not exceed the upper limit of the allowable residence time; and the wall temperature of the deep condensation unit enters below the water dew point range and maintains a continuous water film. The upper limit of the allowable residence time is determined by the flue gas residence time calibration data when the water quality of the segmented condensate reaches the acid purification criterion during the equipment trial operation. The feedback correction weights for the water condensation front and the acid enrichment front are adjusted based on the front confidence level, and the feasible domain is composed of the zone temperature constraints, the upper limit of the pressure difference of each heat exchange zone, the temperature range of waste heat user return water, and the range of acceptable heat. Within the feasible region, the circulating water flow rate, inlet water temperature, and flue gas bypass ratio are determined, and the effective heat exchange area is determined by determining the number of deep condensation units put into operation.

5. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 1, characterized in that, S4 include: Each heat exchange zone is equipped with an independent cooling branch, an independent liquid collector, and a three-way flow divider valve; First, determine whether the pH or conductivity of the condensate in the collection section located at the acid enrichment front and its upstream adjacent collection section meets the acid purification criterion. If it does, direct the condensate in that section to the acid purification branch. If the acid purification criterion is not met, then determine whether the pH and conductivity of the segmented condensate located downstream of the water condensation front meet the reuse criterion. If they do, the segmented condensate is directed to the reusable fine treatment branch, and the remaining segmented condensate is directed to the flushing branch. The acid purification criteria and reuse criteria are determined based on the influent water quality limits of the corresponding treatment branches.

6. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 3, characterized in that, S5 include: The total amount of condensate from the acid purification branch, the reusable fine treatment branch, and the flushing branch within the same pre-set reliability evaluation window is accumulated according to the corresponding collection section to obtain the total amount of condensate from each section. The residual between the total amount of segmented condensate and the theoretical condensate amount is used to correct the flue gas moisture content, the water condensation front, and the theoretical condensate amount obtained by gas phase material balance based on the corrected flue gas moisture content. The segmented water quality data is used to correct the acid enrichment front, and the pressure difference change of each depth condensation unit is used to update the scaling rate. Based on the proportion of the number of samplings within the material balance error band within the evaluation window that are located within the residual between the theoretical condensate volume and the total condensate volume obtained again, the frontier confidence level is redefined, and the redefined frontier confidence level is used to adjust the feedback correction weight in the next control cycle. When the condensate flow rate is abnormal, maintain the flue gas moisture content and water condensation front correction value of the previous control cycle. When the pH or conductivity is abnormal, maintain the acid enrichment front correction value of the previous control cycle. When the differential pressure is abnormal, maintain the scaling rate of the previous control cycle. When any of the above abnormalities occur, multiply the front confidence by an abnormality coefficient less than 1 and issue a maintenance alarm. The abnormality coefficient is determined according to the proportion of the effective sampling number of the corresponding detection quantity to the preset sampling number.

7. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 6, characterized in that, When the load of waste heat users decreases, candidate heat allocation methods are determined under the corrosion constraints and waste heat user return water constraints described in step S3, based on the updated water condensation front, acid enrichment front and front confidence. When the stratified heat storage unit connected to the circulating water loop is in an available state and its remaining heat storage capacity is not less than the heat to be allocated in the current control cycle, stratified heat storage is listed as the first candidate mode, and the available candidate heat allocation modes are activated in the following order: stratified heat storage, reducing the number of deep condensing units put into operation, increasing the inlet water temperature, and increasing the flue gas bypass ratio, until the recovered heat enters the acceptable heat range determined according to the waste heat user return water status. Before each activation of the next candidate heat allocation method, it is verified whether the wall temperature of the sensible heat exchange zone is maintained above the upper boundary of the acid condensation risk zone, whether the residence time of the flue gas in the transition heat exchange zone during the period when the corresponding wall temperature crosses the acid condensation risk zone does not exceed the upper limit of the allowable residence time calibrated by the equipment trial operation, and whether the wall temperature of the deep condensation unit enters below the water dew point range and maintains a continuous water film.

8. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 6, characterized in that, The condensate flow rate of any deep condensation unit is multiplied by the pollutant concentration obtained from the pH and conductivity of the condensate during trial operation water quality calibration to obtain the condensate pollution load of the deep condensation unit. When the differential pressure growth rate of the deep condensation unit reaches the differential pressure growth rate threshold and its segmented condensate contamination load reaches the contamination load threshold, the remaining deep condensation units are kept running and the deep condensation unit is isolated. The low-salt condensate output from the reusable fine treatment branch is then transported to the isolated unit for pulse flushing. The flushing process ends when the differential pressure recovery rate of the isolated unit reaches the differential pressure recovery rate threshold and the pH and conductivity of the flushing discharge meet the flushing end water quality criteria. The differential pressure growth rate threshold, pollution load threshold, differential pressure recovery rate threshold, and flushing end water quality criterion are determined by the unit trial operation clean status, allowable operating resistance, and flushing branch drainage requirements, and the differential pressure and drainage water quality before and after flushing are used to update the scaling rate.

9. The method for recovering waste heat from the condensation of low-calorific-value coal gas flue gas according to claim 6, characterized in that, The lower limit of confidence is determined by the proportion of the number of samplings in which the residual between the theoretical condensate volume and the total condensate volume in the pre-set confidence evaluation window is located within the allowable error band of the material balance to the total number of samplings. The allowable error band of the material balance and the lower limit of confidence are calibrated by the deviation distribution between the theoretical condensate volume and the measured total condensate volume in the segment during the trial operation of the equipment. When the confidence level of the frontier does not reach the lower limit of the confidence level, the number of new deep condensation units is limited, and the wall temperature of the sensible heat exchange zone is kept above the upper boundary of the acid condensation risk zone. Once the confidence level of the front recovers to above the lower confidence level, the restriction is lifted based on the consistency of the positions of the water condensation front and the acid enrichment front over two consecutive control cycles.

10. A low-calorific-value coal gas flue gas condensation waste heat recovery system, used to perform the low-calorific-value coal gas flue gas condensation waste heat recovery method according to any one of claims 1 to 9, characterized in that, include: The exhaust duct is provided with a sensible heat exchange zone, a transition heat exchange zone, and multiple independently switchable deep condensation units in sequence along the flue gas flow direction. Each heat exchange zone is connected to an independent cooling branch and an independent liquid collector. Each deep condensation unit is provided with a liquid collection tank below it that does not cross-contaminate with each other. The independent liquid collector and the liquid collection tank are connected to an acid purification branch, a reusable fine treatment branch, and a flushing branch through a three-way diversion valve, respectively. The reusable fine treatment branch is connected to the flushing inlet of each deep condensation unit. The exhaust duct is provided with a flue gas bypass branch that bypasses at least part of the heat exchange zone. The flue gas bypass branch is provided with a bypass regulating valve. The detection components include wall temperature sensors and differential pressure sensors installed in each heat exchange zone, as well as condensate flow rate, pH and conductivity detectors installed in each liquid collector and liquid collection tank. Data interface for gas combustion process, flue gas status data interface, and waste heat user return water status interface; The data acquisition and interval calculation module is connected to the detection component, as well as the gas combustion process data interface, flue gas status data interface, and waste heat user return water status interface, and is used to determine the flue gas water dew point interval and acid condensation risk interval. A dual-front identification module, connected to the data acquisition and interval calculation module, is used to determine the water condensation front, acid enrichment front, and front confidence level based on the output of the detection component and the interval. The staged heat exchange control module is connected to the dual leading edge recognition module, each independent cooling branch, each deep condensation unit and the bypass regulating valve, and is used to generate and execute control commands for circulating water flow, inlet water temperature, flue gas bypass ratio and effective heat exchange area. The condensate diversion module, connected to the dual leading edge recognition module and the three-way diversion valve, is used to divert condensate according to the collection stage and real-time quality, and output the diverted condensate volume, water quality data and resistance status to the dual leading edge recognition module. The calibration and operation handling module is connected to the dual front identification module, the staged heat exchange control module, the flushing branch, and the stratified heat storage unit in the circulating water circuit. It is used to update the water condensation front, acid enrichment front, front confidence and scaling rate, and to perform heat distribution or unit isolation flushing.

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