A tail gas treatment system and method for graphite felt production

Abstract

The application discloses a tail gas treatment system and method for graphite felt production, wherein the tail gas treatment system for graphite felt production comprises a data acquisition module, which is used for acquiring tail gas temperature at the outlet of a waste heat recovery module, operating parameters of an electric tar collection module, operating states of a first alkali liquid spraying module and a second alkali liquid spraying module, and outlet flue gas component data of a burning module; a control module, which is used for calculating fuel supply feedforward compensation of the burning module based on the tail gas temperature, the operating parameters and the operating states, calculating an excess air coefficient set value of the burning module based on the outlet flue gas component data, and generating a control instruction for the burning module based on the fuel supply feedforward compensation and the excess air coefficient set value. The application improves the problems of sensing lag and response lag caused by long pre-treatment process and large lag in traditional feedback control, and reduces over-oxidized combustion or hypoxic combustion caused by fixed air distribution.

Description

Technical Field

[0001] This invention relates to the field of industrial waste gas treatment technology, and in particular to a tail gas treatment system and method for graphite felt production. Background Technology

[0002] The exhaust gas produced during graphite felt production is complex, typically containing asphalt fumes, tar, dust, acidic gases, and various combustible volatile organic compounds. To ensure environmental compliance, a typical exhaust gas treatment system employs a multi-stage combined process, including modules such as waste heat recovery, filtration, electrostatic precipitator, alkaline scrubbing, incineration, and drying.

[0003] Currently, the industry generally adopts a feedback control strategy based on the incineration module's own operating parameters for control. A common practice is to install temperature sensors and oxygen analyzers at the incinerator outlet. The control system (such as a PLC or DCS) uses a PID algorithm to adjust the fuel (such as natural gas) supply based on the deviation between the measured furnace temperature and the set value, and simultaneously adjusts the combustion air volume based on the oxygen content in the flue gas to maintain a relatively stable combustion state. While this control mode is simple and reliable, it has the following drawbacks: there is a time delay (usually several minutes to tens of minutes) from the generation of the exhaust gas to its arrival at the incinerator after passing through multiple pretreatment modules such as waste heat recovery, electrostatic precipitator, and spraying. When upstream production processes fluctuate (such as changes in raw material feed rate or filter backflushing regeneration) or the efficiency of pretreatment units changes (such as performance degradation of the electrostatic precipitator), the exhaust gas flow rate, temperature, calorific value, and pollutant load entering the incinerator will change. The existing feedback control only begins to respond after the disturbance reaches the incinerator and is detected, resulting in periodic or sudden fluctuations in furnace temperature and combustion efficiency. This can not only cause instantaneous emissions to exceed standards, but also affect the stability of equipment operation. Summary of the Invention

[0004] Therefore, in order to overcome the above-mentioned shortcomings, the present invention provides a tail gas treatment system and method for graphite felt production, so as to improve the problem of perception lag and response lag caused by the long pretreatment process and large lag in traditional feedback control, and reduce the over-oxygen combustion or oxygen-deficient combustion caused by fixed air distribution.

[0005] On one hand, the present invention discloses a tail gas treatment system for graphite felt production, the tail gas treatment system comprising, in sequence, a waste heat recovery module, a first filtration module, an electrostatic tar removal module, a second filtration module, a first alkaline spray module, a second alkaline spray module, an incineration module, and a drying module, the tail gas treatment system further comprising:

[0006] The data acquisition module is used to collect the exhaust gas temperature at the outlet of the waste heat recovery module, the operating parameters of the electrostatic tar removal module, the operating status of the first and second alkaline spray modules, and the flue gas composition data at the outlet of the incineration module.

[0007] The control module is used to calculate the fuel supply feedforward compensation amount of the incineration module based on the exhaust gas temperature, operating parameters and operating status, calculate the excess air coefficient setpoint of the incineration module based on the outlet flue gas composition data, and generate control commands for the incineration module based on the fuel supply feedforward compensation amount and the excess air coefficient setpoint.

[0008] Furthermore, the calculation of the fuel supply feedforward compensation for the incineration module based on exhaust gas temperature, operating parameters, and operating status includes:

[0009] The first feedforward compensation component is calculated based on the deviation between the exhaust gas temperature and the preset temperature.

[0010] The second feedforward compensation component is calculated based on the operating parameters;

[0011] The third feedforward compensation component is calculated based on the operating status.

[0012] The compensation value of fuel replenishment energy is calculated based on the first feedforward compensation component, the second feedforward compensation component, and the third feedforward compensation component.

[0013] The feedforward compensation for fuel supply is calculated based on the compensation value of fuel replenishment energy.

[0014] Furthermore, the first feedforward compensation component is calculated as follows:

[0015] ;

[0016] in, ∆E 1 represents the first feedforward compensation component; K 1 represents the first feedforward correction coefficient; Q 1 represents the exhaust gas volumetric flow rate at the outlet of the waste heat recovery module; C V This is the volumetric heat capacity of the exhaust gas; T 0 represents the preset temperature of the exhaust gas at the outlet of the waste heat recovery module; T t This is the real-time exhaust gas temperature data at the outlet of the waste heat recovery module.

[0017] Furthermore, the calculation method for the second feedforward compensation component is as follows:

[0018] ;

[0019] in, ∆E 2 represents the second feedforward compensation component; K 2 represents the second feedforward correction coefficient; c This represents the real-time concentration of tar in the exhaust gas. lhv 1 represents the average lower calorific value of tar; orThis refers to the real-time tar collection efficiency of the electrostatic tar collector module.

[0020] Furthermore, the calculation method for the third feedforward compensation component is as follows:

[0021] ;

[0022] in, ∆E 3 represents the third feedforward compensation component; K 3 represents the third feedforward correction coefficient; ∆H 1 represents the enthalpy change of the exhaust gas caused by the first alkaline spray module; ∆H 2 refers to the enthalpy change of the exhaust gas caused by the second alkaline spray module.

[0023] The calculation method for exhaust gas enthalpy change is as follows:

[0024] ;

[0025] in, ∆H The enthalpy change of the exhaust gas is caused by the first alkaline spray module or the second alkaline spray module. Q 2 represents the spray liquid volume flow rate of the first alkaline spray module or the second alkaline spray module; r The density of the spray solution; C p The volumetric heat capacity of the spray liquid; T out The outlet spray liquid temperature of the first or second alkaline spray module; T in The temperature of the spray liquid at the inlet of the first or second alkaline spray module.

[0026] Furthermore, the calculation method for the compensation value of fuel-added energy is as follows:

[0027] ;

[0028] in, ∆E This represents the total energy compensation value that needs to be replenished by fuel.

[0029] Furthermore, the calculation method for the fuel supply feedforward compensation is as follows:

[0030] ;

[0031] in, ∆F For fuel supply feedforward compensation; lhv 2 represents the volume-based lower heating value of the gas.

[0032] Furthermore, the calculation method for the excess air coefficient setpoint of the incineration module is as follows:

[0033] Construct a heat loss function with the excess air coefficient as the decision variable;

[0034] Within the preset feasible region of the excess air coefficient, optimization calculations are performed with the goal of minimizing heat loss to obtain the optimal excess air coefficient.

[0035] The optimal excess air coefficient is used as the set value for the excess air coefficient of the incineration module.

[0036] The heat loss function with the excess air coefficient as the decision variable is as follows:

[0037] ;

[0038] in, L ( l () represents the total heat loss; q 1( l This represents heat loss from flue gas exhaust. q 2( l This represents the heat loss due to incomplete chemical combustion. q 3( l () represents heat loss due to incomplete combustion of machinery.

[0039] Furthermore, the control module corrects the excess air coefficient setpoint based on the deviation between the oxygen concentration in the flue gas at the outlet of the incineration module and the target oxygen concentration corresponding to the optimal excess air coefficient.

[0040] On the other hand, the present invention also provides a method for treating exhaust gas in graphite felt production, using the above-mentioned exhaust gas treatment system for graphite felt production, comprising the following steps:

[0041] Acquire tail gas temperature data at the outlet of the waste heat recovery module, operating parameters of the electrostatic tar removal module, operating status data of the first and second alkaline spray modules, and flue gas composition data at the outlet of the incineration module.

[0042] Based on exhaust gas temperature, operating parameters, and operating status, calculate the fuel supply feedforward compensation amount for the incineration module.

[0043] Based on the exhaust gas composition data, the excess air coefficient setpoint of the incineration module is calculated;

[0044] Based on the fuel supply feedforward compensation and the excess air coefficient setpoint, control commands for the combustion module are generated.

[0045] The present invention has the following advantages:

[0046] This invention uses a data acquisition module to capture in real-time the exhaust gas temperature at the waste heat recovery outlet, the operating parameters of the electrostatic precipitator module, and the status of the alkaline spraying, while the control module calculates the feedforward compensation for fuel supply. Fuel quantity is adjusted before changes in exhaust gas load are transmitted to the incinerator, improving upon the perception and response lag problems caused by the long pretreatment process and large delays in traditional feedback control. The control module also corrects the excess air coefficient setpoint in real-time based on the composition of the flue gas at the incineration module outlet, reducing over-oxygen or under-oxygen combustion caused by fixed air distribution. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the logical structure of the exhaust gas treatment system;

[0048] Figure 2 This is a schematic diagram of the exhaust gas treatment system;

[0049] Figure 3 This is a flowchart illustrating the exhaust gas treatment method;

[0050] In the picture:

[0051] 100 Waste heat recovery module; 200 First filtration module; 300 Electrostatic tar removal module; 400 Second filtration module; 500 First alkaline spray module; 600 Second alkaline spray module; 700 Incineration module; 800 Data acquisition module; 900 Control module; 1000 Drying module. Detailed Implementation

[0052] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0053] In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0054] As described in the background section, there is a time delay (typically several minutes to tens of minutes) between the generation of exhaust gas and its arrival at the incinerator after passing through multiple pretreatment modules such as waste heat recovery, electrostatic precipitator, and spraying. When upstream production processes fluctuate (e.g., changes in feedstock input or filter backflushing and regeneration) or the efficiency of pretreatment units changes (e.g., performance degradation of the electrostatic precipitator), the exhaust gas flow rate, temperature, calorific value, and pollutant load entering the incinerator will change. Existing feedback control only begins to respond after the disturbance reaches and is detected in the incinerator, leading to periodic or sudden fluctuations in furnace temperature and combustion efficiency. This can not only cause instantaneous emission exceedances but also affect the stability of equipment operation.

[0055] Example 1:

[0056] Therefore, in order to solve the above-mentioned technical problems existing in the prior art, this embodiment provides a tail gas treatment system for graphite felt production, such as... Figure 1 As shown, the exhaust gas treatment system sequentially includes a waste heat recovery module 100, a first filtration module 200, an electrostatic tar removal module 300, a second filtration module 400, a first alkaline spray module 500, a second alkaline spray module 600, an incineration module 700, and a drying module 1000. The exhaust gas treatment system also includes...

[0057] The data acquisition module 800 is used to collect the exhaust gas temperature at the outlet of the waste heat recovery module, the operating parameters of the electrostatic precipitator module, the operating status of the first alkali spray module and the second alkali spray module, and the flue gas composition data at the outlet of the incineration module.

[0058] The control module 900 is used to calculate the fuel supply feedforward compensation amount of the incineration module based on the exhaust gas temperature, operating parameters and operating status, calculate the excess air coefficient set value of the incineration module based on the outlet flue gas composition data, and generate control commands for the incineration module based on the fuel supply feedforward compensation amount and the excess air coefficient set value.

[0059] Specifically, when using it, such as Figure 2As shown, the high-temperature exhaust gas containing dust, tar, and volatile organic compounds generated during the graphite felt production process first enters the waste heat recovery module. Heat exchange elements recover the heat from the exhaust gas. The cooled exhaust gas then sequentially enters the first filtration module and the electrostatic precipitator module. The first filtration module traps large-diameter particles and tar droplets carried in the exhaust gas. The electrostatic precipitator module utilizes a high-voltage electrostatic field to efficiently capture submicron-sized tar droplets, reducing the adhesion and corrosiveness of the exhaust gas. After electrostatic precipitator treatment, the exhaust gas passes through a second filtration module to further remove residual fine dust. The exhaust gas then enters the first and second alkaline spray modules, where gas-liquid contact fully absorbs acidic components, washes away some water-soluble organic matter, and cools and humidifies the exhaust gas. The purified and cooled exhaust gas finally enters the incineration module, where auxiliary fuel oxidizes and decomposes residual VOCs and odor factors. The high-temperature flue gas is then purified and discharged into the atmosphere or enters a subsequent drying module, where waste heat is used to dry the graphite felt semi-finished product, achieving thermal energy utilization.

[0060] For example, the calculation of the fuel supply feedforward compensation amount for the incineration module based on exhaust gas temperature, operating parameters, and operating status includes:

[0061] The first feedforward compensation component is calculated based on the deviation between the exhaust gas temperature and the preset temperature.

[0062] The second feedforward compensation component is calculated based on the operating parameters;

[0063] The third feedforward compensation component is calculated based on the operating status.

[0064] The compensation value of fuel replenishment energy is calculated based on the first feedforward compensation component, the second feedforward compensation component, and the third feedforward compensation component.

[0065] The feedforward compensation for fuel supply is calculated based on the compensation value of fuel replenishment energy.

[0066] Specifically, in this embodiment, the operating parameters include the secondary current and secondary voltage of the electrostatic tar collector module. The real-time tar collection efficiency is obtained by fitting the measured values ​​of the secondary current and secondary voltage relative to the attenuation under rated operating conditions. The operating status includes the spray liquid volumetric flow rate, inlet spray liquid temperature, and outlet spray liquid temperature of the first and second alkaline spray modules.

[0067] For example, the first feedforward compensation component is calculated as follows:

[0068] ;

[0069] in, ∆E 1 represents the first feedforward compensation component; K 1 represents the first feedforward correction coefficient; Q1 represents the exhaust gas volumetric flow rate at the outlet of the waste heat recovery module; C V This is the volumetric heat capacity of the exhaust gas; T 0 represents the preset temperature of the exhaust gas at the outlet of the waste heat recovery module; T t This is the real-time exhaust gas temperature data at the outlet of the waste heat recovery module.

[0070] Specifically, the first feedforward compensation component represents the heat that needs to be additionally supplemented or reduced by the incineration module due to the upstream exhaust gas temperature deviating from the preset benchmark value. When the real-time outlet temperature of the waste heat recovery module is lower than the preset temperature, the sensible heat carried by the exhaust gas decreases. To maintain the thermal balance of the incinerator and the target oxidation temperature, the fuel supply needs to be increased to compensate for this heat deficit. T 0- T t ) is a positive value, ∆E 1 represents a positive compensation amount; conversely, when it is higher than... T At 0:00, there is excess sensible heat in the exhaust gas, so the fuel input can be reduced accordingly. ∆E 1 represents the negative compensation amount. In this embodiment, the exhaust gas volumetric flow rate is measured in real time by a thermal mass flow meter or differential pressure flow meter installed on the outlet pipe of the waste heat recovery module and converted to standard operating conditions; the exhaust gas volumetric heat capacity is calculated online based on the mass fraction of the main components of the exhaust gas (nitrogen, oxygen, water vapor, CO2, and trace organic matter) or periodically calibrated by an offline gas chromatograph and then incorporated into the control system; the preset temperature is the optimal inlet exhaust gas temperature under the design operating conditions of the incineration module, which is usually adjusted based on the rated processing capacity of the incinerator, the calorific value of the fuel, and long-term operating experience, and the value range is generally 80-120℃. The first feedforward correction coefficient is a dimensionless adjustment parameter used to correct errors caused by model simplification (such as pipeline heat dissipation, heat capacity calculation deviation, etc.), and the value range is usually 0.8-1.2, which can be adjusted through step disturbance tests during the system commissioning phase.

[0071] For example, the second feedforward compensation component is calculated as follows:

[0072] ;

[0073] in, ∆E 2 represents the second feedforward compensation component; K 2 represents the second feedforward correction coefficient; c This represents the real-time concentration of tar in the exhaust gas. lhv 1 represents the average lower calorific value of tar; or This refers to the real-time tar collection efficiency of the electrostatic tar collector module.

[0074] Specifically, the second feedforward compensation component characterizes the heat compensation value that needs to be supplemented or reduced by the fuel system due to the deviation of the calorific value of the combustible components entering the incineration module from the baseline value caused by fluctuations in the electrostatic precipitator efficiency and changes in the tail gas tar load. The tail gas generated from the graphite felt carbonization and graphitization processes contains a high concentration of tar droplets, which, as gaseous combustible components, contribute some of the combustion heat after entering the incinerator. When the operating efficiency of the electrostatic precipitator decreases, or when upstream process fluctuations cause an increase in the tail gas tar inlet concentration, the amount of tar that escapes to the incineration module without being captured (i.e., the escape rate 1-) or As the calorific value of the exhaust gas increases accordingly, the auxiliary fuel supply needs to be reduced accordingly; conversely, fuel compensation needs to be increased. In this embodiment, the real-time concentration of tar in the exhaust gas can be obtained by real-time monitoring using an online total hydrocarbon analyzer (such as one based on the FID principle) or a Fourier transform infrared spectrometer (FTIR) installed on the inlet or outlet pipe of the electrostatic tar precipitator module; alternatively, a photoacoustic multi-gas analyzer can be used. Tar concentration data can be transmitted to the control module in real-time via 4–20 mA analog signal or Modbus digital communication.

[0075] The real-time tar collection efficiency of the electrostatic precipitator module can be based on the operating electrical parameters of the module, such as secondary current, secondary voltage, and flashover frequency, combined with the factory performance curve or machine learning regression model, to fit the instantaneous collection efficiency under the current operating conditions in real time. The average lower calorific value of the tar is pre-calibrated based on the characteristics of the raw materials such as asphalt and resin used in graphite felt production and the offline analysis results of tar components. The exhaust gas volumetric flow rate is the same as the first feedforward compensation component, taken from the measured value of the outlet flow meter of the waste heat recovery module. The second feedforward correction coefficient is a dimensionless adjustment parameter used to compensate for systematic errors introduced by factors such as fluctuations in tar calorific value, concentration detection delay, and efficiency estimation deviation. Its value range is usually 0.7 to 1.3, and it can be tuned through on-site step tests (such as manually adjusting the electrostatic precipitator operating voltage) combined with the incinerator temperature response characteristics.

[0076] For example, the third feedforward compensation component is calculated as follows:

[0077] ;

[0078] in, ∆E 3 represents the third feedforward compensation component; K 3 represents the third feedforward correction coefficient; ∆H 1 represents the enthalpy change of the exhaust gas caused by the first alkaline spray module; ∆H 2 refers to the enthalpy change of the exhaust gas caused by the second alkaline spray module.

[0079] The calculation method for exhaust gas enthalpy change is as follows:

[0080] ;

[0081] in,∆H The enthalpy change of the exhaust gas is caused by the first alkaline spray module or the second alkaline spray module. Q 2 represents the spray liquid volume flow rate of the first alkaline spray module or the second alkaline spray module; r The density of the spray solution; C p The volumetric heat capacity of the spray liquid; T out The outlet spray liquid temperature of the first or second alkaline spray module; T in The temperature of the spray liquid at the inlet of the first or second alkaline spray module.

[0082] Specifically, the third feedforward compensation component characterizes the sensible heat loss caused by direct contact and heat exchange with the low-temperature alkali solution when the exhaust gas passes through the first and second alkali spray modules. This heat is absorbed by the spray liquid and carried away from the system with the circulating liquid or wastewater, and cannot be utilized by the downstream incineration module. Therefore, it needs to be compensated by increasing the supply of auxiliary fuel to maintain the thermal balance of the incinerator and the target oxidation temperature. The exhaust gas enthalpy change is calculated using the spray liquid-side heat balance method, indirectly reflecting the heat loss of the exhaust gas in this module. The volumetric flow rate of the spray liquid can be measured in real time by electromagnetic or ultrasonic flow meters installed on the outlet pipes of the circulating pumps of the first and second alkali spray modules, and transmitted to the control module via 4-20mA analog or digital communication. The spray liquid density can be compensated online based on the alkali concentration and temperature; a preset constant can be used and corrected periodically by laboratory calibration. The volumetric heat capacity of the spray liquid can be looked up in a table or calculated online based on the concentration and temperature. The inlet spray liquid temperature can be collected in real time by a platinum resistance thermometer installed on the inlet pipe of the spray tower. The temperature of the spray liquid at the outlet can be collected in real time using a platinum resistance thermometer installed in the collection tank or outlet pipe of the spray tower. The temperature rises as the spray liquid absorbs heat from the exhaust gas. T out > T in At this point, the calculated enthalpy of the exhaust gas becomes positive, representing an increase in heat on the spray liquid side, that is, the absolute value of the heat lost by the exhaust gas in this module. The enthalpy of the exhaust gas itself becomes negative (the outlet enthalpy is lower than the inlet enthalpy), and its value is related to - ∆H They are equal. In this embodiment, the third feedforward correction coefficient is a dimensionless adjustment parameter used to compensate for errors in heat balance calculations and deviations caused by model simplification.

[0083] For example, the compensation value for fuel-added energy is calculated as follows:

[0084] ;

[0085] in, ∆E This represents the total energy compensation value that needs to be replenished by fuel.

[0086] Specifically, the total energy compensation value represents the thermal power that the auxiliary fuel system needs to replenish or reduce in real time to maintain the thermal balance of the combustion module. ∆E >0 indicates that the incinerator needs to increase fuel input under the current operating conditions; ∆E If the value is less than 0, fuel input needs to be reduced; ∆E When = 0, maintain the existing fuel supply.

[0087] For example, the calculation method for the fuel supply feedforward compensation is as follows:

[0088] ;

[0089] in, ∆F For fuel supply feedforward compensation; lhv 2 represents the volume-based lower heating value of the gas.

[0090] Specifically, the fuel supply feedforward compensation is an instantaneous fuel volume flow rate correction that needs to be added to or subtracted from the current opening of the fuel valve position in the combustion module to address fluctuations in upstream operating conditions. ∆F When the value is greater than 0, it indicates that the fuel supply needs to be increased. The control module will positively superimpose the fuel valve opening command on the current base value, increasing the fuel regulating valve opening or extending the pulse valve conduction time. ∆F When the value is less than 0, it indicates that the fuel supply needs to be reduced, and the control module will correspondingly reduce the valve position command or shorten the conduction time. ∆F When the value is approximately 0, the existing fuel supply is maintained, and the feedforward channel does not intervene. The volumetric lower calorific value of the natural gas is the benchmark parameter for fuel energy metering and flow control. For scenarios using piped natural gas, lhv 2. Values ​​can be determined based on the gas supply agreement or the component report provided by the gas company, generally ranging from 35,000 to 38,000. kJ / Nm 3 If unconventional fuels such as liquefied petroleum gas or coke oven gas are used on-site, recalibration based on actual measured components is required. When the gas composition fluctuates significantly, online monitoring with a gas chromatograph or calorific value analyzer can be introduced, and the real-time calorific value signal can be connected to the control module via analog or digital communication to achieve [further monitoring]. lhv The dynamic update of 2 avoids feedforward compensation deviations caused by calorific value drift. The basic fuel flow rate of the incineration module is output by the furnace temperature feedback PID controller. The feedforward compensation amount and its algebraic sum generate the final flow setpoint, which is then executed through the closed-loop flow regulation loop.

[0091] For example, the excess air coefficient setpoint of the incineration module is calculated as follows:

[0092] Construct a heat loss function with the excess air coefficient as the decision variable;

[0093] Within the preset feasible region of the excess air coefficient, optimization calculations are performed with the goal of minimizing heat loss to obtain the optimal excess air coefficient.

[0094] The optimal excess air coefficient is used as the set value for the excess air coefficient of the incineration module.

[0095] The heat loss function with the excess air coefficient as the decision variable is as follows:

[0096] ;

[0097] in, L ( l () represents the total heat loss; q 1( l This represents heat loss from flue gas exhaust. q 2( l This represents the heat loss due to incomplete chemical combustion. q 3( l () represents heat loss due to incomplete combustion of machinery.

[0098] Specifically, flue gas heat loss refers to the heat loss caused by the sensible heat carried by the flue gas at the incineration module outlet being directly discharged into the atmosphere without being effectively utilized. The specific calculation method is as follows:

[0099] ;

[0100] in, V ( l () represents the volume of dry flue gas produced per unit of fuel; C g The average volumetric heat capacity at constant pressure of dry flue gas is determined online based on the volume fraction of the main components of the flue gas. T p The exhaust gas temperature is measured by the flue gas temperature sensor at the outlet of the incineration module and is affected by the operating conditions of the incinerator and the depth of waste heat recovery. T r For reference temperature, the ambient temperature or the preheating temperature of the combustion air is usually taken.

[0101] The volume of dry flue gas produced per unit of fuel is calculated as follows:

[0102] ;

[0103] in, V 0 This represents the dry flue gas volume under the theoretical air volume. l Excess air coefficient; l 0 The baseline excess air coefficient (usually taken as 1.0).

[0104] Heat loss from incomplete combustion refers to the heat lost due to incomplete oxidation of residual combustible gas components in the flue gas caused by oxygen deficiency or insufficient combustion kinetics. The calculation method is as follows:

[0105] ;

[0106] in, ϵ i For the first i The volume fraction of the combustible gas can be measured in real time by the online gas analyzer at the outlet of the incineration module. q i For the first i The volumetric calorific value of a combustible gas is low.

[0107] Mechanical incomplete combustion heat loss refers to the heat loss caused by solid carbon particles (such as carbon black and tar cracking carbon) or liquid tar droplets in the fuel that do not participate in the combustion reaction, which are discharged with the flue gas or deposited in the furnace and flue. Its calculation method is as follows:

[0108] ;

[0109] in, m ( l () represents the mass flow rate of unburned carbon in the flue gas per unit time; Q c The calorific value of carbon is taken as 32,800. kJ / kg .

[0110] The method for calculating the mass flow rate of unburned carbon in the exhaust gas per unit time is as follows:

[0111] ;

[0112] in, m 0 represents the mass flow rate of tar that was not captured after being processed by the electrostatic tar precipitator module and flowed downstream to the incineration module with the exhaust gas. α The maximum carbonization rate of tar can be pre-calibrated based on the tar composition through thermogravimetric analysis. β The burnout rate coefficient is 2 to 5, which reflects the degree to which the oxidizing atmosphere in the furnace promotes the burnout of carbon particles.

[0113] In this embodiment, the excess air coefficient is typically limited to [ l min , l maxThe range is defined as, for example, 1.1 to 1.8. The lower limit is determined by the risk of incomplete emissions and carbon deposition caused by oxygen-deficient combustion, while the upper limit is constrained by flue gas heat loss and fan energy consumption. The control module acquires the current flue gas temperature, flue gas composition (O2, CO, soot concentration, etc.), and exhaust gas / fuel flow rate in real time, dynamically updates the loss function model, and performs an extreme value search within the preset feasible region in each control cycle (e.g., 1 to 5 seconds) (e.g., golden section method, Fibonacci method, gradient descent method, table lookup interpolation, etc.). The optimization result is set as the target value of the excess air coefficient of the combustion module and sent to the combustion fan frequency converter and fuel flow controller to achieve real-time optimal matching of the air-fuel ratio.

[0114] In this embodiment, the control module can also correct the excess air coefficient setting value based on the deviation between the oxygen concentration in the flue gas at the outlet of the incineration module and the target oxygen concentration value corresponding to the optimal excess air coefficient.

[0115] Specifically, the excess air coefficient setpoint is corrected by using the optimal excess air coefficient output by the heat loss function as the main setpoint, and taking the deviation between the measured oxygen concentration in the flue gas at the combustion module outlet and the corresponding theoretical oxygen concentration target value as the input. The correction amount is dynamically calculated by an incremental PID controller or a fuzzy feedforward-feedback composite corrector, and finally the excess air coefficient setpoint actually issued to the combustion fan and fuel ratio system is generated.

[0116] This embodiment uses a data acquisition module to capture the exhaust gas temperature at the waste heat recovery outlet, the operating parameters of the electrostatic precipitator module, and the status of the alkaline spray in real time. The control module calculates the feedforward compensation for fuel supply. Fuel quantity is adjusted before changes in exhaust gas load are transmitted to the incinerator, improving the perception and response lag problems caused by the long pretreatment process and large delays in traditional feedback control. The control module corrects the excess air coefficient setpoint in real time based on the composition of the flue gas at the incineration module outlet, reducing over-oxygen combustion or oxygen-deficient combustion caused by fixed air distribution.

[0117] Example 2:

[0118] This embodiment provides a method for treating exhaust gas in graphite felt production. This method uses an exhaust gas treatment system for graphite felt production described in Embodiment 1, such as... Figure 3 As shown, it includes the following steps:

[0119] S100: Acquire tail gas temperature data at the outlet of the waste heat recovery module, operating parameters of the electrostatic tar removal module, operating status data of the first and second alkaline spray modules, and flue gas composition data at the outlet of the incineration module.

[0120] Specifically, this embodiment acquires the tail gas temperature and volumetric flow rate at the outlet of the waste heat recovery module in real time. It calculates the tail gas tar concentration and collection efficiency using the operating electrical parameters (secondary current, voltage, flashover frequency) of the online total hydrocarbon analyzer or the electrostatic precipitator module. It also collects the operating status of the first and second alkaline spray modules, including the spray liquid volumetric flow rate, inlet / outlet temperature, density, and circulating liquid pH value. Simultaneously, it uses a flue gas analyzer to continuously monitor the composition data of oxygen, carbon monoxide, nitrogen oxides, and unburned carbon black concentrations in the flue gas at the outlet of the incineration module. All signals are isolated, filtered, and compensated for temperature and pressure before being transmitted to the control module in a standardized format.

[0121] S200: Calculates the fuel supply feedforward compensation amount for the incineration module based on exhaust gas temperature, operating parameters, and operating status.

[0122] Specifically, the control module calculates a first feedforward compensation component based on the deviation between the exhaust gas temperature and the preset temperature, the exhaust gas volumetric flow rate, and the volumetric heat capacity to compensate for changes in the sensible heat of the exhaust gas; it calculates a second feedforward compensation component based on the exhaust gas tar concentration, the real-time collection efficiency of the electrostatic tar collector, and the average lower heating value of the tar to correct fluctuations in the escape calorific value of the tar; it calculates and sums the enthalpy change of the exhaust gas using the spray liquid flow rate, density, volumetric heat capacity, and inlet / outlet temperature difference of the two-stage alkaline spray module, and obtains a third feedforward compensation component by combining it with a correction coefficient to compensate for heat loss caused by spray cooling; it calculates the total energy compensation value by combining the first, second, and third feedforward compensation components according to the calculation method for the fuel replenishment energy compensation value described in Example 1, wherein the third feedforward compensation component is ensured by a negative correction coefficient to ensure that its actual contribution direction is positive compensation.

[0123] S300: Based on the exhaust gas composition data, calculate the excess air coefficient setpoint of the incineration module;

[0124] Specifically, this embodiment uses the composition of the flue gas at the outlet of the incineration module as input to construct a heat loss function with the excess air coefficient as the decision variable. This function includes the flue gas heat loss that monotonically increases with the excess air coefficient, the heat loss from chemical incomplete combustion that rises sharply in the low-oxygen zone, and the heat loss from mechanical incomplete combustion that is affected by carbon deposition and burnout efficiency. Within the preset feasible region of the excess air coefficient, the optimal excess air coefficient that minimizes the total heat loss is solved in real time using optimization algorithms such as the golden section method, Fibonacci method, or gradient descent, and this optimal excess air coefficient is used as the benchmark setting value of the excess air coefficient of the incineration module.

[0125] S400: Generates control commands for the combustion module based on the fuel supply feedforward compensation and the excess air coefficient setpoint.

[0126] The fuel supply feedforward compensation obtained in step S200 is superimposed on the basic fuel flow setting value of the combustion module (output by the furnace temperature feedback PID controller) to form the final fuel valve position command; at the same time, the optimal excess air coefficient setting value obtained in step S300 is converted into the combustion fan inverter frequency setting value and the corresponding air distribution adjustment command after oxygen concentration closed-loop correction; the control module synchronously sends the above commands to the fuel regulating valve and the combustion fan actuator to realize dynamic control of air-fuel ratio through feedforward compensation and feedback optimization.

[0127] In addition, within each control cycle, the control module can refresh the parameters in the heat loss function based on real-time collected data such as exhaust gas temperature and exhaust gas / fuel flow rate, and then perform extreme value search within the preset feasible region to ensure that the optimization result is always based on the current operating conditions.

[0128] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A tail gas treatment system for graphite felt production, characterized by, The exhaust gas treatment system sequentially includes a waste heat recovery module, a first filtration module, an electrostatic tar removal module, a second filtration module, a first alkaline spray module, a second alkaline spray module, an incineration module, and a drying module. The exhaust gas treatment system also includes: The data acquisition module is used to collect the exhaust gas temperature at the outlet of the waste heat recovery module, the operating parameters of the electrostatic tar removal module, the operating status of the first and second alkaline spray modules, and the flue gas composition data at the outlet of the incineration module. The control module is used to calculate the fuel supply feedforward compensation amount of the incineration module based on the exhaust gas temperature, operating parameters and operating status, calculate the excess air coefficient set value of the incineration module based on the outlet flue gas composition data, and generate control commands for the incineration module based on the fuel supply feedforward compensation amount and the excess air coefficient set value. The calculation of the fuel supply feedforward compensation for the incineration module based on exhaust gas temperature, operating parameters, and operating status includes: The first feedforward compensation component is calculated based on the deviation between the exhaust gas temperature and the preset temperature. The second feedforward compensation component is calculated based on the operating parameters; The third feedforward compensation component is calculated based on the operating status. The compensation value of fuel replenishment energy is calculated based on the first feedforward compensation component, the second feedforward compensation component, and the third feedforward compensation component. The fuel supply feedforward compensation is calculated based on the compensation value of the fuel replenishment energy. The first feedforward compensation component is calculated as follows: ； in, ∆E 1 represents the first feedforward compensation component; K 1 represents the first feedforward correction coefficient; Q 1 represents the exhaust gas volumetric flow rate at the outlet of the waste heat recovery module; C V This is the volumetric heat capacity of the exhaust gas; T 0 represents the preset temperature of the exhaust gas at the outlet of the waste heat recovery module; T t This provides real-time exhaust gas temperature data at the outlet of the waste heat recovery module. The second feedforward compensation component is calculated as follows: ； in, ∆E 2 represents the second feedforward compensation component; K 2 represents the second feedforward correction coefficient; c This represents the real-time concentration of tar in the exhaust gas. lhv 1 represents the average lower calorific value of tar; η The real-time tar collection efficiency of the electrostatic tar collector module; The calculation method for the third feedforward compensation component is as follows: ； wherein, ∆E 3 is a third feed-forward compensation component; K 3 is a third feed-forward correction factor; ∆H 1 is the enthalpy change of the tail gas caused by the first caustic spray module; ∆H 2 is the enthalpy change of the tail gas caused by the second caustic spray module; The calculation method for exhaust gas enthalpy change is as follows: ； in, ∆H The enthalpy change of the exhaust gas is caused by the first alkaline spray module or the second alkaline spray module. Q 2 represents the spray liquid volume flow rate of the first alkaline spray module or the second alkaline spray module; ρ The density of the spray solution; C p The volumetric heat capacity of the spray liquid; T out The outlet spray liquid temperature of the first or second alkaline spray module; T in The temperature of the spray liquid at the inlet of the first alkaline spray module or the second alkaline spray module; The calculation method for the compensation value of fuel-added energy is as follows: ； wherein, ∆E Etot is the total energy compensation value to be compensated by fuel The calculation method for fuel supply feedforward compensation is as follows: ； wherein, ∆F is a fuel supply feed forward compensation amount; lhv 2 is the volumetric base lower heating value of the fuel gas; The calculation method for the excess air coefficient setpoint of the incineration module is as follows: Construct a heat loss function with the excess air coefficient as the decision variable; Within the preset feasible region of the excess air coefficient, optimization calculations are performed with the goal of minimizing heat loss to obtain the optimal excess air coefficient. The optimal excess air coefficient is used as the excess air coefficient setting value for the incineration module; The heat loss function with the excess air coefficient as the decision variable is as follows: ； in, L ( λ () represents the total heat loss; q 1( λ This represents heat loss from flue gas exhaust. q 2( λ This represents the heat loss due to incomplete chemical combustion. q 3( λ () represents heat loss due to incomplete combustion of machinery.

2. The tail gas treatment system for producing graphite felt according to claim 1, characterized in that, The control module corrects the excess air coefficient setting based on the deviation between the oxygen concentration in the flue gas at the outlet of the incineration module and the target oxygen concentration corresponding to the optimal excess air coefficient.

3. A method for treating tail gas for graphite felt production, using a system for treating tail gas for graphite felt production according to any one of claims 1 to 2, characterized by, Includes the following steps: Acquire tail gas temperature data at the outlet of the waste heat recovery module, operating parameters of the electrostatic tar removal module, operating status data of the first and second alkaline spray modules, and flue gas composition data at the outlet of the incineration module. Based on exhaust gas temperature, operating parameters, and operating status, calculate the fuel supply feedforward compensation amount for the incineration module. Based on the exhaust gas composition data, the excess air coefficient setpoint of the incineration module is calculated; Based on the fuel supply feedforward compensation and the excess air coefficient setpoint, control commands for the combustion module are generated.

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