Coal-fired unit low-carbon operation output optimization method and system suitable for low-carbon transformation

Abstract

The invention discloses a coal-fired unit low-carbon operation output optimization method and system suitable for low-carbon transformation, and the method comprises the steps: selecting a to-be-studied biomass blending combustion coal-fired coupling carbon capture generator set under coal-electricity low-carbon transformation, and obtaining the related data of a transformed coal-fired unit; a mechanism-data hybrid driven modeling method is adopted, and a mechanism model of the biomass blending combustion coal coupling carbon capture unit obtained after coal-electricity low-carbon transformation is constructed; constructing a low-carbon economic objective function of the biomass blending combustion coal coupled carbon capture generator set after coal-electricity low-carbon transformation, and constructing a calculation model of related low-carbon economic parameters in the objective function; constructing constraint conditions of a biomass blending combustion coal coupling carbon capture generator set after coal-electricity low-carbon transformation, and constraining input and output variables of the mechanism model at the same time; and an optimal low-carbon economic operation output scheme under the scene uncertainty is analyzed and considered, and an optimization result of the operation output of the biomass blending combustion coal coupled carbon capture generator set after coal power low-carbon transformation under the scene uncertainty is obtained through a mode of minimizing an objective function. According to the method, guidance can be provided for the operation output of the biomass blending combustion coal coupling carbon capture power station in each time period in the day.

Description

Technical Field

[0001] This invention relates to the field of energy system operation output optimization technology, and in particular to a method and system for optimizing the low-carbon operation output of coal-fired power units adapted to low-carbon transformation. Background Technology

[0002] SO2 and NO produced by biomass combustion x The emissions are significantly lower than those of coal under the same conditions, while achieving net-zero carbon dioxide emissions. Therefore, the retrofitting of coal-biomass co-fired power plants (CBCFPP) has broad application prospects. In terms of end-of-pipe capture, post-combustion carbon capture (PCC) systems based on chemical absorption can capture CO2 in flue gas, reducing carbon dioxide emissions from thermal power units. They are easy to integrate and have good engineering feasibility. The front-end approach considers co-firing biomass and coal to reduce carbon dioxide input; the end-of-pipe approach considers coupling a carbon capture system to reduce carbon dioxide output. Combining these two technical approaches improves the overall low-carbon flexibility of the unit and helps traditional coal-fired power plants achieve low-carbon transformation and upgrading.

[0003] Due to the significant differences in chemical composition between biomass and coal, the actual co-firing process will affect the original boiler combustion system and related equipment. Increasing the co-firing ratio will alter the boiler furnace outlet flue gas volume, furnace temperature distribution along the height, and boiler efficiency. For the end-of-pipe carbon capture system, the changes in the boiler-side working fluid and flue gas parameters after co-firing will cause fluctuations in the extraction steam parameters on the carbon capture side. Simultaneously, fluctuations in the boiler system's flue gas parameters will also affect the carbon capture effect. Therefore, there are optimal operating conditions under different loads. Based on user-side electricity load demand and carbon dioxide product demand, the overall operating output of the biomass co-firing coal-fired coupled carbon capture generator unit after low-carbon retrofitting of coal-fired power plants is optimized, providing a clean and efficient operating scheme for the coordinated optimization control of the biomass co-firing coal-fired coupled carbon capture generator unit after low-carbon retrofitting of coal-fired power plants. In actual operation, the biomass co-firing coal-fired coupled carbon capture generator unit after low-carbon retrofitting of coal-fired power plants needs to meet the grid's electricity load demand and user-side carbon dioxide product demand. However, due to fluctuations in the power load of the grid caused by the integration of new energy sources, and the significant uncertainty in the demand for carbon dioxide products from the food, chemical, and consumer sectors, the actual unit output optimization needs to comprehensively consider the uncertainties of the electricity and carbon load scenarios in order to improve the adaptability and efficiency of the overall coal-fired unit operation output optimization strategy.

[0004] Current research on biomass-coal co-firing and carbon capture (CCF) generator units after low-carbon retrofitting of coal-fired power plants mainly focuses on the co-firing methods and characteristics of biomass and coal. It primarily examines the temperature distribution and product characteristics within the boiler furnace of coal-fired units with biomass co-firing, and mainly analyzes the thermodynamic parameters and economic characteristics of steady-state models of coal-fired units after low-carbon retrofitting under specific operating conditions. Significant research has explored the modeling and operational output optimization of biomass-coal co-firing and CCF generator units after low-carbon retrofitting at the system level. Existing research on operational output optimization strategies for coal-fired units mainly focuses on optimizing the operational output of the coupled CCF system in coal-fired power plants. Research on operational output optimization of biomass-coal co-firing and CCF generator units is relatively limited. Existing studies often focus on the impact of biomass co-firing amount on the unit's economy and CO2 emission intensity, with fewer studies based on the overall coupled system's mechanistic model and relevant field data for low-carbon and economical operational output optimization. Current research on biomass co-firing in coal-fired power units mainly focuses on the impact of biomass co-firing on the thermal parameters of the boiler furnace system and the optimization of boiler furnace co-firing and integration schemes. However, there is a lack of research on optimizing operating parameters from the overall perspective of biomass co-firing coal-fired power units coupled with carbon capture after low-carbon transformation of coal-fired power plants, which fails to adequately respond to grid load demands and environmental emission targets.

[0005] Therefore, it is necessary to propose a method for optimizing the operating output of biomass-blended coal-fired power plants coupled with carbon capture (CCC) under the low-carbon retrofit of coal-fired power plants. Based on relevant mechanistic models and field data of coal-fired units, and considering the uncertainties of grid load commands and carbon dioxide load demands, the day-ahead operating output of the constructed biomass-blended coal-fired power plants coupled with CCC under the low-carbon retrofit of coal-fired power plants is optimized to obtain the optimal low-carbon and economical operating scheme. This provides a reference for the subsequent coordinated operation control of coal-fired units under the low-carbon retrofit of coal-fired power plants, thereby improving the overall economic and environmental benefits of the units. Summary of the Invention

[0006] Purpose of the invention: This invention provides a method and system for optimizing the low-carbon operation output of coal-fired power units adapted to low-carbon retrofitting, which can provide guidance for the operation output of biomass-co-fired coal-fired power units coupled with carbon capture at different times of the day.

[0007] Technical solution: The present invention provides a method for optimizing the output of coal-fired power units for low-carbon operation in accordance with low-carbon retrofitting, comprising the following steps:

[0008] Step 1: Select the biomass-coal-fired coupled carbon capture generator unit under the low-carbon transformation of coal-fired power plants to be studied, obtain the design parameters of the boiler system, turbine system and carbon capture system of the coal-fired unit after the transformation, and obtain the component analysis data of coal and biomass fuel in the boiler fuel.

[0009] Step 2: Using a mechanism-data hybrid modeling approach, construct a mechanism model for biomass-coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants;

[0010] Step 3: Construct the low-carbon economic objective function for biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants, and construct calculation models for relevant low-carbon economic parameters in the objective function;

[0011] Step 4: Construct the constraints of the biomass co-fired coal-fired power generation unit after the low-carbon transformation of coal-fired power plants. Using the unit design parameters obtained in Step 1 and the mechanism model of the biomass co-fired coal-fired power generation unit after the low-carbon transformation of coal-fired power plants obtained in Step 2, the constraints of relevant parameters are obtained, and the input and output variables in Step 2 are constrained at the same time.

[0012] Step 5: Combining the day-ahead power load and carbon load output plans of the units for the next day, and considering the uncertainty of the actual day-ahead power load instructions and carbon load demand, a scenario generation and back-substitution method is adopted to generate multiple scenarios. Then, the expected value and variance of the objective function are calculated based on the probability of each scenario. The optimal low-carbon economic operation output scheme considering scenario uncertainty is analyzed. By minimizing the objective function in Step 4, the optimization results of the operation output and optimization variables of the biomass co-fired coal-fired coupled carbon capture unit after the low-carbon transformation of coal-fired power plants considering scenario uncertainty are obtained.

[0013] Furthermore, in step 1, the design parameters of the boiler furnace system of the modified coal-fired unit are obtained, including the boiler design coal type parameters. Biomass fuel components The arrangement of each heating surface, damper, and the vertical height of the burner along the boiler furnace height direction. Obtain schematic diagrams of the high-pressure and low-pressure heaters in the steam turbine system, and schematic diagrams of the steam-water flow path. Obtain the diameters and heights of the absorption tower and desorption tower in the carbon capture system, as well as the dimensions of the heat exchangers.

[0014] Furthermore, in step 2, a boiler furnace model for a biomass-coal-fired power plant coupled with carbon capture after low-carbon retrofitting is constructed. This model primarily employs a one-dimensional modeling method. The furnace is divided into different chambers along its height. Heat and mass transfer analyses are performed on these chambers to obtain the flue gas temperature distribution and product distribution in each region after biomass co-firing. This leads to the determination of the flue gas temperature and carbon dioxide emission concentration at the furnace outlet. The typical small cell of the layer is modeled using the lumped parameter method, and the relevant energy conservation, mass conservation, and momentum conservation relationships are shown in the following equations.

[0015]

[0016]

[0017]

[0018] in, express The volume of the small cell layer, m 3 ; Indicates time, in seconds; , They represent the first Flue gas flow rate at the inlet and outlet of the small chamber, kg / s; , They represent the first Enthalpy of flue gas at the inlet and outlet of the chamber, kJ / kg; , They represent the first Flue gas density at the inlet and outlet of the small chamber, kg / m³ 3 ; The specific heat of flue gas is expressed in kJ / (kg⋅K). express The heat absorbed by the small chamber, kJ / s; express The total amount of fuel entering the chamber from the layer. ; , They represent the first Mass flow rate of primary and secondary air in the small chamber. ; , They represent Inlet and outlet pressure of the small chamber ; Represents the flue gas flow resistance coefficient, 1 / m 4 ;

[0019] The enthalpy and density of flue gas can be calculated using thermodynamic equations, as shown below:

[0020]

[0021] in, This indicates the pressure in the small chamber, expressed in Pa. The temperature of the chamber is expressed in °C. This indicates the enthalpy of the flue gas, in kJ / kg. This indicates the density of the flue gas at the outlet of the chamber. ;

[0022] To describe the power generation share of biomass fuel in the fuel mix, the biomass calorific value blending ratio is introduced, defined as follows:

[0023]

[0024] in, Indicates the biomass calorific value blending ratio, %; Indicates entry per unit of time The total calorific value of biomass in the small chambers, ; Indicates entry per unit of time The total calorific value of the fuel in the small chamber, ;

[0025] Combining the information obtained in step 1 regarding the different zones of the heating surface, the arrangement of the dampers, and the distribution height of the burners... The boiler furnace is divided into different compartments, and the material flow in each compartment is analyzed. Combined with the heat transfer equations above, the different compartments in each compartment are connected to construct the overall boiler furnace system, thereby obtaining the temperature in the burner region. and the temperature of each heated surface ;

[0026] The product model is mainly based on the coal and biomass composition analysis data given in step 1, considering the formation mechanisms of carbon dioxide, sulfur dioxide, and nitrogen oxides, and performing relevant calculations in conjunction with chemical reaction coefficients; chemical reaction equilibrium equations are established in different regional chambers, and O2, CO2, SO2, and NO are established respectively. x Dynamic equilibrium equations were used to connect different chambers, constructing a dynamic model of the products generated by biomass-co-fired coal-fired power plants after low-carbon retrofitting, thereby obtaining the carbon dioxide concentration in the boiler furnace outlet flue gas. sulfur dioxide concentration and nitrogen oxide concentration Equal concentration of products;

[0027] The boiler furnace system, turbine system, and carbon capture system are integrated. Biomass and coal fuels are fed into the furnace for combustion. The heat released by fuel combustion is converted into the internal energy of the working fluid. Feedwater absorbs heat to form superheated steam, which then enters the turbine system to generate electricity. A stream of steam is extracted from the intermediate-pressure cylinder stage and sent to the reboiler in the carbon capture system to achieve solvent regeneration and carbon dioxide separation. The reboiler in the carbon capture system extracts steam. A connection was established between the steam turbine system and the carbon capture system. The flue gas generated after boiler fuel combustion passes through denitrification, dust removal, and desulfurization devices, and after a flue gas pretreatment device, it is sent to the carbon capture system for decarbonization. This establishes a connection between the boiler furnace system and the carbon capture system. Through the modeling and coupling relationships of the boiler furnace system, steam turbine system, and carbon capture system, a mechanism model for biomass-blended coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants was formed.

[0028] Select fuel quantity as the input variable. Biomass calorific value and blending ratio and carbon capture steam extraction volume The output variable is the sulfur dioxide concentration at the boiler furnace outlet. Nitrogen oxide concentration at boiler furnace outlet Unit output power Carbon dioxide capture rate Based on the mechanism model constructed above, the optimized output model of the biomass-co-fired coal-fired coupled carbon capture unit after the low-carbon transformation of coal-fired power plants is identified, as shown in the following equation:

[0029]

[0030] To establish the correlation between carbon dioxide products at different times and to buffer the difference between CO2 capture volume and user-side carbon load demand, a carbon storage tank is installed in a biomass-co-fired coal-fired power plant coupled with carbon capture after its low-carbon retrofit. The carbon storage tank model is constructed as shown in the following equation:

[0031]

[0032] in, , Let represent the carbon storage tank capacity at time t and time t-1, respectively, in kg; , , representing the CO2 absorption and release rates of the carbon storage tank at time t, respectively, in kg / h; h represents the time interval between time t and time t-1.

[0033] Furthermore, in step 3, a low-carbon economic objective function is constructed for biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants. The objective function takes into account different electricity and carbon scenarios. The uncertainty of the impact is taken into account, and the overall system's economic and environmental indicators are comprehensively considered; the economic objective function is... Specifically, this includes the total fuel cost of biomass-blended coal-fired power plants coupled with carbon capture after low-carbon retrofitting of coal-fired power plants. System maintenance costs Penalty cost for imbalance between electricity and carbon load Pollutant removal costs and revenue from carbon dioxide products Environmental protection objective function This refers to the net carbon dioxide emissions of biomass-blended coal-fired power plants coupled with carbon capture generators after low-carbon retrofitting of coal-fired power plants. Based on the above indicators, a low-carbon economy objective function is constructed as shown in the following equation:

[0034]

[0035]

[0036] in, The total daily operating cost of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants is expressed in CNY / d under different scenarios. This represents the number of randomly generated electric carbon load scenarios, expressed in units of [number]. This represents the probability of the number of randomly generated electric carbon load scenarios; This indicates the operating output cycle, which is 24 hours, and the unit is h; , These represent the weights of the overall unit's economic benefits and environmental benefits in the objective function, respectively; these are the weighting coefficients. The daily operating economic benefits of biomass-co-fired coal-fired power plants coupled with carbon capture units after low-carbon retrofitting are expressed in CNY / d. , These represent the maximum and minimum daily operating economic benefits, respectively. This represents the purchase cost per unit mass of fuel. The specific value varies depending on the blending ratio and the type of fuel, and the unit is CNY / d. This represents the total operation and maintenance cost of the entire system, expressed in CNY / day. This represents the penalty cost for imbalanced electricity and carbon load, expressed in CNY / d. This indicates the cost of pollutant removal, expressed in CNY / d. This represents carbon trading revenue, expressed in CNY / day. This indicates the daily environmental benefits of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants. , These represent the maximum and minimum values ​​of daily environmental benefits, respectively. This indicates the net carbon dioxide emissions of the entire coupled unit.

[0037] Furthermore, the fuel cost calculation for biomass-co-fired coal-fired power generation coupled with carbon capture generator sets is shown in the following formula:

[0038]

[0039] in, Indicates the operating output cycle, in hours; This represents the fuel cost coefficient per unit mass, and its specific value is related to the biomass calorific value blending ratio. and biomass components Coal composition Regarding CNY / t; express Fuel consumption over a given time period, in kg / s;

[0040] Operation and maintenance costs of biomass co-firing coal-fired power plants coupled with carbon capture units after low-carbon retrofitting of coal-fired power plants The energy consumption costs of power generation from various equipment in the boiler and steam turbine systems of a coal-fired power plant, as well as the operating energy consumption costs of the carbon capture system, are calculated as shown in the following formula:

[0041]

[0042] in, Indicates the operating output cycle, in hours; This represents the unit cost of electricity generated by biomass co-firing with coal, in CNY / MWh; This represents the operation and maintenance cost of a carbon capture system per unit mass of carbon dioxide captured, expressed in CNY / t.

[0043] Electricity and carbon imbalance penalty costs This includes the cost of penalties for power imbalance and carbon load imbalance. The calculation formula is shown below:

[0044]

[0045] in, Indicates the operating output cycle, in hours; The power imbalance penalty coefficient is expressed in CNY / MWh. This represents the carbon dioxide product imbalance penalty coefficient, expressed in CNY / t.

[0046] Pollutant removal costs Mainly includes denitrification systems and desulfurization systems for removing NO. x The economic cost of SO2 is calculated using the following formula:

[0047]

[0048]

[0049] in, Indicates the operating output cycle, in hours; This indicates the mass flow rate of flue gas at the outlet of the furnace outlet chamber, in kg / s; This indicates the composition of the pollutants, here it is... , ; Indicates the removal of pollutants per unit mass Cost of related equipment, CNY / t; This indicates the difference in concentration fraction of pollutants after passing through the relevant equipment; The percentage of pollutant concentration emitted into the air during time period t can be obtained from power plant flue gas monitoring equipment. This indicates the conversion factor for pollutants at the inlet of the corresponding removal equipment;

[0050] Carbon trading revenue This mainly refers to the profit obtained from selling the carbon dioxide products captured by the carbon capture system, calculated as shown in the following formula.

[0051]

[0052] in, Indicates the operating output cycle, in hours; This indicates the transaction price of CO2 products, and its value is affected by various factors such as CO2 purity, purchase scale, and transportation method, in CNY / kg; This indicates the mass of CO2 product released by the carbon storage tank at time t, in kg / s;

[0053] The environmental benefits derived from biomass emissions are mainly based on the net CO2 emissions after biomass co-firing. This primarily considers the CO2 emissions after biomass co-firing and the CO2 fixed during biomass growth. The relevant calculation formula is shown below:

[0054]

[0055] in, Indicates the operating output cycle, in hours; Indicates net carbon dioxide emissions, m 3 ; The volume of flue gas is expressed in m. 3 ; This indicates the percentage of carbon dioxide gas by volume, expressed as % . Indicates the correction factor; This represents the biomass fuel mass flow rate, in kg / s. This indicates the proportion of carbon in the elemental analysis of biomass fuel.

[0056] Furthermore, in step 4, considering the power constraint relationship of biomass-coated coal-fired power generation coupled with carbon capture generator sets, the biomass-coated coal-fired power generation coupled with carbon capture generator sets in... A portion of the system's total output during the time period is used to power the user side; this portion represents the net output power. During the operation of a power plant, energy is consumed by related equipment in the boiler and turbine systems; this portion is referred to as inherent energy consumption. In addition, the carbon capture system consumes a portion of electrical energy for carbon dioxide capture and compressor operation; this portion constitutes the carbon capture system's energy consumption. When the electricity demand far exceeds the total generating load of the power plant, there is an imbalance in power output. Considering the above power balance relationship, the electricity load balance equation is as follows:

[0057]

[0058] in, The total output power of the integrated system during time period t is obtained from the optimized output model, in MWh; This represents the net output power of the generating unit during time period t, i.e., the user-side electrical load, in MWh; This represents the fixed energy consumption (MWh) of various equipment in the boiler and turbine systems during the biomass co-firing coal-fired power generation process in time period t. The energy consumption of the carbon capture system during time period t is expressed in MWh. The power imbalance during time period t is expressed in MWh.

[0059] Considering the carbon emission relationship of power plants, the flue gas from the boiler system of a biomass-co-fired coal-fired generator unit coupled with carbon capture flows into the carbon capture system for CO2 capture. Uncaptured CO2 is released into the atmosphere with the flue gas, while captured CO2 is stored in a carbon dioxide storage tank. Within time period t, the CO2 released from the storage tank and the captured CO2 meet the user's carbon load demand. Excess carbon dioxide continues to be stored in the carbon storage tank to meet subsequent carbon load demands. Based on the above relationship, the carbon emission balance relationship can be obtained, as shown in the following formula:

[0060]

[0061] in, This represents the CO2 capture rate of the carbon capture system in the biomass-co-fired coal-fired power generation unit coupled with carbon capture at time t, in kg / s. This represents the rate at which carbon dioxide is released from the carbon dioxide storage tank at time t, expressed in kg / s. The carbon dioxide absorption rate of the carbon dioxide storage tank at time t is expressed in kg / s. This represents the amount of carbon dioxide out of balance at time t, in kg / s. This represents the user's carbon load demand at time t, in kg / s;

[0062] The mathematical model for the energy consumption of carbon dioxide capture in a carbon capture system is shown in the following equation:

[0063]

[0064] in, This represents the CO2 capture rate of the power plant during time period t, in kg / s. This indicates the energy consumption required for a carbon capture system to capture a unit mass of CO2, expressed in W / kg.

[0065] The optimized output model of the biomass-co-fired coal-fired power generation coupled with carbon capture generator constructed in step 2 can yield constraints on the biomass co-firing ratio and carbon capture rate, as shown in the following equation:

[0066]

[0067]

[0068] in, Indicates the maximum biomass blending ratio, %; This represents the lower limit constraint for carbon capture rate, %;

[0069] The ultimate biomass co-firing ratio in the actual unit model As the load varies under different operating conditions, the limiting blending ratio of biomass is related to the combustion characteristics of the boiler unit. When coal and biomass are co-fired for power generation, the temperature near the burner and the real-time efficiency of the boiler reflect the combustion status of the unit to a certain extent. The limiting blending ratio of biomass can be approximated by these two factors:

[0070]

[0071] in, Indicates the maximum biomass blending ratio, %; A functional relationship representing the limiting biomass blending ratio; This indicates the real-time efficiency of the boiler during operation, expressed as % .

[0072] During the operation of a biomass-coated coal-fired power generation unit, all input and output parameters are subject to upper and lower limits. Therefore, the relevant constraints are shown in the following formula:

[0073]

[0074]

[0075] In actual operation, biomass-co-fired coal-fired power generation coupled with carbon capture and treatment (CCAD) generator units need to maintain a constant water-to-coal ratio on the boiler side to prevent large fluctuations in the temperature or enthalpy of the working fluid at the separator outlet. Therefore, the following constraints exist:

[0076]

[0077] in, The water-coal ratio is a given value, a constant, and the value is selected according to the specific unit boiler type.

[0078] Furthermore, in step 5, the day-ahead electricity and carbon load output plans of the coal-fired units studied in step 1 are obtained, and the day-ahead 24-hour electricity load demand forecast is obtained. 24-hour carbon load forecast as of the date Considering the uncertainties in day-ahead electricity and carbon loads, a scenario-based approach is used to optimize the randomness of the electricity and carbon load scenarios. Assuming that the prediction errors for electricity and carbon loads follow a normal distribution, multiple electricity and carbon load scenarios are generated using the Monte Carlo method based on the predicted values ​​of a typical day-ahead electricity and carbon load. The number of scenarios is then reduced using a synchronous back-substitution reduction method to obtain the electricity and carbon load values ​​for random scenarios. Then, by calculating the expected value and variance of the objective function period through the probability of each scenario, the optimal low-carbon economic operation output result considering the electric load and carbon load under random scenarios is obtained by minimizing the low-carbon economic objective function. This provides guidance for the daily operation output of biomass co-fired coal-fired power generation coupled with carbon capture generator units, and achieves the goal of optimal low-carbon economic operation of coal-fired units.

[0079] Furthermore, the load value and the corresponding load forecast value under random scenarios satisfy the following relationship:

[0080]

[0081]

[0082] in, This indicates either electricity load demand or carbon load demand. Indicates the number of random optimization scenarios. ; express In the scene time The value of the load; express In the scene Time period The error value of the load is a random variable; express Load at The probability value in the scenario.

[0083] Correspondingly, a low-carbon operation output optimization system for coal-fired power units adapted to low-carbon transformation includes: a data acquisition module, a mechanism model construction module, a calculation model construction module, a constraint condition construction module, and an optimization result generation module;

[0084] The data acquisition module selects the biomass-coal-fired coupled carbon capture generator unit under the low-carbon transformation of coal-fired power plants to be studied, and obtains the design parameters of the boiler system, the turbine system and the carbon capture system of the coal-fired unit after the transformation, and obtains the component analysis data of coal and biomass fuel in the boiler fuel.

[0085] The mechanism model construction module adopts a mechanism-data hybrid modeling method to construct a mechanism model of a biomass co-fired coal-fired unit coupled with carbon capture after the low-carbon transformation of coal-fired power plants.

[0086] The calculation model construction module constructs the low-carbon economic objective function of biomass co-firing coal coupled with carbon capture generator units after the low-carbon transformation of coal-fired power plants, and constructs the calculation model of the relevant low-carbon economic parameters in the objective function.

[0087] The constraint construction module constructs the constraint conditions for biomass co-fired coal-fired power generation units after low-carbon retrofitting of coal-fired power plants. By obtaining the unit design parameters and the obtained mechanism model of the biomass co-fired coal-fired power generation units after low-carbon retrofitting of coal-fired power plants, the constraint conditions of relevant parameters are obtained, and the input and output variables of the mechanism model are constrained at the same time.

[0088] The optimization result generation module combines the day-ahead power load and carbon load output plans of the generating units for the next day. Considering the uncertainty of the actual day-ahead power load instructions and carbon load demand, it adopts a scenario generation and back-substitution method to generate multiple scenarios. Then, it calculates the expected value and variance of the objective function based on the probability of each scenario. It analyzes the optimal low-carbon economic operation output scheme considering scenario uncertainty and obtains the optimization results of the operation output of the biomass co-fired coal-fired power generation unit after low-carbon transformation considering scenario uncertainty by minimizing the objective function.

[0089] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: This invention constructs a steady-state operating output mechanism model for biomass-coal-fired power plants coupled with carbon capture after low-carbon retrofitting of coal-fired power plants using a mechanism-data hybrid driven modeling method. Simultaneously, it establishes relevant constraints by combining power plant boiler design parameters and related operating data to construct an optimal low-carbon economic objective function. It obtains the day-ahead electricity and carbon load output plans for coal-fired power plants, then uses the Monte Carlo method to generate multiple sets of electricity and carbon load scenarios, reduces the number of scenarios using a synchronous back-substitution reduction method, and calculates the expected value and variance of the objective function based on the probability of each scenario. By minimizing the objective function, it obtains the optimal operating output scheme for biomass-coal-fired power plants coupled with carbon capture after low-carbon retrofitting of coal-fired power plants, thus obtaining the optimization variables. By considering the uncertainties of electricity and carbon scenarios to reduce the impact of fluctuations in electricity and carbon load predictions, it finally obtains an optimized operating output scheme for biomass-coal-fired power plants coupled with carbon capture under low-carbon retrofitting of coal-fired power plants, providing a reference for lower-level control tracking. Attached Figure Description

[0090] Figure 1 This is a schematic diagram of a typical coal-fired power plant after low-carbon transformation, based on the present invention, featuring biomass co-firing and carbon capture generator sets.

[0091] Figure 2 This is a schematic diagram of the one-dimensional modeling method for the furnace of a biomass-co-fired coal boiler according to the present invention.

[0092] Figure 3This is a schematic diagram of the low-carbon and economical operation output strategy of the biomass-co-fired coal-fired coupled carbon capture unit after the low-carbon transformation of coal-fired power plants according to the present invention.

[0093] Figure 4 This is a graph showing the predicted data for the carbon load scenario of this invention.

[0094] Figure 5 This is a data diagram showing the reduction of electrical load scenarios in this invention.

[0095] Figure 6 This is a data graph showing the reduction of carbon load in the scenario of this invention.

[0096] Figure 7 This is a diagram showing the optimization results of the biomass calorific value blending ratio in this invention. Detailed Implementation

[0097] like Figure 3 As shown, a method for optimizing the output of coal-fired power units for low-carbon operation in accordance with low-carbon retrofitting includes the following steps:

[0098] Step 1: Select the biomass-coated coal-fired power plant coupled with carbon capture (CCC) under the low-carbon retrofit of the coal-fired power plant to be studied, and obtain the design parameters of the boiler furnace system, turbine system, and CCC design parameters of the retrofitted coal-fired unit. Obtain the compositional analysis data of coal and biomass fuel in the boiler fuel.

[0099] Step 2: A mechanism-data hybrid modeling approach is used to construct the mechanism model of the biomass-coal-fired power plant coupled with carbon capture after its low-carbon retrofit. The boiler furnace system, turbine system, and carbon capture system of the biomass-coal-fired power plant coupled with carbon capture after its low-carbon retrofit are modeled using a mechanism-data driven approach. A modular modeling method is used to perform mechanism modeling on the relevant equipment, and the characteristic parameters in the mechanism models of the relevant equipment are obtained by fitting actual operating data. The input variables are set as fuel quantity, biomass calorific value co-firing ratio, and carbon capture steam extraction rate; the output variables are set as the overall power output of the power plant and the carbon dioxide capture rate. The operating output model of the biomass-coal-fired power plant coupled with carbon capture after its low-carbon retrofit is obtained through identification.

[0100] Step 3: Construct the low-carbon economic objective function for biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants, and construct calculation models for relevant low-carbon economic parameters in the objective function.

[0101] Step 4: Construct the constraints for the biomass-coal-fired power plant coupled with carbon capture after its low-carbon retrofit. Using the unit design parameters obtained in Step 1 and the mechanism model of the biomass-coal-fired power plant coupled with carbon capture obtained in Step 2, the constraints for the relevant parameters are obtained, and the input and output variables in Step 2 are simultaneously constrained.

[0102] Step 5: Combining the day-ahead power load and carbon load output plans of the generating units for the next day, and considering the uncertainty of the actual day-ahead power load instructions and carbon load demand, a scenario generation and back-substitution method is adopted to generate multiple scenarios. Then, the expected value and variance of the objective function are calculated based on the probability of each scenario. The optimal low-carbon economic operation output scheme considering scenario uncertainty is analyzed. By minimizing the objective function in Step 4, the optimization results of the operating output and related variables of the biomass co-fired coal-fired coupled carbon capture generator unit after the low-carbon transformation of coal-fired power plants considering scenario uncertainty are obtained.

[0103] Through steps 2, 3, 4, and 5, a method for optimizing the low-carbon economic operation output of biomass-coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants was constructed, providing the optimal low-carbon economic operation scheme for biomass-coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants.

[0104] Step 1 obtains the design parameters of the boiler unit under study, such as the boiler design coal type parameters. Biomass fuel components Vertical height of various heating surfaces, damper arrangement, burners, and other equipment along the height direction of the boiler furnace. The burner location determines the fuel injection position during boiler furnace modeling, and the precision of the corresponding region division is determined by the calculation accuracy requirements of different regions. The distribution of the heating surface affects the division method of different regions in step 2 of the boiler furnace model. Obtain the equipment layout diagram and capacity of each device in the turbine system and carbon capture system of the biomass co-fired coal-fired coupled carbon capture generator unit after low-carbon retrofitting of coal-fired power plants. Construct the mechanism model and relationship of related equipment through the layout of the high-pressure heater and low-pressure heater of the turbine system. The diameter and height of the absorption tower and desorption tower of the carbon capture system, as well as the heat exchanger size, provide the parameter basis for the model construction of related equipment in step 2. A typical schematic diagram of a biomass co-fired coal-fired coupled carbon capture generator unit after low-carbon retrofitting of coal-fired power plants is shown below. Figure 1 As shown.

[0105] Step 2: Construct a boiler furnace model for a biomass-coal-fired power plant with carbon capture after low-carbon retrofitting. The boiler furnace model for this retrofit primarily employs a one-dimensional modeling method. The furnace is divided into different compartments along its height. Heat and mass transfer analyses are performed on these compartments to obtain the flue gas temperature distribution and product distribution in each region after biomass co-firing, thereby determining the flue gas temperature at the furnace outlet and the carbon dioxide emission concentration. Specific heat and mass transfer analyses of the boiler furnace compartment model are as follows: Figure 2 As shown. For The typical small cell of the layer is modeled using the lumped parameter method, and the relevant energy conservation, mass conservation and momentum conservation relationships are shown in equations (1) to (3).

[0106] (1)

[0107] (2)

[0108] (3)

[0109] in, express The volume of the small cell layer, m 3 ; Indicates time, in seconds; , They represent the first Flue gas flow rate at the inlet and outlet of the small chamber, kg / s; , They represent the first Enthalpy of flue gas at the inlet and outlet of the chamber, kJ / kg; , They represent the first Flue gas density at the inlet and outlet of the small chamber, kg / m³ 3 ; The specific heat of flue gas is expressed in kJ / (kg⋅K). express The heat absorbed by the small chamber, kJ / s; express The total amount of fuel entering the chamber from the layer. ; , They represent the first Mass flow rate of primary and secondary air in the small chamber. ; , They represent Inlet and outlet pressure of the small chamber ; Represents the flue gas flow resistance coefficient, 1 / m 4 .

[0110] The enthalpy and density of the flue gas involved in equations (1) to (3) can be calculated using the thermodynamic equation (4), as shown in equation (4):

[0111] (4)

[0112] in, This indicates the pressure in the small chamber, expressed in Pa. The temperature of the chamber is expressed in °C. This indicates the enthalpy of the flue gas, in kJ / kg. This indicates the density of the flue gas at the outlet of the chamber. .

[0113] To describe the power generation share of biomass fuel in fuel, the biomass calorific value blending ratio is introduced, defined as shown in equation (5):

[0114] (5)

[0115] in, Indicates the biomass calorific value blending ratio, %; Indicates entry per unit of time The total calorific value of biomass in the small chambers, ; Indicates entry per unit of time The total calorific value of the fuel in the small chamber, .

[0116] Combining the information obtained in step 1 regarding the different zones of the heating surface, the arrangement of the dampers, and the distribution height of the burners... The boiler furnace is divided into different compartments, and the material flow in each compartment is analyzed. Combined with the heat transfer equations above, the different compartments in each compartment are connected to construct the overall boiler furnace system, thereby obtaining the temperature in the burner region. and the temperature of each heated surface .

[0117] The product model is primarily based on the coal and biomass composition analysis data provided in step 1. Considering the formation mechanisms of carbon dioxide, sulfur dioxide, and nitrogen oxides, relevant calculations are performed using chemical reaction coefficients. Chemical reaction equilibrium equations are established in different regional chambers, and equations are established for O2, CO2, SO2, and NO2, respectively. x The dynamic equilibrium equation was then used to connect different chambers, constructing a dynamic model of the products from a biomass-co-fired coal-fired power plant coupled with carbon capture after low-carbon retrofitting. This allowed the determination of the carbon dioxide concentration in the boiler furnace outlet flue gas. sulfur dioxide concentration and nitrogen oxide concentration Equal concentration of products.

[0118] The modeling of the steam turbine system in the biomass-blended coal-fired power plant coupled with carbon capture after the low-carbon transformation of coal-fired power plants mainly involves constructing models of the superheater, economizer, reheater, main steam valves, turbine pressure stages, feedwater heater, condenser and hot well, deaerator, and feedwater pumps. The size and connection method of each device are based on the relevant design parameters of the steam turbine system in step 1. The lumped parameter method is mainly used for modeling the steam turbine system to analyze the heat and mass transfer processes in each device. Stodola's flow cone law is mainly used for modeling each pressure stage.

[0119] The post-combustion carbon capture system based on chemical absorption mainly includes equipment such as an absorption tower, desorption tower, heat exchanger, reboiler, condenser, and compressor. The tower height and equipment capacity are obtained based on the carbon capture system design parameters acquired in step 1. The absorption tower and desorption tower of the carbon capture system are mainly modeled using the rate method. The reboiler and condenser are both heat exchangers, and their mathematical models are essentially the same as those of heat exchangers, constructed using mass and energy conservation equations. The compressor model is mainly constructed based on the compressor characteristic curves, establishing the relationship between the compressor's CO2 intake mass flow rate and compressor efficiency with the compression ratio, inlet guide vane opening, and rotational speed. During the modeling process, relevant parameters are determined by fitting data from actual power plants.

[0120] The boiler furnace system, turbine system, and carbon capture system described above are integrated. Biomass and coal fuels are fed into the furnace for combustion. The heat released from fuel combustion is converted into the internal energy of the working fluid. Feedwater absorbs heat to form superheated steam, which then enters the turbine system to generate electricity. A stream of steam is extracted from the intermediate-pressure cylinder stage and sent to the reboiler in the carbon capture system for solvent regeneration and carbon dioxide separation. The reboiler in the carbon capture system extracts steam. A connection was established between the steam turbine system and the carbon capture system. The flue gas generated after boiler fuel combustion passes through denitrification, dust removal, and desulfurization devices, and after a flue gas pretreatment device, it is sent to the carbon capture system for decarbonization. This establishes a connection between the boiler furnace system and the carbon capture system. Through the modeling and coupling relationships of the boiler furnace system, steam turbine system, and carbon capture system, a mechanism model for biomass-blended coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants was formed.

[0121] Select fuel quantity as the input variable. Biomass calorific value and blending ratio and carbon capture steam extraction volume The output variable is the sulfur dioxide concentration at the boiler furnace outlet. Nitrogen oxide concentration at boiler furnace outlet Unit output power Carbon dioxide capture rate Based on the mechanism model constructed above, the optimized output model of the biomass co-fired coal-fired coupled carbon capture unit after the low-carbon transformation of coal-fired power plants is identified, as shown in equation (6):

[0122] (6)

[0123] To establish the connection between carbon dioxide products at different times and to buffer the difference between CO2 capture volume and user-side carbon load demand, a carbon storage tank is equipped in the biomass-co-fired coal-fired coupled carbon capture generator unit after the coal-fired power plant has undergone low-carbon transformation. The carbon storage tank model is constructed as shown in equation (7):

[0124] (7)

[0125] in, , Let represent the carbon storage tank capacity at time t and time t-1, respectively, in kg; , , representing the CO2 absorption and release rates of the carbon storage tank at time t, respectively, in kg / h; h represents the time interval between time t and time t-1.

[0126] Step 3: Construct a low-carbon economic objective function for biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants. The objective function takes into account different electricity and carbon scenarios. The uncertainty of the impact is considered, taking into account both the overall system's economic and environmental indicators. Economic objective function. Specifically, this includes the total fuel cost of biomass-coated coal-fired power plants coupled with carbon capture units after low-carbon retrofitting of coal-fired power plants. System maintenance costs Penalty cost for imbalance between electricity and carbon load Pollutant removal costs and revenue from carbon dioxide products Environmental protection objective function This refers to the net carbon dioxide emissions of biomass-blended coal-fired power plants coupled with carbon capture generators after low-carbon retrofitting of coal-fired power plants. Based on the above indicators, the objective function is constructed as shown in equations (8) and (9):

[0127] (8)

[0128] (9)

[0129] in, The total daily operating cost (CNY / d) of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants is expressed in different scenarios. This indicates the number of randomly generated electricity and carbon load scenarios; This represents the probability of the number of randomly generated electric carbon load scenarios; This indicates the operating output cycle, which is 24 hours (h). , These represent the weights of the overall unit's economic benefits and environmental benefits in the objective function, respectively; these are the weighting coefficients. The daily operating economic benefit of a biomass-co-fired coal-fired unit coupled with carbon capture after low-carbon transformation of coal-fired power plants is expressed in CNY / d. , These represent the maximum and minimum daily operating economic benefits, respectively. This represents the purchase cost per unit mass of fuel. The specific value varies depending on the blending ratio and the type of fuel, in CNY / d. This represents the total system maintenance cost, expressed in CNY / day. This represents the penalty cost for an imbalance between electricity and carbon loads, expressed in CNY / d. This indicates the cost of pollutant removal, expressed in CNY / d. This represents carbon trading revenue, in CNY / day. This indicates the daily environmental benefits of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants. , These represent the maximum and minimum values ​​of daily environmental benefits, respectively. This indicates the net carbon dioxide emissions of the entire coupled unit.

[0130] The fuel cost calculation for biomass co-firing coal-fired power generation coupled with carbon capture generator sets is shown in equation (10):

[0131] (10)

[0132] in, Indicates the operating output cycle, in hours; This represents the fuel cost coefficient per unit mass, and its specific value is related to the biomass calorific value blending ratio. and biomass components Coal composition Regarding CNY / t; express Fuel consumption during the time period, in kg / s.

[0133] Operation and maintenance costs of biomass co-firing coal-fired power plants coupled with carbon capture units after low-carbon retrofitting of coal-fired power plants This includes the power generation energy consumption cost of each device in the boiler system and steam turbine system of a coal-fired power plant, as well as the operating energy consumption cost of the carbon capture system. The calculation is shown in equation (11).

[0134] (11)

[0135] in, Indicates the operating output cycle, in hours; This represents the unit cost of electricity generated by biomass co-firing with coal, in CNY / MWh; This represents the operation and maintenance cost of a carbon capture system per unit mass of carbon dioxide captured, expressed in CNY / t.

[0136] Electricity and carbon imbalance penalty costs This includes the cost of power imbalance penalty and the cost of carbon load imbalance penalty. The calculation formula is shown in equation (12):

[0137] (12)

[0138] in, Indicates the operating output cycle, in hours; The power imbalance penalty coefficient is expressed in CNY / MWh. This represents the carbon dioxide product imbalance penalty coefficient, in CNY / t.

[0139] Pollutant removal costs Mainly includes denitrification systems and desulfurization systems for removing NO. x The economic cost of SO2 is calculated using equations (13) and (14):

[0140]

[0141]

[0142] in, Indicates the operating output cycle, in hours; This indicates the mass flow rate of flue gas at the outlet of the furnace outlet chamber, in kg / s; This indicates the composition of the pollutants, here it is... , ; Indicates the removal of pollutants per unit mass Cost of related equipment, CNY / t; This indicates the difference in concentration fraction of pollutants after passing through the relevant equipment; The percentage of pollutant concentration emitted into the air during time period t can be obtained from power plant flue gas monitoring equipment. This indicates the conversion factor for pollutants at the inlet of the corresponding removal equipment.

[0143] Carbon trading revenue This mainly refers to the profit obtained from selling carbon dioxide products captured by the carbon capture system, calculated as shown in equation (15).

[0144] (15)

[0145] in, Indicates the operating output cycle, in hours; This indicates the transaction price of CO2 products, and its value is affected by various factors such as CO2 purity, purchase scale, and transportation method, in CNY / kg; This indicates the mass of CO2 product released by the carbon storage tank at time t, in kg / s.

[0146] The environmental benefits derived from biomass emissions are mainly based on the net CO2 emissions after biomass co-firing. This mainly considers the CO2 emissions after biomass co-firing and the CO2 fixed during biomass growth. The relevant calculation formula is shown in formula (16):

[0147] (16)

[0148] in, Indicates the operating output cycle, in hours; Indicates net carbon dioxide emissions, m 3 ; The volume of flue gas is expressed in m. 3 ; This indicates the percentage of carbon dioxide gas by volume, expressed as % . Indicates the correction factor; This represents the biomass fuel mass flow rate, in kg / s. This indicates the proportion of carbon in the elemental analysis of biomass fuel.

[0149] Step 4: Considering the power constraints of biomass-coated coal-fired power generation coupled with carbon capture generator sets, the biomass-coated coal-fired power generation coupled with carbon capture generator sets in... A portion of the system's total output during the time period is used to power the user side; this portion represents the net output power. During the operation of a power plant, energy is consumed by related equipment in the boiler and turbine systems; this portion is referred to as inherent energy consumption. In addition, the carbon capture system consumes a portion of electrical energy for carbon dioxide capture and compressor operation; this portion constitutes the carbon capture system's energy consumption. When the electrical load demand far exceeds the total power generation load of the power plant, there is an electrical load imbalance. Considering the above power balance relationship, the electrical load balance equation is shown in equation (17):

[0150] (17)

[0151] in, Let MWh represent the total output power of the integrated system during time period t, which can be obtained from the optimized output power model (6). This represents the net output power of the generating unit during time period t, i.e., the user-side electrical load, in MWh; This represents the fixed energy consumption (MWh) of various equipment in the boiler and turbine systems during the biomass co-firing coal-fired power generation process in time period t. The energy consumption of the carbon capture system during time period t is expressed in MWh. The power imbalance during time period t is expressed in MWh.

[0152] Considering the carbon emission relationship of power plants, the flue gas from the boiler system of a biomass-co-fired coal-fired generator unit coupled with carbon capture flows into the carbon capture system for CO2 capture. Uncaptured CO2 is released into the atmosphere with the flue gas. The captured CO2 is stored in a carbon dioxide storage tank. During time period t, the CO2 released from the storage tank and the captured CO2 meet the user's carbon load demand. Excess carbon dioxide is stored in the carbon storage tank to meet subsequent carbon load demands. Based on the above relationship, the carbon emission balance relationship can be obtained, as shown in equation (18):

[0153] (18)

[0154] in, This represents the CO2 capture rate of the carbon capture system in the biomass-co-fired coal-fired power generation unit coupled with carbon capture at time t, in kg / s. This represents the rate at which carbon dioxide is released from the carbon dioxide storage tank at time t, expressed in kg / s. The carbon dioxide absorption rate of the carbon dioxide storage tank at time t is expressed in kg / s. This represents the amount of carbon dioxide out of balance at time t, in kg / s. This represents the user's carbon load demand at time t, in kg / s.

[0155] The mathematical model of energy consumption for capturing carbon dioxide in a carbon capture system is shown in equation (19):

[0156] (19)

[0157] in, This represents the CO2 capture rate of the power plant during time period t, in kg / s. This indicates the energy consumption required for a carbon capture system to capture a unit mass of CO2, expressed in W / kg.

[0158] The optimized output model of the biomass co-firing coal-fired power generation coupled with carbon capture generator set constructed in step 2 can obtain the biomass co-firing ratio constraint and carbon capture rate constraint, as shown in equations (20) and (21).

[0159] (20)

[0160] (twenty one)

[0161] in, Indicates the maximum biomass blending ratio, %; This indicates the lower limit constraint on carbon capture rate, %.

[0162] The ultimate biomass co-firing ratio in the actual unit model As the load varies under different operating conditions, the limiting blending ratio of biomass is related to the combustion characteristics of the boiler unit. When coal and biomass are co-fired for power generation, the temperature near the burner and the real-time efficiency of the boiler reflect the combustion status of the unit to a certain extent, and the limiting blending ratio of biomass can be approximated by these two factors.

[0163] (twenty two)

[0164] in, Indicates the maximum biomass blending ratio, %; A functional relationship representing the limiting biomass blending ratio; This indicates the real-time efficiency of the boiler during operation, expressed as %.

[0165] During the operation of biomass-co-fired power generation units, all input and output parameters are subject to upper and lower limits, as shown in equations (23) and (24):

[0166] (twenty three)

[0167] (twenty four)

[0168] In actual operation, biomass co-firing coal-fired power generation coupled with carbon capture generator sets need to maintain a constant water-to-coal ratio on the boiler side to prevent large fluctuations in the temperature or enthalpy of the working fluid at the separator outlet. Therefore, the following constraint relationship exists (25):

[0169] (25)

[0170] in, The water-coal ratio is a given value, a constant, and the value is selected according to the specific unit boiler type.

[0171] Step 5: Obtain the day-ahead electricity and carbon load output plans of the coal-fired units studied in Step 1, and obtain the day-ahead 24-hour electricity load demand. 24-hour carbon load forecast as of the date ,like Figure 4 As shown. Considering the uncertainty of day-ahead electricity and carbon loads, a scenario-based optimization approach is used to handle the randomness of the load. Assuming that the electricity and carbon loads follow a normal distribution, based on a typical intraday electricity and carbon load scenario, multiple electricity and carbon load scenarios are generated using the Monte Carlo method. The number of scenarios is then reduced using a synchronous back-substitution reduction method, assumed to be reduced to four scenarios. The reduced electricity and carbon loads are... like Figure 5 , Figure 6 As shown. Then, the expected value and variance of the objective function are calculated based on the probabilities of each scenario, and the probabilities of each scenario are... As shown in Table 1, and satisfying the following:

[0172] (26)

[0173] By minimizing the objective function (8), the optimal low-carbon economic operation output considering the electricity and carbon loads under random scenarios is obtained, and the optimized value of the biomass calorific value co-firing ratio for each time period is obtained. ,like Figure 7 As shown, the biomass calorific value blending ratio at different time periods guides the operation output of biomass-blended coal-fired power generation units coupled with carbon capture generators after low-carbon transformation of coal-fired power plants, so as to achieve the goal of optimal low-carbon and economical operation of coal-fired units.

[0174] Table 1. Probability of Occurrence of Typical Electricity and Carbon Scenarios Scene 1 Scene 2 Scene 3 Scene 4 Electrical load scenarios 0.2369 0.2226 0.2564 0.2842 Carbon load scenarios 0.2718 0.2048 0.2542 0.2691

[0175] This invention constructs a method for optimizing the operating output of biomass-coal-fired power plants coupled with carbon capture (CCF) after low-carbon retrofitting. A steady-state operating output mechanism model of the biomass-coal-fired power plants coupled with CCF is constructed using a mechanism-data hybrid driven modeling approach. Simultaneously, relevant constraints are established by combining power plant boiler design parameters and related operating data to construct an optimal low-carbon economic objective function. The optimal operating output scheme of the biomass-coal-fired power plants coupled with CCF after low-carbon retrofitting is obtained by minimizing the objective function. By obtaining the day-ahead electricity and carbon load output plans of the coal-fired units, multiple electricity and carbon load scenarios are generated using the Monte Carlo method. The number of scenarios is reduced using the synchronous back-substitution method, and the expected value and variance of the objective function are calculated based on the probability of each scenario. Finally, the optimal operating output scheme of the entire unit is obtained by minimizing the objective function, and the optimal values ​​of the biomass calorific value co-firing ratio are also obtained for each time period, guiding unit operators in low-carbon economic control. By considering the uncertainties of electricity and carbon scenarios to reduce the impact of fluctuations in electricity and carbon load forecasts, an optimized operating output scheme for biomass-co-fired coal-fired coupled carbon capture generator units under low-carbon transformation is finally obtained, providing a reference for lower-level control and tracking.

Claims

1. A method for optimizing the output of coal-fired power units during low-carbon operation in accordance with low-carbon retrofitting, characterized in that, Includes the following steps: Step 1: Select the biomass-coal-fired coupled carbon capture generator unit under the low-carbon transformation of coal-fired power plants to be studied, obtain the design parameters of the boiler system, turbine system and carbon capture system of the coal-fired unit after the transformation, and obtain the component analysis data of coal and biomass fuel in the boiler fuel. Step 2: Using a mechanism-data hybrid modeling approach, construct a mechanism model for biomass-coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants; Step 3: Construct the low-carbon economic objective function for biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants, and construct calculation models for each low-carbon economic parameter in the objective function; Step 4: Construct the constraints of the biomass co-fired coal-fired power generation unit after the low-carbon transformation of coal-fired power plants. Using the unit design parameters obtained in Step 1 and the mechanism model of the biomass co-fired coal-fired power generation unit after the low-carbon transformation of coal-fired power plants obtained in Step 2, the constraints of relevant parameters are obtained, and the input and output variables in Step 2 are constrained at the same time. Step 5: Combining the day-ahead power load and carbon load output plan of the generator units for the next day, and considering the uncertainty of the actual day-ahead power load command and carbon load demand, a scenario generation back-substitution method is adopted to generate multiple scenarios. Then, the expected value and variance of the objective function in Step 3 are calculated by using the probability of each scenario. By minimizing the objective function in Step 4, the optimized result of the operating output of the biomass co-fired coal-fired coupled carbon capture generator units after the low-carbon transformation of coal-fired power plants considering scenario uncertainty is obtained.

2. The method for optimizing the output of coal-fired power units after low-carbon retrofitting as described in claim 1, characterized in that, In step 1, the design parameters of the boiler furnace system of the modified coal-fired unit are obtained, including the boiler design coal type parameters. Biomass fuel components The arrangement of each heating surface, damper, and the vertical height of the burner along the boiler furnace height direction. Obtain schematic diagrams of the layout of the high-pressure and low-pressure heaters in the steam turbine system, and schematic diagrams of the steam-water flow; obtain the diameter and height of the absorption tower and desorption tower in the carbon capture system, as well as the dimensions of the heat exchangers.

3. The method for optimizing the low-carbon operation output of coal-fired power units adapted to the low-carbon retrofit of coal-fired power plants as described in claim 1, characterized in that, In step 2, a boiler furnace model of a biomass-coal-fired power generation unit coupled with carbon capture after low-carbon transformation of coal-fired power plants is constructed. The boiler furnace model of the biomass-coal-fired power generation unit coupled with carbon capture after low-carbon transformation of coal-fired power plants adopts a one-dimensional modeling method. The furnace is divided into different compartments along its height. Heat and mass transfer analysis is performed in different compartments to obtain the furnace flue gas temperature distribution and the distribution of byproducts in each region after biomass co-firing. This leads to the furnace outlet flue gas temperature and carbon dioxide emission concentration. The typical small cell of the layer is modeled using the lumped parameter method, and the relevant energy conservation, mass conservation, and momentum conservation relationships are shown in the following equations: in, express The volume of the small chamber is expressed in cubic meters. 3 ; Indicates time, in seconds; , They represent the first Flue gas flow rate at the inlet and outlet of the small chamber, in kg / s; , They represent the first The enthalpy values ​​of the flue gas at the inlet and outlet of the small chamber are expressed in kJ / kg. , They represent the first Flue gas density at the inlet and outlet of the small chamber, in kg / m³ 3 ; This indicates the specific heat of the flue gas, expressed in kJ / (kg⋅K). express The heat absorbed by the small chamber is expressed in kJ / s. express Total fuel amount entering the chamber, in units of ; , They represent the first Mass flow rates of primary and secondary air in a small chamber, in units of ; , They represent Inlet and outlet pressure of the small chamber, unit: ; This represents the flue gas flow resistance coefficient, with units of 1 / m. 4 ; The enthalpy and density of the flue gas are calculated using thermodynamic equations, as shown below: in, This indicates the pressure inside the chamber, expressed in Pa. This indicates the temperature of the chamber, in °C. This indicates the enthalpy of the flue gas, expressed in kJ / kg. This indicates the density of the flue gas at the outlet of the chamber, in units of... ; To describe the power generation share of biomass fuel in the fuel mix, the biomass calorific value blending ratio is introduced, defined as follows: in, The biomass calorific value blending ratio is expressed as a percentage (%). Indicates entry per unit of time The total calorific value of biomass in the small chamber, in units of ; Indicates entry per unit of time The total calorific value of the fuel in the small chamber, in units of ; Combining the information obtained in step 1 regarding the different zones of the heating surface, the arrangement of the dampers, and the distribution height of the burners... The boiler furnace is divided into different compartments, and the material flow in each compartment is analyzed. Combined with the heat transfer equations above, the different compartments in each compartment are connected to construct the overall boiler furnace system, thereby obtaining the temperature in the burner region. and the temperature of each heated surface ; The product model is mainly based on the coal and biomass composition analysis data given in step 1, considering the formation mechanisms of carbon dioxide, sulfur dioxide, and nitrogen oxides, and performing relevant calculations in conjunction with chemical reaction coefficients; chemical reaction equilibrium equations are established in different regional chambers, and O2, CO2, SO2, and NO are established respectively. x Dynamic equilibrium equations were used to connect different chambers, constructing a dynamic model of the products generated by biomass-co-fired coal-fired power plants after low-carbon retrofitting, thereby obtaining the carbon dioxide concentration in the boiler furnace outlet flue gas. sulfur dioxide concentration and nitrogen oxide concentration Concentration of product; The boiler furnace system, turbine system, and carbon capture system are integrated. Biomass and coal fuels are fed into the furnace for combustion. The heat released by fuel combustion is converted into the internal energy of the working fluid. Feedwater absorbs heat to form superheated steam, which then enters the turbine system to generate electricity. A stream of steam is extracted from the intermediate-pressure cylinder stage and sent to the reboiler in the carbon capture system to achieve solvent regeneration and carbon dioxide separation. The reboiler in the carbon capture system extracts steam. The connection between the steam turbine system and the carbon capture system was established. The flue gas formed after the boiler fuel combustion passes through denitrification, dust removal and desulfurization devices, and is then sent to the carbon capture system for decarbonization after passing through the flue gas pretreatment device. The flue gas establishes the connection between the boiler furnace system and the carbon capture system. Through the model construction and coupling relationship of the above boiler furnace system, steam turbine system and carbon capture system, a mechanism model of biomass co-fired coal-fired coupled carbon capture power generation unit after the low-carbon transformation of coal power is formed. Select fuel quantity as the input variable. Biomass calorific value co-firing ratio and carbon capture steam extraction volume The output variable is the sulfur dioxide concentration at the boiler furnace outlet. Nitrogen oxide concentration at boiler furnace outlet Unit output power Carbon dioxide capture rate Based on the mechanism model constructed above, the optimized output model of the biomass-co-fired coal-fired coupled carbon capture unit after the low-carbon transformation of coal-fired power plants is identified, as shown in the following equation: To establish the correlation between carbon dioxide products at different times and to buffer the difference between CO2 capture volume and user-side carbon load demand, carbon storage tanks are installed in biomass-co-fired coal-fired power plants that have undergone low-carbon transformation. A carbon storage tank model is constructed as shown in the following formula: in, , These represent the carbon storage tank capacities at time t and t-1, respectively, in kg. , These represent the CO2 absorption and release rates of the carbon storage tank at time t, respectively, in kg / h. This represents the time interval between time t and time t-1, in hours (h).

4. The method for optimizing the low-carbon operation output of coal-fired power units adapted to the low-carbon retrofit of coal-fired power plants as described in claim 1, characterized in that, In step 3, a low-carbon economic objective function for biomass-co-fired coal-fired power generation units coupled with carbon capture and disposal (CCD) after low-carbon retrofitting of coal-fired power plants is constructed. The objective function takes into account different electricity and carbon scenarios. The uncertainty of the impact is taken into account, and the overall system's economic and environmental indicators are comprehensively considered; the economic objective function is... Specifically, this includes the total fuel cost of biomass-blended coal-fired power plants coupled with carbon capture after low-carbon retrofitting of coal-fired power plants. System maintenance costs Penalty cost for imbalance between electricity and carbon load Pollutant removal costs and revenue from carbon dioxide products Environmental protection objective function This refers to the net carbon dioxide emissions of biomass-blended coal-fired power plants coupled with carbon capture generators after low-carbon retrofitting of coal-fired power plants. Based on the above indicators, a low-carbon economy objective function is constructed as shown in the following formula: in, The total daily operating cost of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon retrofitting of coal-fired power plants is expressed in CNY / d under different scenarios. This represents the number of randomly generated electric carbon load scenarios, expressed in units of [number]. This represents the probability of the number of randomly generated electric carbon load scenarios; This indicates the operating output cycle, which is 24 hours, and the unit is h; , These represent the weights of the overall unit's economic benefits and environmental benefits in the objective function, respectively; these are the weighting coefficients. The daily operating economic benefits of biomass-co-fired coal-fired power plants coupled with carbon capture units after low-carbon retrofitting are expressed in CNY / d. , These represent the maximum and minimum daily operating economic benefits, respectively. This represents the purchase cost per unit mass of fuel. The specific value varies depending on the blending ratio and the type of fuel, and the unit is CNY / d. This represents the total operation and maintenance cost of the entire system, expressed in CNY / day. This represents the penalty cost for imbalanced electricity and carbon load, expressed in CNY / d. This indicates the cost of pollutant removal, expressed in CNY / d. This represents carbon trading revenue, expressed in CNY / day. This indicates the daily environmental benefits of biomass-co-fired coal-fired power generation units coupled with carbon capture after low-carbon transformation of coal-fired power plants. , These represent the maximum and minimum values ​​of daily environmental benefits, respectively. This indicates the net carbon dioxide emissions of the entire coupled unit.

5. The method for optimizing the low-carbon operation output of coal-fired power units adapted to the low-carbon retrofit of coal-fired power plants as described in claim 4, characterized in that, The fuel cost calculation for a biomass-co-fired coal-fired power generation unit coupled with carbon capture is shown in the following formula: in, Indicates the operating output cycle, in hours; This represents the fuel cost coefficient per unit mass, and its specific value is related to the biomass calorific value blending ratio. and biomass components Coal composition The unit is CNY / t; express Fuel consumption over a given time period, expressed in kg / s; Operation and maintenance costs of biomass co-firing coal-fired power plants coupled with carbon capture units after low-carbon retrofitting The energy consumption costs of power generation from various equipment in the boiler and steam turbine systems of a coal-fired power plant, as well as the operating energy consumption costs of the carbon capture system, are calculated as shown in the following formula: in, Indicates the operating output cycle, in hours; This represents the unit cost of electricity generated by biomass co-firing with coal, expressed in CNY / MWh. This represents the operation and maintenance cost of a carbon capture system per unit mass of carbon dioxide captured, expressed in CNY / t. Electricity and carbon imbalance penalty costs The cost includes penalties for power imbalance and carbon load imbalance, and the calculation formula is shown below: in, Indicates the operating output cycle, in hours; This represents the penalty coefficient for power imbalance, expressed in CNY / MWh. This represents the carbon dioxide product imbalance penalty coefficient, expressed in CNY / t. Pollutant removal costs Including denitrification systems and desulfurization systems for removing NO x The economic cost of SO2 is calculated using the following formula: in, Indicates the operating output cycle, in hours; This indicates the mass flow rate of flue gas at the outlet of the furnace outlet chamber, in kg / s. This indicates the composition of the pollutants, here it is... , ; Indicates the removal of pollutants per unit mass The cost of the relevant equipment is expressed in CNY / t. This indicates the concentration fraction difference of pollutants after passing through the relevant equipment; This represents the pollutant emission concentration fraction during time period t, obtained from the power plant's flue gas monitoring equipment, and is expressed in percentages (%). This indicates the conversion factor for pollutants at the inlet of the corresponding removal equipment; Carbon trading revenue This mainly refers to the profit obtained from selling the carbon dioxide products captured by the carbon capture system, calculated as follows: in, Indicates the operating output cycle, in hours; This indicates the transaction price of CO2 products. Its value is affected by various factors such as CO2 purity, purchase scale, and transportation method. The unit is CNY / kg. This indicates the mass of CO2 product released by the carbon storage tank at time t, in kg / s. The environmental benefits derived from biomass emissions are mainly based on the net CO2 emissions after biomass co-firing. This primarily considers the CO2 emissions after biomass co-firing and the CO2 fixed during biomass growth. The relevant calculation formula is shown below: in, Indicates the operating output cycle, in hours; This represents net carbon dioxide emissions, expressed in m³ / s. 3 ; This indicates the volume of flue gas, in meters (m³). 3 ; This indicates the percentage of carbon dioxide by volume, expressed in % (%). Indicates the correction factor; This indicates the mass flow rate of biomass fuel, expressed in kg / s. This indicates the proportion of carbon in the elemental analysis of biomass fuel.

6. The method for optimizing the low-carbon operation output of coal-fired power units adapted to low-carbon retrofitting as described in claim 1, characterized in that, In step 4, considering the power constraint relationship of biomass-co-fired power generation coupled with carbon capture generators, the biomass-co-fired power generation coupled with carbon capture generators in... A portion of the system's total output during the time period is used to power the user side; this portion represents the net output power. During the operation of a power plant, energy is consumed by related equipment in the boiler and turbine systems; this portion is referred to as inherent energy consumption. In addition, the carbon capture system consumes a portion of electrical energy for carbon dioxide capture and compressor operation; this portion constitutes the carbon capture system's energy consumption. When the electricity demand far exceeds the total power generation load of the power plant, there is an imbalance in the electricity load. Considering the above power balance relationship, the electricity load balance equation is as follows: in, The total output power of the integrated system during time period t is obtained from the optimized output model and is expressed in MWh. This represents the net output power of the generating unit during time period t, i.e., the electrical load on the user side, in MWh. The unit is MWh, which represents the fixed energy consumption of each piece of equipment in the boiler system and steam turbine system during the biomass co-firing coal power generation process in time period t. The energy consumption of the carbon capture system during time period t is expressed in MWh. This represents the power imbalance during time period t, expressed in MWh. Considering the carbon emission relationship of power plants, the flue gas from the boiler system of a biomass-co-fired power generation unit coupled with carbon capture flows into the carbon capture system for CO2 capture. Uncaptured CO2 is released into the atmosphere with the flue gas, while captured CO2 is stored in a carbon dioxide storage tank. Within time period t, the CO2 released from the storage tank and the captured CO2 meet the user's carbon load demand. Excess carbon dioxide continues to be stored in the carbon storage tank to meet subsequent carbon load demands. Based on the above relationship, the carbon emission balance relationship is obtained as shown in the following formula: in, The value represents the amount of CO2 captured by the carbon capture system in the biomass-co-fired coal-fired power generation unit coupled with carbon capture at time t, in kg / s. This represents the rate at which the carbon dioxide storage tank releases carbon dioxide at time t, expressed in kg / s. This represents the rate at which the carbon dioxide storage tank absorbs carbon dioxide at time t, expressed in kg / s. This represents the amount of carbon dioxide imbalance at time t, in kg / s. This represents the user's carbon load demand at time t, in kg / s. The mathematical model for the energy consumption of carbon dioxide capture in a carbon capture system is shown in the following equation: in, This represents the amount of CO2 captured by the power plant during time period t, in kg / s. This indicates the energy consumption required for a carbon capture system to capture a unit mass of CO2, expressed in W / kg. The optimized output model of the biomass-co-fired coal-fired power generation coupled with carbon capture generator unit constructed in step 2 yields the constraints on the biomass co-firing ratio and the carbon capture rate, as shown in the following equation: in, The maximum biomass blending ratio is expressed in % (%). This represents the lower limit constraint for carbon capture rate, expressed in % (%). The ultimate biomass co-firing ratio in the actual unit model As the load varies under different operating conditions, the limiting blending ratio of biomass is related to the combustion characteristics of the boiler unit. When coal and biomass are co-fired for power generation, the temperature near the burner and the real-time efficiency of the boiler reflect the combustion status of the unit to a certain extent. The limiting blending ratio of biomass can be approximated by these two factors: in, This indicates the maximum biomass blending ratio, expressed in % (%). A functional relationship representing the limiting biomass blending ratio; This indicates the real-time efficiency of the boiler during operation, expressed in % (%). During the operation of a biomass-coated coal-fired power generation unit, all input and output parameters are subject to upper and lower limits. Therefore, the relevant constraints are shown in the following formula: In actual operation, biomass-co-fired coal-fired power generation coupled with carbon capture and treatment (CCAD) generator sets need to maintain a constant water-to-coal ratio on the boiler side to prevent large fluctuations in the temperature or enthalpy of the working fluid at the separator outlet. Therefore, the following constraints exist: in, The water-coal ratio is a given value, a constant, and the value is selected according to the specific unit boiler type.

7. The method for optimizing the low-carbon operation output of coal-fired power units adapted to low-carbon retrofitting as described in claim 1, characterized in that, In step 5, the day-ahead electricity and carbon load output plans of the coal-fired units studied in step 1 are obtained, and the day-ahead 24-hour electricity load demand forecast is obtained. 24-hour carbon load forecast as of the date Considering the uncertainties in day-ahead electricity and carbon loads, a scenario-based approach is used to optimize the randomness of the electricity and carbon load scenarios. Assuming that the prediction errors for electricity and carbon loads follow a normal distribution, multiple electricity and carbon load scenarios are generated using the Monte Carlo method based on a typical day-ahead electricity and carbon load prediction. The number of scenarios is then reduced using a synchronous back-substitution reduction method to obtain the electricity and carbon load values ​​for random scenarios. Then, by calculating the expected value and variance of the objective function period through the probability of each scenario, the optimal low-carbon economic operation output result considering the electric load and carbon load under random scenarios is obtained by minimizing the low-carbon economic objective function. This provides guidance for the daily operation output of biomass co-fired coal-fired power generation coupled with carbon capture generator units, and achieves the goal of optimal low-carbon economic operation of coal-fired units.

8. The method for optimizing the low-carbon operation output of coal-fired power units adapted to low-carbon retrofitting as described in claim 7, characterized in that, Under random scenarios, the load value and the corresponding load forecast value satisfy the following relationship: in, This indicates either electricity load demand or carbon load demand. Indicates the number of random optimization scenarios. ; express In the scene time The value of the load; express In the scene Time period The error value of the load is a random variable; express Load at The probability value in the scenario.

9. A system for implementing the method for optimizing the low-carbon operation output of coal-fired power units as described in claim 1, characterized in that, include: The module includes a data acquisition module, a mechanism model construction module, a computational model construction module, a constraint condition construction module, and an optimization result generation module. The data acquisition module selects the biomass-coal-fired coupled carbon capture generator unit under the coal-fired power plant low-carbon transformation to be studied, and obtains the design parameters of the boiler system, turbine system and carbon capture design parameters of the coal-fired unit after the transformation, and obtains the component analysis data of coal and biomass fuel in the boiler fuel. The mechanism model construction module adopts a mechanism-data hybrid modeling method to construct a mechanism model of a biomass co-fired coal-fired power generation unit coupled with carbon capture after the low-carbon transformation of coal-fired power plants. The calculation model construction module constructs the low-carbon economic objective function of the biomass co-firing coal coupled carbon capture unit after the low-carbon transformation of coal-fired power plants, and constructs the calculation model of the relevant low-carbon economic parameters in the objective function. The constraint construction module constructs the constraint conditions for the biomass co-fired coal-fired power plant coupled with carbon capture after the low-carbon transformation of coal-fired power plants. By obtaining the unit design parameters and the obtained mechanism model of the biomass co-fired coal-fired power plant coupled with carbon capture after the low-carbon transformation of coal-fired power plants, the constraint conditions of relevant parameters are obtained, and the input and output variables of the mechanism model are constrained at the same time. The optimization result generation module combines the day-ahead obtained unit electrical load and carbon load output plans for the next day. Considering the uncertainty of the actual day-ahead electrical load command and carbon load demand, it adopts a random scenario generation and back-substitution method to generate multiple scenarios. Then, the expected value and variance of the objective function are calculated based on the probability of each scenario. The optimal low-carbon economic operation output scheme considering scenario uncertainty is analyzed. By minimizing the objective function, the optimization results of the biomass co-firing coal-fired coupled carbon capture unit operation output and optimization variables after the low-carbon transformation of coal-fired power plants considering scenario uncertainty are obtained.

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