[Objective] Xinjiang high-alkali coal offers low mining costs and stable supply, making it an attractive option for cost reduction in coal-fired power plants through co-firing. However, its high alkali content and low ash fusion temperature lead to severe slagging, limiting the engineering application of high -proportion co -firing schemes. To clarify the influence of blending ratio on combustion characteristics, NO x emissions and slagging behavior in a large -scale tangentially fired boiler, this study conduc ts numerical simulations. 

[Methods] A 660 MW supercritical tangentially fired boiler is taken as the object. A coupled gas-solid combustion and ash particle 2 deposition numerical simulation method is employed, integrating the Standard k -ε turbulence model, P1 radiation model, PDF gas-phase combustion model, and DPM discrete phase model with the stochastic trajectory model for particle tracking to establish a three -dimensional steady -state furnace model. Ash deposition probability is evaluated using the criti cal viscosity criterion with a threshold of 10 5 Pa· s. Grid independence is verified using four grid systems from 1.0 to 2.5 million cells, and the model accuracy is validated against field test data, with relative errors within 5% for furnace outlet gas te mperature, oxygen concentration and NO x emissions. Two Xinjiang coals, Hongyi and Honger, are blended with Menghun reference coal at mass ratios of 20%, 40%, 60% and 80%, respectively. The temperature field, species concentration field, NO x formation and w all slagging distribution under each condition are systematically analyzed. 

[Results] As the Xinjiang coal blending ratio increases, the flame center shifts upward, the furnace outlet flue gas temperature rises by 17~21 K, and the outlet oxygen concentration decreases monotonically. The CO concentration increases in the primary combustion zone but decays faster in the burnout zone, indicating a pronounced backward shift of combustion share. NOx emissions decrease significantly with increasing blending ratio , with the peak concentration in the burner zone dropping by 24%~35% and the furnace outlet reduction ranging from 19% to 26%. Hongyi coal, with a fuel nitrogen content of only 0.58%, exhibits lower NO x emissions than Honger coal under all blending ratios. Regarding slagging behavior, the alkaline components in Hongyi coal ash continuously react with the silica -alumina components of Menghun coal as the blending ratio increases, monotonically aggravating slagging. In contrast, Honger coal, containing 36.75% Fe 2O3, forms an optimal low -temperature eutectic composition at 40%~60% blending ratio, resulting in the most severe slagging; however, at 80% blending ratio, the high -iron ash dilutes this composition and weakens the eutect ic reaction, thereby alleviating slagging and exhibiting a non -monotonic trend. 

[Conclusion] Considering the trade-off among burnout efficiency, NO x emissions and slagging risk, the blending scheme with 60% Menghun coal and 40% Hongyi coal is recommended a s optimal. This scheme ensures controllable slagging, low NO x emissions and satisfactory burnout, providing a theoretical basis for safe and economical high-alkali coal co-firing in existing power plants.

[Objective] To enhance the peak-shaving flexibility and operational economy of coal-fired power units and support the upgrading of next-generation coal power systems. 

[Methods] A multi-objective optimization is carried out using response surface methodology (RSM) for key parameters of a coupled system consisting of a compressed air energy storage (CAES) system and a 670 MW supercritical coal-fired unit. The coupled system model is built in EBSILON software, and an iterative solution strategy is employed to ensure heat balance convergence. During the charging process, the compression heat is recovered by condensed water from the coal-fired plant. During the discharging process, two extraction steam heating schemes (deaerator extraction and No.3 high -pressure heater extraction) are compared. Three design variables are selected: compressor isentropic efficiency, inlet air mass flow rate, and total pressure ratio. The two optimization objectives are downward peak-shaving capacity and annual 2 http ://rlfd.cbpt.cnki.net net electricity sales revenue. A quadratic regression model is established based on Box-Behnken experimental design. Under the optimal parameter combination, the off-design thermodynamic and peak-shaving performance over the load range of 30%–100% turbine heat acceptance (THA) is analyzed, and the economic indicators are evaluated using a life-cycle assessment method. 

[Results] The deaerator extraction scheme is found to be superior during the discharging stage. The optimal parameter combination is: compressor isentropic efficiency 0.91, inlet air flow rate 85.6 kg/s, and total pressure ratio 85.0. The regression model predicts a downward peak-shaving capacity of 41.08 MW and an annual net electricity sales revenue of 13.223 8 million yuan. The simulation validation shows a relative error of less than 4% for both objectives. The energy utilization coefficient of the coupled system increases with load, ranging from 46.97% at 30% THA to 48.67% at 100% THA, which is higher than that of the standalone CFPP. Under off-design conditions, at 100% THA, the round-trip efficiency of the coupled CAES system reaches 64.40%, which is 9.1 percentage points higher than that of a standalone CAES system (55.3%). At 30% THA, the downward peak-shaving capacity is 43.56 MW, corresponding to a peak-shaving depth of 6.5%. The economic analysis reveals a dynamic payback period of 11.56 years, an internal rate of return (IRR) of 13.34%, and a net present value of 119.61 million yuan. The sensitivity analysis shows that when the annual operating days are below 168, the project is not economically feasible; when the operating days reach 350, the dynamic payback period shortens to 9.6 years and the IRR increases to 15.4%. 

[Conclusion] This study provides optimized parameters and operation strategy references for the flexibility retrofitting of coal-fired power units, contributing to the transformation of next-generation coal power systems. An optimal operating strategy is recommended: storing energy during low load (30% 50% THA) and releasing energy during high load (above 75% THA) to maximize system benefits.

[Objective] Coal-fired power units are increasingly required to operate over a full load range and participate in deep peak regulation to accommodate renewable energy integration. However, under such variable conditions, issues such as efficiency deterioration and corrosion at the cold end of the air preheater become prominent. To address these challenges, this study investigates the off-design performance of the flue gas waste heat utilization system in a dual turbine regenerative coal-fired unit. The goal is to achieve efficient and safe operation across the entire load spectrum, from low to full load, by optimizing the allocation of waste heat recovery. 

[Methods] A detailed simulation model of a 1 000 MW dual turbine regenerative coal-fired power unit was developed using Ebsilon professional software. The model incorporates all major components of the power cycle, including the 2 http ://rlfd.cbpt.cnki.net boiler, turbine, regenerative heaters, air preheater, flue gas bypass duct, and air heater. The simulation covers a n entire range of loads, from 20% to 100% turbine heat acceptance (THA). Key parameters influencing the waste heat distribution and overall system efficiency were systematically evaluated. These parameters include: the bypass flue gas ratio (the fraction of flue gas diverted around the air preheater), the mixed flue gas temperature downstream of the air preheater (after mixing bypass and main streams), and the outlet air temperature from the air heater. A collaborative optimization approach was employed to identify the combination of these three parameters that minimizes the net coal consumption rate for power generation at each load level. 

[Results] The simulation results demonstrate that the three key parameters fundamentally determine how the recovered flue gas waste heat is partitioned between “air-side regenerative heating” and “water-side regenerative heating”. This partition strongly influences both the economic performance and operational safety. Specifically, the optimal bypass flue gas ratios were found to decrease as the unit load decreases: 18% at 100%THA, 16% at 80%THA, 15% at 75%THA, 12% at 60%THA, 12% at 50%THA, 11% at 40%THA, and 11% at 20%THA. The corresponding optimal values for the mixed flue gas temperature after the air preheater and the air heater outlet air temperature were de termined as: 132 ℃/85 ℃(100%THA), 134 ℃/87 ℃(80%THA), 135 ℃/90 ℃(75%THA), 137 ℃/92.5 ℃(60%THA), 138 ℃/95 ℃(50%THA), 140 ℃/97 ℃(40%THA), and 140 ℃/100 ℃(20%THA). Compared to a reference configuration without flue gas waste heat utilization, the proposed optimized system reduces the gross coal consumption rate for power generation by 2.88 , 2.66, 2.63, 2.36, 2.17, 2.04, and 1.93 g/(kW·h) at the respective load levels. 

[Conclusion] The off-design characteristics of the flue gas waste heat utilization system in a dual turbine regenerative coal-fired unit are highly dependent on the coordinated control of the air preheater bypass ratio, mixed flue gas temperature, and air heater outlet temperature. Properly matching these parameters to the unit load enables a balanced recovery of waste heat while maintaining the flue gas temperature above the acid dew point, thus mitigating low-temperature corrosion risks. The optimal parameter sets obtained in this s tudy provide a practical reference for the design and variable -load operation of such waste heat recovery systems in large -scale coal-fired power plants aiming for higher flexibility and efficiency.

[Objective] In combined heat and power (CHP) heating systems, long-distance pipelines exhibit thermal inertia, transport delay and heat loss. These characteristics can provide flexibility for CHP dispatch, but they also increase the difficulty of describing temperature dynamics in optimization models. Steady-state and simplified delay models are usually unable to accurately represent temperature propagation, while full dynamic difference models introduce many internal spatial -node variables into online optimization. To improve temperature -propagation accuracy while controlling dispatch-model complexity, this paper proposes a dynamic two-port heat transfer model based on the Crank-Nicolson difference scheme. 

[Methods] The fluid energy conservation equation of the heating pipeline is discretized by the Crank-Nicolson scheme, which has second-order accuracy in both time and space. A four-point space-time grid is used to describe heat transport, and the dynamic mapping relationship between inlet and outlet temperature sequences is derived. By using the linear structure of the discretized equations, an offline matrix-recursion method is developed to algebraically eliminate intermediate spatial nodes. Thus, the outlet temperature of each pipeline is expressed as a linear combination of the inlet temper ature sequence, the initial 2 temperature state and the environmental heat-loss term. The full Crank-Nicolson dynamic model is then transformed into a low-dimensional two-port transmission relationship suitable for electric -thermal coordinated dispatch. The proposed model is embedded into a CHP dispatch framework considering heat network constraints, node mixing, heat source and load balance, temperature limits, CHP operating region constraints, conventional unit constraints and wind power accommodation const raints. 

[Results] Case studies show that the proposed model produces temperature responses close to those of the full Crank-Nicolson direct difference model. In the double-pipe heating system, the average absolute errors of the outlet temperatures of the s upply and return pipelines are 0.12 °C and 0.11 °C, respectively, and the online computation time decreases from 0.22 s to 0.012 s. In the multi-branch heating network, when the spatial step decreases from 20m to 5m, the online computation time of the full Crank-Nicolson model increases from 1.41 s to 5.31 s, whereas that of the proposed model changes only from 0.055 s to 0.060s. 

[Conclusion] The proposed dynamic two-port model retains the temperature propagation characteristics of the full Crank-Nicolson model while reducing the online optimization scale. After being embedded into CHP dispatch, it enables heating-network thermal storage and transport delay to release CHP downward regulation capability during high wind power periods, providing a low-dimensional modeling approach for flexible peak shaving and low-carbon operation of CHP systems in practical engineering applications.

[Objective] In the background of China’s national “dual carbon” (carbon peak and carbon neutrality) strategy, thermal power plants are increasingly tas ked with providing flexible, deep -load-following services. Frequent and pronounced load variations induce substantial transients in key thermal parameters , such as steam temperature, pressure, and metal wall temperature, thereby perturbing the thermo-mechanical equilibrium of high2 temperature, pressure-bearing components, particularly thick-walled headers. To quantitatively characterize stress redistribution and cumulative fatigue damage in the final superheater outlet header under deep load regulation, and to enhance operational integrity during flexible dispatch, this study focuses on a 1000 MW ultra -supercritical unit capable of stable operation down to 15% of rated power (Pe) at a domestic power plant. The lowest peak -load reduction capacity of this power plant reached 15% of the peak load. The peak-load reduction process recorded the relevant thermal parameter changes. 

[Methods] Transient thermo -mechanical simulations rigorously calibrated against high-fidelity DCS-recorded operational data across the full 15%Pe~100%Pe load range are employed to resolve the spatiotemporal evolution of temperature and stress fields during four representative transient phases: 40%Pe~100%Pe (ramp -up), 100%Pe ~40%Pe (ramp -down), 15%Pe ~40%Pe (low -load recovery), and 40%Pe~15%Pe ( deep ramp -down). The thesis mainly studied the transient temperature field changes during different load variations, as well as the stress field changes considering both thermal stress and mechanical stress. By extracting the characteristic temperatures and stresses in the transient temperature field and transient stress field during the variable load process, the relevant fatigue parameters are calculated. Life consumption in each phase is quantified using a fatigue model. 

[Results] Simulation results reve al a critical load -dependent transition in stress dominance: above 40%Pe, pressure -induced mechanical stress governs total equivalent stress, whereas below 40%Pe, thermally induced stress becomes predominant -exhibiting near -identical temporal variation wit h total stress. During ramp-up transients, thermal and mechanical stresses predominantly oppose one another, resulting in partial cancellation and reduced net stress amplitude; conversely, during ramp -down transients, both components generally act in conce rt, producing additive stress effects and higher cyclic loading severity. The 40%Pe ~15%Pe transition exhibits the largest thermal gradient, highest stress rate, and most accelerated life depletion. The lifespan loss of the container can be calculated using the Manson-Coffin equation. 

[Conclusion] This work delivers stageresolved, quantitative life consumption metrics for the final superheater outlet header under deep load regulation. Based on the degree of fatigue life loss in a single instance, the life loss during long-term operation can be calculated. The findings provide a technical foundation for condition-based life assessment, risk-informed inspection planning, and design optimization of thick-walled components in flexibly operated ultra-supercritical units.

[Objective] In order to tap the energy storage potential of the turbine -side thermal system and develop efficient auxiliary frequency modulation technology, the static characteristics of load response capability of a subcritical 300 MW thermal power unit under different regenerative heater extraction adjustment modes are analyzed. 

[Methods] The static simulation model of the unit was bui lt based on the EBSILON platform, and the accuracy of the model was verified. Under the four working conditions of 75%THA, 50%THA, 40%THA and 30%THA, the variable load capacity and static characteristics of various adjustment schemes in the middle and low 2 load sections are compared and analyzed by adjusting the extraction steam of the regenerative heater. 

[Results] When a single high-pressure heater is pumped and throttled, the load response ability of No.1 high-pressure heater is the strongest. The maximum variable load under 75%THA, 50%THA, 40%THA and 30%THA conditions is 7.27 MW, 4.61 MW, 3.47 MW and 2.42 MW, respectively. In addition, this adjustment method has the most obvious influence on feed water temperature and heat consumption rate. When multiple high-pressure heaters are combined for extraction throttling, the influence of combination one on load and feed water temperature is greater than that of combination two and combination three. Under 75%THA condition, the three combinations increase the unit power by 17 MW, 8 MW and 1.8 MW respectively, and the final feed water temperature decreases by about 61.7 °C, 27 °C and 9.8 °C respectively. Through the synchronous adjustment of three high pressure heaters through the large bypass of the feed water, th e greater the bypass flow, the greater the variation of the unit power and the feed water temperature, and load change rate is about 0.038 MW/(t·h-1) under the 75%THA condition. When throttling the lowpressure heater extraction steam, the load response ability of cutting off a low-pressure heater extraction steam alone is very poor. Due to the reaction of the coupling of the thermal system, the unit power does not rise but falls. After switching to condensate throttling and adjusting the extraction steam of four low-pressure heaters at the same time, the load response ability is enhanced, and load change rate of the unit is 0.021 MW/(t·h-1) under 75%THA condition. 

[Conclusion] The load response capacity of the high heating side of the regenerative system is much larger than that of the low heating side, and there is a step difference. The stronger the load response ability is, the higher the sacrifice and control difficulty of feed water temperature are. There is a reverse effect of single throttling on the low pressure side, and only the overall adjustment is meaningful.

[Objective] In the desert-Gobi regions, water resources are scarce and the climate is dry, with the traditional wet cooling system being highly water-consuming. Although air-cooling technology is suitable for such water-scarce environments, existing studies mostly focus on the main unit cooling system, with insufficient research on the heat transfer characteristics and adaptability of air -cooled cooling towers in the auxiliary cooling system, failing to meet the demand for efficient and water-saving operation. 

[Methods] This paper takes the auxiliary cooling water system of a 4×1 000 MW air-cooled unit in the Jiuquan region as the research object, establishes heat transfer models for pre-cooled and combined dry and wet cooling towers, and performs model validation. The influences of ambient temperature, humidity and air velocity on the heat transfer and airflow resistance characteristics of the two types of towers are investigated, and a comparative analysis is conducted from the perspectives of overall performance, regional adaptability and water-saving performance. 

[Results] Under design conditions, the heat flux of the pre-cooled cooling tower is 1.1 times that of the combined dry and wet cooling tower, whereas the pre-cooler increases the system airflow resistance by 30% and raises metal consumption to 1.76 times that of the combined dry and wet cooling tower. The ambient wet‑bulb temperature is the main factor determining the difference in wet mode performance between the two types of cooling towers. Due to its decoupled heat and m ass transfer design, the pre‑cooled cooling tower achieves a greater improvement in heat transfer performance under low ambient 2 humidity conditions compared with the combined dry and wet cooling tower. Climatic analysis indicates that precooled cooling towers are more applicable for arid regions such as Jiuquan in Northwest China, with their heat flux improved by 20%~85% under low-humidity conditions; by contrast, combined dry and wet cooling towers perform better in humid eastern areas such as Tianjin. Benefiting from its efficient heat transfer under dry mode operation, the pre‑cooled cooling tower raises the spray start temperature and reduces the operating time under wet mode operation compared with the combined dry and wet cooling tower. As a resu lt, its annual savings in water cost s amount to 735 000 yuan, and its annual water saving reaches 76%, demonstrating outstanding water‑saving benefits. 

[Conclusion] Therefore, the pre‑cool ed cooling tower offers both water‑saving and efficiency‑enhancing advantages. In water‑scarce and arid regions such as the northwest barren desert‑Gobi area, it is recommended to prioritize this tower as the cooling scheme for the auxiliary cooling system, thereby contributing to the high‑quality construction of new generation coal‑fired power auxiliary cooling water systems in the barren desert‑Gobi region.

[Objective] To investigate the detailed impact and mechanisms of molten salt energy storage systems on the unit’s overall performance of classical industrial steam-supply combined heat and power (CHP) units, this have studied optimizes and reconfigures existing molten salt heat release processes to further identify opportunities for improving system energy efficiency and operational economics. 

[Methods] This study comprehensively investigates various different CHP unit configurations that integrate molten salt thermal storage. Building upon typical molten salt heat release schemes, an improved design was proposed to further enhance energy efficiency: the molten salt was used to preheat boiler feedwater to 315 ℃ and replace some of the high -pressure heaters, reducing partial steam extraction from the high-pressure and medium-pressure cylinders, then returning to the unit to perform work to increase the power output of the unit while maintaining the original steam supply method. Additionally, waste heat of the e xtracted steam from steam generation was recovered to achieve higher thermal -to-mechanical conversion efficiency and improved overall unit performance. Taking a 350 MW supercritical extraction -heating 2 CHP unit from typical region as an example , this study combines the unit ’s heat balance diagram with precise modeling using EBSILON Professional modeling software to conduct comparative analyses of thermodynamic performance, including energy efficiency and flow rates. This revealed the mechanisms by which the improved scheme enhances the performance of the case unit compared to the original typical scheme; Based on actual spot electricity market conditions, a comparative analysis was conducted on peak -shaving capacity, thermal performance, and economic performance under typical daily conditions for both schemes. 

[Results] The results have indicated that the improved scheme could further enhance the system ’s available heat through the molten salt ’s simultaneous heat storage and the release mode, while synergistically optimizing the molten salt heat release process to enhance the coupled system’s heat release efficiency and cycle thermal efficiency. Under peak load conditions, the improved scheme achieves a peak capacity of 39.7 MW, an increase of nearly 11 MW compared to the typical scheme; its equivalent round-trip efficiency and thermal efficiency reach 86.5% and 40.0%, respectively, representing significant improvements over the typical scheme; Under typical daily electricity spot market conditions, the improved scheme’s annual operating revenue can reach 20.949 million yuan, with a static payback period of 5.2 years—both significantly outperforming the typical scheme. 

[Conclusion] The findings of this study provide theoretical justification and case -based suppor t for the efficient and flexible operation of retrofitted combined heat and power (CHP) units.

[Objective] Biomass gasification-coupled co-firing is a feasible low-carbon retrofit route for existing coal-fired units. This study evaluates the carbon reduction effect and economic performance of a biomass gasification-coupled co-firing power system based on a 640 MW coal-fired unit. The effects of different co-firing ratios are examined at 70%, 50%, and 30% load, so as to provide a basis for low-carbon upgrading of large coalfired power plants, flexible power system operation, and future engineering practice. 

[Methods] A framework integrating life cycle assessment (LCA) and techno-economic analysis (TEA) was built. Pure-coal cases and biomass gasification-coupled co-firing cases were compared under different loads and co-firing ratios. The system boundary included fuel supply, biomass gasification, coupled combustion, power generation, auxiliary material use, and emission control. Fossil-based CO2 emission intensity was used to assess the direct carbon reduction caused by biomass substitution, while global warming potential (GWP) was used to measure life-cycle greenhouse gas emissions. Economic performance was assessed by levelized cost of electricity (LCOE) and electricity profit. Biochar revenue and carbon trading revenue were also included to test their effects on system profitability. 

[Results] The results show that biomass gasification-coupled co-firing can greatly reduce the overall fossil-based CO2 emission intensity of the system. Compared with the corresponding pure-coal cases, the 15% co-firing cases reduce fossil-based CO2 emissions by 16.9%, 11.5%, and 10.9% at 70%, 50%, and 30% load, respectively. Contribution analysis shows that direct combustion is still the main emission source, accounting for about 60%~70% of total emissions. Thus, the overall emission reduction is mainly driven by the substitution of fossil coal with biomassderived syngas. In terms of life-cycle greenhouse gas emissions, the GWP of CO70-15, CO50-15, and CO30-15 decreases by 17.3%, 15.1%, and 17.8%, respectively, compared with the corresponding pure-coal benchmarks. 

[Conclusion] Economically, the coupled system generally has a higher LCOE than the pure-coal benchmark because of added biomass supply, gasification, and system integration costs. However, when biochar revenue and carbon trading revenue are included, electricity profit rises with the co-firing ratio. Overall, biomass gasification-coupled co-firing can reduce fossil-based CO2 emissions and life-cycle greenhouse gas emissions, while showing a certain level of economic feasibility for large coal-fired units in practice. These findings further indicate that the proposed system can support low-carbon retrofitting of coal-fired power plants when biomass use, by-product recovery, and carbon market mechanisms are jointly considered.

[Objective] This work focuses on the emission control of volatile organic amine solvents carried in the decarbonization tail gas of coal -fired power plants. 

[Methods] A steady-state and dynamic model of Aspen Plus water washing tower using desalinated water as the washing solvent was developed to control the volatile organic amines contained in the decarbonization tail gas of chemical absorption carbon dioxide capture p rocess. In the steady-state process, a thermodynamic model of the water washing tower was established and the internal structure of the water washing tower was determined. The optimal operating parameters for controlling volatile organic compounds emissions in the water washing tower were obtained through sensitivity analysis. The dynamic response process under disturbance was obtained from the dynamic control model. 

[Results] The simulation results show that the removal rate of VOCs from the tail gas of the water washing tower is 99.41%. The modeling results show that 2 when the number of washing tower plates is 16 and the amount of desalinated water is 1.5 t/h, the concentration of volatile organic compounds can be reduced from 4 377 mg/m3 before washing to 25.85 mg/m3, which meets the national emission standards. The sensitivity analysis results indicate that the theoretical number of trays in the water washing tower is more sensitive to the concentration of volatile organic compounds emissions than the amou nt of desalinated water used. The hydraulic calculation results show that the maximum flooding factor is 55.8%, and the maximum limit value of the washing tower system is 32.03%, which proves the reliability of the washing tower equipment design. The equipment design and dynamic control simulation results of the water washing tower indicate that under disturbances in feed flow rate and composition, the emission concentration of volatile organic compounds at the gas phase outlet of the water washing tower do es not exceed ± 5% of the pre disturbance level, and the emission concentration of volatile organic compounds under all disturbances is less than 30mg/m3, indicating that the water washing tower can effectively control VOCs under both steady -state and dyna mic conditions. 

[Conclusion]The effectiveness of the water washing process proposed in this article for controlling volatile organic compounds in decarbonization tail gas of carbon dioxide capture process has been verified. The research results of this work can provide technical support for achieving standard emissions of volatile organic compounds in carbon dioxide capture processes. The control of volatile organic compounds in decarbonized exhaust gas will become an essential component of advanced carbon capture technology systems.