The operating parameters of coal mills directly affect the safety and combustion performance of coal-fired units. Therefore, it is of great significance to carry out real-time monitoring of CO volume fraction at the outlet of coal mills and accordingly have safety early warning based on the monitored data. In this work, the measurement accuracy and detection limit of wavelength modulation direct absorption spectroscopy(WM-DAS) method were verified based on tunable diode laser absorption spectroscopy(TDLAS) and Herriott multi-pass cell. The experimental results showed that the measured CO volume fraction agree very well with the preset values in the range of 1 to 10 μL/L, and the detection limit can be as low as 5.2×10^–3 μL/L(300 s), which suggests the extremely high measurement sensitivity and accuracy of this method. Subsequently, based on this prototype experiment, an on-line monitoring system for the trace CO volume fraction was developed. Then, combined with the high-fidelity pretreatment technology of fuel gas based on the principle of constant-flow dilution, an on-line monitoring system for trace CO volume fraction was developed and applied to the outlet of coal mill of thermal power unit. The on-line CO monitoring and safety warning at the outlet of 5 coal mills of a single thermal power unit were realized by using multi-point alternating measurement strategy. With the monitored CO volume fraction and temperature of the coal mill outlet, the temperature of the primary air is adjusted to improve the boiler efficiency while ensuring safe operation of coal mill.

During signal sampling process of steam turbine digital electric hydraulic control system (DEH) tests, situations that the instrument can not meet the requirements of Nyquist sampling due to the frequency of the primary components is over high may occur. To solve this problem, the envelope of the signal is calculated through Hilbert transform, and the valve closing time is calculated according to the envelope signal. However, the calculation accuracy is limited due to the time interval of the peak points. To improve the calculation accuracy, the undersampled signal is reconstructed, the primary frequency is analyzed by using fast Fourie transform (FFT), and the primary frequency of the signal is determined based on the nature of the frequency domain. On this basis, the initial phase of the AC signals is calculated using the initial value, and the undersampled signals is reconstructed according to the frequency and initial phase. The closing time is calculated according to the difference between the reconstructed and sampled signals based on Akaike information criterion (AIC). In comparison with the Hilbert transform method, the reconstruction method can improve the calculation accuracy. The reconstruction and analysis method can be used in all kinds of undersampled periodic signals, which can make up the shortcomings of hardware in DEH tests.

In view of the frequent failure of power generation equipment under the background of frequent deep peak regulation, flexible operation, energy saving and consumption reduction of thermal power units, a coal mill fault warning method based on multiple state estimation-analytic hierarchy process is proposed. Firstly, based on the characteristic parameters of coal mill Spearman correlation analysis for dimension reduction, equidistant sampling method is used to extract some samples from a large number of coal mill history data memory matrix, after normalization, memory matrix is formed. Then, multi-state estimation algorithm is adopted to calculate the corresponding memory estimated vector according to the memory matrix and the observation vector. The characteristic parameters are given different weights by using analytic hierarchy process (AHP), and the fusion similarity between the observed vector and the estimated vector is calculated, and the fault warning of coal mill is carried out based on the adaptive threshold method. Finally, the actual fault data of a roller medium speed coal mill is taken as an example to verify the effectiveness of the method. The results show that, this method has less misalarm rate and false alarm rate for coal mill fault warning, which can reduce the actual fault probability of coal mill to a certain extent.

The existing GIS disconnector contact state evaluation method is based on the single state characteristic quantity, the reliability of the evaluation result is low, and it is easy to misjudge and erroneous judgment. So a method of GIS disconnector contact state evaluation based on multi-feature fusion was presented. The multi state quantity comprehensive detection experimental platform of 220 kV GIS disconnector was built. And the relationships between the GIS disconnector shell temperature signal, shell vibration signal, partial discharge signal and the contact state of the disconnector were experimentally studied. On this basis, the temperature rise of GIS disconnector shell, the amplitude of shell vibration signal and the discharge amplitude of partial discharge UHF signal were taken as the state characteristic quantities of disconnector, and the contact state evaluation model of disconnector based on support vector machine was established. The test results show that the accuracy of GIS disconnector contact state evaluation method based on multi-feature fusion is the highest, can reach 92.92%.

In order to avoid disrepair and overrepair, improve the reliability and availability of gas turbine, reduce operation and maintenance cost, and ensure its safe, stable, green and efficient operation, a novel approach is proposed for fault diagnosis of gas turbine in power plants under transient operating condition with variable geometry compressor. The mathematical relationship of the influence of the compressor inlet guide vane position on compressor flow and efficiency characteristics is deduced. A high-precision thermodynamic model for the purpose of performance analysis and gas-path fault diagnosis is established. Moreover, the gas path fault diagnosis strategy of power plant gas turbine, which is suitable for transient and variable conditions and includes variable geometry, is proposed. Through actual operation test, it is verified that the proposed method has high diagnostic accuracy and good real-time performance, and the fault identification under transient and variable conditions is realized.

In order to effectively prevent the slagging of a supercritical 650 MW opposed firing boiler, the influence of different coal types on the flue gas temperature at the furnace outlet and the heat load of the boiler was checked by thermodynamic checking calculation, and the influence of the air distribution in the furnace and the cone-expanding angle of the burner on the flue gas dynamic field and flue temperature of the furnace was analyzed by CFD simulation. The results of the thermodynamic checking calculation showed that the boiler and the coal type were not the main reason for slagging. The variable air volume simulation showed that adjusting the ratio of internal and external secondary air could have effect on the dynamic field of flue gas. But in operation, changing the air volume did not solve the slagging problem well. The simulation results pointed out that the heat load of the water wall area could be reduced by reducing the cone-expanding angle of the burner from 45°to 30°, so as to inhibit the slagging. In the actual adjustment, after changing the cone expansion angle of the burner from 45°to 30°and adjusting the air distribution, the slagging situation of the boiler was greatly improved.The calculation results of variable SOFA wind showed that the appropriate reduction of SOFA wind proportion could reduce the flame height and the flue gas outlet temperature. The simulation of variable secondary air rotation showed that the secondary air rotation had a significant influence on the flow field and the slagging risk would significantly increase if the rotation of the burner was not arranged according to designed value. Further adjustments to SOFA wind ratio and secondary wind swirl could be considered in following adjustments.

Based on the dynamic vibration absorber method, analysis on abnormal vibration of vertical condensate pump motor and vibration reduction measures are carried out. According to the vibration characteristics of the condensate pump motor, the design method of power vibration absorption is studied theoretically, and the power vibration absorber is developed and designed and applied to the actual unit. The results show that, the dynamic balancing method has certain limitations in alleviating the vibration exceedance of the condensate pump motor during varying frequency operation, and cannot reduce the vibration amplitude of the condensate pump motor in both directions at the same time. The mass participating in the vibration of the condensate pump system shows a growing change with the increasing additional mass, and the first-order vibration mass at the top of the condensate pump motor is about 6 000 kg (X direction) and 7 000 kg (Y direction). With mass ratio of 2%, 5% and 10%, the maximum vibration amplitude in X direction is reduced by 80%, 83% and 86%, and the maximum vibration amplitude in Y direction is reduced by 68%, 77% and 83%. The dynamic vibration absorber device effectively reduces the vibration in both directions, and the actual reduction of vibration in X and Y directions is about 53% and 66% during the whole frequency operation period. The vibration control method based on the dynamic vibration absorber of the condensate pump motor has an excellent vibration reduction effect.

Frequency conversion condensate pump is easy to produce structural resonance because of insufficient support stiffness of vertical structure and increased working frequency range. According to the problem of excessive vibration in two resonance zones of a 350 MW vertical variable-frequency condensate pump, this paper introduces the principle and influencing factors of structural resonance, the judgment method of vibration fault and the treatment process. Theoretical calculation and actual treatment results show that, when there is unbalance on the shafting, dynamic balancing can effectively reduce the vibration amplitude in the resonance area of the condensate pump. However, when there are multiple resonance zones at the same time and the counterweight schemes corresponding to different resonance zones are contradictory, the dynamic balance mode cannot be considered at the same time. The angle of the counterweight determines the dynamic balance effect. Due to the limitation of the reserved counterweight angle, the rapid change of the vibration phase near the resonance point, inaccurate measurement and other factors, it is difficult to achieve on-site fine dynamic balance. Increasing the support to improve the system stiffness can change the natural frequency of the structure and reduce the vibration amplitude in the resonance area, which is an effective measure to solve the resonance problem. The vibration reduction effect of radial support is better than that of axial support.

The effects of different heat transfer fluid (HTF) parameters on charging and mechanical performance of the thermal energy storage (TES) tank using phase change material (PCM) capsules are studied by employing the fluid-solid coupling calculation. The results show that, with the inlet HTF flow velocity increased from 0.000 7 m/s to 0.000 9 m/s, the total heat storage quantity is basically unchanged, the average charging power increases from 5.33 MW to 6.79 MW, and the peak maximum mechanical stress (MMS) of the tank wall decreases. When the initial cold HTF temperature decreases from 610 K to 530 K, the total heat storage quantity increases, the average charging power increases from 5.29 MW to 6.81 MW, but the peak MMS of the tank wall also increases. With the initial hot HTF temperature increases from 730 K to 810 K, the total heat storage quantity increases obviously, the average charging power increases from 3.81 MW to 7.97 MW, but the peak MMS also increases to 159.6 MPa. Hence, to improve the charging performance of the TES tank, on the premise of ensuring the structural safety of steel wall of the TES tank, the inlet HTF flow velocity and initial hot HTF temperature should be increased properly, and the initial cold HTF temperature should be reduced properly.

Turbine cooling system is one of the cores of modern heavy-duty gas turbines. How to consider the influence of cold gas admixture is one of the first problems to be solved in gas turbine thermodynamic modeling and analysis of the influence of key parameters. With the continuous deepening of overall design of the gas turbine, a more detailed thermal performance calculation model is required to coordinate and match key components and the whole and ensure the final realization of the design performance. A calculation method of step-by-step blending and overall thermal performance of gas turbine based on one-dimensional aerodynamic analysis of turbine is proposed, and a thermal performance model of heavy-duty gas turbine is established. Moreover, the influence and key parameters and thermodynamic performance scheme of G/H class gas turbine is investigated. The analysis shows that, the turbine initial temperature, pressure ratio and cooling air volume are the key parameters affecting the overall thermal performance of the gas turbine, and the three should be coordinated in the overall design. While improving the turbine initial temperature, the minimum cooling air amount required to reach the temperature level should be studied, the optimal pressure ratio should be analyzed, and the iterative calculation and thorough research should be confirmed after combining the component design. The research results can provide a reference for the overall performance design of autonomous heavy-duty gas turbines.

The main-auxiliary combined indirect dry cooling system has attracted attention from the industry in recent years, while few scholars at home and abroad have conducted studies on its flow and heat transfer performances. In order to investigate the transport characteristics of the main-auxiliary combined indirect dry cooling system under different configurations, this paper establishes six physical models of the combined indirect dry cooling systems with the double-layer/single-layer main and auxiliary radiators. And then the cooling performances are analyzed and compared using the commercial software FLUENT. The results show that, the construction has obviously higher impacts on the auxiliary cooling system than the main one, meanwhile the air mass flow rate presents larger difference than the heat rejection; In absence of wind, the main-auxiliary combined cooling system with double-layer heat exchanger arrangement, has better cooling performance than that with the single layer heat exchanger arrangement, and case A possesses the best cooling performance; Under crosswind effects, case C has highest cooling capability of the auxiliary cooling system, while the behavior of its main cooling system should also be considered before the engineering selection. This research may provide some theoretical guidelines for the engineering design and application of the main-auxiliary combined natural draft dry cooling system.

As the proportion of new energy power generation continues to increase, the stability of grid frequency is severely challenged, and the role of conventional thermal power units in grid frequency regulation has become increasingly prominent. However, the adjustment rate and accuracy of some thermal power units are difficult to meet the demand of grid load fluctuations. Therefore, a response performance optimization strategy for flywheel-thermal power system automatic generation control based on load forecasting was proposed. Firstly, the load is predicted, using the tree-based pipeline optimization tool TPOT library to automatically machine learning to match and train the load regression prediction model, and the automatic generation control day-ahead planned value is introduced into the training data to reduce the prediction error. Then, according to the load prediction value and the current flywheel system, with the optimization goal of minimizing the regulation rate of thermal power units, the flywheel energy storage system is acted firstly in load distribution, and the state of charge of the flywheel is adjusted meanwhile. Finally, a simulation experiment is carried out based on the actual operation data of a power plant in Hubei, and the experimental results prove that the proposed method can effectively improve the frequency modulation performance of thermal power units.

In order to improve the cooling performance of cooling tower, this study takes a 300 MW unit cooling tower in the north as an example, establishes a 3D numerical calculation model of cooling tower, compares the effect of non-equal packing in two and three zones on the outlet tower water temperature, determines the optimal radius dividing point, and cooperates with non-uniform water distribution for optimization, analyzes the effect of different optimization schemes on the air flow rate, tower water temperature and ventilation volume in the outlet tower. The results show that the cooling performance is improved with the exit tower water temperature of 31.798 ℃and 31.696 ℃ under the non-equally spaced packing in the second and third divisions, respectively. The coupling optimization of non-equally spaced packing with non-uniform water distribution significantly improves the uniformity of aerodynamic and temperature fields. With the increase of water distribution in the inner zone, the outlet water temperature and ventilation volume both show a trend of first increase and then decrease, and the optimal water distribution in the inner zone is 50%, and the outlet tower water temperature is 31.36 ℃ and ventilation volume is 7 122.8 kg/s. Compared with 26 mm and 30 mm equidistant packing arrangement, after collaborative optimization, the water temperature of the tower is reduced by 0.768 ℃ and 0.83 ℃, respectively, and the cooling performance is significantly improved.

Under the background of auxiliary heat supply of ejector, in order to study the characteristics of ejector under variable working conditions, the calculation methods of ejector at home and abroad are investigated, the ejector calculation model is established and coupled with the high back pressure unit. Moreover, the effects of working steam, ejected steam, ejector back pressure, and ejector opening on the performance of the ejector under variable working conditions are obtained. The results show that, when the working fluid pressure of the ejector changes from 0.25 MPa to 0.45 MPa, the mass flow of the working fluid first increases and then decreases, and the ejector has the best performance at the design working steam pressure. The critical back pressure increases with the steam injection pressure. The pressure of the mixed fluid after injection will not only affect the work of the ejector but also the work of the condenser. Compared with the back pumping unit, the minimum cooling flow of the low pressure cylinder of the high back pressure coupling injector unit can be reduced by 140 t/h and the power supply range can be increased by 43 MW.

In the context of energy transition driven by "carbon peak and carbon neutrality", an adaptive PID control algorithm in frequency domain is proposed to solve the quality problem of steam turbine back pressure regulation caused by frequent change of operating conditions in flexible air-cooled thermal power units. Considering the practicality and accuracy of the variable working condition model, on the basis of the site operation data, the improved particle swarm optimization (PSO) algorithm is used to identify the dynamic system of multiple working conditions of the air cooling unit. Then, based on the nominal model of the controlled object operated under multiple working conditions, the transfer function configuration mode adaptive method is employed to calculate and optimize the parameters of PID controller in real time, thus to adapt to the change of model parameters of the controlled object under flexible operation and overcome the control quality problems caused by PID controller structure and fixed parameters. The simulation results show that, the adaptive PID controller in frequency domain can well track the variation of model parameters under different load conditions, which makes the back pressure control keep good control quality.

During the operation of selective catalytic reduction (SCR) flue gas denitration system of coal-fired units, NH₃ and SO₃ in the flue gas generate liquid ammonium bisulfate (ABS) at a specific temperature, which is viscous and easy to cause catalyst deactivation at 0~40% low load due to micropore plugging and aggravate the fly ash blockage of heat exchange elements at the cold end of air preheater. Alkali powder injection to remove SO₃ from flue gas is an important method to control ABS. However, the existing grid type multi-nozzle device has problems of uneven injection and low SO₃ removal efficiency. A vertical gas-solid fluidization mixing and distribution injection device is developed to improve the uniformity of absorbent powder injection in the flue section. The pilot test results show that, the SO₃ removal efficiency at upstream of the SCR denitration system reaches 55.6%, the condensation temperature of the catalyst ABS decreases by 8.6 ℃, and the minimum operation temperature decreases by 11.9 ℃, which can expand the lower limit of the catalyst operation temperature and reduce the restriction on the lower limit of the peak load of the unit. The SO₃ removal efficiency at upstream of the air preheater reaches 84.3%, and the ABS deposition influence coefficient decreases by 86.9%, which can delay the ABS ash blockage at the cold end of the air preheater. The SO₃ emission mass concentration from the chimney is 2.5~3.4 mg/m³, which can eliminate blue smoke.

In order to realize the cold end optimization of direct air-cooled units, a cold end operation optimization method of air-cooled units is proposed based on the historical operation data of units and combined with data mining and deep learning algorithm. Firstly, the obtained historical operation data are screened in steady state and divided into working conditions. Combined with the Gaussian mixture model algorithm, the back pressure reference interval of the unit under multiple working conditions is determined. Then, the Spearman coefficient method is used to select the characteristic variables, and the back pressure prediction model of the direct air cooling unit is constructed in combination with the gated circulation unit. The back pressure optimization suggestions and early warning information are given by comparing the back pressure reference interval with the back pressure prediction value. Finally, the method is applied to a subcritical 300 MW air-cooled condensing steam unit. The results show that the back pressure optimization method proposed in this paper can give effective back pressure early warning information and realize optimal operation of cold end of the air-cooled unit.

The denitrification effect of coal-water slurry pyrolysis gas is investigated by numerical simulation in a 330 MW power station pulverized coal boiler, focusing on the influence law of excess air coefficient α₁ in the primary combustion zone (PCZ) and pyrolysis gas ratio β on the combustion characteristics and NO_x emission in the furnace. The results show that, when β is kept constant, the temperature of the PCZ decreases and the temperature of over-fire air (OFA) zone and furnace outlet increases as α₁ decreases. Meanwhile, the decrease of α₁ enhances the reducing atmosphere in the PCZ, which is beneficial to improve the denitrification rate of pyrolysis gas and thus to reduce the NO_x mass concentration at the furnace outlet. But the decrease of α₁ will affect the combustion performance of the pulverized coal and increase the CO concentration at the furnace outlet. With the increase of β, the center of the furnace flame moves up and the reduction rate of NO_x by pyrolysis gas increases. When β increases from 5% to 20%, the overall mass concentration of NO_x in the furnace shows a trend of first decreasing and then increasing, and when β=15%, the NO_x mass concentration reaches the lowest and the NO_x reduction efficiency of the pyrolysis gas reaches 44.35%.

At present, the self-provided power plant has a large generating power, which can not be ignored in the future new energy grid-connected peak regulation. According to the selected factory-owned power plant with power and heat supply, there are the low-pressure cylinder zero output scheme, high back pressure extraction combined exhaust steam heating scheme, absorption heat pump and compression heat pump scheme. four thermo-electrolytic coupling schemes are quantitatively calculated and evaluated to provide guidance for the selection of decoupling schemes for factory-owned power plants. Four schemes were used to optimize the case unit, and the calculation results showed that after decoupling, the heat supply of the heating extraction stage can be separately increase 174.00 MW, 136.18 MW, 168.37 MW and 38.00 MW. The minimum electric load rate was reduced to 44.29%, 73.29%, 73.70% and 80.57%. The maximum heat-to-electricity ratio reached 2.00, 1.50, 1.50 and 1.15. The zero-output decoupling effect of the low-pressure cylinder is the most obvious, the maximum heat supply increases the most, and the electric load rate decreases the most. Economic analysis shows that the absorption heat pump scheme has the most increased investment cost compared to other schemes.

"Three-renovation" (energy-saving renovation, flexibility renovations and heating renovations) of coal-fired power is an effective measure for clean and low carbon utilization of coal. The paper analyzes current energy efficiency, flexibility and heating situation of coal-fired power, and researches the policy requirement, implementation progress and expected effect of "Three-renovation". In terms of technical difficulty, energy saving renovation is the most difficult, followed by flexibility and heat supply. It is anticipated that the coal consumption for power supply will be decreased to about 297 g/(kW·h), the additional peak regulation capacity will be over 40 GW and the heating scope will be further expanded. In view of the problems such as large coal power loss, difficult technical transformation of some types, hidden safety risks of equipment under low load operation, unanticipated input and output of renovation, and small financial support of renovation, this paper puts forward measures and suggestions to promote the "Three-renovation" from the perspectives of policy, technology, standards and market.

A field test of paper mill sludge and coal co-firing was conducted on a 600 MW unit boiler to explore the effect of mix-firing sludge on the formation and emission of dioxins (PCDD/Fs). Under the conditions with and without sludge co-firing, flue gas samples at the inlet and outlet of drying-charring machine, the inlet of selective catalytic reduction (SCR) equipment, the outlet of air preheater and chimney as well as solid samples including raw sludge, dried and partly charred sludge, slag and fly ash were collected, and the PCDD/Fs were analyzed by a high-resolution gas chromatograph combined with high-resolution mass spectrometer. The obtained results indicated that, co-firing sludge (accounted for about 1% (weight percent) of pulverized coal) did not result in the formation of PCDD/Fs via high-temperature gas-phase homogeneous formation mechanism and medium- and low-temperature catalytic formation mechanism, and did not increase the emission of PCDD/Fs to atmosphere. The international toxic equivalence quantity (I-TEQ) concentrations of 6 chimney gas samples collected under the condition with sludge co-firing were in the range of 0.008~0.013 ng/m³ (average value: 0.010 ng/m³), which did not significantly differ from that (0.008~0.015 ng/m³, average value: 0.012 ng/m³) of the 6 chimney gas samples collected under the condition without sludge co-firing. It was found that, a small quantity of PCDD/Fs was formed during sludge drying-charring process. The newly-formed and original PCDD/Fs in sludge could be completely destroyed by high temperature in coal combustor. The SCR catalyst induced the catalytic degradation of PCDD/Fs, especially the highly-chlorinated dioxins. The concentration of the PCDD/Fs in fly ash samples were lower than 0.2 ng/m³, indicating its resource utilization could not pose dioxin pollution risk to ambient environment.