The efficient drying pre-treatment and gasification resource utilization of sewage sludge is one of the important ways to realize green and sustainable city development. Firstly, the thermogravimetric reactor was used to study the drying kinetics of sludge. Then, the influence of high temperature-low speed flue gas and low temperature-high speed flue gas on the sludge drying process was clarified based on Fluent numerical simulation. Finally, a new type of sludge and biomass co-gasification co-generation system was established by Aspen Plus, and the thermodynamic performance of the system was discussed. The results show that, the drying process of sludge in thermogravimetric reactor can be divided into the ascending stage, the first decreasing stage and the second decreasing stage, and the decreasing stage is the main stage. The water diffusion coefficients of SW-60 and SW-80 ranged from 6.34×10–6 to 3.72×10–5 m²/s and 3.69×10–5 to 2.60×10–4 m²/s, respectively. The drying activation energy of SW-60 and SW-80 was 9.55 kJ/mol and 28.25 kJ/mol, respectively, with the increase of initial moisture content. In the drying bed, the drying efficiency of high temperature-low speed flue gas is about 2.67 times that of low temperature-high speed flue gas. In the co-generation system, as the biomass blending ratio increases, the input heat, air flow, low heating value of syngas, yield of syngas and potential of co-generation all increase. However, the electrical efficiency, thermal efficiency and system efficiency will decrease slowly. When the biomass blending ratio is 20%, the blend of 30% moisture dry sludge and biomass can produce electrical energy potential and thermal energy potential of 0.61 kW·h and 4.212 MJ per kg, respectively.

Aiming at the lack of quantitative standards and assessment methods in the current comprehensive assessment of wind turbine control performance, a quantitative assessment method of control performance based on subspace linear quadratic Gaussian (LQG) is proposed. The subspace matrix method is used to solve the assessment trade-off curve, and the benchmark and assessment index of LQG control performance of wind turbines are established. By taking the turbine retrofitted by adding tower damping and load shedding control as an example of the assessment, the multivariate comprehensive quantitative assessment of pitch control performance before and after retrofitting is carried out by using two kinds of data processing strategies. The results show that, both data processing strategies can obtain accurate and effective quantitative evaluation results, and the proposed evaluation method can realize the comprehensive quantitative evaluation of the optimization effect of control strategies.

To study the coupling and oscillation characteristics of power equipment in microgrid, the energy functions of the wind turbine subsystem, generator and excitation subsystem in the doubly-fed wind turbine are deduced based on the transient energy flow method taking into account the wind speed and the control strategy of the unit. Then, the mechanism of the change of the energy consumption of each subsystem is investigated when the wind speed, the control parameters of the unit and other operational parameters change, and the oscillation characteristics of the unit are analyzed. Finally, the energy change and power oscillation characteristics of the doubly-fed wind turbine when the operation parameters change are analyzed by modeling and simulation on PSCAD/EMTDC platform, and the results are compared with the eigenvalue calculation results to verify the reasonableness of the analysis. At last, the influence mechanism of wind speed change on the oscillation of doubly-fed wind turbine is obtained.

A feedback control strategy based on Kalman filter was proposed to quantitatively study the drive train torsional vibration mitigation of doubly-fed wind turbine, and the control effect of drive train torsional vibration was compared through simulation calculation. Taking the drive train of 7.0 MW doubly-fed wind turbine as the research object, the Kalman filter was used to estimate the twist angle of the drive train, and an additional electromagnetic torque of the generator was designed for torque control based on the estimated torsional speed of low-speed shaft. The load and power generation calculations were compared with virtual damping control and no-damping control over 20 years full life cycle. The results show that, the correlation between the twist angle of the low-speed shaft estimated by the Kalman filter and the actual value can reach 0.99. The key differences between the feedback control based on the Kalman filter, the virtual damping control and the non-damping control are as follows. The equivalent fatigue load of the low-speed shaft of the drive train reduces by 2.11% and 4.89%, respectively. The equivalent fatigue load of the high-speed shaft of the drive train reduces by 1.99% and 4.78%, respectively. The power generation reduces by 200 kW·h and 700 kW·h, respectively. It can be concluded that the Kalman filter has a good estimating effect on the twist angle of drive train, and the designed additional electromagnetic torque based on the estimated torsional speed of low-speed shaft obtained by Kalman filtering has a very good suppression effect on the torsional vibration of the drive train.

The working environment of the ring main unit (RMU) in large solar photovoltaic power plants is complex and variable, faced with harsh environments such as temperature differences and humidity, it is extremely easy to cause operational failures of the ring grid cabinet, which seriously affects the safe and stable connection of solar photovoltaic to transmission lines. Based on the measured temperature and humidity data inside the RMU, utilizing the advantages of ARIMA and RBF model in linear and nonlinear data processing, a temperature and humidity prediction model with ARIMA-RBF weight combination is constructed to dynamically predict the temperature and humidity inside the RMU. The dynamic prediction of temperature and humidity in the actual loop cabinet of a photovoltaic power station is carried out. The prediction results show that, compared with the single model, the ARMI-RBF weight combination model has higher prediction accuracy and better stability. The combined model gives full play to the processing ability of a single model for different characteristics of data through appropriate weighting strategies, and can better evaluate the temperature and humidity state inside the RMU. It can provide a reference for the establishment of a more universal prediction model, and help to reduce the failure caused by long-term operation of the ring cabinet under ultra-mild and humid environment.

For the wind-solar-thermal-storage complementary power generation system without conventional power supply support, coordinated planning of installed capacity is of great significance to improve the operation economy and utilization rate of the power generation system. A two-layer optimal configuration method is proposed. The upper layer determines the installed capacity of the system with the minimum levelized cost of energy and the abandonment rate as the goal. The lower layer aims to maximize the consumption of new energy power generation and solve the problem of power distribution. The system capacity configuration is obtained by iterative optimization. Then, the optimization results are selected through Nash negotiation. Finally, the simulation analysis is carried out with the data of Hexi area in Gansu Province. The results show that, the levelized cost of energy is 0.306 4 yuan under the optimal capacity configuration of the wind-solar-thermal-storage complementary power generation system. The optimal ratio of the installed capacity of the wind farm plus photovoltaic power station to the installed capacity of the photothermal power station is 6:1. Compared with the wind-solar hybrid power generation system with the same installed capacity, the wind-solar-thermal-storage complementary power generation system has higher stability.

Building an efficient and pollution-free power generation system is an effective means to solve the current energy shortage and environmental pollution problems. By taking the C65 micro gas turbine produced by Capstone Company as the core power generation component, and coupling with the thermochemical process of solar powered ammonia decomposition to produce hydrogen, this article achieves multi-energy complementarity between renewable energy and ammonia chemical energy. The organic Rankine cycle is used as the bottom cycle to recover the waste heat from the flue gas generated by the micro gas turbine and generate electricity, achieving cascade energy utilization. A detailed simulation process is constructed in the chemical simulation software Aspen Plus. The results show that the complementary use of solar energy and ammonia has improved the calorific value of the generated hydrogen rich synthesis gas. The output power of the micro combustion engine is 89.95 kW, which is 24.95 kW more than the C65 micro combustion engine in the reference system. The electrical efficiency of the system under design conditions reaches 44.81%, and the thermal efficiency is 47.97%, which are 8.51 percentage points and 9.67 percentage points higher than that of the reference system, respectively. The component having the largest exergy loss in the system is the combustion chamber, accounting for 41.67% of the total damage, followed by the evaporator and regenerator, accounting for 14.31% and 11.15%, respectively. Sensitivity analysis shows that the electrical efficiency and thermal efficiency of the system decrease and increase with the increase of solar energy collection, respectively. The research results provide a reference for a distributed micro turbine power generation system using ammonia gas as fuel and coupled with solar energy.

In order to study the effect of backpacking containing barite powder on the heat transfer efficiency of buried pipe boreholes in plain and mountainous areas of Beijing, a comparative analysis of laboratory experiments and field thermal response experiments was carried out. The quaternary boreholes in plain areas were backfilled with medium sand and the bedrock boreholes in mountainous areas were backfilled with cement mortar. When the specific gravity of medium sand barite powder was 5%, the thermal conductivity of medium sand backfill samples increased by 14%. When 5% barite powder was added to cement mortar, the thermal conductivity increased 7.3%. According to the field thermal response test results, under summer conditions in the same site, the heat transfer rate of a backfilling borehole containing barite powder increased by 2.4 W/m and 3.5% per meter compared with that of the medium-sand backfilling borehole in plain area. The heat transfer rate of cement mortar backfill containing barite powder increased by 2.7 W/m and 3.9% per meter. The numerical simulation model of the quaternary system and bedrock area was established. It was found that the content of barite powder increased to 10% and the heat transfer rate of boreholes increased by about 6.0%. In general, the heat transfer capacity of buried pipe is improved and its sustainability gets better after adding barite powder.

In order to ensure safe operation of secondary cycle and reliability of steam generator, it is of great significance to reduce corrosion of equipment & piping of the cycle in nuclear power plant. With the deepening research on organic amines and the continuous accumulation of operation experience, the industry realized that the metal corrosion in the cycle during plant operation depends mainly on the pH at the operating temperature of locations of the cycle, i.e. pHt. To improve pHt at the locations of the cycle, performance characteristics of the main organic amines and their combinations are analyzed in this paper. Combined with the application experience and actual effects of organic amines at home and abroad, the application strategy of the main organic amines and their combinations are discussed and proposed, and the improvement suggestions are put forward with regard to current amine application status of the secondary cycle in China. Selections of amine or its combination should calculate the pHt at various locations to meet anti-corrosion requirements and evaluate effects on service life of resin beds in the system. Ethanolamine with stronger basicity and low volatility is suitably used in plant in which corrosion product is mainly from drain systems and condensate polishers are in continuous operation. 3-methoxyypropyl with strong basicity and moderate volatility can be used in most plants. Morpholine with weaker basicity and moderate volatility is suitably used in plants in which polishers are not in continuous operations. Dimethylamine and ammonia are suitably used with other amines because of their high volatility. Amine mixture application appears advantages on aspects of the anti-corrosion and service life of the resin beds.

The large-scale integration of new energy into the grid has caused increased frequency fluctuations in the grid, making the frequency modulation task of thermal power units heavy and frequent, exacerbating the aging of the unit, flywheel energy storage assisted thermal power unit frequency modulation can improve the frequency modulation performance of the unit. The principle of primary frequency modulation of flywheel energy storage auxiliary unit is discussed, and the flywheel energy storage’s frequency modulation characteristics are analyzed. Combining with the world’s largest capacity flywheel energy storage, the full power control strategy for primary frequency modulation of flywheel energy storage auxiliary units is proposed, and applied to the shakedown test of China’s first set of flywheel energy storage auxiliary thermal power unit’s primary frequency modulation to verify the effectiveness of the control strategy. The field test results show that, the primary frequency modulation performance of the flywheel energy storage auxiliary thermal power unit is good. After the proposed primary frequency modulation strategy is adopted, the qualification rate of the primary frequency modulation action of the unit increases by 21.26%, and the integral electricity contribution index of the primary frequency modulation increases by 3.45 times. The primary frequency modulation mode of flywheel energy storage auxiliary thermal power unit has certain guiding significance to solve such problems.

To address the challenges posed by the reverse peak shaving characteristics of new energy generation units to the smooth operation of the power grid, coal-fired units urgently need to improve their flexible operation and deep peak shaving capabilities. This article proposes three schemes of molten salt heat storage and heat release for a 670 MW reheating unit, including using a steam ejector to allocate the steam inlet flow rate of the reheater. By using Ebsilon to establish the thermal model, this article analyzes the performance of the coupled system. The results show that all schemes can effectively expand the peak shaving range of the unit. Under energy-storage conditions, the thermal economy of steam-extraction is better than using electrical heating at the same peak shaving depth. The heat-storage scheme of integrating steam ejector to allocate extraction steam to compensate for reheat inlet flow can effectively solve the problem of reheater over temperature caused by a large amount of extracted main steam. Under heat-release conditions, using molten salt to heat high pressure feed water can acquire better thermal and economic benefits. In the combination scheme of heat storage and release, C1-S2 exhibits the best economic performance, with an upward peak shaving depth of 76.89 MW, and a cyclic thermal efficiency and thermal efficiency of 42.48% and 41.31%, respectively.

By the end of 2021, over 95% of coal-fired thermal power units in China have achieved ultra-low emission of nitrogen oxides, with the remaining being W-flame boilers that burn anthracite. Due to the high mass concentration of nitrogen oxides generated, which often reaches 750~1 200 mg/m³, achieving ultra-low emissions is difficult, making it the “last mile” for China to achieve ultra-low emission policies. At present, selective catalyst reduction (SCR) denitration flow field technology mainly includes “SCR partition hybrid dynamic leveling technology”, “full flue section mixing flow field technology”, and “conventional accurate ammonia injection technology”, etc. Taking a W-flame boiler of which the design denitration efficiency needs to be up to 95% as an example, this paper compares the performance indicators of various technologies through CFD simulation, and the indicators of the “SCR partition hybrid dynamic leveling technology” are significantly superior to other technologies. After the project transformation, when the mass concentration of nitrogen oxides at the denitration system inlet is 1 000 mg/m³ and that at the system outlet is lower than 50 mg/m³, the ammonia escape can be kept less than 3 μL/L, far exceeding the maximum design efficiency of the conventional SCR denitration system. The research provides a new technical route for ultra-low NO_x emission of W-flame boilers.

In industrial production processes, time delays can have adverse effects on the performance of control systems, and may even lead to system instability. This article investigates the stability issues of time-delay in the load/speed control loop of a heavy-duty gas turbine from the perspective of switching systems. The model of GE MS109FA 275 MW heavy-duty gas turbine under 100% load is taken as the research object. The load/speed control loop with time-varying delay is transformed into a class of switching system by augmenting the state variable and selecting the change of time delay as the switching signal. By using the norm correlation lemma, a necessary and sufficient condition to ensure the stability of the load/speed control loop with time-varying delay is derived and the stability verification algorithm is given. The hardware-in-the-loop simulation is carried out based on the domestic heavy-duty gas turbine NuCON control system. The results of this study can provide theoretical references for the design and parameter adjustment of heavy-duty gas turbine control system.

In order to realize compressor blade fouling and surge faults early warning, a typical fault warning method of gas turbine compressor combining thermodynamic model with artificial neural network was proposed. The simulation model of gas turbine thermodynamic performance was built according to the modularization idea, and the dynamic calibration of the model was completed by using the actual operation data of the gas turbine to form a high-precision gas turbine performance analysis model, and the key indicators such as exhaust flow rate, turbine front temperature and heat consumption can be calculated. Based on the thermal performance simulation model and combined with the compressor typical faults expert experience and professional knowledge, the main characteristic parameters affecting compressor faults were determined, and the compressor blade fouling and surge warning models were abstracted. The historical health data were selected to train the models using the artificial neural network algorithm to obtain the deviation curve, and the early warning of typical compressor faults can be realized by monitoring the deviation changes between the predicted value and the measured value of the early warning model, the example to verify the validity of the measured data of a GE 9F gas turbine compressor was given. The results showed that the method can accurately capture the compressor blade fouling and surge faults, and improve the warning time window compared with the traditional threshold alarm method. The research achievement can be directly deployed in the gas turbine power plant and provide real-time guidance for operation and maintenance personnel to make overhaul and maintenance decisions

In order to achieve the desired flexibility, high efficiency, and cost-effectiveness in the startup and operation of thermal power units, the utilization of the BEST small steam turbine with a small generator for the implementation of a double-turbine reheat system unit is crucial for enhancing the operational economy of the unit. According to the starting mode of the BEST system and unit, combined with the historical process and data of the starting and operation of the debugging and adjustment test, a characteristic analysis test of the BEST system in multi-mode startup and operation was conducted. The existing control logic was optimized, and an operation control strategy for the BEST small steam turbine with a small generator was proposed. The system addresses the issue of lacking control strategies in various aspects, such as the starting and control of the BEST system, converter start-stop control, BEST small steam turbine and converter non-disturbance switching, run back, load dumping conditions, and ensures uninterrupted operation control of the entire process of the BEST system. After optimization, the crucial parameters of the BEST system remain secure and stable during operation. The control method holds significant reference value for similar units equipped with the BEST system.

Labyrinth seals are widely used in various types of turbomachinery due to their simple structure, convenient maintenance, and long service life. The shunt injection devices can reduce the flow-induced vibration caused by the spiral effect and improve the stability of the sealing system by affecting the circumferential flow inside the seal cavity. The three-dimensional numerical models of shunt injection labyrinth seal were established to calculate and analyze the impact of the shunt injection nozzle on the dynamic characteristics of the seal under different structural parameters. The results show that the smaller the tilt angle of the anti-swirl nozzle, the greater the system damping and stability. When the tilt angle is 30°, the effective damping is 4 times that of the vertical angle incident; the shape of the anti-swirl nozzle has a small impact on the sealing dynamic and flow characteristics. The cross stiffness of both nozzle hole types is negative, and the difference in cross stiffness between the two is about 5 kN/m at low frequencies and 1~2 kN/m at high frequencies; the more nozzles there are, the more they can suppress the circumferential flow of the rotor, which is beneficial for system stability.

A comprehensive evaluation model for the start-up and shutdown decision-making of the milling system, taking into account the energy consumption and tracking performance of the unit load, has been proposed to address issues such as subjective decision-making based on manual experience, high labor intensity in operation, and difficulty in exploring energy-saving optimization potential. This model safely incorporates the grid load scheduling command signal as input. Furthermore, a milling system start-stop intelligent decision-making method based on deep reinforcement learning has been studied, and a closed-loop control system for the automatic start-stop of the milling system has been developed. The research results have been verified through simulation and successfully applied to a commonly used coal milling system in a certain ultra-supercritical 1 000 MW unit, achieving energy savings. The findings of this study can provide effective reference for the development of unmanned or minimally manned operation techniques for thermal power units.

A method was proposed to solve the problem of oil sludge treatment environmentally by sending the pretreated oil sludge into a 330 MW pulverized coal boiler co-firing with coal. The combustion characteristics of the oil sludge were studied by thermogravimetric analysis, and it was proved to be easy to ignite with a high calorific value close to coal, which could improve the boiler’s low-load stable combustion ability. Numerical simulation results showed that the combustion center shifted downward slightly after the oil sludge was sent into the boiler, while the NO_x content decreased. The experimental results proved that the minimum stable combustion load rate can be 20.00% by the benefit of oil sludge co-firing. The temperature at the coal-burner layer increased by 30~50 ℃ and the carbon content of the fly ash decreased from 4.79% to 3.80%. The fire detection analog signal of the coal burner was found to be more stable which validated the positive effect of the oil sludge co-firing at low load condition. The boiler efficiency increased by 0.23 percentage point which reduced the net coal consumption rate by 0.7 g/(kW·h). Moreover, about 3.7 t/h coal was saved at 120 MW load. The method was verified to have a significant energy-saving effect.

The urea hydrolysis technology for ammonia production has been widely used in the preparation of denitration reducing agents for thermal power units. However, if the quality of urea is not up to standard, the urea hydrolyzer will leak, and the drainage from the urea hydrolyzer will be reused in the condenser, which will cause great harm to the thermal system. The article analyzes the serious salt accumulation and superheater tube explosion in the water and steam system caused by the leakage of a urea hydrolyzer in a coal-fired unit, and proposes a solution to the salt accumulation problem. The problem has been successfully solved, after the unit is started, all quality criterion of water and steam meet the requirements of Quality Criterion of Water and Steam for Power Plant and Steam-generating Equipment (GB/T 12145—2016). This article provides a solution for analyzing and treating the cause of salt accumulation in the water and steam system for reference.

The fouling of heat exchangers and cooling tower fill surfaces in the external cooling water system of synchronous condenser can significantly impede the heat transfer efficiency of cooling towers, posing a serious threat to the safe operation of synchronous condenser. In order to propose more effective anti-fouling measures and elucidate the causes of fouling, this study employed characterization techniques such as SEM-EDS, XRD, FTIR, etc., to analyze the microscopic morphology and chemical composition of fouling samples. Additionally, chemical analysis methods and ICP-MS were used to analyze the makeup of makeup water and circulating water in the system. The test results revealed that the primary components of fouling in the external cooling system are CaCO₃, SiO₂and CaSiO₃. The fouling in the cooling system is closely related to the absence of wastewater discharge measures in the system, high concentration ratios during operation, and the infiltration of regional windblown sand. This research contributes to proposing targeted anti-fouling measures for on-site operation of such cooling systems, ensuring the economic and operational safety of synchronous condenser.

High temperature steam pipe is an important part of the power plant. In order to coordinate the pipeline thermal expansion and reduce the pipeline thermal expansion stress caused by the higher altitude difference and larger horizontal span, a lot of constant supports and hangers are designed in pipeline. But because friction moment exists on the rotating shafts, constant supports and hangers are not a constant force, the load deviation will make the pipeline deviate from the designed cold and hot line, and the pipeline stress will increase. For controlling the quality of constant supports and hangers, there are two quality performance control indexes among the relevant domestic standards, namely the constant degree and the load deviation degree. This article focuses on the load deviation degree. It finds out that, the load of putting out pin measured by different loading directions is different, resulting in a large difference in load deviation degree due to friction moment of the rotating shaft of the constant supports and hangers. So the load of putting out pin shall not be used as a representative parameter. The study proposes that the average load shall represent the position of the displacement-load curve, which is a representative parameter of constant supports and hangers. A new formula for calculating the average load deviation degree is proposed. It is suggested to modify the related standards to improve the quality of the constant supports and hangers.