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.