A mathematical model of subcritical organic Rankine cycle (ORC) system is established for the flue gas waste heat of 120~150 ℃. Firstly, the thermal performance and economic performance of the system are analyzed at different heat source temperatures by taking R245fa as an example. Then, a multi-objective optimization study is conducted for six pure working fluids based on NSGA-Ⅱ algorithm. At last, working fluid selection and performance analysis of the ORC system with various heat source temperatures are carried out by TOPSIS method and gray correlation analysis. The results show that, in the temperature range of this study, the increase of superheat degree and evaporator pinch point temperature difference is not conducive to improve the system performance. The optimal working fluids are varied at different heat source temperatures, when the heat source temperature is 120 ℃, R601 has the best thermal performance, R245fa has the best economic performance and R1233zd has the best overall performance. The increase of heat source temperature is beneficial to improve the economic performance of the system. The optimal evaporation temperature of each working fluid increases with the heat source temperature. The gray correlation analysis indicates that the comprehensive performance of all six working fluids improves with the heat source temperature.

Against the difficulty of optimal scheduling of integrated energy systems under the operating conditions of multiple energy complementary mechanisms, a multi-objective optimal scheduling study is carried out considering the reduction of system operation and maintenance costs, carbon dioxide emission and renewable energy abandonment. A mathematical model is established for all the equipments in the electric-gas-heat-cold energy system. The constraint conditions that can simulate the long-term operation scheduling of the integrated energy system are established to solve the modeling difficulties of energy storage equipment in the long-term operation simulation, and the comprehensive energy system is optimized by using low-carbon economic operation index. The results of the minimum operation cost scheduling and the minimum carbon emission scheduling are compared. Moreover, the influence of carbon price and operation and maintenance cost increase on scheduling results is simulated. The simulation results show that, using only the minimum operation and maintenance cost or the lowest carbon emission as the scheduling index will lead to high carbon emission or high operation and maintenance cost, and the low-carbon economic scheduling considering the consumption of renewable energy and carbon emission reduction index can reduce the low-carbon economic operation cost of the whole system.

In order to reduce the air and pulverized coal distribution deviation of pulverized coal system, optimize the boiler combustion condition and expand the application range of pulverized coal distributor, a new pulverized coal distributor needs to be developed. By means of test bench model test, a new type pulverized coal distributor is developed. The structural design of the distributor model is completed, and the key performance of the distribution is studied, such as the effects of the pulverized coal distributor's coal amount damper resistance characteristics, the air and pulverized coal distribution and regulating characteristics, and resistance regulation on the distribution characteristics, as well as the effect of system air speed on the distribution characteristics. The results of model test and engineering application show that, the new pulverized coal distributor can effectively control the air volume deviation of the pulverized coal delivery pipeline within ±5% and pulverized coal deviation within ±10%. After the engineering transformation and leveling test of the new pulverized coal distributor for No.3 boiler of a power plant, the thermal load deviation of furnace can be effectively reduced, and the deviation of the two metal wall temperature points, which can reach 150 ℃ before transformation, can be controlled within 15 ℃, which greatly improves the safety and reliability of the boiler operation. The development and engineering application of the new pulverized coal distributor have certain guidance and reference significance for reducing the distribution deviation of pulverized coal in pulverized coal system and solving the series of problems such as partial burning, over temperature and corrosion in boiler operation.

Under the policy of peak shaving and carbon trading, cogeneration units face a more complex background. In order to obtain the carbon emission characteristics, income distribution and carbon trading economy of the traditional extraction condensing cogeneration unit under all operating conditions, and provide a reference for the unit to deal with carbon market fluctuations when participating in carbon trading. Using EBSILON simulation software combined with python program, the carbon emission distribution and income composition of the unit under all operating conditions are obtained. The research results show that the carbon emission kilowatt hour is inversely proportional to the load. Taking 325 MW and 150 MW as examples, the carbon emission intensity of power supply increases from 903.54 g/(kW·h) to 1 015.28 g/(kW·h), and the total carbon emission is proportional to the load; The highest proportion of peak shaving income can reach 55%; The highest proportion of carbon trading income can reach 8%, and the peak shaving income accounts for a large proportion in the low load, while the carbon trading income accounts for a large proportion in the high load. Comparing the change of carbon price from 40 yuan/t to 90 yuan/t and the change of power supply carbon emission standard from 0.9 times to 1.3 times, it is found that the change of power supply carbon emission standard has a greater impact on the proportion of carbon trading income. The formulation of power supply carbon emission standard should be combined with the unit emission level. Too high or too low will affect the enthusiasm of cogeneration power plants to participate in carbon trading.

The implementation of carbon pricing policy will have an important impact on the low-carbon transformation of power industry. This paper constructs a power dynamic stochastic general equilibrium (DSGE) model with carbon pricing policy, and systematically investigates the different impacts of carbon trading and carbon tax on emission reduction of the power industry under the goal of carbon emission peak and carbon neutrality. The results show that, the overall impact of carbon trading policy is greater than that of carbon tax policy, and the impact of carbon trading policy on emission reduction is achieved by inhibiting thermal power output under the carbon peak scenario, while it is achieved by encouraging green power output under the carbon neutral scenario. Different mechanism designs of carbon pricing policies, such as carbon trading and carbon tax, will have different impacts on emission reduction in the power industry under the dual carbon target. In the carbon trading policy, especially in the carbon peak scenario, there is a certain upper limit to achieve emission reduction through the market mechanism, and when the upper limit is exceeded, a "back-forcing" mechanism will be formed. In the carbon tax policy, the rebate mechanism will achieve the goal of emission reduction and the expansion of the rebate proportion will strengthen the impact on electricity emission reduction. Based on the above conclusions, relevant policy recommendations are put forward.

Incoloy 800H is used for high temperature section of heat transfer tubes of the first high temperature gas-cooled reactor nuclear power unit in China, of which the highest design temperature is 675 ℃. The steam oxidation properties of the Incoloy 800H at the design temperature are investigated. The structure of oxide scale of the Incoloy 800H is characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray energy dispersive spectroscopy (EDS). The results show that, the oxidation kinetic curve of the 800H alloy in steam at 675 ℃ is close to the cubic law, namely the cubic of the weight gain is nearly proportional to the oxidation time. The oxide scale has a double-layer structure. The outer layer is mainly composed of Fe₃O₄, Fe₂O₃ and a small amount of Ni, and the inner layer is Cr₂O₃ nanocrystalline with a small amount of Ni, Al₂O₃ and TiO₂ particles distributed in it. Some internal oxide particles of Cr₂O₃, Al₂O₃ and TiO₂ are distributed in the matrix metal adjacent to the oxide layer.

To study the effect of decarbonization on thermal power units, a simulation model is established to analyze the performance changes of the conventional scheme of carbon capture retrofitting in thermal power units. Moreover, a zero-output scheme of a low-pressure turbine is further proposed to improve the flexibility of the units. The conventional method uses the exhaust steam of the intermediate-pressure cylinder as the reboiler heat source, and the zero-output scheme of the low-pressure cylinder cuts off the low-pressure cylinder inlet steam. On one hand, the two methods are analyzed separately by taking a 300 MW coal-fired power unit as an example. On the other hand, the effects of the two schemes on thermal power units of the whole province is predicted by taking a province in northwest China as a research object. The results show that, the unit output range under the conventional scheme is reduced from 87~300 MW to 147~217 MW, and the power supply efficiency under rated operating conditions decreases from 37.32% to 27.02%. The minimum unit load ratio increases to about 70%. The unit load range ise widened to 47~217 MW when the zero output scheme of the low-pressure cylinder is adopted, which is 2.44 times of that of the conventional scheme. For the discussed northwestern province, the thermal power output range is reduced from 1 103~3 940 MW to 1 875~2 793 MW under the conventional scheme, and the output range is widened to 550~2 793 MW under the low-pressure cylinder zero output scheme.

In order to clarify the dynamic characteristics of bed temperature of biomass circulating fluidized bed (CFB) boiler, so as to establish a CFB combustion control system which is more suitable for biomass, a dynamic bed temperature model is established by analyzing the biomass combustion process and combustion mechanism. On the basis of the theory of instant burning carbon combustion, the correlation degree of temperature field in the furnace is calculated and analyzed. The results show that, the calculated bed temperature can be controlled basically stable near the filtering value of the actual bed temperature, and the variation trend of the bed temperature is similar to that of the actual filter bed temperature, which verifies the adaptability and effectiveness of the model. The temperature correlation difference of the upper and lower parts of the biomass CFB boiler is related to the oxygen content and the temperature of the furnace. The temperature difference of the left and right sides is greatly affected by the flue gas flow. In the upper part of the furnace, the material concentration and the uneven heating surface arrangement are also important reasons affecting the temperature characteristics.

For wind power units, both torque control and pitch control are designed based on generator speed, which leads to the coupling between them near the rated speed, further resulting in rotational speed disturbances. Consequently, conventional torque control will frequently change the control logic according to generator speed, thereby causing the torque and power dips. Besides, two kinds of conventional torque control strategies above the nominal wind, constant-torque and constant-power control, have advantages and disadvantages in torque, power and drive-train loads. In order to eliminate the torque and power dips, full load curve was extended to generator speeds below the rated value. Several state variables, relevant to pitch angle, were selected to reduce the frequency of switching the torque control regions near the rated speed. A new full load curve was designed based on weight programming to comprehensively consider the power and torque performances. The transition curve connecting the optimum Lambda curve and full load curve, was optimized dynamically. Moreover, the proposed control strategy was tested under typical turbulent wind conditions. The simulation results show that, the torque and power dips at above nominal wind are eliminated and the power capture increases at rated wind by using the improved torque control strategy. Furthermore, both torque and power achieves good performance by applying the rational weight.

Aiming at the problem of weak internal regularity caused by the characteristics of nonlinear and strong fluctuation of load data, a TCN-WOA-BiLSTM-Attention power load short-term prediction model based on Bootstrap error correction was constructed. Temporal convolutional network (TCN) was used to extract temporal features and the contribution of important information to the features was highlighted through the Attention mechanism. The whale optimization algorithm (WOA) was employed to find the optimal bidirectional long short term memory network (BiLSTM) hyperparameters, thus to reduce the negative impact of manual search hyperparameters and then forecast. Based on Bootstrap analysis on error distribution of the prediction interval, the necessity of correcting the prediction result was judged by whether the PICP was lower than the corresponding confidence, and the reasonable correction range was selected. The results show that, the error correction based on the Bootstrap method can avoid the problem of insufficient correction and excessive correction. Compared with the method of correcting the whole error sequence, it is more scientific and improves the prediction accuracy of the model to the greatest extent.