By riser two-phase flow model and thermodynamic model, exergy analysis for the thermosyphon-based trilateral cycle (TTLC) proposed in the previous work by the authors is carried out to investigate the exergy performance of the system and the relevant influencing factors. The results show that, the system exergy efficiency varies in the range of 15%~30% with the increasing inlet temperature of heat source, which always helps to enhance the exergy efficiency. As the inlet temperature of cooling source decreases, the exergy efficiency changes from 23%to 27% with an optimum value. An optimization opportunity exists for the temperature difference of heater at the hot side, for example, a setting value of 4 ℃ seems to be a better choice. The riser exergy loss rate is a key factor to determine the system efficiency, especially under the condition where the temperature difference of the cycle is relatively larger. Decreasing temperature pinch point of the heater helps to decrease the internal and external exergy loss rates of the heater, but will lead to more exergy destructions in other processes. However, it exerts positive effects on system efficiency on the whole.

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.

Combined heat and power (CHP) units are affected by the output fluctuation of large-scale operating conditions, resulting in poor overall control quality of power generation load-extraction steam flow-throttle pressure in the turbine-boiler coordinated control system. To solve this problem, a multi-condition adaptive control method based on multi-agent deep deterministic policy gradient (MA-DDPG) is proposed. Firstly, according to the nonlinear dynamic mechanism of the unit, multiple operating condition sub-models considering the changes of state parameters are established, and the optimal operating condition sub-model is obtained by the integral function switching mechanism. For the multi-loop complex control requirements of the coordinated control system, a multi-agent synchronous operation mechanism is proposed, and the reward function is designed with the coordinated control objectives of rapid response, stable heating and safe operation. Finally, by training the agent to interact with the environment, the multi-loop gains are continuously adjusted online to achieve multi-condition adaptive control. Simulation results show that, compared with the conventional control method, the proposed method can effectively improve the load response rate under wide range operating conditions, and ensure the stability of heating.

Control of main steam temperature (MST) is becoming more and more challenging because of unknown disturbances caused by frequent and extensive load changes and strict control requirements for the efficiency and safety. To this end, considering the sluggish responses to the disturbances caused by high order dynamics, an anti-disturbance control scheme with stair-like dynamic matrix control (SDMC) algorithm as the core is proposed to solve fundamentally the control problem of large delay, big inertia and multiple disturbances in MST. This study aims to provide technical support for the clean and efficient use of coal and the large-scale consumption of renewable energy sources in China. A simulation example shows that the proposed improved equivalent input disturbance observer (IEIDO) can realize real-time estimation and compensation of disturbances, while SDMC can not only ensure the rapidity and stability of the steam temperature control system, but also achieve disturbance suppression according to the introduction of measured disturbance feed-forward compensation technology. Therefore, the proposed scheme can guarantee the safety, stability, economy and flexibility of the unit operation, which has a promising application future in power industry.

Using ceramic membrane to recover moisture from gas is a feasible way that not only can realize the recycling of resources, but also can alleviate environmental pollution. By taking double-row ceramic membrane module as the research object, the heat and mass transfer of water vapor transport was theoretically analyzed, the physical model was established, and numerical simulation was carried out according to the boundary parameters under actual conditions. Then, a pilot test platform was built on a coal-fired unit to carry out the experimental research on the purified flue gas after wet desulfurization. The results show that, the amount of recovered water decreased linearly from 29.45 kg/h to 18.13 kg/h by increasing the cooling water temperature from 25 ℃ to 36 ℃. With the growing of flue gas flowrate, the recovered water gradually increased, but the growth rate gradually decreased. The deviations of the recovery water amount between the calculated results and the experimental data were less than 7%.

The internal flow and temperature rise characteristics in the last stage of steam turbine low pressure cylinder under low flow rate condition is quite complex, which makes thermal power peak load regulation and cut-off transformation more challenging. By taking the low pressure cylinder of a steam turbine in a power plant as the research object, a five-stage cascade single-channel calculation model of the low pressure cylinder was established, and the working performance, flow structure and temperature rise characteristics of the low-pressure cylinder under different working conditions were numerically investigated. The research shows that, when the flow rate of the low-pressure cylinder decreases to 3.84% of the design condition, the low-pressure cylinder outputs no positive power. When the flow rate is quite low, the low pressure cylinder enters the windage condition, and the flow structures such as the hub endwall separation area, the vane separation area, the casing torus vortex, and the last stage bucket vortex appear in the last stage cascade, by concomitant of obvious windage heating effect at the tip position of rotor-stator clearance area of last stage cascade under low flow rate condition. When the flow rate decreases to 2.23% of the design condition, the average surface temperatures of the last stage vane and blade increase by 219.6 K and 243.7 K, respectively. The working performance and internal flow structure significantly change under windage condition. The temperature rise in the last stage cascade deteriorates the working environment of the blades, which needs to be taken into consideration when the steam turbine works under low flow rate condition.

In order to effectively deal with the complex electricity and coal market, strengthening the smart fuel management has become an important part of thermal power plant management. Aiming at solving the problems that the coal yard of a coal-fired power station occupies small area, the types of incoming coal are complex, and the coal-fired coal stacking is chaotic, by extracting the coal quality information of historical incoming coal, K-means and DBSCAN clustering algorithms are used to analyze the low-level coal. The calorific value, volatile matter and sulfur content are clustered and analyzed, and the two clustering algorithms are compared from the perspective of silhouette coefficient, cluster stability and sample division fineness, and finally K-means with better clustering effect is selected as the calculation method for coal quality division. The K-means algorithm divides the selected historical coal quality information data set into four categories, the contour coefficient is 0.587, and the coal quality components in each category are similar. The incoming coal frequency and the incoming coal weight ratio under different cluster labels are counted, and the coal yard is divided into corresponding proportions. The incoming coal of the same classification is stacked in each partition, and on this basis, the incoming coal in the digital coal yard platform is designed. Coal stacking guidance and information storage process are of great significance to improving the utilization of storage yard space and the efficiency of coal yard management.

Based on the elastic beam theory, a theoretical calculation model for the axial force of the in-service tie rod under transverse loading conditions and the three-dimensional finite element model of the prestressed beam are established. The axial force measurement method of the tie rod of the in-service support hanger is studied, and the influence of different length-to-diameter ratios and transverse loads on the deflection of the midpoint for the tie rod are discussed. The results show that the theoretical prediction results are in good agreement with the finite element calculation results. In terms of engineering applications, an optimal scheme for the length-diameter ratio of the fixed support section of the tie rod is given based on the transverse load tolerance and deflection tolerance value. This method can be used to quickly measure axial load of tie rod when it is not uninstalled.

To realize stable combustion and refined combustion adjustment of boilers and to gain an in-depth understanding of the jet characteristics of direct flow pulverized coal burners, by taking the pulverized coal burner with surrounding air and its horizontal branch of the secondary air of a quadrangular tangentially pulverized coal boiler as research objects, the effects of throttle column height, secondary air door opening, and wind baffle angle on airflow characteristics are analyzed by numerical simulation under thermal condition. The calculation results show that, for the pulverized coal burner with a small nozzle area of the surrounding air and a thicker horizontal branch of secondary air, adding a throttle column at the position of a secondary air door can effectively improve the uniformity of velocity distribution of the nozzle area of the surrounding air. The opening degree of the secondary air door poses no noticeable effect on the airflow velocity distribution near the nozzle area of the surrounding air, and adding a wind baffle at the burner nozzle can improve the rigidity of primary air and the protection of surrounding air to primary air.

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.