Low-temperature SCR denitration is one of the current research highlights in de-NO_x field. Developing efficient and stable SCR catalysts under low temperature conditions (<300 ℃) is the key to solve the problem. Carbon-based materials have developed pore structures and high specific surface area, which can provide space and surface support for the loading of active catalytic components. Carbon-based catalyst for low-temperature de-NO_x technology has broad development and application prospects. The present work introduces the low-temperature de-NO_x reaction mechanism and the commonly used carbon-based materials, and analyzes the factors affecting the low-temperature de-NO_x performance of carbon-based catalysts. Moreover, it summarizes the research progress of carbon-based catalysts from the aspects of pre-treatment to enhance oxygen-containing functional groups, active components to improve de-NO_x performance, reasonable calcination to enhance de-NO_x performance, and anti-poisoning to maintain stable denitrification performance. Finally, the prospective future development directions and suggestions are given.

In the context of carbon peak and carbon neutrality, the development of coal-biomass coupling power generation is one of the important ways to accelerate the transformation and upgrading of electric power and realize low-carbon development of coal power. A coal-fired power generation system directly coupled with biomass combustion was designed for a 300 MW circulating fluidized bed (CFB) boiler, and the combustion characteristics of directly firing biomass with coal were studied by using the system. The results show that, this biomass direct combustion coupling system could run stably and reliably. When wood pellets was co-fired in the CFB boiler, with the increase of wood pellets’ blending ratio, the fly ash carbon content of the mixed fuel decreased, the CO emission reduced, and the burnout performance of the mixed fuel improved. After optimization on the boiler combustion and air distribution, the NO_x emission was slightly lower than that of pure coal burning. The pollutants test under typical conditions showed that, after adding wood pellets, the dioxin emission from boiler flue gas was 0.008 8 ng TEQ/m³ (standard condition, ϕ(O₂)=11%), and the dioxin emission in fly ash was 0.020 6 ng TEQ/m³. The total emission of heavy metals and harmful trace elements such P, As and Se from fly ash was 32.121 mg/l, and that from the bottom slag was 3.918 mg/L. The emission of harmful substances like dioxins and heavy metals in flue gas and fly ash all met the emission limits of national environmental protection standards.

The excessively high temperature gradient inside solid oxide fuel cell (SOFC) can lead to failure of the cell, so it is critical to reduce the temperature gradient in the SOFC and enhance the uniformity of the cell temperature. By combining with the electrical, thermal, flow, and mass transfer physical fields, a multi-physics field coupling model of the SOFC is established. The accuracy of the model is verified by comparing with the experimental data. The SOFC temperature and temperature gradient distributions are investigated by the SOFC model and the maximum temperature gradient in the cell reaction zone is determined as the optimization objective. The obstacle structure in flow channel is designed, and the effectiveness is proved. The shape, height and width of the obstacle structure are discussed and analyzed. It is found that the obstacle affects the maximum temperature gradient in the reaction zone mainly by changing the fluid flow rate and the oxygen molar concentration in the reaction layer. The change of the obstacle for the pressure drop in the flow path mainly affects the power density loss. Finally, the circular obstacle (h=0.8 mm, d₁=4.0 mm) is identified as the optimal structure. With the same net power density as the conventional channel, the maximum temperature gradient is 43.35 K/cm, which is 9.4% lower than that of the conventional channel.

There is a delay in NO_x measurement for flexible operations in coal-fired power plants, which leads to a delayed response in ammonia injection control system of selective catalytic reduction (SCR) reactor, resulting in potential over or under-injection of ammonia and significant fluctuations in NO_x mass concentration at outlet of the SCR reactor. To enable proactive adjustment of ammonia injection and considering the interconnected factors influencing the NO_x emissions from coal combustion, a prediction model for NO_x mass concentration at the SCR reactor inlet is proposed based on convolutional neural networks (CNNs) and long short-term memory neural (LSTM) networks. By using operational parameters from a 330 MW coal-fired power plant, a Pearson coefficient method is employed to calculate the correlation between feature variables. Significant features are extracted to define the model input matrix and output matrix. The random search algorithm is used for hyper-parameters optimization to enhance predictive performance. The SHAP algorithm is then applied to interpret the model structure and explain the black-box model. Finally, the control effects of model with NO_x concentration prediction is verified through Simulink simulation. The results indicate that, the CNN-LSTM prediction model demonstrates higher predictive accuracy for the variable NO_x mass concentration at the SCR reactor inlet during the frequent load fluctuations. It can provide feedback to the ammonia injection control system of 25 seconds in advance. The optimized ammonia injection control strategy not only reduces the standard deviation between the NO_x mass concentration at the SCR reactor outlet and the set value by 28%, but also improves the response speed of NH₃/NO_x regulation, reducing the maximum ammonia slip by 22%. The research findings can provide guidance for intelligent SCR denitration system and combustion optimizing operating during flexible operation of coal-fired power plants.

The coupling of photovoltaic-thermal utilization and ground source heat pump is expected to use photovoltaic waste heat to avoid performance degradation of the heat pump, and also to use photovoltaic electricity to partially meet the energy demand of the heat pump, which has a broad prospect. A simulation model of the integrated system of low-concentration photovoltaic-thermal and ground source heat pump is constructed, and the operational performance of the system is analyzed. Moreover, the key influence laws of the life cycle cost of the system are also analyzed. The research results show that, the annual solar-to-electrical efficiency of the integrated system reaches 17.73%, which is 9.58% higher than that of the single operation system. The photovoltaic waste heat of the photovoltaic-thermal device can effectively reduce the soil temperature decay, and the long-term operation performance of the heat pump is 16.58% higher than that of the reference system. The operation and maintenance cost of the system decreases with the increase of the scale of the photovoltaic-thermal device and the ground source heat pump, while the investment cost increases accordingly. The total life cycle cost of the system decreases at first and then increases with the increase of the scale. Taking the life cycle cost as the objective function, economic optimization of the system based on the particle swarm algorithm is carried out, and the life cycle cost reduces by 31.52% compared with the design of the maximum scale capacity. The relevant results can provide theoretical reference for optimal design of the photovoltaic-thermal-ground source heat pump integrated system.

In order to adapt to the harsh service environment of 700 ℃ advanced ultra-supercritical coal-fired power generation unit (700 ℃ A-USC), and facilitate the development of high efficiency, low consumption and low carbon coal-fired power generation technology, high temperature superalloy will be used to manufacture the high-temperature components in boiler and turbine. Many countries and regions such as the United States, Europe, China, Japan and India have put forward research plans of 700 ℃ A-USC technology with national characteristics, respectively. Due to the variety of elements, high welding difficulty, and high tendency to produce welding defects in high-temperature alloys, welding technology and weld joint comprehensive performance evaluation technology have a significant influence on the factory manufacturing, on-site processing and repair, as well as service safety and integrity of high-temperature components. The current progress in practical application of the 700 ℃ technology at home and abroad is slow, which is mainly due to incomplete resolution of technical barriers such as manufacturing, connection, and testing. The research plans and development prospects of the 700 ℃A-USC technology around the world are summarized. The material selection of high temperature components including the boiler side and the turbine side is discussed. The current status, advantages and disadvantages of the welding technology for superalloy are summarized, and the critical focus points of the joint comprehensive properties evaluation technology for high temperature components are analyzed. Finally, some suggestions on developing the 700 ℃ A-USC technology are put forward.

To accurately assess the overall performance of integrated energy systems, with a focus on their key characteristics of low carbon emissions and high efficiency, and to facilitate the safe integration of renewable energy, this study proposes a weighted energy utilization efficiency index. The integrated energy system in industrial parks is identified as a typical scenario for the application of comprehensive energy. Considering the relatively low energy conversion efficiency of renewable sources in these systems, the study evaluates the performance of the renewable and fossil fuel energy systems using energy efficiency ratios and primary energy utilization rates. Moreover, the proportion of supplied energy is utilized as a weighting factor to indicate the system’s relative significance within the total energy framework, leading to the calculation of the weighted energy utilization efficiency for the park’s integrated energy system. Through comparative analysis with conventional metrics such as primary energy utilization rate and exergy efficiency, the results indicate that the proposed index can effectively reflect the level of renewable energy integration, showcasing the system’s core features of low carbon and high efficiency. This is crucial for directing strategies towards energy saving and consumption reduction.

In the system realizing waste heat utilization through thermal cycle, there is a mutual restriction relationship between the cycle thermal efficiency and the utilization rate of heat source, solving this problem is the key to build an efficient waste heat utilization system. Taking supercritical carbon dioxide cycle as an example, this paper constructs a new cycle, namely the partial expansion cycle, to broaden the waste heat absorption temperature range, so as to enhance the waste heat utilization rate. After coupling gas turbine exhaust, the waste heat utilization system’s power generation efficiency reaches 28.62%, the cycle thermal efficiency reaches 34.03%, and the heat source utilization rate reaches 84.11%. Moreover, to demonstrate the advantages of the partial expansion cycle, a waste heat utilization system is constructed based on the single regenerative Brayton cycle and the recompressed Brayton cycle. Furthermore, the three cycles are compared. Through calculation using the first and second law of thermodynamics, it is found that the power generation efficiency of the partial expansion cycle is higher than that of the other two classical cycles. Via analyzing the circulation process, it is found that the reason for the high efficiency of the partial expansion cycle is that the partial expansion structure broadens the endotherm temperature zone, makes the heat source utilization rate increase greatly, and thus improves the power generation efficiency.

By taking the test bench of a micro gas turbine cycle system as the research object, a mathematical model for regenerative cycle system of the micro gas turbine is established. On this basis, the performance prediction and analysis for the regenerative cycle system is carried out. Considering the performance parameters of the system’s key components are presently unknown, the maximum likelihood estimation method is employed to estimate them by using the experimental data. The results show that, the error between the model predicted value and the experimental value is smaller than 3%, indicating the model can accurately predict the thermal performance of the cycle. Subsequently, based on the established model, a performance simulation of the recuperative cycle is conducted under various working conditions. The variation rules of power, generation efficiency, exhaust gas energy, and exhaust gas temperature with the changes of load and ambient temperature are obtained, and the compressor’s operating range is also obtained. The information regarding the key components of the microturbine and the performance characteristics acquired through this study can serve as valuable references for related research.

Constructing a power system predominantly based on renewable energy sources imposes increasingly stringent demands on deep peak shaving capability and ultra-low-load operation of coal-fired power generating units, thereby presents more severe challenges to the safe operation of steam turbine units under low-load conditions. This paper employs numerical simulation methods, focusing on an in-depth analysis of the operational performance of the last stage of a steam turbine under low-load conditions, and explores various solutions for their working mechanisms and optimization effects under ultra-low-load conditions. It is found that, when the unit transitions from medium-low load to ultra-low load, vortex clusters such as gap vortices, backflow vortices, and separation vortices emerge near the last stage blades, with their extent gradually expanding as the load decreases. Reducing the back pressure of the unit and operating the low-pressure cylinder with cylinder-cutting are effective strategies to attenuate steam turbine vortex flow and enhance the last stage’s performance, with a combined application of these strategies yielding better results. For instance, under 20% turbine heat acceptance (THA) conditions, reducing the back pressure from 4.9 kPa to 2.5 kPa significantly diminishes the influence range of the last stage vortex cluster, increasing the rotor blade torque from −38 N·m to 73 N·m, thereby markedly improves the last stage performance. Under 10% THA conditions, employing a combination of reduced back pressure and low-pressure cylinder-cutting can completely eliminate the tip clearance vortex, with the radial lengths of the backflow vortices and separation vortices reducing by more than 50%. The optimized rotor blade torque increases by approximately 130 N·m, significantly enhancing the last stage performance.