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 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

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.

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.

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.

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.

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.

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.

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.

Infrared spectroscopy detection technology has been widely used in petrochemical, pharmaceutical and other industries due to its fast detection speed, no damage to the sample, no pollution, easy to operate and other characteristics. The infrared spectroscopy detection mainly includes qualitative detection and quantitative detection. The qualitative detection usually uses comparative method, which compares with standard substances or consults standard spectra. The quantitative detection calculates the corresponding components content by measuring the intensity of characteristic absorption bands and combining with chemometrics methods. This article elaborates the applications of chemometric methods (including artificial neural networks and partial least squares) in detection scenes such as acid value, moisture, antioxidants and furfural for electric power oil. Finally, some proposals of infrared spectroscopy in oil detection are put forward.