A simulation study on a 300 MW tangentially-fired boiler with 20% ammonia doping at 60% load was carried out to analyze the combustion process of ammonia doping in pulverized coal boiler, and to seek for the best coal-ammonia co-combustion scheme to ensure the optimal combustion efficiency and the lowest pollutant emission. By adjusting the position of ammonia burners and the ratio of the separated over fire air, the temperature field of the flue gas in the furnace, the molar fraction distribution of the combustion components, as well as the combustion characteristics and the NO_x emission level at the furnace outlet were systematically analyzed using numerical simulation. The comprehensive analysis shows that, the best coal-ammonia co-combustion solution is to place the ammonia burner on top layer (tertiary air) and the CD layer (secondary air) when the ratio of the separated over fire air is 33.5%. This scheme ensures the combustion efficiency and stability while controlling the NO_x emission level comparable to that of the pure coal-fired condition, which provides a new way of thinking for large-scale coal-fired power plants to realize clean and efficient combustion.

Co-combustion of biomass and coal can significantly reduce the pollutants and carbon emissions. However, the pollutants emission, ash characteristics and their influence factors during co-combustion of coal and biomass are still obscure. A micro-fluidized bed reactor was used to investigate the co-combustion of rice husk (RH) and bituminous coal (SC). The effects of combustion temperature, atmosphere and blending ratio on the emission characteristics of NO, SO₂ and ash were studied. The results indicated that, with the increase of temperature, the mass concentration of NO emissions during co-combustion rose at first and then fell, while the SO₂ emissions mass concentration gradually increased. High temperature would promote the interaction of minerals in the ash, generating Na₂Al₂SiO₆ and lowering the melting point of the co-combustion ash. In oxygen-deficient atmosphere, NO and SO₂ emission mass concentrations increased with the O₂ volume fraction. In oxygen-enriched atmosphere, the NO emission mass concentration gradually decreased as the O₂ volume fraction increased, while the SO₂ emission mass concentration increased at first and then decreased. The influence of reaction atmosphere on the main composition and crystal structure of the co-combustion ash was relatively minor. NO and SO₂ emissions during co-combustion can be effectively reduced due to the addition of RH. As the RH blending ratio was increased, Ca₃Al₂O₆ in ash tended to form low-melting-point compounds with SiO₂, leading to a noticeable melting phenomenon.

Ammonia synthesize through hydrogen produced by green electricity offers an effective solution to the widespread abandonment of wind and solar resources and the shortage of green fuel chemicals. A wind-solar-driven proton exchange membrane (PEM) electrolyzer system in dual-mode operation for hydrogen production and hot standby with integrated ammonia synthesis waste heat storage is proposed, addressing issues of frequent start-stop cycles under fluctuating wind-solar outputs and waste heat recovery in ammonia synthesis processes. The results indicate that, the PEM electrolyzer dual-mode operating system, integrated with ammonia synthesis waste heat storage, can significantly shorten the startup time of the electrolyzer. The startup time at 25 ℃ is 512 seconds, while the hot startup from the standby mode at 47.5 ℃ requires only 274 seconds. Under hot standby mode, the system consumes electricity solely from feedwater pumps, achieving a specific hydrogen production power consumption of only 0.49 kW. The dual-tank thermal storage subsystem is configured with 10.8 tons of Dowtherm-G heat transfer oil. In heat storage mode, it absorbs waste heat gas from the ammonia synthesis unit at a flow rate of 3 kg/s, allowing the thermal tank to reach full capacity within 1 hour. In heat release mode, it heats the electrolyzer inlet water at a flow rate of 0.64 kg/s, enabling the electrolyzer to sustain standby operation for 4.68 hours. Furthermore, the new system is expected to generate long-term benefits that consistently exceed costs, ensuring sustained economic viability.

To address the demand for low-carbon transition in coal-fired power plants, ammonia, as a zero-carbon fuel and efficient hydrogen storage carrier, provides a novel pathway for carbon reduction in the thermal power industry. The key technologies and research advances in green ammonia synthesis, storage, transportation, and ammonia-coal co-firing are systematically reviewed from the perspective of the “production-storage-transportation-utilization” whole industry chain, and the economic feasibility is also evaluated. The study reveals that, the second-generation low-temperature and low-pressure synthesis technology (Fe/Ru catalysts) exhibits the greatest industrial potential for green ammonia production, but requires breakthroughs in enhancing catalytic activity and dynamic matching technologies for renewable energy-based hydrogen-ammonia synthesis systems. It is urgent to develop 100 000-ton-level cryogenic storage tanks and long-distance liquid ammonia pipelines, and establish a “West-to-East Ammonia Transmission” network to support large-scale applications. Ammonia-coal co-firing can achieve NO_x emissions comparable to pure coal combustion by optimizing ammonia injection positions (post-injection in low-oxygen zones), air staging (equivalence ratio of 1.1~1.3 in primary zone), and ammonia blending ratios, alongside designing low-NO_x co-firing burners. However, the weakened radiative heat transfer and enhanced convective heat transfer post-co-firing necessitate compatibility adjustments in boiler steam-water systems. When the cost of renewable electricity decreases to 0.10 yuan/(kW·h) with carbon price exceeding 370 yuan/t, or by utilizing curtailed wind/solar power (with near-zero electricity costs), green ammonia is more competitive than coal. In the future, it is necessary to promote the implementation of technology through green ammonia cost reduction, carbon price mechanism and policy support. This study provides comprehensive technical references and economic optimization strategies for scaling up green ammonia co-firing in coal-fired power plants.

To optimize the system configuration scheme for green hydrogen co-firing in coal-fired power units at large renewable bases in desert, gobi, and wasteland areas to achieve decarbonization, a comprehensive system framework encompassing hydrogen production, hydrogen storage, energy storage, and hydrogen co-firing in coal-fired power units is established. It develops a system configuration optimization model aiming for the lowest hydrogen production cost under a decarbonization target constraint. The model is solved and analyzed using mixed-integer linear programming to explore the optimal configuration solutions for a decarbonization system via green hydrogen co-firing in different operating scenarios. The model is demonstrated through a case study. Under the constraint of 10% decarbonization for a single coal-fired power unit, if only curtailed wind and solar power are used for hydrogen production, the annual utilization hours of the hydrogen production equipment are only about 2 000 hours, and the green hydrogen cost is as high as 3.02 yuan/m³ (33.8 yuan/kg). This leads to an increase of 0.217 9 yuan/(kW·h) in the per-unit electricity cost for a single coal-fired power unit. Configuring electrochemical energy storage can reduce the scale of hydrogen production and storage systems and increase the utilization hours of hydrogen production equipment. However, limited by high energy storage construction costs, the energy storage scale needs to be optimally determined, and the green hydrogen cost can be reduced to approximately 2.35 yuan/m³ (26.3 yuan/kg) at its lowest, which leads to an increase of 0.165 2 yuan/(kW·h) in the per-unit electricity cost for a single coal-fired power unit. Furthermore, if a small amount of grid electricity can be introduced to assist hydrogen production within the scope of green hydrogen certification, system construction costs can be further reduced. The hydrogen production cost is expected to decrease to approximately 2.12 yuan/m³ (23.7 yuan/kg) and the per-unit electricity cost for a single coal-fired power unit would increase by 0.142 6 yuan/(kW·h).

Aiming at the difficulties in renewable energy consumption and the demand for low-carbon development in the integrated energy system, an optimal scheduling method considering the joint operation of hydrogen-doped gas-fired units with hydrogen-doped and ammonia-doped coal-fired units is proposed. Firstly, to account for the uncertainty and correlation of wind and solar power outputs, a joint wind-solar output modeling approach based on the Frank Copula function is adopted. Typical wind-solar scenarios are generated through marginal distribution fitting using kernel density estimation, Monte Carlo sampling, and K-means clustering, thereby enhancing the robustness of the scheduling model. Meanwhile, energy conversion models for power-to-hydrogen and hydrogen-to-ammonia processes are developed to enable the efficient transformation of renewable energy into hydrogen and ammonia. Secondly, the refined operation model of hydrogen-doped combustion of gas-fired units and ammonia-doped combustion of coal-fired units is constructed in response to the demand for low-carbon transformation of conventional fossil energy units, so as to optimize the synergistic utilization of hydrogen and ammonia fuels in the power generation process. Then, the optimal dispatching model is constructed by combining with the laddering-type carbon trading mechanism with the goal of minimizing the total operation cost of the system, which is to minimize the total cost of the system. Moreover, the optimal scheduling model is constructed with the objective of minimizing the total operating cost of the system in combination with the stepped carbon trading mechanism and solved by the CPLEX solver. Finally, different scenarios are set up and comparative analysis are carried out. The results indicate that, the introduction of hydrogen-to-ammonia conversion, building upon hydrogen energy utilization, significantly mitigates wind and solar power curtailment within the system. The combined operation of hydrogen-doped gas-fired unit and ammonia-doped coal-fired unit leads to concurrent reductions in both total operational costs and carbon emissions. The study provides a reference for the development of decarbonization of integrated energy systems.

Circulating fluidized bed (CFB) boilers play a pivotal role in China’s power generation landscape. However, the intricate combustion system within the CFB boiler furnace exhibits strong coupling characteristics, characterized by multiple parameters, variables, nonlinearity, and time-varying dynamics, posing a significant challenge for precise system modeling and prediction. Machine learning (ML), with its robust nonlinear processing capabilities and predictive performance, holds immense promise in the domain of CFB technology. This paper delves into the application of ML techniques in this field, encompassing the prediction of minimum fluidization velocity, emissions forecasting, bed pressure forecasting, bed temperature/thermal efficiency prediction, particle circulation rate prediction, reduced-order models of computational fluid dynamics (CFD) flow fields, and boiler safety control system models. The paper critically evaluates the strengths and limitations of these technologies in various scenarios, providing an insightful perspective on the opportunities and challenges faced by CFB boilers in the era of big data. Emphasizing aspects like model interpretability, enhancing generalization capabilities, improving data quality and diversity, integrating models with conventional methods, and experimental validation are crucial areas worth attention for future advancements.

In the context of “carbon peak, carbon neutral”, how to utilize biomass fuel safely, efficiently and environmentally friendly has become a hot research issue in the industry. The research progress of biomass fuel fluidized bed combustion technology both domestically and internationally was summarized based on the extensive practical engineering experience in fluidized bed combustion, providing a comprehensive overview of progress in biomass fluidized bed combustion power generation technology from an engineering perspective. The analysis compares the characteristics and problems of biomass boilers, with particular emphasis on the research and application status of biomass utilization in circulating fluidized bed. In addition, the combustion characteristics of biomass fuels, NO_x pollutant emission control, chlorine corrosion, and ash deposition and slagging issues caused by alkali metals in fluidized bed combustion were discussed. The reaction mechanisms in each process were described, and the future development directions of related technical issues were forecasted.

The industrial production and urban residents’ lives have led to a large amount of wastewater and sludge, and the landfilling of sludge has caused severe ecological damage. To facilitate the large-scale disposal of municipal sludge, transform waste into valuable resources, and prepare low-carbon, low-cost thermal storage materials, an idea is innovatively proposed, in which the silicon carbide, boron nitride, and expanded graphite is added as thermal conductivity enhancers to enhance the thermal conductivity of sludge incineration ash/potassium nitrate composite phase change thermal storage materials (50% sludge incineration ash+50% potassium nitrate). The composite phase change thermal storage materials were prepared, and the effects of thermal conductivity enhancers on thermal performance of these materials were investigated. The results indicate that, the expanded graphite is not suitable as a thermal conductivity enhancer for sludge incineration ash/potassium nitrate composite phase change thermal storage materials. The addition of a thermal conductivity enhancer with a mass fraction of 2% is optimal for improving melting latent heat, with boron nitride performing better than silicon carbide. The samples with 2% boron nitride shows the most significant increase in thermal conductivity, rising by 65%, 93%, 117%, and 203% compared with samples SC3 (without thermal conductivity enhancers) at temperatures of 100 ℃ to 400 ℃, respectively. After undergoing 1 000 cycles of heating/cooling, the samples with 2% boron nitride have a latent heat of 35.29 J/g and a thermal storage density of 292.1 J/g, while the samples with 2% silicon carbide have a latent heat of 40.90 J/g and a thermal storage density of 334.9 J/g. The heat transfer rates for the samples with 2% silicon carbide and 2% boron nitride are 0.16 ℃/s and 0.17 ℃/s, respectively. This preliminary evidence demonstrates the feasibility of using silicon carbide and boron nitride as thermal conductivity enhancers for sludge incineration ash/potassium nitrate composite phase change thermal storage materials.

With the increasing proportion of new energy connected to the grid, the issue of frequency safety in the power system and mastering the regulation ability of the units have become more important. At present, in power system simulation, thermal power unit models suitable for electromechanical transient and medium-long term dynamics mainly adopt the simplified model of drum boilers and the single reheater turbine model recommended by IEEE. If a similar model is also used for the once-through boiler unit, the simulation results of the main steam pressure will deviate significantly from the actual situation due to the dynamic of thermal storage coefficient and the deviation of control system, which leads to a misjudgement of the unit’s regulation ability. By using thermodynamic modeling methods, a supercritical once-through boiler unit model suitable for multi-time scale dynamic simulation is proposed. By establishing a moving boundary model of the water wall and a dynamic heat flow model of the superheater, the heat storage capacity of the once-through boiler can be reflected more accurately. By incorporating feedwater control and superheat control, the control system is more in line with the actual unit. The high simulation accuracy of the model is verified using power plant operation data. Compared with the existing power simulation models, the simulation accuracy of the main steam pressure has been improved significantly. Therefore, the model can describe the dynamics of supercritical once-through boiler units more accurately in primary and secondary frequency regulation and peak shaving, which is helpful for simulating the frequency process of power systems.