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The coal/ammonia co-firing technology for thermal power generation is a feasible method to effectively reduce CO 2 emissions. However, the easy formation of NO x is one of the challenges faced by this technology owing to the high nitrogen content in ammonia. This study proposes a novel swirl burner with a scalable dual-channel ammonia pipe, and evaluates the combustion and NO x formation under different extension lengths of the dual-channel ammonia pipe (i.e., 0 m, 0.4 m, 0.8 m, 1.0 m, 1.2 m). The results show that the extension length of the dual-channel ammonia pipe significantly affects the flow, combustion, and NO x formation. When the extension length of the dual-channel ammonia pipe is above 0.8 m, the ammonia stream can completely penetrate the internal recirculation zone into the high CO environment, which contributes to promoting the ammonia pyrolysis and inhibiting the ammonia oxidation to form NO x. NO x emissions significantly decrease from 846 ppm to 146 ppm as the extension length of the dual-channel ammonia pipe from 0 m to 0.8 m, but change slightly as further increases from 0.8 m to 1.2 m. The carbon content in fly ash decreases from 4.53% to 3.40% as the extension length of the dual-channel ammonia pipe increases from 0 m to 1.0 m. Still, it increases from 3.40% to 3.70% as the extension length of the dual-channel ammonia pipe rises to 1.2 m. Overall, it is reasonable to set the extension length of the dual-channel ammonia pipe at 1.0 m in this studied condition, which can obtain low NO x and low carbon content in fly ash. [Display omitted] • A novel swirl burner with a scalable dual-channel NH 3 pipe is proposed. • Effect of NH 3 pipe extension length on combustion and NO x formation is investigated. • NH 3 pipe extension length significantly affects flow, combustion, and NO x formation. • 1.0 m for NH 3 pipe extension length is reasonable with good performance. [ABSTRACT FROM AUTHOR]

[Objective] As an important type of coarse-grained sedimentary system and oil and gas reservoir in faulted basins, fan delta and slump fan complex deposition has been the hot topic of research on lacustrine sedimentary and reservoir formation, such as distribution area, evolution period and accumulation model. [Methods] Based on high resolution 3D seismic and drilling and logging data in the A Sag of Melut Basin in central Africa region, the sedimentary characteristics and evolution of fan delta-slump fan complex are studied by using core observation, sequence division, seismic reflection characteristics and seismic attribute analysis. [Results and Conclusions] The results showed that the types of sedimentary facies of fan in the study area included fan delta and slump fan caused by gravity flow, slump fan had two types of morphology characteristic, the first one was line source slump fan controlled by slope break, the second one was multistage slump fan with single point source controlled by steep topographic slope. Combined with seismic profiles and well logging features, five periods of fans were recognized in the Cretaceous study section. The single-stage fan all had the characteristics of retrogradation, the vertical evolution of multiple periods of fans was characterized by "first progradation and later retrogradation" . The fan distribution was the largest at the end of Renk Formation deposition in the Lower Cretaceous, reaching 148 km². However, the fan evolution was mainly influenced by tectonic activity, palaeogeomorphology, provenance supply, and base-level cycle. The fan distribution was larger in the period of strong tectonic activity, abundant provenance supply and large short-axis tectonic uplift, and the slump fan was most developed in the early period of relative base-level rising cycle and decreasing cycle. A new understanding of the sedimentary pattern transformation occurred in the Early Cretaceous and Late Cretaceous in the A Sag was put forward. The exploration potential of the fan delta and slump fan complex deposition in the faulted depression is clarified, which guided the exploration deployment. [ABSTRACT FROM AUTHOR]

Grate boilers are widely applied in biomass combustion for heat and energy generation. However, grate-firing systems often suffer from low efficiency and high emission. Computational fluid dynamic (CFD) becomes increasingly popular as a flexible method to obtain the detailed combustion behaviors in the furnace, and to optimize the performance of existing grate boilers. This paper presents efforts toward a reliable baseline CFD model for an industrial biomass-fired grate boiler, where the structure of the fuel-bed was sufficiently considered. The combustion performances in the furnace were investigated experimentally and numerically by coupling the fuel bed and freeboard, to clarify the impact of bed structure on the simulation accuracy. Results show that when the bed structure has been taken into account, the predictions are in better agreement with the various measurements, as the deviations between them are all within 10 %. Moreover, the flame center drops, the total heat transferred to the water-cooled walls increases, and the residence time of flue gas is greatly prolonged from 2.76 s to 3.90 s, resulting in a distinct difference of the temperature and species patterns in the freeboard. The simulations will provide valuable theoretical guidance for the accurate modeling of grate-fired boiler. [Display omitted] • A baseline model is proposed for accurate modeling of biomass-fired grate boiler. • Effect of fuel-bed structure on the simulation of grate boiler is clarified in detail. • Bed structure greatly affects the predicted temperature and species patterns. • Flue gas residence time and heat transfer are also highly impacted by bed structure. [ABSTRACT FROM AUTHOR]

Grate-fired boiler is of considerable interest for burning biomass owing to its reduced sensitivity to variations in fuel composition and size. However, grate-fired technology exhibits unsatisfactory performance in terms of combustion efficiency, contaminant emissions, and flame stability. CFD modelling can provide reasonable optimizations to overcome these drawbacks and ultimately achieve clean and efficient energy production. Conventional approach simulates the fuel-bed and freeboard combustion separately using an in- and over-bed coupling procedure, where data of the gases leaving from the packed-bed top and the radiative heat flux emitted by the high-temperature flame onto the bed cannot be interacted in real-time. This may cause distinct deviations in the calculations. In this paper, a three-dimensional (3D) full-scale integrated model is developed for the simulation of grate-fired boiler, in which the intensive combustion of both the freeboard and fuel-bed is solved in one scheme using the Eulerian-Lagrangian method. The gas phase is considered as a continuous medium and calculated by the Eulerian model, while the solid particles are considered as a discrete phase and tracked via the Lagrangian method. The reliability of the model is well verified through various field measurements and observations. Results shows that the key parameters are non-uniformly distributed along the grate width, i.e., the aerodynamic and combustion environment is poor at the vicinity of water-cooled walls compared with that at the furnace center. This results in a significant lag in volatile gases release and char oxidation near the water-cooled wall on both sides, which finally causes obvious differences in the distribution of temperature and species. For instance, the peak of CO concentration at the center is 12.6 % at 3.3m from the feed entrance, while that near the water-cooled wall is 8.6 % around 3.5m. The char burnout ratio in the bottom ash can be accurately calculated by this model, with a negligible relative error between the simulation of 81.97 % and the measurement of 82.50 %. It also provides a novel method for the calculation of fly ash particles by using size-grouped and non-spherical particles. Small-size particles in the vicinity of the feed inlet, as well as a part of the particles burning at the end of the grate are entrained into the freeboard by the primary air supplied beneath the grate and the high-momentum secondary air on the bed top. This model can provide valuable theoretical guidance for optimizing the refined distribution of fuel and air in grate-fired power plants and mitigating irregular deposition (corrosion) on heat exchangers and water-cooled walls caused by fly ash. [Display omitted] • An integrated model is developed for accurate modeling of travelling grate boiler. • Real-time mass and heat transfer between the fuel bed and freeboard is achieved. • Key parameters are found to be non-uniformly distributed along the grate width. • Non-spherical and size-grouped particles are used to better represent agricultural straw. • A novel method for calculating fly ash in grate-fired boiler has been developed. [ABSTRACT FROM AUTHOR]