Current Issue : January-March Volume : 2025 Issue Number : 1 Articles : 5 Articles
Co-firing zero-carbon fuels as an effective emission reduction strategy in coal combustion processes has garnered widespread attention. This paper proposes utilizing the combustion performance of oxy-hydrogen gas derived from zero-carbon fuels to address issues related to lowconcentration coal powder combustion and nitrogen oxide emissions. A test apparatus for coal powder combustion initiated by oxy-hydrogen gas flames was constructed, and experimental and simulation methods were employed to study the impact of oxy-hydrogen gas flame initiation on the temperature inside the combustion chamber, coal powder gasification combustion reactions, and nitrogen oxide emissions. The results indicate that with an excess air coefficient of 0.8, as the oxy-hydrogen gas flow rate increased from 0.022 kg/h to 0.789 kg/h, the average temperature inside the combustion chamber increased from 801 K to 1459 K. The volatile matter release rate and its combustion reaction rate increased, leading to a decrease in volatile matter content. The peak concentration of volatiles was shifted from a position of 68 mm to 7 mm, and the proportion of Cchar–H2O reaction increased from 5% to 34%. NO emissions decreased from 132 ppm to 68 ppm, and the rate of reduction in NO emissions decreased from 15.38% to 5.49%....
This study proposes and validates a novel combustion control system for oil-fired boilers aimed at reducing air pollutant emissions through flame image prediction. The proposed system is easily applicable to existing ships. Traditional proportional combustion control systems supply fuel and air at fixed ratios according to the set steam load, without considering the emission of air pollutants. To address this, a stable and immediate control system is proposed, which adjusts the air supply to modify the combustion state. The combustion control system utilizes oxygen concentration predictions from flame images via SEF+SVM as control inputs and applies internal model control (IMC)-based proportional-integral (PI) control for real-time combustion control. Due to the complexity of modeling the image-based system, IMC filter constant tuning through experimentation is essential for achieving effective control performance. Experimental results showed that optimal control performance was achieved when the filter constant λ was set to 1.5. In this scenario, the peak overshoot Mp was reduced to 0.19245, and the Integral of Squared Error (ISE) was minimized to 10.1159, ensuring a stable response with minimal oscillation and maintaining a fast response speed. The results demonstrate the potential of the proposed system to improve combustion efficiency and reduce emissions of air pollutants. This study provides a feasible and effective solution for enhancing the environmental performance of marine oil-fired boilers. Given its ease of application to existing ships, it is expected to contribute to sustainable air pollution reduction across the maritime environment....
Catalytic combustion is an effective strategy for alleviating volatile organic compounds (VOCs), including hydrocarbons and aromatic compounds, mostly derived from the petrochemical and pharmaceutical industries. We employed Pd/Al2O3 as a catalyst for combusting aromatic VOCs via hydrogen catalytic combustion. It differs from conventional approaches that do not necessitate additional electric heating. Briefly, when hydrogen (H2) is introduced below its lower explosive limit of 4% on the Pd/Al2O3 catalyst, it completely oxidizes important aromatic VOCs like benzene, toluene, ethyl benzene, and xylene to carbon dioxide and water. The catalytic performance of the integrated system remains stable even after long-term use. Therefore, hydrogen co-combustion on the Pd/Al2O3 catalyst can provide onsite heating for a facility without needing external electric heat. The catalytic performance shows no significant dependence on the sizes of Pd nanoparticles in both fresh and spent conditions, as demonstrated by XRD, XPS, and STEM analyses. Therefore, renewable green hydrogen can effectively reduce aromatic VOC pollutants, providing a more energy-efficient alternative. Our findings suggest that this integrated process is promising for converting aromatic VOCs into carbon dioxide and water without electric heating....
We reported the new synthesis of Sm2Co17 particles by a microwave-assisted combustion (MACS) method. This process enables the controlled decomposition of Sm(NO3)3 and Co(NO3)2 into SmCo-O particles, followed by calcium reduction-diffusion. This SmCo-O particle provides an approach for achieving high magnetic properties in Sm2Co17 magnetic materials. The rhombohedral Sm2Co17 particles can be incorporated into epoxy resin and oriented, displaying a square-like hysteresis loop. The particles display magnetic properties at room temperature, with a saturation magnetization of 112.3 emu/g, coercivity of 5.6 kOe, and a maximum energy product of 9.4 MGOe. This method improves the synthesis efficiency of rare earth cobalt-based nano-materials, expands the synthesis scope, and provides ideas for the synthesis and applications of other rare earth nano-materials....
Low-temperature combustion (LTC) concepts, such as homogeneous charge compression ignition (HCCI) and partially premixed combustion (PPC), aim to reduce in-cylinder temperatures in internal combustion engines, thereby lowering emissions of nitrogen oxides (NOx) and soot. These LTC concepts are particularly attractive for decarbonizing conventional diesel engines using renewable fuels such as methanol. This paper uses numerical simulations and a finite-rate chemistry model to investigate the combustion and emission processes in LTC engines operating with pure methanol. The aim is to gain a deeper understanding of the physical and chemical processes in the engine and to identify optimal engine operation in terms of efficiency and emissions. The simulations replicated the experimentally observed trends for CO, unburned hydrocarbons (UHCs), and NOx emissions, the required intake temperature to achieve consistent combustion phasing at different injection timings, and the distinctively different combustion heat release processes at various injection timings. It was found that the HCCI mode of engine operation required a higher intake temperature than PPC operation due to methanol’s low ignition temperature in fuel-richer mixtures. In the HCCI mode, the engine exhibited ultra-low NOx emissions but higher emissions of UHC and CO, along with lower combustion efficiency compared to the PPC mode. This was attributed to poor combustion efficiency in the near-wall regions and engine crevices. Low emissions and high combustion efficiency are achievable in PPC modes with a start of injection around a crank angle of 30◦ before the top dead center. The fundamental mechanism behind the engine performance is analyzed....
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