Stable and efficient hydrogen production through exhaust gas-natural gas reforming is crucial for the implementation of reformed exhaust gas-fuel recirculation (REGR) technology in marine LNG engines. The reforming reaction is controlled by the physicochemical characteristics of the catalyst and the initial conditions. Ni-based catalysts have been extensively studied for methane reforming at medium-high temperatures. However, there is limited research on the complex multiphase reforming process using Ni-based catalysts at low temperatures, variable gas flow velocity, multi-component, and high dilution exhaust conditions. Therefore, this study aimed to examine and evaluate the reforming characteristics of modified La–Ni/Ca–Al catalysts, as well as the differences in catalytic physicochemical properties before and after the reforming reaction under the simulated exhaust gas conditions. Characterization results of the catalyst samples demonstrated that the modified catalyst exhibited ideal activity in the low-temperature reforming process, along with good resistance to thermal sintering and carbon deposition. The relative content of CH to O (M/O ratio) and the temperature of feedstock were identified as critical parameters controlling the reforming reactions. To achieve efficient hydrogen production, the optimum M/O ratio should be within 1.5–2.5, which could guide the efficient operation of our developed reformer. The study determined the critical feedstock temperatures for methane oxidation, steam reforming, and dry reforming reactions activated in the reforming system to be approximately 300 °C, 400 °C, and 500 °C, respectively. These findings highlighted the promising potential of exhaust gas-natural gas reforming as a means to recover and utilize O, HO, CO, and heat from the exhaust gas. The insights gained from this present investigation provide valuable guidance for the development of the REGR system.

中文翻译：

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船用天然气发动机模拟排气条件下废气-天然气重整的性能：实验和热力学研究


通过废气-天然气重整稳定高效地生产氢气对于在船用液化天然气发动机中实施重整废气-燃料再循环（REGR）技术至关重要。重整反应由催化剂的物理化学特性和初始条件控制。镍基催化剂已被广泛研究用于中高温甲烷重整。然而，对于低温、可变气流速度、多组分和高稀释排气条件下使用镍基催化剂的复杂多相重整过程的研究有限。因此，本研究旨在考察和评价改性La-Ni/Ca-Al催化剂的重整特性，以及在模拟废气条件下重整反应前后催化物化性能的差异。催化剂样品的表征结果表明，改性后的催化剂在低温重整过程中表现出理想的活性，并且具有良好的抗热烧结和积炭性能。 CH 与 O 的相对含量（M/O 比）和原料温度被确定为控制重整反应的关键参数。为了实现高效制氢，最佳M/O比应在1.5-2.5之间，这可以指导我们开发的重整器的高效运行。研究确定重整系统中激活的甲烷氧化、蒸汽重整和干重整反应的临界原料温度分别约为 300°C、400°C 和 500°C。 这些发现凸显了废气-天然气重整作为回收和利用废气中的 O、H2O、CO 和热量的手段的巨大潜力。从本次调查中获得的见解为 REGR 系统的开发提供了宝贵的指导。