Performance of exhaust gas-natural gas reforming under simulated exhaust conditions from marine NG engine: An experimental and thermodynamic study

Abstract

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 CH4 to O2 (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 O2, H2O, CO2, and heat from the exhaust gas. The insights gained from this present investigation provide valuable guidance for the development of the REGR system.