**4. Conclusions**

A series of lab- and bench-scale SRM experiments were performed to identify and solve the problems that could occur during scale-up. In the lab-scale reaction, the effects of temperature, pressure, and steam/methane ratio on methane conversion were investigated in comparison to the corresponding equilibrium conversion. Based on the lab-scale experiments, a bench-scale reaction was designed. The methane conversion in the bench-scale reactor was >90%, and the hydrogen production was >10 L/min if the three consecutive heaters sufficiently supplied the heat required to reach the equilibrium (>800 ◦C). Under these conditions, the heater temperature positioned at the bottom of the reactor (outlet side) largely governed the methane conversion. Under abnormal reactor temperature conditions, where the catalyst bed was not heated sufficiently (<650 ◦C), the reaction was not equilibrated simply by maintaining the temperature of the bottom heater at 800 ◦C. This is similar to the case where the space velocity is relatively high (>10.0 L CH4/(h·gcat)). Using kinetic data obtained from the lab- and bench-scale reactions, the effective factor (0.143) for the pelletized catalysts was calculated. Finally, we proposed effective idling operating conditions that prevented catalyst deactivation during process downtime and reduced the time and costs involved in restarting the process.

**Author Contributions:** H.-G.P., K.-W.J., and S.K.K. conceived and designed the experiments; H.-G.P. and S.-Y.H. performed the experiments; Y.W. and M.-J.P. analyzed and simulated the data; S.K.K. administrated the project; H.-G.P. wrote original draft; M.-J.P. and S.K.K. reviewed and modified the manuscript.

**Funding:** This work was supported by the Korea Gas Corporation R&D program (Project No. IPT17-12) and Korea Research Institute of Chemical Technology (Project No. SI1911-60).

**Acknowledgments:** We thank Jin-Mo Park and Hyung-Sik Kim of Korea Gas Corporation for helpful discussion on this work.

**Conflicts of Interest:** The authors declare no conflict of interest.
