A novel design of a double-tube steam methane reforming (SMR) reactor was evaluated in terms of conversion and reactor temperature, compared with the conventional, single-tube, fixed bed reactor. The heat from the reformate could be recovered through the double-tube reactor, which increased the conversion from 71.7 to 89.3% and lowered the reactor outlet temperature from 732.7 to 674.5 °C. An actual plant was then designed, wherein the entire operating process was tested using the double-tube reactor, which produced 100 N m3/h of pure hydrogen. Last, to maximize the thermal efficiency and to achieve a hydrogen-production rate of >100 N m3/h, the operating conditions were optimized with the decision variables and constraints based on actual operating experiences. Consequently, our developed optimal SMR system gave a thermal efficiency of 81.3%, higher than that of the current commercial products (approximately 70%), and achieved a hydrogen-production rate of 124.8 N m3/h.