The conceptual HEN design illustrated in Fig. 2 is also verified by the simulation in Aspen Plus (see Fig. 3) and the energy efficiency is approximately 83% assuming no heat loss to surroundings and pure methane feed, where the energy efficiency is calculated by Eq. (2). As the calculated efficiency of the developed HEN is close to the maximum, it is concluded that a fuel processor integrating all the reaction zones and heat-exchanging systems can be developed based on the proposed HEN design