The present paper shows how the Schuster-Schwarzschild method developed originally in astrophysics can be adopted to simulate the performance of the primary reforming Furnace in an ammonia plant. This method facilitates the simulation of heat transfer and reaction in the Furnace and improves the computational efficiency. Simulation analysis is carried out to find ways of saving energy. Appropriate reduction in fuel gas loading and partially shifting of the reforming load from the primary to the secondary reformer by regulating the operating conditions can result in substantial energy saving. Optimization calculations with various objective functions and constraints required are performed. The optimization results may serve as guideline for plant operation and control.