This work presents a simulation approach to the design and economic evaluation of fuel oil hydrotreating processes for the control of SO2 and NOx emission in an Iranian steam power plant. The percent of fuel oil desulphurization was estimated from the SO2 emissions standards for power plants. Based on two different scenarios according to (I) European and (II) Iranian standards, the design and simulation of hydrodesulphurization reactors, separation, heat recovery, and amine gas sweetening sections were performed and an economic assessment of the plant was investigated for each scenario. The results indicated the following: the cost price of each barrel of low sulfur fuel oil produced in such plants was estimated at  4.24 US$ for scenario (I) and 3.17 US$ for scenario (II); the levelized cost of desulfurization in power production was estimated at 0.618 c/kWh for (I) and 0.463 c/kWh for (II); and the social cost savings of replacing every barrel of low sulfur fuel oil instead of one barrel of high sulfur fuel oil were estimated at 26.7 US$ for (I) and 13.6 US$ (II).