SIMULASI PENGARUH STEAM-TO-CARBON RATIO DAN TUBE OUTLET TEMPERATURE TERHADAP REAKSI STEAM REFORMING PADA PRIMARY REFORMER DI PABRIK AMONIAK
Steam reforming, the reaction in Ammonia plant between natural gas and H2O becoming H2 and CO/CO2, is occurred in Primary Reformer and being completed in Secondary Reformer. In Primary Reformer, the reaction commonly occurred at 450-800oC and 36 bars. The endothermic reaction occurred in Ni-based catalyst inside the tube. The heat for this reaction came from the heat of reaction of combustion in the furnace (outer-tube). The flow of H2 will increase along with the increasing flow of the feed gas and the heat transferred from outer-tube to inner-tube. In the other side, there will be energy increasing. So there’s a need of optimization. The need of energy influenced by many parameters e.g. Steam-to-Carbon Ratio (S/C) and Tube Outlet Temperature (Tout) of Primary Reformer. Commonly S/C is 3.20 and maximum Tout is 800oC. That’s why; optimization was conducted by energy calculation at various S/C and Tout. Firstly, reaction and heat transfer in inner-tube and outer-tube were modeled, so we can get the data of temperature and gas composition outlet inner-tube. Then, energy consumption which came from process gas, fuel gas and steam generation was calculated. The range of S/C 2.70-3.70 and Tout 700oC-800oC were chosen for the simulation. The simulation result shown that the need of energy per kmol-H2 outlet Primary Reformer at S/C 3.20 and Tout 800oC was 573.11 MJ/kmol-H2. The need of energy per kmol-H2 outlet Primary Reformer at S/C 3.50 and Tout 780oC (20oC below common Tout) was 573.01 MJ/kmol-H2. It means that decreasing Tout (for tube lifetime increasing) must be compensated with increasing S/C.
Keywords: Primary Reformer, Steam to Carbon Ratio, Tube Outlet Temperature