SIMULASI PENGARUH STEAM-TO-CARBON RATIO DAN TUBE OUTLET TEMPERATURE TERHADAP REAKSI STEAM REFORMING PADA PRIMARY REFORMER DI PABRIK AMONIAK

Abstract

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 450-800^oC 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 (T_out) of Primary Reformer. Commonly S/C is 3.20 and maximum T_out is 800^oC. That’s why; optimization was conducted by energy calculation at various S/C and T_out. 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 T_out 700^oC-800^oC 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 T_out 800^oC was 573.11 MJ/kmol-H₂. The need of energy per kmol-H₂ outlet Primary Reformer at S/C 3.50 and T_out 780^oC (20^oC below common T_out) was 573.01 MJ/kmol-H₂. It means that decreasing T_out (for tube lifetime increasing) must be compensated with increasing S/C.

Keywords: Primary Reformer, Steam to Carbon Ratio, Tube Outlet Temperature