PENGARUH PENONAKTIFAN HEAVY HYDROCARBON (HHC) REMOVAL DAN CO2 REMOVAL, PENGATURAN STEAM-TO-CARBON RATIO DAN TEMPERATUR OUTLET PRIMARY REFORMER TERHADAP KEBUTUHAN ENERGI DI METHANATOR DI UNIT AMONIAK

MUHAMMAD NATSIR H, Muslikhin Hidayat, ST, MT, Ph.D.; Ir. Sutijan, MT, Ph.D.

2017 | Tesis | S2 Teknik Kimia

Proses steam reforming di unit Amoniak yang merupakan reaksi antara gas alam dan H2O menjadi gas H2 dan CO/CO2 berlangsung di Primary Reformer dan disempurnakan di Secondary Reformer. Reaksi di Primary Reformer umumnya terjadi pada temperatur 450-800oC dan tekanan 36 bar. Reaksi berlangsung secara endothermis dalam tube berkatalis Ni dengan sumber panas berasal dari reaksi pembakaran di sisi furnace (outer-tube). Jumlah kmol-H2 akan meningkat seiring dengan kenaikan jumlah bahan baku dan jumlah panas yang ditransfer dari outer-tube ke inner-tube. Akan tetapi, hal ini menyebabkan kenaikan kebutuhan energi sehingga perlu dilakukan optimasi. Kebutuhan energi dipengaruhi oleh berbagai parameter, diantaranya konsentrasi HHC dan CO2 dalam gas umpan, serta Steam-to-Carbon Ratio (S/C) dan Tube Outlet Temperature (Tout) di Primary Reformer. Sebelum masuk ke Primary Reformer, umumnya gas alam diproses terlebih dahulu di HHC dan CO2 Removal. Besaran S/C umumnya sebesar 3,20 dan Tout maksimal sebesar 800oC. Dengan demikian, optimasi dilakukan dengan cara simulasi perhitungan kebutuhan energi saat HHC dan CO2 Removal dinonaktifkan, serta kebutuhan energi pada berbagai nilai S/C dan Tout. Simulasi diawali dengan memodelkan reaksi dan transfer panas di inner-tube dan outer-tube, sehingga diperoleh temperatur dan komposisi outlet inner-tube. Selanjutnya simulasi dilanjutkan hingga Methanator. Didapat jumlah H2 outlet Methanator dan kebutuhan energi total, sehingga dapat dihitung kebutuhan energi per kmol-H2. Dipilih kisaran S/C 2,70-3,70 dan Tout 700oC-800oC untuk disimulasikan. Hasil simulasi menunjukkan penonaktifan HHC dan CO2 Removal akan menaikkan jumlah H2 outlet Methanator dan menurunkan kebutuhan energi per kmol-H2 outlet Methanator. Hasil simulasi juga menunjukkan bahwa kenaikan S/C dan Tout berbanding lurus dengan kenaikan jumlah kmol-H2 outlet Methanator, namun tidak berbanding lurus dengan penurunan kebutuhan energi per kmol-H2 di outlet Methanator. Keuntungan maksimum akan didapatkan jika Primary Reformer dioperasikan pada kisaran S/C 3,40 dan Tout 770-790oC, S/C 3,50 dan Tout 760-790oC, S/C 3,60 dan Tout 750-790oC, dan S/C 3,70 dan Tout 740-790oC.

Steam reforming, the reaction in Ammonia plant between natural gas and H2O becoming H2 and CO/CO2, is occured in Primary Reformer and being completed in Secondary Reformer. In Primary Reformer, the reaction commonly occurred at 450-800oC and 36 bar. 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����¯�¿�½������¢������¯������¿������½������¯������¿������½s a need of optimization. The need of energy influenced by many parameters e.g. HHC and CO2 in the feed gas, Steam-to-Carbon Ratio (S/C) and Tube Outlet Temperature (Tout) of Primary Reformer. Before entering Primary Reformer, feed gas generally was processed in HHC and CO2 Removal. Commonly S/C is 3,20 and maximum Tout is 800oC. That����¯�¿�½������¢������¯������¿������½������¯������¿������½s why; optimization was conducted by energy calculation while HHC and CO2 are deactived. The energy calculation at various S/C and Tout was also conducted. 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, the simulation was continued until Methanator. The flow of H2 outlet Methanator and the need of energy were calculated, so we can calculate the energy per kmol-H2. The range of S/C 2,70-3,70 and Tout 700oC-800oC were chosen for the simulation. The simulation result shown that HHC dan CO2 Removal deactivation would increase the flow of H2 outlet Methanator and the need of energy per kmol-H2 outlet Methanator would be decreasing as well. It also shown that the increasing of S/C and Tout were proportional to the increase of the flow of H2 outlet Methanator. But, it was not proportional to the decrease of the need of energy per kmol-H2 outlet Methanator. The maximum profit were gained when the range operation of Primary Reformer were S/C 3,40 and Tout 770-790oC, S/C 3,50 and Tout 760-790oC, S/C 3,60 and Tout 750-790oC, and S/C 3,70 and Tout 740-790oC.

Kata Kunci : Primary Reformer, Steam to Carbon Ratio, Tube Outlet Temperature