Steam reforming is successful technique of converting hydrocarbons like naphtha and natural gas into process synthesis gas. Most petrochemical industries have been developed based on naphtha conversion to synthesis gas and use the synthesis gas to produce desired chemical by a particular catalyst. Converting hydrocarbons from crude oil into petrochemical is not successful in pilot plant scale. The concept of splitting the hydrocarbons to carbon monoxide & hydrogen, and reacting them to develop new structure molecules is much simple.
Naphtha steam reforming process flowsheet description:
Naphtha is vaporized by the preheater and heated to 220oC and increased to hydrogenation temperature by fired heater up to 380oC. Sulphur compounds from naphtha react with hydrogen and form into hydrogen sulphide. By zinc based absorbent, H2S absorber removes the hydrogen sulphide. This operation is required because H2S is poisonous to the catalyst used in the reformer.
Reformer contains catalyst-filled tubes fitted vertically in between the burner walls. Hot flue gases produced from the reformer during combustion drawn out to the stack by a flue gas blower through a stream of heat exchangers network system fitted in the exhaust section of the reformer. Treated naphtha heated in this flue gas stream and passed to adiabatic pre-reformer to convert the high hydrocarbons to simple methane, CO, CO2, H2. The temperature is raised from 320 oC to 500 oC and pressure is maintained at 33 kg/cm2.
Steam is added to the naphtha before adiabatic pre-reformer to split the naphtha on the packed bed catalyst. About 50 mol% of methane is left out in the outlet stream of the adiabatic pre-reformer. Steam reformer decrease this to 12 mol% of methane and finally secondary reformer uses air for partial combustion and drop the methane content to 0.6 mol% in its outlet stream. The synthesis gas from secondary reformer has the composition in mole percentage, H2: 51.52%, N2: 22.79%, CO: 13.57%, CO2: 11.25%, Ar: 0.27%, CH4: 0.60%. Heat recovered from synthesis gas stream by waste heat boiler for production of process steam.