What are the key design considerations for a steam methane reformer (SMR)?

SMR design considerations: Catalyst - Ni on alumina support, must resist sintering and carbon formation. Tube metallurgy - high alloy (25Cr-35Ni or higher) for 850-950C operation, stress from internal pressure and thermal expansion. Tube layout - typically 100-1000 tubes per furnace, arranged for uniform heating. Heat recovery - convection section recovers heat for steam generation, feed preheat, combustion air preheat. Steam/carbon ratio - typically 2.5-4, higher prevents coking but reduces efficiency. Operating pressure - higher pressure reduces compressor cost but shifts equilibrium unfavorably. Fired duty distribution - top-fired, side-fired, or terrace-fired designs. Reliability factors: tube inspection, catalyst replacement every 3-5 years, burner maintenance. Efficiency typically 65-80% (LHV basis). CO2 capture increasingly incorporated.