Saturday 11 February 2017

Primary Reforming Flowsheets


The Theory and Practice of Steam Reforming By: Gerard B. Hawkins Managing Director, CEO Contents  Steam reforming reactions  Steam reforming catalyst  Equilibrium considerations  Carbon formation  Poisonin...Steam Reforming of Methane CH4 + H2O CO + 3H2 (Steam Reforming)) CO + H2O CO2 + H2 (water Gas Shift) • Overall strongly en...Steam Reforming of Heavier Hydrocarbons CnHm + nH2O nCO + (n+m/2)H2  Still endothermic  Easier than methane  More prone...Contents  Steam reforming reactions  Steam reforming catalysts • catalyst activity • catalyst development and testing • ...Steam Reforming Catalyst  Steam reforming can be done without catalyst, but needs very high temperatures • partial oxidat...Steam Reforming Catalyst Activity  Reaction highly endothermic • may be limited by process of getting heat in to reactant...Activity Testing  Define some measure of reaction • exit methane  Measure for a range of catalysts under fixed condition...Reactants Products Reaction Gas Film • Two types: - molecular diffusion - Knudsen diffusion Diffusion Effects Bulk Gas Bul...Diffusion Processes  Molecular diffusion, Dm • determined by rate at which molecules collide with each other • depends on...Check for Knudsen Diffusion  Mean free path of molecules must be greater than pore radius for Knudsen diffusion to domina...Steam Reforming Catalyst Activity  Intrinsic activity (chemical reaction only)  Extrinsic activity (includes heat and ma...Pressure bar (psi) Catalyst B Catalyst A 1 (14.5) 10 (145) 20 (290) Pressure Dependence Adsorption Desorption Adsorption Dehydrogenation Surface Reaction ** OH2 C + 2H2 CH4 * H2O CO + H2 CH4 Surface Science Nickel crystallites No further reaction Reaction zone Catalyst Pellet Pore Reactants Products Effect of gsa Steam Reformer Tubes  Need to get a lot of heat in • narrow bore tubes  High temperatures and pressures • tubes in creep...850 (1560) 900 (1650) 950 (1740) 1000 (1830) Temperature oC (oF) 0.1 0.2 0.5 1 2 5 10 20 Design Effect of Tube Wall Temper...850 (1560) 900 (1650) 950 (1740) 1000 (1830) Temperature oC (oF) 0.1 0.2 0.5 1 2 5 10 20 Design Effect of Tube Wall Temper...





https://image.slidesharecdn.com/theoryandpracticeofsteamreforming-130729071412-phpapp01/95/theory-and-practice-of-steam-reforming-23-638.jpg?cb=1375082097TemperatureDegC(DegF) Tube Wall Temperature Limit Poor stability Good stability Days on Line 0 1,000500100 200 300 400 600...Contents  Steam reforming reactions  Steam reforming catalysts  Equilibrium considerations • equilibrium curves • effec...Methane Steam Equilibrium CH4 + H2O CO + 3H2 P [CH4] P [H2O] Kms = P [CO] P [H2] 3 – equilibrium tables – equilibrium curv...

Equilibrium curves (methane) 508 203 102 Equilibrium%CH4(drybasis) Pressure(psig) Pressure(barg) Steam Ratio 2.0 3.0 4.0 5...Equilibrium curves (methane) Pressure : 30 bar (435 psi) Temperature : 850°C (1562°F) Steam:Carbon Ratio : 3.5 What is exi...
















































on

No comments:

Post a Comment

Subscribe to: Post Comments (Atom)