Steam Methane Reforming (SMR) Equilibrium Calculator
Model industrial primary steam methane reformers (SMR) for hydrogen, ammonia, and methanol production. Solve simultaneous chemical equilibria for reforming and water-gas shift reactions to determine methane conversion, syngas composition, and furnace firing duty.
1. Feed Hydrocarbon & Steam Ratio
2. Thermal & Catalyst Operating Conditions
Equilibrium Yield & Syngas Performance
Dry Syngas Composition (mol %)
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C1 Petrochemical Synthesis Modules
Interactive SMR Radiant Furnace & Catalyst Tube Chamber
Cutaway schematic showing downfiring radiant burners, nickel catalyst-filled HP-alloy reformer tubes, preheated steam+gas inlet manifold, and red-hot syngas collector manifold.
In-Depth Process Chemistry: SMR Dual Equilibrium Thermodynamics
Steam Methane Reforming involves two primary reversible chemical reactions taking place simultaneously over a nickel-alumina catalyst bed:
$$ ext{2. Water-Gas Shift (Exothermic):} quad CO + H_2O ightleftharpoons CO_2 + H_2 quad (Delta H_{298}^circ = -41.2 ext{ kJ/mol})$$
The temperature-dependent equilibrium constants $K_{p1}$ and $K_{p2}$ are computed using thermodynamic Gibbs free energy polynomials:
$$ln K_{p2}(T) = rac{4400}{T} - 4.036 quad [ ext{dimensionless}]$$
Simultaneous Extent of Reaction Residual Equations
Let $\xi_1$ be the extent of the reforming reaction and $\xi_2$ be the extent of the water-gas shift reaction per mole of feed methane ($n_{CH4,0} = 1, n_{H2O,0} = S/C$). The molar quantities of each species in the equilibrium syngas are:
- $n_{CH4} = 1 - \xi_1$
- $n_{H2O} = S/C - \xi_1 - \xi_2$
- $n_{CO} = \xi_1 - \xi_2$
- $n_{CO2} = \xi_2$
- $n_{H2} = 3 \xi_1 + \xi_2$
- $n_{total} = 1 + S/C + 2 \xi_1$
The equilibrium partial pressures ($P_i = \frac{n_i}{n_{total}} \cdot P$) must satisfy the coupled non-linear residual equations solved via 2D Newton-Raphson iteration:
$$f_2(\xi_1, \xi_2) = \frac{P_{CO2} \cdot P_{H2}}{P_{CO} \cdot P_{H2O}} - K_{p2} = 0$$
5 Fatal Engineering Pitfalls in SMR Plant Operations
Operating below the critical thermodynamic carbon boundary ($S/C < 1.8$) triggers methane cracking ($CH_4 o C + 2 H_2$) and the Boudouard reaction ($2 CO o C + CO_2$). Filamentous carbon grows inside nickel catalyst pores, pulverizing pellets into powder. This chokes tube pressure drop and creates localized uncooled "hot bands" that cause catastrophic tube rupture within weeks.
Hot syngas exiting the reformer at 850°C is saturated with CO and H₂. As it cools through the dangerous 450°C–650°C zone in the waste heat boiler, carbon activity ($a_c$) exceeds unity. Carbon diffuses into stainless steel tube walls, disintegrating solid metal into a fine, pyrophoric powder of metal particles and graphite ("metal dusting"), resulting in catastrophic boiler tube blowouts.
Centrifugally cast HP-modified microalloy reformer tubes operate at internal pressures up to 35 bar and skin temperatures of 950°C. A mere 20°C uncorrected localized temperature increase from burner flame impingement reduces remaining tube creep rupture life by over 50% (from 100,000 hours down to less than 40,000 hours).
Metallic nickel catalyst has an extraordinary affinity for sulfur. Even trace levels of H₂S, mercaptans, or thiophenes ($> 0.1 ext{ ppmv}$) entering the reformer chemisorb permanently onto nickel active sites: $Ni + H_2S ightleftharpoons Ni-S + H_2$. Catalyst activity collapses instantaneously, methane conversion plummets, and endothermic cooling ceases, producing dangerous furnace overheating.
If steam flow is interrupted while natural gas continues flowing into the red-hot reformer, thermal pyrolysis creates instantaneous carbon deposition across the entire furnace. The entire million-dollar catalyst inventory is irreversibly destroyed within 120 seconds. Fail-safe automated safety interlocks must trip emergency natural gas shutdown valves immediately upon low steam flow detection.