Steam Methane Reforming

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The Steam Methane Reforming (SMR) process involves reacting methane (CH₄), the main component of natural gas, with steam (H₂O) at high temperatures and in the presence of a catalyst. The purpose of this reaction is to break down methane molecules and convert them into useful H₂ and CO molecules in the form of syngas, which is a widely used intermediate in a variety of chemical production processes.

SMR Process Steps

Source: Steam Methane Reforming, ScienceDirect

The typical SMR process undergoes the following steps:

Desulfurization

The desulfurizing unit cleans the natural gas of sulfur to prevent the production of sulfur oxides, which are environmentally harmful and can contaminate the reformer catalysts by adhering extremely strongly to the metal atoms of the catalyst, blocking the working sites that split methane and activate the steam.

Mix and preheat

The cleaned methane gas is blended with high-temperature steam at a specific steam-to-carbon ratio to prevent coke formation on the catalyst.

Steam reforming reactor

The gas/steam mixture flows through nickel-catalyst tubes inside a fired furnace; burners heat the tubes from the outside while methane reacts with steam (heated H2O) inside to form syngas (H₂ + CO + CO₂). Typical conditions are ~700–1,000 °C and a pressure of ~3–25 bar; SMR is endothermic, meaning that continuous heat input is required to keep the reaction.

Steam-methane reforming reaction:

CH₄ + H₂O (+ heat) → CO + 3H₂

Heat Recovery

The hot syngas leaving the reformer is cooled in a heat-recovery section to raise steam and improve the process efficiency.

Water-gas shift reactor

After a reformer produces hot syngas, the water-gas shift reactor enhances the hydrogen content by catalyzing a simple reaction: CO + steam → CO₂ + more H₂. Plants cool the gas to the right temperature, add a small amount of steam, and pass it through a vessel filled with a solid catalyst. Because the reaction produces heat, it’s usually done in two steps to get both speed and high conversion: a high-temperature shift first (roughly 550–900 °F / 290–480 °C, typically iron-chromium catalysts), then the gas is cooled and sent to a low-temperature shift (around 200–250 °C, often copper-zinc catalysts) to squeeze out most of the remaining CO.

Water-gas shift reaction:

CO + H₂O → CO₂ + H₂ (+ small amount of heat)

Purification

If the goal is hydrogen production, CO2, unreacted methane, and other traces are removed by passing through pressure swing adsorption (PSA) vessels, which separates and purifies the hydrogen.

If the goal is to produce syngas for chemical synthesis, the gas is conditioned to a target H₂/CO ratio via the water-gas shift reactor, and CO₂ is removed or recycled to tune the H₂/CO/CO₂ balance for the methanol catalyst or other downstream use of syngas co-products.