Steam‑methane reforming dominates ammonia’s energy bill, but furnace tuning, smarter catalysts, and deeper heat recovery are moving the needle. Incremental upgrades add up to multi‑million‑dollar savings and lower CO₂ per tonne NH₃.
The hottest box in an ammonia plant is also its hungriest. The steam‑methane reforming (SMR) furnace that makes synthesis gas (syngas) typically consumes over 70% of an NH₃ facility’s fuel, according to technical analyses (www.tandfonline.com). Thermal performance is lopsided: only ~45–60% of burner heat reaches the catalyst tubes (“radiant” efficiency), while the rest exits as hot flue gas that must be recovered or lost (integratedglobal.com).
That waste isn’t entirely wasted. In practice, another ~35–50% of the fired heat can be clawed back downstream in the convection section as process preheat and utility steam (integratedglobal.com). With modern pinch analysis and careful furnace tuning, plants are capturing more, burning less, and pushing output—often at the same time.
These changes may sound incremental. They are. But across a large unit, a few percentage points on fuel can be the difference between standing still and a very healthy year. As Reuters framed the challenge, the chemicals industry is wrestling with its fossil habit and looking for practical decarbonization levers (www.reuters.com).
Primary reformer: heat transfer and operation
SMR (steam‑methane reforming: a fired tubular reactor that converts methane and steam to H₂, CO, and CO₂ over nickel catalysts) is the syngas workhorse, followed by an air‑fired “secondary reformer” or autothermal reformer (ATR; a catalytic reactor where partial oxidation supplies heat internally). The SMR furnace’s radiant section typically achieves ~45–60% thermal efficiency, with the balance conveyed as flue gas; a further ~35–50% of that waste heat is recoverable in the convection section for utility steam or feed preheat (integratedglobal.com). Integrated Global (Cetek) points to high‑emissivity refractory coatings or ceramic tiles that boost radiant heat transfer, enabling the same throughput with less fuel (or more throughput for the same fuel) (integratedglobal.com).
Furnace housekeeping matters. Sealing flue passages and optimizing burner staging—top‑fired configurations help with uniform heat—lets operators achieve higher conversion with lower excess fuel (integratedglobal.com).
Operating set‑points carry trade‑offs. Reformers typically run at 30–50 bar (bar: unit of pressure) to balance equilibrium and equipment size; higher pressure favors conversion and shrinks the furnace footprint but increases reboiler duty. Plants typically use a steam‑to‑carbon ratio (S/C, steam moles per carbon mole in feed) of ~2.5 for full conversion (ammoniaenergy.org). Operating at lower S/C (if catalysts permit) or at higher pressure can slightly cut fuel, at the expense of more advanced hardware (ammoniaenergy.org).
Secondary reformer and ATR choices
Air‑ or oxygen‑blown ATRs (autothermal reformers) integrate combustion at the catalyst inlet, unlike a two‑step SMR plus air reformer that burns fuel externally. Reviews note ATR systems often require ≈3% less natural gas overall—a modest but bankable cut—though the ASU (air separation unit) or pure O₂ shifts energy demand to electricity or high‑pressure air (ammoniaenergy.org).
For existing plants, “simple” fixes still pay: fine‑tuning air/fuel ratios and burner arrangements in the secondary reformer helps maximize conversion with minimal excess heat (ammoniaenergy.org).
Digital models and pinch analysis
Advanced modeling is turning heat into a closed book rather than a mystery. Digital twins have been used to rebalance SMR heat duties, targeting minimal stack temperature—≈120 °C for clean natural gas (NG) combustion—without zone overheating (www.tandfonline.com). The goal is to cool flue gas as much as possible but stay just above the acid‑dewpoint (~92 °C) to maximize steam yield (www.tandfonline.com). Put together, furnace design and tuning commonly deliver 5–10% improvements in fuel consumption, with proportional CO₂ cuts per tonne NH₃ (www.tandfonline.com).
Lower‑S/C and lower‑temperature catalysts
The fastest way to save steam is to need less of it. Traditional SMR plus high‑temperature shift (HTS; a catalyst bed that converts CO and H₂O to CO₂ and H₂ at high temperature) uses Ni‑ and Fe‑based catalysts at ~900–1000 °C and S/C ≈2.5 (ammoniaenergy.org). New formulations are relaxing those constraints.
Topsoe’s SK‑501 Flex™ (a zinc–aluminate HTS catalyst) contains no iron, resists carbide formation, and is designed to operate with lower front‑end S/C. Case studies indicate that reducing S/C from 2.8 to 2.5 (enabled by the new catalyst) boosts NH₃ throughput by roughly 3–5%. For a 2,200 MTPD plant, that corresponds to an extra ~11 MUSD/year in revenue at a price of 350 USD/MT (trea.com). Less steam per unit of gas feed is a direct energy saving.
On the reformer side, promoted nickel catalysts are showing promise. Adding small amounts of precious metals (Rh, Ir, Ru) to Ni/Al₂O₃ delivers substantially higher CH₄ conversion at <900 °C than pure Ni catalysts; other developments (Ni–Au bimetallics, Ni–CeO₂ supports) have achieved significant CH₄ turnover around 550–700 °C in lab tests (www.mdpi.com). These remain pre‑commercial at large scale but point to lower‑temperature or leaner‑steam futures.
More radical process‑intensification has also entered the conversation. Membrane and sorption reactors—think H₂‑permeable “windows” or in‑reactor CO₂ sorbents—shift equilibrium by removing products, enabling lower S/C. Pilot studies have proposed 20–30% steam‑demand cuts with corresponding furnace fuel savings (www.mdpi.com). A rule of thumb from plant revamp cases: every 0.1 decrease in S/C (from ~2.8) is often worth ~1–1.5% more NH₃ capacity (trea.com).
Flue‑gas heat recovery and steam integration
After heating the catalyst tubes, burner exhaust at ~900–1050 °C passes through a convection section (tube‑fin heat exchangers) that preheats feeds and raises steam. Best practice is to cool this gas as far as possible—typically to ~120 °C when burning clean NG—without crossing the acid‑dewpoint (~92 °C), which risks corrosion (www.tandfonline.com).
Waste‑heat boilers are often staged to recover multiple steam pressure levels (high, medium, low), covering preheat duties for reformer feed gas, combustion air, boiler feedwater, and auxiliaries. With integrated design—often guided by pinch analysis—plants can capture ≈40–50% of the fired heat in process utility steam (integratedglobal.com; www.tandfonline.com). Boiler feedwater quality is a direct enabler in this loop; many plants integrate demineralization steps, where a system such as a demineralizer conditions make‑up water for reliable steam generation.
Hitting low stack temperatures around 120 °C generates roughly 12–14 kg steam per kg CH₄ reformed. In practice, ammonia complexes often produce 0.8–1.5 tonne of steam per tonne of NH₃ as a byproduct of reformer heat integration. This co‑generated steam displaces external boilers, cutting overall gas burn by up to 10–15% of plant total (www.tandfonline.com). Plants typically also close the loop on condensate return; where needed, a condensate polisher can help maintain steam‑cycle purity during deep heat recovery.
Electrifying preheat and auxiliary ideas
Electrifying part of the duty is gaining attention. An IEA‑backed analysis cited by Ammonia Energy notes that switching part of the feed preheat duty to electric heaters (resistive or heat‑pump) can “decrease gas consumption” (ammoniaenergy.org). On the furnace side, oxygen‑enriched firing to reduce N₂ ballast in the secondary reformer has also been proposed as an emerging upgrade (same source: ammoniaenergy.org). Where utilities integration is expanded, supporting equipment for water treatment—such as water‑treatment ancillaries—interfaces with the heat‑recovery steam cycle cited above.
Industry upgrades and Indonesian context
Efficiency revamps are now a staple of ammonia modernizations. Long‑serving plants frequently install new reformer tubes and improved burners to extract a few percent more output—gains that translate into large annual savings at scale (trea.com).
Indonesia is moving in step. The new 445 kt/y Pusri IIIB ammonia/urea complex (due ~2025) is being built to replace two older units and “increase the efficiency of ammonia and urea production,” according to company statements (ekonomi.republika.co.id). Government messaging in 2024 similarly emphasizes adopting “green technology” and blue‑ammonia pathways in the fertilizer sector (www.ekon.go.id).
Bottom line and data points
Across furnace efficiency, catalyst choice, and heat integration, the numbers are consistent: the SMR furnace consumes over 70% of plant fuel (www.tandfonline.com); typical radiant efficiency is ~45–60% with 35–50% of waste heat recoverable (integratedglobal.com); reformers run at 30–50 bar and S/C ≈2.5 (ammoniaenergy.org); ATRs often shave ≈3% off natural gas demand (ammoniaenergy.org); digital/pinch optimization targets ~120 °C stacks and ~92 °C acid‑dewpoint limits (www.tandfonline.com); and fuel savings of 5–10% are realistic (www.tandfonline.com).
On the catalyst front, SK‑501 Flex™ supports S/C cuts from 2.8 to 2.5 for 3–5% throughput gains (~11 MUSD/year at 2,200 MTPD and 350 USD/MT), while promoted Ni catalysts and membrane/sorption reactors point to lower‑temperature or 20–30% steam‑demand reductions in pilot studies (trea.com; www.mdpi.com). Every 0.1 drop in S/C from ~2.8 is often worth ~1–1.5% more NH₃ capacity (trea.com). Heat‑recovery best practice yields ≈40–50% of fired heat as steam, roughly 12–14 kg steam/kg CH₄ reformed, and 0.8–1.5 t steam per t NH₃—cutting overall gas burn by up to 10–15% (integratedglobal.com; www.tandfonline.com). To keep that loop tight, plants often return and clean condensate; when quality control is needed, a condensate polisher complements boiler feedwater treatment initiated with a demineralizer.
