Ammonium sulphate: Production route
Four factories that make it without trying
What this tab covers How it is made: the main production routes or, for product families, the main product types and technologies, compared on share of supply, inputs per tonne, plant scale, yield, co-products and unit cost.AS comes from four sources. Caprolactam plants co-produce it when ammonia neutralises the sulphuric acid or oleum used in the process. Coke ovens and coal-gas plants scrub ammonia from gas with acid. Ammonia-based flue-gas desulphurisation at Chinese power and industrial plants makes it from sulphur dioxide. Synthetic plants react ammonia with sulphuric acid on purpose, often to use spent or by-product acid. Because three of the four are by-products, supply is driven by nylon, steel and power output and rarely responds to fertiliser prices.
Routes compared
| Route | Share of supply | Inputs per tonne | Typical scale | Yield | Co-products | Unit cost |
|---|---|---|---|---|---|---|
| Caprolactam by-product | 42% (2025) | about 1.5-4.5 t AS per t caprolactam, depending on process (indicative) | 0.3-1.0 Mt AS a year per site (indicative); AdvanSix in Hopewell, Virginia, is the largest single producer (GMI: 7.4% share) | set by caprolactam chemistry | AS is the by-product | near zero marginal cost: producers must dispose of it |
| Coke-oven and coal gas recovery | about 20-25% (GMI shows 22% for 2035; indicative) | about 0.26 t ammonia from gas plus 0.74 t acid per t (stoichiometry) | tens of kt per coke plant (indicative) | not applicable | the plant's main products are coke and gas | low; disposal route for ammonia |
| Synthetic neutralisation (direct) | 15% (2025) | 0.258 t NH3 and 0.742 t H2SO4 (about 0.24 t sulphur) per t (stoichiometry) | 100-500 kt a year (indicative) | close to 100% | steam from the reaction heat | about $200/t raw materials at the 2025 US Gulf ammonia average ($496/t, USGS) and acid made from sulphur at an assumed $300/t (indicative) |
| Ammonia-based flue-gas desulphurisation and other by-products | remainder, about 15-20% (indicative, GMI lists FGD/gypsum and other by-product segments) | about 0.26 t ammonia per t; sulphur from flue gas | varies | not applicable | clean flue gas | low |
How each route works
Caprolactam by-productIn the classic Raschig and Beckmann rearrangement steps, oleum and hydroxylamine sulphate are neutralised with ammonia, leaving AS solution that is crystallised. Newer processes cut AS yield; Sumitomo's vapour-phase route makes almost none.
Cheap, large volumes; output tied to nylon demand.
Global Market Insights (2025); indicative process data Coke-oven and coal gas recoveryAmmonia in raw coke-oven gas is absorbed in dilute sulphuric acid in a saturator, giving AS crystals. Common at Chinese, Indian and Japanese integrated steel plants and coking plants.
Uses waste ammonia; quality and colour vary; declines with green steel.
Global Market Insights (2025); indicative Synthetic neutralisation (direct)Anhydrous ammonia and sulphuric acid react in a pipe reactor or saturator; often used to consume spent acid from other processes. Granulation plants make premium granular AS.
Controllable quality; costs more than by-product AS.
Global Market Insights (2025); USGS MCS 2026; stoichiometry Ammonia-based flue-gas desulphurisation and other by-productsSO2 in flue gas from boilers is scrubbed with ammonia solution, forming AS that is crystallised. Also from acrylonitrile and methyl methacrylate plants and metallurgical off-gases.
Turns pollution control into fertiliser; impurities (heavy metals) need control.
Global Market Insights (2025); indicative Unit economics are indicative ranges from the sources named; costs move with feedstock and energy prices, plant size and region.