Hydroxylammonium sulfate by catalytic NO hydrogenation (30 kt/a NH2OH, 25 wt% solution)

Nitric oxide made by burning ammonia with oxygen and steam over Pt/Rh is hydrogenated in dilute sulfuric acid over suspended platinum on graphite (BASF-type process) to a 25.4 wt% hydroxylammonium sulfate solution for oximation; ammonia, oxygen, hydrogen and sulfuric acid are boundary feeds. Concept stage, basis set on open patent examples.

Calculation maturity: not assessedDesign maturity: Concept (research)Not independently reviewedInorganic chemicalsReport a problem with this process
Research outputNot engineering advice and not an approved design: do not use it for construction, operation or safety decisions. What this means

Liquid ammonia is vaporised, mixed with gaseous oxygen and LP steam (14 : 18.6 : 67.4 by volume) and burnt on a Pt/Rh gauze; a waste-heat boiler raises MP steam. The small oxygen excess is hydrogenated on a silver-manganese catalyst, the steam is condensed (the condensate, with a little nitric acid, becomes the acid dilution water) and the NO gas is compressed to a stirred-tank cascade. There NO and hydrogen (H2:NO 2:1) react at 313 K and 200 kPa(a) on a suspended, sulfur-modified Pt/graphite catalyst in about 20 wt% sulfuric acid to hydroxylammonium sulfate, with ammonium sulfate and N2O as by-products. The off-gas is recycled; 30 % is purged to a thermal oxidiser. The product carries 25.4 wt% hydroxylammonium sulfate (10.2 wt% NH2OH), 1.9 wt% ammonium sulfate and 1.3 wt% free acid.

All values are concept estimates (scripts/has_balance.py of the engineering files): burner ratios and yields, O2 removal, product analysis, cascade conditions and selectivities are taken from open patents (US 3,110,563; EP 0 945 401; US 4,895,711; EP 1 343 719; US 4,997,635), the burner N2O from the IPCC 2006 default; the per-pass conversion, purge, pressures and all duties are design choices. See DESIGN.md for every assumption and gated step.

Capacity
30 kt/a NH2OH contained, as 293 kt/a of 25.4 wt% hydroxylammonium sulfate solution (ASSUMED)
Operation
8,000 h/a
Location
generic (not chosen)
Engineering gates
Concept and feasibility (no results yet)
Maintainers
Artur Schweidtmann
Design basis and assumptions (7)
  • Burner: NH3:O2:steam 14:18.6:67.4 by volume, Pt/Rh gauze, 98 % of the NH3 nitrogen to nitrogen oxides (US 3,110,563 Example a); N2O 1.40 % of the NH3 nitrogen from the IPCC 2006 atmospheric-pressure default (Vol. 3 Ch. 3 Table 3.3), N2 the rest; adiabatic, 130 kPa(a) ASSUMED (D-005).
  • Excess O2 hydrogenated (90 %) on Ag-Mn before condensation (EP 0 945 401 Example); the rest absorbed as HNO3 in the condensate, which is reused as acid dilution water (EP 0 945 401) (D-005).
  • Hydrogenation: stirred-tank cascade with suspended sulfur-modified Pt on graphite in about 20 wt% H2SO4 (EP 0 945 401: 19 %; US 4,895,711: 4.3 N), 313 K, 200 kPa(a), H2:NO 2.0 at the inlet (EP 1 343 719); NO converted per pass 0.90 ASSUMED; selectivity NH2OH 89.8 %, NH3 8.2 %, N2O 2.0 % (D-007).
  • Off-gas: 30 % purged to a thermal oxidiser (ASSUMED, sets N2O at 6.5 mol% in the loop gas), 70 % recycled; overall NO utilisation 96.8 % (D-007, D-009).
  • Thermal oxidiser: purge H2 burnt with air to 1173 K, no NO or N2O destruction credited, no heat recovery (ASSUMED, conservative; D-009).
  • Heats of reaction in the cascade from NBS aqueous enthalpies of formation, not re-read in this run (O-4); gas-phase enthalpies ideal gas (thermo/chemicals) (D-005, D-006).
  • All flows and duties are concept estimates from scripts/has_balance.py (D-006); accuracy not stated, roughly +/-30 %.

From process/design-basis.yaml.

Engineering model

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Drawing of the process (preview)Open the engineering model

The interactive model (drawings, streams, 3D) is made for larger screens.

Snapshot of c3ab348, cheme-as-code 1.6.0.

What goes in and out

In

  • AmmoniaFeedstockfeed:NH3: liquid ammonia (e.g. ammonia-1), 0.612 kg/kg NH2OH
  • Sulfuric acidFeedstockfeed:ACID: sulfuric acid 98.5 wt% (e.g. sulfuric-acid-1), 1.77 kg/kg
  • HydrogenFeedstock99.9 mol% H2, 0.131 kg/kg NH2OH (ASSUMED boundary feed; e.g. from processes/hydrogen-1)
  • OxygenFeedstockGOX 99.5 mol% at 300 kPa(a), 1.54 kg/kg NH2OH (ASSUMED boundary feed; e.g. from processes/asu-1)
  • WaterFeedstockDemineralised water for the acid make-up, 2.70 kg/kg NH2OH
  • AirFeedstockCombustion air of the off-gas thermal oxidiser

Out

  • Hydroxylammonium sulfateMain productHydroxylammonium sulfate solution 25.4 wt% to storage, counted by mass of the solution (9.78 kg per kg NH2OH)
  • SteamCo-productMP steam 1500 kPa(a) raised in the waste-heat boiler, counted as heat (kWh)
  • NitrogenEmissionThermal-oxidiser flue gas: N2, O2, Ar, water, NO and N2O to atmosphere

Utilities: Electricity (NO gas compressor, cascade agitators, recycle blower, acid pump, oxidiser fan (ASSUMED electric drives)), Steam (LP steam 500 kPa(a) used directly as burner dilution steam (condensed and reused as process water)), Steam (LP steam 500 kPa(a) to the ammonia vaporiser, counted as heat (kWh)), Cooling water (25/35 C (ASSUMED))

Show in the process graph

Reactions

IdAs writtenReactionOther processes
AS_FORM2 NO + 5 H2 + H2SO4 → AS + 2 H2O2NO+5H2+H2SO4H8N2O4S+2H2O
H2_COMB2 H2 + O2 → 2 H2O2H2+O22H2O5 other processes
HAS_FORM2 NO + 3 H2 + H2SO4 → HAS2NO+3H2+H2SO4H8N2O6S
N2O_FORM2 NO + H2 → N2O + H2O2NO+H2N2O+H2O
NH3_N24 NH3 + 3 O2 → 2 N2 + 6 H2O4NH3+3O22N2+6H2O3 other processes
NH3_N2O4 NH3 + 4 O2 → 2 N2O + 6 H2O2NH3+2O2N2O+3H2O2 other processes
NH3_NO4 NH3 + 5 O2 → 4 NO + 6 H2O4NH3+5O24NO+6H2O2 other processes
NO_ABS4 NO + 3 O2 + 2 H2O → 4 HNO34NO+3O2+2H2O4HNO31 other process
O2_HYD2 H2 + O2 → 2 H2O2H2+O22H2O5 other processes

Each reaction's page has the conversion, heat of reaction, catalyst and sources this process states, next to those of other processes with the same reaction. All reactions

Life cycle assessment

Footprint not publishedThe process changed since the LCA was last run; its values return once it is run again. Method, functional unit and inventory are below.
Method and data
Goal
Preliminary gate-to-gate life cycle inventory of hydroxylamine as a 25.4 wt% hydroxylammonium sulfate solution, made by NO hydrogenation in dilute sulfuric acid with NO from ammonia oxidation (BASF-type process), at the concept stage, for the process library: the foreground exchanges per kg of NH2OH contained, with their provenance, and the list of backgrounds still to link. Not an impact result: every background is a gap; only the direct N2O and NO emissions of the plant are elementary flows.
Functional unit
1 kg Hydroxylammonium sulfate solution 25.4 wt% (1 kg hydroxylammonium sulfate)
Boundary
gate-to-gate
Allocation
shares
Characterisation
Factors kept with the process · GWP100
Data quality
Published factors
Result
partial screening carbon footprint · 13 data gaps

Inventory per 1 kg Hydroxylammonium sulfate solution 25.4 wt% (24 flows)

FlowPhaseDirectionQuantityUnitProvenance
Liquid ammonia (boundary feed; e.g. from ammonia-1)operationinput0.6123kgassumed
Gaseous oxygen 99.5 mol% (boundary feed; e.g. from asu-1)operationinput1.538kgassumed
Hydrogen 99.9 mol% (boundary feed; e.g. from hydrogen-1)operationinput0.1307kgassumed
Sulfuric acid 98.5 wt% (boundary feed; e.g. from sulfuric-acid-1)operationinput1.774kgassumed
Demineralised wateroperationinput2.7kgassumed
Ambient air (thermal oxidiser)operationinput1.494kgassumed
LP steam 500 kPa(a), direct use (burner dilution steam)operationinput3.118kgassumed
Electric poweroperationinput0.09472kWhassumed
LP steam 500 kPa(a), indirect (ammonia vaporiser)operationinput0.1983kWhassumed
Hydroxylammonium sulfate solution 25.4 wt% to storageoperationoutput9.782kgcalculated
Thermal-oxidiser flue gas to atmosphereoperationoutput1.585kgcalculated
MP steam export 1500 kPa(a) (waste-heat boiler)operationoutput1.865kWhassumed
Cooling water returnoperationoutput6.491kWhassumed
AR to the environmentoperationoutput0.02885kgcalculated
H2 to the environmentoperationoutput0kgcalculated
H2O to the environmentoperationoutput0.1257kgcalculated
N2 to the environmentoperationoutput1.132kgcalculated
N2O to the environmentoperationoutput0.02594kgcalculated
NO to the environmentoperationoutput0.03371kgcalculated
O2 to the environmentoperationoutput0.2391kgcalculated
Pt/Rh gauze metal lost from the ammonia burneroperationinput0.0000003067kgassumed
Platinum lost from the suspended Pt/graphite hydrogenation catalystoperationinput0.00000004kgassumed
Ag-Mn oxygen-hydrogenation catalyst (R-102) replacedoperationinput0.00002667kgassumed
Disposal: Ag-Mn oxygen-hydrogenation catalyst (R-102) replaced (spent silver catalyst to precious-metal recovery)operationoutput0.00002667kgassumed

Computed by ChemE-as-Code from lca/README.md, lca/dataset.yaml, lca/factors.yaml, lca/gaps.csv, lca/inventory.csv, lca/lca.yaml, lca/mappings.yaml, lca/results.csv, lca/results.md.

In the open LCI database (cheme-as-code-atlas-preview-c3ab348) as Hydroxylammonium sulfate solution 25.4 wt% to storage Preliminary.

Download it for Brightway, openLCA and other tools.

In the LCI database: system model, datasets and KPIs against the benchmarks

In the LCI database

Status
Preliminary 2 unmapped exchanges. Some exchanges have no background mapping yet: they are exported unlinked and count no burden, so the inventory is incomplete.
System model
attributional, cut-off (methodology 1.1.0)
Allocation
shares (deviation, from study) · product:MPS 0 %, product:PROD 100 %
Allocation findings
none
Change report
Not available: this build has no change report against an earlier release.
Dataset pages
Hydroxylammonium sulfate solution 25.4 wt% to storage Preliminary

KPI benchmark positions: not available (no benchmarked KPI for this process's datasets).

Maturity and review

Design maturity Concept (claimed): An idea or first flowsheet; numbers are rough. Concept PFD with closed mass, component and element (reaction extent) balances in every block and step (cheme validate, cheme process streams). The five reactors are conversion models calculated by cheme with conversions from open patents (burner yield, O2 hydrogenation, cascade selectivity) or the IPCC default (burner N2O); the separator outlets and all duties are specified values from an independent script (scripts/has_balance.py). Energy closure is not evaluable in core; aqueous speciation of the salt solution is not modelled (core's electrolyte support covers aqueous NaCl only). cheme maturity: none (feeds, purge and per-pass conversion assumed). The preliminary gate-to-gate LCI in lca/ leaves every background unmapped (gaps); its mass balance closes against the flowsheet. Not reviewed. Main products and feeds are listed under chemistry with their chemicals registry entries (issue #251).

Calculation maturity, from the checked evidenceNot assessed

The process has no maturity report (cheme maturity, checks/maturity.json), so no calculation maturity is established.

No level shownThe design maturity (Concept) is the manifest's claim, not evidence. A level appears here once the process's repository holds a current report from cheme maturity --write.

Artifact completeness

Which deliverables exist. They never raise a calculation maturity level: a drawing from unchecked numbers is still unchecked.

Not reported without a maturity report.

Independent review

Not independently reviewed

No independent engineering review yet. Automated checks passing is not a review.

Set by people only. Reaching a calculation maturity level or passing automated checks is not an independent review or an approval.

Where the evidence comes from
Report
processes/hydroxylamine-1/checks/maturity.json (not in the library)
Design basis
process/design-basis.yaml
Method
How ChemE-as-Code checks the levels (requirement by requirement)

Open items

0 open items · 0 closed

New action itemNew engineering holdNew technical queryNew design changeAll issues

Sources

Engineering project
Hydroxylamine (as hydroxylammonium sulfate) · cheme-as-code>=0.8
Library version
c3ab348 (process last changed in c3ab348)
Drawings rendered by
cheme 1.6.0 (pyDEXPI 2.1.0)
Data
Catalog record (JSON) · CC-BY-4.0
Files
View the files on GitHub · change history and authors

References

How to cite

For the data, cite the Process Atlas paper; for the platform that builds and checks it, the ChemE-as-Code paper.

Schweidtmann, A. M. & Weber, J. M. (2026, in preparation). Process Atlas: an open, git-native, reproducible library and life cycle inventory of chemical processes (working title).

For this process: "Hydroxylammonium sulfate by catalytic NO hydrogenation (30 kt/a NH2OH, 25 wt% solution)", ChemE-as-Code process library, version c3ab348.

BibTeX
@unpublished{schweidtmann_process_atlas,
  author = {Schweidtmann, Artur M. and Weber, Jana M.},
  title = {{Process Atlas: an open, git-native, reproducible library and life cycle inventory of chemical processes (working title)}},
  year = {2026},
  url = {https://atlas.cheme-as-code.org},
  note = {in preparation}
}

Schweidtmann, A. M. (2026, in preparation). ChemE-as-Code: An Open-Source Platform for AI-Accelerated Chemical Process Engineering (working title).

BibTeX
@unpublished{schweidtmann_cheme_as_code,
  author = {Schweidtmann, Artur M.},
  title = {{ChemE-as-Code: An Open-Source Platform for AI-Accelerated Chemical Process Engineering (working title)}},
  year = {2026},
  url = {https://cheme-as-code.org},
  note = {in preparation}
}