Sodium nitrite from ammonia oxidation and soda absorption (with sodium nitrate by inversion)

Nitrous gas from the catalytic oxidation of ammonia absorbed in soda solution near atmospheric pressure, the nitrite liquor evaporated and crystallised to dried sodium nitrite, and the mother-liquor purge inverted with nitric acid to sodium nitrate. Ammonia, soda ash and nitric acid from ammonia-1, soda-ash-1 and nitric-acid-1. Concept stage, 20 kt/a NaNO2, assumed basis.

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 air to 10.3 mol-% and burnt over Pt/Rh gauzes; a waste heat boiler cools the nitrous gas to 200 degC and its steam drives the first effect of the liquor evaporator. In an oxidation volume and absorption towers in series the gas meets a 20 wt-% soda solution; the oxidation degree of the nitric oxide is held near one half (NO : NO2 about 1 : 1, the N2O3 ratio) so that nitrite forms and nitrate stays at about one twentieth of it. The liquor is concentrated, sodium nitrite crystallised by vacuum cooling, centrifuged and dried; most of the mother liquor returns to the evaporator, and a purge that removes the nitrate is converted with nitric acid to sodium nitrate, whose nitric oxide goes back to the absorbers.

All values are concept estimates. The burner outlet and duty are calculated by cheme (conversion reactor, specified selectivities); absorption, crystallisation and inversion are specified values from an independent balance script; the liquors are aqueous electrolytes that no ChemE-as-Code property method covers yet. See DESIGN.md of the engineering files for every assumption and gated step.

Capacity
2 500 kg/h dried sodium nitrite (99.0 wt-% NaNO2) = 20 kt/a (ASSUMED), with 0.40 t/h sodium nitrate
Operation
8,000 h/a
Location
generic (not chosen)
Engineering gates
Concept and feasibility (no results yet)
Maintainers
Artur Schweidtmann
Design basis and assumptions (5)
  • D-001 boundary: liquid ammonia, air, soda ash and 60 wt-% nitric acid at the fence to dried NaNO2 and NaNO3, tail gas, dryer exhaust and surplus condensate; no storage, bagging or utility generation
  • D-005 burner: complete NH3 conversion, NO selectivity 0.97 (ASSUMED), N2O transferred from the IPCC 2006 atmospheric-pressure nitric-acid default, rest N2
  • D-006 absorption: specified model, NaNO2:NaNO3 = 20:1 by mass, 99.5 % NOx-N absorbed; NO/NO2 control by the oxidation degree
  • D-007 the balance is a specified-split model (scripts/balance.py); electrolyte enthalpies are estimates
  • Construction, transport and end of life are outside the preliminary LCI (D-013)

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 from ammonia-1 (1600 kPa(a))
  • Sodium carbonateFeedstockfeed:SODA: dense soda ash from soda-ash-1
  • Nitric acidFeedstockfeed:HNO3: nitric acid 60 wt-% from nitric-acid-1, counted by mass of the acid
  • AirFeedstockPlant ratios per kg NaNO2 before allocation (the LCI gives the allocated values, x 0.862). Combustion air of the ammonia burner, 4.0 kg per kg NaNO2

Out

  • Sodium nitriteMain productSodium nitrite, dried, 99.0 wt-%, to bagging and storage
  • Sodium nitrateCo-productSodium nitrate, dried
  • Carbon dioxideEmissionCO2 from the soda ash, 0.359 kg per kg NaNO2 before allocation, in the tail gas

Utilities: Electricity (Air blower, pumps, centrifuges, dryer fans (ASSUMED), 0.075 kWh per kg NaNO2 before allocation), Steam (LP steam 450 kPa(a) from the site, 0.80 kWh of heat per kg NaNO2 before allocation; the waste-heat-boiler steam is used internally in the evaporator), Cooling water (25/35 C (ASSUMED), absorber coolers and condensers, 2.2 kWh per kg NaNO2 before allocation)

Show in the process graph

Reactions

IdAs writtenReactionOther processes
CARB_NEUNa2CO3 + 2 HNO3 → 2 NaNO3 + CO2 + H2O · Neutralisation of the residual carbonate with nitric acidNa2CO3+2HNO32NaNO3+CO2+H2O
INVERSION3 NaNO2 + 2 HNO3 → 3 NaNO3 + 2 NO + H2O · Inversion of sodium nitrite to sodium nitrate with nitric acid3NaNO2+2HNO33NaNO3+2NO+H2O
NH3_N24 NH3 + 3 O2 → 2 N2 + 6 H2O · Ammonia oxidation to nitrogen (side reaction)4NH3+3O22N2+6H2O3 other processes
NH3_N2O4 NH3 + 4 O2 → 2 N2O + 6 H2O · Ammonia oxidation to nitrous oxide (side reaction)2NH3+2O2N2O+3H2O2 other processes
NH3_OX4 NH3 + 5 O2 → 4 NO + 6 H2O · Ammonia oxidation to nitric oxide4NH3+5O24NO+6H2O2 other processes
NITRATE_ABSNa2CO3 + 2 NO2 → NaNO2 + NaNO3 + CO2 · Absorption of excess NO2 in soda solution to nitrite and nitrate (side reaction)Na2CO3+2NO2NaNO2+NaNO3+CO2
NITRITE_ABSNa2CO3 + NO + NO2 → 2 NaNO2 + CO2 · Absorption of equimolar NO + NO2 (N2O3) in soda solution to nitriteNa2CO3+NO+NO22NaNO2+CO2
NO_OX2 NO + O2 → 2 NO2 · Oxidation of nitric oxide (oxidation volume and tower gas spaces)2NO+O22NO21 other process

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 technical-grade sodium nitrite made by absorbing nitrous gas from ammonia oxidation in soda solution, with evaporative crystallisation and inversion of the mother-liquor purge to sodium nitrate, for the concept stage: the foreground exchanges of the balanced flowsheet (D-007) per kg of product, ready to be linked to background datasets (ammonia-1, soda-ash-1 and nitric-acid-1 first). No impact assessment is claimed.
Functional unit
1 kg Sodium nitrite, dried, 99.0 wt-% (1 kg sodium nitrite)
Boundary
gate-to-gate
Allocation
shares
Characterisation
Factors kept with the process · GWP100
Data quality
Published factors
Result
partial screening carbon footprint · 7 data gaps

Inventory per 1 kg Sodium nitrite, dried, 99.0 wt-% (21 flows)

FlowPhaseDirectionQuantityUnitProvenance
Liquid ammonia from ammonia-1 (battery limit, 1600 kPa(a))operationinput0.2346kgassumed
Ambient airoperationinput3.461kgassumed
Soda ash, dense, from soda-ash-1operationinput0.7465kgassumed
Nitric acid 60 wt-% from nitric-acid-1operationinput0.0826kgassumed
Electric power (AC, grid)operationinput0.06488kWhassumed
Low-pressure steam 450 kPa(a) from the site headeroperationinput0.6877kWhassumed
Sodium nitrite, dried, 99.0 wt-% (to bagging and storage)operationoutput1kgassumed
Sodium nitrate, dried (co-product)operationoutput0.1597kgassumed
Absorber tail gas to stackoperationoutput3.235kgassumed
Dryer exhaust (water vapour, after dust filters) to atmosphereoperationoutput0.02282kgassumed
Surplus process condensate to the site water systemoperationoutput0.2667kgassumed
Cooling water returnoperationoutput1.919kWhassumed
AR to the environmentoperationoutput0.04409kgassumed
CO2 to the environmentoperationoutput0.3098kgassumed
H2O to the environmentoperationoutput0.1663kgassumed
N2 to the environmentoperationoutput2.602kgassumed
N2O to the environmentoperationoutput0.004244kgassumed
NH3 to the environmentoperationoutput0kgassumed
NO to the environmentoperationoutput0.002115kgassumed
NO2 to the environmentoperationoutput0kgassumed
O2 to the environmentoperationoutput0.1292kgassumed

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 Sodium nitrite, dried, 99.0 wt-% (to bagging and storage) Preliminary; Sodium nitrate, dried (co-product) 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 1 unmapped exchange. 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:NANO2 86.2 %, product:NANO3 13.8 %
Allocation findings
none
Change report
Not available: this build has no change report against an earlier release.
Dataset pages
Sodium nitrite, dried, 99.0 wt-% (to bagging and storage) Preliminary · Sodium nitrate, dried (co-product) 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 balances in every block and step (cheme validate, cheme process streams; the absorber and inversion steps balance by elements over their reactions). The burner outlet is calculated by cheme (conversion reactor with specified selectivities NO 0.97, N2O 0.014, N2 0.016) and cheme's reactor duty (2 005 kW) equals the independent script's. The N2O share (79 % of the direct climate result) is an analogy to the IPCC nitric-acid default, uncertain by about a factor of 2 (DESIGN.md D-005, D-013). cheme maturity reaches no level: feed flows follow from an assumed product rate, the absorber, crystalliser and inversion are specified values, and energy closure is not evaluable in core (no package covers the nitrite/nitrate/carbonate liquors). The preliminary gate-to-gate LCI closes in mass and elements; every background is a gap. 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/sodium-nitrite-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
Sodium nitrite (ammonia oxidation and soda absorption) · 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: "Sodium nitrite from ammonia oxidation and soda absorption (with sodium nitrate by inversion)", 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}
}