Solid sodium cyanide from Andrussow HCN (6.25 t/h, 50 kt/a)

Methane, ammonia and air react over a Pt/Rh gauze to HCN (Andrussow); unconverted ammonia is recovered and recycled, HCN is absorbed in chilled water, refined and neutralised with caustic soda, and sodium cyanide is crystallised under vacuum and dried. The tail gas raises steam. Concept stage, assumed basis, preliminary gate-to-gate inventory.

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

An air-operated Andrussow converter (Pt/Rh 90/10 gauze, adiabatic, about 1430 K) converts a methane-ammonia-air mixture at the feed ratios of an open patent example (O2/NH3 1.15, CH4/NH3 0.98) with an HCN yield of 62.9 % on the ammonia fed; the by-products follow a published commercial converter-gas composition. A waste heat boiler raises MP steam, an ammonium phosphate absorber/stripper recycles 99 % of the unconverted ammonia, and HCN is absorbed in chilled water to 2.5 wt% and rectified to 99.5 wt%. Liquid HCN reacts with 50 wt% caustic soda; the 45 wt% NaCN solution is crystallised at 70 C and 100 mm Hg, centrifuged and dried to 98 wt% NaCN. The hydrogen- and CO-bearing tail gas is burned in a boiler, which is the plant's single emission point to air.

All values are concept estimates. The converter yield and feed ratios are taken from US 6,596,251 B2 and the converter-gas by-products and crystalliser conditions from US 4,847,062 A; the absorption, stripping, crystallisation and duty values come from an independent script, because no property package is qualified by ChemE-as-Code for aqueous HCN/NH3 or the NaCN/NaOH electrolyte; see DESIGN.md of the engineering files.

Capacity
6.25 t/h solid NaCN (98 wt%), 50 kt/a (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)
  • ASSUMED converter: air-operated Andrussow converter on Pt/Rh 90/10 gauze, adiabatic, no feed preheat, at the feed ratios and HCN yield of US 6,596,251 B2 Table 2 run 1 (O2/NH3 1.15, CH4/NH3 0.98, 62.9 % on NH3) (D-004).
  • ASSUMED by-product split of the converter gas from the commercial converter gas of US 4,847,062 A Example 1 (NH3, CH4, CO, CO2 per HCN); O2 99.9 % consumed (D-004).
  • ASSUMED ammonia recovery by ammonium phosphate absorption and stripping, 99 % of the converter NH3 recycled, 0.5 % to the process water, 0.5 % slip (D-006); 10 kg LP steam per kg NH3 recovered (no source).
  • ASSUMED HCN absorption in chilled water to 2.5 wt% (US 6,596,251 B2 background: 2-3 wt%), 99.9 % recovery; stripping and rectification to 99.5 wt% HCN; 0.05 % of the HCN to the purge (D-007).
  • ASSUMED neutralisation with 50 wt% NaOH at 343 K; evaporative crystallisation at 343 K and 13.3 kPa(a) (US 4,847,062 A examples 6-7), mother liquor 0.80 kg NaCN per kg water, cake 10 wt% liquor, all filtrate recycled; steam dryer (D-008).
  • ASSUMED complete combustion of the tail gas with 15 % excess air, stack 423 K, no radiation loss (D-009).
  • All absorber, stripper, crystalliser and duty values are concept estimates of scripts/nacn_balance.py (D-011); accuracy not stated.

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:NH3F: liquid ammonia from the ammonia plant (ammonia-1), 0.437 kg/kg NaCN
  • Sodium hydroxideFeedstockfeed:NAOHF: caustic soda 50 wt% from the chlor-alkali plant (chlor-alkali-1), counted by mass of the solution
  • MethaneFeedstockNatural gas modelled as methane (ASSUMED)
  • AirFeedstockProcess air of the converter (oxygen source); combustion air of the tail gas boiler is feed:BAIR

Out

  • Sodium cyanideMain productSolid sodium cyanide (98 wt%) to packing
  • SteamCo-productMP steam 1500 kPa(a) from the waste heat boiler and the tail gas boiler, net of the plant's own use (product:MPSX). Upper bound: adiabatic converter, no converter, waste heat boiler or tail gas boiler losses; probably 15-20 % lower (DESIGN.md D-010)
  • Carbon dioxideEmissionFossil CO2 of the tail gas boiler flue gas, 0.49 kg per kg product
  • WastewaterWasteProcess water with traces of HCN and ammonia to cyanide destruction and wastewater treatment

Utilities: Electricity (Air blower K-101 and an ASSUMED lump for pumps, vacuum pumps, centrifuge, dryer and briquetting; the chiller power (about 0.8-1.2 MW for 4.8 MW of chilled water) is not included, it belongs to the chilled-water background (DESIGN.md D-010)), Cooling water (25/35 C (ASSUMED)), Chilled water (2/10 C (ASSUMED), HCN absorber and lean water chiller; the chiller power is carried by this background, not by feed:POWER)

Show in the process graph

Reactions

IdAs writtenReactionOther processes
ANDRUSSOWCH4 + NH3 + 3/2 O2 → HCN + 3 H2O2CH4+2NH3+3O22CHN+6H2O
CH4_BURNCH4 + 2 O2 → CO2 + 2 H2OCH4+2O2CO2+2H2O9 other processes
CH4_COMBCH4 + 2 O2 → CO2 + 2 H2OCH4+2O2CO2+2H2O9 other processes
CH4_REFCH4 + H2O → CO + 3 H2CH4+H2OCO+3H2
CO_COMBCO + 1/2 O2 → CO22CO+O22CO27 other processes
H2_COMBH2 + 1/2 O2 → H2O2H2+O22H2O5 other processes
H2_OXH2 + 1/2 O2 → H2O2H2+O22H2O5 other processes
HCN_COMBHCN + 5/4 O2 → CO2 + 1/2 H2O + 1/2 N24CHN+5O24CO2+2H2O+2N2
NACN_CRYSTNaCN(aq) → NaCN(s)NaCNNaCN
NEUTRHCN + NaOH(aq) → NaCN(aq) + H2OCHN+NaOHNaCN+H2O
NH3_DEC2 NH3 → N2 + 3 H22NH3N2+3H2

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

No footprint assessed yet; the process is part of the life-cycle inventory below.

In the open LCI database (cheme-as-code-atlas-preview-c3ab348) as Solid sodium cyanide (98 wt%) to packing 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 6 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:MPSX 0 %, product:NACN 100 %
Allocation findings
none
Change report
Not available: this build has no change report against an earlier release.
Dataset pages
Solid sodium cyanide (98 wt%) to packing 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 (cheme validate: 0 errors; cheme process streams: every block and step balanced). The converter outlet is calculated by cheme from conversions that reproduce a sourced HCN yield and a sourced converter-gas composition, and its adiabatic energy balance closes (duty 0.06 kW at 1429 K). Capacity, feed states, recoveries, the crystalliser and every duty are ASSUMED or come from scripts/nacn_balance.py; no property package covers HCN at converter temperature, aqueous HCN/NH3 or the NaCN/NaOH electrolyte, and cheme's crystallizer refuses the free NaOH, so energy closure of the separations is not evaluable in core. cheme maturity: calculation maturity none. 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-cyanide-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 cyanide (Andrussow HCN) · 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: "Solid sodium cyanide from Andrussow HCN (6.25 t/h, 50 kt/a)", 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}
}