Sulfuric acid from sulfur burning, double contact / double absorption (1000 t/d, 98.5 wt%)

Molten sulfur burned in dried air, SO2 oxidised over four V2O5 beds (3+1) with intermediate and final absorption to 98.5 wt% acid; waste heat recovered as exported HP steam. Concept stage, assumed basis, with a preliminary gate-to-gate LCI.

Calculation maturity: not assessedDesign maturity: Concept (research)Not independently reviewedSulfuric acidReport 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

Air is dried in a tower irrigated with 98.5 wt% acid and blown into the sulfur furnace, which burns molten sulfur to an 11.5 mol% SO2 gas. A waste heat boiler cools the gas to the first bed. Four adiabatic V2O5 beds convert the SO2 (63 / 87 / 95 % after beds 1-3, 99.7 % overall, conversion model within the ranges of Speight 2002); the gas is cooled between the beds by a gas/gas exchanger, a superheater and economisers, absorbed in an intermediate tower after bed 3, reheated, converted in bed 4 and absorbed in a final tower before the stack. One acid header serves the three towers; dilution water is added in the pump tank and the product is drawn after the acid cooler.

All values are concept estimates from an independent balance script; core can check the mass, element and reaction balances and the equilibrium distance of the beds, but has no property package for SO2/SO3 gas or aqueous acid to close the energy balance itself (DESIGN.md D-006).

Capacity
1000 t/d H2SO4 as 98.5 wt% acid (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 burner gas 11.5 mol% SO2 in dry air (D-004): sets the air flow.
  • Converter 3+1 with intermediate absorption after bed 3; cumulative SO2 conversion 63 / 87 / 95 % after beds 1-3 and 99.7 % overall, within the ranges of the tech-heavy-chem-sulfuric-acid skill (Speight 2002); a conversion model, not kinetics (D-005).
  • ASSUMED bed inlet temperatures 693 / 713 / 708 / 683 K; beds adiabatic, no heat losses (D-005).
  • ASSUMED SO3 absorption 99.9 % in each absorption tower (D-007).
  • ASSUMED one common acid header at 343 K for the drying, intermediate and final towers; acid outlet temperatures 338 / 383 / 363 K (D-007).
  • ASSUMED main blower isentropic efficiency 0.80, motor efficiency 0.96; acid pump head 35 m, efficiency 0.70 (D-010).
  • All flows, temperatures and duties are concept estimates (scripts/balance.py, D-006); accuracy +/-20 % not demonstrated.

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

  • SulfurFeedstockfeed:SULFUR: molten sulfur, 0.323 kg/kg acid
  • AirFeedstockCombustion and oxidation oxygen
  • WaterFeedstockDilution water to the acid pump tank (0.166 kg/kg acid)

Out

  • Sulfuric acidMain productSulfuric acid 98.5 wt% to storage, counted by mass of the acid
  • NitrogenEmissionTail gas, mostly N2 with 4.5 mol% O2, 0.04 mol% SO2 (1.94 g SO2/kg acid) and SO3/acid mist

Utilities: Electricity (Main air blower and acid pump (ASSUMED electric drives), 0.055 kWh/kg acid), Steam (HP steam 4100 kPa(a), 673 K, 1.34 kg/kg acid (1.03 kWh/kg above boiler feed water)), Cooling water (Acid and product coolers, 0.49 kWh/kg acid, 298/308 K (ASSUMED))

Show in the process graph

Reactions

IdAs writtenReactionOther processes
S_COMBS(l) + O2 → SO2S+O2SO21 other process
SO2_OXSO2 + 1/2 O2 ⇌ SO32SO2+O22SO3
SO3_ABSSO3(g) + H2O(l) → H2SO4(l)SO3+H2OH2SO4

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 98.5 wt% sulfuric acid from a sulfur-burning double-contact plant at the concept stage: which raw materials, utilities, co-products and emissions the plant exchanges per kg of acid, as the foreground for a later cradle-to-gate study. No impact results: the backgrounds are not mapped yet (D-013).
Functional unit
1 kg Sulfuric acid 98.5 wt% (1 kg sulfuric acid)
Boundary
cradle-to-gate
Allocation
shares
Characterisation
Factors kept with the process · GWP100
Data quality
No factors
Result
partial screening carbon footprint · 4 data gaps

Inventory per 1 kg Sulfuric acid 98.5 wt% (15 flows)

FlowPhaseDirectionQuantityUnitProvenance
Molten sulfuroperationinput0.323kgassumed
Atmospheric airoperationinput2.567kgassumed
Process (dilution) wateroperationinput0.1657kgassumed
Electric poweroperationinput0.05454kWhassumed
Sulfuric acid 98.5 wt% to storageoperationoutput1kgcalculated
Tail gas to stackoperationoutput2.056kgassumed
HP steam export 4100 kPa(a), 673 K (heat above boiler feed water)operationoutput1.031kWhassumed
Cooling water returnoperationoutput0.4914kWhassumed
AR to the environmentoperationoutput0.03254kgassumed
H2O to the environmentoperationoutput0kgassumed
N2 to the environmentoperationoutput1.917kgassumed
O2 to the environmentoperationoutput0.1042kgassumed
S to the environmentoperationoutput0kgassumed
SO2 to the environmentoperationoutput0.001936kgassumed
SO3 to the environmentoperationoutput0.00003867kgassumed

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 Sulfuric acid 98.5 wt% to storage.

Download it for Brightway, openLCA and other tools.

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

In the LCI database

System model
attributional, cut-off (methodology 1.1.0)
Allocation
shares (deviation, from study) · product:ACID 100 %, product:HPS 0 %
Allocation findings
none
Change report
Not available: this build has no change report against an earlier release.
Dataset pages
Sulfuric acid 98.5 wt% to storage

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, element and reaction-extent balances (cheme validate, cheme process streams); every bed is short of its ideal-gas equilibrium (cheme process reactors). cheme maturity reaches no level: capacity and feeds are assumed, the bed conversions are values within published ranges rather than a sourced design point, and the tower outlets, temperatures and duties come from an independent script (scripts/balance.py) whose energy balance core cannot check (no property package for SO2/SO3 or aqueous acid: core's property-package qualification and electrolyte support). 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/sulfuric-acid-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
Sulfuric acid (sulfur burning, double contact) · 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: "Sulfuric acid from sulfur burning, double contact / double absorption (1000 t/d, 98.5 wt%)", 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}
}