Urea by CO2 stripping, total recycle, prilling (2000 t/d, concept)
Fertiliser urea from ammonia and CO2 (both from an ammonia plant outside the boundary) by high-pressure CO2 stripping with total recycle, low-pressure recirculation, two-stage vacuum evaporation and prilling with exhaust scrubbing. Concept stage, assumed basis, preliminary gate-to-gate LCI.
Research outputNot engineering advice and not an approved design: do not use it for construction, operation or safety decisions. What this means
Overview
Liquid ammonia and CO2 (with passivation air) are brought to 14 MPa. The CO2 strips the
reactor effluent in a steam-heated falling-film stripper; the stripper gas, the fresh ammonia
and the recycled carbamate condense in the HP carbamate condenser, which raises the LP steam
of the plant, and the urea reactor completes the conversion. The stripped solution is
decomposed in an LP rectifier at 0.3 MPa, the off-gas condensed to carbamate and pumped back
through the HP scrubber. Two vacuum evaporators make a urea melt, which is prilled in a
forced-draft tower; the exhaust is water-scrubbed and the liquor recycled. The process
condensate is desorbed and hydrolysed to boiler-feed-water quality.
The reactor is a conversion model (CO2 conversion per pass assumed within the range the EU
BREF reports), unconverted carbamate is carried as NH3 + CO2, and the separations and duties
are specified values of a provenance script: no thermodynamic model of the NH3-CO2-urea-water
system is qualified in ChemE-as-Code yet. See DESIGN.md for every assumption and gated step.
Capacity
2000 t/d prilled urea (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)
Synthesis: 14000 kPa(a), 453 K, N/C 2.8 at the reactor inlet (BREF Table 8.14, CO2 stripping example); H2O/CO2 0.45 ASSUMED (D-005).
Reactor: conversion model of 2 NH3 + CO2 -> urea + H2O, CO2 conversion 0.58 per pass ASSUMED within the 50-80 % of BREF section 8.2.1; carbamate carried as NH3 + CO2 (D-005).
Stripper: 15 % of the NH3, 12 % of the CO2 and 85 % of the water fed leave with the stripped solution, ASSUMED (D-006).
LP rectifier 300 kPa(a); solution to evaporation 70 wt% urea; process condensate 6 wt% NH3, 4 wt% CO2, 1 wt% urea (ASSUMED after the BREF Table 8.8 remark, D-006).
Evaporation 95 wt% at 33 kPa(a) / 403 K, then melt at 3 kPa(a) / 413 K; biuret formation lumped into the 2nd evaporator (D-007).
All flows, temperatures and duties are concept estimates from specified splits and hand heat estimates; no qualified property method (D-008); accuracy not stated.
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
0.00009kg CO2-eqPreliminarypartial, 5 data gaps
Climate change per 1 kg Prilled urea, cradle-to-gate
Main contributors
CO2 to the environment100 %
Contributions, baseline
Each flow of the inventory into its phase, the phases into the functional unit; band widths are impacts. Hatched: a credit.
Method and data
Goal
Preliminary gate-to-gate life cycle inventory of prilled urea from a CO2-stripping total-recycle plant, for the process library: the foreground exchanges per kg of urea at the gate (raw materials, utilities, emissions, wastes) from the concept flowsheet, ready to be linked to background datasets later. Not an impact assessment: no background is linked.
Functional unit
1 kg Prilled urea (1 kg urea)
Boundary
cradle-to-gate
Allocation
none
Characterisation
Factors kept with the process · GWP100
Data quality
Published factors
Result
partial screening carbon footprint · 5 data gaps
Scenario
Climate change (kg CO2-eq)
baseline
0.00009
Inventory per 1 kg Prilled urea (18 flows)
Flow
Phase
Direction
Quantity
Unit
Provenance
Liquid ammonia from the ammonia plant
operation
input
0.5653
kg
assumed
CO2 from the ammonia plant CO2 removal
operation
input
0.7381
kg
assumed
Passivation air (ambient)
operation
input
0.01392
kg
assumed
Prilling air (ambient)
operation
input
8.478
kg
assumed
Electric power
operation
input
0.09613
kWh
assumed
MP steam 2400 kPa(a)
operation
input
0.408
kWh
assumed
Prilled urea to storage
operation
output
1
kg
assumed
LP absorber vent to atmosphere
operation
output
0.01903
kg
assumed
Scrubbed prilling tower exhaust to atmosphere
operation
output
8.552
kg
assumed
Treated process condensate to battery limit
operation
output
0.2245
kg
calculated
Cooling water return
operation
output
0.5243
kWh
assumed
BIURET to the environment
operation
output
0
kg
assumed
CO2 to the environment
operation
output
0.00009044
kg
assumed
H2O to the environment
operation
output
0.1988
kg
assumed
N2 to the environment
operation
output
6.423
kg
assumed
NH3 to the environment
operation
output
0.0002694
kg
assumed
O2 to the environment
operation
output
1.949
kg
assumed
UREA to the environment
operation
output
0.0002327
kg
assumed
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, lca/uncertainty.csv.
In the open LCI database (cheme-as-code-atlas-preview-c3ab348) as Prilled urea to storagePreliminary.
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
none (single-output, from study) · product:UREA 100 %
Allocation findings
none
Change report
Not available: this build has no change report against an earlier release.
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: all 5 blocks and 22 steps ok). Fresh feeds 565.3 kg NH3 and 731.8 kg CO2 per t urea against 567 and 733 kg/t reported for CO2 stripping (BREF LVIC-AAF Table 8.3): the element balance, not a model validation. Reactor and hydrolyser outlets are calculated by cheme (conversion reactors); the separator outlets and all duties are specified/hand-estimated values of scripts/urea_balance.py (no property package is qualified for aqueous NH3-CO2-urea-carbamate). Energy closure not evaluable in core. Utilities against the BREF benchmarks: steam 0.8 t/t (taken from BREF Table 8.5), electricity 96 kWh/t (BREF 110), cooling water 45 m3/t (BREF 60): the estimate is incomplete for minor drives and coolers. Preliminary gate-to-gate LCI (lca/inventory.csv); lca/dataset.yaml is in the Atlas build, marked preliminary, with feed:CO2 and emission:UREA listed as gaps (DESIGN.md D-014). cheme maturity reaches no level (assumed feeds, unsourced specified separations), so `concept` here is the schema's lowest value, not an evidenced level. Agent-reviewed only (reviews/2026-10-27-pfd-lci-review.md); no human review. 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/urea-1/checks/maturity.json(not in the library)
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: "Urea by CO2 stripping, total recycle, prilling (2000 t/d, concept)", 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}
}
