Gameplay approximation. Molar yield is treated as equivalent liquid volume; values are not suitable for engineering or commercial decisions.
operator controlsmanual
firing follows COT setpoint
trends / last 30 mintop · flash · levels
top Tflash Tdrumsump
alarms and events0 active
NO ACTIVE ALARMS
run controlsscore 000
UNIT REGISTRY / CDU-101
Select operating scenario
Choose a run. Scenarios share the same dynamic model, alarm system, scoring, and synthetic economics.
OPERATING ORDER
Scenario briefing
TECHNICAL GUIDE / CDU-101
How the simulation works
Process intuition, control interactions, quality calculations, economics, and model limitations.
Purpose and scope
This is a dynamic educational model of an atmospheric crude distillation unit. It resolves 25 equilibrium stages, a reflux drum, a column sump, side strippers, two pumparounds, a fired heater, and a condenser. It is designed to reproduce operator cause and effect, not to replace a validated refinery simulator.
The crude assay contains 40 carbon-number pseudocomponents from C5 to C44. Each bucket has a representative normal boiling point. The model treats molar yield as equivalent liquid volume only for gameplay economics.
What advances every 0.5 seconds
Each fixed model step closes component material balances, estimates vapor/liquid equilibrium from temperature and boiling point, moves liquid with a weir-style hydraulic relation, applies stripping steam, and closes a sensible-plus-latent heat balance. Drum, sump, heater metal, analyzers, and product receivers all retain inventory, so changes propagate rather than appearing instantly.
Fixed steps make the result deterministic at ×1, ×10, and ×60.
Separation intuition
Hot feed flashes near tray 22. Light components preferentially travel upward with vapor; heavy components travel downward with liquid. Reflux and pumparounds remove heat above the flash zone, condensing heavier vapor and sharpening cuts. Steam lowers hydrocarbon partial pressure and strips light material from side products or residue. Too little vapor causes weeping; too much vapor or liquid holdup causes flooding. Every product draw also changes internal traffic and the neighboring cut—not just that product's rate.
Raises throughput, tray traffic, fired-duty demand, and all product rates.
Can cool the flash zone, overload the condenser, flood the top, or swell the sump during a heavy-crude change.
Sump circulation
Recirculates hot bottoms through the heater during startup and adds heater-tube flow.
Protects against high tube severity but consumes heater capacity and is unsafe with an empty sump.
COT setpoint
In automatic mode, raises furnace duty until coil-outlet temperature approaches the target. Higher COT vaporizes more crude.
Moves heavier material upward, increases condenser/vapor load, fuel use, and coking severity. Heater metal supplies a 90-second thermal lag.
Heater duty
In manual-firing mode, directly requests MW rather than a temperature.
Feed changes no longer receive automatic compensation. Auto blocks firing without flow; manual operation remains an operator hazard.
Reflux
Returns cool condensed naphtha to the top, lowering top temperature and rejecting heavy material from naphtha.
Reduces net naphtha withdrawal capacity and increases liquid traffic; excessive reflux can flood the top or drain the drum.
PA1 duty
Withdraws liquid near tray 3, cools it externally, and returns it at tray 1. This removes upper-column heat with no net material transfer.
Protects naphtha endpoint and condenser load but shifts condensation and internal liquid traffic.
PA2 duty
Withdraws near tray 17 and returns near tray 15, removing heat around the LGO/HGO region.
Moves middle-distillate cutpoints and can create quality giveaway when overused.
Naphtha draw
Removes liquid from the reflux drum and lowers drum level.
Too little overfills the drum; too much drains reflux inventory. Product quality follows the receiver with a lag.
Kero / LGO / HGO draws
Increase withdrawal from trays 8, 14, and 19 respectively.
A larger draw admits more neighboring material and changes liquid flow below that tray. Cutpoint, flash point, and adjacent-product yield move together.
Residue draw
Lowers sump inventory and removes the heaviest product.
Too little overflows the sump; too much can uncover the circulation system and pull lighter material into residue.
Side steam
Strips low-boiling material from kero, LGO, or HGO back into the column, raising product flash point.
Raises vapor traffic and steam cost; excessive steam can burden upper sections.
Column steam
Strips light material from residue and supports flash-zone vapor traffic.
Improves residue T5 but increases column and condenser loading.
Product quality and delay
Each product has a composition receiver. On cold startup every receiver begins empty; the first representative product flow establishes its composition without carrying a fictional initial sample. Once filled, its response time is approximately 4–8 model minutes, representing product rundown and sample volume. T5 and T95 are interpolated from the cumulative 40-bucket distillation curve. The flash-point proxy is calibrated across the distillate range:
synthetic flash point (°C) = 0.75 × T5 (°C) − 46
The standard minimums are kero 38 °C, LGO 60 °C, and HGO/SGO 100 °C. Winter freeze and cloud values are explicitly synthetic indices derived from T95, not laboratory ASTM results. Analyzer-lag mode publishes every 15 minutes using a 10-minute-old sample.
Difficulty, objectives, and full-duration runs
Training adds an 8 ° allowance, shortens the required on-spec hold, and slows sustained trips. Standard uses the published deck. Hard retains the published quality limits but lengthens the hold and accelerates sustained trips. Instant physical limits such as vessel overflow and absolute heater overtemperature remain unchanged.
“Stop when objective is met” is the shorter operational challenge. “Full-duration / comparable P&L” continues to the published scenario end after the objective is first met. Shared highscores can be submitted only after a successful Hard run covering the complete horizon. The optional operator name and result are published to the cross-device leaderboard; no account is required. Without accounts or server-side replay, submissions are intentionally lightweight rather than cheat-proof.
Economics and limitations
Revenue uses instantaneous equivalent-barrel product rates. On-spec material receives the displayed fictional price; off-spec material receives exactly 50%. Crude, fired duty, pumparound duty, and steam are charged continuously. A fixed fictional refinery OPEX of $3,350/h represents staffing, maintenance, site utilities, and the opportunity cost of keeping the unit online. It is calibrated so an on-spec reference slate does not become profitable until feed is above roughly 50%. Pausing stops both process time and P&L.
Pressure is represented indirectly, physical properties are lumped, equilibrium and hydraulics are simplified, side strippers are reduced-order, and no controller tuning or equipment geometry is plant-specific. Values are suitable for learning interactions and playing scenarios only—not design, safety, commercial, or operating decisions.