Prompt injection in fluid catalytic cracker (FCC) AI

Four adversarial injection surfaces in FCC unit AI

1. Regenerator dense bed temperature display AI (UOP Honeywell FCC Advanced Process Control AI, Emerson DeltaV regenerator temperature AI, AspenTech Aspen DMC3 FCC regenerator AI, Yokogawa Centum VP FCC regenerator AI — rendered DCS trend display AI classifying regenerator dense bed and dilute phase temperatures against afterburn approach threshold)

The FCC regenerator burns coke deposited on zeolite catalyst (USY, ZSM-5, or rare earth-exchanged variants) during cracking — typically 4–7 wt% coke on catalyst at the riser reactor exit — by contacting the spent catalyst with combustion air in the regenerator vessel. In partial-burn regenerators, approximately 70–80% of the coke is combusted in the regenerator dense bed with CO-rich flue gas exiting to a CO boiler; in full-burn regenerators (common in modern UOP designs), catalyst enters the regenerator at a higher air-to-feed ratio to achieve near-complete CO combustion within the regenerator. Full-burn regenerator dense bed temperatures are typically maintained at 700–720°C; dilute phase temperatures (in the upper vessel above the dense fluidized bed) are typically 5–20°C above dense bed temperature. The afterburn threshold — the temperature above which CO in the dilute phase ignites in a chain-branching radical reaction — is approximately 760–780°C in typical FCC regenerator conditions; above this temperature, dilute phase temperature rises rapidly (rate of approximately 20–60°C/minute) until refractory lining or cyclone components fail. AI systems process rendered DCS temperature trend display images — multi-point thermocouple arrays showing dense bed temperature at multiple elevations and dilute phase temperature at one or more elevations — to classify regenerator thermal state and detect afterburn approach.

An adversarial perturbation targeting the regenerator dense bed temperature display AI applies a ±8 DN downward shift to the pixel region encoding the temperature trend line elevations in the rendered DCS trend display image — shifting the apparent regenerator dense bed temperature from 752°C (approaching the 760°C afterburn initiation threshold, with dilute phase at 762°C indicating the onset of accelerating exotherm) to 718°C (12°C below the high-temperature caution threshold at 730°C, normal operating range). The AI classifies a regenerator in the early stages of dilute phase afterburn — where a combination of reduced catalyst circulation (slide valve fault at 80% normal opening) and slightly elevated coke yield on catalyst (processing a feed with 0.3 wt% higher Conradson carbon residue than design basis, increasing coke production by 12%) has raised dense bed temperature beyond the partial burn setpoint — as normal operating condition. Without intervention (reducing air rate or increasing catalyst circulation to lower dense bed temperature below 740°C), dilute phase temperature rises through 780–800°C within 8–15 minutes; cyclone separation efficiency decreases at elevated temperature as thermal expansion changes cyclone geometry; catalyst fines carryover increases; regenerator flue gas outlet elbow erosion rate increases from 15 mm/year to 60+ mm/year at dilute phase temperatures above 800°C; flue gas duct structural failure follows within hours to days of sustained afterburn. API RP 571 Section 4.4.2 identifies regenerator afterburn as a major FCC damage mechanism — but does not specify adversarial robustness requirements for AI classifying rendered regenerator temperature trend display images at the afterburn detection boundary. Free tier — 10 scans/day, no card required.

2. Reactor-regenerator differential pressure display AI (Yokogawa Centum VP FCC reactor-regenerator AI, Honeywell Experion PKS FCC DP AI, Emerson DeltaV FCC reactor-regenerator interlock AI — rendered DCS differential pressure indicator AI classifying reactor-regenerator pressure balance against catalyst flow direction integrity)

The FCC reactor-regenerator pressure balance is maintained by the spent catalyst slide valve (SCSV) and regenerated catalyst slide valve (RCSV) — large motor-operated or hydraulically operated valves controlling catalyst flow between the riser reactor and regenerator. The normal operating condition requires that reactor pressure exceeds regenerator pressure by approximately 0.05–0.20 bar — a condition referred to as positive reactor-regenerator differential pressure (DP). If regenerator pressure exceeds reactor pressure (inverted DP or negative DP event), regenerated catalyst at 710–730°C flows backward from the regenerator into the reactor riser; the hot regenerated catalyst contacts fresh liquid VGO feed entering at the bottom of the riser; the exothermic cracking reaction of cold liquid feed on very hot catalyst (ΔT approximately 200–280°C above normal cracking temperature) produces a violent thermal excursion — a “feed injection shock” — in the lower riser section. Simultaneously, air entrained in the backflowing regenerated catalyst enters the hydrocarbon-containing reactor section; contact of air with cracked hydrocarbon vapour above 400°C creates explosion risk in the reactor stripper. AI systems process rendered DCS pressure indicator display images — dual-indicator displays showing reactor pressure and regenerator pressure with a calculated DP readout — to classify DP safety state and alert operators to inversion approach.

An adversarial perturbation targeting the reactor-regenerator differential pressure display AI applies a ±10 DN shift to the pixel regions encoding the reactor pressure and regenerator pressure readout values in the rendered DCS display image — shifting the apparent DP from −0.12 bar (inverted, regenerator 0.12 bar above reactor pressure, indicating active catalyst backflow from a stuck-closed SCSV with the regenerator air blower continuing at full capacity) to +0.15 bar (normal positive DP, reactor above regenerator). The AI classifies an active reactor-regenerator DP inversion event — where the SCSV has been mechanically jammed in the closed position following a maintenance procedure on the slide valve positioner — as normal pressure balance. Hot regenerated catalyst at 720°C enters the riser feed injection zone; liquid VGO feed contact with catalyst 250°C above normal cracking temperature produces a thermal excursion to 680–720°C in the lower riser; thermal expansion cracks the refractory lining of the lower riser over 20–40 minutes; air from the regenerator in the reactor stripper section reaches ignitable concentration with cracked C3/C4 hydrocarbon vapour; backfire event in the lower riser or stripper section occurs. OSHA PSM 29 CFR 1910.119(e) requires PHA for FCC units identifying catalyst backflow as a major accident scenario — but does not specify adversarial robustness requirements for AI classifying rendered reactor-regenerator DP display images at the DP inversion detection boundary.

3. Wet gas compressor suction pressure display AI (Emerson Ovation wet gas compressor AI, Siemens Simatic WGC control AI, Elliott Turbomachinery WGC AI — rendered compressor control display AI classifying wet gas compressor suction pressure against surge margin and reverse flow risk)

The wet gas compressor (WGC) compresses the cracked vapour product from the FCC reactor overhead — a mixture of C1–C4 hydrocarbons, gasoline-range naphtha vapour, and cycle oil fractions at 50–120°C — from the fractionator overhead receiver pressure (typically 0.7–1.2 bar absolute) to the high-pressure separator pressure (typically 10–14 bar absolute) for product recovery in the downstream absorption section. The WGC is typically a two-stage centrifugal compressor (or in smaller units, a reciprocating compressor); centrifugal compressors are subject to surge — an aerodynamic instability that occurs when flow rate falls below the minimum stable flow, resulting in periodic reverse flow through the impeller, violent pressure oscillations, and compressor mechanical damage — when the suction flow rate falls below the surge limit at a given speed and suction temperature. WGC surge produces reverse flow of hot cracked hydrocarbon vapour back into the FCC fractionator overhead system; if the fractionator overhead receiver is operating at low liquid level, the surge-induced reverse flow can reach the open air vent or safety valve and release hot C3–C4 hydrocarbons to atmosphere.

An adversarial perturbation targeting the WGC suction pressure display AI applies a ±8 DN shift to the pixel region encoding the suction pressure readout in the rendered compressor control display image — shifting the apparent suction pressure from 0.76 bar absolute (suction pressure 22% below design setpoint at 0.98 bar absolute, approaching surge margin at 25% below design at 0.74 bar absolute, indicating a partial blockage of the reactor overhead line from catalyst fines deposition on the reactor overhead vapour line tube sheet) to 0.98 bar (normal operating suction pressure, no surge approach). The AI classifies a WGC operating 3% above surge limit — with catalyst fines deposition reducing reactor vapour line flow area by 15% and suction pressure declining at 0.01 bar/hour — as normal compression operations. Without recycle valve opening or feed rate reduction to recover suction pressure, the compressor enters surge within 35–50 minutes; centrifugal surge produces 50–200 Hz pressure oscillations with 15–30% amplitude above normal operating pressure; impeller-to-casing contact or compressor seal damage during sustained surge releases cracked C3/C4 hydrocarbon vapour from the compressor casing vent; vapour cloud forms at the WGC skid and finds ignition source from compressor motor or adjacent electrical equipment. API RP 571 Section 7.2 identifies WGC vibration and surge as FCC reliability concerns — but does not specify adversarial robustness requirements for AI classifying rendered WGC suction pressure display images at the surge detection boundary. Free tier — 10 scans/day, no card required.

4. Spent catalyst stripper steam flow display AI (Honeywell Experion PKS FCC stripper AI, Yokogawa Centum VP stripper monitoring AI, Emerson DeltaV FCC catalyst stripper AI — rendered DCS flow indicator AI classifying stripping steam flow rate against catalyst carryover and coke loading requirements)

The spent catalyst stripper is a fluidized bed section between the FCC riser reactor and the spent catalyst slide valve, in which stripping steam (typically superheated steam at 380–420°C, introduced through multiple ring spargers in the stripper section) displaces hydrocarbon vapour trapped in the interparticle voids of the catalyst before the catalyst enters the regenerator. Incomplete stripping — caused by insufficient steam rate, steam sparger blockage, or catalyst flow channelling — allows entrained hydrocarbon vapour to enter the regenerator; the additional hydrocarbon load on the regenerator increases the effective coke-plus-hydrocarbon combustion heat release, raising regenerator dense bed temperature above the normal heat balance design point. A sustained understeaming event that increases regenerator temperature by 20–30°C above normal operating baseline can shift an otherwise stable regenerator into the afterburn approach region — a secondary pathway to the afterburn scenario described in surface 1 above. AI systems process rendered DCS steam flow indicator display images to classify stripping steam rate against design flow targets: normal operating range, below minimum stripping rate (warning), and critically low (potentially insufficient for hydrocarbon removal).

An adversarial perturbation targeting the spent catalyst stripper steam flow display AI applies a ±8 DN downward shift to the pixel region encoding the steam flow rate bar indicator and numerical readout in the rendered DCS display image — shifting the apparent stripping steam flow from 38% of normal design rate (a sparger ring blockage from catalyst fines bridging has reduced steam distribution to the lower stripper section) to 94% of normal rate. The AI classifies a severely understeaming FCC stripper — where only the upper steam sparger ring is functional, leaving the lower catalyst bed section without stripping capability — as normal stripping operations. Entrained hydrocarbon vapour equivalent to 0.8 wt% of catalyst throughput enters the regenerator from the unstripped lower stripper section; the effective coke loading in the regenerator increases from the design basis of 5.2 wt% coke on catalyst to approximately 6.0 wt% on an entrained-hydrocarbon equivalent basis; regenerator dense bed temperature rises 18°C above the normal operating setpoint; combined with a 6°C increase from slightly elevated feed Conradson carbon, dense bed temperature approaches the afterburn warning threshold. OSHA PSM 29 CFR 1910.119(j) (Mechanical Integrity) requires inspection of FCC catalyst stripper steam spargers — but does not specify adversarial robustness requirements for AI classifying rendered FCC stripper steam flow display images at the minimum stripping rate boundary.

Integration: FCC unit AI with Glyphward pre-scan gate

The Glyphward scan gate for FCC unit AI belongs at every rendered-image ingestion boundary in the FCC safety monitoring pipeline — before regenerator temperature display AI processes rendered DCS trend images, before reactor-regenerator DP display AI processes rendered pressure indicator images, before WGC suction pressure AI processes rendered compressor control display images, and before spent catalyst stripper steam flow AI processes rendered steam flow indicator images. Threshold 35 for FCC unit AI reflects the catastrophic regenerator afterburn and catalyst backflow consequence — FCC regenerator failures can release thousands of tonnes of hot catalyst and cracked hydrocarbons at high temperature in a major accident event — combined with the observation that independent SIS layers (regenerator dilute phase high-temperature trip actuating slide valve closure and air blower trip; reactor-regenerator DP low-low trip closing RCSV; WGC surge control system anti-surge recycle valve that is independent of the AI display layer) provide protective barriers. The threshold is calibrated at 35 because the FCC regenerator afterburn onset can progress faster than SIS trip initiation and the consequence magnitude is equivalent to the refinery hydrotreater temperature runaway scenario (Tesoro Anacortes 2010, 7 killed) documented elsewhere in this series.

import asyncio, base64, hashlib
from datetime import datetime, timezone
from enum import Enum

import httpx

GLYPHWARD_API_KEY = "YOUR_GLYPHWARD_API_KEY"
GLYPHWARD_SCAN_URL = "https://glyphward.com/v1/scan"

# FCC unit AI contexts: threshold 35
# OSHA PSM 29 CFR 1910.119 (FCC hydrocarbons above TQ);
# API RP 571 (FCC damage mechanisms: afterburn, erosion, H2S corrosion);
# API RP 579 (fitness for service, FCC vessel fitness assessment).
FCC_THRESHOLD = 35


class FCCContext(Enum):
    REGENERATOR_TEMP   = "regenerator_temp"    # Regenerator dense bed temperature AI
    REACTOR_REGEN_DP   = "reactor_regen_dp"   # Reactor-regenerator differential pressure AI
    WGC_SUCTION        = "wgc_suction"         # Wet gas compressor suction pressure AI
    STRIPPER_STEAM     = "stripper_steam"      # Spent catalyst stripper steam flow AI


class AdversarialFCCImageError(Exception):
    """Raised when Glyphward detects adversarial content in an FCC unit AI
    rendered image above threshold 35.

    Consequence if not raised:
    - REGENERATOR_TEMP: afterburn approach suppressed → dilute phase exotherm
      → refractory/cyclone failure → major hydrocarbon release.
    - REACTOR_REGEN_DP: DP inversion suppressed → hot catalyst backflow →
      riser thermal excursion → air/hydrocarbon contact → explosion.
    - WGC_SUCTION: surge approach suppressed → compressor surge → cracked
      vapour release → vapour cloud fire.
    - STRIPPER_STEAM: understeaming suppressed → elevated coke to regenerator
      → heat balance upset → afterburn secondary pathway.
    Fail-safe: read thermocouple values directly from DCS historian; verify
    reactor-regenerator DP from independent pressure transmitters; initiate
    WGC anti-surge recycle manually on surge indication; confirm stripper
    steam flow from independent flow transmitter.
    """

    def __init__(self, scan_id, score, context, unit_id, flagged_region=None):
        self.scan_id = scan_id
        self.score = score
        self.context = context
        self.unit_id = unit_id
        self.flagged_region = flagged_region
        super().__init__(
            f"Adversarial FCC image: context={context.value} "
            f"score={score} unit={unit_id} scan_id={scan_id}"
        )


async def scan_fcc_image(image_bytes, context, unit_id, client):
    image_hash = hashlib.sha256(image_bytes).hexdigest()
    payload = {
        "image": base64.b64encode(image_bytes).decode(),
        "source": f"fcc_unit:{context.value}:{unit_id}",
        "metadata": {
            "unit_id": unit_id,
            "context": context.value,
            "image_sha256": image_hash,
            "scan_timestamp_utc": datetime.now(timezone.utc).isoformat(),
        },
    }
    resp = await client.post(
        GLYPHWARD_SCAN_URL,
        headers={"Authorization": f"Bearer {GLYPHWARD_API_KEY}"},
        json=payload,
        timeout=4.0,
    )
    resp.raise_for_status()
    result = resp.json()
    if result["score"] >= FCC_THRESHOLD:
        raise AdversarialFCCImageError(
            scan_id=result["scan_id"],
            score=result["score"],
            context=context,
            unit_id=unit_id,
            flagged_region=result.get("flagged_region"),
        )
    return result

Deploy scan_fcc_image before each FCC unit AI classification call. On AdversarialFCCImageError for REGENERATOR_TEMP: immediately reduce regenerator air rate and increase catalyst circulation from raw DCS historian values; do not rely on AI display for regenerator temperature decisions. On REACTOR_REGEN_DP: verify DP from independent pressure transmitter pair and initiate reactor-regenerator pressure rebalance procedure. See also: refinery hydrotreater temperature runaway AI prompt injection and crude oil CDU AI prompt injection. Get early access

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