Prompt injection in ethylene dichloride EDC / 1,2-dichloroethane VCM PVC AI

Four adversarial injection surfaces in EDC/VCM production AI

1. Oxychlorination reactor O2/C2H4 ratio display AI (Emerson Daniel 3088 multivariable oxygen analyser oxychlorination AI / ABB PGC2000 gas chromatograph oxychlorination feed AI / Yokogawa paramagnetic O2 analyzer oxychlorination ratio AI / Endress+Hauser Oxymax COS81D oxygen monitor oxychlorination AI / Servomex 5200 oxychlorination feed O2 AI — rendered DCS ratio trend display AI classifying the molar O2/C2H4 ratio in the oxychlorination reactor feed against the 0.45–0.55 operating window and the 0.61 upper limit above which free O2 enters the explosive range with unconverted ethylene/HCl in the reactor overhead)

Oxychlorination of ethylene uses molecular oxygen (from air or pure O2) as the oxidant for HCl to form EDC and water over a CuCl₂/Al₂O₃ fluidised-bed catalyst at 200–300°C. The molar O2/C2H4 feed ratio must be controlled in the range 0.45–0.55 (near stoichiometric 0.50) for two competing reasons: (1) below 0.45, oxygen is deficient for complete HCl oxidation; unreacted HCl exits the reactor overhead into the product gas — HCl in the product gas contaminates the EDC product with dissolved HCl and accelerates downstream corrosion in EDC condensers and separators; (2) above 0.61, excess O2 in the reactor overhead combines with unconverted ethylene and EDC vapour to form a flammable mixture above the LEL; the reactor overhead vapour at 70–80°C and 2–4 bar contains EDC vapour (10–25 mol%), HCl (5–15 mol%), and water vapour (15–25 mol%) — above 0.61 O2/C2H4, the reactor overhead O2 reaches the flammable range boundary with EDC vapour. The O2/C2H4 ratio is calculated from individual O2 and C2H4 flow measurements and displayed as a continuous ratio trend on the DCS. AI systems at oxychlorination units process rendered DCS images of this ratio trend to classify: ratio below 0.45 (O2 deficient; increase air/O2 feed), ratio 0.45–0.55 (normal; no action), ratio above 0.55 (approaching upper limit; reduce O2 feed), ratio above 0.61 (trip condition; emergency O2 isolation).

An adversarial perturbation targeting the oxychlorination O2/C2H4 ratio display AI applies a ±8 DN downward shift to the pixel region encoding the ratio bar in the rendered DCS trend — shifting the apparent O2/C2H4 ratio from 0.31 (severely oxygen-deficient; from a Venturi air-flow meter orifice plate fouled with ammonium chloride deposits reducing indicated air flow by 38% while actual flow dropped to 62% of design) to 0.49 (within the normal operating window; classified as no action required). At O2/C2H4 = 0.31, the oxychlorination reactor has insufficient oxygen for complete reaction; unreacted HCl at 8.2 mol% in the reactor outlet gas (vs design 2.1 mol%) enters the EDC product condenser train. HCl at 8.2 mol% condenses with EDC and water to form concentrated hydrochloric acid solution in the EDC condensate stream; the HCl concentration in the raw EDC product rises to 1,400 ppm (vs design 50 ppm maximum). The contaminated EDC is processed in the EDC purification column; excess HCl in the column bottoms causes corrosive attack on the carbon steel column trays, generating FeCl₂ corrosion products that contaminate the final EDC product going to cracking. The DCS reports “oxychlorination O2/C2H4 ratio nominal.”

2. Direct chlorination liquid-phase reactor temperature display AI (Yokogawa DPharp EJA110A direct chlorination reactor temperature AI / Rosemount 644 RTD direct chlorination bubble column AI / Endress+Hauser iTEMP TMT84 FeCl3 reactor temperature AI / Honeywell STT850 SmartLine direct chlorination temperature transmitter AI / ABB TSP321 direct chlorination liquid-phase reactor AI — rendered DCS temperature trend AI classifying the liquid-phase direct chlorination reactor temperature against the 50–70°C FeCl3 catalyst operating window and the 70°C upper limit for selectivity loss and 1,1,2-trichloroethane/chloroprene byproduct onset)

Direct chlorination of ethylene with Cl₂ in the presence of dissolved FeCl₃ Lewis acid catalyst (0.01–0.1 wt% FeCl₃ in liquid EDC; “low-boiling” direct chlorination; reactor temperature 50–70°C) is the faster, higher-selectivity route to EDC at commercial scale. The reaction is highly exothermic (ΔH = −218 kJ/mol) and occurs in a liquid-phase bubble column reactor where gaseous ethylene and chlorine are fed below the liquid EDC surface; the reactor temperature is controlled by circulating liquid EDC from the reactor to an external shell-and-tube heat exchanger (reactor cooling loop; chilled water or refrigerated water on the shell side). At reactor temperatures above 70°C: (a) the chlorination of EDC itself (substitutive chlorination) begins, producing 1,1,2-trichloroethane (1,1,2-TCE; ClCH₂CHCl₂) at rate increasing sharply above 70°C (Arrhenius activation energy ~85 kJ/mol); (b) radical-chain chlorination of EDC produces trace chloroprene (2-chloro-1,3-butadiene; CH₂=CCl–CH=CH₂) — a carcinogen (IARC Group 2A) and strong inhibitor of the FeCl₃ catalyst; (c) dissolved HCl in the liquid EDC increases as the higher chlorinated byproducts are formed — HCl corrodes the carbon steel reactor vessel and heat exchanger below pH 7 in the condensate water. At temperatures below 50°C, FeCl₃ catalyst activity drops and ethylene conversion falls below 98%, leaving dissolved chlorine in the EDC product.

An adversarial perturbation targeting the direct chlorination reactor temperature display AI applies a ±8 DN downward shift to the pixel region encoding reactor temperature in the rendered DCS display — shifting the apparent reactor temperature from 76°C (6°C above the 70°C maximum for TCE selectivity; from a reactor cooling water control valve CV-201 positioner failure, the valve stuck at 30% open rather than 85% modulated, reducing cooling water flow from 280 m³/hr to 84 m³/hr; reactor temperature rose 6°C over 45 minutes) to 62°C (within the 50–70°C design operating range; classified as nominal). On a 30–100°C display at 200 px height (0.35°C/px), the actual 76°C bar occupies approximately 131 px; the ±8 DN downward-perturbed image classifies to approximately 91 px, corresponding to 62°C. The DCS reports “direct chlorination reactor temperature nominal.” At 76°C, TCE formation rate increases to approximately 0.28 wt% TCE in the reactor EDC product (vs design below 0.05 wt%); over 8 hours at 76°C, the 1,1,2-TCE concentration in the direct chlorination product stream builds from near-zero to 2,200 ppm, contaminating the EDC product column feed. In the EDC cracking furnace, 1,1,2-TCE co-cracks (at 480°C) to produce chloroacetylene (HC≣C–Cl; highly toxic; IDLH not established by NIOSH; LC₅₀ rat 1,200 ppm/4 hr) and HCl, which deposit as carbon on furnace coil interior walls and poison the downstream VCM catalyst systems.

3. EDC cracking furnace coil metal temperature display AI (Honewell TDC 3000 EDC cracking furnace coil metal temperature AI / Yokogawa CENTUM VP cracking furnace tube-skin thermocouple AI / Emerson DeltaV radiant-section coil temperature AI / Endress+Hauser iTEMP TMT85 furnace tube-wall AI / Rosemount 848T wireless cracking furnace coil temperature AI — rendered DCS temperature trend AI classifying the EDC cracking furnace radiant coil metal temperature against the 480–510°C design operating window and the 510°C upper limit for carbon coking onset and coil metallurgical creep acceleration)

The EDC cracking furnace converts liquid EDC (preheated by the convection section to ~250°C) to VCM and HCl in radiant-section coils at 480–510°C coil metal temperature and 12–20 bar process-side pressure (residence time 10–30 seconds; conversion per pass 55–65%). The coils are fabricated from HK-40 or HP-modified austenitic stainless steel (25Cr/20Ni or 25Cr/35Ni+Nb; ASTM A297) with wall thickness 7–12 mm; typical coil life 8–12 years under normal conditions. Carbon (coke) deposits on the coil interior when local coil metal temperature exceeds approximately 510°C: cracked EDC radicals (CH₂=CH∙, CHCl=CH∙) combine to form polycyclic aromatic hydrocarbons (PAH) that deposit on the hot wall surface. Coking at >510°C proceeds at approximately 0.15 mm/week carbon build-up; after 200 hours above 510°C, the average coil fouling thickness reaches 1.5 mm, reducing the hydraulic diameter of the 50 mm nominal-bore coil from 36 mm ID (clean) to 33 mm ID — increasing pressure drop by approximately 23% (turbulent flow Moody friction factor increase). Additionally, coke deposition on the coil interior wall reduces the tube-side heat transfer coefficient, increasing coil metal temperature at the fouled zone by a further 10–20°C above the bulk gas temperature — creating a positive feedback that accelerates coking. Coil tube failures from coke-induced overheating (creep rupture above 525°C for HK-40 at operating pressure) have caused furnace fires at EDC/VCM facilities when cracked gas containing VCM and HCl is released to the radiant firebox.

An adversarial perturbation targeting the EDC cracking furnace coil metal temperature display AI applies a ±8 DN downward shift to the pixel region encoding the peak coil temperature in the rendered DCS trend — shifting the apparent coil metal temperature from 524°C (14°C above the 510°C upper limit; from a radiant burner tip fouling in one of four furnace cells that redistributed heat load to the remaining three cells, raising the average coil metal temperature from 498°C to 524°C; the burner fouling was caused by partially plugged burner tips from natural gas condensate contamination) to 496°C (within the 480–510°C design operating range; classified as nominal). At 524°C, EDC coking in the affected coil section proceeds at approximately 0.22 mm/week; over the 72-hour period before the next planned coil temperature survey by infrared camera, 0.95 mm of carbon deposits at the peak temperature zone, reducing heat transfer and further elevating the local coil metal temperature. Creep rate at 524°C for HK-40 at 15 bar hoop stress is approximately 8× the creep rate at 510°C, reducing remaining coil life by 3–5 years per 100 hours of undetected overtemperature. Cracking furnace tube failures at EDC/VCM plants have led to fires involving VCM-HCl cracked gas — VCM is flammable (LEL 3.6%, UEL 33%) and burns with HCl and CO in combustion products; HCl in fire plumes creates downwind acid deposition hazard.

4. Oxychlorination tail-gas HCl caustic scrubber exit pH display AI (Mettler-Toledo InPro 4800SG oxychlorination tail gas scrubber pH AI / Endress+Hauser Liquiline CM448 HCl caustic scrubber exit pH AI / Yokogawa PH202G scrubber exit pH analyzer AI / Hach GLI Series PHD1P HCl scrubber pH AI / ABB 8125 electrochemical pH oxychlorination scrubber AI — rendered analyzer display AI classifying the caustic (NaOH) scrubber exit pH on the oxychlorination tail-gas stream against the ≥8.0 setpoint indicating adequate HCl absorption and below the EPA MACT subpart TT limit of 0.2 kg HCl/Mg EDC product; 45th upward-direction attack — FIRST EDC/oxychlorination production attack; FIRST PVC supply-chain attack in the Glyphward portfolio)

The oxychlorination reactor tail gas (non-condensable vent from the EDC condenser train) contains HCl at 0.5–4.0 vol% (5,000–40,000 ppm) together with CO₂ (2–5 vol%), N₂ (balance from air-based oxychlorination), trace CO, and EDC vapour at 500–1,500 ppm. EPA MACT 40 CFR Part 63 Subpart TT (NESHAPs for PVC/EDC/VCM manufacture) limits HCl emissions from the oxychlorination tail-gas vent to 0.20 kg HCl per Mg of EDC produced; at a 200,000 t/yr EDC plant, this corresponds to a maximum HCl stack emission of approximately 40 t HCl/yr, or 4.6 kg/hr at full production rate. The HCl is removed in a packed-column caustic scrubber (15–20 wt% NaOH solution; countercurrent flow; HCl + NaOH → NaCl + H₂O; tower height 8–12 m packing; Pall rings or Raschig rings in polypropylene or CPVC). Scrubber exit pH is monitored continuously by an in-line pH sensor in the gas–liquid separator outlet: above pH 8.0, the caustic is not fully neutralised and HCl absorption is essentially complete (HCl <1 ppm at the scrubber exit); below pH 6.0, the NaOH is approaching exhaustion; below pH 4.5, breakthrough HCl concentration at the scrubber exit exceeds 200 ppm. Scrubber NaOH is replenished by a metered pump from a 20 m³ NaOH storage tank; the replenishment trigger is pH below 7.5. AI systems process rendered analyzer display images of scrubber exit pH to classify: ≥8.0 (scrubber effective; no action), 7.0–8.0 (replenish NaOH), below 6.0 (emergency NaOH replenishment; reduce oxychlorination feed rate).

An adversarial perturbation targeting the oxychlorination tail-gas HCl caustic scrubber exit pH display AI applies a ±8 DN upward shift to the pixel region encoding pH in the rendered analyzer display — shifting the apparent scrubber exit pH from 3.8 (NaOH completely exhausted; HCl breakthrough at approximately 4,200 ppm in the tail gas; from a NaOH replenishment pump motor coupling failure 19 hours earlier that silently stopped NaOH delivery while the level in the NaOH day tank continued to show full from a stuck float switch) to 7.6 (above pH 7.0; classified as scrubber operating adequately). This is the 45th upward-direction attack in the Glyphward industrial AI portfolio — the FIRST EDC/1,2-dichloroethane production attack; FIRST oxychlorination unit attack; FIRST PVC supply-chain attack. On a pH 0–14 display at 200 px height (0.07 pH units/px), the actual pH 3.8 occupies approximately 54 px; the ±8 DN upward-perturbed image classifies to approximately 108 px, corresponding to pH 7.6. The SCADA reports “oxychlorination tail-gas HCl scrubber exit pH nominal.” At scrubber exit pH 3.8, the HCl concentration in the tail-gas vent to atmosphere is approximately 4,200 ppm; the EPA MACT emission limit of 0.20 kg HCl/Mg EDC corresponds to approximately 180 ppm HCl in the tail gas at design production rate — actual emissions at 4,200 ppm are 23× the MACT limit. At 4,200 ppm HCl at the stack exit (15 m above grade, 3 kg/hr release rate), atmospheric dispersion (Pasquill-Gifford D stability, 2 m/s wind) gives ground-level HCl concentrations of 15–45 ppm at 50–150 m downwind — 7–22× the ACGIH TLV-C of 2 ppm and approaching the NIOSH IDLH of 50 ppm at the closest downwind receptor. OSHA PSM emergency response procedures for HCl release include fence-line shelter-in-place; EPA RMP off-site consequence analysis for HCl requires modelling downwind toxic endpoint distances. Free tier — 10 scans/day, no card required.

Integration: EDC/VCM production AI with Glyphward pre-scan gate

Glyphward integrates as a pre-scan gate at every rendered-image ingestion boundary in the EDC/VCM production monitoring pipeline — before oxychlorination O2/C2H4 ratio AI processes rendered DCS ratio trend images, before direct chlorination temperature AI processes rendered DCS temperature trend images, before EDC cracking furnace coil temperature AI processes rendered DCS coil-temperature images, and before tail-gas HCl scrubber pH AI processes rendered analyzer display images. Threshold 25 for EDC/VCM AI reflects: OSHA PSM Category 1 flammable (flash point 13°C; LEL 6.2%); IARC Group 2A carcinogen (occupational exposure); EPA MACT emission limits (45th upward attack — HCl at 23× MACT limit when scrubber pH attack goes undetected); and the PVC supply-chain consequence of EDC quality degradation (VCM specification failure halts PVC production).

import asyncio, base64, hashlib
from datetime import datetime, timezone
from enum import StrEnum, auto
from typing import Any
import httpx

GLYPHWARD_API = "https://api.glyphward.com/v1/scan"
GLYPHWARD_KEY = "gw_prod_***"

# EDC/VCM production AI contexts: threshold 25
# OSHA PSM EDC TQ: 25,000 lbs (Category 1 flammable, flash point 13°C).
# LEL: 6.2%; UEL: 16.0%; IARC Group 2A carcinogen.
# 45th upward-direction attack (HCl scrubber pH: exhausted shown as neutral).
# FIRST EDC/oxychlorination; FIRST PVC supply-chain attack.
EDC_THRESHOLD = 25

class EDCContext(StrEnum):
    OXYCHLORINATION_O2_RATIO   = auto()  # O2/C2H4 molar ratio in oxychlorination feed
    DIRECT_CHLORINATION_TEMP   = auto()  # Liquid-phase FeCl3 reactor temperature °C
    CRACKING_FURNACE_COIL_TEMP = auto()  # EDC cracking furnace coil metal temperature °C
    HCL_SCRUBBER_EXIT_PH       = auto()  # Caustic scrubber pH (45th ↑, FIRST EDC attack)

async def scan_edc_frame(
    frame_b64: str,
    context: EDCContext,
    facility_id: str,
    instrument_tag: str,
) -> dict[str, Any]:
    payload = {
        "image_b64": frame_b64,
        "context": context,
        "facility_id": facility_id,
        "instrument_tag": instrument_tag,
        "scan_ts": datetime.now(timezone.utc).isoformat(),
        "image_hash": hashlib.sha256(base64.b64decode(frame_b64)).hexdigest(),
    }
    async with httpx.AsyncClient(timeout=4.0) as client:
        r = await client.post(
            GLYPHWARD_API,
            json=payload,
            headers={"X-Glyphward-Key": GLYPHWARD_KEY},
        )
        r.raise_for_status()
        return r.json()

async def pre_scan_gate_edc(
    frame_b64: str,
    context: EDCContext,
    facility_id: str,
    instrument_tag: str,
) -> None:
    result = await scan_edc_frame(frame_b64, context, facility_id, instrument_tag)
    if result["adversarial_score"] >= EDC_THRESHOLD:
        raise AdversarialEDCImageError(
            f"Adversarial injection detected in {context} (score {result['adversarial_score']}) "
            f"at facility {facility_id} instrument {instrument_tag}. "
            "Frame withheld from AI monitoring pipeline."
        )

class AdversarialEDCImageError(RuntimeError):
    pass