🔥 Steam Cracker — Ethylene Production

Модуль #301. КазМунайГаз GPC (Kazakhstan Petrochemical Complex) Атырау, anonsed 2022 — ethylene plant 600 кт/год + polymer chain. Reference: SABIC Yanbu 4.0 Mt, Reliance Jamnagar 1.5 Mt, Borealis Stenungsund Sweden 0.6 Mt, INEOS Cologne 2.5 Mt. Steam cracking — thermal cracking saturated hydrocarbons (ethane, propane, naphtha) при 800-850 °C × 0.5-2 sec residence в furnace coils → продукты ethylene (C2H4 ~25-50% wt) + propylene + butadiene + pyrolysis gasoline. После cracking — cooling в transfer line exchanger TLE, каскад distillation columns. Linde / Technip / Lummus licensed технологии. EU IED BAT LVOC + API + СН РК 4.04-15.

1. Состав ethylene plant 600 кт/год

Cracking furnace: 6-8 furnaces в parallel, twin-radiant box design Stone & Webster USC type, height 30 м, ширина 5 м; coil tubes Cr-Ni alloy 9%Cr (HK-40) / 25Cr-35Ni-Nb (HP-Mod), inside diameter 60-90 мм длиной 150 м serpentine;
Burners: 80-200 floor + side burners per furnace, dual-fuel natural gas + methane-hydrogen tail-gas, low-NOx selective non-catalytic reduction;
Steam-to-hydrocarbon ratio: 0.3-0.4 wt/wt for ethane crack, 0.7-1.0 для naphtha (steam dilutes hydrocarbon partial pressure → minimises coking);
Transfer Line Exchanger TLE: rapid quench cracked gas from 850 °C to 400 °C в 50-100 ms (HHTE Linde / SHG Technip), generates HP steam 110-120 бар superheated;
Quench tower: water + oil quench cools gas to 200 °C, separates fuel oil + pyrolysis gasoline drop-out;
Cracked Gas Compressor CGC: 4-5 stage centrifugal compressor 80 МВт steam-turbine driven, compresses cracked gas from 1.5 to 35 бар;
Caustic + amine treating: NaOH 10% scrubber removes H2S + CO2 to <1 ppm;
Cold Box (Demethanizer prep): propane refrigeration -40 °C + ethylene refrigeration -101 °C cascade, prepares feed для cryogenic distillation;
Demethanizer: cryogenic column -100 °C × 35 бар, separates CH4 from C2+ hydrocarbons (CH4 used as tail-gas fuel back в furnaces);
Deethanizer: separates C2 (ethylene + ethane) overhead from C3+ bottom;
Acetylene hydrogenation: Pt catalyst @ 50 °C, converts trace acetylene C2H2 → ethylene (acetylene poisons downstream polymer catalyst);
C2 splitter: high-purity ethylene 99.95% overhead, ethane bottom recycled к cracker;
Depropanizer + propylene unit: propylene 99.5% polymer-grade overhead;
BD extraction: butadiene 99.5% via NMP extraction column (BASF process), valuable feedstock для rubber industry;
Pyrolysis gasoline + fuel oil: by-products fed к BTX complex (aromatics extraction) или direct fuel oil sale;
Olefins flare: 100 м tall H ground-flare + elevated flare для emergencies, hydrocarbon emissions 0.05% от throughput per EU IED BAT.

Упражнение 1 — Cracking technology

Простая distillation сырой нефтиТолько catalytic cracking FCCТолько oxidative coupling OCMSteam Cracking thermal pyrolysis Linde/Technip/Lummus furnace coil 850 °C × 0.5-2 sec residence: (1) feed naphtha/ethane/propane + steam 0.3-1.0 ratio в radiant coil тубы HP-Mod alloy 25Cr-35Ni-Nb 150 м serpentine, (2) thermal cracking C-C bond breakage → smaller olefins ethylene 25-35% wt yield (naphtha) или 50-55% (ethane), (3) quench TLE Transfer Line Exchanger 50 ms rapid cool 850→400 °C для prevent secondary reactions, (4) cracked gas compression 4-5 stages centrifugal, (5) cryogenic separation demethanizer-deethanizer-C2 splitter, (6) propylene 99.5% poly-grade + butadiene 99.5% by-products, (7) coke deposition требует de-coking every 30-90 дней (steam-air decoke 800 °C). EU IED BAT LVOC + API RP + AIChE Pyrolysis Conference + СН РК 4.04-15

Упражнение 2 — Cracking temperature

Coil outlet temperature COT для naphtha cracker (°C)?

Упражнение 3 — Капекс ethylene plant 600 кт/год

Cracking furnaces 8× Linde radiant box + TLE = 350 млрд
CGC compressor 80 МВт + steam turbine + intercoolers = 180 млрд
Caustic + amine treating + sour water = 65 млрд
Cold box propane/ethylene cascade refrigeration = 220 млрд
Demethanizer/Deethanizer/C2-C3 splitters + reboilers = 280 млрд
BD extraction NMP + propylene unit + acetylene hydrog. = 95 млрд
Steam ТЭЦ 200 МВт + cooling water + utilities = 90 млрд
Flare 100 м + ground flare + EU IED BAT + проект 4% + PNR = 120 млрд

Упражнение 4 — De-coking maintenance

Никогда не нужно — coke выходит самКаждые 10 лет полная замена furnacesDe-coking каждые 30-90 days по AIChE Best Practices: (1) coke deposition внутри coil tubes снижает heat transfer +30% energy demand + риск burnout, (2) decoke сменяет hydrocarbon feed на steam-air mixture, (3) 800 °C × 24-48 hr controlled burnoff C + 1/2 O2 → CO + CO2, (4) decoke gas routed к decoke drum + CO scrubber + flare, (5) после decoke tube wall thickness measurement + radiography для assess remaining wall, replace coil каждые 5-7 years (creep + carburization wear), (6) decoke schedule 4-12 times/year, lost production 0.5-1% annual, (7) advanced anti-coke coatings BASF CoatAlloy GT-1 + Quantiam CarbosafeOn reduce coking 30-50% + extend decoke interval. AIChE Pyrolysis Conference + API RP 581 + EU IED BAT LVOC + СН РК 4.04-15Только раз в год по графику

Нормативная база

EU IED BAT Reference LVOC — Large Volume Organic Chemicals 2017
API RP 530 — Calculation of Heater-Tube Thickness in Petroleum Refineries
API RP 538 — Industrial Fired Boilers
API RP 581 — Risk-Based Inspection
ASME Section VIII Div 2 — Pressure Vessels
ASME B31.3 — Process Piping
IEC 61511 — Safety Instrumented Systems
NFPA 30 — Flammable + Combustible Liquids
СН РК 4.04-15 — Цветная + нефтехимическая
OSHA PSM 29 CFR 1910.119