Petrochemical Olefins, Naphtha Steam Cracking & Pyrolysis Furnaces
Steam Cracker Ethylene/Propylene (P/E) Ratio & Steam Formula
Calculate Polymer-Grade Ethylene Output (t/hr), Co-Product Propylene Output (t/hr), Cracking Severity P/E Weight Ratio, and Furnace Dilution Steam Rate (t/hr).
Cracking severity is tracked inversely by Propylene-to-Ethylene ratio (P/E)—hotter coils crack propylene into ethylene and methane!
Naphtha and LPG steam-cracking pyrolysis furnaces operate millisecond radiant coils at Coil Outlet Temperatures (COT) of 810°C–860°C mixed with Dilution Steam (Steam-to-Hydrocarbon mass ratio S/HC = 0.40–0.65 t/t to lower hydrocarbon partial pressure, boost bimolecular-suppressing olefin selectivity, and suppress radiant-tube coking)! Operators control cracking severity via the dimensionless Propylene-to-Ethylene Weight Ratio P / E = Propylene_WtPct / Ethylene_WtPct: moderate severity (P/E = 0.50–0.55) maximizes total C2+C3 light olefins when polypropylene prices are strong, whereas high-severity cracking (raising COT by +25°C -> P/E drops to ~0.40) cracks secondary propylene into extra ethylene plus fuel-grade methane!
Verify on a 120.0 t/hr Full-Range Naphtha Cracker—Naphtha_Feed = 120.0 t/hr (B2), Dilution_Steam_Ratio S/HC = 0.50 t steam/t feed (B3), Ethylene_Yield = 31.0 wt% (B4), and Propylene_Yield = 15.5 wt% (B5): Ethylene Production hits 120 * 0.31 = 37.20 t/hr (E2), Propylene Production equals 18.60 t/hr (E3), Severity P/E Ratio equals 15.5 / 31.0 = 0.500 (E4), and Furnace Dilution Steam Injection equals 120 * 0.50 = 60.00 t/hr (E5)! In a cloud collaboration olefins-planning workbook, a `viewer` or `suggester` can leave whole-cell comments on `B4:B5` comparing spot polymer spreads before an `editor` commits updated furnace targets.
| Naphtha Cracker KPI (120 t/hr Feed, S/HC = 0.50, 31.0% C2=, 15.5% C3=) | Formula | Verified Output |
|---|---|---|
| Ethylene Production C2= (t/hr) | Feed_t_hr * (Ethylene_WtPct / 100) | 37.20 t/hr (40.80 @ 34.0% high-sev) |
| Propylene Production C3= (t/hr) | Feed_t_hr * (Propylene_WtPct / 100) | 18.60 t/hr (16.32 @ 13.6% high-sev) |
| Cracking Severity P/E Ratio | Propylene_WtPct / Ethylene_WtPct | 0.500 (0.400 @ high severity) |
| Dilution Steam Injection (t/hr) | Feed_t_hr * Steam_to_HC_Ratio | 60.00 t/hr |
Steam-Cracker Olefins Mass Balance & P/E Severity Formula
Validate Hydrocarbon_Feed > 0, Steam_to_HC_Ratio in [0.20, 1.20], Ethylene_WtPct > 5, Propylene_WtPct >= 0, and combined C2=+C3= <= 85 wt%!
=LET(hc_f, B2, sh_r, B3, et_p, B4, pr_p, B5, IF(OR(hc_f <= 0, sh_r < 0.2, sh_r > 1.2, et_p <= 5, pr_p < 0, et_p + pr_p > 85), "Invalid Cracker Input", ROUND(pr_p / et_p, 3)))High-Severity Coil Outlet Temperature Shift Check (Set C2= = 34.0%, C3= = 13.6%)
Shift furnace coils to High-Severity mode (B4 = 34.0% Ethylene, B5 = 13.6% Propylene): Severity P/E Ratio E4 drops from 0.500 to 0.400, boosting Ethylene E2 to 40.80 t/hr while sacrificing 2.28 t/hr of Propylene E3 (down to 16.32 t/hr)!
=IF(ISTEXT(E4), E4, ROUND(B2 * B3, 2))Try the example
Use the original values or change them to test your understanding.