Industrial Energy Efficiency, Steam Distribution & Plant Utilities
Boiler Condensate Return Ratio & Fired-Fuel Savings Formula
Calculate Steam Plant Blended Feedwater Temperature (°C), Sensible Enthalpy Power Saved (kWth), Boiler-Efficiency-Adjusted Fired Fuel Saved (kW), and Cold Makeup Demand (kg/hr).
Divide sensible condensate heat recovery by boiler thermal efficiency to get true burner fuel savings!
Hot steam condensate returning from process heat exchangers at 85°C–95°C is distilled, treated water packed with sensible heat: every 6°C rise in blended boiler feedwater temperature cuts burner fuel input by ~1%! Two audit mistakes distort condensate-piping ROI: forgetting to compute Blended_Feedwater_Temp = f_return * T_cond + (1 - f_return) * T_makeup, and failing to divide Water-Side Sensible Power Q_sens = (m_fw / 3600) * f_return * c_p * (T_cond - T_makeup) by Boiler_Efficiency eta_boiler (since avoiding 1.00 kWth of water heating saves 1 / 0.84 = 1.19 kW of natural gas at the burner)!
Verify on an 18,000 kg/hr Food-Plant Steam Loop—Total_Feedwater_Flow = 18,000 kg/hr (5.0 kg/s, B2), Condensate_Return_Fraction = 0.75 (75.0%, B3), Returned_Condensate_Temp = 90.0 °C (B4), Cold_Makeup_Temp = 18.0 °C (B5), Water_Specific_Heat = 4.20 kJ/(kg·K) (B6), and Boiler_Combustion_Efficiency = 0.84 (84.0%, B7): Blended Tank Temperature reaches 0.75 * 90 + 0.25 * 18 = 72.00 °C (E2), Water-Side Sensible Heat Saved is 5.0 * 0.75 * 4.20 * 72 = 1,134.00 kWth (E3), Burner Fired-Fuel Saved hits 1,134 / 0.84 = 1,350.00 kW (E4), and Cold Makeup Water drops to 4,500.00 kg/hr (E5)!
| Condensate Recovery KPI (18,000 kg/hr FW, 75% Return @ 90°C vs 18°C, 84% Eff) | Formula | Verified Output |
|---|---|---|
| Blended Feedwater Temp (°C) | Return_Frac * T_cond + (1 - Return_Frac) * T_makeup | 72.00 °C (54.00 °C @ 50% Ret) |
| Sensible Heat Saved (kWth) | (FW_kg_hr / 3600) * Return_Frac * Cp * (T_c - T_m) | 1,134.00 kWth (756.00 @ 50%) |
| Fired Burner Fuel Saved (kW) | Sensible_Heat_Saved_kWth / Boiler_Efficiency | 1,350.00 kW (900.00 @ 50%) |
| Cold Makeup Water Required (kg/hr) | FW_kg_hr * (1 - Return_Frac) | 4,500.00 kg/hr (9,000.00 @ 50%) |
Burner-Adjusted Condensate Fuel-Savings Formula
Validate Feedwater_Flow > 0, Return_Fraction in [0, 1], Condensate_Temp > Makeup_Temp >= 0, Water_Cp > 0, and Boiler_Efficiency in (0.50, 1.0]!
=LET(fw_m, B2, rt_f, B3, t_cd, B4, t_mk, B5, cp_w, B6, et_b, B7, IF(OR(fw_m <= 0, rt_f < 0, rt_f > 1, t_cd <= t_mk, t_mk < 0, cp_w <= 0, et_b <= 0.5, et_b > 1), "Invalid Condensate Return Input", LET(q_sn, (fw_m / 3600) * rt_f * cp_w * (t_cd - t_mk), ROUND(q_sn / et_b, 2))))Sewer-Drained Condensate Penalty Check (Set Condensate Return Fraction = 0.50)
Drop Condensate_Return_Fraction B3 from 0.75 to 0.50 (failed steam traps dumping condensate to drain): Blended Temperature E2 falls to 54.00 °C, Fired Fuel Saved E4 drops from 1,350.00 kW to 900.00 kW (450 kW continuous burner penalty!), and Cold Makeup Water E5 doubles to 9,000.00 kg/hr!
=IF(ISTEXT(E4), E4, ROUND(B2 * (1 - B3), 2))Try the example
Use the original values or change them to test your understanding.