Industrial performance evaluation of air pre-heater integration in visbreaker furnaces for enhanced energy efficiency

Abstract

Abstract

Industrial fired heaters are major energy consumers in petroleum refineries, making recovery of high-temperature flue-gas heat an important route for reducing fuel demand. This study evaluates the industrial performance of a recuperative air preheater (APH) integrated with a visbreaker furnace using plant operating data and a Python-based steady-state energy-balance model. Following installation, combustion-air temperature increased from approximately 35 °C to 180–220 °C, while stack-gas temperature decreased from 280–300 °C to 190–210 °C. Because feed throughput increased from 70,000 to 93,920 kg h⁻¹ and feed inlet temperature increased from 240 to 295 °C, a duty-normalized comparison was performed; the resulting sensible-duty proxy differed by only 0.63%. The measured fuel-gas reduction was 498.95 kg h⁻¹, compared with a model-predicted saving of 529.34 kg h⁻¹. Furnace thermal efficiency increased from 78.5% to 82.3%, corresponding to 3.8 percentage points. Annualization at 8000 operating h yr⁻¹ gives an estimated fuel saving of 3991.6 t yr⁻¹ and, using an assumed fuel-gas value of ₹50 kg⁻¹, a potential fuel-cost saving of ₹19.96 crore yr⁻¹. The corresponding fuel-composition-based estimate is approximately 10,922 t CO₂ yr⁻¹ avoided. An acid-dew-point screening assessment gave 139.2 °C, with a 25.8 °C margin at a minimum cold-end temperature of 165 °C. These results demonstrate the potential of APH integration for improving furnace energy utilization while highlighting the importance of duty normalization, operating variability and long-term plant measurements.