PTQ Q4 2026 Issue

Thermal efficiency evaluation results for a South American ethylene furnace⁴

Metric

Result

Stack temperature reduction Fuel savings/steam gain Estimated annual savings CO₂ emissions reduction Payback period (fuel gas savings/ steam gain scenario)

130°C/234°F 2.2 MW (7.2%)

$900,000 3,500 TPA

40 days

Table 2

heaviest accumulation could be seen in the lower tube banks. Convection section fouling had become the primary cause of reduced heat transfer and declining furnace efficiency. However, the operator needed to confirm whether cleaning would deliver sufficient operational and financial return. Solution Using plant operating data, IGS technicians completed a thermal efficiency evaluation to predict the benefits of con - vection section cleaning, including fuel savings, efficiency improvement, ROI, and payback. The study showed that the project would deliver a strong operational and financial return. Robotic high-pressure water jetting was then deployed to access the affected tube banks and remove deposits from areas that had been difficult to treat effectively using previous methods. The remotely operated technology delivered 95% clean- ing coverage, with no personnel entry into the convection section. Real-time cleaning verification was used during the work, and the system achieved multi-level access to all accessible tube banks. Cleaning was completed in four shifts with zero incidents. Results Following cleaning, stack temperature reduced from 416°C before the turnaround to 286°C, a reduction of 130°C. The project delivered a fuel savings/steam gain of 2.2 MW, equivalent to a 7.2% efficiency improvement, and estimated annual savings of $900,000. CO₂ emissions were reduced by 3,500 tonnes per annum (tpa), and the payback period for the fuel gas savings/steam gain scenario was 40 days. The remotely operated system achieved greater fouling removal than previous cleaning methods used on the fur- nace. The stack temperature reduction was also reported as the largest efficiency improvement recorded on the fur - nace in more than 30 years. Technical significance The project showed how thermal efficiency evaluation can be used before cleaning to quantify expected recovery, and after cleaning to validate the result (see Table 2 ). For oper- ators, this provides a practical model for using plant data to support cleaning decisions. The evaluation established the expected return before the outage, while the completed work verified the value of restored heat transfer through

Figure 3 Before and after robotic convection section clean- ing, showing deposit removal from finned tube surfaces3

• Recommended cleaning interval. • Post-clean performance comparison.

This information allows operators to answer three prac- tical questions: what value is being lost, what value can be recovered, and when does cleaning make financial sense? Post-clean evaluation is equally important. It allows the operator to verify the effect of the intervention, measure the recovered performance, and track the rate at which fouling returns. Over time, this creates a reliable, data-led framework for planning the next cleaning interval. Before-and-after imagery (see Figure 3 ) can support this process by showing deposit removal from finned tube sur - faces. However, visual evidence should be assessed along- side operating data. Case Study 2: Quantifying recovered duty and fuel savings Background An SRT-IV pyrolysis furnace at a large South American ethylene facility had experienced a sustained increase in stack temperature over several years. The furnace convec- tion section comprises four tube coils, each approximately 10.3m (33ft) long, recovering heat from flue gas before it exits the furnace. Ahead of a planned turnaround in 2025, operating data showed that stack temperature had been increasing by approximately 20°C per year, reaching 416°C before the outage. The trend indicated declining heat recovery and increasing fuel demand. Challenge An inspection confirmed deposits embedded between finned tubes, hard scale on bare tubes, and fouling across all four convection coils. According to the author, the

PTQ Q4 2026