Post-project benefit analysis In many cases, the stack temperature is determined to be a key performance indicator to identify and quantify the ben- efit after cleaning (see Figure 6) . To illustrate the benefits, a recent project referred to as Project X is reviewed. On com- pletion of Project X, a sizeable benefit of 40°C in stack tem - perature reduction was achieved. The plant also reported an average increase in overall fuel efficiency from 89.5% to 91.5%, leading to 2 MW less heat loss to the stack under the same operating capacity. The facility reported a pay - back period of less than four months. New data two years after cleaning A balanced heat distribution between sections is crucial in coking-sensitive services. Keeping the convection sec - tion surface clean not only helps to save fuel and increase steam generation but also positively influences the steam cracking process. The achieved benefit on Project X was 16,000 MWh/year fuel savings and 2,500 tons annual CO₂ reduction (fuel is CH₄/H₂ mixture). After almost two years, the client reported a slight ele - vation in stack temperature of 10°C and a stable efficiency increase of 1.5%. The next cleaning is anticipated to take place after six years to reinstate the efficiency. To ensure the obtained benefit is long-lasting, IGS also recommends a combination of the Tube Tech ROV cleaning with Cetek’s proprietary ceramic refractory coatings to protect and Figure 2 The external casing in this instance is cut to create 350mm openings
Figure 3 Plastic tarpaulin at the bottom of the convection section
Figure 4 The ROV on the top of the bundle
encapsulate the ceramic fibre and stop refractory deterio - ration and new fouling formation on the outside surface of the convection tubes. ROV cleaning: ethylene furnace IGS was provided with furnace configuration and process parameters for each bank of the convection section of this referenced ethylene furnace. The objective was to keep the process duty and, thus, the coil outlet temperature the same and compare scenarios before and after (see Table 1 ).
Figure 5a Before cleaning
Figure 5b After cleaning
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