Revamps 2023 Issue

Restoring fired heater furnace heat transfer efficiency

Convection section cleaning of process heaters at an Egyptian facility achieved more than 90% treating of all tube and surface areas

Scott Donson IGS Tube Tech

I nefficient heat transfer in the convection section of a process heater can be readily witnessed by an increase in stack temperature beyond design parameters. The timing and urgency for addressing this situation are related to not only the degree of overheating in the stack but also product demand, economics, and fuel costs. Inspection and technical evaluation For many IGS Tube Tech projects, a site visit is made to complete an inspection of the convection section and col - lect current operating data so an evaluation can be con - ducted. The evaluation determines the baseline operating conditions and estimates the potential project scope and expected benefits. The evaluation is based on calculating the external foul - ing resistance factor for each bundle in the convection sec - tion based on the process data. The factors will be relieved by cleaning, and a further evaluation would determine the post-cleaning performance, based on a constant process - ing duty, for example. The IGS Tube Tech cleaning technol - ogy allows for more than 90% of all the tube and fin surface area to be treated, unlike other more conventional methods, which reach only 20-40% of the tube surfaces, depending on the configuration.

Project planning and execution To perform an effective cleaning using a remotely operated vehicle (ROV) and protect the existing equipment from water exposure, the following five steps are considered for each project (see Figure 1 ): u Creating or using existing access openings (typically 350 x 500mm) to enable placing the ROV on top of each con - w Assembling scaffold at the bottom of the convection sec - tion, allowing the installation of a thick plastic tarpaulin x Protecting refractory walls around convection and radi - ant sections with the tarpaulin (see Figure 3 ) vection bundle (see Figure 2 ) v Isolating the radiant box y Collecting all effluent and debris after cleaning into tar - paulin and moving them safely to ground level in sediment containers. The ROV (see Figure 4 ) is designed to fully clean convec - tion bank coils by penetrating its lance deep between tube rows. The technology removes more than 90% of fouling from all convection bundles (see Figure 5 ). No refractory is damaged since the ROVs are programmed to direct a high-pressure medium to the tubes only. All activities typ - ically can be completed in 72-120 hours (in three to five 12-hour shifts).

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Figure 1 The Tube Tech solution

Revamps 2023