Recovering steam cracker efficiency
Robotic cleaning of convection sections, combined with thermal efficiency evaluations, can restore heat transfer, lower fuel demand, and help operators
Scott Donson IGS TubeTech
S team crackers (SCs) are among the most energy-in- tensive assets in olefins production, where even small losses in thermal efficiency can have a signifi - cant impact on operating margin. As fuel costs, emissions targets, and competitive pressures continue to rise, avoida - ble energy losses are increasingly difficult to justify. One of the most common causes is fouling within the convection section, where deposits on the outside of finned tubes reduce heat recovery, raise stack temperature, and increase firing demand. Since fouling develops gradually, declining performance is often accepted as a normal part of operation. However, across multiple furnaces and operat - ing cycles, the associated fuel penalties and lost efficiency can be substantial. Against this backdrop, the measurable commercial impact of convection section fouling is examined, explaining how thermal performance data can be used to optimise cleaning schedules. Field examples demonstrate how robotic clean - ing technology restores efficiency and reduces operating costs. How fouling reduces heat recovery Steam cracker furnaces contain three broad heat transfer areas: the radiant section, the convection section, and the transfer line exchanger. In the radiant section and transfer line exchanger, coke formation is an expected byproduct of cracking reactions. It is closely linked to run length, tube metal temperature, and decoking requirements. The convection section has a particularly important role in furnace thermal performance because this is where useful heat is recovered from the flue gas. In the furnace convection section, ash, combustion-related deposits, and other partic - ulate matter accumulate on the outside of finned tubes. As fouling builds, heat transfer declines. Less heat is recovered into the process, and the furnace must compensate to main - tain operating conditions. The consequences can include: • Rising stack temperature. • Lower recovered duty. • Increased firing requirement. • Higher fuel consumption. • Reduced steam production or lower superheat. • Higher emissions. • Reduced operating flexibility. • Greater pressure on maintenance and turnaround planning. These inefficiencies make convection section heat trans - fer a performance issue. Cleaning should therefore be
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assessed by recovered duty and operating value, not visual cleanliness alone. Quantifying the cost of lost efficiency The commercial impact of fouling depends on furnace duty, fuel price, operating hours, plant configuration, and fouling severity. The financial impact can be considered across five main areas: • Maintenance costs: Deposit build-up can increase planned and unplanned maintenance activity, adding cost and placing pressure on turnaround schedules. • Energy costs: When heat transfer efficiency declines, the plant may require additional fuel firing to maintain operat - ing conditions. • Yield: Thermal performance loss can affect feedstock con - version and reduce the value recovered from the process. • Annual operating rate: Fouling-related constraints, slow - downs, or unplanned downtime can cause the plant to fall behind its production target. Each of these areas is connected. A fouled convection bank may cost more to operate, recover less useful duty, increase maintenance demand, and create avoidable con - straints elsewhere in the plant. Fuel is often the easiest loss to quantify, making it a clear starting point for assessing the commercial case for cleaning. A typical case, as shown in Figure 1 , is a six-furnace steam cracker unit operating for 324 days per year. If each Figure 1 Cumulative fuel savings from robotic cleaning of a fouled convection bank. Basis: six steam cracker furnaces operating 324 days per year; furnace fired duty: approxi - mately 50 MW per furnace; efficiency loss: 2.0%; fuel cost: $40/MWh¹
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PTQ Q4 2026
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