Inductively Heated Electro-Balance Unit for Studying Coke Formation and Carburization for High-Temperature Alloys during Steam Cracking

Abstract

Steam cracking coils are pushed more and more to their limits during the cracking/decoking cycles, going in some cases to metal temperatures beyond 1100 °C. To accurately mimic actual steam cracking conditions within various parts of an industrial coil and to delve deeper into the alloy behavior during the process, we introduce the so-called inductively heated electro-balance setup (IHEB), which allows conducting steam cracking tests on representative coupons produced from actual coils. The IHEB unit utilizes both inductive and radiative heating to independently control coil surface and gas phase temperatures to mimic the conditions endured in each part of a real steam-cracking coil. As a proof of concept, a study is conducted on coupons made of a commercial heat-resistant Ni-based alloy. The steam cracking test protocol is designed so that the coupon undergoes the same treatment as it would in an industrial furnace. Throughout the test, a magnetic suspension balance (MSB) monitors and measures variations in coupon weight in real time. This enables in situ interpretation of catalytic and asymptotic coking rates over multiple coking/decoking cycles. The microstructure and chemical composition of the coupons are analyzed using mainly scanning electron microscopy and energy-dispersive X-ray spectrometry (SEM/EDX), and transmission electron microscopy (TEM). Results show that the treated coupons exhibit similar microstructures to those observed in real industrial cracking coils, demonstrating that the IHEB unit can provide realistic information about the stability or degradation of high-temperature alloys under the influence of the steam cracking process.