Anticoking

Metal alloys are susceptible to hydrocarbon-based fluids at elevated temperatures, leading to buildup of coke residue, which is a costly problem faced by the energy and chemicals industries for many decades. Now, Cerablak® UTF is showing great promise to solve this age-old problem. Customer-validated tests prove limiting coke buildup on coated metal surfaces by serving as a thermally-stable diffusion barrier to prevent sulfidation and carburization, a precursor to coke nucleation.

Fouling Reduction is Critical

Hydrocarbon fluid processing involves the transport of heavy oil through multiple temperatures, pressures, and steam-containing processing stages. Plaque formation on process pipe walls by certain species is a type of fouling, leading to increased resistance and corrosion. In turn, this causes increased energy and pumping requirements while reducing product throughput and pipe lifetime. When high temperatures are present, carbon-based fouling often results in the formation of crystalline carbon deposits with increased adhesion and thermal stability, known as coking.

Coke formation on process pipe inner diameters is a substantial issue, as coke is a thermal insulator and is not easily removed due to strong chemical bonding with metal surfaces. As coke deposits accumulate in pipe inner diameters, the heat transferred is reduced, thus reducing throughput. Eventually, the process is stopped and the pipe cleaned for coke removal, requiring substantial downtime—an expense that can cripple profit margins.

Cerablak® UTF Limits Coke Buildup

Cerablak® UTF mitigates the formation of coke on process pipe inner diameter (ID) walls by serving as an inert barrier between heated process fluids and the underlying metal substrate, and by planarizing surfaces for decreased particle adhesion. Metal surfaces are highly reactive with species (metallic and non-metallic contaminants) in the fluid—a near-hermetic quality gas barrier is required that is thermally stable and can withstand thermal cycling conditions. Cerablak® UTF has all the ideal attributes along with favorable processing schemes for both cost effectiveness and throughput. Cerablak® UTF can be deposited on internal surfaces of pipes of both small and large diameters (100 µm to 6”) of short to very long lengths (>1000 ft), and a robust deposition process has been developed to address a range of surface morphologies and surface chemistries.

The image shown compares an uncoated and Cerablak™-treated 304 stainless steel tube tested in a petrochemical production environment. The addition of Cerablak® UTF to the tube inner diameter served to substantially prevent coking on the inner wall. This improvement led to increased fluid flow, retention of good heat transfer, and higher product throughput.