(137a) Next-Generation Inert and Catalytic Internal Coil Coatings for High Severity Cracking and External Tubular Coatings for Hydrogen Firing

The manufacture of olefins by steam hydrocarbon pyrolysis now exceeds 350 million tonnes annually, in more than 3,000 furnaces globally. This requires ~5 billion GJ/year, mostly from natural gas firing of furnaces, with consequent Greenhouse Gas (GHG) emissions of ~400 MMT CO2e. Coke formation necessitates furnace shutdown for decoking every 20-60 days, and impacts both energy efficiency and productivity. From a materials perspective, the process is extremely demanding due to its use of high temperatures and cyclic thermal, thermo-mechanical, oxidizing and carburizing corrosive loads on furnace coils. Quantiam has advanced a suite of next-generation coating technologies which enable: (i) increased gains in productivity through coking inertness; (ii) anti-coking gasification functionality; (iii) increased heat transfer; (iv) energy reduction from internal profiles of coatings; and (v) a further step-change in emissions reductions by enabling high levels of hydrogen firing of cracker furnaces.

Significant advancements in anti-coking technology have been made over the last 30 years with development of a wide range of products including chemical additives, coatings inert to filamentous (catalytic) coke-make, catalytic coatings which gasify coke to CO/CO₂, and new alumina-forming base steel alloys. Customer uptake of these technologies has been mixed, with greatest commercial success in lower-severity furnaces with end-of-run tube metal temperatures typically < 1090 °C (1,994 ^oF) and well controlled decoking. Best-in-class performance has been achieved with coatings such as the CAMOL^TM technology when properly utilized within their defined operating envelopes. These have reduced cracker energy consumption by up to 6% and increased run lengths, achieving over 500 days in ethane cracking and 150 days in naphtha cracking, over a full normal life cycle of the coated coils (4 to 7+ years). The coated products can also reduce the need for sulfur additions and are projected to increase coil life. Commercial success in higher severity furnaces has been more limited as these coating and surface technologies currently struggle to survive a full life cycle at EOR-TMTs that can exceed 1,130 °C (2,066 ^oF) and/or are exposed to aggressive oxygen-rich decoking cycles.

Quantiam has conducted five end-of-life coil autopsies, and the results strongly suggest that using EOR-TMTs as a metric for engineering coating properties and operating envelopes is of limited use in predicting coating benefits lifetime. Although only external TMTs are able to be measured, the concentration of key carbide species as a function of their position across the tube wall has allow us to deduce the maximum temperature experienced by the tube innerwall surface region. The formation temperatures of these species, as assigned by an expert third party, allow their use as ‘thermal signatures’ within +/- 25 ^oC (77 °F) against calibrated standards. This has shown that the tube innerwall topmost 2.5 mm (0.10 in) can be exposed over its life to temperatures >70 °C (158 °F) above measured external wall TMTs. This is unlikely to result from the endothermic cracking process or steam-based decoking, but rather from exothermic gasification of localized residual coke deposits within the coil if the air content is increased too rapidly during decoking of furnaces. This creates high temperature excursions on the innerwall’s surface. If the coating is engineered only to the expected EOR-TMTs with a modest buffer, this excess internal surface temperature can be catastrophic because although the total time of decoking is typically <10% of coil lifetime, coating materials degradation rate is highly nonlinear with increasing temperature. This results in a drastically shortened coating benefits lifetime. Other degradation processes must also be considered, for example, carburization, oxidation, sulfidation and erosive wear, however the thermal and thermo-mechanical excursions on the inner wall appear to be the dominant factors which define the lifetime of key coating properties such as anti-coking benefits.

These autopsy findings have driven Quantiam’s advancement of three new coating technologies targeting higher severity furnaces, with the first field trial installed in 2024. These new products are:

1. Inert Coating for Higher Temperature Service: A world-first intrinsically inert coating for mitigating filamentous coke make - inert-1300 High Temperature (i-1300HT). The i-1300HT matrix microstructure is inert to filamentous coke-make without the need for generating or repairing a protective (inert) surface oxide scale. It has high temperature stability and can withstand internal tube wall temperatures of ~1,150 °C (2,102 °F), and, in the event of coating disruption caused by thermal excursion beyond the coating’s operating envelope, provides additional protection as it cannot form any species that catalyze filamentous coke-make. In addition to its intrinsic anti-coking properties, this coating is also available as an MnO-former and an alumina-former. Because of their high oxidation resistance, all three versions of this coating can also be used as external tubular coatings for hydrogen firing of furnaces at high levels.

2. Inert Coating for Lower Temperature Service: A next-generation alumina-forming inert coating - inert-1300 Low Temperature (i-1300LT). This coating has ~30 wt.% aluminum which ties up filamentous coke formers such as iron and nickel in the coating matrix as very stable aluminide phases, preventing their migration into the topmost innerwall surface region. This creates a world-first diffusion barrier with attractive chemical specificity that is stable to temperatures at least 50 °C (122 ^oF) higher than all prior coating technologies, that is, at least 1,100 °C (2,012 °F). Process requirements for formation of a contiguous and dense alumina surface layer are materially reduced compared to current coating state-of-the-art. The weldability of the coated steel remains high.

3. Multi-Functional Catalytic Coke-gasifying Coating: A next generation multi-function catalytic coke-gasifying coating (Super Gasifier SGX). As well as providing inertness to filamentous coke-make, this coating provides two pathways to gasify amorphous coke deposited from the gas phase. The dual function catalysts can utilize both: (i) process steam as a source of oxygen to gasify the coke to carbon monoxide and/or carbon dioxide; and/or (ii) the abundant hydrogen resulting from cracking to gasify the coke to methane.

A comparative assessment of both laboratory results and interim field trial results from the installation of the i-1300 coating will be provided against field learnings and successes to-date in lower severity furnaces. The new i-1300 and SGX anti-coking coatings target to achieve similar or better anti-coking and energy and emissions reduction benefits in higher severity furnaces which have higher operating severity and significantly higher coke-make.