Abstract
Alumina-based coatings have been claimed as being an advantageous modification in industrial ethylene furnaces. In this work, on-line experimentally measured coking rates of a commercial coating (CoatAlloy™) have pointed out its superiority compared to an uncoated reference material in an electrobalance set-up. Additionally, the effects of presulfiding with 500 ppmw DMDS per H2O, continuous addition of 41 ppmw S per HC of DMDS, and a combination thereof were evaluated during ethane steam cracking under industrially relevant conditions (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, dilution δ = 0.33 kgH2O/kgHC). The examined samples were further evaluated using online thermogravimetry, scanning electron microscopy and energy diffractive X-ray for surface and cross-section analysis together with X-ray photoelectron spectroscopy and wavelength-dispersive X-ray spectroscopy for surface analysis. The passivating coating illustrated a better performance than the reference Ni-Cr Fe-base alloy after application of an improved pretreatment, followed by piddling changes on the product distribution. Presulfiding of the coating affected negatively the observed coking rates in comparison with the reference alloy, so alternative presulfiding and sulfur addition strategies are recommended when using this barrier coating.
Highlights
Industrial steam cracker economics suffer from a notorious enemy: carbon formation
The combination of the mentioned set-up together with chemical composition of the samples are analyzed by means of Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX), using a JEOL analyzer, the experimental procedure gives valuable information on the coke formation phenomenon occurring type JSM-7600F (University of Gent, Zwijnaarde, Belgium), with a Schottky field emission gun as an during steamsource
For the conducted analysis the detection limit is 0.1 to 1 at%, so if nitrogen is present on the surface it should be in relatively low concentrations or it reacts with the surface oxides by removing active oxygen atoms from the surface
Summary
Industrial steam cracker economics suffer from a notorious enemy: carbon formation. On the inner wall of the reactor tubes, carbon filaments are catalytically growing starting from small whiskers leading to a porous layer of interwoven filaments. In all coating technologies no exact details are provided on decoking, pretreatment or Materials 2020, 13, x FOR PEER REVIEW cracking conditions, nor a one-to-one comparison is done, the real impact of one particular performance of CoatAlloyTM at a pilot plant, by measuring the total amount of coke and providing element cokeCO formation is difficult to assess. Essential with all coatings applied on high temperature alloys is if they keep (JSR) set-up under industrially relevant conditions in combination with different pretreatment methods Their initial performance and multiple cracking/decoking cycles are carried out on a jet. This allows for the first time to quantitatively assess the performance of this alumina coating and stirred reactor (JSR) set-up under industrially relevant conditions in combination with different understand—supported byThis a variety Of the optimal conditions for minimizing coking with the presented passivating technology
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