The service time of an industrial cracker is strongly dependent on the long-term coking behavior and microstructure stability of the reactor coil alloy. Super alloys are known to withstand temperatures up to even 1400 K. In this work, several commercially available alloys have been first exposed to a long term oxidation at 1423 K for 500 h, so-called metallurgic aging. Subsequently, their coking behavior was evaluated in situ in a thermogravimetric setup under ethane steam cracking conditions (Tgasphase = 1173 K, Ptot = 0.1 MPa, XC2H6 = 70%, continuous addition of 41 ppmw S/HC of DMDS, dilution δ = 0.33 kgH2O/kgHC) and compared with their unaged coking behavior. The tested samples were also examined using scanning electron microscopy and energy diffractive X-ray for surface and cross-section analysis. The alloys characterized by increased Cr-Ni content or the addition of Al showed improved stability against bulk oxidation and anti-coking behavior after application of metallurgic aging due to the formation of more stable oxides on the top surface.

The selection of the reactor material with the lowest coking tendency can result in substantial economic benefits for the steam cracking process. One of the remaining unresolved points of discussion is what the influence is of sulfur addition, in particular dimethyl disulfide (DMDS) on various steam cracking reactor alloys with varying Ni-Cr content. To shine some new light on this topic, an extensive thermogravimetric study was performed in a jet stirred reactor set up (JSR) evaluating on-line the coking behavior of four Ni-Cr-Fe alloys under industrially relevant ethane cracking conditions. For each material, the effect of pre-oxidation/pretreatment with and without the presence of DMDS was evaluated, with as objective to minimize the materials coking tendency. The coking rates show that an increased Ni-Cr content of the material improves the coking rates by a factor 2 or more under the studied process conditions. By continuously feeding DMDS, all non Al-containing alloys indicate 7 times higher coking rates than the Blank runs, while the carbon oxide(s) formation is suppressed by a factor 5. In comparison to continuous addition and presulfiding with DMDS, labelled as 'CA+PreS' experiments, the Al-containing alloy outperforms itself significantly when pre-oxidized at 1223 2 K by 50 % in terms of coking rates. The results indicate that Al addition to Ni-Cr-Fe alloys improves their anti-coking performance, provided that the pre-oxidation temperature is higher than for materials without Al. The overall results from coking rates and off-line SEM and EDX analysis for the coked coupons showed an outstanding oxidation homogeneity for the 40/48 Cr-Ni alloy, which was better than the Al-containing alloy at lower pre-oxidation temperatures.

Sugarcane bagasse ash (SBA) is a solid waste obtained from the boilers of sugar factories after the combustion of sugarcane bagasse. Sugarcane bagasse ash mainly consists of amorphous silica and can be used as a supplementary cementitious material in the production of concrete. In the present study, the physical properties of sugarcane bagasse ash, namely, particle size distribution, surface area, specific gravity, morphology and chemical properties like elemental composition of SBA and ordinary Portland cement (OPC) have been investigated. The microstructural observations were made using Scanning Electron Microscope (SEM). Elemental compositions were analyzed and images coupled to microanalysis by Energy dispersive spectroscopy (EDS). The microstructure observations and elemental characterization of cement concrete matrix was also carried out after 28 days of curing. Blended cement concrete specimens were prepared using SBA up to 30% in regular intervals of 10% by weight of pure Portland cement, coarse and fine aggregate, tap water and superplastisizer. SEM results indicates that substitution of SBA particles by Portland cement produces dense matrix as compared to control mix and EDS analysis shows fluctuations in calcium and silica concentrations as the cement replacement level increases in the blended cement concrete.

In conventional steam cracking feedstocks, contaminants such as sulfur, phosphine, and heavy metal components, present in trace levels, are believed to affect coke formation on high temperature alloys. To gain an understanding of the role of phosphine coking rates on 25/35, CrNi and Al-containing reactor materials were determined in a plug flow reactor during cracking of a propane feedstock doped with ppb levels of PH3 in the presence of DMDS. The presence of phosphine decreased the asymptotic coking rates by more than 20%, while it had a smaller influence on the catalytic coking rate. The coking rate was more severely reduced for the 25/35 CrNi alloy in comparison to the Al-containing alloy. The ppm levels of phosphine did not affect the olefin yields nor the production of undesired carbon monoxide. The morphology of the coked alloys were studied using an off-line Scanning Electron Microscope with Energy Dispersive X-ray detector (SEM with EDX) images of coked coupons. Two types of coke morphology are observed, i.e., filamentous coke with DMDS as an additive and globular coke in the presence of phosphine. The effect of phosphine on the material has a positive impact on the oxide scale homogeneity of 25/35 CrNi alloy, whereas the Al-containing alloy remained unchanged.