Chlorine and sulphur induced high temperature corrosion in a thermal cracking reactor for anthropogenic resources

Alexander Schmid

Research output: ThesisDoctoral Thesis

Abstract

A durable reactor material for a thermal cracking process for anthropogenic resources and post-consumer plastics should be selected within this PhD thesis. A bench scale pilot plant was already built in a previous PhD thesis, and was used for first tests. Additionally alloys P9 steel, 1.4462, 1.4841, Alloy 800HT, Alloy 600 and Hastelloy C-276 were tested under conditions simulating a thermal cracking process. Tests were performed at 480, 580 and 680 °C for 24, 72 and 240 h in a gas atmosphere containing 3, vol.% HCl, 200 ppm H2S, CO, CO2, and N2. It represented the partial pressures of chlorine, sulphur and oxygen, which were present in the reactor for a thermal cracking process for anthropogenic resources. The software FactSage 7.0 and PetroSim were used to calculate the composition of the artificial gas mixture. Reactor pipes of the pilot plant were investigated by means of metallography, SEM/EDX and STEM/EDX. In order to investigate possible carburization of the metal during the process, coked reactor pipes were heat treated for 1600 h, at 680 °C. This should simulate long-term operations. For investigations with the laboratory equipment flat samples were prepared. In order to achieve a uniform surface the samples were ground to 1000 grit SiC paper. After corrosion experiments the samples were analyzed by metallography, SEM/EDX and XRD. Additionally the mass loss of the samples during the experiment was evaluated. No carburization of the reactor material was observed till 1600 h. Detected M23C6 carbides precipitations formed due to the already alloyed carbon in the steel. But, σ-Phase formation was detected after 1600 h. After the tests with the laboratory equipment, samples showed a multilayered surface structure of corrosion products. The outer layer consisted mainly of chromium sulphide, followed by a chromium oxide layer. Below these two layers a layer containing chlorine was detected. This general structure of corrosion products was detected at all tested materials. The FeCl2 was not observed on the samples, but as colorless crystals at the colder parts of the testing equipment. At high testing temperatures the mass loss decreased with increasing nickel content. However, at lower temperatures this effect changed entirely, so that at 480 °C 1.7386 and 2.4816 showed nearly the same mass loss.
Translated title of the contributionChlor und Schwefel induzierte Hochtemperaturkorrosion in einem thermischen Crackreaktor für anthropogene Ressourcen
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Mori, Gregor Karl, Assessor A (internal)
  • Lehner, Markus, Assessor B (internal)
Publication statusPublished - 2018

Bibliographical note

embargoed until 18-06-2023

Keywords

  • High temperature corrosion
  • HCl
  • H2S
  • steel
  • nickel based alloy

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