A simplified kinetic model for continuous hydrotreating of HTL biocrude
Authors
Vipin Manmohandas, Hetune ; De Santos Brandao, Joao Guilherme
Term
4. term
Education
Publication year
2020
Submitted on
2020-05-29
Pages
107
Abstract
Dette projekt modellerer to pakkede leje‑reaktorer til hydrobehandling som led i en to‑trins opgradering af biokrude fremstillet ved hydrotermisk forvæskning (HTL). Målet er at estimere de kinetiske parametre (reaktionshastigheder) for, hvor hurtigt ilt (deoxygenering) og kvælstof (denitrogenering) fjernes, så olien bliver mere brændstoflignende. For at gøre den komplekse kemi håndterbar blev alle ilt‑ og kvælstofholdige forbindelser hver repræsenteret ved én samlet (“lumpet”) komponent, der svarer til det samlede O‑ og N‑indhold i biokruden. Modellen beskrev resultaterne godt op til 370°C, men under mere barske betingelser gav den betydelige fejl for kvælstof. For at imødegå dette blev kvælstof opdelt i to grupper med forskellig reaktivitet (“høj” og “lav”) i en optimeret model. Arbejdet omfattede også hydrobehandlingsforsøg med HTL‑biokrude fra miscanthus ved 250°C, 300°C og 350°C. Denne biokrude viste høj ustabilitet; ved 350°C dominerede koksdannelse (kulstofaflejring), hvilket motiverede undersøgelsen af en to‑trins hydrobehandling.
This thesis models two packed‑bed hydrotreating reactors as part of a two‑stage upgrading of biocrude produced by hydrothermal liquefaction (HTL). The goal is to estimate kinetic parameters (reaction rates) for removing oxygen (deoxygenation) and nitrogen (denitrogenation), making the oil more fuel‑like. To keep the complex chemistry manageable, all oxygen‑ and nitrogen‑containing compounds were each represented by a single lumped component matching the total O and N content in the biocrude. The model fit was good up to 370°C, but at harsher conditions it showed considerable errors for nitrogen. To address this, nitrogen was split into two groups with different reactivity (“high” and “low”) in an optimized model. The study also included hydrotreating experiments on HTL miscanthus biocrude at 250°C, 300°C, and 350°C. This biocrude was highly unstable; at 350°C coking (carbon deposition) dominated, which motivated investigating a two‑stage hydrotreating approach.
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