Browsing by Author "Suominen, Laura"

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Bioetanolin valmistus synteesikaasusta
(2013-04-30) Suominen, Laura
Kemiantekniikan korkeakoulu | Bachelor's thesis
Impurity removal of vacuum gas oil
(2016-06-14) Suominen, Laura
Kemian tekniikan korkeakoulu | Master's thesis
Generally, vacuum gas oil (VGO) is defined as a petroleum distillate boiling between 350 and 550 °C at 1 atm. VGO is produced from atmospheric residue in a vacuum distillation unit. The amount and nature of impurities in VGO depend greatly on the origin of the crude oil but the distillation range of the petroleum cut also affects the impurity level. Typical impurities are nitrogen, sulphur and metals such as nickel, vanadium and iron. As crude oil typically has a large excess of heavy cuts and an insufficient amount of light cuts and middle distillates, the heaviest cuts need to be converted into lighter products. Before VGO is converted into more valuable lighter products, it is fed to a catalytic hydrodesulphurization (HDS) process to reduce the sulphur levels. However, the impurities present in VGO lead to deactivation of HDS catalyst. Therefore, an effective impurity removal method prior to HDS process would extend the catalyst lifetime and reduce refinery downtime. The impurity removal methods discussed in this thesis are solvent deasphalting, demetallization by acids, phosphorous compounds and supercritical water, and photochemical denitrogenation and desulphurization. Based on the advantages and disadvantages of the methods, demetallization using phosphorous compounds was chosen to be preliminarily designed in the applied part of the thesis. The VGO feed contained 10 ppm of metal impurities. When no demetallization pretreatment was applied, the HDS catalyst lifetime was only 8 weeks. In the demetallization process phosphoric acid was used as the phosphorous compound. The acid was mixed with the VGO in a static mixer and the phases were separated in three parallel decanters. Phosphoric acid reduced the concentration of Ni, V and Fe and the removal rates used in the calculations were 32 w%, 23 w% and 22 w%, respectively. As a result, the HDS catalyst lifetime was 9 weeks. The catalyst lifetime was extended only by one week and the demetallization process was not profitable with current costs.