الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 140 |  |  |
| | | from | 140 | | |
Abstract
The progressive depletion and rising cost of high quality crudes created a need for a way to convert heavy oils and residues to high-value light products. Upgrading technologies for heavy feed stocks and residues depend on two ways : carbon rejection like (deasphalting , visbreaking and coking) or hydrogen addition like (hydrotreating , hydrovisbreaking and hydrocracking ). The residues usually contain considerable amounts of asphaltenes. The high asphaltene contents would decrease the efficiency of the refining processes. Moreover, the high distribution of hetero-atoms (e.g. sulfur and nitrogen) in the asphaltene causes some problems such as pollution, corrosion, and catalyst poisoning.
The refineries used to prefer carbon rejection processes for economical point of view , however this way of thinking must be changed, as it produces more coke and less liquid . The main objective of this contribution is to upgrade the crude oil atmospheric residue to maximize the production of the light products, and to assure that catalytic upgrading of residues is more convenient solution nowadays than before, after the great improvements of catalysts.
In the present work, the data presented in (Esmaeel et al. 2015) were used to produce our model ,using Design Expert Software , that can predict the yield of lumps produced from the hydrotreating of the atmospheric residue . Five correlations have been introduced to predict the yield of the products by adjusting the operating variables ( temperature , hydrogen pressure and liquid hourly space velocity ). The introduced correlations were validated statistically by analysis of variance (ANOVA). Then , the optimum conditions for the process were calculated using Lingo software and were found to be 420oC , 100 bar , 0.3 h-1. After that , a comparison between the yields from thermal upgrading methods represented by correlation models of (Ghashghaee 2015), and catalytic upgrading methods represented by our correlation models for hydrotreating of atmospheric residue was done. The results show with no doubt that hydrotreating of the atmospheric residue produces more high-value liquid yields.
We may make benefits from a combination between thermal and catalytic upgrading technologies, if the thermal unit that has much lower cost is already installed in the refinery. We may use a visbreaking or hydrovisbreaking unit before hydrotreating to maximize liquid yield and reduce the viscosity of the residue, so the diffusion of feed molecules into the micro-pores of the catalysts will be easier. The results showed that when thermal upgrading technology is used as a pretreatment before hydrotreating, to minimize gas & coke, then we don’t have the two options for temperature and time ( higher temperature with shorter time & lower temperature with longer time), only operation at low residence time with moderate to high temperatures would be the preferred choice.