Effect Of Aromatic Heavy Gas Oil On Residue Hydrotreating Reactions

A Residue Hydrotreating(RHT) - Residue Fluid Catalytic Cracking (RFCC) integrally combined process (RJCP) is proposed. The process is characterized with that heavy cycle oil(HCO) of RFCC is cycled to RHT unit instead of RFCC unit and mixed into RHT feed vacuum residue (VR) and co-hydrogenated with VR to produce RFCC feed. In RLCP, hydrogen content of HCO increases and the quality of RFCC feed is improved, which result in a higher yield of light oil and a lower yield of coke in RFCC unit. In conventional .RHT - RFCC combined process, I-ICO is cycled to RFCC unit itself and the high content of condensed aromatic in HCO leads to a high yield of coke and a low yield of light oil. Obviously RICP can bring on more profit to RFCC unit than conventional RHT - RFCC combined process. So how will mixing HCO into RHT feed residue affect RHT reactions becomes a key issue.Four kinds of heavy gas oils: HCO, coke gas oil (CGO), vacuum gas oil (VGO) and paraffin wax (WAX) were adopted to study the effects of mixing various heavy gas oil into RHT feed VR on RHT reactions. Experiments were carried out on a dual-reactor pilot. The ratio of heavy gas oil to VR was 1:4 and the space velocity of the blended feed was 25% higher than the space velocity of VR feed to keep the equal processing capacity of VR.Experiments show that mixing heavy gas oil into feed VR can decrease the sulphur(S), Conradson carbon residue(CCR) and asphaltene content in product oil significantly, and the hydrodesulphurization (lIDS), deCCR,deasphaltene reaction rates increase greatly. The S,CCR and asphaltene conversion increases even in a higher space velocity. Mixing certain ratio heavy gas oil into RHT feed VR is a good way to prompt HDS, deCCR anddeasphaltene reactions.Mixing heavy gas oil into RHT feed VR can enhance the hydrodemetalization (HDM) reaction rates, but different heavy gas oil brings forth different effect. Heavy gas oil with high aromaticity can improve HDM reaction greatly while highly saturated oil will slowdown the HDM reaction. To explain the result, a new asphaltene model is proposed, in which the size of asphaltene particle changes with the aromaticity of blended oil. High aromaticity of blended oil results in a smaller size of asphaltene particle and promotes the diffusion of asphaltene. Thus HDM reaction rate becomes higher. High saturation of blended oil leads to larger size of asphaltene and slowdowns the HDM reaction.Mixing heavy gas oil into RHT feed VR can help depress the formation of coke on hydrotreating catalysts. Coke on catalysts was determined and it was much lower in experiments using blended feed than VR feed alone. Lower quantity of coke helps catalysts to keep a high LIDS activity.Heavy gas oil with high aromaticity, such as HCO, can improve both LIDS and HDM activities and therefore is the most suitable oil as heavy gas oil to blend into RHT feed VR, which founds the theory base for RICP.RICP was tested both in RHT aspect and in RFCC aspect. As to RHT, experiments of mixing 1O%,20% nd 35% HCO into feed VR were carried out respectively. Experiments show that mixing HCO into VR can promote HDS, HDM, deCCR and deasphaltene reactions greatly and reactions rates increase with the percentage of HCO increasing. As a result, 5, CCR and asphaltene conversion increases and conversion of metal keeps constant. The 5, metal, CCR and asphaltene content in product oil decreases significantly.Mixing HCO into RHT feed VR can depress the formation ofcoke on RHT catalyst. The more HCO mixed into yR. the lower quantity of the coke on catalyst. The vanadium distribution along radius of catalyst can also be improved by mixing HCO into VR, which helps catalyst hold more metal and extend the operating cycle life of RHT unit.RICP benefits RFCC unit greatly, too. RICP can improve quality of RFCC feed. As a result, the total yield of LPG, gasoline and LCO increases by 3-5%(wt), RFCC heavy oil decreases by 2-3%(wt), and coke on RFCC catalyst decreases by about 1 .5%(wt). The ris...