Quality of Distillates From Recycle Coking Mohamed Shakir Japanwala Department of Chemical & Materials Eng., University of Alberta
Synthetic Crude Oil Storage and Blending Treated Naphtha and Gas Oils Cokers Bitumen Hydrotreaters Hydrocracking Hydrogen Plant Typical Upgrading Scheme
Liquid Products Coking Reactor Feed Recycle Stream Coke Coking Process
Project Objectives • How reactive are the recycled materials to further cracking and coke formation? • What are the characteristics of the cracked products? • How do the products affect hydrotreating catalysts?
1st Stage 2nd Stage 3rd Stage Gas Gas Gas Residue 2 Residue 3 Feed Residue 1 Reactor Reactor Reactor Vacuum Distillation Vacuum Distillation Vacuum Distillation Distillate 1 Distillate 2 Distillate 3 Coke Coke Coke Experimental Plan Vacuum Distillation Vacuum Distillation Vacuum Distillation
Nitrogen in Quartz Tube Reactor U-Tube Acetone Dry Ice Molten Salt Bath Experimental Apparatus • Reactor Temperature - 530oc • Nitrogen Flowrate - 0.17 L/min (NTP) • Reactor Volume - 60 mL
Characterisation • Analytical methods • NMR functional group analysis • Elemental analysis (C, H, N, S) • Average molecular weight • Micro carbon residue (MCR) • Simulated distillation by gas chromatography • High performance liquid chromatography (HPLC)
Hypothetical Hydrocarbon Molecule 6 • Aromatic Bridgehead C • Protonated Aromatic C • Methyl Group on Aromatic C 5 • Naphthenic CH2 3 2 • CHAIN : CH2 that are atleast g from aromatic or terminal methyl or atleast b to cycloparaffin or branch point 1 4 • Terminal Chain Methyl's
Structural Changes • Constant chain length. • Naphthenic carbon decreases. • Aromatic carbon increases.
Undesirable Constituents of Distillate • Nitrogen compounds are known to act as catalyst poison. • PAHs contribute to increased coke formation. • Bitumen derived gas oil vs conventional gas oil • Higher Sulphur and Nitrogen Content • Higher Aromaticity • Higher MCR
UV Absorption Spectra (282nm) Tetraaromatic Diaromatic
Distillate Quality • Weight % Nitrogen increases • MCR content increases • Aromaticity increases • PAHs increase
Coke Quality on Recycle • Coke quality improves. Recycle stream excellent source to make good quality coke!
Implications of Research - Ideal Coker Maximize Distillate Yield Coking Reactor Bitumen Feed • PAHs • Heteroatoms • Metals Coke
Implications of Research • The distillate quality rapidly deteriorates upon recycle coking. • A large amount of aromatic carbon is in the form of polycyclic aromatics in the recycle stream. • There is an increase in the weight % nitrogen.
Distillate Coking Reactor Feed Coking Reactor Recycle Stream Coke Implications of Research
What Next? Distillate Quality Catalyst Deactivation Liquid Yield Is the lower quality worth the higher yield?