Cuts basic nitrogen in coker gas oil from over 1000 ppm to 300–600 ppm while also removing metals and carbon residue, easing the demetallization load on hydrotreater feed and markedly improving the quality of catalytic cracking (FCC) and hydrocracking feeds, and increase the yield of light oil
Coker gas oil (CGO) is a secondary processed middle distillate obtained during the coking process of vacuum residue. The yield accounts for about 20%~30% of the coked product, mainly used as raw material for catalytic cracking (FCC) and hydrocracking. Compared with straight-run wax oil, deeply cracked coker gas oil contains more nitrogen compounds, condensed-ring aromatics and resins, among which the basic nitrogen content is 2-3 times that of straight-run wax oil, usually up to more than 1000ppm.
During the catalytic cracking process, these basic nitrogen compounds (pyridine, quinoline) will Preferentially adsorbed on the acidic centers of the catalyst, causing the catalyst activity to decrease, and further:
Therefore, reducing the basic nitrogen content through the complexation denitrification process is an effective method to improve the catalytic cracking performance of coker gas oil, increase the light oil recovery of the catalytic unit, and improve the economic benefits of the refinery. As a key step in coker gas oil pretreatment (refining), complexation denitrification removes basic nitrogen while also reducing the metal, resin and carbon residue content in the wax oil. It is equally suitable for lubricating oil and other light and heavy wax oils requiring basic nitrogen reduction.
| Project | Illustrate |
|---|---|
| Coker gas oil yield | Accounting for 20%~30% of coking products |
| Basic nitrogen content | Straight-run wax oil 2-3 times |
| Typical base nitrogen levels | often >1000 ppm |
| For FCC catalyst | Adsorb acidic centers and reduce activity |
| processing target | After removal, the basic nitrogen is reduced to 300-600 ppm level |
Large refineries in China and overseas generally use high-pressure hydrodenitrification of residual oil, which has high yields but harsh conditions and high investment; non-hydrogenation complex denitrification improves the feed with lower investment. The 100,000 tons/year coker gas oil denitrification unit commissioned by a CNPC refinery is a long-running industrial demonstration unit.
The above are measured data under typical working conditions. The actual effect varies with the properties and dosage of coker gas oil. It is recommended to send samples for small test evaluation.
according to Lewis acid-base theory, the N atoms of basic nitrogen compounds (such as substituted pyridine and quinoline) in oil products contain unshielded lone pairs of electrons and are electron pair donors (Lewis bases); the N atoms in denitrification agents Quaternary phosphonium salt acidic ionic liquid Has proton properties and can provide the lone pair of electrons for H⁺ and basic nitrogen complex salt, thereby "grabbing" basic nitrogen from the oil.
Nitrogen-containing complexes formed Insoluble in oil, high density, it can be separated from the denitrified oil through static settling in the tank area. Since basic nitrogen is mostly concentrated in aromatic hydrocarbons and colloids,While the coker gas oil is denitrified, the colloid and metal content are also significantly reduced., to achieve "one dose for multiple removal".
| Project | Technical Indicators | Test Method |
|---|---|---|
| Appearance | homogeneous liquid | Visual inspection |
| Density (20°C) g/cm³ | ≥1.70 | GB/T 1884 |
| Freezing point °C | ≤-25 | GB/T 510 |
| Kinematic viscosity (50°C) mm²/s | ≤80 | GB/T 265 |
| Project | Before Denitrification | After Denitrification |
|---|---|---|
| Basic nitrogen μg/g | 2043 | 598 |
| Sulfur μg/g | 9960 | 9135 |
| Gum % | 7.1 | 5.3 |
| H/C atomic ratio | 1.647 | 1.694 |
| Kinematic viscosity (50°C) | 20.48 | 18.98 |
Basic nitrogen is reduced by more than 70%, H/C is increased, sulfur, density, colloid, and viscosity are all reduced, and the catalytic processing performance is significantly improved.
The 95-105°C coker gas oil from the coking unit is combined with the denitrification agent from the metering pump.static mixer Mix thoroughly and react.
Oil/agent mixture enters Denitrification reaction settling tank, heat preservation and sedimentation separation at 80-100°C 24-48 hours.
Denitrification refined oil from settling tank Extract the middle and upper layers, sent to the catalytic cracking or hydrocracking unit as feed.
Base nitrogen complex derivatives (asphaltenoids) from Discharge from the bottom of the tank, mixed with asphalt or petroleum coke and delivered externally, no waste water is produced.
| Index | Numerical Value |
|---|---|
| Raw oil feed temperature | 80-100 °C |
| Settling tank temperature | 80-100 °C |
| Oil residence time | >24 h (24-48h) |
| Nitrogen complex extraction temperature | 105-130 °C |
| Denitrification agent filling amount | 1.0%~1.4% (adjusted according to basic nitrogen) |
| Source of Coker gas oil | Raw Material Basic nitrogen Μg/G | After Removal of Basic nitrogen Μg/G | basic nitrogen removal rate % | Denitrification Agent Dosage % |
|---|---|---|---|---|
| A CNPC Refinery | 1129 | 397.2 | 63.6 | 1.15 |
| Shandong Refinery A | 1136 | 429.8 | 64.2 | 1.1 |
| Shandong Refinery B | 1585 | 772.5 | 73.9 | 1.1 |
| A Central China refinery | 1438 | 450 | 68.7 | 1.4 |
| A Northeast China refinery | 1322 | 313 | 76.3 | 1.3 |
| A North China refinery | 1415 | 268 | 81.1 | 1.4 |
Data source: Summary of Benxin/Run Erhua coker gas oil complex denitrification tests. This agent has good denitrification performance for different coker gas oils. When the dosage is 1.0%~1.2%, the denitrification rate is about 70%~80%.
Benxin prepared a construction plan for the coker gas oil complex denitrification project for a Shandong independent refinery, using tank settlement technology to improve the feed quality of its coker gas oil catalytic cracking.
View case →The coker gas oil from Refinery A and B of the Shandong group was refined with low acid value denitrification agent. The basic nitrogen was reduced from 1136/1585μg/g to 429.8/772.5μg/g, and the acid value after removal was 0.15-0.19mgKOH/g.
View case →The coker gas oil denitrification unit, which has the longest running time in China and is still in production, is a strong evidence that the non-hydrogenation complex denitrification technology is mature and reliable.
Industry DemonstrationProvide the basic nitrogen/acid value and other properties of coker gas oil, and our technical team will provide you with targeted denitrification plans, small-scale evaluation and unit construction suggestions.