In late 2010, Grupa LOTOS SA completed construction of a major residue-upgrading project at its refinery in Gdańsk, Poland. Its 10+ Program was designed to unlock a step change in the facilitys long-term profitability. After two years of operating, this project has had a profound effect on the refinerys economics. Following the project, the refinery increased its crude capacity by 75% to 10 million tpy, achieved higher conversion capacity, and improved margins by $5/bbl. In addition, Grupa LOTOS was able to increase production of higher-margin jet fuel and diesel, while reducing fuel oil production (Fig. 1). Result: The refiner moved closer to its goal of securing the complexs future in response to increasingly stringent fuel specifications and emissions legislation.
| Fig. 1. Side view of the Grupa LOTOS |
Two key process units of the new residue-upgrading complex included an advanced solvent deasphalter and residuum/distillate hydrocracker. The new hydrocracker could process a blend of deasphalted oil (DAO) and vacuum gasoil (VGO).1 In addition, the DAO hydrocracker used state-of-the-art reactor internals and commercially proven demetallization, hydrotreating and hydrocracking catalysts.2 The hydrocracker successfully completed its acceptance test run in May 2011 and has met all performance guarantees.
With the initial cycle now close to two years, the unit has delivered sustained performance in converting the DAO/VGO feedstock directly into Jet A-1 fuel and Euro 5-quality diesel, both with sulfur contents much lower than 10 ppm. Additionally, Grupa LOTOS worked with the hydrocracker licensor and catalyst provider to optimize the DAO hydrocrackers performance. The net conversion increased from the original design level of 60% in once-through mode to 80% conversion in recycle mode. These changes have raised middle-distillate yields, while operating within the refinerys hydrogen availability.
Grupa LOTOS experience integrated the new residue-upgrading complex with minimal modifications to the existing main infrastructure of the refinery.1 The advanced solvent deasphalting unit requires feedstock (atmospheric or vacuum residue) plus utilities from the refinery. It produces DAO, which is sent directly to the hydrocracker, and an asphaltene liquid residue, which can be sent to fuel oil or asphalt blending, a pelletizing unit or a boiler for power production. There are no large product streams requiring further processing or treating.
The DAO hydrocracker requires feedstock (VGO, DAO and hydrogen) and produces finished products, mostly jet fuel and diesel. It also yields hydrowax, which Grupa LOTOS uses as a feed for base-oil manufacturing and as a component for low-sulfur fuel oil (LSFO). The unit also produces some light naphtha. Grupa LOTOS sends most of the naphtha to the isomerization process, although it could also be sent directly to gasoline blending. The heavy naphtha is used as catalytic reformer feed, although this can also be sold as chemical feedstock. Grupa LOTOS uses the asphaltene residue in the production of heavy-sulfur fuel oil (HSFO) and for bitumen blending. Fig. 2 is a simplified block scheme of the new residue-upgrading units installed at Grupa LOTOS.
| Fig. 2. Flow diagram of the Grupa LOTOS |
The project team had to consider numerous counterbalancing aspects when developing the reactor configuration and process design. For instance, although it was desirable to maximize the solvent deasphalter units DAO yield and the hydrocracker conversion level, this led to higher metals and Conradson carbon residue (CCR) content. This route required larger volumes of catalyst, especially demetallization catalyst; it also required larger reactors to achieve an economically viable catalyst run length. The hydrocracker licensor, catalyst provider and Grupa LOTOS worked closely together to find the best design that would optimize the returns against the cost. As shown in Fig. 3, the DAO hydrocracker features three in-series reactors designed for sequential processing of the feedstock into finished products. These reactors are the:
| Fig. 3. DAO hydrocracker configuration.1|
- Demetallization reactor, which reduces metals in feed to less than 1 ppmw
- Pretreatment reactor, which reduces key contaminants such as nitrogen, sulfur and CCR
- Cracking reactor, which is designed to achieve target conversion and to produce on-specification liquid products.
The DAO hydrocracker at Grupa LOTOS has a capacity of 6,000 tpd (2 million tpy), a catalyst cycle length of a minimum of three years and a net conversion level of 60%, which has increased to 80%. The units hydrogen consumption is within the availability from the refinerys hydrogen manufacturing unit. Most of the produced naphtha feeds the gasoline production units; the remainder is sold as chemical feed.
From almost two years of monitoring data, the unit has achieved sustained performance, and it has overachieved in terms of yield and catalyst life. In addition, the catalyst deactivation is very slow and it is on target for the next planned turnaround. Yields are also stable, as is product quality. Since the startup of the new units, Grupa LOTOS, working closely with technical services from the hydrocracker licensor and catalyst providers, adjusted the operation of the hydrocracker to increase jet fuel and diesel production and to minimize unconverted residue make.1, 2
Middle-distillate selectivity was a key consideration; it prevented higher conversion in the once-through operation. To overcome this condition, recycle of the fractionator bottoms (unconverted residue) was implemented, and the conversion was successfully raised from 60% to 80%. DAO yield from the advanced solvent deasphater unit, and, therefore, the percentage of DAO in the hydrocracker feed, has steadily increased in line with the hydrocrackers ability to process more difficult feed with higher metals, nitrogen and CCR content. All of these changes were made in incremental steps and closely monitored.
Demetallization catalyst performance
Feed metals reduction is the most critical performance specification for the demetallization catalyst system, as this determines its ability to achieve a feed quality to the pretreatment catalyst that is more consistent with that of a very heavy VGO feed. The demetallization catalysts installed at Gdańsk are specialty demetallization catalysts that have a very high activity for metals removal, a high metal uptake capacity, and a high crush strength.3 These catalysts are used extensively for:
- Removing metals and CCR in the upgrading of heavy VGOs, residues and DAO
- Protecting the pretreatment catalyst from metal poisoning in the guard bed or reactor of a multi-reactor system.
The deactivation rate of the demetallization catalyst has been low and is on target for the planned cycle length and turnaround date. As shown in Fig. 4 (blue series), the demetallization removal efficiency has been near 100% over the cycle. The DAO hydrocracker design allows the ability to safely obtain a sample of the demetallization reactor effluent and to directly measure the metal slip to the pretreatment catalyst. The accumulation rate of metals on catalyst is calculated and closely monitored on the basis of real performance data. The trend of total metals on catalyst is in line with the plan, as shown in Fig. 4 (red series). From the sampling program across the demetallization reactor, after nearly two years of operation, the demetallization catalyst continued to achieve significant conversion levels of sulfur (approximately 90%), CCR (80%) and nitrogen (50%). In addition to metals removal, the system has unlocked pretreatment catalyst activity and enabled further feedstock optimization.
| Fig. 4. Demetallization catalysts metals |
removal efficiency and metals buildup.3
Pretreatment and cracking catalyst performance
The pretreatment and cracking catalysts are applied in a stacked-bed system over multiple beds across the two reactors.2 This system contains:
- A high-activity nickel (Ni) molybdenum (Mo) catalyst, which has an exceptionally high hydrodesulfurization (HDS) activity and high-metals tolerance2
- A dual-function, HDS/hydrodenitrogenation (HDN) active, mild conversion catalyst, which is applied in the bottom beds of pretreatment service2
- Middle-distillate-selective cracking catalysts.2
This catalyst system, which has been proven commercially in many VGO hydrocracking and fluid-catalytic cracking (FCC) pretreatment applications processing heavy feeds, has shown very stable performance. The activity and selectivity closely match the original performance estimates, and the product qualities of the middle-distillate streams (kerosine and diesel) continue to meet and even exceed specifications.
After a brief initial operation at near-design conditions, the net conversion of the hydrocracker was increased to 80% over the course of the first year of operation. As shown in Fig. 5, the net conversion has remained close to the 80% level, even as the feed quality has changed with increased nitrogen and CCR content, owing to the higher DAO lift in the advanced deasphalter unit and higher DAO level in the hydrocracker feed blend. Despite this increased severity, the DAO hydrocracker has delivered sustained performance over almost two years of operation. The kerosine product continuously achieves full Jet A-1 fuel quality requirements and significantly exceeds the 25-mm smoke-point specification, as shown in Fig. 6. Similarly, the diesel product has been achieving full Euro 5 quality requirements and significantly exceeding the 46 cetane index specification, as shown in Fig. 7. Significantly, both distillate products continue to have very low sulfur levels, below 2 ppmw and well below the 10-ppmw specification for diesel product, as shown in Fig. 8.
| Fig. 5. Net conversion levels achieved by the |
| Fig. 6. Kerosine smoke point.|
| Fig. 7. Diesel cetane index.|
| Fig. 8. Kerosine and diesel sulfur content.|
With the advanced solvent deasphalter, the design of the DAO hydrocracker offers the refinery more flexibility. From a feedstock perspective, different crude blends are possible while still controlling fuel-oil production. From a refined-product optimization perspective, this refinery is able to use the high-quality kerosine as a blending component to increase diesel production; to adjust diesel cold-flow properties; or to be sold as Jet A-1 fuel, depending on the market conditions.
The fractionator bottoms, called hydrowax or unconverted residue, form a high-quality product due to the high-hydrogen and low-sulfur contents and absence of CCR species. A profitable outlet for the hydrowax has been as supplemental feed to the base-oil plant at the Gdańsk refinery, which has improved yields and increased quality of the base-oil products. Hydrowax is also blended into LSFO. In an FCC-based refinery, the low-sulfur content of the hydrowax (below 50 ppm) enables gasoline production from an FCC unit, co-processing the hydrowax, to meet the 10-ppm sulfur gasoline specification more easily.
Grupa LOTOS looks to the future
Grupa LOTOS launched the 10+ Program in response to increasingly stringent product specifications that were threatening its competitiveness. The rewards that it has unlocked are compelling. Based on this success, Grupa LOTOS has commenced the next chapter in its performance improvement journey. The refiner plans to eliminate all liquid fuel residue and provide the best fit with respect to the strategic drivers and return on investment. HP
1 The Residuum Oil Supercritical Extraction (ROSE) solvent deasphalter and Shell Global Solutions distillate hydrocracker, which is processing a blend of deasphalted oil and vacuum gasoilShell Global Solutions DAO hydrocracker.
2 Commercially proven demetallization, hydrotreating and hydrocracking catalysts from Criterion Catalysts and Technologies Ltd. and Zeolyst International.
3 Criterions MaxTrap (Ni,V) and MaxTrap (Ni,V) VGO.
||Desiree de Haan works in hydrocracking technical service at Criterion Catalysts & Technologies and covers units in the EMEAR region. She has worked at the Shell Research and Technology Centre in Amsterdam, The Netherlands, and with Criterion for several years in catalyst research and development and technical service in the fields of distillate hydrotreating, fluidized catalytic cracking pretreatment and (mild) hydrocracking. Ms. de Haan holds an MSc degree in inorganic chemistry and catalysis from Utrecht University, The Netherlands.|
||Mike Street is a principal process engineer at Shell Global Solutions in Amsterdam, The Netherlands. He is primarily responsible for Shells hydrocracking design and technical services in the EMEAR region. Mr. Street has more than 20 years of experience in refining design, operation and technical services, mostly in hydrocracking. He holds a BSc degree in chemical engineering from the University of Birmingham, UK.|
Grzegorz Orzeszko works in Grupa LOTOS hydrocracking department, covering the operation of VGO and DAO hydrocracking units. He has worked in Grupa LOTOS investment department (10+ Program) for five years and was responsible for the Shell Global Solutions DAO hydrocracker from initial basis of design through the investment process to startup. Mr. Orzeszko holds an MS degree in chemical technology from AGH University of Science and Technology, Kraków, Poland.