Straight talk on next-generation hydrocracking technology

In an interview, two senior managers at the refinery reveal to Hydrocarbon Processing how the unit has performed over its first year of operation and the effect that it is having on the facility’s economics.

Q: The global refining industry is extremely interested in your hydrocracker because DAO has traditionally been used as a fluidised catalytic cracker feed. How has it performed over its first year of operation?

Orzeszko: I am pleased to report that it is operating extremely well: there have been no process upsets and, since start-up, all the performance guarantees have been met. There have been no product quality issues, and it is generating an extremely high yield of premium products.

Q: A hydrocracker can provide a refinery with much-needed flexibility in terms of feed and product slate. Have you taken advantage of this?

Kruk: Absolutely. The hydrocracker’s flexibility has been of special significance. We have been able to increase the conversion level from the planned 60% to 80–85%. We also routinely fine-tune the DAO /VGO balance between 40 and 60% in response to processing objectives.

The DAO we currently process is of a better quality than the much heavier design feed, which was 100% DAO derived from 45% atmospheric residue and 55% vacuum residue. At the moment, we have no need to process the design feed because the refinery has been reconfigured.

Since start-up, our focus has been on optimising the profitability of our overall investment, so all our efforts have been on increasing conversion and processing additional DAO.

Q: With the markets for fuel oil diminishing, refiners’ residue strategies can have a substantial bottom-line effect. What do you do with the unconverted residue from the hydrocracker?

Orzeszko: We reprocess it as much as possible. Some streams are routed back to the hydrocrackers, which increases overall conversion, but most go to our lubricant oil block, some via batch vacuum distillation, to produce high-quality base oils. These are usually Group II , but we expect Group III oils to be possible in the future.

Q: And what about other refinery residue streams? Kruk: Currently, we sell the residue as fuel oil in winter, and, in summer, we use it to produce asphalt, which is currently in high demand in Poland. But we recognise that we need to reduce the amount of residue we produce.

We had originally planned to install a gasifier, but the project costs became astronomical owing to the rising costs of steel, engineering and so on. Instead, we worked with Shell Global Solutions to phase the investment. So, first we built the hydrocracker together with an SDA and a hydrogen plant to supply the hydrocracker.

Now, we are considering installing a coker plant. This will match the overall configuration of the refinery, as it will enable the hydrocracker to be run constantly at higher conversion and at high throughput. This will deliver a better feed than we are getting from the SDA only.

Moreover, with both a coker and an SDA plant, we will be able to swing conversion between those two units and strike a balance between minimum coke yield and optimal hydrocracker feed quality.

Q: Since it came on stream, have you taken any steps to optimise the performance and operation of the hydrocracker?

Kruk: Yes indeed. There are small tweaks that you can make to improve efficiency, especially when the feed quality and the severity of the process have changed.

Many steps have been taken. For instance, because the throughput was lower, there has been extra room for optimisation, especially for heat integration. We have changed the operating parameters of the heat exchangers in both the reactor and the fractionation sections. As result, we have cut the plant’s energy consumption by some 25%.

Q: Have you encountered any issues caused by increasing the conversion beyond the design level?

Orzeszko: Yes, there were some, but we had anticipated those anyway. We work closely with our counterparts at Shell Global Solutions and Criterion; they help us throughout the run cycle. They are fully aware of our operating strategy with the unit and what we are trying to achieve. Before changing any process parameters, we always consult them and that approach is paying dividends.

Combining their process and catalyst expertise with our site-specific knowledge is an extremely powerful way of meeting our operational objectives.

Kruk: One of the issues that occurred was an increase in polynuclear aromatics (PNA ), which can lead to heat exchanger fouling and catalyst deactivation. Nothing is free, and this is the price of higher conversion and hydrowax recycling.

For stable hydrocracking operations, the PNA level must be kept within a certain window. So, with Shell Global Solutions, we analyse feed samples and create a PNA balance for the plant’s feed system. This has helped us to identify the most severe PNA streams, and now we preferentially route those away from the hydrocracker feed. Consequently, we have stabilised the PNA levels.

Q: Has the difference in operating duty affected the catalyst’s performance?

Kruk: Even though the catalyst was selected on the basis of a different feedstock and for 60% conversion rather than 80–85% conversion, it is operating extremely well. The selectivity for middle distillates is very good.

Of course, we constantly monitor the unit to make sure that increasing the conversion does not cause complications with the catalyst system or affect the catalyst’s performance. Conventional hydrocracking parameters such as nitrogen remain important and the large quantities of DAO in the feed mean that the metals content and the Conradson carbon level must be carefully monitored.

Orzeszko: Hydrogen consumption is also very important, as we are hydrogen constrained here at Gdañsk like most other European refineries. We monitor hydrogen consumption and, so far, the levels have been within the performance guarantees.

Clearly, the catalysts are doing their job very well. But it is also reassuring that Criterion’s technologists are monitoring the unit and advising on the potential of newly developed catalysts that could help to optimise the unit even further.

Q: This is an extremely large and complex hydrocracker, and you were performing the front-end development and implementation phases during the global economy’s crisis of 2008. Did you see that as a risk?

Orzeszko: The global economic crisis introduced a layer of uncertainty but we had to remain focused on the long-term picture. We always believed that the industry fundamentals remained unchanged – and the investment is now proving robust.

It is true that elsewhere in the industry projects were being put on hold or cancelled. But we were determined to work with Shell Global Solutions to adjust the scope of our project to process a different feed than the one that we had originally designed it for. That has allowed us to phase the project, and we are ready for heavier feedstock in future.

Those changes, which included optimising the conversion level and phasing the project, enhanced the project’s viability and enabled it to go ahead. And now we are seeing the benefits of that. I have no doubt that we would be far less competitive if we had not invested in this project. It has been a tremendous success.

At a glance - The Grupa LOTOS 10+ project

The Gdañsk refinery is highly complex and the second largest refinery in Poland. When increasingly stringent product specifications threatened its competitiveness, it took decisive action by launching the 10+ project, a massive $2 billion upgrade of the refinery.

The initiative, which was completed in 2011, has helped Grupa LOTOS to:

• raise refining capacity by 75%;
• focus production on higher-margin diesel fuels;
• increase market share; and
• enhance margins by $5 per barrel.

Shell Global Solutions’ DAO hydrocracker was key to the scheme. The refiner also installed an integrated crude distillation–vacuum distillation unit, an HDS unit, a solvent deasphalter  (SDA), an amine sulphur recovery unit, a hydrogen manufacturing unit, a refinery–harbour product pipeline, product tanks and pumping stations, and revamped its hydrogen recovery unit.