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When the first tankers loaded with Euro 4 quality diesel and gasoline rolled away from PJSC Ukrtatnafta’s depot in January 2011, it marked the end of a long, demanding business journey for the technologists at the refinery in Kremenchug, Ukraine.

They started to consider how the 18.6-Mt/y refinery, which is the largest in Ukraine, could meet the Euro 4 (50-ppm sulphur content) and Euro 5 (10-ppm sulphur content) clean fuels specifications back in 2004. Valeriy Berlyaev, Chief Engineer, PJSC Ukrtatnafta, explains why they were ahead of the game. “The refinery’s future competitiveness was at stake,” he says. “We knew that meeting those standards would become a prerequisite for selling to international markets and that it would improve our position in the Ukrainian market.”

“However,” adds Berlyaev, “we had a long way to go because we were producing 1,500-ppm-sulphur-content diesel at the time. With the project playing out against ongoing geopolitical issues in Ukraine and, later, the global economic crisis of 2008, it proved to be a tremendously difficult journey.”

Meeting the specifications involved overcoming major challenges and constraints, he explains. For example, the lack of major capital precluded one of the more obvious solutions: the installation of a new diesel hydrotreater. Instead, Berlyaev’s team elected to revamp the existing hydrotreater, which featured two trains in parallel, with two reactors per train. In addition, to avoid disruption to production, it was necessary for the revamp team to execute the project in phases that coincided with scheduled shutdowns.

During the phase 1 revamp, under the direct technical supervision of specialists from Shell Global Solutions, Ukrtatnafta replaced the internals in all four reactors with state-of-the-art internals for improved catalyst utilisation. In addition, Criterion introduced a next-generation, more-active catalyst: ASCENT DC-2531.

The results were impressive: the changes facilitated the refinery’s production of Euro 3 diesel (350-ppm sulphur). Even the Euro 4 specifications could be met if a lighter feedstock was used.

Euro 4 and 5 specifications were the target of the phase 2 revamp. However, this time, sulphur was not the only challenge. The cold flow properties, such as the cloud, pour and cold filter plugging points, of Ukrtatnafta’s middle distillates posed a major challenge. The financial incentive was clear. In the past, the cold flow properties were enhanced by kerosene blending or end-point reduction, which reduced the value or the size of the refinery’s middle distillate pool, or by additivation, which can be expensive.

Ukrtatnafta’s principal challenge was the cloud point: this was much higher than the specification for winter diesel, whereas the cold filter plugging and pour points were close to the specifications. Shell Global Solutions’ experience shows that the cloud point is very difficult to reduce economically without dewaxing technology. For the other techniques, kerosene blending requires large volumes of kerosene, and additivation has a limited effect (it is more effective at addressing the cold filter plugging and pour points).

Following an economic evaluation, Berlyaev’s team chose to include a dewaxing catalyst (Criterion’s SDD-800) in the reactor configuration. Substantial analysis work helped Ukrtatnafta to decide whether to implement single-stage or second-stage dewaxing. Eventually, the single stage option was chosen, as it suited the refiner’s objectives better.

In addition, to meet the sulphur specification, substantially more reactor volume was required. Analysis showed that a new reactor needed adding to each train – and, crucially, the team was able to minimise the cost for this. Kremenchug is an enormous refinery that was built during the Soviet era and has a lot of heavy-duty spare capacity available. The team was able to identify suitable redundant reactors in the facility’s warehouses. These, however, were not designed for a trickle-flow process. Much higher performance was required to meet the sulphur specifications, and so several reactor modifications were made.

For instance, Shell Global Solutions reactor internals were introduced, including high dispersion (HD) trays for highly uniform vapour–liquid distribution and excellent thermal distribution, and filter trays to prevent foulants from entering the catalyst beds. These reactor internals can produce 30–50% activity gains through improved catalyst utilisation and extra volume for loading catalyst. In addition, an even higher activity catalyst was used: Criterion’s ASCENT DN-3531.

Again, the revamp results were striking. Not only was the hydrotreater able to produce Euro 4 and Euro 5 diesel, the cloud point also fell spectacularly to –31°C, substantially lower than the –15°C target. Although this demonstrates the dewaxing catalyst’s very high activity, it also indicated that extra dewaxing activity was occurring, which Criterion’s technologists soon optimised to bring the cloud point closer to the target.

Anatoliy Dyachenko, Chief Process Engineer, PJSC Ukrtatnafta, reflects that Criterion’s relationship with Shell Global Solutions has helped to solve issues like this throughout the project, and has continued into the operational phase. “For instance,” he says, “if we are forced to change feedstock, they are on hand to help us forecast outcomes and, if necessary, to make process adjustments that will help to avoid undesirable consequences.”

Delivering value

Enhanced performance: Ukrtatnafta replaced the internals in four reactors with state-of-the-art

Enhanced performance: Ukrtatnafta replaced the internals in all four reactors with state-of-the-art internals for improved catalyst utilisation.

Ukraine’s domestic markets became harmonised with the Euro 4 and 5 standards in January 2011, just as the phase 2 revamp concluded. Sergey Koshelyuk, Deputy Chairman of the Board, PJSC Ukrtatnafta, says the project has been key to the company’s ongoing competitiveness. “These projects have helped us to maintain and strengthen our market position,” he says.

“The completion of phase 1 in October 2009 meant that we could start to produce batches of Euro 4 diesel. And, when we had completed phase 2 in January 2011, we could produce Euro 5 diesel and the full range of winter diesel grades, including Arctic diesel, at competitive prices.”

Ukrtatnafta has now completed this part of its journey to UL SD production, and the newly installed technology continues to meet its performance guarantees, but Berlyaev is already thinking about new projects. “The bottom of the barrel is our next focus area,” he says. “Because the outlets for heavy fuel oil are shrinking, it is vital that we maximise our conversion levels. Again, we may need capital-constrained solutions and I am sure that we will continue to work with Shell Global Solutions and Criterion to evaluate our options.”

Diesel dewaxing

Diesel dewaxing is emerging as a powerful technique for meeting product specifications and creating additional margin, writes Laurent Huve, Dewaxing and Base Oil Technology Manager, Shell Global Solutions International BV.

“To avoid wax compounds crystallising out and causing engine problems, the cold flow properties of diesel fuels to be marketed in cold climates must meet stringent specifications. Dewaxing can be used to remove the wax to meet the required values for the cloud, pour and cold filter plugging points. This can often be a better economic option than the alternatives, which include additivation and kerosene blending.

“Shell Global Solutions, in association with Criterion, has established an enviable track record of working with customers to design and implement value-adding dewaxing projects that meet their objectives.

“There are two main process configurations for catalytic dewaxing. In single-stage dewaxing, the dewaxing bed is part of the main hydrotreating section, and a base metal dewaxing catalyst that can withstand the severe operating conditions is used. This configuration can provide a low-cost and flexible solution.

“With second-stage dewaxing, a dedicated second-stage reactor downstream of the hydrotreating reactor provides a cleaner environment (low sulphur and nitrogen) so that a high-activity noble metal catalyst can be used. The investment costs may be higher with this configuration, but product qualities and yields can be maximised.

“Diesel dewaxing has helped refiners around the world to unlock substantial value. It has helped them to maximise their yield of high-value distillates. The addition of kerosene to the diesel oil pool is a common solution for meeting cold flow specifications; however, unlike diesel dewaxing, it can detract from the bottom line. Other refiners have reported enhancing their margins through the use of diesel dewaxing, as it avoids the need for expensive additives. In addition, it can facilitate the use of cheaper feedstocks that have a higher cloud or pour point, or more wax.”

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