Working together for better separation

When operators at the Mineraloelraffinerie Oberrhein GmbH (MiRO) refinery in Karlsruhe, Germany, wanted to improve the performance of a high-vacuum unit, installing a new type of inlet device was identified as a key part of the solution. This innovative device enhances gas–liquid separation, reduces coking problems and contributes to higher maximum capacity. Estimates suggest that the MiRO revamp will deliver an additional 535 tonnes a day of vacuum gas oil, which is equivalent to about $18 million a year.

The high-vacuum unit had experienced rapid coking of the wash oil bed caused by the entrainment of heavy materials from the long residue. These heavy materials often included nickel and vanadium, which, if allowed to enter the product stream and pass to the downstream process units, would poison the catalyst.   

In consultation with the refinery operators, Shell Global Solutions suggested an improvement package that included installing a new Schoepentoeter® Plus vane type feed inlet device.

Many of the world’s leading refineries use the original Schoepentoeter device invented by Shell during the 1970s. The Schoepentoeter Plus device was developed under a collaborative agreement between Shell Global Solutions International BV and Sulzer Chemtech Ltd, a leading supplier of separation and mixing technology. This device is one example of Shell collaboration with leading organisations and industry specialists to create the most effective new technologies and it is part of a much wider licensing and catalyst portfolio.

The Schoepentoeter Plus joint programme aimed at optimising separation efficiency without compromising hydraulic capacity, specifically to minimise the pressure drop through the feed nozzle and the device itself. The team wanted a design that would collect the separated liquid and so counterbalance the upward momentum of the ascending vapour. Modifying the back end of the vane in the original device from a straight and flat vertical plate to a sloped and curling one, called the catching rim, achieved this.  

This rim collects the separated liquid and conveys it in a rivulet sufficiently heavy to reach the bottom section of the tower, thereby minimising entrainment. Air–water tests show that the rim reduces entrainment by two-thirds. This helps to prevent coking and other run issues. When customised to specific column conditions, the device can deliver a rapid payback. A long-term benefit of reduced entrainment is greater run length. This could mean the difference between one or two cycles and help operators to avoid the need for a full shutdown. 

The unit’s design at the MiRO refinery does not allow sampling of the liquid running from the wash oil beds, so it is impossible to directly compare the levels of entrainment before and after the Schoepentoeter Plus was installed. 

However, according to Hans Nooijen, Principal Engineer Distillation, Shell Global Solutions, “MiRO has confirmed that the high-vacuum unit with the Schoepentoeter Plus is working fine and has achieved its anticipated performance targets.”

The success of joint improvement programmes such as this has prompted Shell and Sulzer to extend their collaboration. A new 10-year agreement covers a wide range of research and development activities and it is intended to enable customers to gain access to Shell distillation technology through Sulzer.