In discussions with Aggreko on their refinery’s pain points, a JV Refinery raised the issue of their PP-Splitter not achieving desired yields and being further restricted by seasonal temperatures. Given the high market value of this feedstock and the fact that achieving optimum capacity within the PP splitter is also crucial to avoid flaring when capacity isn’t reached, the customer posed the challenge to Aggreko to engineer a bespoke process solution to overcome it. 

A deep understanding of this highly complex process and it’s intricacies was vital. Upgrading the refinery grade propylene (RGP) via thermocompression is a balancing act between the right amounts of liquid and vapour that are introduced to the splitter along with the PGP.

It’s a volatile process which is hugely affected by the liquid element of the process which is cooled water. When this temperature rises by even a few degrees the ripple affect can be complex and costly for refiners.

With the rise in cooled water temperature, overall pressure will increase meaning that the compressor in the production process must accommodate and generate a pressure jump. This however decreases flow rate and the reboiler output is compromised, resulting in a lower grade propane. One option to stop this is a reduction of PGP into the PP-Splitter.

For the customer this was causing a host of problems as the PP-splitter is taken down from its original design capacity, flaring can occur, and the distillation process can be unstable.

Seasonal temperatures were also affecting the cooled water which was as high as 39.5C – Dropping the recovery yield to 60% was forcing the operator to reduce the capacity of the PP-splitter in those instances.

The customer was keen to move away from traditional methods such as the addition of a reboiler or utilisation low-pressure steam and water condensers and with our process engineers understanding that technical changes with cooled water injection could affect yield outcome, we were confident it was a problem we could solve.