Supplementary cooling for refinery | Aggreko UK

Vacuum improvement for distillation column saves millions of pounds


A large UK refinery was experiencing problems with the vacuum in their VDU (Vacuum Distillation Unit) which was reducing the efficiency of the distillation process, resulting in a lower quality and quantity of product.

The poor vacuum was due to insufficient cooling of the overhead condensers and the steam ejectors. The insufficient cooling was a bigger problem during the summer, when the site’s main cooling tower and chiller plant couldn’t produce enough cooling capacity due to the increase in ambient temperature.

The refinery asked Aggreko to support in two ways:

  • Boost the flow of the cooling water to the overhead condensers and steam ejectors
  • Lower the cooling water’s temperature to increase the level of condensation.

Aggreko's solution

Following site visits and discussions with the customer, Aggreko’s process engineering team designed a turnkey cooling package with resilience and redundancy.

We installed high volume pumps to boost the flow of water to the VDU overheads so they could work more efficiently.  It was important that the increase in the flow was measured precisely, to understand the impact on the process, so we installed flow meters to allow this to happen. 

This solved the problem during moderate ambient temperatures, but was insufficient for warmer summer months. We therefore installed mechanic coolers to provide an additional 5 MW of cooling to lower the process cooling water’s temperature during the warmer period.  

Aggreko also provided power for the temporary temperature control equipment. While the site had a high voltage power source, it was too far away from the equipment to provide a safe and cost-effective connection.


Using Aggreko’s flexible temperature control package, the refinery was able to solve their production bottleneck throughout the year, as the ambient temperature changed. As such, our customer was able to keep to their production schedules and improve the quantity and quality of the products being refined.