Refinery cuts compressed-air energy costs

London – An investment in new energy-efficient compressors is expected to save more than 430,000kW/h per annum at Petrochem Carless’s Harwich refinery. The installation followed a datalogging exercise by rotary vane maker Mattei that revealed the potential savings.

The refinery operates continuously, 365 days a year, so the reliability of its compressed air supply is important for the smooth running of the plant and any failure can cause costly downtime.

The air supply serves various requirements, including instrument air, valve actuators and air-driven motors. Prior to the datalogging, Petrochem Carless used two 90kW Mattei compressors installed over 12 years ago and backed up by service support from the manufacturer.

“The existing compressors were doing everything asked of them but as part of a programme to reduce energy consumption in general, the refinery asked us to carry out a datalogging exercise,” said Andy Jones, general manager of Mattei.

“As the existing compressors had put in 12 years of service, this was an ideal opportunity to invest in new technology,” he added. “The decision was made both on the basis of saving energy and the need to secure the supply of compressed air to the plant in the future.”

To first determine the integrity of the air supply, the refinery commissioned an air leakage survey prior to the datalogging exercise. This identified minimal leakage, confirming the effectiveness of the site’s maintenance procedures and enabled the focus to be placed on the energy-savings potential of the compressors themselves.

Datalogging is a non-intrusive process that analyses patterns and volumes of usage. It often reveals a variable requirement, thus dictating a variable-speed option. This was not the case at Harwich, where the logging proved that there is a consistent demand for compressed air due to its continuous operations.

Based on this information, Mattei recommended two Maxima 75kW compressors, which, using the figures from the datalogging exercise, could save around 430,000kW/h annully. Although effectively downsizing from 90kW to 75kW machines, the replacements were shown to be capable of delivering the same volume of 32m’/minute of air.

Maxima technology is able to use a six-pole motor that then runs the air end at the optimum low speed of 1,000rpm, giving the maximum output of air from the minimum consumption of energy. Its blades are designed for more than 100,000 hours of life, significantly reducing maintenance requirements.

Installed in May 2009, the new compressors were datalogged as a monitoring exercise in February 2010.

“The exercise confirmed the estimated annual saving of more than 430,000kW/h and compressor performance has continued to deliver the reliability paramount at the Harwich operation,” said Andy Lee, engineering manager from Petrochem Carless.