Mattei improves energy efficiency for E.ON

Owned and operated by E.ON UK CHP, the £40m CHP plant in Stoke-on-Trent comprises a gas turbine, a heat recovery boiler and steam turbine, together being capable of producing around 60MW of electricity and 60 tonnes per hour of steam. The plant supplies both the electricity and steam to a Michelin Tyre factory (which shares the site) on a continuous 24 hour basis, with the steam being used during the manufacturing process.

To ensure Michelin Tyre has complete security of supply, the plant has three standby boilers, which can each produce 20 tonnes of steam per hour, and the local grid provides back-up electricity. Furthermore, the boilers are capable of using fuel distillate as well as gas.

The plant has been operational since the end of 2002, and will continue to supply Michelin Tyre with its energy needs for at least 15 years. Mattei compressors have been operating at the site for almost ten years, supplying instrument air to both the gas and steam turbines.

Committed to reducing its customers’ carbon footprints, Mattei recently carried out a data logging exercise for E.ON to determine if a more energy efficient compressed air solution could be provided.

Before a customer invests in new equipment, Mattei always recommends a preliminary data logging exercise, which evaluates compressed air needs and the efficiency of the system by recording and measuring air consumption profiles over a seven day period. Though data logging only provides a snapshot of compressed air activity, providing it’s a typical week (though allowances can be made if there are higher or lower demands than usual), it is undoubtedly the best way to identify whether changes to the system or investment in new equipment can result in energy savings.

The data logging exercise carried out for E.ON enabled Mattei to recommend the replacement of one of the two Mattei AC2030H existing compressors with a more energy efficient AC30sH compressor. This, the smallest of Mattei’s 30kW compressors, was well suited for improving efficiency in this application, while offering the best return on investment for E.ON.

The evaluation also highlighted that fitting dew point dependant switching devices to two ancillary desiccant dryers would also achieve energy savings. Previously, the dryers’ desiccant material was dried on a fixed timed cycle, irrespective of whether the desiccant was wet enough to require this or not. The dew point dependant switching devices continually monitor the moisture content of the discharged air, so that compressed air is only used to purge dry the desiccant when it is necessary, thus saving energy.

E.ON’s specification team gave Mattei the responsibility of project managing the installation. With the compressors and ancillary equipment being housed in a self contained steel plant room measuring approximately 20ft by 8ft, this was particularly challenging.

As well as installing the new equipment, it was necessary to make modifications to the steel container, including improvements to access, ducting and pipework. In addition, Mattei had a short window of opportunity to complete the works, while the turbines were undergoing scheduled maintenance, and had to adhere to stringent health and safety procedures.

The Mattei AC30sH compressor has been operating for several months, and further data logging evaluation has shown that the system is performing to within 1.5% of the projected energy savings.

Neil Price, performance co-ordinator at E.ON, said, “The utilisation of CHP – a microgeneration technology that increases efficiency and reduces carbon emissions – means we run a very efficient operation at Stoke-on-Trent. Therefore, we welcomed Mattei’s review of our compressed air system, and the fact we’ve been able to improve its efficiency by around 50%.

“Mattei has also demonstrated that its team is capable of working within very tight parameters, in terms of timescales, health and safety procedures and access.”

Martin Chitty, business development manager at Mattei, added, “This project is another example of Mattei’s commitment to reducing our customers’ energy costs and carbon emissions. At Mattei we are focused on finding appropriate solutions for individual cases, as we know that to operate efficiently, a compressor has to suit the application it’s being installed in. The AC30sH was the most suitable choice for E.ON’s compressed air usage profile – in terms of energy efficiency and cost effectiveness.

“Though the two existing Mattei machines had worked reliably for nearly ten years, we were certain that replacing one of them with an AC30sH would offer increased energy savings – and our subsequent data logging exercise has proven this to be the case.”