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Fan upgrade for Hanson Cement’s Purfleet plant

World Cement,

A fan upgrade by Siemens at Hanson Cement’s highly productive Purfleet plant has resulted in energy savings of more than 36% being made, with payback on the investment anticipated to be well under two years. 

Hanson Cement’s Purfleet Works is situated next to the River Thames in Essex and is capable of producing around 1 million tpa of Regen – a cement replacement in ready-mixed and precast concrete that is manufactured from ground granulated blastfurnace slag.  The plant consists of two closed circuit ball mills and a Loesche vertical grinding mill. It was Mill 3 that required upgrading, as the existing mill fan was fixed-speed, using a 1 MW 11 kV slip-ring machine running at around 980 kW.  The airflow was continuously at full speed and was controlled by a damper.  The fan design airflow was 350 000 m3/hr, but the system was damped to the operational requirement of approximately 241 000 m3/hr.

As Hanson Purfleet’s electrical engineer Dave Jackson explained, the mill upgrade was part of a more general review Hanson Cement was making of all of its sites: “We were looking to make energy savings around the plant and a survey had recommended a new drive and motor for this mill.  The Siemens solution means we are now running with the damper open 100% of the time, yet actual energy consumption has dropped by around 360 – 400 kW.”

The Siemens Total Engineered Solution centred around the integrated drive systems (IDS) concept, which ensures that all products within the drive system are as integrated as possible, supported by Siemens both in specification and throughout their lifecycle.  By optimising the drive system to the highest degree of performance, and by acquiring data through monitoring that system, the best operational performance can be achieved. 

For mill 3, this meant replacing the fixed speed fan with a 1000 kW Sinamics Perfect Harmony 11000/4160 V medium voltage (MV) converter, installed and commissioned to link with the existing Siemens process control systems at the plant.  A new Siemens MV 1000 kW, 4160 V, 6-pole motor was also installed along with new motor cable and a modified motor base (the bed plate was raised by 60 mm).  Siemens was able to provide the full turnkey solution.

Perfect harmony

Every element of the Sinamics Perfect Harmony cell-based drive range is engineered to maximise productivity and protect a customer’s process in a way that other drives are unable to do.  Its modularity allows for a scaleable solution achieving near-100% reliability and 99% availability – two key factors for a busy cement plant like Purfleet.

Benefits of the upgrade included:

  • Greater productivity through optimised speed and process performance.
  • Improved flexibility, with faster run-up/run-down times.
  • Standardisation, reduced size and line attendance.
  • Increased amount of pre-emptive maintenance information.
  • A significantly reduced total cost of ownership over the product’s lifecycle.

“It took about a month before we could clearly identify all the changes in running costs,” said Dave Jackson, “but we were very pleased with the whole system, and more savings were made than originally anticipated.  A follow-up visit by Siemens led to even further savings being made using the new drive system and the entire project was completed on time and within budget.”

The annual savings to Hanson from the upgrade have been estimated at £175 000 – £200 000.

Siemens minerals account development manager Gary Chapman said: “This upgrade proves that using the appropriate software and with the Siemens knowledge of integrated processes and applications, significant savings can be made as well as enhancing the overall lifecycle of the plant.”

Being able to address a reduction in energy usage and increase plant availability have become key targets for industrial companies.  Hanson Cement has been able to reduce its carbon footprint at Purfleet by 1487 t since the new system was installed eight months ago and is continuing to make further savings. 

Hanson’s national operations manager for Regen, Steve Hall, concluded: “The project was a great success, with the new drive and motor enabling us to reduce drive speed and lower power consumption by approximately 37%.  We are continuing to save about 4.5 kWh/t on our total process with this one fan drive, and these energy savings represent a rapid return on investment for us.”

Written by Siemens.

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