Energy optimised operation of mill pneumatic systems
by Andreas Hummel, Chief Technology Officer, Wingmen Group, Switzerland
The mill pneumatic system is usually the biggest energy consumer in a flour mill. In the past, motors had to be oversized due the required torque for direct starting or configured with a star/delta start condition. Over the past ten years, the star/delta configuration was increasingly replaced by frequency converters and soft starters. As a result of the smooth starting conditions, the significant torque reserves for motor startup are not required anymore, resulting in smaller motor sizes and increased operational efficiency.
However, a mill pneumatic system still requires reserves, specifically in the following operations conditions:
Short term operational conditions:
- During the start/stop procedures of a flour mill, some passages are running empty, resulting in negative operational pressure in the pneumatic system
- Throughout a change of the wheat grist or the recipe, the product load of several passages may change
- During the change of a sender/tempering bin, the moisture content and tempering time of the wheat is fluctuating temporarily, causing a preliminary change of the product load on several passages.
Long term operational conditions:
- According to filter sleeve condition, some reserves are required. A flour mill should operate at the same capacity, regardless of filter sleeve condition. Depending on electricity costs, short exchange intervals (every 1-2 months) of the filter sleeves help save energy. However, due to the high required downtime, it is not possible in most flour mills
- Roller and sieve wear can cause a shift of the intermediate products to different passages, increasing load of the pneumatic lifts
- The surface of the pneumatic pipes, bends and cyclones will become smoother over time, improving product flow. After six months of operation, the product contact surface changes completely, significantly reducing the required energy consumption
- As airlocks wear, false air enters the pneumatic system. This air volume increase also increases the overall energy consumption.
With the new mill pneumatic energy optimisation service from Wingmen Group, all unnecessary reserves are eliminated, while keeping all required long- and short-term factors mentioned above in mind, to ensure a stable and trouble-free operation. With our unique adjustments, we deliver significant energy reductions, with full reliability and trouble-free operation of the pneumatic system.
The minimum requirement to execute our services is to install a frequency converter on the high-pressure fan motor. For operational convenience, a remote adjustment possibility from the control room/system is recommended.
For higher savings and full operational convenience, we recommend an automatic pressure control system linked to the control system, which adjusts the speed of the frequency converters automatically according to actual conditions.
The specialists of Wingmen Group provide consultation to flour mills, to match systems to their exact requirements.
According to our experience, all mill pneumatic systems with a high-pressure fan motor size of 18.5KW or greater can provide economic benefit through adjustment with our unique settings. If your flour mill already meets the basic technical requirements as mentioned above, optimisation costs are amortised after only a few months.
If the installation of a frequency converter and a pressure control system is required, the amortization period is between 1.5-3 years based on our typical results (depending on operational days and energy costs).
For a preliminary estimate of energy savings potential, Wingmen Group can support you with an initial, free of charge cost and savings potential overview for your flour mill.
See below some recent energy savings examples from reference plants of different capacities:
- Bischoff Mühle Germany, with a capacity of 70 tonnes per day
In October 2019, their complete pneumatic system was newly adjusted by Wingmen Group. Since then, the flour mill has succeeded with trouble-free operation in the production of all products and recipes. Average energy consumption was reduced by 7KW/h (28 percent of the total) consumption. Thanks to the service of Wingmen Group, energy costs were reduced by several thousand euros per year.
- Kerry Flour Mill Thailand, with a capacity of 250 and 270 tonnes per mill, per day
These two flour mill lines have been in operation with the new adjustment by Wingmen Group since the end of 2019. Total energy consumption was reduced by 51KW per hour (24% of the total energy consumption) . Optimisation of two additional Kerry Flour Mill milling lines and their sister company, President Flour, are planned for later this year, following electrical hardware installation.
Positive side effects
With the new adjustments from Wingmen Group, the overall air volume through the mill pneumatic system will be significantly reduced. The filter load per filter surface area will be reduced, increasing filter cleaning efficiency of the filter sleeves. According to client feedback, the exchange intervals can be extended by up to 60 percent, due to the lower filter load.