A reduction in energy consumption, however minor it may seem, can significantly enhance a mill’s profit margin or mitigate operating costs. This article delves into the multifaceted realm of energy-saving strategies for millers, exploring everything from efficient machinery and renewable energy sources to innovative technologies and meticulous maintenance practices. In a world where every kilowatt-hour saved contributes to a more sustainable and profitable future, these tips in energy conservation offer a valuable roadmap for flour mills seeking to thrive in a dynamic and energy-conscious landscape.
Milling cost is the most important economic consideration of a flour mill feasibility study, designing and operating. One of the most important milling cost factors is the amount of energy used. The cost of the raw material constitutes 70% and the energy cost 4% of the operating costs. Reducing the mill’s cost factor automatically improves the mill’s profit ratio. Thus, decreasing the energy usage will lower the operating cost or enhance the mill’s profits. So, it is important to control the energy consumption of flour mills. Electrical energy cost in the mill operating became one of the most important operating cost items, especially after the dramatic rise of the energy price in the last couple of years. The electricity price varies from country to country. The average electricity price without taxes in the European Union in the second half of 2020 was €0.0820 per kWh. By contrast, in the second half of 2022, there was a steep increase, with the price standing at €0.1986 per kWh.
Energy consumption varies from mill to mill; 60-80 kWh per ton is considered acceptable at an ideal installation. Wheat quality and atmospheric conditions affect energy consumption in a mill. The average energy use structure of the flour mill was about 50% grinding process, 30% pneumatic conveying, 11% mechanical conveying, 4% compressed air, 3% cleaning, and 2% service. Besides this, the most energy use operation after the milling unit was by the packaging unit.
Thus, improving electrical efficiency in flour mills is an important goal in lowering milling costs. An efficient management system of energy consumption has become a necessity instead of a preference. In order to optimize the electrical efficiency, the consumed electricity must be measured by effective sensors and control devices, recorded and visualized at a centralized system which is called nowadays energy management system (EMS). Existing EMS can effectively reduce energy use. However, the existing energy management system is not enough to achieve the desired efficiency improvements unless this system did not include the real-time measurement of the energy use to drive a consciousness of the energy use patterns of every machine in the production process.
One of flour mill installation companies’ main goals is to supply machines, processes and plants that are as energy efficient as possible. Today, some companies offer energy optimization solutions service and an energy automation system.
Improving energy efficiency can be achieved through:
- Optimization of the mill flow diagram.
- Securing quality wheat with low impurities ratio.
- Process optimization through upgrading the control system of the mill to AI (Artificial Intelligence) control system which leads to having maximum capacity usage in the overall process all the time.
- Upgrading to high-quality machines and selecting high-standard parts of the machines and high-quality electrical parts in the maintenance.
- Optimizing pneumatic system.
- Using renewable sources of energy. Renewable energy can play a critical role in meeting the need for electricity. Some of the mills invested in having renewable energy sources like solar panels and wind turbines.
The milling section is one of the most energy-intensive processes. The main machines of the milling section are roller mill, sifter and purifier. Reviewing the mill flow diagram can reduce the number of these machines subsequently reducing electrical energy use. Using the recycle process can reduce the number of machines used at the break system which will reduce the energy consumption compared to the conventional milling process. The amount of energy consumed by motors and drives, which power grinding and milling operations, accounts for about 50% of the energy used in a mill and depends on the kernel hardness, feed rate, roll gap, roll speed, roll differential and tempering procedure. One of the most important factors in the energy consumption of roller machine is the position of the roller and wear of the roller.
Using high-efficiency motors, variable speed drives, installation of soft starters and single motor in double deck roller mill can result in energy savings in the grinding process. There have been many innovations in the roller mill machine, some of which have directly or indirectly led to reducing energy consumption. Unfortunately, none of them was to stop the engine of the roller mill after a specified time from stopping the machine feed roller. Most milling do not stop the engine of rotating machines when they encounter a steam blockage unless they realize that the stop will be rather long. Stopping the roller machine engine automatically during short to moderate time of feed roller stopping can save a fair amount of energy.
MOTORS AND DRIVES
Electrical motors account for approximately about 75% of electricity use in the mill. Motors and pumps that are sized inappropriately result in unnecessary energy losses. Correcting motor size can save about 1.2% of their electricity consumption. Improving preventive maintenance schedules reduces the external load on the motor and frictions, thus saving energy use. The tension of the belts are important parameter for the energy cost.
The mill pneumatic system is the second biggest power consumer in a flour milling plant. Average energy consumption can be reduced up to 30 percent through efficient redesigning the balance of the pneumatic conveying system which ensures that pneumatic lines are sized correctly and thus reduce the overall air volume of the pneumatic system of the mill, ensuring that fans are correctly sized, finding and repairing any air leaks, and replacing worn-out airlock.
MECHANICAL CONVEYING SYSTEMS
Mechanical conveying systems include bucket elevators, screw and chain conveyors, belt conveyors and positive pressure conveying system can account for about 11% of the energy used in a mill. Electric saving efficiency in mechanical systems can be improved by lowering friction losses, operating at full capacity which lowers operating time, and correct maintenance like ensuring proper lubrication of chain and correct tension of belts enhancing energy saving too. Direct drive methods that lower friction losses compared to chain or belt-coupled systems will enhance energy saving.
Selecting the correct blower size in relation to the system’s demands is a good step to save energy. The buildup of dust on the inlet filters of blowers increases motor load and electrical cost. Keeping the right pulley alignment, and belt tension of the blower can improve electrical efficiency.
COMPRESSED AIR SYSTEM
Compressed air system accounts for about 5% of the energy consumed in a mill. First of all, the design of distribution system pipes should be checked to avoid too many individual branches and ensure proper sizing of pipes. Eliminating leakage of compressed air system, avoiding using compressed air for cleaning purposes, switching off compressors when not needed, regular maintenance and ensuring the compressor is operating at the needed pressure level can help to save energy.
An effective maintenance management system is one of the most important factors that play an effective role in saving energy use. For example; on-time lubrication will minimize the friction, improving the efficiency of the engine operation and life of the engines, and decreasing energy consumption.
OTHER WAYS TO SAVE ENERGY
Although the share of energy consumption in mill services like lighting the inside and outside of the mill is low, reducing energy consumption in mill services can contribute to reducing overall energy costs. using a High-efficiency lighting system especially when using super-efficient, light-emitting diode (LED) lights can contribute to saving energy.
About the author
Prof. Dr. Farhan Alfin is a distinguished independent consultant for production and quality control at wheat flour mills. In 2000, he received his Ph.D. from the Department of Food Engineering at Ege University in Izmir, Turkey. From 2015 to 2019, he was employed by Avrasya University in Trabzon, Turkey, where he served as the department’s head for food engineering. Between 2006 and 2010, he served as the department’s chairman at Albaath University in Homs City, Syria, where he worked in the food engineering department from 2000 to 2015. He has provided consulting and education services to various flour mills in Syria, contributing to the improvement of their operations. Furthermore, he served as the executive manager of Alakhras Mill in Homs, where he successfully oversaw its operations from 2009 to 2015. His expertise and knowledge are further demonstrated through his authorship of “Cereal Milling Technology,” a book written in Arabic. Prof. Dr. Farhan Alfin’s unwavering dedication to the wheat flour milling industry, coupled with his extensive experience, makes him an invaluable asset and a respected authority in the field.