The world’s fifth largest milk processing company, La Compagnie des Fromages, has just completed an extensive upgrade to reduce energy use and CO2 emissions.
The upgrade follows an extensive energy audit at its facility located in the town of Vire, France.
The audit recommended replacing four piston compressors, which only provided cooling with a thermorefrigerating pump.
The pump is a thermodynamic heat transfer system that can cool and heat at the same time. The refrigeration system also makes it possible to provide cooling capacity to the evaporator and heating capacity to the condenser to ensure all energy produced is fully recovered.
A 150m3 buffer storage unit allows energy to be used to produce hot water as needed. With the old system, this water was heated by gas. It was also rejected into the atmosphere by a cooling tower instead of being reused. The new system saves 9000m3 of water a year.
At the heart of the system is a 390kW motor and a variable speed drive, which powers a Vilter single screw compressor with 1000kW of cooling capacity.
Cooling and heating are simultaneously produced one third of the time and the refrigerant used is ammonia (NH3).
To raise the water temperature from 15 to 58 degrees Celsius, the ammonia is compressed to get the right pressure and temperature. The ammonia condenses at 59 degrees Celsius. The water is heated by transferring the heat from the ammonia via the condenser and other heat exchangers to optimise heat.
Chilled water (at one to seven degrees celsius) and 200m3 of hot water (at 60 degrees) are produced daily at the Vire plant. To do this, the old system consumed 820kW of energy per tonne of production per year.
With the new system, this level is now only 560kW. Another feature of the project is the Dyneo drive systems. Dyneo LSRPM is a range of permanent-magnet synchronous motors incorporating technology patented by Leroy-Somer.
The magnet rotor can increase efficiency levels to 98 per cent. La Compagnie des Fromages maintenance manager, Patrick Marie, said it is seven per cent more energy efficient than high efficiency induction motors.
“Had we used induction motors, they would have had to be oversized,” he said.
“The low losses of the magnet-rotor technology considerably reduces heating of the bearings. As result, they don’t need to be lubricated as often and the life of the motor is increased.
“We’ve implemented more than 30 applications in four years without experiencing the slightest problem.”
Cofley Axima was in charge of managing every aspect of the project from engineering and installation to control and supervision. Only the electrical wiring was contracted out. Instead of standard twin-screw compressors, the company used single-screw compressors.
Compression is accomplished by a single screw and two star-shaped gate rotors. It is designed to balance the single screw both radially and axially, which ensures few loads are placed on the bearings. Jean-Yves Druillennec, sustainable development manager for Cofely Axima-GDF Suez, said what makes these compressors stand out is their ability to independently adjust capacity and volume ratio.
“This makes a real difference under partial load conditions. We have found Vilter compressors as much as 10 per cent more efficient than standard twin screw technology,” Druillennec said.
“The facility was down for only three hours during the commissioning phase and the return on investment was 18 months.
“Because of the downward pressure on price, clients are only interested in solutions that have a payback of less than two years.”