VFDs Control Costs for Cement Plant
The commissioning and start-up of a Lone Star Industries cement plant in Greencastle, Ind., last June marked the introduction of the semi-dry cement-making process in the United States.
The commissioning and start-up of a Lone Star Industries cement plant in Greencastle, Ind., last June marked the introduction of the semi-dry cement-making process in the United States. It is because of good availability of relatively inexpensive electricity, and the plant's energy efficiency and ability to use alternate fuels for producing clinker that make it competitive with dry-process facilities.
According to Robert Brown, electrical supervisor at the Greencastle plant, the need to maximize capacity and uptime challenged the plant electrical engineers to manage and maintain all electrics for efficient, around-the-clock production. A standard AC variable-frequency drive (VFD) powers motors ranging from three horsepower (hp) up to 800 hp. Six 150-hp drives control the slurry pumping stations and feed pumps into the kilns, while 600-hp drives power the primary air fan and baghouse cooler exhaust. VFDs also control the primary exhaust fan, and a 200-hp drive runs the separator in the finish mill. Smaller motor controllers are used on fuel-feeding applications, such as the alternate pump and agitator, as well as on the feeder from the primary rock crusher to the conveyor at the quarry site.
"The same types of drives are used to control these motors' different functions," says Ross Tennis, chief electrician at the plant. He points out that the standardized operating platform for drives means less training for electrical technicians and fewer mistakes. Using VFDs that control motors to the exact rpm needed has proven to be an efficient, energy-saving approach.
For more information about VFDs and motors from ABB Automation Inc., circle 101 on the Reader Service Card on page 77.