Processing a sugarbeet into pure granulated Pioneer and Big Chief brand sugar requires a lot of equipment and energy as well as the skill of our employees. The process consists of a series of physical and chemical separations with the object being to preserve the natural sugar and remove all other materials. Following is a brief description of the unit operations, their purpose and how they relate to each other, as the sugarbeet becomes sugar.

Preparing the Sugarbeet for Processing

The sugarbeets are taken from storage piles by a front-end loader or front-end loader/truck combination and brought to the factory to be placed in the "wet hopper." The wet hopper is a large bin with a stream of water at the bottom and various water jets. The beets exit the bottom of the wet hopper in a trough of flowing water known as the flume. The beets are submerged as they are swept toward the factory. As they are soaked in this water, any soil or unattached plant material begins to loosen. Material heavier or lighter than the beets will tend to settle to the bottom or rise toward the top of the flume. Various pieces of equipment are used along the way to remove stones, larger weeds and leafy material. The stones are used as fill material or sold for further processing as landscaping products. After entering the factory, the water is separated from the beets and they are elevated to the upper floor or the entire mixture is pumped to an upper floor and the water is separated at that point. The beets now enter a large washing tub where a new supply of water is used for a final vigorous washing. As the beets leave the beet washer, they are rinsed in clean warm water to remove any remaining particles. The water used for washing and from the fluming system is screened to remove any remaining leafy material and beet chips that may have been broken off during storage, handling or cleaning. The beet chips and leafy material recovered on the screens are separated with the chips being returned to the process for recovery of sugar and the leafy material being macerated for subsequent use as part of the pulp for animal feed. The main stream of screened water is sent to a pond where the soil settles out. The clarified water is returned to the factory and the valuable soil is later removed from the basin, dried, and taken back to the farm.

Beet Slicing and Extraction of Sugar

The clean sugarbeets are sliced into very thin strips rather like shoestring potatoes. The objective is to expose the largest possible area of sugar-containing beet cells without unduly damaging those cells. Doing so could release unwanted non-sugar substances into the juice and make purification more difficult. Slicing takes place by forcing the beets against the rotating drum or disc of a slicing machine. The slicer contains many sets of beet knives. Periodically, these knives must be removed from the slicing machine for sharpening. Sharp knives make a cleaner cut and rupture fewer cells. The sliced beets are now called "cossettes." The cossettes are moved countercurrent to a stream of hot water in a large machine called a diffuser. As the mass of cossettes move in one direction and the water in the other, the beet cells are exposed to heat and osmotic pressure to draw out the sugar solution and leave other substances behind. The water, which now contains most of the sugar from the cossettes, exits the diffuser at one end while the de-sugared cossettes exit the opposite end. The sugar-containing water is now called raw juice or diffusion juice and will require purification. The de-sugared cossettes are now termed wet pulp and will be processed into a valuable animal feed.

Pulp Processing

The wet pulp is sent to a set of mechanical presses. These machines press the pulp against perforated screens with a tremendous amount of pressure. The water that is squeezed out contains a small amount of sugar and so it is recycled to the diffuser for further recovery. The pressed pulp is made up of the fiber from the sugarbeet, along with other nutritive substances, and is an important local animal feed. For long-term storage, or shipment to more distant users, the pulp must have most of the remaining moisture removed and be compressed into pellets. Drying of the pulp is carried out in rotating drums with air heated in a furnace or in a steam dryer that uses recycled steam from other factory processes.

Purification

Raw juice from the diffuser must have most of the remaining impurities removed so that the sugar can be crystallized. Lime and carbon dioxide are generated in a lime kiln by heating calcium carbonate stone. The juice is treated first with the lime and then by bubbling carbon dioxide up through the lime-juice mixture. The impurities tend to adhere to the particles of lime and the carbon dioxide acts to convert and precipitate the lime as insoluble calcium carbonate crystals. The lime particles are settled out in a clarifier while the purified juice is filtered to remove all remaining particles of lime. The settled lime is washed and then dried. The lime becomes an excellent soil amendment and is distributed for use in agriculture.

Evaporation

Juice from the purification step is quite thin and consists of much water. The majority of this water is removed by heating the thin juice and boiling it off until the juice becomes considerably thicker. The evaporator station consists of several vessels containing thousands of tubes. Boilers produce steam, which is applied to the outside of the evaporator tubes while the juice passes through the inside. After being filtered again, the thickened juice from evaporation is now ready to have the sugar separated.

Crystallization and Centrifuging

Thick juice from the evaporators is boiled again, this time under vacuum in order to reduce energy usage and prevent coloring of the purified juices. The juice is boiled in large vessels containing many tubes that are heated with steam vapors created by the evaporation of water at the evaporator station. When the boiling juice is at the proper consistency, a finely milled mixture of sugar crystals is introduced to act as seed. As the water is boiled off and the solution becomes more concentrated, sugar from the juice comes out of the solution and becomes part of the crystals. The crystals are carefully grown through control of the vacuum, temperature and feed syrup additions. When the crystals reach the desired size, the mixture of juice and crystals, known as massecuite, is discharged to an agitated holding tank known as a mixer. From the mixer, the massecuite is fed into high-speed centrifugals, in which the liquid is spun to the outer shell, and the crystals are left in the screened basket. The sugar crystals are then washed with pure hot water and are conveyed to the granulator station. The liquid that was separated from the sugar crystals in the centrifugals is called syrup. This syrup serves as a feed for the "second boiling." Sugar separated from the second boiling is melted and is introduced back into the vacuum pans along with the thick juice from the evaporators. The process is repeated once again, resulting in the production of molasses as the final syrup. The molasses is sold as a feedstock for the fermentation industry, used as animal feed, or in the production of numerous other products. With a special process, additional sugar can be separated from the molasses before marketing the final syrup.

Sugar Drying and Conditioning

After leaving the centrifugal station, the damp sugar is sent to the granulators in which the sugar is dried with warm air and then cooled. The dry sugar is conditioned and stored in a sugar silo for subsequent packaging or shipment in bulk trucks or railcars.