Preparation is the first step in the process of removing oil from oilseeds. The best method for preparation will depend on the type of oilseed and the intended market for the products generated after oil removal.
In any preparation process, the soybeans are cleaned prior to further processing. The cleaning step may include aspiration, classification by size, removal of stones and removal of metals.
For Hot Dehulling, the next step is the Vertical Seed Conditioner, which provides both conditioning and drying of whole soybeans. The whole soybeans are then passed through the Jet Dryer, which finishes the conditioning and prepares the soybean hull for easier removal during times when the hull is bound tightly to the soybean. After the Jet Dryer, the soybeans are immediately cracked, and the soybean hulls are removed in the Dryer and Cooler.
After cleaning, the seeds are sent to the First Stage Dehulling Machines, where a number of blades propel the seeds against corrugated impact plates, breaking the seed. The mixture is screened and aspirated to separate the hulls from the meats.
Following the dehulling process, sunflower seeds are cooked and mechanically pressed for oil removal, either by full pressing or pre-pressing before solvent extraction.
The oil is sent to a screening tank for primary fines removal and is then pumped to a decanter or pressure leaf filter for clarification.
Continuous solvent extraction is the most efficient method for producing high-quality vegetable oil and meal from a wide variety of oilseeds. As such, it has become almost universal in the modern oilseed industry. With this growth in popularity and application has come an extensive evolution in solvent extraction techniques and equipment design, an evolution toward every greater economic efficiency, safety and ease of operation.
Energy costs have also caused a significant change in oilseed processing techniques. The rapid rise in fuel costs necessitated new methods and new equipment to reduce energy usage. Increase in solvent cost made solvent conservation a high priority.
After all the oil has been removed from the oilseed flakes or cake, they leave the Extractor with approximately 30% solvent (hexane) content. The Desolventizer-Toaster (DT) is the newest innovation in removing the hexane from the flakes and completing the toasting operation.
From the DT, the flakes are either conveyed to a Dryer-Cooler (DC) or, in the case of a DTDC, they pass through the rotary valve, directly into the drying section of the DC. The drying and cooling are accomplished by blowing heated air in the drying section (dryer trays) and using ambient air to cool the meal in the cooling section (cooling tray).