Solvent extraction processes have three main sections:

During the oil extraction, the vegetable oil is removed from the cell structure using a solvent, usually n-hexane, which is a volatile and inflammable liquid. In order to enable the solvent to penetrate unhindered into the seed, the cell walls have to be broken up and the diffusion paths have to be made as short as possible. So the seeds are mechanically chopped and pressed to create fine flakes (e.g. by roller mills). If required the seeds are heated, to break up more cell walls. In practice, two extraction methods are used, percolation and immersion . Ideally both extraction processes are operated in contra-flow, this means fresh solvent always comes into contact with largely de-oiled seed and fresh seed with largely oil-saturated solvent, known as the miscella.
After the extraction, the solvent is distilled off from the oil and fed back into the process. Ideally, for a high grade oil, the entire amount of hexane is recovered this way. The process objective is to minimise the loss of solvent vapour through venting, and to maximise the condensation of the solvent.