Hexane has maintained the dominant position as a solvent for the major plants which extract oil from oilseeds.
Generally, the quantity of extraction solvent increases in proportion to the raw fiber content in the seed. The miscella concentration also plays a further role. As a general rule, the higher the latter, the less energy is needed to remove solvent at the end of the process.
Most extraction systems are located near the farm fields which supply the oilseeds, or on ports or rail lines suitable to moving the very large volumes of oilseed and products.
Solvent Extraction Process. Solvent extraction is achieved through the grinding of seed. The ground seed or cake is then purged or washed with a petroleum distillate (the most common chemical used is hexane) which releases the oil in the seed. The solvent is then “flashed off” by heating the oil in a sealed chamber.
Solvent extraction is one of the most popular techniques chemists and manufacturers choose when extracting plant compounds. One of the most common compounds that they extract is oil from the seeds of the plant, or in other words, the oilseeds.
Manufacturers choose to use solvents to extract substances due to their high yield of a desirable compound, their reusability, and their efficiency. However, not all solvents are created equally when it comes to oilseed extraction and there are a few that chemists tend to prefer such as:
Whether you know it or not, some of the products you have laying around your house—or more specifically, your kitchen—are oilseed products. For example, you more than likely have one of these oilseed products at home:
If you’re looking to separate oils and other compounds from any part of a plant, then choosing high-quality chemical compounds to use in your extraction processes is crucial. You also may want to consider purchasing solvents in bulk sizing options to make the most of your money.
Generally, the quantity of extraction solvent increases in proportion to the raw fiber content in the seed. The miscella concentration also plays a further role. As a general rule, the higher the latter, the less energy is needed to remove solvent at the end of the process.
However, the five factors below that are of any real significance. Seed Water Content: Being a polar substance, water interferes with wetting of the seed surface and solvent penetration into the seed. In addition, it reduces diffusion.
Solvent extraction is a chemical oil extraction method to process oil out from vegetables, oilseeds and nuts by solvent, and Hexane is the preferred choice. Industrial oil processing for the edible oil generally involves the solvent extraction step which may or may not be preceded by pressing. Hexane-based processes have been in commercial ...
The solvent is then “flashed off” by heating the oil in a sealed chamber. The oil/solvent blend is next heated to 212º F (100º C) to distill off the solvent.
Particle Size and Shape: First of all, the shape of particles in the extraction material must be such as to allow solvent to flow freely, without any great resistance. Secondly, the particle size must allow the best possible extraction from each individual particle, by minimising diffusion pathways.
Therefore, the screw press technology is used before extraction to better prepare the high oil seeds for the extraction process. It is partly practical experience and partly better balancing or optimization of the plant for low energy – but most high oil percent seeds have pre-press systems before extraction.
Reduced solvent viscosity and enhanced solvent function at high temperatures make for improved extraction. Whilst there may well be no major differences, it is worth using heated extraction agents. The increase in oil yield outweighs the cost of heating the solvent.
Various alcohols, isohexane, heptane, butane – many other solvents have found applications in niche markets. For the standard oil removal plant, only isohexane – an isomer with properties very close to hexane - has replaced hexane in a significant number of extraction plants.
Therefore, the screw press technology is used before extraction to better prepare the high oil seeds for the extraction process .
In comparison, solvent extraction with hexane (the primary solvent used worldwide) will remove all but about ½% of residual oil, uses less horse power, and requires less maintenance. It is relatively efficient and reliable, and this is one reason why solvent extraction is the primary means of separating large tonnages of oil from protein meal.
Extraction theory can be put very simply: we are trying to soak oil out of small particles or flakes of material with a solvent, usually hexane. The solvent has to travel into the particles, soften up and dissolve the oil, and the miscella (the solution of oil in the solvent) then must travel out of the particles and be washed away by still more solvent.
However, safety is an important aspect in extraction plants due to the use of several chemicals, the flammability of hexane, the physical requirements of grain storage and handling, and the operation and maintenance of machinery of all sizes and descriptions.
A percolation-type extractor is by far the most commonly used for the removal of oil from oilseeds such as soybeans, canola, or sunflower. Figure 4 shows that in ‘percolation’ a liquid drains down through a porous bed of material and through a screen which supports the material - similar to a coffee percolator.