Alternative hydrocarbon solvents for cottonseed extraction: Plant trials

Hexane has been used for decades to extract oil from cottonseed and is still the solvent of choice for the edible-oil industry. Due to increased regulations as a result of the 1990 Clean Air Act and potential health risks, the edible-oil extraction industry urgently needs an alternate hydrocarbon solvent to replace hexane. Based on laboratory-scale extraction tests, two hydrocarbon solvents, heptane and isohexane, were recommended as potential replacements for hexane. A cottonseed processing mill with a 270 MT/day (300 tons/day) capacity agreed to test both solvents with their expander-solvent process. Extraction efficiencies of isohexane and heptane, judged by extraction time and residual oil in meal, refined and bleached color of miscella refined oil, and solvent loss, were comparable to that of hexane. However, fewer problems were encountered with the lower-boiling isohexane than with the higher-boiling heptane. With isohexane, the daily throughput increased more than 20%, and natural gas consumption decreased more than 40% as compared to hexane.