Gasoline Preblending for Energy-Efficient Bioethanol Recovery

摘要

With over 20 billion gallons produced annually, ethanol is the world's leading biofuel and a key contributor in the drive for sustainable energy. Studies into the effective net energy of ethanol usage have been inconclusive, with some indicating that the energy used to produce ethanol exceeds its energy content as a fuel. This matter is subject to rigorous debate in the scientific and public arenas, and considerable ongoing research has focused on improving the net energy outlook by optimizing the bioethanol production process. However, net energy calculations and optimization research have all been based on a flawed assumption: that it is necessary to obtain pure ethanol. The prevailing use of ethanol is as an additive to gasoline rather than as a fuel on its own, implying that the true end product of bioethanol production is not pure ethanol but rather a fuel blend containing ethanol. This paper shows that rethinking the necessity of the bioethanol purification step offers simple and practical improvements to existing bioethanol production processes. It was found that replacing the final purification steps of ethanol production with a simple gasoline blending step results in a spontaneous liquid phase split producing a viable fuel with desirable ethanol content and high recovery of ethanol, reducing the energy requirements of separation by between 17 and 40%, reducing operating costs of the process, while also eliminating capital expenses. This paper presents an inexpensive and easily implemented modification for existing bioethanol processes but also opens up a broad design space for the synthesis of efficient new separation schemes for ethanol and other biofuels.