Suchergebnisse

Bioethanol is mixed with gasoline according to many countries' legislation pursuing environmental sustainability by reducing the use of fossil fuels. Bioethanol is produced by fermentation of many organic waste or biomass resources in diluted aqueous media. Unfortunately, bioethanol for fuel use must have a low content of water and its recovery is an energy intensive operation. Heterogeneous azeotropic distillation (HAD) is a well-known suitable option for dehydration of alcohols, e.g. ethanol. Many entrainers for this process are studied in literature and, in this study, is checked and verified that gasoline and gasoline additives present the lowest energy consumption. For this purpose, novel processes are proposed and rigorously simulated using AspenPlus® to verify their performance with respect to conventional processes used currently. Based on the simulation results, the processes are then compared in terms of environmental impact (expressed by the Potential Environmental Impact (PEI) index) and economic cost. Ethanol dehydration is a non-spontaneous process that requires energy to be accomplished and, on the other hand, mixing ethanol with gasoline and additives is a spontaneous process. Combining both processes in synergy in a single unit, energy consumption decreases by 50% and Potential Environmental Impact by 80%. Finally, the economic study indicated the benefits of employing the novel proposed scheme of one distillation column as CAPEX is reduced by 20% and the payback time to 1.5 years. Therefore, a novel viable process is proposed that greatly reduces the environmental impact of nowadays gasoline production.

Bioethanol is mixed with gasoline according to many countries' legislation pursuing environmental sustainability by reducing the use of fossil fuels. Bioethanol is produced by fermentation of many organic waste or biomass resources in diluted aqueous media. Unfortunately, bioethanol for fuel use must have a low content of water and its recovery is an energy intensive operation. Heterogeneous azeotropic distillation (HAD) is a well-known suitable option for dehydration of alcohols, e.g. ethanol. Many entrainers for this process are studied in literature and, in this study, is checked and verified that gasoline and gasoline additives present the lowest energy consumption. For this purpose, novel processes are proposed and rigorously simulated using AspenPlus® to verify their performance with respect to conventional processes used currently. Based on the simulation results, the processes are then compared in terms of environmental impact (expressed by the Potential Environmental Impact (PEI) index) and economic cost. Ethanol dehydration is a non-spontaneous process that requires energy to be accomplished and, on the other hand, mixing ethanol with gasoline and additives is a spontaneous process. Combining both processes in synergy in a single unit, energy consumption decreases by 50% and Potential Environmental Impact by 80%. Finally, the economic study indicated the benefits of employing the novel proposed scheme of one distillation column as CAPEX is reduced by 20% and the payback time to 1.5 years. Therefore, a novel viable process is proposed that greatly reduces the environmental impact of nowadays gasoline production.

Nowadays the ventilation design of enclosed spaces is still based on the number of air renewals per hour. This coarse approach was developed in the past but nowadays is a fast and simple computational exercise to determine where and when the Threshold Limit Value (TLV) is surpassed. A rather superficial Computer Fluid Dynamics (CFD) analysis is able to provide insights that are useful to propose measures to keep the pollutants concentrations at safe levels. As illustrative example, the contaminants' level inside a factory is simulated, both in steady and unsteady state, for risk and health assessment to determine the contaminant levels reached as consequence of the normal operation or in case of a sudden release. The case study is based on an example related to the ventilation of a printing factory for which there are field measurements available in literature. Two pollutants are emitted separately; one continuously during operation and the other only sporadically during cleaning. A good agreement is obtained between the simulations and previous field measurements. This case is an example that a design fulfilling the legislation according to the air renewals tabulated can surpass the threshold limit value in practice. The main conclusion is that the legislation should be based on CFD results instead of general tabulated values, as in some cases the ventilation could be too oversized and in others may result insufficient.