Investigation On Energy Saving In The Process Of Ethylene From Biomass Ethanol

The apparent consumption of ethylene in China is over 10Mt. But considering the petroleum resources, it is unpractical to rebuild and extend the current ethylene facilities or construct the new petroleum cracking facilities. China is rich in crop straw resources. It will be a good plan to solve ethylene product shortage and also be sustainable development, if we get ethylene through ethanol which produces by crop straw fermentation. At present, rebuilding extension and process integration of the ethanol dehydration technology are beneficial to improve comprehensive utilization rate of energy and reduce production cost. The price of bio-ethylene with petro-ethylene will be equal or have better economic efficiency. The study on energy-saving process of ethylene from biomass ethanol would have more realistic significance.AnHui Feng Yuan Group newly builted a 17,000t/a ethanol dehydration unit in 2004. The process flow contains two parts: ethanol distillation process and ethanol dehydration process. The ethanol from biomass removes impurities, for example carbon dioxide, fusel oil ect, in ethanol distillation process, and then goes into the reactors for dehydration reaction in gaseous state after preheating vaporization.The current ethylene production from ethanol dehydration facilities, which was build after the fuel ethanol facilities, was dated and high energy consumption. In order to save costs and improve bio-ethylene's competitive power in market, a series of energy-saving measures based on current facilities have been presented combining ethylene from biomass ethanol unit self characteristics. At the same time, a new molecular sieve catalyst which has lower reaction temperature and higher space velocity would be used in the process of ethanol dehydration. A new process suitable for this catalyst will be proposed and simulated, and then the economic efficiency of the two catalysts will be compared.Process simulation of both design condition and reconstruction condition of ethanol distillation and ethanol dehydration processes have been completed by using ASPEN PLUS software. Based on the results of simulation fitted with design data very well, the problem of current process will be analysed using the powerful functions of sensitivity analysis, parameter optimization of ASPEN PLUS. Then the key of process energy saving is found out and energy saving schemes are proposed. There is no stream added in the improved dehydration process, and 21.7% heat consumption is reduced comparing with the current process. If a molecular sieve catalyst is used, no stream added and the heat consumption reduced by 28.5%.