Novel Heat-Pump-Assisted Extractive Distillation for Bioethanol Purification
Novel Heat-Pump-Assisted Extractive Distillation for Bioethanol Purification
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DOI：
10.1021/ie504459c
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发表时间：
2015-02
影响因子：
4.2
通讯作者：
Hao Luo;C. Bîldea;A. A. Kiss-A.
中科院分区：
文献类型：
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作者：
Hao Luo;C. Bîldea;A. A. Kiss-A.
生物乙醇燃料的纯化涉及一个能量密集的分离过程，以浓缩在发酵阶段获得的稀释流，并克服乙醇-水混合物的共沸行为。传统的分离顺序采用三个精馏塔，执行几个任务，受到高能要求的惩罚：乙醇预浓缩，萃取精馏和溶剂回收。为了解决这一问题，我们提出了一种新的热泵辅助萃取精馏过程，该过程发生在分隔壁塔（DWC）中。在这种配置中，萃取DWC的乙醇顶部蒸汽流从大气压再压缩到3.1 bar以上（从而达到更高的温度），并用于驱动DWC的侧再沸器，该再沸器负责水的汽化。为了与先前报道的研究进行公平的比较，我们在这里考虑10%乙醇（100千吨/年工厂产能）的混合物，使用乙二醇作为质量分离剂进行浓缩和脱水。在AspenTech Aspen Plus中对提出的蒸汽再压缩（VRC）热泵辅助提取DWC进行了严格的过程模拟。结果表明，该工艺的比能需求从2.07 kWh/kg（经典序列）降至1.24 kWh/kg乙醇（vrc辅助提取DWC）；因此，可以节省40%以上的能源。考虑到在热泵辅助的情况下对压缩机的要求和电力的使用，与优化的传统分离工艺相比，尽管资本支出增加了29%，但新工艺的年总成本可能降低约24%。
The purification of bioethanol fuel involves an energy-intensive separation process to concentrate the diluted streams obtained in the fermentation stage and to overcome the azeotropic behavior of the ethanol-water mixture. The conventional separation sequence employs three distillation columns that carry out several tasks, penalized by high-energy requirements: preconcentration of ethanol, extractive distillation, and solvent recovery. To solve this problem, we propose here a novel heat-pump-assisted extractive distillation process taking place in a dividing-wall column (DWC). In this configuration, the ethanol top vapor stream of the extractive DWC is recompressed from atmospheric pressure to over 3.1 bar (thus to a higher temperature) and used to drive the side reboiler of the DWC, which is responsible for the water vaporization. For a fair comparison with the previously reported studies, we consider here a mixture of 10 wt % ethanol (100 ktpy plant capacity) that is concentrated and dehydrated using ethylene glycol as mass-separating agent. Rigorous process simulations of the proposed vapor recompression (VRC) heat-pump-assisted extractive DWC were carried out in AspenTech Aspen Plus. The results show that the specific energy requirements drop from 2.07 kWh/kg (classic sequence) to only 1.24 kWh/kg ethanol (VRC-assisted extractive DWC); thus, energy savings of over 40% are possible. Considering the requirements for a compressor and use of electricity in the case of the heat-pump-assisted alternative, it is possible to reduce the total annual cost by approximately 24%, despite the 29% increase of the capital expenditures, for the novel process as compared to the optimized conventional separation process.