Screening of membrane technologies in concentration of bitter extracts with simultaneous alcohol recovery: An approach including both economic and environmental issues

Abstract

In this paper, concentration of a bitter extract with simultaneous recovery of ethanol via either nanofiltration or pervaporation is studied from economic and environmental standpoints. The production of a bitter non-alcoholic beverage requires an extraction plant to produce the bitter extract, and a blending-bottling plant that produces the final product. The processes under study are composed by a feed tank coupled to either a nanofiltration or a pervaporation membrane and operated in batchwise form. While the ethanol contained in the permeate is recycled to the main extraction process, the content of the feed tank at the end of the batch is sent to the bottling plant. There, it is diluted with deionized water to produce 1.1 E + 08 L/year of a non-alcoholic beverage. Apart from a base case in which the bitter extract produced in the extraction plant is sent directly to the blending-bottling plant, the economic and environmental performance of two nanofiltration variants using the membrane NF99 HF (Alfa Laval) and two pervaporation alternatives employing PDMS membranes from Sulzer Chemtech and Pervatech BV are deeply investigated within the framework of a screening methodology that can be applied to different membrane technologies and membrane materials. Beginning from experiments at laboratory scale of each process alternative, the corresponding conceptual designs are performed for different values of the main optimization variable; i.e., the nanofiltration/pervaporation advance defined as the ratio between the amounts of permeate (kg) and the feed charge (kg). From results at conceptual design level, economic figures and environmental scores are obtained from an economic model and a life cycle analysis (LCA), respectively. From the results obtained, the different studied alternatives are ranked from both economic and environmental standpoints. Nanofiltration with the membrane NF99 HF (30 °C and 16 bar) showed the best economic and environmental performance. On the other hand, pervaporation with PDMS membranes may be a suitable choice whenever the operating conditions allow for heat integration between the retentate and the permeate. Finally, the relevance of both process optimization with the aid of conceptual models and LCA as key tools in the screening procedure is highlighted.