Techno-Economic Assessment of the AHP Based Selected Method for Separating Formic Acid from an Aqueous Effluent

Formic acid (FA) is used across the world for a wide variety of applications spanning from chemical production to textile and pharmaceutical industries. FA can be synthesized efficiently from the lignocellulosic biomass constituent carbohydrates by acid hydrolysis in a dilute aqueous reaction media. Since FA forms an azeotrope with water, its purification, water recycle and reuse are vital to establishing a cost-competitive process. In this study, the analytic hierarchy process (AHP) was implemented to determine the desired separation method for isolating FA from a 3 wt.% aqueous solution by considering the advantages and disadvantages of each process. Four parameters named as scalable, quality of the final product, repeatable, and energy consumption were defined as criteria to perform AHP analysis. Furthermore, six alternative approaches namely (i) azeotropic distillation, (ii) extractive distillation with a liquid solvent and (iii) solid salt, (iv) the combination of liquid solvent and solid salt, (v) pressure-swing distillation, and (vi) liquid-liquid extraction (LLE) were examined to decide the most preferred separation method with respect to the goal, which is the desired separation method. The AHP results indicated that the alternative approach, the LLE and the scalable criteria have the highest preference with 39.4% and 54% priority, respectively. The proposed process based on the alternative approach could extract 99% of FA by using diethyl ether. Moreover, an estimated minimum selling price (MSP) of 2.48 $/kg FA with 97.4% purity was achieved by using techno-economic assessment for a typical plant with 1715 ton/day capacity.