Analysis of Energy-saving Schemes for the Purification of Raw Biomethanol

Abstract

Biomethanol can be used as a clean biofuel or as a chemical feedstock. Its production process includes a section for its purification downstream the conversion unit, which is generally carried out by distillation, with relevant energy consumption that may significantly impact on the costs of the whole process. This work analyzes different configurations for the biomethanol purification section, for which no works in the literature focusing on this topic have been found, with the aim of determining the best one which allows for a reduction of the energy consumptions and, thus, of the operating costs. The base scheme is composed of two main sections, one for removing the low boiling impurities present in the mixture mainly composed of biomethanol and water and the second one for separating water and other components so to increase the concentration of methanol to the required high purity (99.85 % wt.), with water content < 0.1 % wt., for obtaining an A grade product. Simulations have been carried out by using the commercial software ASPEN Plus® V11.0, with the thermodynamic method Non-Random Two-Liquid (NRTL), suitable for this system and for the low pressure conditions, and by considering a rate-based approach for the simulation of the columns. On the basis of the obtained results, the scheme which favors a reduction of the total (investment and operating) costs of the plant has been determined.