Optimization of vinasse spray-drying

DAIANA V. TRAPÉ; OLIVIA V. LÓPEZ; MARCELO A. VILLAR

Ciudad Autónoma de Buenos Aires

Congreso; WCCE11 - 11th World Congress of Chemical Engineering; 2023

Asociación Argentina de Ingenieros Químicos

Vinasse is a residue of the sugar cane bioethanol industry and its final disposition generates a negative impact on the environment, such as soil and underground water contamination. This residue can be employed to obtain valuable compounds such as poly(hydroxyalcanoate)s (PHA)s by biotechnological processes. The integration of PHAs production process using vinasse to a bioethanol plant can lead to economic and environmental benefits. Although, since vinasse is a viscous liquid, the cost associated to its transport can be significant if the bioethanol plant is far from the PHAs plant. A way to reduce this cost and facilitate vinasse transport could be by dehydration to obtain a lower volume powder. Spray-drying is a good alternative method to obtained powder with good reconstituting characteristics, low water activity and suitable for storage. Maltodextrin (MD) is usually used as drying aid to facilitate drying due to its beneficial role as a carrier [1]. Spray-drying operating variables and vinasse/MD ratio have effects on the drying yield,therefore the objective of this work was to optimize the vinasse spray-dry process, employing MD as aid-additive. For the optimization of drying conditions, it was employed a Box–Behnken experimental design. The independent variables were: vinasse/MD ratio (V/MD), drying air inlet temperature (T), feed flow rate, and atomizing air rate flow. MD was dissolved in 50 mL of vinasse and then 50 mL of water were added. The suspensions were atomized in a Büchi B-290 Mini Spray Dryer setting the operating conditions indicated by the experimental design: temperature (T)130 ºC, 145 ºC, or 160 ºC, feed flow rate 1.5, 3, or 4 mL/min; atomizing air flow rate 357, 473, or 601 L/h. The solids recovered from the gas-solid separation cyclone, together with those from the product collection vessel, were gravimetrically related to the total feed solids content to determine the drying yield (Y). It was feasible drying vinasse by a spray-dry process obtaining yield values between 42.2 and 87.5 %. V/MD ratio and atomizing air rate flow statistically influenced the drying yield (p = 0.0185 and p = 0, respectively). Air temperature and feed flow not affected statistically the response parameter. Drying yield increased with an increase in the atomizing air flow. Drying yield showed an increase in the V/MD ratio extremes. The optimal value of V/MD ratio, air temperature, feed flow, and atomizing air flow that enhanced drying yield were 0.496, 156.7 °C, 4 mL/min, and 561.3 L/h. The humidity of powders varied between 2 and 3 %. The total organic carbon (TOC) of the obtained powders ranged from 68.5 g/L to 112.6 g/L. TOC is an important parameter since these vinasse powders will be used as carbon source to obtain PHAs. Powder vinasse canbe obtained by spray-drying and the V/MD ratio and atomization flow rate are relevant variables for the process.