Drying energy savings potential of fibrous alcohol-water mixtures

As energy costs rise, the need to save energy in drying also increases. This paper shows how energy savings potential of an alcohol-water mixture is achieved at different alcohol levels. The purpose of these laboratory tests was to confirm that wood fiber-based samples containing alcohol or alcohol-water mixtures as bonding mediums, instead of only water, will dry faster, achieving higher drying rates and lower energy consumption. Ethanol has lower heat of vaporization and boiling than water, which makes this possible. In addition, water-ethanol azeotrope has lower evaporation temperature that can enhance energy savings further. The tests investigate drying time, drying rate, energy consumption, and power needs, with mass change measured during drying.

Ethanol was used as the alcohol in the samples, and chemical softwood pulp (pinus sylvestris) was used as the fibers. Four different liquid mixtures were tested that were not found from literature in fibrous conditions: 100% water, 50% ethanol and 50% water, 75% ethanol and 25% water, and 100% ethanol. The samples were formed using a Buhner-funnel and dried using a Sartorius MA100 moisture analyzer with a halogen heater. Data on mass change was collected and analyzed.

The results indicated that increasing the ethanol concentration in the samples generally led to higher average drying rates. However, maintaining consistent grammage was challenging, particularly with higher ethanol concentrations. Energy consumption and power needs were calculated based on the heating and evaporation of the water/ethanol mixtures.

These findings suggest that using alcohol-water mixtures can enhance the drying efficiency of wood fiber-based samples, potentially leading to significant energy savings in larger-scale applications.