Vacuum and Convective Drying of Wood: FTIR spectra analysis, colour degradation, and antioxidant activity comparison
Chemical Product Design and Engineering (CPD&E)
Chemical Product Design & Engineering - Poster (CPD&E - P)
Keywords: Vacuum-drying, Oakwood, Colour, Antioxydant-activity, FTIR-analysis
S. Sandoval*, F. Marc, W. Jomaa and J.-R. Puiggali
Transferts Écoulements Fluides Énergétique UMR 8508, Laboratoire interétablissements CNRS, ENSAM, ENSCPB, Université Bordeaux 1, Esplanade des Arts et Métiers, 33405 Talence, France. *sadothsan@yahoo.com
Abstract
The colour of wood is one of the most attractive features. Even when timber is chosen for its structural qualities, the attractive and decorative colour is usually an important factor, particularly with modern trends in design and illumination where a preference is given to light coloured surfaces and wood is usually employed without darkening or staining. In many of these applications, particularly with furniture or in the use of decorative veneers, accurate matching of the colour of different samples is required. Lumber attributes and properties are important because they have a direct bearing on market opportunities and consumer acceptance for many types of manufactured wood products like wood office products and wood household furniture.
The formation of colored substances from phenolic compounds oxidized with air and the formation of dark materials from hydrolysis have been considered the causes of discolouration during drying. In order to reduce hydrolysis and oxidation reactions, vacuum drying process can be used, which offers reduced drying times and higher end-product quality in comparison with conventional drying. Operating at low pressures reduces the boiling temperature point of water and oxygen concentration, moreover enables an important overpressure inside the material which is advantageous for drying and especially for species that do not support a high temperature level, where discoloration can arise. Also vacuum drying offers the possibilities of preventing atmospheric emissions, since during wood drying a complex mixture of chemical compounds is released.
In this work, antioxidant activities were evaluated in dust of oak-wood after vacuum drying and convective drying by using ABTS+• cation method, vacuum drying kinetics with conductive heating and FTIR analysis are presented, discolouration mechanisms are disputed, and a product-process mathematical model is solved. The experimental setup (Figure 1) is a vacuum chamber where pressure is regulated between two values (Pmin, Pmax). The chamber is built in glass; one balance is kept inside the chamber in order to log the mass variation of the sample. A thermometer gives the dryer temperature, K-type thermocouples are placed in the wood. The heating source is an electrical resistance which temperature is controlled with the help of a PID controller.
The conductive heat source is maintained at different temperatures (46, 61 and 70°C) and pressure in the chamber is controlled at different intervals (60-100, 150-250, and 250-300 mbar). Temperature inside the wood sample is obtained at three different positions. Conventional drying at 46, 61 and 70°C, 30% Relative Humidity and 2 m/s air speed is carried out for comparison.
Presented Wednesday 19, 13:30 to 15:00, in session Chemical Product Design & Engineering - Poster (CPD&E - P).
