Boiling Point, Specific Heat and Density Measurements and Modeling of Soybean Molasses and Its Aqueous Solutions

Abstract

This work reports a new set of experimental data of boiling point elevation (BPE), specific heat and density for soybean molasses and its aqueous solutions at different total solids concentration and temperatures. BPEs up to 8.2C were measured with an ebulliometer at pressure range of 7.6-86.9 kPa and mass fraction of total solids up to 0.6. The method of mixtures in a quasi-adiabatic calorimeter was used to determine specific heats from 3,394 to 3,948 J/kg/C as a function of mass fraction of total solids between 0.1 and 0.4. Densities of the same product measured by applying the oscillating U-tube method were close to 995-1,104 kg/m 3 at 40-60C in the mass fraction range of total solids from 0.05 to 0.4. Different reliable empirical models (Capriste-Lozano, based on Dühring's and mixing rules) were suggested to estimate the examined properties in a temperature and a solid mass fraction range wider than those experimentally investigated. Transient data of mass fraction of total solids were also obtained in a single-effect evaporator at two different pressure (32.5 and 85.2 kPa). In order to highlight the importance of the measured thermophysical properties, a valid model based on conservative equations of mass and energy was used to simulate the process of concentration of aqueous solution of soy molasses. PRACTICAL APPLICATIONSSoybean molasses is a carbohydrate-rich by-product from soybean meal processing for production of protein concentrate. This product is normally concentrated by evaporation and further used as raw material for animal feed, industrial boiler fuel, production of isoflavones and as a substrate in fermentation processes, especially for the production of alcohols. Despite the large volume generation of this agro-industrial residue and its growing commercial applications, its thermophysical properties, such as boiling point, specific heat and density, are not available in the literature. These properties are fundamental to design, simulate and optimize process operations involving such a by-product. In this context, this study aims to cover this lack, providing the experimental determination and modeling of the properties mentioned earlier.