Mathematical description of sodium chloride diffusion and its practical impact on the processing of animal fleshings

Abstract

Diffusion of sodium chloride plays key role in the pre-tanning treatment of raw hides, namely in the brine curing and soaking operations. Understanding the transport processes related to these operations gives ground for their optimization and thus to reduction of the adverse environmental impact as well as minimization of the consumption of sodium chloride, water and energies. Mathematical model of raw hide curing is presented and its modification for spherical coordinates applied on the description of the desalting of fleshings, a cheap raw material for the production of biodiesel and high quality gelatin. Desalting is the key step in the fleshings complex processing and the quality of the resulting products is highly dependent on the precise performance of the desalting operation. The experimental part includes determination of the effective diffusion coefficient of NaCl during brine curing on model porous material using color indication of the border area, determination of the diffusion coefficient of NaCl in the inner volume of fleshing during desalting, and pilot scale testing of the efficiency of fleshings desalting. The obtained diffusion coefficients were compared with the theoretical value at infinite dilution and factors affecting the diffusion coefficient values were discussed.