Potash is a widely used granular fertilizer and when exposed to high humidities it readily adsorbs water forming a liquid electrolyte solution on each particle. Heat and mass transfer due to air flow through granular potash beds is studied experimentally and numerically. A one dimensional experimental set-up is used to measure the temperature and air humidity response and mass gain of a potash bed subject to a step change in air flow. A porous media mathematical model is developed to predict the transient temperature and moisture content distributions. The transport processes are modelled as non-equilibrium heat and mass transfer between the porous solid and air flow gaseous phases. The state of the surface electrolyte solution is modelled by the thermodynamics of electrolyte solutions. Experimental and numerical results shows that when there is a strong surface heat source due to phase change, especially near the entrance region, non-equilibrium internal moisture and heat transfer processes exist. The temperature difference between potash granules and the air flowing through the potash bed is significant.