Production of soda ash from Trona solution was achieved in a spray dryer reactor. Fractional conversion of NaHCO3 reached to values close to unity in this unit within a residence time of less than a second. Results indicated that above 140 degrees C, heat transfer limitations played a significant role on the calcination process taking place in the spray dryer. Equilibrium limitations may become important only at very low temperatures and at high CO2 and H2O partial pressures. Results obtained in the spray dryer and from the thermal gravimetric analysis of Trona crystals agreed well. It was also shown that the predictions of the unreacted core model are in good agreement with the kinetic data.