Simplified relationships for the equilibrium partial pressure of the gas phase components were presented for the crystallization conditions of sodium bicarbonate in the NaCl–NH3–CO2–H2O system. Based on the partial pressures computed from the validated mixed-solvent-electrolyte (MSE) model, the regression equation coefficients were derived for explicitly correlating the partial pressures with the liquid phase concentrations and temperature in the range of (308.15 to 338.15) K. A good agreement was found between pressures calculated from the algebraic equations and compared with corresponding values computed from the MSE model. The obtained exponential equations can be directly used for the estimation of the equilibrium partial pressures in the process conditions of carbonation columns.