Experimental Study Of The Ion-Exchange Process In The Production Of Potassium Carbonate

At present, the main method used in China in the production of potassium carbonate is ion-exchange method. This method has such advantages as simple process, reliable technology, less investment, good quality and low cost. But some deficiencies still exist. Firstly, the energy consumption of ammonia removal , drying and other succeeded processes increases greatly, because of the low concentration of the ion-exchanged solution with little ammonium bicarbonate; Secondly, the ammonium chloride wastewater with low concentration can not be recovered easily, which doesn't meet the environmental requirement. Thirdly, in ion-exchange process, the utilization rate of potassium chloride of high cost is low, and the recovery of the K+ is difficult, which causes a great loss of K+ and an increase of production cost. To solve the above problems, this paper put forward that, under the premise of not exchanging production technology and with the fact of production, an experimental study should be conducted on the initial ion-exchange process.When in experiment, the influences of ammonia- potassium ratio, flow rate and pH value on the ion exchanging effect were studied,focusing on the ammonia- potassium ratio. The experimental scheme was determined. Using golden section method, the interpolation points of the ammonia- potassium ratio were interpolated between 1:1～2:1. The experiment was made according to those interpolation points; On the basis of the principle of ion-exchange, the flow rate and pH value were changed in order to change the equilibrium state of the ion-exchange process.The results show that the utilization rate of K+ raises with the ammonia- potassium ratio, but the ascending trend becomes slow;the conversion rate of NH4+ increases first and then decreases with increase of ammonia- potassium ratio; the concentration of K+ in ion-exchange solution begins decreasing when ammonia- potassium ratio is 1.25:1 above; the concentration of NH4+ is the lowest when ammonia- potassium ratio between 1.15:1～1.25:1; both the utilization rate of K+ and the concentration of the ion-exchange solution increases with the decrease of flow rate; the regeneration rate of the ion exchange resin increases greatly in alkaline condition, in the same time, the leak quantity of K+ decreases too.Based on production efficiency and economic factors, the best range of ammonia- potassium ratio is 1.25:1～1.3:1, and the optimal flow rate is 2.5×10^-2m/min～3.2×10^-2m/min. In this parameter range, the utilization ratio of K+ is over 91% in single column. The concentration of K+ in the ion-exchanged solution is in a high level, and that the concentration of ammonium bicarbonate is relatively low.