Separation of phosphoric acid sludge: effect of flocculation on settling and P2O5 recovery rates

Phosphoric acid sludge is one of the prominent problems in the phosphate industry. Its formation is co-occurred by considerable losses of P2O5 that affect the process performance. Management and valorization of this waste is a key issue. This work aimed to deal with this industrial concern by studying the influence of the flocculation on the sludge sedimentation and thus the P2O5 recovery rate. The flocculation tests were conducted in the presence of various types of anionic polymers. The effect of dosage, molecular weight, and type of flocculant were examined. The results indicated that all polymers showed settling performance improvement. And, the flocculant with the highest molecular weight (F1), showed the best settling performance with a pace of 3.3 cm/min and the lowest turbidity value of 40.4 NTU using a dosage of 5 ppm. Due to its high molecular weight, this polymer carries a polyelectrolyte bridging mechanism, which allows the absorbed polymer to move further away from the surface of the particle and then increases the particle radius, the number of collisions, and thus the particle size. However, for the P2O5 recovery rate, the sulfonic polymer (F5) was the best performer allowing recovery of 78.8% of the total mass of the sludge. F5 is weakly amphoteric. Polymers containing sulfonic acid groups are known to be inherently powerful than the carboxylic acid groups as they are stable due to their high energy barrier. According to the results, the flocculation increases the recovery of P2O5, which represents a profit of more than 30 kg of clarified phosphoric acid per 1 tone of sludge

Effect of phosphate quality on foam generation during the phosphoric acid production process

International audienceThe presence of organics materials in phosphate ores generates foam during the manufacture of phosphoric acid, thus affecting the production performance and the quality of the products. Today, in the phosphate industry defoamers are used to reduce the negative impact of foam phosphoric production. In the present work, we focusedon root cause evaluation for foam generation during the phosphoric acid production process, we evaluatedthe effect of phosphate rock quality in terms of organic carbon (OC) and carbonate content, on foam generation using a laboratory protocol for foaming ability evaluation. The results show that there is a relationship between the volume of the foam generated and the values of those impurities, while the volume of foam generated is higher when the concentration of OC and Carbonate is high. In our work, we confirm that the foaming ability of the phosphate rock can be avoided if the concentration of organic carbon less than 0.1% and less than 3% for carbonate