Technology Note: CYBREAK® 675 defoamer controls foam, reduces P₂O₅ losses and provides other benefits that increase phosphoric acid recovery

Overview

In the production of phosphoric acid by the dihydrate process, Cytec’s CYBREAK^® 675 defoamer serves several functions. The defoamer enables plants to:

• Eliminate or minimize foam
• Cut P₂O₅ losses
• Reduce moisture
• Increase extraction recovery

Each of the above applications helps increase recovery of phosphoric acid.

Usage of CYBREAK 675 defoamer

Minimizing foam

Added to the top of the digester tank, CYBREAK 675 defoamer has been shown to eliminate 50 cm (20 inches) of foam. The product is also used on the secondary wash sector of the filter, where it removes existing foam or suppresses the formation of foam.

The reduction of foam occurs immediately upon adding the defoamer. Foam is suppressed as long as the product is fed to the tanks. During a plant run with a production rate of 20 t/h P₂O₅, CYBREAK 675 defoamer provided best results when applied neat from the tote at a dosage of 600 g/t P₂O₅.

Cutting P₂O₅ losses

Using CYBREAK 675 defoamer in the digester and/or second wash point reduces P₂O₅ losses significantly, increasing chemical recovery.

The product is added neat by a positive displacement pump. The dose and duration of application varies according to plant and operating conditions.

At a plant trial, a dose of 600 g/t P₂O₅ led to a 72.5 percent reduction of P₂O₅ losses. In another trial, a dose of 14 l/h in the digester and 6 l/h at the secondary wash point (totaling approximately 400 g/t P₂O₅) resulted in a 24.3 percent decrease in P₂O₅ losses. On adding the defoamer only to the second wash at a rate of 1 kg/t phosphogypsum, P₂O₅ loss dropped by 44 percent.

Reducing moisture

CYBREAK 675 defoamer reduces moisture in the gypsum waste from the filter, facilitating its handling and disposal. The product is fed neat from the tote directly to the second wash where water is added, before the removal of the filter cake.

CYBREAK 675 defoamer reduced moisture by 17.9 percent during a plant trial when dosed at 150 l/h or approximately 1 kg/t of phosphogypsum. In cases where the defoamer was applied to both digester and second wash at dosages varying from 400 to 600 g/t P₂O₅, it reduced moisture by 11.5 percent to 13.4 percent.

Increasing extraction recovery

Extraction recoveries can be further increased by adding CYBREAK 675 defoamer to the reactor and second wash. During fieldwork, a dose of 400 g/t P₂O₅ raised extraction recovery from 95.27 percent to 96.19 percent.

Conclusion

Depending on plant conditions and product usage, CYBREAK 675 defoamer improves results of several of the above processes simultaneously. The optimum dosage, duration and point of application are best determined through plant trials.