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