Application of ultrasound in heat exchanger handling supersaturated CaSO4 solution for reduction of scaling by induced precipitation and in-situ cleaning

Application of ultrasound to the heat exchanger handling supersaturated solution of CaSO4 has been investigated with an objective reducing scale formation and in-situ cleaning. A lab-scale double pipe heat exchanger, equipped with 6 transducers each of 33 kHz, was applied to understand effect of various process and ultrasonic parameters. Application of ultrasound for 10 min at 200 W power at every 4 h resulted in reduction in average fouling resistance by 36.82 %, 42.87 % and 43.74 % at flow rate of 150 ml/min, 300 ml/min and 600 ml/min respectively. Quantity of salts precipitated in the bulk under these conditions were 1.4 to 2.6 times more than without the application of ultrasound confirming intensification. SEM analysis revealed that formed scale was dominated by platelets and needle type of CaSO4 crystals. Application of ultrasound on the heat exchanger surface was elucidated as an effective approach for intensified heat transfer.

Automated summary

The application of ultrasound to a heat exchanger handling supersaturated solution of CaSO4 was studied to reduce scale formation and clean the exchanger in-situ. A lab-scale double pipe heat exchanger with 6 transducers of 33 kHz was used to investigate the effect of process and ultrasonic parameters. The results showed that applying ultrasound for 10 minutes at 200 W power every 4 hours resulted in a reduction in average fouling resistance by 36.82%, 42.87%, and 43.74% at flow rates of 150 ml/min, 300 ml/min, and 600 ml/min, respectively. The precipitation of salts in the bulk increased by 1.4 to 2.6 times under these conditions, confirming the intensification. SEM analysis revealed that the formed scale was dominated by platelets and needle-like CaSO4 crystals. The application of ultrasound on the heat exchanger surface was found to be an effective approach for intensified heat transfer.