Electrolytic Cleaning of Milk Fouling from Plate Heat Exchangers
Fouling of heat transfer equipment during thermal processing of milk is a serious industrial problem. Major drawbacks of fouling include lower heat transfer and flow efficiencies, increased pressure drop and product contamination. The related costs to fouling are millions of dollars per year in New Zealand, due to additional equipment and energy consumption, production loss and environmental impact.
This paper outlines a new electrolytic cleaning technique, which can be performed during milk pasteurisation or during the current cleaning-in-place cycle. This technology involves connecting one plate of the plate heat exchanger as the anode and an adjacent plate as the cathode. Water in the cleaning solution, which flows between these plates, decomposes at the anode and cathode producing oxygen and hydrogen gas at the metal surface. This gas formation provides an additional physical force to dislodge the attached foulant, which should give faster cleaning than current methods.
This paper extends previous work at the University of Auckland, by implementing electrolytic cleaning-in-place to a bench-scale plate heat exchanger. Preliminary experiments performed using DC current for electrolytic cleaning, successfully proved that electrolysed plates can give better cleaning compared to non-electrolysed. However, the electrochemical reactions also enhanced corrosion of the electrolysed plates.
Consequently, several strategies have been compared to minimise electrode corrosion, including using an alternating current and an additional low potential oxidant. Results from these trials have shown that the corrosion from the electrochemical reactions can be minimised, potentially making electrochemical cleaning-in-place a viable method of improving the current dairy cleaning-in-place process.