Reduction of milk fouling in a plate heat exchanger system using food-grade surface coating

A plate heat exchanger (PHE) system operated in recirculation mode was used to study the effect of PHE surface modification on fouling. Two commercially available coatings were used to coat stainless steel (SS) PHE plates. Fluid skim milk at two different flow rates was circulated through heating and cooling sections of the PHE unit continuously for 6 h. The amounts of fouling occurring on the coated surfaces were compared with the fouling observed on the SS-316 control surface. The Lectrofluor 641 coated plates exhibited good adhesion qualities with the SS-316 substrate and could minimize the incidence of fouling by 94% to 95% when compared to the control, whereas the Ni-P-PTFE coated plates reduced fouling by 86% to 87.5% but showed signs of discoloration. Chemical analysis using XPS showed no conclusive evidence of Lectrofluor 641 coating material incursion into the deposited foulants, while there was some evidence of incursion of fluorine from the Ni-P-PTFE coating material into the deposited foulants.