Calcium phosphate decontamination of stainless steel surfaces

A primary constituent in high-temperature (120 - 140 degrees C) milk fouling residues is calcium phosphate in the form of calcium phosphate dihydrate (brushite, CaHPO4 . 2H(2)O) and hydroxyapatite [Ca-5-(PO4)(3)OH]. The removal of these mineral-rich deposits from stainless steel occurs by dissolution and mechanical cleaning. This research uses a novel solid scintillation technique to noninvasively and continuously investigate the removal of P-32-labeled mixtures of calcium phosphate from inner surface of stainless steel tubes. The proposed mass-transfer model suggests that the film is initially removed by dissolution, when compared to the experimental results. An alternative first-order model presented includes the effects of the solvent flow rate and solvent pH on decontamination rates. This model agrees with the experimental cleaning data over the range of pH and flow rates studied.