The calcium carbonate deposit control performance of polymer/HEDP blends was compared in laboratory process simulation.  Two primary characteristics were studied: threshold inhibition, where calcium and carbonate were maintained as soluble species in solution, and deposit control measured as resistance to heat transfer (fouling factor) in an "out-of-balance" condition where complete threshold inhibitor was not achieved.  The recirculating water contained 500 ppm each of calcium hardness and total alkalinity (both as calcium carbonate) at either 105 or 130 degrees Fahrenheit.  A homo-polymer of maleic acid was superior to either of two homo-polymer of acrylic acid as a co-additive with HEDP.

89-06: Polymer/HED Blends for Calcium Carbonate Deposit Control