ACID CLEANING OF GYPSUM DEPOSITS FROM A HEAT TRANSFER SURFACE

Abstract

Scale deposits formed from supersaturated calcium sulfate solutions with and without mitigating wood pulp fibers where successfully removed from a stainless steel heat exchanger test section in a separate flow recycle loop with dilute acetic acid. The calcium ion concentration was lower in the cleaning solution when fibers were added to the fouling suspension in the fouling experiments. The calcium ion concentration was lowered further in the cleaning solution when higher fiber concentrations were used in the fouling solution. This confirmed that fibers modified the nature and structure of the deposit and reduced the amount of fouling. When low concentrations of fiber were used (<0.1 mass percent), the corresponding decreased rate of cleaning indicated that some of the foulant had been trapped in the cellulosic structure adhering to the surface, leaving less deposition on the actual metal surface.

Keywords:

• Acetic acid
• Calcium ion
• Fouling deposits
• Heat transfer surface
• Rate of cleaning
• Wood pulp fibers

Notes

^a Basis: number of fibers/unit mass, medium-coarseness pine, length = 2.48 mm, RFN = 100.