Mineral Sulfite Scale Issues: Water Compatibility and Mitigation Assessment

Abstract

Abstract This paper aims to study the compatibility of two mineral waters (containing sulfites and calcium) likely to produce large quantity of sulfites scale if they are mixed. This scale formation impacts the production facilities and is hardly recoverable. Consequently, this work is assessing the scale risks simulation and simple laboratory tests. The results of both methods show very high risks of precipitation likely to disturb process operations. The scale quantity is also very sensitive to pH modification. Then, three different scale mitigations solutions were evaluated to prevent any deposit formation by working either on the sulfites of the first water or on the cations of the second one. These measures are: The formation water divalent cations sequestration thanks to Ethylenediaminetetraacetic acid (EDTA) as complexing agent.The early precipitation of sulfites thanks to CaCl2 or CaCO3 addition.The chemical scale mitigation by antiscalant injection. The injection of scale inhibitors did not show any efficiency whatever the scale inhibitor and the concentration (30, 60 and 120 ppm) for process water at pH = 8 and 12. The sequestration requires a high amount of EDTA (5.9 g EDTA/g divalent cations) to be fully effective due to stochiometric conditions necessity. The early precipitation with 120 g.L-1 of CaCl2 remains the most effective solution and enables the easy separation of sulfites salts by physical methods such as settling. The most promising solution consists in a mix of early precipitation, acidification and scale inhibitor addition.