An Experimental Study of Sulfide Scale Formation in Pipes

Abstract

Results are summarized of an experimental investigation of scale formation in a pipe with four sulfide systems; mixed and and iron The influence of the main system variables (flow velocity. species concentration, temperature) has been established and valuable insight has been gained into the prevailing mechanisms. The data from all four systems are surprisingly similar. They show that appreciable mass of relatively strongly adhering deposits develops only within a narrow range, which is associated with the solubility of each sulfide. With increasing (and supersaturation), precipitation in the bulk solution occurs immediately after mixing of the rich and sulfide-rich reagent streams, which tends to consume a significant part of metal cations, thus causing a drastic reduction of the driving force for surface crystallization and consequently of the deposition rate. All evidence indicates that the process of scale formation, at least within the narrow limits where a significant amount of hard scale develops, is controlled by the convective diffusion of lattice ions to the pipe surface. The implications of the above results, for the development of an appropriate scale control strategy in systems, is briefly discussed.