New Thin Membrane to Reduce Weight and Footprint of Offshore Sulfate Removal Units

Abstract

Abstract In the past three years, several offshore platforms have commissioned sulfate removal units (SRUs) with a new, Thin-Membrane Technology which allows the highest active membrane area to be packaged into the standard spiral wound, sulfate removal element. These newly installed elements are the first of their kind to utilize the new technology and demonstrate how offshore platforms can benefit from this innovation. The spiral wound element was developed in the 1970s to package RO and NF membranes into a compact, efficient, and modular spiral element. Since that time, incremental improvements in element design and materials of construction have led to enhanced efficiencies and productivity. However, the overall element design and membrane construction have remained largely unchanged. Most notably, in recent years, efforts to fit more material into the present spiral element configuration reached an optimal plateau. Advances in automated manufacturing resulted in either increasing the membrane surface area or increasing the thickness of the feed/brine spacer. Either enhancement could be selected depending on the quality of the feedwater or the efficiency of the pre-treatment. However, it was not possible for the designers of SRUs to capitalize on the benefits associated with both enhancements simultaneously. For this reason, when treating high quality feedwater, SRU designers prefer to use spiral elements that contain higher surface area to reduce capital cost, footprint, and weight. When treating high fouling feedwater with minimal pretreatment, SRU designers use elements with the thicker feed/brine spacer to reduce differential pressure losses, minimize fouling and improve cleaning effectiveness. Designers selecting elements with thicker spacer forfeit the benefits associated with higher area elements while designers who select elements with higher area forfeit the benefits of the thicker spacer. But in recent years, thanks to innovations in material science, a new generation of sulfate removal elements are now being manufactured and deployed in full scale systems on offshore platforms. These new elements offer both a larger surface area and a thicker feed/brine spacer. This paper will detail the innovation in the construction of the new membrane material and compare its effects on element performance with the previous generation membranes. The paper will analyze the operation of these new elements in SRUs running on offshore platforms for as much as one year. Based on the operation of these new elements, the footprint, weight, and capital cost benefits of the new membrane relative to current membranes will be analyzed.