A major challenge faced by the oil and gas industry is the minimisation of scale formation within installations; new regulations are requiring conventional inhibitors to be replaced by green scale inhibition strategies, which may involve anti-fouling surfaces. In order to improve inhibition methods, understanding scale formation on surfaces, and the kinetics of surface scaling processes is a necessity. This study focused on two main objectives. Firstly, the ability of different surfaces to reduce or modify calcium carbonate scale formation was assessed with the final objective being to understand what constitutes a surface that minimises the potential for scaling. Seven different surfaces have been tested, stainless steel, stainless steel pre-treated with Polyphosphinocarboxilic Acid (PPCA), Polytetrafluoroethylene (PTFE), Diamond-Like Carbon (DLC), ceramic and polymer coated stainless steels and an isotropic superfinished stainless steel surface (ISF). A subset of these surfaces was eroded within a Submerged Impinging Jet (SIJ) to assess the possible effect of in-service performance. The surfaces were first characterised by contact angle, roughness measurements, and Energy Dispersive X-ray (EDX). The amount of scale and the morphology of the crystals were assessed using Scanning Electron Microscopy (SEM). The second part of the project uses a relatively new way to assess both precipitation and deposition in-situ and in real-time. A new rig has been designed permitting in-situ and real-time measurements of turbidity in the bulk and observation on the surfaces. Twelve different conditions were tested involving 4 brines and 3 temperatures. Image analysis of the image capture was used to assess the surface coverage, number of object and average size of the particles with time, allowing the kinetics to •be evaluated. From the results, a systematic ranking of the surface resistance to scaling has been established together with an improved description of the scale deposition process. The characteristics of the surface involved in the scale process appear to be a combination of surface chemistry, roughness, and topography and varies from one substrate to another. The kinetics (rate constant) of precipitation and deposition differed but a polynomial relation of third order was discovered between both. The kinetics of both processes was found to be highly temperature dependant.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:550812 |
| Date | January 2011 |
| Creators | Eroini, Violette |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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