Olujide Samuel Sanni - White Rose eTheses 2017-02-23¢  Olujide Samuel Sanni Submitted in...

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  • i

    Calcium carbonate surface/bulk scaling mechanisms and kinetics in a once-through in-situ

    flow visualization rig

    A thesis submitted

    By

    Olujide Samuel Sanni Submitted in accordance with the requirements for the degree of

    Doctor of Philosophy The University of Leeds

    School of Mechanical Engineering September, 2016

    The candidate confirms that the work submitted is his own and that appropriate credit has been given where reference has been made to the work of others. This copy has been supplied on the understanding that it is copyright material and that no quotation from the thesis may be published without proper acknowledgement.

    © 2016 The University of Leeds and Olujide Sanni

  • ii

    Acknowledgement

    All glory to God, it is not by power nor by might but by his spirit, the beauty of

    His grace, favour and faithfulness.

    I would like to express my sincere gratitude to Professor Anne Neville for her

    guidance, profound supervision and support. I am very grateful to Dr Thibaut

    Charpentier who has been very helpful and supportive from the first day of this

    project. Their trust, motivation, outstanding advices, encouragement and

    assistance throughout this project are invaluable.

    I would like to thank the FAST group UK, PTDF Nigeria and University of

    Lagos for every support and contributions to the success of the research. The

    technical and administrative supports of Fiona Slade, Ron Cellier, Jordan

    Thomas, Andrew O’ Brien and Michael Huggan are deeply appreciated.

    I appreciate the members of my research group, the Institute of functional

    surfaces (ifs) especially the scale focus group for creating a nice, versatile and

    challenging atmosphere. Special thanks to Doris, Akinola, Demola, Ogbemi

    and Bello for their contributions and to friends like Ike, Sunday, Pessu,

    McDonald, Lukman, Kayode, Jonathan, Laura, Miriam, Michal, Rick, Wassim,

    Abi, Kelvin, Omotayo, Mohsen, Danny, Rehan, Mohammed, Lesor. Deep

    appreciation to the TREM City of Praise (COP) family for the love and care.

    Special appreciation to my mother, Mrs C.A Sanni and all my siblings for the

    bond, pillar and strong foundation upon which this success is built. My late

    father for the great legacy and sacrifice. Great appreciation to my in-laws for

    their support. All the prayers, encouragement and love really made it possible.

    My deepest appreciation and words beyond gratitude goes to my beloved

    wife, Kemi Sanni for the love we share, prayers, sacrifice, perseverance and

    especially for the perfect gifts of God’s grace to us, our children; Darasimi and

    Damilola, the joy they give cannot be quantified. You are my treasures beyond

    measures.

  • iii

    Abstract

    Scale management is usually a complex mixture of prediction, inhibition and

    sometimes removal strategies. Investigations into scale formation have

    largely been focused on precipitation in the bulk solution by assuming that

    surface scaling always results from pre-precipitated crystals in the bulk

    solution. Recent observations have shown that bulk and surface scaling do

    not share the same trends with respect to crystal growth kinetics and inhibition

    as such the relationship between these two scaling processes are being given

    attention in the literature. Despite much recent attention on scale formation on

    surface, there is still not a full mechanistic understanding of how scale layers

    build on component surfaces. Most of the previous studies have been carried

    out in a closed system where the saturation ratio was decreasing as a function

    of time. As such, the understanding of the precipitation/deposition system

    needs a suitable methodology to build an accurate surface deposition kinetic

    model.

    The objectives of this study are to develop a once-through flow rig system

    suitable to distinctively study bulk precipitation and surface scaling processes

    and also to improve on the understanding of surface scale deposition

    mechanisms and kinetics at constant supersaturation. The in-situ flow rig is

    designed to combine measurement of turbidity in the bulk and real-time

    visualization of scale build up on a solid surface. Calcium carbonate (CaCO3)

    surface and bulk scaling deposition were followed in-situ and in real-time in a

    newly developed flow rig that allows assessment and control of various scaling

    indices and parameters. The kinetics and mechanisms of CaCO3 surface

    scaling are evaluated from images taken with time using the image analysis

    protocols to determine the surface coverage, number of particles and average

    size of the crystal.

    Brines with different values of saturation ratio (SR) 15, 25, 45, 60, 70 and 90

    were tested at 25oC and 40oC. The effects of SR, flow rates and temperature

    on scale deposition were studied. The flow rates used are 10ml/min, 20ml/min

  • iv

    and 40ml/min. Also, the influence of SR and inhibitor concentration on surface

    inhibition efficiency of Polyphosphinocarboxylic acid (PPCA) were studied.

    The newly developed set-up allows for a mechanistic understanding of scale

    build up on the surfaces in flowing conditions at constant SR and helps to

    improve the understanding of both bulk precipitation and surface deposition

    scaling kinetics. Results show that at low SR, the residence time from the

    mixing point to sample was shorter than the induction time for bulk

    precipitation and, as a result, there are no crystals in the bulk solution as the

    flow passes the sample. Therefore, in contrast to popular thinking, the study

    has shown that crystals present on the surface are not always the result of a

    secondary deposition process occurring after the precipitation mechanism

    which occurs in the bulk solution. The determination of surface crystallization

    mechanisms and kinetics allow for the correct type and dosage of inhibitor to

    be selected. Addition of inhibitors at the bulk minimum inhibition concentration

    (MIC) actually aggravates surface scaling

  • v

    Table of content

    Acknowledgement....................................................................................... ii

    Abstract ....................................................................................................... iii

    Table of content........................................................................................... v

    List of Figures ............................................................................................ xi

    List of Tables ............................................................................................. xx

    Publications .............................................................................................. xxi

    Nomenclature .......................................................................................... xxii

    Chapter 1 Introduction ...................................................................... 1

    1.1 Mineral scale in the oil industry ..................................................... 2

    1.2 Background and objectives ........................................................... 5

    1.2.1 Background ........................................................................ 5

    1.2.2 Objectives .......................................................................... 6

    1.3 Outline and overview ..................................................................... 7

    Chapter 2 Literature Review ............................................................. 9

    2.1 Scale formation ............................................................................. 9

    2.1.1 Supersaturation .................................................................. 9

    2.1.2 Induction time ................................................................... 12

    2.1.3 Nucleation ........................................................................ 14

    2.1.4 Crystal growth .................................................................. 21

    2.2 Formation of calcium carbonate scale ......................................... 27

    2.2.1 Calcium carbonate reactions ............................................ 28

    2.2.2 Polymorphic phases of calcium carbonate ....................... 29

    2.3 Factors affecting calcium carbonate scale formation .................. 32

    2.3.1 Physical and chemical factors .......................................... 32

  • vi

    2.3.2 Nature of substrate material ............................................. 41

    Chapter 3 Scale removal, control and investigation techniques 44

    3.1.1 Chemical techniques ........................................................ 44

    3.1.2 Mechanical techniques ..................................................... 45

    3.1.3 Scale inhibitors ................................................................. 45

    3.2 Scale study and investigation techniques.................................... 58

    3.2.1 Study of scale precipitation in the bulk ............................. 58

    3.2.2 Study of