14. Advanced thermodynamic modelling for complex fluids
Submitting Institution
Imperial College LondonUnit of Assessment
Aeronautical, Mechanical, Chemical and Manufacturing EngineeringSummary Impact Type
TechnologicalResearch Subject Area(s)
Chemical Sciences: Physical Chemistry (incl. Structural), Theoretical and Computational Chemistry
Engineering: Chemical Engineering
Summary of the impact
The SAFT-VR family of thermodynamic models has made it possible
to predict reliably the behaviour of the many complex and challenging
fluids that are found across a range of industrial sectors, including oil
& gas, chemicals (refrigerants, surfactants, polymers), energy (carbon
capture solvents, carbon dioxide-rich streams) and pharmaceuticals.
The SAFT-VR models have had a wide impact on industrial practice. At BP,
they have been used to design novel surfactants that have increased the
lifetime of oil fields up to five-fold, avoiding maintenance interventions
costing millions of dollars and increasing productivity by 50% (worth $2-3
million per year per well). At Borealis, they have been used to
understand how to increase the productivity of the reactor in the flagship
Borstar process by 30%. At ICI and Ineos/Mexichem, they have been used to
design efficient processes for producing replacement refrigerants with
much reduced reliance on extreme and expensive experiments involving
hydrogen fluoride, a highly corrosive substance. Industrial demand for
access to the predictive capabilities of SAFT-VR has been such that
Imperial College has licensed the software in 2013 to a UK SME in order to
distribute it worldwide to users.
Underpinning research
Fluid mixtures form an integral part of our modern lifestyle, from the
use of simple solvents in chemical processing to opto-electronic devices
with liquid crystalline and polymeric materials. The prediction of the
phase behaviour of these fluids (e.g., in what phase(s) they exist at
given temperature, pressure and composition) and of their thermophysical
properties, underpins the ability to design efficient and competitive
manufacturing processes. Yet, until recently, it had not been possible to
accurately model the phase behaviour of complex mixtures involving, for
example, water, oil, surfactants and salts. With the Statistical
Associating Fluid Theory for potentials of Variable Range (SAFT-VR)
platform, the Imperial College group consisting of Professors Claire
Adjiman (1998-date), Amparo Galindo (2000-date) and George Jackson
(1998-date) has played a central role in developing a theoretical approach
for the description of molecular interactions such as hydrogen bonding,
dipolar forces and chain flexibility, which are of crucial importance in
industrially-relevant fluids. This body of work represents a major advance
in the application of formal statistical mechanics to realistic molecular
interactions. Due to its predictive accuracy, which has been validated
experimentally, its versatility and its firm molecular foundation, the
SAFT approach is rapidly superseding well established chemical engineering
equations of state, putting the UK at the leading edge of molecular
modelling of multicomponent fluids.
The SAFT-VR equation of state, initially developed by Galindo and
Jackson, brought significant flexibility to the modelling of complex
molecular interactions, allowing hydrogen-bonding, dipolar and other
strong interactions to be modelled within a unified approach [1]. The
framework has been demonstrated to offer exceptional predictive
capabilities for complex fluids including polymers, polar fluids (e.g.,
carbon dioxide, refrigerants), strongly associating / hydrogen bonding
fluids (e.g., carboxylic acids, hydrogen fluoride, water), mixed
electrolytes (e.g., inorganic salts, charged surfactants), gas hydrates
and asphaltenes. The same models can be used to describe the behaviour of
a given mixture across wide temperature and pressure ranges. The group has
published 54 papers on the technique and its improvements and applications
since the late 90s, and the approach has been widely taken up by other
academic researchers.
A key milestone in the development of the theory is the extension to
mixtures containing electrolytes and exhibiting salting-out behaviour,
which are pervasive in the oil and fine chemicals industries. This work,
undertaken in collaboration with Schlumberger, showed that a broad range
of electrolytic mixtures could be treated within a single framework, with
transferable parameters for the ions, thereby maintaining the predictive
capabilities of the approach [2].
A further milestone was reached with the development of a group
contribution version, SAFT-f067, by PhD student Alexandros Lymperiadis
(2003-2008; supervisors Adjiman, Galindo, Jackson). In this version, the
basic building blocks are atomic groups (e.g., CH3 or OH), rather than
whole molecules [3]. This dramatically increased the predictive
capabilities of the methodology, by allowing the thermodynamic properties
of new molecules or mixtures to be represented reliably, in the absence of
any experimental data.
While there have been many applications of SAFT-VR to fluids of
industrial relevance, those with the highest impact on practice include
the modelling of hydrofluorocarbon (HFC) replacement refrigerants by a
number of PhD students and PDRAs (1998-2008; supervisors Adjiman, Galindo,
Jackson); this need arose since the original chlorofluorocarbon (CFC)
refrigerants are responsible for the depletion of ozone in the upper
atmosphere. The production of HFCs invariably involves mixtures containing
HF, a highly corrosive material, which renders experiments very expensive
and complex. SAFT-VR models were shown to predict their behaviour well,
while standard methods fail due to the extreme association between the
molecules in these mixtures [4]. At the other end of the molecular scale,
SAFT has been found to provide an excellent description of the phase
equilibria of aqueous solutions of hydrocarbons and micellar solutions of
alkyl polyoxyethylene surfactants by PDRA Blanca Garcia (1998-2000;
supervisor Jackson) and PhD student Gary Clark (2005-2008; supervisors
Galindo, Jackson); the phase diagrams of these non-ionic surfactants and
polymers are characterized by closed-loop cloud curves denoting large
regions of re-entrant miscibility which require a specific treatment of
molecular association [5]. Finally SAFT has been used by PDRA Andrew
Haslam (2002 to date; supervisors Galindo, Jackson) to provide a very
effective representation of the phase behaviour (adsorption) in gas phase
polymerisation reactions [6]; e.g., a gas phase comprising the ethene
monomer and but-1-ene co-monomer in contact with a reacting polyethylene
grain.
As a result of these advances, the academics have been invited to present
keynote lectures at leading international conferences, including at the
Thermodynamics Conference Series (Jackson, UK, 1999; Adjiman, Greece,
2011), European Symposium on Applied Thermodynamics (ESAT — Jackson,
Greece, 2000 and Denmark, 2006; Galindo, St Petersburg, 2011), the EFCE
International Workshops on Methods for Product and Process Design
(Jackson, Germany, 2010, 2013), Properties and Phase Equilibria for
Product and Process Design (PPEPPD — Jackson, Japan, 2001; Galindo, China,
2010), Foundations of Molecular Modeling and Simulation (FOMMS; Adjiman,
USA, 2012), the American Institute of Chemical Engineers Annual meetings
(AIChE; Jackson, USA, 2012). The group launched the SAFT Workshop Series
in 2010; two workshops have taken place so far, in Spain and France.
In addition PhD students and postdocs from the group have undertaken
numerous consultancies (e.g., BP, Shell, Total, Exxon, Schlumberger, Ciba,
BMS, Pfizer, P&G), and as a result of the group interactions a number
of our staff are now employed in key companies (BP, Shell, Qatar
Petroleum, Air Products, Aspen Technology, Genesis Oil & Gas, KBC
Advanced Technologies, Process Systems Enterprise, Solvay etc.).
References to the research
* References that best indicate quality of underpinning research.
*[1] P. Paricaud, A. Galindo, G. Jackson, "Recent advances in the use of
the SAFT approach in describing electrolytes, interfaces, liquid crystals
and polymers", Fluid Phase Equilibria, Vol 194, pp. 87-96, (2002)
ISSN:0378-3812, DOI: 10.1016/S0378-3812(01)00659-8
[2] B.H. Patel, P. Paricaud, A. Galindo, G.C. Maitland, "Prediction of
the salting-out effect of strong electrolytes on water plus alkane
solutions", Industrial & Engineering Chemistry Research, Vol 42, pp.
3809-3823, (2003) ISSN:0888-5885, DOI: 10.1021/ie020918u
*[3] A. Lymperiadis, C.S. Adjiman, A. Galindo, G. Jackson, "A group
contribution method for associating chain molecules based on the
statistical associating fluid theory (SAFT-gamma)", Journal of Chemical
Physics, Vol 127, pp. 234903-234903-22, (2007) ISSN:0021-9606, DOI:
10.1063/1.2813894
[4] A. Galindo, S.J. Burton, G. Jackson, D.P. Visco, D.A. Kofke,
"Improved models for the phase behaviour of hydrogen fluoride: chain and
ring aggregates in the SAFT approach and the AEOS model", Molecular
Physics, Vol 100, pp. 2241-2259, (2002) ISSN:0026-8976, DOI:
10.1080/00268970210130939
[5] G.N.I. Clark, A. Galindo , G. Jackson, S. Rogers and A.N. Burgess,
"Modeling and understanding closed-loop liquid — Liquid immiscibility in
aqueous solutions of poly(ethylene glycol) using the SAFT-VR approach with
transferable parameters", Macromolecules, Vol 41, pp. 6582-6595, (2008),
ISSN:0024- 9297, DOI: 10.1021/ma8007898
*[6] A. J. Haslam, Ø. Moen, C.S. Adjiman, A. Galindo, G. Jackson in
"Multiscale Modelling of Polymer Properties", Laso, M. and Perpète, E.A.
ed. (Elsevier Science, Amsterdam), pp. 301-332, (2006), ISBN-13:
978-0444521873, DOI: 10.1016/S1570-7946(06)80015-5
Details of the impact
A molecular description of matter using statistical mechanical theories
and computer simulation is the key to understanding and predicting the
thermophysical properties of dense fluids and materials. Building on the
theoretical advances in the development of the SAFT-VR equation of state,
and its success in modelling a wide range of complex fluids, SAFT-VR has
attracted increasing attention from industry. The application of the
SAFT-VR approach to industrial problems has occurred primarily through
collaborative projects, secondments and consultancies. Among the more than
20 consultancy and collaborative projects that have been completed
successfully using the SAFT-VR technology, we highlight the following
impacts:
- Design of manufacturing processes for the production of replacement
refrigerants (Chief Scientist, ICI/AkzoNobel [7]): a huge challenge in
the design of such processes is the need for phase equilibria data for
mixtures involving hydrogen fluoride (HF). This is a highly corrosive
and dangerous substance, making experiments difficult, costly and
undesirable. In traditional distillation columns, each tray incurs an
additional cost of £1m in material costs due to the corrosive nature of
HF. Thanks to its predictive capabilities, SAFT-VR was used in lieu of
experiments to generate the data required for process design. SAFT-VR
has also been used to identify erroneous experimental data, in cases
where the formation of two liquid phases had not been correctly
identified, thereby lowering the risk of process development by avoiding
costly design errors.
- Surfactants: SAFT-VR was used in a collaborative project with BP
Exploration to understand the behaviour of surfactants used in enhanced
oil recovery to extend oil field lifetimes by a factor of up to 5. BP
North Sea Operations Manager [8], our collaborator at BP Exploration,
commented that the use of SAFT-VR removed the need for a large
experimental programme to identify a surfactant formulation for squeeze
treatment, focusing the effort onto half a dozen options only, out of an
essentially infinite formulation space. He stated the following: "Large
cost savings can be achieved by extending the squeeze lifetimes: the
average cost of an intervention on BPA's Magnus asset is £130K (with
deferred oil costs) and annual treatment costs run to several million
pounds.I could also point to some side-benefits: one of the wells in
the North Sea was shut in at 8mbd [mbd=thousand barrels per day] for a
scale squeeze. When it was squeezed with the glycol ether treatment,
it came back on at 12mbd. The accelerated value of this production
would be significant, I would imagine order 2-3mm$ [million $] (1.4
million barrels per year accelerated by 1 year at 20$/bbl, say). Also
the business was developed and transferred to TR Oil Services,
creating additional work and benefits to the wider UK oil industry.
(...) I have rarely seen an academic project yield quite such direct
insights and benefits and it remains one of the highlights for me of
what can be done with quality research and development." The
business was developed and transferred to TR Oil Services, creating
additional work and benefits to the wider UK oil industry.
- Increased productivity in polyethylene gas phase reactor (Dr Moen,
Borealis [9]). SAFT-VR was used to identify a mechanism to increase
reactor productivity by 30% during polymerisation in Borealis' Borstar
process [6]. Such an increase in productivity is key to the production
of such a commodity product as polyethylene. By changing the "inert" gas
used in the process, it was shown that the solubility of the key
reactant, ethylene monomer, could be increased significantly, resulting
in an increased reaction rate. Such a prediction is made possible by
SAFT-VR's ability to model the behaviour of highly non-ideal polymer-solvent
mixtures.
The collaborative and consultancy projects created demand for making
SAFT-VR more widely available to industrial users. To enable this, the
software for the SAFT-VR family of models was licensed in 2009 via
Imperial Innovations to Process Systems Enterprise Ltd (PSE), a thriving
SME spun out of Imperial in 1997. In 2012, with customers impressed by the
accuracy and versatility of the platform, PSE acquired the full rights to
the software, which is now marketed as gSAFT [10], [11] and [12]. gSAFT is
a key technological element in the £3m project (partly funded by ETI,
[13], on end-to-end modelling of carbon capture and storage (CCS) chains;
this project alone has created four full-time highly skilled jobs at PSE's
UK headquarters [10]. The development and marketing of gSAFT as a
strategic technology by PSE (Weblink [14]) has re-inforced its impact
across multiple industries.
Sources to corroborate the impact
[7] Chief Scientist, AkzoNobel previously ICI to confirm the use of the
SAFT-VR approach for the for the production of replacement refrigerants
[8] North Sea Operations Manager, BP to Impact on increased lifetime and
productivity of oil fields through squeeze treatment:
[9] Senior Advanced Process Control Manager, Borealis Group to confirm
the Impact on polymerisation reactor productivity
[10] Marketing Director & Deputy Managing Director, Process Systems
Enterprise (PSE) Ltd. to confirm Impact on oil industry and UK process
modelling SME via licensing
Weblinks
[11] "News and Events-One of the most cited pieces of research gets its
due" Imperial College London (2007)
http://www3.imperial.ac.uk/newsandeventspggrp/imperialcollege/newssummary/news_12-10-2007-
9-51-21 (Archived at https://www.imperial.ac.uk/ref/webarchive/wrf
on 5th September, 2013)
[12] "gSAFT-Revolutionising physical property prediction for complex
fluids" Process Systems Enterprise www.psenterprise.com/gproms/options/physprops/saft/index.html
(Archived at https://www.imperial.ac.uk/ref/webarchive/xrf
on 5th September, 2013)
[13] "UK's ETI launches £3 million carbon capture and storage project"
Energy Efficiency News (2011) http://www.energyefficiencynews.com/uk/i/4479/
(Archived at https://www.imperial.ac.uk/ref/webarchive/yrf
on 5th September, 2013)
[14] TCE article "Future foods-Coding caviar to avoid species
extinction"
www.psenterprise.com/gproms/options/physprops/saft/data/tce_saft_feb10.pdf
Archived here
at 17/09/2013