This thesis looks at creating a multidisciplinary simulation tool for rotating plant equipment
selection, specifically gas turbines, for the liquefaction of natural gas (LNG). This is a
collaborative project between Shell Global Solutions and Cranfield University in the UK. The
TERA LNG tool uses a Techno-economic, Environmental and Risk Analysis (TERA)
approach in order to satisfy the multidisciplinary nature of the investigation. The benefits of
the tool are to act as an aid to selection, operations and maintenance planning and it also acts
as a sensitivity tool for assessing the impact of changes in performance, environmental and
financial parameters to the overall economic impact of technology selection. The aim is to not
only select technology on the basis of techno-economics but also on the basis of risk analysis.
The LNG TERA tool is composed of a number of modules starting with the performance
simulation which calculates the thermodynamic conditions in the core of the engine. Next, life
estimates of the hot gas path components are made using a mixture of parametric and
probabilistic lifing models for the turbine first stage blades, coatings, and combustor liner.
This allows for a risk analysis to be conducted before maintenance and economics issues are
dealt with. In parallel, emissions estimations are made based on empirical correlations. The
modelling exemplifies a methodology which is uniquely applied to this application and there
are no studies previous to this which look at so many aspects before making conclusions on
plant machinery selection.
Comparisons have been done between industrial frame engines based on the General Electric
Frame 9E (130 MW) and Frame 7EA (87 MW) engines as well as more complex cycles
involving aero-derivation and inter-cooling such as the LM 6000 (42 MW) and LMS 100 (100
MW). Work has also been carried out to integrate the tool to Shell based systems in order to
utilise the database of information on failure and maintenance of machinery as well as its
performance.
The results of the integrated TERA show a clear favour for the aero-derivative engines and
the main benefit is the fuel saving, though the life of the hot gas path components is
deteriorated much faster. The risk results show that the industrial frame engines have a wider
variation in expected life compared to aero-derivatives, though the industrial frames have
longer component lives. In the context of maintenance and economics, the aero-derivative engines are better suited to LNG applications. The modular change out design of the aero-
derivatives also meant that time to repair was lower, thus reducing lost production.
Application of the LNG TERA tool was extended to power generation whereby a series of 6
engines were simulated. The changes required to the modelling were minimal and it shows
the flexibility of the TERA philosophy. This study was carried out assuming a given ratio of
load split between the engines and hence is sensitive to the way an operator demands power
of the engine as opposed to LNG application where the operator tries to drive the engine as
hard as possible to get the most production out of the train.
The study was limited in the modes of failure which were investigated, a major further work
would be to extend the methodology to more components and incorporate fatigue failure.
Further, the blade creep and probabilistic coating models were very sensitive to changes in
their respective control parameters such as coating thickness allowances and firing
temperature.
The contribution to the project from the MBA is the statistical techniques used to conduct the
risk analysis and data handling as well as financial management techniques such as the Net
Present Value (NPV) methodology for project evaluations
