日揮技術ジャーナル Vol.5 No.1 (2016)

AIRLIZE LNG
JGC’S Innovative Technology Package
for Operating and New Air-cooled LNG Plants
浅香 輝Teru Asaka
第 1 事業本部 LNG プロジェクト部
LNG Project Department, No.1 Business Division

ABSTRACTLNG plant operators often face issues in the performance of their plants that lead to a drastic reduction in
the LNG production rate. The reasons for these issues can be traced back to inadequate design of installed
equipment and unforeseen conditions such as changes in the weather which cause the plant to operate
beyond the design limits. This is especially true for air-cooled LNG plants, which often exhibit similar
patterns of problems. Operators may not be able to come up with viable solutions that can be implemented
while the plant is operating and a shutdown may become unavoidable.
In order to address recurring problems that can be detrimental to these types of plants, JGC hasestablished the highly advanced and innovative technology package, called “AIRLIZE LNG”. AIRLIZE
LNG encompasses innovative technologies that are specific for air-cooled LNG plant design. Solutions canbe offered throughout an LNG project lifecycle to help identify the root cause(s) of issues, improve
performance, and maximize the production rate for a plant. Technologies such as weather simulation andcomputational fluid dynamics (CFD) are effective during the planning and engineering phase, while site
assessment methods for checking the performance of equipment that are common in air-cooled LNG plants
including air-cooled heat exchangers (ACHE) can help improve the energy efficiency of plants without
disrupting operation.
In this paper, the core technologies that form AIRLIZE LNG and the significant benefits that can beoffered for both operating plants and new projects through these technologies are described.

“AIRLIZE LNG” OVERVIEWBACKGROUND
All year long, and in all kinds of environmental conditions, minus 160 degrees centigrade LNG is being
produced around the world. However, occasionally there’s an unwelcome surprise―an unexpected drop in
production. The culprit isn’t feed gas or plant trouble ― but hot air!
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日揮技術ジャーナル Vol.5 No.1 (2016)

Yes, hot air exhausted by the various types of equipment installed in LNG plants, such as gas turbines(GT) and air-cooled heat exchangers, hinders the production of minus 160-degree LNG. Grasping thenature of this phenomenon in actual operating plants - a desire of LNG plant engineers everywhere - waslong-believed to be impossible. However, by devoting long years to measuring more than 100 million
data values and then analyzing and verifying the results ― a breakthrough was achieved by devising acomprehensive technological innovation, and establishing a unique technology package, “AIRLIZE LNG”.
Based on the “AIRLIZE LNG”concept, solutions for technological issues that appear at each phase of
the project life cycle for an air-cooled LNG plant using its proprietary technology are provided.

GT

GT

ACHE

Figure 1. Air-cooled LNG Plant

EIGHT INNOVATIVE TECHNOLOGIES“AIRLIZE LNG” is structured in the three steps of “VISUALIZE”, “UTILIZE” and “REALIZE” which
in turn are materialized by eight technologies as outlined below.
“VISUALIZE” ― Supported by a huge volume of measured data, the weather simulation technology
makes possible the pin-point re-creation of the airflow in the plant area. “VISUALIZE” consists of thetwo technologies of (1) Weather Simulation and (2) Site Survey/Data Analysis.
“UTILIZE” ― Based on the actually measured and/or reproduced weather data, (3) CFD simulation
technology provides an accurate prediction of the hot air recirculation (HAR) flow within a model plant2

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日揮技術ジャーナル Vol.5 No.1 (2016)

area and suggests (4) HAR Mitigation measures that will be most effective against the potential problems
posed by local weather and HAR.
“REALIZE” ― As various merits to the plant designs, we can offer (5) Compact Layout combined with
optimized critical equipment and systems, such as (6) ACHE, (7) GT Intake Air Chillers and (8) Advanced
Process Control (APC), that are ideal in every respect, with consideration given to every detail – including
even HAR behavior.
Figure 2 shows an overview of how “AIRLIZE LNG”that consists of eight proprietary technologies
supports plant operators of both operating plants and those planning new projects.

Figure 2. Overview of “AIRLIZE LNG”

WEATHER SIMULATION
Weather and atmospheric conditions such as air temperature, wind speed, wind direction, humidity, etc.,
have a vital and sensitive impact on process and structural engineering of plants. Since they are different
from one plant to another, creating a store of data regarding changes in weather and atmospheric conditions
that are specific to each plant is beneficial to plant owners and contractors. Weather simulation is able togenerate this beneficial data.
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This simulation service was developed by meteorological experts working with us. Though weather
simulation technology development has a long history, our weather simulation method is the first in theworld to be applied to plant engineering. With public data from the United States on weather patterns forthe whole globe on a large-area scale (e.g. 500 km grid), our technology is able to transfer the data into a
more detailed grid (e.g. 1 km grid), enabling the pinpointing of weather and climate conditions at individual
plant sites.
Commenced with the first application in South-East Asia region, subsequent applications were followed
to compare and verify the simulation data with the actual measured values for numerous sites, theperformance of weather simulation was constantly improved and thereby applicable regions and climate
conditions for weather simulation are being expanded.
LNG plant investors who desire to construct new LNG plants in a new location may enjoy a significant
schedule merit. If plant engineering planning could begin without years of prior measurements of climaticconditions at the site, plant development schedules could be condensed by several years by means ofweather simulation.

Figure 3. Weather Simulation

SITE SURVEY/DATA ANALYSIS
Conducting a site survey and making actual data measurements is easier said than done, in particular, ina broad area like that covered by an LNG plant. Yet actual data collected is often used for setting project
basic design data to be used by all engineering disciplines, and the utmost care must be paid to the accuracyof the data.
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In order to overcome these issues, integrated technology services are provided by joining the work of
meteorological experts together with that of the plant engineering team. After integrated consideration ofvarious conditions, including the specific characteristics of the environment around the plant site, humanresources, and budget constraints, a site survey program addressing measurement items, locations,precision levels, measurement frequency, measurement devices and power supply is established.

Inchoosing data collection methods, planning measurement frequency, etc., rich experience in recording over
100 million actual data values is drawn upon to prevent the collection of incorrect data, and provide
waste-free, hassle-free prompt service.
Specialized know-how is accumulated not only through site survey and actual data measurement but also
through creating a database of the measured data. The points where measurements are actually made differ
depending on the LNG site, but the database is advanced in standardization so that its data can be readily
and rapidly applied to any site. The database has two standard analytical functions for design condition
setting and for HAR visualization. The former function is frequency distribution analyses such as windroses and atmospheric temperature distribution. The latter function enables visual verification throughcomparison with CFD simulations described in the following section.

CFD SIMULATIONThe CFD simulation is unique in that it has been verified using a total of more than 100 million HAR
data values actually measured at operating LNG plant sites. Figure 4 shows a comparison between theactual measured data and CFD simulation data of air temperatures at the intakes of ACHEs and GTs at
MLNG Tiga.
The CFD simulation is being further improved through a synergistic effect produced by integrating thefour elements: CFD simulation, weather simulation (mentioned above), actually measured data (mentioned
above), and HAR mitigation strategies (mentioned below). In this way, a level of accuracy sufficiently
high to support plant design is ensured.
Typically, as shown in Figure 4, the HAR phenomenon between adjacent trains (Figure 5) is one of themost serious problems that disturb LNG plant stable operation. The capability to foresee this phenomenon
has been greatly improved, and has enabled the calculation of the minimum required distance between
adjacent trains combined with HAR mitigation measures.
Determining the amount of data that will enable the formation of a sufficiently detailed CFD model canonly come from long experience of dealing with actual, real-life data. An unnecessarily detailed CFD
model greatly increases calculation time.

Drawing on experts’ know-how and extensive experience in

CFD simulation is essential to carry out a simulation with a good balance between the calculation time andaccuracy within the allowed time frame of the individual project.

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Site
Data

CFD

Figure 4. Temperature Rise above Ambient, site measured data vs. CFD (WNW Wind)

Figure 5. Hot Air Recirculation (HAR)

HAR MITIGATIONIn determining HAR margins and mitigation strategies to be applied for plant layout and criticalequipment, a systematic approach is ideal, which is in sharp contrast with an easy approach such as copying
previous projects.
HAR mitigation strategies against HAR risks proposed for LNG plants are superior in that the best
combination of HAR margins and HAR mitigation strategies is determined at the initial stage of design
engineering. ACHE design margins and HAR mitigation strategies such as adding chimneys have positiveor negative effects on each other from the standpoint of plant performance and plant layout. Using theestablished design guide covering an analysis of such effects, a basic policy for adopting an optimal HAR
mitigation strategy reflecting the cost data of each specific project is determined.
For example, with regard to ACHE, we can look at HAR design margins and mitigation as described
below. For the design margin, the intake air temperature and heat transfer surface area are considered. For
the HAR mitigation strategy, the distance between trains or facilities, and the installation HAR mitigation
measures, such as skirts, winglets, and chimneys, etc., are considered. Among a number of possiblecombinations of these elements, the optimal one is systematically identified by using our HAR design
guide and CFD simulation technique.
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The distance between trains and/or facilities is a core element to be finalized with HAR mitigation
strategies. Increasing the distance is not easily adoptable because it involves layout area expansion, taller
facilities, and significant effects in terms of project delivery date and cost. ACHE design assumes that the
ACHE units will be installed in a space free from high-temperature exhaust air, but in reality plantdesigners who determine plant layout have to cope with the risk of ACHE intake air temperature increasing
due to facilities installed close to each other. This risk has been increased as a result of the recent trend forcompact plant layout and facility modularization. An HAR design guide is required to address how tomanage this risk.

COMPACT LAYOUT
In accordance with recommendations derived from the HAR mitigation strategies, the plot plan of the
LNG plant is designed. Cultivated know-how through nearly half a century of experience in theconstruction of LNG plants is exercised in a professional manner, as is evident from the following two
representative layouts.
One is that refrigerant compressors and heat exchanger units are installed on one side of the pipe rack. It
eliminates extra-large bore pipe runs of refrigerants in the pipe rack to the maximum extent. The other is anaero derivative gas turbine-based layout in which a compressor and a heat exchanger unit for propane
refrigerant are installed on one side of the pipe rack and those for MR refrigerant are installed on the otherside. Both layouts lead to lowering of the pipe rack, and contribute not only to earlier plant delivery dateand cost saving but also the safety of construction work.
As evidenced in these layouts, we can flexibly study all detailed limitations and requirements that are
applied to each individual plant and create an optimum compact layout.

ACHE
ACHE are critical equipment for air-cooled LNG plants. They discharge heat extracted from the feed
gas finally to the atmosphere and contribute to producing minus 160 degrees centigrade LNG from feed gas.
In this way, the performance of the ACHE has a direct impact on LNG production rate. Communication
with various plant operators reports that not a few operators experience lower performance of the ACHE
than the design value in actual operating plants. The root causes of lower ACHE performance range widely.
Cleaning issues – dust, pollen, etc., in the atmosphere are trapped between the fins of the ACHE tube
bundles during several years of operation, and cause decrease in performance of heat exchange. In theworst case, a numbers of ACHE tube fins are too corroded to be usable any longer.
Seasonal issues – water is sprayed over the ACHE tube bundles in mid-summer in some of the operating
plants to compensate for a shortfall in the cooling capacity, while no design consideration is given to suchoccasional water spray operation.

A risk of scale formation between the ACHE tube fins due to poor

quality water is not ignorable, that may cause the same troubles as the cleaning issues.
Local weather issues – strong cross winds beyond specified speed limits cause ACHE cavitation that
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should be avoided in view of the risk of mechanical trouble.
HAR issues - as described above.
None of these issues can be solved easily in actual operation and they require to be managed as a crucialpart of plant operation and maintenance activities.
In collaboration with a specialist ACHE O&M company (Elflow BV), we have completed several
projects in which we focused on the above issues. Through the application of our experience andknow-how of specifying design requirements, supervising detailed engineering and manufacturing, erecting,commissioning and operation support, we have assembled the technologies which are most effective in the
diagnosis and improvement of ACHE performance.

ACHE DIAGNOSISThe measurement of the air flow rate, an essential element for the
diagnosis, can be made without scaffolding so that diagnosis ispossible at any time while the plant is in operation. ACHE diagnosis
compares the design data and actual measurement data on the
air-related performance of ACHEs in operation. It gives reliable
information as it represents a diagnosis made by a third party
unrelated to ACHE suppliers.

Figure 6. ACHE Air Flow Measurement

ACHE PERFORMANCE IMPROVEMENT PACKAGE
Based on the ACHE diagnosis result, a No Cure – No Pay step-wise package is offered with guaranteed
improvement (in figures) in the performance of the air side. It eventually brings benefits, both in the formof the economic benefits of cooling efficiency as well as in terms of environmental protection (noise andvibration). The package includes the revamping of ACHEs as well as the external cleaning of the ACHE
finned tube bundles. A choice of cleaning between wet process (water spray) and dry process (powder
spray) is possible in accordance with the prevailing conditions, and can be carried out while the plant(including the ACHEs being cleaned) is in operation.

GT INTAKE AIR CHILLER
GT Intake Air Chillers are becoming essential equipment for LNG plants that adopt aero derivative GT
as an effective means for improving LNG production efficiency.
By making a comprehensive analysis of the necessary data for GT Air Chillers to suit each individual
LNG site, the specifications for the GT Air Chillers to be issued to the vendors can be decided upon. Of
course, this analysis encompasses the process heat and material balance as well as creating a plant layoutthat includes the supporting facilities (power source, refrigerant storage facility, etc.) for the GT Air
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Chillers on which will be based judgment of the economic aspects of the CAPEX (initial investment),
OPEX (cost of operation), and NPV (net present value) that will enable the recommendations for the mostsuitable GT Intake Air Chillers. Economic study of different balances among these three is carried out inline with the objective of each individual project.
Depending on the desired temperature of the intake air, the most suitable solution will vary. The
solutions include a choice of the system among the evaporation cooler (cooling tower) method, water spraymethod, direct chiller method through condensing the compressor refrigerant with air, indirect chiller
method through condensing the compressor refrigerant with cold water, a choice of refrigerant amongpropane that is mostly used but also freon refrigerant that obviates the need for explosion proofing
measures as well as a number of other alternatives.

APC (ADVANCED PROCESS CONTROL)
APC that is designed to cope with fluctuation of composition and/or flow rate of the feed gas is able toexpand its application as follows. In order to avoid shutdown of the plant as a result of the effect of air
temperature changes or HAR, it has been the practice for operators to reduce the throughput of LNG in
anticipation of such changes. Because it is difficult for the operators to anticipate the fluctuations in the
ACHE intake air temperature, the operation of the plant cannot be maintained at the maximal level,
resulting in an annual production that is less than the optimal (Figure 7). However, with the input from
CFD simulation together with the prediction of wind speed and direction and changes in temperature, it
becomes possible to maintain the level of production at the optimal level. With the installation of a
relatively simple APC, it becomes possible to increase the production rate by several percent. In this way,
the APC is designed in harmonization with weather simulation, site survey/data analysis and CFD
simulation.
The APC makes possible plant operation without depending on the technical skill of an operator andrelieves the stress on the operators should an emergency shutdown occur as a result of external factors.

Figure 7. APC (Advanced Process Control)

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CONCLUSION
The voices of society are increasingly calling for a balance between energy supply and environmental
protection. Unlike the water-cooled LNG plants commonly used in the past, air-cooled LNG plants
produce LNG without causing changes in the surrounding marine environment, providing one effective
solution to meet global expectations.
JGC has established the “AIRLIZE LNG” technology package by focusing on the “AIR” of the
air-cooled LNG plants and streamlining innovative technologies achieved till today to provide
comprehensive solutions for all kinds of issues that plant operators encounter in daily plant operations.
While significant advances have already been made through the application of “AIRLIZE LNG”
technology package, we recognize that none of the eight technologies is perfect and each has room forfurther improvement. However, there is no doubt that we are now in a position to carry out further
innovation that will enable us to respond positively to the pleas of plant owners and operators calling forplants that maximize production efficiency and plant availability while minimizing costs and swift
completion and start of operations for both operating plants and new projects.
In closing, we should add that the AIRLIZE LNG approach is applicable for not only air-cooled LNG
plants but also the whole range of plants that use ACHE, GT, etc., employing air as an energy source.

REFERENCES
1)

Siti Farhana Bt M Shaari and Kei Kubota, Understanding of Hot Air Recirculation Phenomena in Air
Cooled Base Load LNG Plant, Proc. LNG 17 Conference (2013).

This article is published in 18th International Conference & Exhibition on Liquefied Natural Gas(11-15 April 2016, Perth, Australia).

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