next generation of lng regasification terminal … · 2019-01-19 · 3.1 construction of the...
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NEXT GENERATION OF LNG REGASIFICATION TERMINAL THROUGH TG’S PROFOUND KNOWLEDGE
– TOKYO GAS HITACHI LNG TERMINAL –
Tsutomu Endo Tokyo Gas Corporation, Japan
www.tokyo-gas.co.jp
KEYWORDS:knowledge, shortened construction period, limited land area, energy saving
ABSTRACT
Tokyo Gas Co., Ltd., the world's 4th-largest LNG importer, imports 17MTPA of LNG with our own shipping fleet at 3 regasification terminals along Tokyo Bay. It has been steadily supplying city gas, as the Japan's largest gas supplier, which has over 10 million city gas customers and many industrial customers including power stations. The demand for natural gas has been increasing since the magnitude-9 Great East Japan Earthquake, which struck on March 11, 2011. This is giving Tokyo Gas an even greater role to play as an energy supplier in the aspect of providing for energy resources and assuring energy security. Under these circumstances, Tokyo Gas, creating robust supplying chain, decided to construct a fourth LNG regasification terminal in the vicinity of Hitachi, about 130 kilometers northeast of Tokyo. One of the features of the Hitachi LNG Terminal is the ability to deal with LNG of various calorific types, from the conventional rich types to the super-lean types such as coal bed methane (CBM) and shale gas, with new-type LNG jet mixing system against LNG stratification in a tank. Furthermore the terminal will be equipped with an aboveground LNG tank with a capacity of 230,000 cubic meters, the world's largest. It will be constructed in a challengingly short period of time which is less than 3 years with the technology for shortening construction periods. TG's profound knowledge acquired over the last 40 years of experience in engineering, operation and maintenance will enable us to build a terminal of the very latest kind of technology such as accommodating with LNG calorific diversification and the largest LNG tank. This paper presents an overview of the Hitachi LNG terminal facilities, which incorporate the most advanced technology.
1 INTRODUCTION
Since Tokyo Gas first introduced to LNG in Japan in 1969, it has built and operated 3 LNG terminals over the past 40 plus years. Japan’s first LNG plant, the Negishi LNG terminal, was built to supply city gas for the western part of the Tokyo metropolitan area, and imported LNG from Alaska for the first time in 1969. The Negishi terminal was the first in the world to implement a system to utilize the cold energy of LNG for maximizing the cost effectiveness of LNG fuel. Subsequently, for the full scale implementation of LNG supply infrastructure, Tokyo Gas built pipeline in the periphery of the Tokyo metropolitan area, and constructed the Sodegaura Terminal in 1973, one of the largest LNG terminals in the world. Following necessary expansions to the Negishi and Sodegaura Terminals, the third LNG terminal, the Ohgishima Terminal, was built in 1998 to meet the increasing demand for gas. Various state-of-the-art technologies were implemented in the process of constructing the Ohgishima Terminal, including that of fully buried (underground) tanks, an energy-saving BOG processing system, and other features which made it one of the most advanced terminals in the world.
In predicting a further increase in the demand for gas, Tokyo Gas will construct its fourth LNG terminal, the Hitachi LNG Terminal, for the first time in around 20 years after the construction of Ohgisima Terminal.. In planning this new terminal, Tokyo Gas intends to capitalize on the knowledge it has accumulated over the past 40 plus years for the terminal’s design, construction, and operation in order to achieve lower both CAPEX and OPEX and to maintain the established levels of high safety and gas supply stability of other terminals, while managing the existing issues of limited land area and a shortened construction period.
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Location Ibaraki Port, Hitachi district of Hitachi City, Ibaraki Prefecture
Area: approx. 104,000 m2 (about 1/3 the size of the Ohgishima Terminal)
This paper is discribed the overview of Hitachi LNG Terminal together with the associated issues to be addressed in its construction.
2 OVERVIEW OF THE HITACHI LNG TERMINAL
2.1 Site Location As shown in Figure 1, the Hitachi LNG Terminal will be constructed in the north east part of Tokyo. The
planned site location is outlined in Figure 2, and Figure 3 presents a bird’s eye view of the terminal.
:
Figure 1. Location of Hitachi LNG
Figure 2. Planned Site Location of the Hitachi LNG
Figure 3. Bird’s Eye View of the Hitachi LNG Terminal (Phase I)
Kuji gawa river
Pier of 5 Pier of 4
Hitachi LNG Terminal
Hitachi LNG Terminal
Negishi LNG Terminal
Sodegaura LNG Terminal
Ohgishima LNG Terminal
Hitachi port area
TG’s Pipe line
Other company’s Pipe line
TG’s supply area
TG’s group supply area
Other company’s supply area
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2.2 Master Schedule Table 1 shows the master schedule for the construction of the Hitachi LNG Terminal. Construction of the
terminal has been planned in two phases, Phase I and Phase II, with Phase I scheduled to start operation in FY2015. While the most critical part of this schedule is the construction of the above ground storage tank, various ideas will be used to reduce the construction period from an estimated 48 months to 35 months, requiring a mere three and a half years from preparation to finish.
Table 1. Master Schedule
2.3 Terminal Capacity Table 2 shows capacity and other data for the terminal for Phases I and II. The Hitachi LNG terminal will be
designed to allow further increases in plant capacity through the addition of supplementary systems to cope with possible increases in demand in the future.
Table 2. LNG Handling/Send-out Capacity
Item Phase I Phase II
Capacity
Gas transmission
1 million tons /year (1320 million m3 /year)
2.2 million tons /year (2900 million m3 /year)
Liquid delivery
0.6 million tons /year (760 million m3 /year)
1 million ton /year (1270 million m3 /year)
Total 1.6 million tons /year
(2080 million m3 /year) 3.2 million tons /year
(4160 million m3 /year)
Maximum gas delivery 200 t/h
(264,000 Nm3 /hour 500 t/h
(659,000 Nm3 /hour)
Gas calories 45 MJ/Nm3 45 MJ/Nm3
Maximum ship capacity LNG: 177,000 kl LPG: 80,000 kl
2.4 Equipment Specifications Figure 3 below shows the process flow for the Hitachi LNG Terminal while Table 3 outlines the terminal’s
equipment specifications. As the terminal has been designed for the shipping of LNG in addition to supplying city gas via pipelines, those for shipping LNG by coastal tankers and lorry trucks for domestic users are to be constructed. For LNG boil-off gas (BOG) processing, a medium pressure compressor offering lower running costs will be used for reliquefaction, and will be combined with a high pressure compressor for directly sending to pipeline in order to provide less restriction on the terminal’s minimum send out requirements. For LPG BOG processing, an LPG BOG suppression system will also be employed to help with lower running costs.
FY2012
Milestone Preparatory work
Offshore work
Land work
Commissioning
Site preparation Land acquisition and commencement of construction ▼
FY2013 FY2014 FY2015
▼ Commence operations
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TL1 LNG tank
LNG HP
M
LNG RGB
LNG receiving facility
LNG shipping by domestic ships
LPG receiving facility
LNG Line
LPGBOG suppression system
Supply gas
M
ORV
LPG Line
LPG HP
TP1 LPG tank Gas Line
LNG tank lorry shipment
Pipe Line
LPG RGB
LNGBOG recondenser
High pressure LNGBOG comp Middle pressure
LNGBOG comp
Flare stack Vent stack
BOG calorie control system
Figure 3. Process Flow of Hitachi LNG
Table 3. Equipment Specifications
Facility Facility Specifications
LNG/LPG receiving facility
Jetty for import LNG/LPG 16B arm for LNG x3, 16B for LNG RG x 1 12B arm for LPG x3, 12B for LPG RG x 1 LNG RGB 27,000 m3N/h x 1 LPG RGB 2,000 m3N/h x 1 Sampling facility 1
LNG shipping by domestic ships Jetty for shipping LNG for domestic users 8B arm for LNG x1, 8B for RG x 1
LNG storage tank PC above ground storage tank, 230,000 kl x 1
LNG vaporizer ORV100t/h x 3
LNG pump
LP: 130 t/h x 6
HP: 105 t/h x 4
LP for shipping LNG: 350 t/h x 2
LNG BOG processing facility
BOG compressor (medium pressure): 11,500m3N/h x 1 BOG compressor (high pressure): 15,100m3N/h x 2 BOG reliquefaction equipment: 11,500m3N/h x 1
LNG shipping facilities (lorry trucks)
40 t/h x 6 lanes
LNG storage tank PC above ground storage tank, 50,000 kl x 1
LPG pump LP: 46 t/h x 6
HP: 28 t/h x 4 LPG BOG processing facility BOG suppression system: 2,200 m3N/h x 2
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3 CHALLENGES FOR THE HITACHI LNG TERMINAL
3.1 Construction of the world's largest capacity LNG tank For the Hitachi LNG Terminal, Tokyo Gas is planning to construct the company's first, and world's largest
capacity, above-ground LNG storage tank using pre-stressed concrete (hereafter referred to as an "above ground PC tank"). Figure 4 illustrates the major structural elements of this above ground PC tank. The tank is composed of an inner tank made of 9% Ni steel to store LNG, a PC liquid protective barrier to prevent any leakage to the outside in the unlikely event of a leak in the inner tank, support piles to support the structure, and other structural components.
In conventional design, the maximum possible capacity of an above ground PC tank was considered to be 180,000 kiloliters. However, according to March 2008 amendments to the Japanese Gas Business Act, the structural design is now allowed to use a safety coefficient of 3.5 (according to JIS B 8267) for the allowable stress of structural members of the inner tank in addition to the conventional selection of 4.0 as a safety coefficient.
A safety coefficient of 3.5 for allowable stress has made it possible to construct an unprecedented 230,000 kiloliter above ground PC tank. As increased tank capacity allows for a reduced number of necessary tanks, the required area for the site can be reduced.
3.2 Reduced construction period for the terminal The construction period for the LNG tank is the most critical in the construction of the entire terminal. In order
to realize the terminal’s planned FY2015 start, conventional construction methods commonly used in Japan were deemed to be insufficient for meeting this three and a half year schedule. Through the implementation of new procedures, it is now estimated that the construction period for the LNG tank of the Hitachi Terminal will be reduced from its original estimate of 48 months to 35 months. Table 4 shows a comparison of the conventional schedule and the current schedule. The main factors contributing to this reduction in the construction period are described below.
< The implementation of new procedures >
(1) Construction of the inner tank first
(2) Modular construction of reinforced steel frames
(3) Pre-fabrication and marine transport of structural components
(4) Detailed and organized work management to enable parallel work
Insulation
PC Liquid Protective Barrier
Inner Tank
Outer Tank
Figure 4. Schematic Diagram of Above Ground PC
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Table 4. (A) Conventional Construction Methods: Building the Outer Tank First (48 Months)
(5)
Table 4. (B) Construction Method Adopted: Building the Inner Tank First (35 Months)
<Factors in shortening the construction period >
(1) Construction of the inner tank first (Air raising of the inner tank) Figure 5 shows an outline of the two different construction methods, i.e., (a) building the outer tank first and (b) building the inner tank first. Here, the A/R (air raising) method uses air pressure to lift the roof assembled on the tank floor for mounting on top of the tank. With the differential pressure of 2 to 3kPa (referenced to atmospheric pressure), a lifting rate of 250 to 300 mm/min is achieved, and thus the lifting work can be completed in a few hours, while the tilt of the roof is monitored and properly controlled. In the case of a well-practiced outer tank air raising method, air raising is conducted after the liquid protective barrier has been completed and the side plates for the inner tank have been constructed. However, as the inner tank air raising method allows for the simultaneous construction of side plates for the inner tank and the liquid protective barrier, it can significantly reduce the construction period. By reducing the construction period for the LNG tank, the construction period for the entire terminal can also be reduced.
Detailed and organized work management to enable parallel work
Modular construction of reinforced steel frames, etc.
Pre-fabrication and marine transport of structural components
Roofing work
Inner tank
Test
Insulator work
Insulator work
Completion
1st year 4th year 3rd year 2nd year
A/R Civil engineering
work
Mechanical work
Foundation work
Outer tank construction (incl. liquid protective barrier)
Civil engineering work
Mechanical work
Foundation work
Outer tank construction (incl. liquid protective barrier)
Roofing work Inner tank
Test
Insulator work
Insulator work
Completion
1st year 4th year 3rd year 2nd year
Air raising (A/R)
13 months reduction
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Figure 5(a) Construction method to build the outer tank first
Figure 5(b) Construction method to build the inner tank first
3.3 Energy saving measures In the construction of the Hitachi LNG Terminal, a variety of approaches are being taken in order to save
energy and reduce running costs. From among these approaches, the LNG BOG recondenser system and the LPG BOG suppression system, which both offer substantial energy savings, are introduced below.
(1) The LNG BOG recondenser system
In an LNG BOG recondenser system, the cold energy of LNG is used to liquefy boil-off gas (BOG) under medium pressure. The liquefied gas is then pumped for gasification by ORV, a method that has been used in the Ohgishima LNG Terminal. Compared with the direct heat exchange method, an estimated about 30% reduction in the LNG BOG condensing rate can be expected. Figure 6 illustrates the process flow of the LNG BOG recondenser system.
The boil-off gas generated in the LNG tank is pressurized by the LNG BOG compressor and sent to recondenser for liquefaction. The pressurized BOG is first sent to precooler and then introduced to the recondenser. The pre-cooled BOG is liquefied in the LNG BOG condenser through the heat exchange process to use LNG, and the resulting re-liquefied LNG is stored in the LNG condensate drum. The liquefied LNG is then pressurized to the send out pressure with the LNG condensate pump, which pressurizes the liquefied LNG to the send-out pressure (i.e., for gasification), and sent to ORV for regasification..
<Features of the recondenser system>
① As the pipeline network of Tokyo Gas does not have the underground storage systems typically found in the USA and Europe, it is necessary to absorb seasonal and hourly fluctuation on the LNG terminal side. As such, in order to mitigate possible restrictions due to the minimum send-outflow rate , the LNG BOG condensing rate should be kept as low as possible.
② As the process to pre-cool BOG can keep the LNG BOG condensing rate at a low level, the limitation due to the minimum send out requirement can be mitigated.
内槽および内槽・外 槽屋根を施工
防液堤・外槽も 同時施工
防液堤・内槽側板・ 外槽製作後 A/R を行
なう
内槽・外槽屋根 を A/R
内槽および内槽・外 槽屋根を施工
防液堤・外槽も 同時施工
防液堤・内槽側板・ 外槽製作後 A/R を行
なう
内槽・外槽屋根 を A/R
基礎版製作後、防 液堤および外槽の
作成
内槽・外槽屋根 を
防液堤 内Inner tank
槽
アンカー ストラップ
外槽 Construction of the liquid protective barrier and outer tank begins after construction of the base structure is completed
Completion of the outer tank and the roofs of the inner and outer tanks
A/R of the roofs of the inner and outer tanks
Liquid protective barrier
Anchor strap
Inner tank
Parallel construction of the inner tank and the roofs of the inner and outer tanks
The liquid protective barrier and the outer tank are constructed at the same time
Air raising is performed following completion of the liquid protective barrier, side plates of the inner tank, and the outer tank
A/R of the roofs of the inner and outer tanks
Outer tank
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Figure 6. Process Flow of LNG BOG Recondenser System
(2) The LPG BOG suppression system
LPG is stored under atmospheric pressure. Heat leakage into the tanks, therefore, must be transferred out of them as boil-off gas. Conventionally, LPG BOG is pressurized via a compressor and re-liquefied by cooling water. Since large-scale motor-driven compressors have been used in this recovery system, the comsumpiton of electricity is considerable.
In order to cut the cost of recovery of BOG and reduce energy consumption, the suppression system developed by Tokyo Gas has been developed utilizing the cryogenic energy of LNG and introduced to Ohgisima LNG terminal. LPG BOG is forced to condensate in a tank by the super-cooled LPG that is cooled by LNG. This system needs no high-pressure compressors, so that the total cost is much lower than with conventional system. In this system, LPG pumped up from the tank is fed into a heat exchanger and is supercooled with LNG. Then, the supercooled LPG is re-introduced into the gas layer of the tank through a spray device and supercooled LPG cools and condenses the BOG. Figure 7 illustrates the process flow of the LPG BOG suppression system.
Figure 7. Process Flow of the LPG BOG Suppression System
3.4 Facilities for LNG shipment As the Hitachi LNG Terminal is designed with the aim to large scale LNG shipments to the Northern Kanto,
Tohoku, Hokkaido areas and so on, LNG shipment facilities by both coastal tankers and LNG lorry trucks for domestic customers are to be installed. The features of these facilities are described below:
LNG BOG Compressor
LNG Tank
LNG BOG Cooler
LNG Pressurization Pump
LNG Condensate Pump
LNG Condenser
LNG Condensate Drum
LNG Line
BOG
Vaporizer
LNG Pressurization Pump
LPG Cooler
Tank Spray
LPG Tank
LPG BOG Line
LNG Line Vaporizer
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(1) LNG shipment by coastal tankers
The LNG shipment facility is designed for use by large ships of a 10,000 ton class, in addition to servicing conventional 1,000 ton class domestic vessels. To cut down on cost, the LNG receiving facilities are also used for LNG shipments by 10,000 ton class vessels. Specifically, the LNG receiving line is reversely used to send LNG to the domestic ship and the return gas line is used to carry the return gas from the ship.
(2) LNG shipment facility by lorry trucks
With its limited area and layout restrictions, the LNG shipment facility for lorry trucks at the Hitachi LNG Terminal are efficiently designed to maximize shipping capacity. As a high filling rate of 40 t/h has been verified in a verification test conducted at the Sodegaura LNG terminal, the maximum filling rate of 40 t/h is assumed for initial operation. As future increases in the filling rate can be expected through modifications to the tank lorry receiving line facilities, the system is designed to operate at a maximum filling rate of 60 t/h.
3.5 Acceptance of lean LNG Due to the diversification in the types of liquids received in recent years, it is expected that the ratio of lean
LNG will increase in the future. Accordingly, the Hitachi LNG Terminal will be designed to accept unconventional LNG (e.g., CBM) in addition to conventional LNG. In order to avoid density stratification, which may result when different types of LNG are stored in the same tank, appropriate operations are required to monitor the LNG density distribution in the tank. In addition, in the event that layering does occur, remote controlled jet mixing will be performed to prevent rollover.
3.6 New approach for the process control system Various approaches are being studied to improve reliability and operational efficiency of the process control
system (DCS) of the Hitachi LNG Terminal utilizing over 40 years’ experience of operation. Some examples of these approaches are discussed below:
(1) Cyber security measures
In recent years, there has been an increase in cyber attacks targeting various control systems, and a variety of attack methods have been used. In order to respond to the continually evolving cyber security threats, penetration tests based the assumption of cyber attack will be conducted upon introduction of the system. Following the system’s introduction, security diagnosis activities will take place regularly, and will include system vulnerability checks and as well as any necessary actions.
(2) Introduction of operator assistance tools
① Adaptation of alarm management methods In order to avoid any mistakes in recognizing indications of significant trouble due to the temporary generation of a large amount of alarms, the most important alarms are to be placed at the top of an alarm list in order of priority. In addition, in order to prevent any oversight due to frequent or large amounts of alarms generated, past alarm histories will be reviewed and analyzed to reduce any unnecessary alarms in the future.
② Effective use of the operator training system In order to help accelerate the training of operators and to maintain their level of skill, an advanced operator training system employing a plant mode, DCS system simulator will be introduced in this terminal. Furthermore, DCS system will be designed with the aid of process simulation by DCS system simulator, which trial will be for the first time in Japan. The training system will be developed and implemented at an early stage (i.e., before the actual implementation of the control system). The model will be used to represent the design of the control system in order to train operators prior to the start of the LNG terminal operation. In addition, a method that will systematically analyze the actions of individual operators and present objective evaluation results to indicate their rated level of mastery will be introduced.
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③ Introduction of trend-based operation The introduction of "trend-based operation" is also planned for the first time in the world. With this system, through the overlay of current operational data on a template that shows trend plots to represent normal operations, possible equipment failure can be easily detected and the differences clearly and promptly indicated to the operator.
3.7 Cost reduction efforts In past LNG terminal construction cases, equipment suppliers were selected based on an evaluation of the
initial costs of installation. In the case of the Hitachi LNG Terminal, the vendor selection policy has been changed to incorporate consideration for total life cycle cost (LCC), which includes an evaluation of the initial costs and the running cost after operations have begun, e.g., cost of electric power, maintenance costs, etc. This policy enables the low cost and competitive operation of the LNG terminal.
4 CONCLUSION
While the construction of the Hitachi LNG Terminal involves some challenging issues such as land limitations and a shortened construction period, in an effort to resolve issues and realize a competitive LNG terminal, Tokyo Gas aims to maximize the user engineering technologies and knowledge that they have accumulated over their 40 plus years of experience in the design, construction, and operation of their LNG terminals to date.