Sinopec Tianjin LNG_Sinopec Tianjin LNG Terminal Plan Optimization Research

Abstract: From the perspective of navigation safety and ship maneuvering, based on the simulation test of ships entering and leaving the port and berthing and unberthing, some optimization suggestions and plans are put forward for the layout of LNG terminals and supporting channels and breakwaters for engineering purposes. Drawing and reference for design and maritime regulation.

Keywords: LNG terminal channel breakwater

In recent years, the fastest and most feasible way for China to import energy is to import oil and liquefied natural gas by sea through the coastline. The construction of Sinopec Tianjin LNG project has It is conducive to forming a multi-source gas supply pattern in the Beijing-Tianjin region, improving the economy, safety and stability of gas supply in the region; it is conducive to meeting the demand for clean energy in the Bohai Rim region, protecting the environment and promoting economic development. Therefore, the construction of Sinopec Tianjin LNG terminal is very necessary and urgent.

Overview of Nangang Industrial Zone

1. Overview of the channel

The planned effective width of the LNG channel is 300m, the design bottom elevation is -14.9m, and the channel orientation is 270°00′ 00″～90°00′00″, the channel mileage extends to 38,000.

2. Overview of the breakwater

At present, the distance between the tops of the north and south breakwaters in the port area is 1800m. The recommended entrance location is 3000m from the east embankment. The current construction distance is 2000m. The original recommended entrance location The breakwater with a spacing of 1000m at the turning point of the inner south breakwater has not yet been constructed.

3. Hydrology and Meteorology in the Port Area

The normal wind direction in the port area is the S direction, and the sub-normal wind direction is the E direction. The occurrence frequencies are 9.89 and 9.21 respectively. The strong wind direction is the E direction, the second strongest wind direction is the ENE direction, and the frequencies of winds ≥7 are 0.32 and 1.01 respectively.

The average number of heavy fog days with visibility less than 1km is 16.6 foggy days per year. The fog occurs most in autumn and winter every year. The number of heavy fog days in December is about 30 of the total fog days in the year. The longest fog day is The delay can reach more than 24 hours. According to statistics, the actual occurrence time of heavy fog is 8.7 days per year on average.

The regional flow field characteristics of the LNG terminal project are as follows: ① The tidal current in the sea area of ????Nangang Industrial Zone is a reciprocating flow perpendicular to the coastline. Within the port area, the up and down tidal velocity is the largest at the entrance, and the flow velocity in the harbor pool is relatively small. Small. The ebb current velocity in the entrance area is greater than the ebb current velocity. ② From the perspective of flow velocity distribution, the flow velocity at the entrance gate will decrease as the channel grade increases, which is beneficial to ship navigation. ③ Judging from the size distribution of cross currents at times of sudden fluctuations, the cross currents in the dock area are less than 0.10m/s. The maximum cross current in the channel is located near the breakwater entrance, but the maximum cross current does not exceed 0.25m/s.

The layout of the LNG terminal before optimization

The layout of the LNG berth adopts an offshore butterfly layout, which mainly consists of 1 working platform, 2 pairs of docking piers, and 4 pairs of mooring cables It consists of piers, connecting bridges and approach bridges. The length of the berth is 420m, the size of the operating platform is 30×15m, and the height is 12m. It adopts a steel structure with a control room arranged above it. The approach bridge has a clear width of 15m and a length of 90m. All mooring piers of the wharf are arranged on the same straight line and parallel to the front line of the wharf.

Figure 1 LNG terminal layout before optimization

Adaptability analysis of terminal layout

1. Adaptability analysis based on specifications

Mainly study the adaptability of LNG terminal waters, channels and breakwaters, and optimize the design of LNG terminals, channels and breakwaters. Here we mainly select 266,000 m3 LNG ships as the research object.

Table 1 Dimensions of 266,000 m3 LNG ships

1.1 Breakwater adaptability analysis

One of the basic functions of breakwaters as protective buildings is to resist the intrusion of waves from the open sea and improve Mooring conditions in harbor waters. The width of the door is an important parameter that affects the shielding effect. According to the layout characteristics, the door width usually includes three index values: door width BS, door effective width B0 and safety distance d0. The interrelationship among the three is shown in Figure 2.

Figure 2 Schematic diagram of gate width value

According to the "Sea Port Graphic Design Code", the effective width of the gate refers to the width of the gate perpendicular to the axis of the channel; the safety distance refers to The distance from the bottom line of the effective width of the entrance gate to the breakwater should be determined according to the structural type of the breakwater and its safety requirements. Regarding the design width of the breakwater entrance area, the specification requires that the effective width of the breakwater entrance door should be 1-1.5 times the length of the designed ship type.

Table 2 Comparison of the effective width of the entrance door and the length of the ship

It can be seen from Table 2 that the planned effective width of the breakwater entrance door can meet the requirements for the safe entrance and exit doors of 266,000 m3 LNG ships. Considering that LNG ships need to be escorted when entering and leaving the port, two tugs (6000HP Z-type tugs) are selected to escort the front and rear through the gate. The overall fleet length is about 433m, and the gate width/length is about 4.2, which can meet the requirements of LNG ships under escort conditions. Required for safe passage through entrance gates.

1.2 Channel adaptability analysis

1.2.1 Channel water depth

According to the requirements of the "Liquefied Natural Gas Terminal Design Code", the design water depth of the LNG terminal's entry and exit channels The calculation base level should be based on the local theoretical lowest tide level. Various depths in the calculation of design water depth should be determined in accordance with the provisions of the "General Plane Design Code for Harbors". According to the requirements for channel size in the "Sea Port General Plane Design Specifications".

D0=T Z0 Z1 Z3 Z4

D0 - channel navigation water depth (m); D - channel design water depth (m); T - design ship type full load draft (m); Z0 - The hull sinking value when the ship is sailing (the speed is taken as 8 knots); Z1 - the minimum allowance depth under the keel when sailing (m); Z2 - the wave allowance depth (m), taken as 0.9; Z3 - the ship's loading trim allowance depth, taken as 0.15m; Z4 - siltation depth (m), take 0.4m.

Table 3 Channel Water Depth Calculation Table (Unit: m)

1.2.2 Channel Width

According to the requirements of the "Liquefied Natural Gas Terminal Design Code", the Liquefied Natural Gas Terminal Artificial entry and exit channels can be designed as one-way channels. The effective width of the channel should be determined in accordance with the "Sea Port General Plane Design Code" and should not be less than 5 times the design ship width. The effective width of a channel is composed of the width of the track zone between ships and the margin between ships and the bottom edge of the channel. The one-way navigation width is determined by the following formula:

A=n (Lsin? B)

n—ship drift multiple;?—wind and current pressure deflection angle; L— Captain (m); B—Breadth (m).

Table 4 Required navigation width for one-way navigation (m)

The design water depth of the supporting channel for this project is 14.9m and the design width is 300m, which can meet the full load navigation requirements of a 266,000m3 ship .

Through the above analysis, it can be seen that the channels and breakwaters supporting the LNG terminal can theoretically meet the safe navigation and berthing and unberthing requirements of 266,000 m3 LNG ships. Next, we will use ship maneuvering simulation to further analyze the adaptability of LNG terminals, channels, and breakwater facilities from the perspective of actual ship maneuvering.

2. Ship simulation test

Based on environmental parameters such as hydrology, meteorology, channel scale, and ship characteristics of the engineering waters, a full-mission large-scale ship maneuvering simulator is used to model the navigation environment. , simulate the situation of ships entering and leaving the port, berthing and unberthing. One set of simulation test results is selected here. The specific working conditions are shown in Table 3.

Table 5 Designed ship type simulation test condition setting table

The simulation test shows that when the LNG ship enters the port, the ship speed in the main channel is 6 to 10 knots, and the outer section of the main channel The ship speed is generally 8 to 10 knots, and the wind pressure difference is about 3° to 5°. It drops to 5 to 6 knots before entering the breakwater entrance. The wind flow pressure difference during the breakwater section is about 6° to 9°, and it drops to 5 to 6 knots before entering the breakwater entrance. 3 knots, the wind flow pressure difference is about 10° to 15°. In view of the fact that the entrance section of the breakwater in the inbound channel is the braking section for LNG ships to enter the port, it is also the key section for the LNG ship to turn online when leaving the port. LNG ships are significantly affected by wind at low speeds. It is recommended to further widen the entrance section of the inbound channel breakwater.

According to the simulation test trajectory analysis, except for the entrance area section of the breakwater in the inbound channel, the designed effective width of the channel is 300m, which meets the requirements of the specification for one-way navigation of the designed ship type. LNG ships in the inbound channel The transverse offset range of the ship's position in the entrance area of ??the breakwater barrier is approximately 1 times the ship width to the left and right of the channel axis, and the longitudinal offset range is 1.5 times the ship length in front of and behind the breakwater barrier.

Engineering optimization plan

1. Channel optimization plan at the breakwater

According to the previous simulation test, it can be seen that when LNG ships enter and exit the port, especially when unberthing and passing through the gate, In the middle, due to the large wind area of ??the ship and the low speed and poor rudder effect when leaving berth, it is easy to cause a large amount of wind drift. Especially when it is affected by northwest winds, it is very difficult for LNG ships to turn right near the entrance and enter the channel. Large, it is easily affected by the wind when entering the channel and sails into the outside of the harbor and channel, causing stranding accidents. It is recommended that the water area near the northeastern port gate of the LNG berth be appropriately widened and dredged, and dredging point D be extended to point E, up to 350m.

2. LNG terminal optimization plan

Based on the conclusions of the simulation test, under the existing layout, the angle of rotation of the LNG ship is too large when turning around and berthing, making it difficult to maneuver the ship. It is recommended to The pier location has been moved forward by 190m, and the positions of reserved berths and work boat berths have been adjusted.

In addition, given that the pier is located in non-harbour waters, the difficulty of moving the pier further forward is also considered. This project can also dredge the waters on both sides of the pier without moving the pier forward, increasing the water area available for ships to turn around when entering the port, which can reduce the difficulty of maneuvering ships in and out of the port. At the same time, in order to facilitate the timely evacuation of LNG ships from the terminal in an emergency, it is recommended to adjust the direction of the terminal to the north and south.

(First author’s unit: China Petroleum & Chemical Corporation Natural Gas Branch)