LNG Sendout System

13.7.3.1 In-Tank LNG Pumps

Refer to P&ID’s W00031-000-PR-PI-067/069.

LNG from the storage tanks will be pumped by the vertical, submerged in-tank LNG pumps located in the storage tanks (three pumps per tank, six in total in the two LNG tanks to be installed initially) to the BOG condenser (or bypass) and on to the send-out pumps. The in-tank LNG pumps will each be capable of pumping 2353 gpm of LNG at a pressure of 145 psia. At the normal send-out rate of 1,963,390 lb/h, four pumps will be required to operate (leaving one spare pump per tank).

Each in-tank LNG pump will be provided with a recycle (kick-back) loop back to the LNG storage tank to ensure the pumps do not operate below their minimum safe flow.

All in-tank pumps shall be capable of simultaneous operation on total kick-back for tank mixing in case of stratification.

The main technical characteristics of the in-tank LNG pumps are as follows:

• Manufacturer: Ebara or similar

• Service: LNG

• Suction Pressure (min/max): 17.3 / 43.8 psia

• Rated Discharge Pressure: 145 psia

• Motor Size 265 HP

See Appendix B13 for LNG In-Tank Pumps datasheet (W00031-161-PR-DS-002).

13.7.3.2 Sendout Pumps

Refer to P&ID’s W00031-000-PR-PI-013/014/015/016/017.

The five send-out pumps will take their feed from the BOG condenser LNG outlet or bypass line. The send-out pumps will discharge the LNG at approximately 1,320 psia to the vaporizers. At the normal send-out rate of 1,963,390 lb/h, four send-out pumps (each capable of pumping 2398 gpm of LNG) will be required to operate (leaving one pump as spare).

The send-out pumps will be designed to provide vapor send-out from Bradwood Landing to deliver to the Williams Northwest Pipeline at a pressure of 960 psig.

Each send-out pump will be provided with a recycle (kick-back) loop back to the LNG storage tanks to ensure the pumps do not operate below their minimum safe flow.

The main technical characteristics of the send-out pumps are as follows:

• Manufacturer: Ebara or similar

• Service: LNG

• Suction Pressure (min/max): 116 / 225 psia

• Rated Discharge Pressure: 1320 psia

• Motor Size: 2335 HP

See Appendix B13 for Sendout Pumps Datasheet (W00031-561-PR-DS-004).

13.7.3.3 Submerged Combustion Vaporizers

Refer to P&ID W00031-000-PR-PI-020 as typical.

The Terminal operates using 7 submerged combustion vaporizers to re-gasify the LNG.

The vaporizers are arranged in parallel. Under normal operation, only 6 units are in operation. The remaining unit, acts as a spare to enable ongoing maintenance, change out of water baths and to cover single unit downtime without impacting on terminal send-out capacity.

LNG is converted to natural gas in the vaporizers, which operate at approximately 1,291 psia. (NOTE. Due to the fact that the vaporizers operate at a pressure above the critical point, there is no vaporization in the conventional sense and no 2-phase region in the vaporizers.)

The minimum gas out temperature from the terminal is 40°F. At minimum send-out rates where send-send-out pressure is throttled (reduced pipe friction losses) the LNG outlet temperature of the SCV’s can be increased to compensate for Joule-Thompson cooling by increasing the water bath temperature. No trim heating system is required.

The SCV’s are fuelled by send-out gas. A fuel gas system controls the pressure and supply of the fuel gas to ensure continuous SCV operation. Approximately 1½% (w/w) of the LNG send-out is used in the vaporization of the LNG. Fuel gas is burnt under temperature control in order to maintain the temperature of a water bath. The combustion products of the fuel gas are forced through the water bath, thus heating the bath. The LNG passes through the water bath in high-pressure tubing and approaches the water bath temperature (typically 68°F). A typical design of the control system and piping layout along with a general arrangement of the actual heat exchange water bath is shown on pages 16 and 17. The individual gas lines at the inlet and discharge of each SCV unit each have emergency shutdown values to prevent unwanted discharge of gas. These valves are synchronized to prevent LNG being trapped.

As the combustion products are forced through the water bath, carbonic and nitric acid are formed. The water of combustion condenses, increasing the volume of water in the bath. This excess water passes to an overflow. The caustic recirculation system doses caustic to the overflow from each of the SCV water baths under pH control from a sensor in each SCV water bath to counteract the fall in pH resulting from the dissolved acids. This creates sodium carbonate and sodium nitrate in solution. The water bath continuously overflows into the effluent pit, where the pH levels are monitored, before pumping the effluent into the river via a diffusion pipe.

Should the pH drop in the effluent pit, the effluent pumps are switched off and caustic solution is manually added and the agitator is started. Once the pH is neutral, the pumps can be restarted.

• Manufacturer: Selas or Similar

See Appendix B13 for SCV Datasheet (W00031-563-PR-DS-007).

13.7.3.4 Operation and Control

The vaporizers are arranged in parallel. Under normal operation, only 6 units are in operation. The remaining unit, acts as a spare to enable ongoing maintenance, change out of water baths and to cover single unit downtime without impacting on terminal send-out capacity.

It is intended that the sequencing of the vaporizer duty cycles will be performed automatically within the plant DCS.

13.7.4 Vent

Refer to P&ID W00031-000-PR-PI-048.

The vent system is composed of one ignitable vent stack. In normal operation, there will be zero hydrocarbon emissions from the vent; only inert purge gas (nitrogen) will be vented.

The majority of gas phase pressure reliefs at Bradwood Landing will relieve into the BOG header. The exceptions are the storage tanks relief valves and the vaporizer relief valves, which will relieve directly to atmosphere. The advantage of this system is that emissions to atmosphere will be minimized.

The ultimate over-pressure protection of the BOG header will be via the tank relief valves. However, to avoid lifting the tank relief valves and generating a cold release, the BOG header will be protected by a pressure controller, which will allow relief to the process vent, if required.

The vent will be located in a safe (sterile) area to minimize the potential for ignition.

The vent will be designed for a maximum rate of 68,670 lb/h (based on minimum sendout case with carrier unloading and BOG Compressors off-line).

See Appendix B13 for Vent Stack datasheet (W00031-768-PR-DS-021).