Gas Material, Processing and Power Technologies
Part2; Potential of extracting cold energybWorking Principles of the SystembOver ViewbAction of Osaka Gas for LNG cold utilizing power generation system
Recover cold energy from LNG and reduce CO2 emission with the "Cryogenic Power Plant of Osaka system"!
(You can reduce approximately 15,000 ton of CO2 emission per annual when you use a 150t/h LNG plant.)
Why donft you introduce a cryogenic energy recovery system at your LNG re-gasification terminal?
You can recover the cryogenic energy as electric power and reduce electric power consumption at your terminal, which is worth indirect reduction of CO2 emission from thermal power station.
Osaka system has the longest safe and stable operation record (30 years) in the world.
Osaka Gas is the pioneer of LNG cryogenic power generation plant using Rankine cycle as follows:
| LNG Terminal | Units | Operation Start | Generator Rated Output[kW] | System | LNG [t/h] |
Sendout gas Press.[MPa] |
|---|---|---|---|---|---|---|
| Senboku 2 | 1 | Dec. 1979 | 1,450 | Rankine | 60 | 3.3 |
| Senboku 2 | 1 | Feb. 1982 | 6,000 | Rankine{Direct NG Expansion | 150 | 2.5 |
| Himeji | 1 | Mar. 1987 | 2,800 | Rankine | 120 | 3.3 |
Advantages of Osaka system.
- Which do you prefer, complicated but large output power or simple and sufficient power?
- Regarding the Rankine cycle LNG cryogenic power generation plant, there are some complicated processes such as two stage expansions with additional heat exchangers but Osaka system is aiming simple configuration for easy and simple operation and maintenance (O&M).
- Osaka system is simple and consists of three gShell and Tubeh heat exchangers only with a radial expansion turbine as shown in Figure 1.
- Osaka system is space-saving system. This system requires small area compared with ORV with the same vaporization capability. The footprint area is 30m x 35m excluding maintenance area.
- Intermediate Heat exchanging Medium (IHM) is carefully selected and designed for long duration operation without high maintenance cost.
- Quick and automatic start-up within 20 minutes (from keep cool stand-by to full power generating)
Quick and automatic change-over of the operation mode from power generation to vaporization within 10 minutes - Low cost for periodical maintenance.
- Any trouble and/or malfunction of power generating facilities such as a turbine, a generator, an intermediate heat exchanging medium (IHM) circulation pump and oil pumps shall not cause interruption of LNG vaporization. You can keep on vaporizing LNG without any interruption. There is no necessity to prepare any spare vaporizer for continuous re-gasification.
- High tolerability
These heat exchanger tubes on seawater side are made of titanium. Therefore this plant has high tolerability against seawater. Also this results in low maintenance cost.
- Osaka System simple process realizes the following advantages, too:
- Its well designed control system and safety system can prevent seawater from freezing to clog in heat exchanger tubes.
- You can shutdown the whole plant (i.e., the vaporizer and the power generator) by closing one LNG inlet ESV only as a trigger in case of ultimate emergency.
How much can you generate the electric power with Osaka system?
- Our capability.
- Osaka Gas can offer any services from gFeasibility studyh, gFEEDh to gEPC workh with reasonable cost.
- Osaka Gas can also supply main equipments such as the three heat exchangers, turbine on the FOB Japan basis if required.
- Osaka Gas can prepare appropriate Operation and Maintenance manuals.
- Osaka Gas can offer maintenance works if necessary.
- Note; Osaka Gas practices these works with OGE (Osaka Gas Engineering Co., Ltd which is an exclusive Osaka Gas sales arm.)
Potential of extracting cold energy
Osaka Gas imports natural gas as liquefaction natural gas (LNG). This LNG is a liquid with a temperature of -160 C.. If all of the cold energy from LNG is converted to electric energy, it will be possible to recover about 240KWh per ton of LNG. The system that changes this LNG cold into the power of a turbine and recoveries electric energy is the power generation system utilizing LNG cold. However, because of hourly and daily, seasonally difference of LNG demand, actually we can utilize only about 20% of an LNG annual import. From the point of view of saving energy, Osaka gas regards utilizing LNG cold as important. Therefore Osaka Gas grapple aggressively with various technical development such as a new LNG cold utilizing generation system, an LNG cold storage system and so on.
Working Principles of the System
Now three types of system are in operation. First is the Rankine cycle
system in which intermediate fluid drives a turbine. Second is the NG
direct expansion system in which vaporized natural gas drives a turbine.
Third is the combination of the Rankine cycle system and the NG direct
expansion system. The following goes into the details of propane Rankine cycle for example. LNG is boosted up to a pressure of 35 - 45 kgf/cm 2G with LNG pump, heat
exchanged with propane gas at LNG vaporizer (propane condenser) to be
heated up to about -50 C. and heat exchanged with sea water to be heated
up to over 0 in the following NG trim heater. Propane which is condensed
in the LNG vaporizer is boosted up with propane pump and sent to the propane
vaporizer where it is vaporized at a pressure corresponding to the temperature
of sea water. Vaporized propane gas drives the turbine during the expansion
process and generates electric power. Turbine outlet propane gas is sent
to the LNG vaporizer again and condensed by LNG cold.
Over View
Action of Osaka Gas for LNG cold utilizing power generation system
Osaka Gas researched and developed in advance and constructed the first
LNG cold utilizing generation system in the world. After that Osaka Gas
has been researching and developing this system aggressively.
