(107b) LNG Regasification with Integrated Power Cogeneration

The concept of LNG receiving terminals is to receive the LNG, which has been transported from various sources to the terminal, using LNG carriers. This LNG will be re-gasified by pumping it out from storage tanks and vaporized into natural gas to the transmission system (pipeline network) at required conditions of pressure and temperature.

In a LNG Regasification terminal the LNG, at adequate pressure, can be routed from the high pressure pumps to the vaporizers under flow control according to the Terminal send out. In the vaporizers, the LNG would be heated and vaporized.

In order to achieve the most efficient integration and environmental friendly configuration, it is considered a Rankine cycle (very similar circuit to the steam cycle in a conventional thermal power plant) to vaporize the LNG with a two serial vaporizers scheme.

First vaporizer, downstream the LNG Pump, will transfer heat from the working fluid to the LNG and will also acts as a condenser of the Rankine cycle that will produce power. In this manner LNG can be used to generate electricity by the expansion of a working fluid across an expander (turbine).

The working fluid of the Rankine Cycle is condensed in the First vaporizer via heat exchange with LNG is pressurized by the circulation pump and sent to the working fluid vaporizer.

LNG enters the Second vaporizer, where the resultant natural gas is heated to ~0⁰C. Hence this Second vaporizer will cool down the district cooling water. That same water would be previously cooled down when vaporizing the working fluid of the Rankine cycle. In the proposed scheme, sufficient ‘temperature potential’ exists between LNG and water to condense and vaporize the working fluid.

For the LNG vaporisation cycle to work, the working fluid of the Rankine cycle should boil under pressure at district cooling water temperature and condense at low pressure at LNG temperature. Propane is a one of such working fluids that could be used, amongst others.

In these Rankine cycle configurations 100 metric ton per hour (t/h) of LNG can produce power up to 5 MWe. Hence for a 5 MPTA terminal, 35MWe may be achieved with no fuel cost. This recovery on a 100 t/h LNG cryogenic power plant, in form of electric power, reduces power consumption and by extension will reduce CO2 emissions by approximately 10,000 tons a year vs other vaporization schemes.