(707g) Combined Natural Gas Liquefaction and Power Generation Plant With Carbon Dioxide Sequestration

It is generally well accepted that an increase in anthropogenic emissions is a leading cause of the increase in levels of carbon dioxide (CO₂), one of the greenhouse gases, in the atmosphere.  Generation of electrical power is responsible for a roughly 40% of these emissions.  Design of new zero emission power plants is critical in any effort to reduce emissions of CO₂.

We discuss the design of a combined natural gas liquefaction and power generation plant with no atmospheric emissions of greenhouse gases. More specifically, this design relates to (i) a zero emission process for power generation as the CO₂produced during the power generation cycle is sequestered into a terrestrial formation and (ii) a process by which the high pressure natural gas stream is expanded to provide refrigeration and power.  The recovered energy may be used to liquefy part of the natural gas stream to provide pure liquefied natural gas (LNG).

This plant uses natural gas from a well as a fuel.  The high-pressure stream is liquefied in a reverse-Brayton cycle and the remainder of the natural gas stream is fed to a solid oxide fuel cell to produce power.  The effluent of the solid oxide fuel cell is completely combusted to reduce it to CO₂ and water.  This stream is subsequently cooled to remove the condensed water.

Energy recovered in expansion of natural gas is used for CO2 stream compression, reducing the energy required to by 13.7%.  Alternatively, if LNG is not desired as a product, then as much as 30% of the compression energy may be supplied from expansion of natural gas. Overall power plant efficiencies of 50 – 60% are possible.  About 27.5% wt/wt of the incoming natural gas stream may be liquefied in this cycle.