Integrated Coproduction of Power and Syngas from Natural Gas to Abate Greenhouse Gas Emissions without Economic Penalties.

Abstract

Natural gas (NG)-fired power plants are significant greenhouse gas (GHG) emitters because of their substantial CO2 release. To avoid these emissions, precombustion and postcombustion CO2 capture alongside oxy-fuel combustion were considered in the literature. However, because of additional energy requirements, these options generally induce an approximately 7–10% decrease in net heat-to-power efficiencies regarding regular NG-air-fired stations without CO2 capture. To compensate for this declination, in this study, a simultaneous generation of power and syngas (CO and H2) was proposed in an integrated NG-oxygen-fired gas turbine unit (GTU). Hence, the combustion chamber in the NG-oxygen-fired gas turbine cycle was replaced by an NG partial oxidation reactor, which converts it into syngas. The syngas was separated from the working fluid of the cycle by the condensation of water vapor (steam), and a part of it was withdrawn from the GTU to be utilized as a chemical feedstock. A benchmark thermodynamic analysis at the same input–output conditions and requirements for carbon capture was conducted to compare the proposed unit with NG-air and NG-oxygen-fired power plants. The integration effect was shown by increasing the heat-to-power efficiency from 48 to 54%. With carbon monoxide (CO) as an intermediate, the author proposed capturing carbon in NG (methane) in liquid formic acid, which is a good commodity for transportation to a place where it can be reconverted into CO or H2 to manufacture various industrial chemicals. Simple economic considerations show that because of a substantially higher cost of formic acid than an equivalent power, CO conversion into formic acid substantiates the integrated approach as economically attractive.