Tri-reforming of Natural Gas Using CO2 in Flue Gas of Power Plants without CO2 Pre-separation for Production of Synthesis Gas with Desired H2/CO Ratios

Abstract

Most existing CO2 conversion processes use pure CO2 that comes from CO2 recovery, separation and subsequent purification, which are all energy- consuming steps that add up the cost and can lead to additional CO2 emission. A novel process concept, tri-reforming, is proposed for effective conversion and utilization of CO2 in the flue gases from fossil fuel-based power plants in the 21st century. The CO2, H2O, and O2 in the waste flue gas need not be pre-separated because they will be used as co-reactants for tri-reforming of natural gas. The tri-reforming is a synergetic combination of CO2 reforming, steam reforming, and partial oxidation of natural gas. The simultaneous oxy-CO2-steam reforming reactions in the tri-reforming process can produce synthesis gas (CO+H2) with H2/CO ratios (1.5–2.0) and can also eliminate carbon formation which is a serious problem in the CO2 reforming of methane. These two advantages have been demonstrated by a preliminary laboratory experimental study of tri-reforming in comparison to CO2 reforming at 850°C. A comparative analysis by calculation indicated that tri-reforming is more desired for producing syngas with H2/CO ratios of 2.0 compared to CO2 reforming and steam reforming of methane. The tri-reforming process could be applied, in principle, to the natural gas-based power plants and coal-based power plants. The syngas with desired H2/CO ratios can be used for synthesis of chemicals (alcohol, ether, olefins, etc.), ultra-clean fuels (hydrocarbon fuels and oxygenated fuels), and could also be used for generating electricity.