Efficient Utilization of Greenhouse Gas in a Gas-to-Liquids Process Combined with Carbon Dioxide Reforming of Methane

Abstract

A process model for a gas-to-liquids (GTL) process mainly producing Fischer-Tropsch (FT) synthetic oils has been developed to assess the effects of reforming methods, recycle ratio of unreacted syngas mixture on the process efficiency and the greenhouse gas (GHG) emission. The reforming unit of our study is composed of both steam reforming of methane (SRM) and carbon dioxide reforming of methane (CDR) to form syngas, which gives composition flexibility, reduction in GHG emission, and higher cost-competitiveness. With recycling, it is found that zero emission of CO(2) from the process can be realized and the required amount of natural gas (NG) can be significantly reduced. This GTL process model has been built by using Aspen Plus software, and it is mainly composed of a feeding unit, a reforming unit, an FT synthesis unit, several separation units and a recycling unit. The composition flexibility of the syngas mixture due to the two different types of reforming reactions raises an issue that in order to attain the optimized feed composition of FT synthesis the amount of flow rate of each component in the fresh feed mixture should be determined considering the effects of the recycle and its split ratio. In the FT synthesis unit, the 15 representative reactions for the chain growth and water gas shift on the cobalt-based catalyst are considered. After FT synthesis, the unreacted syngas mixture is recycled to the reforming unit or the FT synthesis unit or both to enhance process efficiency. The effect of the split ratio, the recycle flow rate to the FT reactor over the recycle flow rate to the reforming unit, on the efficiency of the process was also investigated. This work shows that greater recycle to the reforming unit is less effective than that to the FT synthesis unit from the standpoint of the net heat efficiency of the process, since the reforming reactions are greatly endothermic and greater recycle to the reformer requires more energy.

Combined steam and CO2 reforming of CH4 using coke oven gas on nickel-based catalyst: Effects of organic acids to nickel dispersion and activity

“…Although the CDR reaction, which can produce syngas having a stoichiometric ratio of H 2 /CO of 1.0, seems to be an effective way to utilize CO 2 directly, it is not yet well established for an industrial application due to the negative characters of sever coke formation and catalyst deactivation and so on. Therefore, steam reforming of methane (SRM), which can produce syngas with a stoichiometric molar ratio of H 2 /CO around 3, has been received much attention due to its possible industry application [6][7][8]. In addition, the combined CDR and SRM, which is called as combined steam and CO 2 reforming with CH 4 (CSCR), has been also largely investigated as an alternative reforming reaction of SRM by producing the syngas having a molar ratio of H 2 /CO around 2, which has been known to be a proper composition for the subsequent application to the Fischer-Tropch synthesis and methanol (or dimethyl ether) synthesis reaction and so on [8].…”

“…In addition, the combined CDR and SRM, which is called as combined steam and CO 2 reforming with CH 4 (CSCR), has been also largely investigated as an alternative reforming reaction of SRM by producing the syngas having a molar ratio of H 2 /CO around 2, which has been known to be a proper composition for the subsequent application to the Fischer-Tropch synthesis and methanol (or dimethyl ether) synthesis reaction and so on [8]. The CSCR reaction is composed with the following characteristic reactions such as SRM, CDR, and water-gas shift (WGS) or reverse WGS (RWGS) reaction [4][5][6][7][8][9]; …”

Combined Steam and Carbon Dioxide Reforming of Methane on Ni/MgAl2O4: Effect of CeO2 Promoter to Catalytic Performance

“…In view of the production of useful chemicals and synthetic fuels, since CDR gives a low H 2 /CO ratio of around 1, the combination of SRM and CDR reactions is an appropriate way to produce syngas which is suitable for methanol or Fischer-Tropsch synthesis reactions which require H 2 /CO ratio of around 2 [9,10]. This reaction, so-called combined steam and carbon dioxide reforming of methane (SCR), recently receives the increased attention from the viewpoint of environmental and efficient resource utilization issues because it would facilitate CO 2 containing natural gas or stranded gas [11,12]. The three representative reforming reactions such as CDR, SRM and SCR could be categorized as follows:…”

Carbon Dioxide Recycling: Emerging Large‐Scale Technologies with Industrial Potential

“…A recent simulation showed that zero emission of CO 2 can be obtained with recycling of unreacted syngas. [112] A recent study [113,114] also proposed tri-reforming as a suitable approach to increase the energy efficiency of fossil-fired power plants (integrated tri-reforming power plants, ITRPPs). Similar approaches were proposed for applications combined to gas turbine power plants [115] or for coke/coal gasification combined with lime carbonation.…”