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The power-to-liquids (P2L) and power-to-gas (P2G) processes which utilize renewable power to convert carbon dioxide and water into value-added syncrude and synthetic natural gas have recently gained much attention as an efficient way for CO2 mitigation. Based on our previously proposed direct P2L and P2L/P2G hybrid processes in the absence of the reverse-water–gas-shift unit, in this work, we developed the indirect P2L and P2L/P2G hybrid processes combined with the reverse-water–gas-shift unit, which produce solely syncrude and the combination of syncrude and synthetic natural gas, respectively. A comparative study of the indirect and direct P2L and P2L/P2G hybrid processes via the process modelling and techno-economic analysis was implemented to quantitatively evaluate their process performance differences, and it was indicated that the indirect P2L and P2L/P2G hybrid processes were also able to be considered as suitable technologies for the transformation of CO2 into high-value hydrocarbons, and the indirect P2L/P2G hybrid process seemed to be more competitive than the indirect P2L process from both technical and economic aspects. Moreover, compared to the direct P2L and P2L/P2G hybrid processes, the indirect P2L and P2L/P2G hybrid processes produce more syncrude, however, they are less efficient in aspects of energy efficiency and net CO2 reduction.

Conceptual design for two options of carbon-dioxide-utilized gas-to-methanol process (CGTM) was implemented by using process simulation software Aspen Plus. The overall mass and energy stream results as well as the thermal and carbon efficiency were obtained from the developed process models. Before the following economic evaluation and sensitivity analysis, total capital investment (TCI) and total product cost (TPC) of both CGTM options were determined. Then, economic evaluation were conducted to assess the economic profitability of the base cases for both CGTM options, using the economic evaluation indicators such as net present value (NPV), internal rate of return (IRR), and discounted payback period (DPBP). Furthermore, sensitivity analysis as well as break-even analysis were also applied to investigate the economic performance of both CGTM options under different circumstances, by changing parameters such as methanol and NG prices, plant scale, and carbon tax. It was shown that the methanol price, CAPEX, and NG price are the most sensitive factors, and the two CGTM options were economically feasible in the plant scale range of 2500–5000 ton per day, according to the economic evaluation indicators NPV, IRR, and DPBP, and were more economically competitive in the case of higher plant scale and carbon tax.

Two process models for modular gas-to-liquids (GTL) process mainly producing Fischer–Tropsch (F–T) synthetic oils were developed by Aspen Plus software. Both models mainly comprised a reforming unit, an F–T synthesis unit, and a recycle unit, with the syngas generation and syngas ratio conditioning methods as the main difference. In the reforming unit, either steam reforming or CO 2 /Steam-mixed reforming was selected to generate the desired syngas. Co-based microchannel F–T synthesis was applied to convert the obtained syngas to synthetic oils. After F–T synthesis, a portion of the unreacted syngas was recycled to improve energy efficiency, and reduce CO 2 emissions. Technical and economic analyses were both employed to investigate the two modular GTL options. For the technical aspect, effects of recycling and splitting ratios on the performance of both options were investigated. Sensitivity analysis and break-even analysis were applied to the economic analysis. It was found that the increased energy efficiency and reduced CO 2 emissions could be achieved by recycling a portion of the unreacted syngas. Both options were economically viable at the plant scale of 2500 BPD, and were more competitive in the event of high carbon tax.

Conceptual design of two options of carbon dioxide utilized gas-to-liquids process (CUGP), which mainly produces light olefins and Fischer–Tropsch (F–T) synthetic oils, has been implemented with the aid of Aspen Plus software. The mass and energy stream results as well as the process efficiencies and CO2 emissions of the proposed options were obtained from the developed models. The capital investment and the product cost estimations were conducted before the following economic analysis. Several indicators such as net present value (NPV), discounted payback period (DPBP) and internal rate of return (IRR) were calculated to evaluate the profitability of the two proposed options. In the economic analysis, sensitivity analysis as well as break-even analysis was carried out. In addition, effects of several sensitive factors such as the prices of synthetic oil, olefin and natural gas, capital investment, carbon tax and plant scale on the IRR of each option were analyzed in detail. It was found that the CUGP, regardless of option, was economically feasible at the plant scale of 40,000 BPD and was more competitive compared with conventional GTL processes, in case of high carbon tax.