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CO 2 -to-olefins (CTO) technology has emerged as a worthy solution for green olefin production and greenhouse gas emissions mitigation. However, most of the present researches focus on the development of high-performance catalysts, while few of them devote to the process design and performance evaluation. Hence, this study proposed three candidate CTO processes via methanol-mediated, direct and indirect FTS-based routes. Based on the rigorous modeling and simulation, exergy-based (i.e., exergetic, exergoeconomic, and exergoenvironmental) analyses were conducted to quantify the overall exergy dissipation, economic cost, and environmental impacts. More specifically, we carefully assessed and compared their comprehensive performances from the system-level, and discern the origins and formation of economic cost and environmental impacts from the component level. As a result, the direct FTS-based process has the highest exergy efficiency of 68.65 %, while the indirect FTS-based process and the methanol-intermediated process exhibit the lowest unit exergoeconomic cost and exergoenvironmental impacts of 0.147 $/kW and 38.55 mPts/kW, respectively. In addition, some pertinent optimization suggestions were proposed to enhance the systems' thermodynamic efficiency, economic and environmental benefits. Overall, this study offers crucial insights into the thermodynamic irreversibility, economic viability, and environmental sustainability of the proposed CTO systems, propelling the frontiers of future sustainable olefin production. [Display omitted] • Indicating the location, magnitude, and causes of the system inefficiencies. • FTS-based CTO process exceed MeOH-based process in exergy efficiency by 3.41 %. • Indirect FTS-based process presents the lowest unit exergoeconomic cost of 0.147 $/kW. • MeOH-based process generates the least exergoenvironmental EI emissions of 38.55 mPts/kW. [ABSTRACT FROM AUTHOR]

[Display omitted] • One traditional and three novel biomass-to-methanol (BTM) processes are proposed. • Clean H 2 production pathways are used to maximize carbon utilization potential. • Novel BTM processes all enhance methanol production and carbon mitigation. • Integration of methane pyrolysis pathway is preferred in technical performances. • Deployment of methane chemical looping pathway shows stronger economic advantages. Concerns about depleted fossil fuels and the climate crisis have intensified the interest in producing biomass-derived methanol. However, the traditional biomass-to-methanol (BTM) process suffers from low carbon conversion ability and serious CO 2 emissions caused by the water–gas-shift (WGS) unit. In this study, three novel BTM processes coupled with solid oxide electrolysis, methane pyrolysis, and methane chemical looping technologies are proposed to eliminate WGS unit, and the systematic heat integration is considered to achieve energy cascade utilization. Meanwhile, process performances are comprehensively evaluated to compare the technical, economic, and environmental attractiveness of three novel BTM processes. It is found that compared with the original BTM process, three novel processes significantly improve carbon efficiency by 22%. Meanwhile, CO 2 emissions are reduced by 60%. Moreover, the application of methane chemical looping technology is more economical, and the associated net production cost decreases by more than 30%. Additionally, the BTM process coupled with solid oxide electrolysis is more environmentally friendly, whereas the process with methane pyrolysis technology is more exergy-efficient. Overall, the integrated processes have significant application prospects for carbon conversion and mitigation ability as well as economic attractiveness. [ABSTRACT FROM AUTHOR]

[Display omitted] • The K/Fe-C catalysts were prepared by the direct pyrolysis of K 2 CO 3 impregnated MIL-100(Fe). • The 4 K/Fe-C catalyst exhibits high liquid hydrocarbon selectivity of 54.78 % at CO 2 conversion of 32.40 %. • A superior stability was observed within 100 h TOS over the 4 K/Fe-C catalyst due to the core–shell-like structure. • The Fe nanoparticles are well dispersed and weakly aggregated over the 4 K/Fe-C catalyst. • The possible reaction pathway for the K/Fe-C catalysts was proposed. Direct hydrogenation of CO 2 to liquid hydrocarbons via modified Fischer-Tropsch synthesis represents an appealing and sustainable route for efficient CO 2 utilization. However, the selective production of liquid hydrocarbons remains a significant challenge. In this work, we designed a series of carbon-coated K/Fe-C catalysts with various K loadings (ranging from 0 to 8 wt%) that enhance C 5+ hydrocarbon selectivity during CO 2 hydrogenation. It is found that the 4 K/Fe-C catalyst exhibits the highest C 5+ selectivity of 54.78 % at CO 2 conversion of 32.40 % and good stability within 100 h time-on-stream. This is attributed to the high dispersion of the Fe nanoparticles and the confinement effect of porous carbon matrix on the aggregation of Fe nanoparticles, resulting in high catalytic activity and selectivity. Meanwhile, the well dispersed K on the porous carbon matrix can reduce the particle size of Fe nanoparticles and promote the production of iron carbide active species for CO 2 -FTS, thus facilitating the selective formation of C 5+ hydrocarbons. Moreover, we also discussed a possible reaction mechanism for the direct hydrogenation of CO 2 to C 5+ hydrocarbons over the K/Fe-C catalysts. This study provides deep insights into the design of efficient Fe-C catalysts for converting CO 2 to liquid hydrocarbons. [ABSTRACT FROM AUTHOR]

• Two options for direct conversion of CO 2 to liquid fuels and synthetic natural gas are proposed. • CO 2 is converted via Fe-based F-T synthesis and CO 2 methanation technologies. • Process modeling and conceptual design are implemented using Aspen Plus. • Techno-economic analysis is performed to evaluate the economic performance. • Both options can be regarded as candidate technologies for direct CO 2 conversion. The conceptual design of a base case power-to-liquids (PTL) process that converts CO 2 to liquid fuels and a hybrid PTL/power-to-gas (PTG) process that converts CO 2 to liquid fuels and high-calorie synthetic natural gas (SNG) was carried out by using an Aspen Plus simulator. Based on the established process models, we conducted a technical study to investigate the effects of recycle ratios on the process performance such as the energy efficiency and the net CO 2 reduction of the proposed hybrid PTL/PTG process, and compared it with the base case PTL process. After the technical study, an economic analysis was further implemented to evaluate the economic performance of the hybrid PTL/PTG and the base case PTL processes and to pursue the optimum process configuration of the proposed hybrid PTL/PTG process. According to the results of the technical study and economic analysis, it can be concluded that both the base case PTL process and the hybrid PTL/PTG process can be regarded as candidate technologies for the conversion of CO 2 to value-added liquid fuels and/or high-calorie SNG. Moreover, the hybrid PTL/PTG process seems to be more efficient and profitable in utilizing CO 2 because of its higher energy efficiency and net CO 2 reduction as well as lower CO 2 reduction cost in comparison with the base case PTL process. [ABSTRACT FROM AUTHOR]

[Display omitted] • Employing LCA to provide opportunities for ecological improvements of PTL/PTG systems. • Identifying the influence of different water electrolysis technologies on the systems' performances. • Indicating the formations of monetary cost and environmental impact based on the exergy streams. • Providing optimization suggestions for PTL/PTG systems from the perspective of components. In the past decades, Power-to-Liquid (PTL) and Power-to-Gas (PTG) technologies, which utilize the captured CO 2 and surplus renewable electricity to produce sustainable fuels and chemicals, have attracted much attention. In our previous study, four PTL/PTG process cases coupled with different water electrolysis technologies (i.e., AWE, PEM, SOEC, and AEM) have been proposed to simultaneously produce syncrude and SNG. To comprehensively examine their technical, economic, and environmental performances, this paper carried out an exergy-based (i.e., exergoeconomic and exergoenvironmental) analysis. Firstly, a Life Cycle Assessment (LCA) was plotted with the material and energy flows data to evaluate the tangible and potential environmental impacts. Secondly, an exergoeconomic and exergoenvironmental analysis that integrate exergy analysis with economic analysis and LCA was suggested to calculate the integrated technical–economic and technical-environmental performances. The formation of exergoeconomic cost and exergoenvironmental impacts in the four cases are illustrated by Sankey diagrams. The results revealed that the case coupled with AEM electrolysis technology has the lowest exergoeconomic product cost and exergovironmental potential emissions. In the certain cases, the components with considerable energy consumption and temperature changes are the main contributors for the total exergoeconomic cost and exergoenvironmental impacts. Regarding the results, this work intends to provide optimization suggestions, aiming at achieving a balance among the better technical and economic performances and less environmental impacts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Establishing a life cycle sustainability evaluation system from technical, economic, and environmental perspectives. • Proposing a novel integrated MCDM model to aggregate multi-dimensional sustainability performances. • Coping with the external and internal uncertainties in judgments and decision-making. • Providing a well-informed benchmark to support the screening and selection of CO 2 conversion technologies. • Exploring the improvement opportunities and limits for short- and mid-term implementation in industries. With the emergence of numerous CO 2 chemical conversion technologies to simultaneously reduce CO 2 emissions and produce value-added products, it is of great importance to compare their difference and select the most sustainable routes for future development. This study quantitatively evaluated the sustainability performances of 21 alternative CO 2 conversion technologies from economic, technical, and environmental perspectives and developed a novel Multi-criteria Decision-making (MCDM) model to prioritize the alternatives. To cope with the external and internal uncertainties during the decision-making, Interval-Rough Numbers (IRNs) were firstly used to deal with subjective vagueness and information incompleteness involved in the group judgements unavoidably. Secondly, DEMATEL-ANP was employed based on IRNs to specify the correlation type and degree among diverse criteria for determining the global weights accurately. Lastly, a Vector-based Algorithm method was applied to measure the alternatives' overall performance and figure out the final ranking scores of sustainability. The results revealed that CO 2 to methane, urea, methanol, dimethyl ether, and acetic acid were the top five promising conversion technologies with the highest R&D priority over the next decades from a sustainability perspective. Moreover, a detailed sensitivity analysis of criteria weights was conducted to scrutinize the effectiveness of the ranking results and to validate the reliability of the new proposed MCDM model. Furthermore, in consideration of the complexity of future technological advance, market transformation, economic and social trends, this life cycle sustainability decision-support framework for CO 2 conversion technologies provides a well-informed benchmark to support the screening and selection of candidate technologies including both the existing and emerging processes, and strategically explore the development opportunities and limits under uncertainties. [ABSTRACT FROM AUTHOR]

CO 2 -to-DME (CTD) technology has been considered as a worthy solution for waste CO 2 upcycling and green DME production. Faced with various emerging CTD routes with pros and cons, it is important to systematically assess and compare their attractiveness and difference, and identify the most sustainable technologies for further development and improvement. Thus, the present study proposed four promising CTD routes (i.e., two-step routes using high- and medium-concentration methanol as intermediates, and one-step routes with and without RWGS reactions) and developed a multi-criteria sustainability assessment and decision-making framework for alternative routes comparison and prioritization. Eleven KPIs were considered from technical, economic, and environmental perspectives to evaluate system sustainability. Exergoeconomic and exergoenvironmental analysis were conducted to pinpoint the location, magnitude, and sources of system inefficiencies from the component level. A TOPSIS method was employed to integrate multidimensional performances and present an informed decision-making process. As a result, all the alternative routes are sustainable for DME synthesis, and therein the one-step route without RWGS reaction always ranks as the most competitive choice through rigorous sensitivity analysis. Moreover, this work provides a strategic decision support for assessing the trade-offs involved in existing and emerging sustainable CO 2 upcycling technologies towards carbon neutrality. [Display omitted] • Four promising DME synthesis routes via CO 2 hydrogenation were proposed and modeled. • A multi-criteria sustainability assessment and decision-making framework for CTD technology prioritization was set up. • Exergoeconomic and exergoenvironmental analysis were implemented to evaluate the CTD system from the component-level. • The one-step CTD route without RWGS reaction was identified as the most sustainable strategy. [ABSTRACT FROM AUTHOR]

[Display omitted] • Conceptual design of four different CO 2 -to-DME (CTD) processes is implemented. • Rigorous process modelling and systematic techno-economic comparison are conducted. • Direct hydrogenation of CO 2 to DME is proved as a preferred and promising strategy for carbon mitigation. • Enhanced system performances are achieved through further process integration and optimization. To achieve efficient utilization of CO 2 and produce clean alternative fuel, nowadays, CO 2 -to-DME (CTD) technology is regarded as a feasible and promising solution. Considering that there is no consensus on the techno-economic performances of the different CTD processes, it is necessary to conduct a comprehensive and systematic comparison of the existing and emerging CTD technologies and to deeply explore the influence of the process integration on technical feasibility and economic profitability. In this study, we proposed four CTD processes via different routes, namely purified methanol-mediated (Case 1), water-containing methanol-mediated (Case 2), CO-mediated (Case 3) and direct CO 2 hydrogenation routes (Case 4). The rigorous system modelling and comprehensive comparison of the process performances of four cases were implemented. From the technical perspective, Case 4 has the highest energy efficiency (77.42%), exergy efficiency (88.46%), and net CO 2 mitigation rate (67.71%). From the economic perspective, Case 2 has the lowest total product cost (1327.14 $/tonne DME), whereas Case 4 has the lowest net CO 2 mitigation cost (589.34 $/tonne CO 2). Moreover, to further enhance the system performance of Case 4, we also proposed effective improvement measures for process optimization, which shows that the net CO 2 mitigation rate is enhanced by 1.94%, while the net CO 2 mitigation cost is reduced by 19.79 $/tonne CO 2. [ABSTRACT FROM AUTHOR]

Power-to-liquid (P2L) and Power-to-Gas (P2G) processes are considered as sustainable pathways to mitigate climate change. In both P2L and P2G processes, H 2 production via water electrolysis has received widespread attentions, including PEM, AEM, SOEC and AWE technologies. Based on the preceding technical study on four P2L/P2G hybrid processes composed of above-mentioned water electrolysis technologies, a systematic study of P2L/P2G processes and economic analysis were conducted to quantitatively evaluate their economic performances in terms of total production cost (TPC) and net CO 2 reduction cost (CRC). The P2L/P2G process coupled with SOEC technology has the lowest TPC of 204 M$/year, while that coupled with AEM technology has the lowest net CRC of 274 $/tonne CO 2. Moreover, we further proposed nine process scenarios for P2L/P2G processes using grey, blue, and green H 2 , and compared their process performances in terms of TPC and global warming potential (GWP). The P2L/P2G process via water electrolysis using wind electricity reduces GWP by 61.50%, whereas its TPC is 1.39 times higher than that with coal gasification due to the relatively high production cost. It is anticipated that a significant cost saving in the water electrolysis units is possible in the future, which will definitely improve the profitability of P2L/P2G process. [Display omitted] • Novel P2L/P2G processes composed of four water electrolysis technologies are proposed. • P2L/P2G processes with SOEC and AEM technologies have the lowest TPC and net CRC, respectively. • P2L/P2G processes using grey, blue, and green H 2 are compared in TPC and GWP. • TPC of P2L/P2G processes using green H 2 are 1.2–1.7 times higher than those using grey H 2. • GWP of P2L/P2G processes using green H 2 decrease by 24–64%. [ABSTRACT FROM AUTHOR]

• Two PtL/PtG hybrid processes are proposed for upcycling CO 2 into green fuels. • CO 2 is converted through RWGS, Fe-based FTS and/or CO 2 methanation. • A comparative analysis of the present & previous PtL/PtG processes is conducted. • The syncrude production of the present PtL/PtG process has been increased by 30.95%. • The total product revenue of the present PtL/PtG process has been increased by 12.73%. Power-to-X (PtX) technologies, especially for the Power-to-Liquids (PtL) and Power-to-Gas (PtG) have attracted extensive attention recently, as promising pathways for carbon upcycling via converting CO 2 into high-value products including liquid fuels and substitute natural gas (SNG). Herein, aiming at further improving the PtX process efficiency, we proposed two novel PtL/PtG hybrid processes, namely an indirect process (with RWGS unit) and a direct process (without RWGS unit) by integrating Fe-based Fischer-Tropsch synthesis (FTS) and olefin oligomerization technologies, which co-produce syncrude and SNG. Both process simulation and techno-economic analysis were implemented to evaluate the overall process performances, through various indicators involving technical indicators (e.g., syncrude production, energy efficiency, and net CO 2 reduction), and economic indicators such as total capital investment, net CO 2 reduction costs together with total product costs. Both proposed PtL/PtG processes are efficient in converting CO 2 into valuable hydrocarbon fuels, and the syncrude production and total product revenues of indirect process are 2.35–14.58% and 7.55–8.51% higher than those of the direct process, respectively. Whereas, the direct process has lower net CO 2 reduction cost of 206.09 $/tonne CO 2. Moreover, the present PtL/PtG processes have higher syncrude production and total product revenues than those of our previous studies including a direct PtL/PtG process coupled with Fe-based FTS and two indirect PTL/PTG processes combined with RWGS and Fe/Co-based FTS reaction, with rates of 30.95 and 12.73% at most. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel PTL/PTG processes combined with four water electrolysis technologies are proposed. • The complete process models include water electrolysis, CO 2 capture and CO 2 hydrogenation units. • The systematic process modelling and comparative technical study are implemented. • An additional case study for PTL/PTG process with SOEC & RWGS is further conducted. • The proposed processes reflect high energy & exergy efficiency, and CO 2 reduction ability. Recently, Power-to-Liquids (PTL) and Power-to-Gas (PTG) processes have been attracting extensive attentions as carbon-neutral technologies because they transform wasted CO 2 into sustainable liquid fuels and synthetic natural gas, meanwhile storing the excess and intermittent renewable energies into stable chemical energies. In both PTL and PTG processes, hydrogen production is a key step, which can be achieved by using different water electrolysis technologies, such as alkaline water electrolysis (AWE), anion exchange membrane electrolysis (AEM), proton exchange membrane electrolysis (PEM) and solid oxide electrolysis (SOEC). In this work, to implement a systematic comparison of the effects of different water electrolysis technologies on the technical performances of the PTL/PTG hybrid process, we proposed four PTL/PTG hybrid process cases coupled with the aforementioned water electrolysis technologies, and conducted a detailed comparative technical analysis in terms of energy efficiency, carbon efficiency, net CO 2 reduction rate and exergy efficiency. The results revealed that all the proposed process cases can be considered as essential candidate technologies for CO 2 transformation, and the PTL/PTG hybrid process combined with SOEC is more competitive in terms of energy and exergy efficiencies, whereas that combined with AEM shows higher carbon efficiency and net CO 2 reduction rate. Moreover, we also compared the process performances of the PTL/PTG hybrid processes combined with SOEC via the direct and indirect routes. It seems that both the indirect and direct ones are comparable in energy and exergy efficiencies. However, the direct one benefits CO 2 mitigation, while, the indirect one favors syncrude production. [ABSTRACT FROM AUTHOR]

Recently, Power-to-Liquids (PtL) and Power-to-Gas (PtG) technologies have been regarded as promising pathways for renewable energy storage and CO 2 mitigation. Herein, we newly proposed two PtL/PtG hybrid processes (Cases A and B) by integrating the Fe-based Fischer-Tropsch (F-T) synthesis and olefin oligomerization, to further enhance the production of value-added liquid hydrocarbons. The process modelling and case study were implemented to evaluate their process performances by using Aspen Plus. In addition, the effects of different feeding conditions (i.e., CO/CO 2 feeding) and process configurations (i.e., F-T synthesis only or two-stage reactor) were also comparatively analyzed. It is found that both Cases A and B are efficient technologies for converting CO 2 into value-added hydrocarbons, and Case A is found to be more beneficial in the aspects of the carbon and thermal efficiencies, and net CO 2 reduction. While, Case B is competitive in producing high-value liquid hydrocarbons. Moreover, the options of CO 2 feeding and two-stage reactor are more preferable than the options of CO feeding and F-T synthesis only, and both Cases A and B are more competitive in the aspects of syncrude production, thermal efficiency, and CO 2 reduction, as compared to the Base cases 1–3. • Two PtL/PtG hybrid process options are proposed for CO 2 transformation. • F-T synthesis and olefin oligomerization are integrated in the proposed PtL/PtG processes. • A comparative analysis of the present and previous PtL/PtG processes are conducted. • The present PtL/PtG processes are technically more competitive than the previous ones. [ABSTRACT FROM AUTHOR]

• The indirect PTL and PTL/PTG processes are proposed for CO 2 mitigation. • CO 2 is transformed via the reverse water-gas-shift and CO 2 methanation reactions. • A comparative analysis of the indirect and direct PTL and PTL/PTG processes is conducted. • The indirect PTL and PTL/PTG processes enhance the production of liquid hydrocarbons. • The direct PTL/PTG and indirect P2L processes favor the energy efficiency and CO 2 mitigation. In recent years, significant attention has been paid to the CO 2 mitigation via the power-to-liquids (PTL) and power-to-gas (PTG) processes because they can efficiently transform CO 2 into high-value products such as liquid hydrocarbons and synthetic natural gas (SNG), and provide a promising solution for the storage of the intermittent renewable energy. Herein, we suggested a PTL process and a PTL/PTG process combined with the reverse-water-gas-shift (RWGS) and Co-based Fischer-Tropsch synthesis (FTS), which respectively produce liquid hydrocarbons only and the combination of liquid hydrocarbons and high-calorie SNG, based on the previous study regarding the PTL and PTL/PTG processes composed of Fe-based FTS. We conducted the process modelling and comparative techno-economic analysis to determine the key performance of the proposed PTL and PTL/PTG processes including the CO 2 mitigation rate, energy efficiency, total product cost and CO 2 mitigation cost. The proposed PTL and PTL/PTG processes can be regarded as feasible technical solutions to convert wasted CO 2 into high-value liquid hydrocarbons and SNG. Additionally, the indirect PTL and PTL/PTG processes were helpful for improving the production of liquid hydrocarbons. Meanwhile, the direct PTL/PTG processes and indirect PTL processes favor the energy efficiency and CO 2 mitigation. [ABSTRACT FROM AUTHOR]

• The indirect CO 2 hydrogenation processes are proposed for CO 2 transformation. • CO 2 is converted via reverse water–gas-shift, Fischer-Tropsch synthesis and CO 2 methanation. • A comparative study between the indirect and direct CO 2 hydrogenation processes are conducted. • The indirect CO 2 hydrogenation processes have higher syncrude production than the direct ones. • The direct CO 2 hydrogenation processes are more energy-efficient than the indirect ones. 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 CO 2 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 CO 2 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 CO 2 reduction. [ABSTRACT FROM AUTHOR]

Aiming at achieving the large-scale CO 2 -equivalent reduction in the landfill industry, conceptual design of two sustainable landfill gas-to-methanol process options without the pre-treatment and methanol upgrading sections were implemented via using Aspen Plus simulator. In both proposed options, the optimum syngas ratio (H 2 /(2CO + 3CO 2) = 1) is fulfilled by either supplying additional H 2 (option 1) or pre-separating the surplus CO 2 in LFG using membrane (option 2). A comparative techno-economic analysis was carried out to determine the energy efficiency and the CO 2 -equivalent reduction rate, as well as the net present value (NPV), the internal rate of return (IRR), and the discounted payback period (DPBP) of both proposed options. It is shown that both options 1 and 2 can be regarded as alternative processes for converting landfill gas to methanol, and option 1 is more energy efficient and eco-friendly, while, option 2 is more economically competitive. Moreover, a sensitivity analysis indicates that the CAPEX, the prices of methanol, CO 2 allowance, and H 2 are the most sensitive factors, and option 1 can be economically comparable with option 2 given that the H 2 price can be lowered down to around 1000 $/Mt. This work provides two candidate process routes for efficient conversion of landfill gas to value-added methanol, which makes the landfill industry become more sustainable and profitable, especially in the event of a future high carbon tax and low H 2 price. Image 1 • Two landfill gas-to-methanol process options were proposed. • CO 2 in landfill gas were converted via CO 2 reforming and CO 2 hydrogenation. • Process simulation and conceptual design were implemented by using Aspen Plus. • Techno-economic analysis was implemented to evaluate the economic feasibility. • Both options have comparable economic performances at a low H 2 price of 1000 $/Mt. [ABSTRACT FROM AUTHOR]

• Three options for converting by-product gases LDG and/or COG to methanol are proposed. • Conceptual design for three proposed options are conducted using Aspen Plus. • Techno-economic analysis is performed to evaluate the process performance. • Three proposed options are considered as candidate technologies for CO 2 mitigation. • The LDG/COG-to-methanol process with H 2 purification is the most competitive case. Aiming at achieving large-scale CO 2 mitigation in the iron & steel industries via efficient utilization of the by-product gases such as the coke oven gas (COG) and Linz-Donawitz converter gas (LDG) in the iron & steel works, conceptual design of a LDG-to-methanol process (option 1) and two LDG/COG-to-methanol processes (options 2 and 3 without or with H 2 purification, respectively) was implemented using the process simulator Aspen Plus. Both the process development and economic analysis for all the three proposed options were conducted to determine the technical performance via indicators such as the energy efficiency and CO 2 reduction rate, and the profitability via indicators such as the total capital investment and the net methanol production cost. Meanwhile, six case studies under different recycle ratios (0.5–0.95) were conducted for each proposed option to investigate the effects of recycle ratio on the technical and economic performance. The techno-economic analysis results clearly show that all the three proposed options are highly efficient for CO 2 mitigation via methanol production using the by-product gases LDG and COG. More specifically, options 1 and 3 seem to be more energy efficient and eco-friendly than option 2, in terms of energy efficiency and CO 2 reduction rate. Whereas, options 2 and 3 seem to be more economically feasible than option 1, considering the net methanol production cost. From the aspects of both technical and economic performance, option 3 is considered as the most competitive process. This work provides candidate process routes for the iron & steel industries to become more sustainable and profitable, especially in the event of a high carbon tax and a low H 2 price in the future. [ABSTRACT FROM AUTHOR]

In the context of global carbon neutrality, carbon capture and storage (CCS) technology has become an important transition pathway to decarbonizing coal-fired power plants (CFPP). However, CCS technology has strict requirements for geological storage and the potential risk of CO 2 leakage. Meanwhile, the deployment of the CCS technology in the CFPP could drastically reduce plant efficiency. To address the aforementioned issues, a novel carbon capture, utilization and storage (CCUS)-assisted electricity-chemical polygeneration process (i.e., ECPP) was proposed to produce electricity, liquid fuels, and high-calorie synthetic natural gas simultaneously. To reduce the efficiency loss caused by the consumption of internal steam and electricity, heat integration and Organic Rankine Cycle (ORC) technologies were adopted to fully recover the available waste heat and achieve the cascade utilization of the internal energy. Meanwhile, a detailed techno-economic assessment was conducted to further determine the benefits of the process integration. The results indicated that the application of heat integration and ORC technologies improves plant efficiency by 6 %. Moreover, it also reduces the cost of electricity and CO 2 conversion cost by 17 and 15 %, respectively. In addition, compared with the traditional CFPPs retrofitted with CCS technology, the CO 2 utilization and waste heat recovery technologies in ECPP enhance net electricity output and plant efficiency by 19 and 34 %, respectively. Therefore, the proposed CCUS-assisted ECPP achieves the efficient utilization of the waste CO 2 , and reduces the efficiency penalty for retrofitting the CFPPs. Overall, the proposed ECPP is an essential alternative for the retrofit of the existing CFPPs, and provides a feasible strategy for establishing a clean and sustainable power polygeneration system. [Display omitted] • CCUS-assisted electricity-chemical polygeneration process is proposed. • Waste heat is recovered by heat integration and Organic Rankine Cycle methods. • Plant efficiency is enhanced by 6 % via cascade utilization of internal energy. • Optimized ECPP reduces the cost of electricity by 17 % for retrofitting CFPP. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 CO 2 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. [ABSTRACT FROM AUTHOR]

A series of Zn modified hierarchical ZSM-5 catalysts with Si/Al ratios of 25 and 40, and Zn loading amounts of 0, 0.5, 1, and 2 wt% was designed to pursue a highly efficient catalyst with excellent catalytic activity and stability toward BTEX formation in the aromatization of light hydrocarbons. The Zn modified hierarchical ZSM-5 catalysts with intracrystalline mesopores were prepared by alkali treatment and Zn impregnation. The effects of the alkali treatment and Zn modification on the textural property, acidity, catalytic performance, and coke formation were investigated in detail via various characterization techniques. It was found that the catalytic stability of the alkali-treated catalysts notably improved. This can be mainly attributed to the fact that the alkali treatment of the pre-synthesized ZSM-5 generated a large amount of mesopores, which could alleviate the diffusion limitations. Moreover, the Zn modification remarkably improved the initial BTEX yield, which was due to the improved Lewis/Brønsted (L/B) ratio in the prepared catalysts. However, as the Zn loading amount increased from 0 to 2 wt%, the catalyst stability dramatically decreased, especially for the 2 wt% case. It seems that the balance between the Lewis and Brønsted acid sites (i.e., the suitable L/B ratio) is the key to obtaining both high BTEX yield and catalyst stability, and the optimum Zn loading amount is determined to be 0.5 wt% with an L/B ratio of around 1. Image 1 • A series of Zn modified hierarchical ZSM-5 catalysts was prepared by alkali treatment and Zn impregnation. • Aromatization of light hydrocarbons was investigated by using ethylene as the model compound. • Zn modified hierarchical ZSM-5 catalysts were investigated in detail via various characterization techniques. • Both the enhanced catalytic activity and stability were achieved by using Zn-modified hierarchical ZSM-5. • The optimum Zn loading amount was determined to be 0.5 wt% with an L/B ratio of around 1. [ABSTRACT FROM AUTHOR]

This study postulated a commercial pyroprocess facility (KAPF+: Korea Advanced Pyroprocess Facility Plus) with a processing capacity of 400 tons/year as a cost object, and utilized an engineering cost estimation method based on a conceptual design to present the results of the total cost and unit cost estimation. According to the calculation results, the total cost and unit cost were calculated with k$779,386 and $781/kgHM, respectively. Moreover, the key cost driver was manifested as the operating and maintenance costs. In particular, equipment replacement cost was identified as an important cost driver. In addition, for an increasingly accurate cost estimation, the calculation results and allocation method of the indirect cost were reanalyzed. Finally the pyroprocess unit cost increased $5 when calculated the indirect cost using the labor time as the allocation standard. Meanwhile, the pyroprocess unit cost increased $22 as a result of allocating the indirect cost using the uniform labor cost as the cost allocation standard. Accordingly, an indirect cost allocation standard was manifested as the factor that exerts a significant effect on the pyroprocess unit cost. [ABSTRACT FROM AUTHOR]