Thermo-environomic evaluation of the ammonia production

Within the global challenge of sustainable energy supply and greenhouse gas emissions mitigation, carbon capture and storage and the deployment of renewable resources are considered as promising solutions. In this study the production of ammonia mainly used in the fertilizer industry and responsible for around 2-3% of the world greenhouse gas emissions is analyzed. Considering natural gas and biomass as a resource and the option of CO2 capture and storage, different process configurations are systematically compared with regard to energy, economic and environmental considerations. A consistent thermo-environonomic optimisation approach combining flowsheeting, process integration techniques, economic performance evaluation, life cycle assessment and multi-objective optimisation is applied for the conceptual process design and competitiveness evaluation. It is highlighted that the quality of the process integration is a key factor for improving the performance by valorizing the heat excess through electricity cogeneration. Including CO2 mitigation in the ammonia production allows to reduce the emissions, but leads to a slight efficiency decrease due to the energy consumption for the CO2 compression. For the natural gas fed process yielding an energy efficiency around 65%, the overall life cycle emissions can be reduced to 0.79kgCO2/kgNH3 with CO2 capture compared to 1.6kgCO2/kgNH3 without capture. Considering the biogenic nature of the carbon in the biomass, the emissions drop to -1.79kgCO2/kgNH3 for the biomass process having an energy efficiency of 50%. The economic competitiveness highly depends on the resource price and the introduction of a carbon tax. This study reveals the potential of the decarbonisation of the fertilizer industry. This article is protected by copyright. All rights reserved

François Maréchal, Matthieu Perrenoud, Laurence Tock

Within the global challenge of sustainable energy supply and greenhouse gas emissions mitigation, carbon capture and storage (CCS) and the deployment of renewable resources are considered as promising solutions. In this context, the production of ammonia mainly used in the fertilizer industry that is responsible for a large part of the global CO2 emissions is analyzed in detail in this study. Considering natural gas and biomass as a resource and the option for CO2 capture and storage, different process configurations are systematically compared with regard to energetic, economic and environmental considerations. A consistent thermo-environonomic optimization approach combining flowsheeting, process integration techniques, economic performance evaluation, life cycle assessment and multi-objective optimization is applied for the conceptual process design and the assessment of the competitiveness and the trade-offs. It is highlighted that the quality of the process integration is a key factor for improving the process performance by valorizing the heat excess through electricity cogeneration. Including CO2 mitigation in the ammonia production allows to reduce the emissions, but leads to a slight efficiency decrease due to the additional energy consumption for the compression. For the natural gas fed process yielding an energy efficiency around 65%, the overall life cycle emissions can however be reduced to 0.79kgCO2/kgNH3 with CO2 capture compared to 1.6kgCO2/kgNH3 without capture and to -1.79kgCO2/kgNH3 for the biomass process having an energy efficiency of 50%. The economic competitiveness highly depends on the resource price and the introduction of a carbon tax. This study reveals the potential of the decarbonization of the fertilizer industry.

SFGP2013

Thermo-chemical H2 production: Thermo-economic modeling and process integration

François Maréchal, Laurence Tock

Within the global challenge of climate change and energy security, hydrogen is considered as a promising decarbonized energy vector to be used in electricity production and transportation. In this paper, the thermo-chemical production of hydrogen by natural gas reforming and by lignocellulosic biomass gasification are analyzed, compared and optimized by developing thermo-economic models. Combining flowsheeting with process integration techniques, thermo-economic analysis and life cycle assessment (LCA), a systematic comparison of different process options with regard to energy, economic and environmental considerations is made. The choice of the technologies is optimized together with the operating conditions using multi-objective optimization. In both natural gas and biomass based H2 pathways, a CO2 removal step is included during the H2 purification which allows for CO2 capture and further sequestration. The potential for greenhouse gas mitigation is assessed and compared with conventional plants without capture based on the CO2 avoidance cost and the overall CO2 equivalent emissions computed from the life cycle chain. The system’s performance is improved by introducing process integration valorizing the waste heat by the combined production of heat and power. The H2 application purpose and the corresponding required purity are key factors defining the process performance. The trade-offs between competing thermoenvironomic (i.e. energy, economic and environmental) objectives are finally assessed using a multi-objective optimization. For natural gas based H2 production overall energy efficiencies up to 80% and production cost of 22-110 USD/MWH2 are computed compared to around 60% efficiency and 75-263 USD/MWhH2 for biomass based processes having the advantage of using renewable resources. The CO2eq emissions are reduced by more than 6.4kgCO2eq/kgH2 for NG and 20kgCO2eq/kgH2 for BM processes compared to the cases without CO2 capture. The competitiveness on the energy market depends strongly on the resource price and on the imposed CO2 taxes. Our study shows that the thermo-chemical hydrogen production has to be analyzed as a polygeneration unit producing not only hydrogen but also captured CO2 and electricity.

2011

Methodology for the identification of promising integrated biorefineries

Ayse Dilan Celebi

Steady increase in global energy consumption, greenhouse gas emissions, and depletion of fossil energy resources, together with increased attention towards sustainable development has prompted researchers to discover economical and environmentally competitive non-petroleum alternatives and biomass is considered to be one of the most promising renewable sources of energy and carbon of this matter to address the aforementioned issues within a biorefinery platform. A biorefinery is an integrated processing facility that converts biomass into transportation fuels, value-added chemicals, heat, and electricity via biochemical and thermochemical conversion routes. Integrated biorefineries are capable of mimicking petroleum refineries via application of advanced process synthesis methods including modeling, simulation, integration and optimization techniques. This thesis presents a comprehensive synthesis methodology for the integration of bioprocessing technologies in biorefineries by addressing techno-economic and environmental sustainability analysis. The proposed systematic design approach combines advanced process modeling approaches, process integration techniques, and multi-objective optimization algorithms to assess the performance of the overall system with respect to economic, environmental, and energetic indicators. The design strategy is applied based on different case studies. Results indicate that multi-product processes can yield significant cost and environmental benefits. Additionally, the integration of biochemical and catalytic processes with thermochemical conversion pathways results in increased carbon efficiency and economic and environmental competitiveness. Synergies between biorefineries and energy system are assessed by integrating industrial plants with a cogeneration system producing biofuels and process heat. In doing so, system efficiency is increased by coupling the proposed cogeneration system with carbon capture and sequestration (CCS) and power-to-gas technologies to store the renewable intermittent electricity in the form of biofuels. The results exhibit that through system expansion, integrated biorefinery systems allow us to imitate fossil refineries with a large spectrum of bio-based products. This further increases the resource efficiency while offering a promising solution to mitigate CO2 emissions and hence reaching the longer-term decarbonization target set by the Paris Agreement.