Hydrogenation of CO2 to produce synthetic methane is a promising alternative to reduce the dependence on fossil fuels of high-temperature industrial processes hard to be electrified, contributing to mitigation of global warming. To reach enough conversion ratios and reasonable reactor sizes, the Sabatier reaction is usually performed via heterogeneous catalysis. Metallic catalysts, as nickel or ruthenium, are the most used supported over mesoporous alumina. The present work proposes and fully investigates for the first time the use of olive kernel biochar obtained from pyrolysis as support of methanation catalyst. The so-obtained biochar, with 530 m2/g specific surface area, is evaluated as a cost-effective and sustainable support. A Ni-based (10 wt%) catalyst was synthesized and tested in a fixed-bed methanation pilot plant. The obtained conversion ratios for gas hourly space velocity of 6000 h- 1 were above 60 % for stoichiometric ratio and atmospheric pressure. A kinetic model was developed and validated with experimental measurements, finding discrepancies below 10 % between predictions and experiments. Even though the H2-TPR analyses revealed incomplete nickel reduction during the activation stage, the preliminary results are very promising as the achieved performance figures are similar, even higher, than that obtained in pressurized facilities and/or using Ni-Ce catalysts.

In response to the growing demand for renewable energy storage solutions, metal fuels have emerged as a promising alternative as recyclable energy carriers. These metals release energy through combustion, forming metal oxides, which can subsequently be regenerated into their metallic state using renewable hydrogen. Recent experimental studies have demonstrated the feasibility of self-sustaining combustion-oxidation of various finely ground metals. For the reduction step, established direct reduction iron (DRI) technology has been successfully used to convert solid iron ore into metallic iron without transitioning to the liquid phase. Through thermodynamic calculations conducted using Aspen, ensuring precise process modelling and efficiency evaluation, this study examines the technical feasibility and preliminary design of an energy storage system that employs iron as a metallic energy carrier. Iron undergoes oxidation and serves as a fuel in high-temperature reactors operating above 1200 degrees C, thereby releasing its stored energy and forming iron oxide. When hydrogen is available, the iron oxide can be reduced back to metallic iron through the well-established Direct Reduced Iron (DRI) process or a comparable method at approximately 750 degrees C. A round-trip thermal efficiency of 77.9 % has been calculated for the overall energy storage and utilization process. To further enhance global efficiency, key recommendations include hydrogen recirculation during the reduction process to ensure complete conversion and mitigating the impact of excess air in the oxidation stage.

Concentrating solar power (CSP) technology with thermal energy storage (TES) could contribute to achieving a net zero emissions scenario by 2050. Calcium looping (CaL) is one of the potential TES processes for the future generation of CSP plants coupled with highly efficient power cycles. Research on CaL as a system for thermochemical energy storage (TCES) has focused on efficiency enhancement based on hybridization with other renewable technologies. This work proposes a novel solid management system to improve the efficiency of a CaL TCES system. The inclusion of a solid–solid separation unit after the carbonation step could lead to energy and size savings. The role of segregation between carbonated and calcined material on plant requirements is assessed, given the experimental evidence on the potential classification between more and less carbonated particles. The results show lower energy (up to 12%) and size (up to 76%) demands when the circulation of less carbonated material through the CaL TCES system diminishes. Moreover, under a classification effectiveness of 100%, the retrieval energy could increase by 32%, and the stored energy is enhanced by five times. The present work can be a proper tool to set the design and size of a CaL TCES system with a partial separation of the carbonated material.

Purpose Aluminium industry emits around 1–2% of the world’s total greenhouse gas emissions. Up to one-third of those are linked to the thermal energy consumed during its initial process: the alumina refining (Bayer process). Previous studies consider the Bayer process a single stage despite its being made of several reaction stages. This work presents a disaggregated energy analysis of the Bayer process that facilitates to find relationships between the main variables in regular alumina production and the environmental impacts. Methods Two different thermodynamic simulations of the Bayer process were carried out using Aspen V11 software. The results of these simulations were validated with referenced data, and afterwards, they were used to perform a life cycle assessment. ISO 14040 and 14,044 standards were followed during the analysis. LCA was implemented on SimaPro 9.0, and ReCiPe 2016 Midpoint (H) method was used to calculate environmental impacts. The influence of bauxite mineral form, type of fuel (energy input), and the distance from the mine to the plant was analysed throughout the study. Results and discussion As expected, the type of fuel was revealed as the most crucial factor in the environmental impact of alumina production, with potential savings of up to 75.5% of CO 2 -equivalent emissions. Nonetheless, the tendency is diverse for other indicators, such as marine eutrophication or terrestrial acidification. On the other hand, while bauxite transportation always has the same impact on the different environmental indicators, bauxite mineral form affects differently depending on the fuel, causing variations in the CO 2-eq emissions from 7.7 to 51.3%. Conclusions Results indicated that the electrification of heat-demanding processes and the use of renewable power is the most effective approach for reducing environmental impacts. This strategy, however, must be considered in combination with others, as interdependent effects exist on the type of mineral used. These results provide strong evidence of the potential for environmentally friendly strategies in the metal industry, including new processes, alternative fuels, or mineral switching to promote more sustainable aluminium production.

Studies seeking to thoroughly couple the environmental and economic performances of a process or product are becoming more prominent as the needs for decarbonisation grow. This study explores the use of Life Cycle Assessment (LCA) and Life Cycle Costing (LCC) in the alumina extraction industry. Models for various thermal energy supply methods and CO2 mitigation strategies were developed to obtain an inventory for analysis and the environmental impacts and life-cycle costs of the supply chain were evaluated. Finally, economic and ecological results were integrated using eco-efficiency indices and a sensitivity analysis of the most significant variables detected was conducted. The research indicated that the integration of a calcium-looping plant to capture post- combusted CO2 could reduce 55.5% of the CO2 equivalent emissions, while also obtaining a better economic performance due to the CO2 avoided taxes. However, other environmental indicators had slightly more significant impacts because of the additional use of natural gas. The potential use of green hydrogen instead of natural gas could enable a 70.0% reduction in CO2 equivalent emissions, as well as a reduction in all other environmental indicators studied, except for water consumption. However, transitioning to green hydrogen production could incur higher costs. This study introduced an eco-efficiency ratio index, indicating that CO2 capture and storage proved to be the most eco-efficient scenario, regardless of economic fluctuations in CO2 emission taxes. The substitution of natural gas with green hydrogen also emerged as a viable eco-efficient solution, provided electricity prices remain below 0.045/kWh.

Hydrogen (H2)-based steel making is expected to become a major driver of intercontinental low-carbon H2 imports. Eight H2 supply scenarios based on either local H2 production at major steel producing locations (Germany/Japan), or liquid H2 carrier (dibenzyltoluene/perhydrodibenzyltiluene, DBT/PDBT) import from the United Arab Emirates, and their integration with H2 direct reduced iron (H-DRI) and electric arc furnace (EAF) processes, are investigated using process modeling. Solar energy-based PDBT import using surplus heat for dehydrogenation is the most cost-competitive H2 import scenario in Germany's case (levelized steel production cost, 685 $/tLS, with carbon emissions, 237 kgCO2/tLS). In Japan's case this scenario is the most economically favorable of all scenarios ( 736 $/tLS), with emissions ( 350 kgCO2/tLS) comparable to natural gas-DRIEAF with 50% carbon capture. Steam methane reforming with carbon capture-based PDBT import is neither environmentally nor economically viable. PDBT-based H-DRI-EAF production cost is sensitive to electricity, H2 production, dehydrogenation energy, and carbon costs.

Aluminium industry stands out as a significant source of CO2 emissions, due partially to the high energy demand of the alumina extraction stage. Accordingly, this study explores the implementation of direct resistive heating of mid-temperature processes in alumina production as an alternative to decrease CO2 emissions. Additionally, two different strategies are evaluated to decarbonize alumina industry: the generation of renewable electricity through solar photovoltaic panels and the integration of a CO2 capture plant based on calcium looping technology. This work comprehends the modelling and sizing of these plants and the assessment of their economic performance through the calculation of their Net Present Value and their respective payback periods. The integration of both strategies into an alumina refinery model reveals that electrification of low and mid-temperature processes yields a 15 % reduction in CO2 direct emissions, whereas calcium looping demonstrates the potential to capture 97 % of emissions with a 7 % energy penalty. Also, economic assessments indicate substantial potential for improvement through in-site electricity generation via solar photovoltaic panels, exhibiting a payback time of 4.5 years. Conversely, the feasibility of a calcium-looping plant is hindered by high capital expenses, necessitating a longer payback period of 19–24 years. Sensitivity analyses underscore the suitability of in-site renewable electricity generation, whereas carbon emission taxes emerge as crucial in incentivizing carbon-neutral processes, with thresholds around 95–125 €/tonne of CO2. Despite potential deviations from real industrial settings, this study provides evidence for environmentally friendly strategies in alumina production that demonstrate limited adverse effects on economic performance.

The iron and steel industry is one of the most energy-intensive industries, emitting 5% of the total anthropogenic carbon dioxide (CO2). The control of CO2 emissions has become increasingly stringent in the European Union (EU), resulting in EU allowance above 90 €/tCO2. Carbon capture will be required to achieve CO2 emissions control, and carbon utilization via power-to-gas could significantly increase interest in carbon capture in the iron and steel sector. This paper presents a new concept that combines amine scrubbing with power-to-gas to reduce emissions in blast furnace-basic oxygen furnace steelmaking plants. Synthetic natural gas (SNG) is produced using green hydrogen from water electrolysis and CO2 from steelmaking. The synthetic natural gas is later used as a reducing agent in the blast furnace, constantly recycling carbon in a closed loop and avoiding geological storage. The oxygen by-produced via electrolysis eliminates the necessity of an air separation unit. By applying these innovations to steelmaking, a reduction in CO2 emissions of 9.4% is obtained with an energy penalty of 16.2 MJ/kgCO2, and economic costs of 52 €/tHM or 283 €/tCO2. A sensitivity analysis with respect to electricity and the CO2 allowances prices is also performed.

This study assesses the environmental performance of an existing petrochemical plant that produces urea fertilizer and liquid ammonia. In urea production facilities, ammonia is always in excess. This excess can be converted back to urea if reacted with CO2 in an ammonia reformer. Such a process can boost the production capacity of the plant without the need for further investment in major equipment, like reformers and reactors. In the plant studied here, a CO2 capture and utilization unit (CCU) is used to capture CO2 from the stack of the ammonia plant to further enhance urea production. The unit recovers about 5500 kg of CO2 per hour. The environmental performance of the petrochemical plant is evaluated with and without CO2 capture and under solar-assisted operation. Although the solar-assisted operation performs better than the plant with CCU in many environmental parameters, the differences between the two cases are relatively small. The outcomes of the life cycle assessment show that the carbon footprint of the solar-assisted operation with CCU is about 10% lower than that of the plant without CCU. In addition to some environmental benefits of the CCU plant, the plant with carbon capture increases the urea production by about 8%.

Integration between Concentrated Solar Power (CSP) and Calcium Looping (CaL) is gaining consideration in the perspective of large shares of renewable energy sources, to smooth the variability of non-dispatchable energy input. The scope of this study is to investigate the CaL process for ThermoChemical Energy Storage (TCES), by performing a dedicated experimental campaign in fluidized bed under realistic process conditions suitable for CaL-CSP integration. Chemical deactivation of the limestone-based sorbent has been assessed by measuring the extent of Ca carbonation along iterated calcination/carbonation cycles, correlated with physico-chemical characterization of the sorbent at selected stages of the conversion. Properties that have been scrutinized were particle size distribution, bulk density, and particle size, density, and porosity of bed solids. The attainable values of energy storage density were evaluated as well. A remarkable finding of the experimental campaign is the pronounced synergistic deactivation of limestone when it is co-processed with silica sand. Chemical interaction of CaO with the silica sand constituents at the process temperatures has been scrutinized as possible responsible for the loss of reactive CaO toward CO2 uptake. Post-process of particle density data, together with N2-intrusion porosimetric analysis, and quantitative and qualitative XRD analyses, suggests that the sand/lime interaction induces a strong reduction of the total and reactive sorbent porosity and, in turn, of reactivity. Density-based classification to separate converted and unconverted limestone particles after the carbonation step has been evaluated with the goal of increasing process efficiency, by avoiding the circulation of streams with unreacted particles through the plant. For this purpose, the minimum fluidization velocity of calcined and carbonated particles has been measured after each reaction step at the relevant process temperature.

A new process concept integrating power to methane with top gas recycling in an oxygen blast furnace (BF) is investigated to reduce the emission intensity of steelmaking. Power to gas produces synthetic methane using hydrogen (H2) generated by an electrolyser operated with renewable electricity, and CO2 captured from the BF gas by amine scrubbing supplied with heat from the methanation process. The clean gas from the amine scrubbing is recycled and injected in the BF (via top gas recycling), together with synthetic methane. A parametric analysis is performed to vary the amount of top gas recycled (from 0 kg/tHM to 270 kg/tHM). Based on the results, CO2 equivalent emissions can decrease by 34% using power to gas technology, and by 30% with power to gas and top gas recycling (compared to conventional BFs). Nevertheless, if both integrations are present, additional benefits on the specific energy consumption (12.0 MJ/tHM), and specific cost (130 €/tHM) are achieved, compared to only applying power to gas (17.5 MJ/tHM and 233 €/tHM). In all cases, the downstream thermal energy needs of the steel plant are fulfilled, contrarily to conventional top gas recycling concepts. The main conclusion is that top gas recycling should be considered together with PtG technology, and vice versa, when integrated in blast furnace ironmaking, in order to both abate emissions while supplying downstream energy needs.

The massive deployment of renewable energy sources and carbon capture technologies are required to achieve net zero emissions target by 2050. Calcium Looping (CaL) is a promising Thermochemical Energy Storage (TCES) system which improves the dispatchability of Concentrating Solar Power (CSP) plants. CaL TCES configurations found in literature focus on a steady-state analysis of thermal-to-electric efficiency of the CSP plants. In this work, the operation of the CaL TCES system for a CSP plant is economically optimized taking into account the seasonal and daily variations of solar resource and electricity prices. The defined methodology determines the operating performance of the CaL TCES which maximize the economic incomes of the CSP and the daily profiles of energy production and storage for representative days of the different seasons/periods of the year. Results show that it is possible to obtain good economic results and operate the CSP + storage for a daily maximization of incomes. Obtained results are also useful for the final design of the system and for the definition of the size required for the storage equipment.

Decarbonization of the iron and steel industry, which accounts for 7-9% of global annual emissions, is a strategic objective to achieve carbon emissions reduction targets in line with climate change policies, while maintaining economic competitiveness. Carbon capture (CC) technologies are of critical importance to achieve these goals. This work presents the first systematic review of the integration of CC technologies in the blast furnace-basic oxygen furnace (BF-BOF) steelmaking route, which is expected to maintain a dominant market share over the coming decades. Integration options for post-combustion, looping cycles, oxy-combustion and pre-combustion are described and compared in terms of energy penalty, carbon emissions abatement potential, cost, technol-ogy readiness level, and practical deployment considerations. The review yielded 188 studies from peer-reviewed articles and technical papers. Research is mainly focused on chemical absorption, physical adsorption, and oxy-blast furnace technologies, but other carbon capture methods including calcium looping, Sorption Enhanced Water Gas Shift, and membranes appear promising in terms of cost and carbon emission reduction. This article provides an in-depth analysis of the current state of the art and crucial considerations for future decision making in the techno-economic selection and integration of CC technologies. Barriers to overcome for practical imple-mentation are also identified and discussed in this article.

In the last years, reduction of CO2 emissions from the steel industry has been of great importance. Carbon capture, oxygen blast furnaces and top gas recycling technologies, among others, have been deeply studied as low carbon solutions. In this paper, a novel integration of carbon capture and power to gas technologies in the steelmaking industry is presented. Green hydrogen via proton exchange membrane (PEM) electrolysis and CO2 via methyldiethanolamine (MDEA) scrubbing from the blast furnace gas (BFG) are used to produce synthetic natural gas in an isothermal fixed bed methanation plant. The latter gas is injected into the blast furnace, closing a carbon loop and reducing coal consumption. The oxygen by-produced in the electrolyser covers the entire oxygen demand of the steelmaking plant and avoids the need for an air separation unit (ASU). The novelty of this work relies on the variation of the oxygen enrichment and its temperature in the hot blast, and how it influences the power to gas integration concept. This power to gas integration is compared with a conventional BF-BOF plant from a technical, economic, energy and environmental point of view. Both plant process configurations were implemented in Aspen Plus simulations, assessing the fossil fuel demand, energy penalty, cost and CO2 emissions. Emission reduction up to 34% can be achieved with power to gas integration, with an energy penalty of 17 MJ/tHM and a cost of 352 €/tCO2.

Emitting up to a 5% of all anthropogenic CO2, the iron and steel industry is one of the most energy-intensive industry. The control of CO2 emissions is becoming crucial in many countries and in order to fight against global warming, carbon capture will be mandatory in coming years. If carbon capture is integrated with power-to-gas, the iron and steel industry could benefit. This paper introduces a new concept proposal that integrates carbon capture using MDEA with a PEM electrolyser and a methanation plant (power-to-gas technology, producing synthetic natural gas). The CO2 is captured from the blast furnace gas, and the SNG is continuously injected into the BF as a reducing agent, recycling the CO2and closing a carbon loop, avoiding geological storage. The oxygen by-produced in the electrolyser allows to eliminate the air separation unit (ASU). By integrating this novel concept, a 9.4% CO2 emission reduction can be achieved, with an energy penalty of 16.2 MJ/kgCO2. Additionally, an economic study has been carried out, varying the electricity price and the CO2 allowances price through a sensitivity analysis.

Power to Methane (PtM) is one of the alternatives explored for chemical storage of electricity. PtM converts surplus renewable electricity into synthetic methane by combining green H2 from water electrolysis with captured CO2 through methanation reaction. It allows the storage of renewable energy and the interconnection between the electric network, gas grid and industrial users. This connection will facilitate the flexibility of the global energy supply and, under specific conditions, the carbon utilization of captured CO2 to produce a ‘CO2 neutral’ natural gas.This work presents the design, start up and operation of a 1 kWH2 experimental facility for the gas phase methanation of CO2 to CH4. The reactor is a single-stage, tubular fixed-bed reactor filled with quartz wool and alumina pellets together with a commercial catalyst (0.5% wt Ru on an alumina support). The set point of the reactor temperature was varied from 250 °C to 450 °C, the gas hourly space velocity (GHSV) ranged from 4.33 to 12.74 (lSPT/(gcath)) and the pressure was set to 1.2 bar. A maximum CO2 conversion of 85.3% was achieved for 100 g of Ruthenium catalyst in a bed of Quartz wool at a temperature of 300 °C and H2/CO2 ratio 4.2. Such conversion can be improved through a suitable temperature control to avoid inhomogeneous temperature distribution within the catalyst bed. The smoother distribution of the catalyst throughout the reactor and an improved heat transfer within the fixed bed results in a better control of temperature.