Amélioration de l'efficacité de turbines à gaz dans l'industrie gazière en utilisant des réfrigérateurs à absorption actionnés par de la chaleur résiduelle

Les climats chauds, accentués par le réchauffement climatique, réduisent l'efficacité énergétique des installations industrielles qui utilisent des turbines à gaz pour la production d'électricité, telles que les usines de transformation du gaz naturel (UTGNs). Un dispositif de récupération de la chaleur des gaz d'échappement de turbines par des réfrigérateurs d'absorption de bromure de lithium (H2O-LiBr) de simple effet, est thermo-économiquement évalué pour le refroidissement de l'air d'admission de turbines à gaz. La performance du système proposé, intégré dans une UTGN au Moyen-Orient, est comparée à celle des refroidisseurs évaporatifs conventionnels et des réfrigérateurs à compression de vapeur. Dans des conditions climatiques extrêmes représentant l'été dans le golfe Persique, trois réfrigérateurs d'absorption activés par la vapeur produite en récupérant 17 MW de chaleur d'échappement de turbines à gaz, pourraient fournir 12,3 MW de refroidissement et réduire la température d'admission de l'air à 10°C. Dans les mêmes conditions ambiantes, des refroidisseurs évaporatifs fourniraient une capacité de refroidissement de seulement 2,3 MW, et consommeraient 0,8 kg/s d'eau déminéralisée. Des réfrigérateurs à compression de vapeur exigeraient 2,7 MW d'énergie électrique supplémentaire pour fournir la même quantité de refroidissement que les réfrigérateurs d'absorption. L'électricité supplémentaire produite due au refroidissement d'air d'admission par réfrigération d'absorption est de 5264 MWh par an, comparé à 1774 MWh pour le refroidissement par évaporation. Le dispositif proposé permettrait non seulement de remplir les charges de refroidissement de l'air d'admission de turbine à gaz tout au long de l'année, mais fournirait également du refroidissement pour d'autre procédés de traitement du gaz naturel durant les périodes de charge hors pointe. La période d’amortissement économique du dispositif proposé varie de 1,3 à 3,4 ans sur la base des prix locaux actuels et futurs de l’eau et de l’électricité. La stratégie proposée réduirait la consommation de gaz naturel pour la production d'électricité dans les UTGNs au Moyen-Orient, permettant de réserver la production de gaz pour l’exportation, tout en réduisant les coûts de production et les émissions associées

High oxygen and SNG injection in blast furnace ironmaking with Power to Gas integration and CO2 recycling

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

CO2 recycling in the iron and steel industry via power-to-gas and oxy-fuel combustion

The iron and steel industry is the largest energy-consuming sector in the world. It is responsible for emitting 4-5% of the total anthropogenic CO2. As an energy-intensive industry, it is essential that the iron and steel sector accomplishes important carbon emission reduction. Carbon capture is one of the most promising alternatives to achieve this aim. Moreover, if carbon utilization via power-to-gas is integrated with carbon capture, there could be a significant increase in the interest of this alternative in the iron and steel sector. This paper presents several simulations to integrate oxy-fuel processes and power-to-gas in a steel plant, and compares gas productions (coke oven gas, blast furnace gas, and blast oxygen furnace gas), energy requirements, and carbon reduction with a base case in order to obtain the technical feasibility of the proposals. Two different power-to-gas technology implementations were selected, together with the oxy blast furnace and the top gas recycling technologies. These integrations are based on three strategies: (i) converting the blast furnace (BF) process into an oxy-fuel process, (ii) recirculating blast furnace gas (BFG) back to the BF itself, and (iii) using a methanation process to generate CH4 and also introduce it to the BF. Applying these improvements to the steel industry, we achieved reductions in CO2 emissions of up to 8%, and reductions in coal fuel consumption of 12.8%. On the basis of the results, we are able to conclude that the energy required to achieve the above emission savings could be as low as 4.9 MJ/kg CO2 for the second implementation. These values highlight the importance of carrying out future research in the implementation of carbon capture and power-to-gas in the industrial sector. © 2021 by the authors

Technical and economic assessment of iron and steelmaking decarbonization via power to gas and amine scrubbing

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

A Review of Projected Power-to-Gas Deployment Scenarios

Technical, economic and environmental assessments of projected power-to-gas (PtG) deployment scenarios at distributed- to national-scale are reviewed, as well as their extensions to nuclear-assisted renewable hydrogen. Their collective research trends, outcomes, challenges and limitations are highlighted, leading to suggested future work areas. These studies have focused on the conversion of excess wind and solar photovoltaic electricity in European-based energy systems using low-temperature electrolysis technologies. Synthetic natural gas, either solely or with hydrogen, has been the most frequent PtG product. However, the spectrum of possible deployment scenarios has been incompletely explored to date, in terms of geographical/sectorial application environment, electricity generation technology, and PtG processes, products and their end-uses to meet a given energy system demand portfolio. Suggested areas of focus include PtG deployment scenarios: (i) incorporating concentrated solar- and/or hybrid renewable generation technologies; (ii) for energy systems facing high cooling and/or water desalination/treatment demands; (iii) employing high-temperature and/or hybrid hydrogen production processes; and (iv) involving PtG material/energy integrations with other installations/sectors. In terms of PtG deployment simulation, suggested areas include the use of dynamic and load/utilization factor-dependent performance characteristics, dynamic commodity prices, more systematic comparisons between power-to-what potential deployment options and between product end-uses, more holistic performance criteria, and formal optimizations

Thermodynamic Performance Investigation of a Small-Scale Solar Compression-Assisted Multi-Ejector Indoor Air Conditioning System for Hot Climate Conditions

In year-round hot climatic conditions, conventional air conditioning systems consume significant amounts of electricity primarily generated by conventional power plants. A compression-assisted, multi-ejector space cooling system driven by low-grade solar thermal energy is investigated in terms of energy and exergy performance, using a real gas property-based ejector model for a 36 kW-scale air conditioning application, exposed to annually high outdoor temperatures (i.e., up to 42 °C), for four working fluids (R11, R141b, R245fa, R600a). Using R245fa, the multi-ejector system effectively triples the operating condenser temperature range of a single ejector system to cover the range of annual outdoor conditions, while compression boosting reduces the generator heat input requirement and improves the overall refrigeration coefficient of performance (COP) by factors of ~3–8 at medium- to high-bound condenser temperatures, relative to simple ejector cycles. The system solar fraction varies from ~0.2 to 0.9 in summer and winter, respectively, with annual average mechanical and overall COPs of 24.5 and 0.21, respectively. Exergy destruction primarily takes place in the ejector assembly, but ejector exergy efficiency improves with compression boosting. The system could reduce annual electric cooling loads by over 40% compared with a conventional local split air conditioner, with corresponding savings in electricity expenditure and GHG emissions

Integration of Municipal Air-Conditioning, Power, and Gas Supplies Using an LNG Cold Exergy-Assisted Kalina Cycle System

A Kalina cycle-based integration concept of municipal air-conditioning, electricity and gas is investigated thermodynamically, economically, and environmentally to reduce the carbon intensity of these supplies, with attention to hot climatic conditions. The proposed poly-generation system is driven by low-grade renewable or surplus heat, and utilizes waste exergy from liquefied natural gas vaporization for refrigeration and power augmentation. At nominal conditions (130 °C driving heat), approximately 561 and 151 kJ of refrigeration and useful power per kg of liquefied natural gas regasified are generated by the proposed system, respectively, at effective first-law and exergetic efficiencies of 33% and 35%, respectively. The Kalina sub-system condenser cryogenic heat rejection condition is found to triple the system useful electrical output compared with high ambient temperature condenser heat sinking conditions. Per million ton per annum of liquefied natural gas vaporization capacity, yearly net power savings of approximately 74 GWhe could be achieved compared to standard air-conditioning, electricity, and gas supply systems, resulting in 11.1 kton of natural gas saved and 30.4 kton of carbon dioxide-equivalent emissions avoided annually. The yearly net monetary savings would range from 0.9 to 4.7 million USD per million ton per annum of liquefied natural gas regasified at local subsidized and international electricity market prices, respectively, with corresponding payback periods of 1.7 and 2.5 years, respectively

Sustainable District Cooling Systems: Status, Challenges, and Future Opportunities, with Emphasis on Cooling-Dominated Regions

A review of current and future district cooling (DC) technologies, operational, economic, and environmental aspects, and analysis and optimization methodologies is presented, focusing on the demands of cooling-dominated regions. Sustainable energy sources (i.e., renewable, waste/excess electricity and heat, natural/artificial cold) and cooling/storage technology options with emphasis on heat-driven refrigeration, and their integrations in published DC design and analysis studies are reviewed. Published DC system analysis, modeling, and optimization methodologies are analyzed in terms of their objectives, scope, sustainability-related criteria, and key findings. The current and future development of DC in the Gulf Cooperation Council (GCC) region, a major developing cooling-dominated market, is examined more specifically in terms of current and future energy sources and their use, and economic, environmental, and regulatory aspects, with potential technical and non-technical solutions identified to address regional DC sustainability challenges. From the review of published DC design and analysis studies presented, collective research trends in key thematic areas are analyzed, with suggested future research themes proposed towards the sustainability enhancement of DC systems in predominantly hot climates

Power to gas and top gas recycling integration in an oxygen blast furnace steelmaking industry

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