• Energy Research

Abstract A large amount of low grade heat is wasted at temperatures below 100 °C but its quantity remains mostly unknown. Therefore, the identification and quantitation of low grade heat availability enables further assessments on whether or not the recovery of this fraction of heat is convenient. By considering the countries composing the European Union (EU), this work quantifies the low grade heat from power generation and industrial sectors (mining, minerals, metals, chemicals, pulp and paper, food) with a particular focus on the faction of heat below 100 °C. The analysis shows that, in the year 2018, 8774.4∙106 GJ (2437.3 TWh) of heat was available in the EU below 100 °C, with the power generation sector accounting for 95% of the total low grade heat emitted. In addition, around 96% of the waste heat was in the temperature range from 25 °C to 80 °C, being of ultralow grade. Similar conclusions were obtained in terms of exergy loss, which was essentially from the power generation sector, especially in the range of temperatures between 40 °C and 60 °C. These results suggest that ultralow waste heat is an untapped source of energy which can be conveniently exploited by the same point-source emitters, primarily in the power generation sector or in wider industrial areas where infrastructure is present.

Abstract A large amount of low grade heat is wasted at temperatures below 100 °C but its quantity remains mostly unknown. Therefore, the identification and quantitation of low grade heat availability enables further assessments on whether or not the recovery of this fraction of heat is convenient. By considering the countries composing the European Union (EU), this work quantifies the low grade heat from power generation and industrial sectors (mining, minerals, metals, chemicals, pulp and paper, food) with a particular focus on the faction of heat below 100 °C. The analysis shows that, in the year 2018, 8774.4∙106 GJ (2437.3 TWh) of heat was available in the EU below 100 °C, with the power generation sector accounting for 95% of the total low grade heat emitted. In addition, around 96% of the waste heat was in the temperature range from 25 °C to 80 °C, being of ultralow grade. Similar conclusions were obtained in terms of exergy loss, which was essentially from the power generation sector, especially in the range of temperatures between 40 °C and 60 °C. These results suggest that ultralow waste heat is an untapped source of energy which can be conveniently exploited by the same point-source emitters, primarily in the power generation sector or in wider industrial areas where infrastructure is present.

AbstractAn exemplary 10MWth biomass-fuelled CHP plant equipped with a FICFB (Fast Internally Circulating Fluidised Bed) gasifier and a Jenbacher type 6 gas engine was simulated using Honeywell UniSim R400 to estimate the power and thermal outputs. The biomass gasification CHP plant was integrated with either a pre-combustion adsorptive capture process or a conventional post-combustion amine process to achieve carbon-negative power and heat generation. The practical maximum of carbon capture rate achievable with an adsorptive CO2 capture process applied to a syngas stream was 49% in overall while the amine process could boost the carbon capture rate up to 59%. However, it was found that the two-stage, two-bed PVSA (Pressure Vacuum Swing Adsorption) unit would have a clear advantage over the conventional amine processes in that the CHP plant integrated with the PVSA unit could achieve 1.7% points higher net electrical efficiency and 12.8% points higher net thermal efficiency than the CHP plant integrated with the amine process.

AbstractAn exemplary 10MWth biomass-fuelled CHP plant equipped with a FICFB (Fast Internally Circulating Fluidised Bed) gasifier and a Jenbacher type 6 gas engine was simulated using Honeywell UniSim R400 to estimate the power and thermal outputs. The biomass gasification CHP plant was integrated with either a pre-combustion adsorptive capture process or a conventional post-combustion amine process to achieve carbon-negative power and heat generation. The practical maximum of carbon capture rate achievable with an adsorptive CO2 capture process applied to a syngas stream was 49% in overall while the amine process could boost the carbon capture rate up to 59%. However, it was found that the two-stage, two-bed PVSA (Pressure Vacuum Swing Adsorption) unit would have a clear advantage over the conventional amine processes in that the CHP plant integrated with the PVSA unit could achieve 1.7% points higher net electrical efficiency and 12.8% points higher net thermal efficiency than the CHP plant integrated with the amine process.

Abstract Pressure swing adsorption systems have been devised to concentrate argon from a binary gas mixture of oxygen and argon (O2:Ar = 95:5 mol%) that an industrial oxygen generation vacuum swing adsorption (VSA) unit produces from air. The kinetically-driven adsorption processes investigated in this study contain a self-purging step and up to two double-ended pressure equalization steps. Three adsorption cycle configurations, each of which has one, two and three beds, were simulated. The effects of pressure ranges of the adsorption cycle, either pressure swing adsorption (PSA, 1–3 bar) or vacuum swing adsorption (VSA, 0.1–1 bar), as well as adsorption step time were extensively assessed with respect to the following separation key performance indicators (KPIs): argon purity, argon recovery, bed productivity and specific energy consumption. It turned out that argon purity and recovery could be significantly improved in the VSA cycles at the expense of bed productivity and energy consumption. The single VSA unit could not concentrate argon up to a purity of 98+% which is typically required for certain applications such as steel production and inert gas welding. Thus, a second VSA unit was added to increase further the argon purity and it was found that the integrated two-stage VSA system is capable of achieving the following overall performances: argon purity of 98.1%, argon recovery of 20.3%, bed productivity of 0.011 molAr kgads−1h−1 and specific energy consumption of 53.2 MJ kgAr−1. Considering real efficiencies of turbomachinery the energy consumption of the proposed VSA unit resulted 75% higher than that of a conventional stand-alone cryogenic distillation system designed to achieve the same separation. However, the VSA technology is expected to be a more attractive option than the cryogenic process in terms of CAPEX.

Abstract Pressure swing adsorption systems have been devised to concentrate argon from a binary gas mixture of oxygen and argon (O2:Ar = 95:5 mol%) that an industrial oxygen generation vacuum swing adsorption (VSA) unit produces from air. The kinetically-driven adsorption processes investigated in this study contain a self-purging step and up to two double-ended pressure equalization steps. Three adsorption cycle configurations, each of which has one, two and three beds, were simulated. The effects of pressure ranges of the adsorption cycle, either pressure swing adsorption (PSA, 1–3 bar) or vacuum swing adsorption (VSA, 0.1–1 bar), as well as adsorption step time were extensively assessed with respect to the following separation key performance indicators (KPIs): argon purity, argon recovery, bed productivity and specific energy consumption. It turned out that argon purity and recovery could be significantly improved in the VSA cycles at the expense of bed productivity and energy consumption. The single VSA unit could not concentrate argon up to a purity of 98+% which is typically required for certain applications such as steel production and inert gas welding. Thus, a second VSA unit was added to increase further the argon purity and it was found that the integrated two-stage VSA system is capable of achieving the following overall performances: argon purity of 98.1%, argon recovery of 20.3%, bed productivity of 0.011 molAr kgads−1h−1 and specific energy consumption of 53.2 MJ kgAr−1. Considering real efficiencies of turbomachinery the energy consumption of the proposed VSA unit resulted 75% higher than that of a conventional stand-alone cryogenic distillation system designed to achieve the same separation. However, the VSA technology is expected to be a more attractive option than the cryogenic process in terms of CAPEX.