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For global survival, we need to launch a rapid regeneration of the nuclear power industry. The replacement of the present fossil fuel industry requires a doubling time for alternative energy sources of 5–7 years and only nuclear energy has the capability to achieve this. The liquid metal cooled fast breeder reactors (LMFBR) have the best breeding criteria but the doubling time exceeds 20 years. Further, the use of plutonium in these systems has the potential of nuclear proliferation. The Thorium Molten-Salt Nuclear Energy Synergetic System [THORIMS-NES], described here is a symbiotic system, based on the thorium–uranium-233 cycle. The production of trans-uranium elements is essentially absent in Th–U system, which simplifies the issue of nuclear waste management. The use of 233 U contaminated with 232 U as fissile material, instead of plutonium/ 235 U makes this system nuclear proliferation resistant. The energy is produced in molten-salt reactors (FUJI) and fissile 233 U is produced by spallation in Accelerator Molten-Salt Breeders (AMSB). This system uses the multi-functional ‘‘single-phase molten-fluoride” circulation system for all operations. There are no difficulties relating to ‘‘radiation-damage”, ‘‘heat-removal” and ‘‘chemical processing” owing to the simple ‘‘idealistic ionic liquid” character of the fuel. FUJI is size-flexible, and can use all kinds of fissile material achieving a nearly fuel self-sustaining condition without continuous chemical processing of fuel salt and without core-graphite replacement for the life of the reactor. The AMSB is based on a single-fluid molten-salt target/blanket concept. Several AMSBs can be accommodated in regional centers for the production of fissile 233 U, with batch chemical processing including radio-waste management. FUJI reactor and the AMSB can also be used for the transmutation of long-lived radioactive elements in the wastes and has a high potential for producing hydrogen-fuel in molten-salt reactors. The development and launching of THORIMS-NES requires the following three programs during the next three decades:

For global survival, we need to launch a rapid regeneration of the nuclear power industry. The replacement of the present fossil fuel industry requires a doubling time for alternative energy sources of 5–7 years and only nuclear energy has the capability to achieve this. The liquid metal cooled fast breeder reactors (LMFBR) have the best breeding criteria but the doubling time exceeds 20 years. Further, the use of plutonium in these systems has the potential of nuclear proliferation. The Thorium Molten-Salt Nuclear Energy Synergetic System [THORIMS-NES], described here is a symbiotic system, based on the thorium–uranium-233 cycle. The production of trans-uranium elements is essentially absent in Th–U system, which simplifies the issue of nuclear waste management. The use of 233 U contaminated with 232 U as fissile material, instead of plutonium/ 235 U makes this system nuclear proliferation resistant. The energy is produced in molten-salt reactors (FUJI) and fissile 233 U is produced by spallation in Accelerator Molten-Salt Breeders (AMSB). This system uses the multi-functional ‘‘single-phase molten-fluoride” circulation system for all operations. There are no difficulties relating to ‘‘radiation-damage”, ‘‘heat-removal” and ‘‘chemical processing” owing to the simple ‘‘idealistic ionic liquid” character of the fuel. FUJI is size-flexible, and can use all kinds of fissile material achieving a nearly fuel self-sustaining condition without continuous chemical processing of fuel salt and without core-graphite replacement for the life of the reactor. The AMSB is based on a single-fluid molten-salt target/blanket concept. Several AMSBs can be accommodated in regional centers for the production of fissile 233 U, with batch chemical processing including radio-waste management. FUJI reactor and the AMSB can also be used for the transmutation of long-lived radioactive elements in the wastes and has a high potential for producing hydrogen-fuel in molten-salt reactors. The development and launching of THORIMS-NES requires the following three programs during the next three decades:

Abstract A carbon dioxide (CO2) based mixture was investigated as a promising solution to improve system performance and expand the condensation temperature range of a CO2 transcritical Rankine cycle (C-TRC). An experimental study of TRC using CO2/R134a mixtures was performed to recover waste heat of engine coolant and exhaust gas from a heavy-duty diesel engine. The main purpose of this study was to investigate experimentally the effect of the composition ratio of CO2/R134a mixtures on system performance. Four CO2/R134a mixtures with mass composition ratios of 0.85/0.15, 0.7/0.3, 0.6/0.4 and 0.4/0.6 were selected. The high temperature working fluid was expanded through an expansion valve and then no power was produced. Thus, current research focused on the analysis of measured operating parameters and heat exchanger performance. Heat transfer coefficients of various heat exchangers using supercritical CO2/R134a mixtures were provided and discussed. These data may provide useful reference for cycle optimization and heat exchanger design in application of CO2 mixtures. Finally, the potential of power output was estimated numerically. Assuming an expander efficiency of 0.7, the maximum estimations of net power output using CO2/R134a (0.85/0.15), CO2/R134a (0.7/0.3), CO2/R134a (0.6/0.4) and CO2/R134a (0.4/0.6) are 5.07 kW, 5.45 kW, 5.30 kW, and 4.41 kW, respectively. Along with the increase of R134a composition, the estimation of net power output, thermal efficiency and exergy efficiency increased at first and then decreased. CO2/R134a (0.7/0.3) achieved the maximum net power output at a high expansion inlet pressure, while CO2/R134a (0.6/0.4) behaves better at low pressure.

Abstract A carbon dioxide (CO2) based mixture was investigated as a promising solution to improve system performance and expand the condensation temperature range of a CO2 transcritical Rankine cycle (C-TRC). An experimental study of TRC using CO2/R134a mixtures was performed to recover waste heat of engine coolant and exhaust gas from a heavy-duty diesel engine. The main purpose of this study was to investigate experimentally the effect of the composition ratio of CO2/R134a mixtures on system performance. Four CO2/R134a mixtures with mass composition ratios of 0.85/0.15, 0.7/0.3, 0.6/0.4 and 0.4/0.6 were selected. The high temperature working fluid was expanded through an expansion valve and then no power was produced. Thus, current research focused on the analysis of measured operating parameters and heat exchanger performance. Heat transfer coefficients of various heat exchangers using supercritical CO2/R134a mixtures were provided and discussed. These data may provide useful reference for cycle optimization and heat exchanger design in application of CO2 mixtures. Finally, the potential of power output was estimated numerically. Assuming an expander efficiency of 0.7, the maximum estimations of net power output using CO2/R134a (0.85/0.15), CO2/R134a (0.7/0.3), CO2/R134a (0.6/0.4) and CO2/R134a (0.4/0.6) are 5.07 kW, 5.45 kW, 5.30 kW, and 4.41 kW, respectively. Along with the increase of R134a composition, the estimation of net power output, thermal efficiency and exergy efficiency increased at first and then decreased. CO2/R134a (0.7/0.3) achieved the maximum net power output at a high expansion inlet pressure, while CO2/R134a (0.6/0.4) behaves better at low pressure.

Abstract The presented study focuses on a thermodynamic analysis conducted on steam gasification of Portuguese municipal solid wastes (MSW). Current literature addressing this issue is extremely scarce due to the complexity in handling MSW’s heterogeneity. To fill this significant gap, a mathematical model built upon a reliable set of experimental runs from a semi-industrial gasifier was used to evaluate the effects of reactor temperature and steam-to-biomass ratio (SBR) on produced gas and tar content. Results from a previously studied biomass substrate were used as benchmark. Numerical results were validated with both experimental results and existing literature. Increase in gasification temperature led to a clear increase in both exergy values and exergy efficiency. On the other hand, increase in SBR led to a sharp increase in the exergy values when steam was first introduced, leading to relatively constant values when SBR was further increased. Regarding exergy efficiency, SBR led to a clear maximum value, which in the case of forest residues was found at SBR = 1, while for MSW at 1.5. In order to promote a more hydrogen-rich gas, data obtained from the numerical model was used to design an exergy efficiency optimization model based on the response surface method. Maximum hydrogen efficiency was found at 900 °C with a SBR of 1.5 for MSW and 1 for forest residues. Surprisingly, forest residues and MSW presented virtually the same maximum hydrogen efficiency.

Abstract The presented study focuses on a thermodynamic analysis conducted on steam gasification of Portuguese municipal solid wastes (MSW). Current literature addressing this issue is extremely scarce due to the complexity in handling MSW’s heterogeneity. To fill this significant gap, a mathematical model built upon a reliable set of experimental runs from a semi-industrial gasifier was used to evaluate the effects of reactor temperature and steam-to-biomass ratio (SBR) on produced gas and tar content. Results from a previously studied biomass substrate were used as benchmark. Numerical results were validated with both experimental results and existing literature. Increase in gasification temperature led to a clear increase in both exergy values and exergy efficiency. On the other hand, increase in SBR led to a sharp increase in the exergy values when steam was first introduced, leading to relatively constant values when SBR was further increased. Regarding exergy efficiency, SBR led to a clear maximum value, which in the case of forest residues was found at SBR = 1, while for MSW at 1.5. In order to promote a more hydrogen-rich gas, data obtained from the numerical model was used to design an exergy efficiency optimization model based on the response surface method. Maximum hydrogen efficiency was found at 900 °C with a SBR of 1.5 for MSW and 1 for forest residues. Surprisingly, forest residues and MSW presented virtually the same maximum hydrogen efficiency.

Abstract Oil reservoirs are deep underground, with the oil and gas contained in porous rock at high temperatures and pressures. Around 5 – 20%, of the oil can be produced from the field under its own pressure (primary production), but in most fields water is injected to displace the oil. This still leaves at least 50% of the oil behind in the reservoir. Further recovery can be obtained by injecting carbon dioxide that both displaces and dissolves the remaining oil. At least 71 projects worldwide use CO2 flooding and produce a total of over 170 000 barrels of oil a day, worth around $1.3 billion a year. The cost of producing an extra barrel of oil ranges from $5 to $8 and thus is profitable at the present price of nearly $20 a barrel. In the majority of these cases, the carbon dioxide comes from natural underground sources and is piped to the oil field. The potential use of CO2 flooding would be considerably greater, if large quantities of the gas, extracted from power stations, were available at low cost. For every kilogramme of CO2 injected, approximately one to one quarter of a kilogramme of extra oil will be recovered. For most projects about as much carbon dioxide is disposed of in the reservoir as is generated when the oil is burnt. When CO2 is at a sufficiently high pressure to form mixtures with the crude oil that are miscible in laboratory tests, up to 40% of the oil remaining in the field after water flooding can be recovered. Approximately half the water flooded oil fields in the US could be exploited profitably by CO2 injection. Carbon dioxide flooding of the larger North Sea fields is a particularly attractive prospect, because the crude oil is light (composed of low molecular weight hydrocarbons) and the geology of the reservoirs is less heterogeneous than the American fields. A profitable project would be possible if the gas could be provided and piped to the reservoir at a cost of around $3.50 per thousand cubic feet or less.

Abstract Oil reservoirs are deep underground, with the oil and gas contained in porous rock at high temperatures and pressures. Around 5 – 20%, of the oil can be produced from the field under its own pressure (primary production), but in most fields water is injected to displace the oil. This still leaves at least 50% of the oil behind in the reservoir. Further recovery can be obtained by injecting carbon dioxide that both displaces and dissolves the remaining oil. At least 71 projects worldwide use CO2 flooding and produce a total of over 170 000 barrels of oil a day, worth around $1.3 billion a year. The cost of producing an extra barrel of oil ranges from $5 to $8 and thus is profitable at the present price of nearly $20 a barrel. In the majority of these cases, the carbon dioxide comes from natural underground sources and is piped to the oil field. The potential use of CO2 flooding would be considerably greater, if large quantities of the gas, extracted from power stations, were available at low cost. For every kilogramme of CO2 injected, approximately one to one quarter of a kilogramme of extra oil will be recovered. For most projects about as much carbon dioxide is disposed of in the reservoir as is generated when the oil is burnt. When CO2 is at a sufficiently high pressure to form mixtures with the crude oil that are miscible in laboratory tests, up to 40% of the oil remaining in the field after water flooding can be recovered. Approximately half the water flooded oil fields in the US could be exploited profitably by CO2 injection. Carbon dioxide flooding of the larger North Sea fields is a particularly attractive prospect, because the crude oil is light (composed of low molecular weight hydrocarbons) and the geology of the reservoirs is less heterogeneous than the American fields. A profitable project would be possible if the gas could be provided and piped to the reservoir at a cost of around $3.50 per thousand cubic feet or less.