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1.
This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO2-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON®Professional. A topping sCO2 cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO2 and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO2 cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s.  相似文献   

2.
In the waste heat recovery of the internal combustion engine (ICE), the transcritical CO2 power cycle still faces the high operation pressure and difficulty in condensation. To overcome these challenges, CO2 is mixed with organic fluids to form zeotropic mixtures. Thus, in this work, five organic fluids, namely R290, R600a, R600, R601a, and R601, are mixed with CO2. Mixture performance in the waste heat recovery of ICE is evaluated, based on two transcritical power cycles, namely the recuperative cycle and split cycle. The results show that the split cycle always has better performance than the recuperative cycle. Under design conditions, CO2/R290(0.3/0.7) has the best performance in the split cycle. The corresponding net work and cycle efficiency are respectively 21.05 kW and 20.44%. Furthermore, effects of key parameters such as turbine inlet temperature, turbine inlet pressure, and split ratio on the cycle performance are studied. With the increase of turbine inlet temperature, the net works of the recuperative cycle and split cycle firstly increase and then decrease. There exist peak values of net work in both cycles. Meanwhile, the net work of the split cycle firstly increases and then decreases with the increase of the split ratio. Thereafter, with the target of maximizing net work, these key parameters are optimized at different mass fractions of CO2. The optimization results show that CO2/R600 obtains the highest net work of 27.43 kW at the CO2 mass fraction 0.9 in the split cycle.  相似文献   

3.
We present a nondispersive infrared spectrometer (NDIRS) for the measurement of the 13CO2/12CO2-ratio in breath samples. A commercial NDIR spectrometer for CO2 concentration measurements in industrial process control was modified using two separate optical channels for the 13CO2 and 12CO2 detection. Cross interference due to overlapping absorption lines of both isotopic gases was successfully eliminated. The sensitivity of this device is ± 0.4‰ of the 13CO2/12CO2-ratio in a range of 2.5 to 5% of total CO2. This is sufficient for biomedical applications. Our spectrometer is small in size, cheap and simple to operate and thus a true alternative to isotope ratio mass spectrometers (IRMS). Several biomedical applications with breath samples were demonstrated and were compared in very good agreement with IRMS.  相似文献   

4.
One of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO2 heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO2, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO2. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO2 pressure drop of 2.7 bar.  相似文献   

5.
Abstract

Although sol-gel method is an easy procedure to form a thin film, it's extremely difficult to coat on the surface of small size particles, fibers, and fiber ceramics, because concentration occurs by capillary phenomena and causes peeling or breakage of film.

In order to solve this problem, we use supercritical CO2 rapid expansion from supercritical solution (RESS), nano-sized particles of TiO2 with high intensity can be sprayed out of a nozzle, then collected on the surface of substrates, but can be absorbed into fibers or porous materials, being not interfered by viscosity of a solution.

TiO2 sol made by hydrolysis process is set in a pressure cell and mixed together with super-critical CO2. Controlling the pressure and the temperature, we could obtain TiO2 sol and super critical fluid mixture, and then discharge to the substrate. At this point, Titania sol viscosity is so low that a surface wettability of the substrate becomes negligible.

By the use of the characteristics of the supercritical fluid, without constraint condition of viscosity or capillarity, this sol can penetrate into the interstices of the substance's structure.

Thus, clearing obstruction of capillary phenomena, supercritical fluid coating method shows its capability to penetrate deep into inside of entangled fiber of the three-dimensional structure so as considered to be a heat resistant filter with 95% porosity.  相似文献   

6.
Pulsed laser ablation (PLA) has been widely employed in industrial and biological applications and in other fields. The environmental conditions in which PLA is conducted are important parameters that affect both the solid particle cloud and the deposition produced by the plume. In this work, the generation of nanoparticles (NPs) has been developed by performing PLA of silver (Ag) plates in a supercritical CO2 medium. Ag NPs were successfully generated by allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures and temperatures of CO2 medium. On the basis of the experimental result, both surface of the irradiated Ag plate and structure of Ag NPs were significantly affected by the changes in supercritical CO2 pressure and temperature. With increasing irradiation pressure, plume deposited in the surrounding crater created by the ablation was clearly observed. In Field Emission Scanning Electron Microscopy (FE-SEM) the image of the generated Ag NPs on the silicon wafer and the morphology of Ag particles were basically a sphere-like structure. Ag particles contain NPs with large-varied diameter ranging from 5 nm to 1.2 μm. The bigger Ag NPs melted during the ablation process and then ejected smaller spherical Ag NPs, which formed nanoclusters attached on the molten Ag NPs. The smaller Ag NPs were also formed around the bigger Ag NPs. Based on the results, this new method can also be used to obtain advanced nano-structured materials.  相似文献   

7.
Ignition Delay Time (IDT) plays a significant role in combustion process of advanced power cycles such as direct-fired supercritical carbon dioxide (sCO2) cycle. In this cycle, fuel and oxidizer are heavily diluted with carbon dioxide (CO2) and autoignite at a combustor inlet pressure range of 10–30 MPa and a temperature range of 900–1500 K. A fuel candidate for sCO2 power cycle applications is syngas (H2/CO mixture); however, its ignition properties at these conditions are not studied. Moreover, the existing chemical kinetics models have not been evaluated for H2/CO mixtures applications relevant to elevated pressure conditions and under large dilution levels of CO2. Therefore, two tasks are performed in this study. First, IDTs of a H2/CO=95:5 mixture at stoichiometric and rich (Φ=2) conditions are measured in a high-pressure shock tube under 95.5% CO2 dilution level and at 10 MPa and 20 MPa for a temperature range of 1161–1365 K. For the experimental conditions considered in this work, Aramco 2.0, FFCM-1, HP-Mech and USC Mech II kinetic models are capable of capturing IDT data. Second, similar experiments are conducted by replacing the CO2 dilute gas with Argon (Ar) to understand the chemical effect of CO2 on IDT globally. Sensitivity analysis results reveal that for both diluents, reaction H + O2(+M)=HO2(+M) is the most important reaction in controlling ignition. Further, a rate of production analysis shows that CO2 has a competing effect on OH radical production. On one hand, CO2 accelerates the consumption of H radicals through H + O2+CO2→HO2+CO2 therefore hindering HO2+HOH+OH reaction for OH production. On the other hand, CO2 is shown to enhance OH production through H2O2+M=OH+OH+M. These kinetic effects from CO2 cancel out, therefore CO2 does not significantly alter the IDT globally when compared to the Ar bath case. This is confirmed by both experimental results and simulation.  相似文献   

8.
In this study, the displacement processes were observed as gaseous or supercritical CO2 was injected into n-decane-saturated glass beads packs using a 400-MHz magnetic resonance imaging (MRI) system. Two-dimensional images of oil distribution in the vertical median section were obtained using a spin-echo pulse sequence. Gas channeling and viscous fingering appeared obviously in immiscible gaseous CO2 displacement. A piston-like displacement front was detected in miscible supercritical CO2 displacement that provided high sweep efficiency. MRI images were processed with image intensity analysis methods to obtain the saturation profiles. Final oil residual saturations and displacement coefficients were also estimated using this imaging intensity analysis. It was proved that miscible displacement can enhance the efficiency of CO2 displacement notably. Finally, a special coreflood analysis method was applied to estimate the effects of capillary, viscosity and buoyancy based on the obtained saturation data.  相似文献   

9.
The transition to the use of supercritical carbon dioxide as a working fluid for power generation units will significantly reduce the equipment′s overall dimensions while increasing fuel efficiency and environmental safety. Structural and parametric optimization of S–CO2 nuclear power plants was carried out to ensure the maximum efficiency of electricity production. Based on the results of mathematical modeling, it was found that the transition to a carbon dioxide working fluid for the nuclear power plant with the BREST–OD–300 reactor leads to an increase of efficiency from 39.8 to 43.1%. Nuclear power plant transition from the Rankine water cycle to the carbon dioxide Brayton cycle with recompression is reasonable at a working fluid temperature above 455 °C due to the carbon dioxide cycle′s more effective regeneration system.  相似文献   

10.
A microprocessor-based algorithm was developed to control the power supply to a CO2 laser using an AC-chopper method. This system was connected directly to a CO2 laser tube without the need for a dc-dc converter or the storage capacitance of a multilevel circuit. The typical CO2 laser power supply system had a full-bridge series resonant inverter or voltage multiplier. AC-to-AC converter schemes using zero voltage switching (ZVS) can be used efficiently and economically for low and medium power applications.This paper reports the performance characteristics of a symmetrical AC-chopper technology that can maintain the quality of the ac output of a CO2 laser tube, regardless of the amount of switching loss. The laser was operated to an output power, maximum system efficiency total gas mixture of 37.2 W, 92%, and CO2:N2:He=1:9:15, respectively. The laser system, AC-chopper power supply and its operation were examined.  相似文献   

11.
ABSTRACT

As part of an investigation of carbonate systems under mantle pressures and temperatures, phase relations in the K2CO3–MgCO3 system have been studied at 3?GPa and 800–1300°C. Subsolidus assemblages comprise the stability fields of K2CO3?+?K2Mg(CO3)2 and K2Mg(CO3)2?+?MgCO3 with the transition boundary near 50?mol% K2CO3 in the system. The K2CO3–K2Mg(CO3)2 eutectic is located at 840°C and 52?mol% K2CO3. The K2CO3 content in the melt coexisting with potassium carbonate increases to 85?mol% as temperature increases to 1050°C. K2CO3 remains solid up to 1250 and melts at 1300°C. K2Mg(CO3)2 melts incongruently at 890°C to produce magnesite and a liquid containing 51?mol% K2CO3. As temperature increases to 1300°C, the K2CO3 content in the liquid coexisting with magnesite decreases to 27?mol%.  相似文献   

12.
Structures of several premixed ethylene-oxygen-argon rich flat flames burning at 50 mbar have been established by using molecular beam mass spectrometry in order to investigate the effect of CO2, or NH3, or H2O addition on species concentration profiles. The aim of this study is to examine the eventual changes of profiles of detected hydrocarbon intermediates which could be considered as soot precursors (C2H2, C4H2, C5H4, C5H6, C6H2, C6H4, C6H6, C7H8, C6H6O, C8H6, C8H8, C9H8 and C10H8). The comparative study has been achieved on four flames with an equivalence ratio (f) of 2.50: one without any additive (F2.50), one with 15% of CO2 replacing the same quantity of argon (F2.50C), one with 3.3% of NH3 in partial replacement of argon (F2.50N) and one with 13% of H2O in replacement of the same quantity of argon (F2.50H). The four flat flames have similar final flame temperatures (1800 K).CO2, or NH3, or H2O addition to the fresh gas inlet causes a shift downstream of the flame front and thus flame inhibition. Endothermic processes CO2 + H = CO + OH and H2O + H = H2 + OH are responsible of the reduction of the hydrocarbon intermediates in the CO2 and H2O added flames through the supplementary formation of hydroxyl radicals. It has been demonstrated that such processes begin to play at the end of the flame front and becomes more efficient in the burnt gases region.The replacement of some Ar by NH3 is responsible only for a slight decrease of the maximum mole fraction of C2H2, but NH3 becomes much more efficient for C4H2 and C5 to C10 species. Moreover, the efficiency of NH3 as a reducing agent of C5 to C10 intermediates is larger than that of CO2 and H2O for equal quantities added.  相似文献   

13.
Carbon dioxide is one of the most important trace gases in the terrestrial atmosphere. The spectral data required in remote sensing are the spectral parameter of each absorption line and a line shape model. This paper describes the absorption properties of CO2 near 2400 cm−1; these properties are of interest to those in the atmospheric temperature sounding field. The shape of the far-wing of N2- and O2-broadened CO2 lines was investigated in the 2200-2500 cm−1 spectral region in a temperature range of atmospheric interest (230-318 K). We focused on the higher rotational quantum number of the R-branch in the ν3 band, where the effect of the far-wing is enhanced. The effect of the far-wing has been studied extensively by others, since the CO2ν3 band is known to exhibit sub-Lorentzian behavior. Here, we show the observed spectra along with calculated spectra for five temperatures. We used first-order line-mixing and the χ-factor, which accounts for the effect of the far-wing, to create the calculated spectra. Our results provide new knowledge of quantum interference of the spectral line in the ν3 band of CO2.  相似文献   

14.
The adsorption of CO2 on metal oxides at ambient temperature received less study largely due to the small adsorption amount. However, the adsorption is of interest in refreshing the atmosphere of isolated spaces. It was shown in the present work that PbO was sensitive to low concentration CO2 in the presence of water. An XPS examination indicated that PbO changed to PbCO3 after the adsorption of CO2; therefore, the adsorption is chemical in nature. In order to enlarge the CO2 capacity, PbO was dispersed on the surface of a silica gel with large surface area (710 m2/g). Both CO2 capacity and adsorption rate indicated that the optimal dispersion manner of PbO is the mono-molecular layer surface coverage. Breakthrough experiments showed that the prepared adsorbent could effectively capture low-concentration CO2 at ambient temperature and pressure yielding a CO2 capacity of 59.1 mg g−1. The saturated adsorbent was regenerated on heating at 380 °C and the CO2 capability was recovered.  相似文献   

15.
An experimental study on CH4–CO2–air flames at various pressures is conducted by using both laminar and turbulent Bunsen flame configurations. The aim of this research is to contribute to the characterization of fuel lean methane/carbon dioxide/air premixed laminar and turbulent flames at different pressures, by studying laminar and turbulent flame propagation velocities, the flame surface density and the instantaneous flame front wrinkling parameters. PREMIX computations and experimental results indicate a decrease of the laminar flame propagation velocities with increasing CO2 dilution rate. Instantaneous flame images are obtained by Mie scattering tomography. The image analysis shows that although the height of the turbulent flame increases with the CO2 addition rate, the flame structure is quite similar. This implies that the flame wrinkling parameters and flame surface density are indifferent to the CO2 addition. However, the pressure increase has a drastic effect on both parameters. This is also confirmed by a fractal analysis of instantaneous images. It is also observed that the combustion intensity ST/SL increases both with pressure and the CO2 rate. Finally, the mean fuel consumption rate decreases with the CO2 addition rate but increases with the pressure.  相似文献   

16.
In this article, the construction of P-type germanium (Ge) photon drag detector which is used to characterize the gain and output powers of a 10 W CO2 laser and a CO2 laser amplifier is described. Gain and laser amplifier output power versus laser input power measurements collected at 4.7 mbar and 12.0 mbar amplifier tube pressures are discussed. Moreover, measurements relating the CO2 laser output power to the laser tube discharge current are provided at 6.9 mbar and 7.3 mbar tube pressures.  相似文献   

17.
Both selectivity and capacity of CO2 adsorption were considerably increased when PZ (piperazine) was added in MDEA (methyldiethylamine) that used to modify the surface of silica gels. The adsorbent saturated with CO2 was regenerated at ambient temperature through nitrogen purge. A set of PSA (pressure swing adsorption) operation with 200 cycles was carried out and applicability of the modified adsorbent was thus illustrated. The CO2 content in the column-top stream decreased from 13% to below 0.05% at steady state.  相似文献   

18.
The objective of this study was to understand fluid flow in porous media. Understanding of fluid flow process in porous media is important for the geological storage of CO2. The high-resolution magnetic resonance imaging (MRI) technique was used to measure fluid flow in a porous medium (glass beads BZ-02). First, the permeability was obtained from velocity images. Next, CO2–water immiscible displacement experiments using different flow rates were investigated. Three stages were obtained from the MR intensity plot. With increasing CO2 flow rate, a relatively uniform CO2 distribution and a uniform CO2 front were observed. Subsequently, the final water saturation decreased. Using core analysis methods, the CO2 velocities were obtained during the CO2–water immiscible displacement process, which were applied to evaluate the capillary dispersion rate, viscous dominated fractional flow, and gravity flow function. The capillary dispersion rate dominated the effects of capillary, which was largest at water saturations of 0.5 and 0.6. The viscous-dominant fractional flow function varied with the saturation of water. The gravity fractional flow reached peak values at the saturation of 0.6. The gravity forces played a positive role in the downward displacements because they thus tended to stabilize the displacement process, thereby producing increased breakthrough times and correspondingly high recoveries. Finally, the relative permeability was also reconstructed. The study provides useful data regarding the transport processes in the geological storage of CO2.  相似文献   

19.
Rationality and feasibility of axisymmetric folded-combined cavity CO2 laser which is reported in this paper have been proved by principle experiments. The laser lays a foundation to manufacture higher power CO2 lasers whose output power can easily reach 1 kW. Faculas at different positions in free space and facula of nine beams which pass through the beam focusing optics have been obtained. Analyses of the experimental results are made. These analyses lay a foundation for beam transformation, transmission and shaping.  相似文献   

20.
In this paper we present a new discharge technique to excite slab CO2 lasers. A uniform stable glow discharge has been obtained in a volume of 3 × 30 × 446 mm3. Output power is 10 W, and a gain of 0.26% cm−1 has been obtained.  相似文献   

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