Papers by Keyword: Carbon Dioxide CO₂

Abstract: The mass transfer coefficients at different axial positions in a bubble column have been measured using a conductivity method. Measurements of CO2 absorption in methyldiethanolamine solutions were carried out in a prismatic column 0.06 m side and 1.03 m height. Five electrode pairs were placed at various axial positions in the column. Measurements were conducted at different gas flow rates and amine concentration. It was found that the local mass transfer varied in the axial direction. An experimental model was developed to obtain the absorption rate values using the electrochemical method data. The model agrees quite well with the experimental obtained data.

Abstract: In order to decrease the heat rejection pressure of pure CO₂ refrigerating system and meanwhile have sustainable environmentally benefits for working fluild, several natural zeotropic CO₂/Propane mixtures are applied to heat pump system to investigate the heating performance. The heat rejection pressure of CO₂/Propane mixtures is reduced when the mass fraction of carbon dioxide is decreased. Under the given conditions, there is an optimum range of mass fraction of CO₂/Propane of which the mixtures have superior heating coefficient of performance. The temperature glide characteristics of CO₂/Propane mixtures at heating mode was also researched to analyze the heat transfer efficiency. Both a sufficient heat exchange area and a good working fluid’s temperature gradient matching with that of the secondary heat transfer fluid contribute to a higher heat transfer efficiency of heat exchanger.

Abstract: There are many attractive features for using CO2 foam injection in Enhanced Oil Recovery (EOR) processes. For understanding CO2 foam rheology in porous media, an experimental study is reported in this paper concerning CO2 film foam flow characteristics in a vertical straight tube. Foam is treated as non-Newtonian fluid and its pseudo-plastic behavior is investigated based on power law constitutive model. It is observed the CO2 film foam flow shows clear shear-thinning behavior, with flow consistency coefficient of K=0.15 and flow behavior index of n=0.48. The apparent viscosity of flowing CO2 film foam is under the shear rate of 50s-1 and under the shear rate of 1000s-1, which are 19 and 3 times higher than the single phase water. It is also found CO2 foam has lower apparent viscosity than the foam with air as the internal gas phase, which is in consistence with experimental observations for lower CO2 foam flow resistance in porous media.

Abstract: In this work, the electrochemical transient behaviors of tubular steel API-P110 in buffered acidic NaCl solutions saturated with 50% H₂S and different content of CO₂ mixture gases, were investigated by single potential step chronoamperometry. Analysis of the results shows that fewer reactants take part in the reduction reaction when adding CO₂ content from 17% to 50% in 50% H₂S containing solution. Anions desorption process controls the reactant transferring process in metal-solution interface in the solution containing H₂S and CO₂. When at higher overpotential, anions desorption enhances and hydrogen absorption depresses with the increasing CO₂ content in H₂S/CO₂.

Abstract: Using cheap and porous diatomite or zeolite as silicon sources, we prepared firstly Li4SiO4 matetials for high temperature CO2 capture through solid-state method, and mainly investigated effects of silicon sources on the CO2 absorption properties of Li4SiO4 materials. Phase composition was analyzed by X-ray diffraction, and the CO2 absorption properties were studied by the simultaneous thermal thermogravimetric analyzer (TG-DSC). The results showed that Li4SiO4 materials using zeolite as silicon source showed little CO2 absorption properties, while Li4SiO4 materials using diatomite as silicon source showed excellent CO2 absorption properties. Compared with the existing literatures, the preparation cost of Li4SiO4 materials was lowered

Abstract: A promising adsorbent for CO₂ removal was prepared by introducing methyl-diethyl-amine (MDEA) into mesoporous silica SBA-15 using impregnation method. The MDEA modified adsorbents were characterized by X-ray powder diffraction (XRD) and nitrogen adsorption/desorption. Surface area, pore size and pore volume of MDEA-modified SBA-15 adsorbent decreased with the increasing of MDEA loading, while the loaded MDEA could not change the structure of the adsorbents. The adsorption performance of CO₂ on the adsorbents was conducted in a dynamic setup. Dynamic adsorption performance changed with change of the amount of loaded MDEA. In addition, not only the adsorbent was regenerable by purging with the purified gas, but also the adsorption performance is stable in adsorption cycles. The results indicated that the MDEA modified adsorbents were novel for removing CO₂ for biogas upgrading.

Abstract: The argon and carbon dioxide co-injection tests were carried out with low carbon steel melts of 100 kg in a multi-function direct current ladle furnace (DC-LF) equipped with a hollow graphite electrode. It is shown that, the heating rates of the heats with argon or Ar-CO2 injection are higher than that of the normal solid graphite electrode heat. The average heating rate of the heat with argon injection is 1.59 times than that of the normal solid graphite electrode heat. The minimal average heating rate of the heat with Ar-CO2 co-injection is 3 times than that of the latter, and the maximum is 5.51 times. When argon or Ar-CO2 is injected into LF, the electric current isn’t change, but the voltage is lower.

Abstract: TiO₂ doped with C was obtained by way of immersion and calcinations method by using citric acid (CA) as dopant material.，and characterized by using XPS、XRD, UV-Vis, FT-IR and SPS. The results of analysis and characterization showed that C substituted partial Ti atoms in the lattice of TiO₂ and formed Ti-O-C structure. The photocatalytic properties of C-TiO₂ photocatalysts had been evidently improved as a result of a noticeable shift to visible region and the enhancement of the charge separation efficiency. The doped carbon lowers the band gap and expends the absorption of visible light region. CO₂ was photocatalytically reduced to form HCOOH by the best C-TiO₂-3/1-600 nanoparticles under the irradiation of the simulated daylight lamp. Methanoic acid yield may achieve 2633.98μmol/g-Cat when irradiation time is six hours.

Abstract: In this paper a gas cooler for trans-critical carbon dioxide water heater was designed and calculated according to the theory basis for the optimal design. The characteristic parameters of gas cooler in heat pump hot water system were compared and analyzed, applying the data from trans-critical carbon dioxide water heater test bed, under one-time heating condition, by different flow of chilled water and hot water, different inlet temperatures of chilled water and hot water. To sum up, coefficient of performance can be increased by increasing the chilled water inlet temperature or hot water circulating flow, while it can be decreased by increasing the inlet temperature of hot water circulating system，the parameters (flow of water, inlet temperature, the refrigerant mass flow, gas cooler pressure and inlet temperature of refrigerant) need to be adjusted to different requirements, for ensuring the high efficiency of system.

Abstract: A fundamental study on the reaction between CO2 and mechanically activated metal powders has been conducted. In this research, the behavior and mechanism of CO2 reaction under various grinding conditions were investigated to fix and reduce CO2. The powder used was placed inside a grinding vessel, and was ground together with the SUJ2 balls in CO2 atmosphere. It was found that only the adsorption of CO2 gas on the ground samples was observed, whereas the decomposition of CO2 was not occurred. The CO2 adsorption increased proportionally with the increase in the grinding speed, weight of sample and number of SUJ2 balls. Furthermore, the CO2 adsorption increased with the decrease in the standard free energy of formation of each metal oxide. The morphology of the sample observed by SEM showed that the samples were not crushed into finer particles, but were only grazed on the sample’s surface. Therefore, it can be said that the CO2 can be adsorbed on the mechanically activated samples by using the centrifugal type ball mill, but in order to enhance the amount of CO2 adsorption, another type of machine with higher grinding intensity should be considered.