New environmentally attractive separation technology for flue gas mixture

ABSTRACT

Separation of gaseous mixtures produced from any process plant can be a major issue for the industry. In comparison to other separation techniques available, hydrate formation can be an appropriate choice in terms of fuel efficiency and degree of separation. In this work, a three-stage process was designed to capture CO₂ from a hypothetical flue gas mixture (comprising 15?mol% CO_2?+?85?mol% N₂). For the hydrate based CO₂ capture process, a detailed analysis was carried out covering the material and energy balance, energy integration and economic analysis. The results show that, at steady state, 91% of the CO₂ in the flue gas can be recovered, resulting into two streams: Stream-A (94?mol% CO₂?+?6?mol% N₂) and Stream-B (1.5?mol% CO₂?+?98.5?mol% N₂). Per 100?mol of the flue gas feed, 3.9?MW of energy is required to achieve such degree of separation. This amount was reduced to 2.4?MW after energy integration was applied to the process. Overall, the process can help in reducing CO₂ emission via flue gas because of the huge difference in the carbon foot print of its energy requirement (500?g CO₂ per kWh) and the amount of CO₂ captured by the process (2190?g CO₂ per kWh).     

One-step fabricated Fe3O4@C core–shell composites for dye removal: Kinetics,equilibrium and thermodynamics

B-Fe₃O₄@C core–shell composites were synthesized via one-pot hydrothermal carbonization (HTC) process and used as an adsorbent for the removal of methylene blue (MB) from aqueous solution. By using sodium borate as the catalyst, the hydrothermal carbonization process of B-Fe₃O₄@C core–shell composites was optimized and a higher surface area was obtained. The adsorbent was characterized by XRD, Raman spectra, SEM, TEM and N₂ adsorption/desorption isotherms. We studied the dye adsorption process at different conditions and analyzed the data by employing the Langmuir and Freundlich models, and the equilibrium data fitted well with both models. Kinetic analyses were conducted by using the Lagergren pseudo-first-order and pseudo-second-order model and the results showed that the adsorption process was more consistent with the pseudo-second-order kinetics. To better understand the dye adsorption process from the thermodynamics perspective, we also calculated ΔH^ο, ΔS^ο, ΔG^ο and E_a, the results suggesting that the MB adsorption process was physisorption endothermic process, and spontaneous at room temperature. The as-synthesized B-Fe₃O₄@C showing high magnetic sensitivity provides a facile and efficient way to recycle from aqueous solution.     

The effect of B2O3 impurity in the original B powder on the phase formation of MgB2 during the sintering process

Combined with the thermal analysis and phase identification, the influence of the B₂O₃ impurity in the original B powder on the phase formation of MgB₂ during the sintering process was investigated. It is found that how the B₂O₃ impurity in the original B powder affects the sintering process of MgB₂ depends on the reactivity of Mg particles in the original powder. If the Mg particles in the original powder are small and reactive enough, the B₂O₃ impurity could react with them before Mg melting during the sintering process and accelerate the solid–solid reaction between Mg and B. Otherwise, the B₂O₃ impurity could not react with Mg particles before Mg melting and depress the solid–solid reaction between Mg and B.     

The study of Ziegler-Natta type organometallic catalysts in hydrogenation

The system, Fe(C₁₇H₃₅COO)₃-Al(C₂H₅)₃, has been studied directly in the process of cyclohexane and phenylacetylene hydrogenation. It is shown that the system composition can vary in the course of the catalytic process. The effect of unsaturated compounds on the system composition depends on their ability to serve as ligands.     

Transition from reversible to irreversible magnetic exchange-spring processes in antiferromagnetically exchange-coupled hard/soft/hard trilayer structures

The demagnetization processes of antiferromagnetically exchange-coupled hard/soft/hard trilayer structures have been studied based on the discrete one-dimensional atomic chain model and the linear partial domain-wall model. It is found that, when the magnetic anisotropy of soft layer is taken into account, the changes of the soft layer thickness and the interfacial exchange coupling strength may lead a transition of demagnetization process in soft layer from the reversible to the irreversible magnetic exchange-spring process. For the trilayer structures with very thin soft layer, the demagnetization process exhibits typical reversible exchange-spring behavior. However, as the thickness of soft layer is increased, there is a crossover point t_c, after which the process becomes irreversible. Similarly, there is also a critical interfacial exchange coupling constant A_sh^c, above which the exchange-spring process is reversible. When A_sh<A_sh^c, the irreversible exchange-spring process is achieved. The phase diagram of reversible and irreversible exchange-spring processes is mapped in the plane of the interfacial exchange coupling A_sh and soft layer thickness N_s.     

Excitation migration among inhomogeneously broadened levels of Eu3+ ions

Excitation migration between ⁵D₀ states of Eu³⁺ ions in Ca(PO₃)₂ glass is studied by using the technique of the selective excitation of the inhomogeneously broadened ⁵D₀ levels. In time-resolved emission spectra for ⁵D₀→⁷F₁ transition after the pulse excitation due to ⁷F₀→⁵D₀ transition by the use of a tunable dye laser at 77°K, a subpeak is observed to appear and to grow in intensity with increasing delay time, besides the main peak excited directly by the excitation light. The observed facts are explained by considering the phonon-assisted energy transfer between ⁵D₀ states involving an acoustic phonon. From the analysis of the results, the probability of the excitation migration due to the phonon-assisted process is estimated to be ≌ 10 A ms^-1. From the theoretical consideration, the rate of the linewidth change and the probability of the excitation migration due to the resonant transfer process are obtained. These results indicate that the phonon-assisted process is more dominant than the resonant process for the excitation migration in the system studied.     

Magnetic pigments for recording media

CrO₂ doped with 1--2 wt% Fe³⁺ on Cr⁴⁺ positions is one of the most important materials for magnetic recording in audio, data and video tapes. ⁵⁷Fe Mössbauer spectroscopy was applied to determine the level of iron doping in newly developed high coercivity CrO₂ particles. It was found that, compared with the conventional preparation process, the new particles contain increased amounts of Fe³⁺ ions in the CrO₂ crystal lattice giving rise to higher magnetocrystalline anisotropy. This is reflected in coercivities of up to over 900 Oe. All samples contain as a secondary iron-containing phase α-(Cr_1-xFe_x)₂O₃, the amount of which is higher in samples of the conventional preparation process than in those of the new BASF process. Details about the mechanism of the development of doped CrO₂ particles in both types of processes were obtained by means of Mössbauer, XRD and wet chemical investigations making possible an optimization of the new BASF process.     

花状NaY(MoO4)2的合成和(MoO4)2:Eu3+的光学性质

用微波辅助水热-煅烧法成功合成了花状NaY(MoO₄)₂颗粒,用XRD、XPS、FESEM进行了表征,提出了花状NaY(MoO₄)₂颗粒可能的形成机理. 采用相同的方法合成了NaY(MoO₄)₂:Eu³⁺荧光体,该荧光材料在612 nm处有一个强的发射峰,可用作白色发光二极管的红色磷光剂. 此外,微波辅助水热-煅烧法可能发展成为制备其他花状稀土钼酸盐的有效途径.     

Observations of photovoltage in Ag photodoping of amorphous As2S3 films

Photovoltage has been measured during Ag photodoping process in amorphous As₂S₃ films. Concerning the driving force on Ag atoms in the process, a tentative energy band model near Ag-As₂S₃ interface has been proposed.     

超细Fe3O4的氧化过程

根据穆斯堡尔谱分析,Fe₃O₄转变为γ-Fe₂O₃是γ-Fe₂O₃成核生长过程。根据氧化过程磁矩的变化确定Fe₃O₄浓度随时间的变化,-(dc)/(dt)=mc³仅在氧化初始阶段适合。