[en] A novel H_2S sorbent based on SnO_2 and Y_2O_3 is developed by a co-precipitation method for steam regenerative removal of H_2S from hot syngas at moderate temperatures (400–500 °C). SnO_2-Y_2O_3 sorbent is stable in a reducing atmosphere (i.e. 500 °C, 50% H_2) and achieves a 99.9% H_2S removal during successive desulfurization and regeneration cycles. The addition of yttrium to SnO_2 decreases the reduction property of SnO_2 and no metallic Sn exists in the reducing atmosphere due to the formation of a pyrochlore-type compound, Y_2Sn_2O_7. The SnO_2-Y_2O_3 sorbent has a desulfurization performance deterioration with the increasing calcination temperature. The newly developed SnO_2-Y_2O_3 sorbent can be regenerated by steam at 500 °C. In the eight successive desulfurization and regeneration cycles, SnO_2-Y_2O_3 sorbent has a cyclic breakthrough sulfur capacity of 9 mg/g without significant sulfur capacity loss. - Highlights: • Reversible warm gas H_2S clean up. • Suppressing SnO_2 reduction by formation of Sn_2Y_2O_7. • Sn2Y-700 steam regeneration and cycling characterization.

[en] Highlights: • Mechanistic modeling of nitrogen oxide electrochemical reduction. • Fundamentals of both alternative and direct current electrolysis. • Theoretical optimal frequency in alternative current electrolysis. - Abstract: A one-dimensional symmetric model on NO electrochemical reduction in solid oxide electrolysis cell(SOEC) considering gas transport, electronic conduction, ionic conduction, and electrochemical process based on multifunctional layer electrode is developed. The simulation results agree well with the experimental results both in the direct current(DC) and alternative current(AC) electrolysis. The distributions of the NO concentration in the electrode are predicted in both DC and AC electrolysis. The effects of temperature, voltage, and O_2 concentration were investigated on NO alternative current electrolysis and direct current electrolysis processes. The modeling results show that the optimal frequency of 0.3 Hz is corresponded to the maximum NO decomposition rate in different temperatures and voltages. The NO decomposition increases with increasing temperature and decreasing O_2 concentration in most cases. At 450 °C, the NO decomposition presents first increased and then decreased trend with different voltages at the frequency of 0.3 Hz. This is similar to the effects of O_2 concentration at 450 °C and 475 °C at the same frequency

[en] Highlights: • A micro-CHP with biogas-fueled flame fuel cell for indigenous source. • Stable biogas fuel-rich combustion in porous media burner. • Maximum power of 1.4 W for a single micro-tubular FFC. • Analysis of performance degradation resulted from carbon deposition. - Abstract: A biogas-fueled flame fuel cell (FFC) unit is proposed for the micro-combined heat and power (CHP) system using indigenous energy source. With fuel-rich flame as both heater and reformer, FFC is advantageous for quick start-up, no sealing, and simple thermal management. In this study, a porous media burner with non-catalytic fuel-rich combustion was utilized to provide both stable high temperature environment and reformed syngas for the solid oxide fuel cell (SOFC). The porous media burner and a micro-tubular SOFC were integrated directly in the biogas FFC reactor. The performance of fuel-rich combustion and electrochemical characteristic was studied for various equivalence ratios from 1.2 to 1.4. Experimental results showed that the reforming efficiency reached 42.3% with the porous media burner, using model biogas of 60% CH₄ and 40% CO₂ as fuel. The maximum power for a single tubular fuel cell reached 1.4 W when fed with model biogas at an equivalence ratio of 1.4. Furthermore, performance degradation caused by carbon deposition at the anode was investigated.

[en] Fluid dynamic models are generally appropriate for the investigation of inductively coupled plasmas. A commercial ICP etcher filled with argon plasma is simulated in this study. The simulation is based on a multiphysical software, COMSOL(TM), which is a partial differential equation solver. Just as with other plasma fluid models, there are drift-diffusion approximations for ions, the quasi-neutrality assumption for electrons movements, reduced Maxwell equations for electromagnetic fields, electron energy equations for electron temperatures and the Navier-Stokes equation for neutral background gas. The two-dimensional distribution of plasma parameters are shown at 200 W of power and 1.33 Pa (10 mTorr) of pressure. Then the profile comparison of the electron number density and temperature with respect to power is illustrated. Finally we believe that there might be some disagreement between the predicted values and the real ones, and the reasons for this difference would be the Maxwellian eedf assumption and the lack of the cross sections of collisions and the reaction rates. (semiconductor physics)

[en] Elevated-temperature pressure swing adsorption could potentially replace wet methods in the field of syngas purification. However, the reversibility of sulfur removal in this technique needs to be validated. In this study, the H₂S adsorption reversibility of two types of activated carbon sorbents were evaluated on a fixed-bed reactor. The effects of desorption method and desorption temperature were studied. Elevated-temperature vacuum desorption was found to be effective for regenerating adsorbents saturated with H₂S. The necessities of both vacuum desorption and elevated temperature were reported. The findings were explained on the basis of the characterization results obtained using pore distribution analysis, inductively coupled plasma, and X-ray photoelectron spectroscopy. The oxidative functional groups or adsorbed O₂ reacted with H₂S on the surface of the adsorbents and the resultant, i.e., elemental sulfur, damaged the pore structure. The richness of the pores with a diameter range of 0.7–0.8 nm decreased by nearly 50% after several adsorption–desorption cycles. At high temperatures and under vacuum atmosphere, element sulfur could be easily distilled and removed from the fixed bed. Thus, element sulfur would not accumulate on the adsorbent, thus ensuring the reversibility of H₂S.

[en] Highlights: • Two-train elevated temperature pressure swing adsorption for H₂ purification. • Optimal process achieves 99.9994% hydrogen purity and 97.51% hydrogen recovery ratio. • Total steam consumption is significantly reduced with reflux structures. The trade-off between hydrogen recovery ratio (HRR) and hydrogen purity (HP) is one of the main drawbacks in normal temperature pressure swing adsorption (NT-PSA) for producing high-purity hydrogen from shifted gas. In this paper, a two-train elevated-temperature pressure swing adsorption (ET-PSA) process that achieved 99.999% HP and over 95% HRR is proposed, which has wide application potentials in fuel cells and chemical industries. Potassium-promoted layered double oxide (K-LDO), which shows reasonable working capacity and fast adsorption/desorption kinetics at elevated temperatures (200–450 °C), is adopted as the CO₂ adsorbent. CO in the shifted gas is co-purified by high-temperature water gas shift (WGS) catalysts added to the columns. The first-train ET-PSA adopted an eight-column thirteen-step configuration with shorter step time to remove most of the CO/CO₂ in the shifted gas, and the second-train ET-PSA adopted a double-column seven-step configuration with longer step time to purify the residual gas impurities. The introduction of co-current high-pressure steam rinse and counter-current low-pressure steam purge is the key to achieve both high HRR and HP. The high-temperature steam is the main energy consumption of ET-PSA rather than low HRR in NT-PSA, and the total steam consumption is reduced by adopting the tail gas from second-train ET-PSA as the purge gas for first-train ET-PSA. The optimal results achieved 97.51% HRR and 99.9994% HP with only 0.188 rinse-to-feed ratio and 0.263 purge-to-feed ratio, which are the highest values reported for PSAs producing high-purity hydrogen from carbon-based fuels.

[en] Objective: To compare the time spent for operation, safety and clinical curative effect of ultrasound-guided (US-guided) radiofrequency ablation (RFA) with those of CT-guided RFA in treating hepatocellular carcinoma (HCC). Methods: From April 2010 to November 2014, 158 admitted patients with HCC received US-guided RFA (US group, n = 59) or CT-guided RFA (CT group, n = 99). The time spent for RFA procedure, intraoperative adverse reactions and postoperative complications were compared between the two groups. The patients were followed up to observe the local recurrence rate, progression-free survival (PFS) time and overall survival (OS) time. Results: There was no significant difference in the occurrence rate of postoperative serious adverse reactions between the two groups (P = 0.193). The safety of the two groups was the same. The average time spent for RFA procedure in US group was 26.03 minutes which was obviously lower than 61.78 minutes in CT group, the difference between the two groups was statistically significant (P < 0.0001). No statistically significant difference in the local recurrence rate existed between the two groups. The PFS and OS in US group were 287.0 d (157.9-416.1 d) and 1907.0 d (1281.7-2532.3 d) respectively, which were 272.0 d (177.9-366.1 d) and 1932 d respectively in CT group (as the number of deaths in CT group did not exceed 50%, it was not able to estimate the 95% confidence interval). The differences in PFS and OS between the two groups were not statistically significant. Conclusion: RFA, regardless of under US guidance or under CT guidance, can be successfully accomplished in HCC patients. US-guided RFA is simpler and quicker, the time spent for procedure is shorter, and its curative effect for HCC is similar to that of CT-guided RFA. (authors)

[en] A two-dimensional axisymmetric inductively coupled plasma (ICP) model, and its implementation in the COMSOL multiphysical software, is described. The simulations are compared with the experimental results of argon discharge from the gaseous electronics conference RF reference cell in the inductively coupled plasma mode. The general trends of the number density and temperature of electrons with radial scanning are approximately correct. Finally, we discuss the reasons why the comparisons are not in agreement, and then propose an improvement in the assumptions of the Maxwellian electron energy distribution function and reaction rate. (semiconductor technology)

[en] Hydrogen from coal-based syngas is usually purified by deep desulfurization and decarbonization scrubbing technologies. Such electricity consuming processes cost a large number of heat exchangers and compressors. In this study, a two-stage demonstration unit had been constructed and demonstrated to purify hydrogen (including useful nitrogen for ammonia synthesis) from on-site sideline shift gas mixture at Yangmei Fengxi ammonia plant. For the first stage, an 8-column hydrogen purification process by novel elevated temperature pressure swing adsorption (ET-PSA, operated at 180 to 220 °C) was developed and demonstrated to capture H₂S and CO₂ simultaneously by hydrophobic activated carbon (AC) to reduce the impurities compared to that of room temperature PSA. Working condition at elevated temperature was proved to be appropriate and stable for reversible H₂S removal by AC. The second stage was a temperature swing adsorption for deep purification of CO to 0.2 ppm by commercial CuCl monolayer dispersed zeolites (PU-1 synthesized by Beijing Peking University Pioneer Technology Co., Ltd.). In order to examine the standard of trace impurities such CO and H₂S in product H₂, the purified H₂ was offered to a 3 kW proton exchange membrane fuel cell (PEMFC) stack to prove that all carbon and sulfur impurities met the demand not only for ammonia synthesis, but for PEMFC as well. Besides, two novel PSA steps: high pressure steam rinse and low pressure nitrogen purge were adopted to improve H₂ recovery to above 93%. To demonstrate its stability, over 2500 h of operation had been carried out on the small-scale demonstration rigs by far.

[en] Highlights: • A SOFC stack integrated with catalytically enhanced porous media combustion. • The coating of 0.5 wt% Rh improved the reforming efficiency from 49% to 64.8%. • The maximum fuel utilization of FFC reached 32.6%. • Significant FFC electrical efficiency of 12.9% was obtained. -- Abstract: The flame fuel cell (FFC) is advantageous for its simple setup, quick start-up, and high fuel flexibility. However, one important drawback of the FFC is its relatively low electrical efficiency, which is mainly limited by the reforming efficiency of the burner and fuel utilization. In this study, to increase the reforming efficiency and fuel utilization, a catalytically enhanced porous media combustor was integrated with a micro-tubular solid oxide fuel cell stack. The second layer of the porous material was impregnated with 0.5 wt% Rh, improving the reforming efficiency from 49% to 64.8%. The fuel utilization was demonstrated to be 32.6% when the equivalence ratio was 1.6 and the inlet flow rate of combustion products to the anode of the stack was 200 mL min⁻¹. The effects of the equivalence ratio and anode gas flow rate on the electrochemical performance and efficiency were investigated. A power density of 72.9 mW cm⁻² and a total electrical efficiency of 12.9% were obtained at a voltage of 0.76 V and an equivalence ratio of 2.4.