Effect of catalyst activity in SMR-SERP for hydrogen production: Commercial vs. large-pore catalyst

In this work, we have evaluated the performance of an SMR-SERP unit (steam methane reforming sorption enhanced reaction process), using two different Ni/Al₂O₃ catalysts: commercial “Octolyst 2001” from Degussa and a large-pore catalyst (Catalyst A). The selective CO₂ sorbent was a potassium modified hydrotalcites. Several experiments were performed under different operating conditions to validate a mathematical model.Experimental results show that the Degussa catalyst is more active and more selective to CO₂ producing hydrogen with higher purity and less CO than the large-pore catalyst. Cyclic SMR-SERP experiments were also performed. The cycles comprise four different steps: reaction, depressurization, reactive regeneration and pressurization. In the cyclic experiments, conversion was 43% higher than in an SMR reactor, while H₂ purity was 75%, which is 25% higher than in normal SMR operation. Results indicate that more active catalysts also promote a better reactive regeneration optimizing the use of part of the product (H₂). The proposed mathematical model was validated in a wide range of operating conditions and in a cyclic experiment. The model was able to describe the SMR-SERP experiments without any fitting parameters.     

Multi-model sensor fault detection and data reconciliation: A case study with glucose concentration sensors for diabetes

Erroneous information from sensors affect process monitoring and control. An algorithm with multiple model identification methods will improve the sensitivity and accuracy of sensor fault detection and data reconciliation (SFD&DR). A novel SFD&DR algorithm with four types of models including outlier robust Kalman filter, locally weighted partial least squares, predictor-based subspace identification, and approximate linear dependency-based kernel recursive least squares is proposed. The residuals are further analyzed by artificial neural networks and a voting algorithm. The performance of the SFD&DR algorithm is illustrated by clinical data from artificial pancreas experiments with people with diabetes. The glucose-insulin metabolism has time-varying parameters and nonlinearities, providing a challenging system for fault detection and data reconciliation. Data from 17 clinical experiments collected over 896 h were analyzed; the results indicate that the proposed SFD&DR algorithm is capable of detecting and diagnosing sensor faults and reconciling the erroneous sensor signals with better model-estimated values. © 2018 American Institute of Chemical Engineers AIChE J, 65: 629–639, 2019     

Processes for industrial production of hydrogen and associated environmental effects

At the present time, hydrogen is an important raw material for the chemical, petrochemical and petroleum industries. There is an abundance of hydrogen in nature, although it is available for exploitation only in the combined state as in water, hydrocarbons or coal. Separating and recovering hydrogen from these compounds requires the application of energy that is mostly derived from the chemical conversion of fossil materials by combustion. This paper examines the principal processes currently employed for the industrial production of hydrogen and the associated environmental problems.     

燃料电池用柴油重整制氢技术现状与展望

现有储氢技术在储氢密度、能耗及相应的基础设施建设等方面存在明显短板,难以满足燃料电池技术商业化发展需求,现场制氢技术得到了广泛关注。其中,柴油重整制氢技术以其理论产氢比率高、适用领域广、基础设施完善、安全性好、成本低等优点,可广泛应用于汽车、船舶、分布式发电等民用领域以及潜艇、舰船等军事领域,成为热点研究之一。本文综述了柴油重整制氢的分类,详细介绍了蒸汽重整、部分氧化重整和自热重整制氢的反应机理,并对三种重整反应的优缺点进行了对比分析;在此基础上,概述了三种重整反应国内外研究现状。总体而言,蒸汽重整产物中氢气浓度最高但系统质量较大,比较适用于固定制氢领域;自热重整技术系统结构较为紧凑,产物氢气浓度适中,比较适用于汽车等移动制氢领域;部分氧化重整技术由于产物H₂/CO比率较低,加之反应温度较高,容易发生结焦反应,目前其应用领域还相对有限。     

碘硫循环制氢中HI浓缩分离工艺的研究进展

综述了碘硫循环制氢中用于HI浓缩分离的3种主要技术路线,即磷酸萃取精馏、反应精馏以及电解电渗析预浓缩-精馏的研究进展,对各路线的过程原理、操作流程、能量利用效率等方面进行了讨论,在此基础上对比了其各自的优点和不足之处,并对其应用前景进行了展望。其中,磷酸萃取精馏开发最早,相对成熟,但操作流程复杂,运行效率需进一步提升;反应精馏流程有望以高集成度取得高效率,但所需条件非常苛刻,其设备开发、工艺实验等工作亟待展开;近年来发展较快的电解电渗析预浓缩-精馏工艺由于具有操作简单,条件温和,浓缩效率高等优点而具有较好的应用前景,其进一步工艺放大、模块化以及与精馏的高效协同等都是未来研究的重点和难点。     

光合细菌的葡萄糖跨膜传输及代谢产氢模型

引言光合细菌产氢具有底物转化效率高、吸收光谱范围广、无污染、能耗低、操作简单的优点[1-2]。目前,关于光合细菌的底物跨膜传输和产氢方面的理论研究相对较少[3-4]。Vrabl等[5-6]研究了葡萄糖的跨膜传输过程,分析了细胞膜上的载体蛋白运输特性;Wayman等[7]建立了Aspergillus niger     

The physical and photocatalytic properties of thallium doped cobalt ferrites for efficient hydrogen fuel production

Herein, a series of CoFe_2-xTl_xO₄ (0.03 ≤ x ≤ 0.15) nanoceramics were prepared via a meso-2,3-dimercaptosuccinic acid assisted solvothermal route. The influence of a thallium ion dopant on the structural, magnetoptical, electrical, and photocatalytic characteristics has been scrutinized. The X-ray diffraction demonstrated that CoFe_2-xTl_xO₄ nanoceramics have a cubic structure at all Tl ions concentrations. The Raman scattering spectroscopy revealed the reshuffling of the iron cation between the tetrahedral and octahedral sites of the structure of ferrite due to the substitution with Tl ions. The magnetic properties showed an increase of the saturation magnetization from 59.5 emu/g to 67.4 emu/g and an increase of the coercive field from 344.2 Gauss to 583.1 Gauss with increasing the amount of Tl cations. The optical band gap decreases with the increase of Tl ion concentration. The activation energy decreases from 0.44 eV to 0.26 eV with increasing the Tl ion concentration. These unique physical properties gave rise to the outstanding capability of the as-synthesized CoFe_2-xTl_xO₄ nanoceramics for the photocatalytic production of hydrogen fuel.     

Steam reforming of bio-ethanol on alkali-doped Ni/MgO catalysts: hydrogen production for MC fuel cell

The effects of alkali addition (e.g. Li, Na, K) on the behavior of Ni/MgO catalyst in the bio-ethanol steam reforming have been investigated. Li and Na promote the NiO reduction but negatively affect the dispersion of the Ni/MgO catalyst, whereas K does not significantly affect either morphology or dispersion. Li and K enhance the stability of Ni/MgO mainly by depressing Ni sintering. Coke formation on bare and doped catalysts occurs but with orders of magnitude lower rates than those claimed for Ni supported on an acidic carrier. The peculiar influence of the mean Ni particle size on the turnover frequency (TOF s⁻¹) has been explained by invoking a structure-sensitive character of the ethanol dehydrogenation reaction considered as being the first step of the reaction which evolves according to the following mechanism: ethanol hydrogenation → acetaldehyde decomposition → steam reforming of methane and water gas shift reactions.     

Alteration of energy metabolism in Enterobacter aerogenes by external addition of pyrophosphates and overexpression of polyphosphate kinase for enhanced hydrogen production

BACKGROUND: Bacterial hydrogen evolution releases excess electrons or energy formed during the metabolic oxidations. Until now, few studies have investigated the global regulation of cellular energy flows, pertaining to bacterial hydrogen production for the improvement of hydrogen production. In this study, the cellular energy metabolism of Enterobacter aerogenes was regulated by the addition of pyrophosphate (PPi) and the overexpression of polyphosphate kinase (PPK), to improve hydrogen production. RESULTS: By overexpressing PPK at 10 mmol L^?1 PPi, total hydrogen yields were increased by 32.7%. Metabolic flux analysis demonstrated that overexpression of PPK in E. aerogenes resulted in a higher cellular ATP level and a higher NADH consumption rate, which changed the cellular redox state and allowed more electrons to flow into the hydrogen production pathway. CONCLUSION: Alteration of the energy metabolism in E. aerogenes can affect hydrogen production. This implies that if one could accurately control the energy flow or the electron flow in the cells, hydrogen productivity would be further greatly improved. Copyright © 2012 Society of Chemical Industry     

Steady-state modeling and bifurcation behavior of circulating fluidized bed membrane reformer-regenerator for the production of hydrogen for fuel cells from heptane

The production of hydrogen for fuel cells by steam reforming of heptane is investigated in a Circulating Fluidized Bed Membrane Reformer-Regenerator (CFBMRR) system (A.I.Ch.E. Journal 49(5) (2003) 1250). Palladium based hydrogen permselective membranes are used for hydrogen removal and dense perovskite oxygen permselective membranes are used for oxygen introduction. A series of pseudo-steady-state simulations show that when the catalyst is not regenerated, the circulating nickel reforming catalyst deactivates quickly and the “half catalyst activity life” for efficient production of hydrogen is quite short, especially at high temperatures. Efficient continuous catalyst regeneration can keep the catalyst activity high (∼1.0). With continuous catalyst regeneration, autothermal operation for the entire adiabatic reformer-regenerator system is achievable when the exothermic heat generated from the catalyst regenerator is sufficient to compensate for the endothermic heat consumed in the riser reformer. This type of autothermal operation becomes less likely at high steam to carbon feed ratios. This is due to the fact that carbon deposition rate decreases leading to the decrease of autothermal circulating feed temperature and energy-based hydrogen yield (adiabatic hydrogen yield in autothermal reformer-regenerator system). Multiplicity of the steady states for the reformer is possible for this configuration. With the steam to carbon feed ratio as the bifurcation parameter, multiplicity occurs between the two bifurcation points 1.444 and 2.251 mol/mol. In this multiplicity region, the energy-based hydrogen yield at the upper steady state with high regenerator output temperature is surprisingly the lowest one. While it is the highest one at the lower steady state with low regenerator output temperature. The maximum energy-based hydrogen yield is about 15.58 moles of hydrogen per mole of heptane fed at the lower steady-state when steam to carbon feed ratio is very close to the bifurcation value of 1.444 mol/mol. After removing the sweep gas steam by downstream cooling and de-humidification, the product hydrogen from steam reforming of hydrocarbons can be used for fuel cells with high purity (∼100%).     

Critical surfactant concentration in the interaction between nonionic surfactants and polymeric acids. effects of temperature,pH and salts

Critical surfactant concentrations at which the binding of nonionic surfactants to polyacrylic acid, or complex formation, abruptly occurred in aqueous solution were lower than the CMC and were temperature-independent. The complex was precipitated by pH lowering or salt addition. At low pH, precipitation limit surfactant concentration (PLC) existed, below which no precipitation of the complex took place, and the PLC coincided with the critical concentration mentioned above. In this case the PLC did not change with temperature either. In the precipitation caused by A1C1```3`` addition, the PLC was a little higher than that at low pH, because Al ions induced not only shrinking and agglomeration of the complex but at the same time blocked the sites on the polymeric acid for hydrogen bonding with the surfactant. By NaCl or CaCl```2`` addition no PLC was found, because in both cases the salting-out effect dominated. Martially presented at the 77th Annual AOCS-JOCS Joint Meeting in May 1986 in Honolulu.     

Continuous aqueous phase extraction of proteins: Automated on-line monitoring of fumarase activity and protein concentration

Automated assay techniques are described for on-line measurements of fumarase activity and total protein concentration, including in-line sample dilution and sample multiplexing during continuous aqueous phase extraction. Fumarase was determined by following the conversion of L-malate to fumurate at a wavelength of 250 nm, while the protein assay was based on the Biuret reaction. Actual assay times of 2 and 4 min were achieved for the fumarase and protein measurements, respectively, with an effective measurement cycle time of 2 min. Standard deviations of c. 3.2 and 2% of the measured values were calculated for the enzyme and protein values, respectively. The assay system was coupled to a computer to allow on-line data visualization and storage.     

Material properties and processing in the production of fuel cell components: I. Hydrogen anodes from Raney nickel for lightweight alkaline fuel cells

The production steps of Raney nickel based, PTFE bonded hydrogen anodes for alkaline fuel cells are examined. The Raney nickel catalyst has been made by leaching the nickel aluminium alloy and additional stabilization. The electrode is fabricated by mixing the catalyst with copper oxide for enhancing electronic conductivity and aqueous PTFE emulsion as a hydrophobic binder. Each process step, starting from the nickel aluminium alloy is described and the physical properties of catalyst and electrode are evaluated. At an overpotential of 100 mV the optimized hydrogen anode exhibits at negligable excess hydrogen pressure (1·02bars) a current density of nearly 400 mA cm^–2 at 80°C in 30 wt% KOH. Long term performance test shows that electrode overpotential of more than 60 mV should be avoided. A life time of 5000 hrs at 50°C and a current density of 100 mA cm^–2 has been proven.     

Phase equilibria for salt-induced lysozyme precipitation: Effect of salt concentration and pH

The salt-induced precipitation of lysozyme from aqueous solutions was studied at 25 °C and various pH values by cloud-point investigations, precipitation experiments (analysing the compositions of the coexisting phases) and microscopic investigations of the precipitates. Sodium sulphate as well as ammonium sulphate were used to induce the precipitation. The experimental results are discussed and used to develop a scheme of the phase equilibrium in water-rich aqueous solutions of lysozyme and either Na₂SO₄ or (NH₄)₂SO₄.     

Directed evolution of Thermotoga neapolitana xylose isomerase: high activity on glucose at low temperature and low pH

The Thermotoga neapolitana xylose isomerase (TNXI) is extremelythermostable and optimally active at 95°C. Its derivative,TNXI Val185Thr (V185T), is the most active type II xylose isomerasereported, with a catalytic efficiency of 25.1 s^–1 mM^–1toward glucose at 80°C (pH 7.0). To further optimize TNXI’spotential industrial utility, two rounds of random mutagenesisand low temperature/low pH activity screening were performedusing the TNXI V185T-encoding gene as the template. Two highlyactive mutants were obtained, 3A2 (V185T/L282P) and 1F1 (V185T/L282P/F186S).1F1 was more active than 3A2, which in turn was more activethan TNXI V185T at all temperatures and pH values tested. 3A2and 1F1’s high activities at low temperatures were dueto significantly lower activation energies (57 and 44 kJ/mol,respectively) than that of TNXI and V185T (87 kJ/mol). MutationL282P introduced a kink in helix     

Microbial treatment of sour gases for the removal and oxidation of hydrogen sulphide

It has been demonstrated that the bacterium Thiobacillus denitrificans may be readily cultured aerobically and anaerobically in batch and continuous cultures on hydrogen sulphide (H₂S) gas under sulphide-limiting conditions. Under these conditions sulphide concentrations in the culture medium were less than 1 μM resulting in very low concentrations of H₂S in the reactor outlet gas. The stoichiometries of both the aerobic and anaerobic reactions were determined and stable reactor operation demonstrated for up to five months. Maximum loading of the biomass was determined to be 5.4–7.6 mmoles H₂S/h-g biomass under anaerobic conditions and 15.1–20.9 mmoles H₂S/h-g biomass under aerobic conditions. Indicators of reactor upset were determined and recovery from upset demonstrated. Heterotrophic contamination was shown to have negligible effect on reactor performance with respect to hydrogen sulphide oxidation. In fact, growth of T. denitrificans in the presence of floc-forming heterotrophs produced a hydrogen sulphide active floc with excellent settling characteristics. A case study of the application of this technology to the removal and oxidation of H₂S from biogas is presented.     

湿法磷酸净化及其盐类生产技术:4.技术创新集成生产磷酸氢钙

概述钙盐净化WPA原理、二段中和法生产磷酸氢钙(DCP)的传统方法。该法生产的DCP质量达到国际先进水平,但存在原料消耗高等问题。介绍采用磷矿粉脱硫、"节硫降钙"、选用钙盐净化WPA和2次中和除氟以减少P2O5损失和副反应发生、溶解白磷肥回收其中的P2O5、母液净化回收磷等一系列技术创新,可提高磷回收率,降低原料消耗,使DCP制造成本下降约10%。     

Mathematical model and process for the production of granulated fuel wood

The results of a mathematical simulation of the process of wood flour granulation in the channels of flat dies are reported and a comparative analysis of currently available and developed mathematical models is performed in this work. A test bench based on a hand-power press and a bench for studying the compression of wood granules are described, and the results of full-scale experiments and the most significant results of the complex thermotechnical analysis of wood granules are presented. The effect of cooling conditions on the mechanical durability of granules is determined, and the dependences of the mechanical durability of the granules on the moisture content and temperature of a die are obtained.