A mathematical approach for oxygenation using micro bubbles: Application to the micro-oxygenation of wine

This work is the logical following of our previous work [Devatine, A., Chiciuc, I., Poupot, C., Mietton-Peuchot, M., 2007. Micro-oxygenation of wine in presence of dissolved carbon dioxide. Chemical Engineering Science 62, 4579-4588] about micro-oxygenation of wine, where, when dissolved carbon dioxide was present in the liquid phase, a surprising decrease in the value of the apparent k_La was pointed out. Only qualitative explanation was given, and no modelling was proposed. Here, we attempted to fill this gap, using very simple equations. Especially, the rising bubble velocity was assumed to follow the Stokes law, and no interaction between rising bubbles was considered. By making the necessary simplifications, analytical solutions to the set of equations are proposed and simple-to-use expressions for the oxygen transfer yield are established. From them, importance of the ratio “column height” to “diffuser pore diameter” is clearly seen. Comparison with our previous experimental results is also done and validates the prominent role of the “dilution effect” inside the bubble in respect to the observed decrease in the apparent k_La.     

A fixed-bed reactor modeling study on the methanation of CO2

The methanation of carbon dioxide has gained renewed interest during the last years as a possible technology to synthesize a feasible chemical energy carrier. This modeling study aims at a basic understanding of the aspects relevant for designing an externally cooled fixed-bed reactor for the methanation of a pure, stoichiometric feed gas. It is shown that the reaction rates and the exothermicity (ΔH° = −165 kJ/mol) prevent a fixed-bed reactor of technical dimensions to be operated at high conversions without runaway of the reactor. The model predictions of differently detailed pseudo-homogeneous reactor models and a heterogeneous reactor model where the intraparticle transport of mass is described according to a dusty-gas approach are compared to assess the needed level of detail in terms of modeling the heat transfer, fluid flow characteristics and transport resistances on the pellet scale. Under specific conditions, intraparticle mass transfer and external heat transfer need to be considered for describing the temperature and concentration profiles adequately. The study is completed by modeling a fixed-bed membrane reactor as an example of a structured reactor that offers improved temperature control by separated and controlled feeding of hydrogen and carbon dioxide.     

Oxygen and hydrogen peroxide reduction catalyses in neutral aqueous media using copper ion loaded glassy carbon electrode electrolyzed in ammonium carbamate solution

An aminated glassy carbon electrode (AGCE) can be obtained by the electrode oxidation of glassy carbon electrode in ammonium carbamate solution. In the cyclic voltammetric experiments, the electrode reduction of the dissolved oxygen began from −0.15 V vs. Ag/AgCl in neutral aqueous media when the aminated glassy carbon electrode was used as a working electrode although it began from −0.40 V vs. Ag/AgCl when a polished GCE was used. The nitrogen containing groups introduced by the electrode oxidation of carbamic acid must be related with the acceleration of the electron transfer rate of oxygen. Moreover, the new reduction wave of the dissolved oxygen appeared at +0.15 V vs. Ag/AgCl when copper (II) ion was coordinated to AGCE surface. This reduction potential of oxygen coincided with that of copper (II) ion and this fact suggests that the coordinated copper ion to the aminated carbon surface works as a redox mediator of oxygen. The reduction product of oxygen was monitored by rotating platinum ring - aminated glassy carbon disk electrode, and it was found that most of oxygen was reduced to water in a potential range negative than −0.4 V vs. Ag/AgCl. By using AGCE, it was recognized that the catalytic reduction of hydrogen peroxide was also taken place as well as oxygen reduction.     

油田污水腐蚀影响因素研究

为研究各种因素对油田污水腐蚀的影响,采用室内静态挂片失重法试验了A3碳钢在不同H2S、CO2、溶解氧、SRB浓度及不同pH值和矿化度的模拟油田水中的腐蚀行为。结果表明,碳钢的腐蚀速率随H2S、CO2、溶解氧、SRB浓度的增加而增大,溶解氧会促进H2S和CO2的腐蚀,H2S会抑制CO2的腐蚀;碳钢的腐蚀速率随矿化度的增加先增大后减小,在矿化度为40 000 mg/L时达到最大;碳钢在碱性环境下的腐蚀速率比酸性环境下的腐蚀速率小的多。     

Continuous O<Subscript>2</Subscript>-CO<Subscript>2</Subscript> production using a Co-based oxygen carrier in two parallel fixed-bed reactors

Oxygen-enriched carbon dioxide stream with oxygen concentration higher than 20 vol% was produced continuously by using a Co-based oxygen carrier packed in two parallel fixed-bed reactors operated in a cyclic manner. Oxygen was absorbed by the oxygen carrier with air being fed. An oxygen-enriched carbon dioxide stream was obtained when the fixed-bed was regenerated with carbon dioxide as a purge gas. Multiple absorption and desorption cycles indicated that the Co-based oxygen carrier had high cyclic stability. XRD analysis determined the absorbed and desorbed products were Co₃O₄ and CoO, respectively. The TGA results indicated that Co-based oxygen carrier did not react with NO or SO₂ during the desorption stage. This Co-based oxygen carrier offers potential for applications in the O₂-CO₂ production for the oxy-fuel coal combustion process. This work was presented at the 7 ^th Korea-China Workshop on Clean Energy Technology held at Taiyuan, China, July 25–28, 2008.     

Chemical-looping combustion of syngas by means of spray-dried NiO oxygen carrier

Chemical-looping combustion (CLC) of syngas has a potential to generate power economically with achieving the inherent carbon dioxide capture. An oxygen carrier with high reactivity and excellent physical properties would make CLC technology more competitive. In this work, oxygen carrier with 70 wt% NiO was prepared by spray drying technique. The prepared oxygen carrier had excellent physical properties for fluidized-bed application of CLC process. The reactivity of the oxygen carrier in repeated reduction-oxidation was measured by thermogravimetric analyzer with simulated syngas. Oxygen carrier calcined at 1,100 °C showed high oxygen transfer capacity of 14.7 wt%, utilizing 98% of the transferable oxygen. Oxygen transfer capacity and oxygen transfer rate was increased with the increase of reaction temperature, and the highest oxygen transfer rate was observed when about half of the transferable oxygen reacted with syngas. The reduction rate of the syngas (mixture of H₂ and CO) appeared to be approximately the sum of the reaction rate of each fuel gas. The experimental results indicated that the spray-dried NiO oxygen carrier prepared in this work could be a good quality oxygen carrier for the CLC of syngas.     

Interaction of transport resistances with biochemical reaction in packed bed solid state fermenters: The effect of gaseous concentration gradients

Mass transfer plays an important role in solid state fermentation (SSF) systems. Earlier work on SSF in tray bioreactors⁷ indicated that steep gaseous concentration gradients developed within the substrate bed, owing to mass transfer resistances, which may adversely affect the bioreactor performance. For all practical purposes these gradients have been eliminated using a packed bed column bioreactor with forced aeration. Gaseous concentrations (oxygen and carbon dioxide) and enzyme activities were measured at various bed heights for various air flow rates during the course of fermentation. The results indicated that concentration gradients were decreased effectively by increasing air flow rate. For example, the actual oxygen and carbon dioxide concentration gradients reduced from 0.07% (v/v) cm^?1 and 0.023% (v/v) cm^?1 to 0.007% (v/v) cm^?1 and 0.0032% (v/v) cm^?1 respectively when the air flow rate was increased from 5 dm³ min^?1 to 25 dm³ min^?1. This resulted in an overall improvement in the performance of the bioreactor in terms of enzyme production.     

Effect of glucose fouling on the dissolved gases permeation through maximum‐crystallized poly(lactic acid) films

In this study, we investigated the effect of fouling on the dissolved oxygen and carbon dioxide permeation in water through maximum‐crystallized poly(lactic acid) (PLA) films by using proton nuclear magnetic resonance, attenuated total reflection‐Fourier transform infrared spectroscopy, wide‐angle X‐ray diffraction, and ultraviolet–visible spectroscopy, contact angle, water content ratio, and dissolved gas permeation. Fouling means the adhesion of contents on a container's internal surface, where content adhesion can directly influence the barrier property of the container. Glucose, a beverage ingredient, was used as a foulant. The permeation of dissolved gases in amorphous PLA film, maximum‐crystallized PLA film, and fouled maximum‐crystallized PLA film was determined. The decreased interstices in the polymer chains during crystallization resulted in the inhibition of the diffusion and decrease in the permeability coefficient of the gases. Moreover, the slope of the permeability coefficient for carbon dioxide in the Arrhenius plot was found smaller than that of oxygen's. This result indicated that the gas barrier property of dissolved carbon dioxide was considerably influenced by solubility and readily decreases during glucose fouling. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46604.     

Aeration control of a wastewater treatment plant using hybrid NMPC

In the operation of wastewater treatment plants a key variable is dissolved oxygen (DO) content in the bioreactors. As oxygen is consumed by the microorganisms, more oxygen has to be added to the water in order to comply with the required minimum dissolved oxygen concentration. This is done using a set of aerators working on/off that represents most of the plant energy consumption. In this paper a hybrid nonlinear predictive control algorithm is proposed, based on economic and control aims. Specifically, the controller minimizes the energy use while satisfying the time-varying oxygen demand of the plant and considering several operation constraints. A parameterization of the binary control signals in terms of occurrence time of events allows the optimization problem to be re-formulated as an nonlinear programming (NLP) problem at every sampling time. Realistic simulation results considering real perturbations data sets for the inlet variables are presented.     

光化学降解溶解有机物及其对生物过程的影响

溶解有机物对控制海洋和淡水水生系统的化学、生物和物理特性有重要的影响．光化学降解溶解有机物改变了生态体系的溶解有机碳、有机物的分子量及光学特性，并且产生复杂的反应性氧化合物、二氧化碳、一氧化碳、小分子量的有机酸、氨基酸、二硫化碳等，对生物过程有重要的影响．本文简要综述了光化学降解溶解有机物的过程机理及其对生物过程的影响．     

Inhibition of penicillin production by carbon dioxide

By means of chemostat culture and automatic control of pH and dissolved oxygen tension the penicillin fermentation was controlled so that the partial pressure of carbon dioxide (P_co2) in the gas phase was the only variable. This reveals that under the conditions used carbon dioxide strongly inhibits penicillin production. The synthesis rate (units/mg dry mycelium x h) was decreased about 50% by a P_co2 of 0.08 atm.     

An investigation on the reaction mechanism for the partial oxidation of methane to synthesis gas over platinum

The partial oxidation of methane to synthesis gas has been investigated by admitting pulses of pure methane, pure oxygen and mixtures of methane and oxygen to platinum sponge at temperatures ranging from 973 to 1073 K. On reduced platinum the decomposition of methane results in the formation of surface carbon and hydrogen. No deposition of carbon occurs during the interaction of methane with a partly oxidised catalyst. Oxygen is present in three different forms under the conditions studied: platinum oxide, dissolved oxygen and chemisorbed oxygen species. Carbon monoxide and hydrogen are produced directly from methane via oxygen present as platinum oxide. Activation of methane involving dissolved oxygen provides a parallel route to carbon dioxide and water. Both platinum oxide and chemisorbed oxygen species are involved in the oxidation of carbon monoxide and hydrogen. In the presence of both methane and dioxygen at a stoichiometric feed ratio the dominant pathways are the direct formation of CO and H₂ followed by their consecutive oxidation. A Mars-van Krevelen redox cycle is postulated for the partial oxidation of methane: the oxidation of methane is accompanied by the reduction of platinum oxide, which is reoxidised by incorporation of dioxygen into the catalyst.     

PRODUCTION OF ACTIVATED CARBON FROM COAL CHARS USING MICROWAVE ENERGY

The microwave induced reaction of carbon with carbon dioxide has been investigated as a method of production of activated carbon using coal char. Factors which control the carbon-carbon dioxide reaction in a microwave environment were also studied.

Results indicate that the reaction rate is primarily controlled by the electric field strength. The reaction rate or conversion follows an Arrhenius type relationship with substitution of the electric field strength for temperature. In other instances, temperature is easily determined and therefore used in these calculations. In this case, the particle temperature is nearly impossible to measure. This means that we need an easily calculated variable to use in our calculations. The input microwave power will serve as this variable. It is easily determined, and is also useful in calculations because, as stated earlier, when input power (in the form of electric field strength) is substituted for temperature in equations of the Arrhenius type, the reaction rate is related in a similar manner, Because of difficulties associated with the direct measurement of particle temperature in the microwave energy field, only reactor skin temperatures were measured.

The char surface area, as calculated using the B.E.T. equation, was increased dramatically by the microwave process. The prod uct had a high degree of microporosity and was a good adsorbent of NO_x gas in air. The solids residence time for the coal char in direct microwave contact was on the order of minutes. Reactor skin temperature measurements at the reaction zone suggest that reaction occurred at approximately 600^°F(316^°C).     

Effect of oxygen chemisorption on char gasification reactivity profiles obtained by thermogravimetric analysis

The gasification reactivity of an Illinois No. 6 bituminous coal char was determined in oxygen and carbon dioxide using thermogravimetric analysis (TGA). Extensive tests were carried out to ensure the absence of diffusional limitations. Measurements of chemically controlled rates were verified by analysing the activation energies for reactions of the char at various conversion levels. The effect of stable carbon-oxygen complex formation on TGA reactivity profiles was investigated. For disordered carbons (e.g. coal chars) gasified in oxygen, the results showed that the observed differences between reactivity profiles obtained by TGA and those obtained by product gas analysis (e.g. non-dispersive infrared spectroscopy, i.r.) can be attributed to significant amounts of stable complex being formed during the initial stages of reaction. The fact that TGA reactivity profiles become equivalent to i.r. reactivity profiles, when corrected to account for stable complex formation, suggests that the former may not be accurate representations of the variations in intrinsic reaction rates and should be used with caution when attempting to validate proposed models of char gasification kinetics. The extent to which stable complex forms during char gasification was used to explain the observed differences in the reactivity profiles obtained for reactions of char in oxygen and carbon dioxide.     

草古一中转站回水管网系统腐蚀原因分析

本文针对现河采油厂草古一中转站回水管网腐蚀严重状况,结合现场实际生产情况,分别从腐蚀产物、采出液、温度、二氧化碳、溶解氧、微生物、流速等方面进行研究,表明：草古一污水温度较高,pH值较低,污水体系为：CO2／HCO3^-为主构成的腐蚀介质,并通过正交实验研究表明腐蚀的主次要因素为：温度〉二氧化碳〉溶解氧〉矿化度〉pH值。温度是最重要的影响因素,其次为二氧化碳和溶解氧。结合草古一腐蚀情况,对目前防腐控制技术进行调研,提出了下步防腐控制措施。     

Behavior of Bubbles of Oxygen and Sulfur Dioxide in Soda-Lime Glass

Bubbles of sulfur dioxide are dissolved by soda-lime glass containing arsenic or ferric oxide at a rate which follows a square-root-of-time law, indicating a diffusion process. Mixtures of sulfur dioxide and oxygen are dissolved very rapidly as long as both gases are present, whereas an excess of either gas remaining in the bubbles is adsorbed at the normal rate, which depends on the composition of the glass. Apparently sulfur dioxide is dissolved by oxidation either by oxygen in the bubble or by oxygen diffusing from oxidizing constituents in the glass, whereas oxygen is dissolved by diffusing into the glass to react with reducing constituents.     

产毒藻培养用光生物反应器结构研究

设计研制了一种新型光生物反应器。该光生物反应器具备光照、温度、pH、二氧化碳、溶氧、营养源等培育条件在线自动化控制功能。采用低剪力搅捧、高效气液交换混合、低功耗高效LED光源设计,解决了海洋产毒微藻工程化培育中的关键技术问题。该反应器结构简单、易于工程化放大,系统可广泛适用于海洋微藻类及其它相关代谢产物的培养生产。并且详细阐述了新型光生物反应器的设计思路和工作原理。     

Discrete system identification and self-tuning control of dissolved oxygen concentration in a stirred reactor

This work presents the applications of discrete-time system identification and generalized minimum variance (GMV) control of dissolved oxygen (DO) level in a batch bioreactor in which Saccharomyces cerevisiae is produced at aerobic condition. Air flow rate and mixing rate were varied to determine the maximum local liquid phase volumetric mass transfer coefficient (K _L a). Maximum K _L a value was determined at a mixing rate of 600 rpm and air flow rate of 3.4 Lmin⁻¹. For control purpose, manipulated variable was selected as air flow rate due to its effectiveness on the K _L a. To examine the dynamic behavior of the bioreactor, various input signals were utilized as a forcing function and three different model orders were tested. A second0order controlled auto regressive moving average (CARMA) model was used as the process model in the control algorithm and in the system identification step. It is concluded that the ternary input is more suitable than the other input types used in this work for system identification. Recursive least squares method (RLS) was used to determine the model parameters. GMV control results were compared with the traditional PID control results by using performance criteria of IAE and ITAE for different types of DO set point trajectories. DO concentration in the batch bioreactor was controlled more successfully with an adaptive controller structure of GMV than the PID controller with fixed parameters.     

Ignition and combustion of single coal and char particles: A quantitative differential approach

A quantitative differential technique for studying the coal particle combustion process and particularly the ignition step was developed. The approach is based on the continuous and simultaneous analysis of the carbon monoxide and carbon dioxide produced when a captive single coal particle is burnt after injection into an isothermal flow reactor swept with a preheated oxygen—nitrogen mixture. To check the results obtained with the new approach, the intensity of the light generated during the particle combustion was also registered. A microcomputer controlled and executed the data collection process in the millisecond time frame. Experiments were performed burning single particles from the 850–1000μm sieve fraction of a Wyoming subbituminous coal in air, at five gas temperature levels ranging from 928 to 1283 K. The gas product curves show the ignition mechanism is defined by the relative rates of volatiles evolution from the particle and oxygen diffusion to the particle. Initial peaks in the rate of formation of carbon monoxide or carbon dioxide allow the determination of the pyrolysis time during combustion. The occurrence of heterogeneous and homogeneous ignition for particles of the same coal was detected using both techniques: gas analysis and light intensity. A transition was detected in the ignition mechanism, from heterogeneous to homogeneous, when the reactor temperature was increased. Even though the light intensity technique is simpler, the results demonstrate that the approach developed in this work has more sensitivity, particularly in the transition zone. An additional advantage of the gas analysis approach is that the total carbon in the original particle and its variation with time can be calculated by integration of the gas product curves. This information provides a method for estimating the fraction of carbon released from the particle as volatile matter during the ignition. After ignition, the variation in the mass of carbon with time can be used to test different combustion mechanisms. As expected, the results show that at the higher temperatures used, the particle burn-off proceeds under external diffusion control. The total combustion times, as obtained from the gas product curves, show good correlation with the results obtained from light intensity measurements.