A Study of the Physical and Chemical Processes Active in Ozone Generation by Carbon Dioxide Fed Corona Discharges

Ozone generation in both positive and negative corona discharges DC corona, both operated in glow regime, feed by dry CO₂ has been studied. Higher ozone concentrations were observed in negative corona discharges. Ozone formation was found to be strongly dependent upon both the flow rate of the gas and on the radius of the outer electrode. The physical characteristics of the discharge were monitored through measurement of the discharge current. Small increases in the gas flow rate were observed to cause a significant increase in the discharge current of a negative corona discharge but little/no effect was observed in positive corona.     

The Influence of Ozone,Oxygen and Chlorine on Biolocical Activity on Biological Activated Carbon

A laboratory study was conducted into the effects of the treatment of activated sludge effluent with different oxidants on the biodegradability of the organic substances. It was found that, under the experimental conditions described, ozone increased the biodegradability, whereas chlorine had no apparent significant effect. The effect of continuous oxidative pretreataent of activated sludge effluent on microbial populations and the biological activated carbon used subsequently in the process also was studied. It was found that ozone, particularly at a dosage of about 5 mg/L promoted biological activity, while chlorine and oxygen (in addition to the dissolved oxygen already in the effluent) had no significant effect on the biological population size.     

Removal of Color and Organic Matter in Industrial Phosphoric Acid by Ozone: Effect on Activated Carbon Treatment

Industrial phosphoric acid at 42-45% P₂O₅ and containing organic matter (OM) in the range of 220 mg/L to 300 mg/L is treated by combined ozonation and activated carbon. Ozonation alone removes the initial dark color of the acid and eliminates the organic content. Adsorption on activated carbon alone can reduce OM levels by 80% for more than 25 g/kg P₂O₅. We find that a preozonation noticeably enhances activated carbon efficiency and reduces its specific consumption. Isoconversion curves are plotted in specific ozone and activated carbon ratio space.     

我国二氧化碳可降解塑料的研究与应用进展

以CO2为原料合成可降解塑料是CO2资源综合利用的一条有效途径。对CO2与环氧化物共聚合成脂肪族聚碳酸酯在我国的研究开发情况进行了综述,并对其在可降解塑料方面的应用前景进行展望。     

Effect of Chemical Structure of Solid Lipid Matrix on Its Melting Behavior and Volumetric Expansion in Pressurized Carbon Dioxide

Supercritical carbon dioxide (SC-CO₂) technology offers new opportunities for green processing of lipids; however, there is little information of the melting behavior and volumetric expansion of solid lipids in pressurized CO₂. In this study, melting behavior and volumetric expansion of two different solid lipid classes and the effect of the structural differences within the same lipid class on the melting behavior in pressurized CO₂ were investigated. The melting point of the solid lipids decreased linearly with increasing pressures up to a certain level; then, it stayed constant. The highest melting point depression was observed for soybean oil monoacylglycerol (SO-MAG) at 51.5 °C/110 bar, whereas the lowest was for fully hydrogenated soybean oil (FHSO) containing 30% SO-MAG at 55.0 °C/79 bar. Melting point depression depended on lipid class. SO-MAG exhibited a higher melting point depression than FHSO (triacylglycerol form), and its blends with SO-MAG. There was no difference in melting point depression between glyceryl 1,2-distearate and glyceryl 1,3-distearate up to 200 bar (P > 0.05). A positive correlation between the melting point depression and volumetric expansion of solid lipids was observed. The highest volumetric expansion was for SO-MAG in the linear region of the melting point depression curve, achieving 14.4% expansion compared to 9.3% for FHSO (P < 0.05). The highest dT/dP value (0.17 °C bar⁻¹) was obtained for SO-MAG, whereas the FHSO (0.09 °C bar⁻¹) had the lowest one. Findings of this study will help optimize solid lipid-involving SC-CO₂ processes for better protection of heat-sensitive compounds while improving energy efficiency.     

The Filtration Properties of Atropa belladonna Plant Cell Suspensions; Effects of Hydrodynamic Shear and Elevated Carbon Dioxide Levels on Culture and Filtration Parameters

The filtration properties of Atropa belladonna plant cell suspensions cultured at different bioreactor stirrer speeds and gas-phase carbon dioxide levels were measured. Cell cake compressibility did not vary significantly with culture time, shear intensity or carbon dioxide concentration. Average cell cake permeability decreased by c. 70% with increasing stirrer speeds between 400 and 1000 rpm, and could be correlated with concomitant reductions in cell aggregate size. Permeability was more responsible than other culture parameters, such as growth, cell membrane integrity and protein release, to levels of hydrodynamic energy dissipation in the range 10⁶–10⁹ J m⁻³. Cell cake permeability was significantly affected by carbon dioxide levels of 10 and 15%, but not 2%. Average permeability at 15% CO₂ was reduced by c. 50% compared with the air-sparged control culture, even though aggregate size, morphological characteristics and filtered cake compressibility were unaltered. A distinctive pattern of permeability change over the course of the cultures was observed when the reactor conditions were not inhibitory to growth; however, this pattern was destroyed at medium-to-high shear levels and high carbon dioxide concentrations. © 1997 SCI.     

同时测定乙烯中烃类杂质及CO、CO_2方法探讨

采用1台气相色谱仪、双阀双通道、双氢火焰检测器一次进样同时完成乙烯中微量CO、CO2及烃类杂质的全分析。通过考察载气流速、柱温、升温速率、分流比对实验结果的影响,确定了最佳实验条件,同时对该方法进行了精密度、准确度和最小检测限考察。结果表明该方法是乙烯中杂质含量测定的一种简单快捷、准确可靠的分析方法。     

Combined Use of Ozone and Granular Activated Carbon (GAC) in Potable Water Treatment; Effects on GAC Quality After Reactivation

Common processes in potable water treatment regarding dissolved organics removal (natural organic matter, NOM, and organic micropollutants, OMP) include oxidation techniques – like ozonation -and adsorption onto granular activated carbon (GAC). This paper deals with combined ozonation and GAC filtration. Effects on water quality are discussed: partial oxidation of dissolved organics by ozone, leading to changing adsorption behavior and enhanced biodegradation in GAC columns. Special emphasis is laid on long term effects of ozone on GAC quality after several thermal reactivations. Long term experience indicates that ozonation prior to GAC filtration, leading to moderate ozone concentrations in the GAC influent, does not influence GAC quality negatively, even after more than ten reactivation cycles.     

The Effects of Ozonation,Biological Filtration and Distribution on the Concentration of Easily Assimilable Organic Carbon (AOC) in Drinking Water

The concentration of easily assimilable organic carbon (AOC) as determined with growth measurements using wo bacterial cultures, increased linearly with ozone dosage at values below 1 mg O₃/mg of C. Moreover, a linear relationship was found between AOC increase and the decrease of UV absorbance of water after ozonation with various dosages. Biological filtration in water treatment reduced AOC concentrations, but the remaining values were above the AOC concentration before ozonation. This AOC removal was attended with an increased colony count in the filtrate. The AOC concentration of drinking water produced by the application of ozone in water treatment decreased during distribution. The greatest decrease was observed with the highest AOC concentration. Also in this situation, the highest colony counts were found. To date, ozonation is applied in seven water treatment plants in the Netherlands.     

Studies on the Effects of Certain Non‐dimensional Groups on Dynamic Simultaneous Adsorption Behaviour of Carbon Dioxide and Moisture in Molecular Sieve, 5A

A non‐isothermal model based on linear driving force approximation for a system like CO₂ – moisture – N₂ – molecular sieve, 5A predicted the experimental results satisfactorily for simultaneous adsorption of CO₂ and moisture in a fixed bed. Moisture being the strongly adsorbed component forces carbon dioxide (weakly adsorbed component) to be rolled up. The thermophysical and transport properties of moisture mainly governs the dynamics of the process, control or manipulation of which could give better separation by adsorption of one component from the other lying together in a stream. The major parameters are inlet adsorbate concentration, particle Reynolds number, bed diameter to bed length ratio, Schmidt number, Equilibrium Distribution coefficient, Sherwood number, and Kutateladze number.