Integrated system for microreactor gas chromatography

A compact unit has been constructed to control and to supply a microreactor apparatus. Features are an ozone generator, gas flow rotameters, solenoid-operated six-way gas valve and a combination temperature-and-ozone meter. The meter monitors and, by means of a built-in relay, controls reaction temperature. It also affords a visual indication of ozone concentration during reactions. Basic electronic circuits and common laboratory items simplify the unit’s construction. Some possible microreactions to which this integrated system may be applied are ozonizationpyrolysis, esterification, transesterification, saponification, reduction and halogenation. Presented at the AOCS Meeting, Chicago, October 1967. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Response Surface Methodology Applied to Ozone Generation

In this work, a strategy is presented to optimize the ozone generation by response surface methodology. A dielectric barrier discharge ozone generator was developed in which it is possible to control electrical current frequency and gas flow entering the generator. Response surface methodology was used to identify ozone generator optimum operational conditions, that is, those that permit considerable ozone productivity and high concentration of ozone gas.     

Gas Phase Ozone Concentration Comparisons From a Commercial UV Meter and KI Wet-Chemistry Tests

Formal ozone system power-production tests conducted at ten (10) different ozone installations have resulted in over 100 comparative UV meter versus KI wet-chemistry ozone concentration tests for fifteen (15) individual UV meters. The wet-chemistry tests were conducted by different individuals, including the ozone generator manufacturer's technician and owner's staff. In all cases, the tests were either conducted or witnessed by one of the authors. This paper presents results focused on: 1) precision of UV meter readings, 2) accuracy of the wet-test meter or the UV meter, and 3) expected range in percent difference between UV meter readings and KI wet-chemistry test ozone concentration results for the particular type of UV meter and wet-test meter used in the tests.     

Ozone and Nitrogen Oxides Generation in Gas Flow Enhanced Hollow Needle to Plate Discharge In Air

Siemens made the first ozone generation system by corona discharge about hundred and fifty years ago. At present mainly two types of atmospheric pressure electrical discharges - corona discharge and dielectric barrier discharge are used for production of ozone. Another type of discharge, which can be used for this purpose, is multineedle to plate electrical discharge enhanced by the gas flow. Contrary to the conventional arrangement when the gas is flowing around the needles we studied the discharge in which the gas was pumped through the needles. Results of studies of ozone and nitrogen oxides production by DC electrical discharge in air at atmospheric pressure with a single hollow needle to plate electrode configuration enhanced by the flow of air through the needle for both polarities of the needle, different airflow rates and currents are presented in this paper.     

Design Considerations in Alternative Ozone Feed-Gas Systems

The design engineer and owner have multiple issues to address when planning to use an ozone process in a water or wastewater treatment plant. Considerations include feed-gas properties and equipment, ozone generator features and size, ozone contactor type and configuration, and methods of off-gas ozone destruction. Many successful ozone systems are in use today. Where performance has suffered, deficient feed-gas treatment often is the problem. The feed-gas to the ozone generator must be oil-free, particulate-free, and dry. In this paper, the factors involved in selecting and operating feed-gas equipment are presented.     

Ozone Plant Operations Under Drought Conditions

The Metropolitan Water District of Southern California (Metropolitan) owns and operates five potable water treatment plants. Currently four of the treatment plants utilize ozone as the primary disinfectant. The Metropolitan ozone contactors are over-under baffled and include 10 chambers, an afterbay, and an effluent channel. Ozone is generally added in either the first countercurrent gas/liquid flow chamber (Chamber 1) or the first and second (co-current gas/liquid flow) chambers. Disinfection credit is received from ozone residuals in Chambers 2 through 6. An ozone destruct system collects and destroys ozone off-gases from Chambers 1 through 9 and an ozone quenching system is used to minimize dissolved ozone from leaving the contactors. Severe drought in California, and resulting water supply limitations, have created significant operational issues ranging from reduced plant flows to source water changes and water quality challenges. The combination of reduced flow and different source water conditions resulted in the ozone systems being operated occasionally under unfamiliar conditions. This article discusses some of the challenges faced in operating the ozone plants at low flows and low ozone production rates. Further, water quality issues required prudent management of operations to meet regulatory requirements. From the lessons learned, several recommendations are offered in preparation for similar conditions in the future.     

On the development of a two-phase flow meter for vertical upward flow in tubes

A new method for measuring the volumetric flow rate of each phase for two-phase, air and water, flowing upwardly in a vertical tube is developed. This noble device, a Two Turbine Flow Meter System (TTFMS), is composed of two turbine flow meters, a valve, two thermocouples, and two pressure transducers. For a given twophase flow, the rate of rotation of the turbine flow meter is found to depend only upon the volumetric flow rates of gas and liquid at the point of measurement. A calibration model is developed for the turbine flow meter, which provides a simple, general, and accurate relationship between the output signal of a turbine flow meter and the actual two-phase flow rate. The volumetric flow rate of each of the two phases is determined by this model. TTFMS is a simple, durable, and inexpensive two-phase flow measuring device that does not require physical separation of a phase from the two-phase mixture.     

Experimental Investigations On Production Of Excited Ozone Species From A Silent Discharge Ozone Generator

Ozone decomposition kinetics are investigated together with the influence of energy input to an ozone generator. Decomposition is considered in a solid bed reactor, a gas phase reactor and a bubbling reactor. Ozone is produced at the same concentration and gas flow rate using two methods: 1) from the generator at a higher power giving higher ozone concentration, then ozone is diluted by oxygen before entering the decomposition reactor, and 2) at a lower power without dilution.     

Optimizing Factors on High Concentration of Ozone Production with Dielectric Barrier Discharge

The gap distance, electrode material, voltage and gas flow velocity were optimized with gas pressure variation of dielectric barrier discharge (DBD) for producing high concentration of ozone. There exists an optimum gas pressure at which the highest ozone concentration is produced with other parameters being fixed. This optimum gas pressure value changes accordingly as the other parameters changed. As the discharge continues at the optimum pressure, the ozone concentration could increase or decrease slowly. This aging effect has different characteristics with the metal electrode material and the impurity level of the oxygen gas used for ozone generation. The aging effect is supposed to be related with the catalytic effect of metal oxide, which is generated in the discharge zone. The change in the characteristic of optimum pressure by the other parameters, indicate that the ozone concentration is deeply related with the filament self-organization characteristics of DBD. At the final optimized condition, the ozone concentration was higher than 22.5 wt.%.     

Technological parameters that influence the production of ozone in A .D. C. Corona discharfe

Experiments using dry oxygen in a wire–to–cylinder ozone generator, submitted to D.C. corona discharges show that technological parameters (diameter and composition of wire and cylinder, length of cell, gas flow and transit time of the gas) greatly influence ozone production. The cell geometry to be used depends on the polarity of the D.C. voltage applied to the wire and, for a predetermined design, the maximum ozone production rate will be obtained by seeking the most suitable gas flow. Lining up a series of optimized cells can give significant results.     

Study of a hybrid gas generator for a ducted rocket

A performance analysis and experimental study of a hybrid gas generator to be used in a ducted rocket are presented. Such a system exhibits potential advantages with regard to safety, performance, costs, availability of the fuel components, storability, and thrust control. A combination of a paraffin wax fuel and oxygen in the gas generator ensures a high regression rate and reveals oxidizer-to-fuel ratios as low as 0.14 in the gas generator (compared to the stoichiometric ratio of 3.4). A fuel regression rate correlation versus the oxidizer mass flux is derived, presenting a major advantage for the fuel flow rate management in comparison to control of the solid propellant gas generator burning rate through the pressure exponent, which requires mechanical interference with the hot nozzle flow to ensure a change in the combustor pressure and a corresponding change in the burning rate. Evaluation of the ducted rocket (with different oxidizers) versus pure ramjet performance shows a higher specific thrust for the former, though the latter exhibits a higher specific impulse.     

Research Note: Measurement of Ozone via an Indirect Gas Chromatography Method

Gas chromatography was used to measure the ozone concentration in oxygen produced by an ozone generator. In this indirect method, the ozone reacts with the coating of the capillary column and produces carbon dioxide, which is then detected. The primary methods of calibration for this technique were based on a wet-chemistry process and absorption of ultraviolet light. This finding also is important if the primary reason for using gas chromatography is detection of carbon dioxide, as artificially high readings of carbon dioxide would be measured in the presence of ozone. The method was tested for ozone concentrations of 3–70?mg/L but the method should also be applicable to higher concentrations.     

基于热力学第二定律的ORC蒸气发生器性能优化

为了更深入地研究低温余热驱动ORC系统的设计与优化,建立了有机朗肯循环蒸气发生器主要热力性能计算模型,基于热力学第二定律,以蒸气发生器单位换热面积工质?升作为性能优化目标函数,选取了R245fa作为循环工质,在给定烟气进口温度以及保证循环工质在蒸气发生器出口为饱和蒸气条件下,对不同工况下的工质质量流速进行优化,并分析了在一系列换热管管径下,烟气入口温度、工质入口压力、管外对流传热系数、单根换热管烟气质量流量对目标函数及工质最优质量流速的影响。结果表明：工质入口压力与管外对流传热系数对最优工质质量流速影响显著,随着工质入口压力与管外对流传热系数的增大,最优工质质量流速增大,对应的换热管径减小;而烟气入口温度、单根换热管烟气质量流量对最优工质质量流速影响甚微。     

A Study of Ozone Formation on the Surfaces of Electrodes

It had been previously thought that ozone production occurred in gaseous space, especially the space between electrodes. However, based on our research, we believe that may only be one of the ozone-producing processes. In this study, we aimed to confirm that a third body, which is present at the interface between oxygen gas and a metal electrode, works to compose ozone. Ozone was not observed in pure oxygen (400x10^?6 Nm³/min flow rate) when electrical discharge was supplied after approximately 6 months. The concentration of ozone increased (approximately 0.07 ppm) when nitrogen (approximately 20x10^?6 Nm³/min flow rate) was added to a gas-mixing chamber. A third body was required to produce ozone when an oxygen molecule and an oxygen atom collided. The same phenomenon was observed on the surface of a copper anode. A simulation confirmed this. Using an industrial ozone generator which utilized ceramic dielectrics and expanded metal electrodes, an increase in the temperature of the cooling water led to a proportional decrease in ozone concentration. After changing from the titanium electrode to a nickel electrode and an antimony electrode, we observed the difference in the enthalpy changes which were calculated using van't Hoff's formula. The antimony electrode increases the efficiency of the ozone generator to produce ozone. We have come to believe that ozone can be composed on the surface of a metal electrode.     

抚顺市污水流量监测技术研究

通过对抚顺市安装污水流量计情况的调查分析,根据各种类型污水流量计的原理和性能特征,研究抚顺市各种排污口所适合安装的污水流量计,从而达到为环境管理部门提供准确污水流量数据的目的。     

Cooling Conditions of Ozone Generators

The efficiency of ozone generators is determined by many factors. Operating conditions such as feed gas quality and especially cooling conditions are of utmost importance. Cooling of ozone generators is absolutely necessary, since ozone destruction reactions increase exponentially with temperature. The most common way to cool an ozone generator is water flowing in close contact to the electrodes. The heat removal out of the discharge gap depends on different parameters. Electrical input power, cooling water flow conditions, electrode geometry and material properties are some of them. Simultaneously lowering cooling water temperature, applied power density and gap width, leads to a lower gas temperature in the discharge gap and thus to increased ozone production efficiency. Minimizing the temperature difference between the cooling water inlet and outlet improves the ozone production efficiency as well. This measure, however, results in high cooling water flows and requires additional cooling water chilling, resulting in higher operational costs and capital expenses. Cooling associated costs rise disproportionally with increasing cooling water flow. Simultaneously, energy consumption of ozone generators decreases as the average cooling water temperature goes down. As a result, there exists an optimum between the operational and capital expenses for the combination of ozone generator and cooling water system related expenses, offering significant cost savings for the customer.     

Verification of Ozone Clusters (O6 & O9)

The use of silica gel for the storing of ozone was investigated. The ozone gas that was discharged from the silica gel was found to be different from normal ozone which is generated by the ozone generator that makes ozone with electric discharge. Ozone clusters could be synthesized by this method, which detaches ozone from silica get without requiring any additional energy. These ozone clusters didn't decompose at room temperature and atmospheric pressure over a half-day. We confirmed that the cluster was heavier than a heavy standard gas, the presence of clusters with an analysis using GC/MS, and the existence of ozone clusters by the bonding energy using a computer simulation by MOPAC.     

管束间气液两相流动特性研究进展

从流型及其转变、含气率、压降和速度分布等几方面对前人在管束间气液两相流动特性的工作做了综述,归纳并探讨了最新进展与方向。     

Experimental Study of Ozone Generation by Negative Corona Discharge in Mixtures of N2 and O2

Ozone generation by negative DC corona discharge in N₂-O₂ mixtures has been experimentally investigated using a coaxial wire-cylinder corona reactor operating at room temperature and atmospheric pressure. The experiments have been carried out under different gas flows (15 cm³ min^?1 to 200 cm³ min^?1) and gas compositions (5% to 90% of O₂), and the effect of these parameters on the corona current, the ozone density and the efficiency of the ozone generator have been analyzed. The global rate coefficients for ozone formation and destruction have also been evaluated, and their values compared with those reported by other authors. The maximum efficiency for ozone production was found in gas mixtures with oxygen content about 70–80%.     

Analysis of local heat transfer and hydrodynamics in a bubble column using fast response probes

A fast response probe is used to measure local heat transfer in a bubble column. It captured the variations in local heat transfer coefficients due to changes in local hydrodynamic conditions in radial and axial directions. These measurements have been used to identify flow regime transitions, variations in flow patterns and local hydrodynamic structure as obtained with different gas distributors and varying gas velocity. Standard deviations of pressure measurements obtained with a fast response probe have been compared with heat transfer coefficient fluctuations for the first time and the similarities and differences have been pointed out. Variations in average heat transfer coefficients and standard deviations in radial and axial directions point to different hydrodynamic conditions and are compared with literature studies. Relationships between local heat transfer measurements and hydrodynamic conditions are shown.