Cylindrical Flow Reactor Research Articles

Removal of Machine industrial from wastewater using cylindrical flow reactor by electrochemical oxidation and optimization of treatment conditions

This work examines the use of electrooxidation for treatment of wash water obtained from industry. Cutting oil was mainly found in the wastewater. The effluent was treated using NaCl as supporting electrolyte using a cylindrical flow reactor in continuous (single pass) mode under various current densities (2-5 A/dm2) and different flow rate (10-40 L/h). By cyclic voltammetric (CV) analysis, the best condition for maximum redox reaction was found. Efficiency of COD reduction and power consumption were studied for each operating conditions. From the results maximum COD reduction of about 93.3 % was obtained at a flow rate of 10 L/h with applied current density of 4 A/dm2. FT-IR spectra studies showed that during electrooxidation, the intensities of characteristic functional groups such as C-H, O-H were reduced and also some new peaks comes to appear. Probable theory, reaction mechanism and modeling were proposed for the oxidation of machine industrial effluent. All the experimental results have indicated that electrooxidation treatment was very effective and was capable of elevating quality of the treated wastewater effluent to the reuse standard of the machine industry.

Thin wetted film cylindrical flow photo reactor for the degradation of Procion blue H‐B dye over TiO2 and ZnO

A thin wetted film cylindrical flow reactor was fabricated for photocatalytic oxidation of Procion blue H‐B dye in textile washwater with the suspensions of TiO2 and ZnO. The disappearance of colour and organic reduction were studied in terms of the removal of colour and chemical oxygen demand (COD). Operating parameters such as effect of pH, UV irradiation with and without catalyst, initial concentration of dye and effect of flow rate were studied and kinetics of Procion blue H‐B dye has been studied over TiO2 and ZnO surfaces. Since adsorption is the prerequisite condition for decolorization / degradation of dye molecules in the presence of heterogeneous catalysis, the Langmuir and Freundlich isotherms were examined to verify the adsorption intensity. The results clearly demonstrated that, the optimum loading of the photocatalyst was found to be 300 and 400 mg/L of TiO2 and ZnO, respectively. The maximum COD reduction efficiency was 68% for TiO2 and 58% for ZnO. On the other hand, the colour removal efficiency was found to be 74% and 69%, respectively for TiO2‐ and ZnO‐assisted systems under optimum conditions. Conclusively, these two semiconductors could degrade Procion blue H‐B dye at different time intervals and both isotherms fit well.

Kinetics, products, and mechanism of ethane destruction in corona discharge: Experiments and simulation

Ethane destruction in corona discharge was studied in a flow reactor. Samples from the reactor were analyzed by GC/MS and on a quadrupole mass spectrometer. Corona discharge was initiated at atmospheric pressure and room temperature in a cylindrical flow reactor with a dielectric barrier and an axial high-voltage electrode. The flow rate of the initial mixture was varied between 0.17 and 4.8 cm3/s; the discharge power, between 0.01 and 8.0 W. The radiation yield was 0.5 molecule/100 eV for 1% ethane in air. Simulation was carried out using the kinetic mechanism consisting of 809 reactions involving 85 types of molecules, atoms, radicals, and excited species. The so-called free-radical mechanism that we developed led to an underestimated ethane destruction efficiency. The model qualitatively describes the product composition and the concentrations of its main components, but it provides no quantitative fit to experimental data, particularly for low initial ethane concentrations. New products hitherto unreported in the literature—methyl nitrate, ethyl nitrate, and acetic acid—were identified and quantified. The results are interpreted in terms of ionic reactions as a part of the destruction mechanism. These reactions are of particular significance in dilute mixtures and at low hydrocarbon concentrations in the initial mixture.

Copper Removal from Aqueous Media Using a Cylindrical Flow Electrochemical Reactor

The construction and application of an electrochemical cylindrical flow reactor packed with copper wires, was used to eliminate Cu2+ ions from dilute aqueous CuSO4 solutions. The cathode of reactor was constructed with a series copper wire cylindrical hanks, piled up one on top of the other. The anode consisted of a graphite road electrode surrounded with a drilled PVC tube wrapped with Celgard® that serves to separate both the cathode and anode electrodes. Current and potential are supplied by an external power source. Results for Cu2+ ion concentration profile for dilute aqueous solutions applying an 8 V potential and a 0.17 cm3/s flow are reported. Copper removal efficiency ranges from 35 to 70% for all the samples examined. The experimental concentration profile fits an exponential decay along the axial reactor coordinate, in agreement with the theory for porous tubular flow reactors. A decrease in both solution conductivity and pH due to the reduction of copper ion concentration and water oxidation was observed.

Removal of pharmaceuticals from wastewater by electrochemical oxidation using cylindrical flow reactor and optimization of treatment conditions

This paper examines the use of electrooxidation for treatment of wastewater obtained from a pharmaceutical industry. The wastewater primarily contained Gentamicin and Dexamethasone. With NaCl as supporting electrolyte, the effluent was treated in a cylindrical flow reactor in continuous (single pass) mode under various current densities (2–5 A/dm2) and flow rates (10–40 L/h). By cyclic voltammetric (CV) analysis, the optimum condition for maximum redox reaction was determined. The efficiency of chemical oxygen demand (COD) reduction and power consumption were studied for different operating conditions. From the results it was observed that maximum COD reduction of about 85.56% was obtained at a flow rate of 10 L/h with an applied current density of 4 A/dm2. FT-IR spectra studies showed that during electrooxidation, the intensities of characteristic functional groups such as N-H, O-H were reduced and some new peaks also started to appear. Probable theory, reaction mechanism and modeling were proposed for the oxidation of pharmaceutical effluent. The experimental results demonstrated that electrooxidation treatment was very effective and capable of elevating the quality of treated wastewater to the reuse standard prescribed for pharmaceutical industries.

Heavy metal removal from copper smelting effluent using electrochemical cylindrical flow reactor

The purpose of this study is mainly to evaluate the performance of the continuous recirculation flow cell at low current density and pH (the pH at which the effluents are available) in removing heavy metals from copper smelting effluent by cathodic reduction. During the electrolysis at different pH, % removal of heavy metals removal, energy consumption and heterogeneous reaction rate constants were investigated at given flow rate and current density on the selected industrial effluent. The overall specific energy consumption at the pH 0.64 was observed to be lowest, which is 10.99 kWh/kg of heavy metal removal.

Electrochemical treatment of Procion Black 5B using cylindrical flow reactor—A pilot plant study

The paper presents the results of an efficient electrochemical treatment of Procion Black 5B—a pilot plant study. Experiments were conducted at different current densities and selected electrolyte medium using Ti/RuO 2 as anode, stainless-steel as cathode in a cylindrical flow reactor. By cyclic voltammetric analysis, the best condition for maximum redox reaction rate was found to be in NaCl medium. During the various stages of electrolysis, parameters such as COD, colour, FTIR, UV–vis spectra studies, energy consumption and mass transfer coefficient were computed and presented. The experimental results showed that the electrochemical oxidation process could effectively remove colour and the chemical oxygen demand (COD) from the synthetic dye effluent. The maximum COD reduction and colour removal efficiencies were 74.05% and 100%, respectively. Probable theory, reaction mechanism and modeling were proposed for the oxidation of dye effluent. The results obtained reveal the feasibilities of application of electrochemical treatment for the degradation of Procion Black 5B.

Influence of ozone, relative humidity, and flow rate on the deposition and oxidation of sulfur dioxide on yellow sand

Abstract To evaluate the influences of O 3 , relative humidity (RH), and flow rate on the reaction between yellow sand and SO 2 , the SO 2 deposition velocity and the oxidation state of sulfur were investigated by means of exposure experiments in a cylindrical flow reactor. Early in the reaction, the deposition velocity was not influenced by the RH or the presence of O 3 ; as the reaction progressed, however, the deposition velocity increased in the presence of O 3 and at high humidity. The oxidation of sulfur from S(IV) to S(VI) was also enhanced under these conditions. The amount of sulfur oxidation was positively correlated with the amount of deposited O 3 . Furthermore, the SO 2 deposition velocity increased with increasing flow rate. However, changes in the flow rate had no noticeable effect on the amount of SO 2 oxidation.

The mass accommodation coefficient of ozone on an aqueous surface

A wetted-wall cylindrical flow reactor was used to measure uptake coefficients, γ, of O3 on aqueous surfaces at 293 K. The loss of O3 from the gas-phase following contact with varying areas of aqueous surface was determined by UV absorption. The use of Na2S2O3 as an aqueous-phase scavenger for O3 ensured that uptake coefficients were in a reaction-controlled rather than mass accommodation-controlled regime. Observed uptake coefficients were corrected for radial gas-diffusion to yield values of γcorr. From extrapolation of a plot of 1/γcorr against the inverse square-root of the Na2S2O3 activity, a value of α = 4 × 10−2 was derived for the true mass accommodation coefficient of O3. Evaluation of uncertainties indicate a conservative lower limit of 10−2 for α. The data do not rule out that the upper limit approaches unity. However, it is shown that the measured value of α is sufficiently high that mass accommodation does not limit heterogeneous processing of O3 in the atmosphere for droplets of diameter >10 μm. A value of 3.7+0.7−0.6 × 108 L mol−1 s−1 is derived for the aqueous-phase reaction rate coefficient between O3 and Na2S2O3 at 293 K.

The effect of gravity on the rate of a simple neutralisation reaction in a small, open cylindrical vessel

We have examined the local and global evolution of the extent of neutralisation in an upright cylindrical flow reactor with a rigid adiabatic base and sidewall but with an open top. The cylinder is initially filled with a dilute aqueous solution of a strong base or a strong acid. A dilute solution of strong acid or strong base is injected as a steady Poiseuille flow towards the centre of the base of the reactor through a large capillary tube coaxial with the cylindrical reactor. Computational fluid dynamics modelling, using the finite-volume method, indicates that each neutralisation reaction progresses at a significantly different rate under conditions of normal terrestrial gravity and microgravity. The gravitational dependence of the conversion of acid or base to salt and water is attributed to secondary flows due, largely, to buoyancy forces associated with the dependence of the local liquid density on the local chemical composition. The influence of these secondary flows on the spatial distribution of the salty product is illustrated. For the rather dilute solutions examined here we find excellent agreement between results from our weakly compressible hydrodynamic treatment and those from a more standard analysis employing the Boussinesq approximation.

Scaling Up of a Photoreactor for Formic Acid Degradation Employing Hydrogen Peroxide and UV Radiation

A model for scaling up a homogeneous photoreactor was developed and experimentally verified in a pilot-plant-size apparatus. The procedure is exemplified by the oxidation of dilute aqueous HCOOH solutions with UV radiation (254 nm) and H2O2. First, the kinetic model and the kinetic parameters of the HCOOH degradation were obtained in a well-stirred, small, batch flat-plate photoreactor (volume=70 ml). The method employed in the analysis of the experimental results yielded reaction-rate expressions for HCOOH and H2O2 that were independent of the reactor configuration. These kinetic equations and the corresponding kinetic constants were then used in a mathematical, fully deterministic model of a continuous-flow, 2-m-long, annular reactor (0.0065 m2 of cross section for flow) operating in a laminar-flow regime to predict exit concentrations of HCOOH. Irradiation was provided in both cases by two different types of germicidal lamps. No additional experiments were made to adjust the reactor-model parameters. Theoretical predictions from the representation of the reactor performance obtained were compared with experimental data furnished by experiments in the much-larger-size, cylindrical-flow reactor. Results showed good agreement for the range of variables explored; they corresponded to expected operating conditions in water streams polluted with low concentrations of organic compounds.

Reaction of BrONO2 with H2O on submicron sulfuric acid aerosol and the implications for the lower stratosphere

Uptake of BrONO2 onto submicron sulfuric acid aerosol was studied in a cylindrical flow reactor coupled to a chemical ionization mass spectrometer. On aerosol particles of ∼0.1 μm radius, the reaction of BrONO2 with H2O to produce HOBr and HNO3 is very efficient, with the reaction probability γ ≈ 0.8 for H2SO4‐content ≤ 70 wt%. The equilibrium constant for the gas phase process, BrONO2 + H2O ⇄ HOBr + HNO3, was measured and the heats of formation of the bromine compounds were deduced. The conversion of HOBr back into BrONO2 via reaction with HNO3 can be neglected in the stratosphere. The heterogeneous hydrolysis of BrONO2, followed by photolysis of the HOBr product, is a major source of HOx in the lower stratosphere. The role of bromine as an activator of chlorine is also discussed.

Laboratory measurement of SO 2 deposition velocities on selected building materials and soils

Measurements of SO 2 deposition velocities have been carried out in the laboratory utilizing a cylindrical flow reactor. Analysis of data from these experiments was carried out using models that specifically account for diffusive transport in the system. Consequently, the resulting deposition velocities were independent of diffusion processes and represent the maximum removal rates that would be encountered in the environment under turbulent atmospheric conditions. The measured values range from 0.04 cm s −1 for asphalt to 2.5 cm s −1 for cement, and were found to be independent of SO 2 and oxygen concentrations, as well as relative humidity and total pressure. Prolonged exposure to SO 2 eventually destroyed the ability of the various solids to remove this species. Overall capacities were found to increase significantly at moderate relative humidities yielding values of 0.4–2.8 g SO 2 m −2 of solid in moist systems. Several experiments indicated that the reactivity of a solid subjected to prolonged SO 2 exposures could be restored by washing the surface with distilled water or exposing the spent solid to ammonia. Some implications of these findings with regard to the environment are discussed.

1576. Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres: H Hedgpeth et al, Rev Sci Instrum, 45 (3), 1974, 344–347

1576. Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres: H Hedgpeth et al, Rev Sci Instrum, 45 (3), 1974, 344–347

Erratum: Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres

Erratum: Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres

Cylindrical flow reactor for the study of heterogeneous reactions of possible importance in polluted atmospheres.

This paper discusses the construction of a cylinder flow reactor used for studying heterogeneous reactions, with particular reference to reactions involving NOx. This system incorporates methods of gas analysis such as optical absorption (NO2), chemiluminescent (NO or O3), gas chromatography (N2 or O2) and mass spectrometry (SO2, etc). The system was constructed such that experimental conditions could be varied over a large pressure range from 1 to 700 Torr with a relative humidity variation of 0–90%.